Fuel and engine properties standards?

[nhnifong]

Has there ever been a standard established by Squad or the community for the realistic range of engine parameters?

things like,

the density of fuel,

the mass of engines

the dry weight and capacity of tanks

the masses of random connection parts

Engine fuel burn rates

It would be nice, for example to say, in a challenge, that only parts which comply to the realistic standard are allowed.

has any attempt been made to derive masses and tank capacities from the mesh? I'm thinking of writing something to do this.

[MKSheppard]

I actually did something like this for my own private mod that I'm still working on in bits and pieces -- it's playable on my computer, and I'm still refining the system a bit before I release it.

Masses of engines?

Check out real world engines, as engines are very "rubber-bandy" that can go up and down a wide range of maximum thrusts and retain their T/W ratios...

[the one exception is Nuclear Thermal Rockets, you can't rubber band them]

Link to Engines on my Website

tl;dr:

1960s Kerosene Engines (H-1/F-1): 95~

1960s Hydrogen Engines (J-2): 50-65~

1960s Hypergolic Engines (LEM Descent Engine, etc): 20-30

1970s/80s Kerosene Engines (NK-33): 125~

1970s/80s Hydrogen Engines (SSME): 70~

So lets say you have a Kerosene engine that puts out 200 kN of thrust. 200 kN is about 20,400~ kilograms-force.

With a T/W of about 90, that means your engine would weigh:

20,400 kgf / 90 = 226.66 kg, or 0.226 tonnes.

The reason you can't "rubber band" Nuclear Thermal Rockets is because you need a minimum amount of fissionable mass in the reactor to achieve criticality (the amount needed depends on how advanced your nuclear science is), and that's constrained by the laws of physics, which appear to work the same in Kerbalistani land as on Earth.

Plus, there's the need for radiation shielding on the NTR, which is a very inflexible parameter.

As for dry masses of tanks; NASA actually did the work for us:

Link to NASA graphs

Basically:

------------

MassTank = 10.41 * (VolumeTank^0.75)

Where:

MassTank: Mass of the propellant tank in pounds

VolumeTank: Volume of the propellant tank in cubic feet (ft3)

-----------

Note that this just considers the propellant tanks and their insulation; and propellant tanks are not perfectly cylindrical.

[Ziff]

Being that the game is in Alpha, and only version .17, many of these things are sure to change. In fact a couple of the engines changed in each of the last 3 versions.