The DC-X, short for Delta Clipper or Delta Clipper Experimental, was an uncrewed prototype of a reusable single-stage-to-orbit launch vehicle built by McDonnell Douglas in conjunction with the United States Department of Defense's Strategic Defense Initiative Organization (SDIO) from 1991 to 1993. Starting 1994 until 1995, testing continued through funding of the US civil space agency NASA. In 1996, the DC-X technology was completely transferred to NASA, which upgraded the design for improved performance to create the DC-XA. After a test flight of DC-XA in 1996 resulted in a fire, the project was canceled. Despite its cancellation, the program inspired later reusable launch systems. Michael D. Griffin has since praised the program as "government R&D at its finest." Blue Origin's New Shepard and SpaceX's Falcon 9 reusable launch vehicles were inspired by the DC-X, with many of the same engineers involved. Elon Musk has noted his program was "just continuing the great work of the DC-X project."
Background According to writer Jerry Pournelle: "DC-X was conceived in my living room and sold to National Space Council Chairman Dan Quayle by General Graham, Max Hunter and me." According to Max Hunter, however, he had tried hard to convince Lockheed Martin of the concept's value for several years before he retired. Hunter had written a paper in 1985 entitled "The Opportunity", detailing the concept of a Single-Stage-To-Orbit spacecraft built with low-cost "off-the-shelf" commercial parts and then available technology, but Lockheed Martin was not interested enough to fund such a program themselves. On February 15, 1989, Pournelle, Graham and Hunter were able to procure a meeting with Vice-President Dan Quayle. They successfully "sold" the idea to SDIO by noting that any space-based weapons system would need to be serviced by a spacecraft that was far more reliable than the Space Shuttle, and offer lower launch costs and have much better turnaround times. Given the uncertainties of the design, the basic plan was to produce a deliberately simple test vehicle and to "fly a little, break a little" in order to gain experience with fully reusable quick-turnaround spacecraft. As experience was gained with the vehicle, a larger prototype would be built first for sub-orbital and then orbital tests. Finally a commercially acceptable vehicle would be developed from these prototypes. In keeping with general aircraft terminology, they proposed the small prototype should be called the DC-X, X being the US Air Force designation for "experimental". This would be followed by the "DC-Y", with Y being the USAF designation for pre-production test aircraft and prototypes (e.g. YF-16). Finally the production version would be known as the "DC-1". The name "Delta Clipper" was chosen to result in the acronym "DC" to draw a connection with the Douglas "DC Series" of airliners, beginning with the Douglas DC-1. The vehicle is inspired by the designs of McDonnell Douglas engineer Philip Bono, who saw single stage to orbit VTOL lifters as the future of space travel. The Delta Clipper was very similar to Bono's SASSTO vehicle from 1967. Bono died less than three months before the DC-X's first test flight.
SDIO requirement SDIO wanted a "suborbital, recoverable rocket (SRR) capable of lifting up to 3,000 pounds (1361 kg) of payload to an altitude of 1.5 million feet (457 km); returning to the launch site for a precise soft landing; with the capability to launch for another mission within three to seven days".
Specification DC-X Specifications:
12 m high, 4.1 m diameter at base, conical shape Empty mass: 9100 kg. Fueled mass: With full load of propellants:18,900 kg Propellants: Liquid oxygen and liquid hydrogen Propulsion: Four RL10A-5 rocket engines, each generating 6,100 kgf thrust. Each engine throttleable from 30% to 100%. Each gimbals +/-8 degrees. Reaction Controls: Four 440-lb thrust gaseous oxygen, gaseous hydrogen thrusters Guidance, Navigation and Control Avionics: Advanced 32 bit, 4.5 mips computer, F-15 Navigation System with ring laser gyros. F/A-18 accelerometer and rate gyro package. Global Positioning Satellite P(Y) code receiver. Digital data telemetry system. Radar altimeter. Hydraulic System: Standard hydraulic aircraft-type system to drive vehicle's five aerodynamic flaps and eight engine gimbal actuators (two per engine). Construction Materials: Aeroshell and base heat shield: graphite epoxy composite with special silicon-based thermal protection coating; Main propellant tanks: 2219 alloy aluminium; Main structural supports: aluminum; Landing gear: steel and titanium
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