Q. Is space travel halachically permissible?
A. It would seem from the T’nach that space is a prohibited realm: the heavens are “the heavens of the Lord” (Psalm 115:16), though Nachmanides says that “heavens” in this sense is a spiritual realm, not the physical cosmos: a state, not a place. Nonetheless the Biblical and rabbinic authors are adamant that neither the people of Babel nor Nebuchadnezzar should have wanted to ascend to heaven (Gen. II; Isaiah 14:13-15; Pesachim 94a, Sanhedrin 109a).
Our reality is that space travel is more than science fiction. Is it a risk to human life, bearing in mind the halachic warning against entering a risky situation? The element of danger depends on what science and technology tell us, and even with the best scientific backing things can go wrong, as we know from the fate of Ilan Ramon and his fellow astronauts.
The element of risk has not yet been conclusively overcome, but in an optimal situation the religious believer would recall the Psalmist’s confidence that “If I ascend to heaven, even there shall thy hand guide me” (Psalm 139:8-10) and would have faith that space travel would increase man’s awe of the Creator (Psalm 19:2).