A Note on Rocket Scaling

# A Note on Rocket Scaling - Comments on Rocket Scaling Dr...

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Comments on Rocket Scaling Dr. Adam London, Ventions, LCC, President and CEO Dr. Daniel Kirk, Florida Institute of Technology, Associate Professor Overview: On traditional liquid-fueled launch vehicles, the engines themselves tend to weight about twice as much as the payload being delivered to orbit. At launch, they are required to produce a thrust slightly larger than the total weight of the vehicle. If they could produce this same thrust while weighing much less, this weight savings could be used to increase the size of the payload. There are two ways that the thrust-to-weight ratio can be increased for a given propellant combination. 1. Higher combustion chamber pressure will lead to a smaller engine for a given thrust level. 2. By making the engine smaller at constant chamber pressure, the thrust-to-weight ratio will increase, everything else being equal. This is because the thrust produced is proportional to the throat area, while the weight of the engine is proportional to its volume. For perfect scaling, the ratio of the throat area to the overall volume will increase as the rocket is made smaller. Example: If one takes a traditional ‘baseline’ engine and makes four copies of it, each exactly half the size (which implies ¼ the exit area and 1/8 th the volume) of the original, the four engines operating together would produce the same thrust as the larger baseline engine, but only weight half as much. One could then do the same with the half size engine, and make a total of 16 quarter-sized engines, which when ganged together would still produce the same thrust as the original, but together weigh a quarter of the original baseline engine. In theory, this process could be continued indefinitely, leading to a massively-parallel thrust system with a very high thrust to weight ratio. The Scaling Laws:

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A Note on Rocket Scaling - Comments on Rocket Scaling Dr...

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