Review: Ed Moore - Rocket Science

Category: Speakers, Academic, General

On Thursday 1st February Marlborough was delighted to welcome Ed Moore from Airborne Engineering for a Physics Department talk.

Ed Moore currently works at Airborne Engineering. His research is based in Westcott Venture Park, which was formerly the Rocket Propulsion Establishment and is now home to leading UK rocket companies European Astrotech, Reaction Engines and Airborne Engineering. 

Moore was quick to reassure the audience that he really was a rocket scientist. He began by igniting a balloon of pure hydrogen gas followed by a mixture of hydrogen and oxygen: the latter was truly explosive. The aim of this was to demonstrate the importance of a rocket’s own oxygen supply. This is what sets rockets apart from airplanes and enables flight in very low atmospheric pressures, which has opened wide the scientific and military applications of aerospace engineering. 

We were then presented with the ideal rocket equation, which describes how the ejection of fuel at high velocity imparts a forward velocity to the rocket. Many of us recognise this as the principle of conservation of momentum, and it is this gain in rocket velocity that we associate with the thrust force of the engine. His derivation of the equation, detailed below, was used to highlight how we can maximise the efficiency of a rocket. 

The first way to maximise efficiency is through the velocity at which exhaust is expelled from the engines. This exhaust leaves through conically-shaped nozzles, which are designed to gradually reduce the pressure of the exhaust as it accelerates. This means that when the exhaust meets external pressures it will not expand, so that all motion is directed along the line of flight.

The second way to maximise efficiency is through the ratio of fuel to total mass. In comparison with a roughly 50% fuel ratio for a typical aircraft, a single-stage rocket must achieve a ratio exceeding 90%. This presents a tremendous challenge in economy of rocket design and is currently overcome through the use of multiple-stage rockets. Fuel is divided into several compartments or stages, and as each stage progressively empties of fuel during flight, it is shed from the main rocket body. Spacecraft effectively use this mechanism to launch probes into space, such as the three-stage Saturn V rocket used to launch the Apollo-11 lunar module.

Whilst each stage can be designed for optimum combustion within the range of pressures for which it will be in use, they require millions of pounds to design, build and test. This is a tremendous waste for something that is intended only for single use. Achieving a similar mass ratio with a single-stage rocket would not only transform the nature of space missions, but also of Earth-bound aircraft. Moore foresees that, within our lifetime, we should be able to access anywhere on the planet within a mere 4 hours. With these exciting prospects, he ignited a small rocket engine to illustrate their immense power.

Moore completed the talk by referencing his recent involvement in the LAPCAT project, which has successfully controlled engine temperatures to minimise harmful nitrogen emissions. We were illuminated of further design considerations as he took questions from the audience. A notable example is the curvature of rocket engines, which elevates centre of mass so that the thrust of the rocket does not cause it to rotate during flight.

The evening provided an opportunity to address the growing interest in aerospace engineering and its potential applications. Throughout the talk, Moore placed the field of rocket science in secure context with the use of video footage and historic engineering landmarks. His approach to the research gave the audience clear insight into the creative and technical flair involved, and his experience showed us just how far this has taken him. We wish him all the best for continued success and are grateful for the time that he took to be with us.

Review by Molly Gibbins (CO U6)

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