TChapman500

Yes, I know it's a game. No, I'm not suggesting a change. All this is doing is comparing KSP to real life. I did another thread a little while back where I compared fuel densities. I referenced that thread but didn't provide a link.

I just did a few calculations on the Jumbo 64 tank and found that the tank (without internal supporting structures) should have a mass of only 371 kilograms. Yet the tank with the internal supporting structures and the separate fuel and oxidizer cells and their supporting structure and the feed lines going to either end of the tank, somehow gives the tank a total mass of 4,000 kilograms. Tank Radius: 1.25 meters Tank Height: 7.50 meters Tank Material: Aluminum (Assumed) Tank Thickness: 0.002 meters (Assumed) Tank Volume: ~36,815 Liters Volume For Fuel: 6,400 Liters (17.4 %) [Note: Using realistic densities without reducing the mass would make this figure about 80%.] This fuel tank has only 1.4% of the volume of the external tank on the space shuttle (if that tank was cylindrical instead of tapered at the ends). 371 kilograms would put the mass of the Jumbo 64 tank at 1.4% of the mass of the space shuttle's external tank. But come to think of it, perhaps 2 millimeters is too thick. If we go with 1 millimeter, that might give us about 371 kilograms of mass with all of the internal components in place (minus the fuel). But my research suggests that the mass using solid aluminum would still be much higher than 371 kilograms (perhaps in the order of 1,000 kilograms?). There are also several repercussions to using a non-alloy such as the metal atoms sliding past each-other under stress. In which case you can forget about adding struts! And you can definitely forget about putting large things (such as landers and Scott Manley's super-heavy satellites) on top of the launchers. The rocket would fall apart in the VAB! The solution for the Kerbals seems to be "add more aluminum." Kerbal engineers can't seem to make the alloys they need to make light, but strong, rocket components, so they put so much aluminum into the internal supports that you get a 4 tonne tank that should weigh less than 1/10 that much. It also explains why the Kerbals need unrealistically dense fuels. Their vehicles would fall apart in the VAB if they tried using real fuels because they wouldn't be able to put enough aluminum in to make the tanks ridged. Note: Most of the references here can be found at Wikipedia. Manufacturer's Note: Warranty of the Jumbo 64 tank is void if anything is attached to the sides of the tank or if anything but decouples, other tanks of similar size or engines are attached to the ends of the tanks. Warranty is also void if an engine is pointed at the tank. Rockomax is not responsible for any rapid, unplanned disassemblies. Warranty void if used by Scott Manley.

You are correct. I have made a correction to the first post.

The units displayed on Wikipedia were in g/L, which when converted to kg/m^3 yield the exact same value. I was quite surprised at the results myself. EDIT: The tanks either have a 1 or 2-meter radius. Rounding out the height, the 1-meter tanks have a 2 (assuming shortest tank has a height the same as it's diameter), 4, or 6-meter height. This gives the 1-meter tanks a volume of 6.283 m^3 -> 6283 L, 12.566 m^3 -> 12,566 L, or 18.850 m^3 -> 18,850 L. Those tanks only hold 200, 400, and 800 L of fuel respectively.

If there's one thing I noticed about KSP, it's that Kerbals really waste their space with ultra-high-density fuels including air from the atmosphere (in the case of jet engines). Note: This thread is NOT intended to criticize KSP, but rather compare it to real life. The fuel densities in KSP are measured in tonnes/L. We will convert these units to kg/m^3. Liquid Fuel, Intake Air, and Oxidizer Density: 0.005 tonnes/L -> 5 kg/L -> 5000 kg/m^3 Mono propellant Density: 0.004 tonnes/L -> 4 kg/L -> 4000 kg/m^3 Solid Fuel Density: 0.0075 tonnes/L -> 7.5 kg/L -> 7500 kg/m^3 In a similar way, we'll convert the real life fuel densities back to tonnes/L. Real Life Liquid Fuel Densities (Source: http://en.wikipedia.org/wiki/Liquid_rocket_fuel#Bipropellants): Hydrogen: 70.85 kg/m^3 -> 0.07085 kg/L -> 0.00007085 tonnes/L Methane: 422.62 kg/m^3 -> 0.42262 kg/L -> 0.00042262 tonnes/L (Correction, http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=41) Kerosene: 915 kg/m^3 -> 0.915 kg/L -> 0.000915 tonnes/L Hydrazine: 1021 kg/m^3 -> 1.021 kg/L -> 0.001021 tonnes/L The liquid fuel that comes the closest to that which the Kerbals use is Hydrazine, with 1/5 the density of whatever fuel that the Kerbals use. How about the oxidizer densities: Liquid Oxygen: 1141 kg/m^3 -> 1.141 kg/L -> 0.001141 tonnes/L Dinitrogen tetroxide: 1443 kg/m^3 -> 1.443 kg/L -> 0.001443 tonnes/L The oxidizer that comes the closest to what which the Kerbals use is Dinitrogen tetroxide, with just under 1/5 the density of whatever oxidizer that the Kerbals use. We can't forget the mono propellant: Hydrazine: 1021 kg/m^3 -> 1.021 kg/L -> 0.001021 tonnes/L Hydrogen peroxide: 1135 kg/m^3 -> 1.135 kg/L -> 0.001135 tonnes/L Whatever mono propellant that the Kerbals use, it's a whopping 4 times denser than the densest mono propellant available to Humans. And finally, the solid fuel (http://spacemath.gsfc.nasa.gov/weekly/6Page38.pdf): Unknown Propellant Name: 1750 kg/m^3 -> 1.75 kg/L -> 0.00175 tonnes/L Whatever solid propellant is being used by the Kerbals, it's almost 4.5 times denser than what we're using in real life. Conclusion: The Kerbals seem to be using a variety of very dense, unknown fuels that apparently are very good at matching the performance of our real life rockets in terms of efficiency. But at a heavy (no pun intended) price. The fuel tanks need to be quite small. If the Kerbals were to fill up those tanks with fuel in order to optimize space efficiency, nothing that the Kerbals build could withstand the extreme weight of the tanks. At least not without some upgrades. Even when realistic fuel densities are applied, the structural reliability is so low that, even as "light" as those fuels are, nothing that the Kerbals can build would be able to support a fully optimized fuel cell.

That was helpful. So how do I extend the physics limit?

Sorry if this has been asked before, but how do I remove the atmospheric 2.5 km limit on objects that are not being controlled by the player?