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Risk management for manned mars missions
For SpaceNut re challenges for settling Mars...
I thought of you when I ran across this video....
https://www.youtube.com/watch?v=b7mjp7MDx_w
It seems to be designed to list all the problems that you might want to see listed all at once.
I watched only a bit of it ... just enough to decide it appears to be a serious attempt to understand the challenges of setting up shop on Mars.
(th)
The cell phone generates a summary of the content
This video, "Mars Has a Fatal Flaw - And No-one Has the Solution (ft.
Veritasium)," discusses the challenges and potential solutions for human
colonization of Mars.
Challenges of Martian Colonization:
Radiation Exposure during Travel: A three-month trip to Mars exposes astronauts to solar
wind and cosmic radiation, which can lead to cancer and Alzheimer's-like symptoms
(1:59-2:29).
Harsh Martian Environment:
Extreme Temperature Swings: Mars experiences significant temperature fluctuations between
day and night, ranging from -43°C at the polar caps to 35°C in the equatorial summer
(4:01-4:19, 7:51-8:00).
Global Dust Storms: Planet-sized dust storms occur every 5.5 Earth years, lasting for
weeks or months, and can block out almost all sunlight, posing a threat to solar-powered
equipment and human settlements (6:15-6:43, 18:51-20:06). These storms are fueled by dust
devils and saltation, where larger sand grains kick up smaller, more cohesive dust
particles (8:44-10:47).
Thin Atmosphere: Mars's atmosphere is less than 1% of Earth's, making it difficult to
retain heat and creating strong winds from CO2 sublimation (7:16-7:42, 5:20-5:31).
Soil and Food Production: While Martian soil has essential nutrients for plant growth, it
also contains toxic perchlorates, requiring processing before use (23:52-26:37).
Communication Delays: The vast distance to Earth results in communication delays of 3 to
22 minutes one way, making real-time assistance impossible during emergencies
(37:09-37:42).
Psychological and Physiological Toll: Living in confined spaces, with limited social
interaction and constant stress, poses significant psychological challenges. Low gravity
also causes health problems like muscle and bone loss, vision issues, and a weaker immune
system (45:01-46:17).
Proposed Solutions and Technologies:
Radiation Shielding: Astronauts could be shielded by hydrogen-rich materials in
spacecraft construction, such as water tanks surrounding the cabin, or by generating a
magnetic field around the spacecraft (2:30-2:59).
Habitat Construction: Autonomous robots could 3D print habitats using Martian regolith
mixed with water ice, and these structures would be covered with more regolith for
radiation protection (40:22-41:46).
Life Support Systems:
Breathable Air: Oxygen can be acquired through water electrolysis or from atmospheric
carbon dioxide using modules like MOXIE (42:25-43:03).
Energy Production: A hybrid approach using solar panels and cold nuclear reactors,
combined with reliable batteries, would provide a stable energy source (43:37-43:54).
Water Production and Recycling: Extracting and purifying water from Martian ice, along
with water recycling systems, can provide the necessary water for settlers (43:56-44:24).
Advanced Robotic Exploration:
Ingenuity Helicopter: NASA's Ingenuity demonstrated the feasibility of powered flight in
Mars's thin atmosphere, using lightweight materials and carbon fiber blades
(27:56-28:28).
Legged Robots (e.g., Spot): Robots like Boston Dynamics' Spot, with their ability to
traverse uneven terrain, avoid obstacles autonomously, and operate independently, are
being developed for exploring challenging Martian environments like caves (30:57-36:22).
These robots could form the backbone of future exploration, labor, and construction
(36:31-36:40).
Genetic Modifications: NASA is considering genetic modifications for astronauts to combat
radiation and microgravity dangers (46:28-46:39).
The video concludes by highlighting that while much of the necessary technology exists,
some critical advancements are still needed for permanent human colonies on Mars to
become a reality (47:05-47:12).
