This is actually worth taking a lot further. We have a huge debris problem up there and with an obvious modification we could bring a lot of that junk down. It is reasonable that the majority of space junk follows fairly common paths and could be fairly easily intercepted by equipment traveling along the same path and direction.
It may work to produce very large parachute like fabrics with a large mesh size that are able to arrest objects traveling largely at the same relative speed. It will not be done to large objects that will need to be avoided and handled separately. For small random debris such a device can work. The parachute itself can be deployed through inflatable tubes that impart some structural rigidity.
The key to design is to attach a balloon that simply produces more drag than the parachute itself. This sets it up properly while it continuously captures space debris as its orbit also decays. Drag can be increased to offset increasing loads by the simple expedient of increasing balloon size.
Giant balloons could clear out space junk
Updated 19:19 04 August 2010 by David Shiga
Helium balloons are known for pulling things up, but they could be a great way to drag defunct satellites down to Earth, a team of engineers says.
Dead satellites pose a hazard to other orbiting spacecraft. In 2009, one of them wandered into the path of a still-functioning satellite, destroying both craft and spawning thousands of pieces of new space junk.
One way to prevent such collisions is to have satellites fire their own engines at the end of their useful lives in order to push themselves into Earth's atmosphere, where they would be incinerated. But this requires launching them with extra fuel, adding mass that drives up the cost of launch.
Balloons would be a cheaper way to solve the problem, says a team of engineers. Kristin Gates of the Global Aerospace Corporation in Altadena, California, presented the idea on Tuesday at the Astrodynamics Specialist conference in Toronto , Canada
Speedy death
Any new satellite could be launched with a folded-up balloon stowed on board. Once the satellite reached the end of its useful life, the balloon would fill with helium or another gas, creating extra drag as the balloon collided with Earth's tenuous outer atmosphere.
A balloon 37 metres across would take just one year to drag a 1200-kilogram satellite from an initial orbit of 830 kilometres to an altitude low enough to burn up in the atmosphere, the Global Aerospace team calculates. Without the balloon, this would take centuries.
The balloon and the equipment needed to inflate it would add just 36 kilograms of mass to the satellite, less than the amount of fuel that would be needed to de-orbit it without the balloon, the team says.
Low-hanging fruit
Brian Weeden of the Secure World Foundation in Washington DC, which promotes the peaceful use of space, says the concept sounds feasible. But he says it would not work for all satellites – geostationary satellites orbit 36,000 km above Earth, where there is too little gas to provide the necessary drag.
Global Aerospace president Kerry Nock admits that the balloon concept would only work below 1500 km or so but notes that this includes a particularly congested region between 750 and 900 km, where the 2009 satellite collision occurred.
A downside of the approach is that the balloon would make the satellite a larger target while inflated, temporarily increasing the risk of a collision with another satellite. But Weeden says the increase would be "pretty minimal".
"The slightly increased risk of making it larger for a short period of time is more than offset by eliminating the risk of that object staying on orbit for decades or longer," he says.
The space debris problem will get worse unless action is taken to combat it, Nock says. "It's a growing problem and it's not going away."
The company is now looking for funding to do a flight demonstration of their concept, called GOLD (Gossamer Orbit Lowering Device).
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