July 31, 2016
Moon Visits Cause Heart Attacks
Astronauts who left Earth's orbit get more heart and circulatory diseases.
TALLAHASSEE, Fla. -- Members of the successful Apollo space program are experiencing higher rates of cardiovascular problems that are thought to be caused by their exposure to deep space radiation, according to a Florida State University researcher.
In a new paper in Scientific Reports, FSU Dean of the College of Human Sciences and Professor Michael Delp explains that the men who traveled into deep space as part of the lunar missions were exposed to levels of galactic cosmic radiation that have not been experienced by any other astronauts or cosmonauts. That exposure is now manifesting itself as cardiovascular problems.
If you want to visit the Moon be prepared to die from a heart attack.
Delp found that 43 percent of deceased Apollo astronauts died from a cardiovascular problem. That is four to five times higher than non-flight astronauts and astronauts who have traveled in low Earth orbit.
These missions did not last long. Apollo 11, the first lunar landing mission with Neal Armstrong and Buzz Aldrin setting foot on the Moon, lasted only 195 hours total and some of that time was near Earth. Imagine a Mars mission with exposures lasting many months rather than one or two weeks.
I've said this before: we need really big advances in biotechnology to adapt us to space travel and colonization of another planet. Without those advances we should stay on Earth.
Randall Parker, 2016 July 31 11:27 AM
What some might call a bug may actually be a feature.
Bioengineering modification for space colonization does offer a social benefit. The act of undergoing such a transformation will by default weed out those who refuse to do so due to luddite beliefs of various flavors (liberal-left socialism, Islamic fundamentalism, social conservative Christians, etc.) and, thus, will make it easier for space pioneers to create societies free from the pernicious influence of these kind of people.
Bio-engineering/synthetic biology is the fastest developing technical field in the world. There is no question the bio-engineering to allow us to handle radiation and other environmental aspects of space will be developed in the next 50 years or so.
People who undergo such bio-engineering will be called "transforms", some more exotic than others. It will be the transforms who will migrate out into space. Non-transform people (I like to call them "baseline humans" can stay here on Earth and fight over all of their BS memes.
"Daddy, when I grow up, I want to become a transform"
During the 1970s the Apollo capsules were not properly shielded from cosmic radiation, because the walls of both the spacecraft and the landing vehicles were very thin. Also the spacesuits of the astronauts on the surface of the moon provided even less protection.
But currently we know a lot more about space radiation, and when we go to Mars or when we colonize Moon, there will be much better shielding against radiation. The walls of the spacecraft will be much thicker, and the crew will move to the interior that will be protected by an additional layer of water. And spacewalks will be more restricted, including the ones on the surface of Mars or Moon.
But anti-radiation vaccines are being developed, to repair the DNA damage.
Underneath the Earth's magnetosphere, astronauts are normally protected from dangerous heavy nuclei (accelerated atoms that are larger that protons). Beyond the Earth's magnetosphere, however, these large atoms can wreak havoc on human body tissue. The retinal flashes that astronauts experience beyond LEO are probably due to heavy nuclei boring through the occipital (visual) area of the brain.
Fortunately,heavy nuclei are also the easiest cosmic rays to shield against. It takes less than 20 grams per cubic centimeter of mass to stop the penetration (~20 centimeters of water or 2.5 centimeters of iron) of heavy nuclei.
For interplanetary journeys, you could just provide about 30 centimeters of water shielding for the habitat areas. And you could dump the heavy water shielding before the last trajectory burn into orbit.
Pressure suits used beyond the magnetosphere could be enhanced with iron shielding (3 centimeters?)to stop heavy nuclei-- including the helmet. The visor might have to include an an external led glass visor perhaps 6 centimeters thick that could be pulled over the transparent bubble of the helmet when the astronaut is not looking directly down at the ground.
When traveling several days within cis-lunar space,powdered iron shielded leisure suits and helmets could be worn during the journey and powdered iron shielded sleeping bags could be used while sleeping. For four to six astronauts, this might had a few extra tonnes to the orbital transfer vehicle and the landing vehicle.
Thin walls was actually a radiation protection strategy, in addition to being forced on them by inadequate mass budgets.
