Prokaryote

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Prokaryote 

Diagram of a typical prokaryotic cell

A prokaryote is a cellular organism that lacks an envelope-enclosed nucleus. The word prokaryote comes from the Greek πρό (pro, 'before') and κάρυον (karyon, 'nut' or 'kernel'). In the two-empire system arising from the work of Édouard Chatton, prokaryotes were classified within the empire Prokaryota. But in the three-domain system, based upon molecular analysis, prokaryotes are divided into two domains: Bacteria (formerly Eubacteria) and Archaea (formerly Archaebacteria). Organisms with nuclei are placed in a third domain, Eukaryota. In the study of the origins of life, prokaryotes are thought to have arisen before eukaryotes.

Prokaryotes lack mitochondria, or any other eukaryotic membrane-bound organelles; and it was once thought that prokaryotes lacked cellular compartments, and therefore all cellular components within the cytoplasm were unenclosed, except for an outer cell membrane. But bacterial microcompartments, which are thought to be simple organelles enclosed in protein shells, have been discovered, along with other prokaryotic organelles. While typically being unicellular, some prokaryotes, such as cyanobacteria, may form large colonies. Others, such as myxobacteria, have multicellular stages in their life cycles. Prokaryotes are asexual, reproducing without fusion of gametes, although horizontal gene transfer also takes place.

Molecular studies have provided insight into the evolution and interrelationships of the three domains of life. The division between prokaryotes and eukaryotes reflects the existence of two very different levels of cellular organization; only eukaryotic cells have an enveloped nucleus that contains its chromosomal DNA, and other characteristic membrane-bound organelles including mitochondria. Distinctive types of prokaryotes include extremophiles and methanogens; these are common in some extreme environments.

History

The division between prokaryotes and eukaryotes was firmly established by the microbiologists Roger Stanier and C. B. van Niel in their 1962 paper The concept of a bacterium (though spelled procaryote and eucaryote there). That paper cites Édouard Chatton's 1937 book Titres et Travaux Scientifiques for using those terms and recognizing the distinction. One reason for this classification was so that what was then often called blue-green algae (now called cyanobacteria) would not be classified as plants but grouped with bacteria.

Structure

Prokaryotes have a prokaryotic cytoskeleton that is more primitive than that of the eukaryotes. Besides homologues of actin and tubulin (MreB and FtsZ), the helically arranged building-block of the flagellum, flagellin, is one of the most significant cytoskeletal proteins of bacteria, as it provides structural backgrounds of chemotaxis, the basic cell physiological response of bacteria. At least some prokaryotes also contain intracellular structures that can be seen as primitive organelles. Membranous organelles (or intracellular membranes) are known in some groups of prokaryotes, such as vacuoles or membrane systems devoted to special metabolic properties, such as photosynthesis or chemolithotrophy. In addition, some species also contain carbohydrate-enclosed microcompartments, which have distinct physiological roles (e.g. carboxysomes or gas vacuoles).

Most prokaryotes are between 1 µm and 10 µm, but they can vary in size from 0.2 µm (Mycoplasma genitalium) to 750 µm (Thiomargarita namibiensis).

Prokaryotic cell structure	Description
Flagellum (not always present)	Long, whip-like protrusion that aids cellular locomotion used by both gram positive and gram negative organisms.
Cell membrane	Surrounds the cell's cytoplasm and regulates the flow of substances in and out of the cell.
Cell wall (except genera Mycoplasma and Thermoplasma)	Outer covering of most cells that protects the bacterial cell and gives it shape.
Cytoplasm	A gel-like substance composed mainly of water that also contains enzymes, salts, cell components, and various organic molecules.
Ribosome	Cell structures responsible for protein production.
Nucleoid	Area of the cytoplasm that contains the prokaryote's single DNA molecule.
Glycocalyx (only in some types of prokaryotes)	A glycoprotein-polysaccharide covering that surrounds the cell membranes.
Cytoplasmic inclusions	It contains the inclusion bodies like ribosomes and larger masses scattered in the cytoplasmic matrix.

Morphology

Prokaryotic cells have various shapes; the four basic shapes of bacteria are:

• Cocci – A bacterium that is spherical or ovoid is called a coccus (Plural, cocci). e.g. Streptococcus, Staphylococcus.
• Bacilli – A bacterium with cylindrical shape called rod or a bacillus (Plural, bacilli).
• Spiral bacteria – Some rods twist into spiral shapes and are called spirilla (singular, spirillum).
• Vibrio – comma-shaped

The archaeon Haloquadratum has flat square-shaped cells.

Reproduction

Bacteria and archaea reproduce through asexual reproduction, usually by binary fission. Genetic exchange and recombination still occur, but this is a form of horizontal gene transfer and is not a replicative process, simply involving the transference of DNA between two cells, as in bacterial conjugation.

DNA transfer

DNA transfer between prokaryotic cells occurs in bacteria and archaea, although it has been mainly studied in bacteria. In bacteria, gene transfer occurs by three processes. These are (1) bacterial virus (bacteriophage)-mediated transduction, (2) plasmid-mediated conjugation, and (3) natural transformation. Transduction of bacterial genes by bacteriophage appears to reflect an occasional error during intracellular assembly of virus particles, rather than an adaptation of the host bacteria. The transfer of bacterial DNA is under the control of the bacteriophage's genes rather than bacterial genes. Conjugation in the well-studied E. coli system is controlled by plasmid genes, and is an adaptation for distributing copies of a plasmid from one bacterial host to another. Infrequently during this process, a plasmid may integrate into the host bacterial chromosome, and subsequently transfer part of the host bacterial DNA to another bacterium. Plasmid mediated transfer of host bacterial DNA (conjugation) also appears to be an accidental process rather than a bacterial adaptation.

