November 26, 2010
Govt To Try Again For Successful Falcon HTV-2 Flight
Scientists with the US Department of Defense are on track to conduct a second test launch next year of the Falcon HTV-2 experimental superweapon after the maiden test flight ended abruptly when the autopilot crashed the unmanned glider into the ocean as a safety measure.
The Falcon Hypersonic Test Vehicle was designed to fly at the top of the atmosphere just below space, and is an important element of the Pentagon's Conventional Prompt Global Strike program, which centers on building non-nuclear weapons that can strike conventionally anywhere in the world in less than 60 minutes.The Defense Advanced Research Projects Agency (DARPA) last week released a statement revealing for the first time that the April 20 test flight ended when the superweapon's autonomous onboard control system deliberately terminated the flight as a safety precaution.
"When the onboard system detects [undesirable or unsafe flight] behavior, it forces itself into a controlled roll and pitchover to descend directly into the ocean," Eric Mazzacone, spokesman for DARPA, explained to The Washington Times in an email.
An independent review board found that the flight was terminated after the aircraft's roll "exceeded the available control capability" of the onboard auto piloting system. Experts said such problems are expected in test flights.
The $308 million Falcon HTV-2 is a suborbital near-space vehicle launched from a Minotaur rocket built from a decommissioned ballistic missile. On the very edge of the atmosphere, in a procedure known as "clamshell payload fairing release," the launch missile deploys the aircraft, which then glides above the Earth at more than 13,000 mph -- more than 20 times the speed of sound.
The Pentagon is pushing to build a generation of hypersonic superweapons that will be able to strike quickly at urgent targets.
The issue has increased urgency after a recent nuclear arms accord negotiated with Russia. Experts say the new generation of hypersonic strike craft would not count against the limit's the treaty places on strategic weapons. However, during negotiations, the US promised to discuss the new weapons in a treaty consultation commission.
But some other proposals for CPGS systems, such as putting conventional warheads on existing submarine-launched ballistic missiles, would count against the caps set by treaty.
Falcon is just one of a series of conventional long-range strike programs. DARPA also has another project in the works, called Arclight. And the Air Force, which developed the Falcon HTVV-2 jointly with DARPA, successfully test-flew a hypersonic powered flight technology called scramjet -- "supersonic combustion ramjet."
The CPGS program will develop weapons that can "strike globally and rapidly with joint conventional forces against high-payoff targets" using such attacks in as little time as minutes or hours, "as opposed to the days or weeks needed for planning and execution with existing forces," according to a Congressional Research Service (CRS) report.
The report said the HTV-2 was being produced by Lockheed Martin, using technology that was developed for a precision-guided warhead called ER.
Richard P. Hallion, a former chief historian for the US Air Force, and a leading authority on hypersonic flight, told The Washington Times that the fiery end to the Falcon's April test flight "raises serious questions about how well DARPA conceived and executed the project."
According to the DARPA statement, the CRS review board found that the Falcon had experienced "a slow divergence about the longitudinal axis (in roll) which continued until the roll rate reached a threshold where the autonomous flight system commanded flight termination."
Inertial coupling, as flight scientists call the process by which yaw generates roll, "is a very old problem," said Hallion. "It was a killer in the early days of test flights" of the first supersonic aircraft in the 1950s.
"It clearly remains a problem in hypersonic flight," he added, noting that the Falcon "is basically a delta wing type vehicle," lacking the large vertical surfaces like an aircraft tail that can be used to control roll.
Hallion questioned whether DARPA had "made certain they had adequate design analysis and [ground] testing before" the test flight.
Mazzacone, when asked whether DARPA had rushed into flight-testing, said there are many unknowns when it comes to hypersonic flight. "A significant amount of preflight analysis was conducted. Which is in essence why we need to fly again. "¦ There's more to learn in this area," he told the Washington Times.
DARPA had conducted "extensive post-flight testing" of the Falcon at the T-9 hypersonic wind-tunnel facility at the USAF Arnold Engineering Center in White Oak, Maryland, according to former USAF chief scientist Mark J. Lewis.
"They have really tried to learn the lessons" of the failed ending to the first test, he said. Such failures are to be expected when testing new technology -- such as hypersonic planes -- that pushes the limits of engineering and human understanding of aerodynamics.
"There cannot be 100 percent confidence in the outcome," said Lewis. "That's the nature of flight testing."
The independent engineering review board had "reviewed and concurred with" a series of corrective measures for the next test flight, DARPA said in its statement.
"Engineers will adjust the vehicle's center of gravity, decrease the angle of attack flown and use [a system of small onboard maneuver rockets] to augment the vehicle flaps when HTV-2 flies next summer," David Neyland, DARPA Tactical Technology Office director, told The Times.
A previous proposal to achieve CPGS capability was shot down by Congressional opposition. That program was aiming to fit conventional warheads on to US submarine-launched ballistic missiles. The concern was that other nuclear-armed nations might mistake the launch of such a weapon for the onset of a nuclear war.
Supporters of hypersonic weapons assured that they would not be launched from an ICBM site, and that the trajectory would be different from that of a nuclear missile.
"It's a totally different flight profile," said Lewis.
But arms control advocates say the risk of a deadly mistake is still too high.
Still, Hallion said, long-range conventional strike weapons will address novel threats -- such as terrorist activity and rogue states building weapons of mass destruction -- and will also help reduce US reliance on nuclear weapons as a strategic option in more conventional conflicts.
"It's a way to turn fleeting intelligence into actionable intelligence," Hallion said. "If you know something is about to happen, you're able to do something about it," he added.
Image Caption: Illustration of Hypersonic Test Vehicle (HTV) 2 reentry phase.
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