December 9, 2015 • 46 mins
How did Sputnik change the world? What do satellites do? And what keeps them in orbit?
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Speaker 1 (00:04):
Get in tech with Technology with tech Stuff from Stuff
stateolland Hey there, and welcome to Tech Stuff. I'm Jonathan Strickland,
your lovable host, and today we're gonna do an episode.
That was a request from Matthew Aisles who wrote to
me on Twitter. He actually requested at two part episode
(00:26):
about satellites. Uh, and I think it's a great idea.
I don't know if I'll do a second part right away,
but this first part is going to be a bit
about the history of satellites, how they work in general,
and also some cool information about them, like how relativity
comes into play. I guess it's relatively cool. Whacketty smacketty do. Alright,
(00:49):
So let's talk about satellites and what they are. So
satellite is something that's in orbit around another object. And
of course Earth has had a satellite for billy of years.
That would be the Moon. That's a natural satellite. But
if we want to look at man made satellites, we
have to go back a few decades. And in fact,
the the foundation for man made satellites, the principles, the
(01:14):
idea of what would be required, go back well before
the space race ever started. That would be Isaac Newton
who came up with the idea of what would be
required to create a satellite. Now that's not what he
necessarily called it, but this was published in a famous
thought experiment back in seventeen twenty nine, and at the
(01:36):
time he was really concentrating on gravity, which is pretty
heavy stuff. So Newton's thought experiment was famous. People have
talked about this a lot. You've probably heard about it.
He said, what if you were to go at the
top of a really really tall mountain, and you build
a cannon on the top of that mountain, and you
(01:56):
aim that cannon so that the barrel is parallel with
the Earth below you, so it's at at the same
you know, same uh angle as the ground down at
the base of the mountain. You fire the cannon. The
cannonball flies out and it moves away from the cannon,
(02:18):
but it also starts to fall because gravity has been
pulling on the cannonball the whole time. You know, the
gravity was pulling on the cannonball when it was in
the cannon. It's pulling on the cannonball now that it's
emerged from the cannon. Eventually, this cannonball is going to
fall to the ground. And by eventually it's it's based
upon the altitude that the cannonball already is at. Uh.
Doesn't have anything to do with the forward velocity so
(02:40):
much as the altitude. He said, Well, what if you
were to to pack more gunpowder in this cannon and
you fire it, might it will go further because it's
moving at a forward velocity that's that's greater than the
previous one. But it still will eventually fall to the earth. Uh. Really,
in that same amount of time, it's just gonna be
further out from their first shot. But then you keep
(03:03):
packing more and more gunpowder in, and eventually you pack
enough gunpowder in so that when you fire the cannonball,
it is flying out at afford velocity at a at
a rate that is equal to how the Earth is
curving away from the cannonball. So, in other words, the
cannonballs falling toward the Earth, but the Earth is curving
(03:24):
away from the cannonball at that same rate, So the
cannonball never falls down to hit the Earth's surface because
the Earth is falling away from the cannonball at the
same rate that the cannonball itself is falling. This would
mean that eventually you would shoot yourself in the back
because the cannonball would make a full rotation around the
Earth and come back to its point of origin. At least,
(03:46):
that was the thought experiment that Newton had proposed, which
seemed like a really clever idea, but there was no
practical means of testing it or putting it to any
use back in Newton's day, it was just an interesting idea.
It would not be until October four, nineteen fifty seven,
and that's when the then Soviet Union made history by
(04:07):
launching the first man made satellite into Earth orbit, and
that satellite was the spot Nick one. But it was
fairly simple. It was a ball that was silver in color.
It was about twenty two point eight inches in diameter,
which is around fifty eight centimeters, so not very big,
and it weighed a hundred eighty three point nine pounds
(04:29):
or eighty three point six ms. The body was made
out of an aluminum alloy, and the shell of that
aluminum was just two millimeters thick. It was actually two
hemispheres of a globe that were connected together by thirty
six bolts around the circumference of those hemispheres. It had
(04:50):
two antennas and each antenna had two beams, so like
four prongs extending backward from the center from the bear itself,
almost like it had four legs. One pair of antenna
where seven point nine feet long or about two point
four meters, the other pair was twelve point eight feet
long or three point nine meters. Inside the satellite, there
(05:14):
wasn't a whole lot, not compared to what had originally
been planned to put in the satellite. Inside it was
a radio transmitter so it could communicate back to Earth,
had three silver zinc batteries that would provide power. It
had a couple of different switches inside of it, remote switches,
a thermal system fan was in there, a controlled thermal switch,
(05:37):
and a barometric switch were in there. So and it
was also filled with nitrogen gas to create internal pressure. Essentially,
the only things this this was really the only thing
this this um satellite could do was monitor its own systems,
like how hot was it? Or cold was it? What
was the pressure like? And then it would beam down
(05:58):
information in a series of beeps. In fact, my former
co host Chris Palette used to refer to Sputnik as
the thing what beats. It actually sounded a bit like
this so if you had had a ham radio back
in n and you were tuning in, you could actually
(06:22):
pick up that signal as sput Nick passed overhead, because
it was broadcasting on a frequency that was within the
citizen band radio frequency, and that meant that people could
actually listen in as sput Nick went overhead. It only
took ninety eight minutes for the satellite to go around
the Earth, so every hour and a half or so
(06:42):
you would be able to pick this up. And it
freaked people out, particularly in the United States. People were
freaking out because they were able to actually hear evidence
of the Soviet Union's ability to send an object into space,
and if they could do that, there was also the
fear that they could perhaps fire a ballistic missile, maybe
(07:04):
with a nuclear warhead at the United States that they
had had now had the capability to fire massive destructive
weapons at the US from a world away, and at
this time the Cold War was going on strong, so
it caused more than a little stir. It was the
(07:25):
fuel for tons of different science fiction films. Uh they're
all these different um uh instructional movies that explained what
you need to do in the case of a nuclear war,
and most of them were freakishly optimistic. At any rate,
it propelled the United States into a new era of
(07:45):
research and development. The US had already been planning on
getting into the space race, but this meant that suddenly
everything was cranked up to eleven, as spinal Tap would say.
So it really literally launched the space race between the
United States and the Soviet Union. Now for the story
of Sputnik itself, you actually have to go back much
(08:08):
further back to the nineteen forties in fact, or even earlier,
when you're looking at the the rocket program out of
the Soviet Union during World War Two. So officially you
would argue that nineteen fifty two was was what got
Sputnik itself going. Within the Soviet Union, that's when an
(08:30):
organization called the International Council of Scientific Unions called for
artificial satellites to be launched in order to study solar activity,
which was going to be reaching a peak in nineteen
fifty eight, and the United States started planning a launch
at least as far back as nineteen fifty five, and
their project was called Vanguard, and pretty much the world
(08:53):
was looking at the United States as the leader it
was going to be the US that would be launching
a UH satellite sometime around the summer of nineteen fifty seven.
But the Soviet Union thought, hey, we have the opportunity
to show up our rival, and so they really put
Sputnik on the fast track. Now to to look at
what was going on in the Soviet Union going back
(09:16):
to the nineteen thirties and nineteen forties, there was a
man named Mikhail ticknor Revov. I'm gonna mess up that
name all the time. Tick Hanravov who led a team
of scientists to design, build, and launch spot Nik one.
But their early work was really looking at missile systems,
ballistic missile missile systems for military use. UH. They just
(09:39):
saw the potential for using those same systems to launch
satellite into space. And they were really looking at the
possibility of using multi stage rockets in order to get
the right amount of acceleration to push an object into orbit.
And they were often relying on research performed not just
by their team, but by other scientific teams around the world.
(10:00):
Often this was information that we're that was pulled in
through espionage. It wasn't necessarily the scientific community openly sharing
this information. And originally UH they were really looking at
how can we make missiles better missiles for the Soviet Union.
The group would form in nineteen forty six, so not
long after the end of World War Two, and the
(10:23):
team worked on satellite plans pretty much in secret because
they weren't sure if the Soviet government would actually appreciate
their interest in scientific research that did not have an
immediate military application. Now keep in mind that until nineteen
fifty three, the Soviet Union was being led by Joseph Stalin,
(10:43):
and he was an incredibly brutal dictator, and paranoia was
rampant in the Soviet Union. There were stories about secret
police and kidnappings in the middle of the night. People
lived in constant fear of being arrested or executed. But
after Stalin died in March nineteen fifty three, people were
(11:05):
able to concentrate on something beyond just not being noticed.
It's hard to imagine how terrifying that time must have been,
but it's probably no coincidence that it was nineteen fifty
four when the Soviet scientists stopped hiding the fact that
they were performing this satellite research. They would talk about
it openly, and the project received support from various scientific
(11:29):
societies within the USSR, but it wouldn't be until nineteen
fifty six that they received official approval from the Kremlin.
