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Protecting interplanetary travelers from radiation will not be easy according to a recent study.

Protecting interplanetary travelers from radiation will not be easy according to a recent study.

The article is detailed and thorough, and outlines the engineering challenges quite accurately.

Conscious Choice cover

Now available in hardback and paperback as well as ebook!


From the press release: In this ground-breaking new history of early America, historian Robert Zimmerman not only exposes the lie behind The New York Times 1619 Project that falsely claims slavery is central to the history of the United States, he also provides profound lessons about the nature of human societies, lessons important for Americans today as well as for all future settlers on Mars and elsewhere in space.

Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space, is a riveting page-turning story that documents how slavery slowly became pervasive in the southern British colonies of North America, colonies founded by a people and culture that not only did not allow slavery but in every way were hostile to the practice.  
Conscious Choice does more however. In telling the tragic history of the Virginia colony and the rise of slavery there, Zimmerman lays out the proper path for creating healthy societies in places like the Moon and Mars.


“Zimmerman’s ground-breaking history provides every future generation the basic framework for establishing new societies on other worlds. We would be wise to heed what he says.” —Robert Zubrin, founder of founder of the Mars Society.


All editions are available at Amazon, Barnes & Noble, and all book vendors, with the ebook priced at $5.99 before discount. The ebook can also be purchased direct from my ebook publisher, ebookit, in which case you don't support the big tech companies and I get a bigger cut much sooner.


Autographed printed copies are also available at discount directly from me (hardback $24.95; paperback $14.95; Shipping cost for either: $5.00). Just email me at zimmerman @ nasw dot org.


  • David M. Cook

    Changing the humans to suit the environment sounds like the wrong approach. Why not construct an inflatable cylinder (much like the Bigelow fabric structures) filled with ordinary water, say 20 meters in diameter, with a 10 meter hollow in the center for humans and electronics? This would provide a 5-meter-thick water barrier to absorb any radiation, and the ends could be protected with removable spheres 15 meters wide. Would 5 meters of water be enough to stop cosmic rays? I’m assuming the Falcon Heavy & larger follow-on vehicles would be available to lift all that H2O up to GEO where the vehicle would be assembled. The water would provide life support to the humans (oxygen and water) and fuel for a giant resistojet, powered by solar panels, for propulsion. Would this work?

  • mpthompson

    What protects us on the Earth? Is it the atmosphere, the magnetic field or some combination of both. It seems a few meters of water should be able to be a substitute for the atmosphere, or is there something beyond molecular density that stops a cosmic ray? The article did a good job explaining what the issue is, but really didn’t go into whether realistic shielding could mitigate the radiation risk to some reasonable level. It doesn’t seem trying to limit missions to solar maximums to reduce cosmic radiation only to have solar flares kill the crew is a reasonable approach.

  • wodun

    “Is it the atmosphere, the magnetic field or some combination of both.”

    According to the Space Show, both with the atmosphere doing most of the work.

    “It seems a few meters of water should be able to be a substitute for the atmosphere”

    IIRC far less than that.

  • wodun

    It isn’t just cancer but all the stuff that happens before you get cancer like loss of cognitive abilities that are equally dangerous.

  • Tom Billings

    “What protects us on the Earth?”

    From cosmic ray protons? Mostly the Earth’s magnetic field. There was work by Dr. Winglee 10-12 years ago for NIAC that showed you could make plasma magnets 10s of kilometers long in Space, which could generate magnetic fields hundreds of kilometers in diameter. Fields on that scale are what are needed to bend the paths of cosmic ray protons enough that they miss the hull of a spaceship. Unfortunately, the money to continue that work was eaten by the Constellation Program instead, as with so many other technical developments.

  • Competential

    The radiation risk is very much smaller than the mechanical risks of total mission failure during a Mars mission! The RAD instrument on MSL on the way to Mars showed that the risk for a complete Mars mission would increase the risk for cancer later in life by just over 3% in terms of sieverts compared with radiation on Earth. NASA wants to be grounded! Since Apollo NASA haven’t traveled further than 3% av Earth diameter above Earth’s surface. Radiation is a politically eficient for NASA to give the blame for having no real manned space program. But others will go to Mars, people who can make rational decisions about risks.

