Wonderful Engineering

The Autophage Rocket Engine Eats Itself To Save Money And The Space

A team of engineers have built a unique ‘autophage’ rocket which eats its own structure from bottom up during the flight. The team believes that this invention can create cheaper, more efficient and less wasteful small satellite launches. Instead of using a heavy tank to store the fuel, the autophage rocket structure is a cylindrical propellant rod which consists of solid, strong plastic fuel on the outside with a core of powdered oxidizer.

When the rod is pushed into the hot engine, it is evaporated. It produces thrust using exhaust gases which produce more heat to burn the next part of the propellant rod. This way, the rocket gets shorter while eating itself from the bottom up. Many solid fuel motors do not have the capability of being throttled. With the autophage engine, this problem is nullified. You can easily increase the speed at which you are feeding the propellant rod if you want more thrust to the rocket.

Dr Patrick Harkness, senior lecturer at the University of Glasgow said, “Launch vehicles tend to be large. You need a large amount of propellant to reach space. If you try to scale down, the volume of propellant falls more quickly than the mass of the structure, so there is a limit to how small you can go. You will be left with a vehicle that is smaller but, proportionately, too heavy to reach an orbital speed. A rocket powered by an autophage engine would be different. The propellant rod itself would make up the body of the rocket, and as the vehicle climbed the engine would work its way up, consuming the body from base to tip. That would mean that the rocket structure would actually be consumed as fuel, so we wouldn’t face the same problems of excessive structural mass. We could size the launch vehicles to match our small satellites, and offer more rapid and more targeted access to space.”

Excluding a large fuel tank from the design will help to remove one of the heaviest components from the rocket engine. This will make the launch much easier and smooth. Since the entire fuel unit is consumed in the launch, it will also help to put less debris in the outer space along with the additional payload. A small-scale test version for 60 seconds has successfully been tested by the team so far. The team is expecting to improve the working of the design.