Advent of Computing - Episode 111 - To Boldly Transmit

Episode Date: July 2, 2023

Space is cool, in all meanings of the word. Not only is it wondrous, vast, and fascinating, it can also be a cold place. It's also a very useful place to put things. This episode we are looking at the first practical use of space: communication satellites.   Selected Source:   https://archive.org/details/BigBounc1960 - The Big Bounce   https://archive.org/details/dtic-ada-141865-ieee-centenial-journal-1984-ocr/page/n67/mode/2up - A Signal Corp Space Opera   https://history.nasa.gov/SP-4308/ch6.htm - The Odyssey of Project Echo

In the body of law known as the Space Treaties, outer space is described as the common heritage of humanity. All peoples throughout history have looked up at the night sky in wonder. Everyone has felt the sun on their skin. Everyone has marveled at a full moon. When space is called our collective heritage, that's not just a lofty turn of phrase. It's quite literally true. Space is very fundamental to the shared human experience. And at the same time, space is a very real thing. Probably shouldn't say concrete because it is somewhat vacuous, but it does exist. It's out there waiting for us. It's not just paintings in the sky. In the past 70 or so years, us humans have sent up countless probes to check out space.

We've expended a huge amount of effort to try and understand what lies beyond Earth. Satellites have been sent into orbit. Probes have been sent to the very edge of our solar system. into orbit. Probes have been sent to the very edge of our solar system. We've even sent people to the moon. All this can make space seem very, well, ethereal. It's this outer realm that us humans have yet to fully comprehend. It's hostile. It's dangerous. It's rarely visited, except by the most intrepid. It has little actual bearing on our day-to-day lives. But that's not really the case. Space, as it turns out, also has its uses. Let me give you an example. I'm a great lover of the outdoors. I spend a lot of time out in the woods or out on mountains. Now, outside isn't always the safest place in the world.

A while back, I was hiking with a group of friends. We were on a trail that we assumed would be pretty straightforward and pretty clear, but after a few miles, it became covered in snowdrifts. We pretty quickly lost the trail. Luckily, we had a way out of that situation. Whenever I'm out in the hinterlands, I carry a GPS, a global positioning device. It's loaded up with topographic maps, and it can work out your location thanks to a fleet of satellites. With that GPS,

we were able to figure out where the trail was. Or, roughly where the trail was. And once things got too hairy, it helped us navigate back to the trailhead. On that day, satellites, something off in space so far away that I'll never see them, well, they had a very real impact on my life. So how do we get from looking up at the night sky to me and my buddies lost in the woods? How do we get from just wondering about space to having actual useful satellites? Welcome back to Advent of Computing. I'm your host, Sean Haas, and this is episode 111, To Boldly Transmit. Today, we're going to be taking a break from the hardcore digital stuff. Instead, we're talking about space. We're going to talk about how the final frontier was first leveraged

to truly useful ends. We're going to be talking about communication satellites. If that sounds boring, well, stifle the groan at least for a minute. The history of comm satellites is actually pretty weird. It's pretty wild. For instance, did you ever hear about the time the US Navy used the moon to relay radio transmissions? This has nothing to do with the Apollo programs or fancy radio gear in space. In 1946, some radio operators in the Navy figured that it might be possible to bounce waves off the moon. They even proved it could work.

The moon was quite literally used as a communication satellite throughout the 1960s. Needless to say, that's some pretty wacky stuff. At the same time, we're looking at a technology that's foundational to the modern world. There are some big, obvious uses of communication satellites, like satellite TV and satellite phones, but those have kind of fallen out of fashion lately. You'll still see TV dishes on occasion, and there are some use cases for satellite phones, but those two technologies aren't showing up everywhere. It's the behind-the- scenes stuff that's a lot more impactful. Satellites are still used to ferry around information on the back end of things. We're talking data distribution here. Things like local TV stations

pulling down programming from a remote satellite feed. Radio stations often bounce beams off satellites to get audio from station to station. Another example of somewhat undercover operation is the GPS. Few of us own dedicated GPS devices, but that functionality is baked into all kinds of modern tech. In these instances, communication satellites kind of blend into the background. There's also something kind of awkward going on here. You see, we have the internet these days. You might have heard of it. The world is wreathed in these crystalline threads that can send data from continent to continent, aka fiber optic cables. Many of the old use cases for satellites have been subsumed by the worldwide

network. The ultimate joke here is that satellite technology gave us a way to break free of cumbersome undersea cables, but in the current day, those very cables have clawed their way back to relevance. But let's disregard that for a little bit. Let's live in the past. Today, we're going to be taking a meandering path, as is custom on Advent of Computing. I want to look at why communication satellites were developed in the first place, what kinds of problems were trying to be solved, and why was space seen as a viable solution. I want to trace the development from literally bouncing beams off the moon to more complex electronic beasts. If we want to be technical, then the first communication

satellite was also the first artificial satellite. I'm referring, of course, to Sputnik. I think there's a fundamental misunderstanding that we have about Sputnik here in the West. I was always taught that the satellite was wildly primitive, that it was really just a metal sphere the size of a softball that put out a radio signal. In most American narratives, Sputnik is almost described as a show of force. At least, that's the subtext. The satellite went up, the USSR announced that they were now in space, and there was a radio signal to prove it. This led directly to the space race, itself something of a proxy battle in the Cold War. This Sputnik crisis, also in kind of a strange connection,

led to a lot of funding for scientific research. It helped to jumpstart a lot of computer science departments. Just something weird that links everything together. Now, parts of this telling are true, but only parts. Sputnik was primitive, but only in comparison to later satellites. That said, we aren't dealing with a simple beeping ball. To start with, this was a pretty large satellite, at least it's bigger than I ever thought it was. I'm used to just seeing photos of the sphere itself, which don't really help you figure out scale. All the models that I've seen in aerospace museums are usually tucked up kind of high. Sputnik was just under two feet across, and it weighed 180 pounds. That's a little bigger than a softball.

