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195-541: The Space Shuttle external tank ( ET ) was the component of the Space Shuttle launch vehicle that contained the liquid hydrogen fuel and liquid oxygen oxidizer . During lift-off and ascent it supplied the fuel and oxidizer under pressure to the three RS-25 main engines in the orbiter . The ET was jettisoned just over 10 seconds after main engine cut-off (MECO) and it re-entered the Earth's atmosphere. Unlike

390-404: A mill by machinists . The archaic term miller was commonly used in the 19th and early 20th centuries. Since the 1960s there has developed an overlap of usage between the terms milling machine and machining center . NC/ CNC machining centers evolved from milling machines, which is why the terminology evolved gradually with considerable overlap that still persists. The distinction, when one

585-418: A nose cone . The nose cone consists of a removable conical assembly that serves as an aerodynamic fairing for the propulsion and electrical system components. The foremost element of the nose cone functions as a cast aluminium lightning rod. The LOX tank volume is 19,744 cu ft (559.1 m) at 22 psi (150 kPa) and −297 °F (90.4 K; −182.8 °C) ( cryogenic ). The tank feeds into

780-1031: A spaceplane to a runway landing, usually to the Shuttle Landing Facility at KSC, Florida, or to Rogers Dry Lake in Edwards Air Force Base , California. If the landing occurred at Edwards, the orbiter was flown back to the KSC atop the Shuttle Carrier Aircraft (SCA), a specially modified Boeing 747 designed to carry the shuttle above it. The first orbiter, Enterprise , was built in 1976 and used in Approach and Landing Tests (ALT), but had no orbital capability. Four fully operational orbiters were initially built: Columbia , Challenger , Discovery , and Atlantis . Of these, two were lost in mission accidents: Challenger in 1986 and Columbia in 2003 , with

975-575: A 17 in (430 mm) diameter feed line that conveys the liquid oxygen through the intertank, then outside the ET to the aft right-hand ET/orbiter disconnect umbilical. The 17 in (430 mm) diameter feed line permits liquid oxygen to flow at approximately 2,787 lb/s (75,800 kg/min) with the RS-25s operating at 104% or permits a maximum flow of 17,592 US gal/min (1.1099 m/s). All loads except aerodynamic loads are transferred from

1170-492: A NASA engineer who had worked to design the Mercury capsule, patented a design for a two-stage fully recoverable system with a straight-winged orbiter mounted on a larger straight-winged booster. The Air Force Flight Dynamics Laboratory argued that a straight-wing design would not be able to withstand the high thermal and aerodynamic stresses during reentry, and would not provide the required cross-range capability. Additionally,

1365-406: A built-in rotary table that allows milling at various angles; this feature is called a universal table . While endmills and the other types of tools available to a vertical mill may be used in a horizontal mill, their real advantage lies in arbor-mounted cutters, called side and face mills, which have a cross section rather like a circular saw, but are generally wider and smaller in diameter. Because

1560-497: A crewed spaceflight engineer on both STS-51-C and STS-51-J to serve as a military representative for a National Reconnaissance Office payload. A Space Shuttle crew typically had seven astronauts, with STS-61-A flying with eight. The crew compartment comprised three decks and was the pressurized, habitable area on all Space Shuttle missions. The flight deck consisted of two seats for the commander and pilot, as well as an additional two to four seats for crew members. The mid-deck

1755-413: A distinct class of machine tool (separate from lathes running rotary files) first appeared between 1814 and 1818. The centers of earliest development of true milling machines were two federal armories of the U.S. ( Springfield and Harpers Ferry ) together with the various private armories and inside contractors that shared turnover of skilled workmen with them. Between 1912 and 1916, Joseph W. Roe ,

1950-449: A finish end mill. Most of the industrial milling operations can be taken care of by 2.5 axis CNC milling. This type of path control can machine up to 80% of all mechanical parts. Since the importance of pocket milling is very relevant, therefore effective pocketing approaches can result in reduction in machining time and cost. NC pocket milling can be carried out mainly by two tool paths, viz., linear and non-linear. In this approach,

2145-465: A fixed elevation; the Z-axis is controlled by moving the head or quill down toward the X,Y table. A mill drill typically has an internal taper fitting in the quill to take a collet chuck, face mills, or a Jacobs chuck similar to the vertical mill. A horizontal mill has the same short but the cutters are mounted on a horizontal spindle, or arbor, mounted across the table. Many horizontal mills also feature

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2340-467: A future reusable shuttle: Class I would have a reusable orbiter mounted on expendable boosters, Class II would use multiple expendable rocket engines and a single propellant tank (stage-and-a-half), and Class III would have both a reusable orbiter and a reusable booster. In September 1969, the Space Task Group, under the leadership of U.S. Vice President Spiro Agnew , issued a report calling for

2535-508: A geared head or electronic speed control. They generally have quite heavy-duty spindle bearings to deal with the lateral loading on the spindle that is created by a milling operation. A mill drill also typically raises and lowers the entire head, including motor, often on a dovetailed (sometimes round with rack and pinion) vertical column. A mill drill also has a large quill that is generally locked during milling operations and released to facilitate drilling functions. Other differences that separate

2730-598: A glider. Its three-part fuselage provided support for the crew compartment, cargo bay, flight surfaces, and engines. The rear of the orbiter contained the Space Shuttle Main Engines (SSME), which provided thrust during launch, as well as the Orbital Maneuvering System (OMS), which allowed the orbiter to achieve, alter, and exit its orbit once in space. Its double- delta wings were 18 m (60 ft) long, and were swept 81° at

2925-573: A greater plurality of formerly competing standards exist. Newer and larger manual machines usually use NMTB tooling. This tooling is somewhat similar to CAT tooling but requires a drawbar within the milling machine. Furthermore, there are a number of variations with NMTB tooling that make interchangeability troublesome. The older a machine, the greater the plurality of standards that may apply (e.g., Morse , Jarno , Brown & Sharpe , Van Norman , and other less common builder-specific tapers). However, two standards that have seen especially wide usage are

3120-492: A hard and temperature-resistant material, so that they wear slowly. A low cost cutter may have surfaces made of high speed steel . More expensive but slower-wearing materials include cemented carbide . Thin film coatings may be applied to decrease friction or further increase hardness. There are cutting tools typically used in milling machines or machining centers to perform milling operations (and occasionally in other machine tools). They remove material by their movement within

3315-439: A lighter, more versatile machine, called a mill-drill. The mill-drill is a close relative of the vertical mill and quite popular in light industry; and with hobbyists. A mill-drill is similar in basic configuration to a very heavy drill press, but equipped with an X-Y table and a much larger column. They also typically use more powerful motors than a comparably sized drill press, most are muti-speed belt driven with some models having

3510-428: A low yield of parts because the machines single blade would cause loss of gear teeth when the cutter hit parallel grains in the wood. Terry later invented a spindle cutting machine to mass produce parts in 1807. Other Connecticut clockmakers like James Harrison of Waterbury, Thomas Barnes of Litchfield, and Gideon Roberts of Bristol, also used milling machines to produce their clocks. It is clear that milling machines as

3705-452: A mill-drill from a drill press may be a fine tuning adjustment for the Z-axis, a more precise depth stop, the capability to lock the X, Y or Z axis, and often a system of tilting the head or the entire vertical column and powerhead assembly to allow angled cutting-drilling. Aside from size, the principal difference between these lighter machines and larger vertical mills is that the X-Y table is at

3900-482: A mobile platform for astronauts conducting an EVA. The RMS was built by the Canadian company Spar Aerospace and was controlled by an astronaut inside the orbiter's flight deck using their windows and closed-circuit television. The RMS allowed for six degrees of freedom and had six joints located at three points along the arm. The original RMS could deploy or retrieve payloads up to 29,000 kg (65,000 lb), which

4095-534: A partial-pressure version of the high-altitude pressure suits with a helmet. In 1994, the LES was replaced by the full-pressure Advanced Crew Escape Suit (ACES), which improved the safety of the astronauts in an emergency situation. Columbia originally had modified SR-71 zero-zero ejection seats installed for the ALT and first four missions, but these were disabled after STS-4 and removed after STS-9 . The flight deck

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4290-530: A partially reusable system would be the most cost-effective solution. The head of the NASA Office of Manned Space Flight, George Mueller , announced the plan for a reusable shuttle on August 10, 1968. NASA issued a request for proposal (RFP) for designs of the Integral Launch and Reentry Vehicle (ILRV) on October 30, 1968. Rather than award a contract based upon initial proposals, NASA announced

4485-558: A phased approach for the Space Shuttle contracting and development; Phase A was a request for studies completed by competing aerospace companies, Phase B was a competition between two contractors for a specific contract, Phase C involved designing the details of the spacecraft components, and Phase D was the production of the spacecraft. In December 1968, NASA created the Space Shuttle Task Group to determine

4680-445: A piece of foam (and/or ice) about 3.9 in (100 mm) in diameter separated from a feedline attachment bracket on the tank, ricocheted off one of the aft struts and struck the underside of the wing, damaging two tiles. The damage was not considered dangerous. The external hardware, ET–orbiter attachment fittings, umbilical fittings, and electrical and range safety system weigh 9,100 pounds (4,100 kg). Each propellant tank has

