Science and Exploration

A Greener Alternative to Hydrazine

By Elizabeth Howell
April 19, 2012
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A Greener Alternative to Hydrazine
Tango after launch.
Swedish Space Corporation

Hydrazine, a mainstay fuel of the space program since the early days, now has a competitor that is easier to store and – when taking all costs into account – is the same price.
A subsidiary of the Swedish Space Corp., called ECAPS, has been developing a High Performance Green Propulsion (HPGP) fuel that is based on ammonium dinitrimide.

Its exhaust gases are benign: water, nitrogen, hydrogen, carbon dioxide. It’s so safe to store that it has a rating in both the European Union and the United States to carry in the cargo area of commercial aircraft, greatly lessening the cost of transportation.

HPGP’s advantage over its competitors is its flight experience, said ECAPS president Mathias Persson in an exclusive interview with SpaceRef at the National Space Symposium in Colorado Springs. The fuel is flying aboard an orbiting demonstration satellite set, called Prisma, that is comparing HPGP and hydrazine performance in orbit. It’s been in orbit nearly two years.

“We’re seeing eight per cent higher (specific impulse) on the green propulsion. That’s really a benefit,” he said.

HPGP can replace hydrazine in most applications, reducing the need for special handling equipment, power outlets, clean rooms and other items associated with its more toxic predecessor.

But for applications such as a landing on Mars, it’s probably best to keep hydrazine instead of HPGP, Mr. Persson said.

“That could be (the case) if you’re looking for water somewhere and you’re looking to land. The exhaust is 50% water vapour and hydrogen. In that case, I would prefer hydrazine.”

ECAPS’ 1 N engine (HPGP) which is tested on Prisma

SSC believes so strongly in the technology that it invests a lot of its own money into ECAPS. Even though the smaller company is not profitable yet, an SSC representative told SpaceRef that they see infinite potential for the technology – especially given the EU is working to find benign alternatives to hydrazine.

“We really believe in this, and this is really changing the space market,” said Anna Rathsman, senior vice-president of SSC’s corporate communications and business development.

But the company still faces a battle for legitimacy in a market that has been used to hydrazine for the past several decades. It will take a massive marketing effort on the part of SSC to make the technology used more often in space missions, but its space testing advantage likely gives them an edge over the competition.

Their key now is to prove the technology works at higher thrust levels. A 1 Newton version of the thruster has been tested in space, but versions with 5, 22, 50 and 250 Newtons are still under development.

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