Gemini 10: The crammed flight plan to end all crammed flight plans

Dates: 18 – 21 July 1966

Duration: 2 days, 22 hours, 46 minutes, 39 seconds

Commander: John Young (second of six spaceflights)

Pilot: Mike Collins (first of two spaceflights)

Back-up crew: Alan Bean and C.C. Williams

Objective: To perform a rendezvous with two different Agena Target Vehicles (a so-called ‘double rendezvous’ – the first of its kind to be attempted) and a docking, and then to perform two EVAs, attempting to remedy the problems encountered during Gemini 9A.

The Crew

John Young (left) and Mike Collins have breakfast the morning of their launch | Credit: NASA

John Young and Mike Collins were both rated very highly by their colleagues.

Young had become the first member of the second group of astronauts to fly in space when he served as pilot of Gemini 3 alongside Gus Grissom. Collins, meanwhile, was the first of third group to be assigned to a flight.

They were another example of NASA having done a very good job during Gemini of pairing astronauts together based, partially at least, on personality. The crew of Gemini 10 shared a similar sense of humour – described by various authors as the driest and most self-deprecating of the entire programme – with the relaxed Collins also helping to balance out the more ‘socially awkward’ Young when it came to publicity events.

The Flight

Gemini 10 lifted off on 18 July 1966.

Young and Collins were both slightly wary of the flight plan they had to now set about completing, knowing that time would be stacked against them from the second they left the launchpad. Two rendezvous, one docking, a major altitude-changing burn, two spacewalks and 15 experiments in just under three days was a lot to ask.

Things didn’t get off to the smoothest of starts. The astronauts began a series of burns to chase after their first Agena Target Vehicle (an unmanned spacecraft used for rendezvous and docking exercises), not realising that their spacecraft was slightly out of alignment. When they arrived at the Agena just over five hours into the mission, they were in the wrong position. Rather than approaching the Agena from almost directly behind as they were supposed to, they were instead coming up alongside it.

The first of Gemini 10’s two Agena targets | Credit: NASA

Young and Collins had to make several major corrections over the following hour to rectify the problem, finally docking with the Agena just under six hours after launch. The error cost them almost 60% of their manoeuvring fuel, virtually twice the anticipated amount.

They didn’t have time to dwell on the mistake though. They were required to almost immediately turn their attention to the mission’s second objective, using the Agena’s engine to boost them to an even higher altitude. It was a strange feeling for them – Gemini 10 and the Agena were docked nose-to-nose and as such Young and Collins were facing backwards to the direction of travel. Their new orbit put them at the highest altitude ever reached by human beings at that time.

The glow from Agena 10’s primary propulsion system lights up the sky out of Gemini 10’s window | Credit: NASA

Their flight plan had been altered slightly as a result of the rendezvous error. They were now going to stay docked to the first Agena for longer than had originally been planned, to allow the astronauts to use some of the Agena’s fuel for manoeuvring and therefore save the fuel in Gemini 10.

After an eight-hour sleep period, Young and Collins fired the Agena’s engine twice more. The burns further adjusted their orbit around Earth and put them on track to achieve yet another one of their objectives – a rendezvous with a second Agena – further down the line.

Next up on their unrelenting schedule was a so-called ‘stand-up EVA’. It is what the name suggests – Collins would stand in the open hatch of the spacecraft to conduct a few photography experiments.

As EVAs go, it was a relatively simple one. The photography experiments went as planned, but Collins re-entered the spacecraft six minutes early after both he and Young reported that something was irritating their eyes and causing their vision to blur. It was eventually concluded that the irritation had been caused by a small leak of lithium hydroxide (the compound used to filter out excess carbon dioxide) in their oxygen supply. Collins had been outside the spacecraft for 49 minutes.

After another rest period and another round of experiments, Young and Collins used the Agena’s smaller ‘secondary propulsion system’ (SPS) to perform two final burns before disconnecting and using Gemini 10’s own propulsion to complete their rendezvous with the second Agena.

