Space History Future The Science Behind It All Common Concerns and Misconceptions		Space : Future What is the Future of Aerospace Nuclear Science and Technology? After many years, new ideas for the use of nuclear power in outer space are being planned and built.  Below are some of the many ideas and projects that will hopefully fly over the coming years.  The fact that fissioning a certain mass of material can give us 10 million times more energy than a chemical reaction using the same amount of material is a compelling argument for the research, testing and use of nuclear energy to power the human race's expansion into the solar system. In the United States, this renewed interest in using nuclear power for space missions is being pursued at NASA under the umbrella of Project Prometheus.  The first major program will be designing and building a fission reactor for an ambitious mission to Jupiter. JIMO - The Jupiter Icy Moons Orbiter An artist's rendition of the JIMO mission. NASA has plans to launch a mission to Jupiter and three of its moons - Callisto, Ganymede and Europa - in the year 2012. These large, icy moons, each the size of a small planet, "appear to have three ingredients considered essential for life: water, energy, and the necessary chemical elements" according to the evidence NASA gained from the Galileo mission.  It is even thought that Europa might have liquid water oceans under a thick layer of ice! To get to Jupiter is one thing.  Missions such as Pioneer, Voyager and Galileo have ventured there in the past.  These missions took impressive pictures and did solid scientific work.  What will set JIMO apart is the large science package it will carry and the cutting-edge ion drive that will propel the orbiter to Jupiter.  The science package and propulsion will both be made possible by a nuclear fission reactor, a reactor system that will give JIMO more than 100 times as much power as any power source with the same weight. This mission will be a proving ground for a new generation of technologies that will prove the safety and reliability of nuclear technologies to be used in the exploration of the solar system and beyond. On NASA's official page for the Jupiter Icy Moons Orbiter mission, you will find documents describing the mission and the proposed reactor in more detail, as well as information on safety questions relating to this mission. Gas-Core Reactor Propulsion A gas core nuclear rocket engine.  Reprinted with permission from Dr. Steven D. Howe of the Los Alamos National Laboratory. One of the most exciting ideas for bringing back the concept of the nuclear-powered rocket is a design known as the Gas Core Nuclear Rocket.  The idea is giant leap past the old NERVA rocket engine designs.  In a gas core nuclear rocket the propellant is passed through a plasma (or superheated, gas-like state) of radioactive material that is kept in a compressed state so that it stays critical (the radioactive material is close enough to sustain a nuclear chain reaction).  This creates temperatures so hot that the fuel in the old NERVA design of rocket engine would have melted.  In one of the most promising designs for a gas-core rocket engine, strong magnetic fields keep the fissioning material in a doughnut-shaped field and the propellant gas is passed through the hole, where it heats up to tremendous temperatures.  The designs being investigated would perform at thrusts 3 or 4 times as strong as the NERVA rocket engine designs. One of the best features of this design is the fact that the system does not to have to be in a critical (fissioning) state when you launch it.  You could launch a space ship with a standard chemical rocket and, once successfully in orbit, the reactor system could be turned on, brought critical and the ship would then proceed under the tremendous power of the gas-core rocket. As of yet, these rocket designs have not made it to the testing stage, but since the rocket engine designs have such enormous potential and pack such a powerful thrust in a small package, much research is being conducted in places such as Los Alamos National Laboratory and the Innovative Nuclear Space Power and Propulsion Institute at the University of Florida. The Next Generation of RTG Not all missions will require an actual fission reactor such as the one proposed for JIMO.  For such missions, a new generation of the Radioisotope Thermoelectric Generator is being researched.  Called the Multi-Mission Radioisotope Thermoelectric Generator, it is being designed to work on both planets and in the cold reaches of space.  It will be designed to produce around 100 watts of electricity while meeting rigid safety standards and providing an even power source for at least 14 years.  They key to the design will be in keeping it flexible and available for many different types of missions. Check out a fact sheet on MMRTGs prepared by NASA and the Department of Energy for an overview of the technology. A close cousin to the standard RTG is a plan to build a Stirling Radioisotope Generator to take advantage of what is called the Stirling Thermodynamic Cycle.  This cycle is almost like a regular piston engine turned inside out, where the gases used to move the pistons never leave the engine, unlike a car which pours the fumes from burning gasoline out of the exhaust pipe.  The gas used to drive the Stirling cycle are heated from the outside, not by burning, which makes it an ideal candidate to pair up with a long-lived nuclear heat source. Take a look at a fact sheet on Stirling Radioisotope Generators for more details. While these technologies may not sound as exciting as exploring the moons of Jupiter, having a safe, reliable power source for a variety of missions will prove invaluable in the future years of space exploration.