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Parachute
A parachute is a soft fabric device used to slow the motion of an object through an atmosphere by creating drag. Parachutes are generally used to slow the descent of a person or object to Earth or another celestial body with an atmosphere. Parachutes are also sometimes used to aid horizontal deceleration of a vehicle (an airplane or space shuttle after touchdown, or a drag racer). The word parachute comes from the French words para, protect or shield, and chute, to fall. Therefore parachute actually means to protect from a fall. Many types of modern parachute are quite maneuverable, and some can be flown like gliders.
Parachutes were once made from silk but these days are almost always constructed from more durable woven nylon fabrics, sometimes coated with a zero porosity coating to improve performance and consistency over time.
History
A few medieval documents record the use of parachute-like devices to allow a person to fall (somewhat) safely from a height. In 852, an Andalusian daredevil named Armen Firman jumped from a tower in Cordoba using a loose cloak stiffened with wooden struts to arrest his fall, sustaining only minor injuries. In 1178, another Muslim attempted a similar feat in Constantinople, but he broke several bones and later died of his injuries. According to Joseph Needham there were working parachutes in China as early as the twelfth century.
twelfth century.]]
Leonardo da Vinci sketched a parachute while he was living in Milan around 1485. However, the idea of the parachute may not have originated with him: the historian Lynn White has discovered an anonymous Italian manuscript from about 1470 that depicts two designs for a parachute, one of which is very similar to da Vinci's. The first known test of such a parachute was made in 1617 in Venice by the Croatian inventor Faust Vrančić. A 1595 sketch of Vrančić's parachute is at left.
The parachute was re-invented in 1783 by Sebastien Lenormand in France. Lenormand also coined the name parachute. Two years later, Jean-Pierre Blanchard demonstrated it as a means of safely disembarking from a hot air balloon. While Blanchard's first parachute demonstrations were conducted with a dog as the passenger, he later had the opportunity to try it himself when in 1793 his hot air balloon ruptured and he used a parachute to escape.
Subsequent development of the parachute focused on it becoming more compact. While the early parachutes were made of linen stretched over a wooden frame, in the late 1790s, Blanchard began making parachutes from folded silk, taking advantage of silk's strength and light weight. In 1797, André Garnerin made the first jump using such a parachute. Garnerin also invented the vented parachute, which improved the stability of the fall. Gleb Kotelnikov invented the first knapsack parachute, later popularized by Paul Letteman and Kathchen Paulus.
At San Francisco in 1885, Thomas Scott Baldwin was the first person in the United States to descend from a balloon in a parachute. On March 1, 1912, US Army Captain Albert Berry made the first parachute jump from a moving airplane over Missouri. Štefan Banič from Slovakia invented the first actively used parachute, patenting it in 1913.
The first military use for the parachute was for use by artillery spotters on tethered observation balloons in World War I. These were tempting targets for enemy fighter aircraft, though difficult to destroy, due to their heavy antiaircraft defenses. Because they were difficult to escape from, and dangerous when on fire due to their hydrogen inflation, observers would abandon them and descend by parachute as soon as enemy aircraft were seen. The ground crew would then attempt to retrieve and deflate the balloon as quickly as possible. Aircraft crews, however, were forbidden from carrying their own parachutes. It was believed to encourage a lack of nerve in action. As well, early parachutes were very heavy, and fighters lacked the performance to carry the additional load through most of WW1. Only in 1918 did the German air service become the world's first to introduce a standard parachute.
The first emergency freefall parachute jump ended in a grape arbor in the back yard of the still-standing house at 335 Troy St in Dayton, Ohio. The jump was made by McCook Field test pilot Lt. Harold H. Harris on Oct 20, 1922. Harris' airplane crashed three blocks away in the yard of a double house that once stood at 403 Valley Street.
Uses
McCook Field
Paratroopers (now called airborne, Soviet/Russian desantniki) are soldiers who arrive in enemy territory by parachutes.
Smokejumpers are firefighters who parachute into remote areas to build firebreaks.
Most space vehicles descend to Earth using several parachutes. The pair of reusable solid-fuel rocket boosters (SRB) of the Space Shuttle have parachutes; they are recovered after falling to the ocean. Some exploration rovers (such as NASA's Spirit and ESA's Beagle 2) descend to their target destination with parachutes. Early reconaissance satellites ejected a film pack that came to earth and was recovered from under its parachute by specially-equipped aircraft.
Some bombs are equipped with a parachute, such as the World War Two "parafrag" (an 11kg fragmentation bomb), the Vietnam-era daisy cutters, and the bomblets of some modern cluster bombs. Parachutes slow the bomb's descent, thus giving the dropping aircraft time to get to a safe distance from the explosion. (This is especially important with airburst nuclear weapons.)
Food aid packages are sometimes delivered by parachute, and military forces routinely drop cargo on pallets under parachutes. Heavy loads have used a special system which uses a braking rocket.
Parachutes (commonly called "drag 'chutes") can also be deployed from a jet aircraft horizontally from the tail cone at the point of touchdown or shortly afterwards to shorten its landing run, for example if landing on an aircraft carrier or with a tailwind, or on a relatively short runway. The parachute will normally be jettisoned after the aircraft has slowed to taxiing speed and then retrieved by ground crew. This technique reduces the chance of it becoming entangled with the airframe. A similar parachute is used to slow the Space Shuttle after touchdown. Drag racers use a related technique.
Jet fighter ejector seats are equipped with automatically deployed parachutes.
Aircraft flight testing has also used parachutes on aircraft to provide additional safety. A recent development led to a method able to safely bring down an entire general aviation aircraft (with passengers), the Ballistic Recovery System.
Parachuting is a hobby and sport based on human parachute jumps. Paragliding instead uses a parafoil as a form of glider.
A paraglider with a motor and possibly wheels is called a powered parachute or, sometimes, a paraplane.
Design
General
A parachute is made from thin, lightweight fabric, support tapes and suspension lines. The lines are usually gathered through loops or rings at the ends of several strong straps called risers. The risers in turn are attached to the harness containing the load.
Deployment systems
Freefall deployed parachutes are pulled out of their containers by a smaller parachute called a pilot chute.
A way of deploying a parachute directly after leaving the aircraft is the static line. One end of the static line is attached to the airplane, and the other to the deployment system of the parachute container.
Types of parachutes
Round parachutes
static line
Round parachutes, which are pure drag devices(ie. they provide no lift like the ram-air types), are used in military, emergency and cargo applications. These have large dome-shaped canopies made from a single layer of cloth. Some skydivers call them "jellyfish 'chutes" because they look like dome-shaped jellyfish. Rounds are rarely used by skydivers these days. Some round parachutes are steerable, but not to the extent of the ram-air parachutes. An example of a steerable round is provided in the picture of the paratroopers canopy; It is not ripped or torn but has a "T-U cut". This kind of cut allows air to escape from the back of the canopy, providing the parachute with limited forward speed. This gives the jumpers the ability to steer the parachute and to face into the wind to slow down the horizontal speed for the landing.
Annular & pull down apex parachutes
A variation on the round parachute is the pull down apex parachute, essentially a round parachute but with suspension lines to the canopy apex that applies load there and therefore pulls the apex closer to the load distorting the round shape into a somewhat flatenned shape often these designs have the fabric removed from the apex to open a hole through which air can exit, giving the canopy an annular geometry. Annular pull down apex designs tend to be stable while offering an increase in drag and therefore reduction in decent rate for the pack volume of the canopy.
Ribbon and ring parachutes
Ribbon and ring parachutes have similarities to annular designs, they can be designed to open at speeds as high as Mach 2 (two times the speed of sound). These have a ring-shaped canopy, often with a large hole in the center to release the pressure. Sometimes the ring is broken into ribbons connected by ropes to leak air even more. The large leaks lower the stress on the parachute so it does not burst when it opens.