Inside that sphere was a big battery, temperature sensors, barometric pressure sensors, and a radio transmitter. The transmitter was wired up to a set of four antennas that trailed behind the satellite. Sputnik would broadcast two signals, one at 40 MHz and one at 20 MHz, that indicated the status of the satellite. megahertz that indicated the status of the satellite. This just sounded like uniform beeps to most observers, but to Sputnik's operators, that beeping encoded information. The duration of those beeps corresponded to the temperature and pressure inside the satellite. The satellite itself was sealed and filled with nitrogen, hence why there is even a barometric pressure sensor inside the thing. There was a good deal more information that could be gleaned from Sputnik's beeps.

Position, of course, could be worked out. As could velocity and acceleration. These measurements were used to calculate things like air resistance while in orbit. The point here is that Sputnik wasn't just a beeping ball. This is very much an experimental satellite that was sent up for scientific purposes. The satellite reached orbit in 1957 and would remain functional for 22 days. It would take about two months for it to burn up in the Earth's atmosphere. That's the general mission profile, which gives us a good starting point. Sputnik isn't exactly a communication satellite, it's more just an experimental platform. But potato patato, it put out radio waves.

It's close enough for our purposes. The first important feature of Sputnik is the most simple one. It's built to survive in space. Outside the Earth's atmosphere, you're subject to an entirely different set of conditions. Space is often called a vacuum, and that's mostly true. There isn't any air in space, or at least there isn't as much as we're used to. This means that there isn't much pressure. There is technically some gas, especially if you're in a low orbit like Sputnik was. This is what eventually got the satellite. After 140 orbits, the drag from the small amount of air it came into contact with caused it to

slow down and re-enter the Earth's atmosphere. There are also different types of radiation encountered in orbit that are normally blocked out by our atmosphere. Throw in the whole temperature thing and, I think it's fair to say, space is truly another country. Even nearby orbits make for extreme conditions. These conditions introduce unique challenges. Normal electronics are designed to work well on Earth. Take something like the

humble and lovable resistor. A resistor is usually rated for some maximum operating temperature. If it gets too hot, then it won't resist the same amount of current. You may even be able to get the magic smoke to come out of the thing, in which case, well, they'll just totally stop operating. If you're running a circuit that you expect to heat up, then you can get around that by providing some type of cooling. Maybe you slap a heatsink on the resistor, throw a fan to blow cold air over the grill, and you're probably good. But what if there isn't any cool air to circulate? What if you're operating in an environment that's already too hot for the resistor to handle? Space-bound temperature control systems just have to be different than their terrestrial counterparts. Sputnik had a pretty primitive pass

at this. The capsule was sealed and filled with nitrogen, which could be circulated with a fan. The fan was controlled by a temperature sensor. The idea was that a little airflow could help cool things off. Not the best solution, but it's something. Temperature in space in general is a little weird. The main driver is direct solar radiation. Here on Earth, a hot day has a number of mediating factors. Cloud cover can change how heat is trapped or dispersed. Different surfaces will hold or reflect heat around the environment. Humidity or wind will change everything.

Even the air plays a role in transferring around energy. You don't get that in orbit. If you're in the sun, you'll be heating up, and if you're in the shade, then you'll be cooling down, at least somewhat cooling down. It gets weird without air. The point is, not only do you have to worry about overheating, but you also have to deal with extreme cold in certain situations. You also get rapid temperature fluctuations.

This will depend on the orbit. How much time is spent in Earth's shadow versus direct sunlight will be determined by how exactly you're orbiting the Earth. Numbers aren't super clear, but we're dealing with hundreds of degrees of difference. On the cold side, a satellite might reach minus 150 degrees Celsius, and on the hot side, you'd be burning up at over 150 degrees. At least, that seems like a rough middle ground between different readings I've seen. This, again, introduces something of a problem. Metals will expand and contract slightly based

off their temperature. This thermal expansion is an issue, especially for tight-fitting parts. That's one of the reasons that Sputnik had a pressure sensor inside. A concern was that the hermetic seal could be broken as the satellite was subjected to temperature changes. I'm not even dealing with radiation effects here, since, well, that's a huge can of worms. Radiation can do weird things to electronics. Suffice to say, space-bound systems have a very unique set of challenges to deal with. Why bother with all this work? Why even send up Sputnik in the first place?

Well, putting aside all the Cold War and all the political implications, let's just look at data. During its short voyage, Sputnik was able to provide a good deal of information about space. All of that information was communicated via radio. We've already touched on this, and I'm going to expand a little here. One of the mission objectives for Sputnik was to measure how radio was attenuated as it travels from low earth orbit back to the ground. This was something of an unknown at the time. Electromagnetic waves are funny things. There's a whole branch of physics that describes how they function, but for today, I want to just pull out one idea. What happens to a wave as it travels? The short answer is, it attenuates. That sounds nice, but it doesn't tell you much.

