Gemini 8 was the Gemini series’ sixth crewed Earth-orbiting spacecraft, carrying Neil Armstrong and David Scott. The mission’s principal goals were to complete rendezvous and four docking tests with the Agena target vehicle, as well as to conduct an ExtraVehicular Activity (EVA) experiment. Other goals included parking the Agena in a 410 km circular orbit, conducting systems evaluation, testing the auxiliary tape memory unit, and demonstrating controlled reentry. On board were ten technical, medicinal, and scientific investigations.
In This Article...
Mission Profile
On March 16, 1966, at 11:41:02 a.m. EST (16:41:02.389 UT), Gemini 8 was launched from Complex 19 and placed into a 159.9 x 271.9 km orbit at 11:47:36 EST. The spacecraft then executed nine maneuvers over the next six hours to meet up with the Gemini Agena Target Vehicle (GATV), which had been launched earlier (at 9:00 a.m. EST). At 4:39 p.m. EST, the rendezvous phase finished with the spacecraft 45 meters apart and no relative motion. After nearly a half-hour of stationkeeping and various maneuvers, Gemini 8 moved in and docked with the GATV on the 5th revolution at 5:14 p.m., making it the first docking ever in space.
The combined vehicle went into a dramatic yaw and tumble around 27 minutes after docking at 5:41 p.m. When Armstrong disconnected the Gemini capsule from the GATV, it began to roll, pitch, and yaw even faster than when it was connected, nearing and potentially exceeding one revolution per second. Armstrong and Scott were able to deactivate the Orbit Attitude and Maneuver System (OAMS), and all 16 reentry control system (RCS) thrusters were used to dampen the roll in a final attempt to stop the rapid tumbling. At 6:06:30 p.m., this maneuver was successful in stabilizing the spacecraft, however it used up 75 percent of the RCS fuel. The tumbling was eventually revealed to be caused by one of Gemini 8’s 25-pound OAMS roll thrusters (roll thruster no. 8) firing repeatedly. It had apparently short-circuited and jammed open while being used to maneuver the Gemini-GATV combination.
Gemini safety guidelines mandated an immediate landing due to the premature use of the reentry control system, so the planned EVA and other activities were canceled. The spacecraft splashed down in the western Pacific Ocean about 800 kilometers west of Okinawa at 25.22 N, 136.00 E, 2 kilometers from the target, on the 7th revolution at 9:45:49 p.m. on March 16, little over 10 hours after launch. The timing at the splashdown site was 10:22:28 p.m. EST, but it was during the day. Within minutes, frogmen from the United States Air Force parachuted from a C-54 rescue plane and attached a flotation collar to the spacecraft. The crew was picked up 3 hours later (1:28 a.m. EST, 17 March) by the recovery ship USS Mason, and the spacecraft at 1:37 a.m. The mission took 10:41:26 to complete.
Many mission objectives were not met due to the mission’s early termination, but rendezvous and docking were completed, as was the evaluation of the auxiliary tape memory unit and demonstration of controlled reentry. Only the Agena micrometeorite collection was successful out of the six scientific trials. The others were lacking: (1) zodiacal light photography, (2) frog egg growth, (3) synoptic landscape photography, (4) nuclear emulsions, and (5) cloud spectrophotography. The Agena Target Vehicle stayed in orbit while ground command made maneuvers, including successfully placing it in circular orbit.
Spacecraft and Subsystems
The Gemini spacecraft had a cone-shaped capsule with two separate modules: a reentry module and an adaptor module. The adapter module served as the spacecraft’s foundation. It was a truncated cone with a height of 228.6 cm, a diameter of 304.8 cm at the base, and a height of 228.6 cm at the top, where it connected to the reentry module’s base. The re-entry module was made up of a truncated cone with a diameter of 228.6 cm at the base and 98.2 cm at the flat top, topped by a short cylinder with the same diameter and another truncated cone with a diameter of 74.6 cm at the flat top. The reentry module was 345.0 cm tall, giving the Gemini spacecraft a total height of 573.6 cm.
