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.'"

Comments

slashdot

[Anonymous Coward]

This is slashdot. The only point of comments now is off-topic nonsense, hopefully modded 'informative'

Re:scientifically..or not

[Anonymous Coward]

Except for the fact it runs on hydrogen peroxide and methanol. Plus, I'm given to understand the proposed full scale version would run on hydrogen slush and LOX.... aka rocket fuel.

Re:WHAT THE FUCK IS THE ALTERNATIVE?

[iceaxe]

So what the fuck is the alternative, then?

Um, it's a glider, launched from a rocket, which would probably use a hydrogen based rocket fuel or some other.. um.. why am I answering an AC?

Link to the actual press release

[DerekLyons]

Here's the actual press release (which Network World just cut-and-pasted): http://www.darpa.mil/NewsEvents/Releases/2012/04/20.aspx

Re:Disposable Vehicles?

[cdrudge]

It depends on how long it takes to get to those speeds. At 9.8m/s^2, easily handled as evident from people parachuting, it would take about 11 minutes to reach mach 20. Once you reach that speed, there's no problem going that fast just because of speed...spacecraft have been doing that for some time. Apollo 10 holds the record for fastest manned vehicle at nearly 25,000MPH.

According to the g-force wiki page, early experiments showed that untrained individuals could survive 17g's accelerating and 12g's decelerating (in a facing forward orientation) which would translate to 40 and 56 seconds respectively.

The maximum recorded g's sustained by a person for more then a split second is 46.2g's and it would take 14.5 seconds of acceleration or deceleration to match that rate.

The hard part about going that speed is the friction and stresses on the aircraft flying through the atmosphere.

Re:Expert opinion predictable whining

[Anonymous Coward]

I fly unmanned hypersonic aircraft. I would call these rockets spacecraft except they don't go to space.

I and nobody else flies "in" them. The temperatures are too high.

Even SS1 had a peak velocity of altitude adjusted 240 knots at sea level.

The goal here is a 1 hour to target RPV. Not a passenger aircraft and not Fedex to China. This is a military thing. Rediculous cost.

BTW you can see my M5 "aircraft" on the web anytime you want. Search for 152mm rocket in the USA. The 229mm one goes faster and the 457mm "can be manned", albiet not hypersonic. Just well above supersonic.

JJ

Re:Close to re-entry speed

[Thundersnatch]

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

also..
* the fucking Internet

you kids these days need to learn your history

Re:scientifically

[HornWumpus]

You realize it was boosted to speed on a conventional rocket? Don't mistake an aerodynamic testbed for a working vehicle.

Re:scientifically

[jd]

In theory, yes. The type of design (a "waverider") places the hypersonic shockwave directly beneath the vehicle. Basically, you're surfing the shockwave. This reduces the stresses involved, improves stability and should allow considerably more control than could be achieved with the space shuttle (you have sufficient lift from a waverider to glide). Waveriders do have disadvantages - most designs only work at specific speeds, the wings have a habit of frying and they rely on cooling by radiation (only effective at high altitude).

Old wisdom on waveriders:
http://research.lifeboat.com/surf.htm
http://www.aerospaceweb.org/design/waverider/waverider.shtml

Published theory:
http://www.waset.org/journals/waset/v79/v79-79.pdf
http://www.dept.aoe.vt.edu/~mason/Mason_f/ConfigAeroHypersonics.pdf

Multi-speed waveriders:
http://www.springerlink.com/content/x75nh2154nuh5464/

Amateur waverider research:
http://www.gbnet.net/orgs/staar/waveriders.html

NB: The STAAR group beat NASA and the US DoD to the first working waverider airfoil, as noted on their site. Perhaps NASA's problem with their current design is that they're not threatening the engineers with bagpipe music.