The Saturn V actually got men to the moon, remember? Several times. Nova was an evolving launcher for a mission profile that had to be abandoned because it was not practical.
Orion, on the other hand... It was actually more practical if executed properly, meaning MUCH more payload to orbit... and beyond. The pulse units were actually nuclear shaped charges, not bombs in the traditional sense, and the entire workings were being carefully crafted for the rigors of spaceflight. It actually made more sense to scale it up than to scale it down.
"No, Orion does not make tons of deadly radioactive fallout. If you launch from an armor plated pad covered in graphite there will be zero fallout. And No, it would not create the apocalyptic horror of EMP making the world's cell phones explode and wiping out the Internet. That's only a problem with one megaton nukes, the Orion's charges are only a few kilotons. Just launch from near the North Pole (at least 276 kilometers from anything electronic) and you'll be fine." - RocketCat from projectrho (Atomic Rockets) http://www.projectrho.com/public_html/rocket/realdesigns2.php
When the Air Force presented Kennedy plans for their Orion-derived space battleship to fight the Soviets, he balked. Wonder why. The program never recovered.
More than 50 years since the Cuban Missile Crisis, yet nuclear pulsed spacecraft STILL cannot be trusted to earthlings. Such a shame.