McDonnell Douglas DC-X
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McDonnell_Douglas_DC-XA.jpg
The McDonnell Douglas DC-X, better known as the Delta Clipper, was an unmanned prototype of a reusable single stage to orbit launch vehicle developed in conjunction with NASA and the DOD SDIO from 1991 to 1993.
According to 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." The DC-X was built as a 1/3 scale prototype of the envisioned orbital launch vehicle. Once testing with the DC-X was completed, the plan called for a second, larger prototype vehicle titled the DC-Y and an eventual a full-size orbital launch vehicle called the DC-1.
The DC-X was never designed to achieve orbital altitudes or velocity, but instead to demonstrate a radical new concept of vertical take off and landing. The rocket would take off as normal, but land again the right way up. This unique design used attitude control thrusters and retro rockets to control the descent, allowing the craft to begin reentry nose-first, but then roll around and gently touch down on landing struts at its base. The craft could be refueled where it landed, and take off again from exactly the same position—a trait that allowed unprecedented turnaround times. Another focus of the DC-X was minimized maintenance and ground support. To this end, the craft was highly automated and required only three people to man its control centre (two for flight operations and one for ground support).
The DC-X flew a series of flight tests successfully, with Apollo astronaut Pete Conrad at the ground-based controls of some. However, on the eighth flight in July 1995, a hard landing cracked the aeroshell.
The DC-X program was transferred from SDIO to NASA. The craft was rebuilt and upgraded with new fuel/oxygen tanks and an improved control system. The upgraded vehicle was called the DC-XA, renamed the Clipper Advanced/Clipper Graham, and resumed flight in 1996. The DC-XA reached a maximum altitude of 3140 m and set a world record of a 26 hour turnaround between launches of a reusable rocket. On the fourth DC-XA test flight, the craft flew correctly, but was destroyed on landing. During testing, one of the LOX tanks had been cracked. When a hydraulic line was left disconnected and a landing strut thereby failed to extend, the DC-XA fell over and the tank leaked. Normally the structural damage from such a fall would constitute only a setback, but the LOX from the leaky tank caught fire and severely burned the DC-XA, completely destroying it.
In light of budget constraints, NASA decided not to rebuild a new DC-X and continue the program.
Many of the DC-X's engineers have since been hired by Blue Origin, and it is rumored that their vehicle is based on it. Additionally, the DC-X provided inspiration for many elements of the Armadillo Aerospace's spacecraft designs.
External links
- Astronautix Page on the Delta Clipper (http://www.astronautix.com/lvs/dcx.htm)
- Data for individual DC-X test flights (http://www.hq.nasa.gov/office/pao/History/x-33/dc-xa.htm)
- Movie of the Clipper Graham crash (http://redstone.ae.gatech.edu/~olds/mm/Miscellaneous/clipper_graham_crash.mov)
- About the DCX (http://media.armadilloaerospace.com/DCX/) – includes a first-person account and video
- Getting to Space (http://www.jerrypournelle.com/reports/jerryp/gettospace.html) – explains X programs and SSTO
- Birth of the DC-X (http://www.jerrypournelle.com/slowchange/simages/dcxpic.html) – selling the DC-X to Dan Qayle