1
00:00:00,720 --> 00:00:03,680
Speaker 1: Hey there, listeners, this is Jonathan. Before we get into

2
00:00:04,280 --> 00:00:09,520
Speaker 1: the episode, I want to acknowledge something. Uh. Twitter user

3
00:00:09,960 --> 00:00:14,920
Speaker 1: Charlie Tango Bravo helpfully pointed out that I made a mistake.

4
00:00:15,120 --> 00:00:19,080
Speaker 1: When we first published this episode, I completely misrepresented the

5
00:00:19,200 --> 00:00:23,400
Speaker 1: inverse square law, and so later in this episode you

6
00:00:23,480 --> 00:00:29,160
Speaker 1: will hear me kind of interrupt to give a proper explanation.

7
00:00:29,680 --> 00:00:33,760
Speaker 1: My apologies for that. Uh and um, yeah, I mean,

8
00:00:34,640 --> 00:00:37,920
Speaker 1: this one's totally on me. I made a mistake, and

9
00:00:38,280 --> 00:00:42,000
Speaker 1: I feel real dumb about it. But you know, mistakes happen.

10
00:00:42,880 --> 00:00:45,040
Speaker 1: It doesn't. It just tells me I need to be

11
00:00:45,440 --> 00:00:48,320
Speaker 1: even more careful in the future to make sure that

12
00:00:48,440 --> 00:00:52,479
Speaker 1: I'm not misrepresenting something, which I totally was in the

13
00:00:52,520 --> 00:00:56,080
Speaker 1: original version of this episode. Anyway, let's get to the episode,

14
00:00:56,280 --> 00:00:58,600
Speaker 1: and when we get to the part where I'll correct it,

15
00:00:58,960 --> 00:01:08,199
Speaker 1: I'm pretty sure we'll be apparent. Enjoy. Welcome to Tech Stuff,

16
00:01:08,440 --> 00:01:15,760
Speaker 1: a production from I Heart Radio. Hey there, and welcome

17
00:01:15,800 --> 00:01:18,880
Speaker 1: to tech Stuff. I'm your host, Jonathan Strickland. I'm an

18
00:01:18,920 --> 00:01:21,840
Speaker 1: executive producer with I Heart Radio and I love all

19
00:01:21,920 --> 00:01:27,400
Speaker 1: things tech and listener Terry A. Carlson, and I apologize

20
00:01:27,440 --> 00:01:32,040
Speaker 1: for very likely Butchering your name, asked if I might

21
00:01:32,120 --> 00:01:35,640
Speaker 1: cover how space vehicles navigate. So we're going to talk

22
00:01:35,680 --> 00:01:38,399
Speaker 1: about navigation, and this is one of those things I

23
00:01:38,440 --> 00:01:44,360
Speaker 1: find really fascinating and also sometimes frequently actually a bit confusing.

24
00:01:44,760 --> 00:01:47,680
Speaker 1: Now I blame part of that confusion on my own

25
00:01:47,760 --> 00:01:51,120
Speaker 1: fascination with stuff like Star Wars, which some folks call

26
00:01:51,200 --> 00:01:53,960
Speaker 1: science fiction. I think of it as fantasy that happens

27
00:01:53,960 --> 00:01:57,240
Speaker 1: to be set in space, or even Star Trek, which

28
00:01:57,640 --> 00:01:59,960
Speaker 1: is closer to science fiction than Star Wars, but can

29
00:02:00,080 --> 00:02:03,440
Speaker 1: play a bit fast and loose with science and technology.

30
00:02:03,680 --> 00:02:06,200
Speaker 1: And these kind of properties gave me a really cool

31
00:02:07,000 --> 00:02:10,720
Speaker 1: but an accurate feel for how space navigation works. Terry,

32
00:02:10,760 --> 00:02:15,560
Speaker 1: you asked that I cover what references and methods do

33
00:02:15,639 --> 00:02:19,839
Speaker 1: space programs used to actually do space navigation? And that's

34
00:02:19,840 --> 00:02:23,000
Speaker 1: a great question, because all of this really does rely

35
00:02:23,320 --> 00:02:29,200
Speaker 1: on reference or relationships between a vehicle and something else,

36
00:02:29,760 --> 00:02:32,600
Speaker 1: Like it's all relative. You know, we're going to talk

37
00:02:32,639 --> 00:02:35,240
Speaker 1: about that a lot in this episode. And I guess

38
00:02:35,840 --> 00:02:39,200
Speaker 1: on some level this is intuitive, but I had not

39
00:02:39,320 --> 00:02:44,320
Speaker 1: really thought about it in concrete terms before. So, for example,

40
00:02:44,800 --> 00:02:47,840
Speaker 1: here on Earth, if you're giving directions to someone, you

41
00:02:47,880 --> 00:02:50,080
Speaker 1: would tell that person how to get to a place

42
00:02:50,560 --> 00:02:54,120
Speaker 1: relative to where they are right now, Right, I mean,

43
00:02:54,120 --> 00:02:56,920
Speaker 1: the same thing holds true for space vehicles. But we've

44
00:02:56,919 --> 00:03:00,120
Speaker 1: got to remember that everything in space is moved ing

45
00:03:00,720 --> 00:03:05,520
Speaker 1: all the time. So here on Earth, if you need directions,

46
00:03:05,520 --> 00:03:08,080
Speaker 1: you can start from a position in which you know

47
00:03:08,200 --> 00:03:10,960
Speaker 1: you're not moving relative to the Earth. You're standing still.

48
00:03:11,080 --> 00:03:14,440
Speaker 1: On Earth, You're still moving, but that's because the arts moving.

49
00:03:14,680 --> 00:03:18,119
Speaker 1: We're going to get to that. And you know you're

50
00:03:18,160 --> 00:03:21,000
Speaker 1: standing still with reference to the Earth. But in space,

51
00:03:21,120 --> 00:03:24,360
Speaker 1: everything is moving in reference to everything else. Now you

52
00:03:24,360 --> 00:03:28,280
Speaker 1: could be moving at a similar velocity relative to your surroundings.

53
00:03:28,520 --> 00:03:31,800
Speaker 1: So from your perspective, it might seem like you're not

54
00:03:31,840 --> 00:03:35,560
Speaker 1: all really moving together, but trust me, you totes are.

55
00:03:36,400 --> 00:03:39,400
Speaker 1: Now what I'm about to go into it really matters

56
00:03:39,560 --> 00:03:43,040
Speaker 1: when we start thinking about the possibility of traveling beyond

57
00:03:43,040 --> 00:03:46,080
Speaker 1: our solar system to another. But it's it's, you know,

58
00:03:46,160 --> 00:03:48,440
Speaker 1: something that we have to take into consideration, even when

59
00:03:48,440 --> 00:03:52,320
Speaker 1: we're talking about travel within our Solar system. So let's

60
00:03:52,320 --> 00:03:54,760
Speaker 1: start with the easiest stuff first and then work our

61
00:03:54,800 --> 00:03:59,120
Speaker 1: way up. The Earth travels in a nearly circular orbit

62
00:03:59,200 --> 00:04:02,000
Speaker 1: around the Sun, right, I mean, this is not news

63
00:04:02,000 --> 00:04:05,360
Speaker 1: to you. I imagine. So the Earth is moving, it's

64
00:04:05,400 --> 00:04:08,600
Speaker 1: moving in an orbital path around the Sun. The orbit

65
00:04:08,920 --> 00:04:12,240
Speaker 1: moves at a speed that's around sixty thousand miles per

66
00:04:12,280 --> 00:04:16,960
Speaker 1: hour if you prefer, that's about or almost thirty kilometers

67
00:04:17,000 --> 00:04:20,920
Speaker 1: per second. Now, if we're talking about going to space

68
00:04:21,000 --> 00:04:24,000
Speaker 1: to do stuff in low Earth orbit, we're pretty much

69
00:04:24,040 --> 00:04:27,040
Speaker 1: thinking to Earth, right, We're not too worried about everything

70
00:04:27,080 --> 00:04:30,680
Speaker 1: else that's going on. The orbital speed of Earth isn't

71
00:04:30,720 --> 00:04:32,920
Speaker 1: as big a deal in that case, we don't have

72
00:04:32,960 --> 00:04:36,520
Speaker 1: to take that into as much account. But let's say

73
00:04:36,520 --> 00:04:39,480
Speaker 1: that we want to travel to Mars. Go from Earth

74
00:04:39,560 --> 00:04:42,559
Speaker 1: to Mars. Well, Mars is further out from the Sun

75
00:04:42,560 --> 00:04:46,679
Speaker 1: than Earth, right, I mean it goes my very educated mother.

76
00:04:46,960 --> 00:04:51,159
Speaker 1: So Mars comes after Earth. Oh, in case you've not

77
00:04:51,279 --> 00:04:55,080
Speaker 1: actually heard that mnemonic device, this is how I learned it.

78
00:04:55,080 --> 00:05:01,000
Speaker 1: It was my very educated mother just served us nine pickles.

79
00:05:01,440 --> 00:05:07,919
Speaker 1: That stands for Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune,

80
00:05:08,000 --> 00:05:11,680
Speaker 1: and Pluto the planets except well, you know, when I

81
00:05:11,720 --> 00:05:13,839
Speaker 1: was a kid, Pluto was a planet, and then Pluto

82
00:05:13,960 --> 00:05:15,760
Speaker 1: kind of got the boot as far as being a

83
00:05:15,800 --> 00:05:18,680
Speaker 1: planet goes. So I guess now you could say, my

84
00:05:18,880 --> 00:05:24,640
Speaker 1: very educated mother just served us nothing. Thanks mom. Okay. So,

85
00:05:24,960 --> 00:05:28,800
Speaker 1: Mars is further out from the Sun than Earth is,

86
00:05:29,360 --> 00:05:33,359
Speaker 1: and Mars's orbit is obviously a bigger circle around the

87
00:05:33,440 --> 00:05:36,240
Speaker 1: Sun than Earth's orbit is, because you know, Mars is

88
00:05:36,440 --> 00:05:39,599
Speaker 1: further out from the center of our solar system. Mars

89
00:05:39,640 --> 00:05:44,000
Speaker 1: also doesn't have the same orbital velocity as Earth. Earth

90
00:05:44,040 --> 00:05:47,120
Speaker 1: completes one orbit of the Sun every three sixty five

91
00:05:47,200 --> 00:05:49,720
Speaker 1: Earth days, with a little bit of change leftover. That's

92
00:05:49,760 --> 00:05:52,560
Speaker 1: why we have to have leap years, and Mars's orbit

93
00:05:52,720 --> 00:05:56,080
Speaker 1: is just a hair under six hundred eighty seven Earth

94
00:05:56,160 --> 00:06:00,839
Speaker 1: days long. But beyond that, Mars's orbital velocity is closer

95
00:06:00,880 --> 00:06:04,320
Speaker 1: to twenty kilometers per second. Remember Earth's is closer to

96
00:06:04,520 --> 00:06:08,159
Speaker 1: thirty kilometers per second. So Mars is not just moving

97
00:06:08,440 --> 00:06:11,800
Speaker 1: in a greater distance because it's orbit is larger, it's

98
00:06:11,839 --> 00:06:15,040
Speaker 1: moving a little slower compared to Earth, you know, and

99
00:06:15,360 --> 00:06:18,560
Speaker 1: again relative to the Sun. So that means if we

100
00:06:18,640 --> 00:06:21,760
Speaker 1: want to plot a course from Earth to Mars, we

101
00:06:21,800 --> 00:06:25,640
Speaker 1: have to take all that into account, right, because we

102
00:06:25,720 --> 00:06:28,880
Speaker 1: can't travel instantaneously. It takes time for us to get

103
00:06:28,920 --> 00:06:31,760
Speaker 1: from point A to point B. We can't just point

104
00:06:31,760 --> 00:06:34,640
Speaker 1: a rocket at where Mars appears to be to us

105
00:06:35,120 --> 00:06:37,960
Speaker 1: right at that moment and then launch the rocket in

106
00:06:38,000 --> 00:06:41,120
Speaker 1: that direction. You know, look at the sky, find the

107
00:06:41,160 --> 00:06:44,600
Speaker 1: red dot and say aim that away, because you know,

108
00:06:44,760 --> 00:06:47,719
Speaker 1: the positions of Earth and Mars are shifting in their orbits,

109
00:06:47,800 --> 00:06:50,520
Speaker 1: and Mars will not be at that same spot by

110
00:06:50,520 --> 00:06:53,240
Speaker 1: the time the vehicle we launch gets there. Heck, it's

111
00:06:53,279 --> 00:06:55,920
Speaker 1: not even at that spot as we look at it,

112
00:06:56,000 --> 00:06:59,560
Speaker 1: because it takes time for light to travel from Mars

113
00:06:59,600 --> 00:07:02,800
Speaker 1: back to us, So we're really looking at where Mars

114
00:07:03,120 --> 00:07:05,760
Speaker 1: used to be, and we would be shooting a rocket

115
00:07:06,000 --> 00:07:09,720
Speaker 1: at where Mars used to be a really long time ago. Uh.