    By sleeping inside a tank och water and methane which is used during the mission, one has a great shield without any extra launch mass and reduces exposure by almost a third (the time astronauts sleep). Performing much work next to such a sleeping tank gives shield which covers a quarter or so of the directions. They could carry a backpack with light weight hydrogen-rich plastics to stop much radiation from hitting almost half their body.

    Radiation is not a big problem for a trip to Mars. Living decades on the surface of Mars would make it a real problem so that outdoor time must be restricted.

  • PeterF

    Water can be in the form of ice like in a comet, but solid. It can be a useful building material as wetland is easily formed in any shape you like with a solar oven. water is probably the most important substance that we would need for prolonged journeys in space.
    There was a lot of speculation a few years back on the uses of room-temperature superconductors. They could be formed into a ring and have a current induced in them that would create a powerful magnetic field that would persist almost indefinitely. most objects in space have a static electric charge that can be acted upon to deflect them. (like on “Star Trek”) solar power collectors would be used to replenish the energy lost. You wouldn’t even need to have “room-temperature” superconductors because you can maintain super cold materials in space through simple engineering.
    A solar power collector could be used as a sail as well as a screen to keep the water and the superconductors cold. The electricity from the collector would also be available to run an ion engine to provide thrust using the water.
    It would even be possible to use the magnetic field to capture the solar wind to replenish materials lost through outgassing

  • PeterF

    I have always maintained that the irrational fear of anything with the word “radiation” is the fruition of soviet propaganda from the 60s and 70s. They knew they couldn’t beat us militarily so they had to get us to defeat ourselves. Don’t forget that NASA is currently spending billions on “climate change”.
    There really is a “hockey stick” graph. It shows that the cancer rates actually DECREASE when we are exposed to small amounts of background radioactivity before increasing due to the direct effects of radiation poisoning.. The speculation being that cancer cells are less hardy than healthy cells, while all cells die when bathed with high doses.

  • Kelly Starks

    Bob Bob Zubrin insists only wimps who don’t want to be colonists would worry about trivia like radiation and cancer!

    Who couldn’t be wrong could he?

    ::blink:: ::blink::


  • Kelly Starks

    Of course if its used during the mission, by the end you have no shielding.

  • Kelly Starks

    Bottom line, build a bigger ship, with at least a ton or two of shielding per meter. Its not a cost driver for the mission, though the extra mass lifted per year would lower the cost per pound proportionately.

  • Competential

    Water would be reused. It doesn’t disaprear when recycled.

  • Competential

    Exactly! That’s why even in the 1950s radioactivity was generally hailed as one of the best things humanity has mastered. It was only around 1970 when Soviet for the first time got the ability to send nuclear bombs to the US (in a militarily realistic way), that fear got the upper hand.

  • Competential

    The rational priority would be to use extra mass for extra backup systems and medical resources. That would help against the real risk of mission failure, which means that all crew members are killed immediately, rather than one of them maybe get cancer 10 years earlier than she otherwise would’ve anyway, 20 years into the future.

  • Pzatchok

    Shielding is easy.
    We know what works. We know how to get it to the ship.

    What I am more worried about exactly what will these people be doing while on their way to some place. Like Mars for this example.

    Exactly how much useless ‘make work’ can be done while in transit?
    Not many if any windows to look out of and exactly what will they be looking at for 99% of the trip? Nothing.
    They could sleep for anywhere from 6 to 12 hours a day depending on mood.
    Make meals and eat for maybe 2 hours a day.
    Exercise for maybe 2 hours a day.

    That leaves them from 8 to 14 hours a day to study towards their education. Maintain the ship. Or figure out ways to kill each other. And unless the ship is a wreck it will not need that much maintenance.
    Even if they are married they will NOT be having sex for 8 hours a day 7 days a week just to kill time.

