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Up, up the long, delirious, burning blue
I’ve topped the wind-swept heights with easy grace.
Where never lark, or even eagle flew—
And, while with silent, lifting mind I’ve trod
The high untrespassed sanctity of space,
—Put out my hand, and touched the face of God.
• John Gillespie Magee, Jr., “High Flight,” 1941
One thing you’ll immediately notice about this poem is that he never once talks about price. This is the kind of glaring technical omission often made in poetry, so we’re adding one more couplet:
And when I asked what space was priced,
I turned around, ’cause HOLY CHRIST!
Right this second, it runs you about $10,000 to send a pound to space.
That’s about $2,500 per cheeseburger.
This is why human beings have only been to the moon’s surface half a dozen times, and it’s why our moon vehicles were paper thin in places. The fact that in 2017 we have a space travel paradigm that would’ve disappointed all the hopes of 1969 is not due to a lack of engineering or scientific genius. It’s because the cost of the way we get to space has remained stubbornly high. If we could dramatically reduce the cost, we would have better space science, better communication systems, access to off-planet resources, better ability to control our climate, and best of all, the solar system would open up for exploration and settlement.
To understand why it’s currently so expensive to get stuff up to space, you need to understand what you’re looking at when you see a rocket.
A rocket is essentially a tube of explosive propellant with a liiiittle bit of cargo on top. For a typical mission going to Low Earth Orbit (LEO; about 300 miles high, and where most launches go), by mass you’re looking at 80% fuel, 16% the rocket itself, and 4% cargo (4% is actually on the high end, and if you’re going farther out, it gets closer to 1 or 2%).
But when you look at cost, things are inverted. The propellant is a negligible component of price—it’s gonna run you a mere few hundred thousand dollars. So most of the cost is taken up by the rocket itself, which is almost always discarded after use.
In sum, launching rockets is really expensive and most of the space onboard is taken up by propellant. This leaves two ways we can try to drastically lower the cost to make space access cheap:
Vehicle recovery suddenly became a reality in 2015, which we’ll get into in the section on reusable rockets. But the basic idea is pretty simple—you can save money if you don’t junk your vehicle after one use.
Using less propellant is a little trickier, even though propellant is 80% of a spacecraft’s starting mass. To understand why, consider a situation where you have to drive from Russia to South Africa and back again. You’re offered two ways to get your fuel:
Of course, you’d rather use option 1. But consider why, in particular.
A car is just a machine that converts fuel into forward motion. If your car is really heavy, it takes more fuel to get a certain amount of forward motion. If you gas up regularly, most of your weight is the car and not the fuel. This means the fuel the engine is using right this second is supplying forward motion mostly to the vehicle (and you, and your luggage) and not to the fuel in the tank.
In the case of option 2, you’re dragging an enormous tanker. The weight of fuel is probably far, far higher than the weight of the car itself. Especially at the beginning, you’re using most of the energy derived from the fuel just to move the fuel itself. So most of the fuel’s energy goes to moving other fuel.
The result? The total amount of fuel you need is far higher in case 2 than in case 1. Your little caravan, just like all space rockets, is mostly made of fuel, not of vehicle or cargo.
Unfortunately, it’s a little hard to build gas stations for rockets. So without a major change, we’re stuck in scenario 2 when it comes to space travel.
All of this sets up some very tantalizing math. If you could make the launch vehicle recoverable, you could potentially eliminate 90% of the cost of space launch. Or, if you could use just three quarters as much fuel, you’d be able to fit six times as much cargo,
instantly dividing the cost per pound by six.
The hard thing here is that you’re fighting fundamental physics. The cheapest orbit available is LEO. People often think that “orbit” means there’s no gravity. This is incorrect. In fact, the International Space Station (which is in LEO right now) is usually around 250 miles high and experiences about 90% of the gravity you experience on Earth. So why do the astronauts float around like there’s no gravity? Because they are going really, really, really fast. About 5 miles per second. Although they are pulled toward the Earth all the time, they always “miss” it.
Think of it like this: Imagine you fire a cannonball from the top of a tower. If you fire it softly, the ball will go a little ways then fall to the ground. If you fire it incredibly fast, it will just fly off into space. But between falling right down and going off into space, there are a lot of intermediate regimes. For a given height, there is some speed that is slow enough that it can’t leave Earth, but fast enough that you’ll never plop to the ground. If you were riding that cannonball, you’d be falling, because gravity is tugging you down. At the same time, because you’re going so fast, you’d be able to see Earth’s curve. As you move from a point on the globe in a straight line, Earth curves down and away from you, increasing your distance from the surface. At this particular speed, you have two balanced effects: Gravity wants you down low, but your speed keeps you up high. So you just keep going around and around and around. You “orbit.”
Even though LEO is the cheapest orbit to achieve, it’s still pretty expensive to get there. Getting a big hunk of metal to 5 miles per second is not an easy task. If we ever want spaceships that look like the ones in movies instead of giant tin cans wrapped in foil, we’re going to need a cheaper way.
Where Are We Now?
Reusable rockets are the best bet for cheaper spaceflight in the short term. They are traditional rockets, but rather than falling into the ocean as they do now, they fall to Earth and land after they finish the mission. This doesn’t fix the problem that the rocket only holds 4% cargo, but it potentially drives the cost way down.
There are a few difficulties with this approach, though. You have to keep extra propellant onboard for the landing phase, which lowers efficiency. You want to carry the smallest amount of extra propellant possible, but this makes the landing phase very hard.
A very serious issue is that nobody yet knows what it’ll cost to refurbish a used rocket. This thing has gone to space, man. You can’t just put a spit shine on it and put it back on the launchpad.
The U.S. Space Shuttle, which was designed to be a reusable launch vehicle, ended up being more costly than a regular rocket precisely because refurbishing was so expensive. There’s an ongoing argument over whose fault this was—the engineers, Congress, the Air Force, a risk-averse public, and more—but the bottom line is that the program was largely done in by the cost of getting the Shuttle launch ready again after a flight. This is why, when lots of people were sad about the Shuttle retiring, a lot of space nerds were glad to see it go.