116
00:07:09,760 --> 00:07:13,400
Speaker 1: The vehicle it would take months to travel there, so

117
00:07:13,520 --> 00:07:15,760
Speaker 1: by the time it would get to that position in space,

118
00:07:16,280 --> 00:07:18,880
Speaker 1: Mars wouldn't be there anymore. By the way, all this

119
00:07:19,000 --> 00:07:21,680
Speaker 1: orbital stuff is why when we talk about sending a

120
00:07:21,840 --> 00:07:25,800
Speaker 1: crew of human astronauts to Mars, we talk about missions

121
00:07:25,840 --> 00:07:28,720
Speaker 1: that typically are on the order of a couple of

122
00:07:28,800 --> 00:07:32,720
Speaker 1: years in length. The trip from Earth to Mars could

123
00:07:32,760 --> 00:07:35,880
Speaker 1: take around eight months, and that's if we time it

124
00:07:35,960 --> 00:07:40,440
Speaker 1: so that the launch vehicle UH shoots the spacecraft up

125
00:07:40,480 --> 00:07:43,400
Speaker 1: and has the spacecraft travel the least amount of distance

126
00:07:44,040 --> 00:07:47,320
Speaker 1: needed in order to go from Earth to Mars. That

127
00:07:47,360 --> 00:07:49,880
Speaker 1: means you're timing it right. You're aiming at where Mars

128
00:07:50,000 --> 00:07:52,000
Speaker 1: is going to be, and you want to time it

129
00:07:52,480 --> 00:07:55,320
Speaker 1: so that Earth and Mars are at one of the

130
00:07:55,360 --> 00:07:59,760
Speaker 1: closest points in their respective orbits to one another. You

131
00:08:00,000 --> 00:08:02,360
Speaker 1: out of time it just right. And because of the

132
00:08:02,360 --> 00:08:04,960
Speaker 1: difference in orbital velocities and the fact that mars Is

133
00:08:05,040 --> 00:08:08,320
Speaker 1: year is significantly longer than Earth's year, that means that

134
00:08:08,360 --> 00:08:11,840
Speaker 1: by the time you would arrive on Mars, Earth and

135
00:08:11,880 --> 00:08:14,880
Speaker 1: Mars would no longer be super close together anymore. Right

136
00:08:15,000 --> 00:08:18,360
Speaker 1: Like they're they're constantly in motion, so now they're moving

137
00:08:18,400 --> 00:08:21,520
Speaker 1: apart from each other. That means for you to get

138
00:08:21,560 --> 00:08:24,400
Speaker 1: back to Earth, you would need way more fuel for

139
00:08:24,440 --> 00:08:27,520
Speaker 1: your return trip than you did for your trip out

140
00:08:27,560 --> 00:08:31,120
Speaker 1: to Mars. Potentially, so the most fuel efficient thing to

141
00:08:31,160 --> 00:08:34,720
Speaker 1: do is to hunker down on Mars and do all

142
00:08:34,760 --> 00:08:37,880
Speaker 1: your science e stuff and you wait for the planets

143
00:08:37,920 --> 00:08:40,920
Speaker 1: to reach a point in their orbits where again you

144
00:08:40,960 --> 00:08:43,320
Speaker 1: will be traveling the least amount of distance you can

145
00:08:43,360 --> 00:08:46,480
Speaker 1: get away with. And all told, that means a mission

146
00:08:46,520 --> 00:08:49,800
Speaker 1: needs to last around two years to get all that done.

147
00:08:49,960 --> 00:08:52,960
Speaker 1: Plus you know, theoretically you could even spend some of

148
00:08:52,960 --> 00:08:55,480
Speaker 1: that time on Mars making rocket fuel, so you wouldn't

149
00:08:55,520 --> 00:08:57,680
Speaker 1: necessarily have to carry all of it with you on

150
00:08:57,760 --> 00:09:00,960
Speaker 1: the way there. Anyway, that's just a simple example of

151
00:09:01,000 --> 00:09:05,839
Speaker 1: how motion in space matters. But we're just getting started, right,

152
00:09:05,880 --> 00:09:08,960
Speaker 1: So I've touched on stuff like low Earth orbit and

153
00:09:09,080 --> 00:09:13,320
Speaker 1: interplanetary travel within a solar system. But it's not just

154
00:09:13,480 --> 00:09:17,080
Speaker 1: that the planets are moving around the Sun. Our entire

155
00:09:17,360 --> 00:09:21,760
Speaker 1: Solar system is hurtling through space. We are part of

156
00:09:21,760 --> 00:09:24,200
Speaker 1: the Milky Way Galaxy, and at the center of the

157
00:09:24,240 --> 00:09:27,880
Speaker 1: Milky Way Galaxy there is a super massive black hole

158
00:09:28,520 --> 00:09:31,880
Speaker 1: that's kind of the you know, it's like the Sun

159
00:09:32,000 --> 00:09:34,760
Speaker 1: is in our Solar system, except there's a supermassive black

160
00:09:34,760 --> 00:09:38,920
Speaker 1: hole in the middle of a galaxy billions of solar systems.

161
00:09:38,960 --> 00:09:43,000
Speaker 1: Scientists estimate that our galaxy has somewhere between a hundred

162
00:09:43,040 --> 00:09:48,000
Speaker 1: to four hundred billion stars in it. So think about that.

163
00:09:48,080 --> 00:09:51,079
Speaker 1: I can't. I tried, but that's just a number that's

164
00:09:51,120 --> 00:09:53,600
Speaker 1: just way too big for me to even get a

165
00:09:53,679 --> 00:09:57,880
Speaker 1: rudimentary grasp on it. Anyway, our solar system is traveling

166
00:09:57,920 --> 00:10:00,600
Speaker 1: in its orbit in the galaxy at a speed of

167
00:10:00,640 --> 00:10:05,480
Speaker 1: around four thousand miles per hour or two kilometers per second.

168
00:10:06,000 --> 00:10:09,439
Speaker 1: Then we have to consider that our galaxy is also

169
00:10:09,480 --> 00:10:13,079
Speaker 1: in motion. We've got other neighboring galaxies in our neighborhood

170
00:10:13,160 --> 00:10:16,120
Speaker 1: is just part of a super cluster of galaxies, and

171
00:10:16,200 --> 00:10:20,080
Speaker 1: that in itself is part of an even bigger super cluster.

172
00:10:20,640 --> 00:10:23,400
Speaker 1: And we're all hurtling through space at around a thousand

173
00:10:23,480 --> 00:10:27,760
Speaker 1: kilometers per second. Where are we going? Well, I mean,

174
00:10:27,800 --> 00:10:30,080
Speaker 1: I want to say, get in loser, we're going shopping,

175
00:10:30,280 --> 00:10:35,080
Speaker 1: but we're not. We're headed to the Great Attractor. And

176
00:10:35,120 --> 00:10:38,760
Speaker 1: to my surprise, that isn't Oscar Isaac. It's a gravitational

177
00:10:38,840 --> 00:10:44,320
Speaker 1: point in the Lania Kia super cluster. Uh. And um,

178
00:10:44,400 --> 00:10:48,079
Speaker 1: you know the Great Attractor is also moving towards another mass,

179
00:10:48,160 --> 00:10:53,480
Speaker 1: the Shapley super Cluster. I guess there's always a bigger fish.

180
00:10:53,559 --> 00:10:56,040
Speaker 1: And you know, we could keep going down this rabbit hole.

181
00:10:56,080 --> 00:10:57,720
Speaker 1: But what I really wanted to point out is that

182
00:10:57,720 --> 00:11:00,920
Speaker 1: we're talking about a lot of body ease in motion here,

183
00:11:00,960 --> 00:11:03,840
Speaker 1: and that makes navigation more tricky, right, I mean, this

184
00:11:03,920 --> 00:11:06,360
Speaker 1: is kind of like saying that you stop to ask

185
00:11:06,400 --> 00:11:09,800
Speaker 1: for directions, but the town you stop in is actually

186
00:11:09,840 --> 00:11:12,240
Speaker 1: moving on the map, and the place you're going to

187
00:11:12,400 --> 00:11:15,600
Speaker 1: is also moving on the map. Maybe it's moving away

188
00:11:15,760 --> 00:11:18,960
Speaker 1: from the town you are in, which is still in motion.

189
00:11:19,200 --> 00:11:21,160
Speaker 1: So the route you are going to take to get

190
00:11:21,160 --> 00:11:24,439
Speaker 1: there is changing by the minute. It gets complicated, so

191
00:11:24,640 --> 00:11:28,040
Speaker 1: you have to take, uh, you know, into account a

192
00:11:28,080 --> 00:11:30,679
Speaker 1: lot of things. You have to take reference points in

193
00:11:30,760 --> 00:11:33,360
Speaker 1: order to make it all makes sense. And of course

194
00:11:33,400 --> 00:11:36,480
Speaker 1: that's like talking about a map that's two dimensional. Obviously

195
00:11:36,480 --> 00:11:40,120
Speaker 1: in space you're talking about three dimensional. You're not limited

196
00:11:40,400 --> 00:11:44,720
Speaker 1: by a two dimensional plane. You're moving in three dimensional space. This,

197
00:11:44,880 --> 00:11:47,880
Speaker 1: by the way, is all before we even consider stuff

198
00:11:47,920 --> 00:11:53,680
Speaker 1: like relativity, which makes things even more weird. Einstein's theories

199
00:11:53,720 --> 00:11:57,360
Speaker 1: of relativity really show how our universe behaves in ways

200
00:11:57,400 --> 00:12:02,000
Speaker 1: that we don't often get to observe of directly. So

201
00:12:02,280 --> 00:12:05,440
Speaker 1: we don't have a lot of direct perspective on these things.

202
00:12:05,720 --> 00:12:09,559
Speaker 1: But let's use an example to explain some of relativity,

203
00:12:09,640 --> 00:12:13,000
Speaker 1: and we'll start with special relativity. That's the I would

204
00:12:13,040 --> 00:12:16,480
Speaker 1: argue the easier of the two to get a grasp on. Alright,

205
00:12:16,520 --> 00:12:19,880
Speaker 1: so we've got two people and we're gonna name them

206
00:12:19,920 --> 00:12:25,000
Speaker 1: Alice and Bob. Alice has superpowers, and Alice can travel

207
00:12:25,120 --> 00:12:28,360
Speaker 1: through space without a space suit and can move at

208
00:12:28,440 --> 00:12:31,480
Speaker 1: near the speed of light. So she flies through space

209
00:12:31,920 --> 00:12:34,320
Speaker 1: close to the speed of light, and she goes and

210
00:12:34,360 --> 00:12:37,360
Speaker 1: flies off on an adventure at top speed. When she

211
00:12:37,400 --> 00:12:40,280
Speaker 1: comes back and she meets up with her best friend Bob,

212
00:12:40,760 --> 00:12:44,360
Speaker 1: the two notice something unusual. So to Alice, it'll seem

213
00:12:44,400 --> 00:12:49,320
Speaker 1: like Bob aged faster than normal, as if more time

214
00:12:49,440 --> 00:12:53,280
Speaker 1: had passed for Bob than it did for Alice. To Bob,

215
00:12:53,640 --> 00:12:56,960
Speaker 1: it will seem like Alice has aged less than normal,

216
00:12:57,440 --> 00:13:00,400
Speaker 1: like not as much time passed for her, like like

217
00:13:00,400 --> 00:13:04,120
Speaker 1: like less time pass less than it should have. And

218
00:13:04,160 --> 00:13:07,959
Speaker 1: the reason for this is that the faster your speed

219
00:13:08,200 --> 00:13:11,600
Speaker 1: is relative to some other reference point. This is why

220
00:13:11,640 --> 00:13:14,920
Speaker 1: we talk about relativity. It is relative to some other

221
00:13:14,960 --> 00:13:19,040
Speaker 1: reference point, the slower time will pass for you relative

222
00:13:19,080 --> 00:13:22,839
Speaker 1: to that reference point. So again, like Bob is our

223
00:13:23,000 --> 00:13:28,400
Speaker 1: our reference point for Alice. So it appears like, you know,

224
00:13:29,720 --> 00:13:32,960
Speaker 1: Alice hasn't aged as much because time appeared to pass

225
00:13:32,960 --> 00:13:36,720
Speaker 1: slower for Alice than it did to Bob. Now to Alice,

226
00:13:37,320 --> 00:13:40,040
Speaker 1: time will have seemed to pass as normal for our

227
00:13:40,080 --> 00:13:42,640
Speaker 1: own frame of reference. So in other words, it wouldn't

228
00:13:42,720 --> 00:13:45,600
Speaker 1: feel to her as if time had slowed down. She

229
00:13:46,120 --> 00:13:48,320
Speaker 1: would feel like time was passing, just as it would

230
00:13:48,360 --> 00:13:51,800
Speaker 1: if she were standing perfectly still on Earth. A second

231
00:13:51,880 --> 00:13:54,280
Speaker 1: would feel like a second to her. And in fact,

232
00:13:54,280 --> 00:13:57,000
Speaker 1: if Alice were wearing a watch with a second hand,

233
00:13:57,679 --> 00:14:00,840
Speaker 1: it would seem to be clicking one second at a time,

234
00:14:01,080 --> 00:14:04,720
Speaker 1: just perfectly. Now, if Bob could somehow observe that watch

235
00:14:05,000 --> 00:14:07,320
Speaker 1: while Alice is traveling at near the speed of light,

236
00:14:07,920 --> 00:14:12,120
Speaker 1: Bob would see that the second hand is moving really slowly.

237
00:14:12,600 --> 00:14:15,800
Speaker 1: It would be taking way longer than a second for

238
00:14:15,880 --> 00:14:20,120
Speaker 1: it to take each tick. In fact, the faster you go,

239
00:14:20,360 --> 00:14:22,160
Speaker 1: the slower it gets. And if you got to the

240
00:14:22,200 --> 00:14:24,880
Speaker 1: point where you could travel at the speed of light,

241
00:14:25,560 --> 00:14:28,920
Speaker 1: it would stop like the second hand wouldn't move anymore.

242
00:14:29,000 --> 00:14:31,600
Speaker 1: For Bob, he wouldn't see the second If somehow Alice

243
00:14:31,600 --> 00:14:34,000
Speaker 1: could move faster than the speed of light, which is

244
00:14:34,520 --> 00:14:37,360
Speaker 1: as Einstein would put it impossible, it would look as

245
00:14:37,400 --> 00:14:39,840
Speaker 1: though the second hand was going backwards. She would be

246
00:14:39,880 --> 00:14:43,560
Speaker 1: traveling back in time. Now that's physically impossible. So I

247
00:14:43,600 --> 00:14:45,000
Speaker 1: just thought I would throw head in there as an

248
00:14:45,000 --> 00:14:47,880
Speaker 1: interesting you know, side note. But again to Alice, it

249
00:14:47,880 --> 00:14:50,800
Speaker 1: would seem like time was passing as normal. And likewise,

250
00:14:51,120 --> 00:14:53,520
Speaker 1: let's say Bob's wearing a watch. He has a second hand.