So if you want to hear a really amazing story
about bureaucracy, science, politics, and how messed up everything was
in the Soviet Union in the nineteen fifties, you should
really research the full story of spot Nik, because it's
(11:54):
amazing that this project ever really got a lot of
of support. In large part the support was coming from
the Soviet Union wanting to demonstrate its power, not to
pursue science, but in order to show the rest of
the world where the Big Bear don't mess with us.
(12:15):
There were a whole bunch of different departments that all
worked on the design of the spot Nick project, and
it's kind of interesting to see how diverse this group was.
So those those different departments included the Academy of Sciences
of USSR, which oversaw the scientific research and development of
the project. There was the organization Okay b DASH one,
(12:39):
which was the U s s R Experimental Design Bureau.
It's essentially was the equivalent of our DARPA here in
the United States. It was a research and development program
that really took big risks to see if they could
find big reward from scientific research implemented in practical ways.
(12:59):
That particularly, that particular department fell under the direction of
the Ministry of Defense Industry, so that group was responsible
for designing the body of the satellite, and in the
satellite biz we refer to this as the bus. The
bus is essentially the the body or shell inside which
(13:20):
all the instrumentation exists, apart from you know, some instrumentation
obviously has to be on the outside of the bus,
like any sort of imagery or antenna, but you get
what I mean. Next, we have the Ministry of Radio Industry.
They were in charge of flight control systems, radio and
telemetry systems. Then you had the Ministry of ship Building.
(13:42):
The ship Building Ministry was responsible for designing the gyroscopes
that would go in the satellite. You had the Ministry
of Machine Building. They were responsible for a ground processing, transport, fueling,
and launch hardware. You had the Ministry of Defense itself,
which was in charge of launch operations. You had the
Ministry of Avia Aviation Industry which was in charge of
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the tracking systems, and the Special Committee of the Soviet
of Ministers, which were all about the management and coordination
of the program overall. Now, originally spot Nick was referred
to as Object D and it was supposed to be
a much larger, much more sophisticated satellite. It was not
supposed to just be the thing what beeps. It was
(14:27):
supposed to have a lot of instrumentation for actual scientific
study with a collection of useful instruments. But the projects
suffered several setbacks in the design process that kept pushing
back when they would be able to launch, and there
was a growing concern that the United States was going
to be able to launch a satellite in orbit starting
(14:48):
on July first, nine seven. So they had a new goal.
They wanted to strip down their ideas to just the
most essential elements to try and beat America to the punch,
and they did. They were able to create a much smaller,
more basic satellite, and they were able to launch it
before the United States could send their own satellite into space,
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and they set a precedent, and in fact only did
the USSR beat the USA, they did it twice. The
second satellite, which was spot Nick two, contained the first
life form sent into Earth orbit, and that was the
dog named Lyca and Lica was always destined to die
during this mission. There was no plan for Lyca to
(15:34):
return to Earth safely. Uhlica was going to die inside
the satellite, either by starvation or thirst. It was just
no or suffocation. That was just known that this was
a one way trip for the dog. Um the dog
likely died due to overheating fairly early in the mission,
(15:54):
based upon what the instrumentation was saying. And there have
been a lot of web comics, card tunes, and an
amazing song, more than one song, but there's a great
song called Space Doggedy which was written by Jonathan Colton
and obviously has uh a lot of influence from Space
Oddity from David Bowie Space Oddity in there. Space Doggedy,
(16:15):
great song. There's actually a video on YouTube someone's put
together with actual footage of like a from spot Nick two.
And that's all I'm going to say about that, because
otherwise I'm gonna get all choked up because to me,
it's a very sad story and necessary story. I totally
understand why we need to use animals to test the systems,
(16:36):
because clearly you can't just put a human in there
and hope everything turns out all right. But it's still
a very sad story to me because I'm I'm a
squishy dog lover. I have a dog, and I when
I look at my dog and imagine what Likeca was
going through, I just fall to pieces. At any rate,
the United States response to sput Nick was to go
(16:59):
back to the drawing board. They had their Vanguard design
that they had planned to launch, but that now felt
that it was no longer a strong enough offering. They
needed to come up with a better satellite to really
be a good response to the Soviet Union's project. So
the new USA project was called Explorer, and it was
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led by a rocket scientist named Werner von Brown. Von
Brown was a brilliant physicist, a very intelligent rocket scientist,
but he had an incredibly dark past. UH. He was
born in Germany in nineteen twelve and he was part
of the Rocket Society as early as nineteen twenty nine.
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As the Nazis gained power in Germany during the thirties,
von Brown chose to work for the German Army to
develop missiles. He wanted to continue his research and work,
and it seemed like the UH the most opportune place,
and his work was instrumental in the development of the
V two ballistic missile, which was a tool the Nazis
(18:11):
used to some effect, perhaps not as great as it
could have been, but certainly was a destructive weapon that
caused a lot of damage and death. He was eventually
awarded an honorary rank in the s s by Heinrich Himler.
It is said, however, that von Brown only accepted that
rank because he and his team were worried that Himmler
(18:33):
would be angry if he had declined it. So at
least some accounts state that von Brown didn't share the
political ideology of the Nazis. He just saw this as
the opportunity for him to actually do his work, and
if he didn't join the Nazis then he would not
be able to do his work. Von Brown realized that
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Germany would lose the war. I think a lot of
people realized that it was getting to a point where
it was undeniable, and so he made plans to surrender
himself and his team of around five rockets scientists to
the Allies and offered to do research for the United
States to help them develop their ballistic missiles. Further so,
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Fan Brown and his scientists would create a rocket research
center that originally fell under the guidance of the United
States Army, but eventually it would get shifted to a
new organization called NASA, which was founded mainly in reaction
to spot Nick and really be part of the space race.
(19:38):
Explorer one would launch on January thirty one, nineteen eight,
and it made an actual scientific discovery on its orbital flight.
It discovered magnetic radiation belts around the Earth, which are
now called the Van Allen Belt after one of the
lead researcher on the project. Now, these days, satellites are
(20:02):
way more sophisticated than spot Nick or even Explorer one,
and they typically use solar panels to capture solar energy
and convert it into electricity that is used to charge
batteries for power. Some of them actually use fuel cells
rather than batteries to generate electricity. And we've used nuclear
power in some probes that we've sent away from our planet,
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but in general we tend to be a bit skittish
about the idea of putting nuclear power into stuff that's
going to be orbiting our own planet. Satellites tend to
have some pretty sophisticated stuff inside them. These days like
computer control systems, which were well beyond the abilities of
the early satellites which had electro mechanical controls. But now
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we've got computer control systems, radio communications, attitude control systems.
Attitude in this case isn't about personality, but rather the
satellites orientation with respect to the position of the Earth.
And satellites can have different shaped orbits. Some have circular orbits,
which are very regular and uh and predictable, but some
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have elliptical orbits. And elliptical orbits are interesting because a
satellite will travel at different speeds along its orbital path.
So there are two points along that path that we
call the foci of the elliptical orbit. The point that's
closest to the planet is the peerage, and that's the
point at which the satellite will be moving fastest through
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its orbit. It's like think of it like the sling
shot effect. The furthest point from a planet. The furthest
point in the orbit of the satellites orbit from a
planet is the apogee, and that's where the satellite will
move the slowest in its orbital path. Now, launching a
satellite into orbit obviously requires rockets and in a rocket launch,
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a special system is used called the inertial guidance system,
which calculates the adjustments needed to push a satellite into
the correct orbit. Talk about the different orbits in a second. Typically,
rockets are fired so that they head eastward, and that
means that the Earth's rotation gives those rockets a speed boost.
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It's like the rockets are actually flying faster than they
really are because of the relative motion of the Earth.
If you were to launch your rocket at the equator,
you would get the biggest boost because the Earth bulgeon
is out there. It's the largest diameter. So here's how
you would determine the boost you get to your speed.
You take the Earth's circumference, which is about four thousand,
nine hundred miles or forty thousand, sixty kilometers. You figure
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out how fast the Earth rotates, which is one full
rotation in approximately twenty four hours, which gives us a
speed of around one thousand, thirty eight miles per hour
or one thousand, six hundred sixty nine kilometers per hour.
That's the rotational speed of the Earth. That's typically that's
actually at the equator. If you were to look at
a launch facility at Cape canaveral. The rotational speed is
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different because you're further north of the equator. You're not
at the thickest part of the Earth. Therefore, the circumference
is smaller and you have a slower speed, so a
slower rotational speed at that point, so it's closer to
around eight miles per hour or one thousand, four hundred
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forty kilometers per hour. But that speed boost gives us
a big help. So to get the satellite into orbit,
you have to be going wicked fast, but not as
fast as what you would need to actually escape Earth's gravity.
