To Mars & Beyond: Our Space Energy Options

Tuesday, June 12th, 2012

We can talk about going to Mars, or asteroids, or beyond, but the orbital track to getting there is going to require a lot of problem solving. Answers to even the basic questions — how much food, fuel, oxygen, water, or equipment  you need to pack  – all depend on how fast it takes to get there.

So, it all comes down to the fact that propulsion and reliable energy will be key to the success of any deep space mission.

What are some of our options? Ion propulsion, solar power, anti-matter fuels, nuclear reactors, and magnetoplasmadynamic thrusters. All of these options are now, or have been, part of a many-layered global discussion about the best way to get there from here.

Credit: Shutterstock.com

The Russian government first settled on the idea of nuclear propulsion for deep-space travel a couple of years ago, and could potentially spend up to 17 billion rubles (or over $580 million) over the next few years in developing and building a nuclear-powered engine, according to a recent report by Ria Novosti, the Russian news agency.

NASA is also exploring nuclear thermal and nuclear electric options, as well as cryogenic and solar electric space propulsion systems.

A propulsion system is something that creates thrust, usually by pushing something forward, employing Newton’s third law. (You remember: “Every action has an equal and opposite reaction.”) Or, as explained by researchers at Northwestern University, “thrust is made by propelling matter out of the back of the ship.”

Rockets like those on the recently retired Space Shuttle create thrust using a chemical engine that combines two propellants — one a fuel, the other an oxidizer — to make a gas that expands and rushes out the back of the engine.

Two often-used propellants are the gases hydrogen and oxygen, which can be cooled to cryogenic temperatures so that they become liquid. While fuels in their cryogenic state are more efficient and easier to handle, they also take up a lot of space. The shuttle needed almost 1.7 million pounds of propellant just to achieve orbit.

While the space shuttle could go up to around 18,000 miles an hour, that’s considered slow for deep-space travel. It would take between six and nine months to get to Mars. Then you have to get back.

While NASA is exploring ways to handle and store cryogenic propellants to use when high-performance thrust is needed on deep space missions, the agency also knows speed is key. 

Nuclear thermal rockets use fissioning radioactive material to create high temperatures to heat a propellant, which then releases the desired exhaust. Nuclear electric propulsion systems use a reactor to generate electricity, which can then power an ion thruster.

Both are fuel efficient, and thermal power could potentially be 100 times more powerful than chemical systems. Though developing a nuclear engine for the rigors of a deep-space mission will require a lot of money that NASA, at least, won’t have any time soon.

Ion propulsion works by using very small amounts of gas and accelerating it to very high speeds, forcing it out the back of the engine. It is so fuel efficient that the greatest limit on an ion engine, says the Northwestern researchers, is getting the electricity to feed it.

Solar electric propulsion uses magnetism and electricity to push a ship through space. A ship’s solar panels generate the electricity, which then gives a positive electrical charge to atoms in the engine chamber. The positive atoms are pulled by magnetism towards the back of the ship, where magnetic repulsion is used to push them out the back of the engine. (Remember as a kid, holding magnets together so that they repelled each other? Like that.)

It’s unfortunate, but one can’t count on the sun to always be available to provide enough electricity, especially in deep space. And while ion propulsion is great for long space journeys, you can’t use it to get a ship into space.

And so we’re back to cryogenic propellants.

It may seem that Mars is just over the horizon — but that could be longer away than it looks.

by AJ Plunkett

AJ Plunkett is a freelance writer in Virginia with experience in covering defense and aerospace industries as well as the military. AJ blogs via Contently.com.