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Classroom with Drs. John Jurist & Jim Logan, Tuesday, 12-17-13 December 16, 2013

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Classroom with Drs. John Jurist & Jim Logan, Tuesday, 12-17-13

http://archived.thespaceshow.com/shows/2145-BWB-2013-12-17.mp3

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Guests:  Dr. Jim Logan, Dr. John Jurist.  Topics: This was a Classroom show on radiation issues for deep space travel, Mars and Moon settlements.  Please direct all comments and questions regarding Space Show programs/guest(s) to the Space Show blog, https://thespaceshow.wordpress.com.  Comments and questions should be relevant to the specific Space Show program. Written Transcripts of Space Show programs are a violation of our copyright and are not permitted without prior written consent, even if for your own use. We do not permit the commercial use of Space Show programs or any part thereof, nor do we permit editing, YouTube clips, or clips placed on other private channels & websites. Space Show programs can be quoted, but the quote must be cited or referenced using the proper citation format. Contact The Space Show for further information. In addition, please remember that your Amazon purchases can help support The Space Show/OGLF. See www.onegiantleapfoundation.org/amazon.htm.

We welcomed Dr. Jim Logan and Dr. John Jurist to this special 2.5 hour Space Show classroom in-depth discussion on space radiation. We focused our discussion on deep space, Mars, the Moon and BLEO missions. Note that on both The Space Show blog (see above) and The Space Show Classroom blog (http://spaceshowclassroom.wordpress.com),  Dr. Jurist has a Power Point presentation on radiation.  During the program, our guests referred to specific slides that you will want to check out.  In our first segment, Dr. Logan started out by telling us about his interest in the subject, why he has been writing a paper on the subject for publication, and how this Classroom show came about.  He cited our short duration spaceflight experience, the Apollo missions, Space Shuttle flights, and then how things started to change when we had six month ISS visits.  Dr. Logan also made it clear that space was not a benign emptiness type of environment.  He said the reality was that interplanetary space was a sea of disruptive ionizing radiation wrecking havoc on biologic systems.  We moved forward in our discussion from that point.  We talked about the findings of the MSL RAD instrument regarding radiation on the way to Mars and on the surface of Mars.  Both John and Jim spent some time putting the RAD numbers through analysis to let us know what this means for human missions to Mars.  We talked shielding, possible materials, passive and active.  We talked extensively about water and the use of hydrogen as well for shielding.  Our guests addressed the two types of radiation, the GCR (galactic cosmic rays) and the CME/solar flare.  Here, John suggested listeners look at his slide 13 as we talked about protons and neutrons.  Jim said there was no magic bullet and talked about shielding effects of Earth’s atmosphere.  Pay attention here as Jim introduced us to the  RP scale.  For being on the surface, he said nothing less than RP100 would suffice.  For the vehicle, an RP5 was required.  John introduced us to career limits for radiation for men and women astronauts of different age but the career limits are for LEO and not BLEO.  BLEO limits are expected to be more restrictive when made public in April 2014.  Earth Mars transit times were discussed, especially in the context of Brian’s email that suggested a 180 day transit time.  Both our guests said that was unlikely with chemical propulsion and all of us again stressed the need for nuclear thermal propulsion.  Microgravity was talked about, especially in the context of side effects due to the radiation environment.  Jim then brought up the EVA subject and spacesuits.  Briefly, Jim said that quite possibly the ISS construction represented the zenith of EVAs which may become a thing of the past.  Don’t miss why he said this plus his description of serious spacesuit limitations.  We talked about life support to Mars and here Jim suggested we should use Open Loop! Again, listen to the rational behind this recommendation.  Don’t miss what our guests said about theories & movies making it sound easy to go to Mars and that the radiation would be nothing more than just a few more cigarette packs a year.  Our last topic addressed informed consent issues.

