Search results
Results from the WOW.Com Content Network
An ablative heat shield consists of a layer of plastic resin, the outer surface of which is heated to a gas, which then carries the heat away by convection. Such shields were used on the Vostok , Voskhod , Mercury , Gemini , and Apollo spacecraft, and are currently used by the SpaceX Dragon 2 , Orion , and Soyuz spacecraft.
Ablative armor is armor which prevents damage through the process of ablation, the removal of material from the surface of an object by vaporization, chipping, or other erosive processes. In contemporary spacecraft, ablative plating is most frequently seen as an ablative heat shield for a vehicle that must enter atmosphere from orbit, such as ...
Early reentry-vehicle concepts visualized in shadowgraphs of high speed wind tunnel tests. The concept of the ablative heat shield was described as early as 1920 by Robert Goddard: "In the case of meteors, which enter the atmosphere with speeds as high as 30 miles (48 km) per second, the interior of the meteors remains cold, and the erosion is due, to a large extent, to chipping or cracking of ...
AVCOAT was used for the heat shield on NASA's Apollo command module. [4] In its final Apollo form, this material was called AVCOAT 5026–39. Although AVCOAT was not used for the Space Shuttle orbiters, NASA again used the material for its Orion spacecraft [5] first for the initial Orion test and then for a different type of heat shield for the later Orions.
In a basic sense, ablative material is designed so that instead of heat being transmitted into the structure of the spacecraft, only the outer surface of the material bears the majority of the heating effect. The outer surface chars and burns away – but quite slowly, only gradually exposing new fresh protective material beneath.
Previous ablative heat shields were very heavy. For example, the ablative heat shield on the Apollo Command Module comprised about 15% of the vehicle weight. The winged shuttle had much more surface area than previous spacecraft, so a lightweight TPS was crucial. Fragile
Additionally, these vehicles had ablative material that sublimates into a gas at high temperature. The act of sublimation absorbs the thermal energy from the aerodynamic heating and erodes the material rather than heating the capsule. The surface of the heat shield for the Mercury spacecraft had a coating of aluminium with glassfiber in many ...
Atmospheric re-entry spacecraft use phenol formaldehyde resin as a key component in ablative heat shields (e.g. AVCOAT on the Apollo modules). As the heat shield skin temperature can reach 1000-2000 °C, the resin pyrolizes due to aerodynamic heating. This reaction absorbs significant thermal energy, insulating the deeper layers of the heat shield.