Date: Wed Sep 15 1993 13:33:04 Subj: +quot;new rocket+quot; 1/2 UFO - In the interest of c

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Date: Wed Sep 15 1993 13:33:04 From: Allen Robinson Subj: "new rocket" 1/2 UFO ------------------------------- In the interest of clearing up some misconceptions about what was and was not involved in last month's initial flight of the DC-X, please take a look at the following information. My principal sources are various weekly "DC-X Update" postings made to the UseNet newsgroup sci.space by Henry Vanderbilt, exec. dir. of the Space Access Society (hvanderbilt@bix.com or 602-431-9283: voice/fax). Much of the following is quoted directly from his postings in July and August. *************************************************************** DC-X is a low-speed flight regime testbed for a proposed reusable rocket-powered Single Stage to Orbit (SSTO) transport, McDonnell- Douglas Aerospace's "Delta Clipper." DC-X is intended to prove out rocket-powered vertical takeoff, nose-first lifting-body to tail-first flight transition, and tail-first landing. It is also intended to prove out rapid turnaround of a reusable rocket by a minimal ground support crew. DC-X is being tested and flown by approximately thirty people. DC-X has already pretty much proved out rapid low-cost develop- ment of an advanced aerospace X-vehicle type engineering testbed by a small highly-motivated engineering team on a tight budget. DC-X was built by less than two hundred people, in less than two years, for about $60 million. DC-X stands 40 feet tall, is 13 feet across the base, and is roughly cone-shaped, with a circular cross-section blending into a square base. The vehicle has four maneuvering flaps, one set into each side near the base, and sits on four landing legs. DC-X masses 22,300 lbs empty and 41,630 lbs fully fuelled, and is powered by four 13,500 lb thrust Pratt & Whitney RL-10-A5 liquid oxygen/liquid hydrogen rocket motors, each able to gimbal +/- 8 degrees. The RL-10-A5 is a special version of the RL-10-A designed for wide throttling range (30% to 100%) and sea-level operation. The single DC-X vehicle was rolled out of its construction hangar at MDA's Huntington Beach, CA, plant in early April of this year, and trucked to White Sands, NM, for for ground and flight tests. Between May 20 and June 17, DC-X underwent a series of nine engine firings/vehicle systems exercises, including two firings in one day with complete defueling/vehicle servicing/refueling in between. On June 18, the DC-X crew began breaking down the ground support equipment and moving it to the WSMR flight test site. Meanwhile the DC-X was stored in a hangar. On July 16, the ground support equipment move was completed. DC-X was taken out of storage, trucked out to the flight test site, and hoisted upright onto its launch pad. On July 19, the DC-X crew began running a series of ground tests to make sure everything had made it intact and was reassembled properly. On Wednesday, August 18, at 4:43:53 local time, DC-X's engines ignited, and the cloud of white vapor silhouetting the ship's mottled gray shape turned into a brief billow of orange flame around the vehicle. A second later, the flame cloud had turned to gray smoke as the vented engine precool hydrogen finished burning off and the rocket exhaust started the concrete under the launch stand smoking. Two seconds more for the engines to settle down to a steady burn, and the DC-X reusable rocket test- bed lifted off on its first flight. DC-X, flying with a partial fuel load, jumped off the pad quickly before easing back on the acceleration and drifting to a stop 150 feet up. As the ship climbed away from the ground, the rocket exhaust cleared up, and by the time she was hovering the exhaust flames were (typically for a hydrogen rocket) almost invisible, showing only an occasional streak of orange as engine throttling produced transient changes in the fuel mix. Thirteen seconds after liftoff, DC-X tilted over a few degrees and began "translating," (sliding sideways at a brisk walking pace) while holding holding altitude, occasional puffs of vapor from a cryo tank vent on her side punctuating her stately pro- gress toward the landing site, 350 feet away. Once over the touchdown point, DC-X drifted to a halt and hovered briefly, then began her careful tail-first descent. At a hundred feet, the landing legs popped out. At about thirty feet, the rocket plumes began kicking up dust from the landing pad, and the clear exhaust flames quickly turned to incandescent pillars of fire, as concrete smoke glowed in burning hydrogen. By ten feet, DC-X was almost hidden by the smoke and dust boiling up, inching down into a swirling white-hot cushion of flame. When the landing legs finally touched ground and triggered engine cutoff, one last billow of vapor rolled out from underneath, then silence fell. DC-X stood there, at first only the nose showing through the smoke, the rest of the ship gradually coming into view as the breeze cleared the smoke away. *** That was it! Sorry if that disappoints some. No diversion. Nothing suspicious. No electromagnetic gravimetric neutrali- zation at work. The worst thing that happened to DC-X during its first flight was that one side of the fiberglass nose cone was scorched. There are several spares. This probably happened right after engine start, when the cloud of vented hydrogen around the vehicle ignited. This looked scary, but it is a routine part of opera- ting DC-X, albeit one that turned out to be a bit more spec- tacular than planned. Liquid hydrogen is run through the en- gines to precool them before startup, then vented to the air, producing the vapor clouds visible engine start. When the en- gines start, unless there's a strong breeze, the hydrogen con- centration nearby is high enough to ignite, producing a half- second fireball around the bottom of the vehicle. This is how DC-X lost its McDonnel-Douglas decals and had its white factory paint job turned to mottled gray during the test stand engine firings back in May and June. Everything below the nose cone is designed to stand the heat, and, of course, in any space- worthy descendant of DC-X the nose cone will not be made of fiberglass. The current DC-X program is funded through flight test and data analysis this fall, and ends after that. There is an ongoing effort to get Congress to fund a three-year followon program, currently called SX-2. This tentatively looks like being a reusable suborbital vehicle powered by 8 RL-10-A5 engines, capable of reaching Mach 6 and 100 miles altitude, built with orbital-weight tanks and structure, and able to test orbital- grade heat-shielding. The SX-2 program goal would be to demonstrate all remaining technology needed to build a reusable SSTO vehicle. Once SX-2 has been tested, all that should be necessary to produce a functioning reusable SSTO is to scale up the SX-2 structures and install more powerful rocket engines. AR --- GEcho 1.00 * Origin: Contemplate, cogitate, cerebrate. |||Think Mail (1:391/1370)

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