![]() SOURCE: James (2005).Ī second approach would be to use a moderate-thrust (100-200 lb), modest-performance chemical propulsion thruster at 350-360 sec I sp, such as liquid oxygen (LOx)/monopropellant hydrazine using a cryocooler to keep the LOx from boiling away. However, large assets accomplish such maneuvers with velocity changes measured in feet per second per hour and would take weeks to travel, say, 10,000 mi.įIGURE 5-1 Responsive space utility. For large strategic and capital assets, one could utilize an onboard, low-thrust, highly fuel-efficient system such as a Hall-effect thruster that would fire continuously to complete a large station change or a repositioning maneuver at high specific impulse ( I sp) (2,000 to 3,000 sec). There are a number of approaches to meeting these various military needs. The elements of the ORS architecture are depicted in a very general form in Figure 5-1.Īs indicated in Figure 5-1, the Air Force will continue to identify needs for responsive and rapid introduction or repositioning of military satellites or space vehicles of various types for surveillance, defensive or offensive deployment, access to local theater military operations, and, secondarily, for situational awareness. The systems architecture for seamless air-space operations has been termed operationally responsive spacelift (ORS). Some of these technologies, such as various types of electrically powered thrusters or high-energy monopropellants, have the potential to be transformational for in-space military systems capabilities.Īir Force and DoD long-range plans have identified some needs and are still working out other needs for many types of operational maneuvers in space and near space. However, in contrast to rocket propulsion for access to space and near space, the range of potential improvements for in-space propulsion thruster performance and for electric power generation and energy storage is still very large. For the kilogram-weight-class satellites with unique mission capabilities that are being developed, micropropulsion systems may be all that is required for maneuvers other than rapid inclination change. It should be noted here that the state of the art has been undergoing major changes over the past 15 years and therefore represents a very advanced capability in many areas. These propulsion needs are being satisfied currently by state-of-the-art chemical propulsion, and, increasingly, by electric propulsion subsystems. strategic satellites and technology platforms require propulsion subsystems operating in space to provide the impulse necessary to adjust velocity, change orbit altitude, and provide attitude control, station keeping, and end-of-life deorbit. Technology development work in space andĪll DoD and other U.S. Strategic assets for communication, early warning, Earth observation, navigation, reconnaissance, surveillance, and weather Current and future strategic and warfighter needs for satellites and in-space vehicles exist in the following areas:
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