GPIM

GPIM [NASA]

Through the GPIM (Green Propellant Infusion Mission) project, NASA is developing a “green” alternative to conventional chemical propulsion systems for next-generation launch vehicles and spacecraft.

The new green propellant will be an enabling technology for commercial spaceports operating across the U.S. With the green propellant, launch vehicle and spacecraft fuel loading will be safer, greener, faster and much less costly. The “shirt sleeve” operational environment GPIM offers will change ground processing time from weeks to days. Building and operating satellites will become easier and simplified. NASA and Ball Aerospace & Technologies Corp. of Boulder, Colo., are collaborating on the Green Propellant Infusion Mission, which seeks to improve overall propellant efficiency while reducing the toxic handling concerns associated with the highly toxic fuel, hydrazine. The space technology infusion mission also strives to optimize performance in new hardware, system and power solutions while ensuring the best value for investment and the safest space missions possible.

The GPIM project will demonstrate the practical capabilities of a Hydroxyl Ammonium Nitrate fuel/oxidizer blend, known as “AF-M315E.” This innovative, low-toxicity propellant, developed by the U.S. Air Force Research Laboratory at Edwards Air Force Base, Calif., is a high-performance, green alternative to hydrazine. NASA and its partners always strive to maintain the strictest safety standards for storage, transport and use of rocket propellants. While all rocket fuels can be dangerous to handle without the proper safety precautions, AF-M315E has significantly reduced toxicity levels compared to hydrazine, making it easier and safer to store and handle. It also requires fewer handling restrictions and potentially shorter launch processing times, resulting in lowered costs.

AF-M315E also is expected to improve overall vehicle performance. It boasts a higher density than hydrazine, meaning more of it can be stored in containers of the same volume. In addition, it delivers a higher specific impulse, or thrust delivered per given quantity of fuel, and has a lower freezing point, requiring less spacecraft power to maintain its temperature. The GPIM payload will fly to space aboard a Ball BCP-100 compact small satellite. During the test flight, researchers will conduct orbital maneuvers to demonstrate the performance of the propellant during attitude control shifts, changes in orbital inclination and orbit lowering.

Once proven in flight, the project will present AF-M315E -- and compatible tanks, valves and thrusters -- to NASA and the commercial spaceflight industry as a viable, effective solution for future green propellant-based mission applications. The project is spearheaded by Ball Aerospace, home to the program’s principal investigator, and includes co-investigators at Aerojet Corp. in Redmond, Wash.; NASA’s Glenn Research Center in Cleveland; and the Air Force Research Laboratory at Edwards Air Force Base. Additional support is provided by the U.S. Air Force Space and Missile Systems Center at Kirtland Air Force Base, N.M.

The GPIM, managed by NASA’s Marshall Space Flight Center in Huntsville, Ala., is part of NASA’s Technology Demonstration Mission Program within the Space Technology Mission Directorate. NASA’s Space Technology Mission Directorate is innovating, developing, testing and flying hardware for use in NASA’s future missions.

The mission will evaluate two thrusters — a 1 Newton and a 22 Newton type. During GPIM’s planned 81-day flight, the thrusters will be fired to simulate a spacecraft’s typical modes of operation in orbit and during re-entry into the atmosphere.

Additionaly a set of experimental Defense Department scientific payloads are flown on GPIM under a $3.4 million payload integration contract. The DoD Space Experiments Review Board selected the Integrated Miniaturized Electrostatic Analyzer Reflight (iMESA-R), Small Wind and Temperature Spectrometer (SWATS) and Space Object Self-tracker (SOS) payloads to be part of the GPIM technology demonstration mission.

The demonstration mission will last approximately two months. Planned on-obit maneuvers include attitude control demonstrations; spacecraft pointing and hold; thruster performance characterization and mapping; inclination change; and orbit lowering. The Green Propellant Infusion Mission was launched aboard a SpaceX Falcon-Heavy (Block 5) rocket in June 2019 on the STP-2 demonstration mission.

GPIM was initially in a 720 km orbit, which it lowered using experimental thrusters. It was decommissioned around 12 September 2020 in a 184 × 638 km orbit and reentered on 14 October 2020.