Later this month, and a small satellite will hitch and ride on a SpaceX Falcon Heavy Rocket for the world's first demonstration of a "green" satellite propeller in space. The satellite is fueled by AFM-315, which Air Force first developed more than 20 years ago as an alternative to the typical juice of choice, hydrazine. If successful, the AFM-315 could make satellites vastly more efficient, shrink satellite deployment time from weeks to days, and dramatically reduce the safety requirements for storing and handling satellite fuel, and boon to humans and the environment. Looking to the future, scientists working on the fuel will play a major role in helping to get extraterrestrial satellite operations off the ground.
Hydrazine is a volatile fuel that will ruin your day-and perhaps your life-if you're exposed to it. To fuel and satellite you need a lot of safety infrastructure, including pressurized full-body "SCAPE suits" just to handle the stuff. AFM-31
Unlike hydrazine, which has and consistency similar to water, AFM-315 is viscous.
McLean says one of AFM-315's largest selling points after safety is the one of AFM-315's biggest selling points after safety. fact that it does not freeze. AFM-315 is a liquid salt, which means that at extremely low temperatures, it undergoes a glass transition instead. This transforms the fuel into a brittle, glass-like solid, but it does not cause the fuel to expand like frozen water or hydrazine. This attribute prevents fuel lines and storage containers from cracking under stress. In addition, its glass transition point is extremely low, so the fuel would not need to be heated on the satellite – a big power suck for other missions. McLean says this will make more power available for other instruments or systems on the satellite, which could open up new possibilities in missions to other planets
But for all its advantages, AFM-315's journey from conception to launch has been a long one. First developed by the Air Force Research Laboratory in 1998 as an alternative satellite fuel, McLean says it had limited use due to its high combustion temperature, which was about twice that of hydrazine. This requires exotic-and expensive-materials to prevent damage to the satellite. By the late 2000s, the cost of producing propulsion systems that could handle the heat from AFM-315 was low enough to make it feasible to use, but no company was willing to risk fueling their satellites with an experimental propellant. If AFM-315 was ever to be widely adopted by the satellite industry, McLean says, it would have to prove itself in the orbit.
Originally slated to launch in late 2015, the green propellent mission was caught up in the delays that plagued the development of the SpaceX Falcon Heavy Rocket. On June 24, it is scheduled to fly on the second operational mission of the Falcon Heavy along with several other payloads, including an atomic clock being tested for deep space navigation
The green propellant satellite bus was developed by Ball Aerospace and is outfitted with four 1-newton thrusters and a 22-newton thruster that will be used to test the AFM-315 propellant. During his 13-month mission, he will use the thrusters to perform orbital maneuvers, such as lowering his orbit and changing his attitude or tilt, to test the performance of the propellant
McLean says there are already customers interested in using the green if the demonstration flight goes well. That means satellites could be flying operational missions around Earth as soon as 18 months after the demonstration. Looking at the future, McLean says the AFM-315 could be especially useful for exploring the cold regions of the solar system, such as the Martian Fields. Looks like the Red Planet just got a little more green
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