Heat shield

A heat shield is a part which protects shielded parts from overheating. almost all heat shields, excluding the Heat Shield (10m) work as ablative heat shields. This means each has a certain amount of ablative material, ablator, which slowly breaks apart carrying heat away. All of the heat shields currently in the game have a maximum temperature of 3,400 Kelvin and an impact tolerance of 9 m/s. As a rule of thumb, it is recommended to use them on capsules which are expected to return from 55 km or higher.

In version 1.1 the Heat Shield (10m) was added. This is the game's first inflatable heat shield. The part begins as a 2.5m component that inflates into a 10m diameter heat shield with a maximum temperature of 3,500 Kelvin.

Note that these can not only be used for atmospheric reentry, but also to separate a heat-sensitive stack from a heat-generating stage like an engine cluster.

All four of the ablative heat shields resemble the heat shield of the Orion MPCV.

As of 1.1, all heat shields can be jettisoned.

In 1.2 a smaller 0.625m heat shield was added.

Function

Heat Shields create a "cylinder of coolness" behind them which protect other parts from heating. Actually any leading part will create a similar zone of coolness behind itself but Heat Shields are particularly effective in this role as they have high temperature tolerances.

Any part within the cylinder of coolness will not experience aerodynamic heating, despite this a small amount of heat will conduct through the heat shield to connected parts, this heat by conduction is not normally a problem but can destroy unusually heat-sensitive parts mounted onto or very close to the heat shield.

A heat shield is only able to completely protect parts which have a smaller radius, a 2.5m heat shield will protect all 1.25m parts, in addition conical parts (such as command pods) of equal radius will typically be protected, a 1.25m heat shield *will* protect a Command Pod Mk1. Cylindrical parts of the same general radius are sometimes protected but most often not, it depends on the precise radius and the presence of protrusions that stick out into the hot air - probe cores for example tend to have pokey out bits that make them difficult to shield from heat, another example is the Science Jr: if the doors are open it will not fit behind a 1.25m heat shield and will be destroyed by heating, if the doors are closed it does fit (just barely). Even if a cylindrical part does fit behind the heat shield, the prograde or retrograde hold must be extremely precise to ensure the part stays precisely behind the heat shield.

Parts

Image	Part	Radial size	Cost ()	Mass (t)	Max. Temp. (K)	Tolerance (m/s)	Tolerance (g)	Ablator
	Heat Shield (0.625m)	Tiny	150 (125)	0.075 (0.025)	3 300	9	50	50
	Heat Shield (1.25m)	Small	300 (200)	0.3 (0.1)	3 300	9	50	200
	Heat Shield (2.5m)	Large	600 (200)	1.3 (0.5)	3 300	9	50	800
	Heat Shield (3.75m)	Extra large	1100 (200)	2.8 (1.0)	3 300	9	50	1 800
	Heat Shield (10m)	Large / 10m	2 400	1.5	3 500 (3 250)	9	50	—