But there is reason to hope that a better reusable launch vehicle can be created. As we were writing this chapter, SpaceX became the first company to successfully put cargo into space, then land part of its rocket.
If it really can bring the price down, this may prove to be the biggest development in space travel in a generation. As we were watching a launch, a reader of ours tweeted that although he had witnessed the moon landing as a young boy, he found the reusable rocket even more exciting. It sounds crazy, but he’s got a point—the moon landing was certainly the greater technical feat, but it was done at a cost that more or less guaranteed it couldn’t become commonplace. Exactly how much the cost can be dropped is a matter of debate. Elon Musk apparently claimed he could eventually get the cost down by a factor of 100. In the more near term, SpaceX’s president Gwynne Shotwell said their current Falcon 9 should be able to offer a 30% discount. But even if reusable rockets only mean a small price drop now, they may yet represent a path to greater future savings. The road to Mars may be paved with small discounts.
Airplanes already go really high. Can’t we just have them go a bit higher so they get to space?
No. Why would you even ask that? Jesus.
If you want to put a satellite in orbit, the hard part is not going really high. The hard part is going really fast. That takes a lot of propellant. But using a spaceplane might allow a serious reduction. To understand why, you have to understand what propellant is.
If you refer to propellant as “fuel,” a NASA engineer will beat you with a TI-83.
Propellant is actually a combination of two things: fuel and oxidizer. When you want a combustion reaction, you need three things: fuel, oxidizer, and energy. For example, when you light a campfire, the fuel is wood, the oxidizer is (you guessed it) oxygen, and the energy is a lit match.
In a rocket, you carry both fuel and oxidizer inside the ship. The actual ratio of oxidizer to fuel varies by rocket and mission, but generally speaking the
majority
of the propellant’s mass is oxidizer. The oxidizer is often just liquid oxygen.
Why carry all that liquid oxygen when the rocket is literally surrounded by oxygen for much of its trip?
The short version is that we’re keeping it simple. A rocket is a brute force way to get to space. You put everything you need in a big tube and blast your way skyward. With an airplane, you might be able to improve your efficiency by getting your oxidizer from the air rather than carrying it with you, but you’re adding a lot more complexity to an already complicated machine.
The big problem for a spaceplane is that you need multiple types of engines to handle all the different speeds and conditions you encounter en route to space. Here’s why:
Most airplanes today use a turbofan engine. They’re a bit complicated, but the basic mechanism is simple. Fans suck air into a chamber. The air is compressed, so you have a lot of oxygen (your oxidizer!) in a small space. Fuel is injected and ignited. The result is hot compressed air that you channel out the back as you suck in more air. Now, you’ve got high-pressure air behind the engine and comparatively low pressure in front of the engine. So you go forward.
Turbofans start having trouble when you get toward the speed of sound, at about 767 miles per hour,
also known as Mach 1. At the speed of sound, the air can’t get around the plane as fast as it builds up. This creates problems if your front intake is a fan.
One solution to getting over this hump is what’s called an afterburner. An afterburner takes leftover oxygen at the back of your turbofan, throws more fuel at it, and ignites it. In short, you make a little ongoing fuel explosion at the back of your plane. By this means you can get toward Mach 1.5, though not terribly efficiently. But once you’re at Mach 1.5, you can use a different type of engine called a ramjet.
A ramjet is an incredibly simple machine, but it’s not necessarily easy to make. Basically, you have a turbofan engine minus all moving parts, including the fan. You don’t need a fan to compress the air because your high speed is doing it for you. You fly fast, and air crams into a chamber where it slows down as you add fuel and ignite. The downside here is that because speed itself is your compressor, you can’t start with a ramjet. You can only use a ramjet once you’re going about 1100 miles per hour. So, for example, on an SR-71 spy plane, you have a turbofan that changes its shape to behave like a ramjet once you get to the right speed.
Once you get really, really fast (but still not fast enough to stay in LEO), you need a supersonic ramjet, or “scramjet.” A scramjet is an even simpler machine that is even harder to build. Basically, supersonic air comes in and, along with fuel, gets ignited directly, without ever slowing it down. You can do this because the oxygen is coming so fast, there’s enough to get a combustion reaction going without compression. But it’s not easy to, so to speak, light a candle in supersonic wind. Scramjets are still experimental, but after about 4500 miles per hour
they become the most efficient way to go. In theory, they can take you all the way up to Mach 25, which is orbital speed. There have been a number of
scramjet programs, most of them military, and all have met with only limited success. None of them have yet come anywhere near orbital velocity.
An ideal spaceplane should be able to make use of all these engine types in sequence to get to space. Once in space, where there is no available oxygen, you will probably switch over to a traditional rocket propellant method. But by using oxygen from the air instead of an onboard tank, you can cut down fuel use enough that you might be able to carry ten times more cargo.
Oh, and since it’s a plane, it can just land afterward. If this can be done repeatedly, without too much damage, you’ve solved the vehicle loss problem and the fuel efficiency problem.
The hard part is that all these machines have to work under extreme conditions. The conditions a scramjet is optimized for are so extreme that they’re expensive just to simulate down here on Earth.
A British firm called Reaction Engines is working on a vehicle called Skylon, which uses an engine called SABRE, for Synergetic Air-Breathing Rocket Engine. We’re guessing they came up with the “ABRE” part quickly, then spent a few days deciding on an S . In short, it’s a rocket, but it takes in ambient oxygen as part of its thrust reaction. Their engine is designed to efficiently switch from a turbofan to a ramjet to a rocket. Presumably they aren’t doing a scramjet phase because, well, nobody really knows how to do the scramjet phase.
It’s an expensive, complicated endeavor, but they do have substantial funding from the European Space Agency
and the British government. If things go well, they hope to field one of these advanced planes in the next decade.
