The creation of Gemini was a logical follow-up manned project to Mercury. The Mercury Mark II Program, as it was originally named, was envisioned as a maneuverable, expanded Mercury, capable of carrying two men for long periods. Mercury was limited to carrying one man for a relatively short mission, but when Apollo began to be viewed in a serious light it was obvious that leaping from Mercury to Apollo in one step would be too hard a task. The Gemini project was needed to investigate the effects of long flights and when rendezvous and docking was adopted for Apollo, experience there was also required.
In October 1961, a NASA summary of projections for 1963-5 described Mercury Mark II as a two man spacecraft to be launched by a modified Titan II ICBM using Lockheed's Agena B as a rendezvous and docking target. It would be very similar in appearance to Mercury with either ejection seats or an escape tower, and on-board computers for navigation. Its most striking difference from Mercury's design would be on the way its systems were modeled. Whenever a component went wrong in Mercury it often proved a time-consuming job to reach the problem area, whereas Gemini would use a modular system with access doors in the spacecraft's external skin. Consumables and the retromotors would be carried in detachable sections. It would have its chance to show the planned improvements over Mercury's orbital manoeuvrability in 12 flights from May 1963 to March 1965.
The 12-mission Mercury Mark II programm was announced by NASA on December 7, 1961, at t time when NASA had less than one year of manned space flight experience. Then on January 3, 1962 the official name changed to "Gemini".
So the program was started with a considerable degree of confidence. The spacecraft was simply an enlarged, modularised version of Mercury, Titan II seemed capable enough of taking it into orbit and Agena B was well under way. This confidence was soon dispelled when snags in virtually every major area were encountered because Gemini was, in fact, a new program and not merely an extension of its predecessor. Agena was almost dropped altogether because of its poor record, Titan II proved to be a stubborn vehicle and the flight schedule of 1961 proved to be highly optimistic. That schedule had foreseen the last flight occurring in March 1965 - the actual date when men first flew into space aboard Gemini.
The Gemini Crew is Chosen
In April 1962, NASA asked for applicants of test pilot standard to join the Gemini Program and received more than 200 replies which were whittled down to 32 for the final interviews. Nine men were selected and announced on September 17, 1962.
Crews for Gemini would first fly under the command of Mercury astronauts (McDivitt was an exception) and finally take over the command during the second half of Gemini. These men would obviously be destined for senior positions in Apollo and, in fact, all did with the exception of Elliot See, who died and training flight accident and Ed White who died on Pad 34 during an Apollo 1 simulated countdown.
The crew for Gemini 3 was announced on 13 April 1964 as Virgil Grissom and John Young, with a backup crew of Wally Schirra and Tom Stafford
Gemini 1 started off the flight portion of the program, almost a year later than the date set by NASA in October 1961. As the difficulties of the Mercury Mark II program became evident, it was obvious that the launch schedule was going to slip and in April 1963 a new schedule was agreed. The first Gemini had been intended to be a sub-orbital test of the spacecraft under intense re-entry conditions but that mission now became Gemini 2, which was excepted to be the first mission to carry men, and Gemini 1 would actually go into orbit attached to its Titan II's second stage. Gemini 3 became a three orbital test and Gemini 4 would be a seven day mission in January 1965.
Tests on spacecraft I started in July 1963 and was instrumented with pallets afixed in the seat areas to record temperatures, vibrations, etc. The remainder of the spacecraft was ballasted to give it the same characteristics as the final production capsules and four holes were punched in the heatshield to make sure that it did not survive the heat of re-entry.
The launch target for Gemini 1 stood at March 17, 1964 but delays meant that the spacecraft and its boosters were not mated until 5 March. More hold-ups forced the launch date to 8 April, when Gemini-Titan 1 lifted off Pad 19 at one second past 11a.m., local time. The 430 000lbf first stage engines burned out at T+150s and 36mi high and the second stage closed down 13 minutes later to leave the 46 ft long, 11,400lb spacecraft / second stage combination in a 99.6 x 204 miles orbit instead of the planned 109 x 186 miles Three orbits later the mission officially ended as a great success, although the spacecraft flew on for another 61 orbits until it burned up on 12 April.
All of Gemini 1's systems had performed as expected and both the capsule and Titan II had withstood the riggers of orbital flight. The lack of problems meant that planned flight for Gemini 2 could go ahead with more severe tests.
