NERVA Question

[Nertea]

A small question for you all that I've been unable to determine. What are the purpose of the spherical tanks at the top of the NERVA? Diagrams seem to omit them, but hey show up on a lot of images and concepts. Tank pressurization?

[MaverickSawyer]

I would guess helium for tank pressurization... but they used liquid hydrogen, so it should be self-pressurizing to an extent. Lemme see what I can dig up.

[Red Iron Crown]

I believe they are the "mixing tanks" shown in this function diagram: http://www.astrodigital.org/space/nuc2.gif Used to cool the exhaust that drives the turbine so it doesn't melt it.

Edit: Nope, see below.

Edited August 16, 2015 by Red Iron Crown

[Starwaster]

I would guess helium for tank pressurization... but they used liquid hydrogen, so it should be self-pressurizing to an extent. Lemme see what I can dig up.

No, you are correct. They are helium pressurization tanks. See page twelve of the linked document.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150002600.pdf