In the second segment, I asked our guests for a readiness timetable were there sufficient funding and technology advancements.  I also inquired if Russia, China, and others assessed the radiation risks in a similar way to the U.S.  We then talked about radiation and space pregnancy, fetus development, birth, and informed consent for the fetus, a baby, and a child under 18.  Ethical issues regarding child birth and space pregnancy were talked about as well.  Curt had sent in email questions which our guests answered, especially about drinking irradiated water and microgravity DNA damage & what this may mean for radiation effects.  Next, I asked Jim and John to tell us their 2-5 steps for the start of designing a Mars human mission.  Jim went first and listed Day 1 and Day 2 activities, John listed his top three priorities which were different than those suggested by Jim.  Don’t miss this discussion as its very instructive as to how to do or at least start mission planning for a human mission BLEO.  Roger sent in a question asking if the crew should be senior citizens since they have more resistance to radiation.  Don’t miss what our guests said about this idea.  It may surprise you.  Our next topic was would going to Deimos be easier.  Yes, it would but it would be a very different kind of human  mission.  Jim had some great comments about Mars gravity.  Briefly, he said it was the “best.” Later, when asked to compare the Moon and Mars, our guests said lunar radiation was worse than Mars.  Also, the Mars atmosphere does provide limited shielding while there is no such thing on the Moon.  Jim had earlier talked about a sphere being the perfect shape for an interplanetary spaceship.  Shelia emailed in wanting to know if heavy lift made a difference and if the sphere was so good, why were capsules being used? Don’t miss the response.  We then talked about the complexities of rendezvous and docking, especially in the context of fewer launches (heavy lift) as compared to many more launches (smaller rockets).  Near the end, I asked our guests if either thought our nation, the public, NASA, our leaders and politicians were sufficiently motivated to do a human Mars mission.  Jim did not think so and had much more to say in reply to this question.  John was more pessimistic.  Both thought it was more likely that the private sector would mount a human Mars mission rather than our seeing a government mission, but raising the needed capital might turn out to be a show stopper.  The three of us then talked about what it was like growing up in the 40’s, 50’s, and 60’s as compared to today.  John and I (John is a bit more than 2 years older than me) were probably more harsh than Jim in our assessment of today, but we all realize that the younger generations will be taking us to space, building the next smartphone and more. I talked about my visits to Google, Apple, SpaceX, etc. and the excitement in the air in belonging in their work forces which does not seem to exist with NASA. This opened the door for Jim to put it on the line about his NASA experiences and the potential opportunities providing NASA can somehow reorganize.  He did not think the type of reorganization he was talking about would happen.  Both our guests left us with excellent takeaway points and concluding pearls of wisdom.

Please post your comments/questions on the blogs. You can reach either of our guests through me.

                                                  Radiation Biophysics and Human Spaceflight

Comments»

1. The Space Show - December 29, 2013

Doug:

I want to respond to your initial comment in your above blog post for the recent Classroom radiation program with Drs. John Jurist and Jim Logan. You commented that we should have used terminology which is easier to understand. I will defer to Jim and John for responses to the rest of your comments. Also, I want to let everyone know that John, Jim, and I are doing a special Classroom program on Monday, January 6 at the special time of 6 PM PST to address evidenced based discussion, analysis, the use of facts over and above fantasy thinking, fantasy agendas, and inappropriate numbers. This new Classroom program on Monday, January 6 is in line with the purpose of Space Show Classroom programs and after feedback received on the radiation program, the three of us believe this coming show to be most appropriate.

Doug, I would like to give you a short history of The Space Show Classroom programs. Drs. Jurist and Logan and I started the Classroom series discussion among ourselves in 2009 with initial Classroom programs starting in 2010. Our purpose for creating the Classroom was to bring to The Space Show a special program, run like a graduate college class that both taught and used science, facts, evidence, real numbers and analysis, etc. in a very high level discussion format for educational and debate purposes. We deliberately chose to limit listener questions to those that were only relevant to the current discussion with the Classroom guests. Listener comments and questions had to be relevant to what we were talking about. We agreed to control the listener input to raise the quality of the Classroom programs and to do our best to manage them as each of us does when we teach our college graduate classes though we realize this is radio and not a graduate school program. Our goal was and still is education so your suggestion to use terminology that is easier to understand goes against the fundamental purpose of the Classroom. Rather than use simplified terminology, we expect listeners to match or exceed the level of our discussion. We are not interesting in dumbing down, we are interested in raising the level of awareness, the knowlege level of listeners, and to help listeners understand many of the critical issues surrounding the topics that make it to a Classroom Space Show program. By doing this, the debate on many controversial issues can and will be more relevant. Frankly, I was a bit surprised by your suggestion as I thought that you as well as other listeners would simply make an effort to understand the terminology used by the guests rather than the opposite.

My personal view in doing the interviews and managing The Space Show is to work to raise people up, not bring them down or enable them to get by as a result of simplifying or lowering standards. If a listener is interested in the topic, the listener should be willing to look up words, do some basic research to understand concepts, ask questions, all of it. Frankly, I hope I never dumb down a Space Show program of any type. That goes against everything I believe in with TSS.

