What's with impact speeds, anyway?

[tater]

Yes, I know there is a mod that shows part damage. Very cool.

Another thread got me looking at impact tolerance of parts, and had me reading a technical paper about the landing dynamics of all the Apollo lunar landings. Yet another thread was about the tier 0 runway, and why using that is dangerous to aircraft wheels, but landing at speed someplace that should be fatal (anywhere, on any world that is not a paved runway) is not.

Since I land with chutes and/or landing legs, and I do so at LEM-like sink rates at touchdown, I never notice the impact stuff, except watching crasher stages hitting sometimes below me.

I think that all the engine parts should have the impact tolerance reduced to effectively zero. Maybe 1 m/s. The engines should be incredibly delicate things you would never land on, ever. Oddly (not really, I suppose, because "spaceplanes!") the spaceplane engines are magically set to far higher impact tolerance for some reason(rapier, etc). 

I realize that in the past there were not so many parts, and you needed to land on wings, etc, but that's simply no longer the case. Making parts more delicate where appropriate creates design challenges, which is sort of the point of the game.

Simple proposals:

1. Add more runways around Kerbin, some at tier 0 level, all the way up to paved and long. Fix tier 0 to be not so awful.

2. Make everywhere else in the solar system at least as bad as the current tier 0 runway to land on for aircraft wheels.

3. Make launch clamps and some landing gear/legs to tier 0.

4. Reduce the impact tolerance of all the engines in the game to near 0, the jet nacelles can be slightly higher (by slightly I mean maybe 1 m/s higher). A Apollo LEM descent engine buckled not from impact with the lunar surface, but from overpressure due to running near the surface.

These can all be easily designed around with the game as it is.

Better damage:

Ideally, there might be a couple levels of damage instead of perfect --> #LOLEXPLOSION. Some parts like landing legs and wheels (do aircraft gear, I don't make planes?) already have this. Add this to other parts, and it could be as simple as a damaged texture. Damaged tanks could leak at some rate, damaged engines would simply not work. Damaged structural parts have impact tolerance reduced by half or something. Engineers could perhaps patch leaks, or allow an engine to work. Damage could occur at the tolerance, and destruction at (tolerance)*3 or some value that works. This gives them something to do, and makes landing something to actually have to think about.

[Nich]

I remember when tanks and engines had better impact tolerance then landing gear.  I think there may be a problem with how the physics works.  If you set tank tolerance to 1 m/s.  Then land at 5 m/s the gear will absorb 3 m/s and transfer 2 m/s to the tank and make it explode.  I am pretty sure the physics transfers the impact through the entire structure with no absorption by higher impact tolerance parts other then gear and wheels. 

Edited April 11, 2016 by Nich

[Skybird0]

19 minutes ago, Nich said:

I remember when tanks and engines had better impact tolerance then landing gear.  I think there may be a problem with how the physics works.  If you set tank tolerance to 1 m/s.  Then land at 5 m/s the gear will absorb 3 m/s and transfer 2 m/s to the tank and make it explode.  I am pretty sure the physics transfers the impact through the entire structure with no absorption by higher impact tolerance parts other then gear and wheels. 

So make it query whether or not it is touching the ground and if so, change the impact tolerance.  Otherwise the impact tolerance (Hereby structural tolerance.)  stays the same.

This should be something you can change in a setting, for instance, you would not want this system to be in effect for new players.

[Nich]

I don't know how the code works but in my mind the best case scenario a rewrite of the entire physics logic on Squads side.  Worst case it is part of the Unity engine and is not modifiable by squad.  @NathanKell knows a lot about the aero so he might know about collisions or can point in the right direction.  I do have to agree a lot of the parts have crazy impact tolerance but I suspect this is a cause of model constraints.

[tater]

Yeah, I suppose I could do some drop tests to see what the deal is with how impact is mitigated by gear/legs. I have no issue with the effects propagating, actually. The LEM landing parameters (the graph of acceptable horizontal vs vertical velocity) was shaped like this:

 ^
/ \
| |

and called "the dog house." (sorry for crappy ascii art)

They had to keep the apex was 0 lateral velocity, and ~3 m/s sink. This was to protect the structures above the landing gear from presumably compression forces (3 m/s to 0 in 0.1s is ~3 gs, in 0.01s is ~30, etc, so more than launch stresses depending on how compressible the soil is, and how quickly the craft decelerates).

I'd like to see something like the landertron mod being a thing (that functionality could be added to the septratron part as an option), and have a real difference between splashdown, and land landings for capsules. Again, it's about having designs in KSP be less universal, because designing novel stuff is kind of the point.