Members of the main crew of the expedition to the International Space Station, Russia’s cosmonaut Oleg Novitsky (L) and US astronaut Peggy Whitson wave as they walk to board the rocket at the Russian-leased Baikonur cosmodrome in Baikonur
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What do humans do on the International Space Station that could not be done by machines?
Serve as Experiment Subjects
The crew are poked, prodded, drained, biopsied and observed every day. They provide biomedical data and samples that are of great use to researchers.
If we are going to one day venture farther out into the solar system, we need to better understand what happens to people that are in space for a long time. What happens to their bones and muscles? Are they psychologically altered? Does their ability to perform a task diminish with time? Through observing the crew over the last 16 years, we’ve learned a lot about long duration spaceflight. We’ve made exercise and dietary changes that have reduced the bone and muscle loss. We’ve observed changes that weren’t predicted, such as changes in eyeglass prescription as the shape of the eye changes during long duration spaceflight.
The crew also serves as analogues for experiments focused more upon people on the ground. For example, studying the rapid bone loss experienced by astronauts while in microgravity and studying the effects of protocols used to affect that bone loss can tell us more about the bone loss experienced by older people on the ground.
Perform Experiments that Require Dexterity
We can certainly design robots on the ground that can do very fine tasks, but those robots are highly specialized and large. Getting robots for each necessary task into space would be prohibitive. We are testing a robot named Robonaut onboard the ISS. It’s not particularly adept yet.
Some experiments require the flexibility and dexterity of human hands. For example, dissecting a fish and preparing slides with thin slices of the anatomy.
Replace and Repair Broken Equipment
Equipment breaks in space. That equipment needs to be serviced, repaired, or replaced.
After the loss of Columbia, the government was planning on canceling the last Hubble servicing mission. A team was put together to design a robotic servicing mission. They concluded that some of the tasks simply could not yet be done via robotics.
About 12 years ago, the central computers on the Russian Segment failed because of interior corrosion. The cosmonauts had to perform visual troubleshooting and then repair of those computers. If they had not been repaired, the ISS thrusters would have remained unavailable and prevented the necessary periodic burns that keep the ISS in orbit.
And last but not least—humans can tell us how small and vulnerable Earth looks from space.