Here is an example. A few weeks ago, Eric Lerner of Focus Fusion returned as a guest for an update. Eric’s discussion was pretty technical dealing with plasma physics and lots more. This was a hard interview for me as my science level and especially my plasma physics level is not where I would like it to be. That said, never once did I ask Eric to simplify or dumb down the discussion. I may have asked him for clarification or to help me understand what he was saying but that is different from asking him to speak at a much simpler level than what he was doing during the show. For those of us interested in fusion, especially the alternative fusion talked about by Eric and other guests, we need to learn at least the basics about aneutronic fusion, plasma physics, and subjects like that. I hope The Space Show can help facilitate our learning about these things and for that matter, anything that we are not that familiar with regarding the topics discussed on the program. I know of no guest that will refuse to clarify or help a listener understand what is being talked about, on or off air, but that is different than asking guests to make a simpler presentation. And of course, they can make a presentation that is far too technical and complex, especially for radio and yes, that does happen but its the exception, not the rule.

So Doug, I absolutely reject your suggestion to simplify. Maybe we can do a better job of clarifying and explaining complex topics and issues but Classroom programs by design are high level programs. Classroom listeners have to do their part as well. Remember, our Classroom series is modeled after a college graduate class. In those classes, most of us stretch to learn, right? The same is true with our Classroom series.
Thanks for your understanding. I hope you can listen live to our follow on program Jan. 6 at 6 PM PST. Call in, ask away, but stay on topic with our discussion.

A very Happy New Year to you and to all Space Show listeners.

All the best for a terrific 2014.

David Livingston, Host
The Space Show

2. DougSpace - December 27, 2013

A clarification. The number of years for each setting is how long you could sustain the radiation there before you exceed the limit set for astronauts in their career.

3. DougSpace - December 26, 2013

Unfortunately, I didn’t listen to the show live and so couldn’t call in, but I want to make a couple of points about how the issue of the human factors could be presented in future shows:
1) Use terminology which is easier to understand, and more importantly,
2) Use solutions-orientation rather than a problem-orientation when addressing these issues.

Briefly the first point. I applaud the development and use of the RP (radiation protection) term because it is easy to understand. But similarly, I think it better to discuss what thickness of water or liquid hydrogen would be needed rather than using the gram/millisievert terms. Similarly, instead of using the millisieverts/day for different settings, one could convert that into how much time it would take for astronauts to reach career limits. Otherwise it is just a number without an understandable context. For example, here are the number of CONTINUOUS days that one could function (completely unshielded mind you):
– 333 years – Earth sea level (4.2 lifespans)
– 6.7 years – On ISS
– 3.9 years – Mars surface
– 3.2 years – Lunar surface
– 1.44 years (526 days) free space
When looking at it from this perspective, a number of statements made on the show seem to be presenting an unnecessarily negative perspective. Yes, being in free space is like getting a whole body CT scan every 5-6 days but apparently one can do that for 526 days before the career limit is reached. We won’t be able to do EVAs on the Moon or Mars? Really? Up to 3.2 years on the Moon is quite a bit of time.

The second point is I think more fundamental and so I want to focus on it. A pessimist looks at a glass as half-empty. An optomist looks at a glass as half-full. An engineer looks at a glass and says, “Yes it is true, the glass is half-empty. That is a problem. What can I do about it”? So the engineer devises a new (untried) solution. He goes to the counter, gets the pitcher, and fills the glass up to full. Problem solved. If one looks only at the problem without adequately considering reasonable solutions then it’s not helping move things forward. I feel like this was the major problem with this show.

Here’s a clear example. It was mentioned that a problem with using consumables such as water for a storm shelter is that the shelter would be consumed with time. The obvious solution is to put the material back in the shelter wall after using it (e.g. a container of urine). So with three people on the show, why wasn’t this obvious solution mentioned? Apparently it wasn’t because there was an overemphasis (reaction to Kook-Aid drinkers) on the problem and not sufficient emphasis on possible solutions.

Likewise, when discussing the amount of radiation exposure in different settings, this was often done without considering obvious mitigations. For example, if you are traveling to Mars, I would hope that you’ll have deceleration propellant. So, by positioning that propellant around the astronauts, how much protection would be provided? Would that alone be sufficient for an RP5? It simply wasn’t discussed. I wish it had been.