Radiation mitigation for a first human mission to Mars is a critical "showstopper" challenge, with crew exposures during a 3-year round trip expected to exceed standard safety limits (600 mSv), likely requiring an exception to current regulations and an reliance on "buying down" risks through advanced shielding. The strategy for a first mission will likely be a, combination of passive shielding (materials), operational mitigation (timing/scheduling), and natural terrain protection on the surface.
Key Radiation Mitigation Strategies
Optimal Mission Scheduling (Solar Max): Launching during the solar maximum (when the Sun is most active) is counter-intuitively the best strategy, as the increased solar wind deflects the more dangerous Galactic Cosmic Rays (GCRs). While this increases the risk of Solar Particle Events (SPEs), they are easier to shield against than GCRs.
Hydrogen-Rich Materials: Passive shielding is more effective using low-atomic-mass materials (hydrogen, plastics, rubber, synthetic fibers) rather than metals like aluminum, which can generate dangerous secondary radiation when struck by GCRs. Polyethylene is a top candidate for lining spacecraft.
Martian Regolith Shielding: On the surface, placing 2–3 meters of Martian soil (regolith) over habitats can significantly reduce radiation exposure.
Natural Terrain Shelter: Using natural geological features, such as lava tubes, cliffs, or canyons, offers significant, immediate reduction in radiation, with data showing a 4% reduction in dose simply by parking near a small butte.
"Storm Cellar" Design: Creating a heavily shielded, specialized, and compact area within the spacecraft or habitat to protect the crew during high-energy solar storms.
First Mission Challenges and Risks
Secondary Radiation: High-energy particles can cause a cascade of radiation when they hit shielding, which can be worse than the initial exposure.
Prohibitive Mass: Bringing massive amounts of shielding from Earth is cost-prohibitive, making the use of in-situ resources (like Martian soil) essential.
Health Consequences: Beyond radiation sickness, the primary risks are increased long-term cancer, cardiovascular disease, central nervous system damage, and cognitive decline.
While active shielding (using magnetic fields to deflect particles) is considered the ultimate goal, it is not considered practical for the first, near-term, missions due to power and structural requirements
Protecting crew members from space radiation is a critical "showstopper" for long-duration missions to Mars, as they will be exposed to high-energy Galactic Cosmic Rays (GCRs) and unpredictable Solar Particle Events (SPEs). Mitigation strategies focus on a combined approach of passive shielding, in-situ resource utilization (ISRU), and advanced, low-atomic-number materials to minimize secondary radiation.
Key Radiation Mitigation Strategies
Passive Shielding with Hydrogen-Rich Materials: Hydrogen-rich materials are the most effective at blocking GCRs without producing dangerous secondary radiation. Ideal materials include water, specialized plastics like polyethylene, and hydrogenated boron nitride nanotubes.
In-Situ Resource Utilization (ISRU): To avoid the massive cost of transporting shielding material, habitats will likely be covered with 2–5 meters of Martian regolith (soil).
Spacecraft and Habitat Design:
Storm Shelters: A heavily shielded "safe room" inside the spacecraft or habitat will be necessary to protect the crew during solar particle events, with shielding equivalent to 40 grams per square cm.
Fuel/Water Storage: Placing water or fuel tanks around the crew habitat acts as an effective, passive shield.
Subterranean Habitats: Utilizing natural features like lava tubes or cliffs can provide significant protection from above.
Operational Procedures: Minimizing Extra Vehicular Activities (EVAs) and avoiding surface operations during solar storms.
Active Shielding (Future Concept): Research into superconducting magnets to generate a localized magnetic field (a "mini-magnetosphere") to deflect charged particles is ongoing but not yet mature for flight.
Protection During Transit
Shielding Optimization: Spacecraft walls will be designed to maximize shielding, potentially using advanced composites rather than just aluminum, which can generate harmful secondary radiation upon impact.
