Space plane, new launch vehicle years away
By ERIC BERGERCopyright 2003 Houston Chronicle Science Writer
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SPACE EXPLORATION
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A view of Earth from Columbia six days before it disintegrated. WHAT THEY SAID • President Bush: • Crew's families:
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Despite the loss of Columbia, NASA's three remaining space shuttles, based on a design three decades old, will probably remain the agency's workhorses for another 20 years.
In the immediate future, NASA simply has no other option. Even if a proposed space plane takes flight in several years, NASA must still rely on the shuttle.
Liftoff for a viable replacement -- which doesn't exist even on paper -- remains at least a decade away.
Last fall, NASA administrator Sean O'Keefe switched the program's focus from a new reusable launch vehicle to an orbital space plane that could ferry humans safely to and from the International Space Station.
"I don't think there's any choice but to push the orbital space plane," said Jerry Grey, director of science and technology policy for the American Institute of Aeronautics and Astronautics.
"The alternative is to depopulate the space station."
But building such a plane will further delay NASA's efforts to develop a new generation of vehicles to lift both people and cargo into orbit far more cheaply and more safely than today. That initiative lost half its funds, $2.4 billion, to the orbital space plane with O'Keefe's decision.
As a result, the space agency has pushed back the deadline to pick a design for the next generation of launch vehicles from 2006 until 2009, at the earliest. Experts say it would take at least a decade to build and test the spaceship.
43%
16%
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14%And the Columbia disaster may delay NASA's already-delayed plans even further. Findings from the investigation will shape the upcoming budget debate in Congress, which will consider NASA's attempt to change its focus to a space plane. It's even possible, though unlikely, that manned space travel will be abandoned altogether in favor of automated probes.
"The future isn't all black," said Grey, a jet-propulsion expert. "But we're not really going to expand the manned space program much until we get to the next-generation launch vehicles, and that is going to take a long time."
NASA probably won't pick an orbital space plane design from versions being worked on by Lockheed Martin, Boeing and other companies until 2004, at the earliest.
Developing the plane should be relatively easy, some experts say, because it would not require large technological leaps. By 2010 it could be ready to serve as a lifeboat for the space station crew. Two years later it might lift humans into orbit, removing that burden from the shuttle.
In addition to taxiing people into space, the shuttle can launch payloads and satellites, service space equipment, do construction, and conduct research.
"The fact is, the space shuttle is a virtual Swiss army knife in space," said Brian Chase, president of the National Space Society, a nonprofit space advocacy organization.
"The problem is that all of that capability makes it inherently expensive to operate," Chase said.
Although the space plane would save money, perhaps eventually costing less than $100 million per launch compared with the shuttle's $450 million cost, it could not carry heavy equipment and materials into space.
Initially, the space plane is likely to be launched aboard Boeing's Delta IV rockets or Lockheed Martin's Atlas 5 boosters, both new generations of expendable launch rockets that had successful test flights last year.
But critics say it won't be as easy as some engineers claim to adapt existing rockets to safely carry a space plane into orbit.
"I think it's a waste of money, and I'm not even sure it will work," said Don Nelson, a retired engineer who spent 36 years with the space agency.
In the near term, however, the space plane may be its only realistic goal.
The Challenger disaster cost NASA an estimated $15 billion, including the investigation, safety upgrades, research delays and $2 billion to build the Endeavour. Columbia may exact a similar toll on the agency's resources.
Today it costs $10,000 to blast a pound of material 150 miles into space. The space plane may be able to carry a crew into orbit, but it's more difficult to safely launch massive payloads.
For the immediate future, that chore is likely to remain with the space shuttle, which can carry about 25 tons.
Like the shuttle, NASA wants the next launch vehicle to be reusable, but with costs below $1,000 a pound and safety risks reduced to one-tenth or even one-hundredth of current levels.
Such a vehicle would save money, savings that could be used on more ambitious exploration beyond Earth's orbit. And it would be cost-effective enough to carry into space the tools, rockets and materials necessary for such expeditions.
The agency's change of immediate focus to an orbital space plane has left the fate of that launch vehicle in the air. But putting it on hold may not be such a bad thing, some experts say, because it will give research time to catch up.
Researchers didn't have that time in the early 1990s, when NASA was developing the space station and began searching for a shuttle replacement.
Eventually the agency selected the concept of a "single stage to orbit" vehicle, meaning the ship and all its components would return to Earth intact. NASA partnered with Lockheed Martin and sank $900 million into the X-33 project. Industry spent another $350 million.
After several failures, the X-33's first flight was delayed in 1999 and eventually scrapped in 2001 with the announcement of the $4.8 billion space launch initiative.
Space experts say NASA erred by locking onto a single design and lost at least six years because of it.
The science of propulsion and materials perhaps needs the most work.
Some of the rocket technology that launches the shuttle predates its design by two decades. Rocket propulsion needs new ideas. And materials science, possibly through nanotechnology, has a long way to go to lighten the shuttle's hull and still meet the rigors of space travel.
Among the propulsion options is a system based on air-breathing technology, which uses the abundant oxygen in Earth's atmosphere instead of carrying oxygen tanks into orbit. These ramjet engines, which burn fuel in a highly compressed stream of oxygen, exist in some airplanes today.
