How to do precise landing on atmospheric planet

[thedanieldude]

I want to know how to do a precise landing on a body with atmosphere WITHOUT trajectories or mechjeb

[The_Rocketeer]

Case by case. Your craft's drag and mass make a big difference, as will the planet in question. Precision in atmo is really hard to keep consistent, so it's best to make a quicksave and experiment.

[thedanieldude]

My save has quick save disabled. I need an efficient way that still allows a good margin for error.

[Tatonf]

Spaceplanes are the way to go. You can easily convert your potential energy to cinetic energy and pick a landing site.

Of course there's some limit, you can't reach the other side of the planet this way. You can add engines for more freedom.

[thedanieldude]

My lander is a sky crane for base parts. I was thinking about spaceplanes but the base parts wouldn't fit.

[Slam_Jones]

A general rule for returning from LKO that I use, is to aim beyond KSC, usually about twice the distance from KSC to the Island Runway (so aim a little past the Island).

Having wings helps a ton, since (as stated above) you can convert some of that vertical speed to horizontal speed, and gracefully land at the intended spot.

The aerodynamics of the individual vessel of course makes a huge difference, but (for me at least) this general rule gets me at least in the ballpark, if not right on the runway.

[Tex_NL]

I want to know how to do a precise landing on a body with atmosphere WITHOUT trajectories or mechjeb

Answer is pretty simple: practice.

That may sound pretty dumb but it is the truth. Only through trail and error will you learn at what point to make your de-orbit burn and how far to drop your Pe. The mods you don't want to use can speed up that learning process a lot.

[The_Rocketeer]

My save has quick save disabled. I need an efficient way that still allows a good margin for error.

I don't know seeing as I've never done it, but I would think if you find the persistent.sfs file, copy and rename it to something else you should be able to use is as though it was a quicksave.

[Red Shirt]

Definitely interested in this topic. I have not been able, even with MJ, to land anywhere close to KSC in 1.04. If MJ can't do it, I don't stand a chance. In .90 it would land on top of the VAB almost every time. On my own, I use to get close. Now, I seldom make it to the correct side of the planet. I'm OK with that, slowing down without burning up is a lot harder now, but I am trying to figure it out.

[Axelord FTW]

Q: I want to know how to do a precise landing on a body with atmosphere WITHOUT trajectories or mechjeb

Short answer: You can't.

Long answer: Any model you can come up with will be dependent on the ship's mass, angular cross sections, shape and orientation. With trial and error, you might end up with something akin to a 5km radius precision on a craft with minimal lift ratio/attitude control.

[genericeventhandler]

Definitely interested in this topic. I have not been able, even with MJ, to land anywhere close to KSC in 1.04. If MJ can't do it, I don't stand a chance. In .90 it would land on top of the VAB almost every time. On my own, I use to get close. Now, I seldom make it to the correct side of the planet. I'm OK with that, slowing down without burning up is a lot harder now, but I am trying to figure it out.

MJ has landed one ship between the pad and the sea for me with lots of returns, but mostly in the sea by overshooting. I don't like the way it aims way too low in an atmosphere and have been doing manual re-entries for a while now, I'm starting my burn to 40 km up, somewhere to the east of the giant crater, I usually come down in the mountains to the west of KSC, I've still not figured out where exactly to do my burn.

[Warzouz]

Answer is pretty simple: practice.

That may sound pretty dumb but it is the truth. Only through trail and error will you learn at what point to make your de-orbit burn and how far to drop your Pe. The mods you don't want to use can speed up that learning process a lot.

With a regular lander (airbrakes and chutes) that may not be enough. Landing site depends on orbit altitude + deorbit burn/PE, atmo density and ship aerodynamics.

Particing can be enough for returning LKO ships (not planes) near KSC. I do that a lot. But even I did it a LOT (50/100 times). I landed on KSC only 3 times, but always in 70km from it (usually 40km). Sure I don't have a precise mark where I must deorbit, but I know where to do it. Eyeballing is not enough for precision landing.

For a specific landing (closing on a pre-landed ship on a laythe or Eve...), you won't be able to do it with parcticing returning on KSC from LKO. You'll need reliable prediction mod like those th OP don't want.

Without that, your lander would need wings to glide and control surfaces, but that a heavy constraint on design.

- - - Updated - - -

MJ has landed one ship between the pad and the sea for me with lots of returns, but mostly in the sea by overshooting. I don't like the way it aims way too low in an atmosphere and have been doing manual re-entries for a while now, I'm starting my burn to 40 km up, somewhere to the east of the giant crater, I usually come down in the mountains to the west of KSC, I've still not figured out where exactly to do my burn.

From LKO, I usually burn 60m/s (exactly) on the western ridge of the big crater (which is usually in the dark, so I've to guess it). I usually land in water very near KSC. But again, that depends on the aerodynamice of the ship (I recover SSTO rocket stage which can weight up to 550T). How many airbrakes you use is very important.

Here is what I use :Cygnus Recoverable SSTO Rockets (15 to 600-tons)

Don't be too eager to land on KSC: KSC is 98%, 50km from KSC is 97% of dry cost. Precision may not be worth it.

But I don't think OP meant KSC reentry.

[Kobymaru]

I want to know how to do a precise landing on a body with atmosphere WITHOUT trajectories or mechjeb

My lander is a sky crane for base parts. I was thinking about spaceplanes but the base parts wouldn't fit.

So let me summarize...