Often a high speed parachute slows a load down and then pulls out a lower speed parachute. The mechanism to sequence the parachutes is called a "delayed release" or "pressure detent release" depending on whether it releases based on time, or the reduction in pressure as the load slows down.
Ram-air parachutes
Most modern parachutes are self-inflating "ram-air" airfoils known as a parafoil that provide control of speed and direction similar to paragliders. Paragliders have much greater lift and range, but parachutes are designed to handle, spread and mitigate the stresses of deployment at terminal velocity. All ram-air parafoils have two layers of fabric; top and bottom, connected by shaped fabric I-beams and/or gores. The space between the two fabric layers fills with high pressure air from vents that face forward on the leading edge of the airfoil. The fabric is shaped and the parachute lines trimmed under load such that the ballooning fabric inflates into an airfoil shape.
Personnel parachutes
terminal velocity
Reserves
Paratroopers and sports parachutists carry two parachutes. The primary parachute is called a main parachute, the second, a reserve parachute. The jumper uses the reserve if the main parachute fails to operate correctly.
Reserve parachutes were introduced in World War II by the US Airborne Unit, and are now almost universal. For human jumpers only emergency bail-out rigs have a single parachute rather than two and these tend to be of round design.
Deployment
Reserve parachutes usually have a ripcord deployment system, but most modern main parachutes used by sports parachutists use a form of hand deployed pilot chute. A ripcord system pulls a closing pin (sometimes multiple pins) which releases a spring loaded pilot chute and opens the container, the pilot chute is propelled into the air stream by it's spring then uses the force generated by passing air to extract a deployment bag containing the parachute canopy, to which it is attached via a bridle. A hand deployed pilot chute once thrown into the air stream pulls a closing pin on the pilot chute bridle to open the container then the same force extracts the deployment bag. There are variations on hand deployed pilot chutes but the system described is the more common throw-out system. Only the hand deployed pilot chute may be collapsed automatically after deployment by a kill line reducing the in flight drag of the pilot chute on the main canopy. Reserves on the other hand do not retain their pilot chutes after deployment. The reserve deployment bag and pilot chute is not connected to the canopy in a reserve system, this is known as a free bag configuration and the components are often lost during a reserve deployment. Occasionally a pilot chute does not generate enough force to either pull the pin or extract the bag, causes may be that the pilot chute is caught in the turbulent wake of the jumper (the burble), the closing loop holding the pin is too tight or the pilot chute is generating insufficient force, this effect is known as pilot chute hesitation and if it does not clear in can lead to a total malfunction requiring reserve deployment.
Paratrooper main parachutes are usually deployed by static lines which release the parachute yet retain the deployment bag which contains the parachute without relying on a pilot chute for deployment, in this configuration the deployment bag is known as a direct bag system, the deployment is rapid, consistent and reliable. This kind of deployment is also used by student skydivers going through a static line progression, a kind of student program.
Varieties of personnel ram-airs
Personnel ram-air parachutes are loosely divided into two varieties. High performance ram-air parachutes have a slightly elliptical shape to their leading and trailing edges when viewed in plan form and are known as ellipticals. These are usually only used by sports parachutists. Usually they have smaller, more numerous fabric cells and are shallower in profile. Lower performance parachutes look more like square inflatable air-mattresses with open front ends. Smaller parachutes tend to fly faster for the same load and ellipticals respond faster to control input, small elliptical designs are therefore often chosen by experienced canopy pilots for the thrill of the flying they provide. This requires much more skill and experience to pilot and is considerably more dangerous to land. With high performance elliptical canopy designs nuisance malfunctions can be much more serious than with a square design and may quickly escalate into emergencies. All reserve ram-air parachutes are of the square variety because of the reliability and handling characteristics.
General charasteristics of ram-airs
Main parachutes used by skydivers today are designed to open softly, rapid deployment was an early problem with ram-air designs. The primary innovation that slows the deployment of a ram-air canopy is the slider; a small rectangular piece of fabric with a grommet near each corner through which four collections of lines are routed to the risers. During deployment the slider slides down from the canopy to just above the risers, the slider is slowed by air resistance as it descends and reduces the rate at which the lines can spread and therefore the speed at which the canopy can open and inflate. The overall design of a parachute still has a significant influence on the deployment speed. Modern sport parachutes deployment speed varies considerably between designs but most modern parachutes open comfortably with individual skydivers preferring different deployment speeds. The deployment process is inherently a chaotic one and rapid deployments can still occur even with well behaved canopies, on rare occasions deployment can even be so rapid that the jumper suffers bruising or even injury. Emergency and reserve parachutes by design tend to deploy more rapidly than sports main canopies, they still have sliders but the sliders are designed to descend rapidly with for example a partial mesh construction to catch less air resistance than a fully fabric slider design.
Safety
A parachute is carefully folded, or "packed" to ensure that it will open reliably. In the U.S. and many developed countries, emergency and reserve parachutes are packed by "riggers" who must be trained and certified according to legal standards. (For saftey, drag racing regulations require professional riggers be used.) Paratroops and sport skydivers are always trained to pack their own primary "main" parachutes.
Parachutes can malfunction in several ways. Malfunctions can range from minor problems that can be corrected in-flight and still be landed to catastrophic malfunctions that require the main parachute to be cut away using a modern 3-ring release system and the reserve be deployed. Most skydivers are also equipped with small barometric computers (known as an AAD or Automatic Activation Device like Cypres, FXC or Vigil) that will automatically deploy the reserve parachute if the skydiver himself has not done so at a preset altitude and descent rate.
Exact numbers are difficult to estimate but approximately one in a thousand sports main parachute openings malfunction and must be cut away, although some skydivers have many thousands of jumps and never cut away, (either they pack their mains more carefully than average or they are just lucky). Reserve parachutes are packed and deployed differently, they are also designed more conservatively and built & tested to more exacting standards so they are more reliable than main parachutes, but the real safety advantage comes from the probability of an unlikely main malfunction multiplied by the even less likely probability of a reserve malfunction. This yields an even smaller probability of a double malfunction although the possibility of a main malfunction that cannot be cutaway causing a reserve malfunction is a very real risk. In the U.S., the average fatality rate is considered to be about 1 in 80,000 jumps. Most injuries and fatalities in sport skydiving occur under a fully functional main parachute because the skydiver performed unsafe maneuvers or made an error in judgement while flying their canopy typically resulting in a high speed impact with the ground or other hazards on the ground.
The average skydiver in the U.S. makes about 150 jumps per year and will leave the sport before the 5th year.
External links
- [http://www.fai.org FAI] The Federation Aeronautique Internationale -- The international governing body for all airborne sports.
- [http://www.uspa.org USPA] The United States Parachute Association -- The governing body for sport skydiving in the U.S.
- [http://www.cspa.ca CSPA] The Canadian Sport Parachuting Association -- The governing body for sport skydiving in Canada.
- [http://www.dropzone.com Dropzone.com] the Premier web resource for information on Skydiving, Dropzones and modern parachuting
- [http://www.aero.com/publications/parachutes/9511/pc1195.htm Parachute]
- [http://www.getkidsgoing.com/parachute_skydiving_skydive.htm Charity Parachute Jumps] Experience skydiving, parachuting and tandem jumps across the UK by raising money for disabled children.
Category:Parachuting
ja:パラシュート
Celestial body
See also
- Lists of astronomical objects
ko:천체
ja:天体
th:วัตถุท้องฟ้า
Celestial body atmosphereAtmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. The gases are attracted by the gravity of the body, and held fast if gravity is sufficient and the atmosphere's temperature is low. Some planets consist mainly of various gases, and thus have very deep atmospheres (see gas giant).