Gemini 1 proved the basic spacecraft and booster structure and Gemini 2 was slated to show that a high altitude was survivable. Spacecraft II and its launcher were mated for the first time on November 5, 1964 and Titan II's first stage engines sprang to life on December 9. A Malfunction Detection System cut them off after little more than a second because the primary hydraulic system had failed and called the secondary system into operation. The system provided the power for steering Titan II's engines and a leak had bled it off pressure.
The aborted launch pushed the date back to January 19, 1965 but this time Gemini 2 flew for 18 minutes before splashing down in the Atlantic, 1900 miles downrange. The beryillium shingles on the exterior of the capsule had reached temperatures of 5500C but largely they had stood up well to the flight.
The Gemini program actually launched two Gemini 2's On August 25, 1965, President Johnson gave his approval for the Manned Orbiting Laboratory (MOL) program to be used by the Air Force. It was to orbit sophisticated manned surveillance and reconnaissance satellites in the late 1960's. The payloads were to take the form of a "Laboratory canister" 41ft long, and 10ft in diameter built by Douglas Aircraft. This second Gemini 2 was launched by a variant of the Titan III, the IIIM, developed specifically for the project. Future MOL missions would see Air Force astronauts would occupy the laboratory for periods of up to 30 days and return to Earth in Air Force owned Gemini spacecraft.
It was decided that during MOL flights, transfering the crew between their Gemini shuttle and the laboratory was via spacewalk by way of a hatch cut into Gemini's heatshield. This put the question of heatshield integrity into considerable doubt. The engineering solution of the hatch had to be verified in an unmanned flight test that subjected the spacecraft and its modified heatshield to the full heat of re-entry.
The second launch of Gemini 2 on November 3, 1966 saw it lift off on a lengthened Titan 3C with a Titan II tank below it to simulate the laboratory. The capsule was targeted on an accelerated ballistic trajectory for re-entry while the 'lab' continued on its way into Earth orbit. The capsule passed its 33 minute flight objective and the heatshield qualification test was a success.
Gemini 3 was the next American space mission since Gordon Cooper's in May 1963. It was to be the third proving flight of the program in preparation for long-duration and rendezvous missions, but even so, it was cut down from an original eighteen orbits to a mere three. The flight would last less than five hours. Mercury had managed up to 28 hours flight time for a single mission, but there were three major differences:
No official name had been approved by NASA, but nick name of Molly Brown stuck Apollo revived the system when it started both the Command Service Module and Lunar. The last official name for a launched vehicle was Faith 7 in May 1963. The next US spacecraft to be named were Gumdrop and Spider of Apollo 9 in March 1969. Apollo 10 used less than serious names - Charlie Brown and Snoopy. After that, all the names reverted to the more serious mold of Mercury.
Just after 9 a.m. local time on March 23, 1965, following a 24 minute hold to fix a leak in their Titan II, the engines ignited and took Gemini 3 towards orbit. It was to the the first orbital experience for both men and Grissom was particularly impressed because the Titan II accelerated some three times faster than his Redstone of 1961. Five and a half minutes after lift off, the stage two engine shut down and Grissom fired the two aft-facing thrusters to enter orbit.
For four and a half hours, the two men sat watching spacecraft systems instruments and used the main thrusters three times to change their orbital path. The first OAMS burn lasted for 75 seconds and the second at T+ 135 minutes shifted their orbital plane by 1/50 degree. A final bun was made shortly before retrofire to decrease their perigee to 52 miles to allow rentry in case the retromotors failed to fire.
The flight plan included sampling some of the food they carriedin to orbit. John Young, who would later fly the first Space Shuttle Mission in 1981, had smuggled aboard a corned-beef sandwich which had been supplied by his back-up commander Wally Schirra. P resentin it to Grissom, he took one bite and then put it away in case the crumbs caused any problems on the environmental or electrical systems.
The four retromotors fired as planned at the end of orbit 3 Gemini 3 sank down towards the Atlantic and its waiting recovery ship Intrepid. The Molly Brown hit the sea 60 miles (97 km) away from the recovery ship and with the delay in recovery, the heat and swell combined to produce an uncomfortable half hour before a helicopter picked them up. They should have waited inside the capsule but Grissom was sick and the impact had been rather severe. On top of that, he had broken his suit's face-plate when the main parachute deployed.