The examples of the problem-oriented versus solutions-oriented point in the show were numerous to the point where I really couldn’t tell whether the radiation problem was “manageable” or not. Without attempting to describe a reasonable management scenario, we didn’t end up with enough information to judge that for ourselves. For example:
– Would a 3-day transit to a fully shielded lunar habitat adequately handle the radiation issue for a permanent lunar base? So, is the radiation issues only a Mars trip issue and not a Moon issue? It really wasn’t clarified.
– How much water mass would it take to provide RP5 on transit to Mars? We were given 50 gm/cm^2. Is that 50 gm of water? if so, then a 50 cm thick sphere with an internal habital diameter of 8 meters would require 1.5 SLS launches to put up the shielding and the propellant to launch it into an Aldrin Cycler orbit (i.e. one-time). Is that a straight-forward solution?
– True, GCRs shoot through Earth’s magnetic field. But we now have electromagnetcs which produce magnetic fields 368,000 times stronger than the Earth’s. So is this a solution?
– Not a lot of discussion was given to possible pharmaceutical mitigators. For example, how about RLIP76?

So, putting it all together, is an expeditionary trip to Mars manageable after all by sending older men (cross-trained), with deceleration propellant and their supplies strategically positioned, taking shelter against SPEs, taking pharmaceuticals, living in a regolith-covered base, making 4-5 hour EVAs every other day in a rover with a storm shelter?

For the next human-factors show, it would be helpful if there was a more solutions-oriented perspective represented.

John M Jurist - December 28, 2013

Although I am posting this response, it was jointly authored by Dr. Logan and myself and is to be considered as being jointly posted.

Before responding directly to Dr. Plata’s comments, some information on our respective backgrounds is relevant:

After earning a BA in physics at UCLA, Dr. Jurist earned an MS in nuclear medicine at the UCLA Medical School. After earning his doctorate there, he completed a postdoctoral fellowship in medical/health physics at the University of Wisconsin Medical School. He subsequently joined the surgical faculty at Wisconsin, and was licensed by the NRC as a radiation safety officer as well as a designated radioisotope licensee for handling radioisotopes used in the medical environment.

Dr. Logan is a physician, board certified in aerospace medicine, and has MS degrees in biological science and aerospace medicine. He has 3 decades of experience as a space medicine specialist in various positions including Chief, Flight Medicine and Chief, Medical Operations at NASA’s Johnson Space Center. He also served as Project Manager for the Space Station Medical Facility, where he developed the initial design for a telemedicine-based inflight medical delivery system for long duration missions. He was the first official Provost for the International Space University and a founding board member of the American Telemedicine Association. He recently completed a medical fellowship in Undersea and Hyperbaric Medicine at Duke University.

We are frequently accused of having an “unnecessarily negative perspective” of the space radiation problem. Almost always, that “criticism” is made by people who know much less about space radiation than we do. Although we are not actively involved in space radiation research, we do consider ourselves to be knowledgeable about the subject. Our perspective, negative or not, is evidence-based; that is, it is based on the medical/radiation literature. It is based on numbers.

We can state categorically that we are Two of the Faithful: We are both space cadets. The vast majority of Dr. Logan’s professional career has been dedicated to human spaceflight. A smaller portion of Dr. Jurist’s career has been directly involved in human spaceflight, but he has credentials in the subject and it has been a life-long passion for him.

We are veritable ‘Oracles of Optimism’ compared to the experts who are actively working the space radiation issue.

Nevertheless, we both believe the eventual success or failure of our species depends in large part upon our ability to get off the planet in sufficient numbers to establish multiple self-sustaining, self-replicating, thriving human communities in space. As a species, our choice seems pretty clear: Leave the planet or perish. It’s just that simple. Single planet species don’t survive! However, the Universe quite frankly doesn’t give a damn about ideologies – yours, ours, or that of anyone else. Space is an unforgiving environment. It is always trying to kill you, one way or another. You may disagree with our perspectives and conclusions. That’s okay. There’s always room for well-intentioned debate – but we believe the vast majority of available data supports our side of the argument. As our friend Dan Adamo often states: “In God we trust, all others bring numbers.”

The first general point that Dr. Plata raises is related to using a terminology that is easier to understand. Dr. Logan and I received criticism from both ends of that spectrum – some said radiation is far more complex that what we discussed, and others said our presentation was too complex. In actuality, the radiation issue is very complex and we simplified our presentation. Many of the show listeners do not have graduate science backgrounds, and we aimed the level of complexity at the audience we perceived to be typical. Had we been presenting at a meeting of the AAPM or RSNA, the complexity of the radiation environment would have been presented in greater detail.

