User:Jlmr

KSP is just what I have been looking for! A creative space simulator! Now if the team at Squad would just add little things like, ships, air balloons, zeplins, bombs, guns, missiles, subs, lasers, ground combat, animals, city/nation building, multiplayer, space colonies, space docks, space construction yards, asteroid mining, resources/economy... Hey, I can hope right? =)

Kerbals at War = OMG!!! *drools*

My stuff

Units of measure

• While units of mass and thrust are not specifically labeled in-game, a bit of logic can quickly determine that thrust is measured in kilonewtons (kN) and mass in metric tons (t). For example, if measured in kilograms(kg), a "9 kg" Rockomax X200-16 Fuel Tank on Kerbin, having a surface gravity of 9.81 m/s2, would be roughly the size of a 48 oz coffee tin and only hold about 1.5 L of fuel. If measured in metric tons, a 9 t Rockomax X200-16 Fuel Tank under the same gravity would be about 0.67 m tall and 2 m in diameter, easily capable of holding the advertised 1600 L of fuel. Only a rocket engine with a thrust around 100 kN could have any chance to lift a 9 t fuel tank.

• Thrust to weight ratio at sea level on Kerbin is calculated by the following equation, which applies only to liquid or solid fuel rocket engines, jet engines use a complicated formula on a vehicle to vehicle basis.

${\frac {T}{W}}={\frac {T\ \mathrm {kN} }{(m\ \mathrm {t} )(g_{\rm {0}})}}$

where:

$T$ is the thrust is the thrust obtained from the engine, in kilonewtons.

$W$ is the weight of the engine at sea level on Kerbin's surface.

$m$ is the mass of the engine in metric tons (t).

$g_{\rm {0}}$ is the acceleration at sea level on Kerbin's surface, in m/s² (≈9.807 m/s²).

• Specific impulse at sea level on Kerbin is is calculated by the following equation.

Justification for t and kN (or 1000's kg and 1000's of N)

• An official NIST/SI publication: http://physics.nist.gov/Pubs/SP330/sp330.pdf states that kilonewton (kN) is a valid SI unit to represent 1000 N and ton (t), while historically a non-SI unit, has been accepted for use in the SI system by CIPM as a valid unit to represent 1000 kg for just over a century.

• We already know that the game uses SI units. These are specifically labeled: meters for units of distance, meters/sec for acceleration, liters for fuel volume, and liters/sec for fuel consumption.

• We know that the Mk1-2 Command Pod weighs 4 "units" from the in-game description. The command pod is roughly 2 m in height and 2 m in diameter. Calculating it's total volume gives us about 2.09 m3. Let's assume the capsule has 0.05 m (2 in) thick walls and subtract the interior void to get only the volume of the capsule walls. This gives us a volume of 1.80 m3.
  • Knowing the volume of the walls, we can calculate the density of the material making up the capsule, taking the 4 in-game units to mean kg, this comes out to be about 13.79 kg/m3. Unfortunately, is about 72.29 times less dense than water at room temperature and closer in density to most gasses! Perhaps Kerbals have discovered a super strong gas-like substance to make spaceships from? =)
  • However, if we take the 4 in-game units to mean metric tons, we get a density of around 13793.10 kg/m3, well within the range of the density of real building materials.

• The wikipage on Kerbin states it has a surface gravity of 9.81 m/s2, roughly that of Earth.
  • Given this we can calculate the following. If measured in kilograms(kg), a "9 kg" Rockomax X200-16 Fuel Tank on Kerbin, having a surface gravity of 9.81 m/s2, would be roughly the size of a 48 oz coffee tin and only hold about 1.5 L of fuel. Unfortunately for our intrepid Kerbals, 1.5 L of fuel would not provide enough energy to lift a 9 kg payload through 75,000 m of atmosphere, much less a few hundred meters.
  • If measured in metric tons, a "9 t" (9,000 kg) Rockomax X200-16 Fuel Tank under the same gravity, being about 0.67 m tall and 2 m in diameter, gives a volume of 2104.87 L, more than enough to hold the advertised 1600 L of fuel. Only a rocket engine with a thrust around 100 kN (100,000 N), could have any chance of lifting the 9 t (9,000 kg) fuel tank.
  • Similarly, a substance weighing only 8 kg with a volume of 1,600 L has a density of 5 kg/m3, only about three times greater than the density of gaseous oxygen, and would not make an efficient fuel. Whereas, a fuel weighing 8 t with a volume of 1,600 L has a density of 5000 kg/m3, closer to a realistic rocket fuel.