Transit Time: Reducing the total travel time (e.g., using nuclear thermal-electric propulsion) is considered one of the best methods to reduce cumulative dose.
Real-time Dosimetry: Real-time monitoring of radiation exposure using personal dosimeters, such as those tested on the ISS, will be essential.
Protection on the Surface
Regolith Protection: Covering habitats with thick layers of Martian soil (5+ meters for long-term bases) is the primary method for long-term surface habitation.
Subsurface Living: Placing habitats inside natural caves or lava tubes can significantly reduce the radiation dose.
Biological Mitigation
Radioprotectors: Research into medications that boost the body's natural defense mechanisms against radiation damage.
Nutritional Countermeasures: Specialized diets to help the immune system manage radiation exposure.
Challenges and Future Directions
Secondary Radiation: Dense materials like aluminum can actually increase radiation doses by producing secondary particles (neutrons, hadrons) upon impact.
Weight Constraints: Massive shielding is too heavy for launch; therefore, leveraging ISRU (using Mars' own resources) is necessary.
Data Acquisition: Current missions are measuring the radiation environment on the surface (e.g., with the RAD detector) to refine future shielding designs.
Ultimately, the first crewed mission to Mars will likely rely on a combination of hydrogen-rich materials for the spacecraft and thick, localized regolith covering for the habitat
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Risk mitigation strategies are action plans to minimize threats, primarily using four approaches: Avoidance (eliminating the activity), Reduction (lowering likelihood/impact with controls like safety measures or backups), Transference (shifting risk via insurance/contracts), and Acceptance (acknowledging minor risks or accepting potential losses). Effective strategies involve identifying, assessing, prioritizing risks, then planning, implementing, and continuously monitoring actions to ensure business continuity and protect operations, says Metricstream, AuditBoard, Monday.com, and Pathlock.
The Four Core Strategies
• Risk Avoidance: Changing plans or stopping activities that create the risk (e.g., not entering a risky market).
• Risk Reduction (or Mitigation): Decreasing the probability or severity of a risk (e.g., safety training, redundant systems, cost management).
• Risk Transference (or Sharing): Shifting the risk burden to another party (e.g., buying insurance, outsourcing to a cloud provider with SLAs).
• Risk Acceptance: Consciously deciding to bear the risk, often when costs to mitigate outweigh the potential loss (e.g., low-impact risks).
Key Steps in a Risk Mitigation Plan
1. Identify Risks: Pinpoint potential threats across the organization.
2. Assess & Analyze: Evaluate the likelihood and potential impact of each risk.
3. Prioritize Risks: Focus on high-impact, high-likelihood threats first.
4. Develop a Plan: Choose and implement appropriate strategies (avoid, reduce, transfer, accept).
5. Implement & Monitor: Put the plan into action and continuously track its effectiveness, adjusting as needed.
Examples in Practice
• Cybersecurity: Using firewalls (reduction) or transferring data hosting to a secure provider (transfer).
• Supply Chain: Vetting multiple suppliers (reduction/avoidance) or insuring goods in transit (transfer).
• Project Management: Hiring backup specialists (avoidance/reduction) or building buffer time into schedules (reduction)Mars risk assessment management systems (MARS) refer to various tools and platforms, notably Bloomberg's MARS for financial risk (market, credit, climate) and other systems for IT/application performance, conservation (MARISCO), or modeling, using strategies like risk identification (registers, brainstorming), analysis (FMEA, SWOT, matrices), treatment (avoidance, reduction, transference, acceptance), and monitoring, to provide integrated, data-driven insights for managing complex exposures and ensuring resilience in dynamic environments.
Key MARS Systems & Tools
• Bloomberg MARS (Multi-Asset Risk System): A comprehensive platform for financial firms analyzing market, credit, and new climate risks (MARS Climate module) across diverse asset classes with powerful analytics and data.
• MARISCO (MAnagement of vulnerability and RISk at COnservation sites): An adaptive management toolbox for conservation, integrating climate change impacts and risk into ecosystem management.
