By Todd Halvorson CAPE CANAVERAL, Fla. Space
Shuttle Discovery will take off this week on NASAs historic 100th shuttle flight, but dont look for the space agency to retire its 20-year-old fleet of winged orbiters anytime soon.With a billion-dollar bid to build a would-be successor mired in technical problems, NASA instead is moving swiftly to ready its shuttles for at least another decade of flight.
| Shuttle Distances Flown and Days in Orbit |
| Tally it all up, and that's how much time space shuttle orbiters have spent in the air and in space during 99 flights combined, to date. |
Consider the number of miles each of NASA's shuttle orbiters have traveled. |
Whats more, it appears the ships could become NASAs version of the B-52, the venerable Air Force bomber that has been flying for nearly a half-century.
"Weve been pushing real hard to get people to understand that there isnt going to be a replacement vehicle in the near-term," said former NASA astronaut Andrew Allen, now a senior manager with shuttle prime contractor United Space Alliance. "Even if you put on your most optimistic hat, the shuttle has to be around at least another 10 or 12 years."
That, however, shouldnt be a problem if NASA pushes ahead with plans to invest an estimated $1.5 billion to $2.2 billion over the next five years in the same type of systems upgrades that have kept the Stratofortress flying so long.
Shuttle Discovery waits on pad 39A for the October 5th launch of the 100th shuttle mission, STS-92.
The shuttle "can be the B-52 of the space fleet theres no question about that if we take care of it," said NASA shuttle program manager Ron Dittemore. "Theres no reason that this machine cannot be flying for 20 or 30 more years."
Just four years ago, though, NASAs $8 billion shuttle fleet was headed for early retirement.
At the time, NASA and industry partner Lockheed Martin set out to build a half-scale prototype of a revolutionary reusable spacecraft that would leap into orbit atop a single stage and cut the high cost of shuttle launches by a factor of 10.
NASA budgeted $841 million for the so-called X-33 project, and Lockheed agreed to pitch in another $220 million. A series of 15 suborbital test flights was slated to start in 1999, leading to the development of a full-scale shuttle replacement dubbed VentureStar.
The idea was to have the heir apparent ready to fly around 2005 so NASAs aging
orbiters could be gradually converted into museum pieces.Those high hopes, however, have been dashed.
Striving for a technological breakthrough, NASA and Lockheed Martin were banking on the successful development of a lightweight fuel tank made from advanced composite materials rather than heavy aluminum.
The X-33s composite tank, however, split open during a 1999 fueling test, dealing a devastating blow to the cutting-edge program.
As a result, test flights have been delayed until at least mid 2002, and the lightweight tank is about to be scrapped for fuel reservoirs made with proven aluminum.
Meanwhile, chances are the full-scale VentureStar might never be built. NASA, consequently, is hedging its bets.
The agency desperately needs a reliable vehicle to carry out its $60
billion International Space Station construction project, which is expected to continue through April 2006. A frequent flyer also will be needed to haul crews and supplies to the outpost during a subsequent decade of scientific research on the station.
So NASA now is turning its attention to the care and feeding of its four-orbiter shuttle fleet.
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"Theres been a tremendous shift in focus because all of the sudden, the shuttle is the only game in town," said Allen.
"We have an International Space Station that cant be built without the space shuttle, and realistically, it probably cant be maintained without the space shuttle," he said. "And thats become very apparent to everybody."
Just as apparent is the resulting need to replace out-of-date shuttle components with new technology, increasing both flight safety and the odds of mission success.
The shuttle is arguably the safest, most reliable and most capable piloted spacecraft ever designed. But every year, spare parts for obsolete components become increasingly difficult to scavenge, and aging systems become more apt to fail.
Thats a potential recipe for disaster, so NASA is aggressively pursuing systems upgrades.
Chief among them are:
- New electric hydraulic power units. Cost: About $224 million.
Current shuttles employ three so-called Auxiliary Power Units (APUs) to provide the hydraulic power needed to steer its main engines and control the ships wing flaps, rudder speed-brake, landing gear and nosewheel steering system.
The units, however, are powered by hydrazine a very toxic, corrosive and combustible fuel that makes the devices vulnerable to leaks, fires and even explosions.
New electric units like those flown on the militarys F-22 jet fighters and Comanche helicopters will be less susceptible to potentially deadly failures.
They also will eliminate toxic hazards now encountered when current-generation APUs are serviced on the ground. And that, in turn, will speed up turnaround time between flights.
- An advanced health-monitoring system for the shuttles powerful main engines. Cost: An estimated $108 million.
Together with twin solid-fuel rocket boosters, the shuttles three liquid-fueled main engines provide the propulsive power needed to launch into space. An inadvertent engine shutdown in flight, however, most likely would trigger a catastrophic explosion.
A suite of advanced engine sensors, along with state-of-the-art monitoring computers, will be able to instantaneously detect failures and automatically cut off engines before inadvertent shutdowns can occur.
"That will give us the capability to determine within a fraction of a second whether we have an incipient engine failure occurring and be able to shut the engines down," McHenry said.
Some 30 to 40 percent of catastrophic engine failure scenarios can be avoided as a result.
- Redesigned engine combustion chambers and nozzles. Cost: About $400 million.
Shuttle main engines now sport combustion chambers and nozzles that feature individual welds that can fail, triggering potentially deadly fuel leaks in flight.
New designs and manufacturing processes pioneered by Russian aerospace companies will significantly reduce the number of welds and potential failure points - within shuttle engines.
Other less dramatic improvements also are in the works.
NASA intends to beef up the shuttles landing gear and its tires to reduce the chance of blowouts and other failures during end-of-mission or emergency landings.
An advanced welding technique is being developed for the manufacture of
shuttle external tanks. The technique will make the 15-story liquid-fuel reservoirs more reliable while reducing the number of required preflight inspections.A new manufacturing process also is being worked up for the
shuttles solid-fuel rocket boosters.The intent: To reduce the number of tiny stress fractures that crop up during curing of solid-fuel propellant. Doing so will slash the amount of time inspectors must spend inside fully fueled segments of the 149-foot (45-meter) boosters.
Said McHenry: "Wed like to cut down the amount of time people have to spend inside the solid rocket motor doing this kind of inspection."
Together, the shuttle upgrades are expected to reduce the odds of a catastrophic failure in flight from 1 in 438 today to 1 in 735 by the year 2005.
And that, project officials say, will go a long way toward ensuring that the shuttle fleet will be around long enough to first build and then operate the International Space Station, NASAs cornerstone project for the early 21st century.
"We know we are going to be flying [the shuttle] until at least 2010 and probably beyond thatand we want it to be safe," McHenry said.
Added senior shuttle program manager Bill Gerstenmaier: "A hundred flights seems like a lot, but I think there is still a lot to come."
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