Asparagus Staging

[rpayne88]

KSP makes Asparagus staging incredibly efficient. Why is this not used in the real world. Is there some aerodynamic issue or something?

[Digestif]

KSP makes Asparagus staging incredibly efficient. Why is this not used in the real world. Is there some aerodynamic issue or something?

It will be used (to a limited extent) by SpaceX.

The reason it's not used is that rocket science requires you to handle tons of explosive stuff and that pumping this stuff around the whole time actually makes your rocket science harder by a whole ****ing lot because that fuel also has some inertia when you move it around. It's complicated A LOT and when you're doing such critical stuff, you wanna keep it as simple (at that means as fail safe) as you can.

[andrewas]

KSP gives us zero mass, zero drag, infinite flow fuel lines. No parts fail in any way, unless the design itself is flawed. And, we don't need to worry about cost. In reality, engineering Asparagus is more difficult. The needed pumps are fairly heavy and add additional points of failure. On top of that, real life engines have a much better TWR than KSP engines, so the advantages of Asparagus over simple parallel staging are not as significant.

That said, the SpaceX Falcon 9 Heavy does use asparagus staging with two boosters.

[metaphor]

The space shuttle also used a fuel line between the external orange tank and the orbiter's main engines. Not quite asparagus staging though.

[rpayne88]

It will be used (to a limited extent) by SpaceX.

The reason it's not used is that rocket science requires you to handle tons of explosive stuff and that pumping this stuff around the whole time actually makes your rocket science harder by a whole ****ing lot because that fuel also has some inertia when you move it around. It's complicated A LOT and when you're doing such critical stuff, you wanna keep it as simple (at that means as fail safe) as you can.

Couldn't a sypion (sp?) be used to replace the pumps, only requiring one to pressurize the entire system?

[DerekL1963]

Couldn't a sypion (sp?) be used to replace the pumps, only requiring one to pressurize the entire system?

It takes a lot of pressurization to keep up with that rate of fuel flow... I suspect it would be heavy.

[rpayne88]

Are you talking about the pipes or the pump. If its the pump, the whole system could be pressurized prior to launch and left at the pad. Since it pressurizes the fuel system for an entire core, if it fails, the launch would be aborted (not different than a complete fuel system failure for an actual rocket. This would still allow engines to be shut down in the event of an individual engine failure. Granted, it would not be possible to restart the entire system, but then again, most first stage engines burn at full power until burnout (the only difference over SRBs is they can be shut down.) In the event of too many engine failures for any rocket, the launch would be aborted, or at least an attempt to salvage it with upper stage engines would be made.

[Temstar]

Pressure feed cycle engines require extremely heavy tanks to withstand that pressure. When you think about it, a burning rocket engine has inside its combustion chamber very high pressures which is what shoots the exhauster out the back at high velocity. When you have a pressure feed cycle you basically have two unobstructed openings in that combustion chamber - one in the back where the nozzle is, and one in front where the fuel and oxidiser are injected into the chamber (kinda sorta, fuel and oxidiser injector are pretty complicated and usually look more like a shower head rather than a single hole, but you get the idea). The hot gases is going to try to push out in both directions so in order to force the fuel and oxidiser under pressure into the combustion chamber you have to have all of your plumbing and fuel tanks able to withstand an even higher pressure than what's inside the combustion chamber. This results in very heavy tanks and rocket hardware compared to turbopump feed engines.

Pressure feed cycle engines have poor thrust to weight ratio due to their heavy hardware, however they are mechanically simple and reliable (as opposed to rocket turbopumps which are some of the most difficult to build and expensive pieces of machinery in all of mankind's history) so is generally only used for small orbital manoeuvring thrusters such as shuttle OMS engines and Apollo's descent, ascent and service module engines.

[Fuzzy Dunlop]

It wouldn't require any extra pumps, rocket engines suck fuel pretty effectivley.