Florida is the southernmost contiguous state in the United States. The state is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Atlantic Ocean, to the south by the Straits of Florida. Florida is the 22nd-most extensive, the 3rd-most populous, the 8th-most densely populated of the U. S. states. Jacksonville is the most populous municipality in the state and the largest city by area in the contiguous United States; the Miami metropolitan area is Florida's most populous urban area. Tallahassee is the state's capital. Florida's $1.0 trillion economy is the fourth largest in the United States. If it were a country, Florida would be the 16th largest economy in the world, the 58th most populous as of 2018. In 2017, Florida's per capita personal income was ranking 26th in the nation; the unemployment rate in September 2018 was 3.5% and ranked as the 18th in the United States. Florida exports nearly $55 billion in goods made in the 8th highest among all states.
The Miami Metropolitan Area is by far the largest urban economy in Florida and the 12th largest in the United States with a GDP of $344.9 billion as of 2017. This is more than twice the number of the next metro area, the Tampa Bay Area, which has a GDP of $145.3 billion. Florida is home to 51 of the world's billionaires with most of them residing in South Florida; the first European contact was made in 1513 by Spanish explorer Juan Ponce de León, who called it la Florida upon landing there in the Easter season, known in Spanish as Pascua Florida. Florida was a challenge for the European colonial powers before it gained statehood in the United States in 1845, it was a principal location of the Seminole Wars against the Native Americans, racial segregation after the American Civil War. Today, Florida is distinctive for its large Cuban expatriate community and high population growth, as well as for its increasing environmental issues; the state's economy relies on tourism and transportation, which developed in the late 19th century.
Florida is renowned for amusement parks, orange crops, winter vegetables, the Kennedy Space Center, as a popular destination for retirees. Florida is the flattest state in the United States. Lake Okeechobee is the largest freshwater lake in the U. S. state of Florida. Florida's close proximity to the ocean influences many aspects of daily life. Florida is a reflection of multiple inheritance. Florida has attracted many writers such as Marjorie Kinnan Rawlings, Ernest Hemingway and Tennessee Williams, continues to attract celebrities and athletes, it is internationally known for golf, auto racing, water sports. Several beaches in Florida have emerald-colored coastal waters. About two-thirds of Florida occupies a peninsula between the Gulf of the Atlantic Ocean. Florida has the longest coastline in the contiguous United States 1,350 miles, not including the contribution of the many barrier islands. Florida has a total of 4,510 islands; this is the second-highest number of islands of any state of the United States.
It is the only state that borders both the Gulf of the Atlantic Ocean. Much of the state is characterized by sedimentary soil. Florida has the lowest high point of any U. S. state. The climate varies from subtropical in the north to tropical in the south; the American alligator, American crocodile, American flamingo, Roseate spoonbill, Florida panther, bottlenose dolphin, manatee can be found in Everglades National Park in the southern part of the state. Along with Hawaii, Florida is one of only two states that has a tropical climate, is the only continental state with either a tropical climate or a coral reef; the Florida Reef is the only living coral barrier reef in the continental United States, the third-largest coral barrier reef system in the world. By the 16th century, the earliest time for which there is a historical record, major Native American groups included the Apalachee of the Florida Panhandle, the Timucua of northern and central Florida, the Ais of the central Atlantic coast, the Tocobaga of the Tampa Bay area, the Calusa of southwest Florida and the Tequesta of the southeastern coast.
Florida was the first region of the continental United States to be visited and settled by Europeans. The earliest known European explorers came with the Spanish conquistador Juan Ponce de León. Ponce de León spotted and landed on the peninsula on April 2, 1513, he named the region Florida. The story that he was searching for the Fountain of Youth is mythical and only appeared long after his death. In May 1539, Conquistador Hernando de Soto skirted the coast of Florida, searching for a deep harbor to land, he described seeing a thick wall of red mangroves spread mile after mile, some reaching as high as 70 feet, with intertwined and elevated roots making landing difficult. The Spanish introduced Christianity, horses, the Castilian language, more to Florida. Spain established several settlements with varying degrees of success. In 1559, Don Tristán de Luna y Arellano established a settlement at present-day Pensacola, making it the first attempted settlement in Florida, but it was abandoned by 1561.
