Green Fuel Thruster Passes Key Preflight Test

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A NASA-backed project to demonstrate a safer and more efficient propellant for in-space propulsion is on track for launch in 2015 following a key ground test proving a small rocket thruster could burn the green fuel for about as long as what would be needed for an operational mission. 

“We got the data we needed. We’re continuing to do a little more testing now, but we’re ready for our flight design,” said Roger Myers, executive director for advanced propulsion at Aerojet Rocketdyne, which is developing the technology for Ball Aerospace & Technologies Corp., NASA’s prime contractor for the Green Propellant Infusion Mission (GPIM).

GPIM is intended to demonstrate an alternative to highly toxic hydrazine that is safer to handle, less expensive and more efficient for use on satellites. Green propellants like AF-M315E have been around for decades but their higher operating temperatures complicate engine operations.

About two years ago, Aerojet developed a new catalyst that resolved the problem, leading NASA to commit about $42 million for the GPIM flight demonstration. 

“Up until that time we were talking about 10 seconds of firing timing before the engine would decay,” GPIM lead scientist Christopher McLean, with Ball Aerospace, told reporters July 9.

The team recently completed a thruster pulsing test culminating in 11 hours of continuous firing, paving the way for a critical design review before the end of the year.

The flight demonstration will showcase two thrusters — a 1 Newton and a 22 Newton type — that have the largest share of the market. They will be integrated into a Ball Aerospace satellite and launched as a secondary payload aboard a Space Exploration Technologies’ Falcon Heavy rocket flying the U.S. Air Force’s Space Test Program-2 mission. The Air Force Space and Missile Systems Center’s Space Development and Test Directorate told SpaceNews in June that the launch is scheduled for September 2015.

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. 

While NASA and the Air Force are interested in the green fuel technology for their own missions, the real target for GPIM is the commercial market. 

“In today’s world you can not — and do not — want to load a spacecraft with hydrazine and ship it. The dangers are just too great. You can do that now with this propellant. That really changes the game of how we do spacecraft processing and get it to the launch site,” said Michael Gazarik, NASA’s associate administrator for space technology. 

“If you get this stuff on your hands, you wash it off. It’s not going to kill you,” McLean added. “I wouldn’t want to drink it, however, the lethal dose on this is pretty good especially compared to the fuels we’ve been using.”

Tests show the green fuel AF-M315E boost performance by 50 percent over hydrazine and is less expensive, though much of the cost savings would stem from simpler ground processing, storage and handling.

AF-M315E was developed by the Air Force Research Laboratory, which is a partner in the project.