The function of a rocket engine nozzle is to expand the hot engine exhaust gases down to ambient pressure, transforming thermal energy to directed kinetic energy in order to produce thrust. As the rocket ascents to the space the air pressure decreases. As a result, the exhaust gasses overexpand, reducing the effective thrust of the rocket. In order to compensate for the changing ambient pressure, the nozzle need to increase its expansion area.
I thought of a solution which may not work but comparably easy to implement. For the solid booster rocket I proposed earlier, the nozzle does not need to have propellent heat exchangers attached on it. This simplifies the design. A nozzle made of high temperature resistant tungsten alloy would be enough. I propose the nozzle to have multiple sections stacked on top of each other. These stacks will hold in place with a low melting metal such as aluminum alloy. Tungsten is not a good conductor of heat compared to aluminum. As the nozzle heats up, each low melting section will melt away and drop the next nozzle section into place. The thickness of the nozzle section holders would be altered to achieve the adequate delay between each nozzle section drop.
This would be a light weight and zero mechanics solution to altitude compensated nozzle design for solid boosters.
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