Difference between revisions of "Overheating"

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m (Int Flux)
(Less engine-centric. Mainsail hasn't been a major problem for a lot of versions now. I'm pretty certain the old small tank method is completely obsolete under 1.0 heat mechanics, or it certainly should be.)
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[[File:Overheat bar.png|thumb|right|Overheat bar next to the fuel bar of an overheating [[SRB]].]]
 
[[File:Overheat bar.png|thumb|right|Overheat bar next to the fuel bar of an overheating [[SRB]].]]
[[File:Rockomax Mainsail transparent.png|thumb|right|The most powerful engines tend to overheat the most.]]
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'''Overheating''' can be caused by a number of different things. Common heat sources are engines while they are active, and aerodynamic heating. Different engines produce different levels of heat, and have different heat tolerances, resulting in some being more problematic than others. Heat flows to adjacent parts via conduction, so it is not always the part producing the heat which explodes, but a less heat tolerant part which is too close to it. Parts which are too close to, or directly in the path of, a rocket exhaust will gain heat and can overheat, and thrust vectoring or gimballing must be considered for that as well.
In the game [[Kerbal Space Program]], the largest and most powerful of the [[engine]]s 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]].
 
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.  
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Historically, certain engines were highly problematic for heat generation, but the significant overhaul to heat in 1.0 has consigned most of those cases to the past.
  
 
== Practical overheat concerns ==
 
== Practical overheat concerns ==
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: ''or: How I Learned to Stop Worrying and Love the Overheat''
 
: ''or: How I Learned to Stop Worrying and Love the Overheat''
  
As of version {{Check version|1.0.2}}, 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.
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As of version {{Check version|1.0.2}}, overheat only really matters if the overheat bar reaches 100%.  If the bar fills up, the part 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.
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In practice, this means that overheating can often be entirely ignored.  For engines, the 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.
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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, such as re-entry aerodynamic heating.
  
  

Revision as of 11:13, 26 May 2015

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Overheat bar next to the fuel bar of an overheating SRB.

Overheating can be caused by a number of different things. Common heat sources are engines while they are active, and aerodynamic heating. Different engines produce different levels of heat, and have different heat tolerances, resulting in some being more problematic than others. Heat flows to adjacent parts via conduction, so it is not always the part producing the heat which explodes, but a less heat tolerant part which is too close to it. Parts which are too close to, or directly in the path of, a rocket exhaust will gain heat and can overheat, and thrust vectoring or gimballing must be considered for that as well.

Overheating can also occur when at close distances to Kerbol.

Historically, certain engines were highly problematic for heat generation, but the significant overhaul to heat in 1.0 has consigned most of those cases to the past.

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 part explodes; if it doesn't fill up, there's no problem.

In practice, this means that overheating can often be entirely ignored. For engines, the fuel supply is frequently exhausted long before it reaches 100%, or the burn is completed and the engine shutdown again.

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, such as re-entry aerodynamic heating.


Internal heating mechanics

File:Parttempdataexample.png
An action menu with thermal values.

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. This value is influenced by heat shields which consume ablator to absorb heat.