For all the downsides of rockets, they have the virtue of simplicity. An old-fashioned rocket works just fine in low speed or high speed, in thick atmosphere, thin atmosphere, and no atmosphere. So, hey, how about we try something even more old-fashioned?
One way to save on rocket fuel is not to use any. Earlier we discussed how rockets are encumbered by the need to use propellant to accelerate propellant. What if instead of running a relatively slow controlled burn all the way to space, we had one giant boom down here on the ground? Sure, you have to use a lot of explosives overall, but none of those explosions are used to lift more explosives. This should save a lot of overall energy.
Mind you, it won’t be cheap. It’s a cannon that would probably be thousands of feet long, with a barrel on the order of 10 feet in diameter, packed with literally tons of explosives. But there are advantages: no discarded parts, no using fuel to carry fuel, and pretty much every bit of each shot actually goes to space.
It’s not quite as crazy as it sounds, and there have been at least two well-funded government projects to explore this method, one of which we discuss in the nota bene for this chapter. But there are two major drawbacks:
First, every time you fire, you have to create an enormous explosion. So if you want to use this thing repeatedly without too much expense, you need some kind of chamber that can withstand several tons of explosive material being detonated regularly.
Second, getting shot out of a cannon isn’t very fun. Well actually, if you were shot out of a space cannon, it wouldn’t be fun or not fun. You’d just be splatted.
It’s not the speed that kills you. It’s the acceleration—the change in speed.
When you go up in an elevator, you feel as if you’re getting squashed. That’s a slight acceleration. By comparison, on a roller coaster, you may feel as much as five times more acceleration. With training, humans can endure about ten or twenty times the elevator without passing out. Much beyond that and you might die. Why? Well, when you accelerate in a car, notice how the water in a cup rushes back and stays back until you stop accelerating. Imagine the cup is your
body and the water is your blood. Oh, and instead of 0 to 60 in 10 seconds, you’re going from 0 to 17,000.
For an explosion-based space cannon, you’re talking around 5,000 to 10,000 times the elevator. Nothing squishy is going to space in a cannon, including squishy little you.
This may not be as bad as it seems. You could still send “hardened” payloads, like specially designed electronics. You could also send all sorts of raw material—metals, plastics, fuel, water, beef jerky. In fact, one idea is to have a sort of orbiting gas station that just receives fuel payloads from a gun.
By itself, a space gun is not a great route to space exploration. But if you coupled a space gun with an orbiting factory in space, we might be in business. The idea here would be to fire raw materials up to your orbiting factory, build gigantic spacecraft at the factory, and then take off from the factory to go explore space. For annoyingly delicate payloads, like humans, you’d still need a wussier form of launch, like rockets. But on a big space mission that’s already in space, most of what you’re toting is metal, plastic, and supplies for the delicate meatbags within. All these things can be “ruggedized” and shot to orbit.
Another option is to have a gun that speeds up slowly enough that the cargo experiences a more human-friendly level of acceleration.
For instance, you could have a sequence of explosions, spreading the acceleration over time. The downside is that you’re taking an expensive and difficult system and making it more expensive and more difficult. Now you’ve got dozens of explosions instead of one, which means a longer barrel and a lot more potential for error.
Another option is to have an electromagnetic railgun. Basically, you start with a magnetically levitated train. These “MagLev” trains float on a magnetic field, which is important because with conventional rail, beyond a certain velocity you’ll start bending and even melting the tracks. You put this vehicle and its track in an airless tube that is about 100 miles long. Then you keep using powerful magnetic fields to boost its speed. It’s basically explosive speed boosts without the boom. The upside is the method is a lot cleaner and easier to reuse. The downside is the necessary materials—specifically the ultralong evacuated tube and train system—would be much more expensive.
But this too has a problem: Even if you spread the acceleration out over time, the projectile at some point must exit the tube, going from an airless environment into the atmosphere at hypervelocity.
To understand what happens when the projectile exits the tube, consider this: Moving through air is the same as having air move past you. It’s air particles thwacking against your body. The most extreme winds on Earth happen in tornados, and the fastest winds recorded are around 300 miles per hour. If you want to reach orbit at the right velocity, you need to be fifty to a hundred times faster than that as you fire out of the cannon.
At that speed, the air is fighting you so hard that it will literally ignite. So not only have you got a lot of air drag, you also have an explosion. Not great for cargo.
One way around this problem is to build the tunnel structure so high that the cargo doesn’t leave the tube until it’s in the thin upper atmosphere. The atmosphere gets less dense very rapidly once you get around 25 miles up. The issue with this approach is that we don’t know how to build anything that stands 25 miles tall. The tallest structure humans have ever made is about half a mile from bottom to top,
and it’s a skyscraper, not a launch track. Even if we knew how to build it, it would cost an insane amount of money.
But people are still trying to make gun methods work, and there are a couple variants on this concept, including two of the best-named ideas in this chapter: the “Slingatron” and the “rocket sled.”
The Slingatron is a railgun on a spiral track. We talked to Jason Derleth from NASA Innovative Advanced Concepts (NIAC), which is a sort of asylum for people with really crazy space ideas that just might work. He told us, “The Slingatron is unfortunately highly unlikely to work. I really like it. I think that it’s a brilliant idea, but what ends up happening is you have to put it at the top of Mount Everest for it to have even a chance, because it’s fighting air resistance the entire time.”
The rocket sled is basically another railgun, but instead of accelerating the projectile, it’s accelerating a sled that carries a rocket. The sled goes really fast, getting you up to high speed into the thinner part of the atmosphere. Once you’re up high, you start up the rocket. The extra speed and height get you a serious fuel savings . Plus, you’ve got a rocket sled.
All these methods could potentially be combined with a ramjet/scramjet system. Remember, those work once you’re fast, and are necessarily designed to handle extreme conditions. But, as with all hybrid systems, you’re developing something even more complicated and perhaps only getting a bit more efficiency.
Which leads us to this other concept we learned about from Mr. Derleth.
