Designs for the Next Space Shuttle

When the space shuttle first launched on April 21, 1981, it opened a whole new era in space exploration for NASA. For the first time, the agency — and the world — had a space vehicle that could be recovered and used repeatedly.

Now, the tragic loss of Columbia may speed up the hunt for the next-generation shuttle — a task the aerospace industry has pursued almost since the current shuttle came into existence.

"The overall general consensus is that NASA needs to move forward in a new [launch] system," said Dennis Smith, a program manager involved with looking at next generation space vehicles at NASA's Marshall Center. "But we're early on in the process [of development]," he said during a teleconference with reporters today.

It's been NASA's call for cheaper, more capable, and safer spacecraft that has prompted the effort for a successor shuttle. And while many of the previous designs never got much past the drawing board, the attempts could help lead the industry and the U.S. space program to newer technologies for reaching the stars.

One example of the more recently attempted shuttle replacement efforts was the so-called Reusable Launch Vehicle, or RLV, program. Commissioned under President Clinton in 1994, the project hoped to develop a truly reusable space "plane."

The experimental shuttle design, dubbed the X-33 by Lockheed-Martin, would be a so-called single-stage-to-orbit vehicle. Launched vertically like the current shuttle, the X-33 would reach orbit using its own internal engines and fuel.

Once the mission was completed, it would glide back to land on a runway just like current shuttle. Its single-piece design meant that a working X-33 craft would need less work — and less expense — to prepare it for the next mission.

Technology Setbacks, Cost Overruns

It was hoped that the X-33 could save as much as 90 percent of current shuttle's launch costs.

But to lift the X-33, its payload and internal fuel without external assistance, designers turned to new rockets called aerospike engines that were supposed to propel the craft at up to 18 times the speed of sound. New lightweight, composite materials were supposed to keep the weight of the X-33 down as well.

Charles Vick, an analyst with space and defense think tank in Alexandria, Va., says that such immature technologies ultimately led to the X-33's downfall.

"[Advanced] materials for the fuel tank really struck out," says Vick, who notes that a fuel tank ruptured during ground testing in 1999 and caused massive delays and cost overruns.

After two years of redesign work — and a total investment of more than $1 billion — the project failed to produce a flying prototype and was subsequently canceled in 2001.

Pushing On

Still, NASA hasn't exactly given up on new launch systems.

Last November, NASA Administrator Sean O'Keefe announced a renewed effort to look at low-cost alternative spacecraft under a revamped program called the Space Launch Initiative, or SLI.

Rather than look for an outright shuttle replacement, the $4.5 billion program will study a variety of inexpensive options that would supplement the shuttle.

One such craft, the X-37 from Boeing, is designed along the lines of the X-33, using lightweight composite materials. However, rather than a single stage vehicle, the X-37 would be lofted into orbit using a large, disposable rocket booster.

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