Our SpaceFlight Heritage: NASA’s first emergency in space – The story of Gemini 8
Fifty years ago today was an exciting and busy day at Cape Canaveral, Florida. However, it would turn into a type of excitement that NASA and the entire Gemini space program would have preferred to avoid.
March 16, 1966, was to mark an important milestone for Project Gemini and in the history of space flight overall. If the day’s events went well, the Gemini 8 crew of commander Neil Armstrong and pilot David Scott would achieve the first ever docking in space, between their Gemini spacecraft and an orbiting Agena target vehicle.
The two prior Gemini missions of Wally Schirra and Tom Stafford aboard Gemini 6, and Frank Borman and Jim Lovell aboard Gemini 7, had successfully rendezvoused two spacecraft for the first time, the two vehicles maneuvering in close proximity for nearly six hours. Now, Gemini 8 would be the first attempt at docking – a major objective of the Gemini program. The successful demonstration of docking was critical to the Apollo program, which featured multiple rendezvous and docking procedures in its plan for landing on the Moon and returning astronauts to Earth.
The day at Cape Canaveral began with a morning liftoff of the Agena target vehicle on its Atlas booster at 10:00:03 EST. It was a pins-and-needles event for those involved in the Agena launch, as the previous target vessel, intended as the target vehicle for the Gemini 6 mission, had exploded shortly after leaving the pad.
That mishap prompted a mission re-write that consisted of launching the long-duration mission of Gemini 7 first, then launching Gemini 6 several days later and using Gemini 7 as its new rendezvous target. However, on the morning of March 16, 1966, the booster carried the Agena on a perfect ascent to orbit and placed it in a 185-mile circular orbit.
Armstrong and Scott were already in their spacecraft atop its Titan booster and working through their countdown at Pad 19 when they got the word that the Agena had achieved orbit – providing a good target vehicle for them to chase. The countdown commenced smoothly, and only one hour and 41 minutes after the Agena lifted off, Gemini 8 thundered off the pad at 11:41:02 EST.
The plan was for Gemini 8 to catch up to the Agena on Gemini 8′s fourth orbit, or M+4. Through the first three orbits, a number of OAMS (Orbit Attitude and Maneuvering System) burns were made to adjust the spacecraft’s orbit in relation to the target vessel.
The crew reported radar lock with the Agena at 206 miles (332 kilometers) and then made the first visual sighting at approximately 86 miles (13 kilometers). Armstrong continued to close the gap between them. Six hours after launch, they were about 150 feet (46 meters) from the Agena.
Armstrong maneuvered Gemini 8 into position to dock. As the spacecraft passed in and out of radio contact with ground stations, Armstrong waited to be given the command to go ahead with the docking. Once he was given the final go ahead, Armstrong gently guided the nose of Gemini 8 into Agena’s docking cradle.
“OK. Just for your information. The Agena was very stable,” Armstrong reported to ground control. “And at the present time, we’re having no noticeable oscillations at all.”
“Gemini 8 was a crucial step in terms of docking,” said Greg Brown, a historical interpreter at the Armstrong Air and Space Museum in Wapakoneta, Ohio, where the Gemini 8 spacecraft resides. “Everybody was happy. Champagne corks popped and cigars were lit. The astronauts had been trained that if anything went wrong or got squirrely during the docking, the problem was probably with the Agena.”
But that was not how it turned out.
Minutes after the docking was achieved, the astronauts noticed that they had gone into a slight roll, the rate of which – was increasing. This occurred while they had again passed out of communication with the ground stations. The astronauts would have to solve the problem on their own. Believing the problem was with the Agena, Scott switched off the Agena’s attitude control system. Armstrong got them stabilized once more, and Scott recycled the Agena’s switches.
But then it all started over again. The rolling came much faster this time. The OAMS propellant reading showed as low as 30 percent, causing the astronauts to believe they had a stuck thruster. Scott tried the Agena switches again and Armstrong cycled the Gemini thruster switches to see if he could find the problem. Nothing worked.
