More highjinks with Conrad. First orbit docking with Agena, followed by boost up to record 800 km orbit, providing first manned views of earth as sphere. Tether attached by Gordon to Agena in spacewalk and after a lot of effort tethered spacecraft put into slow rotation, creating first artificial microgravity.
The primary objective of the Gemini XI mission was to rendezvous with the Gemini Agena target vehicle (GATV) during the first revolution and dock. Five maneuvers completed the spacecraft/GATV rendezvous at 1 hour 25 minutes ground elapsed time, and the two vehicles docked nine minutes later. Secondary objectives included docking practice, extravehicular activity (EVA), 11 experiments, docked maneuvers, a tethered vehicle test, demonstrating automatic reentry, and parking the GATV. All objectives were achieved except one experiment - evaluation of the minimum reaction power tool - which was not performed because umbilical EVA was terminated prematurely. Umbilical EVA began at 24 hours 2 minutes ground elapsed time and ended 33 minutes later. Gordon became fatigued while attaching the tether from the GATV to the spacecraft docking bar. An hour later the hatch was opened to jettison equipment no longer required. At 40 hours 30 minutes after liftoff, the GATV primary propulsion system (PPS) was fired to raise the apogee of the docked vehicles to 741 nautical miles for two revolutions. The PPS was fired again, 3 hours 23 minutes later, to reduce apogee to 164 nautical miles. The crew then prepared for standup EVA, which began at 47 hours 7 minutes into the flight and lasted 2 hours 8 minutes. The spacecraft was then undocked to begin the tether evaluation. At 50 hours 13 minutes ground elapsed time, the crew initiated rotation. Initial oscillations damped out and the combination became very stable after about 20 minutes; the rotational rate was then increased. Again, initial oscillations gradually damped out and the combination stabilized. At about 53 hours into the mission, the crew released the tether, separated from the GATV, and maneuvered the spacecraft to an identical orbit with the target vehicle. A fuel cell stack failed at 54 hours 31 minutes, but the remaining five stacks shared the load and operated satisfactorily. A rerendezvous was accomplished at 66 hours 40 minutes ground elapsed time, and the crew then prepared for reentry. The spacecraft landed less than 5 km from the planned landing point at 71 hours 17 minutes after liftoff. The crew was retrieved by helicopter, and the spacecraft was brought aboard the prime recovery ship, the aircraft carrier Guam, about an hour after landing.
Official NASA Account of the Mission from On the Shoulders of Titans: A History of Project Gemini, by Barton C. Hacker and Charles C. Alexander, Published as NASA Special Publication-4203 in the NASA History Series, 1977.
Conrad was much taken with the notion of a Gemini trip around the Moon. Even after Webb dismissed the scheme, he still wanted to take Gemini as far as it would go. When he was named as command pilot, he recalled, "it didn't look like . . . (a high altitude) flight was ever going to get done on Gemini." Conrad saw a heaven-sent opportunity to resurrect the idea when he calculated that he could save some of the Agena's fuel to power a high ride.
He began a small crusade to convince NASA management that there were good reasons for going really high. Although the Weather Bureau had satellites flying at very high altitudes, their televised pictures of cloud formations had poor resolution. Moreover, the Bureau had been debating the use of a color system. Conrad argued that Gemini Xl could bring back films to help them decide its worth. It was, in fact, to the experimenters that he first turned in his campaign to fly high, asking which experiments might be helped and which degraded by higher altitudes. He learned that Maurice M. Shapiro of the Naval Research Laboratory was concerned that radiation particles from the Van Allen belts might affect his nuclear emulsion experiment at the higher orbit. That almost killed Conrad's plan before it was well started. But he enlisted fellow astronaut Anders, a nuclear engineer, for a trip to Washington to argue against the threat. After Anders got friends at Goddard Space Flight Center to look into the radiation belt hazards and to devise ways of avoiding them, the high apogee excursion soon became part of Gemini Xl.
Another unique objective for XI, direct (first orbit) rendezvous, had been suggested before Gemini flights began. Proposed by Richard R. Carley of GPO, the idea had been put aside when interest had focused on a concentric, fourth-orbit plan. Carley's proposal revived when the Apollo office insisted on a closer simulation of lunar orbit rendezvous. With some signs of reluctance, GPO asked McDonnell to study the maneuver. The first meeting to phrase plans and ground rules for the study revealed some foot-dragging; its results included a curious stipulation: "There should be no artificial restrictions in the plan to make the mission simulate Apollo operations or to simulate lunar rendezvous conditions." That position was soon reversed as Apollo interests prevailed. The first change in the flight plan to include direct rendezvous made any launch delay a reason or shifting the mission to "a modified M = 3 (rendezvous in the third orbit) plan," but the following version "recycled (the launch) to the next direct rendezvous launch opportunity."
