Launching without staging

[davidpsummers]

I've had some like launching a booster and getting up to orbit by pumping fuel around rather than staging. I get as big a rocket I can to orbit (empty or not). Then I just refill it with other missions. It is likely assembling a rocket in orbit, but without the rocket being so darn wobbly (I use one set of couplers to stick the payload up top). Then I can stage it properly as I use it..

Here is the booster I just used on its way round trip to Jool. The part below the couplers was attached to my station until full, then I just attach the payload part in orbit and off I go!

[Geschosskopf]

Quite a monster. Keep it up and you'll turn into Whackjob

[Thomas988]

Wait, did I read that correctly? You pump fuel around and that makes the spacecraft move? Are you brilliant or am I just atrociously bad at comprehending things?

[davidpsummers]

Wait, did I read that correctly? You pump fuel around and that makes the spacecraft move? Are you brilliant or am I just atrociously bad at comprehending things?

No. When the lower stages run out of fuel, I just transfer fuel from the upper stages to the lower stages and keep going. (You left click on one tank and the option-left click, on a Mac, I forget what key you use for PC, and that brings up a menu where you can transfer fuel.)

You don't have a payload, the empty booster is the payload, (just put a little control pod on it to control it, in mine, two (to be symmetrical) of the boosters have OKTO's just behind the nose cones). You can get a fair fraction of the delta-V you would get by staging (the rocket does get lighter, but you don't loose the weight of the empty tanks and unused engines).

You can get quite a decent rocket to low orbit. Then you can refill it at your leasure (if you have docking ports on it).

[davidpsummers]

For the record I did drop some SRB's on the way up. Not sure I wanted them for the controlled burns I would need to follow anyway.

The way to go, IMO, is take the biggest booster you have, replace the payload with docking ports, and see how will it gets to orbit by pumping fuel down rather than staging. If you don't make it, train again where you do the first staging and then skip the rest.

[Cashen]

No. When the lower stages run out of fuel, I just transfer fuel from the upper stages to the lower stages and keep going. (You left click on one tank and the option-left click, on a Mac, I forget what key you use for PC, and that brings up a menu where you can transfer fuel.)

You don't have a payload, the empty booster is the payload, (just put a little control pod on it to control it, in mine, two (to be symmetrical) of the boosters have OKTO's just behind the nose cones). You can get a fair fraction of the delta-V you would get by staging (the rocket does get lighter, but you don't loose the weight of the empty tanks and unused engines).

You can get quite a decent rocket to low orbit. Then you can refill it at your leasure (if you have docking ports on it).

This is useful for Eve landers. Generally if you make a multi-stage rocket that can lift off from Eve, it will be able to make it to Kerbin orbit with staging inhibited and by transferring upper stage fuel into the lower stages, effectively making it an SSTO. Then you can refuel it and send it to Eve, and it can perform its intended staging there. This is really the only use I can think of for this technique.

[Geschosskopf]

Wait, did I read that correctly? You pump fuel around and that makes the spacecraft move? Are you brilliant or am I just atrociously bad at comprehending things?

Although this isn't what Davidpsummers did here, this is in fact an old trick/exploit of KSP physics. Scott Manley even had a video on it a couple years ago. You have 2 tanks separated some distance apart by structure and only enough fuel for 1 tank. You start the ship rotating in pitch or yaw. As the empty tank rotates towards the direction you wish to move, you pump fuel into it. This moves the ship's COM in the desired direction of travel. Because physics treats the ship as a point at its COM location, you have effectively moved the ship by however much you just moved its COM. Repeat pumping from full tank to empty tank as the empty tank rotates toward the desired direction. It doesn't provide much thrust but if you have patience, you can actually make a significant maneuver this way for free.