Short answers, pulled from the story.
Space adaptation syndrome, also called space sickness, is a form of motion sickness experienced by as many as half of all space travelers during their initial adaptation to weightlessness in orbit. Symptoms range from mild nausea and disorientation to vomiting and intense discomfort, and typically last two to four days.
Soviet cosmonaut Gherman Titov was the first human to experience space adaptation syndrome, becoming ill on Vostok 2 in August 1961. He was also the first person to vomit in space.
The Garn scale is an informal NASA measure of space sickness severity, named after Senator Jake Garn, who suffered the most extreme case ever recorded on a shuttle mission in 1985. One Garn represents total incapacitation from space sickness. Most astronauts experience only about a tenth of a Garn.
Space adaptation syndrome is the inverse of ordinary motion sickness. In carsickness or seasickness, the surroundings appear stationary while the body feels in motion. In space sickness, the environment appears to be moving while the vestibular system registers no corresponding bodily movement.
NASA generally allows natural adaptation to occur over the first one to seven days, preferring that to extended use of medication. Transdermal dimenhydrinate anti-nausea patches are used whenever space suits are worn, because vomiting inside a pressurized suit can be fatal. Extra-vehicular activities are typically not scheduled during the first days of a mission, giving the crew time to adapt.
Prolonged microgravity exposure causes muscle loss, bone resorption, and kidney stones from inadequate hydration, as well as cardiovascular changes that can limit an astronaut's capabilities after returning to Earth. Orthostatic intolerance is a specific risk, where the body's adaptation to weightlessness can cause a temporary loss of consciousness upon standing after landing. Space sickness itself can persist for days after a mission ends, as the vestibular system readjusts to gravity.