It is naive and against national interests for the U.S. to rely on expensive, outdated, slow, single-use chemically propelled rockets like SLS to transport astronauts to Mars. Instead, America must aggressively invest in developing space nuclear propulsion systems.

Nuclear technology, including nuclear electric propulsion (or “NEP”) and nuclear thermal propulsion (or “NTP”), will be a space travel game-changer with profound implications for deep space mission speed, agility and capability.

The increased propulsive power of nuclear systems will allow humans to head to Mars on a more regular cadence than the current mission launch windows of “every 26 months.” Nuclear propulsion also will allow power for astronauts on Mars missions to abort and return to Earth in the event of an emergency.

Obviously, science fiction writers are down with this program. I guess I think most strongly of that moment in Heinlein's 1961 novel Stranger in a Strange Land when he describes the crossing to Mars taking place in just nineteen days under Lyle Drive:

The Federation Ship Champion, manned by an all-male crew of eighteen experienced spacemen and carrying more than that number of male pioneers, made the crossing under Lyle Drive in only nineteen days. The Champion landed just south of Lacus Soli, as Captain van Tromp intended to search for the Envoy.

Even earlier, Eando Binder describes a similar journey to Mars in his 1932 short story The First Martian:

(The First Martian by Eando Binder)

The inconceivable distance to be traversed, the enormous energy required to transport a heavy machine from planet to planet, and the all-powerful force of gravity, seemed insurmountable objects to even the most broadminded and optimistic thinkers. Feeble attempts were made even in 1931 to leave this speck of the universe and soar to other worlds, but constant failures dulled the ardor of those who wished to connect our world with the others which acknowledge the same central sun...

Although the fatalities far exceeded these probable successes, the hope of interplanetary travel was still uppermost in our minds. We know now, that our failure can be attributed to the unfortunate lack of radioactive elements, and not to the lack of ingenuity or inventiveness.

It was only too true. as Professor Billings stated in 1945, that the only type of engine which could possibly transport a heavy machine from our earth to some planet, would have to be the atomic-energy engine, which, with a minimum of fuel and the very necessary radioactive element, could develop an unlimited amount of energy.

He even drew plans of the basic principles of such an engine, estimated the amount of radioactive material needed, and worked out the propulsion of the ship.

As far as I know, the first reference to an "atomic engine" can be found in HG Wells' 1914 short story The World Set Free - but not in a space craft:

...the swift aëroplane, with its atomic engine as noiseless as a dancing sunbeam... flew like an arrow to the heart of the central European hosts.