Although schemes for achieving artificial gravity in space preceded real manned space flight by many decades, Gemini offered the first chance to turn science fiction into fact. Half the program had passed, however, before NASA got around to planning tethered vehicle flights. GPO first asked the Engineering and Development Directorate to study the problems involved in tying the Gemini spacecraft to either the Agena or the Pegasus satellite. Its backlog of Apollo work forced the directorate to decline its aid, in view of the extensive simulation required. Appeals to Flight Operations were more fruitful, however, leading to a number of tether simulations, the data from which were duly passed along to McDonnell.
McDonnell's guidance and control group found that nylon or dacron tethers no longer than 50 meters and a spin rate no more than ten degrees per second produced a reasonable amount of cable tension and recommended that the pilots practice spinning on a vehicle simulator to learn how best to conserve fuel.
When NASA planners listed tethered flight as a mission objective, they first thought of it as a way of evaluating the tether as an aid to stationkeeping;12 but it might also be a means of inducing some degree of artificial gravity. The minimum spin rate depended on whether the tethered activity was intended primarily for formation flying or for achieving gravity. NASA decided to try for both, although it would settle for "an economical and feasible method of long-term, unattended station keeping," and chose a 36-meter dacron line.
The Gemini Mission Review Board reviewed all these new activities in depth, especially the first-orbit rendezvous, which might be a heavy fuel user. Young and Collins had expended so much fuel in the Gemini X rendezvous that the board was dubious about trying a first-orbit linkup, largely computed onboard, with an Agena target. But Flight Director Glynn Lunney assured the group that Mission Control could give the crew backup data on orbital insertion and on the accuracy of their first maneuver; the network would have plenty of information to help them begin the terminal phase of rendezvous. The board concluded that if the rendezvous used only half the fuel supply, about 187 kilograms, there would be ample for the rest of the mission. Some skeptics remained; William Schneider, Deputy Director for Mission Operations, bet board chairman James Elms a dollar that it could not be done that economically.
The board seemed less concerned about the high apogee maneuver and the tethered vehicle exercise than about direct rendezvous. Radiation levels on Gemini X having been only a tenth of the preflight estimate, the board simply asked that MSC and Goddard keep track of the latest measurements. The only major question about the tether plan was the method for freeing the spacecraft from the Agena. The board was told that the plan was to fire a pyrotechnic charge, ejecting the docking bar at right angles to the spacecraft path. If that did not work, there was a break link in the tether that could be snapped by a small separation velocity.
As might be expected, extravehicular activity received special attention. After the experience on Gemini IX-A, training methods were sought that would more closely approximate flight conditions. One likely approach simulated zero-g by putting a space-suited subject under water, where buoyancy almost balanced weight, and leaving him to cope with mass and inertia just as he would have to do in space. Despite the degree of EVA success that Collins had in Gemini X, work on this idea went ahead. There were, as MSC Director Robert Gilruth later said, "many mixed emotions here at the Center - some of our people didn't think the neutral buoyancy work was any good." But Cernan, who checked out the method at Gilruth's request, found that moving about under water in a pressure suit closely matched his efforts in space. These findings, however, were not impressed upon Gordon in his training for Gemini XI.
More was needed than a better training medium. Both equipment and body positioning aids had to be improved. Hardware changes included handholds on the target vehicle docking cone, a shorter umbilical, and better foot restraints in the spacecraft adapter. The handholds were simple to design and install. Both Collins and Young had complained about the 15-meter snake that had entangled Collins. They suggested its length be cut to 9 meters, and GPO agreed. Developing better foot restraints took a little more time. McDonnell was working on two kinds - a spring clamp like those on a ski and a bucket type. NASA chose the latter, which were nicknamed "the golden slippers."
Twelve experiments were included in the Gemini Xl flight plan (See Appendix D). Nine were scientific, the other three technological. Two of the science experiments - S-29, Earth-Moon libration region photography, and S-30, dim light photography/orthicon were new to Gemini. The other seven - weather, terrain, and airglow horizon photography; radiation and zero-g effects; ion-wake measurement; nuclear emulsion; and the ultraviolet astronomical camera - and all three technological experiments - mass determination, night image intensification, and power tool evaluation - had been assigned to previous missions. The Gemini Mission Review Board concluded that they fitted properly into the Gemini XI workload. By 25 August, MSC was able to report that all experiments were ready for flight.
When reduced launch intervals required faster delivery to the Cape, the challenge was met. Before the end of July, launch preparations were under way in Florida. On 11 August, NASA announced that the flight would be launched on or about 9 September, only two days after the target date set more than three months earlier.
The countdown-to-launch began on schedule on 9 September 1966, but it did not finish that way. After the booster was fueled, the launch crew detected a pinhole leak in the first stage oxidizer tank, which had to be fixed. Technicians used a sodium silicate solution and an aluminum patch to plug the leak; and Mission Director Schneider reset the launch for 10 September.
