Stronger than expected shockwaves on the outer shell of a hypersonic vehicle designed by the Defense Advanced Research Projects Agency (DARPA) caused it to crash during a test flight last year, an independent engineering review board (ERB) has concluded.
DARPA's Hypersonic Technology Vehicle (HTV-2) successfully flew nearly 13,000mph for about three minutes in its second test flight on August 11 before its safety system sent it crashing into the Pacific Ocean nine minutes into the flight. Shockwaves, 100 times more than the vehicle was designed to withstand, peeled off portions of the aircraft's thermal shell, causing the early flight termination, the ERB said after a seven-month analysis of data collected from the flight.
An artist's concept of the flight of DARPA's HTV-2, which crashed into the Pacific last August after greater than expected shockwaves peeled off parts of its thermal shell. (Source: DARPA)
Official findings of the ERB said that the "most probable cause of the HTV-2 Flight 2 premature flight termination was unexpected aeroshell degradation, creating multiple upsets of increasing severity that ultimately activated the Flight Safety System," according to DARPA. The HTV-2 is an unmanned, rocket-launched, maneuverable aircraft capable of going Mach 20, or about 13,000mph. Flying at such a speed would allow an aircraft to travel from New York to Los Angeles in less than 12 minutes.
The agency put a positive spin on feedback gleaned from the investigation, saying the fact that the flight was able to recover from initial shockwaves before the safety system triggered its Pacific plunge showed that HTV-2's engineers learned valuable design lessons from its first flight, which also ended sooner than expected.
All they need to do is get some materials from one of those UFO's at Area 51 - problem solved! :)
I guess the point is that you'll never know if you don't try. I'm sure they learned a lot about shockwaves that will probably be useful in other applications, including slower speed craft.
It seems to me that ceramics is the answer here - our current technology can handle 2k-3k degree temperatures. I'm not sure how they would hold up to shockwaves since they can be brittle, but at that speed and temperature they may actually be a bit more flexible.
Flying fast within the atmosphere has its applications - there will be times that going out of the atmosphere simply isn't practical - short range applications, for example. I cannot imagine the sonic properties of something travelling Mach 20, it would certainly not be a stealth vehicle; but when you're going that fast you don't need to be stealth.
Avoiding missles, etc doesn't count if it can't get there and burns up on the way. Far better is skipping off the atmosphere or full space flight, both are far easier to do, have far more range, payload. And they are far safer from countermeasures.
There is not much that can withstand 5000F or so the ship has to endure. If you make it bigger for payload, the drag, heat just increases.
I'm having a hard problem find metals, etc that can withstand just 1500F with a decent lifetime which hasn't been easy. Much less the temps a hypersonic craft has to endure.
Over 2500mph just isn't smart in the atmosphere and this, every test before proves this. No?
So please tell me how far can they go and how much payload can they carry? Enquiring minds want to know?
This is a DARPA project. Being able to fly that fast in the atmosphere means that it can outrun anything shot at it (SAM, bullets, etc.) - so that it could get somewhere fast and drop a payload (bombs, etc.). It could also be used to catch anything in the air (planes, missiles, etc.). It would also be extremely difficult to track or anticipate. Even a laser would have a hard time hitting it, especially if it is making random micro adjustments to its flight path. LA to NY in 12 minutes means that it could get to North Korea in under 30 minutes.
Chuck, I was also guessing that the 100x shockwaves might be an anomaly. I just assumed that we knew a lot more about their potential force after all this time, and could therefore compute the relevant loads.
In the early days of SPICE (circuit simulator), the late Bob Pease had a rant in his weekly column. He published a circuit to simulate in SPICE and pointed out a certain resistor dissipated negative power! He said he couldn't wait to put together the real circuit and watch it get colder by the minute. He speculated on the breakthroughs it would bring to food and beer storage.
Then he got serious and made the point: simulations are a good tool but no substitute for hands-on prototypes. Of course simulation software has made huge advances in all disciplines but Pease's point still rings true today.
I absolutely agree...this was a fantastic accomplishment. After all, the whole point of testing something is to determine potential failure modes. Simulations give us a fantastic set of tools to better predict failure, but there is really no subtitute for an actual real world test. So often, we discover important variables or interactions that were not anticipated by simulation.
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