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Mercury Program (1960-1963) Early Unmanned NASA Craft | Mercury |Gemini | Apollo | Clementine | Lunar Prospector | Hubble Space Telescope
Overview The Mercury program - both Atlas and Redstone (different launch vehicles) - is presented here in detail. Probably the most famous of all U.S. missions bar Apollo, this was the first mission to send Americans into space. Mercury Atlas (1960-63) Mercury Atlas 1
The point of this craft was a test, with the primary mission goals being to check the integrity of the spacecraft structure and afterbody shingles for a reentry associated with a critical abort and to evaluate the open-loop performance of the Atlas abort-sensing instrumentation system. The spacecraft was not equipped with an escape system and no test subject was on-board. Lift-off and flight of the vehicle were nominal until 57.6 seconds into the flight. At that time, a shock was registered by both the launch vehicle and spacecraft axial accelerometers. When the shock occurred, the vehicle was at approximately 9.1 km altitude and 3.4 km down range. All Atlas telemetry was lost at 59 seconds after launch, the time at which final missile destruction was believed to have occurred. Spacecraft telemetry, however, continued to be transmitted until 202 seconds. The spacecraft was destroyed upon impact in the Atlantic Ocean, about 8 km down range. Most of the spacecraft, engines, and the liquid oxygen vent valve were recovered later from the ocean floor. None of the primary flight objectives were achieved. Mercury Atlas 2
Mercury Atlas 2 was a sub-orbital test vehicle that was launched to check the maximum heating and its effects during the worst reentry design conditions. Its goals were to:
The trajectory was designed to provide the most severe reentry heating conditions which could be encountered during an emergency abort during an orbital flight attempt. Prior to launch, the reentry heating rate of the trajectory was estimated to be 30% higher than a normal reentry and temperatures were predicted to be about 25% higher at certain locations on the afterbody of the spacecraft. In addition, the deceleration g-load was calculated to be about twice that expected for a normal reentry from orbit. The flight closely matched the desired trajectory, attaining a maximum velocity of just over 21,000 km/hour and an altitude of about 185 km. The spacecraft came down in the Atlantic Ocean some 2,300 km down range. Inspection of the spacecraft aboard the recovery ship indicated that the test objectives had been met and the structure and heat protection elements were in excellent condition. Further evaluation found that the spacecraft afterbody temperatures were somewhat lower than originally anticipated. Mercury Atlas 3
Mercury Atlas 3 was to be an orbital flight test of the Mercury capsule with a mechanical astronaut. After lift-off, the launch vehicle failed to roll to a 70° heading and to pitch over into the proper trajectory. The abort-sensing system activated the escape rockets prior to the launch vehicle's destruction by the range safety officer, approximately 40 sec into the flight. At that time the vehicle had achieved an altitude of about 5 km. The capsule then coasted up to 7 km, deployed its parachutes, and landed in the Atlantic Ocean about 1.8 km north of the launch pad. The capsule was recovered and was found to have incurred only superficial damage. It was subsequently shipped back to the manufacturer for refitting. The refitted capsule was reflown on Mercury Atlas 4. Mercury Atlas 4
This flight was an orbital test of the Mercury Tracking Network and the first successful orbital flight test of the Mercury program (previous flights were sub-orbital). The payload consisted of a pilot simulator (to test the environmental controls), two voice tapes (to check the tracking network), a life support system, three cameras, and instrumentation to monitor levels of noise, vibration and radiation. It demonstrated the ability of the Atlas rocket to lift the Mercury capsule into orbit, of the capsule and its systems to operate completely autonomously, and succeeded in obtaining pictures of Earth. It completed one orbit prior to returning to Earth. The capsule was recovered 161 miles east of Bermuda 82 minutes after splash-down by the destroyer U.S.S. Decatur. Mercury Atlas 5
