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Not enough delta v with RSS


louis.garriga
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Hello, I play Kerbal Space Program with Real Solar System for two weeks now and I always have the same problem: It's really hard to reach the delta-v required to put something in orbit. I never have more than 10 000 m/s of delta v(I know it's enough for an orbit but if I want to send something to the moon or a other planet that's a problem). Did I need something for my engines to fit the mod ? Or did you have any advice to build rockets please ? Thank you for your answers.

 

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Curiously enough, the topic that was at the top of the topic list at the moment you posted talks about getting moar dV! Not that you should be surprised that getting enough dV into a rocket is hard - it's the primary bugbear of all Real Life rocketry.

In general the fixes are:

  • Use more power on your bottom stage so you minimise the amount of energy wasted in lifting the tanks and fuel of the bottom stage. You can achieve this by either swapping the engines for more powerful ones, or adding on bigger/more boosters.
  • If you use LF side-boosters on the bottom stage, then play with using fuel-lines to cross-feed fuel to the core booster. That way, the core stage gets up to some altitude and speed with a full tank of fuel instead of getting there half empty. Yes, the boosters drop off sooner and that can feel wrong, but that way you waste less dV on getting them higher up. (you will need to compensate for the reduced power/weight ration of the core booster by starting with a slightly less aggressive turn, then turn harder once the side boosters have detached.)
  • Use lighter engines on mid and upper stages. Lighter upper-stage engines require less energy to get them up, so the lower stages put more of their energy into lifting payload as opposed to lifting upper-stage engines. Higher Isp mid-stage engines can help get  the upper stage and payload into orbit more efficiently.
  • Play with just how much fuel you use in mid- and upper-stages. You may find you have too much fuel higher up than you actually need, forcing the bottom stage to waste fuel lifting that fuel. Counter-intuitively, it turns out that adding fuel to upper stage can be counter-productive! Above all, make sure your payloads have no more fuel than they need to do their job - adjust their fuel loads in the VAB to trim their dV to the essentials (plus a wee bit) before launch. For example: an imitation Apollo CSM with a full fuel load will be a real pain to launch:- NASA never launched the Apollo CSM with a full load as its engine and fuel tanks were severely over-specified! (Because history.)
  • Experiment with using Real Fuels, and using HydroLox engines. Use RP1/Lox for the bottom stage to give it the best oomph without oversized tanks, and HydroLox for the mid stages to minimise their mass. If you want to play realistically, use hypergolic fuels for your payload engines, ie Apollo-style CSM, otherwise consider using HydroLox.

Good luck!

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Stock parts and stockalike part mods are balanced around smaller scales than RSS. Consider using one of these mods with RSS 10x scale:

The SMURFF mod patches ISP and thrust of existing parts to give a better RSS experience. SMURFF has a relatively small learning curve.

Realism Overhaul mod is a much more comprehensive RSS experience. It changes a lot: throttle can't be adjusted as much, engine restarts are limited, fuel sloshes around in tanks, etc.

I suggest trying SMURFF first. Use a sandbox save, build some rockets, then if you think SMURFF is too easy give RO a try.

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