Quite a while ago we discussed this word quite extensively. I'm still disgusted with OED
talking about "negative ullage". But here's a new use of it, by NASA. You might want to
read whole episode in Engines of Our Ingenuity 934.

"That means containers need complex baffles that let
surface tension position the liquids. NASA uses the
old English word ullage to describe that process.
Ullage once meant the empty space in a barrel of
wine. Now we use it for the empty space in a barrel
of liquid oxygen. "

to see something similar, look at the Pilot liquid ink pen.. it too has a series of baffles, that keep the liquid ink moving from the barrel to the point Pilot pens are well known for writing for a long time even against gravity) and yet keep the pen from leaking the liquid ink.

these are very similar to the kind of baffles uses to keep liquid fuel in fuel tanks moving, even when there is no gravity to feed it. (the example is also in the Engines of our Ingenuity text.)

here is a link to the index
http://www.uh.edu/engines/epiindex.htm