Science-Fiction Style Space-Planes Closer Than Ever


The British aerospace company Reaction Engines Ltd. (REL), the creators of the revolutionary SABRE rocket engine, has received 10 million euros from the European Space Agency (ESA) to create a ground-based demonstrator of the SABRE engine by 2020.

The signing forms the final piece of a £60m investment of grant funding from the British Government which, alongside a £20m purchase of share capital from BAE Systems, will ensure the development of the innovative rocket engine continues.

The SABRE (Synergistic Air-Breathing Rocket Engine) rocket engine is a landmark development in rocketry, allowing a rocket to burn using atmospheric air or conventional liquid oxygen. This could allow a SABRE-powered aircraft, such as the firm’s own Skylon concept (pictured above), to operate at speeds of up to five times the speed of sound or to fly directly into Earth orbit. Previous attempts at a single-stage to orbit aircraft have been largely unsuccessful due to the weight of carrying liquid oxygen in tanks aboard the aircraft – REL claims that a SABRE-powered craft could save 150 tonnes of weight through not carrying as much on-board liquid oxygen. It would take off like a jet aeroplane before switching to rocket power and climbing into orbit.

The SABRE Engine, with the pre-cooler shown in blue. Credit: Reaction Engines Ltd.
The SABRE Engine, with the pre-cooler shown in blue. Credit: Reaction Engines Ltd.

The difficulty in using atmospheric air as rocket oxidiser is that the oxygen must be compressed to 140 atmospheres of pressure before being used, which would raise its temperature so high that it would melt any known material.

The key to this innovative engine is the pre-cooler heat exchanger, which prevents this heat build-up from occurring. The company’s heat exchanger cools the incoming air stream from over 1,000 °C to -150 °C in less than 1/100th of a second, all the while being 100 times lighter than conventional systems. The heat exchanger guides the hot air across spirals of tubes containing cooled Helium gas, creating a turbulent environment which cools the air more efficiently.

Another difficulty created by the super-cooled air is the potential for frozen water vapour to form and damage the engine. A closely-guarded solution, found in 2012, was revealed in 2015 patents to include a metal 3D-printed methanol-injecting de-icer.

The culmination of REL’s innovations are an engine with a thrust-to-weight ratio of 14, compared to about 5 for conventional jet engines, and fuel efficiency approaching eight times that of a typical rocket engine. These innovations could allow reliable and low-cost private access to space by offering reuse, the same strategy taken by SpaceX with their Falcon 9 rockets. All in all, it is a very exciting time for low-cost space travel. A fully realised Skylon space plane could see the cost of putting cargo into space fall from £15,000 (pre-SpaceX) to £650 per kilo – meaning science-fiction style access to space may be closer than we thought.


Jargon Buster

  • A rocket operates on a similar principle to that of a jet-engine: Expand a lot of gas through a nozzle to create a jet of gas which propels the craft forwards. A conventional rocket engine, however, combusts on-board liquid oxygen and a fuel, stored in tanks. The SABRE engine eliminates the need to store heavy liquid oxygen aboard the plane whilst it is flying in the atmosphere, saving weight over a conventional rocket.
  • Conventional rockets are split into multiple different stages, each composed of a fuel tank and a rocket. As the fuel drains the stage is released and dropped back to Earth, saving weight. Each stage’s rocket may also be designed to be most efficient in certain conditions, for instance at low-altitude or in space.
  • A heat exchanger is used to cool down gases or liquids. They are used nearly everywhere where energy is used to produce work: In a car, in your fridge, in air-conditioning. The SABRE’s heat exchanger has an almost unbelievable cooling rate, which is what allows the rest of the rocket to operate on atmospheric air.
  • 3D-printing, otherwise known as Additive Manufacturing, is used to build up layers of material to form a shape, rather than drilling or milling away material as is conventional. It can allow for geometries which standard techniques cannot imagine due to lack of access of tools.

Mechanical Engineering student. Interested in cars, AI, virtual reality, etc. etc.

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