Vostok-K (8K72K)

Vostok-K is an R-7 with a third stage and a human being on top. RussianSpaceWeb gives the total length as 38.36 metres, which is the vehicle as it stood on the pad under Gagarin, spacecraft and shroud included. Encyclopedia Astronautica prints 30.84 metres, but that cannot be the whole stack: the core alone is 28.75 metres and there is a third stage above it. Both sources agree on 4,730 kilograms to a 200 kilometre orbit, and Astronautix puts liftoff thrust at 3,894 kilonewtons, effectively the same engine set as the Sputnik launcher.

The K denotes man-rating, and man-rating here meant changes to the core, changes to the strap-ons, and an improved RD-0109 engine on the Blok E third stage to fix deficiencies in the earlier RD-0105. It did not mean an escape system. Vostok had no launch escape tower. The cylindrical adapter carrying the spacecraft had a large circular opening cut in the fairing so the cosmonaut could eject through it if something went wrong on the pad or early in the climb.

That is the whole design philosophy in one hole. An escape tower is a rocket that pulls a capsule clear of an exploding launch vehicle, and it costs mass, complexity and schedule. An ejection seat costs a hole in the shroud. The Soviet programme was running against a political clock and took the cheaper answer, and it worked, in the sense that it never had to be used.

Thirteen of these flew between 22 December 1960 and 10 July 1964. The one that matters launched on 12 April 1961 with the RD-0109 serial number 17 on the third stage and Yuri Gagarin in the ball, and it circled the Earth once at about 27,400 kilometres per hour in 108 minutes. Nobody outside the programme knew what the rocket looked like. Its general architecture stayed secret until 1967, when a full-scale mockup turned up at the Paris Air Show at Le Bourget.