The Switch Engine

After the premission review, the traditional meal, and the ritualistic suiting up, Young and Collins left the crew quarters on 18 July 1966 for pad 19 - to begin the most complex manned flight so far. They had been awakened at noon for a 5:20 p.m. takeoff, when a 35-second window offered the best chance for rendezvous with the two Agenas. The Atlas lifted its payload toward space at 3:39 p.m., just two seconds late.* One hundred minutes later, the Gemini launch vehicle boosted the spacecraft skyward exactly on time. Except for a slight shaking and a buzzing in their ears, Young and Collins had a nice ride to start chasing their first target.81

At entry into orbit, Gemini X trailed its Agena by 1,800 kilometers. Flight Director Lunney told the crew they were all set for a fourth-orbit rendezvous. Collins unstowed a Kollsman sextant to sight on selected stars for an attempt at optical navigation. Young pointed the spacecraft while his crewmate tried to find the horizon. Collins realized that he was using the wrong reference when he saw stars below the line. He had been mistaking the airglow, a band of radiant light from the upper atmosphere, for the horizon. Even after he corrected this, Collins could not get the lens of the sextant to work properly, as the optical image of the stars did not agree with what he had been taught. He laid the Kollsman aside and tried an Ilon instrument, but that was little help as the Ilon had a severely limited field of view.82

Young and Collins checked their figures with Lunney, who had been watching their activities carefully through telemetry. When the trio found that the numbers did not agree with those of the ground computers, Gordon Cooper, the Houston CapCom, passed the word that the crew would have to use the ground computations. Young then fired the thrusters to adjust their orbit to 265 by 272 kilometers. When he aligned the platform for the terminal phase, the command pilot did not realize that the spacecraft was turned slightly. As he thrusted toward the target, Young needed two large midcourse corrections. The spacecraft path toward the Agena was not lined up properly. So he had to stop thrusting briefly and take off on a new track. The final translational maneuvers to reach the Agena cost nearly 181 kilograms [345] of fuel, or three times more than any earlier mission.83 Five hours and 52 minutes after launch, Young reported a rigid dock.84

Because too much fuel had been used, Lunney decided to omit docking practice - backing away and returning to the target's cone. Young and Collins wondered if the second rendezvous might also be canceled, but, some six and a half hours into the mission, the ground controllers started giving the crew the data they would need for the burn. Then, an hour later, the CapCom at Hawaii cleared them to try for second rendezvous.

The Agena main engine roared into life exactly on time. For 80 seconds, the target vehicle thrust the spacecraft upward, adding 129 meters per second to their speed. The crew, at the moment flying backward, had little to say about their reactions to a negative one-g force (a shove to the front of the body - "eyeballs out" - rather than a push on their backsides - "eyeballs in" - as during launch). They were thrown forward from the seats against the body straps. Young later described the first ride on a space switch engine:

At first, the sensation I got was that there was a pop [in front of our eyes], then there was a big explosion and a clang. We were thrown forward in the seats. We had our shoulder harnesses fastened. Fire and sparks started coming out of the back end of that rascal. The light was something fierce, and the acceleration was pretty good. The vehicle yawed off - I don't remember whether it was to the right or to the left - but it was the kind of response that the Lockheed people had predicted we would get. . . . The shutdown on the PPS [primary propulsion system] was just unbelievable. It was a quick jolt . . . and the tailoff . . . I never saw anything like that before, sparks and fire and smoke and lights.85
Gemini X reached an orbit that measured 763 kilometers at the top and 294 kilometers at the bottom. The Agena had pushed the spacecraft more than 463 kilometers above its initial apogee. Young and Collins now viewed Earth from a higher elevation than any human beings ever had. Instead of gazing at the planet in wonderment, however, they confined their attention to their own little, artificial world. They watched spacecraft systems and kept an eye on the radiation dosage readings (which were within tolerable limits). During his technical debriefing, Young only reported, "We took some pictures at apogee. . . . I don't know where it was, but it shows the curvature of the Earth. . . . We took some pictures coming down hill. I think it was the Red Sea area." Thus, in rating one impression over the other - record high altitude versus Agena ignition - Young and Collins were more affected by the firing of the switch engine than they were by the unique vantage point they had reached. This lack of awe at their record height was caused, at least in part, by the fact that the switch engine blocked much of the downward view.86

[Page 346 displays photos of Gemini X - 18 July 1966]

[347] Nine hours into the flight, the pilots bedded down, sleeping fitfully. Both were still wondering if the second rendezvous would be done. Besides, neither was "really bone-tired," Collins said. Charlesworth's shift in Mission Control was busy that night, reviewing alternate plans for adapting the mission to fulfill its objectives.

