How to land at KSC?

[OldLost]

Someone posted this tip on how to land at KSC (or any other predefined spot), but refused to expand on it:

Know where you will land on Kerbin when you are returning directly to Kerbin without orbiting in between accurately and with little dv cost:

For accurate landing in Kerbin know that the Kerbin day is 6 hours long. So when returning from a high aopsis (mun, minmas or any other planet) as soon as you get into Kerbin's sphere of influence fast forward to the nearest multiple of 6 hours before your projected landing time (6, 12, 18, 24 etc). Check out where you will be landing on kerbin at that time (ie let's say 30 hours before you actually get to Kerbin).

Your landing point shown will be your actual landing point geographically as Kerbin will exactly rotate 5 times before you land (6x5 = 30). Simply adjust your course slightly to pick your preferred landing site. Given you are so far away dv costs are minimal.

You can also use this on any other body as long as you know how long their day is. This usually allows me to land those early missions within 5-10km of the space centre with little do cost.

Could someone explain what he's talking about? How do you "fast forward"? And what does he mean by "your landing point shown"? KSP does not show me where I'm going to land, at least not on a world with an atmosphere; it just shows me where the current orbital path intersects with the the planet, which given atmo drag is quite a bit different.

Or, if you have another way to bring a craft down (spaceplane or rocket) so you end up close to KSC, I'd like to know, as I haven't figured out the trick yet. Thanks.

[Vanamonde]

By "fast forward," OP means the game's ability to accelerate the passage of time, "warp." with the keys: > and < for faster and slower. And by "shown," OP is talking about the point where your blue projected path line intersects the planet's surface. And yes, that is not taking into account atmospheric braking. OP is merely pointing out that the same landing site is presented to you every 6 hours.

[Scarecrow88]

I think what he is saying is that if you are returning from somewhere with a course that will take you straight to the surface i.e. no establishing an orbit first, you should use the time warp function until your flight time to reach the surface is an exact multiple of 6. This will then show which part of the planet you will be arriving at, not allowing for atmospheric drag. Usually you need to aim a bit to the east of your intended landing spot to allow for drag slowing you down, but the exact amount will depend to an extent on your speed on arrival, and the angle that you come in through the atmosphere.

ETA : Ninja'd

[OldLost]

I thought maybe he was talking about warping as well, but then his later statement doesn't make any sense, in that if you warp until you're close then you're no longer "so far away dv costs are minimal". So he must mean something else.

FYI Original post is here: http://forum.kerbalspaceprogram.com/threads/124749-Pro-tips

[A35K]

If you don't mind using mods, MechJeb has a landing guidance thing which basically calculates your landing site including the effect of drag and rotation and shows it to you on the map. It is extremely useful for pinpoint atmospheric landings.

[monstah]

Not until you're really close, just until you're the closest integer multiple of 6 hours away.

So, if you're 20-something hours to periapsis, warp until you're at 24 or 18. If you're 15-ish, warp until 12, et cetera.

[OldLost]

If that were true, then his statement "Check out where you will be landing on kerbin at that time (ie let's say 30 hours before you actually get to Kerbin)" would not make any sense either.

Given this hasn't been answered almost immediately with something akin to "dude, he means do x, y, z to see your landing point, duh", it must mean he's probably FOS like I thought.

[Rhomphaia]

If that were true, then his statement "Check out where you will be landing on kerbin at that time (ie let's say 30 hours before you actually get to Kerbin)" would not make any sense either.

Given this hasn't been answered almost immediately with something akin to "dude, he means do x, y, z to see your landing point, duh", it must mean he's probably FOS like I thought.

If your periapsis is touching the surface of Kerbin, And you are 30 hours from periapsis, then the point where your periapsis is now, is where you will land in 30 hours.

Whats not to understand?

[ajburges]

What he means by minimal dV cost is that the further out you adjust suborbital trajectory, the less dV it costs. You want to do the adjustments a multiple of six hours out so you know where KSC will be. (or use a mod to map body fixed trajectory)

Keep in mind this method of step suborbital reentry will be (relatively) violent. Your ship should have good thermal mass or a heat shield to blunt reentry heating.

Without mods, the only way to predict reentry is through trial and error. Use a reproduceable decent (prograde, retrograde, dead stick, or manual) and see where your reference should be. A popular approach is deorbit burn on the far side from 75² to set Pe to 45 km over KSC. Correct for over/undershoot by adjusting Pe height on future attempts.

Edited June 12, 2015 by ajburges

[OldLost]

Say you're exactly 30 hours out. Your periapsis is 71m above Kerbin ASL, and is exactly on top of KSC. I bet you dollars to donuts you won't be landing at KSC. You won't end up anywhere close. You'll end up hundreds if not thousands of kilometers West.

That's what's not to understand.