Extra fuel tanks with/out engines?

[temetvince]

I've read that with asparagus staging, I should put an engine underneath each fuel tank. If this is true, is there ever a reason to add spare fuel tanks to my craft without putting an engine underneath them?

Thanks.

Edited December 29, 2013 by temetvince

[Murph]

You certainly can do asparagus style staging without engines on the outer columns, but may well find that your TWR is too low. A major feature of the normal asparagus staging is having the extra thrust when the fuel load is heaviest, which is more or less what you need on ascent from the KSC pad. The only time you should really be considering it is if you've got a design which has significantly too much thrust off the pad.

[Vlk]

I don't think i ever did that, but i can imagine a scenario where that may be useful. I think its rare because usually you need more thrust power for additional fuel tanks. And when you ascend from kerbin with a big ship, if the fuel tanks are not "supported" well (with thrusters under them), then the ship can break apart, even if you use struts.

[Tank Buddy]

I do that sometimes, but not usually if I have 6 or more asparagus stacks. The only problem with asparagus is when you drop a stage, you loose, say, 450 kN of thrust, so if you drop one your TWR will only increase. And you don't have to add an extra engine if you have a good TWR, because then you just have extra fuel to burn with no real downside since there is no "useless" dry mass or increased fuel consumption.

[Soda Popinski]

I believe the term is "slack tank" staging.

Here's a thread on it: http://forum.kerbalspaceprogram.com/threads/57294-Different-staging-techniques

[maltesh]

If you need a lot of Delta-V, using drop-tanks can crank up your Delta-V a little higher by getting rid of the fuel tanks once they're empty.

The craft depicted in the image above was designed for a quick intercept of an object in an inclined solar orbit, and has a single LV-N for thrust. It had to kill 5 km/s to do so. It is shown discarding one of the two pairs of daisy-chained drop tanks it brought for that purpose shortly before continuing its deceleration.

[togfox]

I think a lot of people do asparagus without engines. You can take a 'stalk' and make sure it has a reasonable TWR for upper atmosphere, then you can add asparagus tanks until the TWR approaches about 1.5. The higher the TWR the better of course. You'll then have as much fuel as your stalk can support. Put more engines on the stalk (or the asparagus) if you need more thrust.

If you put engines on your asparagus then you risk having too much thrust during your ascent and a lot of the thrust is wasted. This means all those engines actually become dead weight.

[SRV Ron]

Asparagus drop tanks for launch, generally not efficient. However, for interplanetary exploration, they work extremely well.

[temetvince]

Thank you for the responses. How do I mark this thread as answered?