The year 1966 was a busy one for the US space program and its push to reach the Moon by the end of the decade. With less than four years left to reach that goal, NASA had already begun the first unmanned tests of the new Apollo spacecraft in space and it was hoped that the first manned test flights would fly by year’s end (see “The First Flight of the Apollo-Saturn IB”). By the summer of that year, NASA’s Surveyor 1 spacecraft had successfully landed on the Moon (see “Surveyor 1: America’s First Lunar Landing”) confirming that it was possible and the first Lunar Orbiter was being prepared for launch so that it could map potential landing sites (see “Lunar Orbiter 1: America’s First Lunar Satellite“). More importantly, NASA had completed seven crewed flights with their two-man Gemini spacecraft to gain the practical experience needed to fly Apollo to the Moon and back. Despite the successes, there were still challenges to overcome with only three Gemini flights remaining before the planned end of the program. The Gemini 10 mission of July 1966 would begin to address these issues and continue to expand the envelope of NASA’s capabilities.

Gemini Program Objectives

The purpose of NASA’s Gemini program was to develop the technologies and techniques needed to fulfill President Kennedy’s goal of landing a man on the Moon by 1970. The major objectives of the program were:

– Demonstrate that humans and their equipment can survive up to two weeks in space

– Demonstrate rendezvous and docking techniques in orbit

– Demonstrate the technology and techniques needed to perform EVAs (Extra-Vehicular Activities)

Meeting all of these objectives was necessary if the Apollo lunar program were to be successful.

Gemini was a two-man spacecraft that was roughly conical in shape with a base diameter of 3.3 meters which stood 5.8 meters tall. Built by the McDonnell Aircraft Corporation (which merged with Douglas in 1967 to become McDonnell Douglas which subsequently merged with Boeing 30 years later), it consisted of two major sections. The first section was the reentry module which housed the crew, their equipment, food supplies and so on in orbit as well as the recovery systems needed to safely return them to Earth. The nose of this module also contained an L-band radar system for orbital rendezvous operations. Unlike today’s crewed spacecraft, the Gemini crew cabin was pressurized with pure oxygen at about one-third standard atmospheric pressure to save weight. The next section, the adapter section, connected the reentry module to the launch vehicle during ascent and housed equipment needed to support the crew while in orbit. It consisted of a retrograde section which held a set of four solid retrorockets used to start the descent to Earth from orbit and an equipment section which housed the in-orbit propulsion system called OAMS (Orbital Attitude and Maneuvering System), life support, power systems and all other equipment not needed for the return to Earth.

With a typical launch mass of up to about 3,700 kilograms or more, Gemini needed the largest operational rocket available at the time to get into orbit: a modified Titan II ICBM built by Martin Marietta (which is now part of Lockheed Martin). A number of modifications were made to simplify the operation of this rocket, smooth out its ride and improve its reliability to support crewed missions. With the Gemini spacecraft mounted on top, the Titan II GLV (Gemini Launch Vehicle) was 33 meters tall and had a fully fueled launch mass of about 154 metric tons.

Since its first manned mission in March 1965, the Gemini program had made steady progress in meeting its objectives in support of Apollo over the following 15 months. A series of three long duration missions culminating in the two-week flight of Gemini 7 in December 1965 demonstrated that a crew and its spacecraft could operate in space for periods of time longer than that needed for Apollo to land on the Moon and return (see “Gemini 7: Two Weeks in the Front Seat of a Volkswagen“). With this major program objective met, the rest of the Gemini missions concentrated on perfecting rendezvous and docking techniques as well developing the skills needed to perform EVAs.

Gemini 6 successfully performed the first rendezvous using Gemini 7 as a target (see “Rendezvous in Space: Gemini 6 and 7”). Gemini 8 completed the first docking in orbit in March 1966 although its mission was cut short due to a thruster malfunction (see “Gemini 8: The First Docking in Space”). Gemini 9 attempted to repeat the feat of its predecessor in June with a faster and more aggressive rendezvous profile but was unable to dock with its target because its launch shroud had failed to jettison properly (see “The Angry Alligator & The Snake: The Mission of Gemini 9”). Difficulties were also encountered during the mission’s EVA forcing it to be cut short due to astronaut fatigue. The objectives of the Gemini 10 mission were to continue gaining experience in rendezvous and docking testing new tools and techniques as well as addressing the EVA issues.

