Missions to Mars: Nuclear-powered Probes In the Plans for Mars.

March 8, 2000

By Paul Hoversten
Washington Bureau Chief
space.com

WASHINGTON -- NASA is considering the use of nuclear-powered spacecraft in the future to explore Mars -- an idea certain to ignite a firestorm of protest on Earth, SPACE.com has learned.

No such spacecraft would be launched to Mars anytime soon.

Probes targeted for launching in 2001 or 2003 still would carry conventional solar panels or wings that would draw their power from sunlight.

But the plan to use nuclear power at Mars, as was done with the 1970s-era Viking mission, is "not off the table," said Ed Weiler, NASA's associate administrator for space science. "For better or worse, Mars is a faraway planet and using these things makes a lot of sense when you're trying to build a robust program there."

Both the Galileo and Cassini deep space missions have nuclear power packs known as radioisotope thermoelectric generators (RTG's) on board. These are needed to provide electrical power in the far reaches of the solar system where sunlight is minimal.

Dan McCleese, Chief Scientist of the Mars Exploration Directorate at NASA's Jet Propulsion Laboratory said that the space agency is encouraging Mars planners to look again at using RTGs on the Red Planet.

The idea is gaining momentum as NASA puts the final touches on its new multi-year, $1.5 billion martian exploration program. The revamping of the Mars program follows last year's losses of the Mars Climate Orbiter and the Mars Polar Lander.

An independent panel led by former Lockheed Martin executive Thomas Young is studying those failures and is to issue its report on March 15. NASA plans to reveal its restructured plans for Mars the same day. The agency is expected to announce:

It has canceled a lander spacecraft for 2001 and will instead send one in 2003 that lacks a robotic rover but includes new communications gear to help ground controllers better monitor the lander. The added gear would allow NASA to maintain contact with the spacecraft during its descent to the surface and avoid a repeat of Polar Lander, which vanished without a peep on the way down.

It will fly an orbiting spacecraft in 2001 as planned but it will have improved technology that was not aboard the doomed Climate Orbiter.

A mission to return a sample of the martian soil to Earth is still a key scientific goal, but NASA will not be held to a specific time on when it might fly. The mission, which had originally called for separate launches in 2003 and 2005, will still include European participation and will be launched on a French Ariane rocket.

The primary scientific goals at Mars are to search for evidence of past life and investigate the planet's climate and resources. The thread that connects all of those is water and future missions to Mars will strive to find out where the water was on the surface, where it is now and what it did during the transition.

"Let's be bold and say it up front," Weiler said in an interview Thursday. "We're looking for two things. Is there life and can we live on Mars and colonize it. As for the missions, we will fly them when we have a good chance of success. I am not going to sign on the dotted line for any mission unless it stands a good chance of succeeding."

One way to build a more robust exploration of Mars is through nuclear-powered spacecraft. "I'm not saying we're going to use radioactive power sources in the near term," Weiler said. "Something like that takes years to get approved.But people forget that the reason Viking lasted so long on the surface of Mars was because it had one of these."

The Viking 1 and 2 landers were launched in 1975 and arrived at Mars in 1976. Viking 1 lasted until November 1982 and Viking 2 stopped transmitting in April 1980. The solar-powered Polar Lander, by comparison, was designed to last just 90 days, the same life span as that of Mars Pathfinder in 1997.

NASA has flown a total of 25 missions with radioactive power packs since the 1960s.

NASA last sent radioactive material, Plutonium 238, to Mars in 1997. The rover Sojourner carried three radioisotope heater units. Each of the units -- about the size of a C-cell battery -- contained a 0.1 ounce (2.6 grams) of the isotope to keep the vehicle's electronics warm.

As program managers see it, radioactive power would only be needed for spacecraft that land on the surface and any rovers that those craft might carry. Any decision to outfit such landers with nuclear power would have to be made by the White House and would need to be coordinated with such agencies as the Department of Energy and the Environmental Protection Agency.

"NASA doesn't make a decision by itself to fly nuclear material," Weiler said. "There's a long list of requirements and quite a list of agencies that are involved. It takes years to fly those types of missions."

One reason it takes so long is because such missions tend to touch off protracted legal battles. Anti-nuclear protesters filed suit in federal court to stop both the 1989 launch of the Galileo probe to Jupiter and the 1997 launch of Cassini to Saturn, arguing the missions put Americans at risk from radiation exposure in the event of a launch accident.

"We'll be very much on top of it and organizing to stop it," said Bruce Gagnon, of the Global Network Against Weapons and Nuclear Power in Space in Gainesville, Florida. "Our concern goes beyond launch problems. It's also the health and safety of workers who have to produce this material. What NASA has in mind is a massive infusion of nuclear material in the space program"

Gagnon was among those filing a federal suit to stop the Galileo and Cassini launches and said his group might do the same with nuclear-powered Mars missions.

In the case of Mars, nuclear power on a spacecraft "solves the problem of what happens at night," said Carl Pilcher, NASA chief of solar system exploration. "At night you get to stay warm. You need a power system for the heaters in order to keep the lander alive. It's thermal cycling, going from warm in the day to cold at night, that kills you at Mars."


Back to Home Page