“One of the most interesting ideas that I heard was ludicrous on the face of it, okay? Really, really stupid... One person suggested, well, why don’t we just put the shuttle on a pogo stick? I mean, an actual mechanical thing that you can press down, like a big spring, and give it a little bit more oomph at the beginning. It sounds so stupid, and yet, you probably could actually get another percent more payload if you did something like that. It’s brilliant, it’s really neat.”
Rockets basically work by firing hot stuff out the back. The hotter it fires, the more of a boost you get per volume of propellant. One way you might get things really hot would be to have a super-high-powered laser onboard to zap the fuel to extremes of heat. But this would weigh so much that it wouldn’t be worth it.
So scientists had an idea that probably left astronauts unenthusiastic: Could we fire a laser right up the rear end of a flying rocket? When we mentioned this to European Space Agency’s Michel van Pelt, he pointed out, “This may be just something to get used to. I mean, if you told people fifty, sixty years ago that you would go into orbit basically sitting on a pile of rocket fuel, basically a controlled explosion, that also probably doesn’t sound too appealing either.”
You could save a lot of fuel this way. In fact, one group suggested that with a powerful enough laser, you could use zero fuel up to the first 7 miles of atmosphere. You could gain speed simply by megaheating the air under the rocket. Once you get high enough, you have to use fuel, but thanks to the added laser heat you’d still need far less.
The problem? We’re talking a huge, HUGE laser—in terms of power output, something on the order of 50,000 megawatts. That’s roughly equivalent to the combined output of fifty nuclear reactors all at once. Mind you, you only have to fire the laser for about ten minutes. But even if that weren’t an insane amount of energy, well, we don’t even know how to build a laser that powerful. The most powerful lasers that can fire continuously are U.S. military weapons, and they top out around 1 megawatt. And they only fire for about a minute.
That said, if we could build giant megalasers, there might be an additional bonus for rocketry. One group at Brown recently suggested that a powerful laser could be used to reduce air drag by as much as 95%.
Imagine this: As you are being laser-blasted up, a second laser is being fired into the region ahead of you. This makes the air ahead of you less dense, so there’s less to bump into. Now your astronauts might get a little antsy, since they’re flying at well past the speed of sound with ultrapowerful lasers before and behind them, but you could solve this problem by just calling them cowards.
As a bonus, having a thin air patch with denser air around it can even help steer the rocket, for the same reason that if you’re running through a bar, you will naturally move through the area with a less dense crowd.
One issue with all this, if you’re a wimp , is that a 50,000-megawatt laser is an incredible weapon. Like, you could instantly incinerate just about anything from a long distance. This might make for some geopolitical headaches. But hey, maybe if we show other countries how cool our DOUBLE-LASER ROCKET is, they’ll care less about the existential risk it poses to all nations on Earth. Or at least they’ll say less about it.
Okay, so as we discussed, altitude isn’t your main foe—speed is. However, starting at high altitude does mean you start at the thin part of the atmosphere. Once you’re about 6 miles high, the air is 90% thinner. This is why airplanes spend so much fuel to get up high. Once you’re at 38,000 feet (about 7 miles high), there’s way less air drag.
We are going to focus on three proposals for starting up high: the rockoon, the stratospheric spaceport, and the aircraft-launched rocket.
A rockoon is just a rocket that gets floated up by a balloon, then hits the ignition once it’s up high. It’s really not a good way to go for a big rocket. Once a balloon is going up, you pretty much have no fine control over it. This is less than ideal when you’re about to ignite a skyscraper-sized tube of propellant. Rockoons were tried back in the fifties, but were quickly abandoned as a method for space launch. Still, dedicated nerds occasionally fly them to get nifty photos and, we suspect, to use the word “rockoon.”
But couldn’t we have a stratospheric spaceport? Pretty please? Could we?
A modern rigid airship (picture a slightly more sleek zeppelin) can carry around 10 tons of cargo. A modern rocket, fully fueled, weighs about 500 tons. As awesome as a fifty-blimp armada sounds, it’s not going to be cheap or easy to maintain.
Alternatively, you could create the giant spaceport purely to hold up the launch end of the MagLev track described earlier. That way, you get a high-elevation exit from the launch tube without having to build a permanent 25-mile-high structure. But in order to do this, now you need an even larger floating structure, since it has to hold an enormous track.
Long story short, big airships are likely to be a bad way to go. We mention it mostly because it’s the first idea most people have when they think about space launch alternatives. Despite being an idea we’d really, really like to be good, it’s solving the wrong problem. You need speed, not altitude.
The aircraft-launched rocket is a bit more interesting, and has already been employed by Virgin Galactic and others to reach space. Basically, you get a gigantic plane (or, in one proposal, the equivalent of two 747s strapped together) and you tie your rocket to the bottom or top. You get up as fast and high as you can go and launch the rocket. The idea is that by starting out with some speed and altitude, you can save some propellant. Also, because you’re launching from a plane, you don’t have to worry so much about weather conditions. If the weather is bad, just fly the rocket to somewhere with smooth air.
The problem is that you’re only getting a few percent of the speed you need and a few percent of the altitude you need. So the savings are likely to be very small. And the trade-off is that you have to launch a big, hot rocket from a megaplane, which is going to add to cost and complexity while limiting the size of the rocket. SpaceX, which has already shown its interest in changing the way space launch works, rejected the aircraft launch method for just these reasons.
Imagine you’ve got a big rock spinning around Earth. Attached to the rock is a ribbonlike cable, about 62,000 miles long. It goes all the way down to the surface of the Earth, where specially designed elevators take cargo, travelers, and spacecraft up and down.
This idea may seem outlandish, but it’s been quite well studied (particularly by former NIAC fellow Dr. Bradley Edwards), perhaps because it would represent the ultimate solution to space travel needs. All the problems with all the other methods are fixed by a space elevator, though not without adding some new and unique challenges.
