Rotational Cryotechnology

Cryogenic Hibernation

Early deepspace ships from Earth couldn't function on autopilot for great lengths of time and did not possess the power supplies or engine capacity necessary to reach far into deepspace within the lifetime of pre-modern astronauts.
Cryogenics were a pre-modern technology used to combat these issues. It involved lowering the body temperature of the astronauts to preserve their bodily functions for longer. However, there were several problems with early cryogenics. Prolonged and/or frequent use, could often decrease a subject's brain function, resulting in attention problems as well as impulsiveness, amongst other things.
However, despite the problems, rotational cryogenics did allow for Humans to advance their space program far more quickly than they would have without that step.

Utility

So-called rotational cryotechnology was used on the first deepspace ships from Earth. It was used to prolong the life of the Human crew, to an extent, by freezing their ageing processes whenever they were in the cryobeds. However, both the spaceship technology and the cryotechnology of the day prevented the crew from being kept in cryo for the whole journey. Therefore rotational cryotechnology was used in shifts (hence rotational) and often combined with a multigenerational system to allow Humans to venture into deep space.
A well-known example of a ship using rotational cryogenics is the crew that caused the Accidental Infection of K'anam Prime.

Access & Availability

Rotational cryogenics was available on all deepspace vessels from Earth for a relatively short amount of time, from around 2040 to about 2090.
The technology saw a significant decrease in use around 2082, after the investigation into the infection of K'anam Prime resulted in more thorough research into the effects of the technology and alternative solutions.
Rotational cryogenics is no longer used on Human space vessels, though cryogenics as a science has improved greatly since this first step was taken.