Test Mass Mod.

[specter177]

Is there a mod that has a bunch of test masses or something that allows you to put in a test mass of your choice, to test rocket capabilities?

[ScottyDoesKnow]

I've never seen one (though I've never looked). I usually just create weights out of fuel tanks, sometimes with batteries or structural parts to get exact weights. Takes a bit of time, but in the end it's more realistic because the physical size of the payload (and how you attach it) can make a big difference.

[BananaDealer]

Lack Luster Labs has weights... Don't use them myself but I guess they can come in handy for testing out payload capabilities...

Otherwise, Cabana Corp. supplies ballast tanks that can be used for the same purpose...

[blizzy78]

I use the Stretchy Tanks mod to create proofing weights. Usually I modify the tank to contain monopropellant to make sure it won't get used in the ascent.

[pizzaoverhead]

There were a couple of mods in the past: Surface Mounted Counterweights and Weights. They should still work, but the part.cfg files will need "PART {" added to the start and "}" to the end. Scale and rescale factor may need changed too.

[SunJumper]

Using structural parts as well as engines/fuel tanks separated by decouplers can provide sufficient mass to represent your payloads...