Play media

3D animation of a prokaryotic cell that shows all the elements that compose it

Natural bacterial transformation involves the transfer of DNA from one bacterium to another through the intervening medium. Unlike transduction and conjugation, transformation is clearly a bacterial adaptation for DNA transfer, because it depends on numerous bacterial gene products that specifically interact to perform this complex process. For a bacterium to bind, take up and recombine donor DNA into its own chromosome, it must first enter a special physiological state called competence. About 40 genes are required in Bacillus subtilis for the development of competence. The length of DNA transferred during B. subtilis transformation can be as much as a third to the whole chromosome. Transformation is a common mode of DNA transfer, and 67 prokaryotic species are thus far known to be naturally competent for transformation.

Among archaea, Halobacterium volcanii forms cytoplasmic bridges between cells that appear to be used for transfer of DNA from one cell to another. Another archaeon, Sulfolobus solfataricus, transfers DNA between cells by direct contact. Frols et al. found that exposure of S. solfataricus to DNA damaging agents induces cellular aggregation, and suggested that cellular aggregation may enhance DNA transfer among cells to provide increased repair of damaged DNA via homologous recombination.

Sociality

While prokaryotes are considered strictly unicellular, most can form stable aggregate communities. When such communities are encased in a stabilizing polymer matrix ("slime"), they may be called "biofilms". Cells in biofilms often show distinct patterns of gene expression (phenotypic differentiation) in time and space. Also, as with multicellular eukaryotes, these changes in expression often appear to result from cell-to-cell signaling, a phenomenon known as quorum sensing.

Biofilms may be highly heterogeneous and structurally complex and may attach to solid surfaces, or exist at liquid-air interfaces, or potentially even liquid-liquid interfaces. Bacterial biofilms are often made up of microcolonies (approximately dome-shaped masses of bacteria and matrix) separated by "voids" through which the medium (e.g., water) may flow easily. The microcolonies may join together above the substratum to form a continuous layer, closing the network of channels separating microcolonies. This structural complexity—combined with observations that oxygen limitation (a ubiquitous challenge for anything growing in size beyond the scale of diffusion) is at least partially eased by movement of medium throughout the biofilm—has led some to speculate that this may constitute a circulatory system  and many researchers have started calling prokaryotic communities multicellular. Differential cell expression, collective behavior, signaling, programmed cell death, and (in some cases) discrete biological dispersal events all seem to point in this direction. However, these colonies are seldom if ever founded by a single founder (in the way that animals and plants are founded by single cells), which presents a number of theoretical issues. Most explanations of co-operation and the evolution of multicellularity have focused on high relatedness between members of a group (or colony, or whole organism). If a copy of a gene is present in all members of a group, behaviors that promote cooperation between members may permit those members to have (on average) greater fitness than a similar group of selfish individuals.

Should these instances of prokaryotic sociality prove to be the rule rather than the exception, it would have serious implications for the way we view prokaryotes in general, and the way we deal with them in medicine. Bacterial biofilms may be 100 times more resistant to antibiotics than free-living unicells and may be nearly impossible to remove from surfaces once they have colonized them. Other aspects of bacterial cooperation—such as bacterial conjugation and quorum-sensing-mediated pathogenicity, present additional challenges to researchers and medical professionals seeking to treat the associated diseases.

Environment

Phylogenetic ring showing the diversity of prokaryotes, and symbiogenetic origins of eukaryotes

Prokaryotes have diversified greatly throughout their long existence. The metabolism of prokaryotes is far more varied than that of eukaryotes, leading to many highly distinct prokaryotic types. For example, in addition to using photosynthesis or organic compounds for energy, as eukaryotes do, prokaryotes may obtain energy from inorganic compounds such as hydrogen sulfide. This enables prokaryotes to thrive in harsh environments as cold as the snow surface of Antarctica, studied in cryobiology, or as hot as undersea hydrothermal vents and land-based hot springs.

Prokaryotes live in nearly all environments on Earth. Some archaea and bacteria are extremophiles, thriving in harsh conditions, such as high temperatures (thermophiles) or high salinity (halophiles). Many archaea grow as plankton in the oceans. Symbiotic prokaryotes live in or on the bodies of other organisms, including humans.

Phylogenetic and symbiogenetic tree of living organisms, showing the origins of eukaryotes and prokaryotes

Classification

In 1977, Carl Woese proposed dividing prokaryotes into the Bacteria and Archaea (originally Eubacteria and Archaebacteria) because of the major differences in the structure and genetics between the two groups of organisms. Archaea were originally thought to be extremophiles, living only in inhospitable conditions such as extremes of temperature, pH, and radiation but have since been found in all types of habitats. The resulting arrangement of Eukaryota (also called "Eucarya"), Bacteria, and Archaea is called the three-domain system, replacing the traditional two-empire system.

Evolution

Diagram of the origin of life with the Eukaryotes appearing early, not derived from Prokaryotes, as proposed by Richard Egel in 2012. This view, one of many on the relative positions of Prokaryotes and Eukaryotes, implies that the universal common ancestor was relatively large and complex.

