Why the Nuclear Option is a Necessity if Humans Are Ever Going to Get to Mars and Return Alive

In the last two weeks a report from NASA confirms that prolonged stays in outer space are more than just harmful to human health, they can be deadly. Why? Because humans didn’t evolve in the environment of space but rather here on Earth inside the protective envelope of our planet’s magnetic field and thick atmosphere. Outside it, we are just like fish stranded on land flopping about and gasping to survive.

NASA has known this from before Alan Shepard took America’s first suborbital flight. They created the Human Research Program to study the perils humans face when in space. They note five specific ones that include:

1. Space Radiation – Three sources of space radiation can play havoc with us including particles trapped by Earth’s magnetic field, solar flares, and cosmic rays coming from the Milky Way and beyond. The amount of radiation exposure is dependent on not only time served but where it’s served. In near-Earth orbit, there is a level of protection from cosmic rays and solar flares. But on a voyage to Mars and back as well as a stay on the planet’s surface, the risk of radiation exposure means human crews will be susceptible to cancer, heart disease, cataracts, other degenerative diseases, and with the latest findings, chronic anemia.
2. Isolation and Confinement – A trip to Mars using chemical rockets whether NASA’s Space Launch System (SLS) or Elon Musk’s Starship, means a voyage and stay lasting minimally two years. Not only do the crew face the cosmic radiation, but also the emotional and mental stress of living within a confined space for a prolonged period of time. Many of us may have an inkling of what that’s like over the past two years as the pandemic has kept us cooped up in our homes and apartments. But we can still leave and go for a walk, or get takeout from a local restaurant. Imagine enduring multi-year confinement where you can’t step outside. NASA research shows that a restricted environment and human interactions confined to a small group with little outside contact leads to cognitive changes and an increased risk of psychiatric disorders.
3. Distance from Earth –  The ISS is 1,000 times closer to Earth than the Moon. Mars is on average 600 times further than that. When the explosion occurred on Apollo 13, problem-solving involved the human crew aboard and a team of engineers and scientists on the ground who could message each other continuously The latency even as they rounded the Moon was no more than a few seconds. But that won’t be the case in a voyage to Mars. When a problem occurs en route, or on the planet’s surface, the conversation between NASA and the crew will experience as much as a 20-minute lag between the send and receipt. How do deal with a medical emergency involving the crew? What do you have onboard for such emergencies? What if something happens to the spaceship and you have to go into lifeboat mode? How much redundancy can be built into the mission? After the explosion, Apollo 13 and the engineering team at NASA had to construct a CO2 filter from the items on board. A lot of duct tape was involved.
4. Gravity Fields – A trip to Mars involves a long-term ride in microgravity based on current spacecraft designs. That’s because neither NASA nor SpaceX has a rotating module in their current plans to create artificial gravity for long-term crewed flights. Then there is one-third the gravity of Earth that the crew will experience once on Mars. It is likely they will experience orthostatic intolerance and be unable to adjust for a period of time living in microgravity. And on the return trip, the challenge will be even greater in trying to find their legs back on Earth.
5. Closed Environments – A spaceship and the ISS are both self-contained environments in which humans and all the bacteria and viruses that accompany us can find a home. That’s why environmental monitoring is constant. Contaminants like formaldehyde, ammonia, and carbon monoxide gasses can leach from many sources with health consequences for the crew. Before each mission, human crews get screened for health problems that can be transmitted to others on board. As a result, ISS health vigilance is practised with a vengeance. Now think about a spaceship travelling for six months to Mars, and six months back. Just how much more vigilant will the human crew need to be to ensure first, that they don’t get sick on the way, don’t introduce Earth bacteria and viruses in the Martian environment upon arrival, and don’t bring back any exobiology inadvertently on the voyage home.

Going Nuclear Takes Away Some of These Human Risks

If the time to get to Mars and back were shorter, a degree of risk would be alleviated. Currently, using the chemical rocket propulsion method leaves us with at least a two-to-three-year mission. So why not look at an energy source that we began to harness some 75 years ago as an alternative. What I’m talking about is nuclear fission and fusion.

We use nuclear energy on space missions today. Both Perseverance and Curiosity are the beneficiaries of a technology called Radioisotope Thermal Generators (RTG) that use the heat from radioactive decay of a small mass of plutonium fuel to provide energy and warmth. And we have lots of experience with nuclear fission reactors and are getting closer to achieving commercial fusion.

So why not use nuclear to power rockets going to Mars? NASA and America’s Defence Department have flirted with nuclear propulsion systems since the 1970s. And so have the Russians. NASA built a prototype back then called NERVA. But the research was eventually shelved more out of budgetary concerns than anything else.

In a recent article appearing in Scientific American, David Brown describes the nuclear option stating that it is the only way humans will meet the challenge of a Mars mission with reasonable risk. Why? Because to pull off a Mars mission using chemical rocket propulsion technology is more than just about the length of time to get there and back, but also about the support infrastructure to make it work.

Using the conventional chemical rocket technology we have perfected at this time, a single mission to Mars will require the launch of a mass equal to 10 ISS to be put into space. It will involve at least 30 and as many as 40 of the largest rockets we have today to put the spacecraft, crew and fuel needed for the mission. That doesn’t include adding reserves of fuel placed strategically along the route should a problem arise going to Mars and coming back. Brown states that the total cost of a single mission using this approach would exceed $80 billion using the yet-to-be-launched SLS as the primary vehicle. With SpaceX and the Starship and Heavy booster, the cost could be cut by half. But even $40 billion for a single mission seems excessive.

Using nuclear-powered propulsion systems, however, would eliminate the need to put megatons of fuel into orbit. The only time chemical rockets would be used would be in launching the crew and spaceship components to Earth orbit. That could be done in as few as three launches with the final assembled ship going to Mars and back and then being parked in Earth orbit to be used again on future missions.

What additional advantages can be derived from using nuclear? Thermal-powered nuclear is at least twice as efficient as current chemical rockets and requires a tiny fraction of the fuel to get the job done. Electric-powered nuclear starts moving the rocket slowly away from Earth and then continuously accelerates to attain peak speeds of 200,000 kilometres (120,000 miles) per hour. An electric-powered nuclear propulsion system would use even less fuel than thermal-powered nuclear and would shorten the voyage to a month.

Could NASA go nuclear by 2030? Undoubtedly.