• Application Performance Monitoring (APM) MARS: Systems that monitor application load balancers to improve availability, performance, and security through real-time dashboards.
Core Risk Management Strategies
1. Identification: Using tools like risk registers, brainstorming, SWOT analysis, and root cause analysis to find potential risks.
2. Analysis: Assessing risks with Probability & Impact Matrices, FMEA (Failure Mode & Effects Analysis), Bowtie Analysis, or quantitative modeling.
3. Treatment/Response: Applying strategies like:
1. Avoidance: Eliminating the risk activity.
2. Reduction: Mitigating impact or likelihood (e.g., controls).
3. Transference: Shifting risk (e.g., insurance).
4. Acceptance: Acknowledging and budgeting for potential losses.
4. Monitoring & Reporting: Continuous tracking of risks and system performance through dashboards and regular reviews.
Tools & Techniques
• Risk Registers: Central logs for risks, impacts, and responses.
• Data Quality Assessment: Ensuring risk data is reliable.
• Decision Trees & Delphi Technique: Structured decision-making methods.
• Budget & Time Tracking: Managing financial and time-related risks.
These systems and strategies work together to provide a holistic view, allowing organizations to proactively manage uncertainties and build resilience
NASA’s Enterprise Risk Management System
Summary of Results from the Risk Management program for the Mars Microrover Flight Experiment
What would happen if you walked on Mars without a spacesuit?
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Those include radiation protection which SpaceNut has been concerned about.
While the cave is being excavated, the equipment needs a garage for maintenance.
It seems to me the primary purpose of a garage on Mars is to provide a well lit workspace protected from Mars surface conditions.
Radiation protection is important if humans are going to be working in the space, but I think that is unlikely to be the first choice for expeditions planned in 2026.
(th)
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Radiation amount type risk mitigation
The highest priority risk mitigation problems for Mars crews center on Space Radiation, impacting cancer, heart, and cognitive health; Altered Gravity, causing bone/muscle/vision loss (SANS); Isolation & Confinement, affecting psychological well-being and performance; Distance from Earth, complicating emergency medical care and autonomy; and Closed Environments, including life support reliability and Martian dust toxicity. These are prioritized due to their severe impact on crew health, mission success, and long-term survival, requiring advanced technological and medical solutions.
Here's a breakdown by priority:
Highest Priority (Critical "Red" Risks)
Space Radiation: Galactic Cosmic Rays (GCRs) and Solar Particle Events (SPEs) increase cancer risk, cardiovascular disease, and central nervous system damage (cognitive decline).Mitigation: Better shielding (transit & surface), advanced warning systems, pharmaceuticals, genetic screening.
Altered Gravity (Microgravity & Partial Gravity): Bone density loss, muscle atrophy, cardiovascular deconditioning, vision problems (SANS).
Mitigation: Artificial gravity (rotation), rigorous exercise regimes, potential pharmaceuticals.
Isolation & Confinement: Psychological stress, depression, interpersonal conflict, performance decrements, boredom.
Mitigation: Crew selection, mental health support, structured activities, habitat design.
Distance from Earth (Communication Delay & Autonomy): No real-time help for emergencies, requiring self-sufficiency in medicine and problem-solving.
Mitigation: Advanced on-board diagnostics, autonomous medical systems (including potential surgery), extensive training.High-Priority (Environmental & Systemic Risks)
5. Closed Environments & Life Support: System failure risks, air/water quality, and contamination.
* Mitigation: High-reliability ECLSS, resource utilization (ISRU) for water/oxygen, robust spares.
6. Inadequate Food & Nutrition: Ensuring sufficient, varied nutrition for long durations.
* Mitigation: Advanced food systems, potential bioregenerative methods.
