We were at MK on Tues Oct 18. Space Mountain was closed for the majority of the day due to technical difficulties.
We had gotten a FP at 10.30-11.30 slot, and when we returned at 10.45am, they said it was closed due to technical difficulties and to return in an hour. We did, and it was still closed. We returned at 1pm, still closed. We tried again at 2pm, still closed.
It was fairly frustrating to keep walking back to Tomorrowland just for that ride, only to fiind it wasn't working.
We finally got on at 3.30pm. Definitely took something away from the thrill of it for me, a first-timer.