Having vehicles going up and down the cables means you can send fuel as you go. It means you don’t have to accelerate quickly. No discarded parts, no dangerous explosives, and no slamming into an unwelcoming atmosphere. You just ride to the orbit you want, picking up speed relative to Earth’s surface because the tether itself is already in orbit.
Here’s roughly what it might look like:
The main pieces are a counterweight, a cable, and a base station.
The counterweight is there to make sure that the center of mass for the whole system (including the enormous cable) is at what’s called geostationary orbit.
If a thing is in geostationary orbit that just means that if you are sitting at the equator and looking up through a telescope, the thing will always be at the same point. It’s revolving around the Earth as fast as the Earth is turning. And it’s at a particular velocity and distance that means it naturally keeps whirling around Earth without needing a boost at any time.
We’ll skip the orbital mechanics, but the basic results are that the cable is relatively taut, but not so taut that it rips apart; and the counterweight doesn’t loop around the Earth, tying the cable around the equator like a giant spool of thread.
How you would get a counterweight is another matter, but there are three common proposals—capture a near-Earth asteroid, gather a lot of the space crap we’ve left up there over the years, or just have the cable be soooooo long that its sheer mass will hold the cable taut. We find the idea of a gigantic asteroid base to be the most romantic, so we’ll go with that.
Down from your asteroid base, you’ve got a cable that has a high specific strength. This means it’s strong enough to resist breaking, but it’s also very lightweight. This is important, because if the rope is strong but heavy, its own weight will pull it apart. If the rope is weak but light, it’ll snap the first time it encounters rough conditions, like the high atmospheric winds of Earth.
Supposing you can build the cable, the last part is your base station down on Earth. Most proposals call for a moveable sea platform. This is because a moveable platform can maneuver away from bad weather and can adjust the position of the cable in order to avoid space junk higher up. Also, out at sea there is no law.
Well, okay, there’s some law. In fact, it’s called the Law of the Sea. But none of it pertains to cables going to space.
The laws that’ll govern a space elevator are actually pretty important. It was our sense that most scientists who work on this stuff would like the space elevator, if it’s ever built, to be something that no single nation controls. If one nation alone has cheap space access, that’s a pretty big power asymmetry. So, from a let’s-not-all-kill-each-other perspective, having joint ownership of the means of cheap launch might be good.
Once this system is operational, researchers estimate that cargo could go to space for under $250 per pound, very fast and very safe.
As a bonus, once you build one, building another is a lot cheaper. After all, the big initial expense is going to be launching all that cable by conventional means.
Most likely, we will also have base stations along the way up. These can serve as fuel and maintenance depots, as well as launch points for satellites and spacecraft. One of the best features of this design is that you can reach different altitudes just by climbing up and down the cable. Once you reach 300 miles up, you’re in Low Earth Orbit, like most satellites. Go a lot higher and you get to geostationary orbit, which is great for communications satellites, but right now costs a fortune to reach. Beyond that, you get to where Earth has very little gravitational pull. So you’re like a rock at the tip of a sling. If you want to get fired into space, just hop out of the station.
This last point is especially exciting for those of us who watched a lot of Star Trek . If you can get anywhere you want simply by climbing (instead of carrying fuel onboard), not only is satellite launch cheap, launching very large spacecraft is cheap too. More than any other method that seems feasible this century, the space elevator would open up the solar system to human exploration.
So why not do it?
Well, there are a lot of technical challenges, but the greatest of all is what the hell do we make the cable out of?
The unit of specific strength is the Yuri, named for Yuri Artsutanov, a pioneer of the space elevator concept, whose last name was apparently too hard to pronounce. Depending on who you ask, an ideal cable material should be 30 million to 80 million Yuris. For reference, titanium is about 300,000 Yuris and Kevlar is about 2.5 million Yuris. Regular materials will not do.
The most promising candidate material is called carbon nanotube. Imagine a molecule made entirely of carbon atoms, but shaped like a straw, with its width a small fraction of the thickness of a human hair.
It turns out that if you have pure carbon nanotubes with no imperfections,
they can get into the 50- or 60-million-Yuri range, meaning they
might
work as a space cable. The problem is that carbon nanotubes are a relatively recent discovery, and we’re still pretty bad at making them. The longest nanotube ever created was made in 2013, and made headlines all over the place, and... it was about a foot and a half long.
You can, of course, weave these fibers together, but the smaller the pieces of the weave, the worse your specific strength becomes and the more imperfections there are likely to be. A long, taut cable is only as good as its weakest part, and if your cable breaks at any point, someone in a cable car is gonna have a real bad afternoon.
The long-term question is whether a market exists to make better and better materials. According to NIAC’s Dr. Ron Turner, “Theoretically, and materials-wise, the carbon nanotube could become plenty strong enough... for a space elevator. Terrestrially, there wasn’t much of a market after a certain point, so the carbon nanotube fibers have not continued to grow as strong as the space elevator would need.”
Even supposing we could get the fibers long enough, Mr. Derleth points out an issue for carbon nanotubes: “The material is very sensitive to electricity, and so if it ends up having a lightning strike happen, it will disintegrate a large portion of the ribbon.... Thankfully, there’s a solution to this; unfortunately, it’s not a very satisfactory one, intellectually. There is an area of the Pacific Ocean that has never had a recorded lightning strike. So you’d place your space elevator there. That’s the solution. Now if a storm came through, you would have a lot of worry.”
If you could keep cable rope away from lightning strikes, you would still need to worry about debris. There’s a lot of stuff zooming through space, so even if you can dodge the big stuff, little things might wear out the cable over time. According to Dr. Turner, “This concept of continuing to have to refurbish the elevator remains one of its biggest challenges, in my mind, and it’s one that they don’t have a good answer for, yet.”
Plus, the space elevator might make for a particularly good target for terrorists. Dr. Phil Plait (astronomer and author of the blog Bad Astronomy ) points out that someone coming along to snip it might not be such a remote possibility. “It’s a pretty ripe target for people to want to destroy, and not everybody is nice. We have enemies.”
