Their gentle, continuous push produces astounding speeds, using only tiny sips of xenon fuel.
Inside cavernous “Tank 5,” a vacuum chamber as big as a subway tunnel at Cleveland’s NASA Glenn Research Center, a soft sapphire glow spilled from the nozzle of an odd-looking spacecraft engine earlier this month.
The turquoise plume was a familiar sight to the engineers running the test. Ion engines, which spout bluish jets of electrically excited atoms rather than chemical flames like a traditional rocket, have been a Glenn specialty for more than 40 years. Their gentle, continuous push produces astounding speeds, using only tiny sips of xenon fuel.
A Glenn-designed ion engine enabled NASA’s Deep Space 1 probe to swoop past a distant comet for a close-up look in 2001. And the Glenn ion-powered Dawn spacecraft is 260 million miles from Earth, streaking toward a flyby of the dwarf planet Ceres in 2015 and breaking Deep Space 1’s acceleration record along the way.
But the most audacious assignment for the Cleveland center’s ion engines is ahead, as NASA revealed April 10.
Later this decade, a robot spacecraft riding a Glenn engine’s cobalt ion stream will aim for an asteroid circling a million or so miles from Earth. It will nuzzle up to the tumbling, dump truck-sized rock, unfurl a fabric grab-bag to snare it like a Venus flytrap, then fire up the ion engines and haul the asteroid into orbit around the moon.
There, as early as 2021, astronauts will dock with the captive space boulder. They’ll chip off chunks for study and possibly extract water and valuable minerals.
The White House-backed asteroid-lassoing mission sets a clear near-term space exploration goal for an agency that critics said had been floundering since the retirement of the shuttle fleet and President Barack Obama’s 2010 cancellation of NASA’s Constellation moon-landing program.
If Congress goes along, the asteroid-capture effort will mark the first time humans try to alter the path of a celestial body – a crucial step, NASA says, in learning how to deflect much bigger “planet-killer” asteroids and comets. The space agency also touts the project as a testbed for technologies needed to reach deeper-space destinations such as Mars, a boost for commercial and international partnerships, and a chance to mine asteroids for rocket fuel ingredients, precious minerals and other hidden resources.
It also raises the fortunes of Cleveland’s NASA center within the space agency. “The president wants us to put an astronaut on an asteroid by 2025 and here Glenn is right in the middle of that,” said center director James Free. “The work we do is very unique. Glenn has the technology this agency needs to move forward.”
NASA plans to pump $38 million into the Cleveland center in 2014 to speed up development of the more powerful ion engines needed for the asteroid-capture mission. The technology is formally called solar-electric propulsion, or SEP, because it uses the sun’s energy, collected by solar panels, to generate the electricity required to make and expel ions to push the spacecraft. While chemical rockets are more powerful, ion engines are far more efficient, making them the practical choice for such a long-distance flight.
In December, a small team of Glenn engineers quietly began planning the work the center will undertake as it leads the effort to accelerate SEP for the asteroid-capture mission. Making the necessary improvements will be “very challenging,” but achievable, Free said.
The most powerful ion engines currently flying on commercial satellites operate on about 25 kilowatts of electricity, or roughly 250 times the energy needed to make a household light bulb glow. To snag a million-pound asteroid and push it into lunar orbit will take a 50-kilowatt power system, plus large, extremely lightweight solar panels; compact, reliable power-processing equipment to manage the high electrical loads; and thrusters that withstand weeks or months of firing during the multi-year flight.
“It’s taking that junior SEP system and cranking it up,” Free said.
Working closely with NASA’s Jet Propulsion Laboratory in California, the Glenn team aims to build and test prototype “engineering models” of the propulsion components in 2014.
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