When Young and Collins opened for business after 18 hours of flight, their spirits lifted as the CapCom at Carnarvon gave them the numbers for the next target vehicle firing. With the Agena/spacecraft combination faced about so the main engine would fire directly into the flight path, Young made a 78-second burn to reduce the velocity by 105 meters per second and lower the apogee to 382 kilometers. The pilots were again pressed forward in their seats, but this time they were impressed more by the firepower of the Agena than by its fireworks. "It may be only 1 g, but it's the biggest 1 g we ever saw! That thing really lights into you," Young commented.87

Like rendezvous maneuvers in the past, the next Agena burn (and the final one with the main engine) aimed at circularizing the orbit. At 22:37 hours, the target drove the spacecraft along the flight path to add 25 meters per second to the speed. This brought the low point of the orbit up to 377.6 kilometers - only 17 kilometers below Agena 8.88

Although rendezvous and docked maneuvers with the Agena were the high point of the first day, the crew also spent a good part of that time on the 14 experiments they carried.** Twenty minutes after launch, the crew turned on a switch to start the tri-axis magnetometer (MSC-3). This device was used, as it had been in other flights, to measure the radiation levels in the South Atlantic Anomaly. Two other experiments were also devoted to radiation - MSC-6, beta spectrometer (mounted in the adapter to measure potential radiation doses for future missions), and MSC-7, bremsstrahlung spectrometer (installed in the cabin to detect radiation flux as a function of energy when the spacecraft passed through the South Atlantic Anomaly).89

Some of the experiments had to be done outside the spacecraft. Before the third Agena burn, Collins got ready for his first exposure to outer space, a standup EVA. Preparations went well and the hatch opened easily. At sunset, Collins stood in his seat, setting up a 70-mm general-purpose camera for S-13, a photographic study of stellar ultraviolet radiation. Collins aimed the camera at the southern Milky Way, scanning from Beta Crucis to Gamma Velorum, and exposed 22 frames. The entire night pass was devoted to this task. [348] Young helped Collins identify the stars, at the same time controlling the spacecraft and target vehicle combination. With the beginning of daylight, Collins began MSC-8, color patch photography, to see if film could accurately reproduce colors in space. The pilot did not complete this assignment, however, as his eyes began to fill with tears. Young had the same problem. They suspected at first that the anti-fog compound inside their faceplates was irritating their eyes. They closed the hatch at 24:13 hours, about 6 minutes early.90

They had noticed a strange odor that they thought might have been the lithium hydroxide used in the environmental control system, but ground engineers finally concluded that their smarting eyes were caused by having both suit fans on at once. They turned one fan off and, at 30 hours elapsed time, began a second sleep period. Bone-tired this time, they rested well.91

Young and Collins awakened to a "morning" of increased activity. In addition to normal systems check, the ground network also reminded them of the experiments expected this day - the S-26 ion wake measurement, to study the ion and electron structure of the spacecraft's wake (after it undocked from the Agena), S-5 synoptic terrain, and S-6 synoptic weather photography. The pilots also had to work in two maneuvers to help them catch up with Agena 8.

Their Agena switch engine had accomplished its task, and more. After being hooked to it for 39 hours, however, they were getting a little tired of looking at it. Young said that watching the Agena out his window was

just like backing down the railroad [track] in a diesel engine looking at a big boxcar in front of you. . . . The big drawback of having the Agena up there is that you can't see the outside world. The view out of the window with the Agena on there is just practically zilch.92
On freeing themselves from their Agena, the crewmen began preparing for Collins' exit from the spacecraft. Young now needed to make the final maneuvers to get the spacecraft close enough to the Agena 8 for Collins to reach it. Collins connected the 15-meter umbilical to his suit and then fastened it out of the way until time to use it.

