If astronauts were to travel upward in space forever where would they go?

there is on up in space

you just go........!

umm... into a different galaxy

they would just keep on going, maybe reach another galaxy

They would just be way out there in deep space.

well, they'd keep going until they die. or they're might hit some other planet or comet eventually and decompose

nowhere since space is continually expanding faster than people can travel.

"Space" extends almost infinitely far in all directions. Where an astronaut would go would depend on where they started, but almost certainly they would go on in that direction until they died, since the odds of encountering anything in a random direction are virtually zero. We get to destinations in space only by extremely careful navigation, deliberately choosing a destination and then navigating there.

As far I think, they would travel only in the Solar system coz traveliing anywhere outside would need a lot of fuel, time and money!

there is no up or down in space. As for where they would end up at...who knows? They can't go "outside" the universe because there is no outside. If space is curved, and if they travel in a straight line, then they will end up where they started.