Trouble for the second scheduled send-off cropped up in a different area and much later in the countdown. Conrad and Gordon had completed the required rituals and headed toward pad 19 and their spacecraft when they heard that the Atlas, only 1,800 meters away, was having a problem with its autopilot. The General Dynamics test conductor called a hold in the countdown to have this suddenly wayward instrument checked. His engineers told him they were receiving faulty readings and were running checks before deciding whether to replace the part. When the delay had stretched to an hour, Schneider postponed the launch for two more days. The problem was caused by a combination of factors - a fluttering valve, unusually high winds, and a too-sensitive telemetry recorder - none of which required replacement of the autopilot. There would be no further delay.
On l2 September 1966, Conrad and Gordon arrived at the pad and stepped into their seats exactly on time. Guenter Wendt, McDonnell pad leader, signaled his men to close the hatches, but they soon had to reopen Conrad's. He suspected that some oxygen was leaking from his side of the cabin. He was right. When the hatch had been fixed, the countdown went on. At 8:05 a.m., the Atlas roared into action. Gemini XI had its target.
If ever two pilots waited anxiously for the starter's gun to crack, Conrad and Gordon did. For the first orbit catchup, the time to come out of the chute was unbelievably short. It was the shortest launch window in the Gemini program. Gemini X, for example, had 35 seconds in which to launch, Gemini XII would have 30 seconds. Mathews had informed McDonnell and SSD that Gemini XI's launch window was only long enough for an "on-time launch." The postlaunch mission report, however, gave two seconds as the length of the window for a first-orbit rendezvous. Rocketeers of the forties, fifties, and early sixties would have been aghast at the idea of having to launch within two ticks of the clock.
Conrad chanted the count: ". . . 3, the bolts blew, and we got lift-off." This was at 9:42:26.5, just half a second into the two-second period. The Titan booster shoved Gemini XI toward a first-orbit rendezvous with near-perfect accuracy. At six minutes, the flight control circuit carried the glad tidings, "Gemini XI, you're GO for M equals 1." This welcome word came at booster separation, when debris could be seen out the window. Gordon had warned himself not to look, but temptation got the better of him for a brief instant.
Immediately upon insertion, Conrad and Gordon performed an insertion-velocity-adjust-routine (IVAR) maneuver, to correct the flight path up or down, right or left, and add to or decrease speed as needed. During IVAR, any decrease in spacecraft speed (retrograde firing) is done with great care because of the danger of recontact with the launch vehicle. The rules, therefore, say that the pilots must have the booster in sight before they begin to cut their speed at this point. Their computer showed the crew they had made very precise insertion corrections that would help them catch a target 430 kilometers away.
The first onboard calculations had succeeded; now it was time to try again. There would be no help from the ground stations, as Gemini XI was out of telemetry and communications range. At the appointed moment, Conrad made an out-of-plane maneuver of one meter per second. He then pitched the spacecraft nose 32 degrees up from his horizontal flight plane. Now came the test to see if their first figures had been right. They turned on the rendezvous radar - the electronic lockon signal registered immediately. Happily, the crew switched the onboard computer to the rendezvous mode and began preparing for the final part of the catchup. When they could talk to the ground again, Gordon said, "Be advised we're (within) . . . 50 (nautical) miles (93 kilometers)."
Young, the Houston CapCom, then cut in over the remote line through Tananarive to give the crew some numbers for the remainder of the chase. Conrad and Gordon checked these calculations against their own and found the differences so minor they could have used either set to do the job. They decided to stick with their own solutions. Just as the spacecraft neared the high point of the orbit, Conrad fired the thrusters to produce multidirectional changes - forward, down, and to the right - to travel the remaining 39 kilometers to the travel. Suddenly the Agena, whose blinking lights they had been watching in the darkness, flashed into the sunlight over the Pacific and almost blinded them. They scrambled for sunglasses, then Conrad jockeyed the spacecraft to within 15 meters of the target's docking cone. Over the coast of California, only 85 minutes after launch, rendezvous in the first orbit was achieved.
A gleeful crew called out, "Mr. Kraft - would (you) believe M equals 1?" He would. Moreover, they still had 56 percent of their maneuvering fuel. This transmission made a believer out of Mission Director Schneider. He fished in his pants pocket, pulled out a one-dollar bill, and scribbled a notation for Elms: "Sep(aration) 85#, Plane Change 5#, TPI 145#, Midcourse 20#, Braking 150#, (total), 405#. I never lost a better dollar. Bill Schneider.".
After appropriate congratulations, Young told Conrad and Gordon to go ahead and dock. Seconds later, Conrad reported matter-of-factly, "We are docked." The Gemini XI crew now had an opportunity to do something else that NASA had wanted for a long time - docking and undocking practice. Each man pulled out and drove back once in daylight and once in darkness. It was easy - much easier, Conrad said, than in the translation and docking trainer on the ground. For the first time, also, a copilot was given the chance to dock with a target vehicle.
