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  • DARPA's HTV-2 Didn't Phone Home
    Posted by Graham Warwick 3:57 PM on Apr 24, 2010

    DARPA says it lost contact with its HTV-2 hypersonic test vehicle 9min after launch of the dart-like glider atop a Minotaur IV Lite booster from Vandenberg. The agency's brief press release says the Minotaur successfully delivered its payload to the desired separation conditions and deployed the HTV-2, so telemetry was lost after the unpowered vehicle was released at the edge of the atmosphere.

    One possibility is that a sheath of plasma that would form around the vehicle as it reentered the atmosphere at Mach 20-plus could have interfered with telemetry. But in an interview with Aviation Week before the flight, DARPA program manager Paul Erbland said the risk of ionized gases attentuating signals from the vehicle was "relatively modest", particulary at the high altitude the HTV-2 was deployed.

    blog post photo
    Artwork: DARPA

    The release does not say what happened to the HTV-2 - the vehicle had a specially developed autonomous flight safety system designed to detect any deviation from the planned route and automatically terminate the flight.

    The Lockheed Martin-built HTV-2 was supposed to fly 4,100nm across the Pacific in 30min in the first of two flights to demonstrate aerodynamic, thermal-protection, and guidance, navigation and control technology for a prompt global strike weapon able to fly 9,000nm in under 2 hours. The second flight is planned for 2011.

    The sharp-edged, highly swept HTV-2 is designed to demonstrate long endurance at high speed by achieving an "unprecedented" hypersonic lift-to-drag ratio, much higher than the Space Shuttle's, and having a carbon-carbon aeroshell that provides thermal protection with minimal ablation, unlike a reentry-vehicle heat shield that burns off to shed heat.

    Looking for success among the bad news, DARPA says the Minotaur executed "first of its kind" energy-management maneuvers before releasing the HTV-2. These were required, Erbland said, because even with just three Peacekeeper missile stages, the Minotaur IV Lite is more powerful than required. So the third stage maneuvered to bleed off energy before deploying the HTV-2 at the edge of the atmosphere.

    Even then, he said, the booster would overshoot the desired insertion conditions by around 100,000ft, so the HTV-2 was programmed to reenter then pull up to the correct altitude to begin its hypersonic glide - which was planned to start around 200,000ft and Mach 20 and end around 100,000ft with the HTV-2 rolling inverted and pulling down into a hypersonic dive into the ocean off Kwajalein. Well, that was the plan.

    Uncovered by the incomparable flateric on secretprojects.co.uk, this graphic from a December presentation by DARPA Tactical Technology Office director David Nyland suggests contact with the HTV-2 (on the yellow Mission A line) was lost somewhere between beginning reentry and starting its hypersonic glide.

    blog post photo
    Graphic: DARPA

    Investigation of the telemetry failure is under way. But the question now is what this means for the second HTV-2 flight (red Mission B line above). This is intended to demonstrate the cross-range capability provided by the vehicle's hypersonic aerodynamic efficiency - and key to a prompt global strike weapon - involving sustained maneuvers beyond the simple S-turns planned for the first flight. It's more likely the second flight will have to be a repeat of the first.

    Tags: ar99, DARPA, Falcon, hypersonics

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