So, a wave, such as a radio wave, has some characteristic wavelength. That's the measurement from one peak of the wave to the next. This can also be flipped and expressed as a frequency, how many peaks you receive in a given amount of time. A wave also has an associated energy, which gets a little funky to talk about. There's a relationship between energy and frequency, but I want to nix that for now. I just want to talk about energy as how much oomph is behind a wave, how loud the received transmission is. Attenuation just means that as a wave travels, it loses energy. It gets less loud. It loses some of its oomph and impact. That's a huge simplification, and I hope none of my college professors are listening to this episode, but let's just work with this.

Attenuation depends on a number of factors. In a perfect vacuum, a wave could travel on forever, but that doesn't ever actually happen. There's no such thing as a perfect vacuum. A wave will lose energy if it gets absorbed by anything, if it hits anything. This could be gas, liquid, solid, animal, vegetable, or even mineral. Anything that a wave hits can take away some of its energy. In the 1950s, it wasn't entirely clear how much gas would be in low Earth orbit or what kind, so it wasn't exactly known how much Sputnik's radio signals would attenuate. There's also the possibility of interference. If there are waves of similar frequency bouncing

around, your signal will get lost. All these factors come together to mess with communication. But what does get to the ground? Well, that can be very useful. Not only can you pull information from the signal itself, assuming it did arrive, you can also get information based off how the signal has been attenuated or interfered with. A simple beep can turn into pages of data. That's Sputnik, and I think it gives us a good idea of the very basics of communication satellites. You just have to have something in orbit that sends out information. That's easy enough. So what's the next step? Well, that's simple. It's the relay.

Once again, this is a case of context, context, context. Terrestrial communications used to really suck. Electromagnetic signals such as radio, well, they only really travel in a straight line, excepting some weird phenomenons. Now, with most antennas, you do end up with a sphere, but that's just a straight line traced out in all possible directions. The point is, if you aren't in line of sight of a radio tower, then you won't be receiving a signal. in line of sight of a radio tower, then you won't be receiving a signal. The Earth, as it turns out, is spherical. So any radio transmission has this inherent horizon issue. You can pump all the power you want into your transmitter, but you won't be able to reliably push past the visible horizon. There are some caveats here. Certain signals can be bounced off the ionosphere,

which lets them travel past the horizon. This only happens with certain frequency waves and is heavily impacted by atmospheric conditions. You can take advantage of this to pick up very distant shortwave radio transmissions, for instance. You can also sometimes pick up CB radio transmissions from way far away, but it's a limited solution. It only happens sometimes. The other option for communication is the humble wire. You see, by extruding a conductor, you can create a channel which, under specific conditions, can be used to propagate an electrical wave. In other words, you make a wire.

You can run it down, you can make a really long one, and then you send a signal down it. This is first used for telegraphs, and as technology has improved, we've reached the point where any data can be sent down a wire. But this comes with its own set of issues. Electrical signals also attenuate as they travel down a line. This is due to electrical resistance, but it's a very similar phenomenon to radio attenuation. The signal can only travel so far before it becomes useless. So, just like line-of-sight radio, wired communications also have a distinct limit. They have their own type of horizon. The common solution to this problem is the repeater. This is, simply put, something that

can receive a signal and then send it back out. My favorite way to explain this falls back to the very first visual telegraph system. These were composed of towers that were evenly spaced throughout the countryside. Each tower was topped with big flags that could be moved around from a control room. Each tower also contained a human, the brains of the operation. Now, on its own, a message from a tower could only be received at visual range. The system of towers were spaced out so that each tower could see its two neighbors. Repeating a signal was simple. You start by flipping up the flags at one end of the line.

The first tower throws out a signal. The operator in the next tower sees that signal and then adjusts their flags accordingly. This propagates down the line until the final tower is displaying the same signal as the first. This all works because you have these intermediate towers that receive and repeat the signals they see. It's simple, and it's very effective. The same mechanism is used to extend the range of wired and wireless communications. It's allowed us to do some truly wacky things. Take undersea cables, for instance. The first undersea telegraph cables relayed between Europe and North America, and they worked, but there were issues with some signals degrading as they ran across the Atlantic Ocean.

This was fixed in the 1950s by the TAT-1 cables. These ran under the same span of the Atlantic, but they included tiny vacuum tube repeaters. A signal would go down the cable and, before it could degrade entirely, would be picked up, reformed, and amplified by one of these repeating circuits. This meant that a signal coming out of a TAT-1 cable would be much closer to the signal that went into that wire. Radio repeaters work in the same way, just with radio waves instead of electrical currents. For radio, however, repeaters offer other advantages. With wired communications, you can always string a wire somewhere. You just get more of it. You can wrap the entire earth in cables, as we have done in the modern era. That can easily go past the horizon. With radio, however, you have a few options.

