People unsatisfied with their experience in No Man's Sky still have a chance to get a full refund according to Game Informer. Reports from Reddit and Neogaf show users have gotten a refund from both Steam and PSN platforms despite the usual policy that each service has. 

Steam typically does not give refunds on game's with under two hours of gameplay, while Sony will only refund a game within 14 days of purchase. 

It is worth stating that this method is only working for SOME people who attempt it. There's also people who have tried and failed to get a refund. Would you take back No Man's Sky if you could?