Help me improve efficiency

[FancyMouse]

I think you wasted too much landing on Mun - you're using ~1200 where it can be done in about 650.

[Enkiel]

I think you wasted too much landing on Mun - you're using ~1200 where it can be done in about 650.

usually, when i land on the Mun, i need to drop my last orange tank, which still old quite a bit of fuel, which could explain why the difference is so high.

[Acet]

Most of what those large boosters are doing is wasting fuel in lifting their own weight along with that half of an orange-tank of fuel to orbit. Also that stage 0 TWR is a bit low so you'll spend more fuel getting to orbit than with a bit better TWR.

I have a launcher design with a 30 ton payload which is one orange-tank with a Skipper or Mainsail under it (the former on the lower end of payload weights, just aim for 1.40 TWR at launch) surrounded by 8x columns of 1.25 fuel tanks with Reliant engines in an Asparagus staging configuration. I use it to launch entire science stations to Kerbin orbit, so it should be more than enough to launch your later lander design.

You might want use something like that and add a middle stage for the Kerbin-Mun part of the trip by which point the centre of your launch stage will just be for launch and you won't need to drag a half-empty orange tank plus Poodle all the way to the Mun. Something as simple as the smallest large fuel container surrounded by 24-77 engines gives at least 900 dV, enough for a Munar-injection.

As a more general rule, you should be aiming to leave things behind as you go along and progress from stage to stage of a mission, so as not to waste fuel dragging along elements which are not useful anymore. At the most extreme you might end up with a initial launch start stage (MOAR BOOSTERS), intermediate launch stages (asparagus), final orbital injection (the core launcher stage or even a separate stage), Kerbin-Mun injection/orbitter stage, lander stage and maybe even a separate return vehicle (although all this is probably too much).

Fortunately this is balanced with the cost (in credits, weight and complexity) of too many separators and/or not wasting more fuel in separators and extra engines than you gain in leaving them behind so one usually finds a point one stops adding even more stages (the initial launch stage and the separate return vehicle in my example above are usually too much).

In your specific case it seems that you could gain a lot from breaking your final-launch-stage/orbitter stage from your Kerbin-Mun transfer, whereby all the resulting savings in dead weight lifted to orbit would cascade into a 4/5-fold savings in the size of your ship in the launchpad.

[Chaos_Klaus]

Here is my new one ;

Well, this one has too low TWR.

It ist very important to choose the right engine for the right situation. Some engines are made for heavy lifting (Reliant, Mainsail, ...). They produce loads of thrust in atmospheres but don't work very efficiently. These engines are heavy.

Some are optimized for use in vacuum or at high altitudes, but lose thrust and efficiency when atmospheric pressure increases (Terrier, Poodle, ...). These tend to be very lightweight but low thrust.

Then there is engines for atmospheric use that perform slightly better in vacuum than the heavy lifting engines. (Skipper, Swivel, ...)

For andy maneuvers in space, you want the efficient lightweight vacuum engines! The give you more delta v per mass of fuel and dont weigh that much themselves. Remember every bit of weight you save on an upper stage will mean that you can go with a way smaller lifter!

So dont use heavy atmospheric engines for maneuvering in space *ever*.

If you don't have really heavy payloads, you can always go with the hybrid type engines like the Swivel or the Skipper. When you pass 20km, the air is very thin already and these engines will have the upper hand over Mainsails or the Reliant.

Don't automaticly go with asparagus staging. Most of the time it's overdoing it.

Also don't just skip over SRBs. They are terribly inefficient and "moar boosters" doesn't hold true with the new aero. However, SRBs can help you get of the pad. This way you can go with a rocket that has barely a TWR of 1 on the pad, strap some SRBs onto that and have it take of just fine. Use your throttle to stay below 270m/s below 10km to not cross the soundbarrier while in the thick parts of the atmosphere.

[Acet]

Well, this one has too low TWR.

It ist very important to choose the right engine for the right situation. Some engines are made for heavy lifting (Reliant, Mainsail, ...). They produce loads of thrust in atmospheres but don't work very efficiently. These engines are heavy.

In this later design the engine in the middle is a Poodle. This is not used at all until after both boosters are consumed and discarded (look at the staging configuration on the right-hand side). Judging by the dV of the first two stages, that Poodle is used to finalised Kerbin orbit and then for the Kerbin-Mun transfer and orbiting, which is why the author later said that he usually has about half an orange tank left that he has to discard when landing on the Mun.

This strange choice is the cause of the low launch TWR, the excess fuel in Mun orbit and the overall largish size of the whole thing given that the lander is not especially large.