How to do precise landing on atmospheric planet

[Slam_Jones]

Another idea I've used is to equip airbrakes, but only use them intermittently to adjust where you're coming down. It's helped me a ton, might help others, too.

[Warzouz]

Another idea I've used is to equip airbrakes, but only use them intermittently to adjust where you're coming down. It's helped me a ton, might help others, too.

Sure airbrakes are the simplest control you can have. But this is very unprecise. And don't forget they can be absolutely needed not to crash.

Again, the OP didn't mentioned what it meant by "precise landing". 10m, 1km, 50km ?

[peachoftree]

If you're renetering just a capsule, you can do what they did with Apollo, use the bottom of the capsule for steering, it's not as effective as control surfaces but it does work. To steer, point the nose (t the pointy end) of the capsule up to go up, down to go down, left to go left and so on.

https://en.wikipedia.org/wiki/Space_capsule#Reentry

[cantab]

If trial and error isn't an option, a trajectory prediction mod isn't an option, and a spaceplane isn't an option then the only other thing I can think of is a "stop and drop" landing as described by mhoram, where you kill your orbital speed and descend vertically.

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

At Duna the delta-V cost should be manageable. At Laythe, Kerbin, or Eve it will be excessively high.

[mhoram]

And for this method, there is also an addon available:

http://forum.kerbalspaceprogram.com/threads/85838

[Warzouz]

If trial and error isn't an option, a trajectory prediction mod isn't an option, and a spaceplane isn't an option then the only other thing I can think of is a "stop and drop" landing as described by mhoram, where you kill your orbital speed and descend vertically.

At Duna the delta-V cost should be manageable. At Laythe, Kerbin, or Eve it will be excessively high.

Yep, I thought of that but discarded it due to dV. The isue though is you can't stop instantly. You'll deviate from you target and you'll have to close again while falling. But I think this is the best solution except using wings.

You example on Duna is valid. With high TWR engine, you could get quite close. But again, you'll have to eyeball it...

One Eve, that may not work. As LEO speed is 3000m/s, each second you miss the target you increase your distance by 3km. Burn should be ultra precise and quick.

But again eyeballing maybe not precise enough, depending on OP definition of "precise"