The mass of a kerbal.

[Kosmo-not]

Who knows if this information will be of any use to anyone, but I thought it would be fun to figure out how much mass a kerbal has.

I have determined that a kerbal has a mass of 0.032 mass units.

If we take a mass unit to equal 1000kg (a tonne), then a kerbal weighs approximately 70.55 lbs on the surface of Kerbin or Earth.

An important thing to note is that a kerbal has no mass while inside a command capsule.

[MaxMurder]

Interesting. May i ask what method you used to discern the mass of a Kerbal?

[Kosmo-not]

Interesting. May i ask what method you used to discern the mass of a Kerbal?

I took a rocket up to about 70Mm so that gravity would have negligible effect. I then slowed the rocket to a stop, staged to the test stage, and quicksaved. The test stage was the large command capsule, a small half tank, and the vectored thrust engine (6.625 mass with full fuel, 5.625 mass when empty).

1st test (the control test)

Burned horizontally until out of fuel. Final velocity was 593.8 m/s.

2nd test

I ejected 2 kerbals and proceeded. Final velocity was still 593.8 m/s.

3rd test

I ejected one kerbal and positioned him at the nose of the craft. I burned as before, but with the kerbal pushed along. Final velocity was 590.7 m/s.

I then calculated a precise specific impulse with the data from the first test and used it in a second calculation that covered the 3rd test and added the kerbal\'s mass to the equation.

That is how I came to the value of 0.032 mass units for a kerbal.

[maltesh]

You also could have looked in the persistence file.

And yep. You\'re close. 0.03125 mass units. Well done.

[Kosmo-not]

You also could have looked in the persistence file.

And yep. You\'re close. 0.03125 mass units. Well done.

I didn\'t think to do that, lol.

[SkyHook]

You also could have looked in the persistence file.

And yep. You\'re close. 0.03125 mass units. Well done.

LMAO! Excellent work to the OP however. Would not have thought of testing it that way!

[Kaa253]

This information is in fact very useful! If you are building a micro VTOL or a light airship using one or more EAS-1 External Command Seats then the balance of the craft is noticeably different when it is manned compared to unmanned.

[tavert]

Keep an eye on the post dates, this thread was a year old. But it should be noted that the mass of an EVA (or sitting-in-seat) Kerbal was increased by a factor of 3, to 0.09375 tons, in version 0.20. As far as I can tell, the number is the same in 0.21.

[MR4Y]

Okay, now do those in kilograms, since the game doesn't use pounds for mass.

[Crush]

The vessel information in the tracking station or map view, however, reports a mass of 90kg:

[tavert]

Okay, now do those in kilograms, since the game doesn't use pounds for mass.

It uses tonnes. Multiply tonnes by 1000 to get kilograms.

The vessel information in the tracking station or map view, however, reports a mass of 90kg:

That infobox rounds to 2 decimal places (the nearest 10 kg). You can put together craft where a Kerbal getting into a seat appears to increase mass by 0.10 tons, it just depends on the rounding. Look in a persistence file for kerbalEVA, it says a few lines down "mass = 0.09375".

[NERVAfan]

Interesting that they're that heavy... but I guess, without spacesuit, they'd still be significantly smaller than humans...

[Kaa253]

Thanks tavert.

I built a balance beam (like a see-saw with two identical girder constructs with ladders) and crawled a kerbal back and forwards along the ladders and it never tipped. It seems that a kerbal on a ladder might have a mass of zero??? Perhaps it would work differently if I took it off the KSP launch pad?

Then I built a light rocket platform with two command seats on opposite sides and a small engine system at the centre. With a kerbal in only one seat the platform tips over very rapidly to that side on takeoff. I then added and subtracted parts in a cluster around the empty seat until it launched straight up. This way I found the mass of a kerbal when seated as approximately equal to 4x Z100 batteries plus 3x OX-STAT Solar panels. That's 0.095 tonne, so in this case the mass value given for kerbalEVA in the persistence file is correctly being modelled by the physics engine.

So now if I need a crash test kerbal dummy I can use 4 batteries and 3 solar panels

[einsteiner]

A mass unit is a metric ton (1000kg), so they are 32kg.

Edit: I really should've read page two before posting.

Edited August 26, 2013 by einsteiner

[Errol]

I know this is a really old thread. So shoot me, I don't feel like creating a new thread and this is the most recent discussion I can find on the topic through google. 

I remember there used to be a mod that would correct the COM indicator in the editor for kerbals in cockpits and command seats. I cannot for the life of me remember what it is called, and I can't find it anywhere with google. Can anyone help me out? Would be really useful for micro VTOLs, as stated in this very thread. 

[Superfluous J]

17 minutes ago, Errol said:

I remember there used to be a mod that would correct the COM indicator in the editor for kerbals in cockpits and command seats.

For command pods, you don't need a mod. They weigh the same whether there's a Kerbal in them or not (which always bugged me but it does make calculating dV easier).

I'd love one that did the same for command seats. Actually all you'd need is a right click menu button in the VAB "Kerbed" that would increase the mass of the chair by 0.09375 tonnes just in the VAB. Then it'd "just work" both in KER and RCS Build Aid.

"All you'd need" says the guy who isn't going to mod it in

[Errol]

I thought it did add kerbal weight to command pods though. I totally remember using this existing mod of unknown name.

Edited December 16, 2016 by Errol

[Snark]

Kerbal mass doesn't get added to crewed parts in the stock game.  Launch a Mk1 pod empty, check out the mass on the pad.  Then launch it with a kerbal inside, do the same thing.  Same mass.

I recall having seen a mod somewhere once that actually "fixes" this and makes it add mass for crew members, thus being more realistic.  Don't remember the name of the mod.

In any case... this really is an ancient thread.  Resurrecting it is going to confuse people-- posting here bumps the thread to the top of the list, but someone who goes to start reading sees all this ancient stuff that's now totally moot.  Accordingly, locking the thread to prevent further confusion.

Generally, if a thread's been dormant that long... it's generally best to just spin up a new thread.  If you'd like to talk about the mass of kerbals in general, feel free to spin up a new thread here.  If the conversation is about mods, probably the Add-on Discussions forum would be more appropriate.

Thank you for your understanding.