Concept diagram of command module interior | Command module design | Forum

Post edited 3:15 pm – December 28, 2009 by Luke Maurits

I've produced a concept diagram of the interior of the CM that I welcome feedback on.  It's not at all to scale and is just supposed to propose a general lay out:

It uses the same "box in a cone" design of Gemini/Apollo.  There's a main pressure vessel, made out of maybe aluminium, which serves as the cabin.  This vessel is depressurised and repressurised before and after EVA, respectively.  It has a second, smaller pressure vessel inside of it which remains pressurised at all times and contains the atmosphere breathing fuel cells (which will probably help to heat the cabin somewhat).

Vacuum-safe electronic equipment is mounted to the outside of this main pressure vessel, and high pressure tanks of whatever gases and liquids we need to support the astronaut for 24 hours are mounted to the outside too.

This entire assembly slides into a conical outer structure, which could be made of a composite material like carbon fibre, and which acts as a heat/radiation/micrometeoroid shield and provides an aerodynamic shape.  An ablative heat shield acts as a "cap" for the base of the cone.  The basic idea is that the cone and the cap are discarded after each mission (or possibly refurbished if this can be done safely) but everything inside of them are reused (just slot the whole thing into a new cone and throw a new cap on the end).

The ingress-egress hatch is a part of the main pressure vessel, so the outer cone needs to have an appropriately shaped hole in it.

I haven't drawn anything like them but I guess the cone struture will need to feature some struts that the pressure vessel is secured to to hold it in place.

The nose section contains the RCS unit and the parachute / paraglider stowage unit, which are an entirely self contained units that can be manufactured separately from everything else.  The very front of the nose may also have a small electronics module in it containing things like a camera, ranging laser or radar, etc.

After I'd just about finished drawing this I realised that, rather than having the 3 high pressure tanks stored horizontally underneath the main pressure vessel, it might make more sense to store them vertically on the back of the pressure vessel (behind the seat).  This would probably  allowing a smaller cone radius and frees up a position under the pressure vessel for another vacuum-safe electronics storage position (of course, with the tanks under the vessel you could put more electronics on the back of it, but that position will be hard to access for maintenance with the heat shield cap on, so it should be used for something "dumb" like tanks).  I didn't feel like starting the whole thing again right now but I might do a redraw like this later if people agree that it makes sense.

Why go with "cone in a box", instead of having the cone itself be the pressure vessel, ala Mercury?

• Results in a smaller pressure vessel, which will likely save weight – the pressure vessel will have the astronaut in it so it needs to be solid stuff, like aluminium, whereas the outer cone can probably be made of something lighter.
• Easier access to electronics – by opening hatches in the cone structure, 2 or 3 technicans can work on electronics simultaneously.  If everything is inside the pressure vessel you'd need to climb into the capsule to do work, which means one person at a time, and no work can be done once the capsule is pressurised with an astronaut inside before launch.
• Better for distributed construction – cone and box can be made separately.
• Less conductive heating of crew cabin by hot outer surface.

Why mount the gas tanks on the outside of the pressure vessel instead of in the nose as has been proposed? 

• Gas and liquids will also be stored in extension modules attached to the rear of the module.  It will be easier to integrate these two storage positions into a single oxygen injection system etc. if they are nearer together.
• My intuition is that a shorter nose will lead to less drag during launch, but this could be wrong.

Why put the main computer inside the main pressure vessel instead of on the outside like the communication/navigation electronics?

• Free heating for the cabin atmosphere and easier cooling (conduction, not just radiation) for computer, which will probably generate more heat than comms / navigation.
• Main pressure vessel provides an extra layer of radiation and micrometeoroid shielding, and the main computer is probably the last thing you want to have damaged.

Where are the anteannas?

• I don't know enough about what shape/size the antennas will be to propose a good place to put them.

What do people think?  If people feel like this is a decent overall approach to the CM design maybe someone with some good CAD skills could begin work on making some nicer models/diagrams of this?

This reminds me: I was exchanging a few emails with Paul Graham from OLF the other day and I off-handedly (and very unofficially, explaining I hadn't discussed it much with you guys) mentioned the idea of CSTART, OLF and potentially others creating a specific Open SpaceSuit project (and possibly even legal entity).  A fully open source space suit would be of use to both projects and probably others.  There may be eventual interest from commercial space tourism operations and maybe even beginning space agencies (India want to start doing their own manned missions in the nearish future).  Do people think that this is a sensible thing to do?