Before going on to the second point, which is more fundamental and deserves an extended focus, we will address the specifics of Dr. Plata’s first point in some detail. Any discussion of the thickness of water, hydrogen, polyethylene, aluminum, or whatever is needed for adequate crew protection in the deep space environment is premature in that the current numbers are quite “squishy.” Consider the following: The absorbed dose in a mass resulting from a given exposure is expressed in Grays, which is a measure of the energy absorbed by the material per unit mass. Thus, the dose absorbed in bone, for example, differs from that absorbed in lean soft tissue and from that absorbed in fat for a given exposure. The differences vary with the type of radiation in addition to the exposure magnitude. The cosmic background radiation particulate spectrum in deep space is not particularly well characterized, and that from solar coronal mass ejections is highly variable. Next is the biological effect of the absorbed dose. That is expressed in Sieverts, and the conversion from Grays to Sieverts is based on multiplying by the “quality factor” or the RBE (relative biological effect). That multiplier is moderately well established for some types of radiation and some dose rates, but is still quite uncertain in other cases. Therefore, the precision of a bioeffect, expressed in Sieverts, is much more uncertain than that of the measured absorbed dose, expressed in Grays. With respect to the RAD experiment, the on board dosimeters measured absorbed dose, which were then converted into an estimated effective dose (milliSieverts per day) by using a series of assumptions related to the quality factor. Those assumptions, in our opinion, are very imprecise and subject to modification with additional experimentation over time, which is sorely needed. To factor bioeffective dose rate into a career limit, which is also subject to adjustment (and the historical trend is to adjust the career limits downwards), results in even more loss of precision to the point where the concept of tolerance time is essentially useless except for general discussions given the current state of knowledge. None of our current knowledge about human space flight in the deep space environment is based on direct, pragmatic observation and data. All of our human space flight experience except for the short sorties to the Moon during Apollo is limited to LEO and primarily to durations of no more than 6 months, with a couple of exceptions out to a bit over one year.

Dr. Plata’s examples of the “number of CONTINUOUS days that one could function completely unshielded mind you” (his exact words) are complete and utter fantasy:
• FACT: If you are a 35 year old female when you begin your first six month ISS mission and 40 when you begin your second six month ISS mission (i.e. 5 years between missions), you will accrue an estimated 2% increased risk of a fatal cancer directly attributable to your ISS exposure. These are not our numbers, radiation experts at NASA said this.

• FACT: If you are a male (same age and flight schedule), you have a 1% increased risk of a fatal cancer. These are not our numbers, radiation experts at NASA said this.

Conclusion/prediction: 6.7 continuous years on ISS? Don’t bet on it. We won’t see anyone spend more than 1½ years continuous time on ISS – EVER. Very few, if any, astronauts will be assigned to more than three six-month ISS missions separated by months or even years because three standard missions will bump up against their 3% Risk of Exposure Induced Death (REID) career exposure limit.

FACT: Several years ago NASA experts looked at a series of Lunar Surface Mission Profiles in which there were four variables:

1. Solar Cycle (solar max or solar min);
2. Duration (2 week “Apollo-style” missions, 3 month, 6 month or 9 month missions);
3. Shielding (5g/cm2 or 20g/cm2 – keep in mind a 20g/cm2 mission can’t be flown because according to engineers it would be too heavy. The shielding would have to be created from in situ materials once you got there; and
4. Gender (male or female – females are more susceptible to radiation because of their breasts and their reduced total mass compared to most males.

Here is what they found:

Assuming a 3% REID (using LEO standards which will likely prove to be significantly more liberal than the new interplanetary standards expected in April 2014) and a 95% confidence level (CL), all 2-week sortie missions were acceptable – i.e. no astronaut would reach his/her career radiation limit. However, more than half of all astronauts would exceed their career radiation limit for:

• Female, solar max, 6 months, 5g/cm2;
• Female, solar max, 3 months, 5 g/cm2; and
• Male, solar max, 6 months, 5g/cm2.

ALL would exceed their career radiation limits for:

• Female, solar max, 9 months, 5g/cm2; and
• Male, solar max, 9 months, 5g/cm2.

A smaller fraction (probably < 10%) would exceed their career radiation limits for

• Female, solar min, 9 months, 20g/cm2;
• Female, solar max, 9 months, 5g/cm2;
• Female, solar max, 9 months, 20g/cm2;
• Male, solar min, 9 months, 5g/cm2; and
• Male, solar max, 3 months, 5g/cm2.