The Gemini 10 Mission Plan

On January 24, 1966 NASA announced the crew for the Gemini 10 mission. The primary crew consisted of USN Commander John W. Young as the command pilot and USAF Major Michael Collins as the pilot. The 35-year old Young was a test pilot before being selected as part of NASA’s second group of astronauts in September 1962 and had previously flown as the pilot of the Gemini 3 mission with veteran astronaut Gus Grissom in March 1965 (see “The Mission of Gemini 3”). Collins, who was also 35 years old, was a West Point graduate and served as a test pilot before being selected as part of NASA’s third group of astronauts in October 1963. This was going to be his first flight in space.

The original backup crew for the Gemini 10 mission were to be USN Lt. Commander James Lovell, who had been the pilot on the record-setting Gemini 7 mission, and rookie astronaut USAF Major Edwin “Buzz” Aldrin. With the death of the original primary crew of the Gemini 9 mission, Elliot See and USAF Captain Charles Bassett, on February 28, 1966 when their T-38 jet crashed, Lovell and Aldrin became the new backup crew for Gemini 9 as the original back up crew of USAF Major Thomas P. Stafford and USN Lieutenant Eugene A. Cernan moved up to become the prime crew. On March 21, NASA announced the replacement Gemini 10 backup crew: USN Lt. Commander Alan Bean as command pilot and USMC Major Clifton Williams as pilot. Both rookies had extensive experience as test pilots before joining NASA as part of its third astronaut group along with Mike Collins.

Like the previous two missions, the first set of objectives for the Gemini 10 mission centered on orbital rendezvous and docking. The docking target chosen for the Gemini program was a modified Agena D upper stage known as the Gemini Agena Target Vehicle (GATV) launched into orbit using the SLV-3 (Standard Launch Vehicle-3) version of the Atlas booster built by General Dynamics. Built by the Lockheed Missile and Space Company (which is now part of the aerospace giant, Lockheed Martin), the Agena D not only served as an upper stage for use with Thor, Atlas and (by 1966) the Titan IIIB rockets, but could also be integrated into range of Defense Department payloads such as the Corona reconnaissance satellites to provide in-orbit support functions during these missions. The standardized Agena D, with its modular design, could be easily modified to serve as a docking target for Gemini.

In addition to modifications to its primary and secondary propulsion systems to support its role as a docking target, the forward end of the Agena D was fitted with an auxiliary rack holding special rendezvous and telemetry equipment. Also added were strobe lights and an L-band radar transponder to aid in rendezvous operations as well as command equipment to allow the GATV to be controlled from the ground or by the Gemini crew. A cone shaped target docking adapter (TDA), which was under a shroud during launch, was added to the forward end of the stage to allow the nose of the Gemini reentry module to dock with the Agena and mechanically lock the two spacecraft together. Once in orbit, the GATV was 9.7 meters long with a mass of about 3,200 kilograms.

A number of different rendezvous modes with the GATV had been identified during theoretical studies of the technique. For the first Gemini dockings, the “coelliptical” method was chosen where the active spacecraft would first be placed into a circular orbit below and some distance behind the passive target spacecraft. The active spacecraft would then catch up to its target over the course of several orbits then maneuver to match the target’s orbit in order to perform the actual docking. While this approach took longer than other possible methods, it was much more flexible and allowed more time to plan and execute maneuvers – a desirable characteristic for the first attempts of the untried orbital rendezvous procedure. Ultimately it was decided that the Apollo Lunar Module would follow a similar rendezvous profile as it returned to lunar orbit following launch from the surface.

For the three-day Gemini 10 mission, the active Gemini spacecraft would be launched about 100 minutes after its Agena GATV, designated “Agena 10”, just as it was completing its first orbit. Gemini 10 would then follow an “M=4” rendezvous profile where it would rendezvous with its target during the fourth revolution. This was similar to the profile followed during the Gemini 6 and 8 missions but not as aggressive as the “M=3” profile successfully followed by Gemini 9. Unlike the earlier missions which relied on inputs from Gemini’s L-band radar to compute rendezvous maneuvers, Gemini 10 would attempt to use optical navigation data for the task. Apollo engineers had already deleted the rendezvous radar from the Apollo Command-Service Module (CSM) to save mass and were hoping to do the same with the Lunar Module so optical navigation needed to be more fully investigated. Similar optical techniques were used during two of the three rendezvous exercises performed during the Gemini 9 mission revealing some practical limitations of the approach.