We’re guessing a lot of you would like to know what happens if you have a cable to space, and then somebody comes along and snips it. Among the people we interviewed, there was some disagreement on how bad this might be. Dr. Turner and Mr. van Pelt thought that a break in the space elevator tether might not be so catastrophic. They point out that groups have tried modeling what would happen by simulating the results that follow snips at different points. Roughly speaking, it’s something like this:
Anywhere you cut, the stuff above the cut will go into a higher orbit and the stuff below the cut will fall toward earth. The stuff in higher orbit will need to be collected, since it represents some serious space trash.
If you snip high, then a lot of the cable falls in toward Earth. Once that happens, there are a number of complex interactions between gravity, the atmosphere, the motion of the Earth, and possibly some electric charge picked up from the solar wind.
The mechanics get a bit complex, but in short, the cable will start to whiplash back and forth, heating up in the atmosphere, until it breaks apart. Because the material is necessarily lightweight, the individual pieces probably won’t hurt anyone down on the surface. And you could minimize the risk even more if the cable were made into a mesh comprised of thinner strands.
Dr. Plait agrees with some of these particulars, but is a little less optimistic about the implications. “Sure, stuff hundreds of kilometers up might burn up as it falls (not that thousands or millions of tons of material burning up over one area is a great thing to have happen), but what about stuff from lower down? That’ll just fall. And then there’s the space debris. Most of the tower is below orbital speed, so it’ll all fall down to Earth, but 35,000 kilometers of it will fall through the orbital space of Low Earth satellites. I have NOT done the math or physics here, but until someone can tell me how that won’t destroy hundreds or thousands of assets in space I’m not inclined to think a space elevator is a great idea.”
Cheap access to space means our relationship to space will change forever. It will be possible to create large space stations or even settlements in orbit. We see this as a good thing, but it could potentially put power in the hands of bad actors. One idea that originated in the Cold War was the so-called rod from God. Basically, you get a heavy hunk of metal and throw it from space at an enemy. Given its weight, height, and whatever speed bump you can give it, a simple metal rod could do as much damage as a nuclear bomb. Right now, the only people who go to space are ultraqualified supernerds—the sort of people who pass psychological tests and are willing to spend decades training for a chance to get a few months in space. If space becomes more generally populated, we could be putting ourselves in a dangerous position.
Setting aside terrorists, another scary possibility is how we might deal with the ambitions of powerful nations. Outside of the Soviet breakup, the national borders on Earth have been relatively stable since the costliest war in human history ended in 1945. The laws of space that are legally agreed upon essentially say that no nation can claim anything out there. We find it hard to believe that a nation with a space elevator would abide by this. In fact, as we’ll see in the next chapter, the United States is already making a few moves in this direction.
We tend to think of the universe as divided between space and “down here.” But this is sort of like an ant thinking Earth consists of “space” and “inside the anthill.” It’s true, but perhaps a bit chauvinistic on the part of the ant. “Space,” as we use it, refers to everything in the entire cosmos outside one planet in one solar system in one of many billions of galaxies.
If humanity gets cheap access to space, it’s hard to imagine there will be no conflict over claims. And, as seems likely, if only one (or a few) nations have that access first, it may create conflicts on Earth. In other words, if humanity gets cheap space access, it means there may be a sudden political squabble at the same moment a single nation gains the most powerful weapon system in history.
Another concern is ecological. In the near term, going to space is probably going to involve incremental improvements to fuel-intensive methods like spaceplanes and rockets. Some of these fuels are relatively harmless, while others are particularly nasty polluters. According to Mr. van Pelt, the environmental damage “depends on the type of fuel. For instance, the Space Shuttle main engines ran on liquid oxygen and liquid hydrogen, with the resulting exhaust being superheated steam.
So in the end, it is just water coming out of those engines. But the Shuttle’s solid rocket boosters (or any solid rocket booster) are another story, not nice indeed. And releasing water vapor at very high altitude, like the Shuttle did, can apparently also be harmful.” This isn’t a huge deal right now because we don’t launch many rockets. But if reusable rockets make space launch cheap and common, they could be a serious environmental risk.
There’s also the orbital environment to worry about. Since Sputnik, we’ve thrown more and more stuff into space. It’s starting to get crowded, with the rate of collisions increasing. Cheap access to space may mean more space debris. That said, if space launches get cheap, we might be able to invest in some sort of space cleanup vehicle.
According to Mr. van Pelt, “It becomes really an economic issue because if you’ve got your multi-hundreds-of-millions-of-dollars telecom satellite and it gets damaged by some debris, I mean there’s a real price tag on that. You get insurance, the insurance goes up because there’s more and more space debris.”
In the longer term, cheap access to space would make space settlements more feasible, which might result in genetic differences between Earthbound and non-Earthbound humans. Mr. Derleth notes, “It turns out that the mathematics of genetics is different for small, isolated populations. Large populations can have more genetic mutations than small ones, but a small population can spread mutations to the group faster. So, you can imagine, if we had a thousand people on Mars and the colony was self-sufficient, well... it’s very expensive to send more people, right? So there might not be too many new people coming, especially as a percentage of population. And the colonists would be having babies—true Martians—and the little tykes would be growing up at ⅓ G and with little atmosphere and even less of a planetary magnetic field to protect them from radiation. So it’s possible the colonists would get a lot of genetic mutations, more rapidly, from the potential radiation exposure and growing up in ⅓ G, despite being a small population.... At some point there might be ‘Martian humans’ and ‘Earth humans,’ and society would have to try to interpret what it means to have two different kinds of humans.”
I mean, technically we already feel this way about people who talk at the movies. But point taken.
As we read books by people who’d been through the exciting era of Apollo, we got a sense of the frustration people felt as the hopes of a space-age future crashed into the economic reality of rocket launch. If we want those space-age dreams—massive, fast spacecraft with enormous crews, settlements all over the solar system, and trips to distant stars—we need to bring the cost way down.
