Finding Mun Landing Sites

[scola_p]

Hello!

I have been tinkering away with KSP since, I think, 0.24 and I have made it to the Mun and Minimus, built a few orbital stations and even a Minimus surface station.

But, every Mun landing I do results in a craft lying on its side and a... tricky launch that involves a lot of slinding on the the surface, hoping things don't explode.

The main problem I have is finding a flat surface. I never do.

Aim for a big crater, always manage to land on a slope. Aim outside of a crater, always manage to land on a slope. You get the idea.

I play career, so for my first few stabs I generally don't have any Rockomax engines or tanks, so I try to be efficient, which means that I don't have the delta-v to mooch around.

My landing profile is normally:

1. Orbit, obviously.
   
2. Burn prograde so me path crosses my landing site after my landing target
   
3. Over the target, Burn retrograde to kill horizontal velocity.
   
4. Start a suicide burn around 100m before Kerbal Engineer suggests as I bottle it
   
5. Throttle down and gently come down under 6m/s
   

Is there anything anyone can suggest, or am I just being unlucky?

Thanks,

P

Edited May 22, 2015 by scola_p

[Vanamonde]

Are you sure the problem is landing sites, or lander design? Are you building low and wide, like this?

[Prepper-Jack]

Hmm.

When landing, I spend a fair amount of time in navigation mode, and watching where the trajectory is taking me as I burn retrograde. If I'm comfortable that the current speed and trajectory is safe, I'll time-warp a bit to trim it up even more, and repeat the process until I have a vertical path to the target. When in normal view, I just keep an eye as to what is below. Zoom in nav-mode usually helps ensure you don't hit the edge of smaller craters, but sometimes you hit a lump that's apparent only when you get down there. When this happens, just speed up a bit to stop descent, change course slightly, then start your retrograde course to the ground.

[Harry Rhodan]

Aim for a big crater, always manage to land on a slope. Aim outside of a crater, always manage to land on a slope. You get the idea.

Maybe you should aim for the slope then.

[EtherDragon]

Real moon landings had extra dV for the purpose of hunting around for level ground. Suicide burns are the most efficient - but you don't get much control of where you are setting down.

Instead of a full stop suicide burn, go for a retrograde burn that slows you down a lot. Then when you are close enough to make out the terrain, turn vertical and use your engine to hover over the surface while you coast along. Pick out a landing spot and then finish coming to a stop.

[The Yellow Dart]

I'd have to agree with Vanamonde. I would give up on trying to find a flat surface to land on because no matter how flat an area might look from above, odds are it still contains copious amounts of slope that are more than capable of tipping a tall and skinny lander. And any actually flat area is likely quite small and ringed with slopes and pinpoint landing Is a rather advanced skill that you will only learn with time and practice (time and practice can of course be substituted with copious amounts of fuel to make corrections with).

For now, go the other route and adjust your landers to make them more capable of landing on slopes. Then, of course, you have to worry about new aerodynamics pulling on you nice wide lander, but that can(most likely) be solved with fins.

Good luck, Happy Landings!

[Kerba Fett]

Minmus is way easier, but if you really want to go to the Mun and are playing without mods, try to land in the center of a crater. You won't have to hover as long to find a flat spot.

If you're OK with mods, I'm pretty sure Kerbal Engineer shows the slope at your landing spot. (not sure if it's updated for 1.02 since I haven't bothered to look for it yet.)

Daizo's vertical speed controller is also a big help in holding a hover while you're looking for a flat spot.

As mentioned, short and fat helps. I use the smallest 2.5m fuel tank for my Mun landers.

Edited May 21, 2015 by Kerba Fett

[SanderB]

Do a horizontal landing, like so (<- demonstration video):

1. Have a vessel that doesn't have a very narrow angle between the base of its landing legs and its center of mass.
   
2. Be in a low and circular orbit with your orbit going over the target area
   
3. Lower your periapsis to the maximum altitude of terrain features on the target planet (6km on the mun or check kerbalpedia or kerbalmaps.com).
   
4. 90° from the target area, lower the orbit further until from the map view the orbital line hovers just above the surface features
   
5. Place a maneuver node over the target area and maximize the retrograde arm
   
6. Start your retrograde burn when you're halfway to your maneuver node (ie, time to node is 1/2 of burn time). A little earlier if your surface TWR is <1.5.
   
