The rocket that eats itself

When Apollo 11 lifted off from the Kennedy Space Centre 50 years ago to deliver the first humans on the Moon, almost 95% of the weight of the 2.8 million kg Saturn V rocket was made up of propellant and associated tanks, pumps, valves, piping and bodywork.

Improving the payload ratio for scaled-down rockets has since been a challenge for designers but a team, led by Dr Patrick Harkness from Glasgow and Professor Vitaly Yemets of Oles Honchar Dnipro National University in Ukraine, is working on a novel solution – a rocket that “eats” itself.

“Launch vehicles tend to be large because you need a huge amount of propellant to reach space,” says Patrick. “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.”

It takes great ingenuity to work around the laws of physics but the research team believe their “autophage” rocket can overcome these design limitations. “A rocket powered by an autophage engine would be different,” explains Patrick. “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. The rocket structure would be consumed as fuel so we wouldn’t face the same problems of excessive structural mass. And we could match the size of the launch vehicles to individual small satellites, and offer more rapid, affordable and targeted access to space. It would also minimise space debris.”