I'm reasonably sure that the infrared trace of a hypersonic vehicle doesn't make it difficult to detect. Likewise existing approaches to radar stealth are hard to reconcile with hypersonic speeds, which doesn't help avoid radar detection either.
Infrared targeting of multiple hypersonic missiles is easier said than done. The missile you're hitting them with is going to be heating up the air around the camera probably at the same temps as the missile it's intercepting, and a base station wouldn't have enough resolution to guide a missile accurately from 100+km away while being alert for other missiles.
That would only apply if it were to hit it at comparable speeds. That's not necessary in many cases, especially in point defense when the target is heading towards you. Furthermore the limited time of flight of the interceptor might also allow for active cooling of the IR window in that brief period.
Also, even detection from a fixed ground base (or from space - see SpaceX's newest missile detection project) is still detection in the first place, which is what I was commenting on. Wasn't even going to veer into interceptor guidance, but I'm sure there's multiple ways to do it.
If you're going to wait for the hypersonic missile to be close enough that this isn't a problem, you have the issue that your missile won't be able to manoeuvre right and might still be building up velocity. Plus there won't only be one!
> the interceptor might also allow for active cooling of the IR window in that brief period.
The issue isn't the IR window, it's the air directly in front of the interceptor missile, which has to target from the frontal aspect.
>Also, even detection from a fixed ground base (or from space - see SpaceX's newest missile detection project) is still detection in the first place, which is what I was commenting on. Wasn't even going to veer into interceptor guidance, but I'm sure there's multiple ways to do it.
Detection is not enough. We can already detect missiles from satellites even. The issue is calculating their velocity accurately and locating them at +- 10m from 100km+ away is not feasible without really large apertures and pretty long focal lengths. You wouldn't be able to accurately track more missiles than you have optics and the optics would be mind-boggingly expensive. Besides that, the target acquisition radar to maintain a feasible or even physically possible relative aperture for target acquisition would be unable to resolve any detail about the missile, so it would have no way of telling the difference between a missile and a flare of the same brightness and color.
What you're describing is not a matter of kinetic energy (clearly if it were about kinetic energy, this would be defeated by making the interceptor weigh 30 tonnes) but a matter of transverse acceleration. On that matter, as far as I understand it, current AAMs/SAMs are somewhere in the 50g region. I strongly suspect that hypersonic vehicles due to their lower L/D are nowhere near that -- hell, many of them seem to have a hard enough time flying straight, if US military's experience is of any relevance here.
Also, due to low L/D ratio in the high Mach region, if your missile is zig-zagging randomly, it won't stay fast for long. And if it's not zig-zagging randomly, then the question is how it gets the information how to zig-zag, since the nose of a hypersonic vehicle seems to be an extremely poor sensor platform -- which you admitted yourself. It's virtually certain that it won't be able to see the interceptor.
> The issue isn't the IR window, it's the air directly in front of the interceptor missile, which has to target from the frontal aspect.
It seems unlikely that the interceptor will have to fly at a comparable speed in a frontal aspect interception situation (considering that it doesn't need to catch up).
But as for terminal interception, I suspect that here the inverse-fourth-power-of-distance operation of an active radar homing solution might help you if all else fails -- at a small enough distance this will work even better than the inverse square applicable to passive optical/IR detection.
> would be unable to resolve any detail about the missile, so it would have no way of telling the difference between a missile and a flare of the same brightness and color.
It would seem that the easiest way to distinguish a flare would be to look if it's in a controlled flight? Unlike a flare, the hypersonic vehicle will continue flying, and the difference is readily apparent. Besides, you can't have that many flares on it, so you can't keep firing them continuously -- again, the only thing that's available to you if you can't see the incoming interceptor.
Not so. AAMs/SAM can only pull anywhere close to 50g at gigantic cost in drag and can only do that once and briefly. It is a question of kinetic energy because the missile that can regenerate kinetic energy and that loses the least kinetic energy relative to it's mass is at a massive advantage.
>Also, due to low L/D ratio in the high Mach region, if your missile is zig-zagging randomly, it won't stay fast for long. And if it's not zig-zagging randomly, then the question is how it gets the information how to zig-zag, since the nose of a hypersonic vehicle seems to be an extremely poor sensor platform -- which you admitted yourself. It's virtually certain that it won't be able to see the interceptor.
Traditional aerodynamic designs suffer from poor L/D ratios, yes. Waverider designs probably have much fewer issues. Given the advent of HGVs, which are made to turn multiple times without any engine to back them up, we can be fairly confident that this is not the case.
As far as being a poor sensor, this is an oversimplification of a complex mechanism. Plasmas block radar up to a certain frequecy depending on their temperature. So you make it so that the radar is somewhere where the air is slightly colder and make its frequency higher. You don't even have to put the radar in the nose if the target you're trying to hit is sluggish and large enough.
It doesn't need to maneuver in response to the interceptor. The missile knows when it is in LOS to the target, and knows that the interceptor will be fired soon after. So it already knows when the missile will be fired and thus when the missile would hit. The window for interception is pretty short. It would have to do evasive maneuvers at maybe 4G for maybe 30 seconds, all the while gaining back Ke from reducing in altitude in combination with engines.