Worse than cosmic rays, are cosmic ray secondaries: The original cosmic ray will punch a cell wide hole through your body, but if the cosmic ray hits a nucleus in the spacecraft first, it turns into a shower of high energy particles. Each not quite as powerful, but cosmic rays are really overkill in that department anyway.
You have to have either practically no shielding, to cut down on the secondary radiation, or enough shielding to stop the cosmic rays AND the secondaries dead, and that's a LOT of shielding.
That's what I meant before. It will take more than 20 centimeters of water.
However, a large spacecraft can certainly have a safe compartment with a thick combination of water and ceramic/earth shielding in the center of the hull.
In addition, there is some research on magnetic shielding. A powerful nuclear reactor can generate enough electricity for superconducting magnets to deflect a significant portion of the cosmic rays. Robert Heinlein's book "Orphans of the Sky" (1963) actually describes a generational spacecraft that has a magnetic shield against cosmic rays, but at some point a mutiny in the ship damages the reactor or the magnets, and as a result the surviving factions in the disoriented ship have a lot of mutants in future generations. The book is written very laconically (Heinlein's style) but it is extremely descriptive and unforgettable. I have read this book in high school, and I still re-read it once in a while. :)
If you read the study, its pretty clear that the problem is not with the long term exposure to the proton component of cosmic rays, its the short term exposure to heavy nuclei. If just 10 days of exposure to heavy nuclei can cause so much damage to the heart, one can imagine what could occur after 1000 days of exposure during a round trip mission to Mars. Some studies have suggested that as much as 46% of human brain cells (cells that cannot repair themselves) could be destroyed by heavy nuclei over the course of a three year mission.
But, again, heavy nuclei are pretty easy to shield against.
Interestingly, there seems to be no significant difference in the rate of cancer mortality in the study between Apollo astronauts, LEO astronauts, and astronauts that have never flown into space at all.
This article is pessimistic about the cost of passive shielding.
" Scientists such as University of Chicago professor emeritus Eugene Parker are not optimistic it can be solved anytime soon. For passive mass shielding, the required amount could be too heavy to be affordably lifted into space without changes in economics (like hypothetical non-rocket spacelaunch or usage of extraterrestrial resources) — many hundreds of metric tons for a reasonably-sized crew compartment. For instance, a NASA design study for an ambitious large spacestation envisioned 4 metric tons per square meter of shielding to drop radiation exposure to 2.5 mSv annually (± a factor of 2 uncertainty), less than the tens of millisieverts or more in some populated high natural background radiation areas on Earth, but the sheer mass for that level of mitigation was considered practical only because it involved first building a lunar mass driver to launch material. "
It should be pretty easy to passively shield habitats on the surface of the Moon and Mars since both places have plenty of regolith. Permanent habitats in orbit within cis-lunar could also be shielded with water or regolith exported from the lunar surface.
Since journeys to the orbits of Mars or Venus take less than a year, all you really have to worry about are the heavy nuclei which can be shielded with less than 20 centimeters of water and major solar events which might require an additional ten centimeters to keep total radiation levels to reasonable levels (less than 30 Rem per year) during the journey. The NASA limit is 50 Rem per year. Plus a spacecraft could always dump its water shielding just before its last trajectory burn, to reduce fuel requirements, replenishing it at a water depot once in orbit.
However, heavy nuclei are a different type of danger. And this new study may suggest that astronauts need to be almost continuously protected from heavy ions. That means that venturing outside of a shielded habitat on the Moon, will require pressure suits that are dense enough to shield astronauts from brain damaging and apparently heart damaging heavy nuclei. This will require at least 15 to 20 grams of mass per cubic centimeter which will require at least to be enhanced against heavy ions. The martian atmosphere, however, provides about 16 grams of mass on average so astronauts on the martian surface may not require pressure suits with enhanced shielding to protect themselves from heavy nuclei.
I would say that the radiation environment in space strongly suggests that "cyclers" ought to be used for any colonization of Mars. The mass budget for shielding is easier to stand if it can at least be reused.
I can't resist noting that this kind of radiation during a moon mission was the origin story for the Fantastic Four.