Reconsidering the Rules for Space Security

Features of the Environment

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Nancy W. Gallagher and John David Steinbruner
Reconsidering the Rules of Space

The physical requirements of initial launch and subsequent maneuver impose significant burdens on all space activities. Any object resting on the Earth’s surface and therefore moving with the Earth’s own rotational and orbital velocity must acquire nearly 8 km/sec additional velocity to achieve an orbit around the Earth. The cost of imparting that additional velocity has remained constant for several decades despite continuous efforts to reduce it. Once placed in a stable orbit, all objects of whatever mass can be retained in that orbit indefinitely with low-energy housekeeping maneuvers, but a large amount of energy proportionate to the object’s mass is required to change the object’s orbit. The heavier the object, the more expensive it is to launch in the first place and to maneuver out of its initial orbit. Some maneuvers, moreover, are more difficult than others. A proportionate change in altitude—distance to the Earth’s surface—requires less energy to accomplish for a given mass than a comparably proportionate change in inclination—the angle at which an orbit intersects the Earth’s equator. Since the energy required for maneuver must be provided by the object itself and adds to its initial launch weight, satellites have been designed to accomplish their purposes with as little weight and orbital maneuver as possible.

In practical terms all this means that satellite movements are observable and predictable, that they are limited in their ability to evade objects in intersecting orbits, and that they cannot be fortified against the high velocity collisions that could result. This in turn means that satellites are inherently vulnerable to destruction. Billion dollar assets with advanced equipment can be disabled by much less sophisticated means—a fact that provides leverage to disadvantaged antagonists. Disruption is much easier to accomplish in space than constructive use.

Because mass matters disproportionately in these considerations, inherent vulnerability can be somewhat reduced by decreasing the size of satellites. Smaller objects are easier to launch and maneuver and are more difficult to identify and track. That option competes, however, with the aspiration to develop more advanced capabilities. Although the public record does not reveal exactly how that interaction is working out in technical terms, a reasonable presumption is that the balance of advantage between sophisticated use and crude disruption is not likely to be reversed anytime soon. Achieving dominance in space at feasible cost is doubtful for basic physical reasons. Correspondingly likely is that sophisticated utilization will depend on broad acceptance and therefore on equitable rules.