Felted is a term variously applied to hairy or otherwise filamentous material that is densely packed or tangled, forming felt or felt-like structures. Apart from fibres in felted fabric manufactured by humans, the term "felted" may apply to the condition of hair such as in the pathological condition known as felted hair, or it may apply to the tangled threads of the tissue of certain fungi, to matted fibres in animal connective tissue, or to the felted outer coat of certain plants. To say that something is felted need not imply that any processes of matting, condensing and pressing fibres have been applied as in the processes for artificial production of felt fabric. Depending on the nature of the felted material, it might rely purely on the scaly or barbed texture of the matted fibres to prevent unraveling, but commonly it will include clayey or sticky materials for its structural integrity, or for increased density.

Zoological use of the term

Examples of the description of animal tissues as "felted" include classes of connective tissue such as the dermis which the classic Gray's Anatomy describes as: "felted connective tissue, with a varying amount of elastic fibers and numerous bloodvessels, lymphatics, and nerves." Also, in describing the external coat or tunica adventitia of an artery, Gray says: "...consists mainly of fine and closely felted bundles of white connective tissue..."[1] In such classes of connective tissue the felted structure is very important; it is versatile in resisting tearing by distributing localised stresses and it imparts strength together with shock absorption and elasticity in two or three dimensions at once, irrespective of the shape of the tissue.[2] In other words, suitable types of felting can yield controllable isotropy or anisotropy in the behaviour of a structure.[3]

Drawing of cuticular surfaces of hairs of dog, cat, and human (left to right). The surface texture affects the felting behaviour of the various hair types
Down Awn and guard hairs of cat 2012 11 13 9203r
Down (woolly) hair, awn hair and guard hair of domestic cat (left to right).
Carder bee - felted nesting materia IMG 0273s
Felted plant fibre from nest of a Southern African carder bee

Other examples of felted material in animal structures include fibrous structures coating the integument of some insects. Usually such a felted coating is not living tissue, but consists of waxy fibres and is not particularly strong, but serves as protection from either excessive desiccation or moisture. It is particularly common in some families of the Hemiptera. In some species it occurs only as an outer coat of the immature insect, but in others, such as many of the Coccoidea, including the "Australian bug", Icerya purchasi and cochineal, Dactylopius species, it is secreted throughout the life of the insect and serves largely to protect the eggs rather than the insect.[4] In other species, such as many of the "woolly aphids", the Eriosomatinae, the most spectacular fluff is borne on the adult insect itself.[5]

The distinction between felted and other fibrous materials is not always sharp. For example, although truly felted hair on healthy mammals is unusual, many animals, especially in seasonally cold or wet climates or environments, often have a so-called undercoat of down hair plus awn hair that usually lies hidden beneath the outer coat of guard hairs,[6] and may form a mat of lightly felted wool. Such down hairs as a rule are crimped into a finely woolly texture and contain waxy, water-repellent lanolin; in a mass they serve to retain insulating air and exclude water. In many species that live in seasonally frigid zones the winter down hair is shed in clumps during springtime. This is exploited in species such as the muskox; herders collect the wool for commercial purposes without any need for shearing.[7]

Felting activities of animals

Many species of animals actively employ felting behaviour in preparing shelters for themselves or their young. It is not always possible to tell when such felting is purely incidental, but many species show behaviour patterns clearly adapted to the production of felted material suited to shelter and protection. The linings of nests of small rodents and small carnivores are common examples; some mice for example, such as ground-dwelling Mus species in parts of Africa build spherical nests of assorted fibres in burrows or under large flat objects. Some, such as various species of rabbit, in particular Sylvilagus species, use their own fur as a major component of their nesting material.[8] Small predatory mammals such the least weasel largely collect fur from their prey, or occupy prey nests ready lined; such fur commonly forms a felted nest lining.[9]

Common eider nest
Common eider nest, with the eggs deep in the loosely piled down.