So if you wanted to go out into space and
beyond Earth's gravity, you're leaving Earth orbit, you're heading out
to Mars or something. You would have to accelerate to
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at least twenty five thousand, thirty nine miles per hour
or forty kilometers per hour to escape Earth's gravity and
enter outer space. Putting a satellite in orbit requires less speed,
and it all depends upon which orbit you're trying to
insert the satellite into. The orbits determine the speed, so
lower orbits require faster speeds, which might seem counterintuitive at first,
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but you gotta remember those lower orbits that that speed
is meant to counteract the gravitational pull of Earth so
that the object in orbit remains in orbit, doesn't get
pulled back down to the ground. So when you're closer
to Earth, the force of gravity is greater. As you
probably remember, gravity is dependent upon two things, the mass
(24:24):
of two objects and their relative distance to one another.
So as distance increases gravitation gravitational pull decreases, and you
don't need to counteract that with more velocity to make
sure an object stays within its orbital path and doesn't
deteriorate and fall into the Earth. So higher orbits require
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lower speeds, and if you get far enough out there,
you can have a satellite that orbits at the same
speed as Earth's rotation. Uh those would be geostationary orbits.
They would appear to be directly above a fixed point
on the Earth and they would not move from that point.
I'll get into that more in it just a second. First,
let's talk about the various types of orbits from an altitude,
(25:08):
because we can describe orbits in different ways. You can
describe their orbital pathway, whether it's circular or elliptical, you
can describe it in its altitude, and you can describe
it in its orientation as in, is it equatorial, is
it directly above the equator? Is there any degree of inclination? Uh?
Is it a polar orbit which goes north south not
(25:29):
east west? Lots of different ways to describe them. So
from an altitude perspective, we start with lower thorbit. That's
the one closest end to the Earth, and that's an
arrange that's between a hundred eleven miles and one thousand,
two hundred forty three miles above the surface of the Earth.
In kilometers that would be a hundred eighty to two
thousand uh. This tends to be the altitude we use
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for satellites that collect surface observations, photography, weather satellites, that
kind of thing. When you go further out, you get
to medium Earth orbit that's in a zone that's between
one thousand, two hundred forty three miles and twenty two thousand,
two hundred twenty three miles or in kilometers way easier
two thousand to thirty six thousand kilometers. Navigation satellites like
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GPS tend to be at this altitude, although summer at
higher altitudes. Then you get to geosynchronous orbit. That's when
you are at an altitude that's greater than twenty two
three miles, in other words, greater than thirty six thousand kilometers.
The orbital period is the same as the Earth's rotational period,
meaning it takes a full day for the satellite to
(26:36):
go all the way around the Earth. There is a
subset of geosynchronous satellites called geo stationary satellites, So all
geostationary satellites are also geosynchronous, but not all geosynchronous satellites
are geo stationary. If you have a geostationary satellite, that's
one of those satellites that remains over a fixed position
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on the Earth's sir So you could build an antenna
at that point pointed straight up into the atmosphere and
it's going to be aimed directly at that satellite, and
as long as nothing changes in that satellite's orbit. Things
do change over time, so you have to correct it occasionally,
but as long as nothing changes, UH, the antenna and
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satellite will always be in alignment. That's a geostationary satellite. UH.
It doesn't matter if it's day or night. You're always
going to have a direct line of sight between the
antenna and the satellite, and the satellite is gonna be
too far away from you to see it, but there's
a direct line of site as far as the antenna
is concerned. All geostationary satellites are geosynchronous, like I said,
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But if the opposite isn't true, what's going on? How
are geo secret as satellites that aren't geo stationary? How
does that work? Well, the geosynchronous satellite does make one
orbit around the Earth in the same amount of time
it takes Earth to make one rotation in inertial or
fixed space, which is also called a sidereal day. It's
actually not twenty four hours, specifically, it is twenty three hours,
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fifty six minutes and four seconds of mean solar time.
If the satellite has any inclination or a non circular
orbital path, it will not be geo stationary. The satellite
will appear to roam over the Earth's surface, so in
elliptical orbits, those egg shaped orbits, the satellite would be
moving at different speeds along its journey. Remember the paragean apogee.
(28:28):
It's going to be moving at at different velocities as
it goes around the Earth. Inclination, by the way, is
the angle between a reference plane and the orbital plane.
The reference plane in this case, UH, we're talking specifically
about the equator. So imagine you've got the Earth's globe,
You've got it tilted at a slight angle because the
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axis is on an angle, and you've got the equator.
If you have a geosynchronous satellite directly above the equator,
it's going to be geo stationary. It's gonna stay around
that fixed point. But if you go north or south
of the equator and you place a satellite there, it
will it will not stay above a fixed point. Its
(29:12):
orbit is going to be slightly angled. That's the inclination
we would talk about. UH. So as it would go
around the pathway, uh, it would actually roam over the
surface of the Earth. So a satellite that has degrees
of inclination and its orbit with respect to the equator
will move north and south of the equator as it
(29:32):
completes an orbit. So this satellite is going to stay
more or less in the same east west area, but
it's going to go north south as it goes throughout
its orbit. Satellites with an elliptical path will drift east
and west from any fixed point on the Earth as
a satellite moves faster or slower through its Earth orbit.
We have seen there are several satellites that use this
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where they are both the inclination and an elliptical path,
so they make this almost like a figure eight kind
of pattern over a general region of the Earth's surface,
which could be really useful for things like communication satellites
or or even GPS in that in that sense, there
are some GPS satellites that work under this principle. Geo
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stationary satellites have a view of about of the Earth's surface.
Just a single geo stationary satellite can see about of
the Earth's surface from where it is. So if you
just create a network of a few geo stationary satellites,
you can get a view of practically the entire Earth,
really everything between eighty one degree south and eighty one
(30:41):
degrees north. Beyond those those uh those degrees, you wouldn't
be able to see it just from the way the
Earth is curved, but you'd get to see everything between
the two. Geo stationary satellites tend to be used for communications.
It's great solution for us on the ground because you
don't need to move the antenna on the surf to
stay in contact with the satellite. If the satellite we're drifting,
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if it if it orbited the Earth multiple times during
a rotation, you would constantly have to adjust your antenna
to remain in contact with the satellite, and there will
be times where you would be out of contact with
the satellite. It would have the Earth between you and
the antenna. So geo stationary makes this easy because it's
always going to be directly above the antenna. So it
(31:26):
makes an ideal communication satellite in that respect, But there
are a limited number of slots for geostationary satellites. You know,
you could go to different altitudes, but you're going to
be you're going to be stuck at that equator plane.
So you don't want satellites to collide with one another.
Obviously they would destroy or at least damage one or
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both satellites, and you don't want the actual data communication
to interfere with each other, so you have to separate
them out by space. You can't have them to pack
pecked in too closely together, and a satellite geo stationary
orbit will not stay there forever. Other gravitational forces from
the Sun and the Moon, plus the fact that the
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Earth is not perfectly round, will cause the satellites to
increase in inclination over time, so they'll they'll start to
drift a little bit, and then they will no longer
be geo stationary UH satellites. They'll have thrusters on them
and fuel inside them in order to make small corrections,
which is called station keeping, and that's so that they
(32:32):
can stay in the right relative location. But once the
satellite is used up all its fuel, it will experience
an increase in inclination. It's unavoidable. You can't fix it
at that point, and it's possible, depending upon how the
satellite is located, that it could become a hazard to
other geo stationary or geosynchronous satellites. So normally, at the
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end of a geostationary satellites useful lifespan will send a
command to the satellite to say, get the heck out
of the neighborhood. Boost it at a higher altitude, a
higher orbit, which moves out of the way of other satellites,
because it's not gonna be useful anyway, so you might
as well boost it further out and not have it
become space junk closer into the Earth. There's already a
(33:15):
lot of space junk that's out there. Fortunately, space is
really big, so while there's always a threat of space
junk being a problem with satellites, it's such a huge
space that the odds on any given day are fairly
low of an incident. But the more stuff we send
up there, the better the odds are that something bad
(33:35):
will happen. Now, not all orbits are in an east
west orientation. You're probably imagining that these satellites are orbiting
the Earth more or less in the same direction that
the Earth rotates, that they are going around and around, uh,
the same axis of rotation. Not all of them do.
Some of them are rotating north south. They're going around
(33:58):
uh the poles, you know, Poller orbits, which are really
good for photography and mapping because as these satellites move
north to south or south and north, depending upon which
way you're going, UM, the Earth is rotating under the satellites,
so they get a really good view of the Earth.
