Space plane SKYLON
We’ve been collaborating with Reaction Engines for the last 10 years, supplying components for the groundbreaking Skylon space plane.
“No one else has managed to create heat exchangers like this before, due in part to the fact that the specifications for the components are very demanding. There are a few other companies which can produce the kind of high tech tube we need but the Fine Tubes product is extremely high quality, meeting all the project specifications and we are very pleased with its performance.” Dr Robert Bond, Corporate Programmes Director, Reaction Engines.
Skylon is a revolutionary concept. This aircraft will be powered by a unique new propulsion system that combines jet and rocket engines in a single power plant enabling Skylon to take off and land on a runway, but also to exit Earth’s atmosphere. The result will be a reusable space plane operating at just two percent of the cost of existing rockets. The plane is being designed, developed and promoted by Reaction Engines Ltd. in Oxfordshire.
An essential component of Skylon’s Sabre engine is a high performance heat exchange system which cools air for the engine intake. Fine Tubes excels in the manufacture of the tiny tubing essential for heat exchangers (or pre-cooler systems) and has worked in partnership with Reaction Engines to come up with a breakthrough in aerospace heat exchanger design for the Sabre engine.
Key to developing the right solution for the project has been the highly effective working relationship between Fine Tubes and Reaction Engines. Reaction Engines has spent the last 20 years designing, producing and testing key areas of technology for Skylon, and for the last decade Fine Tubes has worked alongside the company developing and trialing various designs for Sabre’s pre-cooler system.
Making heat exchangers of the size, scale and weight required presents a great technical challenge. The pre-cooler and its component parts need to be lightweight but also able to cope with temperatures around 1000°C, and very high pressure helium. They also need to withstand thermal expansions and the inertial and aerodynamic loads experienced during flight.
The project pushed our tube manufacturing process in a number of areas:
- The drawing of matrix tubes in heat-resisting nickel-based alloys, ensuring correct wall thickness and diameter
- Brazing heat exchanger tubes to headers
- Machining of heat exchanger tubes to give a profiled (non-constant) wall thickness to ensure good heat exchange properties without compromising physical strength
- Hole drilling
- Tube forming without ovalisation, wall thinning or buckling
- The assembly of large heat exchanger modules incorporating thousands of tubes
Fine Tubes custom-made a high pressure tube for Reaction Engines which has a wall thickness of just 40 microns – that’s about half the diameter of a human hair. The tube itself is made from Inconel, a nickel alloy that is very resistant to temperature and well suited for use in extreme conditions. Each engine will use over 2,000km of tubing, so its walls have to be extremely thin to minimise weight and to act effectively as a heat exchanger, but also very strong because of the heat, pressure and forces involved.
Inconel is a difficult metal to shape and machine but it was essential that the tube retained its concentricity and overall straightness. Because the wall is so thin, it is also very susceptible to damage. So we installed specialist equipment at our tube mill to carry out the contract, including an apparatus capable of pumping cleaning fluid through the bore holes of such minute tubes.
Reaction Engines Ltd. announced on the 28th November 2012 that major tests had been successfully completed on the critical pre-cooler technology for SABRE, the innovative engine that will propel Skylon into orbit. The European Space Agency (ESA) evaluated the SABRE engine’s pre-cooler heat exchanger, confirming that all demonstration objectives were met. The series of tests proved the cooling technology to be frost-free at the crucial low temperature of -150°C.
Dr Mark Ford, ESA’s Head of Propulsion Engineering said: “One of the major obstacles to developing air-breathing engines for launch vehicles is the development of the lightweight high-performance heat exchangers. With this now successfully demonstrated by REL, there are currently no technical reasons why the Sabre engine programme cannot move forward into the next stage of development.
Reaction Engines Ltd. must now raise the £250m needed to complete the next phase of development, which would see the company prove SABRE's performance across its air-breathing and rocket modes. Dr David Parker, Director of Technology, Science and Exploration at UK Space Agency (UKSA), said: “Both Sabre and Skylon are exciting new technologies that could transform access to space.”
About Reaction Engines Ltd
Reaction Engines Ltd was set up in 1989 to design and develop advanced space transport and propulsion systems. From its base at the Culham Science Centre in Oxfordshire, the company combines established physical principles with innovative engineering design to develop a range of products that will enable the commercial exploitation of space. The company’s cryogenic wind tunnel facility at their Culham Science Centre has been used to develop a frost control system for the 'air pre-cooler' heat exchanger of the SABRE engine, where actual conditions in flight are simulated. The pre-cooler is designed to cool the engine airflow (about 400kg/s) from intake recovered conditions (up to 1000°C at Mach 5) down to -150°C prior to compression. At low altitudes atmospheric moisture will clog the matrix with frost within a few seconds unless preventive measures are taken.