Even while docking and backing away from the Agena, the crew was meeting another flight objective. Attached to the Agena target docking adapter was S-26, an experiment that studied the ion-wake structure during docking practice. Two other experiments were started at that time - S-9, nuclear emulsion, and a modified form of S-29, libration regions photography. The crew turned on the emulsion package shortly after the hookup with the target, and a telemetry check disclosed that it was working. Gordon later retrieved it from behind the command pilot's hatch. S-29, a study of dim light phenomena, could not be carried out as planned because of the three-day mission delay. The Milky Way now obscured the intended target. Instead, the crew photographed the gegenschein and two comets.
After the last docking, the crew used the main Agena engine in a test run before going to high altitude. Facing 90 degrees away from the flight path, Conrad fired the main engine, adding a velocity of 33 meters per second to pull over into a new orbital lane. This really impressed them. Gordon remarked to Young (who had flown the Agena spacecraft combination in Gemini X, "I agree with you, John, riding that PPS (primary propulsion system) is the biggest thrill we've had all day.".
Now, after six hours of hard but frustration-free work, Conrad and Gordon powered down the spacecraft systems, ate a meal, and soon got a "good night" salutation from the network. For eight hours, they dozed and rested, awaking, as Gordon said, brighteyed and bushytailed. The only complaints the pilots had were about their dirty windows. Dirty windows had plagued all Gemini flights. Beginning with Gemini IX-A, all spacecraft carried covers that could be jettisoned after the launch phase, but they did not seem to help much. Earlier, Conrad had asked if Gordon could wipe his window when he went outside. Now Alan Bean, who had taken over from Young as CapCom, told the pilot to rub half the command pilot's window with a dry cloth and bring the rag back for testing.
Conrad and Gordon napped and rested awhile longer, then started their next major task - preparation for EVA. Four hours before they were to open the hatch, the crew began to get their suits ready for the vacuum environment. They had practiced this so many times on the ground, Conrad said, that they soon realized they did not need all that time. Within 50 minutes, the gear was ready and running. Just a few more steps and Gordon could have gone out. So Conrad called a halt, which left them sitting there, as he later said, with all the junk on. An hour later, they hooked up Gordon's environmental support system, and he made some oxygen-flow tests. This was also a mistake, they quickly perceived. The system dumped oxygen into the cabin, which, in turn, had to vent the excess into space. They could ill afford this rate of oxygen loss, and Conrad had Gordon switch back to the spacecraft system. Gordon, uncomfortably warm, was glad to get back on the interior system. The extravehicular system's heat exchanger had been designed to operate in the vacuum of space, not in a pressurized cabin.
Briefly, the two men considered asking Flight Director Clifford Charlesworth to let Gordon go out a revolution early. But they decided to keep on schedule. As they sat and waited, they soon regretted that decision. At last it was almost time to open the hatch. Gordon began putting a sun visor on his faceplate, a real chore and one which should have been done before he put on all this extra gear. Conrad finally got the left side fastened, but he could not reach across Gordon to fasten the other side. Gordon was now getting hot and bothered and had to rest. Time had been hanging on their hands before - now it was rushing past. Gordon wrestled with the right snap for five minutes and finally got it fastened, cracking the visor in the process. He was thoroughly winded before he got out of his seat. But he opened the hatch and stood up at 24:02 hours ground elapsed time exactly on schedule.
"Here come the garbage bags," Conrad warned. Everything in the spacecraft that was not tied down began to float upward and outward - including Gordon. Outgassing of the environmental system caused this, and the crew expected it. Conrad grabbed for a strap on the leg of Gordon's suit and held him in the seat.
Gordon then deployed a handrail - this was easy. Next he picked up the S-9 nuclear emulsion package and handed it to Conrad, who shoved it down between his legs into his footwell. Gordon then tried to install a camera in a bracket to photograph his own movements, but this was more difficult. Finally, Conrad let enough of the umbilical slide through his gloved hand to let the pilot float above the camera and hit it with his fist to drive it into place.
It was now time for the spacewalker to move forward and attach a 30-meter tether, housed in the Agena target docking adapter, to the spacecraft docking bar. When Gordon pushed himself forward, he missed his goal and drifted in an arcing path above the target's adapter and around in a semicircle until he reached the adapter behind the spacecraft. But Conrad had released only 2 meters of the 9-meter umbilical, so he pulled Gordon back to the hatch to start his trek again. This time Gordon reached the target and grabbed some fixed handrails to pull himself astride the spacecraft nose.