    You might as well just lock two people into a one room apartment and wait to see who is left over after two years. Because thats all the science you will be getting out of a trip like this. Sending just two people will be the same as asking them to just kill each other at some point.

    It will be like sending a navy sub around the world as slow as possible with no shore leave. Ever. The whole time underwater.
    Even the Navy doesn’t like spending more than a few months at sea with no prospect of any type of shore leave. Even in an aircraft carrier with everything from movie theaters to full on hospitals on board.

    Once you get away from the stupid idea of just sending two people on a simple sight seeing trip around Mars you open up the possibility of actually having a real mission with a real goal.
    Like actually landing on Mars and and leaving again.
    Leaving behind the starting building blocks of a small colony like habitation domes and green houses. Or a wind or solar farm for power.
    Or at least an automated water collection and storage system which would be needed by the next group.

    Plan of sending a dozen people at least and plan of staying at least a few months on the ground with a few of them.
    Plan on eventually having a real colony on Mars or don’t waste everyones time, effort and money just to fly around the planet and take a picture. Robots can do that. Far cheaper and safer.

    The fact is we already know we have the technology to send people there and bring them back. It just takes time effort and money. Otherwise we wouldn’t even be discussing it.
    Thats like trying to prove gravity works by tossing someone out a 10 story window. We already know gravity works, what are we trying to prove? People bounce?
    We know people can get cancer from radiation. We know how much shielding we need to prevent this. We know how to get it into space and onto a ship.
    What are we trying to prove? That two people locked in a small room will not kill and eat each other in two years of confinement? There are cheaper ways to test this out right here on Earth.

    If you want propaganda just build a permanent Moon base and claim the whole of the Moon as your new military outpost. Leave the idea of tossing rocks back at the nations who don’t like the idea open.

  • Edward

    “You might as well just lock two people into a one room apartment and wait to see who is left over after two years. Because thats all the science you will be getting out of a trip like this.”

    With a little creativity, we can come up with some light-weight science experiments for them to work on. They will be in a great place for radio astronomy in frequencies that we use here on Earth. A telescope would provide better pictures than we get from Earth’s surface, long-term experiments that would/could have been performed on the ISS could be perfect distractions from the annoying habits of fellow astronauts.

    “Once you get away from the stupid idea of just sending two people on a simple sight seeing trip around Mars you open up the possibility of actually having a real mission with a real goal.”

    I agree, it would be nice to have a real goal, but Tito’s plan to send a couple on a sight seeing trip is intended to be a bold effort to get the rest of us, especially governments that have the bucks to do it, excited enough or competitive enough to actually plan *and* go to Mars, rather than kick the idea down the road, as even the US government has done for the past four decades. We keep talking about doing it in the next couple of decades, but the hardware being built now is barely sufficient for the job if we *don’t* worry about the radiation effects.

    “Robots can do that. Far cheaper and safer.”

    Yes, but so far not one of them has inspired us to follow. As you say, we have the technology, so why haven’t we done so? And that is the whole point.

    Why wait until we have a perfect mission complete with colonists? We didn’t do that with the moon, or with Low Earth orbit (LEO), or with the first trip to “The New World.” We didn’t even have a mission for Lindberg’s non-stop flight to Paris, or for the X-Prize in 2004, other than to just do it. Yet both inspired others to follow what had previously been undoable.

    An initial mission would prove that it can be done, sort of like Gagarin, who didn’t do a whole lot in space. But the US chased him, China eventually followed, and now US and British companies are serious about putting people into LEO, too. An initial Mars mission, no matter how scientifically or colonially useless, would get the rest of the rockets off the drawing board and into space.

  • Pzatchok

    Gagerin did it for propaganda. Nothing more. If the US and USSR were not into a cold war by then they were quickly moving into one.

    Even our flights to the moon were for little more than propaganda. As soon as the Soviets said they were not going for the moon we pretty much stopped even trying.

    If we keep with the evidence of history we would need something big propaganda wise to get the rest of the world involved. And then only one or two would even try to compete. China and Russia.
    The next and biggest for of propaganda I can think of that our government would even think of seriously would be a semi permanent Moon base. Make part of it secret and that would force the Russians and Chinese to counter our efforts. They would have to build moon bases also or pretty much admit to giving up on space superiority.

