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DARPA's hypersonic scramjet achieves successful flight

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Re: DARPA's hypersonic scramjet achieves successful flight

#81

Post by jhgb »

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.

Not quite sure why interceptor missiles would have to "fly fast enough to catch up" unless you're shooting at a missile departing from you (that is to say, unless you actually have to catch up with something).

Re: DARPA's hypersonic scramjet achieves successful flight

#82

Post by Gravityloss »

pengaru wrote: post #70
sonofhans wrote: post #28

Earlier quoted context omitted.

The J58 powering the SR-71 is still one of the most complex engines ever built. The space shuttle is a simple rocket by comparison. https://en.wikipedia.org/wiki/Pratt_%26_Whitney_J58

And the SR-71 is so simple the complexity falls off a cliff at the engine, hence your inclination to only care about that in comparing the two. The space shuttle is like a reusable mobile space station, airlocks and all. Occupants of the SR-71 wore space suits the entire time, there's a lot of minimalism on display in the SR-71 which is a large part of what makes it so glorious.

The SR-71 was very complex. For example it had multiple heat exchangers to get rid of heat, to transfer it to the fuel before it was combusted. The titanium structure was complex to maintain. Welding needed to be done in "bubble" work stations under protective gas.

Re: DARPA's hypersonic scramjet achieves successful flight

#83

Post by _moof »

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.

For blunt-body spacecraft, ionization starts at around Mach 10. The aerodynamics of a missile will be different of course. Regardless, there is headroom above the Mach 5 hypersonic threshold before blackout occurs.

Re: DARPA's hypersonic scramjet achieves successful flight

#84

Post by jhgb »

sudosysgen wrote: post #79
jhgb wrote: post #78

> The HAWC vehicle operates best in oxygen-rich atmosphere, where speed and maneuverability make it difficult to detect in a timely way. 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.

Plasma stealth is an existing approach to radar stealth that is made easier by hypersonic speeds. 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 aw…

> 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

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.

Re: DARPA's hypersonic scramjet achieves successful flight

#85

Post by speedybird »

jackschultz wrote: post #2

DARPA has such a list of impressive, world wide useful technologies that wouldn't have been able to be created without funding from the government at the time given the time and money and at time, unlikeliness to be successful [0]. It really sucks that there's a 'D' for 'Defense' at the front of the acronym. Their website says they're "creating breakthrough technologies and capabilities for national security". Horrib…

> It really sucks that there's a 'D' for 'Defense' at the front of the acronym.

Time for a new euphemism? The U.S. Department of Defense was called the U.S. Department of War until the end of the 1940s. Maybe this time we can call it the Department of Peace since defense apparently doesn't sound so good to people anymore.

Re: DARPA's hypersonic scramjet achieves successful flight

#86

Post by speedybird »

masklinn wrote: post #7
mensetmanusman wrote: post #3

Mach 5 is a bit faster than the Virgin Galactic flight (Mach 3). The folks on Inspiration reached ~ Mach 23.

> Mach 5 is a bit faster than the Virgin Galactic flight (Mach 3) Mach 5 is a lot faster than Mach 3, not only in relative terms (it's 40% faster) but in absolute terms as well: around mach 5 is a regime change where the physics of flight get altered and interference effects become extremely significant, small changes to any surface component will have major impact on airflow, and thus will affect any component downs…

> This makes air-breathing hypersonic devices a much bigger challenge than air-breathing supersonic ones.

Indeed, and the Virgin Galactic vehicle isn't even either of those; it uses a hybrid rocket engine instead of breathing air. Hybrid rocket engines are fairly simple compared to liquid fueled rocket engines and are fairly safe compared to solid fuel rocket engines (although the fatal V.G. explosion some years ago should perhaps challenge this wisdom?) However they're probably a dead end technology and I don't think V.G. will ever get to orbit with them.

Re: DARPA's hypersonic scramjet achieves successful flight

#88

Post by avmich »

nradov wrote: post #68
throwaway210222 wrote: post #50

Earlier quoted context omitted.

No, no. Ukraine paid the 'entry price' that was asked of them to be protected by USA, (and France, UK, Russia, China) by surrendering their nuclear weapons. This was a level of vulnerability and trust in third parties the good citizens of USA (and the others above) would never for a second countenance. The USA (and the others) willingly signed up to the deal [1]. And then failed to do any deterring when it was time t…

That was a non-binding memo. If Ukraine wanted protection then they should have insisted on a mutual defense and non-aggression treaty.

> That was a non-binding memo.

That's not the problem of Ukraine. The whole world sees what agreements like that are worth. Alternatively, if that would be the binding memo, and USA broke the "legally binding" promise, nobody would prosecute. The reaction of the world would be about the same.

Bottom line: non-bindingness doesn't matter here.

Re: DARPA's hypersonic scramjet achieves successful flight

#89

Post by Shank »

jhgb wrote: post #81
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.

Not quite sure why interceptor missiles would have to "fly fast enough to catch up" unless you're shooting at a missile departing from you (that is to say, unless you actually have to catch up with something).

You don’t always have missile interceptors on the target land. Aegis is a mobile platform that can be deployed anywhere, and being overflown is a real possibility. For example, your missile defense platform might be off the coast several km, and the target to intercept flies over it aiming for the land behind it. In this scenario, any interceptor launched from that platform would have to “catch up.”

Re: DARPA's hypersonic scramjet achieves successful flight

#90

Post by tomcam »

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

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