"45:38. First sighting of Gemini VIII," Young said. "At this minute it's blurry." After the distance between the two vehicles had been calculated, the Houston CapCom (on the remote line through the Canton station) informed Young, "Your range, Gemini X, is 95 [nautical] miles [176 kilometers]." The crew then learned that what they had been looking at was their own Agena just 5.5 kilometers away. Houston offered consolation, "95 miles is a pretty long range," and Young answered, "You have to have real good eyesight for that." They didn't see the Gemini VIII Agena until it was 30 to 37 kilometers from them, looking to Young like "a dim star-like dot until the sun rose above the spacecraft nose." [349] NORAD's constant care had paid off. They found Agena 8 just where it was supposed to be.93

At 47:26 hours Young started the final closure, with Collins computing the figures for two midcourse corrections. The crew found the old Agena pretty stable, and Young moved in to stationkeep about 3 meters above it. In less than 30 minutes, he told the Houston CapCom that they were going down for a closer look at the micrometeorite collection package. Back in Mission Control Center, fuel usage during stationkeeping was being very closely watched. When it proved to be reasonable, Gemini X received a go for the next extravehicular exercise. "Glad you said that," Young answered, "because Mike's going outside right now."94

Collins emerged from the spacecraft at dawn. Like Cernan on Gemini IX-A, he found that all tasks took longer than he expected. But he picked off the package from the spacecraft exterior. Next, he moved to the adapter to attach his zip gun to the nitrogen fuel supply. Back in the cockpit area once again, he held on while Young moved the spacecraft to within two meters of the Agena.

Collins pushed off from the spacecraft, floated freely in space, and grasped the outer lip of the docking cone on the target. As he clutched at the experiment package, he wished for handholds - or more hands. Cernan had warned him that it would be hard, and it was. He soon lost his grip on the smooth lip and drifted away from the package and from the Agena. He had to decide quickly whether to pull on the umbilical, coiling about like a snake, or to use the hand-held gun. Being about 5 meters away from the spacecraft, Collins chose the gun. It worked, and he propelled himself first to the spacecraft and then back to the Agena, using a series of squirts to get to the package. This time he clung to wire bundles and struts behind the adapter cone and grasped the S-10 experiment. Collins was supposed to attach a replacement device in its place, but he abandoned this idea, fearing he would lose the one he had picked up. Using the umbilical, he pulled himself hand over hand back to the cockpit and gave the S-10 package to Young.

So far, the umbilical had been snubbed so it would extend only 6 meters. The pilot now unsnapped the buckle that released the remaining 9 meters, intending to evaluate the gun. But the gun play stopped before it started. The Hawaii CapCom told Young, "We don't want you to use any more fuel [for stationkeeping]." Young replied, "Well, then, he'd better get back in." To Collins he said, "Come on back in the house."95

Getting back into the spacecraft was surprisingly difficult. Collins had gotten himself tangled in the umbilical. Since the pressurized suit made it difficult to see or feel just where the line had wrapped itself about him, he had to wait while Young helped unwind him and got [350] him back into the seat. But fuel remained the big question. Houston called them, "just . . . to confirm that you're not using any fuel." Young replied, "We've got everything shut off."

More was shut off than he realized. He soon discovered that the radio transmitter had also been turned off. By this time, Collins was back in his seat. Young reported that hatch closing had been easy. With the long lifeline coiling all over the cabin, Young thought it made "the snakehouse at the zoo look like a Sunday school picnic." A little over an hour later, the crew reopened the hatch and tossed out the chestpack and umbilical. This operation only took three minutes. McDonnell had done an excellent job on this righthand hatch.96

Because of the time spent struggling with the umbilical, Collins and Young had to hurry to get set up for an important maneuver that would make the point of reentry more precise. They carried out an orbit-shaping activity exactly on time, at 51:38 hours. This retrograde firing, of 30 meters per second, brought the spacecraft perigee down 106 kilometers, making the orbital parameters safe for reentry. After another round of experiments - this time synoptic terrain and weather photographs taken as the spacecraft drifted through space - the crew began their third sleep period.97