So, the test flight had been judged a complete and Gemini 4 would go ahead for three days. And due to events in Russia, an EVA was introduced to the mission. Ed White would make a space walk.
Following liftoff, after separating from their second stage on June 3, 1965, McDivitt and White tried to get to manually approach within 20ft of it. Using their own judgement, without the benefit of rendezvous radar left them 400ft away. McDivitt had used 42% of their fuel supply and there was still most of the planned four days to go.
The major task of the mission - EVA - was next. White was wearing a 39-layer G4C EVA suit with a gold-covered visor. He also had to deal with three other items. The first was a 25ft communications/electrical tether which would act as a safety rope. He also contended with a Hand-Held Maneuvering Unit (HMMU) and fixed a 35 mm camera on top and finally an emergency chest pack provided him with I 0 minutes of oxygen in case anything went wrong with his umbilical. By the time he was ready to begin the EVA, he had become to tired and the start was postponed until the third revolution.
The cabin atmosphere of 5lb/sq in was bled off into space while the suits were inflated to 3.7lb/sq in and at T+4 hours 18 minutes White opened his hatch with some difficulty and floated out with a heart rate of 150 beats/minute. The HMMU had a very small supply of propellant and after executing two tumbles and spins it was empty and he had to use the tether and spacecraft to maneuver himself. No major problems detected and White managed to float around for 18 minutes without any propellant.
White came back inside 20 minutes after egress but when he turned to close the hatch it took a great deal of effort to latch it shut. The first American EVA, the second would not be untill Cernan in Gemini 9, was over and the astronauts settled down to a drifting mode for two and a half days to conserve propellant. A number of experiments filled out the reaminder of the mission - radiation readings, using a sextant, photographing the Earth and its weather patterns - and on the 20th orbit they sighted an object "with arms sticking out" which was probably a satellite. On 48th orbit the onboard computer failed completely and after number the 62nd the retromotors fired and the crew flew a Mercury- type re-entry without computer assistance. Gemini 4 splashed down some 98 hours after launch and having travelled 1.6 million miles.
Agena, the docking target vehicle was expected for for Gemini 5 but delays in that programme pushed it back to Gemini 6. For Gemini 5, the first long duration flight, the crew of Gordon Cooper and Charles 'Pete' Conrad were named on February 8, 1965. Gemini 4 had been inorbit for four days and no adverse effects on man or machine had been found and as such, an eight day mission for Gemini 5 was a go.
The mission began August 21, 1965 and shortly after liftoff, the mission was in serious trouble. Spacecraft 5 was the first to carry fuel cells in place of batteries. The technology of combining oxygen and hydrogen across a membrane produce power was the backbone for long duration missions. On Gemini 5, pressure in the reservoir tanks fell from 850lb/sq in to 60lb/sq in and stayed there. Had it fallen much further the entire mission would bave been called off, but the crew were able to cut back on power demands by switching off much of their equipment. Unfortunately, that meant the one active experiment had to be dropped even though it had already begun. A Radar Evaluation Pod with radar equipment was released from the rear of the adapter section and the aim was to change orbit and then attempt to rendezvous with it as if it were an Agena docking target. The fuel cell problem terminated the experiment, but Cooper had managed to see their target during the next six orbits.
On August 26 Cooper and Conrad passed the space endurance record originally set in Vostok 5 in June 1963. Later during the flight, on August 27 they began to experience trouble with their thrusters. Two yaw thrusters shut down, followed by four more,shortly before th end of their mission. Because they had no further extensive manoeuvres to make and they were one orbit short of the planned eight days the decision was taken to bring them down. Nevertheless, they still set a space record of 190 hours 56 minutes. Gordon Cooper had become the first man to reach orbit twice even though he had been the last Mercury astronaut to fly. Cooper had also designed a patch with a covered wagon and an "8 days or bust" slogan. The patch was the first to appear on their suits, and this began a trend continuing into the Shuttle program.
The Eight Days in Space mission now held no worries for NASA and the next long duration long duration flight would take place aboard Gemini 7 That record, up to 14 days would clear the hurdle required for a full lunar mission duration. Between Gemini 5 and Gemini 7 Gemini 6 was to carry out one of the most spectacular flights to date - rendezvousing and docking with an Agena in space.