4875-481: A port-side hatch that the crew used for entry and exit while on Earth. The airlock is a structure installed to allow movement between two spaces with different gas components, conditions, or pressures. Continuing on the mid-deck structure, each orbiter was originally installed with an internal airlock in the mid-deck. The internal airlock was installed as an external airlock in the payload bay on Discovery , Atlantis , and Endeavour to improve docking with Mir and

5070-409: A respected founding father of machine tool historians, credited Eli Whitney (one of the private arms makers mentioned above) with producing the first true milling machine. By 1918, he considered it "Probably the first milling machine ever built—certainly the oldest now in existence […]." However, subsequent scholars, including Robert S. Woodbury and others, have improved upon Roe's early version of

5265-675: A result of an O-ring failing at low temperature, the SRBs were redesigned to provide a constant seal regardless of the ambient temperature. The Space Shuttle's operations were supported by vehicles and infrastructure that facilitated its transportation, construction, and crew access. The crawler-transporters carried the MLP and the Space Shuttle from the VAB to the launch site. The Shuttle Carrier Aircraft (SCA) were two modified Boeing 747s that could carry an orbiter on its back. The original SCA (N905NA)

5460-671: A second orbiter. Later that month, Rockwell began converting STA-099 to OV-099, later named Challenger . On January 29, 1979, NASA ordered two additional orbiters, OV-103 and OV-104, which were named Discovery and Atlantis . Construction of OV-105, later named Endeavour , began in February 1982, but NASA decided to limit the Space Shuttle fleet to four orbiters in 1983. After the loss of Challenger , NASA resumed production of Endeavour in September 1987. After it arrived at Edwards AFB, Enterprise underwent flight testing with

5655-670: A separate central processing unit (CPU) and input/output processor (IOP), and non-volatile solid-state memory . From 1991 to 1993, the orbiter vehicles were upgraded to the AP-101S, which improved the memory and processing capabilities, and reduced the volume and weight of the computers by combining the CPU and IOP into a single unit. Four of the GPCs were loaded with the Primary Avionics Software System (PASS), which

5850-414: A separate, pyrotechnically operated, propulsive tumble vent valve at its forward end. At separation, the liquid oxygen tumble vent valve was opened, providing impulse to assist in the separation maneuver and more positive control of the entry aerodynamics of the ET. The last flight with the tumble valve active was STS-36. Each of the two aft external tank umbilical plates mate with a corresponding plate on

6045-512: A slot, a flat surface, and an angular groove , a good method to cut these (within a non- CNC context) would be gang milling. All the completed workpieces would be the same, and milling time per piece would be minimized. Gang milling was especially important before the CNC era, because for duplicate part production, it was a substantial efficiency improvement over manual-milling one feature at an operation, then changing machines (or changing setup of

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6240-410: A speech. After STS-4, NASA declared its Space Transportation System (STS) operational. The Space Shuttle was the first operational orbital spacecraft designed for reuse . Each Space Shuttle orbiter was designed for a projected lifespan of 100 launches or ten years of operational life, although this was later extended. At launch, it consisted of the orbiter , which contained the crew and payload,

6435-420: A system to retract those parts not in use. The choice between vertical and horizontal spindle orientation in milling machine design usually hinges on the shape and size of a workpiece and the number of sides of the workpiece that require machining. Work in which the spindle's axial movement is normal to one plane, with an endmill as the cutter, lends itself to a vertical mill, where the operator can stand before

6630-408: A tanking test determined the cause of the errors to be a fault in a wiring connector, rather than a failure of the sensors themselves. Four pressure transducers located at the top of the liquid oxygen and liquid hydrogen tanks monitor the ullage pressures. The ET also has two electrical umbilicals that carry electrical power from the orbiter to the tank and the two SRBs and provide information from

6825-515: A total of 14 astronauts killed. A fifth operational (and sixth in total) orbiter, Endeavour , was built in 1991 to replace Challenger . The three surviving operational vehicles were retired from service following Atlantis ' s final flight on July 21, 2011. The U.S. relied on the Russian Soyuz spacecraft to transport astronauts to the ISS from the last Shuttle flight until the launch of

7020-401: A two-axis turret enabling the spindle to be pointed in any direction on desires. The two options may be driven independently or from one motor through gearing. In either case, as the work is generally placed in the same place for either type of operation, the mechanism for the method not being used is moved out of the way. In smaller machines, "spares" may be lifted off while larger machines offer

7215-428: A two-part drag parachute system to slow the orbiter after landing. The orbiter used retractable landing gear with a nose landing gear and two main landing gear, each containing two tires. The main landing gear contained two brake assemblies each, and the nose landing gear contained an electro-hydraulic steering mechanism. The Space Shuttle crew varied per mission. They underwent rigorous testing and training to meet

7410-420: A vent and relief valve at its forward end. This dual-function valve can be opened by ground support equipment for the vent function during prelaunch and can open during flight when the ullage (empty space) pressure of the liquid hydrogen tank reaches 38 psi (260 kPa) or the ullage pressure of the liquid oxygen tank reaches 25 psi (170 kPa). On early flights, the liquid oxygen tank contained

7605-449: Is a closed loop system and functions on feedback. These machines have developed from the basic NC (NUMERIC CONTROL) machines. A computerized form of NC machines is known as CNC machines. A set of instructions (called a program) is used to guide the machine for desired operations. There are over 100 different G-codes and M-codes. Some very commonly used codes, which are used in the program are: Various other codes are also used. A CNC machine

7800-471: Is a high degree of standardization of the tooling used with CNC milling machines, and a lesser degree with manual milling machines. To ease up the organization of the tooling in CNC production many companies use a tool management solution. Milling cutters for specific applications are held in various tooling configurations. CNC milling machines nearly always use SK (or ISO), CAT, BT or HSK tooling. SK tooling

7995-420: Is also easier to cut gears on a horizontal mill. Some horizontal milling machines are equipped with a power-take-off provision on the table. This allows the table feed to be synchronized to a rotary fixture, enabling the milling of spiral features such as hypoid gears. A universal milling machine is one with the facility to either have a horizontal spindle or a vertical spindle. The latter sometimes being on

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8190-457: Is an Al-Li alloy designed by Lockheed Martin and Reynolds for storage of cryogenics (and used for the SLW version of the ET - earlier versions used Al 2219). Al 2090 is a commercially available Al-Li alloy. The LOX tank is located at the top of the ET and has an ogive shape to reduce aerodynamic drag and aerothermodynamic heating. The ogive nose section is capped by a flat removable cover plate and

8385-423: Is better. In this approach, tool movement is multi-directional. One example of non-linear tool path is contour-parallel tool path. In this approach, the required pocket boundary is used to derive the tool path. In this case, the cutter is always in contact with the work material. Hence the idle time spent in positioning and retracting the tool is avoided. For large-scale material removal, contour-parallel tool path

8580-452: Is cooled by 1,080 interior lines carrying liquid hydrogen and is thermally protected by insulative and ablative material. The RS-25 engines had several improvements to enhance reliability and power. During the development program, Rocketdyne determined that the engine was capable of safe reliable operation at 104% of the originally specified thrust. To keep the engine thrust values consistent with previous documentation and software, NASA kept

8775-476: Is in the United States. It is claimed that HSK tooling is even better than BT Tooling at high speeds. The holding mechanism for HSK tooling is placed within the (hollow) body of the tool and, as spindle speed increases, it expands, gripping the tool more tightly with increasing spindle speed. There is no pull stud with this type of tooling. For manual milling machines, there is less standardization, because

8970-469: Is made, is that a machining center is a mill with features that pre- CNC mills never had, especially an automatic tool changer (ATC) that includes a tool magazine (carousel), and sometimes an automatic pallet changer (APC). In typical usage, all machining centers are mills, but not all mills are machining centers; only mills with ATCs are machining centers. Most CNC milling machines (also called machining centers ) are computer controlled vertical mills with

9165-413: Is operated by a single operator called a programmer. This machine is capable of performing various operations automatically and economically. With the declining price of computers and open source CNC software , the entry price of CNC machines has plummeted. The accessories and cutting tools used on machine tools (including milling machines) are referred to in aggregate by the mass noun "tooling". There

9360-430: Is pushed off the work piece in tiny clumps that hang together to a greater or lesser extent (depending on the material) to form chips. This makes metal cutting somewhat different (in its mechanics ) from slicing softer materials with a blade . The milling process removes material by performing many separate, small cuts. This is accomplished by using a cutter with many teeth, spinning the cutter at high speed, or advancing

9555-590: Is the most common in Europe, while CAT tooling, sometimes called V-Flange Tooling, is the oldest and probably most common type in the USA. CAT tooling was invented by Caterpillar Inc. of Peoria, Illinois , in order to standardize the tooling used on their machinery. CAT tooling comes in a range of sizes designated as CAT-30, CAT-40, CAT-50, etc. The number refers to the Association for Manufacturing Technology (formerly

9750-406: Is the thread used to hold the pull stud. CAT Tooling is all Imperial thread and BT Tooling is all Metric thread. Note that this affects the pull stud only; it does not affect the tool that they can hold. Both types of tooling are sold to accept both Imperial and metric sized tools. SK and HSK tooling, sometimes called "Hollow Shank Tooling", is much more common in Europe where it was invented than it

9945-472: Is vented through umbilical connections over a large diameter pipe on an arm extended from the fixed service structure. The connection for this pipe between the ET and service structure is made at the ground umbilical carrier plate (GUCP). Sensors are also installed at the GUCP to measure hydrogen levels. Countdowns of STS-80 , STS-119 , STS-127 and STS-133 have been halted and resulted in several week delays in

