GAC: Safe and efficient de-orbit of space junk

[bystander]

Safe and efficient de-orbit of space junk without making the problem worse
Global Aerospace Corporation | via EurekAlert | 02 Aug 2010

Global Aerospace Corporation (GAC) announced that Dr. Kristin L. Gates will present a paper on de-orbiting space junk at the August 2 Artificial and Natural Space Debris session of the AIAA Astrodynamics Specialists Conference in Toronto, Ontario, Canada. Dr. Gates will describe GAC's Gossamer Orbit Lowering Device (GOLD) for safe and efficient removal from Low Earth Orbit (LEO) of dangerous space objects. The patented GOLD system concept uses a very large ultra thin balloon envelope to increase the aerodynamic drag by a factor of several hundred. This will cause the space junk to enter the earth's atmosphere quickly and burn up. It will reduce the natural orbit decay of some objects from centuries to months.

[Henning Makholm]

Dr. Gates will describe GAC's Gossamer Orbit Lowering Device (GOLD) for safe and efficient removal from Low Earth Orbit (LEO) of dangerous space objects. The patented GOLD system concept uses a very large ultra thin balloon envelope to increase the aerodynamic drag by a factor of several hundred.

But how do you get the balloon attached to a piece of LEO junk in the first place?

[Chris Peterson]

But how do you get the balloon attached to a piece of LEO junk in the first place?

In most cases, it would be part of the design from the beginning, so it would launch with the object. If you had some legacy object that needed to be deorbited, a separate launch and robotic attachment would be required. I assume this would normally be reserved only for particularly dangerous LEOs.

I wonder what impact this might have on ground based astronomy? A 100m balloon in LEO would probably be a very bright object.

[bystander]

There are three basic applications for GOLD. The first application is to attach GOLD to satellites and rocket stages that are planned for launch. GOLD is then inflated, de-orbiting the object at the end of its useful life. The second application is in an active debris removal program, which may be important if the orbital debris problem is ever to be reduced. Several GOLD devices could be carried to orbit by an orbital robot and placed on existing space junk like the defunct spacecraft that struck the Iridium satellite, permanently removing them from orbit and making the environment safer. GAC has found that that GOLD is very effective in the 750 to 900 km altitude, high inclination orbit regime, which is a highly used portion of space and where the Iridium satellite was located. In a third application, some large space objects require controlled, targeted de-orbit and reentry because too much material survives reentry and reaches the Earth's surface where it can jeopardize the safety of people or property. In this application, when GOLD has reduced the orbit to the point of imminent entry, the large envelope is allowed to deflate under natural conditions to reduce drag and defer reentry a few days. After making good orbit predictions and using careful timing, the envelope is fully inflated at the correct point in the orbit to achieve a substantial atmospheric drag sufficient for prompt and safe reentry into the ocean.

[Henning Makholm]

But how do you get the balloon attached to a piece of LEO junk in the first place?

In most cases, it would be part of the design from the beginning, so it would launch with the object.

I thought the majority of LEO junk was things that where not "designed" at all (in their present shapes), such as debris from satellites that collide with meteoroids or other existing junk.

Several GOLD devices could be carried to orbit by an orbital robot and placed on existing space junk

Here, "orbital robot" must mean a spacecraft considerably more agile than the average satellite. If you can afford to launch such a thing and have it match velocity with bits of random space cruft in sequence, wouldn't what do to with the junk after rendezvousing be a relatively minor problem? Just grab it with whatever manipulators your robot has, and throw it in an appropriate direction as reaction mass for your next maneuver, such that it ends up in a low-perigee orbit.

[Chris Peterson]

I thought the majority of LEO junk was things that where not "designed" at all (in their present shapes), such as debris from satellites that collide with meteoroids or other existing junk.

I don't think this system is intended to address that kind of debris, which tends to decay quite rapidly as it is. The system is for intact LEOs that exceed their operational life and need to be efficiently deorbited. This is why it could also make sense to robotically place the system on existing satellites. Big objects decay slowly, and are a hazard once their control systems fail. It is likely cheaper to send something up to remove them from orbit than to incur the costs associated with a later collision.

[bystander]

A Real Mess in Orbit: Space Junk to Hang Around Longer Than Expected
Space.com | 03 Aug 2010

Space junk continues to clutter the friendly cosmic skies, posing threats to satellites and spacecraft, with scientists working to identify which bits of orbital rubbish to pluck from the heavens first. But a new study suggests they're fighting an uphill battle.

New research on changes in the Earth's upper atmosphere suggests space debris could remain in orbit for longer than expected.

A science team at the U.K.'s University of Southampton has confirmed a long-term change in the Earth's upper atmosphere. This change, a contraction of the Earth's thermosphere, has been attributed to the buildup of greenhouse gases, such as carbon dioxide. The atmospheric compression is keeping satellites — and space refuse — in Earth orbit for added stints of time.

... prime target objects for active removal would be in altitudes of 900 kilometers [310 miles] — plus or minus 100 kilometers [62 miles] — and in inclination bands near 71, 82, and 99 degrees ...

... the most massive LEO objects are 19 Russian Zenith-2 second stages, each tipping the scales on Earth at 8.2 tons empty mass. All of these are in 71-degree orbits at altitudes of about 5320 miles (840 km) altitude ...

... highest mass concentration overall ... is in the vicinity of 560 miles (900 km) at 82 degrees inclination. Roughly 300 tons of space hardware is in an "altitude shell" spread out over some 31 miles (50 km) ...

[bystander]

New Satellite Launches to Track Space Junk
Universe Today | 27 Sept 2010

The U.S. Air Force successfully launched the Space Based Space Surveillance (SBSS) spacecraft, a first-of-its-kind satellite that can detect and track orbiting space objects from space. The new satellite was blasted into orbit by a Minotaur IV rocket at 9:41 p.m. PDT, September 25th, from Vandenberg Air Force Base in California.

“SBSS will greatly enhance our existing space situational awareness capability, a capability vital to protecting our space-based assets,” said Colonel Richard Boltz from Vandenberg.

There are about 500,000 known pieces of space junk – such as spent rocket boosters, failed satellites, and pieces of satellites – in Earth orbit. Of those, about 21,000 objects are larger than 10.1 cm (4 inches) in diameter. These are being tracked by the Department of Defense, as part of the Space Surveillance Network.

“This satellite is going to revolutionize the way we track objects in space by not being constrained by weather, the atmosphere or the time of day,” said Col. J.R. Jordan, vice-commander of the Space Superiority Systems Wing at the U.S. Air Force Space and Missile Systems Center, in a prelaunch briefing. “This capability will be essential to our space situational awareness architecture for the near future and beyond.”

The satellite will be fully operational and handed over to the Air Force Space Command in about 210 days. The SBSS will be able to detect, identify and tracking man-made space objects from deep space to low-earth orbit. The SBSS space vehicle uses a two-axis gimbal in order to observe in all directions. The spacecraft’s on-board mission data processor performs image processing to extract moving targets and reference star pixels to reduce the downlink data size.

[neufer]

“SBSS will greatly enhance our existing space salvage capability”