In 1565, the settlement of St. Augustine was established under the leadership of admiral and
United States Department of Defense
The Department of Defense is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government concerned directly with national security and the United States Armed Forces. The department is the largest employer in the world, with nearly 1.3 million active duty servicemen and women as of 2016. Adding to its employees are over 826,000 National Guardsmen and Reservists from the four services, over 732,000 civilians bringing the total to over 2.8 million employees. Headquartered at the Pentagon in Arlington, just outside Washington, D. C. the DoD's stated mission is to provide "the military forces needed to deter war and ensure our nation's security". The Department of Defense is headed by the Secretary of Defense, a cabinet-level head who reports directly to the President of the United States. Beneath the Department of Defense are three subordinate military departments: the United States Department of the Army, the United States Department of the Navy, the United States Department of the Air Force.
In addition, four national intelligence services are subordinate to the Department of Defense: the Defense Intelligence Agency, the National Security Agency, the National Geospatial-Intelligence Agency, the National Reconnaissance Office. Other Defense Agencies include the Defense Advanced Research Projects Agency, the Defense Logistics Agency, the Missile Defense Agency, the Defense Health Agency, Defense Threat Reduction Agency, the Defense Security Service, the Pentagon Force Protection Agency, all of which are under the command of the Secretary of Defense. Additionally, the Defense Contract Management Agency provides acquisition insight that matters, by delivering actionable acquisition intelligence from factory floor to the warfighter. Military operations are managed by ten functional Unified combatant commands; the Department of Defense operates several joint services schools, including the Eisenhower School and the National War College. The history of the defense of the United States started with the Continental Congress in 1775.
The creation of the United States Army was enacted on 14 June 1775. This coincides with the American holiday Flag Day; the Second Continental Congress would charter the United States Navy, on 13 October 1775, create the United States Marine Corps on 10 November 1775. The Preamble of the United States Constitution gave the authority to the federal government to defend its citizens: We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America. Upon the seating of the first Congress on 4 March 1789, legislation to create a military defense force stagnated as they focused on other concerns relevant to setting up the new government. President George Washington went to Congress to remind them of their duty to establish a military twice during this time.
On the last day of the session, 29 September 1789, Congress created the War Department, historic forerunner of the Department of Defense. The War Department handled naval affairs until Congress created the Navy Department in 1798; the secretaries of each of these departments reported directly to the president as cabinet-level advisors until 1949, when all military departments became subordinate to the Secretary of Defense. After the end of World War II, President Harry Truman proposed creation of a unified department of national defense. In a special message to Congress on 19 December 1945, the President cited both wasteful military spending and inter-departmental conflicts. Deliberations in Congress went on for months focusing on the role of the military in society and the threat of granting too much military power to the executive. On 26 July 1947, Truman signed the National Security Act of 1947, which set up a unified military command known as the "National Military Establishment", as well as creating the Central Intelligence Agency, the National Security Council, National Security Resources Board, United States Air Force and the Joint Chiefs of Staff.
The act placed the National Military Establishment under the control of a single Secretary of Defense. The National Military Establishment formally began operations on 18 September, the day after the Senate confirmed James V. Forrestal as the first Secretary of Defense; the National Military Establishment was renamed the "Department of Defense" on 10 August 1949 and absorbed the three cabinet-level military departments, in an amendment to the original 1947 law. Under the Department of Defense Reorganization Act of 1958, channels of authority within the department were streamlined, while still maintaining the ordinary authority of the Military Departments to organize and equip their associated forces; the Act clarified the overall decision-making authority of the Secretary of Defense with respect to these subordinate Military Departments and more defined the operational chain of command over U. S. military forces as running from the president to the Secretary of Defense and to the unified combatant commanders.
Provided in this legislation was a centralized research authority, the Advanced Research Projects Agency known as DARPA. The act was written and promoted by the Eisenhower administration, was signed into law 6 August 1958; the Secretary of Defense, appointed by the president with the advice and consent of the Senate, is by federal law (1
David C. Hilmers
David Carl Hilmers, M. D. is a former NASA astronaut. He was born in Clinton, but considers DeWitt, Iowa, to be his hometown, he has two grown sons. His recreational interests include playing the piano, electronics, spending time with his family, all types of sports, his parents are deceased. With five academic degrees, he is the second most formally educated U. S. astronaut, behind Story Musgrave with six. Graduated from Central Community High School in DeWitt, Iowa, in 1968. S. Naval Postgraduate School in 1978, he received a Doctor of Medicine degree from the Baylor College of Medicine in 1995 with honors and a Master of Science degree in Public Health from the University of Texas-Houston Health Science Center in 2002. Hilmers entered active duty with the United States Marine Corps in July 1972. On completing The Basic School and Naval Flight Officer School, he was assigned to VMA-121 at Marine Corps Air Station Cherry Point, North Carolina, flying the A-6 Intruder as a bombardier-navigator. In 1975, he became an air liaison officer with the 1st Battalion, 2nd Marines, stationed with the Sixth Fleet in the Mediterranean.