This was the second and final orbital qualification flight of the Mercury systems prior to manned orbital flight. On-board was a 17 kg, five-year-old chimpanzee named Enos. Enos performed various psychomotor activities during the flight and was found to be in excellent physical condition following splashdown. A metal chip in a fuel supply line caused a problem with the attitude control system, leading to the failure of a roll reaction jet. This resulted in the spacecraft drifting 30° from nominal attitude at which point the automatic controls would bring the spacecraft back to nominal attitude. This entire process caused an extra pound of fuel to be consumed each orbit. In addition to this, a problem developed in an inverter to the electrical system, resulting in an temperature problem in the capsule. Both of these difficulties could have been corrected with a human pilot on-board, but ground control decided to shorten the mission and bring it down after the second orbit. (Three orbits had been planned.) The spacecraft was recovered 410 km southeast of Bermuda by the U.S.S. Stormes 1 hour, 15 minutes following splashdown. The spacecraft was hauled aboard the ship with its lanyard, cracking the window. Enos died at Holloman Air Force Base, New Mexico, one year (November 4, 1962) following his historic flight. He had been under observation, day and night, for two months prior to his death with a case of shigella dysentary, a type resistant to antibiotics. His illness and death were unrelated to his orbital flight. Mercury Atlas 6
Mercury Atlas 6 was the first orbital flight of an American rocket with a human on board. The objectives of of this mission were to:
Originally scheduled for launch in late January, the mission was twice postponed, once (January 27) for weather and once (January 30) for a fuel leak in the Atlas rocket. Even on the day it was successfully launched, there were four holds placed on the countdown due to various problems. Finally all the problems were resolved and Friendship 7 was launched as an estimated 60 million people witnessed it via live television broadcast. During the flight, two major problems were encountered. First, a yaw attitude control jet became clogged, forcing the pilot to abandon use of the automatic control system in favor of the manual-electrical fly-by-wire and manual-mechanical systems. Second, a signal in the heat shield circuit indicated that the clamp which held the shield in place had been prematurely released. This latter problem resulted in the retrorocket pack not being jettisoned prior to reentry, but retained as a safety measure to hold the heat shield in place in the event it had loosened. This signal was later determined to be false and attributed to a faulty switch. Prior to the flight there had been concerns regarding the physiological effects of prolonged weightlessness and exposure to radiation on the astronauts. Glenn reported that the zero g conditions were "very handy" in performing his tasks and that he felt exhilarated during his 4.5 hour weightless period. It was later ascertained by physicians that Glenn had also received less than half of the expected radiation dosage during his flight, proving that the spacecraft walls had provided excellent shielding. A curious event which occurred during Glenn's flight was his report of "fire flies" when he entered the sunrise portion of an orbit. Although this phenomenon was a mystery at the time, it was resolved during the flight of Mercury Atlas 7 when Scott Carpenter accidentally tapped the wall of the spacecraft with his hand, releasing many of the so-called "fire flies". The source was determined to be frost from the reaction control jets. During the flight, the spacecraft attained a maximum velocity in excess of 28,000 km/hour and an altitude of about 260 km. The capsule reentered after completing three orbits, coming down in the Atlantic Ocean some 1,300 km southeast of Bermuda. After splashdown, the Mercury capsule with its pilot still inside were picked up after 21 minutes in the water and returned by helicopter to the destroyer U.S.S. Noa. Mercury Atlas 7
Mercury Atlas 7 was the second orbital flight of an American rocket with a human on board. The pilot was originally planned to be Donald K. Slayton but was changed to be M. Scott Carpenter after a medical examination of Slayton revealed an irregularity in his heartbeat. The objectives of the mission were similar to:
Originally scheduled for launch in early May, the mission was postponed three times, once (May 7) due to checkout problems with the Atlas launch vehicle, once (May 17) to perform modifications to the altitude-sensing instrumentation in the parachute-deployment system, and finally (May 19) due to detected irregularities in the temperature control device on a heater in the Atlas flight control system. During the flight, only one critical component malfunction was encountered. A random failure of the circuitry associated with the pitch horizon scanner, which provided a reference point to the attitude gyros, occurred. During the flight there was also concern about excessive fuel usage resulting from extensive use of the high-thrust controls and the inadvertent use of two control systems simultaneously. To compensate for this, the spacecraft was allowed