What NASA needs is a better propulsion system that can accelerate and decelerate the craft during the entire flight. I believe that would make the trip a few weeks or months. We always heard about ion drives and nuclear propulsion, why are none of those feasible?
Back in the old days - 1958 until 1964 when Project Orion was killed. Their motto was "Mars by 1965, Saturn by 1970." Three day trip to Mars. It would have cost the same or less than Apollo. Design and concept for nuclear explosion propelled vehicle. Concept, design and model built. System worked. Larger the better. Small 10,000 ton vehicle with crew of 150 planed, 40 million ton interstellar vehicle (which equals 265 supersized oil ships) was planned next with crew of thousands. Mega-tons of on board water would have been the shielding - hot showers available for all daily.
The major problem was steering the thing. The US's leading designer of small nuclear bombs left the field in protest. Was perceived as contravening the then new nuclear treaty. "Greatest failure of political will ever" - Freeman Dyson.
See here for rendition:
Mission to Mars: Orion nuclear propulsion (remastered) - Orbiter Space Flight Simulator 2010
See here for history:
To Mars By A Bomb - The Secret History of Project Orion (Nuclear Propulsion)