Birds vary enormously in the nests they make and the materials they use. Among those that use fibres and fibrous materials such as grass for nesting, many tend to weave the nests, but even nests that initially are purely woven, such as those of weaver birds, later are lined with downy materials that largely become felted, both with each other and with the surrounding nest material. Similarly birds such as sparrows, that build large, twiggy nests, line them with downy material. Many kinds of birds however do little weaving in building their nests, but instead construct their nests mainly of fibrous and downy materials such as fine wool, moss, lichen, spiders' nests, tufts of cotton, arachnoid fluff from plants, or bark scales, supported by twigs or the walls of burrows and the like, depending on the circumstances within which they nest. James Rennie remarked: "A circumstance also never neglected, is to bind the nest firmly into the forks of the bush where it is placed, by twining bands of moss, felted with wool, round all the contiguous branches, both below and at the sides. During the nesting season such birds commonly become such avid seekers of suitable materials that down feathers or tufts of wool may be used as bait for trapping them. Birds that concentrate heavily on felted nests include goldfinches (Carduelis species) and related species. Hummingbirds tend to use a lot of spiderweb together with moss and similar material. Small warbler-like birds of many genera such as Prinia and Cisticola make their nests either heavily lined with, or entirely of felted material.[10][11] Ground nesting birds often use felted material rather than woven; it usually suffices and some of the structures can be deceptively sophisticated. For example, the common eider, famous for the valuable down harvested from its abandoned nests, lays its eggs in very lightly felted bowls of its own down; simple though this seems, the thick, soft layer provides exceptional insulation.


Phyllaphis fagi infestation
Phyllaphis fagi, Eriosomatinae, woolly beech aphid on a leaf.
Icerya purchasi 1
Australian bug female on her fibrous waxy protection for the eggs.
Cochenille z02
Cochineal females. Note that the white waxy fibre does not cover the insect, but rather the eggs.
Ctenizidae Cork-lid Trapdoor spider dwelling IMG 4025s
Spider trapdoor of silk and clay

Various insects also create felted materials, generally forming part of the shelter for their young. Burying beetles are known for stripping the fur or feathers from the carcasses that they prepare for their young, and using the material to line and reinforce the crypt that they dig.[12] it is however unclear whether this habit is anything more than incidental, and also how relatively important it is in the different species of the genus. As long ago as the 19th century at least, Jean-Henri Fabre demonstrated that the species that he investigated most certainly did not depend on feathered or hairy food items, being quite able to utilise reptiles and amphibians and fishes.[13] However, there is no doubt about the use of felted fibre by various species of bees, in particular, those members of the Megachilidae that are known as carder bees build their nests mainly of plant fibre collected from arachnoid plants, though they also might add fibre from other sources, such as animal wool. The sheer amount of the material that they gather often is startling, bearing in mind that the species of bees are not at all large.[14]

Some invertebrates other than insects construct felted structures. Among those spiders are the most conspicuous. Many or most spider egg cases are partly or largely felted silk as well as woven or wound. The lids of various species of trapdoor spider burrows vary in their construction, but they are largely of earth and similar material reinforced with partly felted silk.

Botanical use of the term

Oldenburgia grandis Emerging felted bud IMG 5837
Oldenburgia grandis leaves are felted when emerging from the bud, but lose their covering as they mature.
Jardin des plantes Paris Cephalocereus senilis
Cephalocereus senilis, showing felted radial spines
Senecio haworthii Felted leaves 2012 07 19 7536
Senecio haworthii has permanently felted leaves.

In botanical terminology, felted typically is defined in terms such as "matted with intertwined hairs".[15] However, plants may be covered in several different ways, and several different terms have been coined to describe them. Not all textbooks use the same terms, or use them in the same way. The term felted is commonly used in describing any part of a plant covered with dense white fur, whether tangled or not. Part of the reason is that plants themselves vary so much that there seldom is much practical value to trying to be too precise; for example there is no clear boundary to separate terms such as felt(ed), arachnoid, indumentum and tomentose, and usages vary.

In botany, as opposed to mycology, "felted" seldom refers to internal tissues, but rather to furriness on the outside of leaves or stems. The function of the covering is always protective, sometimes against grazing or browsing animals, sometimes against wind or windblown sand, sometimes against intense sunshine or ultraviolet, and sometimes against drought and desiccation. Two illustrative examples are: Oldenburgia grandis, and Senecio haworthii. The former is a tree that grows in moderately harsh circumstances, but with a reasonable amount of seasonal rain. Its leaves are large, being broad and typically about 30 cm long. While growing to their full size they are vulnerable, so it is quite plausible that being felted protects them from browsers, ultraviolet, drought, and heat. Once their tissues have hardened and become rich in fibre and tannins, they can afford to lose their felt. In this respect they resemble many other plants whose leaves pass through vulnerable phases as they mature, though not all strategies are based on felt.

