Problems Landing on Minmus and Mun

[Skylab]

Hi, KSP newbie here! Whenever I try to land on the Mun or Minmus, the slightest amount of thrust sends me hurtling back up, on an unwanted trajectory. When I finally do land, I wind up miles away from my original choice for a landing site. Does anyone have any tips that would help me avoid this?

Edited September 27, 2014 by Skylab

[SlimeCrusher]

Hmm... What engine are you using for the lander? You can maybe post a picture of the craft too.

[Tex_NL]

How do you land on Mun?

Practice, practice, practice!

No, seriously. It can be hard at first but it will get easier over time.

If only a tiny amount of thrust sends you back up your TWR (thrust weight ratio) is too high. Your engine(s) are too strong. An obvious solution is to use a less powerful (and usually more efficient) engine. Another is to right click your engine and limit the max thrust to for example 25%. Now the full length of the throttle slider goes from 0 to 25% power instead of 0 to 100. Making the slider 4 times more accurate.

For max power simply right click the engine again and set max thrust back to 100.

[Broax]

Well... I'm no expert but on the Mun (and much more on Minmus due to its lower mass) small thrust gives much more acceleration then on (for example) Kerbin. Not to mention that there is no atmosphere to give drag...

Anyway, as for precision landing it's a bit hard to accomplish. There are a couple of tutorials around the internet regarding that but as far as I know, one of the most used techniques (aside from just using mechjeb) is to set up a series (two, maybe three is enough) of maneuver nodes near the desired landing spot making sure to first kill all horizontal velocity and then focus on vertical velocity. For that I highly recommend Kerbal Engineer Redux... It's an informational Mod that tells you your horizontal/vertical velocities as well your actual altitude (instead of sea-level altitude that is displayed on the game GUI).

I hope this helps... Good luck..

[Skylab]

Hmm... What engine are you using for the lander? You can maybe post a picture of the craft too.

I'm using an LV-909 for the lander. Do you think I should use a smaller engine?

[BDelacroix]

You can sneeze yourself into escape velocity on minmus. Mun is a bit easier.

[diomedea]

I'm using an LV-909 for the lander. Do you think I should use a smaller engine?

LV-909 is perfect for Mun landings with most "normal" landers, but if yours is very light it may still be excessive. On Minmus gravity is so low, it could be possible to takeoff with RCS only. Really what you should be looking at is the TWR while on Mun or Minmus (that is much higher than it would be on Kerbin), but computing TWR may be a bit much if you are still new to KSP, you may want to use a add-on like Kerbal Engineer Redux to have that reading. A TWR = 2 is generally the best.

Also, practice is very important. Thrust changes may be too sharp if you can't make very fast button presses on left-ctrl and left-shift. I use a joystick and that helps a lot to finely modulate the amount of thrust.

[dzikakulka]

You may also consider some fine controls mod providing thrust increments/decrements on key taps or 100% throttle on tap or even better 100%-0% toggle. Usually they're really helpful while being small, simple and not problematic at all.

[Skylab]

Thanks for the help, guys. I'll be sure to try your suggestions.

[Frank327]

One last tip, you don't have to land at 1m/s. Landing legs can take landing speeds of at least 8m/s, especially on moons. So make sure you're gentle with your throttle and remember that it's better to have a hard landing than to bounce around all the time.

[Sirrobert]

If a tiny amount of thrust throws you off course, at what speed are you trying to land? Sounds like you're aiming for extremely slowly.

The lander legs are actually pritty sturdy, and they'll be fine if you touch down at speeds up to 10m/s (they might even be able to take more, but I usually take that as a max)

[Skylab]

If a tiny amount of thrust throws you off course, at what speed are you trying to land? Sounds like you're aiming for extremely slowly.

The lander legs are actually pritty sturdy, and they'll be fine if you touch down at speeds up to 10m/s (they might even be able to take more, but I usually take that as a max)

I usually aim for about 6 m/s

[Kryxal]

For Minimus, slower is better right there at the end, you don't need to bounce.

[SRV Ron]

If a tiny amount of thrust throws you off course, at what speed are you trying to land? Sounds like you're aiming for extremely slowly.

The lander legs are actually pritty sturdy, and they'll be fine if you touch down at speeds up to 10m/s (they might even be able to take more, but I usually take that as a max)

If your lander is as overpowered as this, you need to pulse the engine at the lowest power setting and watch that your decent speed doesn't slow down too quickly.

[sonicsst]

I think you can also click on the engine and change the thrust limiter in flight. This would help a lot.