Earth, Venus, Mars, and Pluto have atmospheres that envelop their surfaces, as do three of the satellites of the outer planets: Titan, Enceladus (moons of Saturn), and Triton (a moon of Neptune). In addition, the giant planets of the outer solar system - Jupiter, Saturn, Uranus, and Neptune - are composed predominantly of gases. Other bodies in the solar system possess extremely thin atmospheres. Such bodies are the Moon (sodium gas), Mercury (sodium gas), Europa (oxygen) and Io (sulfur).
Initial atmospheric makeup is generally related to the chemistry and temperature of the local solar nebula during planetary formation and the subsequent escape of interior gases. These original atmospheres underwent much evolution over time, with the varying properties of each planet resulting in very different outcomes.
Surface gravity, the force that holds down an atmosphere, differs
significantly among the planets. For example, the large gravitational force of the giant planet Jupiter is able to retain light gases such as hydrogen and helium that escape from lower gravity objects. Second, the distance from the sun determines the energy available to heat atmospheric gas to the point where its molecules' thermal motion exceed the planet's escape velocity, the speed at which gas molecules overcome a planet's gravitational grasp. Thus, the distant and cold Titan, Triton, and Pluto are able to retain their atmospheres despite relatively low gravities.
Since a gas at any particular temperature will have molecules moving at a wide range of velocities, there will almost always be some slow leakage of gas into space. Lighter molecules move faster than heavier ones with the same thermal kinetic energy, and so gases of low molecular weight are lost more rapidly than those of high molecular weight. It is thought that Venus and Mars may have both lost much of their water when, after being photodissociated into hydrogen and oxygen by solar ultraviolet, the hydrogen escaped. Earth's magnetic field helps to prevent this, as the solar wind greatly enhances the escape of hydrogen.
Other mechanisms that can cause atmosphere depletion are solar wind-induced sputtering, impact erosion, weathering, and sequestration—sometimes referred to as "freezing out"—into the regolith and polar caps.
Moreover, on Earth, atmospheric composition is largely governed by the by-products of the very life that it sustains.
From the perspective of the planetary geologist, atmospheres are important in the ways they shape planetary surfaces. Wind can transport particles, both eroding the surface and leaving deposits (eolian processes). Frost and precipitation can leave direct and indirect marks on a planetary surface. Climate changes can influence a planet's geological history. Conversely, studying surface geology leads to an understanding of the atmosphere and climate of a planet - both its present state and its past.
Interstellar planets, theoretically, may also retain thick atmospheres.
See also
- Earth's atmosphere
- Stellar atmosphere
Category:Astronomy
Category:Meteorology
Category:Atmosphere
Space Shuttle). For the first two missions only, the external fuel tank spray-on foam insulation (SOFI) was painted white. Subsequent missions have featured an unpainted tank thus exposing the orange/rust colored foam insulation. This resulted in a weight saving of over 1,000 lb (450 kg), a savings that translated directly to added payload capacity to orbit.]]
: This article is about the NASA Space Shuttle. For information on the Soviet Space Shuttles, see the articles Shuttle Buran, Ptichka, Shuttle 2.01, Shuttle 2.02 and Shuttle 2.03.
NASA's Space Shuttle, officially called Space Transportation System (STS), is the United States government's sole manned launch vehicle currently in service. The Space Shuttle orbiter was manufactured by North American Rockwell, now part of the Boeing Company. Martin Marietta (now part of Lockheed Martin) designed the external fuel tank and Morton Thiokol (now part of Alliant Techsystems (ATK)) designed the solid rocket boosters.
The Shuttle is the first orbital spacecraft designed for partial reusability. It carries large payloads to various orbits, provides crew rotation for the International Space Station (ISS), and performs servicing missions. While the vehicle was designed with the capacity to recover satellites and other payloads from orbit and return them to Earth, this capacity has not been used often; it is, however, an important use of the Space Shuttle in the context of the ISS program, as only very small amounts of experimental material, hardware needing to be repaired, and trash can be returned by Soyuz.
Each Shuttle was designed for a projected lifespan of 100 launches or 10-years operational life.
The program started in the late 1960s and has dominated NASA's manned operations since the mid-1970s. According to the Vision for Space Exploration, use of the Space Shuttle will be focused on completing assembly of the ISS in 2010, after which it will be replaced by the yet-to-be-developed Crew Exploration Vehicle (CEV). However, following the STS-114 return-to-flight mission in August 2005, the Shuttle program is currently grounded pending repairs and the solution of outstanding safety issues.
Further aggravating the shuttle's return to space, also in August 2005, the Space Shuttle external tank construction site, Michoud Assembly Facility located in New Orleans, Louisiana was damaged by Hurricane Katrina, with all work shifts cancelled up to September 26, 2005. This could potentially set back further Shuttle flights by more than two months.
The NASA Chief Administrator Michael Griffin has recently suggested the decision to develop the Space Shuttle and International Space Station was a mistake by saying, "It is now commonly accepted that was not the right path. We are now trying to change the path while doing as little damage as we can." [http://www.usatoday.com/printedition/news/20050928/1a_bottomstrip28.art.htm]
History
The Shuttle decision
NASA had conducted a series of paper projects throughout the 1960s on the topic of reusable spacecraft to replace their expedient "one-off" systems like Mercury, Gemini, and Apollo. Meanwhile, the U.S. Air Force had a continuing interest in smaller systems with more rapid turn-around times, and were involved in their own spaceplane project, the X-20 Dyna-Soar. In several instances groups from both worked together to investigate the state of the art.
With the major Apollo development effort winding down in the second half of the 1960s, NASA started looking to the future of the space program. They envisioned an ambitious program consisting of a large space station being launched on huge boosters, served by a reusable logistics "space shuttle", both providing services for a permanently manned Lunar colony and eventual manned missions to Mars.
However, in reality, NASA found itself with a rapidly plunging budget. Rather than trying to adapt their long-term future to their dire financial situation, they attempted to save as many of the individual projects as possible. The mission to Mars was rapidly dismissed, but the Space Station and Shuttle conserved. Eventually only one of them could be saved, so it stood to reason that a low-cost Shuttle system would be the better option, because without it a large station would never be affordable.
A number of designs were proposed, but many of them were complex and varied widely in their systems. An attempt to re-simplify was made in the form of the "DC-3" by one of the few people left in NASA with the political importance to accomplish it, Maxime Faget, who had designed the Mercury capsule, among other vehicles. The DC-3 was a small craft with a 20,000-pound (9 tonne) (or less) payload, a four-man capacity, and limited maneuverability. At a minimum, the DC-3 provided a baseline "workable" (but not significantly advanced) system by which other systems could be compared for price/performance compromises.
Mercury
The defining moment for NASA was when they, in desperation to see their only remaining project saved, went to the Air Force for its blessing. NASA asked that the USAF place all of their future launches on the Shuttle instead of their current expendable launchers (like the Titan II), in return for which they would no longer have to continue spending money upgrading those designs — the Shuttle would provide more than enough capability.
The Air Force reluctantly agreed, but only after demanding a large increase in capability to allow for launching their projected spy satellites (mirrors are heavy). These were quite large, weighing an estimated 40,000 pounds (18 tonnes), and needed to be put into polar orbits, which require higher energies than lower inclination orbits; and since the Air Force also wanted to be able to abort after a single orbit (as did NASA), and in addition land at the launch site (unlike NASA), the spacecraft would also require the ability to maneuver significantly to either side of its orbital track to adjust for launch-point rotational drift while in polar orbit — for example, in a 90-minute orbit, Vandenberg AFB would drift over 1,000 miles (1,600 km), whereas in more equatorially aligned orbits, the required cross-range would be less than 250 mi/400 km. This large "cross-range" capability for polar orbits meant the craft had to have a greater lift-to-drag ratio than originally planned, requiring the addition of bigger, heavier wings.
