Mass-less parts Really Mass-less?

[worir4]

Are the mass-less parts actually mass-less? Parts such as the cubic octagonal strut and the static solar panel are well known to being over used due to them not having any mass, however if they truly did not have any mass wouldn't any force that applied to them give infinite acceleration? Do they actually have a small mass?

[Taki117]

They are mass-less in that physics are not applied to them during flight.

[Crzyrndm]

You can't build a controllable craft of only massless parts, so you can't get infinite acceleration (all pods and probes have mass, as does a kerbal in a command seat)

[Claw]

What Taki says is true. I believe they are also given a small mass when they end up on their own (such as during disassembly) to help prevent physics problems like infinite acceleration. Although physics problems from physicless parts are not all that uncommon...

Cheers,

~Claw

[Norpo]

Well, in most practical cases you won't have to worry about that.

At all. Even if it's over a ton of "massless" weight.

Flies just fine.

[worir4]

So the parts are totally physics-less until it becomes separate from anything else. Then it has physics applied to it and the mass shown in the VAB/SPH is applied, right?

Also, Norpo, those big batteries are mass-less! I never knew that!

[Laie]

So the parts are totally physics-less until it becomes separate from anything else.

Not totally physics-less. They may still bend and wobble if there is a weight attached to them (end even if not, the game does the wobble calculation and comes up empty).

Depending on the part, there may be more. Every ox-stat has it's angle to the sun / power generation calculated individually, for example.

Note that I do not *know* whether the above is true. But I do know that my part count where the clock starts going yellow is very similar between craft, regardless of whether it's a ion glider (where like 90% of all parts are physicsless) or a heavy SSTO (where no more than 5% are physicsless). If anything, the ion glider lags more at lower part count. Therefore I presume that physicsless parts are not so physicsless after all.

That they can bend is an observation; that ox-stats need to trace the sun is common sense.

Edited February 26, 2015 by Laie

[worir4]

So i wonder what would happen if you edited the part file of say, the monopropelant booster so that it had a probe core within and electricity supply, and then you turned on infinite fuel, what would happen?

[Laie]

So i wonder what would happen if you edited the part file of say, the monopropelant booster so that it had a probe core within and electricity supply, and then you turned on infinite fuel, what would happen?

I know what I'd expect (the same as you), but you won't know until you tried. Or until someone does the experiment for you.

[worir4]

I know what I'd expect (the same as you), but you won't know until you tried. Or until someone does the experiment for you.

I would, but i have no idea how to.

[Yasmy]

Well, this isn't infinite TWR of a modded zero-mass, infinite fuel ship, but it is pretty fun.

Stock, unmodded, but with infinite fuel hack, Kerbin to Jool in under 2 hours:

Edited February 26, 2015 by Yasmy

[Sirrobert]

I would, but i have no idea how to.

An easier sollution would probably making a probe body massless.

I believe there's only a single line in the part file that dictates that

[Commander Jebidiah]

Ive tested this for weapons research aka extremely cheap kinetic warheads and while in orbit testing they flew past the 100km at which you can see there nav marker and were on an escape from kerbol.

While in atmo they got up to speeds of nearly 3.5km/s but the soup like atmosphere slowed them down while below 35km.

[SRV Ron]

Testing landing gear is easy in Career due to being massless. You don't need to place two on the test vehicle for balance either for flight or orbit testing.

[cantab]

I did an all massless ship a while back. Octagonal strut, a whole bunch of O-10 engines, and a few struts. I set infinite fuel on then decoupled from the launcher, and I can start and stop the engines by enabling and disabling infinite fuel.

It accelerated at around 300,000 g. So not infinite.

Now whether that's because there is some small residual mass, or whether it's simply a limit of the game engine, i don't know.

[Red Iron Crown]

I did an all massless ship a while back. Octagonal strut, a whole bunch of O-10 engines, and a few struts. I set infinite fuel on then decoupled from the launcher, and I can start and stop the engines by enabling and disabling infinite fuel.

It accelerated at around 300,000 g. So not infinite.

Now whether that's because there is some small residual mass, or whether it's simply a limit of the game engine, i don't know.

I believe the root part cannot be massless, i.e. if a massless part becomes the root through decoupling or disassembly then the physics engine honors the root parts nominal mass. I haven't looked at it since the reroot tool was added, things might have changed.

[Sirrobert]

I believe the root part cannot be massless, i.e. if a massless part becomes the root through decoupling or disassembly then the physics engine honors the root parts nominal mass. I haven't looked at it since the reroot tool was added, things might have changed.

That would explain the method by which orphaned massless parts regain mass (as was discribed in an earlier post)

[worir4]

I believe the root part cannot be massless, i.e. if a massless part becomes the root through decoupling or disassembly then the physics engine honors the root parts nominal mass. I haven't looked at it since the reroot tool was added, things might have changed.

So it is not possible to make a fully massless vessel.. I wonder what would happen if we did..

[Renegrade]

So it is not possible to make a fully massless vessel.. I wonder what would happen if we did..

Well, I'd have to say divide-by-zero there, with all the associated consequences. Infs and NaNs rampaging throughout the physics engine, looting and burning, until you end up with the rolling altimeter and such.

Basically a lot of things end up being x / mass or mass_wet / mass_dry or such.