You could do the classic repeater thing, setting up loads of towers to bounce signals around. That gets you past the horizon. Or, if you're feeling ambitious, you could make a tall tower. Just make something as tall as you want. Sputnik was heard around the world in part because it was the highest radio transmitter in history. At least, up to that point. Now that I've laid some groundwork, we can start to get into the truly strange story of space-bound radio. We're going to start off by looking at the most basic approach. Passive satellites. And that all starts with a little thing called

Project Echo. The space race would begin in earnest in 1958 with the launch of Explorer 1. This was the first American satellite to reach orbit. I mean, it's not really much of a race if the USSR is the only party playing. During this period, everything was experimental. Satellites were relatively simple with all the caveats I've already explained. Simple takes on a different meaning in the realm of aerospace. While the Sputnik and Explorer satellites were servicing scientific objectives, they weren't really useful. By that, I mean they didn't do anything besides send down data. useful. By that, I mean they didn't do anything besides send down data. That is very nice,

but it's not a real application of cutting-edge technology. The first pass at this, or at least more the first big public passes, was Project Echo, which aimed to create a radio repeater in space. This, by its very nature, would push at the edge of the possible. Echo was planned to be a passive repeater. It's just something to bounce radio waves off of. That may sound kind of, well, dumb. But trust me, this is a totally workable solution. Radio waves will bounce off certain surfaces. In fact, all waves do. I'm sure you've seen this in a body of water. When you throw a pebble into a pond, you first generate waves. After a while, those waves hit the edge of the pond and bounce back. That's the basic idea of Project Echo. Make something good at reflecting specifically radio waves, and then you shoot it into space. The idea of bouncing waves around

wasn't new. Certain radio waves could be bounced around the ionosphere, like I mentioned earlier. But that wasn't a super reliable method of communications. It's a lot more of a cool phenomenon than an actual method for long-distance radio communications. For this type of bouncing to work, you need a reliable reflector. You want to have something with a well-known location and an unchanging reflectivity. Space enters into the whole beam bouncing equation pretty quickly. In To See the Unseen, author Andrew J. Batryka lays out a history of radar astronomy. For the uninitiated, radar is basically a form of radio communications. You're using a transmitter to send out a radio

wave, then you listen for the wave to return. How it bounces back tells you something about what's between you and some target. I didn't expect this to be connected to communication satellites, but here we are. It turns out that radar researchers were some of the first people to contemplate shooting radio waves into space. One of the earliest among those was John DeWitt Jr. He was a radio technician by trade and hobby, working at Bell Labs for a number of years before becoming an engineer at WSM. Now, this took me a second to get. WSM isn't some kind of lab or company.

It's a local radio station. This is all a tangent, but I think you'll find it worthwhile. I'm trying to build up the bones that make Project Echo interesting. So, DeWitt was working at this radio station in Nashville. Around this time, Carl Jansky, also an employee of Bell Labs, discovered something called star noise. There was this known interference around 20 hertz signals that could be detected on any stock radio. Jansky was the first to show that at least some of that interference was coming from outside the Earth's atmosphere. In other words, stars and whatever else was out in space were producing waves around 20 hertz. This discovery inspired DeWitt to try something wild.

It looked like radio waves could be used to pull information out of space. So, why not pick a target nearby? Why not send out your own waves? The closest target at hand was the moon. Now, the moon itself doesn't produce radio waves, but that really doesn't matter. We can make our own at any time given a large enough antenna and enough power. DeWitt figured that he should be able to bounce a radio wave off the moon and then receive the reflection. That reflected wave could be used to glean all sorts of information, specifically about what lay between Earth and the

moon. We're talking data about space, the atmosphere, and maybe even some properties of the moon's surface itself. In To See the Unseen, we get an almost comical accounting of events. As the station engineer at WSM, DeWitt had control of all the radio hardware he could ever want. Sure, it wasn't research-grade equipment like Bell had, but it was something. So here's the setup. It's the summer of 1940. DeWitt is sitting at work, most likely after hours. He switches around some wires and steers a radio dish to point at the moon. At the press of a button, he sends 80 watts of power up from his dish at WSM and nothing happens. DeWitt isn't able to detect any reflected waves, but a lack of detection doesn't necessarily mean nothing was reflected back. The point of this little side adventure is to explain that passive radio repeaters in space, while they may sound far-fetched,

but by 1940 the idea was out there. People were trying it. The technology was also kind of ready. That's where Project Echo comes into play. Instead of using the moon, NASA would send up its own reflector, its own miniature moon. But this wouldn't just be any old mirror. The whole moon bounce idea actually holds some really good merit. The moon is a sphere. That's an irrefutable fact as much as some may deny it. A sphere makes for a good reflector, since it's round and since it's uniform. You can actually just blast it from anywhere and get a reflection. What's more, you don't need to steer a sphere. You just get a big ball up in space and you're done. As long as you know roughly where the ball is, you can send a wave up to it.

The angle of reflection also follows well-known equations, so a transmitter can figure out where their signal will land based off where the sphere is. It just vastly simplifies things. Plus, at this point, almost everything in space was spherical. There are only a few exceptions to this rule, so you gotta stay round. That's the general plan for Project Echo. Just get a big sphere in space. While simple enough, this presents some very annoying issues.

You can't just put a giant steel sphere on the end of a rocket and launch it up and hope all goes well. There are two big problems there, size and weight. Rockets in this era were relatively small, at least compared to later developments. We're not talking about a Saturn V rocket that could probably move a house into space. The Echo satellites were planned to be conservatively 100 feet across. That is way too wide for any rocket. A solid metal ball of that size would also weigh tons and tons. That'd be way too heavy for an old-school rocket to launch into space. The way around this was to make Echo a giant reflective balloon. So yeah, we're basically talking about balloons in space. Once again, this sounds deceptively

simple. You may think that one could just throw a balloon into space, inflate it, and you'd be good to go. That actually just straight up doesn't work. NASA and Norman Krabill, the lead engineer on the project, also fell into this trap. The first attempt at ECHO was just a fancy balloon. To be fair, the plan was a little more complicated than just throw a balloon into space. This test balloon was made out of mylar, a thin plastic sheet that was coated in an equally thin layer of aluminum. It's the kind of stuff that weather balloons are made out of. That balloon was deflated and folded into a tight cylinder, but it wasn't deflated completely.

