Walk me through setting up a landing on a particular spot (the crater 'center mountain' in the water) - how to judge PE / impact point with atmospheric deceleration?

[JoeSchmuckatelli]

I've got Val up in space in a save.  Craft is basically a lander, fuel can and a terrier.  Normal eastward orbit ~80km.

I've enough fuel to do a normalization burn (to get my orbit to pass over the crater) and then decelerate from orbit to get a landing.

I keep falling WAAAAAY short.

How do you guys eyeball this?  How far 'in front' of the intended landing spot should I put the PE/impact point to both account for the rotation and the air resistance?

I'd like to drop her on the island.

[Sorcie]

You can lower your orbit before deorbiting to help a little tiny bit. There is no way unless you did like some crazy math.

I used MechJeb for these functions in KSP 1. It had a landing simulation for aerobraking and landing.  It could deorbit you for a relatively accurate atmospheric re-entry (and land completely if you let it).

I think we're left shooting from the hip for now. F5 and F9 time!

[JoeSchmuckatelli]

Okay - figured it out; starting at ~ 60 km and setting the impact point on the far side of the water from the island did it for me.

 

Landed -almost- on top of it.

Long swim, but that's relative.  Definite "Gravity" vibes there at the end!

[Sequence]

My tactic is to intentionally overshoot the landing zone, and then apply trust towards the horizon when nearly over the landing site, and then descend vertically onto to target (its easier to slow down than speed up in an atmosphere). This isn't fuel efficient and requires keeping a stage with engines until the last minute, which will be harder once re-entry heating is added. 

One alternative is trial and error with quick saves until you get a gut feel for it. 

[thewhitemetroid]

@JoeSchmuckatelliWatch this. Not absolutely necessary but will help a great deal if you make a quick spreadsheet in excel with the info provided here, it will land you on whatever spot you want everytime. Otherwise you can just do the calcs as needed, not hard either.

https://www.youtube.com/watch?v=38IYZUizX3E&list=PLYu7z3I8tdEmqpOkQZCl5SZB5t0vXuxE0&index=9

[The Aziz]

I completely lost him when he got to the "math triangle".

"Quick spreadsheet in excel" bruh I'm playing, not working in JPL. Quick and spreadsheet don't go together very well.

You know, it's all fun when you have engines, but aiming an unpowered vehicle is not that simple when all you have is atmospheric pressure and a parachute. If a game at some point wants me to perform accurate landings, it better provide tools for it. If a mod could do it, the game can as well.

Edited March 19, 2023 by The Aziz

[thewhitemetroid]

8 hours ago, The Aziz said:

"Quick spreadsheet in excel" bruh I'm playing, not working in JPL. Quick and spreadsheet don't go together very well.

HaHa, I hear ya. I get satisfaction out of doing some calculations myself and seeing that translate into the game successfully but I also don't want to be too bogged down with stuff like that. Mod tools would be nice but I resist the idea pointing my cursor at a point and saying "land here mod". A mod tool that functioned like this spreadsheet in game would be very nice for me though because it would make me feel more invested in solving problems with space flight and such. It's a balance and subjective matter though. 

I hadn't considered the possibilities of unpowered vehicles so yeah, this wouldn't work here. I also failed to read carefully the OPs problem facing atmospheric deceleration, which this video does not address,  sooooo...anyway this is still a powerful tool and maybe can still narrow down that entry point even further.

[The Aziz]

11 minutes ago, thewhitemetroid said:

Mod tools would be nice but I resist the idea pointing my cursor at a point and saying "land here mod".

Automatic landings never worked for me anyway, at least not very efficiently. But I'd like to (and I used one) a tool that simply shows me "you'll land here if you do that". Nothing more. Something that takes into account atmospheric drag (assuming you don't wiggle the craft of course), body rotation, actual distance to target at ground level. It's been done before.

[JoeSchmuckatelli]

9 hours ago, The Aziz said:

spreadsheet in excel

Yeah - well I'm nerd enough to give it a try. 

 

Love me some spreadsheets!  (Also - I don't have a job that makes me use spreadsheets... So any time I'm in Excel it's because I am goofing off!)