Researchers Test Asteroid Collector In Zero Gravity Conditions

The test will be a crucial step in proposing a NASA space mission called HERA that would collect samples from three near-Earth asteroids and return those samples to Earth.

The test flight will take place the week of Sept. 25 aboard NASA's KC-135 airplane at Johnson Space Center in Houston. A team led by Derek Sears, professor of cosmochemistry and director of the Arkansas-Oklahoma Center for Space and Planetary Science, (AOCSPS) will fly for several hours while the plane makes parabolic dips in the air, creating pockets of microgravity conditions that last for up to 20 seconds. The researchers will have two days of flights to test the sample collector, and will experience microgravity anywhere from 30-40 times on each day.

"The collector is not only the most technically difficult portion of the mission. It's the only thing that hasn't been flight tested before," Sears said.

Researchers flying on the test mission will include Sears; Melissa Franzen, a AOCSPS summer research student from Loras College in Dubuque, Iowa; Jeffrey Preble and John DiPalma from SpaceWorks, Inc.; and Paul Bartlett of Honeybee Robotics, Inc. Honeybee Robotics recently secured a NASA contract to create tools for the next Mars lander. Engineers from Honeybee designed the asteroid sample collector, modifying a similar prototype for comets, which they had developed some time ago. SpaceWorks, Inc. built the test fixture that will enable the collector to be tested on the plane.

The collector has two sharp blades made of tungsten carbide that counter-rotate at various speeds, chopping up small bits of rock and sending them flying upwards into the collector -- at least in theory, a theory the researchers plan to test on board NASA's KC-135 in September.

To test the collector, the researchers need asteroid-like materials, so Sears and his colleagues have ordered large bags of concrete, gravel, sand and iron filings to create different mixtures for use while in flight. From what scientists know about asteroids from images and from meteorites, Sears speculates that a mixture of iron, sand and gravel will come closest to re-creating an asteroid surface.

The researchers hope to answer several questions through this flight:

* Does the collector work? Can it transfer material from the surface to the container?

* How much of the surface material does the collector pick up?

* What's the largest particle the collector can pick up?

* Does the collector physically change the particles (for example, does it crush them)?

* To what extent does the collector change the composition of the surface particles?

"We don't want to pick up just the light materials, for example," Sears said.

Five people will fly aboard the KC-135 and conduct the experiments. One person will work with the samples. The second person will operate the cutter. A third person will record everything with a digital video camera. And a fourth person will keep records of all the experiments on a laptop computer.

The "asteroid" materials will be mixed together in three different ways -- a combination of sand and iron filings, a gravel mixture and concrete -- to provide a range of possible surfaces that the collector might encounter in space.

"We're not optimistic that we can sample concrete," Sears said. "But these materials get to the heart of the really interesting question -- what will the real asteroid surfaces be like?"

The question has become more pressing in recent years with the discovery of hundreds of near-Earth asteroids. These discoveries have caused an increasing public concern about asteroid collisions and have generated growing scientific interest in asteroid composition.

Scientists can guess at what an asteroid might have in it through examination of pictures from EROS taken by the Near-Earth Asteroid Rendezvous (NEAR) mission or through meteorite data. But investigations of actual asteroid pieces would give concrete answers to some of their questions.

The proposed HERA mission would use technology derived from the NEAR mission to visit three near-Earth asteroids. The spacecraft would then collect samples of rocks upon the surface of all three bodies before returning to Earth.

An official proposal for the mission could be sent to NASA sometime next year, but first the collector must pass another test -- this one in a vacuum created by the AOCSPS Andromeda Chamber, a barrel-like collector that researchers can use to simulate the conditions of space. Those tests are planned for December.