>It would seem that the easiest way to distinguish a flare would be to look if it's in a controlled flight? Unlike a flare, the hypersonic vehicle will continue flying, and the difference is readily apparent. Besides, you can't have that many flares on it, so you can't keep firing them continuously -- again, the only thing that's available to you if you can't see the incoming interceptor.
This is a REALLY hard problem, and it's the reason why imaging infrared guidance was invented. It takes a lot of time to be certain that a flare in a ballistic trajectory at high speed is different from a missile coming towards you! Those are precious seconds you can't afford. Remember that you have no way of estimating distance.
Except since the interceptor has only one chance at interception, the situations of the interceptor and the missile are not symmetrical. "Doing that once and briefly" seems quite acceptable for the interceptor. The missile pretty much must regenerate kinetic energy, or its subsequent suboptimal flight regime might make it even more vulnerable to the second interceptor incoming, or the third one after that.
> The window for interception is pretty short.
With early detection (orbital, for example), the window seems to be as long as the range of the longest-range applicable interceptor missile.
> It would have to do evasive maneuvers at maybe 4G for maybe 30 seconds
That definitely seems to be a "too little, too late" kind of situation. Especially in a point defense scenario where maneuvering away from your line to target means not hitting the target in the first place (which is as good as a successful hit of the interceptor), and where being close to the target really favors the short-range defense systems.
> Remember that you have no way of estimating distance.
You may very well have that way in the end if SpaceX's/L3Harris's system gets implemented.
"This isn't one of your church picnic flare gun firings". Smarter people than Homer have been working on flare technology for 40+ years.
(2003) https://www.nationaldefensemagazine.org/articles/2003/11/30/...
>> Also, due to low L/D ratio in the high Mach region, if your missile is zig-zagging randomly, it won't stay fast for long.
These are not airplanes with wings. These are missiles very high in the atmosphere flying complex flight paths more accurately describes as trajectories. The air is thin, the drag low, the energies extraordinarily high. A successful zig-zag maneuver could be as small as one degree left or right, up or down. And sacrificing speed to escape an interceptor is a valid tradeoff considering that, not being an airplane, the missile intends to slam into the ground/target in a minute or two no matter what its speed.
> Plasma stealth is an existing approach to radar
> stealth that is made easier by hypersonic speeds.
No. They still travel far slower than ballistic missiles. Their advantages are in being able to fly low and (theoretically) manoeuvre to avoid interceptors.
They’re an evolution of cruise missiles, not strategic ballistic missiles.
Also the 3M22 is estimated to only cost around 2 million dollars.
The strategic systems hypersonics are hyped to hit have been hardened against ballistics. Hypersonics are slower than ballistics. (Their plasma envelope also makes them easier to track by satellite.)
This is a tactical evolution. Meaningful. Helpful. But not a strategic shift.
I agree that they're not that different from ballistics but they still have considerable advantages.
I don't see how this would work, unless of course you're talking about nuclear weapons. With a conventional warhead you still need to hit your target.
Once you manage to make significant net thrust making a bit more isn't that big of deal, it's really a critical point you have to pass.
You’re still limited by your fuel and flight envelope. The latter which bleeds the former.
Hypersonic missiles will be harder to intercept than cruise missiles. Due to their novelty, they’ll also be harder than ballistics. (Ballistic projectiles don’t continuously illuminate their flight path. That permits for subterfuge options an air-breathing missile forfeits.)
As for flight envelope we know from the X-15 that not that much is required to pull 10Gs at hypersonic speeds. There is no need for much more.
One, this leaves the missile, which is screaming through the atmosphere, vulnerable in a way ballistics are not. (And visible in a way cruise missiles aren’t, either.) Two, if you have a carrier strike group in the middle of the ocean, this strongly restricts how much manoeuvring can be done. The target knows where you’re ultimately headed—if you tactfully manoeuvre into a blank patch of ocean, the strike group is fine.
> flight envelope we know from the X-15 that not that much is required to pull 10Gs at hypersonic speeds
The flight envelope restriction isn’t a structural one. If you have a known target, there is only so much manoeuvring the vehicle can aerodynamically do without slowing down to sub-scram speeds. Yes, you could supercharge the engine, but that cascades through another host of factors.
As far as only so much maneuvering you can do before being too slow for the engine, yes that's probably an issue for the HAWC, but scramjet missiles have been demonstrated to achieve Mach 9 in atmospheric flight which allows a lot of energy to bled out before you drop out below Mach 4.
Ballistics cruise quietly. An RCS impulse can covertly re-aim it. Hypersonics scream bloody murder their whole flight path. Every satellite over the horizon will see it.
Hypersonic manoeuvres are, moreover, expensive. You have to deflect a lot of molecules to make small changes. That costs you in speed, fuel and time to arrival. If you need to maintain scram airspeed, your options are seriously limited.
This weapon has a place on the battlefield. But it’s not a strategic element.