What are the units of measure used in Kerbal Space Program

kerbal-space-program

Kerbal Space Program is, ostensibly, all about having fun with rocket science. Of course, much of rocket science is dependent upon mathematics. Sure, there's plenty of mods and tools to help you out with calculating delta-V, TWR, and the like. But sometimes you want to stretch out and go beyond what the tools are designed to do for you. Without having an actual, deep understanding of the physics and all behind these things, this leaves many of us Googling up equations and tossing numbers at them to see what they spit out.

However, certain equations are designed around specific units of measure so that their results are properly scaled to the forces expected to be in play. This presents a problem when we try to carry over details from Kerbal Space Program where the measurement units are not specified in-game. In order come up with correct (or even remotely accurate) answers to our questions, we need to know which units of measure are being used in-game and how they compare to real-world units.

Some of the most critical units that are unspecified in-game are seen in the Vehicle Assembly Building and Space Plane Hangar, where we're dealing with various properties of the parts that will make up whatever it is we're hoping to not have blow up in our face. (Or, for some of us, whatever we're hoping to make blow up in our face spectacularly!) There may be others used in these or other interfaces I'm not thinking of, but I'm particularly looking to at least get the following defined:

Standard unit of mass used to measure parts and fuel.
Units of mass and/or volume used to measure all fuel types.
- Liquid Fuel
- Oxidizer
- Solid Fuel
- Monopropellant
- Xenon Gas
- Intake Air
Units used to describe applied forces.
- Thrust
- Torque

For each of the above (and any I've missed), I want to know:

What is the unit of measure used for in-game displays?
If the unit is unique to Kerbal Space Program, how can I convert it to a usable real-world unit? (Or is proper conversion impossible?)

(Note: This should probably be a Community Wiki)

Best Answer

Everything in Kerbal Space Program uses the Metric system

Distances are measured in (kilo)metres

Masses are measured in metric tons (this applies to both parts and fuels).

Xenon Gas is measured as mass per unit not volume: 0.1 kg per unit
All other gasses are 5kg per unit

Volumes (for all other liquid fuel, oxidizer, monopropellant, solid fuel etc), are measured as 2-2.5 litres per unit.

Thrust is measured in kilo-newtons.

No real world analogue exists for electric charge. It is speculated a unit of electric charge is, as estimated from the capacity batteries and the consumers, it is about 10 kJ (power of 10 kW for a second).

Source

Related Solutions

Escape Kerbin’s gravitational pull

Technically, you can escape Kerbin's gravity at any height, as long as you're going fast enough.

To orbit the planet at any given altitude, you only need to be travelling at the corresponding horizontal speed, as shown in the table below. The only reason that you can't orbit the planet consistently at low altitudes is that it's difficult to maintain your orbital velocity in the presence of atmospheric drag.

For example, to enter an orbit at 100km above the surface, you need a horizontal speed of 2245.8 meters per second.

Kerbin's atmosphere tapers off at approximately 68-70 km above the surface. Any orbit below this altitude will require corrections due to atmospheric drag, or else your ship will begin losing orbital speed and eventually deorbit. You can also do this intentionally if you want to deorbit your spacecraft - reduce your speed enough to drop below the minimum horizontal speed given in the table, and your spaceship will begin to descend.

I've snipped portions of this table to save space. The full thing can be found on the Kerbal Space Program Wiki:

Altitude (m)    Horizontal Speed (m/s)  Orbital Period (min)
35000                2357.9                   28.20
40000                2348.7                   28.54
45000                2339.6                   28.87
50000                2330.6                   29.21
55000                2321.7                   29.54
60000                2312.8                   29.88
65000                2304.1                   30.22
70000                2295.5                   30.56
75000                2287.0                   30.91
80000                2278.6                   31.25
85000                2270.3                   31.60
90000                2262.0                   31.94
95000                2253.9                   32.29
100000               2245.8                   32.64
110000               2229.9                   33.34
120000               2214.4                   34.05
130000               2199.2                   34.76
140000               2184.3                   35.48
150000               2169.6                   36.20
160000               2155.3                   36.93
170000               2141.3                   37.66
180000               2127.5                   38.39
190000               2114.0                   39.13
200000               2100.7                   39.88
300000               1980.6                   47.59
400000               1879.0                   55.73
500000               1791.5                   64.30
600000               1715.3                   73.26
700000               1648.0                   82.61
800000               1588.0                   92.32
900000               1534.2                   102.39
1000000              1485.5                   112.79
2,868,378            1008.9                   6 hours
8,140,000             635.4                   24 hours

Kerbal Space Program – Science Experiments on and Near Kerbin

In Kerbal Space Program, Science depends on the location and the type of experiment.

Altitude Corridor

In detail, for Kerbin, this makes five altitude corridors (with some caveats):

On the Ground (0m)
Lower Atmosphere (≤ 18km)
Upper Atmosphere (≤ 69km)
Near Space (≤ 250km)
Outer Space (> 250km)

Biomes

On top of that, Kerbin knows various biomes:

Grasslands
Highlands
Mountains
Deserts
Badlands
Tundra
Ice Caps
Water
Shores

Additionally, the Space Center also has various mini-biomes which return separate results, but only when on the ground (above ground, the whole space center counts as "Shores"):

Administration
Astronaut Complex
Crawlerway
Flag Pole
LaunchPad
Mission Control
R&D
Runway
SPH
Tracking Station
VAB

Experiments

Depending on the experiment, some of these altitude corridors have per-biome results, others only have one result for the entire corridor.

In particular:

The Surface Sample is a biome-dependant surface-only experiment.

The EVA Report is biome-dependant on the surface, in the lower atmosphere and in near space; it is global everywhere else.

The Crew Report is biome-dependant on the surface and in the lower atmosphere; it is global everywhere else.

The Mystery Goo Observation (available through the Mystery Goo™ Containment Unit from the Basic Rocketry tech node) is biome-dependant on the surface; it is global everywhere else.

Storing Experiments

There can only be one crew report per part that produces a crew report (that is, per capsule), which is stored in the part. It can be transmitted, in which case it makes space for a new crew report.

Both the EVA report and the Surface Sample experiments can be stored in the capsule as well, with each combination of altitude corridor and biome once. So, you can store a surface sample from every biome, and EVA reports from every biome all at once.

Transmitting Results

Results can either be recovered by landing the craft on Kerbin and then recovering it from the Tracking Station (or from the craft view, where it's hidden at the top of the screen), or by transmitting them home.

Transmission is hardly effective this early into the tech tree - you lack the electricity to send the results back. Nevertheless, you can - for example - send back one crew report to make space for another, so here's some information about transmission as well:

Every experiment has a transmission efficiency, which reduces the Science yield on transmission (as opposed to recovery).

In the case of the Surface Sample this is 25%, which makes them an undesirable candidate for transmission.

Similarly, the Mystery Goo Observation has only 30% efficiency.

All reports (be that EVA or Crew), however, return a full 100%.