Deep Space: The new frontier of radiation controls
In commercial nuclear power, there has always been a deliberate tension between the regulator and the utility owner. The regulator fundamentally exists to protect the worker, and the utility, to make a profit. It is a win-win balance.
From the U.S. nuclear industry has emerged a brilliantly successful occupational nuclear safety record—largely the result of an ALARA (as low as reasonably achievable) process that has driven exposure rates down to what only a decade ago would have been considered unthinkable. In the U.S. nuclear industry, the system has accomplished an excellent, nearly seamless process that succeeds to the benefit of both employee and utility owner.
All this came about because of a tiny snippet of well-supported science that, over the course of more than a century, declares this single conclusion, as defined by the Nuclear Regulatory Commission in “Biological Effects of Ionizing Radiation” (nrc.gov/docs/ML0511/ML051190314.pdf):
A linear no-threshold (LNT) dose-response relationship is used to describe the relationship between radiation dose and the occurrence of cancer. This dose-response model suggests that any increase in dose, no matter how small, results in an incremental increase in risk. NRC accepts the LNT hypothesis as a conservative model for estimating radiation risk. (emphasis added)
In sharp relief from this civil nuclear framework, the government’s approach to its class of nuclear workers called astronauts destined for deep space is very different. It has set an inverted example for near-future commercial deep-space travelers.
Through the NRC, the government developed a legal construct to protect commercial nuclear workers with the full force of the law, including possible civil and criminal penalties as enforced by the Occupational Safety and Health Administration and the NRC. But when the U.S. government polices itself, there is an immediate conflict of interest between who protects the worker and how that protection is balanced with the government agency’s reason to exist. NASA’s reason for existing and the associated tangible product is human space exploration, long considered a vital strategic national priority.
NASA assumed responsibility for regulating its workers’ occupational exposure to ionizing radiation (IR) when OSHA permitted it to set its own radiation exposure guidelines. Under 29 CFR 1960.18, NASA was granted a waiver by OSHA, expressed as “emergency temporary and permanent supplementary standards,” to institute independent limits for IR exposure for their astronaut crews. OSHA’s occupational IR protection limits no longer apply to NASA employees, as NASA’s Office of the Chief Health and Medical Officer now establishes radiation exposure limits sans conflict from any other interest.
Apollo 17 Commander Gene Cernan streaked with moon dust inside the lunar lander on the surface of the moon after the longest of the Apollo excursions, lasting 7 hours, 36 minutes, and 56 seconds. The three-member Apollo 17 crew was exposed to the longest single dose of unfiltered GCR at over 12 days, 14 hours in the functionally unshielded Apollo command module and lunar lander. On the lunar surface, the GCR dose was reduced by half compared to lunar or trans-lunar orbits because of the shielding of the moon itself. (Photo: NASA)
What inevitably happened next makes sense from the perspective of an entity—NASA—that was tasked with planning future, fundamentally unshielded missions to deep space, well outside the protective envelope of our planet’s Van Allen galactic cosmic radiation (GCR) shield. When on lunar or Mars missions, crews inside spacecraft traveling in deep space with current shielding packages in place (which would be ineffectual for this type of mission) would exceed annual federal radiation dose limits in 28 days. Even at the International Space Station, under the Van Allen shield, the OSHA limit is exceeded after 128 days. Obviously, something had to give to allow U.S. crews “reasonable access” to the deep-space environment sans effective shielding.
In this case, the prevarication that evolved from the limitations of antiquated Apollo space launch system (SLS)–type rockets is that adequate shielding to achieve federal guidelines was not possible with these types of vehicles. Therefore, crews would just have to take big risks for the greater good.
With modern space exploration technology, this is no longer true by any means, yet this ”reality” has gone unchallenged and has even metastasized into the private commercial sector.
In the end, the ”reality” is just that—something that has the near-certain potential to cause crewed mission failure in the near future, accompanied by injured or incapacitated humans with permanent internal trauma.
Future deep-space missions are being openly planned, with real dates attached, and with human crews as radiation research subjects. NASA’s Office of Inspector General described this outcome in these terms in a 2015 report (No. IB-16-003): “Although the Agency plans to continue efforts to develop countermeasures to address the radiation risk, NASA is likely to seek an exception from the current standards for those that cannot be fully mitigated” (emphasis added). In other words, aligned with OSHA’s 29 CFR 1960.18 NASA waiver, adequate GCR radiation shielding is not possible.