The adaptor module was a stringer-framed structure with magnesium stringers and an aluminum alloy frame that was externally skinned. The adaptor was divided into two sections: a base with equipment and a top with retrorockets. A fiber-glass sandwich honeycomb blast barrier separated the equipment area from the retrorocket section, which housed fuel and propulsion components. The capsule’s re-entry rockets were stored in the retrorocket section.
The pressurized chamber in which the two Gemini astronauts were housed made up the majority of the reentry module. A curved silicone elastomer ablative heat shield separated the reentry module from the retrorocket component of the adaptor at its base. With beryllium shingles, the module was mostly made of titanium and nickel-alloy. The cylindrical reentry control system part was at the thin top of the module, and above it was the rendezvous and recovery section, which held the reentry parachutes. In a total pressurized capacity of around 2.25 cubic meters, the cabin featured two seats with emergency ejection devices, instrument panels, life support equipment, and equipment stowage compartments. Two big hatches with small windows, one over each seat, could be opened outward.
Control, Propulsion, and Power
Two translation-maneuver hand controllers, an attitude controller, redundant horizon sensor systems, and reentry control electronics were used to manage the ship’s attitude, with guidance provided by an inertial measurement unit and radar system. A hypergolic propellant combination of monomethylhydrazine and nitrogen tetroxide was used in the orbital attitude and maneuver system, which was delivered to the engines via a helium system pressurized at 2800 psi. Two 95-pound translation thrusters and eight 23-pound attitude thrusters were attached along the adaptor’s bottom rim, while two 79-pound and four 95-pound thrusters were put in the front. A fuel cell power system supplied power to a 22- to 30-volt DC two-wire system. Four 45 amp-hour silver-zinc batteries provided power during reentry and after landing.
Communications
At 296.9 MHz, a 3 W output power was used for voice conversations. A backup transmitter-receiver with a 5 W output power was also available at 15.016 MHz. A total of two quarter-wave monopole antenna systems were used. Three systems were used to transmit telemetry: one for real-time telemetry, one for recorder playback, and one as a backup. With a minimum power of 2 W, each system was frequency-modulated. Two C-band radar transponders and an acquisition-aid beacon were used to follow the spacecraft. One transponder with a peak power output of 600 W is mounted in the adaptor and connected to a slot antenna on the bottom. The other is in the reentry section, with three helical antennae positioned at 120 degree intervals just forward of the hatches and delivering 1000 W. The acquisition-aid beacon, which had a power of 250 mW, was attached to the adaptor.
Reentry
The spaceship would be adjusted to the proper position before reentry, and the equipment adaptor piece would be removed and jettisoned, revealing the retrorocket module. The retrorockets were four spherical-case polysulfide ammonium perchlorate solid-propellant motors with 11,070 N thrust apiece, positioned towards the middle of the reentry adaptor module. They’d fire to start the spacecraft’s entrance into the atmosphere, using a reentry control system of 16 engines, each with 5.2 N thrust, maintaining the spacecraft’s attitude. The retrorocket module would subsequently be destroyed, revealing the reentry module’s heat shield at the base. Thermal protection during reentry was given by thin Rene 41 radiative shingles at the module’s base and beryllium shingles at the top, in addition to the ablative heat shield. A layer of MIN-K insulation and thermoflex blankets was installed beneath the roofing. The astronauts would deploy a 2.4 meter drogue chute from the rendezvous and recovery portion at an altitude of around 15,000 meters. The team releases the drogue, which extracts the 5.5 meter pilot parachute, at 3230 meters altitude. 2.5 seconds later, the rendezvous and recovery section is launched, deploying the 25.6 meter main ring-sail parachute stored at the bottom of the section. After that, the spacecraft is rotated from a nose-up position to a 35-degree angle in preparation for a water landing. A recovery beacon is turned on at this moment, and it transmits via an HF whip antenna positioned near the front of the reentry module.
