Slightly altered CM structure concept | Command module design | Forum

I've been thinking some more about the CM structure concept diagrams now featured in the CLLARE Overview Document and I think they can be improved upon.  My main concern is that putting the electronics pressure vessel in the front bottom of the main pressure vessel leads to an inefficient use of space overall.  It (i) makes the pressure vessel longer than strictly necessary and (ii) wastes a lot of space inside the cone, underneath the pressure vessel.  I also fear that there simply won't be enough room in there for a redundant set of avionics and the fuel cells.

The obvious solution to all of these problems is to put the secondary pressure vessel underneath the first one, as pictured here:

This results in a shorter cone, with less wasted space underneath, and ample room for both electronics and a power plant.  Thoughts?

Also note that in this diagram I have proposed a new solution to the well known problem of making sure there is enough room to get an EVA suit on in the capsule (and, indeed, enough room to store an EVA suit).  The first basic idea is to have the cabin be slightly longer than it strictly needs to be, so that there is considerable room behind the seat where the suit can be stored.  When it comes time to don the suit, the suit is pulled from behind the seat into the astronaut's lap.  The second basic idea is to have the seat be capable of sliding linearly toward or away from the front of the capsule, just like a standard automobile chair.  Once the astronaut has the suit in their lap, they can slide the chair maximally backward, away from the control console, leaving themselves with a rather large space in which to suit up.  The big downside to this approach is that it results in a longer capsule than strictly necessary, but it might be the most straightforward way to deal with the changing room problem.  This idea is completely separate from the repositioning of the second pressure vessel idea, so if people don't like this one due to wasted space, we can just ditch it.  Consider, though, that the "wasted" space could be put to very interesting use, e.g. satellites small enough to fit back there could be "hand launched" during EVA.

A third idea: on the outer sides of the pressure vessel where we originally planned to mount electronics, ala Gemini, we could have radiators.  The cabin atmosphere could be pumped past 0, 1 or 2 of these radiators depending on how badly cooling was needed.

It certainly solves the space problem handily, and there is a huge existing knowledge base on how to actually implement the adjustable seating from the automobile industry.  The only thing that stops me from outright loving it is that it involves so much extra space in the cabin, and hence extra size-mass of the CM.

An unrelated thought I've had recently: the long and thin horizontal second pressure vessel under the main vessel in this diagram could just as easily be placed vertically behind the main pressure vessel.  This could result in an overall pressure vessel shape that is practically conical itself, absolutely minimising wasted space inside the main CM shell.  It may also result in allow a steeper slope of the cone, which could (1) improve visibility through the window and (2) reduce CM length.  It would probably necessitate moving the breathing gas tanks inside the cabin, but I actually think that might be a good idea.  In an absolute worst case emergency, the astronaut could always perform manual oxygen injection into the cabin with hand valves if the automatic system fails.