US space agency announces validation of much less toxic spacecraft propellant

4th September 2020

By: Rebecca Campbell

Creamer Media Senior Deputy Editor

     

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The US National Aeronautics and Space Agency (Nasa) has reported that, following just under 13 months of operational testing and evaluation in orbit, it had validated a new type of propellant for spacecraft. This new propellant is much less toxic than the standard current propellant, hydrazine. Like hydrazine, the new propellant is a monopropellant – that is, it can burn on its own with no need for a separate oxidiser.

Originally designated AF-M315E, the new propellant was developed by the US Air Force Research Laboratory. Nasa now calls it Ascent, which is an acronym for Advanced Spacecraft Energetic Non-Toxic. It was tested in space by a purpose-built small spacecraft, called the Green Propellant Infusion Mission (GPIM).

“This is the first time in 50 years [that] Nasa tested a new, high-performing monopropellant in space,” highlighted Nasa Marshall Space Flight Centre GPIM mission manager Tim Smith. “It has the potential to supplement or even replace hydrazine, which spacecraft have used since the 1960s.”

Ascent is a hydroxyl ammonium nitrate fuel/oxidiser blend. Whereas the handling of hydrazine requires personnel to wear protective suits and implement very strict loading procedures, with Ascent personnel only need to wear goggles, gloves and lab coats. It is because of this much-reduced toxicity that the new propellant is considered ‘green’. Consequently, it is easier and safer to store, with fewer handling restrictions. It could reduce the time required for launch processing and so promises to reduce costs.

Further, the new propellant has a higher density than hydrazine, meaning that a fuel tank of a given size could contain more Ascent than hydrazine. Moreover, it can deliver greater thrust per given amount of fuel than hydrazine. But it does not need more heater power to avoid freezing. Ascent thus either gives longer life and range than hydrazine (50% more range, in fact), or allows the same life and range but with a smaller fuel tank. The new propellant is especially attractive for small spacecraft but could also benefit larger spacecraft.

The GPIM spacecraft, which is the size of a mini refrigerator, was designed and built for Nasa by US company Ball Aerospace. The spacecraft’s five thrusters were designed and built by renowned enterprise Aerojet Rocketdyne. The other elements of its control system were co-designed by both companies. Also involved in the project were the Air Force Research Laboratory, the Air Force Space and Missile Systems Centre (which is focused on space systems, not missiles, and is being transferred to the new US Space Force) and, in addition to Marshall, three other Nasa field centres: the Glenn Research Centre, the Goddard Space Flight Centre, and the Kennedy Space Centre. The GPIM project was sponsored by the Nasa Space Technology Mission Directorate.

“We are excited to announce flight operations have been very smooth, with the new propulsion system operating as we anticipated,” reported Ball Aerospace GPIM principal investigator Christopher McLean. “We greatly appreciate the partnership and continuous support throughout this mission from Nasa’s Space Technology Mission Directorate, and programme management office at Marshall.”

With its mission now nearly completed, the GPIM is in a process of deorbiting. It has started making the necessary burns – there will be seven in all – that will reduce its orbit to some 180 km and empty its propellant tank. The spacecraft will then fall into the Earth’s atmosphere and burn up. This is expected to happen late this month.

The first operational mission to use Ascent will be Lunar Flashlight. This will be a tiny (briefcase-sized) spacecraft that will orbit the Moon and use near-infrared lasers and a spectrometer to map water ice deposits believed to lie in permanently shadowed areas at the bottom of craters in the lunar south pole region. It will be launched as a secondary payload on the Artemis I mission. Artemis I will be an uncrewed integrated demonstration flight test of Nasa’s new Orion crewed spacecraft and Space Launch System rocket.

Edited by Martin Zhuwakinyu
Creamer Media Senior Deputy Editor

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