Spotlight: High Performance Green Propulsion
SAN FRANCISCO — In the wake of a yearlong demonstration of a new rocket propellant that is significantly less toxic than conventional propellants, ECAPS and its U.S. partner, Moog Inc., are sharing the results of a Swedish space mission in an effort to spark NASA and U.S. Defense Department interest in conducting similar tests onboard U.S. satellites.
SSC, formerly known as the Swedish Space Corp., launched the two-satellite Prototype Research Instruments and Space Mission technology Advancement (PRISMA) mission in June 2010 to demonstrate new technologies to facilitate autonomous formation flying and rendezvous. The PRISMA mission, which received financial backing from the Swedish National Space Board as well as the French and German space agencies, also was designed to showcase technologies developed by Swedish companies including High Performance Green Propulsion (HPGP), developed by ECAPS, a wholly owned subsidiary of SSC.
The PRISMA mission completed its initial goals in June 2011 and has been extended to provide further data on mission technologies including HPGP, a propulsion system fueled by LMP-103S, a storable liquid monopropellant that blends ammonium dinitramide with water, ammonia and methanol. When used in a new temperature-resistant thrust chamber and catalyst combination, the propellant offers improved performance at a lower weight than hydrazine, said Paul King, engineering manager for spacecraft fluid controls at Moog’s Space and Defense Group in East Aurora, N.Y. Moog is working with ECAPS to offer the HPGP technology to U.S. customers.
The PRISMA mission features two satellites, the 150-kilogram Mango and the 40-kilogram Tango spacecraft. Mango carries both hydrazine and HPGP propulsion systems to offer a side-by-side comparison of the two propellants and thrusters, including their handling and performance.
High Performance Green Propulsion at a Glance
Developer: ECAPS, a wholly owned subsidiary of SSC
Demonstrated: June 2010 to June 2011 on the Swedish National Space Agency PRISMA mission’s Mango spacecraft
Components: LMP-103S propellant, high-temperature thrust chamber and high-temperature catalyst
Performance: Specific impulse 8 percent higher and density 24 percent greater than Mango’s hydrazine propulsion system
Testing conducted on the Mango satellite showed that HPGP’s specific impulse, a measure of rocket engine performance, was 8 percent greater than that of the hydrazine propulsion system, King said. Since LMP-103S is 24 percent denser than hydrazine, the new fuel also offers mission planners the ability to fly smaller propellant tanks or to extend a mission’s duration, he added.
Because HPGP is less toxic than hydrazine, the new propellant gives mission officials the added benefit of eliminating the need for Self Contained Atmospheric Protective Ensembles, or SCAPE suits, which protect workers from toxic fumes and corrosive chemicals. That feature may be particularly important when more than one spacecraft is scheduled to launch on a single rocket, as was the case in 2010 when PRISMA and the French Picard satellite were launched on the Russian Dnepr rocket from Russia’s Yasny spaceport.
Yasny range safety officials classified the LMP-103S propellant as nonhazardous, which allowed workers to continue integrating the French Picard satellite onto the Dnepr rocket while PRISMA’s propellant was loaded, King said. “In contrast, all activities were stopped and both the [French space agency] and SSC teams vacated the Yasny Launch Base for two days during the fueling of hydrazine,” according to an SSC paper presented in August at the American Institute of Aeronautics and Astronautics’ Joint Propulsion Conference in San Diego.
For the last 15 years, U.S. government and industry officials have been eager to identify spacecraft propellants that do not harm the environment or pose significant risks in the event of an accident. “A lot of people are trying to develop propellants with similar performance characteristics to existing rocket engines and fewer environmental impacts,” said Bryan Palaszewski, leader of advanced fuels at NASA’s Glenn Research Center in Cleveland. That work has been stymied somewhat by a lack of funding in recent years and by the fact that some green propellants have proved to be less energetic than their conventional counterparts, he added.
The fact that HPGP has demonstrated success during a one-year flight test is “an excellent achievement,” Palaszewski said.
Still, SSC and Moog face hurdles in persuading U.S. mission planners to adopt the new propulsion system due, in part, to the fact that the fuel currently costs more in the United States than hydrazine. That price difference is likely to decrease once the fuel is produced in larger batches, King said. In addition, “PRISMA demonstrated that HPGP reduces the number of people and the amount of time required for fueling,” King said.
Although HPGP could one day be used to propel large satellites in orbit and to maintain attitude control for rocket engine upper stages, the technology currently available is designed for the small-satellite market. In addition to the one-newton thrusters flying on the PRISMA mission, ECAPS has developed five-newton and 22-newton thrusters. ECAPS is developing more powerful thrusters for large satellites and launch vehicle upper stages, according to the paper delivered at the Joint Propulsion Conference.
Founded in 1951 to supply aircraft and missile components, Moog has grown into a firm with more than 10,000 employees worldwide and 2010 revenue of more than $2.1 billion. The company specializes in supplying high-performance motion control technology for a variety of applications, including aircraft, medical equipment and industrial devices. In 2010, Moog’s Space and Defense Group reported revenue of $326 million. The company’s space business generated approximately $147 million, King said.