After additional exercises were performed following its initial docking, Gemini 10 would use the propulsion systems of Agena 10 to perform a series of maneuvers and boost the docked spacecraft into a much higher elliptical orbit. From this new orbit, Gemini 10 would then perform a rendezvous with a second but unpowered Agena target from the earlier Gemini 8 mission, GATV-5003 now designated “Agena 8”, which was in a circular 398-kilometer storage orbit. Since the batteries on Agena 8 were depleted, this second rendezvous would have to rely on optical navigation by the astronauts as well as tracking information from the ground. No docking would be attempted with Agena 8.

The other major mission objectives centered on gaining EVA experience. While the first short EVA performed by Ed White during the Gemini 4 mission in June 1965 went well (see “The Forgotten Mission of Gemini 4”), the same could not be said for the next EVA performed by Gene Cernan during the Gemini 9 mission a year later. Cernan became dangerously fatigued during his long EVA as he struggled to perform the simplest tasks. Suit-related mobility problems, the lack of adequate handholds and foot restraints as well as fogging issues with Cernan’s helmet faceplate conspired to force an early end to this EVA. Performing EVAs was turning out to be more difficult and dangerous than originally expected and more experience was sorely needed.

In order to breakup the EVA tasks, Mike Collins would perform two EVAs during the Gemini 10 mission that were shorter with less ambitious goals than the previous mission. For these EVAs, Collins would wear a modified G4C spacesuit similar to that was used during the Gemini 8 mission along with a 19-kilogram, chest mounted Extravehicular Life Support System (ELSS) to control his life support and provide 30-minutes of emergency oxygen if a problem arose with the ship’s supply. The first EVA would be a simple “stand up” EVA performed as the docked Gemini/Agena 10 spacecraft was catching up to the Agena 8 target for the mission’s second rendezvous. During this 75-minute EVA, Collins would simply stand in his open hatch and perform a series of tasks. These included taking ultraviolet (UV) images of selected star fields using a camera fitted with an objective grating to create spectra covering wavelengths from 200 to 400 nanometers.

The second EVA would be performed after Gemini 10 had undocked from its Agena 10 target and was station keeping with the inert Agena 8 target following the mission’s second rendezvous. For this EVA, Collins would use a Hand Held Maneuvering Unit (HHMU) to help move outside the ship while attached to Gemini by a 15-meter umbilical which also supply Collins with oxygen and electrical support. The HHMU would use nitrogen gas supplied via a hose that Collins would connect to an outlet on the spacecraft’s exterior early in the EVA. In addition to assessing the HHMU, Collins was tasked with retrieving micrometeoroid sample panels from the exterior of the Gemini 10 spacecraft and a similar panel from Agena 8 which had been exposed to space for four months.

After completing the second EVA, Gemini 10 would start a series of maneuvers to separate from Agena 8 and enter a new orbit for its eventual return to Earth. After performing additional experiments in orbit, the astronauts would fire Gemini’s retrorockets for a splashdown in the Atlantic Ocean 480 kilometers east of Cape Kennedy where the mission had started 70 hours and 17 minutes earlier. The now free-flying Agena 10 target vehicle would perform a series of engineering tests and be left in a storage orbit where it could serve as a dual-rendezvous target for a future Gemini mission just as Agena 8 had.

Since the Gemini 6 and 9 missions both had experienced the unexpected loss of their Agena targets, back up plans were put in place to deal with the same possibility with Gemini 10. In case of the loss of Agena 10, an alternate “Gemini 10A” mission plan called for Gemini to be launched into an initial 162 by 385 kilometer orbit. From there, Gemini 10A would perform a rendezvous directly with Agena 8 on the 16th revolution. With its larger 426-kilogram load of OAMS propellant, Gemini 10 would be able to reach Agena 8 safely unlike the earlier Gemini 9A mission with its smaller 316-kilogram propellant load. Alternate plans for the EVA, engineering tests and experiments would also be followed. With a dual rendezvous involving three spacecraft and a pair of EVAs accomplished during less than three days in orbit, the Gemini 10 mission would be the most complex crewed spaceflight attempted to date.

