U.S. Prepares Flight Test of “Green” Satellite Propulsion

By Frank Morring, Jr.
Source: Aviation Week & Space Technology
July 22, 2013
Credit: Aerojet Rocketdyne

Satellite manufacturers may soon have a second source of green propellant for their spacecraft thrusters, if space testing of a U.S.-developed alternative to highly toxic hydrazine monopropellant goes well. Ball Aerospace and Aerojet Rocketdyne say their system, which uses a hydroxyl ammonium nitrate (HAN) mixture designated AF-M315E, with a special catalyst, has greater density than hydrazine for better storage efficiency, and produces better performance than both hydrazine and a different “green” spacecraft propellant already tested by Sweden. It has passed ground testing, paving the way for a satellite flight test as early as 2015.

“When we look at this compared to a hydrazine monopropellant type of system, where we have a single fluid driving the system on the spacecraft, we have a 50% increase in performance over the standard hydrazine,” says Christopher McLean of Ball, principal investigator on NASA's upcoming Green Propellant Infusion Mission (GPIM).

GPIM is designed to fly as a secondary payload on a SpaceX Falcon 9 Heavy, using a Ball Configurable Platform (BCP) 100 spacecraft bus and an Aerojet Rocketdyne thruster system that combines a 22N (5-lb.) thruster with four 1N units, all burning the green fuel to put the satellite testbed through the maneuvers an operational small satellite would see.

“These were selected because they have the largest market share, [so] we are developing the technologies that really meet the needs of the marketplace for this type of attitude control on a spacecraft,” McLean says.

Ecological Advanced Propulsion Systems (Ecaps), a unit of the Swedish Space Corp., has tested a different green propellant—based on ammonium dinitramide—in space. The fuel was used in tandem with a hydrazine system on the Prisma mission's Mango satellite to maneuver in formation with a smaller spacecraft.

Despite the completion of space qualification, sales of the Ecaps system have been slow to take off. Roger M. Myers of Aerojet Rocketdyne's Redmond, Wash., facility says the performance of the U.S. system in the ground test is better than the Swedish approach, and suggests there may be safety issues with the by-products of its evaporation.

Ultimately, Aerojet Rocketdyne hopes to “infuse” its new green technology into applications other than small satellites, including tactical missiles and large geostationary satellites, Myers says. As this photo of an Aerojet Rocketdyne technician with a beaker of AF-M315E shows, the green propellant requires none of the special handling or equipment mandatory for hydrazine.

“We can move, we think, to a shirtsleeve environment with this new fuel,” says Michael Gazarik, associate administrator for NASA's Space Technology Mission Directorate, which is funding the GPIM mission. “That means less ground-processing time [and] less ground-processing cost in order to load the spacecraft with the fuel.”

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