Right, but this baffle approach - with one way valves - provides a tank that doesn't unsettle in the first place. The plates create a segmented tank with one way flow. Instead of having a continuous plunger that moves smoothly down the length of the tank, these plates provide a discrete plunger. Any given plate would have to withstand only the mass of the propellant that is between it and the next lower plate.
As I mentioned earlier, the plates serve to avoid unsettling in the first place.
In truth, I dismiss everything I come up with out of hand because I'm undoubtedly ignoring some fundamental consideration. I'm a software engineer with a lot of time on my hands, not a SpaceX design team.
That's my understanding.
That's the idea. I'd love to hear from the SpaceX guys on why they wouldn't want to do this, but things will never even get that far.
Right. That segment doesn't need to be able to hold all of the propellant that you'd use for a booster landing. It only needs to hold enough to relight an engine to settle the tank.
Sounds sensible (and lighter), but hey, I'm a brain surgeon, not a rocket scientist
I expect the eventual plan will simply be to fine-tune the hot-staging burn to practically eliminate forward slosh in the booster tanks, rendering the baffles and secondary tanks unnecessary. A slight change in timing (e.g. staggering the startup of Ship’s engines so it pulls away a bit slower with less force on the hot-staging plate, or keeping >3 booster engines lit for the first moments of separation) should allow the booster to keep say >=0.1 g forward acceleration throughout staging, enough to suppress forward slosh. For landing, the booster propellant is settled by gravity+drag, same as Falcon 9. (The same is mostly true for for Ship, but AIUI the Ship needs the forward header tank for proper weight distribution during reentry.)
Certainly if they can eliminate the need for an entire system like that, they'd gain a tremendous advantage.
It's worth burning an extra ton of propellant if it can eliminate two tons of baffles. Not an easy optimization problem; will no doubt take many iterations for them to figure out the best strategy. The boostback flip will cause the propellant to slosh sideways, but maybe that's ok if it doesn't uncover the intakes, or else maybe they could just put all the intakes on the side the propellant sloshes to?
True, it's a different problem for Starship. (Booster never needs to do a zero-g restart.) Baffles with one-way valves is an interesting idea, although spaceship valves always seem to have their own difficulties.
I was thinking that perhaps they could put the baffles only on the side of the booster that the propellant sloshes to. But they may actually have done that. With boosters, they can optimize for a very specific flight profile. Boosters do one very specific thing.
Spaceship valves are invariably gas tight, with a large pressure gradient across the valve. These have no pressure gradient and aren't gas tight, so they're extremely low performing valves. They only serve to prevent fluid backflow. As always, I'm sure it's more complex than that, but that's the idea.
The SpaceX launch livestream just stated that the reason for planning to dump the hot staging ring on IFT-4 is to lighten the vehicle for landing. It was also stated to be a temporary measure.
Sounded like they had designed a better, lighter hot staging ring that would be reusable. I suspect it’s either not ready yet, or is a lot more expensive, so this jettison idea makes sense while they are still lofting test ships that they don’t plan to reuse.
