So how realistic is this? The basic premise that human beings could be cloned is reasonable. Animals have been cloned over many years now using a range of reprogramming technologies – famously Dolly, but also cows, pigs, subhuman primates, and for all we know in some parts of the world, humans. However, in the film it is suggested that the original Sam left for the moon while his wife was still pregnant with his daughter and we find out that his daughter is now 15. Thus, assuming that the clones were derived when Sam was selected to go to the moon, we have a relatively short time for them to be produced. With current technology, cloning would require that the cloned embryos are implanted back into a womb and that they then proceed through development, are born, and then have to go through a normal process of maturation and development. 15 years would be too short a time, unless it could be accelerated in some way. Another possibility is that Sam was selected at birth for cloning or even that he was cloned at conception.
A related, but even more troublesome issue is the mechanism by which memory, personality and other aspects of what makes Sam a particular human being are produced in all the clones. When the clones are woken they have language, knowledge about the space station, and appear to have a rich and emotionally relevant memory of a former life with Sam’s wife and daughter. With today’s technology this would entail first bringing up the clones through infancy and childhood into adulthood, allowing them to grow and learn (perhaps with the aid of “brainwashing” techniques ie producing false memories). This would take years and perhaps this was part of Gerty’s job .
However, although we aren’t told so, I think there is an implicit suggestion that the memories are transferred in some more direct way. This is something that would be very difficult to even envision at the current time. Memory and habit formation are complex and involve tiny changes in billions of neurons. There are over 80 billion neurons in the adult human brain and each of those neurons may make thousands of connections with other neurons through synapses. Memories probably involve subtle changes in strength of these synapses and may involve large networks of neurons acting in concert. Currently it would be difficult to envisage how we could ever map that degree of complexity in a living human brain, never mind transfer it to another brain. So, although cloning Sam is a real and present possibility, producing multiple clones with identical knowledge banks is probably out of reach for the foreseeable future.