The Start of the Mission

The first major piece of mission hardware to be shipped for launch was Gemini spacecraft number 10 which left McDonnell’s facility in St. Louis, Missouri on May 13, 1966. Three days later, the GATV-5005 which would serve as the Agena 10 rendezvous and docking target arrived at Cape Kennedy. As testing on Gemini and the Agena spacecraft began, the mission’s Titan II launch vehicle, GLV-10 serial number 62-12565, arrived at the Cape on May 20 and was erected on its pad at Launch Complex 19 on June 8 – just five days after the successful launch of the Gemini 9A mission.

The Atlas rocket that was originally earmarked to launch Agena 10, serial number TLV-5304, had already been diverted to launch a backup target known as the Augmented Target Docking Adapter (ATDA) for the Gemini 9A mission on June 1 after the loss of its original GATV. A replacement Atlas, TLV-5305, was delivered on June 19 and erected on the pad at LC-14 six days later. The Agena 10 target was mated to the Atlas on July 1. Spacecraft number 10 was mated with its Titan II launch vehicle on July 5 for the start of a series of final tests. With the successful completion of the Simulated Flight Test on July 13 with dual countdowns for the launch of the Agena and Gemini, the first launch attempt was set for July 18.

Because of the need to rendezvous with the unpowered Agena 8 in its storage orbit about two days after liftoff, the launches for this mission were scheduled for much later in the day than the previous Gemini flights. The first craft scheduled for launch was Agena 10 at 3:39 PM EDT which would be followed by Gemini 10 and its 35-second launch window about 100 minutes later as the Agena was completing its first orbit. In order to make the most of their first hours in space and dock with the Agena during the fourth revolution, Young and Collins went to bed at 2:00 AM on launch day and were woken up at about noontime. By 2:00 PM, they were enjoying a pre-launch brunch of steak and eggs with Deke Slayton and representatives of the primary and back up crews of the previous mission, Jim Lovell and Gene Cernan. Afterwards, Young and Collins got suited up and were on their way to their spacecraft waiting for them at LC-19.

Just two seconds into its launch window, Agena 10 lifted off from LC-14 at 3:39:46 PM EDT on July 18 and was successfully placed into its prescribed orbit. At 5:20:27 PM, Gemini 10 followed with its launch from LC-19. The 3,763-kilogram Gemini 10 successfully reached an initial 160 by 269 kilometer orbit 1,800 kilometers behind its target for the start of its five-plus hour chase. With difficulty, Collins used a Kollsman then an Ilon sextant to get a fix on his position but the numbers the crew calculated based on their optical navigation differed from those calculated on the ground using tracking telemetry. The decision was made to use the ground-based figures and Young performed the first maneuver placing Gemini 10 into a 265 by 272 kilometer orbit.

Using a similar sequence of maneuvers as had been successfully employed during the Gemini 6A and 8 missions, Gemini 10 closed in on its target during the succeeding orbits. Unfortunately when Young attempted to align his craft’s guidance platform in preparation for the terminal phase of the rendezvous, he had not noticed that Gemini 10 had drifted slightly during the procedure resulting in a misalignment. The error required a pair of additional large maneuvers to correct as Gemini approached Agena 10. Rendezvous was completed five hours and 21 minutes after launch and hard docking was achieved 31 minutes later. Unfortunately, Gemini 10 had consumed 181 kilograms of OAMS propellant during its first docking because of the extra maneuvering required from the alignment error – 63 kilograms more than had been budgeted and triple the amount consumed during earlier missions. Mission control cancelled subsequent docking and station keeping exercises that had been planned. Gemini and Agena would remain docked for the next 38 hours and 47 minutes.

About six and a half hours into the mission, Young and Collins started preparations for the next phase of their mission: a series of maneuvers of the combined spacecraft using the Agena’s propulsion system for the first time. Because of the extra propellant that had been consumed, the crew was concerned that the rendezvous with Agena 8 would be cancelled. To their relief, the decision was made to proceed and at a mission elapsed time of 7 hours, 38 minutes and 34 seconds the main engine of Agena’s primary propulsion system was ignited. With the astronauts thrown forward against their restraints, the Agena’s primary propulsion system added 129 meters per second to the combined spacecraft’s velocity. When Agena’s engine finally shutdown, the docked Gemini/Agena 10 were now in a 294 by 763 kilometer orbit – a recording setting altitude for a manned spacecraft which handily beat the previous record of 495 kilometers set during the Soviet Voskhod 2 mission by Pavel Belyayev and Alexei Leonov in March 1965 (see “The Mission of Voskhod 2“).

