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Ion drive
An artist’s concept shows a space probe powered by ion thrusters. (Credit: Aerojet Rocketdyne)

Aerojet Rocketdyne’s next-generation ion thrusters could well make their debut in space during NASA’s robotic mission to grab a piece of an asteroid and bring it back to lunar orbit in the 2020s.

Earlier this week, NASA announced that Aerojet’s operation in Redmond, Wash., would be getting in on a 36-month, $67 milllion contract to develop a high-power electric propulsion system for future spacecraft. Today, NASA officials explained what the system would be used for.

“Basically, we’re building a whole new drive train for deep-space exploration,” Bryan Smith, director of NASA’s Space Flight Systems Directorate at Glenn Research Center in Ohio, told reporters.

Engineers at the Ohio center have been working on electric propulsion technology since the 1950s, and low-power ion thrusters have been used on probes such as the Dawn spacecraft, which is currently orbiting Ceres. Such thrusters use solar-generated electrical power to accelerate xenon ions to incredibly high speed.

The thrust amounts to just a whisper – roughly equivalent to the weight of a piece of paper pressing down on your hand. But over time, the acceleration can build up to more than 200,000 mph.

Today’s ion thrusters reach a power level of 4.5 kilowatts in space operations, and around 12.5 kilowatts in the lab. Aerojet is tasked with developing a 50- to 100-kilowatt system that puts thrusters together to provide the oomph required to get to an asteroid or Mars.

Steve Jurczyk, associate administrator of NASA’s Space Technology Mission Directorate, said the first in-space test of the system could well come during the Asteroid Redirect Robotic Mission. ARRM’s goal is to go out in 2020 or 2021, snatch a boulder from a near-Earth asteroid, and deliver it to lunar orbit in 2025 or 2026 for study by a crew of astronauts.

The mission is expected to yield deeper insights into what asteroids are made of, what it would require to divert a potentially threatening asteroid, and how the technology could work to send payloads to Mars.

Despite what you see in the “Star Wars” movies, ion drives aren’t that great for sending humans through deep space. They’re not powerful enough to send a crew into space straight from an earthly launch pad, and they build up speed too slowly. Smith estimated that it might take two years for a spacecraft driven by electric propulsion to get to Mars, compared with nine months using chemical propulsion systems.

But the slow buildup isn’t as much of an issue for cargo shipments, and Aerojet’s ion thrusters are projected to be 10 times as fuel-efficient as today’s chemical thrusters. That means less fuel mass would be needed to send equivalent payloads to Mars.

After the launch to an asteroid, the electric propulsion system could next come into play for sending a telecommunication orbiter to Mars in the 2022 time frame, Jurczyk said. Another potential application would be to send a probe to Mars, pick up a sample of rocks and soil, and return the sample to Earth – an idea that NASA and its partners have been talking about for more than a decade.

NASA is making its own research into electric propulsion available to all comers, but Aerojet’s work is likely to bring the company long-term commercial benefit.

“The plans for Aerojet Rocketdyne are to productize what they develop for us, and then sell it as a propulsion system option for spacecraft developers and spacecraft systems integrators, for NASA missions, missions for other government agencies or for missions for commercial applications,” Jurczyk told GeekWire.

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