A man is woken up from hibernation.  The world has destroyed itself and the survivors are living on a simple level.

He was woken up because he had developed a space defense system and an asteroid or meteor was coming at the Earth and the people needed him to activate his system and destroy it.

While working on it, the asteroid changes course and he realizes he is being lied to.  It is not an asteroid, but a ship.  The people tell him it is a ship of the leaders who destroyed the world long ago, and they are coming to take over with their war like ways again.  He is convinced and destroys the ship.

It ends with him feeling badly that man will never go to the stars.  The people tell him that they've developed their minds since technology ended, and they can travel to the stars mentally any time they wish.  They help him travel to a new planet astrally at the very end.

What episode is this?

I suppose this could have been from one of the Twighlight Zone reboots.