Hypersonic Missiles Have Almost Made It Across the Valley of Death

The US Air Force will be flying operational prototypes of hypersonic weapons by 2020. At least that's according to Major General Thomas Masiello, commander of the Air Force Research Laboratory, who spoke last Friday at the Air Force Association Air Warfare Symposium in Orlando, Florida.

This may mean that hypersonics are just about through what engineers and program managers call the "Valley of Death," which is a sort of Catch-22 where a lot of good ideas languish and die. Taking any idea from the drawing board to operational deployment is expensive. There's one phase where that development starts getting really expensive, but it's before anyone has enough confidence in the new idea that they're will to lay out enough money to make that technology usable in practical terms. Once a program makes it through the Valley of Death, it's pretty much a given that it'll go from being an exotic idea to an actual thing in the US arsenal.

That 2020 target is ambitious, and quite simply because going hypersonic is not easy at all. Hypersonic speeds begin at, roughly, Mach 5 — one mile per second or five times faster than the speed of sound. That's a sort of generic cutoff at the low end, while the top end runs all the way up to Mach 25, (depending on who you ask). However, the actual, not-completely-arbitrary, laws-of-physics cutoff is a bit harder to precisely define.

An object travelling at hypersonic speeds is going so fast that it generates enough heat, shock, and pressure to alter the basic chemistry (and therefore aerodynamic properties) of the air it's plowing through. It just so happens that this kind of disruption is a pretty major factor by the time a vehicle has hit Mach 5. But the transition isn't sharp. As you go faster, the whole engineering problem gets increasingly screwed up in new and extremely difficult ways.

The big problem is that computer modeling of hypersonics is really hard when the individual elements start becoming recursive and, therefore, computationally very demanding. Beyond that, the vehicle itself is putting tons of energy into the system; thermal loading becomes an enormous pain in and of its own right. And on top of that, trying to keep a jet engine lit at 3,000 miles per hour is a nightmare, too. Blah blah blah.

Or something. The basic deal is that hypersonic stuff is well into the range of super-duper hard even for the bright bulbs at NASA and DARPA, the Defense Advanced Research Projects Agency.

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While it's been a huge pain to do hypersonic stuff, it's also been something that aircraft designers have wanted pretty bad. Ever since people started making combat aircraft, making them faster has been a pretty surefire way to guarantee a better warplane. But in the 1960s, designers started hitting a wall up around Mach 3 or 4, after which it starts becoming very difficult and expensive to make the plane go faster.

By the 1970s, designers quit pushing speed limits, and focused on how to camouflage aircraft instead. They did this first by flying super close to the ground so enemy radar had a hard time picking planes out against the terrain. Later, this approach was overtaken by stealth technology that made it hard for enemy radars to pick out the plane against much of anything at all.

In a way, stealth and hypersonics represent two completely opposite solutions to not getting shot down. Stealth is all about being so ninja-like that nobody can see you. On the other hand vehicles at supersonic speeds and above generate a huge amount of heat, which makes them easy to spot. But they are cruising along so fast that it's tough to intercept them and shoot them down.

But there's more. Hypersonic aircraft can get anywhere pretty quick, and that's important if you want to react quickly to something that's happening far away from you — which is a big deal if you are the United States.

The US already does have a global reconnaissance network of satellites and drones, which hugely expands the area in which it might find super important and timely targets. But often it doesn't have the ability to actually do anything about those targets. Even if you do have bombers on standby, there's no point in them even taking off if it's going to be 12 hours before they can get into firing position.

In fact, a couple times before 9/11, the US caught Osama bin Laden and his buddies hanging out at various training camps in Afghanistan and was totally going to blow those guys up with cruise missiles. But the cruise missiles arrived too late, and blowing up the place where your enemy was hanging out eight hours earlier is considered a rather poor use of millions of dollars' worth of sophisticated weaponry.

With hypersonic technology in hand, one could build a system that could, in theory, deliver a conventional strike to any place on the planet within an hour. This is the basis behind the Prompt Global Strike or PGS program that the US has been fussing with for more than a decade. (There's a huge set of arguments for and against this particular kind of weapon, including the risk of setting off an accidental nuclear war because it's hard to tell the difference between an incoming nuke and incoming hypersonic conventional strike. But that's a separate article altogether.)

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Weapons range is an increasingly important factor these days. While the US was preoccupied with low-tech and tough conflicts in the Middle East and nearby areas, Russia and China were busy figuring out how to offset US advantages in fancy aircraft and missiles. One big development has been long-range anti-aircraft and anti-ship missiles, which would push US forces way the hell back from anywhere useful. But the range that's kind of inherent in hypersonics starts doing a lot to erode the advantage those new Russian and Chinese weapons might buy.

Now, while it's almost a certainty that hypersonic weapons will turn out to be more expensive than their slow-ass counterparts, combining hypersonic and slower missiles can be pretty powerful. For instance, if you were launching a big attack intended to saturate enemy defenses, you could mix in a few hypersonic missiles to take out known defenses, opening up a gap for a larger, slower cloud of missiles and decoys.

Hypersonic weapons can also pack a smaller warhead to achieve the same damage to a given target, simply because flying into anything at a dozen times the speed of sound is going to really, really hurt it bad. At about Mach 12.5, a 1,000 lb warhead has as kinetic energy equivalent to 1,000 lbs of TNT. This abundance of kinetic energy comes in very handy when you start talking about digging out very deeply buried targets, like Evil Genius Headquarters. Or, say, a nuclear facility, or a command bunker.

What makes this relevant now is the idea that the US may almost be through what call that "Valley of Death." Generally speaking, there are a lot of different stages of development for new technology, from the level of things that exist only in concept and a handful of calculations, up through basic technology demonstrations, all the way up to something operational in the real world. But the really ugly part is in the middle, where programs go to die.

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All the math, simulations, and modeling at the very beginning are pretty cheap. But after a while, computer models alone won't cut it anymore and you just need to start making and testing actual hardware to learn more. This can quickly get a lot more expensive than the theoretical work.

On the other hand, at that point, the technology is not reliable or well-understood enough to actually be anything you want to bank on. Thus, no actual, real-life program wants to pick up all the extra costs and risks associated with trying to use technology that's still pretty far from prime time. Everyone's under cost and schedule pressure already, so why gamble on the unproven?

Hypersonics have been a Technology of the Future for half a century, but a lot of those technologies never made it anywhere and are now just curious artifacts. Some, like fusion power, seem insurmountably difficult. Others, like airships, are less technologically challenging, but never seem to find a market. But so many technologies and programs that get stuck aren't too difficult to fix, they just can't get enough backing to make it all the way through.

Hypersonic technology isn't just one thing, but a whole host of things, like aerodynamics, propulsion, cooling, and so on. That means that it's not a matter of getting this or that particular technology through the Valley of Death, but smuggling a whole family of stuff across to the land of opportunity. So if the Air Force claims it will be flying prototypes of operational systems by 2020, what it's really saying is that it expects to have many if not all of the subsidiary technological stuff completely (or most of the way) through.

And if the Air Force is right, there's a pretty good chance that we'll see hypersonics arriving in the real world before we know it.

Follow Ryan Faith on Twitter: @Operation_Ryan