The result was that the simple "DC-3" was clearly irrelevant because it had neither the cargo capacity nor the cross-range the Air Force demanded. In fact, all existing designs were far too small, as a 40,000-pound (18 tonnes) delivery to polar orbit equates to a 65,000-pound (29 tonne) delivery to an eastwardly launched orbit with typical 28-degree inclination. Additionally, any design using simple straight or foldout wings was not going to meet the cross-range requirements, so any future design would require a more complex, heavier delta wing.
Of further concern, any increase in the weight of the upper portion of a launch vehicle, which had just occurred, required an even bigger increase in the capability of the lower stage used to launch it. Suddenly, the two-stage system had grown in size to something larger than the Saturn V, and the complexity and costs to develop it soared.
While all of this was going on, others were suggesting a completely different approach to the future. They stated that NASA would fare better using the existing Saturn to launch their space station, supplied and manned using modified Gemini capsules on top of the Air Force's newer Titan II-M. The cost of development for this looked to be considerably less than the Shuttle alone, and would have a large space station in orbit earlier.
In reply, advocates of the Shuttle answered that given enough launches, a reusable system would more than pay for the cost of development when compared with the launch costs of disposable rockets. Another factor in the cost-benefit analysis was inflation, and in the 1970s this was high enough that the payback from the development had to happen very quickly to see a positive return. Hence, a high launch rate was needed to make the system economically feasible.
But it was infeasible that a space station or Air Force payloads could demand such rates (roughly one or two a week), so they insisted and suggested that all future U.S. launches would take place on the Shuttle, once built. In order to do this, the cost of launching the Shuttle would have to be lower than any other system, with the exception of very small rockets, ignored for practical reasons, and very large boosters, which were rare and excessively expensive in any case.
With a baseline project now gelling, NASA started to work through the process of obtaining stable funding for the five years the project would take to develop. Once again, they found themselves in an increasingly deplorable situation.
With the budgets being pressed by inflation in the U.S. and the Vietnam War abroad, Congress and the Administration were generally uninterested in long-term projects such as space exploration. Some members were therefore looking to further cut NASA's budget; but with a single long-term project confirmed, they could do little in terms of cutting whole projects — the Shuttle was the single one left, and its cancellation would mean that there would be no U.S. manned space program by 1980.
Instead, they looked to reduce the year-to-year costs of development to a stable figure. That is, they wished to see the development budgets spread out over several more years. This was somewhat impractical and in conflict with the planned funding and development. The result was another intense series of redesigns in which the reusable booster was eventually abandoned due to its high price. Unsurprisingly, some designs for reusable boosters amounted to vehicles the size of the then-new Boeing 747, which would have to fly faster than the record-holding — and considerably smaller — X-15 rocket plane. Instead, a series of simpler rockets would launch the system and then drop away for recovery. Another change was that the fuel for the Shuttle itself was placed in an external tank instead of internal tanks as in the previous designs. This allowed a larger payload bay in an otherwise much smaller craft, although it also meant throwing away the tankage after each launch.
The last remaining debate was over the nature of the boosters. NASA had been looking at no less than four solutions to this problem: one a development of the existing Saturn lower stage, another using simple pressure-fed liquid-fuel engines of a new design, and finally either a large, single solid rocket, or two (or more) smaller ones. The decision was eventually made on the smaller solids due to their lower development costs (a decision that had been echoed throughout the whole Shuttle program). While the liquid-fueled systems provided better performance and enhanced safety, delivery capability to orbit is much more a function of the upper-stage performance and weight than the lower; the money was hence spent elsewhere.
Development
Vietnam War
The Shuttle program was launched on January 5, 1972, when President Richard M. Nixon announced that NASA would proceed with the development of a reusable, low-cost Space Shuttle system.
The project was already to take longer than originally anticipated due to the year-to-year funding caps. Nevertheless, work started quickly and several test articles were available within a few years.
Most notable among these was the first complete Orbiter, originally to be known as Constitution. However, a massive write-in campaign from fans of the Star Trek television series convinced the White House to change the name to Enterprise. Amid great fanfare, the Enterprise was rolled out on September 17, 1976, and later conducted a successful series of glide-approach and landing tests that were the first real validation of the design.
The first fully functional Shuttle Orbiter, built in Palmdale, California, was the Columbia, which was delivered to Kennedy Space Center on March 25, 1979, and was first launched on April 12, 1981—the 20th anniversary of Yuri Gagarin's space flight—with a crew of two. Challenger was delivered to KSC in July 1982, Discovery was delivered in November 1983, and Atlantis was delivered in April 1985. The Shuttle was meant to visit Space Station Freedom, announced in 1984, an ambitious and much-delayed project later downsized and merged into the International Space Station program. Challenger was destroyed in an explosion during launch on January 28, 1986, with the loss of all seven astronauts on board. Endeavour was built to replace it (using spare parts originally intended for the other Orbiters) and delivered in May 1991. Columbia was lost, with all seven crew members, during reentry on February 1, 2003, and has not been replaced.
Description
2003
The Shuttle has a large 60 by 15 ft (18 by 4.6 m) payload bay, filling most of the fuselage. The payload bay doors have heat radiators mounted on their inner surfaces, and so are kept open for thermal control while the Shuttle is in orbit. Thermal control is also maintained by adjusting the orientation of the Shuttle relative to Earth and Sun. Inside the payload bay is the Remote Manipulator System, also known as the Canadarm, a robot arm used to retrieve and deploy payloads. Until the loss of Columbia, the Canadarm had been used only on those missions where it was needed. Since the arm is a crucial part of the Thermal Protection Inspection procedures now required for Shuttle flights, it will probably be included on all future flights.
The Space Shuttle system has undergone numerous improvements over the years.
The Orbiter has changed its thermal protection system several times in order to save weight and ease workload. The original silica-based ceramic tiles need to be removed for inspection for damage after every flight, and they also soak up water and thus need to be protected from the rain. The latter problem was initially fixed by spraying the tiles with Scotchgard, but a custom solution was adopted. Later, many of the tiles on the cooler portions of the Shuttle were replaced by large blankets of insulating feltlike material, which means huge areas (notably the cargo bay area) no longer have to be inspected as often.
Internally the Shuttle remains largely similar to the original design, with the exception that the avionics continue to be improved. The original systems were "hardened" IBM 360 computers connected to analog displays in the cockpit similar to contemporary airliners like the DC-10. Today the cockpits have been replaced with "all glass" systems and the computers themselves are many times faster. The computers use the HAL/S programming language. In the Apollo-Soyuz Test Project tradition, programmable calculators are carried as well (originally the HP-41C). In addition to the "glass cockpit," several improvements have been made for safety reasons after the Challenger explosion, including a crew escape system for use in a narrow range of situations that require the Orbiter to "ditch." With the coming of the Space Station, the Orbiter's internal airlocks are being replaced with external docking systems to allow for a greater amount of cargo to be stored on the Shuttle's mid-deck during Station resupply missions.
HP-41C
The Space Shuttle Main Engines have had several improvements to enhance reliability and power. This is why during launch you may hear curious phrases such as "Go to throttle-up at 106%." This does not mean the engines are being run over limit. The 100% figure is the power level for the original main engines. The actual engine contract requirement was for 109%. The original flight engines could handle 102%. The 109% number was finally reached in flight hardware with the Block II engines in 2001.
For STS-1 and STS-2 the external tank was painted white to protect the insulation that covers much of the tank, but improvements and testing showed that it was not required. This saved considerable weight, and thereby increases the payload the Orbiter can carry into orbit. Additional weight was saved by removing some of the internal "stringers" in the hydrogen tank that proved unnecessary. The resulting "light-weight external tank" has been used on the vast majority of Shuttle missions. STS-91 saw the first flight of the "super light-weight external tank". This version of the tank is made of the 2195 Aluminum-Lithium alloy. It weighs 7,500 lb (3.4 t) less than the last run of lightweight tanks. As the Shuttle cannot fly unmanned, each of these improvements has been "tested" on operational flights.
