Low Earth orbit is the region of space within 2,000 kilometers of the Earth's surface. It is the most concentrated area for orbital debris.
Low Earth orbit is the region of space within 2,000 kilometers of the Earth's surface. It is the most concentrated area for orbital debris.

Invention: Physicist and Engineers at the U.S. Naval Research Laboratory Plasma Physics Division and Naval Center for Space Technology have researched a technique to 'sweep' Low Earth Orbit (LEO) debris from space using an Active Debris Removal (ADR) system of deployed micron-scale dust.

The essential idea is that dust, if artificially deployed on orbit in opposite direction to the debris trajectory, can induce an enhanced drag on the debris. The novelty is that by choosing the dust characteristics, for instance, mass density, size, etc., it is possible to synchronize the rate of dust and debris descent. This offers the possibility to clear a very large volume of small debris by deploying a modest amount of dust in a narrow layer and "sweeping" of the debris volume by the dust layer.

It is well known that the natural drag due to neutral atmosphere decays satellite orbits. However, the magnitude of the drag is too small on the orbital debris above 600-700 km but significant on the micron-scale dust grains. The method would use the natural atmospheric drag to decay the deployed dust orbits and simultaneously use the descending dust layer to induce enhanced drag on the orbital debris. Like the natural dust, most of the deployed dust as well as the small orbital debris will incinerate while reentering the Earth's dense atmosphere. So the environmental effect of releasing the dust is expected to be benign. Research indicates that the dust based ADR system can be a cost effective means to clear deadly untrackable small orbital debris with manageable risks to existing space assets and can be developed with off-the-shelf type technologies in the near term. This same concept can be utilized for removing larger debris with a suborbital dust deployment. Preliminary analysis suggests tungsten be a prime candidate for the dust because of its high density, relative abundance, availability in powder form and modest cost, all contributing factors to the efficiency and economy of the system.

Background: In LEO, below 2,000 kilometers, orbital debris can travel in excess of 8 kilometers per second, or greater than 17,000 miles per hour, wreaking havoc on invaluable space assets like the International Space Station (ISS), Hubble Space Telescope and numerous weather satellites, damaging solar arrays, instrument panels and solar shields.

The National Aeronautical and Space Administration (NASA) Orbital Debris Program Office estimates there are more than 21,000 orbital debris objects larger than 10 centimeters (roughly 4 inches) in diameter in LEO, and approximately 500,000 object particles between 1 and 10 centimeters, with the number of debris particles smaller than 1 centimeter in excess of 100 million. In 2011, the National Research Council (NRC) conducted an exhaustive study to assess NASA's meteoroid and orbital debris program. The report concludes that LEO orbital debris is at the 'tipping point' - the threshold for collisional cascade, or Kessler effect, in which the number of objects in LEO is dense enough that collisions between objects could cause a cascade. This exponentially increases the likelihood of further collisions and makes it increasingly risky to maintain space assets without clearing the debris population.

Orbital debris mitigation
Schematic illustration of the suborbital dust deployment: A ballistic rocket is used to release dust in the path of debris fragments. The debris population is engulfed by the dust cloud, experiencing enhanced drag and results in the loss of debris altitude. The debris population descends to an altitude of X0 kilometers, within one debris revolution time, below which Earth's natural drag is sufficient to force reentry within a desired time. The dust cloud also descends under gravity and re-enters the atmosphere.

Technology Status: The technology is Technology Readiness Level 2, technology concept and/or characteristic proof of concept.

Licensing or Collaboration Opportunity: Collaborative research and development is available under a Cooperative Research and Development Agreement (CRADA).

Lead Inventor: Gurudas Ganguli

Patents:
US Patent No. 8,469,374 entitled “Technique for de-orbiting small debris from the near-earth space environment” Issued on June 25, 2013 to Gurudas Ganguli, Scott S Chappie, Leonid I Roudakov, Christopher E Crabtree

US Patent No. 8,579,235 entitled “Technique for de-orbiting small debris from the near-earth space environment” Issued on Nov 12, 2013 to Gurudas Ganguli, Scott S Chappie, Leonid I Roudakov, Christopher E Crabtree

Navy Case Number: 100,214

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