to drift in attitude for an additional 77 minutes beyond the time already built into the flight plan. Two experiments were on-board MA-7. One was a balloon, deployed and inflated to measure drag and provide visibility data. The other was a device to study the behavior of liquid in a weightless state. The balloon experiment failed when it did not properly inflate on deployment, but the liquid experiment behaved as anticipated. During the flight, the spacecraft attained a maximum velocity in excess of 28,000 km/hour and an altitude of about 267 km. The capsule reentered after completing three orbits, coming down in the Atlantic Ocean some 200 km northeast of Puerto Rico at 19° 29 minutes N, 64° 05 minutes W, about 400 km beyond the planned impact point. The overshoot was traced to a 25° yaw error at the time the retrograde rockets were fired. Retrofire was also about 3 sec late, accounting for about 20 miles of the overshoot. After the firing of the retrorockets, computers at NASA's Goddard Space Flight Center successfully predicted the area of splashdown and naval ships and aircraft were deployed to the new location. An Air Rescue Service SA-16 amphibian aircraft was the first to establish visual contact with the spacecraft some 39 minutes after splashdown with the U.S.S. Farragut being the first ship to reach the area. Carpenter was picked up after 2 hours and 59 minutes in the water and returned by helicopter to the aircraft carrier U.S.S. Intrepid. He experienced no adverse physical or biomedical effects due to the flight. The Mercury capsule was not retrieved until about 6 hours later when special equipment on-board the U.S.S. John R. Pierce arrived to retrieve it. Mercury Atlas 8
Mercury Atlas 8 was the third manned orbital flight of the Mercury program. The objectives of MA-8 were to:
Originally scheduled for launch in early September, the mission was postponed twice to provide additional time for flight preparation. The launch was the first to be relayed live (via the Telstar satellite) to television audiences in Western Europe. Two major modifications were made to the spacecraft to eliminate difficulties encountered during the previous two flights. The first was an alteration of the reaction control system to disarm the high-thrust jets and to permit use of the low-thrust jets only in manual operation (to conserve fuel). The second was the addition of two high-frequency antennas (mounted on the retro package) to assist and maintain spacecraft and ground communications throughout the flight. Astronaut Schirra called his mission a "textbook flight", the only difficulty having been attaining the correct temperature adjustment on his pressure suit. A considerable amount of attitude drift time was built into the MA-8 timeline to study fuel conservation methods. This included 18 minutes during the third orbit and 118 minutes during the fourth and fifth orbits. The result was that 78% of the fuel supply remaining in both the automatic and manual tanks at the start of reentry. The pilot was therefore able to use the automatic mode for reentry. Four experiments were conducted as a part of the MA-8 flight. One was a light visibility experiment, similar to those conducted on the two previous missions. The second was a nuclear radiation experiment, in which radiation-sensitive emulsions were used to study the flux and composition of galactic cosmic rays. A third was an investigation in which the ablation of various materials due to heating during reentry was measured. The final experiment used a 70 mm Hasselblad camera with various filters to gather imagery for assembling a catalog of Earth photography for comparison with similar images obtained by other satellite programs. During the flight, the spacecraft attained a maximum velocity slightly higher than previous flights (28,092 km/hour) and an altitude of about 281 km. The capsule reentered after completing six orbits, landing 440 km northeast of Midway Island in the Pacific Ocean, about 8.2 km from the prime recovery ship, U.S.S. Kearsarge. Mercury Atlas 9
Mercury Atlas 9 was the fourth and final manned orbital flight of the Mercury program. The objectives were to:
Originally scheduled for launch in April, the mission was delayed twice. The first delay (February) was due to a decision to rewire the Mercury-Atlas flight control system. The second (May 14) occurred on the scheduled day of launch when a problem developed with the fuel pump in the diesel engine used to retract the gantry from the launch vehicle. This resulted in a delay of roughly 129 minutes after countdown had already reached T-60 minutes. Subsequent to the repairs on the gantry engine, however, a separate problem, the failure of a computer converter at the Bermuda tracking station, forced the cancellation of the launch at T-13 minutes. The launch was rescheduled for the following day (May 15). The countdown then proceeded without a hitch until T-11 minutes and 30 seconds when a problem developed in the guidance equipment and a brief hold was called until it was resolved. Another hold was called at the T-19 second mark to ascertain whether the systems had gone into automatic sequencing as planned. The liftoff ended up being excellent, however, with flight sequencing (booster engine cut-off, escape tower jettison, sustainer engine cut-off) operating perfectly and the spacecraft being inserted into orbit at a velocity described as being "almost unbelievably correct." A number of alterations were made to the MA-9 spacecraft, most of them due to the extended duration of the flight. Among these were the increased capacity of several life support system components (additional oxygen and water, increased urine and condensate capacity, etc.), a larger capacity fuel tank, and larger capacity batteries (two 3,000 W-hour vs. two 1,500 W-hour). Deleted from the flight, due to weight considerations, were several backup or other components deemed unnecessary. These included the periscope, the backup UHF voice transmitter, the rate control system, and the backup telemetry transmitter. Also installed was a slow-scan television unit for in-flight evaluation in monitoring the astronaut and instruments. A number of improvements were also made to the pressure suit worn by Cooper. These included a mechanical seal for the helmet, new gloves with an improved inner liner and link netting between the inner and outer fabrics at the wrist, and a torso section redesigned for increased mobility. The boots were also now integrated with the suit to provide increased comfort for the longer mission, to reduce weight, and to decrease the time required to don the suit. Another change moved the life vest from the center of the chest to a pocket on the lower left leg, thus reducing the bulkiness from the suit and, again, providing more comfort during the flight. A number of in-flight experiments were planned for and carried out during the MA-9 flight. They included two visual acquisition and perception studies, several photographic studies, two radiation packages, a tethered balloon experiment, a study of the behavior of fluids in zero gravity, and a micrometeorite study. A flashing beacon was deployed on the third orbit and Cooper reported that he was able to see it on the night side of the fourth orbit. Two attempts were made to deploy the balloon, both of which failed. On the seventeenth orbit Cooper photographed the zodiacal light. Cooper also became the first to sleep in orbit. In addition to a planned rest period beginning the tenth orbit, he also drifted off to sleep during the second orbit for a short period. (In fact, Cooper had also reported taking a short nap during the countdown phase.) During the planned sleep period Cooper's suit temperature rose and he roused, reset the temperature control, and resumed his rest. The first malfunction of concern on MA-9 occurred during the nineteenth orbit when the 0.05 g light came on. The light, sensitive to changes in gravity, normally lit during reentry. The pilot proceeded to check out the necessary attitude information and all telemetry indicated the spacecraft was in the correct orbit. It was therefore concluded that the light was erroneous. However, because of this, it was determined that the potential existed that not all of the automatic system for reentry would function. The pilot was advised to use the manual mode for reentry, becoming the first astronaut to use this method exclusively. During the flight, the spacecraft attained a maximum velocity of 28,075 km/hour and an altitude of 265 km. The capsule reentered under the manual control of the pilot after completing 22 orbits, landing about 130 km southeast of Midway Island in the Pacific Ocean, about 6.4 km from the prime recovery ship, U.S.S. Kearsarge. Mercury Redstone (1960-1961) Mercury Redstone 1
Mercury Redstone 1 was the first scheduled flight of the Mercury capsule mated to the Redstone booster. The objectives of MR-1 were to:
Launch of MR-1 was attempted on November 21, 1960, but after rising a few inches from the pad, the engines cut off and the rocket settled vertically back on the launcher. The termination of thrust resulted in the escape tower being jettisoned, but the spacecraft did not separate from the booster due to g-load sensing requirements not being met. However, because the barostats properly sensed the altitude as being less than 10,000 feet, the drogue, main, and reserve parachutes were released in the proper sequence. The failure of MR-1 was determined to be due to the power and control connectors not disconnecting simultaneously. The power plug disconnected 29 ms prior to the control plug, permitting part of a 3 amp current (which normally would have returned to ground via the power plug) to pass through the relay for "normal cut-off" and its ground diode. This proved the need for all electrical connections to be grounded prior to launch. A ground strap was added for subsequent launches. The Mercury capsule was refurbished and mated to a new launch vehicle to be launched as Mercury Redstone 1A. Mercury Redstone 1A
