[KeplerBoy]

Maybe the tank is just not a large hollow structure but contains fins/compartments/whatever to restrict the sloshing motion and it's not that big a contribution to the overall motion.

If it's no stronger than a sudden wind gust, it's just something the controller has to be able to take care of without a heads-up.

[kaonwarb]

These are indeed part of the solution and are known as baffles. They have risks of their own, e.g.: https://wccftech.com/baffling-baffles-musk-explains-why-spac...

[nuancebydefault]

In the first spacex rocket Musk thought that it was a good idea to not install baffles. He learned from experience that they are indeed needed.

[m4rtink]

I remember a very similar anecdote about Von Braun & the early Juno/Jupiter rockets - with someone pointing out issues with sloshing on a press conference & Von Braun brushing it off as insignificant.

Then the next launch crashed due to slosh induced oscillation - and the one rocket after that had anti-slosh baffles. ;-)

[vocram]

That’s how tanks in race cars are made. Another solution is fill the tank with some kind of sponge-like material.

[486sx33]

Sometimes… the baffles break off, and then become surfboard projectiles inside the tank.

More fluid dynamics

[m4rtink]

That would be far too heavy in this case. :)

[TowerTall]

That is how they build the tank in Formula One Racing (and probably many other race cars, I guess)