Rockets For The Red Planet

There is a problem, though. Tiny cracks can form in the core, releasing some of the uranium into the propellant. In space, radioactive sputter isn’t a big deal. But without ground testing, the reactors won’t ever get to space. ”If we’re trying to sell the public on a Mars mission and the image is of us leaking a radioactive gas, that’s going to be a problem,” notes Steven Howe, the director of the Center for Space Nuclear Research at the Idaho National Laboratory, in Idaho Falls.

Because human exploration of Mars has yet to receive its mandate, none of the work-arounds that could save nuclear propulsion is getting more than theoretical consideration. No space agency is building big enough reactors, and there’s a solid chance they will live on just as a testament to the scientific exuberance of the 1960s. Any dream of humans harnessing the great beyond would be mothballed, with an unbuilt Martian settlement languishing next to a missing philosopher’s stone and a nonexistent flying car.

That’s not to say humans will never make it. A chemical rocket may indeed deliver a small crew to Mars [see sidebar, ”Exotic Options for Chemical Rockets” ]. But it wouldn’t be for much more than bragging rights: Humans went all the way to Mars and they didn’t even get the lousy T-shirt or the reinvention of life science—and they certainly didn’t get the space colony.

Ad Astra’s vasimr shares some of the technical and political problems of nuclear thermal propulsion. Only a nuclear reactor can deliver the megawatts needed for a Mars mission. But given a reactor, Chang Díaz is confident he can easily convert at least 60 percent of its electrical power into rocket power. For now, he plans to build his business around closer targets, such as solar-powered moon visits and trips to investigate near-Earth objects.

The ventures would be scaled-up versions of the activities now performed by Hall thrusters and other ion engines, whose related technologies propel space probes and nudge satellites. Ion thrusters have taken European Space Agency and Japanese probes to the moon and to an asteroid named 25143 Itokawa, and one spacecraft is now hurtling toward another asteroid and the dwarf planet Ceres. Solar panels power the thrusters, which rarely use more than a couple of kilowatts.

Size is everything. Says Brent Sherwood, a space architect at NASA’s Jet Propulsion Laboratory, in Pasadena, Calif.: ”The real question is, how do you scale up from a thing that’s got a blue glow in a lab to a thing that sends half a dozen people to Mars and back?” To test higher-powered VASIMRs, Ad Astra will need a vacuum chamber even bigger than the aluminum monolith it has in Houston. In fact, it would be so big and expensive that Chang Díaz figures he might as well test the rocket in space.

Under this model, Ad Astra employees would blast off on assignment to the moon for a few months at a time, touching down near a facility surrounded by vast arrays of solar panels. Working within the moon’s peculiar schedule—two weeks of light followed by two weeks of night—the lunar operatives would fire their engine, accumulating performance data in preparation for an eventual flight to Mars.

Then will come the hard part. No amount of testing can mimic humanity’s first flight to Mars. That knowledge gap could be Ad Astra’s greatest challenge. Les Johnson, deputy manager for the Advanced Concepts Office at NASA’s Marshall Space Flight Center, in Huntsville, Ala., puts it this way: ”Imagine getting in a Winnebago with your four best friends and saying, ’We’re not going to leave this Winnebago for three years.’ And between us and complete death is a thin aluminum skin, and the lowest bidder is going to send us out.” Then he pauses. ”I would be a bit more mundane,” he says. That is, he would rather see the advanced technology invested in better life-support systems, perhaps in the form of artificial gravity on board a familiar chemical rocket.

In rocket science as in life, differences of opinion are often cultural. On a table next to Chang Díaz’s desk in Houston lies a DVD of a television show he grew up watching in the 1950s. It’s about an eccentric scientist named Captain Video who defended law and order by jumping into his spaceship from his mountain retreat. Before each episode, a voice booms across the mountaintops: ”Captaaaaaaiinn Video! And his Videoooo Rangers!” Then antics ensue. Chang Díaz’s name may not echo across the suburbs of Texas, but in the world of rockets, his presence is booming.

For more articles, go to Special Report: Why Mars? Why Now?