A very small amount of air was left inside the balloon. This theory here is pretty smart. The pressure in space is much lower than on Earth. If you put a sealed container in space, it will experience a pressure differential that could cause it to expand. You've probably seen this demo done using a vacuum chamber. You put just a little bit of air in a balloon, tie it off, and throw it into a vacuum chamber. At normal pressure, the balloon isn't anywhere near inflated. It looks kind of sad and floppy. Once the vacuum comes on, you can watch the balloon expand as if by magic.

This isn't actually magic, however. It's just how pressure works in a vacuum. The first Echo satellite was supposed to do the same thing. It worked, just perhaps too well. James Hansen gives a really fun description of this whole fiasco in the book Spaceflight Revolution, which I've been pulling from heavily for this section. But to quote directly, in the early hours of 28 October 1959, five days after the close of the first NASA inspection, people up and down the Atlantic coast witnessed a brilliant show of little lights flashing in the sky. The strange display, not unlike that of distant fireworks, lasted for about ten minutes.

From New England to South Carolina, reports of extraordinary sightings came pouring into police and fire departments, newspaper offices, and television and radio stations. What were these mysterious flecks of light flashing overhead? Was it a meteor shower? More Sputniks? UFOs? Something NASA had finally managed to launch into space? End quote. NASA had finally managed to launch into space? End quote. What was causing this light show? Let's think back to that vacuum chamber demo. What would happen if you put a little too much air into the balloon before putting it in the vacuum chamber? Well, that's pretty simple. You end up with a burst balloon, assuming there's enough space in the chamber for the balloon to expand. That's exactly what happened during this first test of Project Echo. The balloon made

it up around 60 miles, just to the edge of space. It detached from the rocket, it started to inflate, and it didn't stop inflating. The whole thing just burst and it came raining down somewhere over the Atlantic Ocean. There had just been too much air in the folded balloon. It would take some re-engineering to get Echo up and running. Eventually, there would be two successful launches that didn't burst. The first, named Echo 1, was a lot more complicated than the test flight. Gone was the semi-filled balloon. In its place was an active inflation system. Echo-1 was inflated by sublimation.

It had a chamber full of some chemicals that, under certain conditions, would sublimate from a solid into a gas. This provided positive pressure inside the balloon, instead of relying on prepackaged air. I'm not super clear on the reaction going on here. The chemicals involved were benzoic acid and anthraquinone. I assume there must have been some kind of relation between the rate of sublimation and pressure. Otherwise, Echo-1 would have also exploded, but my chemistry is rusty and it was never very good in the first place. So, if a chemist is listening, I'd love to hear an explanation for this.

Now, when fully inflated, Echo One was 100 feet across. That makes it, frankly, real darn big. That also made it a nice target for radio dishes. It also also made it a nice target for micrometeoroids. If you haven't heard of this phenomenon before, then let me just say you're in for a bit of a treat. Micrometeoroids are just tiny little dudes that buzz around in space. We're talking objects anywhere from the size of a grain of dust up to maybe a small pebble. Space isn't exactly full of these little fellas, but there are a surprising amount of them floating around. So here's the issue. Micrometeoroids tend to move very fast.

It's hard to pin down exact numbers, but I've seen one figure from NASA that pegs it at 22,000 miles an hour. That is a wild amount of speed. These little dudes are a problem for modern spacecraft, even with mitigation measures. For Echo 1, well, micrometeoroids were a macro problem. were a macro problem. The skin of the balloon was microscopically thin, so an object didn't even need to be going that fast to puncture it. This was another reason for the sublimation-based inflation. The idea was that echo would have a constant source of gas to counteract the effects of a leak. It kinda worked, but after a few days, the sphere became a little bit off-round. This wasn't ideal for prolonged use, but it was enough to prove a point.

Echo 1 was sent into service in August of 1960. Soon thereafter, the first transmission would be bounced through that relay. Bell Labs had been involved during the whole project because, well, they're Bell. At this point, Bell was involved with almost anything electronic. It's thanks to this connection that we get a beautiful promotional video called The Big Bounce. Preserved in this tape is the moment of the first transmission. Either that or perhaps a recreation. Anyway, the first transmission was actually from

a tape recorder. The Jet Propulsion Laboratory in California pointed a radar dish up to Echo 1 and blasted off the message, while a special-built receiver at Bell Labs in New Jersey was listening. The process went in the other direction as well, with the lab in New Jersey sending a wave back to the lab in California. The first message? Why, it was a recording of sitting president Dwight D. Eisenhower. Apparently, NASA also liked Ike. I'm going to play you the message that shows up in the big bounce, but I want to make one thing clear. I'm not entirely sure this is an actual recording of what was bounced off and received from Echo. You'll see what I mean in a second here, so let's run the tape. This is President Eisenhower speaking. It is a great personal satisfaction to participate in this first experiment in communications involving the use of the satellite

balloon known as Echo. This is one more significant step in the United States program of space research and exploration. The program is being carried forward vigorously by the United States for peaceful purposes for the benefit of all mankind. The satellite balloon which has reflected these words may be used freely by any nation for similar experiments in its own interest. Information necessary to prepare for such participation was widely distributed some weeks ago.