7. Martian Dust (Regolith): Abrasive, potentially toxic dust affecting equipment and human respiratory/skin health.
* Mitigation: Dust mitigation strategies for suits and habitats, air filtration.Prioritization Logic: These risks are prioritized using impact-versus-probability matrices, focusing on those with high potential for severe outcomes that threaten the crew's survival or mission completion, with radiation and gravity effects often topping the list due to their fundamental biological impact
Seems its number 1, no ones a near death or dead crewman on return...
2 seems to me with health as a result of mars lesser gravity
3 appears to be toxic condition found on Mars
Key Risk Categories & Challenges
Radiation Exposure: Galactic Cosmic Rays (GCR) and Solar Particle Events (SPEs) increase cancer, CNS damage, and tissue degradation risks.Microgravity & Partial Gravity: Causes significant muscle atrophy, bone density loss, and cardiovascular deconditioning, with current countermeasures potentially insufficient.
Martian Dust (Regolith): Its fine, oxidative nature poses respiratory and other health risks, potentially causing disease.
Life Support & Systems Reliability: Systems must be highly reliable for multi-year missions far from Earth, demanding robust, fault-tolerant designs.
Human Factors & Psychology: Crew stress, social dynamics, and isolation during long voyages are critical.
Medical Emergencies: The inability to easily return or get immediate help means any injury or illness is a severe risk.
Assessment & Mitigation Strategies
Probabilistic Risk Assessment (PRA): Tools like NASA's Integrated Medical Model (IMM) quantify medical risks for different mission profiles.Faster Transit: Reducing overall mission time minimizes exposure to deep space hazards.
Shielding & Monitoring: Advanced techniques for radiation protection and early warning of solar events are crucial.
Mission Timing: Optimizing launch windows to align with lower solar activity.
Health & Performance Models: Developing models to understand how performance changes with different crew compositions and medical capabilities.
Mars-Specific Solutions: Addressing Martian dust toxicity and developing robust, closed-loop life support systems
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Seems the second requires
To counter risks from reduced gravity (microgravity and Mars' 38% gravity) on Mars missions, astronauts use a combination of exercise systems, fluid loading, compression garments, medications, and the promising, though complex, concept of artificial gravity (like onboard centrifuges) to prevent bone/muscle loss, cardiovascular issues, and sensorimotor problems, with advanced radiation shielding also critical for the deep space journey itself.
Countermeasures for Microgravity (Transit to Mars)
Exercise: Intensive resistance and aerobic workouts are crucial for bone and muscle health.Fluid & Salt Loading: Increases fluid volume and blood pressure to combat cardiovascular deconditioning before gravity shifts.
Compression Garments: Help maintain blood pressure and reduce orthostatic intolerance (fainting) upon return to gravity.
Lower Body Negative Pressure (LBNP): Uses suction to pull fluids downward, mimicking gravity's effects.Artificial Gravity (AG): A major goal involves rotating sections of the spacecraft or using an onboard centrifuge for daily exposure to simulated gravity, potentially preventing most microgravity effects
Of course we know that these must be planned into the travels to or from mars with AG and only exercise remains for the surface of mars.
Exercise Countermeasures As used on the ISS.
Of course the compressive suits are something that can be used within the dome structure and repair garage use.
Mars crew compression space suits (Mechanical Counterpressure suits, or MCP) are experimental, skintight elastic suits designed to provide pressure with mechanical force, not gas, offering better mobility and reduced fatigue for Mars exploration, contrasting traditional gas-pressurized suits and tackling issues like microgravity's effects on bones and muscles. Concepts like NASA's Bio-Suit, the Australian MarsSkin, and Gravity Loading Countermeasure Skinsuits aim to use elastic fabrics or shape-memory alloys to mimic Earth's gravity, helping astronauts stay healthy during long-duration missions by simulating normal loading on the body.
Key Features & Concepts
Mechanical Pressure: Instead of inflating with gas, these suits use stretchy, form-fitting fabrics (like Lycra) to press against the astronaut's skin, providing necessary counter-pressure in Mars' thin atmosphere.
