Mjölnir engine proves itself in successful hot fire tests

Backed by NASA and defence grants, the compact engine completed tests that will enable New Frontier Aerospace’s VTOL UAS and orbital spacecraft.

New Frontier Aerospace (NFA) has completed a series of successful hot fire tests for its Mjölnir engine, described as the most advanced compact pump-fed rocket engine in the world. The full-flow staged combustion cycle design aims to maximise efficiency for reusable rockets, hypersonic vehicles and orbital transfer spacecraft.

Mjölnir uses liquid natural gas and can be net carbon negative when fuel is sourced from bio-waste. The engine will power two upcoming NFA platforms: the Pathfinder hypersonic VTOL UAS, which is expected to hover in 2026, and the Bifröst orbital transfer vehicle, which is scheduled to fly by 2027.

Mjölnir has also become available as a standalone propulsion option for third-party aerospace programmes.

“We are proud of the amazing team that built this program and thrilled with the engine's performance during this series of hot fire tests,” said Bill Bruner, CEO of New Frontier Aerospace. “Mjölnir's compact design, unmatched efficiency, and clean fuel make it a game-changer for hypersonic flight and space propulsion. It is poised to power our ambitious roadmap and open new possibilities for our customers.”

Development was supported by seed funding from National Security Innovation Capital and the Defence Innovation Unit. The latest testing phase was backed by NASA.

The sustained performance across hot fire tests represents a major advance for NFA as it continues its push toward environmentally responsible propulsion technologies.