They're great if you want to have a satellite map
(34:21):
of a region. They're also not bad if you're hoping
for satellite to pass over a certain region on the
Earth so you can get a better look. In other words,
these are used for spying. And one particular type of orbit,
very specific type of orbit, is the mulnia or lightning orbit,
(34:41):
and the orbit takes its name from Soviet satellites that
use this particular style of orbit for communications networks. It's
an elliptical shape, which means the satellite spends a lot
of its time near the apogee poet point the of
the orbit, because that's where it moves the slowest. So
if you plan out the telemetry of your satellite in
(35:03):
such a way so that the apogee is over a
specific region, you know that when the satellite orbits the Earth,
it's gonna be spending the majority of its orbit over
where the apogee is. So if you locate it in
a place that you're interested in, you're gonna get more
coverage of that region throughout the duration of the orbit
(35:24):
of the satellite. So the Soviets planned the apoge to
be over the northern hemisphere so that they could serve
as a communications network and maybe also you know, spy
on Europe a little bit. Perhaps one thing we use
satellites for is to spread a signal from one location
to another. And this is a pretty simple idea. Actually,
it's just bouncing a signal off of a satellite. It's
(35:46):
almost like the satellite acts as a mirror, although it's
also an amplifier. So we use an antenna on the
Earth pointed up towards the satellite we're interested in, and
we beam as signal into space. It might be audio,
it might be video, it could be anything really, and
that antenna is the up link. Now the satellite receives this.
They have it has its own antenna and receives the
(36:08):
signal and then runs it through an amplifier and the
beams the amplified signal back down to the Earth. And
on Earth we have other antenna known as the down links,
that receive the incoming signal from the satellite. And using
this model, we can beam all sorts of useful stuff
like communication signals. Television studios would send feeds up to satellites,
(36:31):
which then act as a distribution system. So you would
have a centralized location where you would have the the
video feed, video and audio feed. You would send that
through an up link to a satellite that would receive
it and beam it back down to receiving stations, and
that was how you know, that's how we get television
broadcast beyond just over the air broadcast. In fact, if
(36:54):
you have a cable company, you could receive these signals
yourself using satellites. Right, you could have part of the
satellite TV system and you have your own little satellite
that's pointed up and you receive your television signals that way.
Or you could end up having cable but cable companies
also use this method. You would have a centralized location
(37:15):
that beams a signal up, it comes down so that
various cable distribution networks received the signal and then they
send that through the actual cables that eventually terminate at
your television. So this is a very important way of
using satellites. Now, I want to conclude this episode with
a quick discussion about how relativity affects satellites, both special
(37:41):
and general relativity. Now, these, of course, are the the
theories proposed by Einstein that ultimately proved true at least
in the case of time dilation, because we see it
in practice with satellites. One of the things we use
satellites for is GPS, the Global position system. So GPS
(38:03):
positioning system, I should say, and GPS is incredibly useful.
That's what lets us use real time maps on our
phones and GPS devices to go from point A to
point B. But in order for GPS to work, it
needs to be able to measure time very accurately, both
for the person who's on Earth and the satellite that
(38:25):
is providing the very satellites I should say that are
providing the information that allows us to UH to triangulate
where we are on the service of Earth. So here's
the problem. Time dilation. Einstein's theory gives us some uh
some issues with time. Special relativity tells us that the
faster we move relative to an independent observer, the slower
(38:52):
time seems to pass for ourselves. Um again, based upon
the relative observer to us, time will pass exactly the
same way. No matter how fast we're going we will
it will feel the same. So if you get on
a spaceship that's going near the speed of light and
you look at your watch, the second hand is going
to take away as if you were on Earth. But
(39:15):
to an independent observer, it would look like that second
hand is going super slow, and it would mean that
when you finished your journey and came back to Earth,
more time would appear to have passed on Earth than
it did for you, even though for people on Earth
time was passing normally, for you on the spaceship time
(39:36):
was passing normally. It's really only when you have this
point of reference that you realize that you've experienced different
amounts of time. Uh, it's kind of a mind bender, right. Well,
special relativity tells us that these clocks on board the
satellites will take a little more slowly because they're moving
so fast out in space. Uh, they should actually fall
(39:59):
behind the clocks here on Earth by about seven micro
seconds per day, which doesn't sound like a lot, but
if you're talking about very precise measurements to give you
an idea of where you are before long, that becomes
an insurmountable problem. So seven microseconds per day slower on
(40:21):
the satellites compared to the clocks on Earth. If that
were all there were to it, then we would just say, well,
we have to find a way, like a program that
will build in this error so that we know ahead
of time how to adjust for it. But it gets
more complicated than that. So that's special relativity. But general
relativity also plays a part. So one of the predictions
(40:44):
made by general relativity is that clocks closer to a
massive object will seem to tick more slowly than those
that are further away from a massive object. So if
we look at it that way, these satellites are very
are away from the surface of the Earth, so the
clocks on the surface of the Earth are much closer
to a massive object. The clocks on the satellites are
(41:07):
much further away from a massive object, and it's enough
to make a big difference. It also means that the
clocks on the satellites appear to be taking faster than
the clocks on the ground. So if you calculate a
prediction using general relativity as your basis for how fast
those clocks will be ticking on the satellites, you would
(41:28):
see that they'd be ahead of our ground clocks by
about forty five micro seconds per day. Now, this actually
means that you have to take the difference between the
forty five seconds in advance and the our forty five
micro seconds I'm sorry, forty five micro seconds in advance
from general relativity, and you have to subtract the seven
micro seconds behind from special relativity, and it tells you
(41:52):
that the clocks on board the satellites should take a
little bit faster than the clocks here on the ground,
by the tune of thirty eight my acrow seconds per day.
You take those forty five microseconds ahead general relativity, subtract
the seven microseconds from behind from special relativity, and you
get thirty eight microseconds ahead. Uh net. So it again
(42:15):
is enough for it to cause a high precision system
like GPS two have errors after just a few days,
so you have to correct for that. You actually have
to create a navigational fix so that the system is accurate. Uh.
(42:36):
Otherwise you would get errors in where the map would
say you were. You would look at the map, and
as time would go by, these errors would get worse
and worse, to the point where it would show you
locations that are just ridiculous, you blocks away from where
you actually were. And uh and more if time went
on long enough in the GPS satellite system was limited,
(43:00):
so you're talking about you know, errors of around ten
kilometers every day. That's that's a big deal. You know,
you're trying to get from point A to point B,
and you're getting errors that are ten kilometers off that
could be disastrous, so it would actually be useless after
a very few days. That's why you have to have
(43:22):
algorithms built in that take these relativistic effects into account
so that the results you get on your GPS device
remain accurate. So I think that's pretty cool that you know,
satellites are a practical way for us to see how
relativity can affect us, and that relativity is in fact real.
(43:44):
It's it's it's not it's not quote unquote just a theory.
It's something that we can observe directly and though and
know that this is at play. So I wanted to
mention that because you know, it's it's pretty cool stuff
and on slee When I was first looking into it
years ago, when I was looking at how GPS works,
(44:06):
I had a handle on special relativity. I understood that
the speed of the movement of the satellites would affect
how time passes compared to what we see here on
Earth on the surface, but I was not aware of
the effects of general relativity. That was something I had
(44:26):
to learn when I looked up GPS back in the day,
which I think was a Tuesday. If I'm not mistaken
so relatively obviously a very fascinating subject. I would love
to go into further detail, but I think that's more
of a stuff to blow your mind than a tech
stuff topic. We have, of course touched upon relativity a
(44:47):
few times in our conversations about various types of technology.
But maybe one day I'll get some stuff to blow
your mind folks in here, and then we'll have a
big discussion about relativity, not just what it is is,
but how it directly affects some of the things we do. Alright,
So that wraps up this discussion about satellites, and I
(45:10):
may do a future episode where I go into more
detail about the different types of satellites, the instrumentation that
is aboard these satellites, how they work, who owns them,
maybe some interesting stories about notable discoveries that satellites have
made and notable incidents that have happened because of satellites.
(45:32):
There's a lot of information out there and it's really
fascinating stuff. So that might end up being a future episode. Heck,
it might be the next one. I haven't yet scheduled
what my next episode will be, so keep any year
out for that. But if you guys have suggestions for
future episodes. Why don't you do what? What aisles? Did
(45:52):
you know? It was very helpful sending me a message,
whether it's on Twitter or Facebook or email. So the
email address for this show is text stuff at how
stuff works dot com or drop me a line on
Facebook or Twitter to handle it both of those as
tech stuff H s W and I'll talk to you again.
(46:14):
Really see for more on this and thousands of other topics.
Is it how stuff works dot com
Get in tech with Technology with tech Stuff from Stuff
stateolland Hey there, and welcome to Tech Stuff. I'm Jonathan Strickland,
your lovable host, and today we're gonna do an episode.