Mobility & Comfort: They offer greater reach, dexterity, and comfort, with less fatigue than bulky, gas-pressurized suits, making tasks like geology sampling easier.
Gravity Loading: Suits like the Gravity Loading Countermeasure Skin (GLCS) apply downward pressure to simulate Earth's gravity, combating bone and muscle loss in microgravity.
Advanced Materials: Researchers are exploring shape-memory alloys that can shrink-wrap the wearer when activated by heat or current, creating a truly skin-tight fit.
Mars-Specific Design: While MCP suits are ideal for microgravity, Mars suits need to handle lower gravity (about 38% of Earth's) and abrasive dust, requiring robust yet light designs.
Examples in Development
Bio-Suit (MIT): Based on the original SAS concept, using elastic garments for mechanical counterpressure.
MarsSkin (Mars Society Australia): Tested by crews, providing enhanced comfort and dexterity for EVAs.
Gravity Loading Countermeasure Skinsuit: Designed to help maintain bone mass and muscle strength during long missions.
Benefits for Mars Missions
Health Preservation: Reduces physiological deconditioning (bone density loss, muscle atrophy) during transit and on the surface.
Enhanced Exploration: Lighter weight and better mobility enable more effective and less tiring surface activities.
Reduced Logistics: Potentially lighter and more compact than traditional suits, reducing launch mass
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Humans can safely stay on the Mars surface for a maximum of approximately four years before cumulative radiation exposure from cosmic rays and solar particles becomes too dangerous. While short-term, unprotected exposure would cause death from freezing or suffocation in seconds, long-term, unshielded surface survival is limited by high-energy radiation to about four years.
Key factors and findings regarding radiation on Mars:
Total Mission Time: Studies suggest a round-trip mission (including transit and stay) should be kept under four years to avoid exceeding safe, long-term exposure limits.
Radiation Source: The primary dangers are Galactic Cosmic Rays (GCRs) and solar particle events, which are not blocked by the thin Martian atmosphere.
Surface Risks: Without adequate shielding (e.g., habitat shielding), a person would face high cancer risks and potential acute radiation sickness over long durations.
Mitigation: Optimal mission timing during the "solar maximum" can provide some protection, as the sun's activity helps deflect harmful cosmic rays.
Without a protective spacesuit, an individual would instantly succumb to Mars' near-vacuum atmosphere and freezing temperatures. The four-year limit specifically refers to the cumulative dose of radiation, not immediate, acute, unprotected, unshielded environmental conditions
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A 4-year round-trip mission to Mars represents a long-duration, high-safety-margin, or potentially, a lower-energy, extended-stay scenario often discussed in human spaceflight studies. While, theoretically, minimum-energy missions (Hohmann transfers) take roughly 2-3 years, a 4-year limit is proposed to mitigate cosmic radiation exposure. A typical 3-year mission involves a 6-9 month transit each way with a long, ~18-month, stay.
Radiation Safety Limits: Research indicates that limiting the total round-trip, including the surface stay, to roughly 4 years is crucial to keep astronaut radiation exposure within acceptable limits.
Mission Structure: A 4-year timeframe allows for a more relaxed, extended scientific exploration on the Martian surface compared to "short-stay" missions that only last 2 years but are higher-risk, faster transits.
Alternative Mission Durations: While 4 years is a safe, long-duration option, most near-term mission architectures with current chemical technology focus on 2 to 3-year round trips to manage logistical constraints.
The extended duration of a 4-year mission provides more time for surface operations and potentially reduces the fuel required for rapid orbital maneuvers, at the cost of increased health risks from radiation, which requires robust shielding solutions
The radiation showstopper for Mars exploration
Beating 1 Sievert: Optimal Radiation Shielding of Astronauts on a Mission to Mars
Moon 2 Mars Space Radiation Protection “Buying Down” Risks to Crew
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Cosmic ray exposures in the inner solar system more-or-less in the vicinity of Earth vary between 24 and 60 REM per year, varying more-or-less sinusoidally with the nominally-11-year sunspot cycle. High solar activity is the lower value of cosmic ray exposure. Exceeding slightly the 50 REM/year exposure standard (twice that of Earthly workers in nuclear plants) increases the risk of cancer late in life beyond about 3%. 60 REM/year in a peak year is just not that much a risk!
