by Steve Duda

We recently reported on Elon Musk’s (of Tesla Motors fame) and his commercial rocket/space vehicle company’s use of solar power in its spacecraft. That mission, which used solar panels and battery storage to power parts of the craft, had full NASA backing. Now, we learn that NASA’s commitment to the use of solar as an important source of power while in space is strengthening.

The space agency recently put out a request for proposals looking for a company to prepare a high-power solar electric propulsion flight system technology for NASA deep space and human exploration missions. NASA’s goal is to develop a “space tugboat” that can ferry satellites from low Earth orbit (LEO) to geosynchronous Earth orbit (GEO), saving fuel and secondary booster costs. The availability of a solar-powered vehicle would make it possible to launch spacecraft to LEO, then ferry them to GEO, allowing much heavier payloads to reach GEO while still using existing launch vehicles.

Sounds like the typically awesome, big-brain concepts we’ve come to expect from the guys who brought us Tang! and microwave ovens, but just what is high power solar electric propulsion, anyway?

Warning: Science. Solar electric propulsion takes advantage of magnetism and electricity to push a ship through space. Electricity, generated by the ship’s solar panels, gives a positive electrical charge to atoms inside the chamber. They are pulled by magnetism toward the back of the ship and then pushed by magnetic repulsion out of the ship. (This is like what happens when you hold the same pole of two different magnets close to each other. They repel each other.)

This steady stream of atoms going out of the spacecraft gives it the thrust it needs to go forward through space. This is also known as ion thrust or propulsion. Ion propulsion needs to be constantly fed a stream of electrical power to function properly. The only way to ensure a constant stream of electrical power to the solar ion drive is to generate power as a craft travels through space. Solar panels are the best way to do that.

All together, five companies bid on the job: Analytical Mechanics Associates, Ball Aerospace & Technologies, Boeing, Lockheed Martin and Northrop Grumman. In a recent press release, NASA announced that Northrop Grumman had been awarded the contract.

“We are working on alternatives to the typical solar array approach,” said Jim Munger, Northrop Grumman’s solar electric propulsion program manager, “Our concept will be scalable to 300 kilowatts and beyond and have the potential for reducing the cost and complexity of high-power requirements.”