One of the major objectives of Gemini was target aquisition and docking. Gemini 6 was thus a most important mission because its crew would be launched soon after an Agena target, chase after it, rendezvous and then dock. Astronauts Schirra and Stafford had also followed the lead of Cooper and Conrad in designing a mission patch to wear on their suits - this time a Gemini chasing an Agena against a background of stars in a '6' pattern was adopted for their hexagonal patch.
October 25, 1965, the Atlas-Agena stood on Pad 14. Shortly before Atlas launch, Wally Schirra and Tom Stafford entered their craft to begin their own countdown. Near 10 a.m. local time the Atlas engines ignited to produce their 390,000lbf thrust and lift the combination off the pad. The first Atlas climbed straight up for 15 seconds, then pitched down and continued flying until the two outer booster engines cut off at T+131s. The main central engine burned for another 140 seconds before shutting down. Agena then separated from the booster adapter. Two retrorockets on the adapter fired to slow Atlas down, allowing Agena to slide smoothly out on four roller bearings mounted at the forward end. Agena had now reached 118 miles high. Signs of trouble appeared just after separation when Agena seemed to be wobbling. Its horizon sensors and control system should have been establishing the proper attitude for main engine ignition but they do not seem to have been successful. The secondary engines then pressurised and fired their 16lbf thrusters to settle the propellants in the main tanks. Ignition was achieved on time but the burn seems to have gone on a little longer.
As a result of the incorrect burn, NASA control lost contact with the Agena and it was assumed the Agena vehicle went into the Atlantic some 5500 miles short of the required escape velocity. The Air Force reported tracking five pieces but, certainly, nothing was picked up in orbit. The conclusion was that Agena had exploded but the cause has never been definitely identified
With Gemini 6's Agena lost, and Gemini 6 still on the pad, the question was, what should happened next? It would take a long time to bring another Agena up to flight standard - besides, that would take one away from a later Gemini launch At one time, Stafford was going to make an EVA but Schirra vetoed it because he thought they had enough to do with the planned rendezvous and docking.
The only answer seemed to be that Gemini 6 and 7 would fly at the same time. Gemini 7 was to be the long duration mission of the programme and the spacecraft could serve as the target for Gemini 6, although no docking could be attempted. The major problem, though, was with the launch pad. Pad 19 was the only Gemini launch complex available and it took quite a beating during each launching and had to be extensively refurbished. Yet the plan called for Gemini 7 to be fired into orbit first with Gemini 6 leaving nine to ten days later. Nevertheless, NASA decided that it could be done and the dual flight was announced in a press conference of October 28, 1965. Gemini 7 would carry strobe lights and a radar transponder to help Gemini 6 lock on to it.
A planned lauch of a Gemini capsule normally took 40,000 man-hours. As Gemini 6 had been fully checked out, it was expected that Gemini 7 could be placed in orbit and Gemini 6 would follow shortly while 7 was still in orbit. Over October 28-29 Gemini 6 and its launcher were taken down and put into storage, followed by the preperation of Gemini 7 during the next two days. Lauched December 4, Frank Borman and Jim Lovell began a 14 day mission and waied for Gemini 6. During the flight Lovell took off his G5C 16 lb (7 kg) lightweight spacesuit - the first time an American had spent time in space without a spacesuit - and Borman was later allowed to remove his after lengthy discussions on the ground. The suits were specially designed for comfort but, even so, they would have proved very uncomfortable after days in cramped conditions.
Renamed Gemini 6a, shortly the launch of Gemini 7, Schirra and Stafford climbed aboard on December 12, and waited for their turn. As, "Ignition" was called out, the men saw their spacecraft clock ticking away but they felt none of the vibration of a launch. GT-6A was still sitting on gound. They stayed and their booster remained quiet after shutting down. Borman and Lovell had been passing overhead at the time and Borman saw the ignition and shutdown through a telescope.
An automatic sequencer had detected that something was happening out of order. A Titan II connector designed to drop away just after liftoff had fallen off just before and the and had ordered a shutdown.