And, of course, the SRBs (Solid Rocket Boosters) have undergone improvements as well. Notable is the adding of a third O-ring seal to the joints between the segments, which occurred after the Challenger accident.
A number of other SRB improvements were planned in order to improve performance and safety, but never came to be. These culminated in the considerably simpler, lower cost, probably safer and better performing Advanced Solid Rocket Booster which was to have entered production in the early to mid-1990s to support the Space Station, but was later cancelled to save money after the expenditure of $2.2 billion. The loss of the ASRB program forced the development of the SLWT, which provides some of the increased payload capability, while not providing any of the safety improvements. In addition the Air Force developed their own much lighter single-piece design using a filament-wound system, but this too was cancelled.
A cargo-only, unmanned variant of the Shuttle has been variously proposed and rejected since the 1980s. It is called the Shuttle-C and would trade re-usability for cargo capability with large potential savings from reusing technology developed for the Space Shuttle.
Components
The Space Shuttle consists of three main components: the reusable Orbiter itself, a large, brown, expendable external fuel tank, and a pair of white, reusable solid-fuel booster rockets. The fuel tank and booster rockets are jettisoned during ascent, so only the Orbiter goes into orbit.
- The reusable Orbiter Vehicle (OV), with a large payload bay and three main engines (fed from the external tank) and an orbital maneuvering system with two smaller engines (used after jettisoning the external tank). There are currently three orbiters, rotated between missions.
- A large expendable external fuel tank (ET) containing liquid oxygen and liquid hydrogen (at the forward and aft ends, respectively) for the three main engines of the Orbiter; it is discarded 8.5 minutes after launch at an altitude of 60 nautical miles (111 km) and breaks up in the atmosphere upon reentry. The pieces fall in the ocean and are not recovered.
- A pair of reusable solid-fuel rocket boosters (SRB); the propellant consists mainly of ammonium perchlorate (oxidizer, 70% by weight) and aluminum (fuel, 16 %); they are separated two minutes after launch at a height of 36 nautical miles (67 km) and are recovered after landing in the ocean, their fall slowed by parachutes.
Initial plans for the so-called Space Transportation System included space tugs and extra fuel tanks for the orbital-maneuvering-system engines, among many other concepts. None of this hardware has actually ever been built.
Technical data
parachute Shuttle Carrier Aircraft (SCA), 1998 (NASA)]]
- System stack height: 184.2 ft (56.14 m)
- Orbiter length: 122.17 ft (37.236 m)
- Wingspan: 78.06 ft (23.79 m)
- Gross liftoff: 4.5 million lb (2,040,000 kg)
- ET: 1.7 million lb (751,000 kg)
- SRBs: 1.3 million lb (590,000 kg) each (x 2)
- Orbiter: 240,000 lb (109,000 kg)
- Total liftoff thrust: 7.82 million lbf (34.8 MN)
- SSMEs: 400,000 lbf (1.8 MN) each (x 3) = 1.2 million lbf (5.3 MN)
- SRBs: 3.30 million lbf (14.7 MN) each (x 2) = 6.61 million lbf (29.4 MN)
- Maximum landing: 230,000 lb (104,000 kg)
- Maximum launch payload: 63,500 lb (28,800 kg)
- Operational altitude: 100 to 520 nmi (185 to 1000 km)
- Speed: 25,404 ft/s (7743 m/s, 27 875 km/h, 17 321 mi/h)
- Passenger capacity: 10 Astronauts (crews other than 5 to 7 are uncommon)
Normal ascent
Initially the main engines are lit and checked out; if successful, the SRBs are lit and the vehicle is then committed to takeoff.
At takeoff the vast majority (~90%) of the thrust is provided by the SRBs. Shortly after clearing the tower the Shuttle rotates so that the vehicle is below the main tank and SRBs. The vehicle climbs in a progressively flattening arc, accelerating as the weight of the SRBs and main tank reduces. To reach orbit, the vehicle needs to reach high altitude, but more importantly it needs to achieve mach 25 sideways, and so must spend as much time as possible accelerating horizontally.
Around a point called "max-q", where the aerodynamic forces are at their maximum, the main engines are temporarily throttled back to avoid overspeeding and hence overstressing the Shuttle (particularly vulnerable parts such as the wings).
126 seconds after launch, the SRBs thrust reduces and then explosive bolts release them from the vehicle and they fall back to the ocean to be reused. The Shuttle then begins accelerating to orbit on the Space Shuttle Main Engines. The vehicle at that point in the flight has a thrust to weight ratio of less than one — the main engines actually have insufficient thrust to exceed the force of gravity, and the vertical speed given to it by the SRBs temporarily decreases. However, as the burn continues, the weight of the propellant reduces, the ever-lighter vehicle produces more and more acceleration until the thrust to weight ratio exceeds 1 again and the vehicle can hold itself up.
The vehicle continues to climb and takes on a somewhat nose-up angle to the horizon — it uses the main engines to gain and then maintain altitude whilst it accelerates horizontally towards orbit.
Finally, in the last tens of seconds towards the end of the main engine burn, the mass of the vehicle is low enough, that the acceleration is throttled back to keep the vehicle accelerating at no more than 3g, largely for astronaut health and comfort.
Before complete depletion of propellant (running dry would destroy the engines) the main engines are shutdown, and the empty main tank is released by firing explosive bolts. The tank then falls to largely burn up in the atmosphere, with some fragments falling into the Indian Ocean.
At this point the Shuttle is still slightly suborbital, since the trajectory intersects the atmosphere. The Shuttle then fires the OMS engines to circularize the orbit and avoid reentry.
Ascent abort modes
There are five abort modes available during ascent, classified as intact aborts and contingency aborts [http://www.shuttlepresskit.com/STS-93/REF86.htm]. The choice of abort mode depends on estimates of what the orbiter's situation would be at the time of main engine cutoff (TMECO). The abort modes cover a wide range of potential problems, but the most common expected problem is that the orbiter failing to achieve orbital speed by TMECO, technically known as "MECO underspeed".
Intact abort modes
There are four intact abort modes. Intact aborts are designed to provide a safe return of the orbiter to a planned landing site.
- Return To Launch Site (RTLS) — has never been tried, but would involve turning the Shuttle around while continuing to burn the SSMEs, jettisoning the ET, and gliding to a landing at Kennedy Space Center.
- East Coast Abort Landing (ECAL) — involves landing at predetermined locations on the east coast of North America in the U.S. and Canada. This has never occurred.
- Transoceanic Abort Landing (TAL) — involves landing at predetermined locations in Africa and western Europe. This has never occurred.
- Abort to Orbit (ATO) — occurs when the intended orbit cannot be reached but a stable alternate orbit is possible. This occurred on STS-51-F mission; required mission replanning, but the mission was nevertheless declared a success.
- Abort Once Around (AOA) — occurs when entering a stable orbit is not possible. This has never occurred.
Contingency abort mode
Contingency aborts are designed to permit flight crew survival following more severe failures when an intact abort is not possible. A contingency abort would generally result in a ditch operation.
To the extent that the hydrogen and oxygen are not needed, they are used up deliberately to allow the ET to be discarded safely.
The designated sites for ECAL are Bangor, Maine, Wilmington, North Carolina; MCAS Cherry Point, North Carolina; NAS Oceana; Wallops Flight Facility; Dover Air Force Base; Atlantic City, New Jersey; Gabreski, New York; Otis ANGB; Pease International Airport (all USA); Halifax; Stephenville; St John's; Gander; and Goose Bay (all Canada).
