A rocket nozzle that delivers optimal thrust across a much wider range of altitudes and which could be used for a UK spaceplane concept is to be tested again this year. This follows analyses of four 1s firings in February and March that indicated a successful outcome.

In theory rocket engines with an expansion, deflection (ED) nozzle should provide increased performance in atmospheric flight as the nozzle compensates for the effect of the changing ambient pressure, maximising thrust.

The nozzle's test rig is called the Static Test Expansion/Deflection Rocket Nozzle (Stern) motor and its four firings were part of a long-term programme by Culham, Oxfordshire based-Reaction Engines to understand how ED works.

Funded by Reaction Engines and built by UK company Airborne Engineering, the University of Bristol helped develop and test the 30kg (66lb) Stern rocket engine that produces 1,100lb thrust (5kN).

Because its combustion chamber reaches 2,100°C (3,800°F) the firings have to be limited to less than 2s otherwise the chamber wall would melt.

"The nozzle is designed to test our computer models. We want to design the tool for developing the ED nozzle to go on [Reaction Engines' Sabre engine]," says consultant to Stern, Bristol University space technology senior lecturer Mark Hempsell.

The test rig was built in 12 months. Hempsell will not disclose Stern's cost. Reaction Engines funded the research as it would like to use the ED nozzle on its Sabre engine.

This hydrogen, air-fuelled engine would power the company's horizontal take-off, horizontal landing Skylon spaceplane concept.

The ED nozzle is calculated to deliver sufficiently more thrust during take-off so that its payload could be increased by 500kg and the runway length shortened by 500m (1,600ft).

The Stern test rig also used igniter and injector designs for the Sabre. An analysis of the engine's performance suggests these worked as expected.

Source: FlightGlobal.com