New Space Engine Could Turn Tiny CubeSats into Interplanetary Explorers

Artist's Concept of 'Interplanetary CubeSat'
Artist's concept of a tiny CubeSat equipped with the new CubeSat Ambipolar Thruster system, or CAT. (Image credit: Ben Longmier - University of Michigan)

Researchers plan to launch a tiny spacecraft to Earth orbit and beyond within the next 18 months, in a key test of new propulsion technology that could help cut the cost of planetary exploration by a factor of 1,000.

The scientists and engineers are developing a new plasma propulsion system designed for ultrasmall CubeSats. If all goes well, they say, it may be possible to launch a life-detection mission to Jupiter's ocean-harboring moon Europa or other intriguing worlds for as little as $1 million in the not-too-distant future.

"We want to enable new missions that right now cost about $1 billion, or maybe $500 million — to go, for example, explore the moons of Jupiter and Saturn," said project leader Ben Longmier, a plasma physicist and assistant professor at the University of Michigan. [6 Promising Places for Alien Life in the Solar System]

To get the ball rolling, Longmier and his team launched a crowdfunding campaign on the website Kickstarter Thursday (July 4). They hope to raise a minimum of $200,000 by Aug. 5, which should be enough to loft the miniature thruster on its maiden space voyage.

Miniature thruster technology

CubeSats are cheap and tiny spacecraft that weigh just 11 pounds (5 kilograms) or so. At present, they're generally restricted to Earth orbit, where they circle passively until their orbits decay and they die a fiery death in the planet's atmosphere.

But the new propulsion system — which the team calls the CubeSat Ambipolar Thruster, or CAT — could change all that, turning such bantam spacecraft into interplanetary probes, Longmier and his colleagues say.

The different components of the new CubeSat Ambipolar Thruster, which its developers say could turn tiny spacecraft into interplanetary probes. (Image credit: Ben Longmier - University of Michigan)

CAT is a plasma engine, generating thrust by accelerating superheated ionized gas out of a discharge chamber. The CAT thruster is powered by solar panels, and permanent magnets will guide the plasma out the back of the spacecraft.

CAT is similar in concept to the ion engine that powers NASA's Dawn spacecraft, which orbited the protoplanet Vesta for more than a year and is now on its way to study Ceres, the largest body in the main asteroid belt between Mars and Jupiter. Over long periods of time, such thrusters can accelerate spacecraft to higher speeds than typical chemical rockets can achieve.

But with CAT, everything must work on the micro scale. The thruster and power systems will weigh less than 1 pound (0.5 kg), while the supply of propellant — likely either iodine or water, though many different substances could be used — will be capped at about 5.5 pounds (2.5 kg), researchers said. [Gallery: The Solar System's Deep-Space Probes]

Most of the CAT components have been built and tested individually, and the team is making good progress toward incorporating them into a unified whole, researchers said.

"The hurdles that exist right now are getting our newly designed thruster up and running. We think we're about three weeks from that," Longmier told "We're really sort of ramping up and hitting full tilt right now."

To Earth orbit and beyond

The main goal of the new CAT Kickstarter campaign is to raise enough money to space-test the engine in Earth orbit. The team is planning to launch its first probe within the next 18 months, though it may be possible to get off the ground even sooner, Longmier said.

The team plans to send the maiden CAT-equipped probe out into deep space as well — not all the way to Europa or Saturn's geyser-spewing moon Enceladus, but far enough to demonstrate CAT's capabilities.

"Our secondary goal is getting it out of Earth orbit and proving to the community that this thing works," Longmier said. "If it does work, it's a lot easier to get funding and write grants in the traditional sense."

Raising $200,000 should make all of this possible, while meeting other funding milestones will allow the CAT team to tackle "stretch goals." If the Kickstarter campaign nets $500,000, for example, the team will fast-track its space trip by purchasing a commercial launch, while raising $900,000 will enable a two-CubeSat "space race" to escape Earth orbit.

Longmier and his core team at the University of Michigan are working with experts at a variety of institutions, including three different NASA centers — Ames Research Center in Moffett Field, Calif., the Jet Propulsion Laboratory in Pasadena, Calif., and Glenn Research Center in Cleveland, Ohio.

The asteroid-mining firm Planetary Resources is another partner. The billionaire-backed company, which counts Google execs Larry Page and Eric Schmidt among its investors, is interested in possibly using CAT-equipped probes to do up-close asteroid reconnaissance on the cheap, Longmier said.

"That's sort of where we come in — sending that small spacecraft out as a scout, a radio beacon, to go radiotag it," he said.

Asteroid tagging is just one of many potential applications for the technology, CAT team members say. A fleet of CAT-powered CubeSats could also provide cheap global Internet access, for instance, or study the impacts of solar eruptions on Earth's neighborhood, helping scientists better understand and predict space weather.

And then there's the lure of mounting stripped-down, $1 million life-detection missions to Europa, Enceladus or other intriguing and farflung worlds. Such efforts may be possible soon, thanks to CAT, the increasing efficiency of solar panels, the decreasing size of microprocessors and other technological advances, Longmier said.

"I think we have the opportunity — for the first time, more or less, in history — to go and see if we can make these detections of life within our own solar system," Longmier said. "Not just looking at them, but going and taking sensors, doing in situ measurements, flying through the plumes of Enceladus with small spacecraft. We think we can do that in the relatively near future."

To learn more about the CAT engine and Kickstarter campaign, visit:

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Mike Wall Senior Writer
Michael was a science writer for the Idaho National Laboratory and has been an intern at, The Salinas Californian newspaper, and the SLAC National Accelerator Laboratory. He has also worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz.