Intelligence

Ultra-Persistent Propulsion and Power System (UP3S)

TEAL RAIN looked at several different nuclear propulsion systems (RTG and "other") back in the early 1980s. But these efforts remain little more than rumors, as far as the open literature is concerned.

In 2012 Sandia National Laboratories and Northrop Grumman Corporation Integrated Systems, Unmanned Systems (NGIS UMS) collaborated to further ultra-persistence technologies for unmanned air vehicles (UAVs). The greatest shortfalls in UAV capabilities have been repeatedly identified as 1) insufficient flight persistence or “hang time”, 2) marginal electrical power for running higher power avionics and payload systems, and 3) inadequate communications bandwidth and reach. NGIS UMS requested support from Sandia to develop an ultra-persistent propulsion and power system (UP3S) for potential incorporation into next generation UAV systems. The team members tried to determine which energy storage and power generation concepts could most effectively push UAV propulsion and electrical power capabilities to increase UAV sortie duration from days to months while increasing available electrical power at least two-fold.

The effort contrasted and compared eight heat sources technologies, three power conversion, two dual cycle propulsion system configurations, and a single electrical power generation scheme. Overall performance, specific power parameters, technical complexities, security, safety, and other operational features were successfully investigated. Large and medium sized UAV systems were envisioned and operational flight profiles were developed for each concept. Heat source creation and support challenges for domestic and expeditionary operations were considered.

Sandia conducted computer-based engineering and literature-based process analyses to meet the technical and programmatic requirements. Sandia assisted NGIS UMS to baseline at least one future UAV configuration with new energy and power systems to meet emerging U.S. military operational needs. Sandia conducted analyses at component and system-levels that emerged during the project. No physical asset testing or demonstrations was performed during this effort. Sandia and NGIS UMS developed technology development requirements, projected costs, schedule, manpower, facilities, equipment, associated resources, key experiments, demonstrations, tests, and decisions, operational system modifications versus new system acquisition.

The effort concentrated on propulsion and power technologies that went well beyond existing hydrocarbon technologies. It contrasted and compared eight heat sources technologies, three power conversion, two dual cycle propulsion system configurations, and a single electrical power generation scheme. Overall performance, specific power parameters, technical complexities, security, safety, and other operational features were successfully investigated. Large and medium sized UAV systems were envisioned and operational flight profiles were developed for each concept.

An earlier Sandia study concluded that such a UAV could be tested within a decade. It will not be, because it is nuclear-powered, and politics make it impossible. But the technical and operational case is powerful. Sandia stated "None of the results are currently in use by DOE and it is doubtful that they will be used in the near-term or mid-term future. Currently, none of the results can be shared openly with the public due to national security constraints."

Sandia was heavily involved by 2001. A paper from the Center for Strategic and Budgetary Assessments noted that Sandia's Special Projects Department had proposed an “extremely long-endurance vehicle (ELEV)” or “air-breathing satellite.” The ELEV could fly at 70,000 ft. and stay on station for six months to a year with up to a 5,000-lb. payload.