Yet in the present day, NASA’s deep space–bound crews and their families should breathe a sigh of relief. After establishing crew radiation safety margins for their employees at rates that would shutter a civilian nuclear plant for safety violations, NASA’s crewed deep-space program SLS/Orion/Artemis is in the throes of collapse. Thus, NASA astronauts flying beyond the Van Allen belts are going to be few and far between.
Another concern is in the making: private seats to deep space on fundamentally unshielded spacecraft will soon number in the thousands. These ambitious flight schedules are being openly discussed by a space technology company that can make good on its claims. With the largest rocket ever built by an order of nearly three times the power of a Saturn V, the space technology company is already publicly acknowledging that it will fly tens of thousands of permanent settlers with cargo to Mars in the next few decades.
The unknown
Current GCR exposure scenarios are often directly compared with terrestrial sources utilizing a radiation weighting factor (wR) to convert absorbed dose to equivalent dose, as well as NASA’s space radiation transport codes, such as high charge and energy transport. Trusted as these may be, they are still just scientific guesses because the only data to make comparisons are terrestrial examples, such as the Life Span Study (LSS) of Japanese atomic bomb survivors, which has tracked approximately 120,000 survivors of the Hiroshima and Nagasaki bombings since 1950.
Fundamentally, there is no valid comparison between terrestrial sources of IR and galactic sources, and there have never been any peer-reviewed investigations in the deep-space environment on vertebrate animal research subjects. This circumstance, sufficiently enabled by the scientific guesses, is where we find ourselves today. The accepted risk of continuing into the unknown without adequate research and preparation has finally come to its conclusion—after the clock for the first launch of extended human flights into interplanetary space is already racing toward T−0.
Today, humanity stands at the shoreline of our next migration, braced not by actual data but instead by administrative bureaucratic jargon supplied by NASA’s own OIG “watchdog,” because adequate shielding has been deemed “impossible”. Thus, when we consider what is coming for our interplanetary crews, we must understand why we simply cannot compare our planet’s BB pellets (terrestrial IR) with the universe’s 50-caliber magnum ammunition (GCR).
For example, when I go to my orthopedic doctor and receive an X-ray of my knee, I can go back to my laboratory, which features the world’s most advanced electron microscope, and carefully look for traces of that X-ray in my cellular substrate. I will never detect anything.
Interior cell matrix traces of linear energy transfer damage inside the cell matrix by simulated GCR—iron nucleus—at Brookhaven National Laboratory. These images show regions of dense ionization along the path of the particle, resulting in complex and often irreparable damage to cellular structures, including DNA, organelles, and the extracellular matrix. (Images: H. Wang and Y. Wang, Rad. Research [2014]; doi.org/10.1667/RR13857.1)
But if any part of my body, including my brain, is impacted by a cosmic primary particle traveling at relativistic velocities, cell death is highly probable—and the linear energy transfer of that particle, measured in kilo-electron volts per micrometer, will leave a visible trail of destruction inside the cellular matrix that would be clearly visible with a standard microscope. Indeed, “brain flashes” have been detected by Apollo lunar astronauts and even on space stations in low earth orbit. A brain flash is a burst of light emitted by the brain’s visual cortex. Most flight surgeons believe that each of these flashes signals the death of a neuron struck by a cosmic particle.
U.S. astronaut Jerry Linenger was so vexed by this phenomenon on the Russian MIR space station that he could not sleep because of the incessant flashes of light in his brain. He finally stacked two rows of lead acid batteries and rested with his head shielded between them to allow sleep. It is notable that he also reported that even these stacked lead shields did not stop all of the bright bursts.
However, the visual cortex is not the only cellular target. The whole body and every system are impacted by cells that do not immediately report their demise. Research has indicated these sensitive tissues that are not killed will certainly make their damage known decades later.
Cancer is not the only focus
I have never met anyone who has expressed much concern or knowledge of any appreciable risks other than downstream cancers from GCR exposure that fit the old terrestrial IR paradigm. This is because our experience for more than a century has been that terrestrial IR exposure is strongly associated with cancers such as leukemia, breast, thyroid, lung, colon, bladder, liver, esophagus, ovarian, stomach, and multiple myeloma. However, owing to the lack of any deep-space research data, the physiological risks of exposure to GCR on long-duration spaceflights are virtually unknown. What research has been done on ISS astronauts is application of scientific guesses to the list of cancers above, because there was almost nothing else to study.
Until 2007.