A TAL would be declared between roughly T+2:30 minutes (liftoff plus 2 minutes, 30 seconds) and Main Engine Cutoff (MECO), about T+8:30 minutes. The Shuttle would then land at a predesignated friendly airstrip in Africa or Europe. Potential sites include Istres Air Base in France; Banjul International Airport in The Gambia; and Zaragoza Air Base and Morón Air Base in Spain. Prior to a Shuttle launch, two of them are selected depending on the flight plan, and staffed with standby personnel in case they are used. The list of TAL sites has changed over time; most recently Ben Guerir Air Base in Morocco was eliminated due to terrorism concerns. Past TAL sites have included Kano, Nigeria; Easter Island (for Vandenberg launches); Rota, Spain; Casablanca, Morocco; and Dakar, Senegal.
Emergency landing sites for the Orbiter include Lajes, Beja, (both Portugal), Keflavik (Iceland), Shannon International Airport (Ireland), RAF Fairford (UK), Köln Bonn Airport (Germany), Ankara (Turkey), Riyadh (Saudi Arabia), Diego Garcia (British Indian Ocean Territory).
Were the Orbiter unable to reach a runway, it could ditch in water, or could land on terrain other than a landing site. It would be unlikely for the flight crew still on board to survive. However, if the Orbiter ascent were aborted in a narrow set of circumstances in which controlled gliding flight could be achieved, the In-flight Crew Escape System would allow the crew to escape with parachutes. A special Escape Pole would take each crewmember on a trajectory beneath the Orbiter's left wing.
In the two disasters, things went wrong so fast that little could be done. In the case of Challenger, the SRBs were still burning as they tore free from the rest of the stack. The orbiter disintegrated almost instantly because of aerodynamic stresses as the stack broke up. The Columbia disaster occurred high in the atmosphere during reentry. Even if the crew had been able to bail out, they would have been killed by the heat generated by the friction of the air.
Shuttles
Columbia disaster, Discovery, Atlantis and Endeavour. Not illustrated: Enterprise and Pathfinder.]]
Individual Orbiters are both named, in a manner similar to ships, and numbered using the NASA Orbiter Vehicle Designation system. Whilst all three are externally very similar, they have minor internal differences; new equipment is fitted on a rotating basis as they are maintained, and the newer Orbiters tend to be structurally lighter.
- Handling test article designed with no spaceflight capability whatsoever:
- Pathfinder (Orbiter Simulator, no series number)
- Main propulsion test article, with no spaceflight capability whatsoever:
- MPTA-ET (External Tank) which is now attached to Pathfinder
- MPTA-098 suffered major damage due to engine failure.
- Structural test article, with no spaceflight capability:
- STA-099 which became Challenger
- Test vehicle suitable only for glide/landing tests, with no spaceflight capability without major refit:
- Enterprise (OV-101)
- Lost in accidents (see below):
- Challenger (OV-099, ex-STA-099) - destroyed after liftoff - January 28, 1986
- Columbia (OV-102) - destroyed during reentry February 1, 2003
- In use:
- Atlantis (OV-104)
- Discovery (OV-103)
- Endeavour (OV-105)
Applications
- Crew rotation of the ISS
- Manned servicing missions, such as to the Hubble Space Telescope (HST)
- Manned experiments in LEO
- Carry to LEO:
- Large satellites — these have included the HST
- Components for the construction of the ISS
- Supplies
- Carry satellites with a booster, the Payload Assist Module (PAM-D) or the Inertial Upper Stage (IUS), to the point where the booster sends the satellite to:
- A higher Earth orbit; these have included:
- Chandra X-ray Observatory
- Many TDRS satellites
- Two DSCS-III (Defense Satellite Communications System) communications satellites in one mission
- A Defense Support Program satellite
- An interplanetary orbit; these have included:
- Magellan probe
- Galileo spacecraft
- Ulysses probe
Flight statistics (as of August 25, 2005)
† Satellites deployed
- This was flight STS-80, during November 1996.
Accidents
Two Shuttles have been destroyed in 114 missions, both with the loss of the entire crew of seven:
- Challenger — lost 73 seconds after liftoff, January 28, 1986; see STS-51-L.
- Columbia — lost during reentry, February 1, 2003; see Space Shuttle Columbia disaster.
This gives a 2% death rate per astronaut per flight.
While the technical details of the accidents are quite different, the organisational problems show remarkable similarities. In both cases events happened which were not planned for or anticipated. In both cases, instead of dealing with the issue as unexpected and in need of complete explanation, at significant cost in time and money, the lazy attitude was to allow the unexpected events to happen as the damage done was not deemed to endanger the shuttle, although this was not actually known to be the case.
In the case of Challenger, an O-ring which should not have eroded at all did, in fact, erode on earlier shuttle launches. Instead of finding out why, it was noted that it had not eroded by more than 30%, and the assumption was made was that this was not a hazard as there was a safety margin of a factor of 3. Despite repeated pleas by NASA's engineers to cancel or reschedule the launch, the managers allowed the shuttle to launch. Challenger's O-ring eroded right through, fatally, shortly after its last launch.
Columbia failed as a consequence of damage caused by being struck by a piece of foam which broke off from the bipod during ascent. The foam had not been designed or expected to break off, but had been observed in the past to do so without incident.
Retrospect
Space Shuttle Columbia disaster
Costs
While the Shuttle has been a reasonably successful launch vehicle, it has been unable to meet its goal of radically reducing flight launch costs, as the average launch expenditures during its operations up to 2005 accumulates to $1.3 billion [http://sciencepolicy.colorado.edu/prometheus/archives/space_policy/], a rather large figure compared to the initial projections of $10 to $20 million. The total cost of the program has been $145 billion as of early 2005 ($112 billion of which was incurred while the program was operational) and is estimated at $174 billion when the Shuttle retires in 2010. NASA's budget for 2005 allocates 30%, or $5 billion, to Space Shuttle operations. [http://www.space.com/news/shuttle_cost_050211.html]
The original mission of the Shuttle was to operate at a high flight rate, at low cost, and with high reliability. It was intended to improve greatly on the previous generation of single-use manned and unmanned vehicles. Although it did operate as the world's first reusable crew-carrying spacecraft, it did not improve on those parameters in any meaningful way, and is considered by some to have failed in its original purpose.
Although the design is radically different from the original concept, the project was still supposed to meet the upgraded USAF goals, and to be much cheaper to fly in general. One reason behind this apparent failure appears to be inflation. During the 1970s the U.S. suffered from severe inflation, driving up costs about 200% by 1980. In contrast, the rate between 1990 and 2000 was only 34% in total. This magnified the development costs of the Shuttle. The original process by which contractors bid for Shuttle work has also inflated overall project costs as there were political and industrial pressures to spread Shuttle work around. For instance, the need for a single-piece SRB design was dismissed as only one company, Aerojet, was located close enough to the launch site to make this viable. The company that secured the SRB contract, Morton Thiokol, is based in Utah, necessitating the modular design that contributed to the Challenger loss. Ironically, the U.S. aerospace mergers of the 1990s mean that the vast majority of the STS contracts are now held by a single company (Boeing).
However, this does not explain the high costs of the continued operations of the Shuttle. Even accounting for inflation, the launch costs on the original estimates should be about $100 million today. The remaining $400 million arises from the operational details of maintaining and servicing the Shuttle fleet, which have turned out to be tremendously more expensive than anticipated. Some of this can be attributed to operating beyond the 10-year anticipated lifespan of each Shuttle.
