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Exploradio: Cleveland's ion engines power NASA's deep space dreams
Cleveland's NASA Glenn Research Center is building the ion engines that will capture an asteroid and someday take humans into deep space
by WKSU's JEFF ST. CLAIR
This story is part of a special series.


Reporter / Host
Jeff St. Clair
 
A flexible tube encircles a 30 foot wide asteroid and ensnares it for study. This is the dream of NASA's Asteroid Retrieval Mission. The vessel and its ion thrusters are being designed and built by engineers at Cleveland's NASA Glenn Research Center.
Courtesy of NASA
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NASA has set a goal to capture an asteroid and bring it to the moon for study. The engines to power that mission are being built at Cleveland’s  NASA Glenn Research Center.

In this week’s Exploradio, WKSU’s Jeff St.Clair explores the technology behind NASA’s deep space dreams.

Exploradio: NASA's ion engines

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The Asteroid Retrieval Mission
The star of the NASA video, set to dramatic music, is a massive rock hurtling through silent space toward a rendezvous with destiny.  Suddenly the school-bus sized asteroid meets a spaceship equipped with what looks like a big, rubber catcher’s mitt.  Blue light glows from the ship’s thrusters as it sneaks up, encircles the asteroid, and slowly pulls it in. The blue thrusters kick in again and push the whole package toward the moon where astronauts arrive to sample the exotic space rock.  This is NASA’s dream, the asteroid retrieval mission, and Cleveland’s NASA Glenn Research Center is helping make it real.

An eerie blue glow and a gentle nudge
The spaceship’s blue thrusters are being designed and built at NASA Glenn by engineers like Dan Herman. He’s forced to shout over the incessant pulse of cryo-pumps that create a space-like vacuum inside a tanker-sized chamber by freezing stray atoms inside it. A glowing blue drum inside the chamber emits a faint cloud of vapor. Herman says this tank has been under vacuum for over eight years, and the glowing blue ion thruster, “has operated for over 46,000 hours of operation…”

That’s more than five years of constant use for this ion engine under Herman’s watchful eye. NASA’s ion engine is the future of deep space trave. The blue glow of the ionized xenon gas, as Herman notes, will deliver tiny amounts of thrust to the several kiloton asteroid payload. Herman says the ion engine delivers the equivalent amount of thrust as two pieces of paper pushing on your hand. But in space, that’s enough, over years, to move mountains.

Slow and steady wins the race in outer space 
Lead engineer Rick Manella compares the ion thruster to the familiar blast of a rocket’s engine.  He says the fiery chemical propulsion provides, “large thrusts for short periods of time, this is low thrusts for long periods of time.”  He says space travel with ion engines is not for the impatient.  Manella estimates the asteroid capture vessel will take two years to get to the rendezvous location and about a year and a half to bring it back to lunar orbit where astronauts can access it. But Manella says the energy sipping ion engines require ten times less fuel than chemical engines, which means lighter payloads, and cheaper missions. 

NASA's dreams of deep space
Right now about 200 commercial satellites are kept in orbit with smaller versions of the ion engine. The asteroid retrieval mission will be NASA’s highest profile use of the technology since it was invented at Glenn more than 50 years ago. Manella says Glenn is developing more powerful ion engines for this mission, which he says is merely a stepping stone to further exploration.

Manella says, "it’s a good combination of science and unlocking deeper space where we all want to go.”

The plan over the next three years is to find a suitable asteroid.  Then in 2017 launch the retrieval capsule, push it to lunar orbit with the ion engines, and send astronauts to rendezvous near the moon in 2021. They’ll take samples of the asteroid to learn more about these rocks and where they come from.  Beyond that lies Mars and dreams of deep space, all powered by ion engines built in Cleveland.

 


(Click image for larger view.)

A jet of ionized xenon gas exits an ion engine at NASA Glenn Research Center.  Glenn engineers invented the ion engine around 50 years ago, and are designing more powerful units for new deep space missions.
Lead engineer Rick Manella, left, and engineer Dan Herman. Herman is testing the durability of NASA's ion engines which must operate non-stop for years at a time.
Ion engines come in a variety of sizes, designs, and power requirements. They run on electricity provided by large solar arrays alongside spacecraft.  The ion engines for the asteroid mission will require about 50MW of power.  Building and deploying solar arrays of that size is a considerable challenge for NASA engineers.
This is called a Hall ion engine, notable for the screen design that helps accelerate the xenon ions.  The propulsion comes from ions exiting the engine at high speeds, about 60,000mph, providing tiny increments of thrust over long periods of time.
The dream of asteroid capture dates back to the 1970's when this concept drawing was made.  Part of the reason for the current asteroid retrieval mission is to generate excitement about NASA's dreams of deep space exploration.
 
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