He graduated from the U. S. Naval Postgraduate School in 1978 and was assigned to the 1st Marine Aircraft Wing at Marine Corps Air Station Iwakuni, Japan, he was stationed with the 3rd Marine Aircraft Wing at Marine Corps Air Station El Toro, California, at the time of his selection by NASA. Hilmers was selected a NASA astronaut in July 1980, completed the initial training period in August 1981. In 1983 he was selected as a member of the launch-ready standby crew, his early NASA assignments have included work on rocket upper stages such as PAM, IUS, Centaur, as well as Shuttle software verification at the Shuttle Avionics Integration Laboratory. In addition, he was the Astronaut Office training coordinator, worked on various Department of Defense payloads, served as a spacecraft communicator at Mission Control for STS-41-D, STS-41-G, STS-51-A, STS-51-C and STS-51-D, worked Space Station issues for the Astronaut Office, served as head of the Mission Development Branch within the Astronaut Office.
In May 1985 he was named to the crew of STS-61-F, to deploy the Ulysses spacecraft on an interplanetary trajectory using a Centaur upper stage. This mission was to have flown in May 1986, but the Shuttle Centaur project was terminated in July 1986, Hilmers worked in the areas of ascent abort development, payload safety, Shuttle on-board software. During 1987 he was involved in flight software development, he became head of the Mission Development branch in the astronaut office. A veteran of four space flights, he has logged over 493 hours in space, he served as a mission specialist on STS-51-J, STS-26, STS-36, STS-42. Hilmers retired from NASA and the United States Marine Corps in October 1992, went on to complete medical school and residency in the combined Internal Medicine/Pediatrics program at Baylor College of Medicine, he holds the rank of Professor in the departments of Internal Medicine and Pediatrics, the Center for Space Medicine, Baylor Global Initiatives at the Baylor College of Medicine in Houston, Texas.
In addition to his teaching and clinical duties, he is involved in research in global health and malnutrition in many countries. He spends much of his spare time providing humanitarian medical care locally in Houston and in developing nations, including disaster relief efforts in Iraq, Sri Lanka, the Philippines, in Liberia during the Ebola outbreak in 2014. STS-51-J Atlantis, a classified Department of Defense mission, launched from Kennedy Space Center, Florida, on October 3, 1985; this was the maiden voyage of the Orbiter Atlantis. Hilmers had prime responsibility for a number of on-orbit activities during the mission. After 98 hours of orbital operations, Atlantis landed at Edwards Air Force Base, California, on October 7, 1985. STS-26 Discovery, the first mission to be flown after the Challenger accident, was launched from the Kennedy Space Center, Florida, on September 29, 1988. During the four-day mission, the crew deployed the Tracking and Data Relay Satellite, subsequently carried to orbit by the Inertial Upper Stage rocket.
They operated eleven mid-deck experiments. Discovery completed 64 orbits of the Earth before landing at Edwards Air Force Base, California, on October 3, 1988. STS-36 Atlantis launched from the Kennedy Space Center, Florida, on February 28, 1990; this mission carried a number of secondary payloads. After 72 orbits of the Earth, the STS-36 mission concluded with a lakebed landing at Edwards Air Force Base, California, on March 4, 1990, after traveling 1.87 million miles. STS-42 Discovery launched from the Kennedy Space Center, Florida, on January 22, 1992. Fifty-five major experiments conducted in the International Microgravity Laboratory-1 module were provided by investigators from eleven countries, represented a broad spectrum of scientific disciplines. During 128 orbits of the Earth, the STS-42 crew accomplished the mission's primary objective of investigating the effects of microgravity on materials processing and life sciences. In this unique laboratory in space, crew members worked around-the-clock in two shifts.
