How does Hack Gravity work in the game?

[airelibre]

(Read - not "how do I hack gravity?")

Surely, with the lateral movement you have from Kerbin's rotation, when you hack gravity, you should start drifting straight upwards from the "centrifugal force" which is no longer counteracted by gravity. Instead, you stay roughly in the same spot.

Also, when you fly straight upwards without enough speed to escape the atmosphere, you should eventually lose speed and stay stationary, but I tried this just now, taking off with around 30 m/s, reaching around 1500m and then dropping back down to hit the ground at around 7 m/s. I know that irl there are many considerations such as density and air pressure, but these surely aren't factored in in ksp?

[Cmdr. Arn1e]

I know that irl there are many considerations such as density and air pressure, but these surely aren't factored in in ksp?

In few words, yes they are!

You might see people talking about NEAR or FAR - these are mods that change the factors involved, so it is a bit more realistic (including, with FAR, pressure tolerances on wing parts, so flying too fast through too thick an atmosphere can result in the wings getting ripped off!) and users of these usually refer to the 'stock' arodynamic model as the 'soup-o-sphere' hehe

Edit; and I think hack gravity doesn't completely turn it off, just reduces it by a large factor... happy to be corrected on that though!

Edited November 23, 2014 by Cmdr. Arn1e

[electronicfox]

I doubt that centrifugal forces are programmed in to KSP on a planetary level, and the hack pretty much just turns the gravity in the physics setting to 0. From there I guess other subtle forces just kinda butt your craft around.

When I use the hack-gravity cheat, I slowly float around a fair distance without hitting any controls.

[sal_vager]

Things still fall back to Kerbin when gravity is hacked, just really slowly, so you can assume there's at least enough on any given body to stop you from being flung into space

[Norpo]

I wonder if the amount of gravity remaining is calculated using the planets mass, e.g you'd fall back sooner on Tylo than on the Mun.

Maybe it just sets the gravity to a certain amount, or maybe it changes the planets mass?

I imagine the way it calculates gravity has a gravity coeffecient/multiplier somewhere, so if it changes THAT, then the effect of the "lack of gravity-ness" would also depend on the bodies mass.

EDIT: Of course, then you also have to deal with this: what happens when you exit a sphere of influence? Surely, if all the gravity was weakened, then if you exit Kerbin to go to a solar orbit, 10000 m/s or so would fling the planet or ship out of the solar system (But planets wouldn't be effected, since they're on rails)

EDIT2: Okay, the wiki has an oh-so-brief description of it. "Hack/Unhack Gravity: When enabled, reduces the gravity of all celestials greatly."

But by how much? 1/100ths? 1/50ths?

Further testing is needed!

Edited November 23, 2014 by Norpo
found a source

[Commissioner Tadpole]

Things still fall back to Kerbin when gravity is hacked, just really slowly, so you can assume there's at least enough on any given body to stop you from being flung into space

I'm really curious as to what would happen if one hacked gravity on Gilly.

Oh well, HyperEditâ„¢ time!

[merendel]

I'm really curious as to what would happen if one hacked gravity on Gilly.

Oh well, HyperEditâ„¢ time!

If I had to guess the difference would be unnoticeable. Its hard to get any closer to 0 gravity than gilly's natural state.

[boxman]

I doubt that centrifugal forces are programmed in to KSP on a planetary level, and the hack pretty much just turns the gravity in the physics setting to 0. From there I guess other subtle forces just kinda butt your craft around.

When I use the hack-gravity cheat, I slowly float around a fair distance without hitting any controls.

There was a planet in planetfactory mod that spun so fast that it actually did do that. The only place it was possible to land on was on the poles while at equator regions you would have to constantly thrust downwards to keep yourself to the ground. So there does seem to be some kind of centrifugal effects.

[CalculusWarrior]

I seem to recall (though I'd have to fire up KSP to confirm) that Hack Gravity simply reduces the gravity of whatever planet you're on by a factor of 100. Thus, Kerbin's acceleration due to gravity becomes 0.0981 m/s/s. Interestingly, this is twice Gilly's g value (0.049 m/s/s).

[Tex_NL]

I seem to recall (though I'd have to fire up KSP to confirm) that Hack Gravity simply reduces the gravity of whatever planet you're on by a factor of 100. Thus, Kerbin's acceleration due to gravity becomes 0.0981 m/s/s. Interestingly, this is twice Gilly's g value (0.049 m/s/s).

This could very well be correct. I clearly remember a YouTube video (probably Scott Manley) stating normal gravity on Gilly is higher than hacked gravity on Kerbin.

[Norpo]

I seem to recall (though I'd have to fire up KSP to confirm) that Hack Gravity simply reduces the gravity of whatever planet you're on by a factor of 100. Thus, Kerbin's acceleration due to gravity becomes 0.0981 m/s/s. Interestingly, this is twice Gilly's g value (0.049 m/s/s).

Yup, I can confirm this, While I do have 6.4x kerbin, it doesn't change the gravity (not by much, I think, anyways), so, according to the Gravioli detector... 00.10/m/s^2 gravity while hacked, 09.82/m/s^2 not hacked.

However, it doesn't change the ASL Gravity or the mass of the planet while looking at it through map mode, so it must be changing something else.

[airelibre]

There was a planet in planetfactory mod that spun so fast that it actually did do that. The only place it was possible to land on was on the poles while at equator regions you would have to constantly thrust downwards to keep yourself to the ground. So there does seem to be some kind of centrifugal effects.

That was because the escape velocity was lower than the orbital velocity at the equator, which is different kind of situation to centrifugal forces, I think.