Gliding back to KSC...On Earth

[G'th]

So I've been playing with my new shuttle design, and up to this point its essentially 100% operational except for one key aspect, which as the title says is managing that glide back to the Runway. Now, the actual glide is easy. I can land my shuttle any day in any condition. The issue is putting it in a position to actually land at the runway.

On Kerbin, this was easy as I as able to use the Trajectories mod to put my projected landing site on the landmass on the other side of the water from KSC, and as I re-entered, the landing site would adjust to just ahead of the KSC mountains, which was perfect for a glide to the runway.

However, I'm not on Kerbin anymore, I'm on a Kerbin-sized Earth. As such, the 28 * inclination of KSC makes getting that trajectory a bit trickier. Thus far, the best I've managed was a landing in Cuba. No amount of tweaking my trajectory has been able to give me that perfect site at KSC yet. Or even anywhere near it so that I could then use my glide time to get to the runway.

So, my question is do you guys have any tricks for actually accomplishing this?

 

Should also be noted that while yes, I could just add jet engines to my shuttle and greatly reduce the requirement of getting as close to KSC as I can, that kind of defeats the point.

[Vaporized Steel]

I have no actual answer for you to get to precise landing calculations. But we may be able to nail it down closer then Cuba.
First of all, can you use the trajectories mod in RSS still for calculatinr orbital Trajectories?
The reason you land short is because of Earths rotational speed while being on a inclined trajectory. So even although you may be able to land near or exact to the location based on a orbital trajectory calculation the rotation of earth shifts your surface landing area when your orbit is inclined against the landing target.

You know this ofcourse, the reason I'm telling is because I want to ask if this is the only parameter that causes you to land off target.
Can you confirm this, can others confirm this?

You could try the following.

If it is the only reason for missing your target then what you may do is use a maneouvre node where you'll retro burn to calculate the amount of time from a set maneouvre node to the KSC (let's say it's 50 minutes).
First do a hyperedit test and see how much  time is added to that maneouvre node calculation in actual flight time. Because the actual flight time will take longer because of aerobraking.
If you do that you'll only know the added time for aerobraking under the same descend profile and it will never be the same exactly depending on your maneouvring through the atmosphere but you may be able to nail it down within 10-20 seconds difference. Let's say the maneouvre node said 50 minutes, and a static descend profile test get's it to 52minutes and 30 seconds.

Now calculate how much the earth surface would have rotated in 52 minutes and 30 seconds. Thats 3150seconds!
3150 x 465.1 = 1451112 meters. Which is 1451.1112 kilometres. Your landing in Cuba seems plausible depending on your time through the atmosphere from your maneouvre and to land.

This method does assume there still is a Trajectories mod function for orbital calculations for RSS or any similar mod, and I don't think it covers everything to make your precise landing. But it will probably get you closer to KSC then Cuba.
You may also want to calculate the surface distance change in case you land at a target on a higher or lower latitude as they will have a slower surface speed. I'm not sure how exactly the KSC is located on the equator, meaning whether it is exact. But land anywhere else and you have to deduct earths rotational surface speed since the constant of it is based on that of the equator.

As for knowing how to calculate the distance needed for aerobraking to know whether you land long or short, I don't know. In any case it seems a very hard thing to do in RSS. I wouldn't even try it. If your shuttle is capable of steeper descends, coming in from a higher alttitude on a steep aerobrake descend can make for a more precision landing. The question is, how steep of a descrend profile and your shuttle take without exploding into pieces.

Edited June 22, 2016 by Vaporized Steel

[bewing]

Are you waiting until KSC is at a node before you try your reentry? Are you orbiting on the equator? Or is your orbit inclined, too? As VaporizedSteel says, you have a significant job to do, predicting the location of KSC, half an orbit in advance -- when you are doing your reentry burn.

[G'th]

Ya know I appreciate the wonderful info @Vaporized Steel listed, but in the end I just decided to cheat and look up where the real Shuttle started its de-orbit burn for most missions. Ergo, wait until my orbit is intersecting KSC and the Indian Ocean, put a node, and bam Trajectories gave me a projected landing right where I needed it to be. After that it was just a matter of using RCS to maintain the position as I re-entered. (Which is realistic, IIRC, as the Shuttle did have to adjust its trajectory high in the atmosphere with its RCS, just as Apollo did*)

Trajectories Mod does give me decent Trajectory info, but unfortunately it doesn't automatically compensate for the issues that were causing me to be off target thus far. It projects where I'm going to land but it doesn't actually lock to any landmass or ocean point, and instead appears to lock to a position in the atmosphere at X altitude (Which correlates to whatever the altitude is at my landing point) rather than the actual surface I'm going to be landing on, which in turn means that by the time I reached this point, the Earth has rotated away from me. This may be something I have to bring up to the mod author, for if the mod can actually compensate for these issues properly that would be a huge boon. 

Granted, this is just for a basic 28* orbit, but it does give a better idea of the angle I need to have between my node and KSC, which will help when coming from different inclinations.

 

*IT should be noted that Vaporized's info is more for ballistic re-entry more than anything else. As my Orbiter has significant glide time, it doesn't actually need more than what I'm able to get now as far as a trajectory goes. I can come out of reentry short or long and still make it to my landing point. For a propulsive rocket landing, ala Space X, Vaporized's info would apply more to it. My needs were more for how to determine where to de-orbit in order to get close enough to KSC for my glide time to be able to cover the rest. Using the real Shuttle as an example has given me a baseline to go off of for other inclinations.

Edited June 23, 2016 by G'th
Clarifying.