'Self-eating' rocket engine under development

Posted on 12 Jun 2018 and read 667 times
'Self-eating' rocket engine under developmentA ‘self-eating’ rocket engine that could place small satellites in orbit more easily and more affordably is under development at universities in Scotland and the Ukraine.

In a paper published in the Journal of Spacecraft and Rockets, engineers from the University of Glasgow (www.gla.ac.uk) and Oles Honchar Dnipro National University (www.dnu.dp.ua) discuss how they have built, fired and (for the first time) throttled up and down an ‘autophage’ engine that could change how small satellites are sent into space.

Most rockets use tanks to store their propellant as they climb, and the weight of the tanks is usually many times greater than the weight of the useful payload.

This reduces the efficiency of the launch vehicle and contributes to the problem of space debris.

However, a launch vehicle powered by an autophage engine would consume its own structure during the ascent, so the payload could be bigger and less debris would enter orbit.

The autophage engine consumes a propellant rod with solid fuel on the outside and oxidiser on the inside. The solid fuel is a strong plastic, such as polyethylene, so the rod is effectively a pipe full of powdered oxidiser.

By driving the rod into a hot engine, the fuel and oxidiser can be vaporised into gases that flow into the combustion chamber.

This produces thrust, as well as the heat required to vaporise the next section of the rod. By varying the speed at which the rod is driven into the engine, the researchers have shown that the engine can be throttled — a rare capability in a solid motor.

Currently, the team have sustained rocket operations for 60sec at a time in their laboratory tests.

Patrick Harkness, senior lecturer at the University of Glasgow’s School of Engineering, who leads Glasgow’s contribution to the work, said: “Over the last decade, Glasgow has become a centre of excellence for the UK space industry, particularly in small satellites known as CubeSats, which give researchers affordable access to space-based experiments.

“There’s also potential for the UK’s planned spaceport to be located in Scotland.

“However, launch vehicles tend to be large, because 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 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, with the rocket structure 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 we could offer more rapid — and more targeted — access to space.

“While we’re still at an early stage of development, we have an effective engine test-bed in the laboratory in Dnipro, and we are working with our colleagues there to improve it still further.

“The next step is to secure further funding to investigate how the engine could be incorporated into a launch vehicle.”

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