Sea Dragon Design Questions

Burncycle · February 3, 2018

I picked up what looked like a re-release of a vintage kit that contained a 1:200 scale Saturn V, Saturn IB, Atlas and Titan and decided to make a 1:200 scale Sea Dragon that I can 3d print to join the collection and for other uses (maybe a simplified version for orbiter or similar games). I am running into some questions though so I thought I'd pick the brains of the experts because while I love this stuff I'm not very knowledgeable in how it all works.

The more I look at the available schematics, the more I realize the drawings are very preliminary and the actual look (especially where the payload goes) would probably have changed quite a bit depending on if they were lofting fuel or oversized cargo. One example is the Apollo CSM that is often seen in the drawings -- it wouldn't fit as it stands, because there's a tank wall just below. My plans is to create a classic Sea Dragon (as per drawings found online) and then a possible evolution of the design with different uppers to accommodate various payloads such as fuel, oversized probes, Project Orion drive, station pieces, etc. Apparently the large upper tank in the drawing is the "payload" stand in, presumably bulk fuel to LEO, so in future versions I may remove and reshape the aerodynamic shell to fit other payloads.

This is one of the reference images I'm using

I am fleshing out a rough shape, some inner tanks are not modeled since they won't be visible, but have some specific questions about some of the parts so that I get it right overall.

This first picture is an overall cross section of what I have so far. As you can see the small rocket motors sticking out from the sides on the 2nd stage have not yet been modeled, because this is an area where I have some questions.

As you can see, there doesn't seem to be any sort of interstage section that falls away between stage one and stage two, and if there was one and the drawings just don't indicate it, then it may be an issue due to the positions of the small side rockets (not modeled here yet but visible in the reference images above). But that means there's almost ZERO detail visible from the outside with regards to the 2nd stage engine, and no room for the 2nd stage engine to expand at all like the 1st stage. Is that correct? If so, while it makes it easy to model (I can get rid of a lot of that interior actually) it is rather boring to look at... I wonder if a production version would have had an interstage of some sort. I'm finding it unusual that the engine bell would be "embedded" in the stage body like that, would it actually fire like this or is it supposed to retract or something?

This is a view of the first stage from below. The reference pictures indicate that the first stage engine bell is capable of 3 degrees of movement off center, and I assume all the bits and bobs drawn in the cross sectional view are actuators to move the main engine bell. The problem is, I'm having trouble visualizing what those parts look like in 3d so I can replicate them. Are they spheres or flat sided cylinders of some sort? They would partially fill the void at the narrow part of the cone here. I only see 2 actuators in some reference pictures, 90 degrees apart

Finally, below is a cutaway of the structure near the top. For 3d printing purposes, I have holes in the Apollo CSM so that small neodymium magnets can be glued in order to keep the capsule on the service module for display purposes. But this shows how the reference drawings don't necessarily match up to what is possible; if the CSM was buried about halfway in as in the drawings, the engine bell and the upper portion of the internal tank would conflict. It's just about perfect sticking out like it does on the Saturn V though.