Lander control methods

[cephalo]

So I am getting a bit greedy and trying to land a science lab for my very first Mun landing. Since I've never really landed any type of lander before, I've been trying to practice on Kerbin, with entertaining but also worrisome results. (For one thing, you shouldn't try to land stuff on the launch pad. It's fragile.)

It's possible for me to take off and land this thing on Kerbin, but very difficult to get the appropriate thrust for velocity changes. Going up is easy, but coming down requires a very precise amount of thrust. Almost more precision than I can handle. A couple of pixels on the thrust indicator is the difference between coming down at 5 m/s for a soft landing or 20 m/s which tends to break things.

I'm at work thinking about what I'll try next, and I'm thinking that maybe the key is, instead of trying to land with the engines and possibly failing, I'll find a hovering thrust some distance from the ground where it's safe, and then push down with RCS. Not sure if RCS works in Kerbin's atmosphere.

How does everyone else do it?

Edited May 12, 2015 by cephalo

[Skorpychan]

First, I quicksave. That's the important bit.

Then, I get into an approximate hover before cutting thrust a little and cutting it back in to lose height in bits at once. If I'm on the Mun, this will generally be a few seconds of fiddling before I throttle slowly down into descent of the last few meters.

On Minimus, I tend to just say 'screw it' and kill the throttle, giving it a quick burst if I need to slow down.

Using RCS means taking my hand off the mouse and the camera control it gives. Not gonna happen, and I'm more comfortable using main engine thrust anyway.

Hell, I've even docked a craft using nothing but main engine thrust, because I forgot the RCS fuel. That was fun.

[andruszkow]

I usually burn retrograde until my horizontal velocity is near 0 and I'm falling directly down. Its easier this way, because you dont have to worry about anything but pointing your lander upwards when you reach the ground.

Then I make sure that for the last 1500 meters that Im not dropping with more than 60m/s which seems to be easy to recover from. Cut throttle and then throttle up bit by bit, until I see that my velocity is dropping slowly, continuously. I usually aim to land on the illuminated side of the Mun, so I can use my vessels shadow as a reference. When I start to see my own shadow, I aim to be falling at about 20-30 m/s, slowly increasing my thrust. Makes for controlled, soft landings at 5 m/s or less

- - - Updated - - -

See this youtube video, it's a nice guide

[TheXRuler]

To get a reasonably efficient and reasonably safe landing I recommend watching this video:

You can be quite a bit more efficient by doing kind of a reverse gravity turn by starting higher up and then coming down more steeply right at the end.

[Warzouz]

I would recommend not to land it but to send it on a somewhat polar orbit with pile of fuel and use an small(est) lander/hopper with a scientist to get data back. You can strip Mun of science in one mission. I did that on Eeloo and brought back 18000 science in beta 0.9. All biome visited in kerbal 2 days.

Simply just wait that you sation is nearly above the biome you want to visit to leave and land. Do some hops if you can (to save return fuel). then wait the "station" is above your lander to take off and you get a cheap docking

[Gaarst]

Practicing moon landing on Kerbin is a bad idea because gravity is 6 times stronger on Kerbin than on the Mun. You accelerate at a rate of ~10 m/s² on Kerbin which makes landings very delicate.

Hovering won't work because you consume fuel with engines on. Suppose you get a TWR of 1.00 (hovering) on the Mun at a moment, then say 20 sec later, you lander will go upwards because of your TWR going up as fuel is consumed.

Anyway hovering is extremely fuel inefficient and will waste huge amounts of fuel.

The most fuel efficient technique to land on a body is called suicide burn (basically falling and full thrust right before landing to brake), but there's a reason why it's called that way. It is very difficult, requires practice and not recommended for your first landings.

A good compromise is to let the ship fall and gain some velocity and brake every so often to maintain a reasonable speed of descent. Then when approaching the ground (you'll know using your shadow on the Mun, radar altitude in IVA or KER) brake to a few m/s to land softly and cut engines at touchdown to avoid bouncing. It may not be the most efficient way of landing, but it is rather easy and is what I used myself for early Mun landings without problems.

If you're not confident with landing on the Mun, try landing on Minmus first: gravity is far weaker (1/20 of Kerbin's gravity) and it has huge flat regions at sea level (0 m on altimeter) which are easy to land on.

