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The Texas A&M Computational Physics Group's Jeff Chancellor '17 prepares for his inaugural public presentation at Texas A&M Research Computing Week on new research with the potential to revolutionize materials research and biological experiments related to space travel.

COLLEGE STATION --

Two years ago, Jeff Chancellor put a promising 15-year private-sector career in space radiation research and risk assessment on hold to concentrate full-time on finishing his Ph.D. at Texas A&M University. Although he may have taken a professional leave of absence, Chancellor never left behind the job of protecting NASA's astronaut corps -- an understandably personal mission, considering that his wife, Serena Auñón-Chancellor, is a member.

"I was a program manager working with NASA involved in radiation risk assessment and management, and I decided to give the Ph.D. one more try," said Chancellor, Texas A&M Class of '17. "A friend of mine was a professor at Texas A&M, and I had started working with him for a year or two before enrolling full-time in 2015. When he left, I asked Dr. [Donald] Naugle for recommendations, and he directed me toward Helmut Katzgraber and his computational physics group."

One small step for man, one giant leap for mankind -- or more accurately, the safety of future astronauts following in the late Neil Armstrong's galactic footsteps, thanks to new research by Katzgraber's group published last week on arXiv.org that has the potential to revolutionize materials research and biological experiments related to space travel.

Using well-established physics principles, Monte Carlo simulations and state-of-the-art supercomputing and data-analysis technology at both Texas A&M High Performance Research Computing and the Texas Advanced Computing Center (TACC), the Texas A&M-led team produced a model that simulates the highly complex space radiation environment and delivers results that stack up data point for data point in comparison to publicly available radiation-dose-related information obtained from three past NASA missions: Shuttle MIR, the International Space Station and Orion's recent Exploration Flight Test Mission (EFT-1).

"What we have done is used well-versed, fundamental nuclear science principles combined with high-performance computing and shown that you can selectively degrade a heavy ion beam so that the emerging field actually mimics the space radiation environment found inside of these space vehicles -- something that has never been done before and has not been utilized yet," Chancellor told an audience assembled Jun. 9 in Texas A&M's Interdisciplinary Life Sciences Building for a two-day Research Computing Week symposium. "Our approach is the first time that a true ground-based analog can be applied to mild studies of biological models for human health outcomes but also to evaluate satellite and orbiting hardware to RAD-hard test their capabilities."

A is for Accuracy

Chancellor says existing space radiation studies using mono-energetic, single-ion beams and mice as test subjects are problematic on two analog-related fronts -- biological and environmental, neither of which accurately reflect the extremes found in space. While mice are considered a model organism for many research purposes, Chancellor notes they do not accurately approximate human physiology. For starters, they are not nearly wide enough to capture most of the dose from a proton, let alone all the higher energy particles present in the multi-ion, multi-frequency space environment.

Furthermore, Chancellor says such studies have shortcoming when attempting to describe the actual environment and medium considered. He takes issue with just a few manuscripts published in the past year indicating that astronauts are going to die of cardiac failure, suffer severe cognitive impairments caused by the galactic cosmic ray (GCR) spectrum or, most recently, come back from Mars with increased rates of cancer and reduced to babbling idiots, courtesy of space radiation.

"Each one of these studies has only used a single-ion, single-radiation source representing a very small percentage of the actual radiation field distribution," Chancellor said. "They aren't necessarily bad studies; they're simply all based on analogs that do not mimic the environments they're testing and biological models that are not like humans."

Chancellor emphasizes that radiobiology studies on the effects GCR radiation are of paramount importance to space exploration in tandem with solar particle events (SPE), a second, more intense type of indirect ionizing radiation that astronaut crews are exposed to, often without warning. While Chancellor views SPEs as the bigger threat, he describes GCRs as the arch-nemesis of space radiation research, both because they include every ion in the periodic table at a wide spectrum of energies and because they are extremely difficult to shield. In fact, shielding can make the intravehicular (IVA) dose much worse.

"Although solar particle events can mostly be shielded, shielding for the galactic cosmic ray threat can actually be worse than it is by not shielding," Chancellor said. "Much of it is such a high energy, it will go through your body without really causing too much biological impact. If you shield it, you slow it down, increasing the interaction with critical tissues or creating lower-energy spallation products and neutrons that could have the potential to be biologically devastating."