251
00:14:53,640 --> 00:14:56,880
Speaker 1: To Bob, time is passing just as normal. A second

252
00:14:56,920 --> 00:14:59,640
Speaker 1: takes a second, he can watch the little second hand

253
00:14:59,680 --> 00:15:02,800
Speaker 1: click on buy on this on his watch. Now, let's

254
00:15:02,800 --> 00:15:05,640
Speaker 1: say that Alice is able to see Bob's watch. While

255
00:15:05,720 --> 00:15:09,040
Speaker 1: Alice is traveling at near light speed, it would look

256
00:15:09,040 --> 00:15:11,440
Speaker 1: to her as if the second hand was going way

257
00:15:11,520 --> 00:15:15,040
Speaker 1: too fast, like it was just spinning around the watch face.

258
00:15:15,440 --> 00:15:18,480
Speaker 1: And again, Bob and Alice would each feel the passage

259
00:15:18,480 --> 00:15:21,240
Speaker 1: of time as if it were just normal. It's only

260
00:15:21,480 --> 00:15:23,920
Speaker 1: when they compare it to a point of reference, when

261
00:15:23,920 --> 00:15:28,200
Speaker 1: they are relative to something else, that they see that

262
00:15:28,320 --> 00:15:32,280
Speaker 1: there is any type of difference. Now, for most of

263
00:15:32,280 --> 00:15:35,760
Speaker 1: our experiences on Earth, we don't notice this effect, and

264
00:15:35,800 --> 00:15:39,280
Speaker 1: that's partly because we're usually traveling at a similar velocity

265
00:15:39,360 --> 00:15:42,400
Speaker 1: relative to one another. We're all on this planet. Most

266
00:15:42,440 --> 00:15:45,440
Speaker 1: of us aren't going super duper fast. However, there are

267
00:15:45,560 --> 00:15:49,560
Speaker 1: cases where we can measure a difference. It wouldn't be

268
00:15:49,600 --> 00:15:53,640
Speaker 1: observable like to our normal senses, but with very sensitive

269
00:15:54,680 --> 00:15:57,720
Speaker 1: you know, metrics, we could see that there was a

270
00:15:57,760 --> 00:16:01,000
Speaker 1: difference there. It's settled because we are not able to

271
00:16:01,040 --> 00:16:03,920
Speaker 1: go anywhere close to the speed of light, at least

272
00:16:03,920 --> 00:16:07,200
Speaker 1: not yet. So for example, we have the case of

273
00:16:07,240 --> 00:16:11,080
Speaker 1: Mark and Scott Kelly. These are twin brothers who are

274
00:16:11,080 --> 00:16:14,880
Speaker 1: both astronauts. Now, both of the Kelly's have spent time

275
00:16:14,960 --> 00:16:19,720
Speaker 1: in orbit. Mark Kelly was born first, he's the older

276
00:16:19,760 --> 00:16:23,040
Speaker 1: of the two twins, and he's logged fifty four days

277
00:16:23,040 --> 00:16:27,760
Speaker 1: in space. Pretty respectable, right, I mean extremely respectable, Mr Kelly.

278
00:16:27,800 --> 00:16:32,560
Speaker 1: I don't mean to, you know, dismiss that incredible achievement.

279
00:16:32,920 --> 00:16:37,080
Speaker 1: But Scott Kelly has spent five hundred twenty days in orbit,

280
00:16:37,120 --> 00:16:40,760
Speaker 1: almost ten times as much time in orbit, and a

281
00:16:40,800 --> 00:16:44,160
Speaker 1: lot of that was aboard the International Space Station, which

282
00:16:44,240 --> 00:16:46,520
Speaker 1: orbits the Earth at the speed of around twenty eight

283
00:16:46,520 --> 00:16:50,480
Speaker 1: thousand kilometers per hour or seventeen thousand, five hundred miles

284
00:16:50,520 --> 00:16:54,120
Speaker 1: per hour. So for a significant amount of time, Scott

285
00:16:54,160 --> 00:16:58,320
Speaker 1: was traveling much faster relative to his brother Mark, who

286
00:16:58,360 --> 00:17:01,960
Speaker 1: was back here on Earth. And since traveling faster means

287
00:17:02,000 --> 00:17:05,720
Speaker 1: that time passes more slowly relative to an outside observer,

288
00:17:06,440 --> 00:17:09,920
Speaker 1: it means that the gap between Mark and Scott actually

289
00:17:09,960 --> 00:17:14,880
Speaker 1: got bigger. Mark aged faster here on Earth than Scott

290
00:17:14,960 --> 00:17:18,159
Speaker 1: did out in space because of that speed of travel.

291
00:17:18,520 --> 00:17:20,959
Speaker 1: Mark once said that he used to be six minutes

292
00:17:21,040 --> 00:17:23,760
Speaker 1: older than his brother, but now, thanks to all that

293
00:17:23,880 --> 00:17:27,040
Speaker 1: space travel that Scott did at high speeds, Mark is

294
00:17:27,240 --> 00:17:32,640
Speaker 1: six minutes five milliseconds older. And that's a funny thing

295
00:17:32,680 --> 00:17:35,680
Speaker 1: to say. Uh And sure you could argue, well, that's

296
00:17:35,680 --> 00:17:38,520
Speaker 1: not really significant to our normal frame of reference. I mean,

297
00:17:38,560 --> 00:17:41,680
Speaker 1: what's five milliseconds, But it does show that we actually

298
00:17:41,720 --> 00:17:44,119
Speaker 1: have to keep this in mind when it comes to

299
00:17:44,240 --> 00:17:48,760
Speaker 1: space travel. It does matter. Now when we come back,

300
00:17:49,600 --> 00:17:52,720
Speaker 1: we're gonna tackle a little bit more of a relativity.

301
00:17:52,920 --> 00:18:05,200
Speaker 1: But first let's take a relatively quick break. Okay, we're back,

302
00:18:05,240 --> 00:18:08,199
Speaker 1: and we are not done with relativity yet. The speed

303
00:18:08,200 --> 00:18:12,000
Speaker 1: and time thing is all part of special relativity. But

304
00:18:12,160 --> 00:18:16,240
Speaker 1: Einstein was a real you know Einstein, and he also

305
00:18:16,320 --> 00:18:21,399
Speaker 1: published his theory on general relativity. This includes an explanation

306
00:18:21,440 --> 00:18:24,320
Speaker 1: that if you were to have two clocks and one

307
00:18:24,359 --> 00:18:27,679
Speaker 1: of them is closer to a gravitational mass than the

308
00:18:27,720 --> 00:18:29,840
Speaker 1: other one, the other one is much further out from

309
00:18:29,880 --> 00:18:33,760
Speaker 1: that gravitational mass. The one that's closer to the gravitational

310
00:18:33,760 --> 00:18:37,680
Speaker 1: mass will take more slowly than the one that's further out.

311
00:18:38,520 --> 00:18:41,440
Speaker 1: This is separate from the whole you know, speed thing.

312
00:18:41,560 --> 00:18:45,040
Speaker 1: So in other words, gravity also affects the rate at

313
00:18:45,080 --> 00:18:48,720
Speaker 1: which time passes. It passes more slowly when you're closer

314
00:18:48,760 --> 00:18:53,720
Speaker 1: to a big center of gravity. And this becomes really

315
00:18:53,760 --> 00:18:57,119
Speaker 1: important for navigation just here on Earth, not even just

316
00:18:57,240 --> 00:19:01,200
Speaker 1: space navigation, but navigation here. And you might wonder why

317
00:19:01,240 --> 00:19:04,439
Speaker 1: that is. Well, a lot of us depend upon GPS

318
00:19:04,520 --> 00:19:07,600
Speaker 1: apps or devices, right like we pull that up whenever

319
00:19:07,640 --> 00:19:11,720
Speaker 1: we're going someplace new, and these devices they work by

320
00:19:11,720 --> 00:19:15,800
Speaker 1: relying on signals that are coming from GPS satellites. It

321
00:19:15,840 --> 00:19:17,920
Speaker 1: gets a few of these different signals and then it's

322
00:19:17,960 --> 00:19:22,000
Speaker 1: able to pinpoint the location where on the surface of

323
00:19:22,000 --> 00:19:25,280
Speaker 1: the Earth we happen to be at that given time. Well,

324
00:19:25,320 --> 00:19:28,720
Speaker 1: those satellites are really far away from us. They are

325
00:19:28,760 --> 00:19:32,199
Speaker 1: beyond low Earth orbit, so they're beyond where the International

326
00:19:32,200 --> 00:19:36,040
Speaker 1: Space Station is, for example. They're out in medium Earth

327
00:19:36,119 --> 00:19:40,480
Speaker 1: orbit somewhere around twenty two KOs out from the Earth,

328
00:19:40,560 --> 00:19:46,560
Speaker 1: or around twelve fifty miles. So these satellites are much

329
00:19:46,840 --> 00:19:50,800
Speaker 1: further out from the Earth's gravitational mass than say your

330
00:19:50,880 --> 00:19:54,040
Speaker 1: watch or come on, we'll be real here your smartphone.

331
00:19:54,400 --> 00:19:58,359
Speaker 1: So because of that, the clocks on the GPS satellites

332
00:19:58,440 --> 00:20:04,840
Speaker 1: tick slightly fat stir. Then the clocks here on Earth tick. Remember,

333
00:20:04,880 --> 00:20:08,560
Speaker 1: the closer you are to a gravitational mass, the slower

334
00:20:08,600 --> 00:20:13,439
Speaker 1: time will pass for that particular frame of reference compared

335
00:20:13,480 --> 00:20:15,280
Speaker 1: to a different frame of reference. I always have to

336
00:20:15,320 --> 00:20:20,280
Speaker 1: throw that part in because again, in the moment it passes,

337
00:20:20,359 --> 00:20:22,879
Speaker 1: the way time passes, like the way our experience of

338
00:20:22,920 --> 00:20:26,400
Speaker 1: time is remains the same, not to our own frame

339
00:20:26,440 --> 00:20:30,439
Speaker 1: of reference. Now, the GPS satellites are also traveling really

340
00:20:30,640 --> 00:20:33,679
Speaker 1: fast relative to us, so that actually means that we

341
00:20:33,680 --> 00:20:36,240
Speaker 1: have to take a bit off the top right, because

342
00:20:36,640 --> 00:20:40,800
Speaker 1: we know that the faster you travel, the slower time

343
00:20:41,640 --> 00:20:45,160
Speaker 1: uh affects you relative to someone who's not traveling at

344
00:20:45,200 --> 00:20:48,960
Speaker 1: that speed. So the effects of general relativity mean that

345
00:20:49,000 --> 00:20:51,960
Speaker 1: a clock on a GPS satellite has on average around

346
00:20:51,960 --> 00:20:55,040
Speaker 1: forty five micro seconds more than an Earth clock at

347
00:20:55,080 --> 00:20:58,520
Speaker 1: the end of a day, a full day. But again,

348
00:20:58,600 --> 00:21:02,520
Speaker 1: because these satellites are link faster relative to us, the

349
00:21:02,600 --> 00:21:07,000
Speaker 1: clocks also have a negative seven micro seconds two factor,

350
00:21:07,040 --> 00:21:10,000
Speaker 1: and compared to our clocks, due to special relativity, so

351
00:21:10,040 --> 00:21:12,520
Speaker 1: we have to combine those two together forty five and

352
00:21:12,600 --> 00:21:16,600
Speaker 1: negative seven. That gives us thirty eight micro seconds that

353
00:21:16,720 --> 00:21:22,119
Speaker 1: are extra on the GPS clocks. So if if we

354
00:21:22,119 --> 00:21:25,160
Speaker 1: were to stop it right at midnight for both clocks,

355
00:21:25,359 --> 00:21:28,080
Speaker 1: you know here on Earth and at the GPS satellite,

356
00:21:28,280 --> 00:21:31,840
Speaker 1: we would see midnight on our clock and midnight plus

357
00:21:31,880 --> 00:21:35,679
Speaker 1: thirty eight million micro seconds, not milliseconds micro seconds on

358
00:21:35,720 --> 00:21:39,520
Speaker 1: the GPS side. Now, because our navigation depends upon taking

359
00:21:39,560 --> 00:21:42,960
Speaker 1: signals from satellites and essentially measuring how long it took

360
00:21:43,520 --> 00:21:46,040
Speaker 1: for that signal to go from the satellite to us,

361
00:21:46,400 --> 00:21:50,040
Speaker 1: in order for us to calculate where we are on Earth,

362
00:21:50,680 --> 00:21:53,879
Speaker 1: we actually have to account for that difference between our

363
00:21:53,880 --> 00:21:58,560
Speaker 1: clocks and the satellite satellites clocks, or else we start

364
00:21:58,600 --> 00:22:01,639
Speaker 1: to get some drift, and that means that over time,

365
00:22:01,960 --> 00:22:04,600
Speaker 1: and and we're actually talking about years here, but it

366
00:22:04,640 --> 00:22:08,800
Speaker 1: does happen, our navigation systems would become less accurate, which

367
00:22:08,800 --> 00:22:11,800
Speaker 1: would eventually get to a point where our GPS device

368
00:22:12,280 --> 00:22:15,040
Speaker 1: wouldn't even really show us where we are because it

369
00:22:15,080 --> 00:22:20,400
Speaker 1: would be miscalculating based upon the the differences in the

370
00:22:20,520 --> 00:22:24,080
Speaker 1: clocks on the GPS satellites versus the clock on our

371
00:22:24,119 --> 00:22:27,560
Speaker 1: phone or that our phone is connected to, and instead

372
00:22:27,560 --> 00:22:30,720
Speaker 1: it would show you where it thinks you are, but

373
00:22:30,880 --> 00:22:33,640
Speaker 1: there would be a growing gap between where it thinks

374
00:22:33,680 --> 00:22:36,160
Speaker 1: you are and where you really are. Based upon this

375
00:22:36,200 --> 00:22:39,080
Speaker 1: gap in time. It would take like seven years for

376
00:22:39,160 --> 00:22:41,520
Speaker 1: that to get to a point where we might even

377
00:22:41,560 --> 00:22:45,240
Speaker 1: notice it, and we do correct for it. So essentially

378
00:22:45,280 --> 00:22:48,080
Speaker 1: what happens is we shave thirty eight micro seconds off

379
00:22:48,200 --> 00:22:53,239
Speaker 1: the clocks every midnight that the that the clock's hit.