Prompted by retired Skylab flight surgeon Dr. Duane Graveline, a NASA and Brookhaven National Laboratory team was assembled that year to take a closer look at the effects of unfiltered GCR in deep space on vertebrate animal subjects, and I was a principal investigator for that research project. While human astronaut crews have been flying in low earth orbit protected by our natural radiation shield (the Van Allen belts), we had only a single set of 24 human subjects exposed to unfiltered full-spectrum GRC—the Apollo lunar mission astronauts (1968–1972).
Our investigation was conducted in 2006 and 2007, and our findings were published in the Journal of Experimental Neurology in the article “Quiescent Adult Neural Stem Cells are Exceptionally Sensitive to Cosmic Radiation” (doi.org/10.1016/j.expneurol.2007.10.021). We discovered that the most sensitive brain stem cells and neural epithelia responsible for neurogenesis were virtually eliminated by our acute dose of simulated GCR, equivalent to a round-trip Mars mission (a terminal exposure for our animal subjects due to extensive brain effects).
The only human study to investigate the sole cohort of humans exposed to full flux and spectrum GCR was published in a 2016 Scientific Reports article, “Apollo Lunar Astronauts Show Higher Cardiovascular Disease Mortality: Possible Deep Space Radiation Effects on the Vascular Endothelium” (doi.org/10.1038/srep29901). The target tissue types were of the same variety as in our study: endothelial and epithelial cells, fast-growing and sensitive cells vital for most human metabolic processes throughout the body. The research pointed to GCR as a probable cause of the higher cardiovascular mortality among this cohort—the only humans ever to be exposed to full-spectrum GCR.
These are just a pair of many studies in the recent past, with most reporting the same findings—the acute target of GCR is the body’s most sensitive stem cells responsible for supporting brain function, as well as the epithelial and endothelial cells responsible for circulatory, gut, and lymphatic physiology. Further, Apollo lunar explorers were exposed for an average of less than 10 days and still received a dose that resulted in a statistically increased probability of, not cancer, but an epithelial–endothelial disease, in this case cardiovascular dysfunction, up to three decades later. In my pair of books, Departing Earth Forever, I designated this suite of uniquely GCR-associated injuries cosmic radiation–induced sensitive-tissue pathology disorders (CRISP).
Cliffs of Hathor on Comet 67P/Churyumov-Gerasimenko image revealing cosmic radiation streaking on the CMOS image sensor. The longer streaks in this image are likely caused by cosmic rays impacting the camera’s detectors. Taken October 21, 2015. (Photo: Rosetta Spacecraft Image #180426-rosetta-European Space Agency)
NASA has sponsored a comprehensive array of research programs aimed at investigating the potential neurobehavioral and neurocognitive impacts of simulated space radiation on animal subjects, with a primary focus on rodents. A significant proportion of these studies have identified radiation-induced alterations in behavior and cognitive performance, indicating modifications in multiple central nervous system functions. These effects have been observed at absorbed-dose levels projected to be encountered during extended deep-space exploration missions.
Further, these GCR radiobiology effects are in many cases amplified in vertebrate physiology by such off-nominal conditions as the toxicity of extended exposure to microgravity, elevated exposure to carbon dioxide (hypercapnia), and even social aberrations such as crowded conditions and communication delay stresses, according to a 2019 National Council on Radiation Protection and Measurements report, Radiation Exposures in Space and the Potential for Central Nervous System Effects: Phase II (report no. 183). This suite of maladaptive responses that amplify the body’s systemic responses to GCR exposure and other environmental challenges is termed “multimorbidity” and is covered in detail in my Departing Earth Forever: Book One.
Humanity’s future in deep space
AI-rendered art of an astronaut in a deep-space capsule surrounded by GCR. (Image: Chamberland/Wonder Art AI)
If I go to work in nuclear power or any industry in the U.S., I am protected by OSHA and NRC rules and enforceable laws from exposure to excess IR. But if I get on a spaceship to Mars launched by any U.S. company from a U.S. launch pad today, I have no protection at all. A NASA astronaut can be exposed to GCR up to a career limit of 600 mSv—with no exposure window for how much time it takes to add up.
If I intend to fly to Mars, 600 mSv will certainly not cover what I will receive—a fact openly acknowledged by NASA, which estimates the dose closer to 1,200 mSv per mission. The government expresses the relatively acute exposure as a “REID probability” (risk of exposure-induced death), which enumerates how many bullets are in the chamber of the gun that I have enthusiastically jammed to my head.
As of today, private civilian astronauts are not protected by any laws. They will volunteer by the hundreds of thousands, as was evidenced by the 202,586 people from 140 countries who signed up for a one-way trip on the Mars One Project (for which I was an unpaid advisor).