Senecio haworthii grows under far more dramatically arid conditions than Oldenburgia; its native habitat also is hotter and with a higher irradiation intensity. The plant is fairly poisonous, so it is not much browsed, though some caterpillars will eat its succulent leaves. Accordingly, its need for protection does not change much at any time of the year, and some leaves will survive for several years, retaining their felting throughout.

In Cephalocereus senilis (old man cactus) radial spines grow into a tangled coating of spectacular white hair that conceal both the green tissue and the formidable sharp central spines beneath. It is only marginally felted, but forms a powerful simultaneous protection against intense radiation, wind, frost, and herbivores of various sizes.[16] The woolly masses of fibres on such cacti have been used as stuffing for pillows and for similar applications.[17]

Mycological use of the term

Amanita muscaria G2
Amanita muscaria growing through the volva, the remnant felted tissue forming spots on the surface

Most fungal tissue is filamentous; its very nature predisposes it to grow into tangles that lend themselves to felting. Whereas vascular plants seldom have cells that grow into forms that can form massive tangles, fungi hardly can form tissues at all except by tangling and felting their hyphal filaments. Practically every mass of mushroom tissue, including cords and membranes, is formed of anastomosed and felted hyphae. The picturesque spots on the caps of Amanita muscaria consist of felted patches of remnant tissue from the volva.[18]


  1. ^ Gray, Henry. Anatomy of the Human Body. 20th ed. Revised by Lewis, Warren H. 1918. May be downloaded from https://archive.org/details/anatomyofhumanbo1918gray
  2. ^ Vogel, Steven. Cats' Paws and Catapults. Chapter 5. Penguin 1999. ISBN 0-14-027733-1
  3. ^ Gordon, J. E. Structures, or Why Things Don't Fall Down. Publisher: Da Capo 2003. ISBN 978-0306812835
  4. ^ Alan Weaving; Mike Picker; Griffiths, Charles Llewellyn (2003). Field Guide to Insects of South Africa. New Holland Publishers, Ltd. ISBN 1-86872-713-0.
  5. ^ Costa, James T. The Other Insect Societies. Chapter 9. Publisher: Belknap Press 2006. ISBN 978-0674021631
  6. ^ Robinson, Roy. Genetics for Cat Breeders. Pergamon 1977. ISBN 0-08-021209-3
  7. ^ Feldhamer, George A. Mammalogy: Adaptation, Diversity, Ecology. Publisher: The Johns Hopkins University. ISBN 978-0801886959
  8. ^ Long, Charles A. The Wild Mammals of Wisconsin (Faunistica). Pensoft Publishers 2008. ISBN 978-9546423139
  9. ^ Jackson, Hartley H.T. et al. Mammals of Wisconsin. Publisher: University of Wisconsin 1961. ISBN 978-0299021504
  10. ^ Rennie, James. Natural history of birds : their architecture habits and faculties. Chapter VIII. New York : Harper 1845 May be downloaded from: https://archive.org/details/naturalhistoryof00renn
  11. ^ Phil Hockey; Peter Ryan; Richard Dean. Roberts Birds of Southern Africa. Publisher: John Voelcker Bird Book Fund. 2005 ISBN 9780620340533
  12. ^ Burton, Maurice; Burton, Robert. International Wildlife Encyclopedia. Publisher: Marshall Cavendish 2002. ISBN 978-0761472698
  13. ^ Fabre, Jean-Henri. Tr. Teixeira de Mattos, Alexander. The glow-worm and other beetles Publisher: New York : Dodd, Mead and Company, 1919
  14. ^ Fabre, Jean-Henri; Translated by Alexander Teixeira de Mattos; The Bramble-bees and others; Pub: Dodd, Mead, New York, 1915. Download from: https://archive.org/details/bramblebeesother00fabr
  15. ^ Jackson, Benjamin, Daydon; A Glossary of Botanic Terms with their Derivation and Accent; Published by Gerald Duckworth & Co. London, 4th ed 1928
  16. ^ Mauseth, James D. Structure–Function Relationships in Highly Modified Shoots of Cactaceae. Annals of Botany 98: 901–926, 2006 doi:10.1093/aob/mcl133, available online at www.aob.oxfordjournals.org
  17. ^ Powell, A. Michael, Weedin, James F. Cacti of the Trans-Pecos and Adjacent Areas. Publisher: Texas Tech University Press 2004. ISBN 978-0896725317
  18. ^ Moore, David. Robson, Geoffrey D. Trinci, Anthony P. J. 21st Century Guidebook to Fungi. Publisher: Cambridge University Press 2011 ISBN 978-0521186957

Anthotroche is a genus of shrubs in the family Solanaceae. The genus is endemic to Western Australia.Species include:

Anthotroche myoporoides - Myoporum-like anthotroche C.A.Gardner

Anthotroche pannosa - Endl. Felted anthotroche

Anthotroche walcottii F.Muell.The genus was first formally described by Austrian botanist Stephan Endlicher in 1839 in Novarum Stirpium Decades.