Experiments investigated the microgravity effects on the growth of protein and semiconductor crystals. Biological exper
Cape Hatteras is a thin, broken strand of islands in North Carolina that arch out into the Atlantic Ocean away from the US mainland back toward the mainland, creating a series of sheltered islands between the Outer Banks and the mainland. For thousands of years these barrier islands have survived onslaughts of sea. Long stretches of beach, sand dunes and maritime forests create a unique environment where wind and waves shape the topography. A large area of the Outer Banks is part of a National Park, called the Cape Hatteras National Seashore, it is the nearest landmass on the US mainland to Bermuda, about 563 nautical miles to the east-southeast. The treacherous waters off the coast of the Outer Banks is known as the Graveyard of the Atlantic, Over 600 ships wrecked here as victims of shallow shoals and war. Diamond Shoals, a bank of shifting sand ridges hidden beneath the turbulent sea off Cape Hatteras, has never promised safe passage for ships. In the past 400 years the graveyard has claimed many lives.
As early as the 1870s, villagers served in the US Life-Saving Service. Others staffed lighthouses built to guide mariners. Few ships wreck today, but storms still uncover the ruins of the old wrecks that lie along the beaches of the Outer Banks. Cape Hatteras National Seashore protects parts of three barrier islands: Bodie Island, Hatteras Island, Ocracoke Island. Beach and sound access ramps, nature trails, lighthouses can be found and explored on all three islands; the community of Buxton lies on the inland side of the Cape itself, at the widest part of Hatteras Island. It is the largest community on the island, is home to the governmental offices and schools for the Island. Cape Hatteras is a bend in Hatteras Island, one of the long thin barrier islands that make up the Outer Banks, it is the site. The cape's shoals are known as Diamond Shoals. Cape Hatteras has a humid subtropical climate, with long hot summers, short cool winters. Most of the area falls into USDA Plant Hardiness Zone 9. Cape Hatteras is surrounded by water, with Pamlico Sound to the west and the Atlantic Ocean to the east.
The proximity to water moderates conditions throughout the year, producing cooler summers and warmer winters than inland areas of North Carolina. The cape is the northern limit of tropical fauna. During the summer, average daily highs are in the 85 °F range, occasional intense thundershowers occur; as a result of its proximity to water, temperatures above 90 °F are rare, with an average of only 2.3 days annually above 90 °F. The coolest month, has a daily high of 52 °F, with lows well above freezing; the average window for freezing temperatures is from December 12 to March 11, between which there is an average of 21 nights with lows at or below the freezing mark. Extremes in temperature range from 6 °F on January 21, 1985 up to 97 °F on June 27, 1952. Snowfall is observed only and very light. Precipitation in the form of rain, is over 58 inches per year, making it the wettest coastal location in North Carolina. Precipitation is evenly distributed throughout the year; however and May represent a drier season, while August to October are the wettest months.
On average, August is the wettest month, owing to high frequencies of both summer thunderstorms and tropical systems that affect the area from August to early October. Due to its exposed position, Cape Hatteras is the highest-risk area for hurricanes and tropical storms along the entire U. S. Eastern seaboard. Cape Hatteras can experience significant wind and/or water damage from tropical systems moving near or over North Carolina's Outer Banks, while other areas experience much less, minimal or no damage; the Cape Hatteras area is infamous for being struck by hurricanes that move up the East Coast of the United States. The strike of Hurricane Isabel in 2003 was devastating for the area. Isabel devastated the entire Outer Banks and split Hatteras Island between the two small towns of Frisco and Hatteras. NC 12, which provides a direct route from Nags Head to Hatteras Island, was washed out when the hurricane created a new inlet. Students had to use a ferry to get to school; the inlet was filled in with sand by the Army Corps of Engineers which took nearly two months to complete.
The road and water lines were rebuilt when the inlet was filled. The name Hatteras is the sixth oldest surviving English place-name in the U. S. An inlet north of the cape was named "Hatrask" in 1585 by Sir Richard Grenville, the admiral leading the Roanoke Colony expedition sent by Sir Walter Raleigh, it was applied to the island and cape as well, modified to "Hatteras." Hatteras is the name of the Hatteras Indians. Because mariners utilize ocean currents to speed their journey, many ships venture close to Cape Hatteras when traveling along the eastern seaboard, risking the perils of sailing close to the shoals amid turbulent water and the frequent storms occurring in the area. So many ships have been lost off Cape Hatteras that the area is known as the "Graveyard of the Atlantic." Cape Hatteras is well known for surfing. The first lighthouse at the cape was built in 1803.