The killer is solar flare events, not cosmic rays! Those occur erratically, though more often during high sunspot years, and they comprise an enormously-larger huge flood of much less energetic particles than cosmic rays. They can vary from 1 REM per hour to 10,000 or more REM per hour. Such exposures are a few to several hours long. Not the whole trip!
The older astronaut high-exposure limits are no more than 25 REM accumulated in any single month, and no more than 50 REM accumulated in a single short event. Somewhere near 200-300 REM accumulated in a short event is about a 50% chance of dying quickly from severe radiation sickness, and 500 REM accumulated in a short event is pretty much a 100% chance of dying quickly.
The outdoor fallout after a nearby fission bomb explosion is somewhere near 5000-50,000 REM per hour, for a few days after the event. That stuff requires feet of lead or yards of earth (and concrete) for adequate shielding.
However, solar flare radiation, being far less energetic particles than cosmic rays, is far easier to shield! It only takes about 15-20 gram/cm^2 worth of shielding on your craft's hull to adequately protect from a high-end solar flare event, such as what occurred in 1972 between two Apollo missions to the moon.
Cosmic rays are not impacted very much by any shielding we might use, but it is known that the lower the molecular weight of the atoms in the shielding materials, the lower the secondary radiation shower intensity produced by scattering events hitting atoms in the shielding. That's why you do not want metal shielding for cosmic rays!
Cosmic rays are just NOT the fatal problem! Anyone who points to that as a show-stopper is lying! The solar wind, and especially solar flare events, are! That exposure really does build up over time toward some kind of career exposure limit. The old one was 400 REM max lifetime accumulation, reduced by age and gender. There was a formula for that. NASA published this stuff, decades ago.
I do hear that those older astronaut exposure limits have recently been reduced some, but that is small change compared to what I am talking about! And the truly high-exposure limits have been known since the atmospheric atomic tests in Nevada in the 1950's, not to mention the two Japanese cities that were A-bombed in 1945. Only the really low-dose exposure limits were found in the decades since.
GW
Last edited by GW Johnson (Yesterday 17:42:33)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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I think we've beaten the radiation problem to death.
There's a 6 month transit period where GCR exposure will be high, for the reason GW already mentioned. The maximum exposure is on-par with the annual radiation dose experienced by residents of Ramsar, Iran, over their entire lifetime, although the doses are not precisely equivalent because GCR is more energetic, and therefore more damaging, relativistic nuclei, mostly Protons with some heavier nuclei up to the weight of Iron or so. Once we get to the surface of Mars, regolith shielded structures provide adequate mitigation of all forms of radiation exposure. The same is true of lunar regolith. SPE / CME from the Sun, as GW also noted, absolutely can be a lethal event within minutes to hours of exposure. Fortunately, SPE / CME radiation is also very easy to shield against. Water or plastic works best for SPE / CME shielding, although any material containing Hydrogen has roughly the same molecular weight as the stream of Protons from the Sun or most GCR for that matter, thus elastic collisions between the Protons and Hydrogen-rich material can absorb all or most of the radiation dose.
SPE / CME / GCR exposure on the surface of Mars is significantly reduced because the planet itself blocks half of the potential dose. The Martian atmosphere, thin as it is, also provides substantial protection unless the SPE / CME / GCR Proton stream is almost directly overhead, which is where most of a habitation structure's regolith shielding needs to be to absorb the dose. If you build a structure in a natural depression or one created through excavation, then regolith is only required for overhead shielding.
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