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By
Wikipedia, Project Mercury was the first human spaceflight program of the United States. It ran from 1959 through 1963 with the goal of putting a human in orbit around the Earth. The Mercury-Atlas 6 flight on 20 February 1962 was the first Mercury flight to achieve this goal. Early planning and research was carried out by the National Advisory Committee for Aeronautics, and the program was officially conducted by the newly created NASA. The name comes from Mercury, a Roman mythological god who is often seen as a symbol of speed. Mercury is also the name of the innermost planet of the solar system, which moves faster than any other and hence provides an image of speed, although Project Mercury had no other connection to that planet. The Mercury program cost approximately $384 million, or about $2.7 billion in 2007 dollars. It was developed by a team of predominantly German rocket engineers who had emigrated to the United States after World War II. Spacecraft
Because of their small size it was said that the Mercury spacecraft were worn, not ridden. With 1.7 cubic meters of habitable volume, the spacecraft was just large enough for the single crew member. Inside were 120 controls: 55 electrical switches, 30 fuses and 35 mechanical levers. The spacecraft was designed by Max Faget and NASA's Space Task Group. During the launch phase of the mission, the Mercury spacecraft and astronaut were protected from launch vehicle failures by the Launch Escape System. The LES consisted of a solid fuel, 52,000 lbf (231 kN) thrust rocket mounted on a tower above the spacecraft. In the event of a launch abort, the LES would fire for 1 second, pulling the Mercury spacecraft and the astronaut away from a defective launch vehicle. The spacecraft would then descend on its parachute recovery system. After booster engine cutoff (BECO), the LES was no longer needed and was separated from the spacecraft by a solid fuel, 800 lbf (3.6 kN) thrust jettison rocket that fired for 1.5 seconds. Unfortunately, as with the later Apollo and Gemini programs, the scientists believed that if there was a catastrophic failure with the launch vehicle, then the possibilities of survival were minimal even with the tower in place. There simply wasn't enough time between the detection of the problem and the resulting consequences. There was never a problem during launch that caused the firing of the tower, and in Project Gemini (which didn't use the LES), Gemini 6 misfired but was aborted before any trouble arose. To separate the Mercury spacecraft from the launch vehicle, the spacecraft fired three small solid-fuel, 400 lbf (1.8 kN) thrust rockets for 1 second. These rockets are called the Posigrade rockets. The spacecraft was only equipped with attitude control thrusters - after orbit insertion and before retrofire they could not change their orbit. There were three sets of high and low powered automatic control jets and separate manual jets - one for each axis (yaw, pitch, and roll), supplied from two separate fuel tanks - one automatic and one manual. The pilot could use any one of the three thruster systems and fuel them from either of the two fuel tanks to provide spacecraft attitude control. The Mercury spacecraft were designed to be completely controllable from the ground in the event that something impaired the pilot's ability to function. The spacecraft had three solid-fuel, 1000 lbf (4.5 kN) thrust retrorockets that fired for 10 seconds each. One was sufficient to return the spacecraft to earth if the other two failed. The firing sequence (known as ripple firing) required firing the first retro, followed by the second retro five seconds later (while the first was still firing). Five seconds after that, the third retro fired (while the second retro was still firing). There was a small metal flap at the nose of the spacecraft called the "spoiler". If the spacecraft started to reenter nose first (another stable reentry attitude for the spacecraft), airflow over the "spoiler" would flip the spacecraft around to the proper, heatshield-first reentry attitude, a technique called 'Shuttlecocking'. During reentry, the astronaut would experience about 4 g-forces. Initial designs for the spacecraft suggested the use of either beryllium heat-sink heat shields or an ablative shield. Extensive testing settled the issue - ablative shields proved to be reliable (so much so that the initial shield thickness was safely reduced, allowing a lower total spacecraft weight), easier to produce (at that time, beryllium was only produced in sufficient quantities by a single company in the US) and cheaper. NASA ordered 20 production spacecraft, numbered 1 through 20, from McDonnell Aircraft Company, St. Louis, Missouri. Five of the twenty spacecraft, #10, 12, 15, 17, and 19, were not flown. Spacecraft #3 and #4 were destroyed during unmanned test flights. Spacecraft #11 sank and was recovered from the bottom of the Atlantic Ocean after 38 years. Some spacecraft were modified after initial production (refurbished after launch abort, modified for longer missions, etc) and received a letter designation after their number, examples 2B, 15B. Some spacecraft were modified twice; for example, spacecraft 15 became 15A and then 15B. A number of Mercury Boilerplate spacecraft (including mockup/prototype/replica spacecrafts, made from non-flight materials or lacking production spacecraft systems and/or hardware) were also made by NASA and McDonnell Aircraft. They were designed and used to test spacecraft recovery systems, and escape tower and rocket motors. Formal tests were done on test pad at Langley and at Wallops Island using the Little Joe and Big Joe Atlas rockets. Boosters
The Mercury program used three boosters:
Little Joe and a Mercury Boilerplate was used to test the escape tower and abort procedures. Redstone was used for suborbital flights, and Atlas for orbital ones. Starting in October, 1958, Jupiter missiles were also considered as suborbital launch vehicles for the Mercury program, but were cut from the program in July, 1959 due to budget constraints. The Atlas boosters required extra strengthening in order to handle the increased weight of the Mercury spacecraft beyond that of the nuclear warheads they were designed to carry. Little Joe was a solid-propellant booster designed specially for the Mercury program. The Titan missile was also considered for use for later Mercury missions; however, the Mercury program was terminated before these missions were flown. The Titan was used for the Gemini program which followed Mercury. The Mercury program used a Scout booster for a single flight, Mercury-Scout 1, which launched a small satellite intended to evaluate the worldwide Mercury Tracking Network. The rocket was destroyed by the Range Safety Officer after 44 seconds of flight.
Unmanned flightsThe program included 20 robotic launches. Not all of these were intended to reach space and not all were successful in completing their objectives. Four of these flights included non-human primates, starting with the fifth flight (1959) which launched a Rhesus macaque named Sam (after the Air Force's School of Aerospace Medicine). The Mercury program's complete roster of non-human space-farers is given below:
Manned flightsAstronauts
The first Americans to venture into space were drawn from a group of 110 military pilots chosen for their flight test experience and because they met certain physical requirements. NASA announced the selection of seven of these - known as the Mercury Seven - as astronauts on 9 April 1959, though only six of the seven flew Mercury missions, after Slayton was grounded due to a heart condition.
Beginning with Alan Shepard's Freedom 7 flight, the astronauts named their own spacecraft, and all added "7" to the name to acknowledge the teamwork of their fellow astronauts. Piloted Mercury launchesPiloted Mercury Launches.Mercury Flight insigniasFlight patches that purport to be patches from various Mercury missions are available to the public. In reality, these patches were designed by private entrepreneurs long after the Mercury program ended. When genuine flight patches were created by crews in the Gemini program, this caused a public demand for Mercury flight patches, which was filled by these private entrepreneurs. The only patches the Mercury astronauts wore were the NASA logo and a name tag. Each manned Mercury spacecraft, however, was decorated with a flight insignia. These are the genuine Mercury flight insignias. See also
External links
Text from Wikipedia is available under the Creative Commons Attribution/Share-Alike License; additional terms may apply.
Published in July 2009. Click here to read more articles related to aviation and space!
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