...determine when should I begin braking while landing on Mun?

[Ascimator]

I use the smallest engine. My problem with landing on Mun is that I either start braking too soon, and then I am forced to freefall again, or I start braking while too low and crash.

I do not want to use MechJeb, as that does not feel like an accomplishment to me.

[Cykyrios]

There is no rule for this, but you should always keep an eye on both your speed and altitude. Assuming you have already killed horizontal velocity, make a short burn (a few seconds) and see how your speed changes. That should give you an idea as to how your ship is able to slow its free fall. Keeping in mind that getting close to the Mun means you will need more thrust, you can eyeball when to burn.

I personally like to make several burns rather than a big one that may begin too late, but with practice, you can save some fuel.

[Serratus]

My tip would be to make sure that when You are below 10Km 1) You don't have any horizontal velocity, 2) Your vertical speed is <300m/s

Then Burn/free-fall until You get to ~1000 (assuming You don't want to land on a mountain), keep speed uner 100m/s and keep slowing down until touch-down at ~2-1m/s

One long burn is not really possible since we don't know at what alt. we are landing... And You would need to be able to do an enormous amount of maths in Your head anyway.

[maltesh]

On the first few attempts at landing, I would recommend putting your spacecraft into a low Munar orbit first (say 10-15km or so). It's not as efficient as going straight on in, but definitely relieves the pressure on a straight-in descent

My general rule-of-thumb for final descent is below 10,000 m, keep velocity at about 1/100 altitude in meters... e.g., 50 m/s at 5 km. When I hit the danger zone (about 1 km above the local altitude), it's <10 m/s all the way down, with a soft-landing at ~ 1m/s.

If I'm not Mechjebbing, I typically determine the local altitude through prior knowledge (Minmal lakes are 0 altitude, Most of the Munar surface at moderate latitudses is about 1-2 km altitude), or by throwing my last pre-lander stage at the Mun and seeing how far away it is when it explodes.

Edited August 21, 2012 by maltesh

[bsalis]

Keep at it. You will get better with practice.

I use the smallest engine.

Might help to have more thrust until you get a better feel for it. Plenty of fuel is also nice.

[Rwisaak]

I find that using your shadows for the final few dozen meters helps get that last bit done as well. Without them it can be hard to tell sometimes how far you are from the surface. Obviously landing on the dark side doesn't help.

[Kosmo-not]

I do my braking burn at about 3km (at periapsis) since that's pretty much the lowest safe altitude for the Mun. If I don't like my landing area, I can always stop my burn after I circularize and wait for another one. I don't worry about my horizontal velocity because it can be easily zeroed out just before touchdown (when velocity is around 5 m/s). This is the easiest, safest, and most fuel efficient way to land.

[EndlessWaves]

It'll depend on the weight of your lander as well as how much thrust you have. If you've got a 3 kerbal pod and a jumbo sized fuel tank you'll have to start burning long before you would with a 1 kerbal pod and mini fuel tank.

My first munar rocket required around 50,000m to slow down, the second one would do it in 15,000m.

Have a look at which height you stop at and subtract that from the height your started at to get an estimate of what you need to start at next turn. I'd guess it's probably an underestimate (gravity is stronger near the surface) so start a bit above that.

[sal_vager]

Gods Kosmo-not, 3km?

I tend to deorbit at 5km as a minimum, and that's only with very light landers, it'd be much higher with a large vessel, say about 10 to 15km.

[Shadownailshot]

I only do it the complicated, slow myself down slowly way when landing munbases, or my standard apollo-style lander that only has the large lander engine on it. After I saw the curiosity landing though, I decided it was time for a very risky, high speed landing with a rover made from stock parts! I drop in towards my base at an angle similar to an atmospheric entry, and slowly burn (simulating a parachute) with the four aerospikes I have mounted around my rover, until I'm going vertical, then I freefall till I'm about 500m actual altitude, then dumb a ton of thrust into it. By the time I'm 10m off the surface, I'm about to start going back up, so I drop the rover, and let my makeshift skycrane fly off into oblivion.

EDIT: Oh, and yes, my rover is equipped with a rocket in case I get bored on the mun and have enough fuel to return home.

[Binky]

If I'm landing in a crater or mare, I generally work on decending at a rate, in m/s, of 10% of my altitude ( ie at 2000 m, decending at 200m/s, 100m at 10m/s etc) This does require knowing the TWR and Delta-v of the lander module so you know you can both slow down at that rate and not run out of fuel 47 metres off the ground (... like I've done >.<), which the Engineer mod is very helpful for. Or good ol' maths, which is my prefered method.

In the highlands, I tend to halve my descent rate below 3000m, because suddenly seeing your shadow come up to meet you when your altimeter is saying '2100m' is... unpleasant