Fuel Densities and Cost per Litre

[SDIR]

I was just calculating cost benefit of my shuttle program versus my rocket program when I came upon a road block, the cost of fuel. Now, KSP provides us with empty and full fuel masses, but does not disclose the cost per litre of fuel/oxidizer, or the cost of an empty tank, so we cannot use regular methods to calculate the cost of fuel per volume. Additionally, the cost of the tank also increases as the volume of fuel also increases, as the tank must get bigger to accommodate more fuel. If anybody has spent the time to find out, it would be much appreciated if they could tell me or show the method to calculating the cost per litre of fuel. I've already used the method used in the Millikan oil drop experiment with no avail. If anybody can help it would be great!

[SuperWeegee4000]

Yes, a liter calculator would be nice. Try making a suggestion to the modding community.

[kahlzun]

Keep in mind that the 'units' of fuel in the game aren't litres.

Near as we can tell, the units are about 1/5 Litre (200mL)

[CaptainArbitrary]

Keep in mind that the 'units' of fuel in the game aren't litres.

Near as we can tell, the units are about 1/5 Litre (200mL)

Other way around. It's exactly 5 liters per unit of "fuel" in the stock game. Fixing that is always the first thing I do on a new install of the game.

[ialdabaoth]

Five? By my calculations it's 6.25

[SDIR]

However, the amount of litres doesn't really matter when calculating the cost per unit volume of fuel. I'm not sure if the devs just made up the cost of each fuel tank or used a formula that calculated the cost factoring in the surface area of the tank plus the volume of the fuel (hopefully the last one) but I just want to know if figuring out the cost per unit volume is even possible.

[CaptainArbitrary]

Five? By my calculations it's 6.25

You can get it to be anywhere in that neighborhood, depending on which stock part you choose as your reference and what utilization factor you assume for it. But for me, the controlling factor is that if you peg the conversion factor at 5 liters to the "fuel unit," you get a utilization factor of around 85%, and also both the stock "LiquidFuel" and "Oxidizer" resources have exactly the same density as water. So I settled on 5 liters to the "fuel unit" last year sometime. I thought it was universally agreed upon, but maybe there's been new debate about it since that I didn't see.

[Sirrobert]

Where do you people get these numbers? Only numbers I see in the game are the units

[KerbMav]

You can get it to be anywhere in that neighborhood, depending on which stock part you choose as your reference and what utilization factor you assume for it. But for me, the controlling factor is that if you peg the conversion factor at 5 liters to the "fuel unit," you get a utilization factor of around 85%, and also both the stock "LiquidFuel" and "Oxidizer" resources have exactly the same density as water. So I settled on 5 liters to the "fuel unit" last year sometime. I thought it was universally agreed upon, but maybe there's been new debate about it since that I didn't see.

How is that relevant and for what?

Where do you people get these numbers? Only numbers I see in the game are the units

And what he said.

[Burgled]

I don't think it's possible to calculate.

The prices seem arbitrary and dry masses are at a fixed ratio.

That being said one thing we can figure out (assuming there is any logic to the prices) is an upper bound on the price of fuel.

It is $2.29166666667 per unit of fuel, from the Mk3 fuselage. This would be assuming the fuselage itself is free.

[Horn Brain]

Fuel is free compared to hardware. If the cost of your shuttle program is anything like the cost of your expendable rocket program, then you're doing your shuttle wrong.

Assuming the fuel is something like RP-1, you can use aviation kerosene as a ballpark estimate. That costs $925 per metric ton right now according to the IATA (http://www.iata.org/publications/economics/fuel-monitor/Pages/price-analysis.aspx), so call it $1000 per ton. Liquid oxygen is cheaper than that, so I would just use $1000 per ton of fuel/oxidizer. Those are real dollars, not kerbal dollars, which I have no idea how to convert, but the point is that even large rockets running on RP-1 aren't going to have even $1,000,000 in fuel costs, while the cost of a large rocket launch is often in the hundreds of millions of dollars range. Ignore fuel cost.