VentureStar (X-33) and X-34 Prototype

by Jeanette Cain

Eugen Sanger proposed an aircraft to be boosted into orbit by rockets and gliding back to land on Earth in 1944. Space travel is extremely expensive-greater than $20,000 per each kilogram of payload carried. When using a multi-stage rocket to launch into orbit, large sums of money are lost. An SSTO, single-stage-to-orbit, spacecraft, would be one way of overcoming the problem. With modern engine designs and light, but strong, materials being manufactured, the SSTO may soon become a reality. In 1999, a single-stage reusable space plane, the X-33 began its final testing phase.

The first United States test vehicle was the X-15, which flew 199 times during 1959 through 1968. The X-15 space plane reached Mach 6.7. From the lessons learned with the X-15 and the X-20A, the U.S. Air Force's Dyna-Soar, engineers were able to design the space shuttle in the 1970's. During the mid-1970's, the lifting body principle was developed by the U.S. Air Force as a part of the X-24A project.

The DC-XA Clipper Graham, was a subsonic test vehicle for future space technologies. It was designed and constructed from lightweight composite material. It passed the operation of temperature and pressure, which would be needed for the SST0 space plane to operate. After four flights in 1996, the Clipper Graham crashed. The X-34 Prototype was tested using lightweight materials, landing systems and thermal protection, which will be needed for the SSTO. It was given 27 test flights, with each one tougher than the previous. It will also need to be tested in a suborbital flight at Mach 8.

Conventional rocket engines do not work at maximum ability (for the most part). The shape of the nozzle does not change when exhaust gases leave the engine. A more efficient nozzle would need the ability to change shape as the rocket ascended into the atmosphere and with an aerospike engine, peak performance would be maintained all the way to orbit. The usual bell-shaped nozzle is turned inside out, which nozzle provides the inner solid surface. Air pressure decreases with altitude, but the nozzle will change shape as the rocket ascends into the atmosphere. The Roton rocket was the idea of making rockets light enough for SSTO launches. The Roton would have a motor on the launchpad to turn its engines and the engines would throw propellant in the combustion chambers. Rotor blades, akin to a helicopter's, would provide a soft landing and stability during re-entry.

NASA's VentureStar (X-33) has a wedge shape, which provides a lifting body design for flying. The VentureStar will take off in a vertical position, but on re-entry it will have a glide landing. It is the prototype for the SSTO, and may take over the space shuttles role. NASA will test its performance in the atmosphere with a crew, which results will determine if NASA proceeds with the prototype.

Scientists have already begun following up the VentureStar with the X-34 and X-37 future space planes. NASA's one rule: it must be fully reusable. The vehicle that may be used to return the crew back to Earth for the ISS, International Space Station has been given the name X-38. The first test flight of the Japanese HOPE, H-II Orbiting Plane, in 1999, would take supplies to the ISS and return to Earth with a load of cargo. The HOPE does not fly with a crew; scientists continue to study its ability to withstand re-entry into Earth's atmosphere.

Space tourism may eventually become so affordable, that many will achieve their dreams of space travel. One idea is to place a hotel in a 1,200 km orbit, connected to a 1,000 km long tether with a space dock 250 km above Earth's surface. Travel would be accomplished with the use of a reusable, suborbital plane connecting to the space dock, where visitors would ride an elevator to the hotel.

Sources:
1. Editors. Secrets of the Universe. International Master Publishing: US. 1999

2. Couper, Heather and Nigel Henbest. Space Encyclopedia DK Publishing, Inc.: NY 1999