Arachnoid (botany)

Arachnoid as a descriptive term in botany, refers to organs such as leaves or stems that have a cobwebby exterior appearance, from being covered with fine white hairs, usually tangled. Such material is one common cause of plants having a grey or white appearance. The usages of various authors in distinguishing between "arachnoid" and a few other terms referring to hairiness, such as floccose, pubescent, tomentum, cottony, or villous, tend to be arbitrary, but as a rule the term is best reserved for hairiness lighter than a felted layer, and inclined to rub off or to be easily damaged in other ways. The arachnoid appearance is common on the leaves and stems of various sclerophyllous members of the Asteraceae, such as some thistles.

Nonetheless, "cobwebbiness" is a subjective impression, and in the likes of Hayworthia arachnoidea the arachnoid impression arises from the thicket of spinescent leaf denticles that are not at all fine, tangled, or fragile. In the cactus Cephalocereus senilis, the arachnoid effect arises from long-lasting hairy spines.

Beaver hat

A beaver hat is a hat made from felted beaver fur. They were fashionable across much of Europe during the period 1550–1850 because the soft yet resilient material could be easily combed to make a variety of hat shapes (including the familiar top hat). Smaller hats made of beaver were sometimes called beaverkins, as in Thomas Carlyle's description of his wife as a child.Used winter coats worn by Native Americans were actually a prized commodity for hat making because their wear helped prepare the skins; separating out the coarser hairs from the pelts.To make felt, the underhairs were shaved from the beaver pelt and mixed with a vibrating hatter's bow. The matted fabric was pummeled and boiled repeatedly, resulting in a shrunken and thickened felt. Filled over a hat-form block, the felt was pressed and steamed into shape. The hat maker then brushed the outside surface to a sheen. Beaver hats were made in various styles as a matter of civil status:

the Wellington (1820–40)

the Paris beau (1815)

the D'Orsay (1820)

the Regent (1825)

the clerical (18th century).In addition, beaver hats were made in various styles as a matter of military status:

the continental cocked hat (1776)

Navy cocked hat (19th century)

the Army shako (1837).The popularity of the beaver hat declined in the early/mid-19th century as silk hats became more fashionable across Europe.


Bergamasco Shepherd

The Bergamasco Shepherd (Italian pastore bergamasco) is a breed of dog with its origins in the Italian Alps near Bergamo, where it was originally used as a herding dog.

Boiled wool

Boiled wool is a type of fabric primarily used in creating berets, scarves, vests, cardigans, coats, and jackets. To create this fabric, knit wool or wool-blend fabrics are agitated with hot water in a process called fulling. This process shrinks the fabric and results in a dense felted fabric that resists fraying and further shrinkage.

Cedar bark textile

Cedar bark textile was used by indigenous people in the Pacific Northwest region of modern-day Canada and the United States. Historically, most items of clothing were made of this material.

The name of the trees which provide the bark material are of the genus Thuja, which has two species redcedar and cypress which are both known by the common name 'cedar' in North America. After the western redcedar or yellow cypress (often called "yellow cedar") bark was peeled in long strips from the trees, the outer layer was split away, and the flexible inner layer was shredded and processed. The resulting felted strips of bark were soft and could be plaited, sewn or woven into a variety of fabrics that were either dense and watertight, or soft and comfortable.Women wore skirts and capes of redcedar bark, while men wore long capes of cedar bark into which some mountain goat wool was woven for decorative effect.

Cloth modeling

Cloth is a woven or felted fabric made from wool, cotton, or a similar fiber. Cloth modeling is the term used for simulating cloth within a computer program, usually in the context of 3D computer graphics. The main approaches used for this may be classified into three basic types: geometric, physical, and particle/energy.

Croaking cisticola

The croaking cisticola (Cisticola natalensis) is an Old World warbler in the genus Cisticola. This genus is sometimes split off with various other southern warbler genera and given family status as the Cisticolidae.

The croaking cisticola is a resident breeder in Africa south of the Sahara. It is a very small insectivorous bird.