On awakening (about 63 hours into the flight) on homecoming day, Young and Collins spent more time on experiments and did their packing. Then, 70 hours and 10 minutes after liftoff, the crew felt the first retrorocket ignite as they passed over the Canton Island tracking station during their 43rd revolution. Reentry went remarkably well, with Young steering bank angles by computer solutions. Landing in the western Atlantic at 70:46 hours (4:07 p.m., 21 July 1966) was only 5.4 kilometers from the aiming point. The crew of the primary vessel, the Guadalcanal, watched the spacecraft hit the water. Once the swimmers had attached the flotation collar and positioned the raft, Young and Collins climbed out. They were lifted by helicopter to the deck of the recovery ship.98

With that part of the mission completed, the flight controllers put the Gemini X Agena through its paces. Over a 12-hour period, the main engine was fired twice and the small engine once. Since the first maneuver was intended to study temperatures at higher altitudes, the controllers sent the Agena up to a 1,390- by 385-kilometer orbit. They watched it for almost seven hours and found that the temperatures varied little from those at lower orbits. The vehicle was then returned to a circular orbit (352 kilometers) that would make it available as an alternate target for later flights.99

Gemini IX-A and X had successfully grappled with some of the specific needs of the Apollo program, acquiring operational experience while fostering healthy debates between the two programs on procedures and equipment. Perhaps the greatest benefit to Apollo was the [351] demonstration and practice of several types of rendezvous. Each provided a storehouse of information. In addition, the orbit-shaping maneuvers to the higher altitudes established that the trapped-radiation hazards could be avoided on trips into deep space. Then, too, the very fact that one spaceborne vehicle could meet another, latch onto it, and use it as a kind of space tug offered many possibilities for such space flight concepts as shuttles, space stations, and space laboratories.

There had been problems, but missions IX-A and X had logged a combined total of three hours and 41 minutes open-hatch experience. Although the extravehicular hiatus between the fourth and ninth flights adversely affected both equipment and operational development, Cernan and Collins had shown that tasks outside the spacecraft were feasible. They found that all chores took longer than foreseen and that body positioning was difficult. During technical debriefings, each extravehicular pilot had pointed out the need for more and better restraints and handholds. These aids were being developed. Overall, perhaps, extravehicular activity remained Gemini's greatest problem. It was and is dangerous, difficult, and deceptive, despite its delights.

The ninth and tenth flights also took several steps forward in experiment performance. Despite operational constraints, usually brought on by limited fuel resources, each situation had been modified to wring the utmost from specific experiments. More and more, principal investigators were being brought in to help with modifications and to assist in rescheduling their tasks for later in the missions, if necessary. These realtime flight changes could not have been carried out in an unmanned flight and would not have been done in an earlier Gemini mission. So, in Gemini IX-A and X, the experiments program began to achieve maturity.

By the end of Gemini X, many of the men and women who had worked full time on the program had begun to have a strong feeling of anticlimax and to wonder about their next jobs. Some had already gone on to other fields, but Mathews tried to control this exodus and to hold enough together to finish the flights. Shortly after IX-A, he told his staff that the Gemini Program Office, as such, would not be continued. The people would be absorbed into other MSC activities - mainly Apollo and Apollo Applications. By early August, a personnel placement committee*** had begun work. It soon arranged four to six interviews for each of the 193 project office people. [352] This allayed any immediate fears, but Mathews still warned his staff to refrain from making personal contacts for new jobs until the committee could complete its arrangements.100 There were two more flights in the Gemini program, but it already seemed to be heading into history.

* This was the 299th Atlas launch - the 100th for NASA.

** Originally scheduled to do 16 experiments, Gemini X lost MSC-5 (lunar ultraviolet spectral reflectance), which was to determine the ultraviolet spectral reflectance of the lunar surface and aid in designing equipment to protect Apollo astronauts from sunburn and eye damage. Because the Moon was out of phase, this chore was deleted before the flight. M-5, bioassays of body fluids had been the bane of all crews from Gemini VII and XI-A. Mathews had tried in vain to get it out of the earlier missions. This time he succeeded - its cancellation on 12 July 1966 marked the end of medical experiments in the Gemini program.

*** The committee consisted of Augustine A. Verrengia (Gemini), Robert J. Bailey (Apollo), Donald T. Gregory (Flight Crew Operations), James Null (Apollo Applications), Chris C. Critzos (Flight Operations), and Elwyn H. Yeater (Engineering and Development).

