Thus it is desirable to pile almost as much fuel onto the engine as it can lift to get maximum burn time out of the engine. Now, why is this the optimal TWR for making cost-effective rockets both in KSP and IRL? What it comes down to is rocket engines are expensive but fuel and tankage is cheap, relatively speaking. In KSP when you want to build a rocket which launches payload as cheaply as possible, often a launch TWR of around 1.25-1.3 is exactly what you want to use - at least for rockets which aren't using SRBs. At this time cost per tonne to orbit became a new and more legitimate metric for judging rocket performance. A little background: In KSP players who were optimizing for launcher weight would go for a TWR of 2.0 or higher, so players wishing bragging rights of "I launched 100t into orbit for only X tonnes of rocket" would go for a TWR of about 2.0 or even higher and this worked because a high TWR is extremely effective at mitigating gravity drag, a rocket with a TWR of 1.25 loses 80% of its thrust to gravity, while a rocket with a TWR of 2.0 loses only 50% of its thrust to gravity, a much greater fraction of the thrust is thus available for building velocity rather than fighting gravity and that makes the rocket significantly more efficient in terms of weight.īut as KSP development continued, career mode was released and the cost of rocket parts was balanced. So six 200 I sp engines still yields only 200 I sp.It is no longer generally considered optimal to use a launch TWR of 1.5-3 in KSP. When I sp is the same for all engines in a stage, then the I sp is equal to a single engine.Xenon (max full/empty mass ratio = 4.167)
Monopropellant (max full/empty mass ratio = 8.5) (These calculations use a full/empty fuel-tank mass ratio of 9 for all engines except those noted.) ISP(Vac) (s) No matter how much fuel you add you will never reach these ΔV without staging to shed mass or using the slingshot maneuver. Maximum Δv chart This chart is a quick guide to what engine to use for a single stage interplanetary ship. Use the atmospheric and vacuum thrust values for atmospheric and vacuum Δv, respectively. Fortunately for Jebediah, our dear Kerbals only have one brand of fuel to worry about.ĭelta-v (Δv) Basic calculation → See also: Tutorial:Advanced Rocket Designīasic calculation of a rocket's Δv.
#Ksp mac adjust thrust mods#
In real life, specific impulse is governed by things like combustion chamber pressure and propellant energy (hydrogen/oxygen is more efficient than kerosene/oxgyen). high thrust ratio (creates wobbling and reduces accuracy of burns) non-equatorial launch site (requires thrust offset, which screws with delta-v) non-equatorial target orbit (MJ have problems with inclinations) other mods (warranty void if used with other mods ) In your case you certainly scored on atmosphere, non-equatorial orbit and other mods. The higher the specific impulse, the more efficient an engine is! Specific impulse is used in important equations like THE ROCKET EQUATION (see next section) to determine how much oomph (or "delta-vee") you can get out of a given amount of propellant. Most engines are designed for optimal performance either at Sea Level (the big ones that drive your first stage and boosters, which have lots of thrust!) or Vacuum (where they won't burn as much propellant, but can be VERY efficient). Because this depends on the pressure of a rocket's surroundings, this can change between Sea Level and Vacuum (in space).
Specific impulse measures the efficiency of a particular engine. Specific Impulse (I sp) → See also: Specific impulse Most rockets, straight off the launch pad, will utilize a TWR between 1.5 and 2.0. If TWR is significantly above, say, 2.0, your rocket will ZOOM! But it might ZOOM too hard for your poor Kerbalnauts. You will need more engines, or perhaps MOAR BOOSTERZ! If TWR is less than one, then your rocket will not be going into space.
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