A widespread current model of the evolution of the first living organisms is that these were some form of prokaryotes, which may have evolved out of protocells, while the eukaryotes evolved later in the history of life. Some authors have questioned this conclusion, arguing that the current set of prokaryotic species may have evolved from more complex eukaryotic ancestors through a process of simplification. Others have argued that the three domains of life arose simultaneously, from a set of varied cells that formed a single gene pool. This controversy was summarized in 2005:

There is no consensus among biologists concerning the position of the eukaryotes in the overall scheme of cell evolution. Current opinions on the origin and position of eukaryotes span a broad spectrum including the views that eukaryotes arose first in evolution and that prokaryotes descend from them, that eukaryotes arose contemporaneously with eubacteria and archaebacteria and hence represent a primary line of descent of equal age and rank as the prokaryotes, that eukaryotes arose through a symbiotic event entailing an endosymbiotic origin of the nucleus, that eukaryotes arose without endosymbiosis, and that eukaryotes arose through a symbiotic event entailing a simultaneous endosymbiotic origin of the flagellum and the nucleus, in addition to many other models, which have been reviewed and summarized elsewhere.

The oldest known fossilized prokaryotes were laid down approximately 3.5 billion years ago, only about 1 billion years after the formation of the Earth's crust. Eukaryotes only appear in the fossil record later, and may have formed from endosymbiosis of multiple prokaryote ancestors. The oldest known fossil eukaryotes are about 1.7 billion years old. However, some genetic evidence suggests eukaryotes appeared as early as 3 billion years ago.

While Earth is the only place in the universe where life is known to exist, some have suggested that there is evidence on Mars of fossil or living prokaryotes. However, this possibility remains the subject of considerable debate and skepticism.

Relationship to eukaryotes

Comparison of eukaryotes vs. prokaryotes

The division between prokaryotes and eukaryotes is usually considered the most important distinction or difference among organisms. The distinction is that eukaryotic cells have a "true" nucleus containing their DNA, whereas prokaryotic cells do not have a nucleus.

Both eukaryotes and prokaryotes contain large RNA/protein structures called ribosomes, which produce protein, but the ribosomes of prokaryotes are smaller than those of eukaryotes. Mitochondria and chloroplasts, two organelles found in many eukaryotic cells, contain ribosomes similar in size and makeup to those found in prokaryotes. This is one of many pieces of evidence that mitochondria and chloroplasts are descended from free-living bacteria. The endosymbiotic theory holds that early eukaryotic cells took in primitive prokaryotic cells by phagocytosis and adapted themselves to incorporate their structures, leading to the mitochondria and chloroplasts.

The genome in a prokaryote is held within a DNA/protein complex in the cytosol called the nucleoid, which lacks a nuclear envelope. The complex contains a single, cyclic, double-stranded molecule of stable chromosomal DNA, in contrast to the multiple linear, compact, highly organized chromosomes found in eukaryotic cells. In addition, many important genes of prokaryotes are stored in separate circular DNA structures called plasmids. Like Eukaryotes, prokaryotes may partially duplicate genetic material, and can have a haploid chromosomal composition that is partially replicated, a condition known as merodiploidy.

Prokaryotes lack mitochondria and chloroplasts. Instead, processes such as oxidative phosphorylation and photosynthesis take place across the prokaryotic cell membrane. However, prokaryotes do possess some internal structures, such as prokaryotic cytoskeletons. It has been suggested that the bacterial order Planctomycetes has a membrane around the nucleoid and contains other membrane-bound cellular structures. However, further investigation revealed that Planctomycetes cells are not compartmentalized or nucleated and, like other bacterial membrane systems, are interconnected.

Prokaryotic cells are usually much smaller than eukaryotic cells. Therefore, prokaryotes have a larger surface-area-to-volume ratio, giving them a higher metabolic rate, a higher growth rate, and as a consequence, a shorter generation time than eukaryotes.

Phylogenetic tree showing the diversity of prokaryotes. This 2018 proposal shows eukaryotes emerging from the archaean Asgard group which represents a modern version of the eocyte hypothesis. Unlike earlier assumptions, the division between bacteria and the rest is the most important difference between organisms.

There is increasing evidence that the roots of the eukaryotes are to be found in (or at least next to) the archaean asgard group, perhaps Heimdallarchaeota (an idea which is a modern version of the 1984 eocyte hypothesis, eocytes being an old synonym for crenarchaeota, a taxon to be found nearby the then unknown asgard group) For example, histones which usually package DNA in eukarotic nuclei, have also been found in several archaean groups, giving evidence for homology. This idea might clarify the mysterious predecessor of eukaryotic cells (eucytes) which engulfed an alphaproteobacterium forming the first eucyte (LECA, last eukaryotic common ancestor) according to endosymbiotic theory. There might have been some additional support by viruses, called viral eukaryogenesis. The non-bacterial group comprising archaea and eukaryota was called Neomura by Thomas Cavalier-Smith in 2002. However, in a cladistic view, eukaryota are archaea in the same sense as birds are dinosaurs because they evolved from the maniraptora dinosaur group. In contrast, archaea without eukaryota appear to be a paraphyletic group, just like dinosaurs without birds.

