V0.2 - 17-04-2020
The major milestone
While the first human space flights of Yuri Gagarin and Allen Sheppard are remarkable milestones in space flight, they are less of a milestone in entry descent and landing technology. The EDL system of Gagarin was pretty identical to the system of Belka and Strelka. What makes the human EDL systems interesting is the effort that goes into increasing the systems' reliability and redundancy. Both Mercury and Vostok had single-canopy parachutes. For Mercury, a backup parachute was included, but it is unclear if this was the case for Vostok.
Gagarin’s Vostok capsule used a parachute system combined with an ejection seat. This allowed for a softer and more reliable landing. A total of six cosmonauts flew onboard the Vostok capsule including Gagarin (first human in space), Titov (first full-day flight), Nikolayev and Popovich (first simultaneous flight), Bykovsky (first 4-day flight) and Tereshkova (first woman in space). All six ejected before landing and did not land with their spacecraft. Even though this is a small note on their achievements it is the cause of controversy. The FAI stated that an astronaut has to lift off and land with the capsule. At firs, Gagarin and the Soviet officials did not admit Gagarin ejected before landing. Only when Titov flew this became public. The FAI did recognise the achievements of Gagarin and changed the rules. He is generally recognised as the first hum to go to and return from space.
As the Vostok capsule is spherical with only an offset in mass to stabilise it the entry was very rough.
The complete spacecraft came equipped with a service or instrument module which housed, amongst others, the propulsion. This propulsion system was required to slow the capsule down sufficiently such that it would dip into the atmosphere. During the first flight, the capsule started spinning after the engine shut down. To make matters worse the expected separation of the service module did not occur on time. Fortunately for Gagarin, the stresses of atmospheric entry did cause the modules to separate.
Render of the Vostok capsule
The first steps into space for the US were onboard the Mercury capsule. Most noticeably the Mercury capsule was quite different in shape to Vostok. Mercury had the, now more typical, conical shape. The first flights of Mercury were done on top of a Redstone rocket. These flights peaked at 117 and 118 km and carried Allen Shepard and Gus Grisson on a suborbital path. Later Mercury capsules flew on top an Atlas rocket and managed to reach orbit. With the longest flight lasting just over 1 day and 10 hours, the Mercury project was ended. Interestingly the first two flights of Mercury did not have a heat shield. As the flights were suborbital this was not required.
The Vostok capsule (1964-1965) was modified into the Voskhod capsule, allowing multiple cosmonauts to fly at the same time. This did mean that the capsule had to be modified. The inclusion of a second or third cosmonaut meant the ejection seat system had to go. This in term led to a retro-rocket pack for landing marking the first Soviet capsule to land with the crew onboard. Two flights were performed, one with a three-man crew and one performing the first spacewalk.
The second-generation US capsule was the Gemini capsule (1965-1966). Gemini carried two astronauts to space and performed all features required for the Apollo missions. These included US spacewalks, docking in space and general living in space.