81 NASA News Release No. 66-155, "Gemini 10 Launch Set for July 18," 17 June 1966; TWX, Mathews to SSD, Attn: Hull and Lt. Col. Fountain M. Hutchison, "Flight Safety Review for Gemini Launch Vehicle 10," GP-7613, 12 July 1966; TWX, Mathews to SSD, Attn: Gardner, "Gemini X Atlas-Agena Target Vehicle System Flight Safety Review," GP-7614, 12 July 1966; Gemini 10 News Center Release No. 12, "Status Report," 17 July 1966; [Ivan D. Ertel], Gemini X: Multiple Rendezvous, EVA Mission, MSC Fact Sheet No. 291-G (Houston, September 1966); Gemini 10 mission commentary transcript, 18-21 July 1966, tape 3, p. 1, tape 4, p. 1, tape 5, p. 1; "Gemini Program Mission Report, Gemini X," MSG-G-R-66-7, August 1966, pp. 1-1, 4-1; TWX, Kleinknecht to NASA Hq., Attn: Webb, and MSC, Attn: Gilruth, "Launch Summary Report, Gemini X Mission," GT-11215, 19 July 1966; "Gemini X Technical Debriefing," 26 July 1966, pp. 1-12; Michael Collins, interview, Houston,17 March 1967; Frank Thistle, Rocketdyne: The First 25 Years. . . . (Van Nuys, Calif., 1970).

82 "Gemini X Debriefing," pp. 12-19; "Gemini X Mission Report," pp. 5-14, -15, 7-2, -23, -24; "Gemini X Voice Communications (Air-to-Ground, Air-to-Air and On-Board Transcription)," McDonnell Control No. C115883, n.d., pp. 10-20, passim; William H. Allen, ed., Dictionary of Technical Terms for Aerospace Use, 1st ed., NASA SP-7 (Washington, 1965), p. 9.

83 "Gemini X Voice," pp. 57, 61-67, 69, 71, 72, 73, 76; "Gemini X Debriefing," pp. 28, 29, 32-41; John Young and Collins interviews; memo, Mathews to Asst. Dir., Flight Ops., "Ground support required for the Gemini X onboard M=4 rendezvous," GS-64121, 19 April 1966; Elms, "Second Interim Report, Gemini Mission Review Board, August 18, 1966," n.d., p. 1; memo, Mathews to Chief, Gemini Spacecraft Procurement Sec., "Contract NAS 9-6408, additional postflight analysis on Gemini X mission," GP-62332, 3 Aug. 1966; Meyer, notes on GPO staff meeting, 18 Aug. 1966, p. 2.

84 "Gemini X Voice," p. 78; "Gemini X Mission Report," p. 1-2.

85 "Gemini X Mission Report," pp. 1-2, 4-8, -25, 5-151; "Gemini X Voice," pp. 85, 89, 90, 91, 92; "Gemini X Debriefing," pp. 47, 50; Gemini 10 News Center Release No. 3, "Gemini 10 Flight Controllers," 13 July 1966.

86 James M. Grimwood and Barton C. Hacker, Project Gemini Technology and Operations: A Chronology, NASA SP-4002 (Washington, 1969), pp. 266-67; "Gemini X Voice," pp. 93-99; "Gemini X Debriefing," p. 51; "Gemini X Mission Report," pp. 4-8, -21, -26.

87 "Gemini X Technical Debriefing," pp. 52-53; "Gemini X Voice," pp. 99-107; "Gemini X Mission Report," pp. 4-8, -25.

88 "Gemini X Voice," pp. 112, 113; "Gemini X Debriefing," pp.59, 60; "Gemini X Mission Report," pp. 4-8, -21, -26.