Mike Collins snaps a ‘selfie’ inside the Gemini 10 spacecraft | Credit: NASA

This second Agena was the one left over from the curtailed Gemini 8 mission of four months previous. It had long run out of batteries and therefore had nothing to power its radar, leaving Young and Collins to rely on what they could see out of their windows along with information from the ground to perform the rendezvous. 47 hours and 26 minutes into the mission, they came to a ‘stop’ three metres away from the vehicle. It was the first time in history that rendezvous with two separate targets had been completed in the same flight.

There was, unsurprisingly, no time for celebrations. An hour later, Collins once again opened the hatch above him. This time he left the spacecraft properly, pushing off towards the Agena with the intention of retrieving a micrometeorite experiments package installed on the outside of the vehicle and replacing it with a new one. He was attached to Gemini 10 by a 15 metre-long (50 ft) tether and had in his grasp a ‘zip gun’ which he could use to help move himself around.

Once he reached the Agena though – and doesn’t this sound familiar? – he struggled with a lack of handholds and footholds. In his attempt to retrieve the package he built up too much momentum and went cartwheeling past because there was nothing for him to hold onto to stop himself with. The tether span him back round in a long arc towards Gemini 10 where he grabbed onto the rim of the hatch.

When he set back off towards the Agena, his foot snagged on something and sent him into another slow tumble. This time he used the zip gun to steady himself but he was still forced to reach out and grab a bundle of wires near the Agena’s docking collar to stop himself from sliding right past again. Briefly disoriented because of his tumble, Collins was initially unsure where the micrometeorite package was in relation to him but after a few moments he was able to successfully locate and remove it.

The flight plan had called for him to then replace it with a new experiment, but his scrabbling around had caused the Agena to start to spin. What’s more, out of the corner of his eye Collins could see a jagged two foot-long piece of the Agena’s docking appartus which he had apparently bumped into at some point and dislodged. It was slightly too close to him for comfort and so he decided to not push his luck.

It had also been planned for him to carry out further tests using the zip gun and for Young to manoeuvre over to Collins, but due to concerns over fuel – Collins’ struggles had often jarred the spacecraft and caused its thrusters to fire to keep itself steady, further emptying the tanks that had already been depleted due to the earlier rendezvous error – it was decided to end the EVA early.

Despite his problems, Collins did not run into any of the fogging-up problems that Gene Cernan had experienced during Gemini 9A. He would no doubt have been very glad about this, as he admitted in his autobiography to having experienced several episodes of claustrophobia during suit training in the build-up to Gemini 10.

Back inside their spacecraft after 39 minutes, Collins started to painstakingly untangle himself from the 15 metre-long tether with Young’s help, complaining to Mission Control, “This place makes the snakehouse at the zoo look like a Sunday school picnic!”

They opened the hatch one last time to jettison the tether along with empty food bags and other waste and, after a few last housekeeping tasks, settled down for their final night’s sleep in space.

The Western Sahara as seen from inside Gemini 10 | Credit: NASA

In the ‘morning’ they tucked into their last meal in space, with Collins in particular seeming to gulp down his portion. “Shoot, you should see him,” Young told Mission Control. “He’s eating my last meal too!”

Two and a half hours later, Young and Collins splashed down in the Atlantic and were recovered by the USS Guadalcanal. Their total mission duration was 2 days, 22 hours, 46 minutes and 39 seconds.

They had proven that NASA had the art of rendezvous and docking pretty much down to a fine art, but the same couldn’t be said of spacewalking. They still had a lot to learn, but that is perhaps unsurprising given that Gemini 10 was just the third American mission to attempt an EVA.

Collins returned to space as command module pilot for the historic Apollo 11 and became the first director of the Smithsonian National Air and Space Museum in the late 1970s. Young, meanwhile, would make four further spaceflights. Two of those were during the Apollo programme (Apollo 10 and the Apollo 16 lunar landing) and two were during the Shuttle programme. He only retired from NASA in 2004, making him the agency’s longest-serving astronaut.

Young (left) and Collins aboard the USS Guadalcanal | Credit: NASA

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