Absurdity is a relative term...
Of course the practice of praying would seem absurd to an atheist outsider looking into any faith ("but dahllling! It is sooo ABSURD, no?"), but then it is the same from the inside looking out, as it were.
Now being a muslim, if it was down to me (and I somehow found myself without advice from a scholar or decided not to follow it for some reason), I would base 5 prayers on a generic 24 hour cycle while I was up there, maintain a relative position to Mecca by retaining the position I assumed when I began the specific prayer I was on, and as for ablution? Water is not the only accepted resource to use to clean yourself. Dry ablution is possible with something like sand. The only problem would be, how do you ensure that you don't have sand all over the Zero-G place? I am sure that this last matter is already taken care of by the ISS.
In the worst case, if I found it all unmanageable, I would make up for all missed prayers/fasts on return to Terra Firma. To the people who take the now-accepted line of saying stuff like "Muslims are crazy", "it is absurd" etc, all I can say is (a) what's it to you? and (b) I always found non-muslims a little crazy until I took the time to actually understand them.