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Anaraxes · 04-14-2021, 08:36 AM

If nothing else about the engine changes, then yes. If you have to triple the mass moving through your engine, you need to triple the area through which it moves. (Area, so the radius of the nozzle goes up by a factor of sqrt(3), not 3.) Or, you have to change other things about your engine - pressure, temperature, other characteristics of the gas produced.

More than you wanted to know from NASA.

If the rest of the ship is the same (shape, but really just density), then if mass triples, the volume triples. If the shape is the same, then the dimensions grow by the cube root of 3. Since that nozzle area grows with a square root, the nozzle area does increase relative to the rest of the ship.

But then, even a Spaceships ship doesn't scale that way. The walls don't have to get proportionately thicker just because the room gets bigger, for instance. Structural members need to handle more force (same acceleration times higher mass); a quick glance at a beam support calculator suggests that does scale with mass (beam length and support positions as l^1/3, 3x force) -- which is going to mean in practice that the ship gets redesigned, not just scaled up.

But I'm not an engineer, much less a structural one.

04-14-2021, 08:36 AM	#6
Anaraxes Join Date: Sep 2007	Re: [Spaceships] Engine size and performance If nothing else about the engine changes, then yes. If you have to triple the mass moving through your engine, you need to triple the area through which it moves. (Area, so the radius of the nozzle goes up by a factor of sqrt(3), not 3.) Or, you have to change other things about your engine - pressure, temperature, other characteristics of the gas produced. More than you wanted to know from NASA. If the rest of the ship is the same (shape, but really just density), then if mass triples, the volume triples. If the shape is the same, then the dimensions grow by the cube root of 3. Since that nozzle area grows with a square root, the nozzle area does increase relative to the rest of the ship. But then, even a Spaceships ship doesn't scale that way. The walls don't have to get proportionately thicker just because the room gets bigger, for instance. Structural members need to handle more force (same acceleration times higher mass); a quick glance at a beam support calculator suggests that does scale with mass (beam length and support positions as l^1/3, 3x force) -- which is going to mean in practice that the ship gets redesigned, not just scaled up. But I'm not an engineer, much less a structural one.