Most of the books and papers we read about nonrocket spaceflight attempted to calculate the cost per launch their system could provide. The lowest we saw was around $5 to $10 per pound, with more conservative estimates more in the $250 to $500 per pound range. If even the conservative goal can be achieved, humanity’s interactions with the rest of the universe would be forever changed.
In terms of commerce, here’s one way to think about it. A typical space elevator proposal is for once-per-day climbers to be able to lift 40,000 pounds into orbit. The International Space Station weighs about 900,000 pounds. That means that even if the elevator operator takes weekends off, we could launch a huge space station once a month. And the cost would be something like $5 billion total, instead of the currently estimated final price tag of $100 billion.
Cheap launch would also facilitate big improvements in satellite systems, which should mean better communication methods and really, really accurate GPS systems.
It could also help with global climate change. Scientists have estimated that just a few percentage points more cloud cover might entirely offset all the warming expected to occur over the next century. One way to artificially do this would be to launch a large screen to block some of the incident light. One day you may look up to a friendly dark patch floating in the sky, protecting you from catastrophe. Ideally, it would say something like “ FOR THE LOVE OF GOD, HUMANS! HOW COULD YOU LET THIS HAPPEN?! ” on the Earth-facing side.
Speaking of humans, we might go up to space just for fun. Right now space tourism is so expensive and so controlled that (as far as we can tell) all the private space flight people are slightly crazy, very nerdy billionaires. We’re happy they’re doing their thing, but it might be nice if a mere millionaire could get in the game. The possibilities for space tourism are probably pretty sizable. The few space tourists who’ve been able to hitch a ride have spent around $20 million for the privilege. Not bad considering most people spend a lot of their time in zero G puking.
Yes, puking. As we discussed earlier, astronauts experience “weightlessness” because they’re in free fall. Another time you experience free fall is when you start zooming downward in a roller coaster. Your caveman ancestors didn’t have a lot of experience with satellites and roller coasters, so you aren’t evolved to deal with it very well. Your stomach isn’t used to food floating around in every direction, and your sense of balance isn’t used to a world where you somersault every time you lean back. This is why the International Space Station keeps a ready supply of barf bags, even for trained space professionals.
In a space elevator, as long as you don’t go too high, you’re experiencing something pretty close to normal Earth gravity. This is true even if you’re as high as a satellite like the International Space Station.
But wait, didn’t we say people in the International Space Station don’t “feel” any gravity, because they’re in free fall? Why don’t people in the elevator feel the same way?
The short answer is that in the elevator, you’re going around the Earth much more slowly. You know the Earth rotates once every twenty-four hours, because that’s how often the big bright thing in the sky comes up. It follows that your space cable also has to go around once every twenty-four hours—any faster or slower and it’d start wrapping around the Earth like a thread on a spindle. By contrast, the International Space Station is going around the Earth so fast that it sees a new purple-red sunset every ninety minutes. That’s sixteen times the romance per day.
In the International Space Station, the ground, so to speak, keeps moving away from your feet as the space station curves around the Earth. Your space elevator doesn’t go fast enough to pull off that trick. So as you rise up the elevator cable, you mostly lose the feeling of gravity simply by getting farther and farther from Earth. If you want to go above the atmosphere for a dramatic view of the stars above and the sky below, you can probably do it without a barf bag.
So when do you start puking? That’s up to your stomach, but what we can tell you is when (and why) you experience total weightlessness. To experience weightlessness, you want to be in free fall. You want to be moving at such a speed that you keep “missing” the Earth even as you fall toward it. This gets easier to do as you get far away from Earth, because you’ve got a lot of room to fall into, and because the Earth doesn’t yank nearly as hard on you. For any given distance from Earth, there’s a particular speed you need to reach in order to loop around it in a circle.
With respect to Earth’s equator, the space elevator never changes speed. It’s always turning around Earth once every twenty-four hours. But, as you go farther up the cable, you eventually reach the height at which the elevator’s speed of rotation matches the speed required for it to stay in free fall. This particular speed and distance is the geostationary orbit we referred to earlier, and it’s very special. If you toss out a sign that reads EARTH IS FOR BUTTHEADS , not only will it orbit forever, but it will stay at the same position in the sky for any observers. It’s too far to see any regular-sized objects with the naked eye, but any observer who points a telescope at the right point on a cool evening of stargazing will always see your douchey signage.
Perhaps the most exciting possibility of all will be the sense of adventure that would come with inexpensive spaceflight. Some people wonder why the dreams of the space age never became a new age of exploration. The core problem is that it’s just too damn expensive, which means it’s largely been a public-sector project. In the modern world, that means there’s a pretty serious aversion to risk, as Rand Simberg argued in his book
Safe Is Not an Option: Overcoming the Futile Obsession with Getting Everyone Back Alive That Is Killing Our Expansion into Space.
As long as space travel is extremely expensive, and not merely
pretty darn expensive
, you’re not going to get people willing to take wild risks and go on bizarre adventures. More to the point, even if there are (as we suspect)
astronauts willing to take a one-way trip to Mars,
such a program would never be approved.
All this is to say, we hope we haven’t made you pessimistic about the possibility of fundamentally changing the way we get to space, and thereby fundamentally changing our relationship with the universe. It will not be easy to make any of these technologies work, but once they do work, we can finally turn heaven over to the adventurers.
Gerald Bull did not have an easy childhood. When he was still a boy, his mother died. As the Great Depression struck Canada, his father remarried and sent his many children to live with different parts of the family. Bull was lucky to end up with family members who were well off enough to get him into university at a young age. He studied aeronautics and quickly gained a reputation as a brilliant engineer and as someone who would do anything to finish a job and finish it cheap.
In the 1950s, Canada was trying to develop a domestic missile program called Velvet Glove. The project had a great deal of trouble attracting talent, as students went to the United States for higher wages and greater prestige. Bull, at this time a strident Canadian patriot, was willing to stay behind and stand by his country. And so, still in his twenties, and looking young for his age, Bull was a major part of the Canadian missile program.