Based on the accumulated data gathered from peer-reviewed simulated GCR investigations, such as our 2007 study and all others since, there is a probable suite of GCR pathologies the crew will accumulate during a mission. They will very likely be inflicted with some unknown degree of inevitable brain damage, particularly limbic and stem cell impairment that may affect their cognitive abilities to some unknown degree during the mission and long after. They will all develop cataracts at some future point, and it is very likely that they will all experience systemic epithelial and endothelial pathologies in their later decades of life. We do not know the effects on the human body beyond 10 days of exposure, and the scientific guesses are totally useless to even begin to forecast these effects.
But it doesn’t have to be this way. Not only is the solution not impossible, but it is also a relatively easy fix for today’s space transport technologies. Now that NASA’s Apollo-era cloned albatross has been retired, fundamental ethics demand that the United States must hand regulation back over to OSHA and the NRC, as every employee requires the same protections.
No handwringing necessary
The speculation that “providing adequate shielding for deep-space crews is impossible” was true when considering the Apollo system of the 1960s. They were so mass-limited that there were no seats in the Apollo lunar module and the astronauts had to land standing up. But with launching rockets several times a month, the idea that adequate shielding is impossible is no longer even remotely true.
One space technology company was founded to build a permanent human colony on Mars to ensure the continuation of our species in the event of a planetary catastrophe. Based on estimates, at least 1 million people plus 1 million tons of cargo and supplies must be landed on Mars by 2050 to start the colony on the path to true independence.
Adequate shielding to protect the passengers according to current radiation protection standards does not appear to figure into this scenario. Yet, aside from slowing the pace of migration down slightly, installing adequate shielding certainly does not prevent it.
The lowest cost, fastest shielding solution I have devised comes from mining lunar regolith (soil), launching it into lunar orbit from the moon’s low-gravity well with a mass driver, and then lining starship hulls with a layer by crews in orbit. All these technologies have been developed and could be employed today.
Even better, instead of flying fleets of starships to Mars and then heading back to Earth for the next load, an Earth-Mars cyclic orbiter is one answer. The adequately shielded, artificial gravity–enabled cyclic orbiter is launched only once into its Earth-to-Mars/Mars-to-Earth perpetual orbit. Transports dock when near either planet and swap crews. These orbital parameters have already been determined, including one extensive set of calculations by astronaut Buzz Aldrin.
An interplanetary demonstration craft was launched inadvertently on February 6, 2018, in the form of a space technology company’s initial trial launch of a heavy-payload rocket with a heavy, dummy payload. That trial payload will now eternally cycle between planets and will pass near Earth—within 5–10 million kilometers—roughly every 20–30 years.
But a true cyclic orbiter with refined orbits would approach very near Earth in a strategic rendezvous every 2.14 years or so (780 days). A pair of orbiters—one an up-cycler (Earth-to-Mars-to-Earth) and one a down-cycler (Mars-to-Earth-to-Mars)—enhances planetary encounters even more.
A chance to get it right
Right now, we are standing at the dock, one foot on the gangway leading to the great ships designed for the infinitely deep, vast ocean of the cosmos. We are champing at the bit to leave right now, and yet, we need to pause for a moment: We are about to deliberately launch human beings into the void in the same way that we launch prototype rockets just to see what happens to them and adjust accordingly at some frantic pace to leave Earth behind.
Genetically we understand that ethics trumps engineering every time and that we are capable of learning from our history. Therefore, let us, as we have always done, do science and medical research on vertebrate animals (rats) in deep space so that we will finally know the effects of this powerful cosmic energy on the human body—before we send humans into deep space.
In this way, we can discover in short order what we need to understand about deep-space GCR biological effects and risk nothing in the process. By gaining this real knowledge in advance, no mission or historic first migration will be colored by misstep and tragedy. We have the intellect to act in ways that demonstrate we have learned a few things from our forefathers.
At least, I hope so. Because I will be a passenger on one of those one-way ships departing Earth forever. I will fly safely and securely, protected by moon dust, headed out to my new home on the red planet that beckons to me each night as a ruddy dot winking from the night sky.
Dennis Chamberland is a bioengineer, nuclear engineer, author, space life scientist, and aquanaut.
Opinions expressed in this article are the author’s own and do not necessarily reflect the opinions of the editors, the American Nuclear Society, or the organizations with which the authors are affiliated, nor should publication of author viewpoints or identification of materials or products be construed as endorsement by this publication or the Society.
