Hypersonic Test Aircraft Peeled Apart After 3 Minutes of Sustained Mach 20 Speed

coondoggie writes "DARPA's experimental Hypersonic Technology Vehicle (HTV-2), lost significant portions of its outer skin and became uncontrollable after three minutes of sustained Mach 20 speed last August. That was the conclusion of an independent engineering review board investigating the cause of what DARPA calls a 'flight anomaly' in the second test flight of the HTV-2. Quoting the report: 'The resulting gaps created strong, impulsive shock waves around the vehicle as it traveled nearly 13,000 miles per hour, causing the vehicle to roll abruptly. Based on knowledge gained from the first flight in 2010 and incorporated into the second flight, the vehicle's aerodynamic stability allowed it to right itself successfully after several shockwave-induced rolls. Eventually, however, the severity of the continued disturbances finally exceeded the vehicle's ability to recover.'"

Expert opinion

[Anonymous Coward]

As a person who flies hypersonic aircraft for a living this is notable on several layers.

1. They did a test and it went far past hypersonic (M5).

2. They achieved M20, altitude adjusted

3. All that happened after 3 minutes is the materials failed

4. It lasted 3 minutes!

To me this is a stupendous success.

I am a hyper-critic of most of the hypersonic tests we all hear about.

Spend more money on this.

JJ

Re:Close to re-entry speed

[networkBoy]

And while they're busy doing that they often manage to put on one hell of a show:
* this effort
* the autonomous vehicle DARPA Challenge
* other random bits that we read about
* certainly other random bits we have no idea about, but I bet they're cool!
-nB

Re:Expert opinion

[Anonymous Coward]

You fly hypersonic aircraft regularly? You either are: an space shuttle pilot, a military test pilot breaking his clearance, or making shit up. Who modded this up?

Re:Expert opinion

[Grayhand]

What I found interesting is something similar happened to Chuck Yeager when he was trying to hit Mach 1. The aircraft developed a strong vibration as he approached Mach 1. At the time Mach 1 was pushing the limits of what materials and technology could handle. The forces involved at Mach 20 are insane so I would also consider it a major success and it proves the technology. Now it's a matter of refining the construction and materials to avoid the failure issue but it looks very possible. I do have to question the commercial potential though. I'm not convinced that material fatigue won't be an ongoing issue with that kind of constant stress. Even with the space shuttles which didn't face a fraction of the stresses they had two blow up. Both accidents were avoidable but what accident isn't with prior knowledge. The engines are capable but it could be a very long time until the materials are reliable enough for extended commercial use.

Re:Expert opinion

[Anonymous Coward]

You fly hypersonic (mach 5+) aircraft for a living? Really?

Re:scientifically

[zippthorne]

If you can go that fast in an atmosphere, you can use an air-breathing engine to get you most of the way to LEO...

Re:Expert opinion

[El_Oscuro]

Mach 20 happens to be about orbital velocity. [freemars.org] Assuming they can improve the materials somewhat, being able to do that in a plane instead of a rocket would be pretty useful.

Re:scientifically

[Cyberax]

What's even cooler, that speed is close to orbital speed. So with little additional thrust this plane can make it into orbit!

Atmospheric hypersonic flight waste of money

[caseih]

The only practical way to obtain hypersonic speeds is to go suborbital, and that really enters the realm of rockets as heat shields are very heavy.

  I think the developers of the SR-71 could have predicted these failures. The SR-71 _only_ went Mach 4 or so, at altitudes of greater than 60,000 feet or so. And at full speed the plane was so hot that pilots couldn't touch the canopy of the cockpit (I think the skin temps were at least a 1000 degrees pick your unit) and the plane lengthened by some considerable amount. To handle those speeds special materials were developed and required, which we haven't really exceeded to this day. Given the temperatures produced at Mach 20 in an atmosphere, even thin (think rocket reentry), building control surfaces and heat shields light enough to actually fly is very very difficult, if not impossible. The shuttle had heat tiles to withstand the atmospheric heating but hey were somewhat heavy and the shuttle didn't really fly during reentry so much as plow through the air belly down until the shuttle slowed down to lower mach numbers and in thicker air. And the failure of any heat shield at these Mach numbers will always lead to total destruction of the vehicle as this test and the Columbia tragedy proved.

All this said, having materials that could allow a craft to actually fly under under such conditions as reentry poses would actually be a real boon to space flight I think, but I doubt we will ever find materials that can provide this.

Re:scientifically

[HornWumpus]

ICBM systems are sunk costs. Some possible salvage value as booster stages, but basically the money is gone. Better to keep them functioning lest someone try to collect on our debt.

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