3 ms·

Or maybe giant syringes? There can't be sloshing if there is no free space because top of cylinder just moves to adjust volume.

TeMPOraL 3y ago
This actually makes perfect sense, so I'm hoping some rocket scientist will come and explain what are the "devils in the details" that prevent rockets from being built like this.
- raducu 3y ago
  I'm sure it's easy: some liquids like oxygen and methane are stored under high pressure, you would need an incredibly well built seal and powerful piston. If it's a room temperature liquid probably there are less complicated solutions like baffles and bladders. And then you'd gave to over engineer the rocket iself to not break when tipping over, not just the fuel tanks.
littlestymaar 3y ago
“Non-Newtonian fuel sponges” sounds way cooler though.
regularfry 3y ago
It's a moving part to go wrong. But more than that, the fuel tank has very thin walls. I can imagine you don't want a solid object inside the tank that's able to get any momentum. You do get baffles in liquid fuel tanks to cut down the effect, and some people have tried flexible bladders inside the rigid tanks for a similar reason but they don't work well with cryogenic fuels.
raducu 3y ago
When does a syringe become a piston?
- yetihehe 3y ago
  When you remove outer wall?
  - raducu 3y ago
    my bad, the piston is indeed just the inner moving part, my point was that we think of syringe as easy because it is not under pressure, but if you think in terms of car piston/cylinder you appreciate more why this can't work in a rocket fuel tank.
two_handfuls 3y ago
Some fighter planes go this. They use a bladder they compress, works the same.
KMag 3y ago
I believe https://en.wikipedia.org/wiki/MGM-52_Lance https://en.wikipedia.org/wiki/MGM-52_Lance used roughly this configuration, with a gas generator pushing the back of the pistons. As I remember, the oxidizer and fuel pistons were physically connected (concentric, with concentric propellant tanks) to simplify getting the mixture correct.

TeMPOraL 3y ago

This actually makes perfect sense, so I'm hoping some rocket scientist will come and explain what are the "devils in the details" that prevent rockets from being built like this.

raducu 3y ago
I'm sure it's easy: some liquids like oxygen and methane are stored under high pressure, you would need an incredibly well built seal and powerful piston. If it's a room temperature liquid probably there are less complicated solutions like baffles and bladders. And then you'd gave to over engineer the rocket iself to not break when tipping over, not just the fuel tanks.

littlestymaar 3y ago

“Non-Newtonian fuel sponges” sounds way cooler though.

regularfry 3y ago

It's a moving part to go wrong. But more than that, the fuel tank has very thin walls. I can imagine you don't want a solid object inside the tank that's able to get any momentum. You do get baffles in liquid fuel tanks to cut down the effect, and some people have tried flexible bladders inside the rigid tanks for a similar reason but they don't work well with cryogenic fuels.

raducu 3y ago

When does a syringe become a piston?

yetihehe 3y ago
When you remove outer wall?
- raducu 3y ago
  my bad, the piston is indeed just the inner moving part, my point was that we think of syringe as easy because it is not under pressure, but if you think in terms of car piston/cylinder you appreciate more why this can't work in a rocket fuel tank.

two_handfuls 3y ago

Some fighter planes go this. They use a bladder they compress, works the same.

KMag 3y ago

I believe https://en.wikipedia.org/wiki/MGM-52_Lance https://en.wikipedia.org/wiki/MGM-52_Lance used roughly this configuration, with a gas generator pushing the back of the pistons. As I remember, the oxidizer and fuel pistons were physically connected (concentric, with concentric propellant tanks) to simplify getting the mixture correct.