    We will only make a serious effort if there is a profit to be gained or security to be established.
    Prove one of those two things and the purse strings will be opened.

    What profit could be gained from building a moon base. More cheap metals? More cheap energy? Rare Earth elements? Or is a military base on the Moon the next mad deterrent to global war, nuclear or not?

    Building a base on Mars gives us nothing. Not wealth or security. So all that is left is a colony that might eventually give back one or the other.

    Sending a pair of people around Mars to get nice pictures is little more than the equivalent of sending Gagarin into space. If no other nation follows up with a better mission then it was for very little propaganda and no one will spend any more wealth on doing it again.

    The US sent people to the deepest parts of the ocean but just how many other nations followed up with better missions? And how much propaganda did it create? A few very short years after and it was virtually forgotten about.

  • Kelly Starks

    Depends if it is recycled. Obviously the food isn’t recycled, but the water in it might be.

    And of course ships leak.

  • Kelly Starks

    Actually that was about when folks realized radiation was much more dangerous then previously assumed. Bluntly a lot of folks died under the old safety limits.

  • Kelly Starks

    You need to cover both risks to a reasonable degree. Allowing risks because it won’t impact the crew until after the missions done and you don’t need the doesn’t cut it.

  • Edward

    “If we keep with the evidence of history we would need something big propaganda wise to get the rest of the world involved.”

    You mean like someone going to Mars?

    If Tito and a few investors want go to Mars, who are we to complain? I am unconvinced that if we were to do so then others would fail to follow. As you said, they would have to admit giving up on space superiority. Sounds like a new space race, to me.

  • Pzatchok

    The thing is that before it even gets started they will be asking for government funds and tax breaks.
    And that makes it all of our business. Not just him and a few investors.

    This will take a multi billion dollar investment. And the costs will balloon as it goes along. At some point a few congressmen will get “bought off” by his group and told to make the proposal that the government start to make an investment.
    You know it will happen. It always happens.

    Just admit now that it will not be done without US government funding in some way then we can get off the idea that it will be privately funded.

    Billionaires don’t spend their own money unless they have a plan to make it all back and then some. And the best way to make it all back is to get the government to buy their service or product.

  • By way of illustration…

    If you play professional football without a helmet or padding, you are likely to get fractures, concussions, and you might even die!  So…don’t play professional football without a helmet or padding!

    > the sun could unleash a potentially deadly solar flare, frying astronauts in their spaceship.

    OK, so position supplies to create a “storm shelter” during periods of solar flares.  QED.

    > cosmic rays aren’t stopped much by shielding.

    Not entirely true.  Look at the following graph and you’ll see that GCR radiation can be significantly reduced with shielding:

    It would take only about 80 tonnes of water shielding in a hollow ice sphere craft in order to reduce the GCR radiation to about 50% thereby keeping astronauts on a Mars mission well within their career limits.  That amount of water could be launched to LEO on two Falcon Heavies for only 1.5% of one year’s NASA budget.  Sent by ion propulsion into an Aldrin Cycler orbit means that one-time investment could be used multiple times.

    > Mars mission…receive around…nearly 1,000 times more.
    > astronaut’s lifespan…would be shortened between 15 and 24 years

    This becomes irrelevant when one takes into account the protection provided by a hollow ice sphere.

    > It would take about three days for every single one of your trillions of body cells to be hit by a high-energy proton (the lightest and most common galactic cosmic ray).

    So the Apollo astronauts had all of their cells struck 3-4 times?  I guess having your cell struck doesn’t mean they die.  So what are we to name of this point?

    > nobody knows exactly how much is too much.
    > NASA gather far more data

    So, study the problem for a decade? How certain can we be that their conclusion won’t be that we need to do more studies?

    Factual Errors:

    > During solar maximum, the sun’s radiation blows counteractively against the cosmic rays streaming in to our solar system, reducing an astronaut’s exposure. 

