Speed

[royalkingofgames]

speed is a funny thing and very complicated.

when landed on kerbin your at 0m/s but your not. the planet is rotating so your at 174.5m/s but then kerbin is orbiting the sun so youre at over 9284.5m/s.(K)

This gets more complicated orbiting kerbal. say your orbiting at 100km and say your moving at 4000m/s (S)then when your ships orbit is traveling kerbins pro-grade your traveling k+s which is13284.5m/s. and when your pointing kerbin retro-grade your traveling k-s which is 5284.5m/s.

this is subject to many laws about circles and angles but this is just a generalization.

Also i made up the names k and s and theres probably proper names for it.

dont be to harsh im only 12

any-way now planets are implemented this will come into account when interplanetary transfers are possible. this info should be displayed to help.

BUT HOW that is why i said all this

Edited September 7, 2012 by royalkingofgames

[Legoasaurus]

A very intresting point! While this is, of course, very true, I'm afraid i don't think that it'll be very relevant to transferring from planet to planet. The whole thing is relative to the body you're currently in orbit (or not) around, and so when moving from one body to another, the velocity readout changes. In a mission to another planet, the most efficient way to do so is (at least as I see it) to move to orbiting Kerbol and then grow the orbit out to the other planet. But I digress. The system should work perfectly fine for interplanetary transport, just as it does for Mun-Minmus missions. Besides, the only time I really use it is when I'm coming down to a body, and I don't want to know my total velocity relative to Kerbol at that point.

[royalkingofgames]

true but it should be for advanced calculatins

[maltesh]

A very intresting point! While this is, of course, very true, I'm afraid i don't think that it'll be very relevant to transferring from planet to planet. The whole thing is relative to the body you're currently in orbit (or not) around, and so when moving from one body to another, the velocity readout changes. In a mission to another planet, the most efficient way to do so is (at least as I see it) to move to orbiting Kerbol and then grow the orbit out to the other planet.

I'm afraid you're incorrect here. You can save large amounts of fuel by taking advantage of the Oberth Effect, and burning from low orbit into a trajectory that allows you to coast directly into your transfer orbit.

For instance, consider a spacecraft starting from a 100km Kerbin orbit, going at about 2.1 km/s. Assume you want to get it to escape Kerbol. (Escape velocity at Kerbin's altitude, about 13.1 km/s)

To run that spacecraft up to Kerbin escape velocity from that altitude (about 3.2 km/s) requires a delta-V of about 1.1 km/s. That will put you just outside Kerbin's SOI at rest relative to Kerbin, moving at Kerbin's orbital velocity of 9.3 km/s, and you'll need a delta-V if about 3.9 km/s to reach Kerbol escape.

Total Delta-V from 100km orbit by burning to escape, then escaping and burning to Kerbol escape velocity, about 5.0 km/s.

Instead, let's take advantage of the Oberth affect, and burn up to about 5.0 km/s from that 100km orbit, (Delta-V 2.8 km/s) timed so that we cross the SOI boundary, we do so in precisely the direction that takes us across the SOI boundary moving in the direction of Kerbin's orbit. When we cross the SOI boundary, we'll still have 3.2 k/ms of that velocity with us, which, when added to Kerbin's orbital velocity, takes you on Kerbol escape.

Total delta-V, 2.8 km/s. In this case, a 44% saving in required delta-V to reach Kerbol escape, which results in very significant savings in fuel and corresponding spacecraft mass.

When going from Kerbin to interplanetary destinations, in almost every case, you wind up with significant fuel savings by burning directly into your tranfer orbit from as low a Kerbin orbit as you can manage.

[Rickenbacker]

speed is a funny thing and very complicated.

when landed on kerbin your at 0m/s but your not. the planet is rotating so your at 174.5m/s but then kerbin is orbiting the sun so youre at over 9284.5m/s.(K)

This gets more complicated orbiting kerbal. say your orbiting at 100km and say your moving at 4000m/s (S)then when your ships orbit is traveling kerbins pro-grade your traveling k+s which is13284.5m/s. and when your pointing kerbin retro-grade your traveling k-s which is 5284.5m/s.

Hence the 'surface' and 'orbital' speed modes, when close enough to the surface of a body, your speedometer shows your speed relative to the surface, which means 0 m/s when landed.

[sp_blazer]

Got to love good old relativity