That was a request from Matthew Aisles who wrote to
me on Twitter. He actually requested at two part episode
(00:26):
about satellites. Uh, and I think it's a great idea.
I don't know if I'll do a second part right away,
but this first part is going to be a bit
about the history of satellites, how they work in general,
and also some cool information about them, like how relativity
comes into play. I guess it's relatively cool. Whacketty smacketty do. Alright,
(00:49):
So let's talk about satellites and what they are. So
satellite is something that's in orbit around another object. And
of course Earth has had a satellite for billy of years.
That would be the Moon. That's a natural satellite. But
if we want to look at man made satellites, we
have to go back a few decades. And in fact,
the the foundation for man made satellites, the principles, the
(01:14):
idea of what would be required, go back well before
the space race ever started. That would be Isaac Newton
who came up with the idea of what would be
required to create a satellite. Now that's not what he
necessarily called it, but this was published in a famous
thought experiment back in seventeen twenty nine, and at the
(01:36):
time he was really concentrating on gravity, which is pretty
heavy stuff. So Newton's thought experiment was famous. People have
talked about this a lot. You've probably heard about it.
He said, what if you were to go at the
top of a really really tall mountain, and you build
a cannon on the top of that mountain, and you
(01:56):
aim that cannon so that the barrel is parallel with
the Earth below you, so it's at at the same
you know, same uh angle as the ground down at
the base of the mountain. You fire the cannon. The
cannonball flies out and it moves away from the cannon,
(02:18):
but it also starts to fall because gravity has been
pulling on the cannonball the whole time. You know, the
gravity was pulling on the cannonball when it was in
the cannon. It's pulling on the cannonball now that it's
emerged from the cannon. Eventually, this cannonball is going to
fall to the ground. And by eventually it's it's based
upon the altitude that the cannonball already is at. Uh.
Doesn't have anything to do with the forward velocity so
(02:40):
much as the altitude. He said, Well, what if you
were to to pack more gunpowder in this cannon and
you fire it, might it will go further because it's
moving at a forward velocity that's that's greater than the
previous one. But it still will eventually fall to the earth. Uh. Really,
in that same amount of time, it's just gonna be
further out from their first shot. But then you keep
(03:03):
packing more and more gunpowder in, and eventually you pack
enough gunpowder in so that when you fire the cannonball,
it is flying out at afford velocity at a at
a rate that is equal to how the Earth is
curving away from the cannonball. So, in other words, the
cannonballs falling toward the Earth, but the Earth is curving
(03:24):
away from the cannonball at that same rate, So the
cannonball never falls down to hit the Earth's surface because
the Earth is falling away from the cannonball at the
same rate that the cannonball itself is falling. This would
mean that eventually you would shoot yourself in the back
because the cannonball would make a full rotation around the
Earth and come back to its point of origin. At least,
(03:46):
that was the thought experiment that Newton had proposed, which
seemed like a really clever idea, but there was no
practical means of testing it or putting it to any
use back in Newton's day, it was just an interesting idea.
It would not be until October four, nineteen fifty seven,
and that's when the then Soviet Union made history by
(04:07):
launching the first man made satellite into Earth orbit, and
that satellite was the spot Nick one. But it was
fairly simple. It was a ball that was silver in color.
It was about twenty two point eight inches in diameter,
which is around fifty eight centimeters, so not very big,
and it weighed a hundred eighty three point nine pounds
(04:29):
or eighty three point six ms. The body was made
out of an aluminum alloy, and the shell of that
aluminum was just two millimeters thick. It was actually two
hemispheres of a globe that were connected together by thirty
six bolts around the circumference of those hemispheres. It had
(04:50):
two antennas and each antenna had two beams, so like
four prongs extending backward from the center from the bear itself,
almost like it had four legs. One pair of antenna
where seven point nine feet long or about two point
four meters, the other pair was twelve point eight feet
long or three point nine meters. Inside the satellite, there
(05:14):
wasn't a whole lot, not compared to what had originally
been planned to put in the satellite. Inside it was
a radio transmitter so it could communicate back to Earth,
had three silver zinc batteries that would provide power. It
had a couple of different switches inside of it, remote switches,
a thermal system fan was in there, a controlled thermal switch,
(05:37):
and a barometric switch were in there. So and it
was also filled with nitrogen gas to create internal pressure. Essentially,
the only things this this was really the only thing
this this um satellite could do was monitor its own systems,
like how hot was it? Or cold was it? What
was the pressure like? And then it would beam down
(05:58):
information in a series of beeps. In fact, my former
co host Chris Palette used to refer to Sputnik as
the thing what beats. It actually sounded a bit like
this so if you had had a ham radio back
in n and you were tuning in, you could actually
(06:22):
pick up that signal as sput Nick passed overhead, because
it was broadcasting on a frequency that was within the
citizen band radio frequency, and that meant that people could
actually listen in as sput Nick went overhead. It only
took ninety eight minutes for the satellite to go around
the Earth, so every hour and a half or so
(06:42):
you would be able to pick this up. And it
freaked people out, particularly in the United States. People were
freaking out because they were able to actually hear evidence
of the Soviet Union's ability to send an object into space,
and if they could do that, there was also the
fear that they could perhaps fire a ballistic missile, maybe
(07:04):
with a nuclear warhead at the United States that they
had had now had the capability to fire massive destructive
weapons at the US from a world away, and at
this time the Cold War was going on strong, so
it caused more than a little stir. It was the
(07:25):
fuel for tons of different science fiction films. Uh they're
all these different um uh instructional movies that explained what
you need to do in the case of a nuclear war,
and most of them were freakishly optimistic. At any rate,
it propelled the United States into a new era of
(07:45):
research and development. The US had already been planning on
getting into the space race, but this meant that suddenly
everything was cranked up to eleven, as spinal Tap would say.
So it really literally launched the space race between the
United States and the Soviet Union. Now for the story
of Sputnik itself, you actually have to go back much
(08:08):
further back to the nineteen forties in fact, or even earlier,
when you're looking at the the rocket program out of
the Soviet Union during World War Two. So officially you
would argue that nineteen fifty two was was what got
Sputnik itself going. Within the Soviet Union, that's when an
(08:30):
organization called the International Council of Scientific Unions called for
artificial satellites to be launched in order to study solar activity,
which was going to be reaching a peak in nineteen
fifty eight, and the United States started planning a launch
at least as far back as nineteen fifty five, and
their project was called Vanguard, and pretty much the world
(08:53):
was looking at the United States as the leader it
was going to be the US that would be launching
a UH satellite sometime around the summer of nineteen fifty seven.
But the Soviet Union thought, hey, we have the opportunity
to show up our rival, and so they really put
Sputnik on the fast track. Now to to look at
what was going on in the Soviet Union going back
(09:16):
to the nineteen thirties and nineteen forties, there was a
man named Mikhail ticknor Revov. I'm gonna mess up that
name all the time. Tick Hanravov who led a team
of scientists to design, build, and launch spot Nik one.
But their early work was really looking at missile systems,
ballistic missile missile systems for military use. UH. They just
(09:39):
saw the potential for using those same systems to launch
satellite into space. And they were really looking at the
possibility of using multi stage rockets in order to get
the right amount of acceleration to push an object into orbit.
And they were often relying on research performed not just
by their team, but by other scientific teams around the world.
(10:00):
Often this was information that we're that was pulled in
through espionage. It wasn't necessarily the scientific community openly sharing
this information. And originally UH they were really looking at
how can we make missiles better missiles for the Soviet Union.
The group would form in nineteen forty six, so not
long after the end of World War Two, and the
(10:23):
team worked on satellite plans pretty much in secret because
they weren't sure if the Soviet government would actually appreciate
their interest in scientific research that did not have an
immediate military application. Now keep in mind that until nineteen
fifty three, the Soviet Union was being led by Joseph Stalin,
(10:43):
and he was an incredibly brutal dictator, and paranoia was
rampant in the Soviet Union. There were stories about secret
police and kidnappings in the middle of the night. People
lived in constant fear of being arrested or executed. But
after Stalin died in March nineteen fifty three, people were
(11:05):
able to concentrate on something beyond just not being noticed.
It's hard to imagine how terrifying that time must have been,
but it's probably no coincidence that it was nineteen fifty
four when the Soviet scientists stopped hiding the fact that
they were performing this satellite research. They would talk about
it openly, and the project received support from various scientific
(11:29):
societies within the USSR, but it wouldn't be until nineteen
fifty six that they received official approval from the Kremlin.