380
00:22:53,320 --> 00:22:56,640
Speaker 1: So when the clocks hit midnight on the GPS satellites,

381
00:22:56,680 --> 00:22:59,600
Speaker 1: they kind of hold for thirty eight microseconds, which puts

382
00:22:59,600 --> 00:23:02,000
Speaker 1: them I can sync with the clocks here on Earth.

383
00:23:02,400 --> 00:23:03,920
Speaker 1: And then we have to do it every single day

384
00:23:04,000 --> 00:23:08,080
Speaker 1: because every single day we get the effects of relativity.

385
00:23:08,640 --> 00:23:11,400
Speaker 1: All right, well, that's something we have to take into

386
00:23:11,480 --> 00:23:16,919
Speaker 1: account with navigation, Like these are things that we don't again,

387
00:23:16,960 --> 00:23:20,320
Speaker 1: we don't necessarily have to think about here on Earth. Typically,

388
00:23:21,160 --> 00:23:24,399
Speaker 1: most of us don't come into situations where special and

389
00:23:24,480 --> 00:23:28,800
Speaker 1: general relativity have a noticeable impact on our day to

390
00:23:28,880 --> 00:23:34,119
Speaker 1: day experience. UM. One really important element in space navigation

391
00:23:34,720 --> 00:23:37,960
Speaker 1: is something called the deep Space Network, which is not

392
00:23:38,040 --> 00:23:41,280
Speaker 1: a really cool science fiction channel, uh, no, it's it's

393
00:23:41,320 --> 00:23:44,920
Speaker 1: actually a bunch of antennas, and it's it's more than that.

394
00:23:45,040 --> 00:23:47,959
Speaker 1: But that's a big part of it. If we go

395
00:23:48,040 --> 00:23:51,120
Speaker 1: back to the nineteen fifties, we had the space race

396
00:23:51,280 --> 00:23:54,800
Speaker 1: ramping up. In nineteen fifty seven, the then Soviet Union

397
00:23:54,880 --> 00:23:58,840
Speaker 1: launched spot Nick into orbit. The US was already working

398
00:23:58,840 --> 00:24:02,200
Speaker 1: on its own satellite, and of course there were reasons

399
00:24:02,240 --> 00:24:05,800
Speaker 1: for this beyond the scientific push. Scientific push was a

400
00:24:05,840 --> 00:24:08,479
Speaker 1: big part of it, but there were other political reasons.

401
00:24:08,520 --> 00:24:11,200
Speaker 1: For one thing, Demonstrating that you could put a payload

402
00:24:11,200 --> 00:24:15,359
Speaker 1: into space also sent the message of hey, comrade, we

403
00:24:15,400 --> 00:24:17,800
Speaker 1: can build rockets big enough to reach you, even though

404
00:24:17,800 --> 00:24:19,679
Speaker 1: we're on the other side of the world, and you know,

405
00:24:19,800 --> 00:24:24,280
Speaker 1: nuclear weapons are a thing, so you know, this wasn't

406
00:24:24,640 --> 00:24:29,840
Speaker 1: just you know, a science thing. But that's another tangent

407
00:24:29,960 --> 00:24:32,320
Speaker 1: that I won't go down any further. But on the

408
00:24:32,440 --> 00:24:35,280
Speaker 1: U s side, one of the things that the Jet

409
00:24:35,280 --> 00:24:39,679
Speaker 1: Propulsion Laboratory or JPL undertook was a job from the

410
00:24:39,760 --> 00:24:43,400
Speaker 1: United States Army, which effectively you know, ran the jp

411
00:24:43,640 --> 00:24:47,639
Speaker 1: L to establish radio tracking stations in certain parts of

412
00:24:47,640 --> 00:24:53,160
Speaker 1: the world, including places like Singapore, Nigeria, and California. So upon,

413
00:24:53,280 --> 00:24:57,120
Speaker 1: launching the first successful US satellite, which was called Explorer one.

414
00:24:57,960 --> 00:25:01,240
Speaker 1: These ground stations would receive data from the satellite to

415
00:25:01,240 --> 00:25:05,280
Speaker 1: be able to track it as it passed over overhead.

416
00:25:05,640 --> 00:25:08,760
Speaker 1: This was essentially telemetry data, and you might wonder what

417
00:25:08,800 --> 00:25:12,399
Speaker 1: does that mean. Well, telemetry is essentially the process of

418
00:25:12,520 --> 00:25:15,680
Speaker 1: using some sort of device to measure something. It could

419
00:25:15,680 --> 00:25:18,960
Speaker 1: be temperature, it could be pressure, it could be speed

420
00:25:19,160 --> 00:25:23,680
Speaker 1: or velocity, and then it transmits that information to a

421
00:25:23,760 --> 00:25:27,439
Speaker 1: distant receiver. Now, in this case, the telemetry was mostly

422
00:25:27,480 --> 00:25:31,680
Speaker 1: about the Explorer one's orientation and velocity as it went

423
00:25:31,720 --> 00:25:35,879
Speaker 1: through its orbit. Engineers at mission control could take that

424
00:25:36,040 --> 00:25:40,560
Speaker 1: data and plot out the Explorer one's orbital path. In October,

425
00:25:41,800 --> 00:25:45,320
Speaker 1: the US government established NASA, and this was really to

426
00:25:45,359 --> 00:25:49,840
Speaker 1: consolidate the space efforts from various independent groups, mostly in

427
00:25:49,920 --> 00:25:52,960
Speaker 1: the military, like the Army, Navy, and Air Force all

428
00:25:53,040 --> 00:25:58,800
Speaker 1: had independent space exploration UH initiatives, so this was to

429
00:25:58,880 --> 00:26:03,120
Speaker 1: kind of bring them all under one civilian umbrella and

430
00:26:03,240 --> 00:26:07,679
Speaker 1: combine all those resources to be more effective. So this

431
00:26:07,760 --> 00:26:12,720
Speaker 1: included the Jet Propulsion Laboratory that had previously been run

432
00:26:12,800 --> 00:26:16,040
Speaker 1: by the U. S Army that became part of NASA.

433
00:26:16,080 --> 00:26:19,159
Speaker 1: In December of nineteen and NASA would assign to the

434
00:26:19,240 --> 00:26:22,879
Speaker 1: jp L the responsibility of planning out planetary and lunar

435
00:26:22,960 --> 00:26:27,800
Speaker 1: exploration missions that would use unscrewed spacecraft, that is, spacecraft

436
00:26:27,840 --> 00:26:30,760
Speaker 1: that did not have human beings abort robotic spacecraft if

437
00:26:30,760 --> 00:26:34,119
Speaker 1: you prefer. Now. That would necessitate a network system of

438
00:26:34,200 --> 00:26:37,919
Speaker 1: receivers here on Earth to be able to receive communications

439
00:26:38,000 --> 00:26:41,119
Speaker 1: with and then to send communications too, as well as

440
00:26:41,160 --> 00:26:45,000
Speaker 1: to just keep track of these robotic spacecraft as they

441
00:26:45,040 --> 00:26:48,560
Speaker 1: traveled away from the Earth. You can't just have one

442
00:26:48,840 --> 00:26:52,960
Speaker 1: really big antenna in Houston, because you know, the Earth

443
00:26:53,080 --> 00:26:57,119
Speaker 1: rotates and sometimes Houston would be pointing the wrong way.

444
00:26:57,320 --> 00:27:02,120
Speaker 1: Get together, Houston. So yeah, to establish that these antenna

445
00:27:02,280 --> 00:27:04,880
Speaker 1: around the Earth need to be pointing outward in such

446
00:27:04,920 --> 00:27:09,800
Speaker 1: a way that you have maintained contact with distant spacecraft. Moreover,

447
00:27:10,240 --> 00:27:13,919
Speaker 1: as the spacecraft move further from the Earth, the signal

448
00:27:13,960 --> 00:27:17,120
Speaker 1: strength will decrease. In fact, you know, here on Earth

449
00:27:17,160 --> 00:27:20,880
Speaker 1: we describe radio frequencies as obeying the inverse square law,

450
00:27:20,960 --> 00:27:23,800
Speaker 1: which means that the power of a signal is inversely

451
00:27:23,840 --> 00:27:30,600
Speaker 1: proportional to the distance from a source. Hey, it's Jonathan

452
00:27:30,640 --> 00:27:34,479
Speaker 1: from one day further out from when this episode originally published. Okay,

453
00:27:34,520 --> 00:27:37,119
Speaker 1: so the first time I tried to explain this, I

454
00:27:37,640 --> 00:27:41,000
Speaker 1: just playing god it all wrong. Uh, we published the episode,

455
00:27:41,240 --> 00:27:43,879
Speaker 1: they had an error in it, and this was because

456
00:27:43,880 --> 00:27:48,080
Speaker 1: of a fundamental misunderstanding on my part. But fortunately Charlie

457
00:27:48,160 --> 00:27:50,480
Speaker 1: Tango Bravo on Twitter set me straight and I'm gonna

458
00:27:50,480 --> 00:27:54,000
Speaker 1: try harder to get it right this time. So the

459
00:27:54,040 --> 00:27:56,919
Speaker 1: inverse square law will first imagine that you have a

460
00:27:56,960 --> 00:28:00,520
Speaker 1: source of electro magnetic radiation. And this can be anything

461
00:28:00,640 --> 00:28:06,000
Speaker 1: from you know, a radio antenna to a microwave source

462
00:28:06,040 --> 00:28:09,560
Speaker 1: to light. In fact, let's talk about light because that's

463
00:28:09,560 --> 00:28:11,600
Speaker 1: pretty easy for us to wrap our heads around it

464
00:28:11,600 --> 00:28:14,440
Speaker 1: because we can directly observe it. Right, We've all seen

465
00:28:14,560 --> 00:28:16,720
Speaker 1: that as you move away from a source of light,

466
00:28:17,200 --> 00:28:20,719
Speaker 1: then you get less light to work with, Right, that's intuitive.

467
00:28:21,080 --> 00:28:24,520
Speaker 1: So if you're walking around I don't know, a spooky

468
00:28:24,600 --> 00:28:28,000
Speaker 1: attic and it's lit by a single light bulb hanging

469
00:28:28,040 --> 00:28:31,600
Speaker 1: down from a chain, well you know that as you

470
00:28:31,640 --> 00:28:33,840
Speaker 1: get towards the corners, a ghost is gonna get you.

471
00:28:34,520 --> 00:28:37,720
Speaker 1: I'm kidding. Ghosts don't exist, but you do know that

472
00:28:37,760 --> 00:28:39,640
Speaker 1: as you move further away from the light, bulb, it

473
00:28:39,680 --> 00:28:44,320
Speaker 1: gets darker, Right, That just something we've experienced. Well, we

474
00:28:44,320 --> 00:28:48,280
Speaker 1: can actually describe this phenomena with the inverse square law

475
00:28:48,320 --> 00:28:52,760
Speaker 1: of propagation. We can think of radiation moving out from

476
00:28:52,880 --> 00:28:57,560
Speaker 1: a source as similar to that of an expanding sphere,

477
00:28:58,040 --> 00:29:01,000
Speaker 1: like it's going out in all directions and growing as

478
00:29:01,040 --> 00:29:03,560
Speaker 1: it moves outward. Right, the sphere gets bigger and bigger.

479
00:29:03,960 --> 00:29:09,280
Speaker 1: The center is still stationary in this frame of reference.

480
00:29:09,720 --> 00:29:12,200
Speaker 1: So the further we get out from the center of

481
00:29:12,240 --> 00:29:17,000
Speaker 1: the sphere, the more surface area that electromagnetic radiation is covering. Right,

482
00:29:17,080 --> 00:29:21,280
Speaker 1: the the outside of the sphere is bigger. That means

483
00:29:21,320 --> 00:29:23,360
Speaker 1: that the signal strength is growing weaker. You have the

484
00:29:23,400 --> 00:29:26,880
Speaker 1: same amount of signal to go around, but you're covering

485
00:29:26,960 --> 00:29:28,760
Speaker 1: a larger area, so you can think of it as

486
00:29:28,800 --> 00:29:32,480
Speaker 1: spreading across more space. And we can describe the relationship

487
00:29:32,480 --> 00:29:37,440
Speaker 1: between signal intensity and distance as intensity equals one divided

488
00:29:37,480 --> 00:29:41,800
Speaker 1: by r, that being the distance squared. So if you

489
00:29:42,000 --> 00:29:45,080
Speaker 1: double the distance between you and a source, if you

490
00:29:45,480 --> 00:29:48,520
Speaker 1: make are twice as big, the intensity you observe will

491
00:29:48,600 --> 00:29:51,400
Speaker 1: drop by a factor of four. So if you went

492
00:29:51,400 --> 00:29:54,640
Speaker 1: from one to two, then the intensity would go down

493
00:29:54,680 --> 00:29:56,880
Speaker 1: to a quarter of what it used to be, you've

494
00:29:56,880 --> 00:29:59,200
Speaker 1: reduced it by a factor of four. If you were

495
00:29:59,240 --> 00:30:03,840
Speaker 1: to triple the distance between you and the source, then

496
00:30:04,160 --> 00:30:07,880
Speaker 1: the intensity would reduce by a factor of nine. Three

497
00:30:07,920 --> 00:30:11,400
Speaker 1: squared is nine, and so on and so forth. So

498
00:30:12,120 --> 00:30:15,840
Speaker 1: I described in the previous version that signal does decrease

499
00:30:16,040 --> 00:30:19,040
Speaker 1: as distance increases. That part was right, but the relationship

500
00:30:19,080 --> 00:30:22,120
Speaker 1: I got totally wrong. The important thing to remember is

501
00:30:22,160 --> 00:30:25,080
Speaker 1: that the signal strength drops off as we get further

502
00:30:25,160 --> 00:30:27,760
Speaker 1: away from the source. So for spacecraft that are traveling

503
00:30:27,800 --> 00:30:30,640
Speaker 1: further from Earth, that's a big factor we have to

504
00:30:30,640 --> 00:30:35,160
Speaker 1: take into consideration. All right, let's get back to the

505
00:30:35,160 --> 00:30:39,760
Speaker 1: original episode, and again, thank you to Charlie Tango Bravo

506
00:30:39,920 --> 00:30:42,360
Speaker 1: for setting me on the right path. I appreciate it.

