[SunkenCiv]

Looks like those NASA guys are right — the pressure tank.

Older model:

http://fernlea.tripod.com/tank.html

Diagram:

http://encyclopedia2.thefreedictionary.com/Liquid-Propellant+Rocket+Engine

Nice timeline:

http://www.braeunig.us/space/timeline.htm

Russian designs with German post-war contribs:

http://www.friends-partners.org/partners/mwade/lvfam/earsiles.htm

[kitchen]

Thanks. I'll pass the links on.