(CNN) — The wonders of spaceflight never ceased in 2020, despite the pandemic's best efforts. Four launches — including two historic missions from US soil — to the International Space Station carried on as planned, and the crews were able to remain safe on their journeys to and from Earth. Quarantine has become the new normal for many over the last year, but it has long been part of the routine for astronauts launching to space. "NASA's had a robust quarantine plan for a long time," said Robert Mulcahy, flight surgeon for the Health Stabilization Program at Johnson Space Center in Houston. "It's nothing new for us. NASA implemented a prelaunch quarantine starting with the Apollo 14 mission (in 1971) because we saw some infectious disease occurrences in flight or in the preflight period for some of the earlier Apollo launches."