507
00:30:45,800 --> 00:30:47,560
Speaker 1: And we also have to remember that there's a lot

508
00:30:47,560 --> 00:30:50,520
Speaker 1: of stuff that generates radio signals. I mean, there's a

509
00:30:50,520 --> 00:30:53,320
Speaker 1: ton of stuff here on Earth that we create, like

510
00:30:53,640 --> 00:30:57,360
Speaker 1: TV and radio and cell phones and that kind of stuff.

511
00:30:57,560 --> 00:31:00,360
Speaker 1: Those generate radio signals. But they're also a lot of

512
00:31:00,400 --> 00:31:04,360
Speaker 1: things in space that generate radio signals, like pulsars and

513
00:31:04,560 --> 00:31:08,320
Speaker 1: nebula and quasars. So in other words, there's a lot

514
00:31:08,360 --> 00:31:12,000
Speaker 1: of potential noise to deal with when we're looking for

515
00:31:12,080 --> 00:31:16,200
Speaker 1: a radio signal. So again, finding that that signal amid

516
00:31:16,280 --> 00:31:19,560
Speaker 1: all the noise is a big challenge. It doesn't it's

517
00:31:19,560 --> 00:31:23,360
Speaker 1: not just important that our antenna is sensitive. We have

518
00:31:23,440 --> 00:31:26,080
Speaker 1: to have it really directional so that we can make

519
00:31:26,160 --> 00:31:29,520
Speaker 1: certain that we're pointing at the thing we want to

520
00:31:29,520 --> 00:31:35,560
Speaker 1: to listen to. Otherwise we might mistake some errant Earth

521
00:31:35,680 --> 00:31:39,840
Speaker 1: generated signal as being our spacecraft and then we're on

522
00:31:39,880 --> 00:31:43,920
Speaker 1: the wrong track. So to meet these challenges, NASA, through

523
00:31:43,960 --> 00:31:47,680
Speaker 1: the JPL, established the Deep Space Network or d s N.

524
00:31:48,320 --> 00:31:51,760
Speaker 1: The DSN has three facilities that are approximately a hundred

525
00:31:51,800 --> 00:31:56,200
Speaker 1: twenty degrees apart in longitude, so that means they're roughly

526
00:31:56,360 --> 00:32:01,680
Speaker 1: equidistant from each other Longitudinally, you multiply one twenty by three,

527
00:32:01,920 --> 00:32:06,080
Speaker 1: you get three sixty. That's a circle, right. So one

528
00:32:06,120 --> 00:32:09,400
Speaker 1: of the three is in Goldstone, California. That's actually in

529
00:32:09,440 --> 00:32:13,200
Speaker 1: the desert. It's northeast of Los Angeles, it's south of

530
00:32:13,320 --> 00:32:16,360
Speaker 1: Death Valley, and it's pretty far away from stuff that

531
00:32:16,400 --> 00:32:21,200
Speaker 1: generates radio waves. The second is in Madrid, Spain, so

532
00:32:21,200 --> 00:32:24,600
Speaker 1: that's almost smack dab in the middle of Spain. The

533
00:32:24,720 --> 00:32:28,920
Speaker 1: third is in Canberra, Australia, which is on the coast

534
00:32:28,920 --> 00:32:33,560
Speaker 1: in the southeast of Australia, and it's probably covered with

535
00:32:33,720 --> 00:32:39,040
Speaker 1: venomous animals. I mean it's Australia, so it's a safe bet.

536
00:32:39,600 --> 00:32:42,040
Speaker 1: So again, because these sites are a hundred twenty degrees

537
00:32:42,080 --> 00:32:45,280
Speaker 1: apart from each other, we get that three hundred sixty

538
00:32:45,400 --> 00:32:49,440
Speaker 1: degree view if you will, of the space around Earth.

539
00:32:50,000 --> 00:32:52,560
Speaker 1: And what this means is that at any given time,

540
00:32:52,760 --> 00:32:56,160
Speaker 1: at least one of the three DS insights has the

541
00:32:56,160 --> 00:33:00,200
Speaker 1: ability to establish a line of sight communication channel with

542
00:33:00,440 --> 00:33:05,280
Speaker 1: a distant spacecraft. And as the world rotates and one

543
00:33:05,480 --> 00:33:09,720
Speaker 1: of these sites begins to lose contact, the next one

544
00:33:10,120 --> 00:33:13,680
Speaker 1: will pick it right up, so communications can remain online.

545
00:33:13,720 --> 00:33:16,960
Speaker 1: You don't have an interruption. This is a big thing.

546
00:33:17,040 --> 00:33:21,280
Speaker 1: Like you might remember when I was talking about space stations.

547
00:33:21,400 --> 00:33:26,160
Speaker 1: When the most recent as of this recording, anyway, when

548
00:33:26,160 --> 00:33:29,760
Speaker 1: the most recent module joined the International Space Station, it

549
00:33:29,880 --> 00:33:35,200
Speaker 1: was the Naka from the from Russia. When it docked,

550
00:33:35,560 --> 00:33:39,600
Speaker 1: its thrusters misfired. They weren't supposed to fire, but they did,

551
00:33:40,080 --> 00:33:44,320
Speaker 1: and it caused the space station to rotate and move

552
00:33:44,360 --> 00:33:48,400
Speaker 1: into the wrong orientation relative to the Earth. Well, when

553
00:33:48,440 --> 00:33:52,239
Speaker 1: that happened. The space station was not in range of

554
00:33:52,520 --> 00:33:56,160
Speaker 1: Russia's mission control because that was on the wrong side

555
00:33:56,200 --> 00:33:58,040
Speaker 1: of the Earth at the time, and that was a

556
00:33:58,040 --> 00:34:01,880
Speaker 1: problem because Russia was the only entity that had the

557
00:34:01,920 --> 00:34:06,240
Speaker 1: ability to control the thrusters on the Knocka. So that's

558
00:34:06,240 --> 00:34:10,200
Speaker 1: an example of why it's important to have established these

559
00:34:10,239 --> 00:34:15,239
Speaker 1: points where we can have uninterrupted contact. All right, we've

560
00:34:15,280 --> 00:34:18,520
Speaker 1: got more to say about navigation, but before I get

561
00:34:18,560 --> 00:34:29,839
Speaker 1: totally lost, let's take another quick break. So at these

562
00:34:29,880 --> 00:34:35,359
Speaker 1: different sites at Goldstone, California, and Madrid, Spain, Canberra, Australia,

563
00:34:35,960 --> 00:34:41,040
Speaker 1: they have a series of radio telescopes, including one really

564
00:34:41,080 --> 00:34:43,799
Speaker 1: big one at each of these sites, and the deep

565
00:34:43,840 --> 00:34:47,960
Speaker 1: space radio antenna can be extremely impressive. So the Goldstone

566
00:34:48,480 --> 00:34:52,319
Speaker 1: Mars dish, that's the biggest one at gold Stone, California.

567
00:34:52,760 --> 00:34:55,399
Speaker 1: That one was built in nineteen but it was later

568
00:34:55,560 --> 00:35:00,800
Speaker 1: upgraded in night so today it measures seventy eaters across,

569
00:35:00,920 --> 00:35:04,880
Speaker 1: that's about two thirty feet. Now, this dish has a

570
00:35:04,920 --> 00:35:10,239
Speaker 1: surface area of around an acre or square feet or

571
00:35:10,400 --> 00:35:14,400
Speaker 1: three thousand, eight hundred fifty square meters. It weighs nearly

572
00:35:14,520 --> 00:35:20,080
Speaker 1: three thousand tons. It's mounted on massive machinery that can

573
00:35:20,120 --> 00:35:23,160
Speaker 1: tilt and turn the dish so that it can be

574
00:35:23,239 --> 00:35:27,960
Speaker 1: aimed precisely where a spacecraft is overhead and get you know,

575
00:35:28,200 --> 00:35:32,600
Speaker 1: that laser like focus with a communications channel with a

576
00:35:32,600 --> 00:35:36,680
Speaker 1: spacecraft that could be millions or billions of miles from

577
00:35:36,719 --> 00:35:40,200
Speaker 1: the Earth. And the purpose of those big big dishes,

578
00:35:41,120 --> 00:35:44,080
Speaker 1: I mean, it's all about collecting the very weak radio

579
00:35:44,280 --> 00:35:47,560
Speaker 1: energy that's being sent back from the spacecraft. You know,

580
00:35:47,560 --> 00:35:51,839
Speaker 1: because again that distances is intense, like the signals are

581
00:35:52,080 --> 00:35:55,160
Speaker 1: very very weak by the time they get back to Earth,

582
00:35:55,280 --> 00:35:59,520
Speaker 1: especially for super distant spacecraft. So this big dish is

583
00:35:59,520 --> 00:36:03,400
Speaker 1: able to like that energy and then direct it toward

584
00:36:03,440 --> 00:36:07,440
Speaker 1: the antenna itself, so you can think of it this parabola.

585
00:36:07,560 --> 00:36:11,960
Speaker 1: It's all focusing that radio energy to a specific point,

586
00:36:12,000 --> 00:36:16,160
Speaker 1: that point being the end of the actual radio antenna.

587
00:36:16,320 --> 00:36:18,919
Speaker 1: Otherwise the signal would be so weak that it would

588
00:36:18,920 --> 00:36:21,799
Speaker 1: be difficult, if not impossible, to detect that signal through

589
00:36:21,840 --> 00:36:25,360
Speaker 1: all the noise, and engineers have to position and antenna

590
00:36:25,480 --> 00:36:29,319
Speaker 1: precisely to beam radio instructions back to the distant spacecraft.

591
00:36:29,840 --> 00:36:32,840
Speaker 1: If you're off even by a little bit, the message

592
00:36:32,880 --> 00:36:34,960
Speaker 1: is not going to end up going to where you

593
00:36:35,000 --> 00:36:37,719
Speaker 1: need it to. Go, and the further out the spacecraft

594
00:36:37,800 --> 00:36:40,399
Speaker 1: is from Earth, the more critical it becomes to get

595
00:36:40,400 --> 00:36:44,319
Speaker 1: that just right. So all of that is to set

596
00:36:44,400 --> 00:36:48,320
Speaker 1: up the actual talk about navigation itself. We had to

597
00:36:48,360 --> 00:36:52,400
Speaker 1: set all those parameters to talk about the process. Without

598
00:36:52,440 --> 00:36:54,840
Speaker 1: the system like the Deep Space Network in place to

599
00:36:54,880 --> 00:36:58,560
Speaker 1: communicate with spacecraft navigation would be impossible. We would not

600
00:36:58,600 --> 00:37:03,000
Speaker 1: be able to build a spacecraft capable of detecting its

601
00:37:03,040 --> 00:37:07,239
Speaker 1: own orientation and velocity and to make changes on the fly.

602
00:37:07,760 --> 00:37:10,520
Speaker 1: It's not like Star Trek or Star Wars, where you

603
00:37:10,560 --> 00:37:12,760
Speaker 1: just tell an on ship computer to plot a course

604
00:37:12,800 --> 00:37:18,799
Speaker 1: for Javin or whatever. NASA describes space navigation as being

605
00:37:19,080 --> 00:37:23,880
Speaker 1: the domain of three large departments within NASA. There's mission design,

606
00:37:24,520 --> 00:37:29,600
Speaker 1: there's orbit determination, and there's flight path control. These three

607
00:37:29,640 --> 00:37:33,040
Speaker 1: things all inter relate to one another. So first we

608
00:37:33,080 --> 00:37:36,320
Speaker 1: have mission design. Now, this is the part of navigation

609
00:37:36,320 --> 00:37:39,719
Speaker 1: in which mission control has to determine what the intended

610
00:37:40,040 --> 00:37:45,359
Speaker 1: trajectory is for the spacecraft, where is it supposed to go. Now,

611
00:37:45,360 --> 00:37:47,959
Speaker 1: this alone is tricky for all the reasons that I've

612
00:37:47,960 --> 00:37:50,759
Speaker 1: talked about earlier in this episode. You've got to take

613
00:37:50,920 --> 00:37:54,920
Speaker 1: all those different elements into consideration, like relativity. You know,

614
00:37:55,080 --> 00:37:57,560
Speaker 1: what is it that you're hoping to do? What what

615
00:37:57,680 --> 00:38:00,960
Speaker 1: is the purpose of the spacecraft? What are the things

616
00:38:01,000 --> 00:38:03,720
Speaker 1: that are going to affect the spacecraft as it travels

617
00:38:03,760 --> 00:38:06,040
Speaker 1: from Earth to get to where it's supposed to go.

618
00:38:06,520 --> 00:38:09,719
Speaker 1: How do you account for those things? And how do

619
00:38:09,760 --> 00:38:14,239
Speaker 1: you either incorporate stuff so that it, you know, it

620
00:38:14,320 --> 00:38:16,720
Speaker 1: becomes part of your mission, or how do you find

621
00:38:16,760 --> 00:38:21,680
Speaker 1: a way around an obstacle or challenge. Now, keep in mind,

622
00:38:22,480 --> 00:38:25,759
Speaker 1: we learn new stuff the more we send spacecraft up,

623
00:38:26,040 --> 00:38:29,080
Speaker 1: Like we learn more every single time, and some of

624
00:38:29,120 --> 00:38:32,760
Speaker 1: that stuff is important and it affects calculations, like important

625
00:38:32,760 --> 00:38:35,680
Speaker 1: for the sense of navigation, that is, it's always important.