- ANY body, not just Kerbin

- No MechJeb, no Trajectories

- No Wings

Yeah, you're pretty much screwed. I don't thinkt there is a way under these terms. Reentries are a very very "non-linear" procedure, if you are slightly higher or slightly lower in a specific phase of the descent, you might end up on the other half of the planet.

There's no way a human brain can do that, so you need math (in the form of a mod like MechJeb or Trajectories) to figure out where you're going to land.

Definitely interested in this topic. I have not been able, even with MJ, to land anywhere close to KSC in 1.04. If MJ can't do it, I don't stand a chance. In .90 it would land on top of the VAB almost every time. On my own, I use to get close. Now, I seldom make it to the correct side of the planet. I'm OK with that, slowing down without burning up is a lot harder now, but I am trying to figure it out.

I have no experience with MechJeb in 1.0.4, but I gotta say, the Trajectories Mod brings me really really close. Especially if I can do small corrections with a spaceplane.

[Warzouz]

I didn't test MJ for atmo renetry, but I use it on some vacuum landings I already did a lot of time. (I use the "land anywhere" feature). Beware that MJ can go very wrong with shallow angles... It crashed me quite a few time...

Now I only use it for touchdown (50/100 last meters) to get a very slow one (< 1m/s).

[genericeventhandler]

I didn't test MJ for atmo renetry, but I use it on some vacuum landings I already did a lot of time. (I use the "land anywhere" feature). Beware that MJ can go very wrong with shallow angles... It crashed me quite a few time...

Now I only use it for touchdown (50/100 last meters) to get a very slow one (< 1m/s).

Landing on Mun with MJ, if you start from 20km up (my standard orbit for mun) and use land at target, either chosen off of the map or at another lander. It will constantly put you down within 10m of the touchdown.

[mhoram]

The V1.0 atmosphere became much more complex that it was before. So doing atmospheric precision landings became really tough. Even with the trajectories mod I am happy when I get within 10km of the spaceport.

The following method should get you to a precision landing:

1. above the atmosphere reduce your orbital velocity to match the planets rotation speed

2. adjust your position to be exactly above the place where you want to land

3. descend through atmosphere

The viability of this method is however limited by a few factors:

- huge amount of dV for reducing the orbital velocity

- additional dV needed for slowing down the descent

- fast reentry makes additional protection against heating necessary

[RizzoTheRat]

I landed on KSC only 3 times, but always in 70km from it (usually 40km).

If you're regularly within 40km then you're not doing badly.

[Nathair]

If you're regularly within 40km then you're not doing badly.

[Warzouz]

To improove the landing at KSC, I should send a plane/rover to the crater to have a point of reference. By night, you can't even see the ridge or the crater itself. As the west KSC moutains are insta-kill for reentry, I prefer overshooting.

Delaying the deorbit by 10s will change you're landing location by 23km. This is less tahn 3° of a full orbit, so eyeballing is highly volatile.

Deorbiting from 60 to 65m/s make me going from overshooting 70km east of KSC to crashing to the mountains (100km west of KSC ?). Numbers are very important here.

[thedanieldude]

So let me summarize...

- ANY body, not just Kerbin

- No MechJeb, no Trajectories

- No Wings

Yeah, you're pretty much screwed. I don't thinkt there is a way under these terms. Reentries are a very very "non-linear" procedure, if you are slightly higher or slightly lower in a specific phase of the descent, you might end up on the other half of the planet.

There's no way a human brain can do that, so you need math (in the form of a mod like MechJeb or Trajectories) to figure out where you're going to land.

I have no experience with MechJeb in 1.0.4, but I gotta say, the Trajectories Mod brings me really really close. Especially if I can do small corrections with a spaceplane.

I am fine with using wings if I need too. I just don't want to use so many it becomes a plane.

[arise257]

I always tack wings onto my second stage lifters, then just deorbit them from LKO over the eastern coast of the continent west of "Africa". They glide very close to the base, then I pop the chutes -- easy peasy.

I totally don't mind my lifters and vehicles looking like aircraft. I mean, aren't they?

[Tarheel1999]

Precise landings are hard with trajectories. I'm not sure how you will accomplish it without. Not only do you have to make the right deorbit burn but you also have to carefully manage your attitude. To get an idea of what it is you are asking, I would recommend installing trajectories just to see how challenging it is with the data provided by the mod.

[Admac]

I'd say it's a combination of pilot skill and ship design. With no tools and the right ship I've been able to get within 2-5 km of a target on Eve, back in my Karborundum mining days.

Like an earlier poster mentioned, slowing down is pretty important. your trajectory is a lot easier to manage if it's more of a fall. on the same note, airbrakes and a hilarious amount of reaction wheels will allow you to rotate as you fall for minor corrections. it might take a few quicksaves to figure out the ideal entry vector and speed, but once you have it dialed in, you can be pretty reliable. I like trying to overshoot by 30-50 km so I can bleed of excess speed with parachutes and airbrakes on final approach.

Disclaimer: I totally used mechjeb to get detailed feedback on my exact position and predicted landing.

[Warzouz]

I am fine with using wings if I need too. I just don't want to use so many it becomes a plane.

As you would need at least some control over it to glide and target location, it'll be very much like a plane (or a space shuttle not able to climb)

[mpk10]

It's not a full solution, but one of the tricks I like to use for this problem is the altitude trigger on the parachutes. If you aim to overshoot your landing spot, then change the altitude trigger to something higher than your current altitude right as you pass over where you want to land. Drone chutes first if you're going too fast.