As much as 70 percent of the shuttle's weight comes from fuel and the oxygen needed for it to burn.
"The analogy we like to use is that the shuttle is sort of like a fish swimming around with a canteen filled with water," said Mark Lewis, an aerospace engineering professor at the University of Maryland who is leading a NASA-sponsored group researching future launch vehicles.
Getting into space this way would require two stages -- a launch vehicle and a rocket vehicle. The launch vehicle could resemble a large plane with modified ramjet engines that could reach Mach 25, or 25 times the speed of sound. Once the launcher reaches the upper atmosphere, where there is virtually no oxygen, the rocket vehicle would blast into Earth's orbit.
Both vehicles would return to Earth and land as the shuttle does.
The trick is designing a ramjet that can travel at hypersonic speeds, described as much like keeping a candle lit in a hurricane.
NASA's X-43 plane, part of its Hyper-X series, is an effort to do this. The first attempt to fly Mach 7 failed in June 2001, but U.S. researchers are aiming to try again this summer. Engineers may try to reach Mach 10 next year.
Scientists in Russia and Australia have already had some success in testing hypersonic ramjet engines.
An aerospace engineer at the University of Florida's Institute for Future Space Transport, Corin Segal, said NASA will have to increase funding if it is serious about developing a revolutionary new launch vehicle.
"If you look at how much money is being put into hypersonic activities, you will see it is far from adequate," he said.
NASA spends a few hundred million dollars or less each year on Hyper-X research.
Waiting 10 or 15 years may also allow time to see if nanotechnology research -- in which scientists are trying to make stronger, lighter materials on the atomic scale -- pans out and becomes a backbone for spacecraft frames.
Carbon nanotubes, although only a few billionths of a meter long, offer a strength five times that of steel at one-sixth the weight. Scientists simply can't make them in sufficient quantities yet.
"The promise is there because of the properties we see in the nanoscale, and it's starting to bear out in composites we're making," said Enrique Barrera, a Rice University engineer working with several NASA centers.
He and other researchers are eager to begin working with large-scale versions of nanomaterials to see if the promise holds up.
Among the possibilities are materials with more than one use, such as a shield that could not only protect astronauts from radiation in space but also sense stress to instantly alert astronauts of a breach. Once in space, there is currently no way for astronauts to determine, for most areas of the vehicle, whether the shuttle's protective tiles are damaged.
Along with those who push for new launch vehicles, there are proponents of recycling existing technologies.
Nelson, the former NASA engineer, believes the space shuttle should be overhauled and automated, lowering its costs and increasing its cargo area. Passengers could ride in individual escape pods on the way into space, ejecting if needed.
Other scientists say the orbital space plane is sufficient for carrying people and that newer rockets, like the Delta IV, are all NASA needs to launch payloads into space.
What most space scientists agree on is that, without a major overhaul or redesign, flying the shuttle is only going to get more hazardous as its basic architecture continues to age.
"The shuttle needs to be replaced," said Robert Zubrin, president of the Mars Society. "We should not be flying the shuttles in 2025. It's ludicrous.
"It's not an invitation to disaster, it will be disaster."
Even if NASA ultimately develops a new launch vehicle, the ship will perform the same unromantic task as the shuttle: ferrying stuff into low Earth orbit, hardly new or exciting.
Can the public take pride in America's space program, and willingly spend billions annually, when its primary goal has remained the same for half a century -- especially when NASA took less than a decade to go to the moon?
Zubrin is among those who worry the public may not, and he argues for a much more aggressive drive to Mars or beyond.
He says the shuttle should be mothballed and its basic booster technology adapted to launch payloads of 100 tons or more.
"We would have the capability to launch an entire space station in an afternoon," he said.
Zubrin argues that existing chemical propulsion technologies -- readily available, unlike a theoretical fusion engine -- could get a crew to Mars in six months.
With just two launches, he said, humans could build an outpost on Mars. The first launch would send a return vehicle to Mars, as well as a small nuclear reactor to power life-support functions. The return vehicle could draw carbon dioxide from Mars' atmosphere to mix with hydrogen, creating methane and water -- meeting needs for return fuel. The second launch would include a habitat and a crew that could stay for six months before flying home.
Certainly many of the technical obstacles to a Mars journey are unsolved. How do you combat the risks of long-term space travel, such as muscle loss? What happens if an astronaut breaks a leg? Can a spacesuit be made that doesn't need to be cleaned by a hundred technicians before reuse?
Places like the National Space Biomedical Research Institute in Houston, with a $20 million annual budget, are working to answer such questions.
But critics urging NASA to go further say these researchers' budgets are too small, allowing too few experiments, with insufficient money to deliver flight-ready technologies.
In 1989, President George H.W. Bush sought an aggressive space initiative, calling for a mission to Mars. But the effort failed when a largely indifferent Congress learned the program could cost as much as $500 billion, though spread out over decades.
Zubrin and others argue that interplanetary travel could be accomplished for much less, especially if NASA reuses existing technology and strives to get more bang for its buck.
Between 1961 and 1973, when NASA went to the moon and launched Skylab, the country's first space station, NASA spent an average of about $16 billion a year, in present-day dollars.
That's $1 billion more than NASA's proposed budget for next year.