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Propelling satellites towards a greener future

The onboard propulsion system is an essential element of most satellites, required for performing orbital insertion after launch and to perform station-keeping and collision avoidance throughout the satellite’s mission lifetime.
While there is a small but steady growth in the use of electrical propulsion and solar sails for relatively low-thrust and interplanetary applications, most Earth-orbiting satellites use chemical systems as their primary means of propulsion. Surrey’s low Earth orbit small satellites use butane or xenon propulsion systems because they are simple and provide safe propulsive capability at a low cost.  However, these fuels are not sufficiently energetic for larger satellites, such as Surrey’s three-ton GMP-T Geostationary spacecraft, or for missions requiring many maneuvers, without requiring impractical volumes of fuel. These types of missions require more efficient propellants with a higher specific impulse.

Hydrazine has been the dominant propellant for most space missions for the past four decades, due to its high specific impulse and successful track record. However, there are concerns about its risk to people and the planet. Hydrazine is highly toxic, meaning that ground handling, transport, and storage of the substance is complex and expensive.  In addition, environmental regulations will mean its use will become more difficult in the coming years.

These concerns, along with advances in technology, are stimulating the development of new affordable green propulsion systems. Surrey has been investigating a number of options for so-called “green propellants” that offer performance that is equivalent to, or even better than, that of hydrazine and reduce the risk of handling, storage, and disposal, thereby cutting the cost of manufacturing and preparing the propellant as well as reducing overall mission costs.

The success of the Swedish PRISMA technology demonstration mission was encouraging, during which, over the course of a year starting in Summer 2012 the two spacecraft (TANGO and MANGO) performed a series of formation flying and rendezvous experiments. One of the key technologies proven was a green ADN (ammonium dinitramide) propulsion system. Another promising technology we look forward to seeing in action is Aerojet’s HAN (hydroxylammonium nitrates) green propulsion system in the NASA sponsored Green Propellant Infusion Mission (GPIM) that is currently planned for a 2015 launch.

As well as helping active satellites maneuver and avoid collisions, the development of more efficient fuels could also help satellites avoid becoming part of one of space’s biggest problems: space junk. After retirement, having completed their mission, satellites with more efficient propulsion systems could use remaining propellant to maneuver themselves into graveyard orbits or towards Earth for eventual burn-up.

Forty years ago, every car was gasoline-fueled and electric vehicles were a pipe dream- now hybrid and electric vehicles are a rapidly developing technology. NASA is leading the way for the replacement of traditional hydrazine systems in future missions, and the next big hurdle is to demonstrate these new propellants in flight. As for Surrey, we’re sure the simplicity of green propulsion systems, allied with the safety, environmental, and cost benefits, will stimulate their use for future small satellite missions.


07 January 20131 Comments1 Comment

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Anders Classon
See an article from the AAAF-ESA-CNES Space Propulsion Conference

11:30 a.m.
Two years of in-space demonstration and qualification of an ADN-based propulsion system on Prisma
2/5/2013 9:10:36 PM