Linear Staging, Going Beyond Asparagus

[Leonon]

I've come up with a method of increasing efficiency above asparagus staging. This may be old news but since asparagus staging is still most commonly used it probably bears repeating. By placing a cubic octagonal strut below an engine you can have it active and producing thrust while things are below it. It doesn't overheat the parts below it and this configuration allows dropping tanks individually instead of in pairs like asparagus does. This also reduces drag since all parts are in a straight line instead of spread around drag producing parts are dropped sooner. This does reduce stability somewhat and tends to lead to using a very large number of stages, so it's not perfect.

It's also very, very unrealistic.

I've put examples in an Imgur album but I'll also go over them here.

I used the following mods during these examples

Mechjeb2 2.0.9.0

Engineer Redux 0.6.1.1

The first example also used

RemoteTech 0.5.0.1

Deadly Reentry 2.3

This illustrates the basic concept. The top engine is a LV-909 and the bottom one is a 48-7S.

1385dV of 4689dV remaining, 3304dV used

Since the engines were started simultaneously the craft was able to get out of the thick lower atmosphere quickly. As it went up the fuel drained from the bottom tanks upwards and tanks were discarded as they individually emptied.

I call it Linear staging.

I made a few craft and had Mechjeb get them to orbit to compare dV usage. The first flight limited top speed to terminal velocity, the second limited acceleration to 23m/s squared. All other flight parameters are left the same.

Asparagus using LV-909 engine and dropping 4 tanks in groups of 2

4753 dV in hanger

Flight 1 1370 dV left, 3383 dV used

Flight 2 1378 dV left, 3375 dV used

Linear using LV-909 engine and dropping 4 tanks individually

4810 dV in hanger

Flight 1 1465 dV left 3345 dV used

Flight 2 1472 dV left 3338 dV used

Asparagus using Skipper engine and dropping 4 tanks in groups of 2

4986 dV in hanger

Flight 1 1228 dV left 3758 dV used

Flight 2 1283 dV left 3703 dV used

Linear using Skipper engine and dropping 4 tanks iindividually

5022 dV in hanger

Flight 1 crashed

Flight 2 crashed

Asparagus with SAS module using Skipper engine and dropping 4 tanks in groups of 2

4895 dV in hanger

Flight 1 1120 dV left 3775 dV used

Flight 2 1182 dV left 3713 dV used

Linear with SAS module using Skipper engine and dropping 4 tanks individually

4931 dV in hanger

Flight 1 1166 dV left 3765 dV used

Flight 2 1226 dV left 3705 dV used

It's definitely not perfect. I'm pretty sure it's not even as big of a change as asparagus changing is to onion staging, but it's definitely an improvement.

Edited September 10, 2013 by Leonon
I Learned something!

[pxi]

The line between genius and insanity is indeed razor-thin. This is probably the most kerbal staging yet.

[Javster]

Drag is calculated by part count isn't it??

[Jackissimus]

Drag is calculated by part count isn't it??

times drag coefficient of the parts

[Eric S]

times drag coefficient of the parts

And the mass of the parts, so low mass parts need a HUGE drag coefficient in order to significantly affect the overall drag of a craft.

No, I have no doubt this is as efficient as claimed. And enough of an abuse of KSP physics to feel REALLY creepy.

[Leonon]

I did not consider that the cross section wouldn't matter for drag. After reading your posts I checked the wiki and it says drag is based on total mass, not part count. Whichever it is, it loses part count and total mass more efficiently than asparagus staging.

That's why I compared their used dV and not just their total dV and remaining dV. Linear staging starts with more and uses less to get to orbit.

The line between genius and insanity is indeed razor-thin. This is probably the most kerbal staging yet.

Not even close. I saw one guy a while ago who had a craft that consisted entirely of solid boosters. It dropped at least one of its stages by overheating it with a higher stage. Apparently it was more efficient than having to lift a decoupler.

Edited September 10, 2013 by Leonon

[SRV Ron]

Drop tanks are an efficient way of shedding weight for interplanetary flight when TWR is not an issue. And, asparagus type staging of drop tanks is feasible.

One set dropped;

Both sets dropped;

Unrealistic is the tanks directly below the engine Goddard style. However, future updates could make that impossible without the use of a heat shielded cone.

Edited September 11, 2013 by SRV Ron

[Jackissimus]

And the mass of the parts, so low mass parts need a HUGE drag coefficient in order to significantly affect the overall drag of a craft.

Oh thanks, I actually wasn't aware of this! But it's stated clearly in here: http://wiki.kerbalspaceprogram.com/wiki/Atmosphere

[SRV Ron]

"Not even close. I saw one guy a while ago who had a craft that consisted entirely of solid boosters. It dropped at least one of its stages by overheating it with a higher stage. Apparently it was more efficient than having to lift a decoupler. "

Tried that once. The booster remained attached and killed all the thrust of the one firing nearly crashing the rocket as it fell back to kerban.