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Scaled Composites X-Prize vehicle flying again after mods
Aviation Week & Space Technology 10/27/2003, page 14 Scaled Composites' SpaceShipOne is flying again after testing was halted to address a pitch hangup that occurred on a Sept. 23 flight (AW&ST Oct. 6, p. 43). The company conducted a full-scale wind tunnel test of the winged spacecraft's tailboom and tail surfaces, identified the source of the pitchup, developed a fix and flew it on SpaceShipOne on Oct. 17. ----------------------------------------------------------- Partial reprint of 10/06 article... Aviation Week & Space Technology 10/06/2003, page 43 Michael A. Dornheim Los Angeles Pitch hangup will result in delay and changes to design SpaceShip1 Hiccups... The glider was dropped from the White Knight carrier at 46,600 ft. and 115 kt., and Melvill spent 5-10 sec. trimming it in roll. He then began the stall entry that led to the pitchup. The recovery placed the aircraft inverted, and after airspeed had built, a 2g pullout put SpaceShipOne in a secondary departure to the left. Rudder and stick weren't stopping the departure, so Melvill added right roll trim. That halted the departure, but caused further oscillations until the roll trim was removed. "I had several iterations of overcontrol," Melvill said. "There is no feel on the stick at high altitude. Things happen slowly, but there's not much control with the stick alone. The trim has a huge amount of control, intended for supersonic flight." The departure occurred above 40,000 ft., where there is less damping of body rates than at low altitude. "Eighty-five knots in denser air could have been OK," Melvill said. The aft operational CG had not been flown before and was achieved by bolting about 170 lb. of steel plates by the dummy nozzle at the fuselage end. They were not jettisonable. There was a tank of liquid ballast in the tail that could be dumped, but it was empty. The rocket engine's nitrous oxide oxidizer and rubber fuel are placed fore and aft of the CG, respectively, so there is little change in balance during the engine firing, which is nominally at a mid-CG. |
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