The United States will continue to make freely available to the world the scientific information acquired from this and other experiments in its program of space exploration. The degradation there, I'm pretty sure, is from the archival scan of this tape. I don't think it was ever produced with the best quality, but I want you to notice how clear the actual spoken word is there. If this was actually bounced off Echo, there should be some amount of weird degradation going on.

It should at least sound muffled, but it doesn't. That's kind of what makes me think that this big bounce video might have just been using the pre-recorded tape instead of the actual recording of the received transmission. I also want to make one other thing clear. Echo One wasn't technically the first relay satellite. It was the first passive relay satellite, and we'll get to why that distinction matters later. The moral of this project is that even simple things get complicated in space. Out in the inky black, things go wrong. The very conditions themselves lead to strange solutions.

This is very easily reinforced by Echo 2, the second successful launch by Project Echo. Echo 2 was a much more engineered balloon. It was bigger than the first Echo, coming in at 148 feet across. It inflated using a similar sublimation method, but here's the biggie. Echo 2 was rigid, or at least semi-rigid. This is where we get into wild engineering that I only partially understand. Previous Echo balloons were made out of a metalized mylar, just a thin plastic polymer sheet with a thin metal coating on one side. Echo 2, on the other hand, was made out of separate layers of material. It had an outer aluminum foil layer, then a layer of non-metalized mylar, then another layer of aluminum foil. Between each layer was a thermal-sensitive glue.

As the balloon unfolded and inflated, the layers would push up against each other and the glue would start to set. I'm not entirely sure where the heat to set the glue is coming from, and it's described by NASA as a proprietary chemical, so we just have to trust them on this one. The balloon would slightly over-inflate during this process. That over-inflation would stretch the aluminum layers so they would hold the less flexible mylar tight as the layers laminated together. Once the glue finished setting, Echo 2 was rigid. At least, it was rigid enough that it didn't require internal pressure to stay spherical. In this way, the balloon wasn't as susceptible to micrometeoroids. That's about as far as we get with these artificial reflectors. They worked, and we found ways to make them

relatively reliable, but they were also kind of a blip on the radar. There are just inherent problems with these types of radio systems. We can best see the issues by circling back to the moon. During World War II, DeWitt, the one-time radio engineer of WSM Nashville, worked as a radar technician. The two fields are pretty related, after all. Both used radio transceivers just for different applications. In 1946, just after the war, DeWitt was still in charge of a radar outfit at Camp Evans. He took the opportunity to revisit his old experiment. He and his team made modifications to an existing radar dish and were successful in bouncing a

signal off the moon. A series of pulses were sent up, bounced off the surface of the moon, and then received back at Camp Evans. The change in those pulses was then used to tease out new data about the moon, space, and our very atmosphere. It's a cool application of existing technology. In the coming years, these moon echoes would be used by the US military for a number of applications. But there's an issue. It takes a lot of power to bounce radio off the moon. DeWitt's first successful experiment used a 3-kilowatt transmitter.

That's not a massive amount of power, but it's enough that you need a dedicated setup. You couldn't do this with a handheld antenna, for instance. The signals that bounced back were also very weak. You need powerful antennas to receive the echoes. DeWitt was finally successful because he had access, quite literally, to military-grade equipment. The way around these issues was, of course, some kind of active satellite relay, something that would receive and either amplify or reshape a signal before retransmitting it. But that would introduce its own problems. At least, it could. Here's where the timeline gets muddy and kind of falls apart. Remember how I said Echo-1 was the first passive relay satellite? Well, here's when that distinction matters. By the time Echo-1 was

in space, the US military had already constructed and launched an active relay satellite. However, we don't get super great details about this program. The project was called SCORE, Signal Communications by Orbiting Relay Equipment. It was launched in 1958, which puts it about two years before ECHO-1. in 1958, which puts it about two years before Echo 1. The story of SCORE not only ruins my earlier narrative about space leading to unique challenges, it also messes up a lot of timelines. It's also kind of difficult to track down details about SCORE. This is partly because SCORE was a pretty secret project. It was funded by ARPA, the development of the payload was handled by the Army Corps of Engineers, and the launch was handled by the Air Force. It would

become public, but only after it was in space, and it was quickly overshadowed by other developments. SCORE was also kind of a slapdash affair, reaching orbit in the winter of 1958. This was scant months after the project began. Is that enough of a tease for you? The best source on SCORE that I've been able to track down is an article written by Brigadier General H. McD. Brown, titled A Signal Core Space Odyssey, SCORE and Beyond. It's a good source because, among other things, Brown was heavily involved in the project. The only scan I can find is in pretty rough condition, but it's enough to give us a window into this weird satellite project. Brown doesn't trace the origins of SCORE back to

radar or Russian satellites. Instead, he invokes science fiction. This is something that you'll see brought up in any discussion of the history of satellites. At first, I kind of assumed that was an anachronism. It sounded similar to how the history of computer viruses is often traced back to a sci-fi short story. That story, The Scarred Man, wasn't very well known until well after the first viruses hit the scene. The whole satellite sci-fi thing must be similar, right? Well, no. Here's what Brown has to say on the matter. Right from the start of the satellite program in 1955, the Signal Corps, and particularly SRDI,

the Signal Corps, and particularly SRDI, had been crusading through proposals, presentations, and recommendations for the early utilization of satellites for its communications needs. The basic idea was by no means new. In science fiction stories, satellites had long been loaded with communications gear, and realistic and detailed theoretical studies existed in the open literature since 1952, but something practical had to be done about it now. End quote. We don't get a citation to that 1952 year, but we can tease out a fun story. There were books and short stories discussing space travel as far back as the 1930s. And that, I might add, is a conservative date. We could make stretches to interpret even older writings as depicting space travel and