With the Agena dominating the view out of their windows, Young and Collins could not fully appreciate the perspective from their new high orbit. Instead, their post-flight descriptions were dominated by the spectacular sight of the Agena’s engine firing and the odd sensation of pulling negative-gs. Nine hours into the flight, the crew started their first sleep period in orbit as their spacecraft slowly got into phase with the orbit of Agena 8.

The Second Day

After sleeping fitfully, Young and Collins were ready to start their first full day in orbit at the end of their rest period 18 hours after launch. At 20 hours and 20 minutes after launch, the Agena’s main engine was fired once again to slow the docked vehicles by 105 meters per second. This lowered the apogee to 382 kilometers in preparation for the rendezvous with the inert Agena 8. Two hours and 17 minutes later, a third and final burn of Agena’s main engine was performed. This changed the velocity by 25 meters per second and raised the spacecraft’s perigee to 377.6 kilometers. The orbit of Gemini/Agena 10 was now 17 kilometers below that of Agena 8 allowing Young and Collins to catch up with their second rendezvous target over the course of the next 25 hours.

With their major Agena maneuvers completed, the Gemini 10 crew started preparations for Collin’s standup EVA with its 131-item check list. At 23 hours and 24 minutes mission elapsed time, Collins opened his hatch to begin his first EVA. After orbital sunset, Collins successfully exposed 22 frames of film to observe the southern part of the Milky Way from the stars β Crucis to γ Velorum at UV wavelengths. Young helped identify the stars as he controlled the attitude of the spacecraft during the session. By orbital dawn, Collins began his next set of tasks but was unable to complete them as his eyes began to fill with tears. Initially Collins thought that maybe the new anti-fogging compound applied to the inside of his helmet’s faceplate was the cause but Young soon started having the same problem as well as noticing a strange smell.

The decision was made to cut the standup EVA short to assess the problem. After an EVA of only 49 minutes, the hatch was finally secured about six minutes earlier than originally planned. Young and Collins suspected that the strange smell might have been caused by the lithium hydroxide used to remove the carbon dioxide from the crew’s air. Eventually the problem was traced having both suit fans on simultaneously. One of the fans was shut down and the strange smell disappeared. After a good meal, the crew began their second sleep period about 30 hours after launch. Fatigued by the day’s activities, Young and Collins slept much better this time around.

The Last Day and the Return Home

After a getting some much needed sleep, the astronauts’ second full day in orbit started with system checks, a meal and experiments. A couple of hours after the end of their rest period, Young and Collins fired the Agena’s smaller secondary propulsion system (SPS) for 18 seconds at mission elapsed time of 41 hours and four minutes to align their orbital plane with that of Agena 8. A four second firing of the SPS 31½ minutes later lowered the apogee by 1.8 kilometers. With this final phasing maneuver, Agena 10 was no longer needed and Young undocked the two craft 44 hours and 40 minutes into the mission. Gemini 10 would use its own propulsion system to finish the rendezvous with Agena 8.

Relying solely on tracking information from the ground, Young continued the rendezvous with Agena 8 while Collins prepared for his second EVA to start shortly after they arrived. At one point Young thought he had sighted Agena 8 at the impossible range of 176 kilometers but it turned out to be the newly freed Agena 10 only 5½ kilometers away. Agena 8 was finally spotted at a range of 30 to 37 kilometers right where it was predicted to be. At mission elapsed time of 47 hours and 26 minutes, Young started the final closure maneuvers and finally came to a stop about three meters from Agena 8. Despite having no power, their target was pretty stable and was deemed safe for Collins to approach during his EVA.

With Young closely watching his propellant usage, Collins opened his hatch at orbital dawn for his second EVA 48 hours and 41 minutes after launch. Attached to Gemini 10 by his 15-meter umbilical, Collins exited the spacecraft and retrieved a micrometeoroid package from the exterior of his spacecraft. Collins next connected a line on his umbilical to an outlet to supply compressed nitrogen gas to his HHMU. With 4.9 kilograms of compressed gas available, the HHMU could provide a delta-v of almost 26 meters per second. After Young had maneuvered so that the hatches of the Gemini were just 1½ meters from the Agena, Collins pushed off towards the Agena using the HHMU to maneuver.

