Skip to comments.Finish the X-33
Posted on 02/01/2004 12:02:54 AM PST by Destro
President Bush's new plan for space exploration is welcome. Although the needed funding may never materialize for a mission to Mars, NASA will begin dismantling the Space Shuttle/Space Station jobs program and move onward after decades of "exploring" space just 100 miles from the Earth's surface. After moon landings ended in the 1970s, NASA hoped for missions to Mars. It realized that a direct flight from the Earth's surface to Mars would be impossible due to the mass of the spacecraft required. Since putting an object into orbit is half the challenge, the idea was to assemble a Mars spacecraft in orbit, or perhaps on the Moon.
This would prove extremely expensive using expendable rockets, so NASA needed a low cost method of placing things into orbit which resulted in the Space Shuttle. Unfortunately, the Shuttle design is extremely complex, somewhat dangerous, only semi-reusable, and even more expensive. For example, it costs much more to recover and rebuild the two Solid Rocket Boosters after they parachute into the ocean than using new expendables each time. This is because after they are retrieved off the Florida coast, they are disassembled into segments and shipped by rail to Utah for refurbishment, then back to Florida for fueling and reuse. The end result is that NASA failed to achieve the first step with the Shuttle, low cost space launch, needed to perform the second step, an orbiting space station, which is needed for the third step, a mission to Mars. Undaunted by the failure of the Shuttle to launch things cheaply into orbit, NASA began an ambitious plan to assemble a space station. However, since step one failed, step two was doomed from exorbitantly high launch costs, so now it's back to step one.
Hopefully, NASA will not waste limited funds preparing for step three (a mission to Mars) until it solves step one. NASA cannot afford to waste billions of dollars for another "clean sheet" design for a Reusable Launch Vehicle (RLV). Unless NASA demonstrates real progress in the form of something flying about within the next few years, Congress is likely to scrap the entire agency. NASA should simply finish the X-33, which was the prototype for the Lockheed Marin Venturestar RLV. This was funded by NASA in the late 1990s and incorporates all the latest technologies. The X-33 was almost complete when NASA discovered that math errors made years before meant the single-stage Venturestar could not make orbit. The entire program was quickly cancelled in 2001 to conceal this embarrassing billion dollar error while "funding cuts" were blamed.
Many were upset since much expertise had produced a modern RLV design whose prototype was almost ready to fly sub-orbital hops. They wanted to complete the X-33 and then find a way to make orbit with weight reductions, expendable boosters, or ground-based assisted launch. Former Lockheed Martin executive, Peter B. Teets, told Aviation Week last year (2-17-03 issue): '"we were probably two inventions away' from success. For instance, the launcher needed a lighter engine, which is why Teets would like to see ceramic turbine work as one of the technologies addressed in the road map. The Pentagon is primarily interested in an unmanned system, while NASA wants a man-rated vehicle. Teets noted the first iteration would likely be unmanned until reliability is proven." Hopefully, Mr. Teets will prevail in resurrecting the X-33, which could be finished and flying in a couple years after the X-33 team is reassembled. An affordable NASA X-33 roadmap for low cost spaceflight should consist of four parts:
1) Complete the X-33, which was already 85% when the program was canceled in 2001 after years of research and over billion dollars invested. If the composite fuel tanks don't work, use aluminum. If the aerospike engines don't work, use the new RS-83s developed as part of the $4 billion spent on NASA's recent Space Launch Initiative (SLI).
2) Build an inclined ramp to assist launch the X-33 with a rocket sled using two of the SLI developed RS-84 engines, or a jet powered sled, or a pneumatic assist. This greatly reduces the mass of an RLV and is a much safer method. An X-33 launched near the end of a ramp at over 10,000 feet encounters 31% less air resistance and allows 5% greater thrust at launch since rocket plumes are not "pinched" by thick air. The Space Shuttle uses half its fuel to push its fully loaded body through the Earth's dense lower atmosphere to reach Mach 1.3, then uses the other half to reach orbit at Mach 24. An ground assist "Skyramp" cheats with a big push off the Earth's surface.
3) Fit an expendable payload fairing to the nose of the X-33. Since the X-33 was experimental, it would carry no payload. In 2000, Venturestar designers concluded that an internal payload bay required a much wider body, greatly increasing drag. The final design put the payload bay on its back. Fitting expendable payload fairings is an even better idea since little development funding is needed and current satellites are already designed for them. This reduces drag during ascent, reduces the surface area needing heat shielding during reentry, and allows the X-33 to jettison its payload during an abort. Internal payload bays are inherently dangerous since landing an RLV after a mission abort with payload is tricky, something Space Shuttle planners worry about. In addition, crew vehicles mounted on the nose of an RLV in place of a payload fairing make escape easy during an abort.
4) A ramp launched X-33 with payload could make orbit on its own. However, NASA may be reluctant to build the 2.5 mile inclined ramp needed for the Mach 2 assist. Problems with "Max Q" (the spacecraft's structure) at Mach 2 ~10,000 feet would have to be addressed, but could be overcome with a stronger and more aerodynamic payload fairing. Nevertheless, NASA may feel more comfortable with a compromise; a shorter ramp pushing the X-33 up to 500 mph, something that a jet sled with reliable commercial jet engines can accomplish. Then the X-33 would carry a large strap-on expendable on its back, like the GEM-60. The X-33 was designed with a reinforced lifting point on its back so an arm can move it about on the ground. There should be no problem with mounting a strap-on booster there. Using a $5 million expendable strap-on for each launch is not ideal, but much cheaper than the $80 million first-stage expendables now used.
This is a reasonable and cost effective approach integrating proven technologies using recent NASA investments in spaceflight. If NASA attempts to build a futuristic "crew exploration vehicle", it will never progress beyond the design phase as testing and development will cost billions dollars. A ramped launched X-33 roadmap is affordable and should produce an orbital RLV within five years. If it lacks the needed payload capacity, NASA can upscale to a Venturestar size RLV, add more strap-ons, substitute lightweight engines or composite fuel tanks, or build a longer ramp. Lower launch costs will also generate profits from commercial businesses to subsidize a Mars effort. NASA hasn't the resources or time to start a design from scratch ; it needs to capitalize on recent investments and put a new RLV into orbit before the Shuttle retires in 2010.
Carlton Meyer editor@G2mil.com
G2mil editorials may be freely distributed without permission
Why not use a Stargate instead?
But the Russians use real corruption rather than the "pork barrel" type corruption our Congress uses. Much more efficient.
Can you tell me where's the X-33 Today? was it scrapped after its cancellation in March 2001 ? or is it standing in lockheed plant, almost finished?
thank you very much for your answer
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