Some time last week, Ian Blatchford, director of London’s Science Museum, received a text message about a Russian spacecraft. “Vostok 6 has cleared customs at Dover,” it read.

Vostok 6 is no ordinary spacecraft. It is one steeped in history, having carried Valentina Tereshkova, the first woman in space, into space (and back). It has faced much harder crossings than British customs officials. But its latest journey is a significant one: It marks the first item to arrive in London for what will be the most complete collection of artefacts showcasing the history of the Soviet space program outside of Russia.

Also on display will be items from the failed Soviet lunar mission, which was kept a secret from the world until 1989. Speaking at the Science Museum this week, Alexei Leonov, the first human to do a spacewalk and the Soviet candidate for the first man on the moon, talked about the comradeship between American and Soviet astronauts at the time.

Alexei Leonov/The Memorial Museum of Cosmonautics Alexei Leonov painted this self-portrait after his 1965 spacewalk. It shows him orbiting above the Black Sea.

“We knew about the program in the US,” in the 1960s, he said. “I knew those people personally and they knew me and we wished the best to each other although there was competition. That was the best competition. Olympic Games come and go and people forget about them. But this was in the service of mankind.”

The Soviet program was cancelled in 1974. “The leadership said it was too risky. And we were not the first anyway,” Leonov said. Reflecting on his own missed opportunity, he said, “It didn’t work out for me. I was so close to it. I passed all the tests and exams. Instead I was put in charge of the Soviet [space] station.”

The exhibition, titled “Cosmonauts: Birth of the Space Age,” opens at the Science Museum in London on Sept. 18 this year and runs until 13 March 2016. Tickets are available now.

Alexei Leonov, Museum of the Yuri Gagarin Cosmonaut Training Centre. Alexei Leonov drew this sunrise in the logbook of the Voskhod 2 spacecraft, soon after his pioneering spacewalk. He used the pencils shown with wrist ring and threads to stop them floating away.

State Museum and Exhibition Centre ROSIZO The Soviet Union launched Sputnik, the first artificial satellite of the Earth, in 1957. It had been developed in six months as it was feared the United States could launch its own satellite first. Chief Designer Korolev is said to have insisted on Sputnik’s shiny appearance as he believed that one day replicas would be displayed in the world’s museums.

Memorial Museum of Cosmonautics. This poster celebrates the pioneering mission of Yuri Gagarin, on April 12 1961. The style blends the realistic with the abstract: Gagarin’s features are recognizable yet he holds the light of the cosmos in his hand and his rocket is heavily stylized, which also disguises its classified status.

State Museum and Exhibition Centre ROSIZO This surrogate cosmonaut was flown around the moon on Zond-7. The aim of the Zond mission in 1969 was to estimate the effects of cosmic radiation on living tissue. The mannequin was flown again in 1970 on the Cosmos-368 mission around Earth. Its face was made in the image of Yuri Gagarin.

State Museum and Exhibition Centre ROSIZO This is the craft in which Valentina Tereshkova flew into space, the first woman ever to do so. Much of the brown-coloured heat shield is charred and burned from its hurtling back to Earth through the atmosphere at a speed of some 27,000 kilometres per hour.