Gemini Program
The Gemini program was created to serve as a link between the Mercury and Apollo programs, allowing astronauts and ground staff to test equipment and mission operations in Earth orbit while also preparing for future Apollo missions. Long-duration flights exceeding the requirements of a lunar landing mission; rendezvous and docking of two vehicles in Earth orbit; development of operational proficiency of both flight and ground crews; space experiments; extravehicular operations; active control of reentry flight path to achieve a precise landing point; and onboard orbital navigation were among the program’s general objectives. Each Gemini mission sent two astronauts into Earth orbit for 5 to 14 days. The program included ten crewed launches, two uncrewed launches, and seven target vehicles at a total cost of $1.280 million.
What happened to Agena and Gemini 8?
On March 16, 1966, the Gemini VIII astronauts accomplished the world’s first space docking, which was shortly followed by the first life-threatening in-flight emergency in the US human spaceflight program’s brief history. Gemini VIII began spinning and gyrating after docking with its Agena target spacecraft; as the astronauts disembarked, Gemini’s rotation accelerated to the point where the crew could black out and perish.
The mission’s goal was to demonstrate space docking, a technology crucial to the Apollo lunar landing program. Neil Armstrong directed the mission. As captain of Apollo 11, he would become the first human to walk on the Moon forty months later. David Scott, the command module pilot of Apollo 9 and the commander of Apollo 15, the first lunar landing to deploy a roving rover, was his Gemini crewmate. Their calm demeanor during the Gemini VIII crisis insured that they would play pivotal roles in the Apollo program.
I recently wrote about Gemini VI-terrifying A’s pad shutdown on December 12, 1965, and how it was followed three days later by a successful launch and rendezvous with Gemini VII. The major goal of Gemini VIII was to do what Gemini VI-A couldn’t: dock with an Agena, a rocket stage powered by an Atlas Intercontinental Ballistic Missile (ICBM). The Atlas-Agena that Wally Schirra and Tom Stafford were supposed to dock with had blown up during launch on its Atlas rocket the day before, prompting an alternate mission plan. Armstrong and Scott’s secondary goal on Gemini VIII was to gain more expertise with the spacecraft “Another key technique for Apollo was “extravehicular activity” (EVA). Scott was scheduled to conduct the second spacewalk in the US program, following Ed White’s on Gemini IV in June 1965, during a three-day journey.
The mission’s Atlas-Agena blasted off from Pad 14 at Cape Canaveral Air Force Station in Florida at 10:00 a.m. on March 16 and successfully orbited the Agena. Armstrong and Scott’s Gemini-Titan II rocket climbed from Pad 19 an hour and forty-one minutes later, after it had completed one circuit and passed over Florida. After enduring the extreme G-forces of riding America’s second-generation ICBM, the Titan II, the two were in orbit five minutes later. They were supposed to make a sign in Gemini “M=4 rendezvous”approximately six hours to catch up to the Agena in four orbits. Everything went smoothly, and Armstrong and Scott docked at 6:33 a.m., the mission’s end time.