Prokaryotes may split into two groups

Unlike the above assumption of a fundamental split between prokaryotes and eukaryotes, the most important difference between biota may be the division between bacteria and the rest (archaea and eukaryota). For instance, DNA replication differs fundamentally between bacteria and archaea (including that in eukaryotic nuclei), and it may not be homologous between these two groups. Moreover, ATP synthase, though common (homologous) in all organisms, differs greatly between bacteria (including eukaryotic organelles such as mitochondria and chloroplasts) and the archaea/eukaryote nucleus group. The last common antecessor of all life (called LUCA, last universal common ancestor) should have possessed an early version of this protein complex. As ATP synthase is obligate membrane bound, this supports the assumption that LUCA was a cellular organism. The RNA world hypothesis might clarify this scenario, as LUCA might have been a ribocyte (also called ribocell) lacking DNA, but with an RNA genome built by ribosomes as primordial self-replicating entities. A Peptide-RNA world (also called RNP world) hypothesis has been proposed based on the idea that oligopeptides may have been built together with primordial nucleic acids at the same time, which also supports the concept of a ribocyte as LUCA. The feature of DNA as the material base of the genome might have then been adopted separately in bacteria and in archaea (and later eukaryote nuclei), presumably by help of some viruses (possibly retroviruses as they could reverse transcribe RNA to DNA). As a result, prokaryota comprising bacteria and archaea may also be polyphyletic.

Cape Canaveral

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https://en.wikipedia.org/wiki/Cape_Canaveral 

Cape Canaveral
Spanish: Cabo Cañaveral
View of Cape Canaveral from space in 1991
Location in Florida Show map of FloridaShow map of the United StatesShow all
Location	Florida, United States
Coordinates	28°28′N 80°32′WCoordinates: 28°28′N 80°32′W
Offshore water bodies	Atlantic Ocean
Elevation	3.1 m (10 ft)

Cape Canaveral (Spanish: Cabo Cañaveral) is a prominent cape in Brevard County, Florida, in the United States, near the center of the state's Atlantic coast. Officially Cape Kennedy from 1963 to 1973, it lies east of Merritt Island, separated from it by the Banana River. It is part of a region known as the Space Coast, and is the site of the Cape Canaveral Space Force Station. Since many U.S. spacecraft have been launched from both the station and the Kennedy Space Center on adjacent Merritt Island, the two are sometimes conflated with each other.

Other features of the cape include Port Canaveral, one of the busiest cruise ports in the world, and the Cape Canaveral Lighthouse. The city of Cape Canaveral lies just south of the Port Canaveral District. Mosquito Lagoon, the Indian River, Merritt Island National Wildlife Refuge and Canaveral National Seashore are also features of this area.

History

A section of a map from the 1584 edition of Abraham Ortelius's Theatrum Orbis Terrarum, Additamentum III showing the name C. de Cañareal

Humans have occupied the area for at least 12,000 years.

During the middle Archaic period, from 5000 BC to 2000 BC, the Mount Taylor period culture region covered northeast Florida, including the area around Cape Canaveral. Late in the Archaic period, from 2000 BC to 500 BC, the Mount Taylor culture was succeeded by the Orange culture, which was among the earliest cultures in North America to produce pottery. The Orange culture was followed by the St. Johns culture, from 500 BC until after European contact. The area around the Indian River was in the Indian River variant of the St. Johns culture, with influences from the Belle Glade culture to the south.

During the first Spanish colonial period the area around the Indian River, to the south of Cape Canaveral, was occupied by the Ais people, while the area around the Mosquito Lagoon, to the north of the Cape, was occupied by the Surruque people. The Surruque were allied with the Ais, but it is not clear whether the Surruque spoke a Timucua language, or a language related to the Ais language.

In the early 16th century, Cape Canaveral was noted on maps, although without being named. It was named by Spanish explorers in the first half of the 16th century as Cabo Cañaveral. The name "Canaveral" (Cañaveral in Spanish, meaning "reed bed" or "sugarcane plantation") is the third oldest surviving European place name in the United States. The first application of the name, according to the Smithsonian Institution, was from the 1521–1525 explorations of Spanish explorer Francisco Gordillo. A point of land jutting out into an area of the Atlantic Ocean with swift currents, it became a landing spot for many shipwrecked sailors. An early alternative name was "Cape of Currents". By at least 1564, the name appeared on maps.

English privateer John Hawkins and his journalist John Sparke gave an account of their landing at Cape Canaveral in the 16th century. A Presbyterian missionary was wrecked here and lived among the Indians. Other histories tell of French survivors from Jean Ribault's colony at Fort Caroline, whose ship the Trinité wrecked on the shores of Cape Canaveral in 1565, and built a fort from its timbers.

In December 1571, Pedro Menéndez was wrecked off the Coast of Cape Canaveral and encountered the Ais Indians. From 1605 to 1606, the Spanish Governor of Florida Pedro de Ibarra sent Alvaro Mexia on a diplomatic mission to the Ais Indian nation. The mission was a success; diplomatic ties were made and an agreement for the Ais to receive ransoms for all the shipwrecked sailors they returned.

The first Cape Canaveral Lighthouse was completed in January 1848 to warn ships of the coral shoals off the coast.

The hurricane of August 1885, pushed a "wall of water" over the barrier island (elevation, 3.1 m (10 ft)) devastating Cape Canaveral and adjacent areas. The ocean waves flooded the homesteaders and discouraged further settlement in the area. The beach near the lighthouse was severely eroded prompting its relocation 1.6 km (0.99 mi) west inland.

The 1890 graduating class of Harvard University started a gun club called the "Canaveral Club" at the Cape. This was founded by C. B. Horton of Boston and George H. Reed. A number of distinguished visitors including presidents Grover Cleveland and Benjamin Harrison were reported to have stayed here. In the 1920s, the grand building fell in disrepair and later burned to the ground.

