AVCOAT 5026-39 is a

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

code for two versions of a specific ablative heat shield material originally created by Avco for the Apollo program. It is composed of

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

fibers in an

epoxy Epoxy is the family of basic components or Curing (chemistry), cured end products of epoxy Resin, resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide fun ...

novolac resin. The original AVCOAT was used for the Apollo Command Module heat shield. A reformulated version was used for the initial Orion heat shield and later for a redesigned Orion heat shield.

History

AVCOAT was used for the heat shield on NASA's Apollo command module. 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 first for the initial Orion test and then for a different type of heat shield for the later Orions. The Avcoat used on the two types of Orion shield was reformulated to meet environmental legislation that was enacted after the end of Apollo.

Specifications

* Material:

phenol formaldehyde resin Phenol formaldehyde resins (PF), also called phenolic resins or phenoplasts, are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Used as the basis for Bakelite, PFs were the first commercial syntheti ...

with special additives originally for use in a

fiberglass Fiberglass (American English) or fibreglass (English in the Commonwealth of Nations, Commonwealth English) is a common type of fibre-reinforced plastic, fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened i ...

honeycomb A honeycomb is a mass of Triangular prismatic honeycomb#Hexagonal prismatic honeycomb, hexagonal prismatic cells built from beeswax by honey bees in their beehive, nests to contain their brood (eggs, larvae, and pupae) and stores of honey and pol ...

matrix. * Density: * Post-ablation char-layer composition: of

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

and of

AVCOAT-based heat shields

Apollo Command Module

AVCOAT was first used on the parts of the Apollo spacecraft orbiter and as a unit attached to the crew module. The heat shield is a honeycomb structure filled with the AVCOAT. NASA confirmed that this is made of silica fibers with an epoxy novolac resin filled in a fiberglass-phenolic manufactured directly onto the heat shield. The paste-like material was gunned into each cell of the fiberglass honeycomb individually. NASA's Apollo Flight Test Analysis, AVCOAT 5026-39/HC-G material was tested on the nose cone of a Pacemaker sounding rocket. The temperature and ablation measurements were made at four locations on the nose cap. The report noted that the wear of the shield is due to the aerodynamic shear and heating rate. The report also noted that scientists believed that the ablation was done in a controlled manner.

Orion EFT-1 Crew Module

To protect the Crew Module during Earth re-entry, the dish shaped AVCOAT heat shield ablator system was selected.

announced that this module would encounter temperature as high as 5,000 degrees Fahrenheit (2760 °C). Licensed by

Textron Textron Inc. is an American industrial Conglomerate (company), conglomerate based in Providence, Rhode Island. Textron's subsidiaries include Arctic Cat, Bell Textron, Kautex, Textron Aviation (which itself includes the Beechcraft and Cessna b ...

, AVCOAT material is produced at New Orleans's Michoud Assembly Facility by

Lockheed Martin The Lockheed Martin Corporation is an American Arms industry, defense and aerospace manufacturer with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta on March 15, 1995. It is headquartered in North ...

. This ablative heat shield was installed at the base of the crew module to provide a controlled erosion moving heat away from the crew module into the atmosphere. John Kowal, Orion's thermal protections systems manager at

Johnson Space Center The Lyndon B. Johnson Space Center (JSC) is NASA's center for human spaceflight in Houston, Texas (originally named the Manned Spacecraft Center), where human spaceflight training, research, and flight controller, flight control are conducted. ...

, discussed the biggest challenge with AVCOAT has been reviving the technology for manufacturing with similar performance as demonstrated in the Apollo Missions. After the Apollo missions, Avcoat variants were produced and studied. Orion Chief Engineer requested the heat shield to be redesigned, however the final design was not selected. The Orion Crew Module was first designed for the NASA's

Constellation program The Constellation program (abbreviated CxP) was a crewed spaceflight program developed by NASA, the space agency of the United States, from 2005 to 2009. The major goals of the program were "completion of the International Space Station" and a " ...

. The heat shield was designed and manufactured similarly to the Apollo version as a monolithic fiberglass honeycomb which was then filled with the AVCOAT. The honey comb consisted of 330,000 small cells. Each cell was individually filled with AVCOAT one at a time by a technician with a pressure gun, with the process taking more than six months for the shield. The EFT-1 mission performed two orbits of Earth providing the opportunity for Orion's systems to be tested. It took about four hours with the splash down in the ocean. This was the only flight with this heat shield.

Orion Artemis Crew Module

After the end of the Constellation program, Orion was adapted for use with the

Space Launch System The Space Launch System (SLS) is an American Super heavy-lift launch vehicle, super heavy-lift Expendable launch system, expendable launch vehicle used by NASA. As the primary launch vehicle of the Artemis program, Artemis Moon landing progra ...

to replace the Space Shuttle program. This spacecraft was planned to take astronauts to the

International Space Station The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...

(ISS) in 2015 and to the moon in 2024. However, Orion was never used for ISS. Its first flight after EFT-1 was the uncrewed

Artemis I Artemis I, formerly Exploration Mission-1 (EM-1), was an uncrewed Lunar orbit, Moon-orbiting mission that was launched in November 2022. As the first major spaceflight of NASA's Artemis program, Artemis I marked the agency's return to lunar e ...

