In the three-year-old NASA/industry cooperative effort to develop a reusable space launch vehicle to eventually take over launchings for a fraction of today's cost of space transportation (around $10,000 per pound of mass to orbit) with turnaround rates considerably lower than those of the space shuttle, work is continuing at Lockheed Martin on the development of the X-33 as a technology demonstrator for a Single-Stage-to-Orbit (SSTO) Reusable Launch Vehicle (RLV). During 1999, most manufacturing for the X-33 was completed, and assembly was getting underway for a rollout of the demonstrator vehicle originally envisioned in January 2000 and first flight in July of that year. However, structural weaknesses in the advanced solid-graphite composite liquid-hydrogen tank, which resulted in structural failure of the tank's outer skin during a pressure test with cryogenic loading on 11/3, caused a major setback for the program, delaying it by perhaps several years.

Also part of the RLV program is the smaller air-launched X-34, being built by Orbital Sciences Corp. (OCS), which will test reusable launch vehicle (RLV) technologies. X-34 flights began on 6/29 with the first of several captive-carry flights of the vehicle under the belly of an L1011 aircraft. Also during 1999, key rocket engine tests continued on the revolutionary propulsion systems for the winged booster testbeds, the 60,000 lbs. thrust liquid oxygen (LOX)/kerosene Fastrac engine for X-34, and the 500,000 lbs. XRS-2200 LOX/liquid hydrogen linear aerospike engine for the X-33.

NASA is also developing the X-43 as part of the Hyper-X program which bridges aircraft-type vehicles and space launch vehicles. Its goal is to demonstrate hydrogen-powered, air-breathing propulsion systems that could ultimately be applied in vehicles from hypersonic (speeds higher than Mach 5, i.e. five times the speed of sound) aircraft to reusable space launchers. In 1999, the first of three experimental vehicles, designated X-43A, arrived at NASA's Dryden Flight Research Center in California to prepare for flight in mid-2000. The 12-ft. (3.6 m)-long, unpiloted, non-rocket-propelled X-43 vehicles are powered by supersonic combustion ramjets ("scramjets") after having been accelerated by a Pegasus booster rocket airlaunched from a B-52 airplane. At least three flight tests are planned -- two at Mach 7 and one at Mach 10.

Specifically for the ISS, NASA is also developing a Crew Return Vehicle (CRV) to eventually take over the emergency lifeboat function for the space station from the currently chosen Russian Soyuz three-seater capsules. CRV will require a shirtsleeve environment for seven crewmembers in reclined couches, standard-sized for 95% of all U.S. males. It must have a minimum lifetime of one year attached to the ISS, with a possible extension to three years, must be capable of supporting medical equipment, carrying out a 9-hr. orbital free-flight mission and allowing access for a medical officer to an injured or ill crew member during such a mission. In 1999, NASA continued with full-scale flight testing of the X-38, the prototype test vehicle for the CRV, by dropping it from a B-52 at 23,000 ft (7000 m) altitude. Purpose of the tests with the first prototype, V-313, was to study the latter stages of the CRV's mission, when it transitions from subsonic lifting body flight to descent and landing under a large parafoil.

Questions or comments? Send a message to Jesco von Puttkamer

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