The main reasons for higher costs can be ascribed to:
the reentry tiles turned out to be very expensive (averaging about 1 person week to replace a tile, with hundreds damaged with each launch)
engines were highly complex and marginal necessitating removal and maintenance after each flight
launch rate is much lower than ideal (studies showed that launching 50 times per year would have dramatically cut costs- the current shuttle launches about 4 times per year- the written record shows that NASA never installed any infrastructure to launch more than 12 times per year)
original costs of $118/lb were marginal costs, not total costs
Shuttle operations
When originally conceived, the Shuttle was to operate similarly to an airliner. After landing, the Orbiter would be checked out and start "mating" to the rest of the system (the ET and SRBs), and be ready for launch in as little as two weeks. Instead, this turnaround process takes months. Decisions to cut short-term development costs have resulted in a continued high-cost maintenance schedule. The documentation requirements have become extremely thorough. Dramatically increasing the number of support personnel needed to launch also caused a significant increase in costs. This was exacerbated in the aftermath of the Challenger disaster. Even simple changes require significant amounts of documentation. This paperwork results from the fact that, unlike current expendable launch vehicles, the Space Shuttle is manned and has no escape systems mode for most of the flight regime, and therefore any accident which would result in the loss of a booster would also result in the loss of the crew. Because loss of crew is unacceptable, the primary focus of the Shuttle program is to return the crew to Earth safely, which can conflict with other goals, namely to launch payloads cheaply. Furthermore, because there are cases where there are no abort modes — no potential way to prevent failure from becoming critical — many pieces of hardware simply must function perfectly and so must be carefully inspected before each flight. The result is a massively inflated labor cost, with around 25,000 workers in Shuttle operations and labor costs of about $1 billon per year.
Initially NASA hoped the Shuttle's manned capacity would be justified as a "space taxi" to a revived Skylab or a Saturn V-launched "Skylab 2". With the go-ahead for the large, modular "Freedom" Space Station proposal the Shuttle appeared to have a continued justification with the prospect of a 6- to 10-crew outpost only being serviceable by the Shuttle. The scale back of the Space Station concept in the 1990s ultimately made the utility of the Shuttle as a manned ferry obsolete.
NASA's justification of the STS for its own unmanned science missions has also declined. Following the Challenger disaster, use of the powerful Centaur upper stages required for interplanetary probes was ruled out. The Shuttle's history of unexpected delays also makes it liable to miss the narrow launch windows. Advances in technology over the last decade have made probes smaller and lighter, and as a result it is possible to reach Mars using a relatively cheap and reliable Delta launcher.
Another possible impediment to the Shuttle system was the politically required participation of the United States Air Force. To receive the funding required, Congress mandated that the Shuttle replace all other launch vehicles in the national inventory as a cost-cutting measure. This requirement dramatically altered the size and scope of the program as the Air Force needed significant capabilities to allow it to meet national defense objectives. Ironically, neither NASA nor the Air Force got the system they wanted or needed, and the Air Force eventually returned to their older launch systems and abandoned their Vandenberg shuttle launch plans; many of the Air Force-imposed capabilities that most seriously hobbled the Shuttle system have never been used.
Opinions differ on the lessons of the Shuttle. In general, however, future designers look to systems with only one stage, automated checkout and, in some cases, overdesigned (more durable) low-tech systems. Another consideration for future manned space flight is to pursue the construction and operation of "space planes", which could fly up to the edge of the atmosphere and then rocket out into Earth orbit, thereby being more efficient and versatile than such vehicles as the space shuttle.
Terrestrial transportation vehicles
- The Crawler-Transporter moves the Space Shuttle from the Vehicle Assembly Building to Launch Complex 39
- The Shuttle Carrier Aircraft is a modified Boeing 747 that flies the Space Shuttle from alternative landing sites back to Cape Canaveral.
See also
- Space Exploration
- Shuttle Derived Launch Vehicle
- Reusable launch system
- HOPE-X the Japanese (cancelled) shuttle program.
- Kliper Reuseabe Russian lifting body spacecraft that is likely to replace the Soyuz system in 2011
- EADS Phoenix the European Shuttle successor to the cancelled Hermes.
- Shuttle Buran the Soviet Union's (cancelled) shuttle program.
- Shuttle SERV
- Manned space mission
- List of space shuttle missions
- List of human spaceflights
- List of human spaceflights chronologically
- List of space disasters
- Lifting body
- Space Shuttles in fiction
References
- [http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/stsref-toc.html Reference manual]
- [http://science.howstuffworks.com/space-shuttle.htm How The Space Shuttle Works]
- [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19810022734_1981022734.pdf NASA Space Shuttle News Reference - 1981 (PDF document)]
- [http://science.ksc.nasa.gov/shuttle/resources/orbiters/orbiters.html Orbiter Vehicles]
- [http://www.house.gov/science/hot/columbia/rs21411.pdf Shuttle Program Funding 1992 - 2002]
External links
- [http://www.chrisvalentines.com/sts107/index.html Columbia Disaster Multi-Media]
- [http://spaceflight.nasa.gov/shuttle/ NASA Human Spaceflight - Shuttle] Current status of Shuttle missions
- [http://www.nasa.gov/ntv NASA TV] View live streaming of launch and mission coverage
- [http://www.globalsecurity.org/space/facility/sts-els.htm List of all Shuttle Landing Sites]
- [http://www.srh.noaa.gov/smg/lsitegif.htm Map of Landing Sites]
- [http://gmaps.tommangan.us/spacecraft_tracking.html Track the Shuttle] with Google Maps
- [http://www.idlewords.com/2005/08/a_rocket_to_nowhere.htm "A Rocket To Nowhere"] criticism of the Space Shuttle program
- [http://www.washingtonmonthly.com/features/2001/8004.easterbrook-fulltext.html "Beam Me Out Of This Death Trap, Scotty"] Critical article on the Space Shuttle program, from 1981
- [http://www.theatlantic.com/doc/200311/langewiesche "Columbia's Last Flight"] Article from the Atlantic Monthly on the Columbia disaster and the subsequent investigation
- [http://www.spacedaily.com/news/shuttle-03p1.html "Explaining 30 years of Fudge"] - how the shuttle program was miss-sold to congress and where the $118/lb supposed costs came from
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Drag racing
Drag racing is a form of auto racing in which cars or motorcycles attempt to complete a fairly short, straight and level course in the shortest amount of time, starting from a dead stop. Drag racing originated in the United States and is still the most popular there. The most common distance is one quarter of a mile (1320ft/402m), although one-eighth of a mile (201 m) tracks are also popular. The dragstrip extends well beyond the finish line to allow cars to slow down and return to the pit area.
While usually thought of as an American and Canadian pastime, drag racing is also very popular in Australia, New Zealand, Japan, the Caribbean, England, Mexico, Greece, Malta, South Africa and most European and Scandinavian countries. At any given time there are over 325 drag strips operating world-wide.
History
The origins of the sport lie in illegal street racing in the United States. The format of the sport shows these origins: two cars line up next to each other, and await a green light as the signal to start, just as if they were sitting next to each other at a stoplight. The straight course mimics the straight streets of most American cities. By the 1930s, hot-rodders had begun to race away from the roads, on Southern California's dry lake beds, and by the late 1940s, attempts to codify the sport were underway. The first drag strip opened on a Santa Ana, California airfield in 1950.
Southern California was the hot bed for development of the sport in the 1950s as various clubs organized races. Hot Rod magazine and its editor, Wally Parks began to promote racing safety and standardization. The magazine sponsored national "Safety Safari" tours to spread drag racing to other parts of the country. The NHRA was founded as a national sanctioning body and Parks eventually left the magazine to head the organization.
Initially contests were between modified street vehicles, but over time racers got more innovative and classes proliferated to reflect the different approaches.
Racing organization
Most (although not all) drag racing involves two cars racing each other to the end of the measured distance. The elapsed time from the light turning green to the car's front end passing through the "traps" at the other end ("far end") of the track determines the winner; this is the "E.T." or "time". In practice, it is necessary for the driver to "jump the gun" by a faction of a second, starting the car during the split-second interval between when the yellow light goes out and the green light goes on. However, if the car crosses the electric eye ("the beam") in front of it before the green light comes on, the driver has "red-lighted" and is disqualified. (If both cars "red-light", only the first car to cross is disqualified.) A driver who gets a substantial lead at the start is said to have gotten a "holeshot". The driver's reaction time and the car's top speed are also recorded, in addition to the e.t., on the "timeslip". The car that crosses the finish line first wins. A car can actually blow an engine part way down the strip and coast to the end of the track at a (relatively) lower top speed than the competitor, and still win with a lower elapsed time. This is called "heads-up racing", and is used in all professional ("pro") classes.