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10140-433: Is well known. In 1783, Samuel Rehe invented a true milling machine. In 1795, Eli Terry began using a milling machine at Plymouth Connecticut in the production of tall case clocks. With the use of his milling machine, Terry was the first to accomplish Interchangeable parts in the clock industry. Milling wooden parts was efficient in interchangeable parts, but inefficient in high yields. Milling wooden blanks results in

10335-400: Is widely used because it can be consistently used with up-cut or down-cut method during the entire process. There are three different approaches that fall into the category of contour-parallel tool path generation. They are: In this approach, the tool travels along a gradually evolving spiral path. The spiral starts at the center of the pocket to be machined and the tool gradually moves towards

10530-513: The Columbia disaster . Beginning with STS-114 , the orbiter vehicles were equipped with the wing leading edge impact detection system to alert the crew to any potential damage. The entire underside of the orbiter vehicle, as well as the other hottest surfaces, were protected with tiles of high-temperature reusable surface insulation, made of borosilicate glass -coated silica fibers that trapped heat in air pockets and redirected it out. Areas on

10725-499: The Clean Air Act . In its place, a hydrochlorofluorocarbon known as HCFC-141b was certified for use and phased into the shuttle program. Remaining foams, particularly detail pieces sprayed by hand, continued to use CFC-11 through the end of the program. These areas include the problematic bipod and PAL ramps, as well as some fittings and interfaces. For the bipod ramp in particular, "the process of applying foam to that part of

10920-780: The Crew Dragon Demo-2 mission in May 2020. In the late 1930s, the German government launched the " Amerikabomber " project, and Eugen Sanger 's idea, together with mathematician Irene Bredt , was a winged rocket called the Silbervogel (German for "silver bird"). During the 1950s, the United States Air Force proposed using a reusable piloted glider to perform military operations such as reconnaissance, satellite attack, and air-to-ground weapons employment. In

11115-571: The ISS , along with the Orbiter Docking System . The airlock module can be fitted in the mid-bay, or connected to it but in the payload bay. With an internal cylindrical volume of 1.60 metres (5 feet 3 inches) diameter and 2.11 metres (6 feet 11 inches) in length, it can hold two suited astronauts. It has two D-shaped hatchways 1.02 m (40 in) long (diameter), and 0.91 m (36 in) wide. The orbiter

11310-740: The Kennedy Space Center (KSC) in Florida . Operational missions launched numerous satellites , interplanetary probes , and the Hubble Space Telescope (HST), conducted science experiments in orbit, participated in the Shuttle- Mir program with Russia, and participated in the construction and servicing of the International Space Station (ISS). The Space Shuttle fleet's total mission time

11505-610: The Martin Marietta X-24B . The program tested aerodynamic characteristics that would later be incorporated in design of the Space Shuttle, including unpowered landing from a high altitude and speed. On September 24, 1966, as the Apollo space program neared its design completion, NASA and the Air Force released a joint study concluding that a new vehicle was required to satisfy their respective future demands and that

11700-553: The Shuttle Carrier Aircraft , a Boeing 747 that had been modified to carry the orbiter. In February 1977, Enterprise began the Approach and Landing Tests (ALT) and underwent captive flights, where it remained attached to the Shuttle Carrier Aircraft for the duration of the flight. On August 12, 1977, Enterprise conducted its first glide test, where it detached from the Shuttle Carrier Aircraft and landed at Edwards AFB. After four additional flights, Enterprise

11895-537: The Solid Rocket Boosters , external tanks were not re-used. They broke up before impact in the Indian Ocean (or Pacific Ocean in the case of direct-insertion launch trajectories), away from shipping lanes and were not recovered. The ET was the largest element of the Space Shuttle, and when loaded, it was also the heaviest. It consisted of three major components: The ET was the "backbone" of

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12090-633: The Tracking and Data Relay Satellite System and the Spacecraft Tracking and Data Acquisition Network ground stations to communicate with the orbiter throughout its orbit. Additionally, the orbiter deployed a high-bandwidth K u  band radio out of the cargo bay, which could also be utilized as a rendezvous radar. The orbiter was also equipped with two UHF radios for communications with air traffic control and astronauts conducting EVA. The Space Shuttle's fly-by-wire control system

12285-540: The external tank (ET), and the two solid rocket boosters (SRBs). Responsibility for the Space Shuttle components was spread among multiple NASA field centers. The KSC was responsible for launch, landing, and turnaround operations for equatorial orbits (the only orbit profile actually used in the program). The U.S. Air Force at the Vandenberg Air Force Base was responsible for launch, landing, and turnaround operations for polar orbits (though this

12480-484: The qualification requirements for their roles. The crew was divided into three categories: Pilots, Mission Specialists, and Payload Specialists. Pilots were further divided into two roles: Space Shuttle Commanders and Space Shuttle Pilots. The test flights only had two members each, the commander and pilot, who were both qualified pilots that could fly and land the orbiter. The on-orbit operations, such as experiments, payload deployment, and EVAs, were conducted primarily by

12675-405: The 1950s and 1960s. He quotes Battison as concluding that "There is no evidence that Whitney developed or used a true milling machine." Baida says, "The so-called Whitney machine of 1818 seems actually to have been made after Whitney's death in 1825." Baida cites Battison's suggestion that the first true milling machine was made not by Whitney, but by Robert Johnson of Middletown. The late teens of

12870-405: The 1969 plan led by U.S. Vice President Spiro Agnew for a system of reusable spacecraft where it was the only item funded for development. The first ( STS-1 ) of four orbital test flights occurred in 1981, leading to operational flights ( STS-5 ) beginning in 1982. Five complete Space Shuttle orbiter vehicles were built and flown on a total of 135 missions from 1981 to 2011. They launched from

13065-406: The 19th century were a pivotal time in the history of machine tools, as the period of 1814 to 1818 is also the period during which several contemporary pioneers ( Fox , Murray , and Roberts ) were developing the planer , and as with the milling machine, the work being done in various shops was undocumented for various reasons (partially because of proprietary secrecy, and also simply because no one

13260-448: The 2195 aluminum-lithium alloy, which was 40% stronger and 10% less dense than its predecessor, 2219 aluminum-lithium alloy. The SLWT weighed 3,400 kg (7,500 lb) less than the LWT, which allowed the Space Shuttle to deliver heavy elements to ISS's high inclination orbit. The Solid Rocket Boosters (SRB) provided 71.4% of the Space Shuttle's thrust during liftoff and ascent, and were

13455-452: The Air Force required a larger payload capacity than Faget's design allowed. In January 1971, NASA and Air Force leadership decided that a reusable delta-wing orbiter mounted on an expendable propellant tank would be the optimal design for the Space Shuttle. After they established the need for a reusable, heavy-lift spacecraft, NASA and the Air Force determined the design requirements of their respective services. The Air Force expected to use

13650-567: The ET remain unchanged. The last SWT, flown on STS-7 , weighed approximately 77,000 pounds (35,000 kg) inert. Beginning with the STS-6 mission, a lightweight ET (LWT), was introduced. This tank was used for the majority of the Shuttle flights, and was last used during the launch of the ill-fated STS-107 mission. Although tanks vary slightly in weight, each weighed approximately 66,000 pounds (30,000 kg) inert. The weight reduction from

13845-432: The ET, thus protecting the orbiter's thermal protection system during launch. There are eight propellant-depletion sensors, four each for fuel and oxidizer. The fuel-depletion sensors are located in the bottom of the fuel tank. The oxidizer sensors are mounted in the orbiter liquid oxygen feed line manifold downstream of the feed line disconnect. During RS-25 thrusting, the orbiter general-purpose computers constantly compute

14040-473: The ET. The SRBs were jettisoned before the vehicle reached orbit, while the main engines continued to operate, and the ET was jettisoned after main engine cutoff and just before orbit insertion , which used the orbiter's two Orbital Maneuvering System (OMS) engines. At the conclusion of the mission, the orbiter fired its OMS to deorbit and reenter the atmosphere . The orbiter was protected during reentry by its thermal protection system tiles, and it glided as

14235-680: The IMU, INS, and TACAN systems, which first flew on STS-118 in August 2007. While in orbit, the crew primarily communicated using one of four S band radios, which provided both voice and data communications. Two of the S ;band radios were phase modulation transceivers , and could transmit and receive information. The other two S band radios were frequency modulation transmitters and were used to transmit data to NASA. As S band radios can operate only within their line of sight , NASA used

14430-470: The IMUs while in orbit. The star trackers are deployed while in orbit, and can automatically or manually align on a star. In 1991, NASA began upgrading the inertial measurement units with an inertial navigation system (INS), which provided more accurate location information. In 1993, NASA flew a GPS receiver for the first time aboard STS-51 . In 1997, Honeywell began developing an integrated GPS/INS to replace

14625-485: The KSC. The Space Shuttle was prepared for launch primarily in the VAB at the KSC. The SRBs were assembled and attached to the external tank on the MLP. The orbiter vehicle was prepared at the Orbiter Processing Facility (OPF) and transferred to the VAB, where a crane was used to rotate it to the vertical orientation and mate it to the external tank. Once the entire stack was assembled, the MLP