626
00:38:36,600 --> 00:38:39,879
Speaker 1: Someone has to take the things we've learned and then

627
00:38:39,960 --> 00:38:43,799
Speaker 1: build that into software that we use to calculate complex

628
00:38:43,800 --> 00:38:47,440
Speaker 1: equations in order to plot out navigation. So space navigation

629
00:38:47,840 --> 00:38:50,640
Speaker 1: is something that has evolved over time, and as we

630
00:38:50,760 --> 00:38:54,759
Speaker 1: learn more and incorporate what we've learned into the next

631
00:38:54,840 --> 00:38:59,440
Speaker 1: generation of software, it's constantly in a state of change.

632
00:38:59,800 --> 00:39:02,719
Speaker 1: So one thing that engineers have to factor in is

633
00:39:02,760 --> 00:39:06,160
Speaker 1: the fact that a spacecraft is always orbiting. Something I

634
00:39:06,239 --> 00:39:08,760
Speaker 1: kind of indicated this at the top of the show.

635
00:39:09,520 --> 00:39:11,440
Speaker 1: You know, it could orbit the Earth. It could be

636
00:39:11,480 --> 00:39:14,160
Speaker 1: in low Earth orbit and just stay there, but it's

637
00:39:14,200 --> 00:39:18,120
Speaker 1: in orbit. Or you might want it to leave Earth

638
00:39:18,280 --> 00:39:21,960
Speaker 1: orbit and enter into a solar orbit, so now it's

639
00:39:22,040 --> 00:39:26,799
Speaker 1: orbiting the Sun just like Earth or Mars, or you know,

640
00:39:26,840 --> 00:39:28,960
Speaker 1: any of the other planets are. Maybe you want to

641
00:39:29,080 --> 00:39:33,319
Speaker 1: enter into a different planets orbit. Maybe you want it

642
00:39:33,360 --> 00:39:36,080
Speaker 1: to leave the Solar System entirely, in which case it's

643
00:39:36,120 --> 00:39:39,080
Speaker 1: in a galactic orbit. It's orbiting the center of the

644
00:39:39,120 --> 00:39:42,319
Speaker 1: Milky Way, just like our Solar system is. It does

645
00:39:42,400 --> 00:39:44,800
Speaker 1: require an awful lot of velocity in order to escape

646
00:39:44,800 --> 00:39:47,520
Speaker 1: the Solar System. By the way, but we have done it,

647
00:39:47,920 --> 00:39:50,960
Speaker 1: not with you know, humans obviously, but with spacecraft we've

648
00:39:51,000 --> 00:39:56,160
Speaker 1: sent out anyway. Orbits are a huge part of navigation calculations.

649
00:39:56,280 --> 00:40:00,000
Speaker 1: And again you're talking about an origin and a destination,

650
00:40:00,080 --> 00:40:03,560
Speaker 1: and that are from an outside reference both in motion,

651
00:40:04,120 --> 00:40:07,080
Speaker 1: and we have to take into account the effects of

652
00:40:07,080 --> 00:40:10,000
Speaker 1: stuff like relativity with spacecraft. That's going to affect things

653
00:40:10,080 --> 00:40:13,759
Speaker 1: like the clocks on board the spacecraft. That means we

654
00:40:13,760 --> 00:40:16,719
Speaker 1: have to account for those changes due to relativity or

655
00:40:16,760 --> 00:40:20,080
Speaker 1: else we risk losing track of the spacecraft. We might

656
00:40:20,200 --> 00:40:24,160
Speaker 1: point an antenna at where a spacecraft either used to

657
00:40:24,200 --> 00:40:28,120
Speaker 1: be or might be in the future, but isn't right now,

658
00:40:28,320 --> 00:40:32,280
Speaker 1: just because we have these deviations from between our earthbound

659
00:40:32,280 --> 00:40:35,319
Speaker 1: clocks and the ones that are aboard the spacecraft. So

660
00:40:35,719 --> 00:40:39,440
Speaker 1: the software has to plot a trajectory that has to

661
00:40:39,480 --> 00:40:42,600
Speaker 1: take all these different things into consideration, and as you

662
00:40:42,600 --> 00:40:47,040
Speaker 1: can imagine, this means those calculations get pretty darn complicated,

663
00:40:47,080 --> 00:40:51,000
Speaker 1: particularly when you're looking at something you know, really ambitious,

664
00:40:51,480 --> 00:40:53,959
Speaker 1: which sounds a little weird to say, because I still

665
00:40:54,000 --> 00:40:56,680
Speaker 1: think just getting something into low Earth orbit is being

666
00:40:56,760 --> 00:41:00,600
Speaker 1: really ambitious. But you know, there's there is a scale,

667
00:41:00,680 --> 00:41:03,640
Speaker 1: I guess, and as I'm sure we're all aware, software

668
00:41:03,680 --> 00:41:06,440
Speaker 1: does not always come out perfect, right. You've probably used

669
00:41:06,480 --> 00:41:09,719
Speaker 1: software where you've encountered a bug or a glitch, Like

670
00:41:10,160 --> 00:41:13,360
Speaker 1: maybe you're playing a video game and the textures failed

671
00:41:13,360 --> 00:41:17,640
Speaker 1: to load and everything looks weird. Well, that's irritating when

672
00:41:17,640 --> 00:41:20,279
Speaker 1: it's a video game, but when you're talking about like

673
00:41:20,520 --> 00:41:25,279
Speaker 1: interplanetary navigation, a bug or glitch can become an enormous challenge. Now,

674
00:41:25,280 --> 00:41:27,600
Speaker 1: it might not be a show stopper. You might be

675
00:41:27,640 --> 00:41:30,600
Speaker 1: able to work around it, but it likely will require

676
00:41:30,640 --> 00:41:32,239
Speaker 1: a lot of people to work out a solution on

677
00:41:32,280 --> 00:41:34,120
Speaker 1: the fly in order to make a sure that a

678
00:41:34,160 --> 00:41:38,000
Speaker 1: spacecraft's route is in fact the right one to do

679
00:41:38,080 --> 00:41:41,359
Speaker 1: whatever it is you want that spacecraft to do, all right. So,

680
00:41:42,640 --> 00:41:45,120
Speaker 1: once all of that has been taken into account, engineers

681
00:41:45,160 --> 00:41:49,560
Speaker 1: calculate the navigational route for a spacecraft. This planned route

682
00:41:49,880 --> 00:41:53,880
Speaker 1: is the reference trajectory, so this is the route the

683
00:41:53,920 --> 00:41:59,200
Speaker 1: spacecraft should be on. Also, there's a cesall relationship between

684
00:41:59,239 --> 00:42:02,560
Speaker 1: the navigator for a mission and the software developers who

685
00:42:02,560 --> 00:42:05,840
Speaker 1: are making the navigation software. So as navigators find bugs

686
00:42:05,960 --> 00:42:09,600
Speaker 1: or they encounter new situations that necessitate new features in

687
00:42:09,640 --> 00:42:12,960
Speaker 1: the software, they can relay that to the developers, and

688
00:42:13,000 --> 00:42:15,520
Speaker 1: then they take the feedback and they produce new versions

689
00:42:15,520 --> 00:42:19,279
Speaker 1: of the software. I imagine that gets increasingly challenging to do,

690
00:42:19,400 --> 00:42:22,799
Speaker 1: especially to incorporate new features. Any developer can tell you

691
00:42:23,280 --> 00:42:26,600
Speaker 1: that it can be a nightmare to put something new

692
00:42:26,680 --> 00:42:29,040
Speaker 1: into code that you've just gotten to work, because the

693
00:42:29,360 --> 00:42:31,960
Speaker 1: chances are you're going to break something that previously had

694
00:42:32,000 --> 00:42:35,359
Speaker 1: been working. Okay, just imagine that for things that are

695
00:42:35,400 --> 00:42:38,799
Speaker 1: traveling through space and you have to deal with relativity

696
00:42:38,840 --> 00:42:43,360
Speaker 1: and stuff. Now, even when you do that correctly, which

697
00:42:43,440 --> 00:42:46,439
Speaker 1: you know obviously requires a lot of work. It does

698
00:42:46,480 --> 00:42:48,920
Speaker 1: not mean that a spacecraft is just going to magically

699
00:42:49,040 --> 00:42:53,879
Speaker 1: stick to that reference trajectory. All sorts of things can

700
00:42:53,920 --> 00:42:57,879
Speaker 1: cause the spacecraft to deviate from the planned route. In

701
00:42:57,920 --> 00:43:00,879
Speaker 1: some cases, it might be on purpose us such as

702
00:43:01,280 --> 00:43:03,640
Speaker 1: you know, you might have to do a maneuver to

703
00:43:03,719 --> 00:43:07,640
Speaker 1: avoid a potential collision. Or it might be that your

704
00:43:07,680 --> 00:43:11,279
Speaker 1: pathway is taking you close to a planet and you're

705
00:43:11,320 --> 00:43:15,680
Speaker 1: planning on using a gravity assist two make the spacecraft

706
00:43:15,680 --> 00:43:19,560
Speaker 1: continuance journey. But in other cases, something might pop up

707
00:43:19,840 --> 00:43:25,080
Speaker 1: that wasn't anticipated, Like it happens very quickly. Maybe the

708
00:43:25,080 --> 00:43:29,080
Speaker 1: spacecraft passes some large asteroids and the gravitational attraction between

709
00:43:29,120 --> 00:43:32,040
Speaker 1: the spacecraft and the asteroids pulls the craft out of

710
00:43:32,080 --> 00:43:35,080
Speaker 1: its trajectory a bit. Or maybe it turns out that

711
00:43:35,160 --> 00:43:37,400
Speaker 1: the software had a bug in it or a blind

712
00:43:37,440 --> 00:43:40,480
Speaker 1: spot that failed to account for something, and the spacecraft

713
00:43:40,560 --> 00:43:43,399
Speaker 1: is veering off course a bit as a result. I mean,

714
00:43:43,480 --> 00:43:50,000
Speaker 1: even solar pressure, that is pressure from light itself hitting

715
00:43:50,000 --> 00:43:53,959
Speaker 1: the spacecraft can be enough to push the spacecraft off

716
00:43:54,040 --> 00:43:59,399
Speaker 1: its reference trajectory. This is where orbit determination comes in. Now,

717
00:43:59,440 --> 00:44:03,080
Speaker 1: as the name implies, this part of space navigation is

718
00:44:03,120 --> 00:44:07,640
Speaker 1: just keeping track of a spacecraft's actual position. We know

719
00:44:07,920 --> 00:44:11,279
Speaker 1: where we want the spacecraft to go, but this is

720
00:44:11,400 --> 00:44:16,200
Speaker 1: about us figuring out where the spacecraft actually is. And

721
00:44:17,080 --> 00:44:20,960
Speaker 1: that is another kittle of fish. NASA breaks down orbit

722
00:44:21,000 --> 00:44:27,120
Speaker 1: determination into three sub processes or subgroups, So there's orbit reconstruction.

723
00:44:27,520 --> 00:44:31,200
Speaker 1: This is asking the question where has this spacecraft been?

724
00:44:31,719 --> 00:44:35,200
Speaker 1: This is all about determining the past route, the past

725
00:44:35,239 --> 00:44:40,360
Speaker 1: locations for the spacecraft to understand its actual trajectory versus

726
00:44:40,440 --> 00:44:44,719
Speaker 1: the reference trajectory. Then you've got orbit determination. This is

727
00:44:44,760 --> 00:44:47,759
Speaker 1: like asking where the heck is the ding dang thing

728
00:44:47,880 --> 00:44:51,600
Speaker 1: right now? Then you've got orbit prediction. This is like

729
00:44:51,640 --> 00:44:54,400
Speaker 1: asking where the heck is this thing going to next?

730
00:44:55,080 --> 00:44:56,440
Speaker 1: And and at this point I kind of wish I

731
00:44:56,480 --> 00:44:59,960
Speaker 1: hadn't burned the mean Girls reference about gettin loser we're

732
00:45:00,000 --> 00:45:04,080
Speaker 1: going shopping, But I did that one already. Anyway, A

733
00:45:04,120 --> 00:45:08,440
Speaker 1: bit of consideration reveals that all three of these things

734
00:45:08,480 --> 00:45:13,680
Speaker 1: are important. See, we're not controlling these spacecraft in real time.

735
00:45:13,920 --> 00:45:17,080
Speaker 1: You know, you don't have someone sitting looking at a monitor.

736
00:45:17,239 --> 00:45:20,040
Speaker 1: They get a first person view of a spacecraft's viewscreen.

737
00:45:20,360 --> 00:45:22,920
Speaker 1: They've got a joystick and they're just making it fly

738
00:45:23,080 --> 00:45:25,840
Speaker 1: all over the place. That's not how this works. And

739
00:45:25,960 --> 00:45:28,319
Speaker 1: it does take time for a signal to pass from

740
00:45:28,400 --> 00:45:31,160
Speaker 1: one point in space to another. The fastest that this

741
00:45:31,320 --> 00:45:34,200
Speaker 1: can happen at is the speed of light, and you know,

742
00:45:34,480 --> 00:45:38,200
Speaker 1: light is wicked fast. It's in fact the fastest stuff

743
00:45:38,320 --> 00:45:43,400
Speaker 1: there is. But light can't traverse great distances in an instant.

744
00:45:43,760 --> 00:45:46,279
Speaker 1: I mean it takes about eight minutes for light to

745
00:45:46,320 --> 00:45:49,560
Speaker 1: go from the Sun to hit us here on Earth.

