Overheating
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In the game Kerbal Space Program, the largest and most powerful of the engines tend to overheat. To avoid overheating, thrust should never be at 100% for a long time. Depending on the configuration it may need to be kept below about 66%. Different engines have different overheating rates and levels.
This is most noticeable on the most powerful engines, such as the Rockomax "Mainsail" Liquid Engine, which overheat very easily. It is possible to dampen overheating by using smaller fuel tanks. For example, using the Mainsail engine and Rockomax Jumbo-64 Fuel Tank overheats the engine very quickly, while using the tank one size smaller, the Rockomax X200-32 Fuel Tank, allows the engine to run at a higher thrust level without overheating.
Overheating can also occur when at close distances to Kerbol.
As of Version 1.0, the new 'Drill-O-Matic' Mining Excavator can cause overheating, and solar panels are capable of acting as radiators.
Contents
Practical overheat concerns
- or: How I Learned to Stop Worrying and Love the Overheat
As of version 1.0.2[outdated], overheat only really matters if the overheat bar reaches 100%. If the bar fills up, the engine explodes; if it doesn't fill up, there's no problem.
In practice, this means that overheating can often be entirely ignored. Fuel supply is frequently exhausted long before it reaches 100%, or the burn is completed and the engine shutdown again.
Even the Mainsail under a pair of stacked Jumbo-64 tanks can run at 100% for long enough to fully drain both tanks, without exploding, so it's frequently unnecessary to make changes to eliminate the overheat. One way to approach it is to simply ignore overheat entirely when designing, then try the craft on some normal flight profiles. If the overheat bars stay comfortably below 100% (e.g. no more than about 80%), it's not an issue. With the new thermal system added in 1.0, it has now become important to additionally factor in leaving sufficient unused overheat capacity if heat from a source other than the running engine is expected.
Internal heating mechanics
Since 1.0.2, all parts have heating values which can be shown by enabling "Display Thermal Data in Action Menus" underneath the Thermal tag of the Physics branch of the Debug Toolbar. When enabled, seven extra values will be shown in the action menus of each part (shown when a part is right-clicked). These are the numbers that influence how parts of a rocket heats up.
Thermal Mass
This number influences how likely heat is to conduct into that part through other parts. For example, a part with a high thermal mass and a part with low thermal mass that are equidistant from a heat source will likely have more heat conducted into the part with high thermal mass.
Temp
This is the temperature, in Kelvin, of the part.
Temp Ext
This is the temperature, in Kelvin, of the air or space surrounding that part.
Cond Flux
This is the speed that heat is conducting into or out of the selected part. Conduction is the spreading of heat through contact. A positive number means that the part is gaining heat due to conduction, while a negative number means that it is losing heat.
Conv Flux
This is the speed that heat is convecting into or out of the selected part. Convection is the spreading of heat through the surrounding atmosphere. This number only applies in the atmosphere. A positive number means that the part is gaining heat due to convection, while a negative number means that it is losing heat.
Rad Flux
This is the speed that heat is radiating into or out of the selected part. Radiation is the spreading of heat through the surrounding vacuum. A positive number means that the part is gaining heat due to radiation, while a negative number means that it is losing heat.
Int Flux
This is the speed that the part is generating heat internally. This number usually only applies to engines and drills.