In the 20th century, several communities sprang up in Cape Canaveral with names like Canaveral, Canaveral Harbor, Artesia and De Soto Beach. While the area was predominantly a farming and fishing community, some visionaries saw its potential as a resort for vacationers. However, the stock market crash of 1929 hampered its development. In the 1930s, a group of wealthy journalists started a community called "Journalista Beach", now called Avon by the Sea. The Brossier brothers built houses in this area and started a publication entitled the Evening Star Reporter that was the forerunner of the Orlando Sentinel.

Construction of Port Canaveral for military and commercial purposes was started in July 1950 and dedicated on 4 November 1953. Congress approved the construction of a deep-water port in 1929, half a century after it was first petitioned by the U.S. Navy in 1878. It is now the major deep-water port of Central Florida.

Rocket launch site

Cape Canaveral with Kennedy Space Center shown in white; Cape Canaveral Space Force Station in green

Cape Canaveral became the test site for missiles when the legislation for the Joint Long Range Proving Ground was passed by the 81st Congress and signed by President Harry Truman on 11 May 1949. Work began on 9 May 1950, under a contract with the Duval Engineering Company of Jacksonville, Florida, to build the Cape's first paved access road and its first permanent launch site.

The first rocket launched at the Cape was a V-2 rocket named Bumper 8 from Launch Complex 3 on 24 July 1950. On 6 February 1959, the first successful test firing of a Titan intercontinental ballistic missile was accomplished. NASA's Project Mercury and Gemini space flights were launched from Cape Canaveral, as were Apollo flights using the Saturn I and Saturn IB rockets.

Cape Canaveral was chosen for rocket launches to take advantage of the Earth's rotation. The linear velocity of the Earth's surface is greatest towards the equator; the relatively southerly location of the cape allows rockets to take advantage of this by launching eastward, in the same direction as the Earth's rotation. It is also highly desirable to have the downrange area sparsely populated, in case of accidents; an ocean is ideal for this. The east coast of Florida has logistical advantages over potential competing sites. The Spaceport Florida Launch Complex 46 of the Cape Canaveral Space Force Station is the easternmost near the tip of the cape.

Name changes

A post office in the area was built and listed in the U.S. Post Office application as "Artesia" and retained this name from 1893 to 1954. It was "Port Canaveral" from 1954 to 1962, and lastly the City of Cape Canaveral from 1962 to 1963, when a larger post office was built.

Cape Kennedy

From 1963 to 1973, the area had a different name when President Lyndon Johnson by executive order renamed the area "Cape Kennedy" after President John F. Kennedy, who had set the goal of landing on the Moon. After Kennedy's assassination in November 1963, his widow, Jacqueline Kennedy, suggested to President Johnson that renaming the Cape Canaveral facility would be an appropriate memorial. Johnson recommended the renaming of the entire cape, announced in a televised address six days after the assassination, on Thanksgiving evening. Accordingly, Cape Canaveral was officially renamed Cape Kennedy. Kennedy's last visit to the space facility was on 16 November 1963, six days before his death; the final Mercury mission had concluded six months earlier.

Although the name change was approved by the U.S. Board on Geographic Names of the Department of the Interior in December 1963, it was not popular in Florida from the outset, especially in the bordering city of Cape Canaveral. In May, 1973, the Florida Legislature passed a law restoring the former 400-year-old name, and the Board went along. The name restoration to Cape Canaveral became official on 9 October 1973. Senator Ted Kennedy had stated in 1970 that it was a matter to be decided by the citizens of Florida. The Kennedy family issued a letter stating they "understood the decision", and NASA's Kennedy Space Center retains the "Kennedy" name.

The Gemini, Apollo, and first Skylab missions were all launched from "Cape Kennedy". The first manned launch under the restored name of "Cape Canaveral" was the final Skylab mission, on 16 November 1973.

In 1999, the North American Numbering Plan Administration allocated telephone area code 321 (as in a launch countdown) to the Cape Canaveral area in homage to its spacefaring heritage.

SpaceX launch vehicles

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/SpaceX_launch_vehicles 

Flown SpaceX launch vehicles to scale – from left to right, the Falcon 1, Falcon 9 v1.0, Falcon 9 v1.1, Falcon 9 Full Thrust, Falcon 9 Block 5, Falcon Heavy, and Falcon Heavy Block 5

SpaceX manufactures launch vehicles to operate its launch provider services and to execute its various exploration goals. SpaceX currently manufactures and operates the Falcon 9 Full Thrust family of medium-lift launch vehicles and the Falcon Heavy family of heavy-lift launch vehicles – both of which powered by SpaceX Merlin engines and employing VTVL technologies to reuse the first stage. As of 2020, the company is also developing the fully reusable Starship launch system, which will replace the Falcon 9 and Falcon Heavy.

SpaceX's first launch vehicle, the Falcon 1, was the first privately developed liquid fuel launch vehicle to be launched into orbit, and utilized SpaceX's Merlin and Kestrel engines for its first and second stages, respectively. It was launched five times from Omelek Island between 2006 and 2009 – the Falcon 1e and Falcon 5 variants were planned but never developed. The Falcon 9 v1.0, utilizing upgraded Merlin engines on both its stages, was developed as part of the United States Air Force's Evolved Expendable Launch Vehicle program and NASA's Commercial Orbital Transportation Services program. It was first launched from Cape Canaveral in 2010 and later replaced by the Falcon 9 v1.1 series in 2013, which was also launched from Vandenberg. The Falcon 9 Full Thrust and Falcon Heavy variants followed in 2015 and 2018, and are both launched from Kennedy, in addition to Cape Canaveral and Vandenberg.