746
00:45:49,960 --> 00:45:53,560
Speaker 1: So as as spacecraft gets further from the Earth, the

747
00:45:53,640 --> 00:45:58,120
Speaker 1: information that we get back from those spacecraft becomes more dated. Right,

748
00:45:58,239 --> 00:46:01,439
Speaker 1: it's more about where the space was at the time

749
00:46:01,480 --> 00:46:05,399
Speaker 1: it transmitted, but minutes have passed between then and when

750
00:46:05,440 --> 00:46:08,319
Speaker 1: we're able to actually look at the data. So as

751
00:46:08,400 --> 00:46:11,960
Speaker 1: engineers get the latest telemetric data, they're actually looking at

752
00:46:12,239 --> 00:46:15,600
Speaker 1: stuff that's several minutes old. So we're not observing the

753
00:46:15,680 --> 00:46:19,880
Speaker 1: spacecraft directly. We're getting information back from the spacecraft, and

754
00:46:20,000 --> 00:46:22,640
Speaker 1: then we have to draw conclusions about what's going on

755
00:46:23,320 --> 00:46:26,520
Speaker 1: based upon the information we have. So if the data

756
00:46:26,600 --> 00:46:29,879
Speaker 1: indicates that perhaps a ship is drifting away from its

757
00:46:29,960 --> 00:46:32,919
Speaker 1: reference trajectory, we need to be able to look back

758
00:46:33,360 --> 00:46:36,239
Speaker 1: and see what the data has said about that. When

759
00:46:36,320 --> 00:46:39,759
Speaker 1: did that deviation begin? How long has it been going on?

760
00:46:40,280 --> 00:46:43,239
Speaker 1: Where is the spacecraft now? Based on the information we have,

761
00:46:43,760 --> 00:46:47,680
Speaker 1: keeping in mind we're projecting forward a few minutes because

762
00:46:47,880 --> 00:46:52,320
Speaker 1: the information we have is older. And then, knowing that

763
00:46:52,680 --> 00:46:56,919
Speaker 1: our ability to pinpoint a spacecraft position with precision decreases

764
00:46:57,400 --> 00:47:00,120
Speaker 1: the further out the spacecraft gets from us, we have

765
00:47:00,200 --> 00:47:02,879
Speaker 1: to start building in margins of error, and then, based

766
00:47:02,960 --> 00:47:06,560
Speaker 1: upon all we know, where is it heading to now

767
00:47:06,760 --> 00:47:09,560
Speaker 1: and how can we get it back on track? If

768
00:47:09,640 --> 00:47:12,800
Speaker 1: we were not able to determine this, we wouldn't know

769
00:47:13,360 --> 00:47:16,040
Speaker 1: where to point the antenna with the d s N

770
00:47:16,560 --> 00:47:20,239
Speaker 1: in order to track the spacecraft. We would lose the spacecraft,

771
00:47:20,840 --> 00:47:23,440
Speaker 1: let alone being able to figure out how to correct

772
00:47:23,680 --> 00:47:27,360
Speaker 1: its its course. And you know space is big, so

773
00:47:27,560 --> 00:47:30,480
Speaker 1: if you lose something like a spacecraft, good luck finding

774
00:47:30,520 --> 00:47:34,920
Speaker 1: it again, because you'd you'd just be scanning regions of

775
00:47:35,040 --> 00:47:38,520
Speaker 1: space looking for the faintest of radio signals to try

776
00:47:38,600 --> 00:47:41,480
Speaker 1: and get back on track. It's not something you want

777
00:47:41,560 --> 00:47:44,399
Speaker 1: to have happen. Well, we've got some more to talk

778
00:47:44,480 --> 00:47:48,480
Speaker 1: about with navigation before we wrap all this up, So

779
00:47:48,640 --> 00:47:59,279
Speaker 1: let's take one last break. Okay, I was talking about

780
00:47:59,440 --> 00:48:02,719
Speaker 1: orbit re construction before the break, and we also need

781
00:48:02,800 --> 00:48:05,320
Speaker 1: to reconstruct the path of the spacecraft in order to

782
00:48:05,400 --> 00:48:08,759
Speaker 1: make sure that the scientific data that we're collecting with

783
00:48:08,840 --> 00:48:11,640
Speaker 1: this satellite. I mean, presumably we've sent it up there

784
00:48:11,680 --> 00:48:16,799
Speaker 1: to do something, well, some of it is determined by

785
00:48:17,400 --> 00:48:20,080
Speaker 1: the trajectory path, Like we have to know the trajectory

786
00:48:20,200 --> 00:48:23,000
Speaker 1: path in order for the data to make sense. There's

787
00:48:23,080 --> 00:48:26,080
Speaker 1: imaging data. There's like a type of imaging called synthetic

788
00:48:26,239 --> 00:48:29,719
Speaker 1: aperture radar imaging, and that requires that we have a

789
00:48:29,880 --> 00:48:34,960
Speaker 1: precise knowledge of the spacecraft's trajectory so that the software

790
00:48:35,040 --> 00:48:39,280
Speaker 1: we use to process that information can create a meaningful

791
00:48:39,440 --> 00:48:43,160
Speaker 1: image from that data. Like it's not like it's sending

792
00:48:43,200 --> 00:48:45,719
Speaker 1: a JPEG to us. It's sending us data that we

793
00:48:46,080 --> 00:48:50,840
Speaker 1: then use to create an image with sophisticated software we

794
00:48:50,880 --> 00:48:53,839
Speaker 1: have running on computers here on Earth. If we don't

795
00:48:53,920 --> 00:48:57,320
Speaker 1: know the trajectory precisely, then it's almost like we're building

796
00:48:57,360 --> 00:48:59,719
Speaker 1: a picture, but we're doing it from the wrong perspective,

797
00:48:59,840 --> 00:49:02,080
Speaker 1: and it would leave us with an image that's nothing

798
00:49:02,200 --> 00:49:05,520
Speaker 1: like what we were actually trying to capture with the satellite.

799
00:49:05,920 --> 00:49:11,480
Speaker 1: So it is imperative that we know the actual trajectory

800
00:49:11,600 --> 00:49:15,800
Speaker 1: of a spacecraft. Then we have flight path control, the

801
00:49:15,960 --> 00:49:19,200
Speaker 1: third of the three departments I was talking about. Again,

802
00:49:19,280 --> 00:49:21,520
Speaker 1: you could probably guess what this is about based on

803
00:49:21,600 --> 00:49:24,560
Speaker 1: the name. We can summarize this by saying that this

804
00:49:24,960 --> 00:49:28,120
Speaker 1: is the part of space navigation where we figure out

805
00:49:28,239 --> 00:49:31,440
Speaker 1: how to get the spacecraft from where it actually is

806
00:49:32,120 --> 00:49:34,880
Speaker 1: to where it is supposed to be. How can you

807
00:49:34,960 --> 00:49:39,160
Speaker 1: get the spacecraft to return to the reference trajectory that

808
00:49:39,520 --> 00:49:42,239
Speaker 1: you had set in the beginning. And here's another good

809
00:49:42,320 --> 00:49:46,200
Speaker 1: reason to put so much emphasis on orbit determination, because

810
00:49:46,239 --> 00:49:49,000
Speaker 1: spacecraft have a very limited set of options that they

811
00:49:49,080 --> 00:49:51,760
Speaker 1: can use in order to return to the correct course.

812
00:49:52,320 --> 00:49:57,160
Speaker 1: An interplanetary spacecraft, like a satellite that's designed to fly by, say,

813
00:49:57,640 --> 00:50:01,200
Speaker 1: one of Saturn's moons, it needs to on course once

814
00:50:01,239 --> 00:50:04,200
Speaker 1: it separates from the launch vehicle. You know, once it

815
00:50:04,360 --> 00:50:07,680
Speaker 1: separates from the rocket that pushes it up into space.

816
00:50:08,440 --> 00:50:11,200
Speaker 1: So this is kind of like a bowler releasing a

817
00:50:11,320 --> 00:50:14,120
Speaker 1: bowling ball. You know, once that ball leaves your hand,

818
00:50:14,920 --> 00:50:18,040
Speaker 1: there ain't no amount of you waving or leaning that's

819
00:50:18,080 --> 00:50:21,200
Speaker 1: really going to affect the ball's trajectory. You've set it

820
00:50:21,280 --> 00:50:25,000
Speaker 1: on a path and you can't really influence it anymore. Well,

821
00:50:25,600 --> 00:50:30,600
Speaker 1: we can still influence spacecraft a little bit, but that

822
00:50:31,040 --> 00:50:35,719
Speaker 1: initial release from the launch vehicle is the primary thing

823
00:50:35,800 --> 00:50:39,920
Speaker 1: of putting it on its proper trajectory. So spacecraft can

824
00:50:39,960 --> 00:50:42,800
Speaker 1: have like thrusters or rocket engines that can fire to

825
00:50:42,880 --> 00:50:45,680
Speaker 1: adjust their course a little bit. But obviously there's actually

826
00:50:45,680 --> 00:50:49,040
Speaker 1: a limit to how much fuel any spacecraft is able

827
00:50:49,080 --> 00:50:52,280
Speaker 1: to carry. And there ain't no gas stations in space,

828
00:50:52,760 --> 00:50:55,640
Speaker 1: at least not in our neighborhood. So fuel is a

829
00:50:55,760 --> 00:51:00,120
Speaker 1: limited resource. And that's you know, an understatement, but it's

830
00:51:00,120 --> 00:51:04,080
Speaker 1: important to remember. So let's say a spacecraft has gone

831
00:51:04,200 --> 00:51:07,000
Speaker 1: a little bit off course. The flight path control group

832
00:51:07,080 --> 00:51:10,320
Speaker 1: then has to figure out how far off course is it.

833
00:51:10,719 --> 00:51:13,120
Speaker 1: Then they have to figure out the commands needed to

834
00:51:13,320 --> 00:51:16,560
Speaker 1: have the spacecraft returned to its reference trajectory. So they

835
00:51:16,600 --> 00:51:20,160
Speaker 1: take the data from the orbit determination group that tells them, okay,

836
00:51:20,360 --> 00:51:22,959
Speaker 1: how far off course are we. Then they start running

837
00:51:22,960 --> 00:51:25,040
Speaker 1: the calculations how much is it going to take for

838
00:51:25,160 --> 00:51:27,600
Speaker 1: us to get back to where we need to be? Uh?

839
00:51:27,920 --> 00:51:30,560
Speaker 1: This means figuring out the proper change in velocity for

840
00:51:30,719 --> 00:51:33,120
Speaker 1: the spacecraft and if it's been a while since you've

841
00:51:33,160 --> 00:51:36,080
Speaker 1: had physics, I want to remind you that velocity isn't

842
00:51:36,280 --> 00:51:39,600
Speaker 1: just speed. A lot of folks use the word velocity

843
00:51:39,800 --> 00:51:42,800
Speaker 1: to stand in for speed, but that's just part of it.

844
00:51:42,960 --> 00:51:46,400
Speaker 1: Velocity is a vector. So in addition to speed, we

845
00:51:46,520 --> 00:51:49,360
Speaker 1: have to have a direction. So a change in velocity

846
00:51:49,840 --> 00:51:52,080
Speaker 1: is an acceleration. It can be a change in speed

847
00:51:52,600 --> 00:51:56,800
Speaker 1: or direction or both. The flight path control team figures

848
00:51:56,800 --> 00:52:00,680
Speaker 1: out what change in velocity is necessary, so they indicate

849
00:52:00,760 --> 00:52:04,000
Speaker 1: the magnitude and the direction that is required in order

850
00:52:04,080 --> 00:52:07,680
Speaker 1: for the spacecraft to return to its reference trajectory. Now,

851
00:52:07,760 --> 00:52:10,880
Speaker 1: the flight path control team doesn't initiate the actual maneuver.

852
00:52:11,400 --> 00:52:14,040
Speaker 1: They just designed the maneuver, or at least they design

853
00:52:14,120 --> 00:52:17,200
Speaker 1: the parameters of the maneuver. It needs to have this

854
00:52:17,440 --> 00:52:21,200
Speaker 1: change in direction and this magnitude. They send that information

855
00:52:21,400 --> 00:52:25,200
Speaker 1: to another team, a spacecraft engineering team, and it's this

856
00:52:25,320 --> 00:52:28,680
Speaker 1: group that then use stuff like attitude control systems and

857
00:52:28,840 --> 00:52:32,560
Speaker 1: thrusters or rocket engines to produce the change in velocity

858
00:52:32,680 --> 00:52:35,520
Speaker 1: that was indicated by the flat flight path control teams. So,

859
00:52:35,520 --> 00:52:38,200
Speaker 1: in other words, they're the ones to take this data

860
00:52:38,719 --> 00:52:41,360
Speaker 1: that says, here's what we need to have happen, and

861
00:52:41,400 --> 00:52:44,040
Speaker 1: they're the ones to actually activate the systems to make

862
00:52:44,080 --> 00:52:47,760
Speaker 1: it happen. NASA refers to small flight path control maneuvers

863
00:52:48,120 --> 00:52:52,200
Speaker 1: as trajectory correction maneuvers, which makes sense. You're trying to

864
00:52:52,239 --> 00:52:55,879
Speaker 1: correct it move it back to its reference trajectory. Now,

865
00:52:56,239 --> 00:52:59,200
Speaker 1: as we conduct more space exploration, we learned things that

866
00:52:59,280 --> 00:53:02,520
Speaker 1: are really able for future missions. So, for example, if

867
00:53:02,600 --> 00:53:04,640
Speaker 1: we were to plot out a fly by satellite to

868
00:53:04,680 --> 00:53:08,839
Speaker 1: go to Saturn, we would incorporate some gravity assist fly by.

869
00:53:08,880 --> 00:53:12,000
Speaker 1: It's most likely this is where you leverage the gravitational

870
00:53:12,120 --> 00:53:16,880
Speaker 1: pull of celestial body like another planet, to assist the

871
00:53:17,000 --> 00:53:18,920
Speaker 1: spacecraft on its way by giving it kind of a

872
00:53:19,000 --> 00:53:23,279
Speaker 1: slight pull slash push towards its destination and a change

873
00:53:23,280 --> 00:53:26,560
Speaker 1: in velocity. It's a boost, kind of like someone giving

874
00:53:26,600 --> 00:53:28,799
Speaker 1: you a little push when you're swinging on a swing set,

875
00:53:28,960 --> 00:53:32,280
Speaker 1: although it can also you know, change your direction somewhat.

