Basically, every time you cast it once successfully you are then able to instantly transport one fleet to a planet you own without a portal. Even though a planet would be defended instantly it would still allow some 24+ ticks for another attacker to be able to clear/DU it.

Pros:
Would allow for outposts to be formed, maximising more spread earlier on in explo phase.
Some newly explored planets could be defended instantly for bankers.
Making DU a more valuable op.

Cons:
Thining out attackers somewhat?
Making it too hard for families to clear someone quick enough?

Not really sure if the cons out weigh the pros. Think it would be a handy addition and increase the warfare side of the game!