Vandenberg Air Force Base
Vandenberg Air Force Base is a United States Air Force Base 9.2 miles northwest of Lompoc, California. It is under the jurisdiction of Air Force Space Command. Vandenberg AFB is a Department of Defense space and missile testing base, with a mission of placing satellites into polar orbit from the West Coast using expendable boosters and reusable boosters. Wing personnel support the Service's LGM-30G Minuteman III Intercontinental Ballistic Missile Force Development Evaluation program. In addition to its military mission, the base leases launch pad facilities to SpaceX, as well as 100 acres leased to the California Spaceport in 1995. Established in 1941, the base is named in honor of former Air Force Chief of Staff General Hoyt Vandenberg; the host unit at Vandenberg AFB is the 30th Space Wing. The 30th SW is home to the Western Range, manages Department of Defense space and missile testing, places satellites into near-polar orbits from the West Coast. Wing personnel support the Air Force's Minuteman III Intercontinental Ballistic Missile Force Development Test and Evaluation program.
The Western Range begins at the coastal boundaries of Vandenberg and extends westward from the California coast to the Western Pacific, including sites in Hawaii. Operations involve dozens of commercial interests; the wing is organized into operations, mission support and medical groups, along with several directly assigned staff agencies. 30th Launch GroupThe 30th Launch Group is responsible for booster and satellite technical oversight and launch processing activities to include launch and test operations. The group consists of an integrated military and contractor team with more than 250 personnel directly supporting operations from the Western Range. 1st Air and Space Test Squadron 4th Space Launch Squadron30th Operations GroupThe 30th Operations Group provides the core capability for West Coast spacelift and range operations. Operations professionals are responsible for operating and maintaining the Western Range for spacelift, missile test launch and space surveillance missions.30th Mission Support GroupThe 30th Mission Support Group supports the third largest Air Force Base in the United States.
It is responsible for quality-of-life needs, personnel, civil engineering and security.30th Medical GroupThe 30th Medical Group provides medical, bio-environmental and public health services for people assigned to Vandenberg Air Force Base, their families and retirees. Tenant organizations assigned to Vandenberg are: Fourteenth Air Force Joint Functional Component Command for Space 9th Space Operations Squadron 21st Space Operations Squadron 576th Flight Test Squadron 381st Training Group 148th Space Operations Squadron 216th Operations Support Squadron NASA Resident Office Air Force Office of Special Investigations Detachment 1, 18th Intelligence Squadron The Space and Missile Heritage Center is located at Space Launch Complex 10, site of the first IRBM tests of the Thor and Discoverer series of launches, it is Vandenberg's only National Historic Landmark, open for scheduled tours through the 30th Space Wing's Public Affairs office. The Center preserves and displays artifacts and memorabilia to interpret the evolution of missile and spacelift activity at Vandenberg from the beginning of the Cold War through current non-classified developments in military and scientific space endeavors.
The current display area is made up of two exhibits, the "Chronology of the Cold War" and the "Evolution of Technology". The exhibits incorporate a combination of launch complex models, launch consoles, rocket engines, re-entry vehicles and computer displays as well as hands-on interaction where appropriate. There are plans to evolve the center in stages from the current exhibit areas as restorations of additional facilities are completed. In 1941 the United States Army sought more and better training centers for the rapid development of its armored and infantry forces. In March 1941, the Army acquired 86,000 acres of open ranch lands along the Central Coast of California between Lompoc and Santa Maria. Most of the land was purchased. Smaller parcels were obtained either as easements. With its flat plateau, surrounding hills, numerous canyons, relative remoteness from populated areas, the Army was convinced it had found the ideal training location. Construction of the Army camp began in September 1941.
