Formula to find impact force?

[Dewm]

So I'm trying to find out how much "impact force" something will have landing on the Mun.. And I'm pretty sure it'll be gravity + speed + mass, something like that. but I'm not sure on it.

Secondly how do I find the total weight/mass of one of my crafts?

and last but not least.. With wheels they say they can handle "15 impact force" (or landing gear), does that get divided by the number of wheels you have?

Example: I have 2 wheels landing force would be 100 each, but if I upgraded it to 4 wheels then it would be 50 each.

Thanks!

[NASI Director]

You can find the mass by using a mod or by going into map view and click on the tabs on one of the sides. As for the impact force, I think that means that each wheel can handle 15m/s of vertical downward force. The Mk1 Aircraft Cockpit has an impact tolerance of 45, so it can handle smashing into the ground at anything less that 45m/s. I think.

[SofusRud]

what you want is Kinetic energy

the formula for that is Ke=0.5*(mv*v)

as in Kinetic energy is equal to one half times mass times velocity squared

thats the "impact force", but I believe what the part specs refer to is velocity rather than force

[Dewm]

what you want is Kinetic energy

the formula for that is Ke=0.5*(mv*v)

as in Kinetic energy is equal to one half times mass times velocity squared

thats the "impact force", but I believe what the part specs refer to is velocity rather than force

I am horrible with math, BUT if I understand correctly...

Example:

Mass = 100

speed = 100m/s

50 x 100²m/s = impact force

This correct?

[Dewm]

edit:

Just saw the bottom part of your post, SO if landing gear says impact force of 12.. then I can land 12m/s or below?

Thanks!

[rryy]

To find the total mass of a craft, go into map view and click on the info button on the right side. It will show the current mass of the craft.

[Pixel of Life]

Weight can be found in the map view, by focusing on your craft and opening the craft info tab from the right side of the screen.

Kinetic energy can be calculated by 0.5 x mass x velocity squared. Impact force can be calculated by kinetic energy / distance required to stop the object. You do not, however, have to include the distance in the equation since things in KSP stop instantly (they do not sink into the ground or become deformed). I tested this with an imaginary spacecraft: Weight 5000 kg, impact velocity 100 m/s. Using the equation, I got an impact energy of 25,000,000 J. That's equivalent to 1 kg of TNT. I think that's about right.

Edit: I just noticed I only calculated the amount of energy released in the impact. I don't think one can calculate impact force though. Force in newtons is 1 J / m, which in the above example would be 25,000,000 J / 5000 kg, but that leaves me with 5000 N, which is only a tenth of the force the craft would exert on the body if it was just lying on the ground.

Edited July 30, 2013 by CaptainKorhonen

[Dewm]

Thanks for the info everyone.

I am building a lander and wanted as few parts as necessary. But it sounds like weight of the craft doesn't really factor into the landing legs etc..

[Dewm]

So after a bit of testing... the "impact force" listed under wheels and/or landing gear is NOT m/s.

I got the BIG wheels which were listed as impact force: 150.. and I tried to land at 30 m/s and it exploded..

Sooooo anyone have any other ideas what "impact force" is? or how to measure it?

[arq]

Maybe it's measured in delta-V? So the part alone could handle a 150m/s impact, but if it was only 10% of the mass of the vessel it could only handle 15m/s?

[Dewm]

Maybe it's measured in delta-V? So the part alone could handle a 150m/s impact, but if it was only 10% of the mass of the vessel it could only handle 15m/s?

Sorry still getting used to all of the terms (only had the game a week or so)

What is Delta-V

and where did you get the 10% from?

Thanks!

[Anton P. Nym]

Sorry still getting used to all of the terms (only had the game a week or so)

What is Delta-V

Delta V is short for change in velocity. (The Greek letter "delta", or "d", is used as an abbreviation for "change" a lot in physics) It's the total change in speed for a maneuver, or in this case the shock of a landing.

I don't know it that's how landing shock is measured in KSP, but it'd make sense to me if it was the case.

-- Steve

[Frederf]

Impacts are often expressed as a momentum change, i.e. an impulse. The severity of the impulse is its duration. The common expression of force is F=ma but Newton actually expressed force as F=dp/dt or in words the time rate of change of momentum. Impulses (changes of momentum) with short durations result in high forces and impulses that take a while are low forces. For short duration interactions the local gravity is insignificant compared to the existing momentum due to motion. Basically a 60mph crash is the same sideways or downward.