In fact, it got worse, as they were now spinning on a second axis, both roll and yaw. Their only choice was to disengage from the Agena. Scott quickly switched control of the Agena from the spacecraft to the ground, protecting its command control for future use. He then hit the undocking control, and Armstrong gave a long forward thruster burst to back Gemini 8 away from the Agena.
Their suspicions that they had a stuck thruster were confirmed immediately. Now free of the Agena, the spacecraft’s tumbling rate, instead of decreasing, increased alarmingly until they were making one complete revolution every second. They were starting to experience tunnel vision, and if the tumbling continued or increased, they would black out.
As they came back into communication with ground control through the tracking ship Coastal Entry Quebec, Armstrong reported the nature of their emergency.
“We’ve got serious problems here,” Armstrong said. “We’re tumbling end over end and we’re disengaged from the Agena.” Several moments passed as ground controllers tried to grasp what Armstrong was telling them had happened. With each moment, the tumbling worsened. Armstrong struggled to control it. Fuel was running low.
“We’re rolling,” Scott confirmed to ground control. “We can’t turn anything off. Increasing in a left roll.”
Unable to make any progress in dampening the roll, Armstrong had no choice but to engage the RCS (Reaction Control System) thrusters in the nose of the spacecraft. He reported to ground control that the RCS was armed and that he was using it to try to address the emergency. Through several dicey minutes, his efforts with the hand-controller gradually brought them out of the tumble and roll, and the spacecraft slowly stabilized. The emergency appeared to be over, as Armstrong regained control of the spacecraft.
However, mission rules dictated that any emergency use of the RCS meant a return to Earth as soon as possible. This was to prevent the possibility of any further emergencies causing too much RCS fuel to be used, leaving too little fuel to provide control for a safe re-entry. Gemini 8 was therefore commanded to make an emergency re-entry, splashing down in a contingency zone in the Pacific Ocean just ten hours after the mission had got underway.
Although the planned 3-day mission was cut short and David Scott was unable to conduct his spacewalk, Gemini 8 did successfully dock with the Agena, and Gemini 8’s emergency proved to have much significance.
“Its significance was twofold,” Brown said. “It was the first in-flight emergency of the space program, It was the first rapid and unguided solution. They had no contact with ground control for much of this crisis. Essentially, the astronauts had proven their ability to handle an emergency and find solutions to their in-flight problems independently from ground control. This also sort of solidified Neil Armstrong’s reputation as an astronaut, as a commander, and as a pilot.”
“And it wasn’t just Neil,” Brown added. “Dave (Scott) had the presence of mind to actually relinquish control of the Agena through the command link system back down to the ground so that they could later control the Agena. That took some heads-up situational awareness.”
NASA’s evaluation of the problem was difficult, given that the thruster’s hardware was aboard the adapter module, which is jettisoned from the spacecraft before re-entry and burns up in the atmosphere. However, investigation of the spacecraft and various flight data indicated the problem came from a short circuit in the number 8 thruster. In future Gemini craft, the system was changed so that in the “off” position, no electrical power could be fed to the thruster.
Other, more extensive, docking maneuvers and experiments, as well as spacewalks and other activities, awaited future missions in the Gemini program. This would eventually prove out procedures that were needed in preparation for Apollo. Even the tense moments of Gemini 8 proved significant in the evaluation of astronauts’ abilities to deal with problems and emergencies in space.
As for Armstrong, his calm and skillful performance during a life-threatening emergency in space had proved his worthiness to be a serious contender for making the first landing on the Moon.
Michael Cole is a life-long space flight enthusiast and author of some 36 educational books on space flight and astronomy for Enslow Publishers. He lives in Findlay, Ohio, not far from Neil Armstrong’s birthplace of Wapakoneta. His interest in space, and his background in journalism and public relations suit him for his focus on research and development activities at NASA Glenn Research Center, and its Plum Brook Station testing facility, both in northeastern Ohio. Cole reached out to SpaceFlight Insider and asked to join SFI as the first member of the organization’s “Team Glenn.”