Again three days later, Schirra and Stafford climbed aboard on the DecemberI5th for a third attempt. Now in a 100 x 162 mile orbit they began the chase Gemini 7. Reaching orbit, they trailed their target by 1226 miles and by the beginning of the second orbit- their lower (and therefore faster) orbit had narrowed the distance to 729 miles. By the second third orbit they had established radar contact. By T+5 hours 47 minutes the two craft were 120ft apart and not moving relative to each other. The first rendezvous had been achieved. For the next 20.4 hours the two craft moved around each other taking photographs and at times came to within 12in.
Gemini 6, splashed down in the Atlantic on December 16th, while Gemini 7 continued on to its 14-day target. Gemini 6 had also been the first flight to make a computer- controlled re-entry. After a flight of 5.7 million miles, 330 hours 35 minutes, Gemini 7 came down December 18, The crew proved to be in good condition despite their record- breaking endurance of weightlessness. Long duration flights had been proven and this opened the door for the first lunar trip which had been planned for 1968.
The end of 1965 finally saw Americans realising that they were ahead of the Soviets in the space race. The next obstical for Gemini which had still to be achieved was docking. The other issue, now a formality, EVA seemed to be no problem.
The Agena launch for the planned docking with Gemini 8 was near-perfect. The main engines ignited and continued and a suitable orbit bad been achieved about 530 seconds after liftoff. During the burn, the attitude control system switched off, control was tranferred to the hydraulic servos on the main engine and the nose fairing separated to expose the docking collar at the forward end. Agena was to coast mode to await Gemini's arrival. Gemini 8 lifted off about 40 minutes later within 1240 miles of Agena. Radar lock-on was achieved at 200 miles and Scott and Armstrong sighted their target at 87 miles Once at a range of 63 miles Gemini's computer was switched from catch-up to rendezvous mode. Rendezvous was considered accomplished when the craft were stabilised 150ft apart. Forty minutes later Armstrong gently approached the docking collar and guided Gemini's nose in to make the first orbital docking.
Once docked, the astronauts could send their own commands to Agena via a band controller down to the right of Scott's right hand seat. An indicator panel with nine lights, two clocks and a synchro-indicator above the docking collar showed the status of Agena's vital functions. Scott's first major order commanded Agena to yaw the two spacecraft through 90" and then switch on the tape recorder. The astronauts soon noticed a roll and, thinking that Agena was at fault, Scott ordered the attitude control system to switch off. The roll continued, thus showing that Gemini itself was at fault, and Armstrong undocked. The roll immediately worsened to about one revolution/second so the orbital thrusters were switched off and the re-entry thrusters powered up to stop the roll. The move was successful but unfortunately ground rules stated that once this reentry system was activated the mission had to end soon afterwards.
Eventhough problems forced an early end to the mission, rendezvous and docking bad been achieved and Agena had behaved perfectly.
The early end to Gemini 8 was a particular blow to Dave Scott as part of his mission he was to test out an EVA system greatly improved since Ed White's efforts in Gemini 9. The considerable difference was in his wearing a backpack. During his two and a half hour EVA be would have moved around to the rear of Gemini's adapter and seated himself in the 92lb Extravehicular Support Package and used that to provide his manoeuvring gun with considerably more propellant than White had had at his disposal. The backpack also provided 79 minutes of oxygen as a supply independent from the spacecraft and allowed him to move out on the end of a 75 ft tether.
Astronauts See and Bassett were told that they would fly Gemini 9 sometime in May 1966. Bassett would make the most ambitious spacewalk planned so far by donning an Astronaut Maneuvering Unit and using it for moving about instead of relying on a hand- held "zip" gun. He would move to Gemini's rear and strap on the 170lb unit with its oxygen supply, radio and hydrogen peroxide thrusters, and test it out on the end of a tether.
Sadly on the 28th all of them climbed aboard T-38 jets to make the journey to McDonnell's plant in St. Louis where the Gemini 9 and 10 spacecraft were being finished. In poor weather, See guided his plane in, he touched the factory roof with a wingtip, bounced off and crashed into a nearby courtyard. Both of Gemini 9’s crewmen were dead.
