Maybe this question sounds snaive to some educated people, but I'm not clear if the Space Shuttle could and was ever used without a crew.
And what was the smallest and the biggest crew size it ever flown?
Maybe this question sounds snaive to some educated people, but I'm not clear if the Space Shuttle could and was ever used without a crew.
And what was the smallest and the biggest crew size it ever flown?
It always flew crewed.
After the Columbia failure, provision was made to fly a damaged Orbiter uncrewed back to a west coast landing site, leaving the crew on the ISS. This was called the Remote Control Orbiter and it required an In-flight Maintenance kit to be installed after docking at the ISS. It was never used.
The smallest number was two (STS-1, 2, 3, and 4)
The largest number was eight (twice, on STS-61A and on STS-71’s return from Russian space station Mir)
The Space Shuttle was America's only crewed spacecraft to fly crewed from the very first flight. Commander John Young and pilot Robert Crippen flew an historic and heroic flight. They were accommodated with ejection seats although over most of even the early flight profile would likely have been at mortal risk ejecting from the vehicle. I had the pleasure in 1981 of Bob Crippen's company over lunch and he confided that once the countdown passed the final possible abort time (at T-31 seconds), his heart rate jumped instantly (in a heartbeat so to say) from 60 BPM to over 120.
I think this question sounds strange to many, but I'm not clear if the Space Shuttle could and was ever used without a Crew.
That depends on your definition of "used", I guess. Several Orbiters are currently "used" as museum exhibits without any (flight) crew.
And what was the smallest and the biggest crew size it ever flown?
That depends on your definition of "flown". During ferry flights on the Shuttle Carrier Aircraft, there was no crew on board the Orbiter. It also depends on your definition of "crew", because there was a flight crew on the SCA for those flights.
It was, however, not capable of autonomous operation. For that, it always needed a crew. (In particular, it had to be landed by a human pilot.)
This is in contrast to the Soviet Buran, which was capable of autonomous operation, and in fact had its only flight without any crew, and also the unofficial successor to the Shuttle, the Boeing X-37, which doesn't even have the possibility of carrying a crew.