[Fun Maths]Centrifuge Fun

[ijuin]

Well it depends how you build it. 14.5 psi isn't terribly dangerous, and you don't necessarily need to keep the sea level pressure. Also note you can go down to near 5 psi if you use an oxygen only environment.

Take note that an ordinary automobile tire is generally pressurized to about 30 PSI, or about twice the pressure differential as that between sea level air and vacuum. Likewise, a soda can that has been shaken up endures three to five atmospheres of internal pressure--and it's just a layer of aluminum sheet only a few hundred microns thick! Retaining atmosphere is less about the strength of your materials and more about making sure that the seams where they meet are free of any gaps or leaks.

 

[francisdrake]

The picture above shows an interesting concept of a 'lateral centrifuge' spaceship. This ship rotates around the x-axis (as shown in the picture). The engines are located at -x, the crew is at +z and the reactor at -z. This arrangement gives a good separation of the reactor and crew, and a long baseline (d=125 m) for the centrifuge.

The disadvantage is that it can only be used for low-thrust engines, as the thrust leads to a bending stress in the mast stucture. This is why it has a lot of sailing-ship-like stays and spars, to strenghten the structure with least weight penalty.

The idea is to send it up in one piece, with self-deploying masts and an inflatable transhab. It would be part of a dual mission, as the lander would go separately on a cargo flight.

This design reminds me of Stuhlinger "Ion ships to Mars". Compared to a 'tomahawk' (or 'tumbling pigeon' design, as the Atomic rocket site calls it ) it retains the long centrifuge baseline of the whole ships length with the possibility to have continous thrust.

I think the design would be suitable for an ion or weak VASIMR drive. A slight disadvantage is that the floor of the centrifuged compartment will feel slightly inclined (front higher than rear), like on an airliner of today flying in a slightly nose-high attitude.

The main engines should be somewhat tiltable to allow controlling the rotation with the main engines, not only with the RCS system.

Before docking to the lander the rotation has to be stopped, but this would only be for a few days in Mars orbit, when preparing the descent to the surface.

Note: There is a NASA-paper on this design called "Preliminary Assessment of Artificial Gravity Impacts to Deep-Space Vehicle Design" by a guy called Kent Joosten.