14820-525: The LOX tank at a bolted, flange-joint interface with the intertank. The LOX tank also includes an internal slosh baffle and a vortex baffle to dampen fluid slosh. The vortex baffle is mounted over the LOX feed outlet to reduce fluid swirl resulting from slosh and to prevent entrapment of gases in the delivered LOX. The intertank is the ET structural connection between the LOX and LH 2 tanks. Its primary functions are to receive and distribute all thrust loads from

15015-688: The Morse #2 and the R8, whose prevalence was driven by the popularity of the mills built by Bridgeport Machines of Bridgeport, Connecticut . These mills so dominated the market for such a long time that "Bridgeport" is virtually synonymous with "manual milling machine". Most of the machines that Bridgeport made between 1938 and 1965 used a Morse taper #2, and from about 1965 onward most used an R8 taper. Many cutting tools exist for milling machines, including milling cutters, slitting cutters, gear cutters, end mills, etc. Pocket milling has been regarded as one of

15210-615: The National Machine Tool Builders Association (NMTB)) taper size of the tool. An improvement on CAT Tooling is Bridgeport Taper (BT) Tooling, which looks similar and can easily be confused with CAT tooling. Like CAT Tooling, BT Tooling comes in a range of sizes and uses the same NMTB body taper. However, BT tooling is symmetrical about the spindle axis, which CAT tooling is not. This gives BT tooling greater stability and balance at high speeds. One other subtle difference between these two toolholders

15405-528: The RS-25 experienced multiple nozzle failures, as well as broken turbine blades. Despite the problems during testing, NASA ordered the nine RS-25 engines needed for its three orbiters under construction in May 1978. NASA experienced significant delays in the development of the Space Shuttle's thermal protection system . Previous NASA spacecraft had used ablative heat shields, but those could not be reused. NASA chose to use ceramic tiles for thermal protection, as

15600-434: The SRBs and ET to the orbiter. The ET has external cameras mounted in the brackets attached to the shuttle along with transmitters that can continue to send video data long after the shuttle and the ET have separated. Earlier tanks incorporated a range safety system to disperse tank propellants if necessary. It included a battery power source, a receiver/decoder, antennas and ordnance . Starting with STS-79 this system

15795-497: The SRBs and transfer loads between the tanks. The two SRB forward attach fittings are located 180° apart on the intertank structure. A beam is extended across the intertank structure and is mechanically fastened to the attach fittings. When the SRBs are firing, the beam will flex due to high stress loads. These loads will be transferred to the fittings. Adjoining the SRB attach fittings is a major ring frame. The loads are transferred from

15990-505: The SRBs provided structural support for the orbiter vehicle and ET, as they were the only system that was connected to the mobile launcher platform (MLP). At the time of launch, the SRBs were armed at T−5 minutes, and could only be electrically ignited once the RS-25 engines had ignited and were without issue. They each provided 12,500 kN (2,800,000 lbf) of thrust, which was later improved to 13,300 kN (3,000,000 lbf) beginning on STS-8 . After expending their fuel,

16185-558: The SRBs were jettisoned approximately two minutes after launch at an altitude of approximately 46 km (150,000 ft). Following separation, they deployed drogue and main parachutes, landed in the ocean, and were recovered by the crews aboard the ships MV Freedom Star and MV Liberty Star . Once they were returned to Cape Canaveral, they were cleaned and disassembled. The rocket motor, igniter, and nozzle were then shipped to Thiokol to be refurbished and reused on subsequent flights. The SRBs underwent several redesigns throughout

16380-531: The SWT was accomplished by eliminating portions of stringers (structural stiffeners running the length of the hydrogen tank), using fewer stiffener rings and by modifying major frames in the hydrogen tank. Also, significant portions of the tank were milled differently so as to reduce thickness, and the weight of the ET's aft solid rocket booster attachments was reduced by using a stronger, yet lighter and less expensive titanium alloy. The Super Lightweight Tank (SLWT)

16575-399: The Space Shuttle through ascent, orbit, and reentry, but could not support an entire mission. The five GPCs were separated in three separate bays within the mid-deck to provide redundancy in the event of a cooling fan failure. After achieving orbit, the crew would switch some of the GPCs functions from guidance, navigation, and control (GNC) to systems management (SM) and payload (PL) to support

16770-526: The Space Shuttle to launch large satellites, and required it to be capable of lifting 29,000 kg (65,000 lb) to an eastward LEO or 18,000 kg (40,000 lb) into a polar orbit . The satellite designs also required that the Space Shuttle have a 4.6 by 18 m (15 by 60 ft) payload bay. NASA evaluated the F-1 and J-2 engines from the Saturn rockets , and determined that they were insufficient for

16965-405: The Space Shuttle. The external tank's orange color, which would become iconic of the Space Shuttle program, is the color of the spray-on foam insulation. The first two tanks, used for STS-1 and STS-2 , were painted white to protect the tanks from ultraviolet light during the extended time that the shuttle spent on the launch pad prior to launch. NASA engineer Farouk Huneidi told the agency that

17160-583: The Spacelab module through a 2.7 or 5.8 m (8.72 or 18.88 ft) tunnel that connected to the airlock. The Spacelab equipment was primarily stored in pallets, which provided storage for both experiments as well as computer and power equipment. Spacelab hardware was flown on 28 missions through 1999 and studied subjects including astronomy, microgravity, radar, and life sciences. Spacelab hardware also supported missions such as Hubble Space Telescope (HST) servicing and space station resupply. The Spacelab module

17355-470: The ability to move the spindle vertically along the Z-axis. This extra degree of freedom permits their use in diesinking, engraving applications, and 2.5D surfaces such as relief sculptures. When combined with the use of conical tools or a ball nose cutter , it also significantly improves milling precision without impacting speed, providing a cost-efficient alternative to most flat-surface hand- engraving work. CNC machines can exist in virtually any of

17550-585: The aft seating location, and also controlled the data on the HUD. In 1998, Atlantis was upgraded with the Multifunction Electronic Display System (MEDS), which was a glass cockpit upgrade to the flight instruments that replaced the eight MCDS display units with 11 multifunction colored digital screens. MEDS was flown for the first time in May 2000 on STS-101 , and the other orbiter vehicles were upgraded to it. The aft section of

17745-453: The aft surfaces prevents liquified air from pooling in the intertank. The middle cylinder of the oxygen tank, and the propellant lines, could withstand the expected depths of frost accumulation condensed from humidity, but the orbiter could not take the damage from ice breaking free. The thermal protection system weighs 4,823 lb (2,188 kg). Development of the ETs thermal protection system

17940-468: The anti-geyser line. This line paralleled the oxygen feed line, providing a circulation path for liquid oxygen. This reduces accumulation of gaseous oxygen in the feed line during prelaunch tanking (loading of the LOX). After propellant loading data from ground tests and the first few Space Shuttle missions were assessed, the anti-geyser line was removed for subsequent missions. The total length and diameter of

18135-401: The associated propellant tanks. The AJ10 engines used monomethylhydrazine (MMH) oxidized by dinitrogen tetroxide (N 2 O 4 ). The pods carried a maximum of 2,140 kg (4,718 lb) of MMH and 3,526 kg (7,773 lb) of N 2 O 4 . The OMS engines were used after main engine cut-off (MECO) for orbital insertion. Throughout the flight, they were used for orbit changes, as well as

18330-401: The broad outlines are known, as summarized below. From a history-of-technology viewpoint, it is clear that the naming of this new type of machining with the term "milling" was an extension from that word's earlier senses of processing materials by abrading them in some way (cutting, grinding, crushing, etc.). Rotary filing long predated milling. A rotary file by Jacques de Vaucanson , circa 1760,

18525-562: The built-in hold at T−9 minutes, the countdown was automatically controlled by the Ground Launch Sequencer (GLS) at the LCC, which stopped the countdown if it sensed a critical problem with any of the Space Shuttle's onboard systems. At T−3 minutes 45 seconds, the engines began conducting gimbal tests, which were concluded at T−2 minutes 15 seconds. The ground Launch Processing System handed off

18720-461: The bulk of the ET, and was 29 m (96.7 ft) tall. The orbiter vehicle was attached to the ET at two umbilical plates, which contained five propellant and two electrical umbilicals, and forward and aft structural attachments. The exterior of the ET was covered in orange spray-on foam to allow it to survive the heat of ascent. The ET provided propellant to the Space Shuttle Main Engines from liftoff until main engine cutoff. The ET separated from

18915-419: The characteristic finish of a face milled surface. Revolution marks can have significant roughness depending on factors such as flatness of the cutter's end face and the degree of perpendicularity between the cutter's rotation axis and feed direction. Often a final pass with a slow feed rate is used to improve the surface finish after the bulk of the material has been removed. In a precise face milling operation,

19110-550: The contract to build the orbiter to North American Rockwell. In August 1973, the external tank contract to Martin Marietta , and in November the solid-rocket booster contract to Morton Thiokol . On June 4, 1974, Rockwell began construction on the first orbiter, OV-101, dubbed Constitution, later to be renamed Enterprise . Enterprise was designed as a test vehicle, and did not include engines or heat shielding. Construction

19305-477: The control to the orbiter vehicle's GPCs at T−31 seconds. At T−16 seconds, the GPCs armed the SRBs, the sound suppression system (SPS) began to drench the MLP and SRB trenches with 1,100,000 L (300,000 U.S. gal) of water to protect the orbiter vehicle from damage by acoustical energy and rocket exhaust reflected from the flame trench and MLP during lift-off. At T−10 seconds, hydrogen igniters were activated under each engine bell to quell