satellites, but let's stick with the 30s as a good, reasonable starting point. The most common work cited as pre-space age writing is a 1945 article by Arthur C. Clarke. The article, titled Extraterrestrial Relays, was published in the magazine Wireless World. Now, it's easy to get confused about this. Clarke was a sci-fi author. His stuff is actually quite good. I can recommend it. Specifically, he writes pretty hard sci-fi. His books are very detail-oriented and usually grounded in some type of reality. That reality might be speculative, but everything comes back to some kind of scientific explanation. But this article isn't science fiction. It's a real discussion of the hows and whys of communication relays in space. Clark even has

diagrams and references. You don't usually see works cited in sci-fi. This Clark article, at least in my head, bridges a gap between earlier science fiction and more speculative work by actual scientists. As it turns out, research wasn't far behind the speculation. By the early 50s, we do get honest-to-goodness studies on satellites and space travel. These early writings give way to early plans. By 1955, Project Orbiter, the first coordinated attempt in the US to throw something into space, was underway. This was followed by a number of other teams and projects, both public, private, and covert. The point I'm getting to is there was movement in this sector. One early concern was, quite frankly, public relations. You see, NASA wouldn't be

established until 1958. By the time we reach Project ECHO, the new National Aeronautics and Space Administration is ready to roll. This is really important to our story because NASA is a civilian organization. It's funded by the government, but it exists somewhat independently from the feds. It's not actually administered by the executive branch, and it's not part of the military. That all would get hammered out as NASA formed. Previous to that, oh, things were a bit up in the air, if you pardon the pun. Was space going to be handled by the federal government? If so, which branch would be in charge of things? Would the military build satellites and operate missions outside our atmosphere, or should that fall to the judiciary?

Perhaps private companies and universities should pick up the slack. These were all open questions. One very specific question was, what kind of launch vehicles would be used for space exploration? Now, that might sound kind of trivial. It's gotta be rockets, right? But what kind of rockets? The U.S. Army favored the use of Atlas rockets, while the Navy preferred the use of non-military craft. The distinction here matters because the Atlas wasn't just any rocket. It was an ICBM, an Intercontinental Ballistic Missile. It was literally a weapon of war. The Army plan was to just flip some switches and change its

target from the USSR to up. I think it's clear to see why flying an ICBM into orbit might raise some eyebrows. That's not to mention the fact that Atlas was running behind schedule in the 1950s, while the Feds were trying to figure out the whole space thing. When Echo 1 was launched, a variant of a Delta rocket was used. This was still based off an earlier ballistic missile, but it's not on the same level as Atlas. It's not a tool meant to destroy Moscow. Getting back to the point, things were in flux during this period. In the middle of the whole shakeup, we get the start of SCORE. As Brown explains, the Army and its Signal Corps were keen on getting their own satellites into orbit. The Army proper was interested in space-based surveillance, while the Signal Corps was more interested in, what else, signaling.

They wanted to work up some kind of space-based relay system for radio messaging. With the launch of Sputnik, things kicked into overdrive for basically any program that was at all related to space. Initially, the Signal Corps was offered a space on some other space-bound payload. Brown calls it, quite aptly, a piggyback ride. But priorities would shift. Through a series of meetings, the folk at the Signal Corps were able to convince the Secretary of the Army that communication, not surveillance, should take priority. From there, everything went really quickly, to quote Brown again. Within a few days, we received an urgent telephone call from the office of the chief signal officer, prompted by ARPA.

It requested a quick answer to what kind of satellite communications equipment we could put together in 60 days if we were allowed a weight of 150 pounds on a rocket which would be sent into orbit. End quote. I just gotta love this image. Score goes from, hey, maybe you'll get some space sometime to, what can you give me in 60 days? For context, Project Echo took about two years to land their first balloon in orbit. so SCORE was really set up to move at a breakneck pace. Once we get to the technical details of the satellite, things get, well, they get more wacky. That's just the best way I can put it. The launch vehicle supplied by

the Army was of course an Atlas ICBM. Specifically, an Atlas B rocket was used. Previously, these had been tested as bomb delivery systems, but they had an extra one. This isn't some special variant that was kitted out for space either. This is 100% an ICBM. The only difference is that instead of carrying a warhead, the army would throw in whatever 150-pound payload the Signal Corps cooked up. So far, all the satellites we've talked about have pretty similar mission profiles. The payload is loaded into a rocket. The rocket is shot up into space. Sometimes there are multiple stages that separate out. But once the rocket reaches the right spot, the payload,

read satellite, separates from the rocket. The satellite then does its business and eventually burns up on re-entry. The separation here is a key feature of these missions. The actual satellite is housed in some protective shell that flies away once it's in orbit. The satellite and the rocket are separate entities in that sense. Maybe you'll see where I'm going with this. As Brown put it, the entire 9,000 pound Atlas missile was going to be launched into orbit. No separation, no stages, just a whole ICBM parked above Earth. No separation meant that the payload was actually just going to be sitting in some empty space inside the missile. That space was the nose cone, the so-called fairing pod. During normal operations, that would be where a bomb would be. So, just to make this as clear as possible,