[RizzoTheRat]

Useful tip on the thrust limiter but I'd be worried that I'd get it wrong and need full power but can't access it fast enough

If you've not already seen it watch Scott Manley's tutorial on landing on Minimus, his approach of burning retrograde to keep your speed to 100m/s or so on the way down mean's you get a good feel for the controls before you get low enough that it really matters.

I used an LV-909 on my Mun lander which was probably quite a bit heavier than it needed to be and I still ended up over doing the thrust a few times at low altitude. I think the above post has got the gist of it, practice, practice, practice.

[capi3101]

If the LV-909 is giving you too much thrust, you might consider switching to a 48-7S; it's still plenty powerful for Mun and Minmus landings and it's what I generally use on my designs once it's available.

What's the configuration of your lander, anyway? By which I mean what parts are you using? It'd give us an idea of just exactly how light of a lander you're using. I suspect it's a very basic design - maybe a Mk1 Pod, Mk16 Chute, FL-T400, LV-909, 2xZ-100 batteries, 2xOX-STAT solar panels, and 4xLT-1 landing struts - and if that's the case there's definitely some suggestions we all can give you to improve your general design.

[Skylab]

If the LV-909 is giving you too much thrust, you might consider switching to a 48-7S; it's still plenty powerful for Mun and Minmus landings and it's what I generally use on my designs once it's available.

What's the configuration of your lander, anyway? By which I mean what parts are you using? It'd give us an idea of just exactly how light of a lander you're using. I suspect it's a very basic design - maybe a Mk1 Pod, Mk16 Chute, FL-T400, LV-909, 2xZ-100 batteries, 2xOX-STAT solar panels, and 4xLT-1 landing struts - and if that's the case there's definitely some suggestions we all can give you to improve your general design.

Yep, my lander is pretty much exactly how you described it. I'm not sure I actually need to change my design that much though; I'm starting to think that I can probably solve my landing problem with a bit more practice. Still, if you have any design tips you think I should know, I'm all ears.

[Wanderfound]

Yep, my lander is pretty much exactly how you described it. I'm not sure I actually need to change my design that much though; I'm starting to think that I can probably solve my landing problem with a bit more practice. Still, if you have any design tips you think I should know, I'm all ears.

For building:

* Build wide, not tall.

* You don't need a lot of thrust, or a lot of fuel. You also don't need that much RCS fuel.

* You probably don't need as many lander legs as you think, either. Place them as low as you can, though.

* Balance your RCS.

* One or two goo pods are plenty, you don't need a bunch. Go easy on the lights and other gadgets.

For landing:

* Set a low (<10km, <5km is better) periapsis, taking care not to clip a hill on the way in.

* Once you're almost over the target, point retrograde and burn.

* Watch your VSI (to the right of the altitude meter). Reduce vertical speed by pitching up, increase it by pitching down.

* Aim to have the VSI around 10 by the time you get within 1km of the surface.

* Also aim to have your horizontal speed zeroed by this time. If it isn't, keep burning with enough pitch-up to maintain a near-zero VSI.

* Once you're close to horizontally stationary, point straight up and turn on the RCS. Use translation RCS controls to hold the retrograde vector at centred 90° up, and use the main thruster to control your vertical speed.

* Try to use the thrusters as little as possible, and aim to touch down below 5m/s.

* Kill your engines as soon as the feet hit dirt, but keep RCS and SAS on until you're sure that you're stable.

[Sirrobert]

Yep, my lander is pretty much exactly how you described it. I'm not sure I actually need to change my design that much though; I'm starting to think that I can probably solve my landing problem with a bit more practice. Still, if you have any design tips you think I should know, I'm all ears.

No, that's actually a very basic lander design that almost always works.

You could make it a little more stable by having a wider base.

So in the middle a FL-T400 tank, and directly, radially attatched to that (without decouplers) 3 fuel tanks (FL-T100 is fine, you could do a 200) with 48-7S below that.

Fuel lines that feed FROM the inner tank INTO the outer tanks (also with symetry). Now 1 lander leg on the outside of each of the outer fuel tanks.

This creates a wide base, which is more stable and thus harder to tip over. This means that you can still land with a little vertical velocity without tipping over

[capi3101]

Wanderfound and Sirrobert have given you the advice I would've - widen the base; depending on how far along you are in the tech tree, the easiest way to do that is to replace the single FL-T400 with an FL-T100 and attach 3-4 additional FL-T100s radially, using fuel ducts to feed those tanks. You then set your lander legs on those outboard tanks, which then widens and shortens your stack and makes it less prone to tipping over on landing (which is an issue a lot of us have faced the first few times we make it down without 'sploding - correctable with pod torque on Minmus but a catastrophic mission killer on Mun). If you haven't got fuel ducts, keep the FL-T400 but put the lander legs out on Modular Girder Segments; this does nothing to shorten the stack but it at least makes it wider and you should still have enough fuel to make it there and back. Consider adding an FL-T100 to the stack offset the delta-V lost to the mass of the girders.

