It is 50 years since the last hurrah of the Apollo program, with a mission that saw the final launch of an Apollo vehicle, and a subsequent docking with a Soviet Soyuz spacecraft in orbit.
The mission was the first and only spaceflight of Deke Slayton, one of the original Mercury 7 group of astronauts, who had been disqualified from flight. By the time he was cleared, the Apollo-Soyuz mission was Slayton’s last opportunity before the first flight of the Space Shuttle in 1981.
In his book Flight, Chris Kraft said: “I was overjoyed to sign off his [Deke’s] appointment to the crew … Of the Original Seven, Deke got his ride last. We owed him that.”
On the Soviet side, the first spacewalker – Alexei Leonov – would command the two-person Soyuz crew on what would be his final spaceflight.
The mission consisted of an Apollo spacecraft (occasionally referred to as Apollo 18), a docking module, and Soyuz 19. Apollo launched from the “milkstool” platform on a Saturn 1B from Kennedy Space Center’s Launch Complex 39B. The Soyuz launched from Baikonur in the Soviet Union.
Both launches occurred on the same day – July 15, 1975 – just over seven hours of each other. The docking module was carried in the S-IVB upper stage of the Saturn IB rocket and required extraction by the Apollo spacecraft, a little like the Apollo Lunar Module.
The first docking occurred on July 19 at 1609 UTC.
ASTP docking module diagram (pic: NASA) – click to enlarge
The docking module was a critical part of the mission because the Apollo and Soyuz spacecraft could not dock directly. The Apollo capsule was pressurized to approximately five psi of pure oxygen while the Soyuz spacecraft used a nitrogen/oxygen atmosphere at sea level pressure (approximately 15 psi, although this pressure could be reduced down to 10.2 psi to make the docking phase easier). Making one spacecraft match the other was not a realistic option, so mission planners went for a module that could function as an adapter. The Apollo was fitted with the probe-and-drogue mechanism used during the Apollo program, while the Soyuz used the APAS mechanism, which endured well into the era of the International Space Station.
After docking, the crews exchanged places in their respective spacecraft, shook hands, exchanged gifts, ate meals together, and gave televised tours of their vehicles. In the book Two Sides Of The Moon, Leonov recalled the moment when the hatches opened and the crew saw each other in space for the first time. “At that moment,” he wrote, “I felt that everything I had been through in my career as a cosmonaut … had been worth it. This was the highlight of the mission.”
Leonov had a few surprises for the US crew, one of which was some tubes of borscht onto which he had carefully placed the labels of famous brands of vodka. “Before we eat, we must drink to our mission!” he said, handing the tubes to Slayton and the US Commander, Tom Stafford. The Americans were understandably concerned – the optics of the Apollo crew knocking back vodka live on TV were less than ideal. “Look, Tom,” Leonov said, “don’t worry. I’ll show you how it’s done.” The cosmonaut then squeezed the contents of the tube into his mouth and swallowed. Stafford followed suit and exclaimed, perhaps slightly disappointed according to Leonov: “Why, it’s borscht!”
ASTP sketch by Leonov (pic: NASA) – click to enlarge
After almost two days connected, the Apollo and Soyuz spacecraft separated to perform some additional rendezvous maneuvers before docking for a second time. “The second docking did not go as smoothly as the first,” recalled Leonov.
Flirting with disaster
Slayton was at the controls of the Apollo and, according to Leonov, “inadvertently fired one of Apollo’s side roll thrusters, which had the effect of pushing both vehicles off centre, folding them towards one another.”
“There was a real threat of damaging the joint docking mechanism and the possibility of a catastrophic depressurization of our orbital module.”
The mistake was quickly corrected, and Leonov observed: “We never spoke about the incident afterwards. It would not have been very diplomatic for us to reveal how close Apollo had come to crippling Soyuz.”
Slayton’s version of events is a little different. In the book Deke! Slayton acknowledged that he’d “tweaked the hand controller the wrong way” after the Soyuz had been captured, “causing the two spacecraft to shake a little.” He also blamed the glare of the Sun – the spacecraft were conducting a solar experiment – for some of his difficulties.
The US crew was not, however, out of the woods. Regardless of how serious the problems encountered during the second docking actually were, worse was to come during the spacecraft’s return to Earth. Apollo’s reaction control systems (RCS) allowed it to maneuver and orient the Command Module. The fuel used was highly toxic, and a critical part of the re-entry checklist was to ensure RCS had been properly shut off.
Slayton recalled: “Either Tom didn’t call for RCS close, or he did and Vance [Brand, the Command Module pilot] just didn’t hear it. The small drag chute deployed with a big whap, and suddenly we had a cockpit full of yellow gas. We knew pretty quickly what the problem was, because the RCS was still firing.”
The system was swiftly shut down, but the crew were hacking and coughing by the time the capsule hit the water.
“Then it was my turn to screw up,” wrote Slayton. “We were in the water a few minutes, still hacking, when they dropped the frogmen. One of them appeared in the window, and like a dumb shit, I gave him the thumbs-up sign. Everything’s OK.”
It wasn’t. But everybody outside thought it was, and so there was no special effort to evacuate the Command Module.
“I think Vance might have passed out,” said Slayton. “Tom was scrambling around in the bay getting gas masks.”
It wasn’t until later that the extent of the near-disaster was realized, and the astronauts were pumped full of cortisone. “A good thing too,” said Slayton. “We hadn’t felt too bad once we got out of the Command Module and onto the ship … but about three-quarters of an hour later, suddenly we all felt like we had pneumonia.
“A lethal dose of that gas was four hundred parts per million. They estimated that we had inhaled it at three hundred parts per million. Pretty close.”
Back down to Earth
The mission was the last crewed flight for the US until the Space Shuttle launched in 1981, and it was the last time a crewed capsule took off from US soil until SpaceX’s Crew Dragon in 2020.
The mission was also Tom Stafford’s last spaceflight. The Apollo Command Module Pilot, Vance Brand, would go on to fly on three Space Shuttle missions, his final being as Commander of STS-35 in 1990. Slayton officially retired from NASA in 1980, having never flown in space again. He died in 1993 from brain cancer.
Additionally, it was Leonov’s last flight. He was promoted to General on his return, but would never fly in space again. The Soyuz Flight Engineer for the mission, Valery Kubasov, went on to fly a mission to the Salyut 6 space station in 1980. Kubasov died in 2014, and Leonov died in 2019.
Stafford and Leonov became firm friends, with Stafford giving a eulogy at Leonov’s funeral in 2019.
The legacy of the Apollo Soyuz Test Project is difficult to quantify. US-Soviet relations worsened not long after, and the mission carried more than a hint of political theater. Yet it also proved that scientists and engineers on both sides could collaborate – and succeed – in space.
“Our mission,” said Leonov, “had paved the way for future cooperation in space, but it was to be many years before our two countries again undertook a joint space venture.” ®
Further Reading
David Scott and Alexei Leonov collaborated on Two Sides Of The Moon, which was referenced in this piece, as was Deke!, authored by Deke Slayton and Michael Cassutt. Brian Harvey’s Russia In Space was also a valuable resource, as was Soyuz: A Universal Spacecraft by Rex D. Hall and David J. Shayler.
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