After over 13 months of operation, NASA is satisfied with the results from its Green Propellant Infusion Mission (GPIM), proving a "greener" fuel could be a practical alternative for future missions. The program set out to demonstrate the properties of a new type of rocket fuel significantly less toxic than hydrazine, which has been used for decades to power the maneuvering thrusters of spacecraft like the Space Shuttle and Martian landers.

The new fuel is known as Advanced Spacecraft Energetic Non-Toxic (ASCENT). It is a monopropellant, which means it doesn’t need an oxidizer to burn, it can burn by itself, making it useful in space where there’s no oxygen. It also performs more efficiently than hydrazine, meaning that with less fuel, spacecraft can go further.

“This is the first time in 50 years NASA tested a new, high-performing monopropellant in space,” Tim Smith, GPIM mission manager at NASA’s Marshall Space Flight Center, said in a statement. “It has the potential to supplement or even replace hydrazine, which spacecraft have used since the 1960s."

Hydrazine is extremely toxic so workers have to don protective suits to deal with it, and the loading procedures are extremely rigorous. A hydrazine spill could be extremely harmful. ASCENT on the other hand is safer to store and use; whoever handles it just needs gloves, a lab coat, and goggles.  

Launched in June 2019, GPIM was a test mission to test out ASCENT's propellant and propulsion abilities to alter and stabilize its orbit and other maneuvers. The mission has shown that ASCENT has 50 percent more mileage than an equivalent volume of hydrazine, making it a viable, effective alternative for the spaceflight industry.

GPIM has now begun its curtain call. The spacecraft has begun its deorbiting burns, which will take it down to 180 kilometers (110 miles) of altitude. With its propellant depleted, the small craft will burn up in the atmosphere later this month.

NASA is already planning it's next test for this green new fuel. ASCENT will be employed in the Lunar Flashlight mission expected to launch on Artemis I, the first integrated flight test of NASA's Orion spacecraft and Space Launch System (SLS) rocket, next year.