During the last thirty years it was claimed by NASA that without significant reductions in the cost of launch operations to Low Earth Orbit (LEO) and faster transit times to Mars and the other outer planets, manned spaceflight was stuck in LEO for the foreseeable future.

This position ignored the fact that we had already developed and paid for the Nuclear Engines for Rocket Vehicle Applications (NERVA) program that produced 250klb thrust Nuclear Thermal Rockets that could have gotten a crew to Mars in half the time that chemical rockets could.

Alas, in 1972 the Nixon Administration shut down the NERVA program due to budgetary constraints brought on by the Vietnam War, lack of interest in manned Mars missions and concern over how to continue testing them on the ground.

So, what can we do now if we want to explore the solar system first hand? Without nuclear powered spacecraft, manned missions are marooned in low Earth orbit.

It has become apparent with the Russian Mir Space Station program that living periods in space that are longer than four-to-six months are detrimental to the stationed personnel due to zero-g de-conditioning compounded by the physical isolation from family and friends.

The data from the human factors studies obtained from the newer International Space Station (ISS) have verified these early human factor results from the Russian MIR. Add to that the knowledge from recent robotic Mars missions that the space radiation exposures that an astronaut crew would suffer on a chemically powered, six-month long trip to Mars, using standard shielding practices for manned flight vehicles, would be very detrimental to the crew's health and that's during quiet solar-flare times.

If a solar flare comes along, the astronauts would be cooked in very short order unless they are supplied with a very massive radiation "Storm Cellar" or an Earth like magnetic shield to hide in during the solar flare induced radiation storms. Both of these solutions will increase the mass and/or the power requirements for the mission, which in turn increases the mission's total energy requirement.

Where is this extra energy for faster transits times, as well as the extra shielding mass or extra shielding power going to come from? Chemical reaction based propulsion and power sources are already taxed to their limits with the current barebones, low mass, six-month Mars missions. The only other solution currently available to this problem is to use higher energy density propulsion and power generation fuels.

Nuclear fuels can supply over ten million times more energy per unit mass than chemical reactants can. NASA's Sean O'Keefe has the right of it then. Until we can get past the "Age of Sail" in the space exploration program as exemplified by our current fleet of chemical rockets, and migrate to the "Age of Steam", i.e., rocket energy and perhaps propellant supplied by nuclear fission or fusion power, humanity will not leave Earth in any great numbers.

In addition, for those who sing the solar power mantra, the numbers are not good. If you are going out to Mars and points outward bound where it is VERY COLD, some form of nuclear power is the only feasible solution.

If nuclear power is the danger that the anti-nuclear people say it is, why have there been a disproportionate number of deaths and injuries due to non-nuclear effects since the end of World War II?

For comparison's sake, the worst single chemical spill accident in the world occurred at the Union Carbide/India's insecticide plant in Bhopal, India where over 6,400 people were killed and ~35,000 people were injured from a methyl isocynate gas release in December 1984.

Has Mr. Gagnon and/or Dr. Kaku been trying to shut down those chemical industries that supply our farm and automobile industries?

I do not remember them complaining about the oil, gas and plastics needed to grow their food or build their automobiles. We also have the little issue of the yearly volcanic eruptions that spew out more toxic chemicals into the atmosphere than humanity's entire industries put together.

For context, consider the 1991 article by Dr. Michio Kaku, entitled "NASA shuffles shuttle's death card", where he explained NASA's insensitivity to the environment by noting that "the US space effort is a deformed scientific program that was born out of the Cold War and twisted by the demands of anti-Communism", with the Pentagon still secretly "in the driver's seat".

In the Guardian article one of his major claims was that "Solid-fueled rockets emit large quantities of harmful hydrochloric acid, which can rapidly deplete the fragile ozone layer." Yet over a decade later, there has been no convincing study that the Space Shuttles has ever contributed more than a fraction of one percent of the annual hydrochloric acid impact on the ozone layer.

Continued statements of this nature are not reflective of a balanced view. There is also displayed a single-minded view of nuclear power at work as well.

The US Navy has an enviable safety record of operating nuclear power plants over several generations. With proper engineering, training and investment, this can be accomplished with the space program as well.

Invocation of Chernobyl as a reason for ceasing the research, engineering and use of nuclear power and citing Plutonium as the most dangerous element to humankind is fear mongering at its most base.

There are other schools of thought even on the question of the hazards of exposure to low-level radiation such as Radiation-Hormesis that deserve consideration.

If we are in a multinational effort to go to Mars with nuclear power, I think it unlikely that the nuclear power in space effort is a cover for maturing the technology for use within the Dept. of Defense.

Surely the other nations on-board such a program will be able to learn the same engineering and technology lessons for their own needs. This "everyone else knows how to do the same thing" approach to nuclear space power is not the sort of competitive advantage our military wants.

I think that ground based nuclear power reactors can be built and operated safely with the appropriate safety design, proliferation safeguards and a middle of the road concern for the environment.

This goes as well for flying uranium-235 enriched nuclear reactors for use in space with little risk to the public. I believe that NASA understands that the risks of flying open-cycle NERVA like nuclear thermal rockets in the Earth's atmosphere while low, are still non-zero and that it wouldn't be prudent to fly such a rocket from the Kennedy Space Center (KSC).

Flying NERVA type rockets or hybrid nuclear RAM-jets from the middle of the Pacific Ocean, off a Lockheed/Russian Zenit like mobile oil barge on the other hand, might make sense and would definitely lower the cost to get into orbit.

What NASA is now proposing though with their Prometheus Project is to fly CLOSED-Cycle enriched U-235 fueled nuclear-electric reactor/rockets, cold, i.e., it has never been activated and thus virtually non-radioactive, from KSC.

If the rocket carrying such a closed-cycle reactor system should crash, the cleanup would be no worse than any other industrial chemical spill and a small one at that.

Until we have one or more reliable aneutronic fusion sources that use hydrogen/deuterium with He-3, Boron-7 or some other aneutronic fuel combination, or an even more exotic vacuum based energy source, nuclear fission is the only way to produce the energies needed to pursue manned spaceflight and solar system exploration in any serious manner.

Just look at the leap in capability that submarines had when they went from chemical fuels to using nuclear energy for their propulsion. It was a quantum leap in naval capability and even the two US nuclear boats and all the Russian nuclear boats as well that were lost to accidents at sea over the last 40 years did not ruin the environment.

And a question for Mr. Gagnon in your statement, "During the Cassini RTG fabrication process at Los Alamos, 244 cases of worker contamination were reported to the DoE. " What is the reference for this and how badly contaminated were these workers?

NASA has to adopt an environmentally sound but non-timid approach to nuclear powered space flight or we are stuck on earth for the foreseeable future. Perhaps that is what Mr. Gagnon's & Dr. Kaku's group is really after, that is having what's left of the human race, after we've reduce our numbers to "sustainable levels", go back to being "Noble Savages", waiting for extinction from a Yellow Stone like super volcano eruption or the impact of another dinosaur killer asteroid or comet.

I for one do not plan to wait around for that outcome.

Ad Astra!

Paul March is a space industry professional working for a major aerospace contractor. His views expressed here are is own and do not represent those his employer.

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