Hyper-intelligent monkeys bred especially to serve on Solar Survey space vessels.
"Simps," as Superchimps are often called, are not actually chimpanzees. They are carefully bred descendants of the Monkey Kingdom, having ancestors from both Old and New World monkeys. Simps also benefit from synthetic genes not found in nature.
The labor and expense involved in rearing and educating Simps is comparable to that of the average crewmember's. However, they weigh less than 30 kilos (66 lbs.), require half the food and oxygen of humans, and can replace 2.75 spacehands each. Simps perform housekeeping, elementary cooking, tool-carrying, and other routine chores. They are capable of, and even enjoy, 15 hour work days, relieving human hands for more complex tasks.
Being specially and synthetically bred, Simps are docile, obedient, and uninquisitive. Simps are cloned and therefore sexless, which avoids certain behavioral problems. They are fully house-trained and also vegetarian.
Simps command a equivalent IQ of sixty. They understand several hundred words of spoken English but do not speak. It has still proved impossible to breed or implant useful vocal chords. However, Simps are adept at sign language.
Unfortunately, Simps can only be trained for routine tasks. Unique, unusual, and emergency situations totally befuddle the Simps. In a true emergency, they can easily endanger themselves as well as human crewmembers. Moreover, it has also proved impossible to train Simps to properly use spacesuits.
In the event of an evacuation, it is necessary to administer euthanasia to the Simps. Originally, this duty fell to their trainer. However, on the first and so far only occasion that euthanasia was required, the trainer intentionally poisoned himself as well. If the procedure must be repeated, the duty will now fall upon the chief medical officer.From Rendezvous With Rama by Arthur C. Clarke