"Ride 'em, cowboy!" Conrad shouted. Riding bareback, with his feet and legs wedged between the docked vehicles, was hard to do. In practice sessions in zero-g aircraft flights, Gordon had been able to push himself forward, straddle the reentry and recovery section, and wedge his feet and legs between the docking adapter and the spacecraft to hold himself in place, leaving his hands free to attach the tether and clamp it down. But this did not seem to work so well in the actual conditions of space. He had to fight his pressurized suit to keep from floating away, and he had neither saddle nor stirrups to help him. All he could do was hold on with one hand and try to operate the tether clamp with the other. He struggled for six minutes, finally securing the line. At least, they were ready for the tethered flight experiment that would come later in the mission. To Conrad, it was obvious that Gordon was running out of steam. What had been relatively easy in zero-g airplane flight training had become a monumental task. With his face streaming with sweat and his eyes stinging, Gordon groped blindly about. He tried to unstow a mirror on the docking bar so Conrad could watch him when he went to the back of the spacecraft. Gordon tugged at the attachment, but it would not budge. He abandoned the frozen mirror as not worth the effort. So far, he had not had a chance to wipe Conrad's window, either.
As the pilot inched his way back to the hatch area, Conrad helped him as much as he could. They then discussed whether Gordon should go to the adapter and get the maneuvering gun stored there. His right eye was still burning, and Conrad could see just how exhausted his pilot was. The command pilot soon told Young (through the Tananarive remote station) that he had "brought Dick back in . . . He got so hot and sweaty, he couldn't see." Gordon had no trouble getting into the spacecraft, nor did he have any difficulty closing the hatch. It had been open only 33 minutes, instead of the planned 107. One experiment (D-16, power tool evaluation) was a casualty on Gemini XI as it had been on VII. Also scheduled for Gemini XII, it had been moved forward one flight because its release mechanism would interfere with that for the sensor covers on D-10 (ion-sensing attitude control): it would require additional engineering for thermal and structural impact; and it would ease the weight load (already growing too fast) on Spacecraft 12. When Gordon got so exhausted that he never reached the adapter area, the power-tool experiment that David Scott had mourned on Gemini VIII had to wait for Apollo. Because Conrad and Gordon were surrounded by so much loose gear, they opened the hatch an hour later and jettisoned all the umbilical extravehicular equipment.
Although there was a standup EVA period still before them, spacewalking (or swimming) on this mission was finished, and the feasibility of working outside the spacecraft was not settled by Gemini XI. Cernan had told Collins and Gordon about his problems, and Collins had further emphasized his experiences to Gordon. Yet, as the flights progressed, each successive pilot continued to be amazed that the simplest tasks were so much harder than he expected. "Gene Cernan warned me about this and I took it to heart," Gordon later said. "I knew it was going to be harder, but I had no idea of the magnitude." Apparently the supporting engineers had no idea, either, since they still had not provided satisfactory restraints to help the crews.
The extreme exhaustion of past EVA pilots had sometimes adversely affected the rest of the mission. But Gordon's did not. Flight planners had learned to schedule periods of lesser activity immediately after heavy workloads. Conrad and Gordon began leisurely repacking equipment and restoring order to the cabin. Communications with the ground had dwindled to brief transmissions about spacecraft systems and crew medical checks. Conrad tested a thruster that had been sluggish and found that it was working better. The crew also ate a meal and photographed the airglow horizon. Half an hour before the sleep and rest period, the Rose Knot Victor tracking ship flight controller sent them the numbers for their next big event - the high ride.
Next day, Conrad and Gordon skipped breakfast to get the cabin ready before the hard shove in their midsections sent them upstairs. They wanted things buttoned up as though for reentry. So they suited themselves, closed their faceplates, and stowed everything they could.
As the crew made a prefiring check of the Agena, they noticed that it was not accepting their commands immediately. Orders had to be repeated before they were acknowledged. Conrad told Bean about this and learned that the Agena was responding properly. The trouble was apparently, in the spacecraft displays. "It (is) a heck of a time to have a . . . glitch like that show up," Conrad complained. But the Canary Islands communicator told them everything was fine and to "GO for the burn."
At 40:30 hours into the flight, in the 26th revolution, Conrad triggered the firing signal to the target vehicle's main engine. For 26 seconds it belched a fiery stream to add 279.6 meters per second to their speed. "Whoop-de-doo!" Conrad yelled, "(that's) the biggest thrill of my life." Since they faced the Agena, the acceleration forced the crew forward onto the seat harnesses. They watched the great round ball of Earth recede. What about orbital mechanics now? they wondered. Were they going to stop? From Carnarvon, 1372 kilometers below came, "Hello, up there." Conrad answered, "I'll tell you, it's GO up here, and the world's round. . .. you can't believe It . . . I can see all the way from the end, around the top . . . about 150 degrees." When Bean asked him to enlarge on his impressions from his high vantage point, the command pilot continued, " . . . it really is blue. That water really stands out and everything looks blue. . . The curvature of the earth stands out a lot. (There are) a lot of clouds. . . over the ocean . . . (but) Africa, India, and Australia (are) clear." He went on, "Looking straight down, you can see just as clearly . . . there's no loss of color and details are extremely good . . . ."