7. Control your vertical velocity by pitching up or down as appropriate down. Reduce thrust as you approach your target area but keep controlling your vertical velocity. Burn off prograde left or right to adjust your direction and thus your landing site.
   
8. Throttle down and pitch up to keep on progressing toward your intended landing site, to prevent canceling your horizontal velocity too early.
   
9. When hovering over the landing site, cancel horizontal velocity and approach landing site and monitor your radar altitude and keep your surface velocity at 1/10th your radar altitude.
   
10. Touch down at no more than 2m/s.
    
11. Quicksave & Load a few times. Successful horizontal landings take practice.
    

As long as you don't burn too much (more than 30°) off of your retrograde, you shouldn't expend much more dV than necessary.

*note: in the video I raise a landing leg which turned out to be a mistake. Don't try to adjust to a slope by raising a landing leg if your extended landing legs are level with your engine.

[moronwrocket]

KER has a SURF module, that will tell you slope when close to landing. Horizontal Landing Aid can help if you want to use a mod to go to a specific spot. SCANSat's SAR map will show you accurate slopes pre-landing.

[scola_p]

Thanks everyone.

Big thing I am taking away is a wider lander. I tend to have a long lander, rather than a squat one.

And I will turn Surf back on in Kerbal Engineer - I tend to use it for launch so I can keep an eye on atmospheric efficiency. Not that I have got close to 100% in 1.0.2!

I have some time tomorrow so I will knock a quick lander together,see how it goes and post an update!

P

[MarvinKitFox]

Don't bother looking for a flat surface, they are rare and hard to get to. If you have the skill to redirect your landing to a flat spot, you have *more* than the skill needed to land on a slope.

Rather, build a ship that cannot tip, or one with active balance.

1) Cannot tip: Make your lander wider than it is tall, by a factor of 1.4 or better.

This will allow landing on a 30 degree slope.

Anything much more than 30 degrees and your problem is grip, not balance.

or

2) Self balancing.

6 legs are a lot better than 4, or 3

Put a **lot** of RCS thrusters right at the top of your rocket.

When landing, use sas only in maintain position mode, and augment with active input to counter any tipping.

This should handily prevent the immediate falling over after landing.

Now quickly select your landing gear on the downslope side, r-click and select "lock". This stiffens that leg.

All of your RCS *must* be above your center of mass when using this method. Otherwise it tries to slide your legs around, which can be very bad.

P.S.

Your landing speed of "<6m/s" sounds a bit scary.

If you are approaching a slope, one of your legs *will* impact before the rest.

It is, of course, the upslope one.

It will compress, and then kick back, starting to tip your rocket in exactly the direction you do NOT want it to start tipping.

On a slight slope, keep your speed below 3m/s

On a severe slope, drop your descent speed down to <<0.5m/s

Edited May 21, 2015 by MarvinKitFox

[Chaos_Klaus]

I wouldn't go as far as to put RCS on a lander. The extra weight will reduce delta v.

[scola_p]

Well, I made it.

I upped the Delta-v, mostly due to having 5 rockomax engines and fuel tanks opened up due to MOAR SCIENCE and then onion staged. My orbiter stage was so overpowered it lasted until the orbital burn round the Mun, so I had the whole of my transfer stage to find a spot.

And on a 17.9 degree slope too.

Thanks again!

Now I am off to build a station round Kerbin that holds 4000 units off fuel and 5000 electric charge. I will be very good at docking very, very soon!

P

[heng]

congrats!

you do know, that you have space on top of your fuel tanks for science junior and goo canisters?

if you attach the tanks not directly to the center tank, but with a radial decoupler, you can just leave the empty fuel tanks, landing legs, emptied(!) science thingy's, and any lights you might bring on the surface... return only the center.

[scola_p]

Thanks for the tips, heng.

My sideways landed mun missions were all packed with science, but I will make sure I load up next time!

[Randal Kerbin]

Happens all the time man.

Apollo 15.

Check out some real lunar module pilots talking landing tips. http://www.jpl.nasa.gov/news/news.php?feature=1990

[scola_p]

Well now I don't feel so bad. And I am glad KSP doesn't have dust!