For the first timeNASA's crew backup system came into play as Stafford and Cernan stepped into their predecessors' shoes. On May 17, 1966, Stafford and Cernan sat aboard Gemini 9 waiting for their Agena target vehicle to be launched from a nearby pad, Agena 5004 took off but three minutes later booster engine number 2 of the Atlas went hard over to one side and another docking target ended up in the Atlantic. Fortunately, McDonnell bad built an Augmented Target Docking Adapter after Gemini 6's Agena had failed and although it had a short stubby body with no engine it did carry an Agena- type docking section.
The ATDA went into an 186 mile orbit on June 1, 1966. Eventhough telemetry showed that its nose fairing had not separated to expose the docking collar, Stafford and Cernan moved on to their own launch. After three attempts failed, the crew had to climb down for a two day wait.
One year after Gemini 4’s flight, Gemini 9 took off and rendezvoused with the ATDA. NCE in vissual range, Stafford flew around it and commented; "We've got a wierd- looking machine here. It looks like an angry alligator...." The explosive bolts had fired but the strap holding the two fairing sections together still held. Continued docking trials would have to wait for Gemini 10.
During Cernan's EVA, he soon began to tire performing even simple tasks. When he tried to put the AMU on he sweated so much that he fogged his visor, and by the time he was actually on the Unit he was so exhausted that he was ordered back inside after 2 hours 27 minutes.
The flight of Gemini 10 would be the most ambitious mission yet. Gemini 10 would rendezvous and dock with Agena, fire its engine for the first time in a manned flight and finally rendezvous with Gemini 7's Agena. Collins would also make an EVA and collect samples from the dead vehicle.
Launched on July 10, 1966, they ad successfully docked and remained attached to their Agena for almost 39 hours. While attached to their Agena, they made six burns to transfer to Gemini 8's Agena orbit. They undocked from their Agena, rendezvoused with their orbital partner and Collins left his right-hand seat to go over to the old Agena on the end of his 50ft tether. He collected a micrometeorite experiment but, like his camera, be later lost it. A third and final EVA had been used to take short stand-up photographs and to throw the now-unwanted EVA equipment out.
The problems of rendezvous seemd to have been beaten, but he demands of a Lunar Module taking off from the Moon would have to rendezvous in its very first revolution - a much more demanding method than Gemini had demonstrated.The crew of Gemini 11 were named in March 1966 as Conrad and Gordon and their primary objective would be to achieve early rendezvous and docking with Agena.
Launched September 12, 1966, Conrad and Gordon completed rendezvous in one hour and 25 minutes. Nine minutes later they were docked. Gordon emerged from Gemini 11 during day two in orbit and his main job was to attach a 100ft tether from the Agena on to the docking bar at the front of their spacecraft. The EVA was called off early after lasting only 33 minutes, but he had managed to attach the tether. Again the EVA bad been disappointing, so for Gemini 12 much simpler tasks would be scheduled and, certainly, the Air Force's AMU would be dropped.
Conrad undocked the two craft and was able to make them rotate at 55 degrees/minute to produce a small amount of artificial gravity. The only method of detecting the gravity was by the astronauts watching objects drifting towards the heatshield end of the cabin but it was an interesting engineering exercise in weightless dynamics.
Gemini 11 became the first manned spacecraft to reach an apogee height of 850 miles after firing the Agena's main engine for 26 seconds. Two orbits later they returned to their original orbit. iginited it again to bring their apogee back down.
Lovell and Aldrin were certain to get the Gemini 12 flight because they had become Gemini 9 backups after the deaths of See and Bassett, and Cooper and Cernan were named as their backups. Being backups for any of the last three flights was not exactly welcomed with excitement by the astronauts because they would never fly in Gemini. Backups were rotated into the primary flight crew three missions later. There were no flights left, and Apollo was the next target. The first Apollo crews bad been named as early as March 1966 so these later Geminis were preventing the backups from moving on to the newer training. There had been hopes of flying Gemini 12 and Apollo 1 together but delays in Apollo's schedule precluded such a mission. It left the flight of Gemini 12 looking very much like Gemini 11 because there was so little left for Gemini to achieve.
The launch of Gemini 12 was November 1, 1966 and telemetry had shown thrust problems, the main engines had wavered but the it was not server enough to abort. Once in orbit the radar readings stopped while approaching Agena, leaving Aldrin to use a set of his own charts to complete the job. The main engine was then to have been used to raise their apogee to 450 miles but and ground controllers decided not to risk an ignition considering the thrust iproblems at launch. The crew spent their time photographing a solar eclipse instead.