But the Canadians were not big on funding their missile ambitions, so Dr. Bull had to get it done on the cheap. When he couldn’t even get access to a wind tunnel he’d helped build, a friend suggested skipping the wind tunnel and just firing projectiles. The young engineer duly acquired an old 6-inch field gun and refitted it to fire missiles at 4500 miles per hour.
This is how Dr. Gerry Bull fell into ballistics, which led him to wonder if you could create a gun big enough to fire projectiles into space.
He was an extremely clever engineer, but had a reputation for hating to work with lesser minds—especially bureaucrats. According to Wilderness of Mirrors by Dale Grant, in the late 1960s, he once stormed out of a meeting with a Canadian defense minister, shouting that the minister had “the technical competence of a baboon.”
Dr. Bull developed his supergun method as an alternative to rockets, but as he made more and more enemies in Canada, he had a harder and harder time getting funding. However, he had developed a few true believers in the American military and was able to leverage those connections into access to things America has in abundance: funding and surplus giant guns. With help from the United States’ Department of Defense and Canada’s (somewhat reluctant) Department of National Defence, Bull began what eventually became called Project HARP—the High Altitude Research Project.
With the kind of speed Gerald Bull was known for, the guns got bigger and the projectile designs got better and better. By 1962, from a massive gun installed in Barbados, Bull’s team were making regular shots that went high enough to probe the upper atmosphere. Atmospheric data and research on high-velocity projectiles became a good source of funding for the project, but Dr. Bull had bigger goals. He believed that with the right modifications, a larger gun could fire satellites directly into orbit.
By 1965, they could fire significant payloads at about 7,000 miles per hour. This is a great start, but you need to hit 25,000 out of the barrel if you want to have a chance to reach orbit. Dr. Bull’s idea was to “mate” a rocket to the payload, so the gun could get you most of the speed, while the rocket gave you a final boost to insert you into the proper orbit.
Things were going reasonably well when funding was pulled. HARP lost American funding as NASA pushed the U.S. Army out of space operations.
Then HARP lost Canadian funding due to the burgeoning peace movement, which didn’t look kindly on a giant megagun.
Dr. Bull responded by forming a private space research company. It wasn’t building mega-space-guns, but it was making money through a variety of government contracts. But on the side, Dr. Bull began working out ideas for a cannon to dwarf his old designs. A skyscraper-sized gun, it was to have a 64-inch barrel and be 800 feet long, able to fire 6-ton projectiles into space.
As the 1970s progressed, aerospace spending began to dry up. Dr. Bull, who was perhaps less brilliant at business management than engineering, expanded the company more and more, which required greater and greater bank loans. In his struggle to keep things afloat, he entered the international arms trade.
Things soon unraveled. Dr. Bull got into a tangled situation involving the CIA, the Canadian government, and an illegal shipment of weapon parts and technology to apartheid South Africa. During a shipment through Antigua, the shippers informed the locals (who are mostly of African heritage) where the goods were going. News agencies got word, and it became an international incident.
A round of spy games for the sake of political ass-covering began, and Dr. Bull apparently was unable or unwilling to understand what was happening. He was brought up on charges of illegally transferring munitions. In a plea bargain, Dr. Bull’s company was fined and he was sentenced to a year in jail, of which he served only four months due to good behavior. He fell into rage, depression, and alcoholism, feeling he’d been betrayed and scapegoated. As he served his time in humiliation, his company finally collapsed. All the holdings, all the technology he’d built, were sold off cheap. Basically, if you were trying to create a supervillain, this would be a pretty good way to go.
Dr. Bull, who had formerly considered himself a patriot of Canada, decided he was willing to work with anyone who would bring some version of HARP back.
Things get a little murkier at this point, due to the secrecy and disinformation of many parties, but in the late 1980s, Dr. Bull shows up in Saddam Hussein’s Iraq, working on a supercannon called Project Babylon.
Let’s say that once more: Dr. Bull shows up in Saddam Hussein’s Iraq, working on a supercannon called Project Babylon.
This happened. Like, in real life.
The really weird thing is that the design for Project Babylon really does not appear to have had military applications. It was to be laid astride a mountain, which meant it could only fire in one direction. As it happens, that direction contained no significant enemy targets. It was also pointing in the proper direction (as the Earth spins) to fire into orbit.
In his book, Bull’s Eye: The Life and Times of Supergun Inventor Gerald Bull , James Adams claimed that the evidence is clear that Bull was designing military weapons for Iraq in addition to the supergun. Given Bull’s need for money, and his well-known ability to improve weapons systems on the cheap, the arrangement makes a twisted sort of sense. Why Hussein was willing to fund the supergun is harder to pin down. Saddam Hussein was said to have a messianic notion of his place in the Arab world, so the supergun concept may have served the dual purpose of giving Iraq the military utility of a cheap satellite launcher and the political capital that would go to the only nation in the region with a serious space program.
Or maybe they had the greatest miscommunication in history.
Western nations (and countries near Iraq) grew concerned. A slightly insane ballistics genius with access to a network of shadowy munitions companies was shipping tons and tons of metal parts and liquid propellant to a belligerent dictatorship. What could go wrong?
Apparently, somebody didn’t want to find out.
In March 1990, Gerald Bull was found dead in a Brussels hotel, with $20,000 on his body. Given the sheer number of people who stood to gain from Dr. Bull’s death, the potential enemies list is enormous. His own son suspected the CIA or Mossad, and according to Arms and the Man: Dr. Gerald Bull, Iraq, and the Supergun by William Lowther, “One CIA official, speaking on the strict understanding that he not be named, says it is the general understanding of Western intelligence agencies that Mossad gave the order to kill Bull.”
There has been precious little written about Dr. Bull since the early nineties. In all likelihood, we’ll never know for certain who cut short his strange and tragic career.
