Toulouse-based startup Alpha Impulsion has completed a short test firing of an autophage rocket engine. The company plans to use the novel propulsion system to power its 25-metre Grenat rocket.
The Alpha Impulsion autophage engine features a solid fuel tube with a liquid oxidiser sealed in its core. Two pistons push the tube into the combustion chamber where a catalyst converts the oxidiser into hot gas. This gas then reacts with the solid fuel, generating thrust. Put simply, the engine consumes its own structure as it burns.
Autophage rocket engines differ from solid fuel motors in that combustion can be controlled, and no heavy casing is left behind as dead weight. They also stand apart from hybrid engines, as there is no need for complex plumbing, a fixed casing for the solid fuel, or a separate oxidiser tank, as the oxidiser is stored within the fuel structure itself.
Despite offering advantages over solid and hybrid propulsion systems, developing and operating an autophage engine presents several challenges. These include maintaining stable and efficient combustion while feeding both solid and liquid elements into the combustion chamber, sufficiently sealing the liquid oxidiser within the solid-fuel tube, and, in larger engines, integrating a piston system powerful enough to generate the force required to push the tube into the combustion chamber.
In late May, Alpha Impulsion conducted a six-day test campaign at Agen Airport in the south of France. On 27 May, the company carried out a 17-second static fire test of what it described as the “largest autophage rocket engine in the world.”
According to a press release published by the company following the test, all of its technical goals were achieved. These included stable ignition and controlled combustion, as well as confirmation that the structure remained intact under operational pressure. The test also validated the tightness of the engine’s dynamic seals and confirmed the correct functioning of the oxidiser filling procedure.
“We have demonstrated that it is possible to develop an alternative and innovative technology capable of significantly reducing the cost of space access,” said Marius Celette, CEO and cofounder of Alpha Impulsion. “This test sends a strong message: Europe can be a leading player in the race for space innovation.”
Alpha Impulsion initially plans to use its autophage engine technology in a satellite propulsion system called Opal. The company aims to complete an initial development test of the system in late 2025, followed by a qualification campaign in 2026. The technology will then be scaled up for use aboard the Grenat rocket, which is designed to deliver payloads of up to 1,000 kilograms to low Earth orbit. The inaugural flight of Grenat is expected to take place in 2028.
A lot of complexity for what benefit? Liquid is easier to fuel quickly and is better environmentally and better performance. Most of the cost of a rocket is the engines and less so the structure, reusability is what matters not combusting the plastic rocket structure and rebuilding it every flight.
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[…] named Alpha Impulsion, recently completed a short test-firing of an autophage rocket engine, European Spaceflight reports. These aren’t your normal rocket engines that burn conventional kerosene, methane, or […]