Copyright 2006 by Eric M. Jones. All rights reserved.
As can be seen in more detail in Scott Sullivan's excellent Virtual LM, particularly on page 169 and pages 183 to 192, the foward portion of the cabin where the crew stood, is a very short cylinder standing on its side with its symmetry axis pointing fore and aft. The portion of the cabin to the rear was part of the Midsection Assembly and, most importantly for the purposes of this discussion, had a 'lower deck' that was 18 inches higher than the floor on which the astronauts stood. This rise from the cabin floor to the midsection lower deck was called the "midstep".
Last revised 26 August 2006.
A plan view of the cabin from a 1966 LM Orientation Course ( 2.8Mb ) shows the the Midsection Lower Deck with the Ascent Engine Cover in the middle.
Plan view of the cabin
As can be seen in the plan view and in a righthand-side cutaway drawing (below), various components of the Environmental Control System (ECS) take up most of the Midsection Lower Deck forward of the Engine Cover on the LMP's side of the cabin.
(click on the image for a larger version).
As can be seen in the plan view and a lefthand-side cutaway drawing (below), the portion of the Midsection Lower Deck on the Commander's side of the cabin part was clear and could be used, for example, as a place to stand a PLSS during recharge. The astronauts often described this a 'putting the PLSS on the midestep'.
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