Although its completion was still months away, the Army activated the camp on 5 October, named it Camp Cooke in honor of Major General Phillip St. George Cooke. General Cooke was a cavalry officer whose military career spanned half a century, beginning with his graduation from West Point in 1827 to his retirement in 1873, he participated in the Mexican War, the Indian Wars, the Civil War. A native of Virginia, General Cooke remained loyal to the Union during the Civil War, his most enduring achievement came when as a colonel during the Mexican War, he led a battalion of Mormons from Missouri to California. The route led by Colonel Cooke in 1847 opened the first wagon route to California, today the railroad follows much of the early wagon trails. Although the construction of Camp Cooke continued well into 1942, troop training did not wait; the 5th Armored Division rolled into camp in February and March, the steady roar of its tanks and artillery soon became part of the daily scene. From until the end of the war, other armored
Space Shuttle thermal protection system
The Space Shuttle thermal protection system is the barrier that protected the Space Shuttle Orbiter during the searing 1,650 °C heat of atmospheric reentry. A secondary goal was to protect from the cold of space while in orbit; the TPS covered the entire orbiter surface, consisted of seven different materials in varying locations based on amount of required heat protection: Reinforced carbon–carbon, used in the nose cap, the chin area between the nose cap and nose landing gear doors, the arrowhead aft of the nose landing gear door, the wing leading edges. Used where reentry temperature exceeded 1,260 °C. High-temperature reusable surface insulation tiles, used on the orbiter underside. Made of coated LI-900 silica ceramics. Used where reentry temperature was below 1,260 °C. Fibrous refractory composite insulation tiles, used to provide improved strength, resistance to coating cracking and weight reduction; some HRSI tiles were replaced by this type. Flexible Insulation Blankets, a quilted, flexible blanket-like surface insulation.
Used where reentry temperature was below 649 °C. Low-temperature Reusable Surface Insulation tiles used on the upper fuselage, but were replaced by FIB. Used in temperature ranges similar to FIB. Toughened unipiece fibrous insulation tiles, a stronger, tougher tile which came into use in 1996. Used in high and low temperature areas. Felt reusable surface insulation. White Nomex felt blankets on the upper payload bay doors, portions of the mid fuselage and aft fuselage sides, portions of the upper wing surface and a portion of the OMS/RCS pods. Used where temperatures stayed below 371 °C; each type of TPS had specific heat protection, impact resistance, weight characteristics, which determined the locations where it was used and the amount used. The shuttle TPS has three key characteristics that distinguish it from the TPS used on previous spacecraft: Reusable Previous spacecraft used ablative heat shields which burned off during reentry and so couldn't be reused; this insulation was robust and reliable, the single-use nature was appropriate for a single-use vehicle.
By contrast, the reusable shuttle required a reusable thermal protection system. Lightweight Previous ablative heat shields were heavy. For example, the ablative heat shield on the Apollo Command Module comprised about 15% of the vehicle weight; the winged shuttle had much more surface area than previous spacecraft, so a lightweight TPS was crucial. Fragile The only known technology in the early 1970s with the required thermal and weight characteristics was so fragile, due to the low density, that one could crush a TPS tile by hand; the orbiter's aluminum structure could not withstand temperatures over 175 °C without structural failure. Aerodynamic heating during reentry would push the temperature well above this level in areas, so an effective insulator was needed. Reentry heating differs from the normal atmospheric heating associated with jet aircraft, this governed TPS design and characteristics; the skin of high-speed jet aircraft can become hot, but this is from frictional heating due to atmospheric friction, similar to warming one's hands by rubbing them together.
The orbiter reentered the atmosphere as a blunt body by having a high angle of attack, with its broad lower surface facing the direction of flight. Over 80% of the heating the orbiter experiences during reentry is caused by compression of the air ahead of the hypersonic vehicle, in accordance with the basic thermodynamic relation between pressure and temperature. A hot shock wave was created in front of the vehicle, which deflected most of the heat and prevented the orbiter's surface from directly contacting the peak heat; therefore reentry heating was convective heat transfer between the shock wave and the orbiter's skin through superheated plasma. The key to a reusable shield against this type of heating is low-density material, similar to how a thermos bottle inhibits convective heat transfer; some high-temperature metal alloys can withstand reentry heat. This technique, called heat sink thermal protection, was planned for the X-20 Dyna-Soar winged space vehicle. However, the amount of high-temperature metal required to protect a large vehicle like the Space Shuttle Orbiter would have been heavy and entailed a severe penalty to the vehicle's performance.
Ablative TPS would be heavy disturb vehicle aerodynamics as it burned off during reentry, require significant maintenance to reapply after each mission. The TPS was a system of different protection types, not just silica tiles, they are in two basic categories: tile TPS and non-tile TPS. The main selection criteria used the lightest weight protection capable of handling the heat in a given area; however in some cases a heavier type was used. The FIB blankets were adopted for reduced maintenance, not for thermal or weight reasons. Much of the shuttle was covered with LI-900 silica tiles, made from very pure quartz sand; the insulation prevented heat transfer to structure. These tiles were such poor heat conductors that one could hold one by the edges while it was still red hot. There were about 24,300 unique ti