Conclusion/prediction: 3.2 continuous unshielded years on the lunar surface? Don’t bet on it. If humans ever live continuously on the moon, they will have to live like ants, earthworms or moles. Frequent repetitive EVAs on the moon? Don’t bet on it.

The above Lunar Surface Mission Profile analysis didn’t take any EVAs into account. The moon has no magnetosphere and no atmosphere. The space suit provides less than 1g/cm2 shielding equivalent (i.e. less than one-tenth of one percent of the protection of Earth’s atmosphere or RP0.1). Routine repetitive EVAs by the same crewmembers would significantly revise downward the time on the lunar surface before career radiation limits were exceeded. Plus, we don’t have the suit technology for frequent repetitive lunar EVAs.

FACT: According to NASA/TP-2013-217375, Space Radiation Cancer Risk Projections and Uncertainties – 2012 by Dr. Frank Cucinotta, et al., published in January of 2013, the number of solar minimum “Safe Days” in deep space assuming 20gm/cm2, 3% REID (for LEO) and 95% confidence level range for NASA 2012 “never smokers” range from 187 days for 35 year-old females to 351 days for 55 year-old males. If one assumes the deep solar minimum of 2009, the numbers are revised downward to 180 days vs. 335 days respectively.

Conclusion/prediction: 526 unshielded free space days? Don’t bet on it.

Shielding equivalents will have to be significantly better than 20g/cm2 in our opinion for interplanetary human spaceflight. How to achieve that shielding level is worthy of debate and discussion as an engineering issue.

Dr. Plata’s second point could be considered as containing two somewhat different aspects:

First, the presentation was too negative and overemphasized the problems rather than the solutions. Perhaps this is valid, but a discussion of the pros and cons of possible solutions requires a degree of understanding of the problems. We distinctly recall discussions of the pros and cons on passive versus active shielding, active magnetic versus electrostatic shielding, use of a "storm shelter" within a spacecraft, reduction of transit time with, for example, nuclear thermal propulsion (NTP) rather than chemical propulsion, possible pharmaceutical measures to reduce the severity of responses to radiation exposure, and consideration of genetic modification for long range abatement of the problem. The issue of risk of mission loss versus risk of personnel loss was also discussed both in terms of the concept and the uncertainties of human responses to long term exposures to radiation. Some of the legal and regulatory issues were identified, but the potential solutions revolve around issues that are far too complex (and too vague) to be discussed in the present context. Given the duration of the show, which ran considerably longer than most classroom series shows, we thought the discussion of potential solutions was both sufficiently extensive and adequately detailed for the audience. Others may disagree.

Second, Regarding Mars, people are tired of hearing the negatives and the problems. We discussed use of regolith for shielding on the surface of Mars, use of tele-operated robotic exploration to reduce human surface time, and basing on one of the Martian moons to reduce radiation exposure and also to provide a potential means of dealing with reduced gravity if that turns out to be a significant additional problem. We gave potential solutions that may allow dealing with each of the problems, but narrowing the uncertainties of the various problems is needed before rational solutions can be chosen and optimized to the degree possible. To not discuss and at least identify the problems in specific terms reduces the discussion to a "rah rah rah sis boom bah" level that is markedly unrealistic with a high fantasy content.

Now, we can address the specifics of Dr. Plata’s second point:

His short treatise on engineers ‘filling the glass up to full – problem solved’ notwithstanding, we will believe engineers are serious about the radiation problem when we start seeing serious redesigns of interplanetary human spacecraft that surround the crew with the mass of the entire vehicle in all directions including propellant rather than putting the crew in the pointy end of a vehicle exposed 24/7 to the seething cauldron of ionizing radiation.

During his career at NASA, Dr. Logan frequently witnessed engineers and their managers use the absurd simplicity of PowerPoints to routinely violate, oversimplify, supercede, or circumvent fundamental laws of nature. We have nothing against engineers or engineering. Most of the conveniences bestowed by modern civilization are courtesy of engineers. But quite frankly we have never understood their collective aversion, if not outright hostility, to basic, if brutal, biomedical facts. We are aware of the ‘bad rep’ that space flight surgeons and life scientists have. They have the reputation of being killjoys. (We call it the cultural gap, and it was outlined in the PowerPoint accompanying the show’s discussion.)