Going up, the crew had not been merely sightseers, although they had used the tourists' favorite instrument - the camera. Gordon snapped synoptic terrain and synoptic weather photographs. The weather experiment needed cloud cover, and the terrain had to have clear views of the land areas. Conrad's at-a-glance description of the eastern hemisphere thus elated the principal investigators. They eagerly awaited the more than 300 pictures clicked off.
Radiation dosage at high altitude had caused some premission concern. The Van Allen belts (two doughnut-shaped radiation zones around Earth, named for James A. Van Allen, State University of Iowa physicist) are not constant about the planet, being denser in some regions than others. High apogee orbits for Gemini XI were therefore planned to take place over Australia, because the level there is comparatively low. Now Conrad reported to Carnarvon, ". . . our dosimeter reads .3 rads per hour up here." Gordon amended this, saying, "Houston, radiation is revised to .2 rads per hour." To which Bean replied, "Sounds like it's safer up there than a chest x-ray." Conrad later stated that "we got less radiation in our two 850-(nautical) mile (1,570- kilometer) orbits than the X crew got in their longer period of time at 450 (nautical) miles (830 kilometers)."
Over the United States in the 28th revolution, Conrad used lie Agena to lower the apogee of the orbit. Firing for 23 seconds decreased speed by 280 meters per second and lowered the spacecraft orbit from 1,372 to 304 kilometers. Another mission objective could be stamped "achieved.".
After their high-flying excursion, Conrad and Gordon were supposed to get ready for the next EVA period. Instead, Conrad told Bean, "We're trying to grab a quick bite. We haven't had anything to eat yet today." The CapCom replied, "Be our guest." After they had eaten, they still had plenty of time before the exercise was to start. In revolution 29, above Madagascar, Gordon opened the hatch and watched the sunset.
Gordon stood on the spacecraft floor, held down by a short tether like the one Collins had on Gemini X. It allowed him to forget about maintaining body position and left both hands free for his tasks. He mounted cameras in brackets without any difficulty. "Most enjoyable," he said of his two-hour standup period. So relaxed and well oriented was he that the monitoring physicians reported, "From a medical viewpoint, the standup EVA was relatively uneventful."
Gordon's main task during two night passes of open-hatch work was to photograph several star fields, using the S-13 ultraviolet astronomical camera. Because of his dirty window, Conrad had some difficulty in pointing the spacecraft Agena combination in the right direction; but Gordon, with his unimpaired view into open space, coached his commander into position. Agena stabilization was somewhat erratic, but the docked vehicles were steady enough to give excellent results in about one third of the photographs.
Although neither man was really tired after the first half of the picture-snapping, Conrad considered closing the hatch and resting until the next night pass. He asked the Hawaii CapCom if there was enough oxygen. The answer was yes. But the skies were clear over the United States, and they might want to take more pictures there. In that case, said Conrad, the hatch would stay open.
Soon the crew marveled at the view of their home area - Houston. They passed quietly across Florida and out over the Atlantic with nothing to do. Suddenly, Gordon broke the silence to announce that they had just taken a catnap. "There we were. . . he was asleep hanging out the hatch on his tether and l was asleep sitting inside the spacecraft," Conrad reported. "That's a first," John Young answered, "first time sleeping in a vacuum."
"Boy, my legs are tired," Gordon said after closing the hatch. "I'm tired all over. Man, I'm beat!" Conrad answered. This time their fatigue stemmed mainly from concentration on an experiment; it bore little relation to the hard physical struggle Gordon bad endured outside with the umbilical.
Now the crew rested and discussed the next major mission event - the tethered vehicle exercise. There were two ways of carrying out this experiment. In the first (called gravity gradient), the docked vehicle combination assumed the position of a pole always pointing toward Earth's center. The Agena engine nozzle represented the tip, the adapter section on the spacecraft the top of the pointer. Once the pole was pointed correctly, the crew then backed the spacecraft out of the Agena docking cone slowly, until the 30-meter tether became taut. If properly positioned, a slight thrust of only three centimeters (one-tenth foot) per second would keep the line taut, and the now elongated pole would drift around Earth, with the two vehicles maintaining the same relative position and attitude.
Should Conrad and Gordon fail to execute these procedures, they were then to try the spinup, or rotating, mode that had been studied by McDonnell. In this case, once the two vehicles were undocked, Conrad fired the spacecraft thrusters to induce a rotation of one degree per second to the Gemini XI-Agena combination. The two craft would then continue on their orbital path, with their mutual center of gravity at a specific point on the tether around which they would do a slow and continuous cartwheel. Centrifugal force would be expected to keep the line taut and the two vehicles apart, while the tether itself provided centripetal force to keep the two spacecraft in equilibrium.
