Starting, As We Must, In Congress
In Congress-speak, an “authorization” is different than an “appropriation,” in that money must be “authorized” by Congress to be used for a particular purpose first, which is different than “appropriating” it. Appropriations are what actually fund a program after it has been authorized. An annual ritual of Congress is the passage of a bill that is always called something similar to “National Defense Authorization Act.” Because it it basically has to pass or else the military doesn’t get any money, and because it only authorizes rather than appropriates money, it’s a pretty safe place for Members to stuff all sorts of pet projects and ideas.
This normally arcane bit of legislative ritual has grabbed some headlines thanks to the actions of the Chairman of the House Armed Services Strategic Forces Subcommittee, Mike Rogers. His idea is to create a Space Corps, which will be a distinct subdivision of the Air Force, much like the Marine Corps is a distinct subdivision of the Navy. The idea is not original to him; some trace the concept back to at least the 1990’s.
Space Marines? Are You Kidding Me?
Hey, this is not a silly idea. There are a multiplicity of assets already in space upon which other segments of the military rely. GPS satellites. Communications relay satellites. Surveillance satellites. Having the ability to communicate and access information anywhere in the world represents a tremendous advantage to all segments of the military. It’s what allows U.S. pilots in North Dakota to fly their craft on missions in Iraq and Afghanistan well out of harm’s way, while the enemy is forced to confront live ordinance. War is not a sportsmanlike exercise, after all.
So if a war ever takes place against a sophisticated enemy — Russia, China, or some other nation with its own spacefaring capability — it’s pretty obvious that this enemy would want to reduce or eliminate the ability of the U.S. military to rely on this advanced technology, and one way to do it would be to disable the ability of terrestrial assets to access the rich flow of information those satellites provide. It seems all but inevitable that this will become a sphere of military activity.
What would this eventual sixth branch of the U.S. military actually do? It’s certainly cool to think about video-game type stuff. Massive fleets of spacecraft vying to outshoot one another, Space Marines in armored space suits, seizing enemy spacecraft and satellites, shooting frickin’ laser beams at each other:
But I think we all know that this isn’t particularly realistic, at least not for the bulk of our lifetimes. The reality of it is, satellites and space stations are pretty fragile things. And, very few of them are all that far outside of the measurable atmosphere. “Space” is mostly thought to begin at 100 km above the surface, when aerodynamic lift no longer keeps an object aloft, a demarcation called the Kármán Line.
Assets and Targets
From there, there are three tiers of orbital distances: 180-2,000 km is “low earth orbit,” which is where most satellites are (it takes much less fuel and therefore a lot less money to put satellites there). This is where most of the action in any outer-space military activity will take place. Because equipment and supplies necessary to sustain human life are particularly heavy from a space-travel perspective, the International Space Station and any reasonably imaginable other space station with life support systems would also be in this range. Bear in mind that a space station like the ISS will be particularly fragile when thought about from a military perspective because of the life support systems.
Geosynchronous orbit, to keep a satellite apparently stationary above a particular longitude on the planet below, is at 35,780 km, which is the demarcation point between “mid earth orbit” and “high earth orbit.”
“Mid earth orbit” is interesting because that’s where the bulk of the GPS tracker satellites are, and as far as I can tell, the 2,000 km demarcation line is derived from some arbitrary decision about how eccentric (that is, how far away from truly circular the elliptical orbit’s shape is) the satellite’s orbit needs to be to remain stable at that distance from the earth.1
That’s where the targets are. Basically, communications relay and surveillance satellites will be in low earth orbit, the network of GPS satellites will be in mid earth orbit, and the best surveillance satellites focused on areas of particular strategic interest will be in geosynchronous high earth orbit. Scientific research satellites would almost certainly be of little interest to any military action.