Once it's available, swap out the Mk1 Command Pod with a Mk1 Lander Can. Less dead-mass = more delta-v, and only slightly less steering authority (still enough for your purposes). I might also suggest a light or two aimed at the surface once they're available; the reflection off the surface will give you an idea of how close you are to the deck (i.e. how much longer you've got until you really should be slowing down).

RCS is also unnecessary for a lander that light; the command pod will provide plenty of steering authority on its own. It's generally less necessary unless you plan to do docking operations with your craft; then it becomes almost essential.

As far as science is concerned, there are varying schools of thought. I personally subscribe to the Geschosskopf school of "hit that biome once and never have to go back ever again", but whatever works best for you works best for you. The science pack is a pretty handy way of gathering a boatload of science at a time, though (particularly if you use an action group to set up a "sci bomb" like Geschosskopf suggests, activating all the tests simultaneously with a single keystroke). Still relatively cheap to construct as well. Something to consider when you've got more practice with landing.

Lessee....other advice. IIRC somebody mentioned going IVA to use the radar altimeter; I can't stress enough how good that advice is if you're playing without a piloting assistance mod like KER (which I highly recommend) or Mechjeb (which I've never used so I can't say one way or another how good it is). When I play the demo, I still use that method. What you do is after you've made your braking burn and you're pretty much vertical, go IVA and look for a gauge that looks like this one:

The needle won't twitch until you're closer than 2,500 meters to the surface. Once it reads 2,000, go back to staging view (hit "c" to toggle between IVA and staging view) and note your altimeter reading. Take 2,000 off of that reading; the result is the rough elevation of the deck. Use that estimate to slow down. If you need to, occasionally go back to IVA and glance at the gauge again to figure out how much further you've got.

With the basic design I mentioned in my last post, bingo fuel is at 80 liquid fuel units. At 90, be thinking about heading back into space if you're not close to the deck. At 80, you better be hitting space. At 70, you might as well finish landing because you're not making it back to Kerbin...

Last bit of advice I can give: hit F5 before you make the landing attempt and hit F9 when you mess it up. Practice, practice, practice until you get it right.

Best of luck.

Edited September 30, 2014 by capi3101

[Sirrobert]

Note that radar altimeter is, as I recal, only available in the lander cans, not in the MK1 pod

[RizzoTheRat]

I use the smallest Rockomax tank on my lander to give a nice wide base for the feet, and enough fuel for a 909 land me on the mun and get back to Kerbin with a materials lab, a couple of goo canisters, and a Mk1 capsule.

Good tip on the radar altimeter, I'd assumed that was something I'd eventually be able to research and add on to the ship. On my second foray to the Mun I had Jeb (should have been Floyd really) land on the dark side of the mun, only to realise he'd forgotten to specify landing lights on his craft. He reverted to the tried and tested technique of the "temporal altimeter"...namely quicksaving and making a note of the altitude the crash happened at

[capi3101]

Note that radar altimeter is, as I recal, only available in the lander cans, not in the MK1 pod

No, it's there in the Mk1 Command Pod - right side of the navball, just below the altimeter (which is just below the rate of ascent/descent gauge)

I use the smallest Rockomax tank on my lander to give a nice wide base for the feet, and enough fuel for a 909 land me on the mun and get back to Kerbin with a materials lab, a couple of goo canisters, and a Mk1 capsule.

Good tip on the radar altimeter, I'd assumed that was something I'd eventually be able to research and add on to the ship. On my second foray to the Mun I had Jeb (should have been Floyd really) land on the dark side of the mun, only to realise he'd forgotten to specify landing lights on his craft. He reverted to the tried and tested technique of the "temporal altimeter"...namely quicksaving and making a note of the altitude the crash happened at

The X200-8 trick works pretty well; it actually provides the same amount of fuel as an FL-T800 - more than you need, but definitely gives you a nice margin for error.

[RizzoTheRat]

Change "nice margin for error" to "reserve to cope with poor piloting skills" and you're spot on. I've landed that configuration on Mun twice now and both times used aerobraking to get back down to Kerbin as I've been worried I wouldn't have enough fuel to deorbit

Having just read the first bit of the "science bomb" thread linked above I've now got a better idea how the science works and will go for a quad materials bay/goo lander next time. Thanks to the science from the last trip I've now unlocked the mainsail and big orange tank so I reckon I should be able to launch a big mission with 2 or 3 landers on it which separate in mun orbit and return independently.