Scott saw that they were also rolling twenty-seven minutes later, when the Agena was completing a programmed maneuver to flip the combined spacecraft 90 degrees. Armstrong activated the thrusters on the Gemini to arrest the roll, but it quickly resumed and worsened, resulting in a combination roll and tumble. Armstrong struggled to regain control after losing contact with Houston controllers on the other side of the world and being cut off from any tracking stations. They soon began to gyrate at such a fast rate that it was difficult to view the instrument panel. The two were concerned that the Agena might disintegrate and explode. They opted to undock because they expected an attitude-control failure on the docking target. Scott had a small control panel that he used to operate the Agena; he set it to ground control and pressed the undock button. As it got further away from the target vehicle, Gemini VIII began to roll even faster. The problem was discovered to be a jammed thruster in the Armstrong and Scott spacecraft’s Orbital Attitude and Maneuvering System (OAMS) on the white adapter module. Armstrong turned off the OAMS and triggered the Reentry Control System (RCS), two rings of thruster rockets around the nose, because he couldn’t turn off individual thrusters and was in risk of losing consciousness due to the ever-accelerating rotation. He halted the spin after expending three-quarters of their RCS propellants. After the retrorockets were launched and the adapter parted, the RCS thrusters were needed, therefore mission rules required a quick return to Earth. Armstrong was well aware of the implications of his decision, but he had no option. Later, Scott stated: “The guy was a genius. He was an expert in the system. It was my lucky day to be flying with him since he found the solution and triggered it under harsh conditions.” (The dilemma is also represented in the Neil Armstrong documentary First Man; see the Smithsonian Channel video.)
The crisis was over by the time they got back in touch with Mission Control via a tracking ship in the Pacific. Armstrong and Scott were able to get to a contingency splashdown zone after Houston permitted them to continue up for one more orbit. They reentered over Communist China, which made them apprehensive, and landed 600 miles east of Okinawa island, south of Japan, right in the midst of the target region. The operation took 10 hours and 41 minutes to complete. When an Air Force Rescue C-54 plane spotted them parachuting into the ocean, it dropped three pararescue divers to attach a flotation collar to the spacecraft. Then they had to wait three hours for the USS Leonard F. Mason, a Navy destroyer. To reach to the landing zone, it had been steaming at top speed.
Following further inspection, it was discovered that OAMS thruster number 8 had short-circuited, allowing the two liquid propellants to ignite on contact, as anticipated. The errant engine could not be recovered and investigated because the adapter module was ejected before reentry, therefore the investigators had to rely on instrumentation recordings. The astronauts had circuit breakers from Gemini IX onwards to turn off particular sets of thrusters, allowing them to pinpoint a potential problem, albeit the problem was never repeated thanks to thruster upgrades. Because Scott missed his chance to go outside, NASA was unable to learn from the mission about the difficulty of doing any work during EVA. Eugene Cernan’s next spacewalk, on Gemini IX, was much more ambitious in terms of objectives and would prove to be highly perilous, in part due to the lack of experience on Gemini VIII. However, Armstrong and Scott’s mission should be remembered for one thing: the first ever space docking.
Michael J. Neufeld is a senior curator in the Museum’s Space History Department, where he is in charge of, among other things, the Mercury and Gemini spacecraft.
Was the mission of Gemini 8 a success?
Gemini 8 was the world’s first on-orbit docking of two spacecraft after a successful twin launch and docking with the Gemini Agena Target Vehicle (GATV). The mission was supposed to last three days, however it was canceled on the first day in orbit.
On March 16, 1966, the Gemini 8 GATV was launched from Cape Canaveral Launch Complex 14 as the second stage of an Atlas-Agena rocket at 10:00 a.m. EST. The GATV spacecraft launched around 101 minutes before the human Gemini 8 mission.
The Gemini 8 spacecraft was adjusted nine times during the first six hours of the voyage in order to approach the GATV. Rendezvous operations were accomplished with the Gemini 8 spacecraft around 150 feet near the GATV after a mission elapsed time of 5 hours, 58 minutes.
The Gemini 8 spacecraft and the GATV docked successfully after a mission duration of 6 hours and 33 minutes. This was the first time a docking in space has been accomplished. However, a significant and potentially life-threatening malfunction soon ensued.
A fault arose just 27 minutes after the docking was completed, forcing the mission to be aborted. Fuel was drained through the capsule’s #8 thruster due to a short-circuit in the Orbital Attitude Maneuvering System (OAMS). The astronauts had no idea what was happening, but the consequences were devastating.
