LOS
ANGELES (AP)—An unmanned hypersonic glider likely aborted its 13,000
mph flight over the Pacific Ocean last summer because unexpectedly large
sections of its skin peeled off, the U.S. Defense Advanced Research
Projects Agency said Friday.
The
Hypersonic Technology Vehicle-2, launched from Vandenberg Air Force
Base, Calif., atop a rocket and released on Aug. 11, 2011, was part of
research aimed at developing super-fast global strike capability for the
Department of Defense.
The
vehicle demonstrated stable aerodynamically controlled flight at speeds
up to 20 times the speed of sound, or Mach 20, for three minutes before
a series of upsets caused its autonomous flight safety system to bring
it down in the ocean, DARPA said in a statement.
A
gradual wearing away of the vehicle’s skin was expected because of
extremely high temperatures, but an independent engineering review board
concluded that the most probable cause was “unexpected aeroshell
degradation, creating multiple upsets of increasing severity that
ultimately activated the Flight Safety System,” the statement said.
Initial
shockwaves created by the gaps in the skin were more than 100 times
what the vehicle was designed to withstand, but it was still able to
recover and return to controlled flight, said Kaigham J. Gabriel,
DARPA’s acting director.
Eventually the upsets grew beyond its ability to recover.
The 2011 flight was the second time an HTV-2 was launched. The first flight, in April 2010, also ended prematurely.
Data
from that flight was used to correct aerodynamic design models for the
second test, resulting in controlled flight, and now data from the
latest flight will be used to adjust assumptions about thermal modeling,
Air Force Maj. Chris Schulz, the DARPA program manager, said in the
statement.
“The
result of these findings is a profound advancement in understanding the
areas we need to focus on to advance aerothermal structures for future
hypersonic vehicles. Only actual flight data could have revealed this to
us,” he said.
Most
specific details of the program are secret. DARPA has released artist
renderings showing a craft that looks something like the tip of a spear.
After the 2011 flight the agency released handheld video, taken aboard a
monitoring ship, that showed a dot streaking across the sky.
The
HTV-2 would have splashed down in the ocean regardless of the anomaly.
The vehicles are intended to be used once and are not recovered.
Source: The Associated Press