Nomenclature

Elon Musk, CEO of SpaceX, has stated that the Falcon 1, 9, and Heavy are named after the Millennium Falcon from the Star Wars film series.

Current launch vehicles

Falcon 9 "Full Thrust"

The Dragon capsule sits atop the Falcon 9 rocket before the Demo-1 launch.

The "Full Thrust" version of Falcon 9 is an upgraded version of the Falcon 9 v1.1. It was used the first time on 22 December 2015 for the ORBCOMM-2 launch at Cape Canaveral SLC-40 launch pad.

The first stage was upgraded with a larger liquid oxygen tank, loaded with subcooled propellants to allow a greater mass of fuel in the same tank volume. The second stage was also extended for greater fuel tank capacity. These upgrades brought a 33% increase to the previous rocket performance. 5 sub-variants have been flown, only Falcon 9 Block 5 is still active.

By default the first stage lands and gets reused, although it can be expended to increase the payload capacity.

Falcon Heavy

Falcon Heavy on pad LC-39A

Falcon Heavy (FH) is a super heavy lift space launch vehicle designed and manufactured by SpaceX. The Falcon Heavy is a variant of the Falcon 9 launch vehicle comprising three Falcon 9 first stages: a reinforced center core, and two additional side boosters. All three boosters are designed to be recovered and reused, although expendable flights are possible to increase the payload capacity. The side boosters assigned to Falcon Heavy's first flight were recovered from two prior Falcon 9 missions. SpaceX successfully launched the Falcon Heavy on February 6, 2018, delivering a payload comprising Musk's personal Tesla Roadster (playing "Life On Mars?", by David Bowie) onto a trajectory reaching the orbit of Mars.

In development

Starship

The SpaceX Starship is planned to be a fully reusable super heavy-lift launch vehicle. The vehicle is under development by SpaceX, as a self-funded private spaceflight project. While the Starship is currently being tested at suborbital altitudes only, it will be used on orbital launches with an additional booster stage, the Super Heavy, where Starship will serve as the second stage on a two-stage-to-orbit launch vehicle. The combination of spacecraft and booster is called Starship as well by SpaceX.

Retired

Falcon 1

The first Falcon 1 at Vandenberg AFB. This vehicle was removed from VAFB due to delays and eventually launched from Kwajalein.

The Falcon 1 is a small, partially reusable rocket capable of placing several hundred kilograms into low earth orbit. It also functioned as a testbed for developing concepts and components for the larger Falcon 9. Initial Falcon 1 flights were launched from the US government's Reagan Test Site on the island atoll of Kwajalein in the Pacific Ocean, and represented the first attempt to fly a ground-launched rocket to orbit from that site.

On 26 March 2006, the Falcon 1's maiden flight failed only seconds after leaving the pad due to a fuel line rupture. After a year, the second flight was launched on 22 March 2007 and it also ended in failure, due to a spin stabilization problem that automatically caused sensors to turn off the Merlin 2nd-stage engine. The third Falcon 1 flight used a new regenerative cooling system for the first-stage Merlin engine, and the engine development was responsible for the almost 17-month flight delay. The new cooling system turned out to be the major reason the mission failed; because the first stage rammed into the second-stage engine bell at staging, due to excess thrust provided by residual propellant left over from the higher-propellant-capacity cooling system. On 28 September 2008, the Falcon 1 succeeded in reaching orbit on its fourth attempt, becoming the first privately funded, liquid-fueled rocket to do so. The Falcon 1 carried its first and only successful commercial payload into orbit on 13 July 2009, on its fifth launch. No launch attempts of the Falcon 1 have been made since 2009, and SpaceX is no longer taking launch reservations for the Falcon 1 in order to concentrate company resources on its larger Falcon 9 launch vehicle and other development projects.

Falcon 9 v1.0

The first version of the Falcon 9 launch vehicle, Falcon 9 v1.0, was developed in 2005–2010, and was launched for the first time in 2010. Falcon 9 v1.0 made five flights in 2010–2013, when it was retired.

Falcon 9 v1.1

SpaceX's Falcon 9 rocket carrying the Dragon spacecraft, lifts off during the COTS Demo Flight 1 on 8 December 2010

On 8 September 2005, SpaceX announced the development of the Falcon 9 rocket, which has nine Merlin engines in its first stage. The design is an EELV-class vehicle, intended to compete with the Delta IV and the Atlas V, along with launchers of other nations as well. Both stages were designed for reuse. A similarly designed Falcon 5 rocket was also envisioned to fit between the Falcon 1 and Falcon 9, but development was dropped to concentrate on the Falcon 9.

The first version of the Falcon 9, Falcon 9 v1.0, was developed in 2005–2010, and flew five orbital missions in 2010–2013. The second version of the launch system—Falcon 9 v1.1— has been retired meanwhile.

Falcon 9 v1.1 was developed in 2010-2013, and made its maiden flight in September 2013. The Falcon 9 v1.1 is a 60 percent heavier rocket with 60 percent more thrust than the v1.0 version of the Falcon 9. It includes realigned first-stage engines and 60 percent longer fuel tanks, making it more susceptible to bending during flight. The engines themselves have been upgraded to the more powerful Merlin 1D. These improvements increased the payload capability from 9,000 kilograms (20,000 lb) to 13,150 kilograms (28,990 lb).

