I had a ~6ton(ish) craft, that was in earth atmosphere going down with chutes. When designing it and expected it to go down with about 8 meters per second while the touching module was going to be a PPD-10 Hitchhiker, I considered placing LT-05 Micro Landing struts under it, to just play safe.
The vessel went down with 7 meters per second. the container while tolerating 10 m/s was anyway protected by the 12m/s tolerating struts. but when touching down, the struts got destroyed and the container remained undamaged. I had no idea why the more tolerant part got destroyed and the container remained intact. I just could think it has something to do with the weight. But I couldn't find any hint about it yet at all.
Can anyone explain this behavior?
Best Answer
When the crash tolerance of a part is calculated during a landing, it's not just a single part that is used. It matters what parts are connected to which, as landing struts (for example) absorb initial shock, but also transfer some of that impact force to other parts. The connection (of landing gear to struts, for example) will determine what part(s) may get sheared off or destroyed.
In short, if you're finding that the velocity of touchdown is less than the crash tolerance, then most likely it is a design issue. Try moving the land struts, or the structural struts around to see if a better design is more successful.
I had the same incident trying to land a Mun Base -- it landed almost vertically but I had to flip it down to be horizontal on the planet, and found with RCS thrusters easing it's descent, it still would break the landing struts. In the end I found that moving the struts to a different part of the ship prevented this from happening.