Over the tracking station in Hawaii, the crew separated the two vehicles cautiously to try the gravity-gradient method. There was enough initial tension in the tether to upset the Agena and to cause the Gemini spacecraft to move to the right, toward the target's docking adapter. Conrad quickly adjusted his spacecraft's motion, and the Agena righted itself without difficulty. The command pilot continued to back away from the Agena, but the tether stuck, probably in the stowage container, when about 15 meters had been released. Conrad gave a burst to his thrusters to jerk the cable free. Then, it hung up again, this time on some Velcro that had been used to hold Agena's end of the line until the spacecraft was loose. Conrad had to shift the spacecraft out of vertical alignment to peel the tether off the Velcro pad. This disturbed the Agena again, and there were still about three meters of the line to be pulled out. To do the "Non Spun Up" maneuver, as Conrad called it, the spacecraft and Agena had to be tethered and aligned vertically to Earth. The engineers expected that it would take about seven minutes for the Agena to stabilize. When the target seemed to be taking longer, they feared something was wrong with the Agena's attitude control system and told the crew to abandon the attempt and proceed to the second mode.
When Conrad tried to start the rotation, he found he had another problem. He could not get the tether taut. It seemed to rotate counterclockwise. Surprised, he reported to Young, "This tether's doing something l never thought it would do. It's like the Agena and l have a skip rope between us and it's rotating and making a big loop." He continued, "Man! Have we got a weird phenomenon going on here. This will take somebody a little time to figure out." Strangely, although the spinning line was curved, it also had tension. "I can't get it straight," Conrad muttered. For ten minutes, the crew jockeyed, using the spacecraft thrusters to straighten the arc. Finally, they got an even tether, but neither of them could ever recall exactly what they had done to stop the odd behavior of the rope.
When the tether was taut, Conrad rolled his spacecraft and blipped the thrusters to begin the slow cartwheel motIon. Although this had been done gently, so to speak, Conrad felt be must have stretched the tether because it had a big loop in it when he stopped firing. The command pilot itched to do something else, but the ground engineers told him to leave it alone.
"So we really gritted our teeth" and waited, Conrad said. Sure enough, centrifugal force took over and the line smoothed out. The vehicles at either end of the rope wigwagged, but they, too, soon settled down without the pilots having to do anything. A 38-degree-per-minute rotational rate was obtained and remained steady throughout the nightside pass. The crew became so accustomed to the sight of the Agena hovering nearby that they rarely bothered to look at it. Instead, they ate their evening meal.
Conrad's satisfaction with this stationkeeping was soon disrupted. As they passed into daylight, the Hawaii CapCom told him to accelerate the spinup rate. Somewhat reluctantly, the crew agreed to try. Gordon suddenly shouted, "Oh, look at the slack! . . . It's going to jerk this thing all to heck." "That's what I was afraid of, darn it," Conrad replied. To Flight Director Charlesworth in Houston, Gordon complained, "You just ruined a good thing." When the added acceleration started, the line tightened and then relaxed. The crew felt what Conrad called "this big sling shot effect." They were being seesawed in pitch up to 60 degrees. Conrad could not accept this oscillation, so he used the spacecraft controls to steady his vehicle. To their surprise, the Agena stabilized itself again.
The rotation rate checked out at 55 degrees per minute, and the crew could now test for a minute amount of artificial gravity. When they put a camera against the instrument panel and then let it go, it moved in a straight line to the rear of the cockpit and parallel to the direction of the tether. The crew, themselves, did not sense any physiological effect of gravity.After they had been roped to the Agena for three hours, the pilots ended the exercise by jettisoning the spacecraft docking bar. All in all, it had been an interesting and puzzling experience.
There had been some disappointment that the gravity-gradient mode could not be completed, but confidence rose when the spinup proved that stationkeeping could be done economically. The flight controllers had asked the crew about the remaining fuel on several occasions; they were using less fuel than had been expected. And now there was a chance for some realtime planning on the credit side of the ledger. In the past, realtime planning had been in response to such problems as degraded fuel cells, "angry alligators," or whirling spacecraft. An exercise that had been in a contingency plan, if something had gone wrong, was now fitted into the mission because almost everything had gone right.
After the two vehicles separated, Conrad had intended to decrease the spacecraft speed so Gemini XI, in a lower orbit, would pull ahead, leaving the Agena behind. Instead, the flight controllers told him to get ready for what was called a "coincident-orbit" (later renamed "stable-orbit") rendezvous. The spacecraft would follow the Agena by 28 kilometers and in its exact orbital path. If the plan succeeded, the crew would, in essence, be stationkeeping at very long range and with the use of very little fuel.