Environment and Weapons
Space isn’t like other areas where military activity has taken place. Things move at terrific speeds: an object in low earth orbit moves at a rate of about 27,500 kilometers per hour (relative to the Earth’s surface). I’m no physicist, but I know that F=ma. When each object’s velocity is 27,500 kph2 if you line up your vectors right, you aren’t going to need a lot of mass to do a lot of damage.
Distances are also huge. The volume of the areas that are within low earth orbit is about 571 billion cubic kilometers. By comparison, the total area of the earth’s atmosphere is about 52 billion cubic kilometers.
Freedom of movement is much greater in space than in the air or worse yet, on the ground or in water. In the microgravity and low-resistance environment of space, a satellite with appropriate equipment can change its attitude and spin at will relative to the path of its velocity. Put another way, unlike an airplane that has to face forward as it travels, a satellite (equipped with thrusters, which basically vent something like compressed air in a controlled direction) can move in one direction, look in a different direction, and spin around an axis chosen in three dimensions as it chooses. Also unlike naval or aerial operations, once a desired velocity is attained, no further effort need be expended to maintain that speed. Once you’re going as fast as you want, you turn your engine off and don’t use it again until you want to maneuver. The interior of the cabin is completely automated, using linear actuators to keep it steady. Way back in the 1990’s, the CGI artists who created space battles on Babylon 5 did a pretty good job of illustrating this.
So you don’t need to make frickin’ laser beams to take out a satellite. Something the size and mass of a bullet that you might fire from, say, a .50 caliber rifle would work just fine. It won’t need a nuclear warhead, just some appreciable mass. At the kinds of relative velocities we’re talking about, it probably doesn’t matter all that much how the target is armored. The trick is getting your bullet to hit its target at all, in the vast, empty reaches of this 1,900 kilometer wide battle zone.
Getting your bullet, or missile, or whatever other projectile you wish to deploy to intersect the satellite you wish to destroy, is something a human being simply cannot do. So you’ll need to rely on a radar detection system to find your target and a guidance system to get your projectile to travel to where the target is, preferably along an opposing vector to transfer the huge power of orbital velocity to your projectile’s impact on the target.3
And that means that guidance systems are going to be what space combat is all about. As it happens, a problem of this magnitude currently confronts missile-defense systems in R&D as we speak — the challenges of shooting a missile out of the sky are not all that unlike the challenges of shooting a projectile at a satellite. An ICBM’s re-entry velocity is about 6 kilometers per second, compared to the velocity of a low-earth-orbit satellite of about 7.8 kilometers per second. To my knowledge, guidance systems are approaching the point of being able to do this, at least in controlled circumstances, so while they aren’t quite there yet they are approaching the point where orbital interception will become a possibility.
Rods From God
I know what you’re thinking. Yes, I saw that episode of The X Files too. Among other things, it depicted a satellite-launched weapon of indeterminate description. We don’t know if it was a frickin’ laser beam or a rail gun or a missile, but we were told that the Baddie shot some kind of a satellite-launched weapon at Agents Mulder and Scully in a cargo container yard. Good fun on those dateless Friday nights back in the 90’s.
The principal satellite-to-ground weapons system that has been talked about in real life, “Project Thor,” involves positioning a group of very high density tubes, proposed to be made out of tungsten carbide with a core of depleted uranium, that would be braked out of a satellite, to then drop from orbit down onto their targets. Easy to see how that would get really destructive — that portion of the projectile that survived atmospheric re-entry would have a very high terminal velocity due to its high density and aerodynamic shape.
At the practical level, though, we encounter some problems. First, there’s expense: In order to have a useful projectile survive atmospheric re-entry, it would need to be about the size of a telephone pole upon launch. Then, you have to somehow transport this really heavy piece of ammunition to the launcher satellite. We could do that, I suppose, but it would be really expensive.