Collins struggled to get a grip on the Agena’s docking collar so that he could remove its micrometeoroid package – the same one Dave Scott was suppose to retrieve the previous March before the Gemini 8 mission was cut short due to a thruster malfunction. Collins experienced difficulties with his task just as Cernan had during his EVA with every task taking much longer than planned or rehearsed during training. Ultimately, Collins was unable to attach a replacement experiment panel for fear of losing the panel he had just retrieved. While struggling to get his sample back into the Gemini cabin, he lost to space the 70 mm camera that was being used to record his work. Because of this and the malfunction of a second camera Young was using, there are no images of Collins EVA or of Agena 8.

Collins then unsnapped a buckle on his umbilical allowing it to unfurl from six meters to its full 15 meter length so that he could better evaluate the performance of the HHMU. But before he had a chance to perform his evaluation, Mission Control cut the EVA short because of their concerns about propellant use during station keeping. Every time Collins pushed off Gemini or tugged on his umbilical line, Young had to fire Gemini’s thrusters to maintain position and attitude expending precious propellant in the process. With some difficulty as Collins struggled with his rigid pressure suit and his long umbilical, he got back inside with Young’s help and closed the hatch 39 minutes after the EVA had started. Between Cernan on Gemini 9A and Collins on this mission, a total of three hours and 41 minutes of EVA time had been logged. Although problems had been encountered which remained to be rectified, at least it had been shown that astronauts could perform tasks outside their spacecraft.

An hour and 12 minutes after the end of the second EVA, the hatch was opened for one last time so that the umbilical, ELSS and other equipment no longer needed could be thrown overboard. At mission elapsed time of 51 hours and 38 minutes, Young fired the OAMS thrusters to slow Gemini 10 by 30 meters per second lowering the perigee to just 106 kilometers in preparation for the return home. For the balance of the day, Young and Collins performed more experiments including photography of the Earth and its weather before settling down for their last rest period of the mission.

Young and Collins woke up about 63 hours after launch for a meal, systems checks and more experiments before their return. At mission elapsed time of 70 hours and 10 minutes, Gemini 10 fired its four solid retrorocket motors to start their half-hour descent back to Earth. Using bank angles provided by Gemini’s computer, Young steered the reentry module to a splashdown at 4:07 PM EDT on July 21 in the primary west Atlantic recovery zone only 5.4 kilometers from the aim point and within view of their recovery ship, the Iwo Jima-class amphibious assault ship USS Guadalcanal. Young and Collins had successfully completed their mission after 70 hours, 46 minutes and 39 seconds of flight. After recovery divers had attached flotation gear to the reentry module, Young and Collins climbed out of their capsule for a helicopter recovery and were flown to the waiting USS Guadalcanal. Gemini 10 itself was hoisted aboard about an hour after splashdown.

As Young and Collins went through their post-flight debriefings and exams, ground controllers proceeded to put Agena 10 through its paces in orbit. During the course of 12 hours, the Agena burned its main engine twice and its smaller SPS once. The spacecraft spent almost seven hours in a 385 by 1,390 kilometer orbit to see how Agena’s temperatures varied compared to lower orbits. Afterwards Agena 10 was placed into a 347 by 352 kilometer storage orbit where it could serve as a target for a future Gemini mission. With only two Gemini flights left and with much work still left to do, it was time to take stock and plan for the most ambitious missions of the series that were yet to come.

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Related Video

Here is a short NASA documentary summarizing the Gemini 10 mission.

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Related Reading

“Gemini 8: The First Docking in Space”, Drew Ex Machina, March 16, 2016 [Post]

“The Angry Alligator & The Snake: The Mission of Gemini 9”, Drew Ex Machina, June 6, 2016 [Post]

General References

David Baker, The History of Manned Space Flight, Crown Publishers, 1981

Barton C. Hacker and James M. Grimwood, On the Shoulders of Titans: A History of Project Gemini, SP-4203, NASA History Division, 1977

David J. Shayler, Gemini: Steps to the Moon, Springer-Praxis, 2001

“Gemini 10 Press Kit”, NASA Press Release 66-179, July 15, 1966

“Gemini Program Mission Report: Gemini X”, MSC-G-R-66-7, NASA Manned Spacecraft Center, August 1966