Multidisciplinary Magic

In their analysis, which was funded in part by the National Science Foundation, Chancellor and team decided to concentrate on GCRs -- specifically, iron as the most prolific ion in the distribution that causes a significant IVA dose. They made two assumptions based on longstanding physics principles and material-specific properties: that a charged particle moving through a medium would lose energy and break up into smaller particles, and that they should focus on linear energy transfer (LET) or "stopping power" as the primary measure of biological impact and normalizer across space's broader energy spectrum.

Prior to determining means and methodology, however, they took care of critical multidisciplinary business, recruiting a research team that includes nuclear, space, health and computational physicists as well as a radiation oncologist and a radiobiologist, ensuring their ability to attack the problem from all possible angles. Chancellor credits that diversity, along with his own extensive background in science, space vehicle design and spaceflight operations, for the team's ultimate success.

"The model and the outcomes we're having is a direct result of an interdisciplinary project that involves a lot of computations and some different and unique aspects to it," said Chancellor, who earned both bachelor's and master's degrees in physics at the University of Houston. "A lot of it came from my experience working, not only doing research in nuclear physics but also doing operations as a flight controller in Mission Control and risk analysis for the Space Shuttle missions and then applying real-world examples and some other feasibility projects I've been involved with."

One of those real-world examples dates back long before Chancellor entered the workforce -- all the way to the 1960s, when the United States Congress established the National Council on Radiation Protection and Measurements as the nation's governing body for radiation exposures for all U.S. workers, including astronauts. At the request of NASA in 2014, the NCRP re-examined its recommendations for space radiation protection, reaching the same conclusion in 2016 that it originally did in 1998.

"The overarching recommendation was this elusive three percent radiation exposure induced death (REID) that says that astronauts, over their career, are not allowed to get an exposure of radiation that would exceed the average U.S. population's by three percent," Chancellor said. "That's a very vague metric that doesn't really mean anything. But in the big picture, in 30 years, there's been no change in the actual risk posture on space radiation. In this time period, there have been zero operationally implemented medical countermeasures.

"What we're doing right now in terms of protecting astronauts is the same thing we did during Mercury, Gemini, Apollo and Shuttle. It's not from lack of effort, however. This should amplify just how hard of a problem it is and will be to finally conquer."

Hard Problem, Surprising Results

The Texas A&M team's approach the problem involves taking a heavy ion beam -- a one gigaelectronvolt (GeV) iron beam, to be precise -- and slamming it into a moderator block composed of hydrogen-rich polymers capable of selectively containing some of the energy while simultaneously breaking apart the ions. The material in combination with geometry serves to create an emerging field that closely matches the energy distribution measured inside an actual space vehicle in space in three test cases -- Shuttle, ISS and the EFT-1.

"We chose these very carefully, specifically because the radiation dose measured inside the vehicle is also considered a protected health record and can be problematic to get publicly," Chancellor said. "We chose missions that had information that was usable for us but also publicly published so that we wouldn't have to worry about us or people trying to replicate what we worked on having to go through many hoops and bureaucracy to get that information."

Chancellor said much to his surprise, all three tests cases compared favorably to the team's initial results, which were nearly identical with regard to energy distribution -- their original target in LET -- and also strikingly similar in charge distribution.

"We nailed it," Chancellor said. "I first saw these results last summer, and I don't think I actually believed they were true until January or February this year. I didn't expect to get this close.

"For three different vehicles -- the Space Shuttle, which I would say is just a little more heavily shielded than the Apollo space vehicles; the ISS, which is a hulk of a machine when it comes to radiation shielding, and then the EFT-1, which is very minimally shielded -- we were able to reproduce the IVA spectrum in all three cases. Adaptability in a model, but because it is a model, I'll be the first to say that how right it is depends on how closely it mimics the actual radiation environment.

"From the beginning, our motivation was to do the LET distribution. We in no way at all tried to mimic the exact charge distribution. This outcome was actually just a big bonus to us and very spectacular, because now, if you look at it, the distribution very closely follows the actual predicted one."

Vindication in Validation

In addition to being spot-on with NASA's analyses, Chancellor said the team received further validation of the accuracy of their model when they were able to apply it successfully to some experimental data they found to a recent study published in Physical Review C, using both single-ion and compound target blocks and predicting that silicon would be enhanced.

"Our model was on par with what was expected, and the fundamental physics in the dynamics of computation were also agreeing with reality," Chancellor said. "Otherwise, it's just a model."