    No.  It is not the solar wind which blows away the GCRs, it is the Sun’s large magnetic field which deflects some of them.

    > astronauts on the International Space Station would receive doses that exceed their lifetime limits after just 18 months for women and two years for men. 

    No.  The ISS is exposed to 150 millisieverts / year.  A 35 year old female has a career limit of 497 mSv.  So it would take more than 3 years to reach that limit.  For a 47 year old male it would take about 6.7 years to reach that limit.  So, first send older males to Mars.

  • It’s not one or the other. Two Falcon Heavies could lift 80 tonnes of supplies and redundant equipment into an Aldrin Cyer orbit. That amount of shielding would significantly reduce the cancer risk while also adding redundancy and spare parts thereby reducing the risk of fatal equipment failure.

  • Sending people to Mars for a real mission still has the problem of what they should do while traveling. But you could have them do the same thing that the Mars 500 program had — play chess, watch videos, read books, exercise…yes, pretty much killing time. But the certainty that they will kill each other is unreasonable. The Mars 500 people didn’t kill each other. So let’s drop that meme.

    The purpose of the one-time Mars flyby mission is not science so much as it is to prove once and for all that being in deep space for that amount of time is not a showstopper. This is not an irrelevant point since a decent number of people including some NASA researchers openly question whether it is actually possible. So, conducting a flyby mission would put that question behind us and allow us to make a real step towards Mars without waiting until we had the money to design, build, and test an expensive Mars lander.

  • Edward

    “Billionaires don’t spend their own money unless they have a plan to make it all back and then some.”

    There are a few billionaires who have donated their money without expecting to make it back at all. Bill Gates and Warren Buffet famously come to mind. It all depends upon how much they believe in the mission of the group that receives the donations.

    “You know it will happen. It always happens.”

    No, we don’t know that. How many X-Prize entrants asked for government money? Ansari donated the prize, but has yet to ask the government to repay her. Paul Allan hasn’t, either. How about Google’s Lunar X-Prize entrants and Google itself?

  • Pzatchok

    Look at the details of a trust like Bill Gates.

    He is not donating the whole of the trust. Only a portion of the profits it makes each year.
    According to law. So that it stays a non profit charitable trust. The fact is all directors of that trust can also draw a wage, agreed to by the directors. Then the left over is given away.

    Its how the Kennedy wealth stays in their hands. Everything they own is in the trust. Cars, homes and businesses. Each family member then gets a wage for being on the board of directors. The rest of the profits are given away.

    They do not give away their own money. The money they give away would otherwise be paid in taxes.

  • Pzatchok

    The Mars 500 experiment was conducted inside of a facility over 19 thousand square feat in area.
    And several separate compartments they could become isolated in.

    Mars 500 had 6 people not just 2.

    Mars 500 was not locked. If someone got sick they could be pulled out.

    They had no risk of death if a system shut down or became damaged. They knew they were always 3 inches and 3 minutes away from safety. Not 30 million miles and 300 days.

    They had gravity which makes everything better.

    And they knew that would touch down more or less on Mars at some point.

    Your thinking a few billionaire are going to spend the cash needed to build a ship bigger than the ISS and send it off to Mars. For just a few billion. In total expenditure how much has it cost so far to build the ISS?
    If you only count the cost of launching the shuttle and not the cost of building it. It did move some cargo up to it and did a little of the work. Then add in the costs of all the Russian launches. And don’t forget what the other nations have given.
    And now we are talking about putting not just 80 tons but possibly 10 to 20 times that amount of water around it as shielding.

    You can add together the total wealth of the top 15 billionaires on the planet and you might get a good start.

    This is a trillion dollar and a 10 to 15 year project.

  • Kelly Starks

    Actually equipment could actually increase radiation exposure. Metals hit by cosmic rays then shower more short lived particles. So without a thicker shield between that and the people, things get worse.

  • Kelly Starks

    X-prize cost entrants tens of millions, Mars trips would be in the tens of billions…. that’s beyond what a few billionarys coud toss into a hat for fun.

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