Then there’s the matter of guidance. Even assuming advanced guidance systems capable of doing satellite-to-satellite interception, such a projectile would almost certainly not be able to use them on its re-entry path. After a few kilometers of picking up friction during re-entry, the entire tungsten carbide log would develop a sheath of plasma. Which would look really awesome, but which would also pretty much prevent any way a guidance system could function. So the target would have to be known and programmed upon launch, and once launched, there’d be no way to steer it. Perhaps that wouldn’t matter, if the initial targeting were good enough. Before I published this, our man Oscar Gordon suggested to me that an ablative shell with a terminal guidance system could mitigate this issue, at least until the ablative shell ablates4 on its way through the atmosphere and towards the target. And the shell would add still more weight and expense to each shot the weapon fires.
Note also that the satellite that mounted these weapons would require a lot of maintenance because unlike communications or observations satellites, it would necessarily have a lot of internally moving parts. Sending a software update to a satellite is one thing — sending an astronaut to go maintain it is something else.
For now, this sort of weapon is beyond our grasp — although as with the advanced guidance system, it seems plausible enough to imagine developing the ability to create it in the foreseeable future.
It strikes me as a poor cost-to-benefit choice though. Pretty obviously, the satellite(s) that had such a weapon would become a high-priority target for our hypothetical spacefaring enemy. We couldn’t really hide the thing. The satellite itself would be large, and the maintenance trips would have to be frequent enough that they’d be tracked, so it would be pretty easy for our potential enemies to detect where the Thor platform was. So Thor would become a locus of missile/anti-missile efforts for the Space Corps of both combatants, consuming already-expensive resources that could be used to protect or attack other assets.
This sort of thing would be a long way away, if it ever happens at all.
We Have So Many Things That We Have To Do Better, And Certainly The Cyber Is One Of Them
Remember that the basic goal of space warfare is to protect our own ability to use information from satellites and to deny our enemy that same ability. So here’s the real rub: the enemy might be able to deny us our use of satellites without launching a single missile. Hackers could pretty conceivably figure out how to do the same thing from the comfort of any dacha with a sufficiently robust internet connection.
Right now, this sort of thing is the province of the U.S. Cyber Command, which works juxtaposed with the National Security Agency. I’m less able to make inferences about what is or is not within a military’s cybersecurity capabilities, but I mention this in the context of thinking about a Space Corps because all of the magnificent technology we’re ruminating about here could be rendered moot at the electronic level, and Space Corps would need to be deeply concerned about that.
Where Would Space Corps Fight?
Sure, the idea sounds silly. The name, unfortunately, mirrors elements of not-to-be-taken-too-seriously-science-fiction stories exactly. Nevertheless, whether it gets started this year or next or next decade, I feel confident predicting that within most of our lifetimes, a part of the U.S. military will make shooting missiles at satellites and other missiles its bread and butter mission.
With that said, calling this new realm of military activity “Space Corps” is a bit of a misnomer, because it seems exceedingly unlikely to me that a human Space Corps warrior would probably ever need to leave the ground. We’ve been using airplane-launched missiles to destroy satellites since 1985, and nowadays the launcher airplane can fly and land itself. The work that would need to be done to fulfill this mission requires speeds and technologies faster than human beings could realistically handle.
There will not be Space Marines shooting frickin’ laser beams at one another in orbital infantry actions. But there will be ridiculously fast and scary missiles aimed at tiny, hard-to-hit, fragile, and high-value pieces of orbiting hardware. Welcome to the future.
Thanks to Oscar Gordon for taking the time to school me up on some of the physics and technology here. Any errors or mistakes that have persisted despite his best efforts to explain rudimentary physics to a lowly liberal arts major are strictly my own.
- There are a couple other interesting places to consider, like four of the five LaGrange Points, but these are very distant from the Earth and to my knowledge, only populated or useful for by devices used for scientific research that would be of little concern during a war. [↩]
- About 17,000 miles per hour if you don’t care to do the metric conversion. [↩]
- If your guidance system is good enough to hit your target head-on, the relative velocity at impact would be 55,000 kph. So you see why I don’t think armoring satellites is going to do a damn bit of good. [↩]
- Is that a verb? It is now. [↩]