The UK space industry’s specialisation in small ‘cube-sat’ satellites shot into orbit for scientific or educational purposes. As we launch more and more of these cube-sats into the Earth’s immediate orbit, two major problems are rearing their heads. The first is that it’s an expensive undertaking due to the latest technology in the world of the rockets needed to take them there being relatively inefficient. Most of what is launched is the rocket itself, whose only function is transport. The second is that when the rockets are detached from their payload, they add to the growing quantity of man-made ‘space debris’ cluttering up the Earth’s orbit.
The expense of launching cube-sats with current rocket technology means that several are usually loaded onto one rocket launch. While this collective economy helps make getting them into orbit financially feasible for their owners, they also have to compromise on the positioning of the satellites. The group are dropped off together in one locale selected as the optimal average. The large rockets then become space junk, which is becoming an increasing collision hazard for satellites as it expands in volume.
A team of scientists from Scotland’s Glasgow University, working in partnership with peers from Ukraine’s Oles Honchar Dnipro National University, believe they have the answer. They are working on a rocket that ‘eats itself’ from the inside. By the time it gets to its destination, the new rocket technology is reduced to its payload and an empty engine. With no rocket body remaining, the volume of debris that results from the delivery is greatly reduced. The gradually lightening structure as the rocket body self-cannibalises also means less fuel is required for the journey, making it cheaper.
The approach works through a clever combination of the rocket’s body and fuel supply. The main rod of the rocket consists of an outer layer of solid fuel surrounding an oxidiser. As the rocket travels into space, the rod is driven into the rocket’s engine one section at a time. The solid fuel casing’s combustion is achieved through the oxidiser ensuring enough oxygen.
The team believe rockets using their technology will eventually be scalable enough to cheaply send individual cube-sats into precise orbits. There is already sufficient successful test-evidence, recently published in the Journal of Spacecraft and Rockets, to demonstrate that the engine works. The team is now applying for European funding to continue research and development on a vehicle that the engine can be integrated into.