P

[Khazar]

I use wheels for my landers. I usually perform near suicide burn (aimed for stoping around 100-200 meters for safety reasons), then vertical, gentle descent up to the point where my engines are almost touching ground, then I go little bit up and rotate to be horizontal. This way I can land on slopes and I can easily drive to better location after touchdown. I think its easier way and it gives more freedom in designing your craft.

[Murph]

Apollo 11 had to delay landing and fly over the surface, as they initially were coming in to an unsuitable spot. "30 seconds" from CAPCOM in the transcript immediately before landing refers to their fuel state, and the time remaining to either find a spot and land, or abort and return to Earth without landing. Neil Armstrong explained shortly after landing was complete and essential tech admin work was done.

http://apollo11.spacelog.org/04:06:55:16/#log-line-370516

Hey, Houston, that may have seemed like a very long final phase. The AUTO targeting was taking us right into a football field sizeâ€â€football field sized crater, with a large number of big boulders and rocks for about … one or two crater diameters around it, and it required a … in P66 and flying manually over the rock field to find a reasonably good area.

The earlier "turn blue" comment from CAPCOM immediately after landing refers to the landing taking much longer than just a simple touch down at initial target.

http://apollo11.spacelog.org/04:06:46:06/#log-line-369966

Roger, Tranquility. We copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot.

Apollo 11 was less than 30 seconds from mission abort and failure because it is tricky to find a good landing spot on the lunar surface.

[SanderB]

I didn't know that undercover smurfs worked at NASA, why else would people turn blue?

[Murph]

I didn't know that undercover smurfs worked at NASA, why else would people turn blue?

Holding their breath. The entire mission (possibly the entire Apollo program and NASA itself) was hanging in the balance and extremely close to the point of no return (or abort). It was all literally in Neil's hands (with Buzz assisting), with absolutely nothing that Houston could do to help or change the outcome. There were several just about equally likely outcomes:

1) Successful landing, mission success, return to Earth viable.

2) Successful landing, mission partial success, return to Earth not viable (due to either craft damage/failure or Neil pushing it past minimum fuel in his determination to succeed).

3) Failed landing, mission failure, return to Earth impossible (not quite so likely given Neil's training and skill, but the failure might not be down to him).

4) Aborted landing, mission failure, return to Earth viable.

5) Possibly other more minor cases and variations, but those are the major ones.

Prior to Neil's successful landing, success and return were not guaranteed, there were many quite possible failure scenarios. Everything they had been working towards was about to be determined, and they had a not-great landing site from "AUTO", several computer alarms (the 1201 and 1202, which were basically overload failure (too many parallel tasks to complete with the available processing power) and actual reboot in the middle of the landing sequence, but it was designed such that an active reboot was actually ok for critical functions, and that was the designed in response to recover from overload), and Neil hand flying and looking for a reasonable landing solution with mark 1 eyeball, while almost out of fuel.

Edited May 25, 2015 by Murph

[Skorpychan]

It's been solved, but there are general rules to be restated:

- LANDER DESIGN. At the very least, a 2.5m tank with legs on the outside. Also, three legs gives the best stability on a slope AS LONG AS you point one leg directly downhill.

- PICK YOUR LANDING. You can do this right from the moment you knock yourself out of orbit, if there's no atmosphere to get in the way. Burn retrograde and straight horizontally until your landing path is a vertical plummet. Then you can do your landing burns from there.

That's something I learned without KER. I've gotten very good at eyeballing and hovering landers because of some very poor choices.

- THE MIDDLE OF A CRATER IS FLAT. No, really. Aim for a crater, adjust from there.

- BRING ENOUGH BLOODY FUEL. Redesign the whole mission if you have to.

- HAVE A RESCUE CRAFT HANDY. Plenty of DeltaV, a Klaw, and a high-thrust engine. Rendezvous with your stranded craft, smack into it at a few m/s with the Klaw armed, and push it bodily into the orbit you want.

Or just use docking ports and a tanker. But that's not a very Kerbal solution, is it?

[HyperbolicKerbonaut]

Three lander legs are better than four. Keep your SAS or RCS on as you land and use them to correct any wayward wobble.