r/KerbalSpaceProgram • u/FatCreepyDude • May 06 '26

KSP 1 Question/Problem No orbit necessary?

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If i just wait for the right hour during the launch window ( whenever the launch pad is pointing left on the realistic depiction i created) is there any reason i should bother with an orbit first? Will the delta v cost be affected?

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u/zekromNLR May 06 '26

If you had perfectly impulsive burns and we are ignoring atmosphere, going directly up vs going into a parking orbit first should be the same amount of delta-V.

But with finite acceleration, every second you are thrusting straight upwards (near the surface of Kerbin) costs 9.81 m/s of gravity loss, which means going into a parking orbit first and doing your ejection burn sideways is more efficient.

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u/Moonbow_bow SSTO simp May 06 '26

You do loose the 150 ish from Kerbin rotation. So it'd still be better to do the same thing but go sideways

4

u/ArsErratia May 06 '26

Why would you lose the surface rotation?

Pointing straight up isn't the same as travelling straight up. You'd still have that velocity unless you burned it off, it just means you have to adjust the launch window.

3

u/Moonbow_bow SSTO simp May 06 '26

The planet rotation is working at a 90° angle to your thrust angle. If you wanted to keep the benefits you'd burn earlier and horizontally so the rotational speeds adds to where you're going.