19500-548: The cutters have good support from the arbor and have a larger cross-sectional area than an end mill, quite heavy cuts can be taken enabling rapid material removal rates. These are used to mill grooves and slots. Plain mills are used to shape flat surfaces. Several cutters may be ganged together on the arbor to mill a complex shape of slots and planes. Special cutters can also cut grooves, bevels, radii, or indeed any section desired. These specialty cutters tend to be expensive. Simplex mills have one spindle, and duplex mills have two. It

19695-637: The delivered LH 2 . The baffle is located at the siphon outlet just above the aft dome of the LH 2 tank. This outlet transmits the liquid hydrogen from the tank through a 17 inches (430 mm) line to the left aft umbilical. The liquid hydrogen feed line flow rate is 465 lb/s (12,700 kg/min) with the main engines at 104% or a maximum flow of 47,365 US gal/min (2.9883 m/s). The ET thermal protection system consists primarily of spray-on foam insulation (SOFI), plus preformed foam pieces and premolded ablator materials. The system also includes

19890-421: The deorbit burn prior to reentry. Each OMS engine produced 27,080 N (6,087 lbf) of thrust, and the entire system could provide 305 m/s (1,000 ft/s) of velocity change . The orbiter was protected from heat during reentry by the thermal protection system (TPS), a thermal soaking protective layer around the orbiter. In contrast with previous US spacecraft, which had used ablative heat shields,

20085-516: The development of a space shuttle to bring people and cargo to low Earth orbit (LEO), as well as a space tug for transfers between orbits and the Moon, and a reusable nuclear upper stage for deep space travel. After the release of the Space Shuttle Task Group report, many aerospace engineers favored the Class III, fully reusable design because of perceived savings in hardware costs. Max Faget ,

20280-619: The ease of refurbishing them for reuse after they landed in the ocean. In January 1972, President Richard Nixon approved the Shuttle, and NASA decided on its final design in March. The development of the Space Shuttle Main Engine (SSME) remained the responsibility of Rocketdyne, and the contract was issued in July 1971, and updated SSME specifications were submitted to Rocketdyne in that April. That August, NASA awarded

20475-492: The effects of aerodynamic and thermal stresses during launch and reentry. The beginning of the development of the RS-25 Space Shuttle Main Engine was delayed for nine months while Pratt & Whitney challenged the contract that had been issued to Rocketdyne. The first engine was completed in March 1975, after issues with developing the first throttleable, reusable engine. During engine testing,

20670-569: The engines before the oxidizer pumps cavitate (run dry). In addition, 1,100 lb (500 kg) of liquid hydrogen are loaded over and above that required by the 6:1 oxidizer–fuel engine mixture ratio. This assures that cutoff from the depletion sensors is fuel-rich; oxidizer-rich engine shutdowns can cause burning and severe erosion of engine components, potentially leading to loss of the vehicle and crew. Unexplained, erroneous readings from fuel depletion sensors have delayed several shuttle launch attempts, most notably STS-122 . On December 18, 2007,

20865-512: The engines during powered flight and fly the orbiter during unpowered flight. Both seats also had rudder controls, to allow rudder movement in flight and nose-wheel steering on the ground. The orbiter vehicles were originally installed with the Multifunction CRT Display System (MCDS) to display and control flight information. The MCDS displayed the flight information at the commander and pilot seats, as well as at

21060-673: The external tank was Lockheed Martin (previously Martin Marietta ), New Orleans, Louisiana. The tank was manufactured at the Michoud Assembly Facility , New Orleans , and was transported to Kennedy Space Center by barge . The ET has three primary structures: an LOX tank, an intertank, and an LH 2 tank. Both tanks are constructed of aluminium alloy skins with support or stability frames as required. The intertank aluminium structure utilizes skin stringers with stabilizing frames. The primary aluminium materials used for all three structures are 2195 and 2090 alloys. AL 2195

21255-605: The feasibility of reusable boosters. This became the basis for the aerospaceplane , a fully reusable spacecraft that was never developed beyond the initial design phase in 1962–1963. Beginning in the early 1950s, NASA and the Air Force collaborated on developing lifting bodies to test aircraft that primarily generated lift from their fuselages instead of wings, and tested the NASA M2-F1 , Northrop M2-F2 , Northrop M2-F3 , Northrop HL-10 , Martin Marietta X-24A , and

21450-623: The final decision to scrub a launch was announced. In addition to the weather at the launch site, conditions had to be acceptable at one of the Transatlantic Abort Landing sites and the SRB recovery area. The mission crew and the Launch Control Center (LCC) personnel completed systems checks throughout the countdown. Two built-in holds at T−20 minutes and T−9 minutes provided scheduled breaks to address any issues and additional preparation. After

21645-532: The first four Shuttle missions, astronauts wore modified U.S. Air Force high-altitude full-pressure suits, which included a full-pressure helmet during ascent and descent. From the fifth flight, STS-5 , until the loss of Challenger , the crew wore one-piece light blue nomex flight suits and partial-pressure helmets. After the Challenger disaster, the crew members wore the Launch Entry Suit (LES),

21840-561: The first milling machine" or "the inventor of interchangeable parts". Such claims are oversimplified, as these technologies evolved over time among many people.) Peter Baida, citing Edward A. Battison's article "Eli Whitney and the Milling Machine," which was published in the Smithsonian Journal of History in 1966, exemplifies the dispelling of the " Great Man " image of Whitney by historians of technology working in

22035-481: The first time NASA performed a crewed first-flight of a spacecraft. On April 12, 1981, the Space Shuttle launched for the first time, and was piloted by John Young and Robert Crippen . During the two-day mission, Young and Crippen tested equipment on board the shuttle, and found several of the ceramic tiles had fallen off the top side of the Columbia . NASA coordinated with the Air Force to use satellites to image

22230-421: The fittings to the major ring frame which then distributes the tangential loads to the intertank skin. Two panels of the intertank skin, called the thrust panels, distribute the concentrated axial SRB thrust loads to the LOX and LH 2 tanks and to adjacent intertank skin panels. These adjacent panels are made up of six stringer-stiffened panels. The intertank also functions as a protective compartment for housing

22425-551: The flange for attaching the LH 2 tank to the intertank. The aft major ring receives orbiter-induced loads from the aft orbiter support struts and SRB-induced loads from the aft SRB support struts. The remaining three ring frames distribute orbiter thrust loads and LOX feedline support loads. Loads from the frames are then distributed through the barrel skin panels. The LH 2 tank has a volume of 53,488 cubic feet (1,514.6 m) at 29.3 psi (202 kPa) and −423 °F (−252.8 °C) (cryogenic). The forward and aft domes have

22620-635: The flight deck contained windows looking into the payload bay, as well as an RHC to control the Remote Manipulator System during cargo operations. Additionally, the aft flight deck had monitors for a closed-circuit television to view the cargo bay. The mid-deck contained the crew equipment storage, sleeping area, galley, medical equipment, and hygiene stations for the crew. The crew used modular lockers to store equipment that could be scaled depending on their needs, as well as permanently installed floor compartments. The mid-deck contained

22815-410: The form of add-on heads to change horizontal mills to vertical mills (and later vice versa) have been commonly used. Even in the CNC era, a heavy workpiece needing machining on multiple sides lends itself to a horizontal machining center, while diesinking lends itself to a vertical one. In addition to horizontal versus vertical, other distinctions are also important: A milling machine is often called

23010-400: The forms of manual machinery, like horizontal mills. The most advanced CNC milling-machines, the multiaxis machine , add two more axes in addition to the three normal axes (XYZ). Horizontal milling machines also have a C or Q axis, allowing the horizontally mounted workpiece to be rotated, essentially allowing asymmetric and eccentric turning . The fifth axis (B axis) controls the tilt of

23205-502: The forward separation motors and the parachute systems that were used during recovery. The rocket nozzles could gimbal up to 8° to allow for in-flight adjustments. The rocket motors were each filled with a total 500,000 kg (1,106,640 lb) of solid rocket propellant ( APCP + PBAN ), and joined in the Vehicle Assembly Building (VAB) at KSC. In addition to providing thrust during the first stage of launch,

23400-725: The history and suggest that just as much credit—in fact, probably more—belongs to various other inventors, including Robert Johnson of Middletown, Connecticut ; Captain John H. Hall of the Harpers Ferry armory; Simeon North of the Staddle Hill factory in Middletown; Roswell Lee of the Springfield armory; and Thomas Blanchard . (Several of the men mentioned above are sometimes described on the internet as "the inventor of

23595-402: The inner leading edge and 45° at the outer leading edge. Each wing had an inboard and outboard elevon to provide flight control during reentry, along with a flap located between the wings, below the engines to control pitch . The orbiter's vertical stabilizer was swept backwards at 45° and contained a rudder that could split to act as a speed brake . The vertical stabilizer also contained

23790-404: The instantaneous mass of the vehicle due to the usage of the propellants. Normally, main engine cutoff is based on a predetermined velocity; however, if any two of the fuel or oxidizer sensors sense a dry condition, the engines will be shut down. The locations of the liquid oxygen sensors allow the maximum amount of oxidizer to be consumed in the engines, while allowing sufficient time to shut down