So if you want to hear a really amazing story
about bureaucracy, science, politics, and how messed up everything was
in the Soviet Union in the nineteen fifties, you should
really research the full story of spot Nik, because it's
(11:54):
amazing that this project ever really got a lot of
of support. In large part the support was coming from
the Soviet Union wanting to demonstrate its power, not to
pursue science, but in order to show the rest of
the world where the Big Bear don't mess with us.
(12:15):
There were a whole bunch of different departments that all
worked on the design of the spot Nick project, and
it's kind of interesting to see how diverse this group was.
So those those different departments included the Academy of Sciences
of USSR, which oversaw the scientific research and development of
the project. There was the organization Okay b DASH one,
(12:39):
which was the U s s R Experimental Design Bureau.
It's essentially was the equivalent of our DARPA here in
the United States. It was a research and development program
that really took big risks to see if they could
find big reward from scientific research implemented in practical ways.
(12:59):
That particularly, that particular department fell under the direction of
the Ministry of Defense Industry, so that group was responsible
for designing the body of the satellite, and in the
satellite biz we refer to this as the bus. The
bus is essentially the the body or shell inside which
(13:20):
all the instrumentation exists, apart from you know, some instrumentation
obviously has to be on the outside of the bus,
like any sort of imagery or antenna, but you get
what I mean. Next, we have the Ministry of Radio Industry.
They were in charge of flight control systems, radio and
telemetry systems. Then you had the Ministry of ship Building.
(13:42):
The ship Building Ministry was responsible for designing the gyroscopes
that would go in the satellite. You had the Ministry
of Machine Building. They were responsible for a ground processing, transport, fueling,
and launch hardware. You had the Ministry of Defense itself,
which was in charge of launch operations. You had the
Ministry of Avia Aviation Industry which was in charge of
(14:05):
the tracking systems, and the Special Committee of the Soviet
of Ministers, which were all about the management and coordination
of the program overall. Now, originally spot Nick was referred
to as Object D and it was supposed to be
a much larger, much more sophisticated satellite. It was not
supposed to just be the thing what beeps. It was
(14:27):
supposed to have a lot of instrumentation for actual scientific
study with a collection of useful instruments. But the projects
suffered several setbacks in the design process that kept pushing
back when they would be able to launch, and there
was a growing concern that the United States was going
to be able to launch a satellite in orbit starting
(14:48):
on July first, nine seven. So they had a new goal.
They wanted to strip down their ideas to just the
most essential elements to try and beat America to the punch,
and they did. They were able to create a much smaller,
more basic satellite, and they were able to launch it
before the United States could send their own satellite into space,
(15:11):
and they set a precedent, and in fact only did
the USSR beat the USA, they did it twice. The
second satellite, which was spot Nick two, contained the first
life form sent into Earth orbit, and that was the
dog named Lyca and Lica was always destined to die
during this mission. There was no plan for Lyca to
(15:34):
return to Earth safely. Uhlica was going to die inside
the satellite, either by starvation or thirst. It was just
no or suffocation. That was just known that this was
a one way trip for the dog. Um the dog
likely died due to overheating fairly early in the mission,
(15:54):
based upon what the instrumentation was saying. And there have
been a lot of web comics, card tunes, and an
amazing song, more than one song, but there's a great
song called Space Doggedy which was written by Jonathan Colton
and obviously has uh a lot of influence from Space
Oddity from David Bowie Space Oddity in there. Space Doggedy,
(16:15):
great song. There's actually a video on YouTube someone's put
together with actual footage of like a from spot Nick two.
And that's all I'm going to say about that, because
otherwise I'm gonna get all choked up because to me,
it's a very sad story and necessary story. I totally
understand why we need to use animals to test the systems,
(16:36):
because clearly you can't just put a human in there
and hope everything turns out all right. But it's still
a very sad story to me because I'm I'm a
squishy dog lover. I have a dog, and I when
I look at my dog and imagine what Likeca was
going through, I just fall to pieces. At any rate,
the United States response to sput Nick was to go
(16:59):
back to the drawing board. They had their Vanguard design
that they had planned to launch, but that now felt
that it was no longer a strong enough offering. They
needed to come up with a better satellite to really
be a good response to the Soviet Union's project. So
the new USA project was called Explorer, and it was
(17:23):
led by a rocket scientist named Werner von Brown. Von
Brown was a brilliant physicist, a very intelligent rocket scientist,
but he had an incredibly dark past. UH. He was
born in Germany in nineteen twelve and he was part
of the Rocket Society as early as nineteen twenty nine.
(17:46):
As the Nazis gained power in Germany during the thirties,
von Brown chose to work for the German Army to
develop missiles. He wanted to continue his research and work,
and it seemed like the UH the most opportune place,
and his work was instrumental in the development of the
V two ballistic missile, which was a tool the Nazis
(18:11):
used to some effect, perhaps not as great as it
could have been, but certainly was a destructive weapon that
caused a lot of damage and death. He was eventually
awarded an honorary rank in the s s by Heinrich Himler.
It is said, however, that von Brown only accepted that
rank because he and his team were worried that Himmler
(18:33):
would be angry if he had declined it. So at
least some accounts state that von Brown didn't share the
political ideology of the Nazis. He just saw this as
the opportunity for him to actually do his work, and
if he didn't join the Nazis then he would not
be able to do his work. Von Brown realized that
(18:56):
Germany would lose the war. I think a lot of
people realized that it was getting to a point where
it was undeniable, and so he made plans to surrender
himself and his team of around five rockets scientists to
the Allies and offered to do research for the United
States to help them develop their ballistic missiles. Further so,
(19:17):
Fan Brown and his scientists would create a rocket research
center that originally fell under the guidance of the United
States Army, but eventually it would get shifted to a
new organization called NASA, which was founded mainly in reaction
to spot Nick and really be part of the space race.
(19:38):
Explorer one would launch on January thirty one, nineteen eight,
and it made an actual scientific discovery on its orbital flight.
It discovered magnetic radiation belts around the Earth, which are
now called the Van Allen Belt after one of the
lead researcher on the project. Now, these days, satellites are
(20:02):
way more sophisticated than spot Nick or even Explorer one,
and they typically use solar panels to capture solar energy
and convert it into electricity that is used to charge
batteries for power. Some of them actually use fuel cells
rather than batteries to generate electricity. And we've used nuclear
power in some probes that we've sent away from our planet,
(20:24):
but in general we tend to be a bit skittish
about the idea of putting nuclear power into stuff that's
going to be orbiting our own planet. Satellites tend to
have some pretty sophisticated stuff inside them. These days like
computer control systems, which were well beyond the abilities of
the early satellites which had electro mechanical controls. But now
(20:45):
we've got computer control systems, radio communications, attitude control systems.
Attitude in this case isn't about personality, but rather the
satellites orientation with respect to the position of the Earth.
And satellites can have different shaped orbits. Some have circular orbits,
which are very regular and uh and predictable, but some
(21:07):
have elliptical orbits. And elliptical orbits are interesting because a
satellite will travel at different speeds along its orbital path.
So there are two points along that path that we
call the foci of the elliptical orbit. The point that's
closest to the planet is the peerage, and that's the
point at which the satellite will be moving fastest through
(21:30):
its orbit. It's like think of it like the sling
shot effect. The furthest point from a planet. The furthest
point in the orbit of the satellites orbit from a
planet is the apogee, and that's where the satellite will
move the slowest in its orbital path. Now, launching a
satellite into orbit obviously requires rockets and in a rocket launch,
(21:51):
a special system is used called the inertial guidance system,
which calculates the adjustments needed to push a satellite into
the correct orbit. Talk about the different orbits in a second. Typically,
rockets are fired so that they head eastward, and that
means that the Earth's rotation gives those rockets a speed boost.
(22:11):
It's like the rockets are actually flying faster than they
really are because of the relative motion of the Earth.
If you were to launch your rocket at the equator,
you would get the biggest boost because the Earth bulgeon
is out there. It's the largest diameter. So here's how
you would determine the boost you get to your speed.
You take the Earth's circumference, which is about four thousand,
nine hundred miles or forty thousand, sixty kilometers. You figure
(22:36):
out how fast the Earth rotates, which is one full
rotation in approximately twenty four hours, which gives us a
speed of around one thousand, thirty eight miles per hour
or one thousand, six hundred sixty nine kilometers per hour.
That's the rotational speed of the Earth. That's typically that's
actually at the equator. If you were to look at
a launch facility at Cape canaveral. The rotational speed is
(22:57):
different because you're further north of the equator. You're not
at the thickest part of the Earth. Therefore, the circumference
is smaller and you have a slower speed, so a
slower rotational speed at that point, so it's closer to
around eight miles per hour or one thousand, four hundred
(23:17):
forty kilometers per hour. But that speed boost gives us
a big help. So to get the satellite into orbit,
you have to be going wicked fast, but not as
fast as what you would need to actually escape Earth's gravity.
