HN Theater @HNTheaterMonth

This shows the contents of a tank (I think it's the oxygen tank as there's no transfer tube in the middle of the tank as it would be in the RP-1 tank (that's short for "rocket propellant-1" a sort of refined kerosine - and yeah, very imaginative name!)) sloshing around during SECO-1 (Second Engine Cut-off 1) during the CRS-4 mission.

https://youtu.be/7YkCh7uOw1Y?t=1442

⬐ ChuckMcM

Interesting internal shot of what I presume is the fuel tank? Clearly some sort of liquid. I note that the Wikipedia page [1] had this one as an F9R mission but the rocket did not include the landing legs. In theory the next mission they will try to re-land the first stage on something solid. I am so looking forward to that.

[1] http://en.wikipedia.org/wiki/List_of_Falcon_9_launches

⬐ rrmm

That's what it looked like to me. I wonder what they wanted from that shot; looking for slosh, remaining fuel, or how the remainder of the fuel influences the momentum of the craft after engine cut-off?

If it's something operational, I'm kind of surprised that they would show that on the public stream.

⬐ ChuckMcM

It is entirely unclear to me how they 'pick' what are the things they put into the feed. I have wondered if the initial decision to stop doing live coverage of launches was to enable more operational stuff to be done "live" but hard to know.

One of the more interesting parts of the ULA discussion of on orbit refueling capacity was how you might "settle" the tanks. Gravity does that wonderfully, and of course while you're accelerating you have it covered, but when you want to 'restart' you are in a microG environment and the fuel might not be at the end of the tank where you want it. Simple pressurization doesn't help, the fluid gets evenly distributed in the volume. Not much help. A fuel bladder might work but you'd something that was very light and compressed well. I also discussed with one of the ULA folks a movable "piston" on one end of the tank. Basically do it like a pneumatic cylinder without the rod, You just pushed it to the other end. He pointed out that there aren't any pneumatics that work with hydrogen. It is just too "small" a molecule for wall seal to hold. That leaves things like spinning to create a centripetal 'hold' on the fuel with a narrower 'top' than bottom so that an axially spinning tank will accumulate fuel to the bottom. Ok for payloads, not great for astronauts though.

⬐ rrmm

Traditionally, they use ullage motors, right? (http://en.wikipedia.org/wiki/Ullage_motor).

Perhaps they could dock with it a little harder than is strictly necessary or use a maneuvering thruster burn.

It seems like it'd be easier to use non-cryogenic fuels (hypergolics, or kerosene + LO2) which may make the piston idea workable. How do they keep cryogenic fuels cool in space in the long term? good insulation and vent a little of it off regularly?

⬐ mzaccari

Nice! Took me a while to find what looks like the internal shot: http://www.youtube.com/watch?v=7YkCh7uOw1Y&t=22m42s