final propulsive maneuver. Although direct deorbiting into the Earth's atmosphere eliminates debris from orbit rapidly, it requires more fuel than maneuvering to reduce orbital lifetime. In orbital regions that are too high above the atmosphere for economical deorbiting or orbital lifetime reduction maneuvers, spacecraft or rocket bodies can be moved to "disposal orbits" a safe distance away from valuable orbital regions at the end of their functional lifetimes. Disposal orbits are not a viable alternative within LEO because perturbing forces make all such orbits unstable; objects in LEO disposal orbits will eventually cross heavily trafficked orbital regions. Neither the committee nor the wider debris community can agree on whether disposal orbits should be used by all spacecraft and rocket bodies in GEO.

As with other environmental issues, decisions on the adoption and implementation of particular debris reduction methods must balance political and economic as well as technical factors and thus must be made in forums that are capable of balancing all of these factors. Since implementation of debris mitigation measures can impose additional costs on space operations, international rules are needed to ensure that those engaging in debris mitigation activities are not penalized. For this reason, the committee recommends that the spacefaring nations develop and implement debris reduction methods on a multilateral basis.

Given the long development cycle for new space vehicles with debris-minimizing features, the technical development, cost—benefit assessments, and international discussions required to implement countermeasures should start as soon as possible. Although these multilateral discussions cannot be conducted on a purely technical basis, it is crucial that they be based on sound technical advice. The committee's consensus technical assessment of the actions that should be taken to reduce future growth in the debris hazard, based on our current understanding of the debris environment and of the costs and benefits of various mitigation measures, is represented in the following recommendations:

  • Space system developers should adopt design requirements to dissipate on-board energy sources to ensure that spacecraft or rocket bodies do not explode after their functional lifetimes.

  • The release of mission-related objects during spacecraft deployment and operations should be avoided whenever possible.

  • Spacecraft and rocket bodies should be designed to minimize the unintentional release of surface materials, including paint and other thermal control materials, both during and after their functional lifetimes.

  • Intentional breakups in orbit (especially those expected to produce a large amount of debris) should be avoided if at all possible. No intentional breakups expected to produce numerous debris with orbital lifetimes longer than a few years should be conducted in Earth orbit.  



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