A suction cup will not work in outer space because there is no air.
Suction cups rely on external air pressure to hold them in place, but outer space is a vacuum. They only work when there's air pushing against them and space has none.
Here on Earth, when you press a suction cup against a surface, you’re squeezing out the air inside it. The air pressure around it then pushes it tight against the wall, like a tiny invisible hug.
Outer space is a vacuum, meaning it’s completely empty with no air, no pressure. So when you try to use a suction cup out there, nothing holds it in place. It just floats away like a rogue rubber ducky.
Here’s a fun twist: astronauts actually need sticky things in space, but they can’t rely on suction. Instead, they use Velcro, clamps, and even gecko-inspired adhesives that mimic how lizards stick to walls using microscopic hairs.