Nuclear Rockets Could Shorten Flight Time to Mars

Paraphrased by Steve Waldrop
February 3, 2003

Scientists are drawing up plans for a new age of space travel, using nuclear-powered rockets that could make it easier to carry astronauts to Mars.

Sean O'Keefe, administrator of the National Aeronautics and Space Administration, has said that President Bush will endorse increased funding to develop atomic propulsion. Despite the fact that nuclear propulsion has consistently come up as one of the most-promising propulsion concepts for human missions beyond Earth orbit, little more than study has been done since the Nuclear Engine for Rocket Vehicle Applications, or NERVA, program was killed in 1972.

Advocates of nuclear power note that a quantity of uranium the size of a soft-drink can hold as much energy as 100 of the space shuttle's mammoth external fuel tanks. Nuclear-reactor rockets, conduct nuclear fission reactions -- the same kind employed at nuclear power plants -- in which uranium atoms are split apart, releasing tremendous volumes of energy. In a nuclear thermal rocket, this energy is used to heat hydrogen propellant, which is stored aboard the rocket as liquid in supercooled fuel tanks.

The strength of nuclear propulsion is that it is more efficient than traditional chemically-propelled rockets. All rockets require fuel. Chemical rocket engines burn it, heating up the fuel and accelerating the combustion byproducts out a rocket nozzle. Nuclear thermal engines employ a very compact mass of nuclear fuel to release tremendous amounts of energy. That energy is used to heat lightweight hydrogen gas, and shoot it through a nozzle to get thrust. The nuclear reaction heats the hydrogen to much higher velocities than chemical combustion can.

O'Keefe has pointed out that today's spacefarers travel at the same speed John Glenn did more than 40 years ago when he became the first American to orbit the Earth.

With today's rockets, getting to Mars would take at least six months. In addition, the crew would need to stay on the Red Planet a year and a half until Mars is again at its closest point to Earth- so a round trip would take up to three years. Such a journey could debilitate astronauts from extended exposure to interstellar radiation and zero or limited gravity. Nuclear-powered rockets could cut a one-way trip to a more manageable two months.

Astronauts are among the most enthusiastic boosters for nuclear rockets. The nuclear thermal rocket has the advantage of being able to dramatically reduce trip times to and from Mars. This reduces the amount of time that astronauts are exposed to the dangerous solar and cosmic radiation that permeates space.

Compared to the radiation released from a well-designed, adequately shielded nuclear rocket engine, the radiation environment of space is tremendously more dangerous.

NASA asked last year for funding of almost $1 billion over five years to develop nuclear rockets.