Apart from two stand-up EVA'S, Aldrin spent most of his time on another tether attachment and working at a 30 in (76 cm) square board in a series of work evaluation tasks. There were nuts and bolts to loosen and tighten, and electrical and fluidic connectors to experiment with. The unknown of working in space was at issue, but the experiences of Geminis 9 and 11 had shown that even the simplest of ground jobs could prove to be difficult in space. For that reason, Aldrin was one of the first astronauts to spend a large part of his EVA training under water to simulate weightlessness. His total EVA time came to five and a half hours and proved that everything had to be done slowly and deliberately, with considerable planning beforehand.
The major goals for Gemini had been accomplished: rendezvous and docking, Apollo mission durations and EVA operations and had orbited 16 men to do it. Apon the completion of Mercury, NASA had accumulated 54 man-hours in space, but with Gemini they had a total of more than 1994 hours. Of the 16 who orbited in Gemini, six would latter walk on the surface of the Moon. Another five reached lunar space.
The conclusion of Gemini was marked by an swelling in NASA's confidence. A successful programme plus three Apollo-Saturn 1B test flights had been completed by the end of 1966. Apollo was expected to reach for the Moon in February 1967. January would see a dark cloud fall as Gus Grissom, Ed White and Roger Chaffee lost their lives. NASA would be rounded.
Gemini was divided into three main sections: capsule, re-entry and equipment.In contrasr, Mercury was in one complete unit.
The Titan I was a two-stage ICBM and was ordered into development in 1957 as a backup to the earlier Atlas missile, entering service in 1962. It did not last long, however, because its big brother Titan II was fully deployed by 1965 in underground sites across the United States. Titan II still holds the record for being the West's largest missile at 103ft long and 10ft in diameter. Its size made it an obvious choice for the follow-up launcher spacecraft to Mercury. Its thrust was 2.5 times that of Atlas - 430,000lb first stage, 100,000lb second stage but just as important was the fact that its propellants were not cryogenic.
Redstone and Atlas had both carried liquid oxigen as an oxidiser and the mechanics of low temperature engineering meant that such a rocket has to be launched as soon as possible after fuelling. Otherwise it begins to deteriorate. Titan II was designed to carry nitrogen tetroxide (oxidiser) and Hydrazine 50 (fuel). It could then stand ready in its silo ready for launching at a few minutes' notice. A second advantage was that he propellants ignited on contact (hypergolic) thus simplifying the engine design.
The propellant types greatly interested NASA's planners. Mercury was using an escape tower to blow the capsule away in case of Atlas failure. Apollo followed a similar path. Gemini, however, could manage with ejection seats because of its boosters' safer propellants. That fact alone weighed heavily in Titan's favour. Besides, no other launcher of the time was anywhere near as suitable. Titan II would be it and Martin were notified in October 1961, before Gemini was formally announced by NASA the following December.
Unfortunately, Titan II development trod the same route as the rest of Gemini. It started out as an apparently simple exercise in modifying equipment for the programme and then discovered there were large and expensive problems to be overcome. Neither did it help matters that Titan was primarily being developed as a missile, and nothing could be allowed to hold up that programme.
Titan II was launched on its first full-scale test on March 16, 1962. It travelled 5000 miles out over the Atlantic in a flight that pleased its military masters but put a scowl on the collective face of NASA. The same problem that would eventually cause problems in building the Saturn 5 had reared its head - severe oscillations along the length of the rocket had built up as some source of vibration caused the whole vehicle to oscillate like a plucked wire. This would have subjected an astronaut to a varying acceleration of about 2.5 g eleven times a second and probably caused him some difficulty in reading his instruments or reacting to an emergency. Clearly, NASA could not tolerate the situation so they requested the Air Force to reduce it to an acceptable level of 0.25g. That was not too easy because it would require money and involve delays and Air Force resistance brought in the question of using Titan II for Gemini at all. It was not until the 21st development flight, on November 1, 1963, that the "pogo" effect fell within the 0.25g limit. By then Titan was carrying equipment to reduce vibration caused by propellants flowing through pipes on their way to the engines. This was also the second flight to carry Gemini's Malfunction Detection System, to detect any situation dangerous to the men on board and signal emergency action.