89 "Interim Report, Manned Space Flight Experiments, Gemini X Mission, July 18-21, 1966," MSC TA-R-67-1, March 1967, pp. 1, 5; William Dan Womack, "Experiment M405 (MSC-3), Triaxis Magnetometer," ibid., pp. 919; James Marbach, "Experiment M408 (MSC6), Beta Spectrometer," ibid., pp. 21-36; Reed S. Lindsey, "Experiment M409 (MSC-7), Bremsstrahlung Spectrometer," ibid., pp. 37-48; Frank B. Newman, "Lesson Plan and Handout, Special Technical Data, Gemini X Experiments," SCD, No. M35, 17 June 1966, pp37-39, 53-60; Malik and Souris, Gemini Technical Summary, pp. 310, 311-12; "Abstract of Meeting on Experiments for Gemini X and XI, May 11 and 12, 1966," 1 June 1966; "Abstract of Meeting on Gemini X Experiments Functional Verification Review Board, June 20, 1966," 24 June 1966; memo, Mathews to Asst. Dir., Flight Crew Ops., "Gemini VI experiments and associated equipment," EX1365-0223, 17 Nov. 1965; memo, Mathews to Mgr., EXPO,"M-5 Experiment on Gemini VIII," GP- 61958, 24 Jan. 1966; letter, Day to Piland, 23 June 1966; TWX, Gilruth to NASA Hq., Attn: Mueller, EX42/T65-66, 12 July 1966; TWX, Charles A. Berry to NASA Hq., Attn: Actg. Dir., Space Medicine, 29 June 1966; Gemini 10 News Center Release No. 5, "Changes in the experiment schedule," 14 July 1966; letter, Berry to NASA Hq., Attn: Brig. Gen. Jack Bollerud, "Medical reasons for deletion of Experiment M-5 from the remaining Gemini and first manned Apollo flights," 25 July 1966; TWX, Kleinknecht to NASA Hq., Attn: Webb, and MSC, Attn: Gilruth, "Daily Report Number 1 - Gemini X Mission," GT-11216, 19 July 1966, p. 13; "Gemini X Mission Report," pp. 8-5, -7.

90 "Gemini X Debriefing," pp. 60-68; "Gemini X Voice," pp. 118-25, 131, 132-49; "Gemini X Mission Report," pp. 7-5, -6, -31, -32, -47, -48, 8-62, -63, -64, -65; Karl G. Henize and Lloyd R. Wakerling [sic], "Experiment 8013 (S-13), Ultraviolet Astronomical Camera," in "Gemini X Experiments Interim Report," pp. 97-104; John R. Brinkmann and Robert L. Jones, "Experiment M410 (MSC-8), Color Patch Photography," ibid., pp. 49-53; TWX, Mathews to McDonnell, Attn: Burke, "Contract NAS 9-170, Gemini, Extravehicular Activity Meeting," GP-7586, 16 June 1966; memo, Mathews to Dirs., Flight Crew Ops. and Flight Ops., "Gemini X extravehicular flight plan," GS-64160, 15 July 1966.

91 "Gemini X Voice," pp. 151-59, 165, 167, 168, 171, 174, 175, 182; "Gemini X Debriefing," pp. 68, 69, 71, 72; Gemini 10 mission commentary, tape 109, pp. 2-3; TWX, Kleinknecht to NASA Hq., Attn: Webb, and MSC, Attn: Gilruth, "Daily Report Number 2 - Gemini X Mission," GT-11217, 20 July 1966, pp. 7, 10, 12; Mathews memo, GS-64 160, 15 July 1966.

92 "Gemini X Voice," pp. 183-90, 192, 194, 196-97; "Gemini X Mission Report," pp. 4-8, -21, -26, 6-17, -18, 7-27; "Gemini X Debriefing," pp. 75, 76; Kleinknecht TWX, GT-11217, 20 July 1966, pp. 13-14; "Abstract of Meeting on Gemini Experiment S-26, Ion Wake Measurement, Gemini X and XI, September 13, 1965," 23 Sept. 1965; TWX, Electro-Optical Systems, Inc., to MSC, Attn: James W. Campbell, No. 15, 1 Aug. 1966; David B. Medved, "Experiment 8026 (S-26), Ion-Wake Measurement," in "Gemini X Experiments Interim Report," pp. 105-14; Paul D. Lowman, Jr., and Herbert A. Tiedemann, "Experiment 8005 (S-5), Synoptic Terrain Photography," ibid., pp. 63-72; Kenneth M. Nagler, "Experiment 8006 (S-6), Synoptic Weather Photography," ibid., pp. 73-79.