23985-567: The introduction of the SLWT were of this configuration, one LWT remained in inventory to be used if requested until the end of the shuttle era. The SLWT provided 50% of the performance increase required for the shuttle to reach the International Space Station . The reduction in weight allowed the Orbiter to carry more payload to the highly inclined orbit of the ISS . SLWT specifications LOX tank Intertank LH 2 tank The contractor for

24180-504: The largest solid-propellant motors ever flown. Each SRB was 45 m (149.2 ft) tall and 3.7 m (12.2 ft) wide, weighed 68,000 kg (150,000 lb), and had a steel exterior approximately 13 mm (.5 in) thick. The SRB's subcomponents were the solid-propellant motor, nose cone, and rocket nozzle. The solid-propellant motor comprised the majority of the SRB's structure. Its casing consisted of 11 steel sections which made up its four main segments. The nose cone housed

24375-575: The late 1950s, the Air Force began developing the partially reusable X-20 Dyna-Soar . The Air Force collaborated with NASA on the Dyna-Soar and began training six pilots in June 1961. The rising costs of development and the prioritization of Project Gemini led to the cancellation of the Dyna-Soar program in December 1963. In addition to the Dyna-Soar, the Air Force had conducted a study in 1957 to test

24570-488: The later cases due to hydrogen leaks at this connection. This requires complete draining of the tanks and removal of all hydrogen via helium gas purge, a 20-hour process, before technicians can inspect and repair problems. A cap mounted to the swing-arm on the fixed service structure covers the oxygen tank vent on top of the ET during the countdown and is retracted about two minutes before lift-off. The cap siphons off oxygen vapor that threatens to form large ice accumulations on

24765-490: The launch pad, the Space Shuttle was used to verify the proper positioning of the launch complex hardware. Enterprise was taken back to California in August 1979, and later served in the development of the SLC-6 at Vandenberg AFB in 1984. On November 24, 1980, Columbia was mated with its external tank and solid-rocket boosters, and was moved to LC-39 on December 29. The first Space Shuttle mission, STS-1 , would be

24960-430: The leading edge of Space Shuttle Columbia 's wing at a few hundred miles per hour. The impact is believed to have damaged one comparatively large reinforced carbon-carbon panel on the leading edge of the left wing, believed to be about the size of a basketball which then allowed super-heated gas to enter the wing superstructure several days later during re-entry. This resulted in the destruction of Columbia and

25155-405: The liquid hydrogen tank. One of the liquid oxygen tank umbilical valves is for liquid oxygen, the other for gaseous oxygen. The liquid hydrogen tank umbilical has two valves for liquid and one for gas. The intermediate-diameter liquid hydrogen umbilical is a recirculation umbilical used only during the liquid hydrogen chill-down sequence during prelaunch. As the ET is filled, excess gaseous hydrogen

25350-451: The loss of its crew. The report determined that the external fuel tank, ET-93, "had been constructed with BX-250", a closeout foam whose blowing agent was CFC-11 and not the newer HCFC 141b. In 2005, the problem of foam shed had not been fully cured; on STS-114 , additional cameras mounted on the tank recorded a piece of foam separated from one of its Protuberance Air Load (PAL) ramps, which are designed to prevent unsteady air flow underneath

25545-410: The machine (e.g., a ball nose mill) or directly from the cutter's shape (e.g., a form tool such as a hobbing cutter). As material passes through the cutting area of a milling machine, the blades of the cutter take swarfs of material at regular intervals. Surfaces cut by the side of the cutter (as in peripheral milling) therefore always contain regular ridges. The distance between ridges and the height of

25740-491: The machine and have easy access to the cutting action by looking down upon it. Thus vertical mills are most favored for diesinking work (machining a mould into a block of metal). Heavier and longer workpieces lend themselves to placement on the table of a horizontal mill. Prior to numerical control , horizontal milling machines evolved first, because they evolved by putting milling tables under lathe-like headstocks. Vertical mills appeared in subsequent decades, and accessories in

25935-571: The material through the cutter slowly; most often it is some combination of these three approaches. The speeds and feeds used are varied to suit a combination of variables. The speed at which the piece advances through the cutter is called feed rate , or just feed ; it is most often measured as distance per time (inches per minute [in/min or ipm] or millimeters per minute [mm/min]), although distance per revolution or per cutter tooth are also sometimes used. There are two major classes of milling process: Many different types of cutting tools are used in

26130-431: The milling process. Milling cutters such as end mills may have cutting surfaces across their entire end surface, so that they can be drilled into the work piece (plunging). Milling cutters may also have extended cutting surfaces on their sides to allow for peripheral milling. Tools optimized for face milling tend to have only small cutters at their end corners. The cutting surfaces of a milling cutter are generally made of

26325-437: The mission specialists who were specifically trained for their intended missions and systems. Early in the Space Shuttle program, NASA flew with payload specialists, who were typically systems specialists who worked for the company paying for the payload's deployment or operations. The final payload specialist, Gregory B. Jarvis , flew on STS-51-L , and future non-pilots were designated as mission specialists. An astronaut flew as

26520-406: The most widely used operations in machining . It is extensively used in aerospace and shipyard industries. In pocket milling the material inside an arbitrarily closed boundary on a flat surface of a work piece is removed to a fixed depth. Generally flat bottom end mills are used for pocket milling. Firstly roughing operation is done to remove the bulk of material and then the pocket is finished by

26715-443: The occasional use of mills for turning operations. This led to a new class of machine tools, multitasking machines (MTMs), which are purpose-built to facilitate milling and turning within the same work envelope. Milling is a cutting process that uses a milling cutter to remove material from the surface of a workpiece . The milling cutter is a rotary cutting tool , often with multiple cutting points. As opposed to drilling , where

26910-400: The operational instrumentation. The LH 2 tank is the bottom portion of the ET. The tank is constructed of four cylindrical barrel sections, a forward dome, and an aft dome. The barrel sections are joined together by five major ring frames. These ring frames receive and distribute loads. The forward dome-to-barrel frame distributes the loads applied through the intertank structure and is also

27105-434: The operational mission. The Space Shuttle was not launched if its flight would run from December to January, as its flight software would have required the orbiter vehicle's computers to be reset at the year change. In 2007, NASA engineers devised a solution so Space Shuttle flights could cross the year-end boundary. Space Shuttle missions typically brought a portable general support computer (PGSC) that could integrate with

27300-424: The optimal design for a reusable spacecraft, and issued study contracts to General Dynamics , Lockheed , McDonnell Douglas , and North American Rockwell . In July 1969, the Space Shuttle Task Group issued a report that determined the Shuttle would support short-duration crewed missions and space station, as well as the capabilities to launch, service, and retrieve satellites. The report also created three classes of

27495-436: The orange foam itself was sufficiently protected, and the ET was no longer covered in latex paint beginning on STS-3. A light-weight tank (LWT) was first flown on STS-6, which reduced tank weight by 4,700 kg (10,300 lb). The LWT's weight was reduced by removing components from the hydrogen tank and reducing the thickness of some skin panels. In 1998, a super light-weight ET (SLWT) first flew on STS-91 . The SLWT used

27690-437: The orbiter vehicle 18 seconds after engine cutoff and could be triggered automatically or manually. At the time of separation, the orbiter vehicle retracted its umbilical plates, and the umbilical cords were sealed to prevent excess propellant from venting into the orbiter vehicle. After the bolts attached at the structural attachments were sheared, the ET separated from the orbiter vehicle. At the time of separation, gaseous oxygen

27885-467: The orbiter vehicle and would be removed and replaced in between flights. The RS-25 is a staged-combustion cycle cryogenic engine that used liquid oxygen and hydrogen and had a higher chamber pressure than any previous liquid-fueled rocket. The original main combustion chamber operated at a maximum pressure of 226.5 bar (3,285 psi). The engine nozzle is 287 cm (113 in) tall and has an interior diameter of 229 cm (90.3 in). The nozzle

28080-510: The orbiter vehicle's computers and communication suite, as well as monitor scientific and payload data. Early missions brought the Grid Compass , one of the first laptop computers, as the PGSC, but later missions brought Apple and Intel laptops. The payload bay comprised most of the orbiter vehicle's fuselage , and provided the cargo-carrying space for the Space Shuttle's payloads. It

28275-549: The orbiter vehicle's heat, and were opened upon reaching orbit for heat rejection. The orbiter could be used in conjunction with a variety of add-on components depending on the mission. This included orbital laboratories, boosters for launching payloads farther into space, the Remote Manipulator System (RMS), and optionally the EDO pallet to extend the mission duration. To limit the fuel consumption while

28470-528: The orbiter was docked at the ISS, the Station-to-Shuttle Power Transfer System (SSPTS) was developed to convert and transfer station power to the orbiter. The SSPTS was first used on STS-118, and was installed on Discovery and Endeavour . The Remote Manipulator System (RMS), also known as Canadarm, was a mechanical arm attached to the cargo bay. It could be used to grasp and manipulate payloads, as well as serve as

28665-408: The orbiter. The plates help maintain alignment among the umbilicals. Physical strength at the umbilical plates is provided by bolting corresponding umbilical plates together. When the orbiter GPCs command external tank separation, the bolts are severed by pyrotechnic devices. The ET has five propellant umbilical valves that interface with orbiter umbilicals: two for the liquid oxygen tank and three for