Beyond selecting appropriate analogs to more accurately reflect everything from environment, to a specific type of radiation and related charged energy, to exact biological sample affected, Chancellor acknowledges that, in many respects, it boils down to the benefit of timing.

"I think one of the reasons this has not been done yet is because this is a highly parallel computational model," Chancellor said. "Each of our test cases used anywhere from five to 10,000 cores. We sampled over a million single primaries. The data generated was a massive two and a half terabytes per case, and each one of the test cases is equivalent to about 135,000 CPU hours. So you can see how, prior to the recent advances in multi-core supercomputing capabilities, this was not feasible. Furthermore, being able to do the Monte Carlo three-dimensional analysis to take a particle and simulate movement through a medium and a parallel environment was not even developed yet. We would not be able to do this without high-performance computing."

Maximizing Return on Investment

Contrary to most space-related projects making headlines these days, Chancellor says this one wouldn't require millions of dollars -- more likely, just additional experimentation using a block that would probably involve minimal costs and be usable for a week or two before it becomes too degraded and in need of refabricating.

"One does not have to be a material scientist to do this kind of research," Katzgraber added. "In fact, a combination of a solid base in theoretical physics, computer simulation techniques, as well as input from radiation experts and experts in the biological effects of radiation is all you need to make sure that future space missions are safer and cost less."

Sooner rather than later, such altruistic pursuits would give scientists the exact field -- crucial measurements that could pave the way for elimination of uncertainties in risk-case evaluations and security of mind for Chancellor, who has both a vested interest and a limited window, given that Auñón-Chancellor's flight to the ISS tentatively is set to launch from Russia in November 2018.

"Perhaps we could start moving toward a clinical interpretation of the actual health outcomes and risk to our space crews, as opposed to, 'They may live and they may die,' or 'They may come home babbling idiots,'" Chancellor said.

The team's paper, "Emulation of the space radiation environment for materials testing and radiobiological experiments," can be viewed online along with related figures and captions.

To learn more about research underway within Katzgraber's computational physics group, visit https://intractable.lol/.

See a related feature story in the Bryan-College Station Eagle.

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About Research at Texas A&M University: As one of the world's leading research institutions, Texas A&M is at the forefront in making significant contributions to scholarship and discovery, including that of science and technology. Research conducted at Texas A&M represented annual expenditures of more than $892.7 million in fiscal year 2016. Texas A&M ranked in the top 20 of the National Science Foundation's Higher Education Research and Development survey (2015), based on expenditures of more than $866.6 million in fiscal year 2015. Texas A&M's research creates new knowledge that provides basic, fundamental and applied contributions resulting, in many cases, in economic benefits to the state, nation and world. To learn more, visit http://research.tamu.edu.

-aTm-

Contact: Shana K. Hutchins, (979) 862-1237 or shutchins@science.tamu.edu, Jeff Chancellor, jeff@chancellor.space or jchancellor@tamu.edu or Dr. Helmut G. Katzgraber, (979) 845-2590 or helmut@katzgraber.org

Hutchins Shana

  • Artist's rendering of the effects of the moderator block geometry. The one gigaelectronvolt (1 GeV) 56 iron primary beam enters the moderator block from the right and is subjected to specific spallation and energy loss processes that result in a radiation field with the desired distribution of ions and energies emerging from the right. (Credit: Nicole Stott and Eric Gignac.)

  • Chancellor, breaking down the strongest ions involved in galactic cosmic rays, the primary focus of the team's study.

  • Schematic of the moderator block designed to emulate specific space radiation spectra. See the group's arXiv.org paper for complete details.

  • For Chancellor, the job of protecting NASA's astronaut corps is both a professional and personal mission, considering that his wife, Serena Auñón-Chancellor, is a member of it. This past spring, she was selected for a future International Space Station crew assignment, tentatively set to start in November 2018.

  • Jeff Chancellor '17

    Chancellor is dedication to a worthwhile cause down to a "T" -- as in, the space-themed tie he selected to wear as part of his presentation attire. Even as a full-time graduate student, he still has strong ties within the NASA research community and serves as a consultant in the aerospace industry.

  • Serena Auñón-Chancellor

    Serena Auñón-Chancellor, NASA Astronaut Candidate Class of 2009 (Credit: NASA / Robert Markowitz.)

  • Dr. Helmut G. Katzgraber

  • Chancellor hones in on both the description and danger of two of the four types of indirect ionizing radiation present in space -- galactic cosmic rays (above) and solar particle events (below).

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