What is the unit of measure for rocket fuel? It does NOT appear to be liters!

[stringyquark]

I think this discussion is just about ripe enough for a move to the science section.

I've read this thread from cover to cover, and it's a very interesting discussion. Main issue I have with it is most of the talk about propellant has appeared to be centered around what seem like liquid propellants at room temp.

http://www.nasa.gov/topics/technology/hydrogen/hydrogen_fuel_of_choice.html

If we go with kerbals using H O rockets then we're talking about cryogenic fuels. I'm not sure if you can just use regular liquid measures, needs more research.

And if we're talking blutonium, from my understanding a sixth dimensional quasi antimatter dark energy, sustained in a renormalized tau neutrino weak field oscillation. Who knows what is really going on in those gas tanks.

Either way the answer is 42

Now carry on gentlemen, and ladies.

[wasmic]

Well, as the quote from Greys on page two states, the volume of a unit is different depending on what you're trying to measure. A unit of XenonGas takes up less space than a unit of LiquidFuel, but at the same time, a unit of XenonGas also weighs less than a unit of LiquidFuel.

As none of the fuels (except for xenon) are specified, the only reliable way to figure out the density of the fuel is to measure a tank - how much fuel does it contain (in mass) versus how big is said tank.

[-Velocity-]

Well, as the quote from Greys on page two states, the volume of a unit is different depending on what you're trying to measure. A unit of XenonGas takes up less space than a unit of LiquidFuel, but at the same time, a unit of XenonGas also weighs less than a unit of LiquidFuel.

As none of the fuels (except for xenon) are specified, the only reliable way to figure out the density of the fuel is to measure a tank - how much fuel does it contain (in mass) versus how big is said tank.

Yes, as I noted very early in the thread, if we assume that most of the volume of a fuel tank is used to store fuel, then the density of fuel is around the density of water, 1000 kg/m^3. If we assume that only like 15% of a fuel tank is actually used to store fuel, which is, to me, a nonsensical, stupid assumption, then we arrive at a density of fuel of being 5000 kg/m^3.

In the end, what I did for my xenon tanks was make my converted Jumbo64 hold 28 m^3 of liquid xenon, for a total of 856000 units of xenon fuel (assuming a density of 3057 kg/m^3). As the Jumbo 64 has a volume of 36.8 m^3, my xenon Jumbo 64 utilizes 76% of its volume to store xenon.

It also turns out that the stock xenon tank included with the game is rather inefficient, holding only like 50% of its volume in xenon fuel (though, I haven't actually measured it precisely). However, I think that is roughly in line with other very small fuel tanks that hold rocket fuel. I also doubled the dry mass of my liquid xenon Jumbo 64 on the premise that it needed more structural reinforcement due to the high mass of liquid xenon.

Now, can someone make a model of a nuclear reactor with actual heat sink fins? All the nuclear reactors I have seen in various mods (like the DSM mod) have terribly unrealistic models. You've got to have a heat gradient to harvest energy from your nuclear reactor, and the only way to get that heat gradient in space is a bunch of black heat radiator panels. In a good model, the radiator panels probably ought to glow a faint red from the heat near the reactor, too.

Is there a huge barrier to entry in 3D modelling, like having to buy ten thousand dollar 3D modelling software?

[Jackaboy79]

On 9/7/2013 at 10:12 PM, capi3101 said:

Well...let's do some math. Almost every fuel tank in the game (exceptions are the Round-8 and Oscar- has a wet mass to dry mass ratio of 9:1 - the best example of course being the X200-16 tank (mass 9 tonnes, dry mass 1 tonne). That means that the fuel in that tank weighs eight metric tonnes, and a metric tonne is of course 1000 kg or 1,000,000 g. So, the fuel in that tank has a mass of 8,000,000 g. Now by definition, one gram equals one cubic centimeter equals one milliliter, so the volume of fuel in the tank is 8,000,000 milliliters.

With me so far? We know that the fuel in the X200-16 tank consists of 720 units of liquid fuel and 880 units of oxidizer; this is totally consistent with the 9:11 fuel to oxidizer ratio that the game utilizes. 1600 total units (720 + 880 = 1600) between the two = 8,000,000 milliliters, so therefore a single unit equals 5000 milliliters (8,000,000/1600 = 5000), or 5 liters.

There's your answer: one unit equals five liters.

You could also think of it as one unit equals 0.5 decaliters, though I don't know if that's a common unit of measure in practice in countries that practice the metric system (such as Mexico, where Squad is based) or not.

I suppose by extension, one unit has a mass of five kilograms and represents a volume of .005 cubic meters. Pretty sure that's consistent with the listed 5 kg/L density; I'll have to do more math on tht one.

I figured this math was pretty solid, but using other numbers given by the game I have obtained a very similar result. The engine used for this math is the J-33 "Wheesley" turbofan engine due to its convenient numbers. Now, most of you probably know that the equation for specific impulse in seconds is  where F is the thrust (in newtons), g0 is gravity (9.81 m/s2), Isp is specific impulse in seconds, and m is fuel flow in kg/s. In order to find the fuel flow, I rearranged the equation to F/g0/Isp = m. With the wheesley, f = 120,000 newtons, g0 = 9.81, and Isp = 10500. So, the new equation is 120,000/10500/9.81 = m. Do the math, and you get 1.164991990680064. Divide 1.164991990680064 by the flow listed in the game (2.33U) and you get 4.999965625236327, or approx. 5 kg.

[Snark]

Interesting math, but this thread is four year old and long since dead.  Everyone originally involved has presumably long since moved on.  Locking the thread to prevent further confusion; if there's still interest or discussion about this topic, feel free to spin up a new thread.