28860-400: The orientation of the rotating spindle upon which the cutter is mounted. However, there are alternative classifications according to method of control, size, purpose and power source. In the vertical milling machine the spindle axis is vertically oriented. Milling cutters are held in the spindle and rotate on its axis. The spindle can generally be lowered (or the table can be raised, giving

29055-549: The originally specified thrust at 100%, but had the RS-25 operate at higher thrust. RS-25 upgrade versions were denoted as Block I and Block II. 109% thrust level was achieved with the Block II engines in 2001, which reduced the chamber pressure to 207.5 bars (3,010 psi), as it had a larger throat area. The normal maximum throttle was 104 percent, with 106% or 109% used for mission aborts. The Orbital Maneuvering System (OMS) consisted of two aft-mounted AJ10-190 engines and

29250-576: The paint did not actually protect the foam. Martin Marietta (now part of Lockheed Martin ) reduced weight by leaving the rust-colored spray-on insulation unpainted beginning with STS-3 , saving approximately 272  kg (600  lb ). The original ET is informally known as the Standard Weight Tank (SWT) and was fabricated from 2219 aluminum alloy , a high-strength aluminum-copper alloy used for many aerospace applications. After STS-4 , several hundred pounds were eliminated by removing

29445-596: The pocket boundary. The direction of the tool path changes progressively and local acceleration and deceleration of the tool are minimized. This reduces tool wear. Milling machines evolved from the practice of rotary filing—that is, running a circular cutter with file -like teeth in the headstock of a lathe . Rotary filing and, later, true milling were developed to reduce time and effort spent hand-filing. The full story of milling machine development may never be known, because much early development took place in individual shops where few records were kept for posterity. However,

29640-405: The program's lifetime. STS-6 and STS-7 used SRBs 2,300 kg (5,000 lb) lighter due to walls that were 0.10 mm (.004 in) thinner, but were determined to be too thin to fly safely. Subsequent flights until STS-26 used cases that were 0.076 mm (.003 in) thinner than the standard-weight cases, which reduced 1,800 kg (4,000 lb). After the Challenger disaster as

29835-400: The propellant for the Space Shuttle Main Engines, and connected the orbiter vehicle with the solid rocket boosters. The ET was 47 m (153.8 ft) tall and 8.4 m (27.6 ft) in diameter, and contained separate tanks for liquid oxygen and liquid hydrogen. The liquid oxygen tank was housed in the nose of the ET, and was 15 m (49.3 ft) tall. The liquid hydrogen tank comprised

30030-465: The requirements of the Space Shuttle; in July 1971, it issued a contract to Rocketdyne to begin development on the RS-25 engine. NASA reviewed 29 potential designs for the Space Shuttle and determined that a design with two side boosters should be used, and the boosters should be reusable to reduce costs. NASA and the Air Force elected to use solid-propellant boosters because of the lower costs and

30225-685: The reusability of the orbiter required a multi-use heat shield. During reentry, the TPS experienced temperatures up to 1,600 °C (3,000 °F), but had to keep the orbiter vehicle's aluminum skin temperature below 180 °C (350 °F). The TPS primarily consisted of four types of tiles. The nose cone and leading edges of the wings experienced temperatures above 1,300 °C (2,300 °F), and were protected by reinforced carbon-carbon tiles (RCC). Thicker RCC tiles were developed and installed in 1998 to prevent damage from micrometeoroid and orbital debris , and were further improved after RCC damage caused in

30420-401: The revolution marks will only be microscopic scratches due to imperfections in the cutting edge. Gang milling refers to the use of two or more milling cutters mounted on the same arbor (that is, ganged) in a horizontal-milling setup. All of the cutters may perform the same type of operation, or each cutter may perform a different type of operation. For example, if several workpieces need

30615-437: The ridges depend on the feed rate, number of cutting surfaces, the cutter diameter. With a narrow cutter and rapid feed rate, these revolution ridges can be significant variations in the surface finish . The face milling process can in principle produce very flat surfaces. However, in practice the result always shows visible trochoidal marks following the motion of points on the cutter's end face. These revolution marks give

30810-458: The same machine) to cut the next op. Today, CNC mills with automatic tool change and 4- or 5-axis control obviate gang-milling practice to a large extent. Milling is performed with a milling cutter in various forms, held in a collet or similar which, in turn, is held in the spindle of a milling machine. Mill orientation is the primary classification for milling machines. The two basic configurations are vertical and horizontal – referring to

31005-449: The same modified ellipsoidal shape. For the forward dome, mounting provisions are incorporated for the LH 2 vent valve, the LH 2 pressurization line fitting, and the electrical feed-through fitting. The aft dome has a manhole fitting for access to the LH 2 feedline screen and a support fitting for the LH 2 feedline. The LH 2 tank also has a vortex baffle to reduce swirl resulting from slosh and to prevent entrapment of gases in

31200-411: The same relative effect of bringing the cutter closer or deeper into the work), allowing plunge cuts and drilling. The depth to which blades cut into the work can be controlled with a micrometer adjustment nut . There are two subcategories of vertical mills: the bed mill and the turret mill. Turret mills are generally considered by some to be more versatile of the two designs. A third type also exists,

31395-529: The shuttle could then be constructed of lightweight aluminum , and the tiles could be individually replaced as needed. Construction began on Columbia on March 27, 1975, and it was delivered to the KSC on March 25, 1979. At the time of its arrival at the KSC, Columbia still had 6,000 of its 30,000 tiles remaining to be installed. However, many of the tiles that had been originally installed had to be replaced, requiring two years of installation before Columbia could fly. On January 5, 1979, NASA commissioned

31590-585: The shuttle during launch, providing structural support for attachment with the Space Shuttle Solid Rocket Boosters (SRBs) and orbiter. The tank was connected to each SRB at one forward attachment point (using a crossbeam through the intertank) and one aft bracket, and it was connected to the orbiter at one forward attachment bipod and two aft bipods. In the aft attachment area, there were also umbilicals that carried fluids , gases , electrical signals and electrical power between

31785-441: The stagnant gas inside the cones before ignition. Failure to burn these gases could trip the onboard sensors and create the possibility of an overpressure and explosion of the vehicle during the firing phase. The hydrogen tank's prevalves were opened at T−9.5 seconds in preparation for engine start. Milling machine Milling can be done with a wide range of machine tools . The original class of machine tools for milling

31980-478: The tank and the orbiter. Electrical signals and controls between the orbiter and the two solid rocket boosters were also routed through those umbilicals. Although the external tanks were always discarded, it may have been possible to re-use them in orbit. Plans for re-use ranged from incorporation into a space station as extra living or research space, as rocket fuel tanks for interplanetary missions (e.g. Mars), to raw materials for orbiting factories. Another concept

32175-430: The tank had not changed since 1993." The "new" foam containing HCFC 141b was first used on the aft dome portion of ET-82 during the flight of STS-79 in 1996. Use of HCFC 141b was expanded to the ETs area, or larger portions of the tank, starting with ET-88, which flew on STS-86 in 1997. During the lift-off of STS-107 on January 16, 2003, a piece of foam insulation detached from one of the tank's bipod ramps and struck

32370-646: The tank's cable trays and pressurization lines during ascent. The PAL ramps consist of manually sprayed layers of foam, and are more likely to become a source of debris. That piece of foam did not impact the orbiter. Reports published concurrent with the STS-114 mission suggest that excessive handling of the ET during modification and upgrade may have contributed to the foam loss on Discovery 's Return to Flight mission. However, three shuttle missions ( STS-121 , STS-115 , and STS-116 ) were later conducted, all with "acceptable" levels of foam loss. However, on STS-118

32565-426: The tool is advanced along its rotation axis, the cutter in milling is usually moved perpendicular to its axis so that cutting occurs on the circumference of the cutter. As the milling cutter enters the work piece, the cutting edges (flutes or teeth) of the tool repeatedly cut into and exit from the material, shaving off chips (swarf) from the work piece with each pass. The cutting action is shear deformation; material

32760-407: The tool itself. When all of these axes are used in conjunction with each other, extremely complicated geometries, even organic geometries such as a human head can be made with relative ease with these machines. But the skill to program such geometries is beyond that of most operators. Therefore, 5-axis milling machines are practically always programmed with CAM . The operating system of such machines

32955-537: The tool movement is unidirectional. Zig-zag and zig tool paths are examples of linear tool paths. In zig-zag milling, material is removed both in forward and backward paths. In this case, cutting is done both with and against the rotation of the spindle. This reduces the machining time but increases machine chatter and tool wear . In zig milling, the tool moves only in one direction. The tool has to be lifted and retracted after each cut, due to which machining time increases. However, in case of zig milling surface quality

33150-418: The underside of Columbia , and determined there was no damage. Columbia reentered the atmosphere and landed at Edwards AFB on April 14. NASA conducted three additional test flights with Columbia in 1981 and 1982. On July 4, 1982, STS-4 , flown by Ken Mattingly and Henry Hartsfield , landed on a concrete runway at Edwards AFB. President Ronald Reagan and his wife Nancy met the crew, and delivered

33345-467: The upper parts of the orbiter vehicle were coated in tiles of white low-temperature reusable surface insulation with similar composition, which provided protection for temperatures below 650 °C (1,200 °F). The payload bay doors and parts of the upper wing surfaces were coated in reusable Nomex felt surface insulation or in beta cloth , as the temperature there remained below 370 °C (700 °F). The Space Shuttle external tank (ET) carried