The stage separation system has been redesigned and reduces the number of attachment points from twelve to three, and the vehicle has upgraded avionics and software as well.

The new first stage was also supposed be used as side boosters on the Falcon Heavy launch vehicle.

The company purchased the McGregor, Texas, testing facilities of defunct Beal Aerospace, where it refitted the largest test stand at the facilities for Falcon 9 testing. On 22 November 2008, the stand tested the nine Merlin 1C engines of the Falcon 9, which deliver 770,000 pounds-force (3,400 kN) of thrust, well under the stand's capacity of 3,300,000 pounds-force (15,000 kN).

The first Falcon 9 vehicle was integrated at Cape Canaveral on 30 December 2008. NASA was planning for a flight to take place in January 2010; however the maiden flight was postponed several times and took place on 4 June 2010. At 2:50pm EST the Falcon 9 rocket successfully reached orbit.

The second flight for the Falcon 9 vehicle was the COTS Demo Flight 1, the first launch under the NASA Commercial Orbital Transportation Services (COTS) contract designed to provide "seed money" for development of new boosters. The original NASA contract called for the COTS Demo Flight 1 to occur the second quarter of 2008; this flight was delayed several times, occurring at 15:43 GMT on 8 December 2010. The rocket successfully deployed an operational Dragon spacecraft at 15:53 GMT. Dragon orbited the Earth twice, and then made a controlled reentry burn that put it on target for a splashdown in the Pacific Ocean off the coast of Mexico. The first flight of the Falcon 9 v1.1 was September 29, 2013 from Vandenberg Air Force Base carrying several payloads including Canada's CASSIOPE technology demonstration satellite. The Falcon 9 v1.1 features stretched first and second stages, and a new octagonal arrangement of the 9 Merlin-1D engines on the first stage (replacing the square pattern of engines in v1.0). SpaceX notes that the Falcon 9 v1.1 is cheaper to manufacture, and longer than v1.0. It also has a larger payload capacity: 13,150 kilograms to low Earth orbit or 4,850 kg to geosynchronous transfer orbit.

Grasshopper

Grasshopper vehicle in September 2012

Grasshopper was an experimental technology-demonstrator, suborbital reusable launch vehicle (RLV), a vertical takeoff, vertical landing (VTVL) rocket. The first VTVL flight test vehicle—Grasshopper, built on a Falcon 9 v1.0 first-stage tank—made a total of eight test flights between September 2012 and October 2013. All eight flights were from the McGregor, Texas, test facility.

Grasshopper began flight testing in September 2012 with a brief, three-second hop. It was followed by a second hop in November 2012, which consisted of an 8-second flight that took the testbed approximately 5.4 m (18 ft) off the ground. A third flight occurred in December 2012 of 29 seconds duration, with extended hover under rocket engine power, in which it ascended to an altitude of 40 m (130 ft) before descending under rocket power to come to a successful vertical landing. Grasshopper made its eighth and final test flight on October 7, 2013, flying to an altitude of 744 m (2,441 ft; 0.462 mi) before making its eighth successful vertical landing. The Grasshopper test vehicle is now retired.

Canceled

Falcon 1e

The Falcon 1e was a proposed upgrade of the SpaceX Falcon 1. The Falcon 1e would have featured a larger first stage with a higher thrust engine, an upgraded second stage engine, a larger payload fairing, and was intended to be partially reusable. Its first launch was planned for mid-2011, but the Falcon 1 and Falcon 1e were withdrawn from the market, with SpaceX citing "limited demand," before its debut. Payloads that would have flown on the Falcon 1 were instead to be flown on the Falcon 9 using excess capacity.

The Falcon 1e was to be 6.1 m (20 ft) longer than the Falcon 1, with an overall length of 27.4 m (90 ft), but with the same 1.68 m (5 ft 6 in) diameter. Its first stage had a dry mass of 2,580 kg (5,680 lb), and was powered by an upgraded pump-fed Merlin 1C engine burning 39,000 kg (87,000 lb) of RP-1 and liquid oxygen. The first stage burn time was around 169 seconds. The second stage had a dry mass of 540 kg (1,200 lb) and its pressure-fed Kestrel 2 engine burned 4,000 kg (8,900 lb) of propellant. The restartable Kestrel 2 could burn for up to a total of 418 seconds.

The Falcon 1e planned to use Aluminum Lithium alloy 2195 in the second stage, a change from the 2014 Aluminum used in the Falcon 1 second stages.

Falcon 1e launches were intended to occur from Omelek Island, part of Kwajalein Atoll in the Marshall Islands, and from Cape Canaveral, however SpaceX had announced that they would consider other locations as long as there is a "business case for establishing the requested launch site". Following a demonstration flight, the Falcon 1e was intended to make a series of launches carrying Orbcomm O2G spacecraft, with a total of eighteen satellites being launched, several per rocket. EADS Astrium had been responsible for marketing the Falcon 1e in Europe.

Falcon 5

Early Falcon 5 design

The Falcon 5 was a proposed two-stage-to-orbit partially reusable launch vehicle designed by SpaceX, canceled in preference of the larger, more powerful Falcon 9.

The first stage of Falcon 5 was to be powered by five Merlin engines, and the upper stage by one Merlin engine, both burning RP-1 with a liquid oxygen oxidizer. Along with the Falcon 9, it would have been the world's only launch vehicle with its first stage designed for reuse.