the plan was to straight up replace a bomb with some radio equipment, launch it, and call it a satellite. The equipment in question sounds pretty simple. It was just a radio relay. The only major complications were that it held a tape recorder and could be controlled by radio signaling. The tape here is an interesting choice. SCORE could operate in a store and forward mode. The ground crew would send up a message for SCORE to store on its magnetic tape. Once the message was received, the satellite would simply replay the audio as it flew through the inky black. This makes SCORE a little more complicated than a normal relay. It does a few more steps than just repeating a message. The reason for this complication is simple. The signal core wasn't sure they'd be

able to test a normal relay given SCORE's orbit. SCORE was sent up to a pretty low orbit. It was, at most, 114 miles above the Earth's surface. To add some context, it's pretty well agreed upon that space starts at 60 miles up. Sputnik 1's height was somewhere around 133 miles up. That was its highest point. There are more factors, but in general, things in lower orbits tend to fall back to Earth more easily. These orbits are more like spirals than circles. Sputnik only lasted two months. Score would orbit lower, weigh more, and be bigger, more area for drag to build up on. So it wouldn't even stay up for one month. The short projected lifespan made the whole store and forward mode of operation sound pretty good.

Now, this should already sound kind of janky, but it gets better. The Signal Corps was concerned that their relay system might fail once it was in space. This is the final frontier, after all. We just don't know exactly how well electronics hold up in orbit. At this point, the US had successfully launched four satellites into orbit, so we had some data, but not very much. So what did Brigadier General Brown and his co-workers do? Did they over-engineer some fancy tape deck? Did they create a new type of antenna? Well, they might have. We don't have a whole lot of good detail

on the actual payload. I have one multi-generational photocopy of an image of the relay. But from what I can tell, overengineering wasn't their primary solution. Oh no. They just made two radio relays. They straight up went for two of them. Which, I mean, fair enough. That's redundancy. They must have each weighed less than 75 pounds. On launch day, this would actually pay off. Once SCORE was in orbit, it was discovered that the first relay, the primary in the system, just didn't work. It wouldn't respond to commands and it didn't transmit. So, with a shot of a radio beam, SCORE was switched to its redundant systems.

Luckily, the second take worked a charm. Now, we should stop and appreciate the absurdity of this all. SCORE was a straight-up ICBM with two tape recorders and an antenna jammed into it. The entire rocket was put into orbit, which, at the time, made SCORE the biggest human-made object in space. The payload, the tape-based relay, was built in a matter of months. The actual timeline got pushed out a little bit, I think it ended up being 90 days for development, but that's still a really fast turnaround, might have been the fastest satellite ever developed at that point. To top this all off, we have the initial message. SCORE was set to launch with its tapes pre-recorded

This way, if there was a total system failure, then hey, maybe SCORE would still transmit something According to Brown, the signal core recorded some test message, but at the last minute, it was changed It was the Eisenhower administration, after all So, who better to deliver the message than the big man himself? Now, we get a pretty similar message to what we heard in Echo, but with the added twist of the overall militant context. It sounded like this. This is the President of the United States speaking. speaking. Through the marvels of scientific advance, my voice is coming to you from a satellite circling in outer space. My message is a simple one. Through this unique means,

I convey to you and to all mankind America's wish for peace on Earth and goodwill toward men everywhere. This message is also kind of why I think that what was recorded in the big bounce is not actually what was bounced. This audio already is a little bit degraded from coming down from SCORE's antennas. And that's with an active relay, a good relay. If we actually did have a recording that was bounced off Echo, it should sound worse than this active recording from SCORE. Anyway, that's the first honest-to-goodness communication satellite. It's an ICBM that was thrown into orbit,

and it came with a message of peace and goodwill from President Eisenhower. With a few flips, switches, and a different payload, the same rocket would have been used for World War III. I think that should give us an idea of just how rough and ready some of these early satellites really were. early satellites really were. Alright, that brings us to the end of this episode, the conclusion to today's space opera. What can I say? This hasn't been a super digital episode, but I wanted to talk about space, and it's my podcast anyway, so sometimes I get to talk about space as a treat. my podcast anyway, so sometimes I get to talk about space as a treat. I thought there'd be some grand lesson here about the design challenges of satellites, about how new technology would rise to the occasion, but that's not exactly the case. You can work up a really fancy machine to launch

out into space. Even Sputnik, the first artificial satellite, was pretty sophisticated. Even the echo satellites, literally giant balloons, they had complicated engineering behind them. Those were both doing space the right way, if there is a right way. On the other hand, we have SCORE, a very Wild West approach to the whole endeavor. And hey, who am I to judge? SCORE worked even without special sealed domes and inert nitrogen atmospheres or self-laminating walls. You can, actually, just throw stuff into a missile and point it up. There's something I really like about that.

Now, these early probes would set the stage for more advanced communication satellites. In 1962, only a few years after Project Echo, the first TV broadcast was relayed from Europe to America via space. That broadcast traveled through a satellite known as Telstar-1, a purpose-built satellite designed for the challenges of space. Telstar-1 was, as is traditional, a sphere. And its launch vehicle, the Thor-Abel rocket, was partly derived from earlier ballistic missiles. I think it's only fitting that, even as technology changes, some things will stay very firmly

within the family. Thanks for listening to Advent of Computing. I'll be back in two weeks' time with another piece of computing history. And hey, if you like the show, there are a few ways you can support it. If you know someone else who'd be interested in the computing's past, then please take a minute to share the show with them. You can also rate and review on Apple Podcasts. If you want to support the show directly, you can sign up as a patron on Patreon or get Advent of Computing merch. Patrons get early access to episodes,

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