33540-429: The use of phenolic thermal insulators to preclude air liquefaction. Thermal isolators are required for liquid hydrogen tank attachments to preclude the liquefaction of air on exposed metal, and to reduce heat flow into the liquid hydrogen. While the warmer liquid oxygen results in fewer thermal requirements, the aluminum of the liquid oxygen tank forward areas require protection from aeroheating . Meanwhile, insulation on

33735-519: Was 1,323 days. Space Shuttle components include the Orbiter Vehicle (OV) with three clustered Rocketdyne RS-25 main engines, a pair of recoverable solid rocket boosters (SRBs), and the expendable external tank (ET) containing liquid hydrogen and liquid oxygen . The Space Shuttle was launched vertically , like a conventional rocket, with the two SRBs operating in parallel with the orbiter's three main engines , which were fueled from

33930-462: Was 18 m (60 ft) long and 4.6 m (15 ft) wide, and could accommodate cylindrical payloads up to 4.6 m (15 ft) in diameter. Two payload bay doors hinged on either side of the bay, and provided a relatively airtight seal to protect payloads from heating during launch and reentry. Payloads were secured in the payload bay to the attachment points on the longerons . The payload bay doors served an additional function as radiators for

34125-499: Was Space Shuttle-specific software that provided control through all phases of flight. During ascent, maneuvering, reentry, and landing, the four PASS GPCs functioned identically to produce quadruple redundancy and would error check their results. In case of a software error that would cause erroneous reports from the four PASS GPCs, a fifth GPC ran the Backup Flight System, which used a different program and could control

34320-641: Was a modified airport jet bridge that was used to assist astronauts to egress from the orbiter after landing, where they would undergo their post-mission medical checkups. The Astrovan transported astronauts from the crew quarters in the Operations and Checkout Building to the launch pad on launch day. The NASA Railroad comprised three locomotives that transported SRB segments from the Florida East Coast Railway in Titusville to

34515-466: Was carried for 5.6 km (3.5 mi) to Launch Complex 39 by one of the crawler-transporters . After the Space Shuttle arrived at one of the two launchpads, it would connect to the Fixed and Rotation Service Structures, which provided servicing capabilities, payload insertion, and crew transportation. The crew was transported to the launch pad at T−3 hours and entered the orbiter vehicle, which

34710-565: Was closed at T−2 hours. Liquid oxygen and hydrogen were loaded into the external tank via umbilicals that attached to the orbiter vehicle, which began at T−5 hours 35 minutes. At T−3 hours 45 minutes, the hydrogen fast-fill was complete, followed 15 minutes later by the oxygen tank fill. Both tanks were slowly filled up until the launch as the oxygen and hydrogen evaporated. The launch commit criteria considered precipitation, temperatures, cloud cover, lightning forecast, wind, and humidity. The Space Shuttle

34905-686: Was completed on September 17, 1976, and Enterprise was moved to the Edwards Air Force Base to begin testing. Rockwell constructed the Main Propulsion Test Article (MPTA)-098 , which was a structural truss mounted to the ET with three RS-25 engines attached. It was tested at the National Space Technology Laboratory (NSTL) to ensure that the engines could safely run through the launch profile. Rockwell conducted mechanical and thermal stress tests on Structural Test Article (STA)-099 to determine

35100-412: Was disabled, and was completely removed for STS-88 and all subsequent flights. Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program . Its official program name was Space Transportation System (STS), taken from

35295-551: Was entirely reliant on its main computer, the Data Processing System (DPS). The DPS controlled the flight controls and thrusters on the orbiter, as well as the ET and SRBs during launch. The DPS consisted of five general-purpose computers (GPC), two magnetic tape mass memory units (MMUs), and the associated sensors to monitor the Space Shuttle components. The original GPC used was the IBM AP-101B , which used

35490-657: Was equipped with an avionics system to provide information and control during atmospheric flight. Its avionics suite contained three microwave scanning beam landing systems , three gyroscopes , three TACANs , three accelerometers , two radar altimeters , two barometric altimeters , three attitude indicators , two Mach indicators , and two Mode C transponders . During reentry, the crew deployed two air data probes once they were traveling slower than Mach 5. The orbiter had three inertial measuring units (IMU) that it used for guidance and navigation during all phases of flight. The orbiter contains two star trackers to align

35685-653: Was first flown in 1975, and was used for the ALT and ferrying the orbiter from Edwards AFB to the KSC on all missions prior to 1991. A second SCA (N911NA) was acquired in 1988, and was first used to transport Endeavour from the factory to the KSC. Following the retirement of the Space Shuttle, N905NA was put on display at the JSC, and N911NA was put on display at the Joe Davies Heritage Airpark in Palmdale, California . The Crew Transport Vehicle (CTV)

35880-478: Was first flown in 1998 on STS-91 and was used for all subsequent missions with two exceptions ( STS-99 and STS-107 ). The SLWT had basically the same design as the LWT except that it used an aluminium-lithium alloy ( Al 2195 ) for a large part of the tank structure. This alloy provided a significant reduction in tank weight (about 7,000 pounds or 3,175 kg) over the LWT. Manufacture also included friction stir welding technology. Although all ETs produced after

36075-403: Was later improved to 270,000 kg (586,000 lb). The Spacelab module was a European-funded pressurized laboratory that was carried within the payload bay and allowed for scientific research while in orbit. The Spacelab module contained two 2.7 m (9 ft) segments that were mounted in the aft end of the payload bay to maintain the center of gravity during flight. Astronauts entered

36270-406: Was located below the flight deck and was where the galley and crew bunks were set up, as well as three or four crew member seats. The mid-deck contained the airlock, which could support two astronauts on an extravehicular activity (EVA), as well as access to pressurized research modules. An equipment bay was below the mid-deck, which stored environmental control and waste management systems. On

36465-617: Was moved to the Marshall Space Flight Center (MSFC) on March 13, 1978. Enterprise underwent shake tests in the Mated Vertical Ground Vibration Test, where it was attached to an external tank and solid rocket boosters, and underwent vibrations to simulate the stresses of launch. In April 1979, Enterprise was taken to the KSC, where it was attached to an external tank and solid rocket boosters, and moved to LC-39 . Once installed at

36660-602: Was never used). The Johnson Space Center (JSC) served as the central point for all Shuttle operations and the MSFC was responsible for the main engines, external tank, and solid rocket boosters. The John C. Stennis Space Center handled main engine testing, and the Goddard Space Flight Center managed the global tracking network. The orbiter had design elements and capabilities of both a rocket and an aircraft to allow it to launch vertically and then land as

36855-422: Was not launched under conditions where it could have been struck by lightning , as its exhaust plume could have triggered lightning by providing a current path to ground after launch, which occurred on Apollo 12 . The NASA Anvil Rule for a Shuttle launch stated that an anvil cloud could not appear within a distance of 19  km (10 nmi). The Shuttle Launch Weather Officer monitored conditions until

37050-433: Was problematic. Anomalies in foam application were so frequent that they were treated as variances, not safety incidents. NASA had difficulty preventing fragments of foam from detaching during flight for the entire history of the program: In 1995, chlorofluorocarbon-11 (CFC-11) began to be withdrawn from large-area, machine-sprayed foams in compliance with an Environmental Protection Agency ban on CFCs under section 610 of

37245-418: Was tested on STS-2 and STS-3, and the first full mission was on STS-9. Three RS-25 engines, also known as the Space Shuttle Main Engines (SSME), were mounted on the orbiter's aft fuselage in a triangular pattern. The engine nozzles could gimbal ±10.5° in pitch, and ±8.5° in yaw during ascent to change the direction of their thrust to steer the Shuttle. The titanium alloy reusable engines were independent of

37440-534: Was the milling machine (often called a mill). After the advent of computer numerical control (CNC) in the 1960s, milling machines evolved into machining centers : milling machines augmented by automatic tool changers, tool magazines or carousels, CNC capability, coolant systems, and enclosures. Milling centers are generally classified as vertical machining centers (VMCs) or horizontal machining centers (HMCs). The integration of milling into turning environments, and vice versa, began with live tooling for lathes and

37635-444: Was the top level of the crew compartment and contained the flight controls for the orbiter. The commander sat in the front left seat, and the pilot sat in the front right seat, with two to four additional seats set up for additional crew members. The instrument panels contained over 2,100 displays and controls, and the commander and pilot were both equipped with a heads-up display (HUD) and a Rotational Hand Controller (RHC) to gimbal

37830-471: Was to use the ET as a cargo carrier for bulky payloads. One proposal was for the primary mirror of a 7-meter aperture telescope to be carried with the tank. Another concept was the Aft Cargo Carrier (ACC). Over the years, NASA worked to reduce the weight of the ET to increase overall efficiency. The weight reduced from the ET resulted in an almost equal increase of the cargo-carrying capability of

38025-551: Was vented from the nose to cause the ET to tumble, ensuring that it would break up upon reentry. The ET was the only major component of the Space Shuttle system that was not reused, and it would travel along a ballistic trajectory into the Indian or Pacific Ocean. For the first two missions, STS-1 and STS-2 , the ET was covered in 270 kg (595 lb) of white fire-retardant latex paint to provide protection against damage from ultraviolet radiation. Further research determined that

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