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Guest; Dr. Charles Limoli; Topics: Low dose radiation experiments for BLEO human spaceflight, cognitive, neurological, and behavioral challenges and more.
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We welcomed back Dr. Charles Limoli to discuss his most recent deep space human spaceflight radiation simulation experiments using lab rodents but with low dose rate neutron radiation rather than high dose rate front loaded radiation used for past experiments. Results from the low dose rate recent experiment continue to produce concerns for neurocognitive function during deep space human spaceflight. During our one segment 65 minute program, we discussed the experiments, findings, radiation and much more in detail. For the first part of the show, the discussion was technical regarding the details of the radiation experiments. I suggest you download his paper, "New Concerns For neurocognitive Function During Deep Space Exposures to Chronic, Low Dose Rate neutron Radiation" which can be found at www.eneuro.org/content/6/4/ENEURO.0094-19.2019. This paper, while technical, does explain the type of radiation used, the experimental details, radiation parameters, challenges, and more. I consider it a must read document an important supplement part to this excellent interview with Dr. Limoli. Note the type of radiation used, the isotope, and the measuring system. More about this in a few minutes. One of my first questions was to ask our guest to explain the difference with the new low dose experiment compared to his previous high dose front loaded experiment and how the findings differed from each other, if a difference was even noticed. Our guest spent substantial time answering this question in detail.
Joe from Denver sent in the first email. He wanted to know why things seemed different regarding cognitive issues with the ISS astronauts. Don't miss what our guest had to say about radiation on the ISS, then he talked about the Apollo astronauts for radiation information and said there was no additional human information available. He also indicated that testing was challenging and limiting.
Dr. Chris Morrison, a regular Space Show guest on radiation and nuclear power for space was our first caller. Chris started out thanking Charlie for the excellent explanation regarding high dose versus low dose radiation experiments. Next, he asked Charlie why he was using the gray measurement value for radiation, not the more "common" measurement unit, the sievert. Dr. Limoli spent considerable time answering this questions. It was an excellent question with an important answer so please don't miss it. In addition, Chris inquired as to why neutron radiation was used which was not so great for simulating GCR radiation. Once again, make sure you hear how our guest responded to this question. X-rays were talked about as was using CF 252 (Californium), all of which our guest explained. As many of you know, my hearing is not as sharp as it used to be so I kept hearing our guest talking about California radiation, as if he was using a product from here in CA. I asked him to explain what "California" radiation was. This time Dr. Limoli spoke very clearly and I finally heard Californium! Sometimes even a minor hearing loss can result in a big and silly misunderstanding. I certainly plead guilty in this instance.
Next, we heard from listener John about mitigating radiation. The subject of using pharmacology came up along with shielding. Dr. Limoli addressed this subject in detail, plus we learned his lab was also working on a pharmacology radiation mitigation product. As part of this discussion, our guest wanted to be sure he was clear on the subject of radiation as a deal breaker for solar system human spaceflight. He said not was not a deal breaker but mitigation strategies and tools needed to be developed and used. He thought research would solve the problem and that radiation would not be a show stopper but that spaceflight would of course remain risky.
Marshall called to talk about galactic cosmic radiation (GCR). Marshall asked about many of the radiation components and particles. Following the Marshall-Charlie exchange, Cheryl from Las Vegas sent in a note asking about the mice and rats used in the experiments, how they were used, their treatment, was the radiation exposure panful and more. Our guest explained their animal testing protocols in details, including cages, treatment and more. I then asked our guest the difference in a lab mouse or rat versus what I see running around in the fields when I walk my dog. Charlie did explain the difference, plus he said some rodents are unique to different types of stresses and work better in different types of experiments. He briefly talked about the mice/rats had different strains and why those strains were significant for different types of experiments. Along the same subject, Robert from San Diego sent in a note asking why primates were not used and if they would be better subjects than rats. The answer was that they would be better subjects but the list of reasons they are not used was lengthy. Don't miss what our guest said about using nonhuman primates in experiments. One thing I will say was that I was surprised to learn that there were only six primate research centers and facilities in the U.S.
For a change of pace topic, Wanda sent in an email asking about radiation, space settlement, pregnancy, childbirth, raising children and other related topics. Dr. Limoli had much to say in his response to Wanda so don't miss it. That said, he did say much of this was unknown and untested at this moment in time. We even through in a what if regarding going to Mars component to this discussion. After you hear what was said, please post a comment on our blog for this program and let us know what you think.
The Mars comments led me to asking our guest about radiation on a one way trip to Mars to stay there and then later, a what if question if the Mars crew was to return to Earth. Our guest had much to say about a one way trip to Mars. We talked about the isolation, even discussed isolation in our homes due to the Covid-19 shelter in place protocols impacting most of us. Dr. Limoli described radiation sheltering needs once the crew got to Mars. Your thoughts on this topic are certainly welcome on our blog.
Another listener asked Charlie to explain how the Brookhaven experiments work and how they can accurately simulate GCR here on Earth. Charlie described the experiment process, days on and off, plus more in detail. I followed up asking him how much power it took to run these experiments plus the cost. He said NASA picked up the beaming expenses which were $3-4 million each time they ran the 28 day experiment using 33 beams. Charlie's group picks up the other expenses. These experiments are open to lots of researchers and they get scheduled for use of the beaming during the relevant time period. Don't miss how all of this works plus what it costs and how the costs are paid for, either by NASA or the researchers. Charlie also described how many animals they used at a time, why only two per cage and what the cages were like. As we were now coming to the program end, an 11th hour question came in from Larry wanting to know if there were gender differences regarding the radiation impact. The answer was yes with females being more resistant to radiation damage than males. He also talked about the difference in using gender versus sex. Before signing off, I asked about the accuracy of the claims made that older people are more resistant to radiation damage so Mars crews should consist of older people. I will let Charlie's response to this final question be a surprise for you. No hint from me on this one.
Please post your comments/questions for Dr. Limoli on our blog for this show. You can reach our guest through me or his faculty page at UCI in Irvine, CA. Dr. Limoli will be return with updates on his latest research which he briefly mentioned at the end of today's program.