Looking to Mars as the next frontier

By Charles Q. Choi

updated 7:37 p.m. ET July 22, 2009

As the 40th-anniversary celebrations of the moon landing end, a human voyage to Mars remains a holy grail for NASA.

"We're still looking at human exploration of Mars as one of the goals of the future at the top level," said NASA researcher Bret Drake with Lunar and Mars Integration at Johnson Space Center in Houston. "Having a human actually set foot on another planet would be one of the greatest adventures possible, one of the greatest monuments to history."

A crewed mission to the red planet is a daunting challenge that lies at the edge of current technological capabilities and possibly beyond. Still, NASA keeps a strategy to go there and constantly keeps up to date with new ideas.

"Mars is one of those targets of fascination that has been around a long time," Drake said.

How to get there
A voyage to Mars would take a crew about 180 days. So far NASA is exploring two options for propulsion there — a nuclear thermal rocket and a chemical engine.

A nuclear thermal rocket, based off designs from the '60s and '70s, would use a nuclear reactor to super-heat a gas and blast it out the nozzle to generate thrust. "It's a very high-performance vehicle, and we think it's very safe, not radioactive at launch, but it is a nuclear system," Drake said. "The idea for the chemical engine is similar to that used on the space shuttle, liquid oxygen and liquid hydrogen. It's a fairly well-known technology, but it's not as efficient as nuclear thermal."

To reach the Martian surface, NASA envisions an aerodynamic lander that flies down with thrusters to help it descend. The ascent vehicle that takes the crew back into space for the six-month trip home will likely rely on a combination of methane and liquid oxygen. "Oxygen is present in the Martian atmosphere in the carbon dioxide, so you can use resources on Mars to make it," Drake said.

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Before the crew even gets to Mars, the plan is to send as much cargo there ahead of time as possible.

"That way we can know it's operating right before we ever commit the crew," Drake said. "A Mars mission is not like a lunar mission where you can come home at any time — once they're committed, a crew is out there for years."

By current NASA estimates, a crewed mission to Mars needs to lift about twice the mass of the International Space Station into space — roughly 1.76 million lbs. (800 metric tons) of technology. To launch the equipment, NASA plans on using the Ares V rocket, designed to be the most powerful rocket ever built and capable of carrying about 414,000 lbs. (188 metric tons) to low Earth orbit at one time.

"We're going to try to minimize the amount of assembly needed," Drake said. "The heavy lift capacity we'll have with the Ares V will allow for simple automatic rendezvous in orbit and docking of components."

The crew would ride up in one of the upcoming Ares I rockets before starting the voyage to Mars.

"Having humans in place could bring a wealth of experience and training and the ability to put into context what they see and to make real-time decisions, all things difficult to do with robots," Drake said.

The very habitat the crew stays at on the Martian surface would be sent ahead of time. "You can also do things like produce and store oxygen from resources at Mars beforehand for the crew and the ascent vehicle. You could generate water as well."

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