Only spaceships equipped with a special force field can enter hyperspace, because exposure to hyperspace even for short period of time is hazardous to unprotected humans.

There are other things out there to kill unprotected humans besides radiation.

The Klingon had released twenty unprotected humans into space, forcing the Yorkshire to drop its shields to try to recover them.

The Yorkshire couldn't use torpedoes so close to the unprotected humans floating in space.

The planetary beachhead is still tenuous in the extreme, and the surface battlefield a poor environment for unprotected humans.

That engagement, with unprotected humans on the surface at close quarters to the combat, could easily kill them.

This radiation contains both a neutron and gamma ray component and is extremely dangerous to unprotected humans nearby.

It may even withhold its fire, since its primary weapons, if discharged too close to unprotected humans, could injure them.

The pulse of neutron radiation would cause immediate and permanent incapacitation to unprotected humans out to 900 meters, with death occurring in one or two days.

But the cloud of subatomic particles it blew into space could kill unprotected humans in seconds.