In the common Eliminator racing format, the losing car and driver are removed from the contest, while the winner goes on to race other winners, until only one is left. There are some instances where there are 3 cars remaining, and in this case one car, either chosen at random or the car with the fastest elapsed time thus far, gets a "bye run" where his or her car goes down the track by itself (in order to at least partially eliminate the advantage that would otherwise come from the engine having one less run on it), and then awaits the winner of the other two for the title. However, in most Eliminator formats, the bye runs take place only in the first round. Drivers are about equally divided between making a nice easy pass on the bye run so as not to stress the car unduly, or making a real effort for the benefit of the spectators.
The National Hot Rod Association (NHRA) oversees the majority of drag racing events in North America. The next largest organization, the International Hot Rod Association, (IHRA), is about one-third the size of NHRA. Nearly all drag strips will select one or the other of these sanctioning bodies to be associated with. The NHRA is more popular with large, 1/4 mile nationally-recognized tracks, while the IHRA is a favorite of smaller 1/8th mile local tracks. One reason for this (among others) is the IHRA is less restrictive in its rules and less expensive to be associated with.
There are literally hundreds of different classes in drag racing, each with different requirements and restrictions on things such as weight, engine size, body style, modifications, and many others. The NHRA and IHRA share some of these classes, but many are solely used by one sanctioning body or the other. The NHRA boasts over 200 classes, while the IHRA has fewer. There is even a class for aspiring youngsters - Junior Dragster.
In 1997, the FIA began sanctioning drag racing in Europe with a fully established European Drag Racing Championship, in cooperation with the NHRA with rules established from the NHRA. The major European drag strips include Santa Pod Raceway in Podington, England and the Hockenheimring in Germany.
However, there are only 5 pro classes (4 NHRA, 4 IHRA), which are:
- Top Fuel Dragster (TF/D) The rail dragsters, or "diggers", the fastest class. (NHRA and IHRA both). There are also a Top Alcohol and Top Gas Dragster.
- Top Fuel Funny Car (TF/FC) Nearly as fast as the rails, the "floppers" (marginally) resemble actual cars. IHRA will be bringing back Top Fuel Funny Car in 2006, and Alcohol Funny Car is already a pro category in IHRA. (NHRA and IHRA both)
- Pro Modified (Pro Mod) Some engine restrictions, very high power. Cars can run superchargers or nitrous oxide. Cars running blowers are limited to 527 cubic inches (8.6 L) while cars with nitrous oxide can run up to 740 cubic inches (12.1 L).
- Pro Stock Must maintain stock appearance. NHRA cars can run no more than 500 cubic inches (8.2 L) while IHRA cars can run a maximum of 820 cubic inches (13.1 L) ("Mountain Motors"). (NHRA and IHRA both)
- Pro Stock Bike Heavily modified motorcycles. (NHRA only)
In addition to the above professional classes, these are some other popular classes:
- Top Alcohol Dragster
- Top Alcohol Funny Car
- Super Comp/Quick Rod
- Super Gas/Super Rod
- Super Street/Hot Rod
- Super Stock
- Stock
- Sport Compact (Smaller cars, with smaller engines)
- Top Sportsman (IHRA only, but at NHRA Divisional Races)
- Top Dragster (IHRA only)
A complete listing of all classes can be found on the respective NHRA and IHRA official websites (see external links).
To allow different cars to compete against each other, some competitions are raced on a handicap basis, with faster cars delayed on the start line enough to theoretically even things up with the slower car. This may be based on rule differences between the cars in stock, super stock, and modified classes, or on a competitor's chosen "dial-in" in bracket racing.
A "dial-in" is a time the driver estimates it will take his or her car to cross the finish line, and is generally displayed on one or more windows so the starter can adjust the starting lights on the "Christmas tree" (commonly just "tree") accordingly. The slower car will then get a head start equal to the difference in the two dial-ins, so that if both cars perform perfectly, they would cross the finish line dead even. If either car goes faster than its dial-in (called breaking out), it is disqualified regardless of who has the lowest elapsed time; if both cars break out, the one who breaks out by the smallest amount wins. This eliminates any advantage from putting a slower time on the windshield to get a head start. The effect of the bracket racing rules is to place a premium on consistency of performance of the driver and car rather than on raw speed, in that victory goes to the driver able to precisely predict elapsed time, whether it is fast or slow. This in turn makes victory much less dependent on large infusions of money, and more dependent on skill. Therefore, bracket racing is popular with casual weekend racers. Many of these recreational racers will drive their vehicles to the track, race them, and then simply drive them home. Most tracks do not host national events every week, and on the interim weekends host local casual and weekend racers. Organizationally, however, the tracks are run according to the rules of either the NHRA or the IHRA (for the most part). Even street vehicles must pass a safety inspection prior to being allowed to race.
Besides NHRA and IHRA, there are niche organizations for muscle cars and nostalgia vehichles. There is even an organization called the National Electric Drag Racing Association, (NEDRA), which races electric vehicles against high performance gasoline-powered vehicles such as Dodge Vipers or classic muscle cars in 1/4 and 1/8 mile races.
Drag racing performance facts
The fastest top fuelers can attain terminal speeds of over 330 mph (530 km/h) while covering the quarter mile (402 m) distance in roughly 4.45 seconds. It is often related that Top Fuel dragsters are the fastest accelerating vehicles on Earth; quicker even than the space shuttle launch vehicle or catapult-assisted jet fighter (however this ignores the rocket dragsters). In fact, if you take a vehicle traveling at a steady 200 mph (322 km/h) as it is crossing the start line, a top fuel dragster starting from a dead stop at the same moment will beat it to the finish line one quarter of a mile (402 m) away. Additionally, through the use of large multiple braking parachutes, the astounding performance of 0 to 330 mph (531 km/h) and then back to 0 in 20 seconds can be obtained. Deceleration of up to five "gee" can be attained, enough to cause separated retinae in TF drivers.
The faster categories of drag racing are an impressive spectacle, with engines of over 7000 horsepower (4.5 MW) and noise outputs to match, cars that look like bizarre parodies of standard street cars (funny cars), and the ritual of burnouts where, prior to the actual timed run, the competitors cause their wheels to spin while stationary or moving slowly, thus heating up the tires and laying down a sticky coat of rubber on the track surface ( which may have been coated with VHT Trackbite or similar to increase traction) to get optimum grip on the all-important launch.
The Blown Alcohol and Nitrous Oxide injected Pro Modifieds with their 2000 horsepower motors are capable of running in the low six second range at over 230 miles per hour. The IHRA Pro Stocks are just behind, running in the 6.3 second range at over 210 miles per hour, while the NHRA Pro Stocks run in the high sixes at over 200 miles per hour. Top Sportsman and Top Dragster, the two fastest sportsman classes, run a bracket style race and can range from the 6.4 second range at 210 miles per hour to the high sevens at over 170 miles per hour. Cars in Super Comp/Quick Rod are either dragsters or doorcars, but run with a throttle stop. Some cars can run as low as a 7.50 at around 180 miles per hour without a throttle stop, but use it in order to hit the 8.90 index. Super Gas/Super Rod and Super Street/Hot Rod run with a 9.90 and 10.90 index respectfully, but they both run with a throttle stop.
Drag racing has traditionally been the domain of big - usually American - cars with high capacity engines. However, the power to weight ratio of lighter, usually imported, cars has allowed them to be successful when their engines are modified and bodies lightened. The VW Beetle was one of the first to be exploited this way. Recently there has been an increase in Sport Compact racing, where smaller cars, especially Japanese, but recently some American and European, are raced. Use of a turbocharger | | |