These small passerines are found in rank grassland habitats, often near swamps or water. Male cisticolas are polygamous; the female builds a discreet nest deep in the grasses, often binding living leaves into the soft fabric of felted plant-down, cobwebs, and grass. The croaking cisticola's nest is a ball shape with a side entrance; 2-4 eggs are laid.

This is the largest cisticola. This warbler is grey-brown above, heavily streaked with black. The underparts are whitish, and the tail is broad, pale-tipped and flicked frequently. It has a chestnut wing-panel and a heavy bill.

It is very similar to other members of its genus. It is best distinguished from its many African relatives by its size and froglike croaking breep-breep song. The song is always the easiest identification criterion for this genus.

These birds are more easily heard than seen, and because of their small size (about 14 cm) not always easy to recognise, particularly outside the breeding season when they seldom emerge from their grasses.


Druggett or drugget is "a coarse woollen fabric felted or woven, self-coloured or printed one side". Jonathan Swift refers to being "in druggets drest, of thirteen pence a yard".Formerly, a drugget was a sort of cheap stuff, very thin and narrow, usually made of wool, or half wool and half silk or linen; it may have been corded but was usually plain. The term is now applied to a coarse fabric having a cotton warp and a wool filling, used for rugs, tablecloths, etc.

Eriocephalus africanus

Eriocephalus africanus is a bushy shrublet indigenous to South Africa. It has a wide distribution in the Western and Eastern Cape, and in Namaqualand. The plant has several common names in various languages. It is known as the Cape Snow Bush or Kapokbossie (the Afrikaans word for "snow bush"); other common names refer to its fancied resemblance to rosemary, for example "African rosemary" or "Wild rosemary" (Afrikaans "(wilde) roosmaryn"). The superficial resemblance is in the foliage, which, though softer and not glossy, grows in a habit similar to that of the common Mediterranean rosemary, although the two species are not related.

Eriocephalus africanus is fragrant, with lightly felted foliage that gives the plant a matt silvery appearance. The inflorescences are small brown and pale yellow heads borne in corymbs; each head bears a few bisexual disk florets with abortive ovaries and snowy white petals that practically cover a bush in flower. The disk florets surround usually some four to eight female florets in the centre.Ecologically the plant is important to many insects as a source of nectar and pollen, and as a minor browse to flocks and antelope. Essential oil derived from E. africanus is used as an ingredient in medicinal and perfume products. The plant has been used in traditional medicine and in cooking.


Felt is a textile material that is produced by matting, condensing and pressing fibers together. Felt can be made of natural fibers such as wool or animal fur, or from synthetic fibers such as petroleum-based acrylic or acrylonitrile or wood pulp-based rayon. Blended fibers are also common.

Glass art

Glass art refers to individual works of art that are substantially or wholly made of glass. It ranges in size from monumental works and installation pieces, to wall hangings and windows, to works of art made in studios and factories, including glass jewelry and tableware.

As a decorative and functional medium, glass was extensively developed in Egypt and Assyria. Invented by the Phoenicians, was brought to the fore by the Romans. In the Middle Ages, the builders of the great Norman and Gothic cathedrals of Europe took the art of glass to new heights with the use of stained glass windows as a major architectural and decorative element. Glass from Murano, in the Venetian Lagoon, (also known as Venetian glass) is the result of hundreds of years of refinement and invention. Murano is still held as the birthplace of modern glass art.

The turn of the 19th century was the height of the old art glass movement while the factory glass blowers were being replaced by mechanical bottle blowing and continuous window glass. Great ateliers like Tiffany, Lalique, Daum, Gallé, the Corning schools in upper New York state, and Steuben Glass Works took glass art to new levels.


Horsehair is the long, coarse hair growing on the manes and tails of horses. It is used for various purposes, including upholstery, brushes, the bows of musical instruments, a hard-wearing fabric called haircloth, and for horsehair plaster, a wallcovering material formerly used in the construction industry and now found only in older buildings.

Horsehair can be very stiff or very fine and flexible; mane hair is generally softer and shorter than tail hair. The texture of horsehair can be influenced by the breed and management of the horse, including natural conditions such as diet or climate. Processing may also affect quality and feel.

Horsehair is a protein fiber that absorbs water slowly, but can be dyed or colored effectively using traditional dyes suitable for protein fibers. It can be felted, but not easily.

