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DARPA's hypersonic scramjet achieves successful flight

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Re: DARPA's hypersonic scramjet achieves successful flight

#151

Post by pageandrew »

speedybird wrote: post #97
corndoge wrote: post #87

Is it just me or has the Pentagon and the complex largely replaced the word "soldier" with "warfighter"? Feel like I've seen it a lot lately and I'm not sure what the change implies

It simply means that marines, sailors, etc get bent out of shape when you call them "soldiers." In their lingo, soldiers are in the Army. In common parlance, a 'soldier' is anybody who is part of a military and an 'army' is any and all military. But I would not expect the Pentagon to be so casual with their use of terms relating directly to their affairs.

The common parlance is just wrong. Soldiers do not serve on ships

Re: DARPA's hypersonic scramjet achieves successful flight

#152

Post by pageandrew »

_2d30 wrote: post #102
tomcam wrote: post #90

Earlier quoted context omitted.

Good call. Seems unnecessary, like the slow transformation of “emergency room “which used to be known as the ER to “emergency department“.

In fairness, emergency department is more sensible. They generally aren't a single room. Soldier to warfighter seems unnecessary. EDIT: It seems possibly using "warfighter" is more accurate as marines and pilots aren't soldiers?

Army has soldiers, Navy has Seamen/sailors, Air Force has airmen, Marines has marines, coast guard has coast guardsmen.

Re: DARPA's hypersonic scramjet achieves successful flight

#153

Post by pageandrew »

JumpCrisscross wrote: post #113
jack_pp wrote: post #110

Earlier quoted context omitted.

Isn't the point of these weapons that even if you can detect them they are too fast to intercept?

> even if you can detect them they are too fast to intercept? 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.

They are slower than ballistic missiles, but fly more unpredictably. Ballistic missiles fly a parabolic trajectory and therefore an intercept can be calculated, whereas hypersonic missiles fly in the atmosphere at high speeds and can change their direction

Re: DARPA's hypersonic scramjet achieves successful flight

#154

Post by eunos »

sudosysgen wrote: post #13
masklinn wrote: post #11

Earlier quoted context omitted.

> Announcing breakthrough, surprising even, HAWC tech seems to clue in opponents about what sorts of countermeasures they'd want to start developing. It's pretty hard to hide hypersonic devices these days, and the concept is not exactly a secret: Russia and China are testing devices, and multiple other countries are working on developing their own.

Russia is not really testing devices per se anymore, they are preparing for mass production of hypersonic air breathing missiles. We don't know too much as for China.

> We don't know too much as for China https://en.wikipedia.org/wiki/DF-ZF

Re: DARPA's hypersonic scramjet achieves successful flight

#155

Post by SiempreViernes »

dgregd wrote: post #73

How a such hypersonic missile locks a target? Does it use a radar or some optic system? I guess that plasma around the body might disrupt conventional guiding systems.

All actually deployed systems are nuclear capable, for them aiming is not a huge concern because the boom is very big.

What the US is playing at with their strictly conventional warheads is anyone's guess, the overall impression is a of a "we want that toy too!" program.

Re: DARPA's hypersonic scramjet achieves successful flight

#156

Post by bobthepanda »

BobbyJo wrote: post #119
bobthepanda wrote: post #71

Earlier quoted context omitted.

Shrinking the world would be a good use of it if we could get it to work for commercial air travel (and if we solve the sonic boom problem, but that's another issue a different part of government is working on)

It's very hard for me to imagine a world in which scramjet technology is both useful for commercial travel, and impossible to develop without massive government funding. It seems to me like technology needs to reach a point that it can be developed entirely commercially before it can be made safely and consistently enough enough for commercial passengers. Take rockets for instance. Technology had to catch up to make…

pretty much all of air travel had direct government subsidy in the form of postal contracts in its early days and later price controls. automakers also had a huge subsidy in the form of the massive capital expenditure on highways that were free to use.

developing technologies at taxpayer expense for strategic purposes is nothing new. if private airlines were left to their own devices we probably won't ever move away from the basic shape of subsonic, fossil-fueled jet travel. as it is, the airplane manufacturer duopoly is half kept afloat by defense spending, and it remains to be seen whether or not the full financial cost of 737MAX will result in requiring taxpayer bailout.

Re: DARPA's hypersonic scramjet achieves successful flight

#157

Post by jhgb »

sudosysgen wrote: post #150
jhgb wrote: post #134

Earlier quoted context omitted.

> Interception against an actively manoeuvring target is a question of kinetic energy. If the intecepting missile is smaller all the hypersonic missile has to do is zig-zagging randomly and you're toast. 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 ma…

>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…

> 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.

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.

Re: DARPA's hypersonic scramjet achieves successful flight

#158

Post by wongarsu »

JumpCrisscross wrote: post #147
speedybird wrote: post #94

Earlier quoted context omitted.

Unless you're trying to go to space, there really isn't much reason to go this fast in the first place. Even relatively modest supersonic passenger flight has proven to be a commercial failure (good luck to Boom Tech inc... you guys will need it.) If you're going to space, an SSTO with scramjets would be interesting. But I think if SpaceX's reusable Starship succeeds without that tech, it would be hard to justify the…

> relatively modest supersonic passenger flight has proven to be a commercial failure Tried it once in the 70s. Didn’t work. Everyone go home.

We tried with the British-French Concorde, the US Boeing 2707, and the Russian Tupolev Tu-144. That's three tries (or maybe two, the Boeing version was cancelled before prototype completion).

Maybe we can do better today with the lessons learnt and the advances in material science since then. There's several startups banking on that. But so far commercial supersonic flight has only worked out as prestige projects, not as commercial successes.

Re: DARPA's hypersonic scramjet achieves successful flight

#159

Post by twistedpair »

patagurbon wrote: post #65
amelius wrote: post #6

US's answer to Russia's Zircon missile? https://www.military.com/equipment/weapons/why-russias-hyper... > U.S. Aegis missile interceptor systems require 8-10 seconds of reaction time to intercept incoming attacks. In those 8-10 seconds, the Russian Zircon missiles will already have traveled 20 kilometers, and the interceptor missiles do not fly fast enough to catch up.

I'm not convinced you want air breathing missiles for interception, you want solid rockets or something of that sort. There are Standard Missiles (SM-3) faster than Zircon, although they are for BMD defense. Faster ESSM/SM-2/SM-6 could be developed, and reaction time could be lowered. This is instead the equivalent to the Zircon.

The Sprint[1] missile accelerated at 100g. That's 0-mach 10 in 5s flat. It flew so fast in the lower atmosphere that it glowed white hot.

So, just saying there were some pretty fast missiles decades ago. There was also the HIBEX missile, with 400g acceleration.

[1] https://en.wikipedia.org/wiki/Sprint_(missile)

Re: DARPA's hypersonic scramjet achieves successful flight

#160

Post by JumpCrisscross »

pageandrew wrote: post #153
JumpCrisscross wrote: post #113

Earlier quoted context omitted.

> even if you can detect them they are too fast to intercept? 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.

They are slower than ballistic missiles, but fly more unpredictably. Ballistic missiles fly a parabolic trajectory and therefore an intercept can be calculated, whereas hypersonic missiles fly in the atmosphere at high speeds and can change their direction

> but fly more unpredictably

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.

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