So if you wanted to go out into space and
beyond Earth's gravity, you're leaving Earth orbit, you're heading out
to Mars or something. You would have to accelerate to
(23:38):
at least twenty five thousand, thirty nine miles per hour
or forty kilometers per hour to escape Earth's gravity and
enter outer space. Putting a satellite in orbit requires less speed,
and it all depends upon which orbit you're trying to
insert the satellite into. The orbits determine the speed, so
lower orbits require faster speeds, which might seem counterintuitive at first,
(24:03):
but you gotta remember those lower orbits that that speed
is meant to counteract the gravitational pull of Earth so
that the object in orbit remains in orbit, doesn't get
pulled back down to the ground. So when you're closer
to Earth, the force of gravity is greater. As you
probably remember, gravity is dependent upon two things, the mass
(24:24):
of two objects and their relative distance to one another.
So as distance increases gravitation gravitational pull decreases, and you
don't need to counteract that with more velocity to make
sure an object stays within its orbital path and doesn't
deteriorate and fall into the Earth. So higher orbits require
(24:45):
lower speeds, and if you get far enough out there,
you can have a satellite that orbits at the same
speed as Earth's rotation. Uh those would be geostationary orbits.
They would appear to be directly above a fixed point
on the Earth and they would not move from that point.
I'll get into that more in it just a second. First,
let's talk about the various types of orbits from an altitude,
(25:08):
because we can describe orbits in different ways. You can
describe their orbital pathway, whether it's circular or elliptical, you
can describe it in its altitude, and you can describe
it in its orientation as in, is it equatorial, is
it directly above the equator? Is there any degree of inclination? Uh?
Is it a polar orbit which goes north south not
(25:29):
east west? Lots of different ways to describe them. So
from an altitude perspective, we start with lower thorbit. That's
the one closest end to the Earth, and that's an
arrange that's between a hundred eleven miles and one thousand,
two hundred forty three miles above the surface of the Earth.
In kilometers that would be a hundred eighty to two
thousand uh. This tends to be the altitude we use
(25:51):
for satellites that collect surface observations, photography, weather satellites, that
kind of thing. When you go further out, you get
to medium Earth orbit that's in a zone that's between
one thousand, two hundred forty three miles and twenty two thousand,
two hundred twenty three miles or in kilometers way easier
two thousand to thirty six thousand kilometers. Navigation satellites like
(26:15):
GPS tend to be at this altitude, although summer at
higher altitudes. Then you get to geosynchronous orbit. That's when
you are at an altitude that's greater than twenty two
three miles, in other words, greater than thirty six thousand kilometers.
The orbital period is the same as the Earth's rotational period,
meaning it takes a full day for the satellite to
(26:36):
go all the way around the Earth. There is a
subset of geosynchronous satellites called geo stationary satellites, So all
geostationary satellites are also geosynchronous, but not all geosynchronous satellites
are geo stationary. If you have a geostationary satellite, that's
one of those satellites that remains over a fixed position
(26:59):
on the Earth's sir So you could build an antenna
at that point pointed straight up into the atmosphere and
it's going to be aimed directly at that satellite, and
as long as nothing changes in that satellite's orbit. Things
do change over time, so you have to correct it occasionally,
but as long as nothing changes, UH, the antenna and
(27:19):
satellite will always be in alignment. That's a geostationary satellite. UH.
It doesn't matter if it's day or night. You're always
going to have a direct line of sight between the
antenna and the satellite, and the satellite is gonna be
too far away from you to see it, but there's
a direct line of site as far as the antenna
is concerned. All geostationary satellites are geosynchronous, like I said,
(27:42):
But if the opposite isn't true, what's going on? How
are geo secret as satellites that aren't geo stationary? How
does that work? Well, the geosynchronous satellite does make one
orbit around the Earth in the same amount of time
it takes Earth to make one rotation in inertial or
fixed space, which is also called a sidereal day. It's
actually not twenty four hours, specifically, it is twenty three hours,
(28:06):
fifty six minutes and four seconds of mean solar time.
If the satellite has any inclination or a non circular
orbital path, it will not be geo stationary. The satellite
will appear to roam over the Earth's surface, so in
elliptical orbits, those egg shaped orbits, the satellite would be
moving at different speeds along its journey. Remember the paragean apogee.
(28:28):
It's going to be moving at at different velocities as
it goes around the Earth. Inclination, by the way, is
the angle between a reference plane and the orbital plane.
The reference plane in this case, UH, we're talking specifically
about the equator. So imagine you've got the Earth's globe,
You've got it tilted at a slight angle because the
(28:49):
axis is on an angle, and you've got the equator.
If you have a geosynchronous satellite directly above the equator,
it's going to be geo stationary. It's gonna stay around
that fixed point. But if you go north or south
of the equator and you place a satellite there, it
will it will not stay above a fixed point. Its
(29:12):
orbit is going to be slightly angled. That's the inclination
we would talk about. UH. So as it would go
around the pathway, uh, it would actually roam over the
surface of the Earth. So a satellite that has degrees
of inclination and its orbit with respect to the equator
will move north and south of the equator as it
(29:32):
completes an orbit. So this satellite is going to stay
more or less in the same east west area, but
it's going to go north south as it goes throughout
its orbit. Satellites with an elliptical path will drift east
and west from any fixed point on the Earth as
a satellite moves faster or slower through its Earth orbit.
We have seen there are several satellites that use this
(29:54):
where they are both the inclination and an elliptical path,
so they make this almost like a figure eight kind
of pattern over a general region of the Earth's surface,
which could be really useful for things like communication satellites
or or even GPS in that in that sense, there
are some GPS satellites that work under this principle. Geo
(30:18):
stationary satellites have a view of about of the Earth's surface.
Just a single geo stationary satellite can see about of
the Earth's surface from where it is. So if you
just create a network of a few geo stationary satellites,
you can get a view of practically the entire Earth,
really everything between eighty one degree south and eighty one
(30:41):
degrees north. Beyond those those uh those degrees, you wouldn't
be able to see it just from the way the
Earth is curved, but you'd get to see everything between
the two. Geo stationary satellites tend to be used for communications.
It's great solution for us on the ground because you
don't need to move the antenna on the surf to
stay in contact with the satellite. If the satellite we're drifting,
(31:04):
if it if it orbited the Earth multiple times during
a rotation, you would constantly have to adjust your antenna
to remain in contact with the satellite, and there will
be times where you would be out of contact with
the satellite. It would have the Earth between you and
the antenna. So geo stationary makes this easy because it's
always going to be directly above the antenna. So it
(31:26):
makes an ideal communication satellite in that respect, But there
are a limited number of slots for geostationary satellites. You know,
you could go to different altitudes, but you're going to
be you're going to be stuck at that equator plane.
So you don't want satellites to collide with one another.
Obviously they would destroy or at least damage one or
(31:48):
both satellites, and you don't want the actual data communication
to interfere with each other, so you have to separate
them out by space. You can't have them to pack
pecked in too closely together, and a satellite geo stationary
orbit will not stay there forever. Other gravitational forces from
the Sun and the Moon, plus the fact that the
(32:10):
Earth is not perfectly round, will cause the satellites to
increase in inclination over time, so they'll they'll start to
drift a little bit, and then they will no longer
be geo stationary UH satellites. They'll have thrusters on them
and fuel inside them in order to make small corrections,
which is called station keeping, and that's so that they
(32:32):
can stay in the right relative location. But once the
satellite is used up all its fuel, it will experience
an increase in inclination. It's unavoidable. You can't fix it
at that point, and it's possible, depending upon how the
satellite is located, that it could become a hazard to
other geo stationary or geosynchronous satellites. So normally, at the
(32:53):
end of a geostationary satellites useful lifespan will send a
command to the satellite to say, get the heck out
of the neighborhood. Boost it at a higher altitude, a
higher orbit, which moves out of the way of other satellites,
because it's not gonna be useful anyway, so you might
as well boost it further out and not have it
become space junk closer into the Earth. There's already a
(33:15):
lot of space junk that's out there. Fortunately, space is
really big, so while there's always a threat of space
junk being a problem with satellites, it's such a huge
space that the odds on any given day are fairly
low of an incident. But the more stuff we send
up there, the better the odds are that something bad
(33:35):
will happen. Now, not all orbits are in an east
west orientation. You're probably imagining that these satellites are orbiting
the Earth more or less in the same direction that
the Earth rotates, that they are going around and around, uh,
the same axis of rotation. Not all of them do.
Some of them are rotating north south. They're going around
(33:58):
uh the poles, you know, Poller orbits, which are really
good for photography and mapping because as these satellites move
north to south or south and north, depending upon which
way you're going, UM, the Earth is rotating under the satellites,
so they get a really good view of the Earth.
