Kerbal X (Stock): Two questions

[MetricKerbalist]

Hi KSP colleagues,

I have a question pertaining to the Kerbal X (Stock), please:

As you can see, a cluster of seven engines initially powers the rocket.  The central engine is an RE-M3 Mainsail Liquid Fuel Engine, so we would expect it to be have differently from the six other engines forming the circumference of the cluster.  These are all LV-T45 "Swivel" Liquid Fuel Engines, and each one of those six burns the same kind of fuel and the same kind of oxidizer.  But those six engines burn their fuel at different rates in pairs.  Thus, two of the engines complete their burn at one time, and then two of the engines complete their burn next, and finally the third pair complete their burn.  How is this possible, since they are all using the same engines with the same amount of identical fuel?

Thank you.

Stanley

[Bej Kerman]

21 minutes ago, MetricKerbalist said:

As you can see, a cluster of seven engines initially powers the rocket.  The central engine is an RE-M3 Mainsail Liquid Fuel Engine, so we would expect it to be have differently from the six other engines forming the circumference of the cluster.  These are all LV-T45 "Swivel" Liquid Fuel Engines, and each one of those six burns the same kind of fuel and the same kind of oxidizer.  But those six engines burn their fuel at different rates in pairs.  Thus, two of the engines complete their burn at one time, and then two of the engines complete their burn next, and finally the third pair complete their burn.  How is this possible, since they are all using the same engines with the same amount of identical fuel?

This is Asparagus staging - the fuel is all flowing clockwise, coming out of the first pair quickly because that first pair of tanks is pouring fuel into the other two pairs. then the second, and the third. In onions staging, these tanks would not share their fuel, and would take longer to burn through. They'd drop off at the same time but the rocket has to drag this mass for longer, hence why asparagus staging is used on the Kerbal X, and why asparagus staging is better than onion staging.

[Reactordrone]

If you right click on the fuel tanks you'll see that the only tanks draining at the start are the first two booster tanks, so you have seven engines feeding from two tanks. Once you drop two engines you have five engines feeding from two booster tanks, then three engines feeding from two booster tanks then the mainsail feeding from full core tanks. The rate at which the tanks drain varies depending on the number of engines using the fuel.

[FleshJeb]

https://wiki.kerbalspaceprogram.com/wiki/Asparagus_staging

[MetricKerbalist]

Hi Bej Kerman, Reactordrone, and FleshJeb,

Thank you all for your informative answers.  I especially enjoyed the link to the Kerbal Space Program wiki, which nicely tidied up the issue.

I am grateful for the help that all of you provided.

Stanley