Mercury Redstone 1A was a repeat of the earlier Mercury Redstone 1 flight which had failed. The objectives of MR-1A were identical. With the exception that the launch vehicle cut-off velocity was slightly higher (about 80 m/s) than normal, all flight sequences were satisfactory. All measured abort parameters remained below the limits and the abort system functioned as expected. Tower separation, spacecraft separation, spacecraft turnaround, retrofire, retropackage jettison, and landing system operation occurred or were controlled as planned. The spacecraft achieved a maximum altitude of 210 km and a maximum velocity of just under 8,000 km/hour. The spacecraft traveled downrange of the launch facility 375 km. 15 minutes after landing in the Atlantic Ocean, the recovery helicopter picked up the spacecraft. Mercury Redstone 2
Mercury Redstone 2 was the third attempted flight of the Mercury/Redstone launch configuration and the first to include a living organism, a 17 kg chimpanzee named Ham (in honor of Holloman Aerospace Medical Center). The objectives of MR-2 were to:
During the flight, the thrust controller ran above nominal performance, depleting the propellant 0.5 sec before deactivation of the abort pressure sensor. The abort system detected the early shutdown and aborted the spacecraft. The higher-than-normal cut-off velocity coupled with the thrust of the escape engine resulted in the capsule landing well beyond the recovery area. The abort properly signaled the requisite Mayday message to the recovery forces, putting them in motion for a computed rendezvous point further downrange. Because of the over-performance of the launch vehicle and the added velocity of the escape engine, MR-2 achieved a velocity of about 9,400 km/hour (as opposed to the intended 7,000 km/hour) and an altitude of 250 km (rather than 185 km). Ham's trip took 2 minutes and 24 seconds longer than intended (16 minutes and 39 seconds total flight time) and went 670 km downrange (205 km further than planned). His peak g-load during reentry was 14.7, almost 3 g more than planned. Problems also occurred with regard to the cabin pressure when, just prior to the abort, at 2 minutes and 18 seconds into the flight, it dropped from 5.5 psi to 1 psi. The problem was ultimately traced to the air inlet snorkel valve. Vibrations had loosened the pin which held the valve closed, thus allowing the valve to open, an event which was normal only after the main parachute was deployed. Ham did not suffer from this sudden depressurization of the cabin. However, the open valve contributed to problems after splashdown. Ham's performance during the flight went well, with reaction times for his required tasks of lever pulling comparable to his pre-flight testing despite his vehicle's performance problems. When MR-2 splashed down, no ships had yet reached the vicinity, having landed some 100 km from the nearest recovery ship, the destroyer U.S.S. Ellison. A P2V search plane located the capsule about 27 minutes after splashdown. Helicopters were dispatched from the U.S.S. Donner as at least two additional hours were still required for the Ellison to arrive. Although when the search plane had located the capsule it was floating upright, by the time the helicopters arrived they found MR-2 on its side and taking on water. It was determined that the beryllium heat shield had skipped on the water on impact, bouncing against the capsule bottom and puncturing two holes in the titanium pressure bulkhead. In addition, the plastic landing bag had worn badly, resulting in the heat shield being torn free. Water entering the cabin became worse when the capsule capsized, allowing more water to enter via the open cabin pressure valve. When the helicopter latched onto the capsule, the pilot estimated an extra load of nearly 800 pounds due to the sea water. Ham was returned safely to the Donner, apparently no worse for the wear. Sometime later, after his flight, he was shown the spacecraft and it was visually apparent he had no further interest in cooperating with the program. Mercury Redstone BD (Booster Development)