Because of the change in plan, the separation maneuver would be different. Instead of a retrograde firing, so the Agena would trail above and behind them, Conrad and Gordon added speed and height to the spacecraft's orbit so the target passed beneath and in front of their vehicle. When the crew saw the Agena below them, moving swiftly across the South American terrain, they understood why Thomas Stafford and Cernan had trouble keeping their target in sight during the rendezvous-from-above exercise on Gemini IX-A.
Next they fired the thrusters to place the spacecraft in the same (coincident) orbit as the Agena and trailing it. Three-quarters of a turn around the world, Conrad decreased his forward speed and, as expected, the spacecraft dropped into the Agena's lane 30 kilometers behind the target and with no relative velocity between the vehicles.
While doing their long-distance formation flying, Conrad and Gordon began to work on night image intensification (D-15), which they thoroughly enjoyed. This was a test to see if their night vision could be enhanced by equipment that scanned objects on the the ground and relayed what it saw to a monitor inside the spacecraft. While Conrad aimed the spacecraft at desired targets - lights of towns and cities, cloud formations, lightning flashes. horizon and stars, airglow. coastlines, and peninsulas - Gordon watched the displays. Each pilot described what he was seeing to the spacecraft tape recorder. Conrad was handicapped by his dirty window. And the glow from the television monitor prevented him from becoming fully dark adapted. Still, the two revolutions (or about three hours) of just riding, watching, and taking pictures were very pleasant. Perhaps the most exciting sight was the lights of Calcutta, India. Outlined on the monitor was a shape almost identical to an official map of the city.
On one occasion during the experiment, the crew noticed the lights of the Agena and asked the ground how far from the target they were. The flight controller on the Rose Knot Victor replied that they were still 30 kilometers behind and closing very slowly. They could expect it to be about 26 kilometers away when they woke the next morning. But, when the crew broke their sleep period, in revolution 41, the target was 46 kilometers ahead. This, however, presented no problems for the re-rendezvous.
The second rendezvous in Gemini XI, like the first, took only one orbit. At 65:27 hours of flight time, Conrad tilted the spacecraft nose 53 degrees above level flight and fired the forward thrusters. This slowed the spacecraft speed and moved it closer to Earth. Now the spacecraft was in a lower orbit than the Agena and ready for the catch-up maneuver. While they waited for the final approach, the crew did the S-30 dim light photography/orthicon experiment, taking pictures of the gegenschein and zodiacal light, and completed D-15. They also turned off the switch to raise the temperature of the S-4 radiation experiment and then turned it back on. At 67:33 hours, S-4 was turned off for the last time.
An hour after the catchup maneuver began, with his ship almost level and aimed directly ahead, Conrad gave the aft thrusters a burst to raise the spacecraft orbit. Now the Agena floated just above them, its tether pointing straight up. At 66:64 hours elapsed time, Conrad began to brake his spacecraft; six minutes later, he reported that he was on station and steady with the Agena. Gordon noticed that the tether on the target had started waving slowly and surmised that this was caused by the exhaust from Gemini XI's thrusters. Twelve minutes later, the crew broke away from the Agena for the last time. Conrad later said, "We made the 3 foot 1 meter) per second retrograde burn and left the best friend we ever had." Gordon added, "We were sorry to see that Agena go. It was very kind to us.".
Conrad suggested that Flight Director Lunney might send up a tanker - the crew would be happy to refuel, remain in orbit, and do some more work. But, while this air-to-ground joking was going on, the crew was getting ready to land.
There was only one significant event left before Conrad and Gordon wrapped up their mission. A secondary objective called for the crew to make an automatic reentry. The commanders of other Gemini flights had flown their spacecraft down from 120,000 meters, using the spacecraft's offset center of gravity to generate lift for changes in direction. This had enabled them to make corrections up to 550 kilometers downrange and 50 kilometers crossrange. Conrad, however, would not fly the spacecraft with his handcontroller in conjunction with computer directions; the spacecraft would follow these commands automatically.
On 15 September 1966, after 70:41 hours of flight and in the 44th revolution of Earth, the retrorockets fired. Conrad and Gordon watched the computer closely. It certainly seemed to be working right. Conrad then disengaged his handcontroller and put the system on automatic. When the first crossrange errors developed, the computer commanded bank angle changes. On several occasions, the spacecraft displayed an almost human characteristic, hesitating before accepting its orders. But the system recovered quickly and performed beautifully, using a minimum of the reentry system's control fuel. The accuracy of automatic reentry was thoroughly demonstrated when the spacecraft landed within 4.6 kilometers of the U.S.S. Guam, the prime recovery ship, a sea-going platform for helicopters. As the spacecraft floated down to its landing, after 71:17 hours elapsed time, Young told them, "You're on TV now." The Gemini XI flight had ended; next came the usual round of examining, debriefing, evaluating, and reporting. References: 1 , 2 , 5 , 6 , 26 , 33 , 60 .