The Falcon 5 would have been the first American rocket since the Saturn V to have full engine-out capability, meaning that with the loss of one engine, it can still meet mission requirements by burning the other four engines longer to achieve the correct orbit. In comparison, the Space Shuttle only had partial engine-out capability, meaning that it was not able to achieve proper orbit by burning the remaining engines longer.

In 2006, SpaceX stated that the Falcon 5 was a Falcon 9 with four engines removed. Since the launchers were being co-developed, work on the Falcon 9 was also applicable to the Falcon 5.

Falcon 9 Air

Falcon 9 Air would have been an air-launched multi-stage launch vehicle under development by SpaceX in 2011–2012. Falcon 9 Air was to be carried to launch position and launch altitude by a Stratolaunch Systems carrier aircraft, the world's largest aircraft by wingspan. Payload to low Earth orbit was projected to be 6,100 kg (13,400 pounds).

Propulsion for the rocket was planned to be provided by four Merlin 1D rocket engines, engines that were also to be used in the Falcon 9 v1.1 beginning in 2013, and also on the Falcon Heavy in 2014. First flight for the air-launched Falcon 9 Air rocket was notionally planned for 2016.

In December 2011 Stratolaunch Systems announced that it would contract with SpaceX to develop an air-launched, multiple-stage launch vehicle, as a derivative of Falcon 9 technology, called the Falcon 9 Air, as part of the Stratolaunch project. As initially conceived with the SpaceX Falcon 9 Air (F9A) launch vehicle, Stratolaunch was to initially place satellites of up to 6,100 kg (13,400 pounds) into low Earth orbit; and once established as a reliable system, announced that it would explore a human-rated version. The system can take off from airfields with a minimum 3,700 m (12,100 feet) length, and the F9A carrier aircraft was proposed to travel to a launch point up to 2,200 km (1,200 nautical miles) away from the airfield and fly at a launch altitude of 9,100 m (30,000 feet).

A month after the initial announcement, Stratolaunch confirmed that the first stage of the F9A launch vehicle would have only four engines, not the five that were shown in the mission video in December, and that they would be SpaceX Merlin 1D engines.

As initially announced, Stratolaunch Systems was a collaborative project that included subcontractors SpaceX, Scaled Composites, and Dynetics, with funding provided by Microsoft co-founder Paul G. Allen's Vulcan investment and project management company. Stratolaunch set out to build a mobile launch system with three primary components: a carrier aircraft (aircraft concept was designed by Burt Rutan, but the aircraft will be designed and built by Scaled Composites); a multi-stage launch vehicle to be developed and built by SpaceX; and a mating and integration system — allowing the carrier aircraft to safely carry and release the booster — to be built by Dynetics, a Huntsville, Alabama-based engineering company. The whole system will be the largest aircraft ever built; with the first test flight of the carrier aircraft originally expected in 2015 from Scaled Composites' facilities in Mojave, California, while the first test launch of the rocket was not expected before 2016 at the time of the project getting underway.

As the Stratolaunch development program progressed, it became clear that Stratolaunch and the system integrator, Dynetics, wanted modifications to the SpaceX basic launch-vehicle design that SpaceX felt were not strategic to the direction they were growing the company. These included requested modifications to the launch vehicle to add chines.

Development ceased in the fourth quarter of 2012, as SpaceX and Stratolaunch "amicably agreed to end [their] contractual relationship because the [Stratolaunch] launch vehicle design [had] departed significantly from the Falcon derivative vehicle envisioned by SpaceX and does not fit well with [SpaceX's] long-term strategic business model".

On 27 November 2012 Stratolaunch announced that they would partner with Orbital Sciences Corporation—initially on an air-launched vehicle study contract—instead of SpaceX, effectively ending development of the Falcon 9 Air.

In May 2013, the Falcon 9 Air was eventually replaced in the development plan by the Orbital Sciences Pegasus II air-launched rocket.

Competitive position

SpaceX Falcon rockets are being offered to the launch industry at highly competitive prices, allowing SpaceX to build up a large manifest of over 50 launches by late 2013, with two-thirds of them for commercial customers exclusive of US government flights.

In the US launch industry, SpaceX prices its product offerings well below its competition. Nevertheless, "somewhat incongruously, its primary US competitor, United Launch Alliance (ULA), still maintained (in early 2013) that it requires a large annual subsidy, which neither SpaceX nor Orbital Sciences receives, in order to remain financially viable, with the reason cited as a lack of market opportunity, a stance which seems to be in conflict with the market itself."

SpaceX launched its first satellite to geostationary orbit in December 2013 (SES-8) and followed that a month later with its second, Thaicom 6, beginning to offer competition to the European and Russian launch providers that had been the major players in the commercial communications satellite market in recent years.

SpaceX prices undercut its major competitors—the Ariane 5 and Proton—in this market.

Moreover, SpaceX prices for Falcon 9 and Falcon Heavy are much lower than the projected prices for Ariane 6, projected to be available in 2020, respectively.

As a result of additional mission requirements for government launches, SpaceX prices US government missions somewhat higher than similar commercial missions, but has noted that even with those added services, Falcon 9 missions contracted to the government are still priced well below US$100 million (even with approximately US$9 million in special security charges for some missions) which is a very competitive price compared to ULA prices for government payloads of the same size.

ULA prices to the US government are nearly $400 million for current launches of Falcon 9- and Falcon Heavy-class payloads.