The Mercury Redstone Booster Development flight was the last unmanned Mercury Redstone. The purpose of the flight test was to provide a final check of the launch-vehicle system prior to the manned suborbital flights. The objective was to investigate corrections to booster problems resulting during the MR-2 flight. These problems included (1) structural feedback to the control system producing vane "chatter"; (2) instrument compartment vibration; and (3) thrust control malfunction. The launch vehicle achieved a maximum velocity of about 8,200 km/hour and an altitude of 180 km. The capsule traveled nearly 500 km down range. All test objectives of the flight were met. As a result, the launch vehicle was approved for the planned manned suborbital flights. Mercury Redstone 3
Mercury Redstone 3 was the first flight of an American rocket with a human on board, occurring twenty-three days after Yuri Gagarin's orbital flight of Vostok 1. The objectives of MR-3 were to:
The Redstone booster performed well, although there were some vibrations. After separation, Shepard exercised manual control of the spacecraft in both the "fly-by-wire" and manual proportional modes. The attitude control system operated nominally, with few thruster fuel leaks. Re-entry and landing were accomplished without any difficulty. The Mercury capsule lacked a window through which Shepard could view his surroundings, but a periscope allowed him views of the outside during the pre-launch and weightless phases of the mission. During the flight, the spacecraft attained a maximum velocity of 8,200 km/hour and an altitude of 186.4 km. The capsule landed 483 km downrange from Cape Canaveral, at 75° 53 minutes W longitude, 27° 13.7 minutes N latitude in the Atlantic Ocean. Shepard experienced a maximum g-force of 6 during the booster acceleration phase of the mission and slightly less than 12 on re-entry. After splashdown, the Mercury capsule and its pilot were returned by helicopter to the aircraft carrier U.S.S. Lake Champlain. Just three weeks following this first successful manned mission, President Kennedy addressed Congress and set the nation's goal to send a man successfully to the moon and back. Mercury Redstone 4
Mercury Redstone 4 was the second flight of an American rocket with a human on board and the last suborbital manned flight. The objectives of MR-4 were to:
From lift-off to re-entry, operational sequences were similar to those of the first manned suborbital flight and Grissom's flight experience was similar to Shepard's in that there was a five minute period of weightlessness. As with Shepard, no ill effects resulting from this condition were reported. Control tests of spacecraft attitude in manual mode were also successfully completed and demonstrated their ease of use. The main configuration differences from the MR-3 spacecraft was the addition of a large viewing window and an explosively actuated side hatch. During the flight, the spacecraft attained a maximum velocity of 8,270 km/hour and an altitude of 189 km. The capsule landed 483 km down range from Cape Canaveral. After splash-down, the explosive hatch activated prematurely while Grissom awaited helicopter pickup. Grissom exited the capsule immediately and remained in the water while a helicopter attempted to lift the rapidly sinking spacecraft. The attempt to raise the spacecraft failed and Grissom was lifted to another helicopter after spending 3-4 minutes in the water and transported to the aircraft carrier U.S.S. Randolph. Despite the failure of the explosive hatch to properly function and the loss of the spacecraft, MR-4 was deemed a successful mission. Subsequent investigation into the premature firing of the explosive egress hatch resulted in more testing, but no premature firings occurred. A mechanical hatch was designed to replace the explosive hatch, but due to weight constraints was never implemented. The incident resulted in a change of procedures which required the firing safety pin to remain in place until after the helicopter hook was attached and tension applied to the recovery cable. Liberty Bell 7 was finally raised from its resting place on the bottom of the Atlantic Ocean, 4.8 km below the surface and 830 km northwest of Grand Grand Turk Island, in 1999 after a number of expeditions. Two expeditions to the area, in 1992 and 1993, were unsuccessful in locating the capsule. The next expedition succeeded in locating the capsule on May 2, 1999, but the cable which linked the surface ship to the submersible (which would have towed the capsule to the surface) broke, resulting in the loss of the submersible and temporarily dashing the hopes of those who intended to retrieve a piece of history. A final expedition, to recover both the submersible and the capsule, succeeded on July 20, 1999, in raising the capsule to the surface. Still attached to the capsule was the recovery line from the helicopter which tried to save it from going under in 1961. Also among the artifacts found inside were some of Grissom's gear and some Mercury dimes which had been taken into space as souvenirs. 
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