Funding boost for SKYLON

Oxfordshire rocket developer Reaction Engines (REL) has been awarded €1m by the British National Space Centre and ESAto develop a propulsion system for SKYLON, a proposed reusable spaceplane.

The funding will go toward demonstrating the core technologies for the so-called synergic air-breathing rocket engine (SABRE). This hybrid engine will use air when in the Earth’s atmosphere and behave like a rocket engine when in space.

In air-breathing mode air is first cooled by a heat exchanger pre-cooler before being compressed and fed to the rocket engine to be burned with hydrogen fuel. When in rocket mode the hydrogen is burnt with liquid oxygen.

Abingdon-based REL is to develop and test the precooler that cools the incoming air as it enters the engine. REL was involved with the UK’s first space shuttle programme HOTOL (horizontal take-off and landing) that was abandoned in 1988.

Mark Hempell, REL’s future programmes director, said: ‘SABRE is a bigger and better engine based on the STERN [Static Test Expansion deflection Rocket Nozzle] static test engine, which was built to explore expansion deflection nozzles. It’s heat-sink cooled and can only be fired for half a second in which time it gets up to 300°C.’

Part of the programme’s work will be to decide whether SABRE will use the expansion deflection (ED) nozzle employed by STERN or a dual bell system.

‘At the moment the baseline SABRE uses what is known as an expanded bell,’ explained Hempell. ‘It expands much more than is needed for flight in the earth’s atmosphere so we are actually taking a penalty hit as the gas flow coming out of it is below atmospheric, so part of the thrust is literally sucked away. The ED nozzles or the dual bell will allow us to get over this sucking effect and that will put half a tonne on the possible payload and knock half a kilometre off the runway length.’

He said the biggest challenge in developing REL’s part of the engine would be frost control.

‘You need to cool the air before you can compress it to put it in the engine,’ added Hempell. ‘We have got heat exchangers and often use radiators in front of the airflow which cool it down until it’s almost liquid, around minus 130°C. In doing that the water vapour in the air condenses out into ice. If you don’t do something about it the heat exchange clogs up, literally in seconds.

REL has a solution in mind and will demonstrate it as part of the programme, but is currently keeping it under wraps.

The programme team aims to have the engine technologies successfully demonstrated by 2011. The final engine could be finished by 2018, with entry into service with operators and paying public in 2020.

Hempell said that this initiative from the British National Space Centre represented a significant sea change in the UK government’s position on funding for manned space vehicles.

Other areas of engine development covered by the project are the cooling of the combustion chamber to be investigated by EADS Astrium and DLR in Germany, and exploration of advanced exhaust nozzles by Bristol University.

An animation of SKYLON can be viewed here.

Berenice Baker