Mittwoch, 15. Juni 2016 - 22:00 Uhr

Raumfahrt - Eine Lösung für Weltraumschrott ?


The Aerospace Corp. won a NASA grant to research whether it will be possible to develop a spacecraft thin enough and powerful enough to navigate to pieces of space junk, wrap around them, and pull them into the atmosphere to be burned up. This rendering shows what a final product may eventually look like. (Rendering courtesy of The Aerospace Corporation)


El Segundo-based aerospace engineer Siegfried Janson has a pretty good idea of how to get rid of space junk — an as-yet unsolved problem that threatens the integrity of future space missions.
Janson’s proposed Brane Craft, which received NASA research funding at The Aerospace Corp. this year, would be a meter-wide Kapton membrane thinner than a hair, propelled by thrusters, powered by the sun, and manipulated by electroactive polymers that contract like muscles.
The robotic device, weighing less than a pound, would rocket over to floating trash, wrap its membrane around the debris like gift-wrap and drag it out of orbit and into the Earth’s atmosphere to burn it up. Janson’s idea is among 13 research ideas nationwide supported with NASA Innovative Advanced Concepts development grants this year.
Millions of pieces of floating debris orbiting the Earth are increasingly a problem for space exploration because they move at extremely high speeds. Junk the size of a piece of chewing gum can pack the punch of a bullet or falling anvil. Something the size of a DVD or a book could hit like a bomb, according to NASA officials.
Janson started developing the space-cleaning device to protect miniature satellites called CubeSats that he and his team develop at The Aerospace Corp. CubeSats, each about the size of a tissue box, weigh less than 3 pounds. They are relatively cheap to make and can hitch a ride on spacecraft into orbit, where they can be used to track large-scale weather changes and animal migrations and monitor natural disasters, among other things.
Mini-satellites are one of the many new frontiers in space exploration and are expected to proliferate exponentially in coming years.
Though aerospace engineers work hard to ensure spacecraft return to the Earth’s atmosphere so they aren’t abandoned in orbit, more satellites inevitably mean increasing trash.
“Whatever you put in space, you better be darn sure it’s going to work well because you can’t send a repairman to space,” Janson said. “I’ve gotten the call from the Joint Space Operations Center saying one of your satellites is about to get hit (by space junk). If our little satellites can run into trouble in space, imagine what the big spacecraft has trouble with. It’s just a matter of time before space junk hits something important and takes it out.”
Space is full of broken and exploded pieces of satellites, abandoned launch vehicles and tiny pieces of old equipment zipping around in constant orbit. NASA has documented millions of cranberry- and walnut-size trash speeding like bullets through space along with tens of thousands of junk pieces the size of limes.
The agency tracks thousands of larger bits of trash that are 5 to 10 centimeters long or more, but smaller debris is tougher to keep tabs on. The Aerospace Corp. has an entire division dedicated to the issue called the Center for Orbital and Reentry Debris Studies.
“The population of stuff in orbit is going up over time. People are worried that, at some point, one incident will start a chain reaction. If nothing’s done, that could happen at some point in the future,” Janson said.
The challenge with getting rid of the trash is the extreme expense of getting things in and out of the Earth’s atmosphere. Generally, it costs $5,000 to $10,000 per kilogram to send something into space, Janson said. So his Brane Craft would be extremely light and dextrous, to maintain low costs and maximum efficiency.
“A lot of people think space is a pure vacuum, but it’s not,” Janson said. “There are atmospheres. The air gets very, very thin, and that’s why things stay in orbit a long time. The closer they are to Earth, the faster they come down. If you go higher up, it can stay up thousands of years.”
Janson’s $100,000 grant from NASA this year will fund the Brane Craft’s initial study. If all goes well, the agency will provide more research and development funding in future years to actually build and test the device.
Highly fuel-efficient electrospray mini-rocket thrusters being developed by NASA would generate ions that, combined with solar-powered electric voltage, would move Brane Crafts around space, Janson said.
“It’s like a ‘green’ propulsion system,” he said. Researchers are now working to improve the new mini-rocket technology’s thrust power. “If I make the craft very thin, I will cut down the weight dramatically. The trick is to make it very thin so I can get all the solar power I need for the sensors and antennas. It would weigh less than a pound.”
The Brane Craft would have two plastic wrap-like Kapton sheets sandwiching propellant used in the electrospray thrusters. Attached to the Kapton would be transistors to communicate with people on the ground and batteries to power them.
Electricity inductors, capacitors and a GPS receiver — along with some sort of camera — will have to fit on the film as well.
“The technology is fairly well-advanced. We have to make it radiation-hardened. We’re taking thin film technology used in TV and computer displays and applying it to satellites,” Janson said.
While Janson figures out how to make Brane Craft a reality, a dozen other NASA-funded innovative research projects are also in the works to expand space access, including four projects at the agency’s Jet Propulsion Laboratory in La Cañada Flintridge. Those include generating a long-lasting, nonsolar power source to probe deeper regions, like the interior of Venus; building a robotic explorer that can withstand conditions on icy moons and climb around cavernous craters; developing an electric glider that can investigate airless asteroids, comets and moons despite the ever-present photoelectric-charged dust surrounding them; and making an automaton rover that can withstand the searing heat, sulfuric acid clouds and intense surface pressures on Venus.

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