Kapa moe

A kapa moe is a traditional Hawaiian bedcovering made from tree bark, then beaten and felted to achieve a soft texture and dye stamped in geometric patterns. Several layers of kapa would be stitched together at the edges to form a kapa moe.

Oldenburgia grandis

Oldenburgia grandis is a shrub or small, gnarled tree in the family Asteraceae. It occurs in the mountains around Grahamstown in South Africa. It grows to a height of about 5m on sandstone outcrops. It has thick corky bark and large leaves clustered at the ends of branches. The leaves are dark green and leathery, reminiscent of loquat leaves, but generally a good deal larger. The emergent leaves are densely and completely felted with white hair. Most of the felt is lost as the leaf matures, but some persists on under-surfaces. Flowers are purple and in large heads about 12 cm in diameter. The flowerheads are solitary and terminal.

It is threatened by habitat loss.

Pachycerianthus fimbriatus

Pachycerianthus fimbriatus is a cerianthid anemone that burrows in substrate and lives in a semi-rigid tube made of felted nematocysts. The anemone is often seen in bright orange to red.

Like most anemones, the tube-dwelling anemone contains stinging cells or nematocytes along its tentacles, however, the cells are not toxic to humans.

Plica neuropathica

Plica neuropathica, also known as felted hair, is a curling, looping, intertwisting, and felting or matting of the hair in localized areas of the scalp.

Songar tit

The Songar tit (Poecile montanus songarus, formerly Parus songarus) is a passerine bird in the tit family. It is the southern counterpart of the willow tit P. montanus, and is usually included in it as a subspecies.

It breeds in the deciduous mountain forests of southeast Kazakhstan, Kyrgyzstan and northern China.

The 13 cm long Songar tit has a dark brown cap, blackish bib, rich brown upperparts, white cheeks and cinnamon buff underparts. The sexes are similar, but juveniles are somewhat duller.

The most common call is a nasal zee, zee, zee, but the notes of the bird evidently vary considerably

The Songar tit usually excavates its own nesting hole, often in a rotten stump or in a tree, more or less decayed. Most nests examined are cups of felted material, such as fur, hair and wood chips, but feathers are sometimes used. The number of eggs is from five to six, white with small reddish spots or blotches.

They feed on caterpillars, insects and seeds, much like other tits.


The TR-201 or TR201 is a hypergolic pressure-fed rocket engine used to propel the upper stage of the Delta rocket, referred to as Delta-P, from 1972 to 1988.

The rocket engine uses Aerozine 50 as fuel, and N2O4 as oxidizer. It was developed in early 1970s by TRW as a derivative of the lunar module descent engine (LMDE). This engine used a pintle injector first developed by TRW in late 1950s and received US Patent in 1972. This injector technology and design is also used on SpaceX Merlin engines.The thrust chamber was initially developed for the Apollo lunar module and was subsequently adopted for the Delta expendable launch vehicle 2nd stage. The engine made 10 flights during the Apollo program and 77 during its Delta career between 1974 and 1988.

The TRW TR-201 was re-configured as a fixed-thrust version of the LMDE for Delta's stage 2.

Multi-start operation is adjustable up to 55.6 kN and propellant throughput up to 7,711 kg; and the engine can be adapted to optional expansion ratio nozzles. Development of the innovative thrust chamber and pintle design is credited to TRW Aerospace Engineer Dr. Peter Staudhammer.The combustion chamber consists of an ablative-lined titanium alloy case to the 16:1 area ratio.

Fabrication of the 6Al4V alloy titanium case was accomplished by machining the chamber portion and the exit cone portion from forgings and welding them into one unit at the throat centerline. The ablative liner is fabricated in two segments and installed from either end.

The shape of the nozzle extension is such that the ablative liner is retained in the exit cone during transportation, launch and boost.

During engine firing, thrust loads force the exit cone liner against the case.

The titanium head end assembly which contains the Pintle Injector and propellant valve subcomponents is attached with 36 A-286 steel ¼ inch bolts.

In order to keep the maximum operating temperatures of the titanium case in the vicinity of 800 °F, the ablative liner was designed as a composite material providing the maximum heat sink and minimum weight. The selected configuration consisted of a high density, erosion-resistant silica cloth/phenolic material surrounded by a lightweight needle-felted silica mat/phenolic insulation.

The installed pintle injector, unique to TRW-designed liquid-propulsion systems, provides improved reliability and less costly method of fuel–oxidizer impingement in the thrust chamber than conventional coaxial distributed-element injectors typically used on liquid bipropellant rocket engines.

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