By Ryan Faith
ic regime begins at Mach 5 or so — about one mile per second — and goes up from there. There’s not a super-precise, fixed definition, exactly, but these are the speeds at which all those equations on supersonic airflow start going off and begin to require some pretty big tweaks. That’s because interesting things begin to happen at hypersonic speeds. For instance, the airflow chemistry becomes relevant. Or rather, objects moving at hypersonic speeds air hit the air in front of them so hard and heat it up so much that it affects the chemistry of the air it’s travelling through, thus changing the aerodynamic loads on the vehicle.If you see hypersonics mentioned today, people seem to be waiving the term around like a magic wand of panic and alarm. Some assert that hypersonics will spark off a new nuclear arms race, because of what the technology portends for the delivery of strategic nuclear weapons. Others claim hypersonics will be the death knell for US aircraft carriers. And still others wring their hands about the possibility that hypersonic weapons could end up accidentally sparking a nuclear war. After a while, you kind of wonder if hypersonics aren’t really just fodder for late-night infomercials advertising advanced, exotic weapons systems to tech geeks and policy wonks.
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People have been closing in on hypersonic military vehicles since the 1990s. During the 1990s, three things happened, more or less at the same time, which collectively rejuvenated interest in hypersonics. First, the outer limits of stealth technology came into focus. Stealth doesn’t make aircraft invisible; stealth is more like really good, but very specific camouflage in radar wavelengths. At some point, aircraft leave other unavoidable traces of their passage like turbulence, or even the slight atmospheric heating that comes from flight even at subsonic speeds. The physics knowledge of what is theoretically possible is still a long way ahead of the practical technology, but the writing is on the wall: stealth won’t live forever.
The idea behind stealth is that you can’t hit what you can’t see. So if you develop a new way to spot the aircraft that gets around stealth’s camouflaging effects, the stealth advantage disappears. Hypersonic aircraft are very easy to spot, but offer a different approach: you can’t hit what you can’t hit.
Second is the matter of blowing up stuff superdamn quick. In September 2000, a year before 9/11, the CIA had spotted Osama bin Laden in Afghanistan. But there was no way to kill him before he moved somewhere else and went on with the rest of his day. That lesson was learned before, in 1998, when a strike on Taliban training camps in Afghanistan took two hours to arrive, blowing everything up after bin Laden and his buddies had already split the scene. This “find it now, hit it later” problem got people interested in faster missiles, and if hypersonic weapons do one thing well, it’s fast.
Third was the growing discussion of missile defense coming out of the 1991 Gulf War, there was some back and forth at the time and in the immediate aftermath of the conflict about Patriot missiles hitting inbound Iraqi Scud missiles. To some extent it doesn’t matter whether or not the Patriot missiles intercepted some, all, or none of those incoming Scuds. The important part was that intercepting missiles was now shown to be possible at the time, or within the grasp of existing technology. Vehicles that could maneuver and steer at hypersonic speeds are a lot harder to hit. Thus, developments in hypersonics could turn the tables on the then brand-new missile defense technology.
The thing is, we’ve had hypersonic technology since Feb 24, 1949. Or, to be more precise, we’ve had the ability to get things up to hypersonic speeds for two-thirds of a century. Ever since then, folks have been working on getting to advanced tasks, such as turning, steering, or doing something other than going in a straight line at hypersonic speeds.
Getting beyond just dumb ballistic entry to actually flying — and doing all that normal aircraft stuff like generating lift, steering, or using engines — is difficult. There’s only been a handful of crewed vehicles that operate at hypersonic speeds. All of which have been spacecraft (except for the X-15 rocket plane) that have been mostly focused on dealing with hypersonic speeds on their way to or from Earth. So overall, hypersonic technology is still a very early, emerging sort of thing. Development has, coincidentally, been mostly limited to countries that have active space programs.
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In recent decades, the US and China have had programs to get better at hypersonics, but they’re still working out a lot of basics of hypersonic flight. Like how to keep an engine lit in a 4,000 mph wind. Or how to manage thermal load when the skin of the aircraft is heated up beyond 1,800 degrees. Or how to keep that test vehicle skin from peeling off the airframe in flight. That kind of thing.
So will hypersonics dramatically alter some specific aspects of warfare? Undoubtedly — eventually. The technology is pretty hard to get right and developing it will be pricey. If I had to guess, I’d rank it as being harder than spaceflight, but not quite to the sheer, daunting improbability of controlled fusion power. The thing to watch for is whether or not anyone is moving beyond trying to figure out the basic science and technology, and is looking to put their knowledge into practice.
The Chinese and US are both moving along the technology development track at a fairly aggressive (but not yet breakneck) clip, so the next big indicator will be whether or not they’re moving to a developmental program. In other words, it’s like we all know everyone is working on internal combustion engines; the thing to watch for is when someone starts to build a vehicle around one.
So, where does this all leave us? On the one hand, the Chinese just conducted their fourth test of a hypersonic vehicle, but all this talk makes it sound like a purely theoretical proposition. Here’s the difference: as stated above, people have had the ability to make things go at hypersonic speeds for a long time, but they can’t steer the vehicle or generate thrust. The fourth and most recent Chinese test isn’t important because the vehicle is traveling at hypersonic speeds, it’s the fact that they were able to steer it during hypersonic flight. But the ability to carry out maneuvers at hypersonic speeds in a test scenario is a long way off from having a working hypersonic weapon. In the end, hypersonic speeds are possible. The part about doing anything useful with that speed is still a ways off.
Follow Ryan Faith on Twitter: @Operation_Ryan – Vice News
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By Ryan Faith