NASA is an organization of engineers, by engineers and for engineers. Engineers want to boldly go where no one has gone before and they want to do so without constraints from anyone else. If they could have sent men to the moon and back without any life science whatsoever, they would have done so. The problem, of course, is they couldn’t. That is still the case. And for interplanetary space flight by humans it is true to the second power. For colonization of space, it is true to the third power.

Rather than direct ire at space medicine people for being ‘unnecessarily negative’ for identifying real problems, how about putting pressure on the aerospace engineering communities to start solving real problems we identify. Mass shielding? That’s an engineering problem. Advanced propulsion to limit the number of exposed days in transit? Another engineering problem. And so it goes….

Of course, some engineering solutions have to be based on good research – and better numbers for the ill-defined issues related to human response to the space environment. Since NASA consciously refused do its homework preparing for the era of interplanetary human spaceflight (despite the best efforts of the life science and medical people), we will likely need another generation of robust, well-funded basic science research.

Space colonization? The radiation issue is even more serious from a regulatory standpoint. The NRC set the public radiation dose limit from sources other than terrestrial background and medical applications to 1 mSv/year. This is roughly ¼ of 1% of the 3% REID career limit for a 30 year old female astronaut. If colonists are considered to be the general public rather than radiation workers or astronauts, good luck!

Another factor to remember when considering the above is that the 3% REID is an absolute estimate for the population under consideration. Since roughly 20-25% of nonsmoking women are estimated to eventually die from malignancies, a 3% jump in the population actually increases the number of cancer deaths in that group by roughly 12-15%.

To recap our response to Dr. Plata’s second point, we know that 100% atmosphere-equivalent shielding is adequate. Perhaps 80% is adequate, and perhaps it is not. Given the current uncertainties in radiation responses for age as moderated by overall health status, genetics, uncertainties and variations in radiation quality in space, etc., who gets to decide the acceptable levels of morbidity and mortality for other people or eventually for colonists? How many average years of loss of life is appropriate? What is the distribution around that average? Does that acceptable duration change with age? That is a different issue than whether the number of lost years changes with age, which it does. As Dr. Jurist has observed, 2 weeks of additional life span of reasonable quality looks a lot more precious to some patients when their expected quality survival time is estimated in months or weeks rather than in years. Answers to these kinds of questions/issues must come from the people directly involved before they can be appropriately translated into policy.

We talked extensively about solutions: Dr. Logan talked about RP5 (radiation protection 5% of Earth's protection) in transit, RP100 at destination, older crews, faster transit times (e.g. NTP), and Dr. Jurist touched upon the possibility of electrostatic or magnetic shielding, although there are formidable engineering challenges in their implementation. Other than a brief mention, we did not discuss the issues related to reduced gravity and their possible synergisms with radiation effects. That discussion would really ignite a firestorm.

We are weary of well-meaning but ultimately uninformed space advocates trying to demonize the messenger rather than listen to the message. Remember, In God We Trust, All Others Bring Numbers! Debate is both fine and fun. Honest differences of opinion are fine – but they are best based on some kind of verifiable reality. Quasi-religious shouting matches, based on some self-anointed space advocacy Gospel, are a waste of everyone’s time.

The ‘Inconvenient Truth’ is that what might be “impractical” for an engineer is “absolutely essential” for a space medicine doctor. By the way, as far as we know, there has never been a single recorded case of a space life scientist or flight surgeon telling an engineer that Escape Velocity is “impractical.” People who didn't like our discussion, didn't like our answers, and didn't like our negativity (which was actually realism based on the best available current knowledge) are angry because we didn't echo their dismissive stance toward a very real "potential showstopper" problem. If they can argue with data, facts or even extrapolation from numbers (although extrapolation past the existing real data range is dangerous), we will listen to their criticism. If they just don't like our position because it was "too negative," they can listen to their own echo chamber. Quite frankly, we don't care about being popular or being "liked," especially by people advocating little more than fantasy. We just want to be a force for truth and inject reality into a complex discussion.

Robert Walker - January 3, 2014

I found your spaceshow classroom really interesting, thanks! You totally convinced me that a long term space settlement needs to think in terms of something approaching RP100 (might e.g. RP50 also do??), especially for children (who also unlike adults can’t give informed consent for the dangers of radiation exposure).

My own line on all this is that present day spacesuits anyway are cumbersome, especially the gloves, and as you say not really re-usable. Unless there is some major advance in spacesuit technology, perhaps the future may be in telerobotics and autonomous or semi-autonomous robots more so than spacesuits.

