What does the writer mean by "a machine can be lost but a crew must come home"?

Sending a satellite into space is hard. Sending people is much harder, because a machine can be lost but a crew must come home. Gaganyaan is ISRO's project to show that India can do it.

The plan is simple to state. A crew of three is to be launched into an orbit about 400 km above the Earth, stay there for a mission of three days, and then be brought back safely, landing in the sea in Indian waters.

What makes it difficult is everything that has to be built first. The rocket itself must be "human-rated", meaning it has been made and tested to the far higher standards of safety needed for carrying people. The spacecraft needs a life support system to give the crew an environment like the Earth's, with air to breathe and the right temperature and pressure. There must be a way for the crew to escape if something goes wrong during the launch. And the astronauts must be chosen, trained, recovered from the sea and cared for once they return.

ISRO's Human Space Flight Centre leads the work, drawing on its own experience, on Indian industry and universities, and on technology available from other space agencies. The skills it builds are meant to last beyond this first flight, towards future work such as docking spacecraft together and building a space station.