[Geschosskopf]

So I am getting a bit greedy and trying to land a science lab for my very first Mun landing. Since I've never really landed any type of lander before, I've been trying to practice on Kerbin, with entertaining but also worrisome results. (For one thing, you shouldn't try to land stuff on the launch pad. It's fragile.)

...

I'm at work thinking about what I'll try next, and I'm thinking that maybe the key is, instead of trying to land with the engines and possibly failing, I'll find a hovering thrust some distance from the ground where it's safe, and then push down with RCS. Not sure if RCS works in Kerbin's atmosphere.

How does everyone else do it?

Well, the 1st thing is, do you plan on bringing the lab back home or leave it on Mun for future use? If you plan on bringing it home, 4 blue-tip chutes (or 8 gray-tips, or 16 radials) will set it down quite safely back on Kerbin so that's the easy part. Just have it shed any redundant parts like engines and fuel tanks after your do the deorbit burn and before re-entry and you'll be fine. This just leaves landing on Mun.

The most fuel-efficient, but also the most skill-required, method for landing on an airless world is the so-called "suicide burn". In this case, you do a deorbit burn from a reasonably "high" low orbit (30-100km or so, depending on the world) and then coast most of the way down. Then, at a point just before it's too late, you fire the engines full blast, timed so you stop just above the surface.

This takes a lot of trial and error to get right, and it also makes it hard to have fine control over the terrain of your landing spot because you can't really tell what the terrain will be like until you get down to it, by which time it's too late to do much about it without wasting all the fuel you were trying to save. Landing spot terrain is a big factor in Mun landings because the terrain alternates rapidly between reasonably flat and OMGTOOSTEEP! all over the surface due to scads and scads of small, steep craters you can only see from low altitude.

Thus, I do all my Mun landings using the way less-efficient but way easier and safer "stop and drop" method. In this scenario, you're the lowest safe orbit, which is about 10km. As your ship goes along, you carefully note the terrain just ahead. You get a very good idea of what it'll actually be like on the surface this way. When you see a likely spot coming, burn hard retrograde to kill off all your horizontal velocity right over that area. Then you just fall straight down, burning a little as needed to keep from getting too fast, then settle down gently once you get close to the ground.

Because I like explosions, I usually incorporate a Soviet-style "crasher stage" in my landers. This is also does the transfer, capture, and deorbit burns. Then it has some fuel remaining to be the "speed brake" for most of the descent from 10km down to the surface. When it runs out of fuel at low altitude (like 1km), I jettison it and finish the descent with the lander, enjoying the explosions as the crasher stage impacts. The range icons on the debris also tell me exactly how high above the ground I really am without having to look at the radar altimeter inside the pod. The lander then has the fuel needed to take off again and return to Kerbin.

[Dreambish]

I like to pulse the thrusters by spamming X and Z really fast. This removes the problem of fiddling with the clumsy shift/ctrl buttons and it also looks and sounds awesome.

(and is really inefficient I really shouldn't try to give logical advice. Just watch Scott Manley. Seriously.)

[Vanamonde]

As Gaarst says, landing on Kerbin is far harder than landing on Mun. Everything happens faster in heavier gravity. Have you tried adding a parachute to slow your fall to a more Mun-like pace? But really, you might be better off flying to Mun and practicing landing there.

[match]

You also can adjust the thrust on your engine to give you greater control. Right click the engine to adjust your max thrust to a more suitable range (multiple engines should be set to same level to avoid asymmetrical thrust). You can use this to fine tune orbits as well.

-Just remember to set them back up before you want to leave!

-oh, and learn to trust the nav ball... I also will use shadow to gauge altitude, but when trying to use outside references to make adjustments, it never ends well!

Edited May 12, 2015 by match

[Scarecrow88]

To get a reasonably efficient and reasonably safe landing I recommend watching this video:

You can be quite a bit more efficient by doing kind of a reverse gravity turn by starting higher up and then coming down more steeply right at the end.

I still plan my landings on Mun along the basis of that video, but it's not quite possible to do it exactly like that anymore, ever since the Mun surface was re-modelled and it's nowhere near as flat as that now. If you try to follow that method exactly these days, you're more than likely going to run into the side of a hill before you slow down enough to actually land.

[Rickenbacker]

Landing on the Mun is much easier than landing on Kerbin with engine power alone. Minmus is even easier.

And if you have a pilot that's level 2, cancel your horizontal velocity, hit the "retrograde" button and then just brake when you get close to the ground. The pilot will hold the ship reasonably straight, as long as you don't start going up again .