Landing Legs Annoyance

[DockingHater]

So....I built a lander for the Mun, which uses four of the LT-2 landing legs. EVERY time I try to land, one or two of the legs explode. Even at speeds of 3.0m/s. I'm landing on a slope of around 15-20 degrees, but this happens even when landing on all of the legs equally. Are these things seriously this poorly programmed? They're supposed to survive 12m/s.  It's not unreasonable to expect them to survive even half of that. My craft is 15 tons, so that shouldn't be the issue. Is there anything I can do to fix this? Is there a file I can edit to increase their impact resistance? I've seen posts with this exact issue from years ago, so apparently the developers haven't gotten around to fixing it themselves.

Edited May 12, 2021 by DockingHater

[Guest]

15T is quite heavy for a lander? Based on say mk2 lander can which is ~ 1.2t. Only options I can think are:

- reduce lander weight

- add more legs

- land as close to 0m/s as possible

- consider some add on legs

- tweakscale the stock legs

- use wheels instead these seem more robust

[OHara]

Landing legs and wheels, specifically the  suspension, do not work very well for KSP.  Some explanation of the reasons is here:

https://forum.kerbalspaceprogram.com/index.php?/topic/184798-are-we-sill-pretending-the-wheelslegs-arent-broken/&do=findComment&comment=3607517

Landing gear can break from being be 'overstressed', and while that may have worked in KSP 1.0, with version 1.1 the new Unity game-engine with hidden automatic adjustments made use of wheels frustrating.

In your specific case, I suspect that the automatic adjustment of the spring strength makes the springs very soft while you are descending, too soft to decelerate 15t from 3m/s to zero, so the landing legs compress fully and the old KSP rules count that as being 'overstressed'.

Maybe you will be happier to turn off the 'Spring/Damper: auto' setting on the landing gear (after first enabling 'Advanced Tweakables' in the in-flight 'Settings' menu that you get with the 'Esc' key). Then sliding the spring strength and damping higher might help.

Or retract landing gear and land directly on the ground.

Or you might enjoy trying to land so softly that the landing legs don't break.

Edited May 12, 2021 by OHara
15t, not 1.2t

[king of nowhere]

i've never noticed anything like that. in fact, i use those same LT-2 landing legs as armor for my rover to cushion impact, and i've never seen one break.

 can you post a picture of your lander?

[18Watt]

Although it looks awful, my technique is to just land on the engines.  If the craft is really heavy, sometimes I add short girder sections to the bottom, and land on those.  Landing gear are finicky.  Just about the time I figure out how to make them work, there is a KSP update which changes how they behave.  Too unpredictable.  

60% of the time, just landing on my engines works every time.

[Echo__3]

15t landing at 3 m/s is 135000N of force. That is like having those landing legs supporting the weight of 2 African Elephants on Earth.

Edited May 12, 2021 by Echo__3

[OHara]

Well, decelerating from 3m/s to zero, over the 1-metre distance that the stut seems to compress, is an acceleration   (3m/s)² / 2 / (1m) = 4.5m/s²  about half a 'G'.

So decelerating the 15t calls for 15×4.5 = 68kN of force, provided by whichever landing legs can participate.   

(If an elephant weighs 6t, that is 6t×9.8m/s² = 60kN on earth.  So if you want to measure in elephants, the landing force would be about 1.2 elephant, no?)    

Four of the LT-2 struts does seem sufficient to land 15t on the Mun, though, and would usually work in KSP.

Edited May 12, 2021 by OHara
Oops, I had misread 20 elephants rather than 2, in the post above

[DockingHater]

6 hours ago, Echo__3 said:

15t landing at 3 m/s is 135000N of force. That is like having those landing legs supporting the weight of 2 African Elephants on Earth.

5 hours ago, OHara said:

So decelerating the 15t calls for 15×4.5 = 68kN of force, provided by whichever landing legs can participate.  

I'll give reducing the lander's mass a try, then. I did use...quite a bit of fuel.

[jimmymcgoochie]

A dozen LT-2s can support a ~100 ton craft landing on Eve at 5m/s, so I see no reason why four can’t support a 15t craft at 3m/s on the Mun. 15 tons does seem a bit heavy for a Mun lander though, screenshots please?

[Guest]

If he’s landing in a slope but the lander is straight, 2 of those legs are taking all that load. In fact, if his y-axis (as per game point of view) is changed (ie he’s rotated slightly) it’s possible a single leg could momentarily take the full force even.