If that’s so then it might not matter much that space colonists live underground. They might live in lunar caves, or in massively shielded shelters at the poles, perhaps first of all in the peaks of eternal light. They would explore the surface via telerobotics which also gives the advantage of minimizing danger to the humans, and giving automatically enhanced vision.

The reason for the colony on the Moon rather than control from Earth would be because of the almost zero latency. The same could be done from the lunar L1 or L2 positions – but only at a later stage once we can easily supply materials for adequate shielding either through space mining or hugely reduced lift costs from Earth.

But whether that is enough motivation for a colony in the near term I don’t know – perhaps you can explore the Moon and even do things like construct telescopes etc using rovers on the surface controlled from Earth, depends how much the latency matters, and how much you can control the machinery in real time with a 2 second latency. I can imagine that probably more robotic exploration would come first and feel we have rather neglected the Moon in all our explorations of Mars in that respect.

With Mars, then I think that the best bet is to send habitats to Mars orbit in advance of colonists, I see no value at all in going to the surface because there are way too many unproved technologies in the mission anyway – and spacesuits are so clumsy that the value of actual humans on the surface is way over-rate in my view chances they would hardly ever bother to put on a spacesuit but do most of the work remotely from within the shelter as for the Moon – but overwhelming reason for me is I see no way with current technology to do that and comply with planetary protection given increasing evidence of possible present day habitability of Mars surface, also the interest of past and present life on Mars and the very sensitive life detection experiments we can send to Mars that would be messed up by a single DNA molecule or amino acid froma human.

Anyway an orbital mission lets you explore entire surface of Mars for far less cost than a surface mission and more science return. And in place of surface habitats and rovers able to move humans around you can have numerous telerobots on the surface of Mars with superhuman capabilities (e.g. small and able to fly) for the humans to control as avatars from orbit for far less cost than a surface mission..

Then – was already thinking like that but after what you say in your show, think, that as well as habitats (I’d say at that distance and at current levels of knowledge to do everything at least in triplicate) you should send the shielding for them sent in separate launches if it can’t be done in one launch,, enough to shelter them so they can last for a few years there and so have a chance to build up more shielding using materials from the Martian moons – and if they don’t succeed they just have to come back to Earth at next opportunity and future missions continue the task.

But surely before we can do any of that we need to do a lot more closer to home. So, exploring the Moon telerobotically and then with humans would give a lot of ground truth for all this.

For microgravity again I’m astonished at how little has been done on this. Really simple experiments. I think was Gemini 11 tether experiment only attempt at artificial gravity in orbit. Surely e.g. with supply vessels to ISS just rescheduling so human occupied ship and a supply vessel can tether to each other and try some simple tether experiment to test generating artificial gravity. I’m not sure how much here is easy and feasible. Also at some point want to go ahead and do a centrifuge module for the ISS as for the Nautilus X plan. But we have hardly any data points there. Experiments on Earth can’t simulate it at all because always at least 1 g and go over that when testing coriolis effect. And – sailors adapt to being seasick pretty easily and can spend months at sea no problem, maybe astronauts similarly can adapt to coriolis effect especially if you build up to it gradually, And is different anyway axis of rotation exactly perpendicular to the direction of the artificial g, we can’t simulate that on Earth.

Ideally I’d like to see an experiment where an astronaut from the ISS spends some months in a passenger vessel, tethered to a supply vessel, set to rotate around c of g using a tether, and try different lengths of tether and generate different amounts of artificial gravity with coriolis force. I don’t think personally you need a large multi-kilometer type radius probably just 200 meters and maybe as small as a few tens of meters would do just fine, maybe even so small you can easily build a rotating hab that large. Which you could also use on the Moon to allow astronauts of your subterrranean habitat to have full 1 g, or whatever g is needed, or intermittently for sleep etc.

Very long term I see self enclosed radiation shielded habitats in space and paraterraforming of the Moon as both possibilities.

It would be a longer term program. I think we simply don’t have the knowledge to totally spell out how it would go. Instead can think about various possibilities for the future but for now encourage open research with the idea that we don’t know what the answers will be – but need to know more data which is much more easily done in Earth orbit and on the Moon. For instance if coriolis effects don’t matter down to even tens of meters, or we need 1 g but only for a few hours a day or we do fine in low g, all that simplifies the missions and makes radiation shielding easier.

Anyway interested in your thoughts on all that in the spirit of accepting the radiation figures and issues you raise and wondering how you go forward. Thanks for a really interesting show!.


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