Editing Heat shield (section)

===Passive cooling===
Passive cooled protectors are used to protect spaceships during [[atmospheric entry]] to absorb heat peaks and subsequently radiate heat to the atmosphere. Early versions included a substantial amount of metals such as [[titanium]], [[beryllium]] and [[copper]]. This greatly increased the mass of the vehicle. Heat absorption and ablative systems became preferable.

In modern vehicles, passive cooling can be found as [[reinforced carbon–carbon]] material instead of metal. This material constitutes the thermal protection system of the nose and the front edges of the Space Shuttle and was proposed for the vehicle [[Lockheed Martin X-33|X-33]]. [[Carbon]] is the most refractory material known with a sublimation temperature (for [[graphite]]) of 3825&nbsp;°C. These characteristics make it a material particularly suitable for [[passive cooling]], but with the disadvantage of being very expensive and fragile. Some spacecraft also use a heat shield (in the conventional automotive sense) to protect fuel tanks and equipment from the heat produced by a large [[rocket engine]].  Such shields were used on the Apollo [[Apollo Command/Service Module#Service Module (SM)|Service Module]] and [[Apollo Lunar Module|Lunar Module]] descent stage. The [[Parker Solar Probe]], designed to enter the corona of the Sun, experiences a surface temperature of 2,500 °F.<ref>{{Cite web |date=2018-07-05 |title=Cutting-Edge Heat Shield Installed on NASA's Parker Solar Probe - NASA |url=https://www.nasa.gov/centers-and-facilities/goddard/cutting-edge-heat-shield-installed-on-nasas-parker-solar-probe/ |access-date=2024-04-30 |language=en-US}}</ref> To withstand this temperature without damage to its body or instruments, the spacecraft uses a heat shield using a carbon-carbon ceramic with a layer of carbon foam in between.<ref>{{Cite web |last=Grossi |first=Stefano |title=Parker Solar Probe Heat Shield |url=https://ultramet.com/parker-solar-probe-heat-shield/ |access-date=2024-04-30 |website=Ultramet |language=en-US}}</ref> The probe was launched into space on August 18, 2018.<ref>{{Cite web |title=Parker Solar Probe - NASA Science |url=https://science.nasa.gov/mission/parker-solar-probe/ |access-date=2024-04-30 |website=science.nasa.gov |date=March 2019 |language=en-US}}</ref>