876
00:53:32,560 --> 00:53:35,160
Speaker 1: And as we understand these things and we're able to

877
00:53:35,239 --> 00:53:38,920
Speaker 1: build it in, we can have that planned from the beginning,

878
00:53:39,120 --> 00:53:42,960
Speaker 1: so we can build them into an actual mission. When

879
00:53:43,000 --> 00:53:45,600
Speaker 1: we've got a good handle on those things, NASA can

880
00:53:45,680 --> 00:53:48,319
Speaker 1: call any sort of velocity maneuvers that we know we're

881
00:53:48,360 --> 00:53:52,480
Speaker 1: going to have to do deterministic. That is, we have

882
00:53:52,560 --> 00:53:56,320
Speaker 1: already determined the velocity maneuvers that we will need to

883
00:53:56,840 --> 00:54:01,239
Speaker 1: conduct in order to maintain our reference true jectory given

884
00:54:01,280 --> 00:54:04,200
Speaker 1: the route that we're following. We know that they are

885
00:54:04,280 --> 00:54:07,440
Speaker 1: going to be maneuvers necessary to stay on course, and

886
00:54:07,520 --> 00:54:10,440
Speaker 1: we have a good idea of what they are and

887
00:54:10,600 --> 00:54:13,120
Speaker 1: when we will need to execute them. But there are

888
00:54:13,160 --> 00:54:17,279
Speaker 1: other types of maneuvers that will call stochastic. These are

889
00:54:17,360 --> 00:54:20,360
Speaker 1: maneuvers that we know we're gonna need to make, but

890
00:54:20,520 --> 00:54:23,320
Speaker 1: we don't necessarily know. More like, we don't know what

891
00:54:23,520 --> 00:54:26,719
Speaker 1: the magnitude of those changes might have to be. We

892
00:54:26,920 --> 00:54:30,440
Speaker 1: might not fully understand the effect of those maneuvers ahead

893
00:54:30,480 --> 00:54:35,040
Speaker 1: of time, because we're going through uncharted ground, if you

894
00:54:35,320 --> 00:54:38,279
Speaker 1: if you will. We're not following something that we've already done,

895
00:54:38,360 --> 00:54:41,200
Speaker 1: where we already kind of have a grasp on what

896
00:54:41,400 --> 00:54:44,640
Speaker 1: we need to do. And then, of course occasionally sometimes

897
00:54:44,680 --> 00:54:46,840
Speaker 1: we have to do these maneuvers when something we didn't

898
00:54:46,840 --> 00:54:50,040
Speaker 1: anticipate at all happens and we have to design and

899
00:54:50,200 --> 00:54:54,120
Speaker 1: conduct a maneuver kind of on demand. Also, I should

900
00:54:54,160 --> 00:54:58,080
Speaker 1: mention that attitude control I mentioned it earlier Attitude control

901
00:54:58,360 --> 00:55:01,320
Speaker 1: is not about whether or not you're spacecraft is sassin you.

902
00:55:02,160 --> 00:55:05,360
Speaker 1: It has nothing to do with sass. Attitude refers to

903
00:55:05,520 --> 00:55:09,480
Speaker 1: the angular orientation of a spacecraft given some other point

904
00:55:09,480 --> 00:55:12,160
Speaker 1: of reference. Again, you have to have a point of reference,

905
00:55:12,760 --> 00:55:16,280
Speaker 1: because I mean, if you think about it, outer space

906
00:55:16,320 --> 00:55:19,400
Speaker 1: doesn't really have an up or down. You have to

907
00:55:19,440 --> 00:55:23,360
Speaker 1: have a point of reference and compare your position to

908
00:55:23,600 --> 00:55:26,400
Speaker 1: that point of reference, or you have to, you know,

909
00:55:26,560 --> 00:55:28,279
Speaker 1: use your point of reference to in order to make

910
00:55:28,520 --> 00:55:32,440
Speaker 1: a determination about something's positions. So you've gotta have a

911
00:55:32,520 --> 00:55:34,279
Speaker 1: point of reference to start from in order for you

912
00:55:34,360 --> 00:55:37,200
Speaker 1: to say something like that durned things upside down or

913
00:55:37,280 --> 00:55:41,480
Speaker 1: backwards or you know, or whatever. Also, there are interesting

914
00:55:41,560 --> 00:55:45,719
Speaker 1: ways to change the angular orientation of a spacecraft, and

915
00:55:45,880 --> 00:55:49,760
Speaker 1: some of them do not involve thrusters or rocket engines. Instead,

916
00:55:49,840 --> 00:55:54,040
Speaker 1: they might involve something like momentum wheels, as in, you know,

917
00:55:54,280 --> 00:55:58,719
Speaker 1: physical wheels a rotor spun by a motor. Now I

918
00:55:58,719 --> 00:56:02,280
Speaker 1: would get into this further, but that requires a pretty

919
00:56:02,400 --> 00:56:05,480
Speaker 1: long discussion about things like the conservation of momentum and

920
00:56:05,719 --> 00:56:08,360
Speaker 1: equal and opposite reactions and stuff like that, and we

921
00:56:08,640 --> 00:56:11,200
Speaker 1: don't really have time for that this episode. Is already

922
00:56:11,239 --> 00:56:13,840
Speaker 1: going super long, and I don't want Tardy to hate

923
00:56:13,880 --> 00:56:19,240
Speaker 1: me more than she does already. So she doesn't hate me, folks,

924
00:56:19,400 --> 00:56:21,040
Speaker 1: She's super nice to me. I just want to make

925
00:56:21,080 --> 00:56:23,840
Speaker 1: that clear. That was more of a jest. But the

926
00:56:24,239 --> 00:56:27,160
Speaker 1: short version of all this is that using stuff like

927
00:56:27,280 --> 00:56:30,759
Speaker 1: momentum wheels can make it possible to change the attitude

928
00:56:30,880 --> 00:56:34,120
Speaker 1: of a spacecraft without having to use thrusters. And as

929
00:56:34,200 --> 00:56:38,640
Speaker 1: we've previously established, fuel is a precious resource. So that's

930
00:56:38,680 --> 00:56:41,400
Speaker 1: a good thing to know, right to build in systems

931
00:56:41,680 --> 00:56:45,600
Speaker 1: that allow us to make changes to a spacecraft's orientation,

932
00:56:45,719 --> 00:56:49,600
Speaker 1: for example, without having to burn fuel to do it. Still,

933
00:56:50,000 --> 00:56:53,240
Speaker 1: it's not uncommon that the spacecraft engineering team will actually

934
00:56:53,320 --> 00:56:56,280
Speaker 1: have to initiate a rocket engine or a thruster ignition

935
00:56:56,680 --> 00:56:59,840
Speaker 1: to provide the thrust needed to get back onto the

936
00:57:00,040 --> 00:57:03,640
Speaker 1: reference trajectory. Uh, the timing on these maneuvers has to

937
00:57:03,719 --> 00:57:07,520
Speaker 1: be incredibly precise, both because you don't want to waste

938
00:57:07,600 --> 00:57:09,680
Speaker 1: even a drop of fuel if you can help it,

939
00:57:10,239 --> 00:57:13,359
Speaker 1: and also that if you fire a thruster for too

940
00:57:13,440 --> 00:57:15,520
Speaker 1: long or not long enough, then you're not going to

941
00:57:15,600 --> 00:57:19,320
Speaker 1: return to your reference trajectory. So imagine, for a moment

942
00:57:19,360 --> 00:57:23,200
Speaker 1: that you're sitting in mission control and you are relying

943
00:57:23,320 --> 00:57:27,640
Speaker 1: on complex calculations from data sent back to you from

944
00:57:27,800 --> 00:57:32,200
Speaker 1: space just to tell you where that something is right,

945
00:57:32,680 --> 00:57:35,880
Speaker 1: and that's something the spacecraft is so far away that

946
00:57:36,000 --> 00:57:38,560
Speaker 1: there is no means for us to observe it directly.

947
00:57:38,800 --> 00:57:41,600
Speaker 1: All you have is the data coming back to go by,

948
00:57:42,400 --> 00:57:44,360
Speaker 1: and then you have to come up with the command

949
00:57:44,760 --> 00:57:48,560
Speaker 1: to send via radio back up to this object to

950
00:57:48,680 --> 00:57:50,880
Speaker 1: get it back onto the course it's supposed to be

951
00:57:50,960 --> 00:57:54,320
Speaker 1: following the data you have indicates that the thing you

952
00:57:54,400 --> 00:57:57,840
Speaker 1: know was in this one particular position several minutes ago,

953
00:57:58,160 --> 00:57:59,880
Speaker 1: So you have to figure out where it is now

954
00:58:00,520 --> 00:58:04,640
Speaker 1: based on calculations with the data that you have, knowing

955
00:58:05,000 --> 00:58:09,240
Speaker 1: that that is at best maybe a precise approximation, but

956
00:58:09,320 --> 00:58:12,320
Speaker 1: still an approximation. Then you figure out the command you

957
00:58:12,400 --> 00:58:15,120
Speaker 1: need to send to where the spacecraft is going to

958
00:58:15,280 --> 00:58:18,680
Speaker 1: be in order to get it to take the action

959
00:58:18,960 --> 00:58:22,080
Speaker 1: to get it to where it should be. This whole

960
00:58:22,160 --> 00:58:25,439
Speaker 1: thing is mind boggling to me. It kind of makes

961
00:58:25,480 --> 00:58:29,680
Speaker 1: me think of like submarine navigators who use precise charts

962
00:58:30,200 --> 00:58:33,440
Speaker 1: and timing like a stop watch in order to plot

963
00:58:33,600 --> 00:58:37,560
Speaker 1: underwater courses. Because they're not able to just look outside.

964
00:58:37,640 --> 00:58:40,840
Speaker 1: I mean, at the depths that submarines can travel. You

965
00:58:40,920 --> 00:58:44,560
Speaker 1: can't have windows because they would collapse in from the pressure.

966
00:58:45,040 --> 00:58:50,520
Speaker 1: So you're in a tin can underwater, and you're using

967
00:58:51,200 --> 00:58:54,880
Speaker 1: very precise maps and a stopwatch and knowledge of how

968
00:58:55,000 --> 00:58:58,600
Speaker 1: fast you're moving in order to make calculations to determine

969
00:58:58,640 --> 00:59:01,080
Speaker 1: whether or not you're going to bump into something. It's

970
00:59:01,880 --> 00:59:05,800
Speaker 1: hard for me to even contemplate. Well, once the spacecraft

971
00:59:05,840 --> 00:59:09,480
Speaker 1: engineering team has done their thing, that whole process has

972
00:59:09,520 --> 00:59:12,160
Speaker 1: to repeat itself. The orbit determination team has to figure

973
00:59:12,160 --> 00:59:14,880
Speaker 1: out if the spacecraft is in fact back on its

974
00:59:14,960 --> 00:59:19,080
Speaker 1: reference trajectory, or if they'll need to conduct another maneuver,

975
00:59:19,600 --> 00:59:22,000
Speaker 1: and so on and so forth. And because there's so

976
00:59:22,120 --> 00:59:25,919
Speaker 1: many little things that can pull a spacecraft off track,

977
00:59:26,360 --> 00:59:31,840
Speaker 1: this becomes a continuous process. It's incredible to me that

978
00:59:31,960 --> 00:59:34,480
Speaker 1: people figured this stuff out, that they figured out how

979
00:59:34,600 --> 00:59:37,640
Speaker 1: to not just not just how the universe works, Like

980
00:59:37,680 --> 00:59:40,880
Speaker 1: it's already incredible to me that Einstein was able to

981
00:59:41,000 --> 00:59:46,160
Speaker 1: determine these in incredible theories of special and general relativity,

982
00:59:46,600 --> 00:59:49,360
Speaker 1: but then for people to build on that and to

983
00:59:49,440 --> 00:59:54,240
Speaker 1: make technologies that take that into account, it's it's phenomenal.

984
00:59:54,320 --> 00:59:57,240
Speaker 1: It also tells you by the way science works, right,

985
00:59:57,560 --> 01:00:01,280
Speaker 1: because if science didn't work, the technology we build that

986
01:00:02,200 --> 01:00:07,040
Speaker 1: leverages that science, it wouldn't work. So science works or

987
01:00:07,120 --> 01:00:09,840
Speaker 1: else are tech wouldn't work, especially when it comes to

988
01:00:09,880 --> 01:00:12,760
Speaker 1: space navigation. Now, there is a lot more that we

989
01:00:12,800 --> 01:00:16,080
Speaker 1: could say about spacecraft navigation. I haven't really gone into

990
01:00:16,360 --> 01:00:21,280
Speaker 1: deep details here, uh like how do you determine what

991
01:00:21,360 --> 01:00:24,400
Speaker 1: a spacecraft's velocity is? For example? I haven't talked about

992
01:00:24,440 --> 01:00:27,920
Speaker 1: that process, but I felt this was a good if

993
01:00:27,960 --> 01:00:31,280
Speaker 1: you will high level overview of the topic. If you

994
01:00:31,320 --> 01:00:34,919
Speaker 1: would like to know more details, let me know. I'll

995
01:00:35,200 --> 01:00:38,000
Speaker 1: research and write and do a follow up episode and

996
01:00:38,160 --> 01:00:40,400
Speaker 1: it will reference this one, but it will go into

997
01:00:40,480 --> 01:00:43,680
Speaker 1: much more detail to talk about the actual processes and

998
01:00:43,760 --> 01:00:46,400
Speaker 1: technologies we use to do the things I've talked about

999
01:00:46,480 --> 01:00:49,520
Speaker 1: in this episode. If you want that episode or any

1000
01:00:49,600 --> 01:00:52,760
Speaker 1: other topic on tech Stuff, reach out to me on Twitter.

1001
01:00:52,920 --> 01:00:54,200
Speaker 1: That's the best way to get in touch with me.

1002
01:00:54,640 --> 01:00:57,120
Speaker 1: The handle we use for the show is tech Stuff

1003
01:00:57,520 --> 01:01:03,000
Speaker 1: H s W and I'll talk to you again really soon. Yeah.

1004
01:01:07,080 --> 01:01:10,080
Speaker 1: Text Stuff is an I Heart Radio production. For more

1005
01:01:10,200 --> 01:01:13,560
Speaker 1: podcasts from I Heart Radio, visit the I heart radio, app,

1006
01:01:13,680 --> 01:01:16,840
Speaker 1: Apple podcasts, or wherever you listen to your favorite shows.