Found these interesting sci-fi diagrams inside a textbook from 1929. Couldn’t find a name, but wanted to share a real retro retrofuturist’s work

I used to draw similar cross sections as a kid and was floored when I found these two drawings inside a set of illustrated medical encyclopedias I bought as part of an antique book lot. The copyright date of the books was 1929, so these may have been drawn sometime after. I think it is some kind of massive tank and diving bell/submarine. I imagine some young sci-fi enthusiast imagining a future battlefield in the interwar years.