Long before vertical takeoff and landing rocket experiments being conducted by companies like Blue Origin, Masten Space Systems, and SpaceX, the Delta Clipper roared in the skies over White Sands, New Mexico, starting in August, 1993.
The DC-X, or Delta Clipper as it was called, was conceived as a one third experimental vehicle that would eventually lead to a vertical takeoff and landing spacecraft capable to reaching low Earth orbit. The proposed spacecraft was being developed by the Strategic Defense Initiative Organization for the ostensive purpose of servicing space based missile defense facilities.
The philosophy behind the DC-X program was to conduct rigorous and increasingly challenging series of flight tests, the better to learn how an VTVL landing vehicle could be made to work.
The DC-X first flew in August 18, 1993 for a duration of 59 seconds. It successfully flew twice more, on September 11, 1993 and September 30, 1993. Then the test program was ended, due to the downsizing of the SDI program under the Clinton administration.
Thanks to funding provided by NASA and the Advanced Projects Research Organization, the DC-X conducted another series of flight tests, starting on June 20, 1994 for 136 seconds. A minor explosion occurred on the next test on June 27, 1994, but the vehicle managed to abort and autoland. After the damage was fixed, three more flights occurred on May 16, 1995, June 12, 1995, and July 7, 1995. The aeroshell was cracked during the last flight and then funding ran out once again.
NASA agreed to take on the Delta Clipper project, performing repairs and modifications to the original vehicle, now designated as DC-XA. The main modification was a new, lightweight fuel tank built by the Russians.
The first DC-XA test took place on May 18, 1996, resulting in a minor fire upon landing. Then the DC-XA flew twice within 26 hours, on June 7, 1996 and June 8, 1996. The second flight flew for 145 seconds for an altitude of 3,140 meters. DC-XA’s final flight took place on July 7, 1996. The vehicle suffered a cracked liquid oxygen tank. Then one of the landing struts failed to extend, toppling the vehicle over, and starting a fire that all but destroyed it.
The Delta Clipper represents a path not taken in the development of crewed space travel. As part of NASA’s X-33 program to develop a spacecraft that might have replaced the space shuttle, the prime contractor for Delta Clipper, McDonnell Douglas, teamed with Boeing to proposed a test flight vehicle similar to the DC-X/XA. However NASA chose a Lockheed Martin proposal for a vertical takeoff horizontal landing spacecraft instead. The program eventually was cancelled due to cost overruns and technical challenges.
Some have suggested that a Delta Clipper derived craft might have served as a prototype lunar/Mars lander.
However, the dream of a vertical takeoff and landing spacecraft lives on, at private companies such as Blue Origin, Masten, and SpaceX, and with NASA’s Morpheus and Mighty Eagle.
One final interesting fact. One of the controllers who remotely piloted the Delta Clipper was former Apollo moonwalker and Skylab astronaut Pete Conrad. Thus Conrad’s career spanned both the glory days of NASA and the early days of experimental flights that helped to inspire the current era of commercial space.