Message posted by Peter Merlin on August 13, 2011 at 0:04:43 PST:
I find it astonishing that people can't see the significance of the HTV-2 flight tests. Newspaper reporters and people on a variety of discussion forums keep describing the tests as failures. The first HTV-2 flight, on April 22, 2010, produced nine minutes of unique hypersonic flight data, including 139 seconds of aerodynamic data at speeds between Mach 17 and Mach 22 – up to 16,700 miles per hour. By comparison, the X-43A scramjet demonstrator made two flights to around Mach 7 and Mach 10, with a planned engine operation time of about 11 seconds, followed by additional data collection as the vehicles plummeted toward the ocean. The many “firsts” achieved during the maiden flight of the HTV-2 included validation of two-way communication with the vehicle during high-speed flight, verification of the effectiveness of the craft’s reaction control system, and demonstration of the vehicle’s capability to maintain Global Positioning System signals while traveling 3.6 miles per second. It was also the first use of an autonomous flight termination system. It would have been nice to get the full planned 30-minute flight time but things often go wrong with new cutting-edge technology. That is why they call it flight test. The vehicle’s flight profile was extremely challenging for mission planners. Before separation of the HTV-2, the Minotaur rocket had to execute unusual energy-management maneuvers because even with just three stages, the Minotaur IV Lite was more powerful than required. To compensate, the rocket’s third stage maneuvered to bleed off energy before deploying the HTV-2 at suborbital altitudes. After separation from its booster, the HTV-2 used reaction-control thrusters to orient itself for atmospheric reentry. Using a combination of RCS and aerodynamic controls, the HTV-2 followed its dive with a pull-up maneuver to control speed and altitude. During the ensuing glide phase the vehicle autonomously performed aerodynamic test maneuvers to test aerodynamic performance. Like the X-43A, the HTV-2 was not designed to be recovered after a flight. The only thing researchers got back was data. While the two recent flights did not last as long as hoped, they each provided valuable hypersonic data before telemetry contact was lost.
In Reply to: Re: DARPA - we have a problem ... posted by Mark Lincoln on August 12, 2011 at 15:37:55 PST:
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