By then, both stages had arrived at Pad 19 for Gemini I and on January 31, 1964 they were fired side-by-side and then mated to form the complete booster. Despite the drawn- out pogo problems and difficulties with the stage 2 engines, Titan II was eventually ready to take America's first two-man capsule into space.
The Agena target vehicle was launched by an Atlas booster, and Agena, a liquid propellant upper stage was first ordered in 1956 for use in a reaconnaissance satellite system launched by Atlas. NASA had approached Lockheed, Agena's builders, in August 1961 to investigate the possibility of using their Agena B vehicle as a target and when Gemini was announced it was expected that Geminis 5, 7, 9 and IO would be rendezvous and docking missions. Agena B could orbit 21,00lb but each one had to be built specially for each mission, whereas Agena D was a standard stage with modules for individual missions. NASA switched to this new version in July 1962. The Gemini Agena Target Vehicle (GATV) could be divided into seven sections:
The docking adapter and cone were mounted on the auxiliary equipment rack where satellites were usually positioned. Basically, the adapter was a 24.5in long cylinder carrying equipment vital to rendezvous and docking, while the docking cone was a truncated cone - two end diameters of 58in and 37in - with a V-shaped notchi to accept Gemini's nose and docking bar. The cone was held out during rendezvous manoeuvres and the shock of docking was absorbed by a hydraulic system. Latches locked into depressions in Gemini's nose and switches activated by the mating started a motor to pull the cone into the adapter. This created a rigid connection and effectively transformed the two vehicles into one, with the astronauts' commands going through a hard connection in Gemini's nose.
The adapter carried other items for rendezvous. An Lband antenna was used to recieve signals for the radar transponder so that the astronauts could detect Agena with their instruments before they could find it visually. Command signals - for example, for a small engine burn - also went through this antenna for decoding and routing to the rest of Agena.
Modifying and man-rating the engine proved to be one of the most difficult tasks in converting Agena D into the Gemini Agena Target Vehicle. The new Bell 8247 version was basically the same as the standard 8096 model. Hypergolic propellants were pump- fed from their integral tanks into the single-chamber engine and ignited on contact. The chamber, extended by a titanium nozzle, was cooled by oxidizer before it entered the chamber, allowing a total burn time of 240 seconds with an average thrust of 16,000lb. The two propellants were separated in their tanks by a diaphragm which changed shape with pressure as the tanks emptied. This was fine, but GATV had to be able to reignite at least five times in orbit and the previous design simply could not do this. The 8096 used 'starter cans' - small solid propellant charges - to provide the energy for a turbopump to send the propellants into the chamber. The number of starts was therefore limited by the number of starter cans carried so, to reach the magic number of five, the designers had to scrap that system and replace it with one relying on liquid-propellant start-ups. Two small stainless steel tanks carried small quantities of the propellants pressurised by nitrogen gas behind bellows. When a burn was ordered, the bellows pushed the start tanks' contents into a gas generator where the ignited propellants provided the gas to drive the main propellant pumps. A simple system, but one which would produce delays later on. Its main advantage was that the number of restarts was limited by the nitrogen and propellants supply - one ground test achieved 15 burns.
The fuel pump also provided hydraulic power to move two servommotors connected to the engine nozzle for control during main burns. NASA approved the new system in September 1962 but the engine had to go through extensive ground tests before it could be used in man-carrying missions. These tests were not particularly hurried at first because Agena was not scheduled for use until Gemini 5 (in October 1962 this was scheduled for August or September 1964), but numerous small problems soon ate away the previously ample leeway. Bell's own tests finished in March 1963 and an engine was then taken to the Air Force's Arnold Engineering Development Center in Tennessee for a long series of test firings. On July 15 a firing ended catastrophically when a valve regulating the flow of propellant to the gas generator stuck open and allowed the turbine to go out of control. The test stand was destroyed and forced subsequent firings to be made at Bell's own site in Buffalo. The valve was redesigned and a sensor added to watch for turbine overspeed, all at a cost of months on the test schedule. It was February 1964 before testing could be restarted, and by this time a radar evaluation pod previously scheduled for Geminis 3 and 4 had been slipped to Gemini 5, thus forcing the first Agena to Gemini 6.
