New Delhi, March 19 -- Indian-descent American astronaut, Sunita Williams, returned safely to earth in the early hours of Wednesday India time-after being stuck in space for more than nine months.

In one of the most politicised and closely-followed human space missions of late, Williams spent 286 days in space-even as her original mission was intended to last for as less as eight days. The mission's conundrum raises a key question: why is spaceflight still so difficult for humans?

Williams' original mission, aboard a spacecraft built by US aviation major Boeing, was meant to last for eight regulated days. However, a mechanical failure in Boeing's Starliner-expected initially to be an alternative to Elon Musk-backed SpaceX's Crew Dragon ...