, which flew in 2022. Manufacture of the EFT-1 heat shield was labor-intensive and there were concerns that the monolithic honeycomb design was inappropriate for the large Orion shield. Therefore, the shield was redesigned to use carefully shaped Avcoat blocks instead. The AVCOAT material heat shield went through several rounds of testing before being chosen for the installation. During the investigation of the thermochemical response of Avcoat TPS (based on first principles for comparison with EFT-1 data), things being tested on the heat-shield included: modeling of gas transport, heat transfer, and TPS material regression. Orion's 16.5 feet AVCOAT heat shield was secured onto the Orion Crew Module using 68 bolts by Technicians at NASA's Kennedy Space Center (KSC) in Florida. This heat shield is covered in titanium truss and a composite substitute with an addition skin made of carbon fiber layers. Orion's heat-shield was designed and manufactured by Lockheed Martin. The heat shield is like pieces of a puzzle that all must fit together perfectly and the bolt fittings must be lined up. After the heat-shield's installation, access to components of the crew module became difficult or no longer accessible.

Flight use

Uncrewed

* Several subscale test flightsFLIGHT-TEST ANALYSIS OF APOLLO HEAT-SHIELD MATERIAL USING THE PACEMAKER VEHICLE SYSTEM

Technical Note D-4713, pp. 8, 1968-08, accessed 2024-10-29. ''"Avcoat 5026-39/HC-G is an epoxy novolac resin with special additives in a fiberglass honeycomb matrix. In fabrication, the empty honeycomb is bonded to the primary structure and the resin is gunned into each cell individually. ... The overall density of the material is 32 lb/ft³ (512 kg/m³). The char of the material is composed mainly of silica and carbon. It is necessary to know the amounts of each in the char because in the ablation analysis the silica is considered to be inert, but the carbon is considered to enter into exothermic reactions with oxygen. ... At 2160 ° R (1200° K), 54 percent by weight of the virgin material has volatilized and 46 percent has remained as char. ... In the virgin material, 25 percent by weight is silica, and since the silica is considered to be inert the char-layer composition becomes 6.7 lb/ft³ (107.4 kg/m³) of carbon and 8 lb/ft³ (128.1 kg/m³) of silica."'' * AS-201Apollo Experience Report - Thermal Protection Subsystem (Jan. 1974)
/ref> * AS-202 * Apollo 4 * Apollo 6 * EFT-1 * Artemis 1

Crewed

Apollo 7 Apollo 7 (October 11–22, 1968) was the first crewed flight in NASA's Apollo program, and saw the resumption of human spaceflight by the agency after the fire that had killed the three Apollo 1 astronauts during a launch rehearsal test ...

Apollo 8 Apollo 8 (December 21–27, 1968) was the first crewed spacecraft to leave Sphere of influence (astrodynamics), Earth's gravitational sphere of influence, and the first human spaceflight to reach the Moon. The crew orbited the Moon ten times ...

Apollo 9 Apollo 9 (March 3–13, 1969) was the third human spaceflight in NASA's Apollo program, which successfully tested systems and procedures critical to landing on the Moon. The three-man crew consisted of Commander James McDivitt, Command Modul ...

, Apollo 10 *

Apollo 11 Apollo 11 was a spaceflight conducted from July 16 to 24, 1969, by the United States and launched by NASA. It marked the first time that humans Moon landing, landed on the Moon. Commander Neil Armstrong and Lunar Module pilot Buzz Aldrin l ...

, Apollo 12,

Apollo 13 Apollo 13 (April 1117, 1970) was the seventh crewed mission in the Apollo program, Apollo space program and would have been the third Moon landing. The craft was launched from Kennedy Space Center on April 11, 1970, but the landing was abort ...

Apollo 14 Apollo 14 (January 31February 9, 1971) was the eighth crewed mission in the United States Apollo program, the third to Moon landing, land on the Moon, and the first to land in the Geology of the Moon#Highlands, lunar highlands. It was the las ...

Apollo 15 Apollo 15 (July 26August 7, 1971) was the ninth crewed mission in the Apollo program and the fourth Moon landing. It was the first List of Apollo missions#Alphabetical mission types, J mission, with a longer stay on the Moon and a greate ...

Apollo 16 Apollo 16 (April 1627, 1972) was the tenth human spaceflight, crewed mission in the United States Apollo program, Apollo space program, administered by NASA, and the fifth and penultimate to Moon landing, land on the Moon. It was the second o ...

Apollo 17 Apollo 17 (December 7–19, 1972) was the eleventh and final mission of NASA's Apollo program, the sixth and most recent time humans have set foot on the Moon. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on the Moon, ...

* Skylab 2, Skylab 3,

Skylab 4 Skylab 4 (also SL-4 and SLM-3) was the third crewed Skylab mission and placed the third and final human spaceflight, crew aboard the first American space station. The mission began on November 16, 1973, with the launch of Gerald P. Carr, Edwar ...

* Apollo–Soyuz Test Project

References

External links

Apollo Experience Report - Thermal Protection Subsystem (Jan. 1974)

Apollo Seals: A Basis for the Crew Exploration Vehicle Seals (Nov. 2006)

Notes on Earth Atmospheric Entry for Mars Sample Return Missions (Sept. 2006)

NASA paper on Artemis I heat shield damage

NASA press conference with extensive description of AVCOAT history and details
{{DEFAULTSORT:Avcoat 5026-39 Spacecraft components