The mated spacecraft began spinning quickly seconds after the malfunction as a result of the pressure released by the defective engine. By firing the OAMS thrusters in sequence, astronaut Armstrong was able to temporarily remedy the problem, but the spinning always continued.
The fault was considered to be with the GATV by mission managers on the ground and the astronauts themselves, therefore an undocking was requested and carried out quickly. However, after undocking, the Gemini 8 spacecraft proceeded to spin even faster, reaching a maximum speed of one revolution per second.
The astronauts were so bewildered by the motion that they couldn’t see clearly. Worse, communication with the ground was becoming increasingly difficult. Before the astronauts lost consciousness, and most likely their deaths, Command Pilot and future Moonwalker Neil Armstrong would have to make a rapid choice on his own.
And he did make a decision. To stabilize the spacecraft, Armstrong manually disabled the OAMS thrusters and engaged the re-entry control system (RCS) thrusters, which was a rule-breaking operation. The capsule’s appropriate motion was restored once the hand controllers aboard the spacecraft were repaired.
However, this process used up so much RCS fuel that the mission was called off for the rest of the way. The Gemini 8 capsule landed successfully in the Pacific Ocean’s designated emergency splashdown area. It was the only Gemini splashdown in the Pacific Ocean, and it happened within three miles from the recovery ship.
Scott’s planned spacewalk has been postponed. Even though the mission was cut short, two of the ten experiments were partially completed, and a number of technical objectives were met. Armstrong and Scott both experienced acute space sickness, which persisted after the ship was recovered.
Did the Apollo 1 astronauts endure any consequences?
Grissom received serious third-degree burns over one-third of his body, according to the Board, and his spacesuit was mostly destroyed. Almost half of White’s body had third-degree burns, and a fourth of his spacesuit had melted away. Chaffee had third-degree burns to over a fourth of his body, as well as damage to a tiny piece of his spacesuit. The primary cause of death for all three astronauts was cardiac arrest induced by excessive carbon monoxide levels, according to the autopsy findings. The crew’s burns were not thought to be major issues, and it was determined that the majority of them occurred postmortem. The astronauts died of asphyxiation after the fire melted their suits and oxygen tubes, exposing them to the cabin’s fatal atmosphere.
Do you think it’s possible to age in space?
“Many of us believe that being exposed to radiation or other forms of harm in space will result in faster aging. But, as Jamaji C. Nawanaji-Enwerem, a Berkeley Public Health postdoctoral fellow and first author of a study published in Cell Reports in November 2020, pointed out, “there has also been a lot of research that has proven the contrary.” The research looked at data from six people who took part in the Mars-500 project, which was launched by the European Space Agency in 2010. It was a simulated space travel and habitation experiment.
People in space are exposed to environmental stresses such as microgravity, cosmic radiation, and social isolation, all of which can have an affect on aging. Long-term space flight studies frequently evaluate aging biomarkers like telomere length and pulse rates, rather than epigenetic aging. To bridge the gap, Nawanaji-Enwerem and his colleagues looked at epigenetic biomarkers such DNAmPhenoAge, a reliable marker of illness risk, and DNAmGrimAGE, a predictor of mortality risk.
The findings demonstrate that longer space missions result in a slower aging process, which appears to be a good thing. “However, if the assignment lasts longer, it may be detrimental to your health,” Nawanaji-Enwerem explained.
Is it true that any Gemini missions have failed?
Gemini 8 (formally Gemini VIII) was NASA’s Gemini program’s sixth crewed spaceflight. It was the 14th crewed American mission and the 22nd crewed spaceflight overall when it launched on March 16, 1966. The mission accomplished the first orbital docking of two spacecraft, but it also had the first severe in-space system failure of a US spacecraft, endangering the astronauts’ lives and forcing the mission to be aborted immediately. The crew arrived back on Earth safely.
The voyage was the second time a US citizen travelled into space and the first time a US civilian flew into orbit, and it was piloted by David Scott and command pilot Neil Armstrong.