DARPA is still unsure how its Hypersonic Test Vehicle (HTV-2) lost contact with range controllers and destroyed itself before completing a planned 30-min Mach 20 gliding flight across the Pacific Ocean.


By Tariq Malik, SPACE.com Managing Editor
11 August 2011

 The U.S. military lost contact with an unmanned hypersonic glider shortly after it launched on a test flight today (Aug. 12) as part of a global strike weapons program to develop vehicles capable of flying at Mach 20 and reach any target in the world in an hour.

The DARPA glider, called the Falcon Hypersonic Test Vehicle 2 (HTV-2), blasted off from Vandenberg Air Force Base in California atop a Minotaur 4 rocket at 7:45 a.m. PDT.

Falcon Hypersonic HTV-2

Payload Fairing Falcon Hypersonic HTV-2 Jettisoned

According to DARPA updates, the test flight appeared to go well until the glide phase, when monitoring stations lost contact with the HTV-2 vehicle. [Photos: DARPA Hypersonic Glider’s Mach 20 Test]

“Range assets have lost telemetry with HTV2,” DARPA officials wrote in a Twitter post about 36 minutes after launch.

Monitoring stations further down range of the vehicle’s flight path over the Pacific Ocean also did not find the hypersonic HTV-2 glider. The vehicle is designed to crash itself into the ocean at the end of its mission.

“Downrange assets did not reacquire tracking or telemetry.  HTV2 has an autonomous flight termination capability,” DARPA officials wrote.

Whether the test flight met all of its objecties still remains unclear, but this is the second test flight of the Falcon HTV–2 program that ended prematurely. An April 2010 test flight ended nine minutes into flight, also due to loss of contact.

The HTV-2 vehicle was expected to reach suborbital space, then re-enter Earth’s atmosphere and glide at hypersonic speed to demonstrate controllable flight at velocities of around Mach 20, which is about 13,000 mph. At that speed, more than 20 times the speed of sound, a vehicle could fly from New York City to Los Angeles in 12 minutes, DARPA officials said.

A video animation of the HTV-2 flight test depicts how the the hypersonic vehicle was expected to pop free of its rocket, then soar through Earth’s atmosphere for an inevitable, and intentional, plunge into the Pacific Ocean at the end of its mission.

A global strike capability

The HTV-2 is part of a program called Prompt Global Strike called DARPA (which is short for Defense Advanced Research Projects Agency) to develop advanced weapons systems with extreme range.

“The ultimate goal is a capability that can reach anywhere in the world in less than an hour.” DARPA officials wrote in a mission description. [7 Sci-Fi Weapons of Tomorrow Here Today]

Today’s launch is the second test flight for DARPA’s Falcon HTV test program. An April 2010 launch lasted only nine minutes, when DARPA lost contact with its HTV-1 vehicle shortly after it separated from its rocket booster. The HTV vehicles were built for DARPA by Lockheed Martin Corp.

“The HTV-2 vehicle is a ‘data truck’ with numerous sensors that collect data in an uncertain operating envelope,” DARPA stated in a mission description.darpa aircraft

This diagram details the sequence of events of the hypersonic Falcon HTV-2 flight. CREDIT: DARPA

How the hypersonic HTV-2 should fly

For today’s hypersonic flight test, the HTV-2 vehicle was expected to launch into suborbital space, separate from its Orbital Sciences Corp.-built Minotaur 4 rocket, then re-enter the atmosphere. During the re-entry phase, the vehicle was expected to use rocket thrusters to help maintain its course, according to a DARPA description.

After the re-entry maneuver, the HTV-2 was slated to enter a pull-up phase to control its speed and altitude ahead of the long glide back to Earth. During the glide, the vehicle is programmed to perform maneuvers to test aerodynamic performance, DARPA officials said.

The HTV-2 was expected to end its hypersonic test flight by performing a roll maneuver to intentionally crash into the Pacific Ocean. DARPA officials said more than 20 observing stations will monitor the entire flight from space, land, ships and aircraft.

Hypersonic tests in wind tunnels on the ground can typically recreate conditions at speeds only up to Mach 15, and only for a few milliseconds at a time, Schulz said.

“And even then we wouldn’t know exactly what to expect based solely on the snapshots provided in ground testing,” Schulz said. “Only flight testing reveals the harsh and uncertain reality.”

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Ares Defense Technology

Aug. 11, 2011

The hunt is on for clues as to why Darpa’s second, and final, Hypersonic Test Vehicle (HTV-2) lost contact with range controllers and destroyed itself before completing a planned 30-min Mach 20 gliding flight across the Pacific earlier today.

Darpa was doing a good job of keeping everyone informed on the progress of the test using Twitter until the appearance of the ominous words “Range assets have lost telemetry with HTV-2. More to follow.” A while later the site said simply “Downrange assets did not reacquire tracking or telemetry. HTV-2 has an autonomous flight termination capability.”

Prior to this, the vehicle had been deployed successfully into its glide phase by an Orbital Minotaur IV Lite launcher which separated from HTV-2b at around Mach 20.

 In its first statement on the loss, Darpa says, “the Minotaur IV vehicle successfully inserted the aircraft into the desired trajectory.  Separation of the vehicle was confirmed by rocket cam and the aircraft transitioned to Mach 20 aerodynamic flight.  This transition represents a critical knowledge and control point in maneuvering atmospheric hypersonic flight.  More than nine minutes of data was collected before an anomaly caused loss of signal.  Initial indications are that the aircraft impacted the Pacific Ocean along the planned flight path.”

Darpa HTV-2 program manager Air Force Maj. Chris Schulz says “we know how to boost the aircraft to near space.  We know how to insert the aircraft into atmospheric hypersonic flight.  We do not yet know how to achieve the desired control during the aerodynamic phase of flight.  It’s vexing; I’m confident there is a solution. We have to find it.”

An independent engineering review board is being set up to review and analyze data from the August 11 flight. “This data will inform policy, acquisition and operational decisions for future Conventional Prompt Global Strike programs—the goal of which, ultimately, is to have the capability to reach anywhere in the world in less than one hour,” says Darpa.

Click here to see a video simulation of what HTV-2b had planned to do during the flight.

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