To answer a common question, this does exist for people who have never been before, it is way up, only accessible by flying stands such as Zenith and MUI but other stands have also been able to get passed the layer like Crystallized's jump combo and PLANET // SHAPER's Y.( P//S users can also hold spacebar and use the short jump cooldown to their advantage.) Also Star Platinum Requiem can fly up close to space, but it will be cancelled and you will be shot down, Cake Platinum is also able to get up into space via using their pose and jump move to get up. Casey can also get to space if you roll in the right way.
Any stand/spec will be brought to space if a PLANET // SHAPER uses their H, though you will most likely be killed when they use this.
Flight in space is infinite, yet you can move pretty decently without a flying stand, just takes some time to master.
Space seems to have some type of gravity affect on the world, making bosses like Brando and DIO fly straight up, rendering them unkillable and pretty much useless. Do not expect to grind for Dio Diary's til this is fixed.
PLANET // SHAPER users may be posing in space just to have a nice, quiet place to hang out with other stands like them. They can reach space via their Y button, which instantly brings them to it.
Look down and hold W to fly down
Look up and hold W to fly up (or hold space)
Look forward and hold W to fly forward.