93 "Gemini X Mission Report," pp. 1-3, 7-27; "Gemini X Voice," pp. 202, 208-11, 218, 219; "Gemini X Debriefing," pp. 79-81; memo, Mathews to dist., "Mission Planning," GV-66170, 2 Sept. 1965; TWX, Mathews to SSD, Attn: Gardner, "Stability of Non-Powered Agena," GV-12186, 6 Sept. 1965; "Abstract of Meeting on Atlas/Agena Coordination, April 21, 1966," 10 May 1966; Gemini 10 News Center Release No. 13, "NORAD role in Gemini 10," 17 July 1966.

94 "Gemini X Mission Report," p. 4-9; "Gemini X Voice," pp. 219-34, 236-38; Gemini 10 mission commentary, tape 165, p. 1, tape 167, p. 1, tape 169, p. 3.

95 "Gemini X Mission Report," pp. 7-32, -33, 8-59, -60; "Gemini X Debriefing," pp. 95-107; Kleinknecht TWX, GT-11216, 19 July 1966, p. 13; "Gemini X Voice," pp. 170, 238-50; Mathews TWX, GV-12376, 14 March 1966; memo, Mathews to Chief, Engineering Div., Attn: Head, Test Systems Sec., "Government-furnished aeronautical equipment 50foot umbilical support to McDonnell Aircraft Corporation for Gemini X," GP-62088, 22 March 1966; "Abstract of Meeting on Experiment S-10 (Agena Micrometeorite Collector), August 9, 1965," 18 Aug. 1965; TWX, Gilruth to NASA Hq., Attn: Mueller, "T-017 Meteoroid Impact," 8 July 1966; Curtis L. Hemenway, "Experiment 5010 (S-10), Agena Micrometeorite Collection," in "Gemini X Experiments Interim Report," pp. 81-95; Burns et al., "Gemini Extravehicular Activities," pp. 3-12, -13; Collins, John Young, and Johnson interviews.

96 "Gemini X Voice," pp. 251-54, 255-57; "Gemini X Debriefing," pp. 108-13, 115-16; Gemini 10 mission commentary, tape 1 12, p. 1, tape 113, p. 1, tape 174, p. 1; TWX, Mathews to McDonnell, Attn: Burke, "Contract NAS 9-170, Gemini Hatch Closing Loads," GS-10108, 7 April 1966; TWX, Mathews to McDonnell, Attn: Burke, "Contract NAS 9-170, Gemini, Zero G Flight Article," GS-101 19, 1 June 1966; Grimwood and Hacker, Gemini Chronology, p. 270.

97 "Gemini X Debriefing," pp. 116-17, 120, 121, 122; "Gemini X Mission Report," pp. 4-2, -13, -33; "Gemini X Voice," pp. 273, 275, 280-83; TWX, Kleinknecht to NASA Hq., Attn: Webb, and MSC, Attn: Gilruth, "Gemini X Mission Summary Report," GT-11218, 21 July 1966, pp. 6, 9, 10.

98 Kleinknecht TWX, GT-11218, 21 July 1966, pp. 1-3, 11-12; "Gemini X Mission Report," pp. 1-3, 5-28, -29, 6-14, -15, 7-37, -38, -39; Grimwood and Hacker, Gemini Chronology, p. 265; [Ertel], Gemini X; "Gemini X Debriefing," pp. 128-42; Gemini 10 mission commentary, tape 236, pp. 1-2.

99 Memo, Mathews to Dir., Flight Ops., "Post-reentry Agena testing," GV-66479, 13 July 1966; "Gemini X Mission Report," pp. 5140, -142, -143; TWX, Kleinknecht to NASA Hq., Attn: Webb, and MSC, Attn: Gilruth, "Gemini X Interim Report," GT-11219, 30 July 1966, pp. 19, 27, 33, 39.

100 Letter, Mueller to Gilruth, 1 Aug. 1966, with enclosure, "Gemini Objectives and Accomplishments"; Meyer, notes on GPO staff meetings, 8 and 14 June 1966; memo, Mathews to GPO personnel, "GPO Phasedown," GA-60428, 15 Aug. 1966; memo, Mathews to Albert B. Triche, "Phasedown planning," GA-60422, 12 Aug. 1966; memo, Mathews to Harle L. Vogel, "Phasedown planning," GA-60423, 12 Aug. 1966; Augustine A. Verrengia, telephone interview, 10 Aug. 1973.

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