Why is the fuel tank refilled from the beginning after abort?

[caglayankutay]

After an abort during rocket takeoff, why does the rocket refill its fuel tank? Why is it not preferable to use the already existing fuel?

[Jim]

After an abort during rocket takeoff, why does the rocket refill its fuel tank? Why is it not preferable to use the already existing fuel?

Which rocket and which launch?

[whitelancer64]

After an abort during rocket takeoff, why does the rocket refill its fuel tank? Why is it not preferable to use the already existing fuel?

If a rocket aborts a launch and tries again the next day, there's no reason to keep the fuel in the tanks for the entire day. So they will drain the fuel and keep it in a storage tank.

Storage tanks are better insulated than the rocket body is, so you reduce issues like liquid oxygen boil-off. Also, fuel loading is part of the standard pre-launch procedure, and there's no good reason to change that procedure. It's usually much safer to keep procedures the same, for consistency.

[Nomadd]

After an abort during rocket takeoff, why does the rocket refill its fuel tank? Why is it not preferable to use the already existing fuel?

If you mean Falcons, the fuel has to be recycled when it warms up too much. Short delays don't always need the fuel drained.
 
 I'm sure Jim can give you specifics on any rocket ever built, but there are a hundred scenarios depending on time of delay, which rocket and what mission. Launch windows can be hours long or instantaneous.

[libra]

If the oxidizer is liquid oxygen, it will boil away plus the cold takes a toll on the rocket guts... so better to siphon out, check, and fill all over again.

[caglayankutay]

After an abort during rocket takeoff, why does the rocket refill its fuel tank? Why is it not preferable to use the already existing fuel?

Which rocket and which launch?

For example, Falcon 9?

[Jim]

After an abort during rocket takeoff, why does the rocket refill its fuel tank? Why is it not preferable to use the already existing fuel?

Which rocket and which launch?

For example, Falcon 9?

Falcon 9 uses sub cooled propellants.  The vehicle has limited capability hold these propellants at temperature.  If the temperature gets too high, the propellants have to be offloaded and fresh sub cooled propellant loaded.  This only happens if there is launch window available.  The offloaded propellants are saved.

[skater]

I would assume that SX has a refrigeration plant near the pad? Does this cool the fuel through cold air, circulating the fuel through the refrigeration plant or circulating refrigerant through cooling tubes in the tank(s)?   

[Comga]

I would assume that SX has a refrigeration plant near the pad? Does this cool the fuel through cold air, circulating the fuel through the refrigeration plant or circulating refrigerant through cooling tubes in the tank(s)?   

Concept 2, a special refrigeration system
“Air” cannot get that cold. It’s essentially supercooling a liquified air component.
Thete are no cooling tubes within the tanks.

[Jim]

I would assume that SX has a refrigeration plant near the pad? Does this cool the fuel through cold air, circulating the fuel through the refrigeration plant or circulating refrigerant through cooling tubes in the tank(s)?   

There are no such tubes in the launch vehicle tanks.  The cooling is done to the ground tanks.

[skater]

I would assume that SX has a refrigeration plant near the pad? Does this cool the fuel through cold air, circulating the fuel through the refrigeration plant or circulating refrigerant through cooling tubes in the tank(s)?   

There are no such tubes in the launch vehicle tanks.  The cooling is done to the ground tanks.

I should've clarified that I was referring to the storage tanks on the ground, not the vehicle tanks. I was curious how the prechill for RP-1 is performed in those.

[Jim]

I would assume that SX has a refrigeration plant near the pad? Does this cool the fuel through cold air, circulating the fuel through the refrigeration plant or circulating refrigerant through cooling tubes in the tank(s)?   

There are no such tubes in the launch vehicle tanks.  The cooling is done to the ground tanks.

I should've clarified that I was referring to the storage tanks on the ground, not the vehicle tanks. I was curious how the prechill for RP-1 is performed in those.

They flow LN2 through tubes in a heat exchanger I believe

[butters]

ULA doesn't drain RP-1 from the Atlas V booster after a pad abort. They roll back to the VIF with a full fuel tank. That's possible because they use ambient-temp RP-1 and vertical vehicle processing. It's not a good idea to leave propellant in the tank(s) when lowering and raising a horizontally-processed launch system. Since Delta II was retired, I don't think there's been any other vertically-processed storable-propellant launch systems outside outside of China and India.