They're great if you want to have a satellite map
(34:21):
of a region. They're also not bad if you're hoping
for satellite to pass over a certain region on the
Earth so you can get a better look. In other words,
these are used for spying. And one particular type of orbit,
very specific type of orbit, is the mulnia or lightning orbit,
(34:41):
and the orbit takes its name from Soviet satellites that
use this particular style of orbit for communications networks. It's
an elliptical shape, which means the satellite spends a lot
of its time near the apogee poet point the of
the orbit, because that's where it moves the slowest. So
if you plan out the telemetry of your satellite in
(35:03):
such a way so that the apogee is over a
specific region, you know that when the satellite orbits the Earth,
it's gonna be spending the majority of its orbit over
where the apogee is. So if you locate it in
a place that you're interested in, you're gonna get more
coverage of that region throughout the duration of the orbit
(35:24):
of the satellite. So the Soviets planned the apoge to
be over the northern hemisphere so that they could serve
as a communications network and maybe also you know, spy
on Europe a little bit. Perhaps one thing we use
satellites for is to spread a signal from one location
to another. And this is a pretty simple idea. Actually,
it's just bouncing a signal off of a satellite. It's
(35:46):
almost like the satellite acts as a mirror, although it's
also an amplifier. So we use an antenna on the
Earth pointed up towards the satellite we're interested in, and
we beam as signal into space. It might be audio,
it might be video, it could be anything really, and
that antenna is the up link. Now the satellite receives this.
They have it has its own antenna and receives the
(36:08):
signal and then runs it through an amplifier and the
beams the amplified signal back down to the Earth. And
on Earth we have other antenna known as the down links,
that receive the incoming signal from the satellite. And using
this model, we can beam all sorts of useful stuff
like communication signals. Television studios would send feeds up to satellites,
(36:31):
which then act as a distribution system. So you would
have a centralized location where you would have the the
video feed, video and audio feed. You would send that
through an up link to a satellite that would receive
it and beam it back down to receiving stations, and
that was how you know, that's how we get television
broadcast beyond just over the air broadcast. In fact, if
(36:54):
you have a cable company, you could receive these signals
yourself using satellites. Right, you could have part of the
satellite TV system and you have your own little satellite
that's pointed up and you receive your television signals that way.
Or you could end up having cable but cable companies
also use this method. You would have a centralized location
(37:15):
that beams a signal up, it comes down so that
various cable distribution networks received the signal and then they
send that through the actual cables that eventually terminate at
your television. So this is a very important way of
using satellites. Now, I want to conclude this episode with
a quick discussion about how relativity affects satellites, both special
(37:41):
and general relativity. Now, these, of course, are the the
theories proposed by Einstein that ultimately proved true at least
in the case of time dilation, because we see it
in practice with satellites. One of the things we use
satellites for is GPS, the Global position system. So GPS
(38:03):
positioning system, I should say, and GPS is incredibly useful.
That's what lets us use real time maps on our
phones and GPS devices to go from point A to
point B. But in order for GPS to work, it
needs to be able to measure time very accurately, both
for the person who's on Earth and the satellite that
(38:25):
is providing the very satellites I should say that are
providing the information that allows us to UH to triangulate
where we are on the service of Earth. So here's
the problem. Time dilation. Einstein's theory gives us some uh
some issues with time. Special relativity tells us that the
faster we move relative to an independent observer, the slower
(38:52):
time seems to pass for ourselves. Um again, based upon
the relative observer to us, time will pass exactly the
same way. No matter how fast we're going we will
it will feel the same. So if you get on
a spaceship that's going near the speed of light and
you look at your watch, the second hand is going
to take away as if you were on Earth. But
(39:15):
to an independent observer, it would look like that second
hand is going super slow, and it would mean that
when you finished your journey and came back to Earth,
more time would appear to have passed on Earth than
it did for you, even though for people on Earth
time was passing normally, for you on the spaceship time
(39:36):
was passing normally. It's really only when you have this
point of reference that you realize that you've experienced different
amounts of time. Uh, it's kind of a mind bender, right. Well,
special relativity tells us that these clocks on board the
satellites will take a little more slowly because they're moving
so fast out in space. Uh, they should actually fall
(39:59):
behind the clocks here on Earth by about seven micro
seconds per day, which doesn't sound like a lot, but
if you're talking about very precise measurements to give you
an idea of where you are before long, that becomes
an insurmountable problem. So seven microseconds per day slower on
(40:21):
the satellites compared to the clocks on Earth. If that
were all there were to it, then we would just say, well,
we have to find a way, like a program that
will build in this error so that we know ahead
of time how to adjust for it. But it gets
more complicated than that. So that's special relativity. But general
relativity also plays a part. So one of the predictions
(40:44):
made by general relativity is that clocks closer to a
massive object will seem to tick more slowly than those
that are further away from a massive object. So if
we look at it that way, these satellites are very
are away from the surface of the Earth, so the
clocks on the surface of the Earth are much closer
to a massive object. The clocks on the satellites are
(41:07):
much further away from a massive object, and it's enough
to make a big difference. It also means that the
clocks on the satellites appear to be taking faster than
the clocks on the ground. So if you calculate a
prediction using general relativity as your basis for how fast
those clocks will be ticking on the satellites, you would
(41:28):
see that they'd be ahead of our ground clocks by
about forty five micro seconds per day. Now, this actually
means that you have to take the difference between the
forty five seconds in advance and the our forty five
micro seconds I'm sorry, forty five micro seconds in advance
from general relativity, and you have to subtract the seven
micro seconds behind from special relativity, and it tells you
(41:52):
that the clocks on board the satellites should take a
little bit faster than the clocks here on the ground,
by the tune of thirty eight my acrow seconds per day.
You take those forty five microseconds ahead general relativity, subtract
the seven microseconds from behind from special relativity, and you
get thirty eight microseconds ahead. Uh net. So it again
(42:15):
is enough for it to cause a high precision system
like GPS two have errors after just a few days,
so you have to correct for that. You actually have
to create a navigational fix so that the system is accurate. Uh.
(42:36):
Otherwise you would get errors in where the map would
say you were. You would look at the map, and
as time would go by, these errors would get worse
and worse, to the point where it would show you
locations that are just ridiculous, you blocks away from where
you actually were. And uh and more if time went
on long enough in the GPS satellite system was limited,
(43:00):
so you're talking about you know, errors of around ten
kilometers every day. That's that's a big deal. You know,
you're trying to get from point A to point B,
and you're getting errors that are ten kilometers off that
could be disastrous, so it would actually be useless after
a very few days. That's why you have to have
(43:22):
algorithms built in that take these relativistic effects into account
so that the results you get on your GPS device
remain accurate. So I think that's pretty cool that you know,
satellites are a practical way for us to see how
relativity can affect us, and that relativity is in fact real.
(43:44):
It's it's it's not it's not quote unquote just a theory.
It's something that we can observe directly and though and
know that this is at play. So I wanted to
mention that because you know, it's it's pretty cool stuff
and on slee When I was first looking into it
years ago, when I was looking at how GPS works,
(44:06):
I had a handle on special relativity. I understood that
the speed of the movement of the satellites would affect
how time passes compared to what we see here on
Earth on the surface, but I was not aware of
the effects of general relativity. That was something I had
(44:26):
to learn when I looked up GPS back in the day,
which I think was a Tuesday. If I'm not mistaken
so relatively obviously a very fascinating subject. I would love
to go into further detail, but I think that's more
of a stuff to blow your mind than a tech
stuff topic. We have, of course touched upon relativity a
(44:47):
few times in our conversations about various types of technology.
But maybe one day I'll get some stuff to blow
your mind folks in here, and then we'll have a
big discussion about relativity, not just what it is is,
but how it directly affects some of the things we do. Alright,
So that wraps up this discussion about satellites, and I
(45:10):
may do a future episode where I go into more
detail about the different types of satellites, the instrumentation that
is aboard these satellites, how they work, who owns them,
maybe some interesting stories about notable discoveries that satellites have
made and notable incidents that have happened because of satellites.
(45:32):
There's a lot of information out there and it's really
fascinating stuff. So that might end up being a future episode. Heck,
it might be the next one. I haven't yet scheduled
what my next episode will be, so keep any year
out for that. But if you guys have suggestions for
future episodes. Why don't you do what? What aisles? Did
(45:52):
you know? It was very helpful sending me a message,
whether it's on Twitter or Facebook or email. So the
email address for this show is text stuff at how
stuff works dot com or drop me a line on
Facebook or Twitter to handle it both of those as
tech stuff H s W and I'll talk to you again.
(46:14):
Really see for more on this and thousands of other topics.
Is it how stuff works dot com
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