NASA tinkering to make space travel a go
"The technology for space is there; it's been worked on for years," said Charles Vick, an aerospace expert formerly with the U.S. Space & Rocket Center in Huntsville and now a senior fellow at GlobalSecurity.org, a nonprofit in Washington, D.C.
The technology "needs to be refined and improved, but it's there," Vick said. "We don't have to start from scratch to build a way to go to the moon. We just need the political will to use what we have."
President Bush yesterday outlined a plan to send astronauts back to the moon, establish a lunar base and move into an advanced Mars exploration program. According to space experts, the National Aeronautics and Space Administration has been developing concepts and technology to accomplish those missions.
A major challenge is traveling quickly and efficiently. Today's rockets take about three days to make a trip to the moon and more than six months to reach Mars.
And space is dangerous. Cosmic radiation can fry spaceships or a meteor can strike. These are two important reasons for cutting travel time.
NASA is looking to Marshall to develop nuclear propulsion, which would be used once a craft is in space. Nuclear reactors would produce electricity for the spaceship, including power to drive electric engines.
Depending on the mission, a trip to Mars could take weeks with such a system, said Steve Rodgers, director of Marshall's Propulsion Research Laboratory. "I can't give a definitive answer, but I know we can reduce the travel time significantly," he said.
There are no brake pedals in space
Reaching the moon or Mars quickly is a wonderful goal, Rodgers said, but higher speeds make it more difficult to stop. Astronauts can't slam on the brakes like motorists. Speed must be bled off or counteracted. Thrusters would slow the rocket to allow it to slip into orbit, but thruster engines and propellant add weight.
Marshall scientists are developing a technique called aerocapture to counter the high speeds of new rocket motors. Aerocapture uses a planet's atmosphere to slow a spaceship, said Les Johnson, manager of NASA's In Space Propulsion Project Office.
The space shuttle, the Apollo capsules and the recent Mars missions used the atmosphere's friction on heat shields to slow down from thousands of miles per hour. The craft lands like an airplane, or a parachute pops out and slows it for a ground or sea landing.
Aerocapture uses a planet's atmosphere to slow down, but it does this by skimming the craft across the outer atmosphere. A spaceship traveling to Saturn's moon Titan or to a planet with an atmosphere would deploy a shell or perhaps a large balloon that would burn away as the spaceship skims the upper atmosphere, Johnson said.
"Aerocapture is something we've never done before," he said. "It's been talked about for a long time. It's our job to develop the technology so somebody could come along and use it. The benefit to aerocapture is that a vehicle would not have to take all the propellant to slow itself down. ... It saves a lot of weight."
Aerocapture is being developed for robotic probe missions such as the Mars rovers. But Johnson said a similar system is possible for a manned mission.
NASA is spending about $10 million a year to develop aerocapture, and engineers expect to have test results on advanced designs by 2006.
Propulsion engineers also are developing solar sails to harness solar winds. Stars, our sun included, emit high-energy particles. These particles push on objects.
"We know that the orbits of satellites are affected by these solar particles," Johnson said. "We have to adjust their orbit. If we could put out a large sail on a robotic explorer, then those particles could be used to push the (probe) around."
Sail wouldn't work for manned missions
The sail is impractical for manned missions because a large spacecraft would require a prohibitively large sail. But Johnson notes that a moon or Mars base would need supplies, and solar sails could be used to haul unmanned supply tugs into space.
"Length of time for supply ships isn't the same as a crew vehicle," he said. "You could put the tugs in space and launch before the humans were launched and (the supply tugs) would be on the moon or Mars before a crew arrived."
Boom hardware for solar sails has been tested at NASA's Goddard Space Flight Center in Maryland, and companies are working to develop lightweight material for the sail. Johnson said the technology could be ready for preparation of a flight demonstration by 2006.
Another way to trim a rocket's waistline is to produce fuel at the destination. A pound saved is more than a penny earned when it comes to the weight of spacecraft.
"Roughly, it takes about $10,000 a pound to go to low Earth orbit," said Peter Curreri, of Marshall's Biological and Physical Space Research Laboratory. "To put the lunar lander on the moon, it was about $250,000 per pound. For the previous rover Sojourner (24 pounds) to be put on Mars, it took about $750,000 a pound."
Curreri's lab is studying ways to take moon rocks or martian soil and rocks and, through a chemical process, extract such things as water or oxygen or hydrogen and turn those into fuel for rockets or water for people.
"You could send up an unmanned mission before and basically have a refueling truck when a manned mission lands," Curreri said.
The concept doesn't stop on the moon or Mars. Asteroids could be mined for minerals for use on Earth.
"It's a theory, and there would have to be a lot of work, but we are going to need a way to travel, live and return from these places. ... There are compelling reasons to go for research, science and commerce, but we've got to figure out a way to get there that won't generate (large) costs."