NASA does not have the funds to carry large programs like manned lunar landings. If they want to go back to the Moon, it must be an international effort to spread the costs. Start with the Space Station as a starting point and work your way back to lunar landings. Its cheaper to build ships in orbit than on Earth.They should stick to unmanned robots which they are having a lot of success with. If they want an interstellar flight, they will have to wait until theoretical physics catches up.