Posted: May 15, 2015 3:46 pm
by SkyMutt
:think: Bloomberg calls it a drone, and I suppose that it is: "The Secret Air Force Space Drone Heads Back Into Orbit" | Bloomberg (autoplay video on the linked page)

A classified Air Force space drone is returning to orbit again, and this time NASA will use the flight to see how 100 or so “materials of interest” hold up in the murderous environment of space.

Space stresses materials with temperature extremes, debris, micrometeoroids, direct sunlight, and atomic oxygen and can erode many of the paints, polymers, and composites that NASA and private space companies use as protective coatings on their craft. Such research becomes only more critical as the agency contemplates longer, deep-space explorations, such as a mission to Mars in the 2030s. NASA now has some space in the 29-foot-long Air Force drone to carry out the testing—which involves samples about the size of a quarter and extends research that began in 2001—for possible use in future spacecraft.

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Besides the materials research, the Air Force plans to test an experimental propulsion system.

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For more on that last sentence: "New details emerge about electric propulsion experiment aboard X-37B" | Spaceflight Now

It is a Hall thruster electric propulsion test to enable in-space characterization of design modifications that are intended to improve performance to the units onboard Advanced Extremely High Frequency military communications spacecraft, officials said Monday.

Produced by Aerojet Rocktdyne, the AEHF satellites’ Hall thrusters are 4.5-kilowatt units that use electricity and xenon to produce thrust for maneuvering satellites in space. The novel electric propulsion system produces a whisper-like thrust by ionizing and accelerating xenon gas.

Unlike conventional chemical engines that deliver substantial boosts with each brief firing, the electric system needs the stamina to operate for exceptionally long periods of time to harness its 0.06-pound-thrust into orbit-changing power.

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