Conscious Choice cover

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.


Available everywhere for $3.99 (before discount) at Amazon, Barnes & Noble, and all ebook vendors, or direct from the ebook publisher, ebookit. And if you buy it from ebookit you don't support the big tech companies and I get a bigger cut much sooner.

New data says going to Mars involves significant radiation exposure

New data from Trace Gas Orbiter, part of Europe’s ExoMars project, says a journey to Mars will expose humans to significant radiation.

The results imply that on a six-month journey to the Red Planet, and assuming six-months back again, an astronaut could be exposed to at least 60% of the total radiation dose limit recommended for their entire career.

The ExoMars data, which is in good agreement with data from Mars Science Laboratory’s cruise to Mars in 2011–2012 and with other particle detectors currently in space – taking into account the different solar conditions – will be used to verify radiation environment models and assessments of the radiation risk to the crewmembers of future exploration missions.

This data was gathered during the spacecraft’s journey to Mars during a time of falling solar activity. Thus, the radiation exposure came more from cosmic rays than from solar activity.


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  • Tom Billings

    It seems that with GCRs providing more of the total dosage, we will need the squadron transits proposed by SpaceX, even more, when combined with Dr. Winglee’s plasma magnets. Cluster the crewed ships of the squadron in the center, and put the cargo ships around the periphery. Send the plasma sheaths from one cargo ship to another around the periphery, over radii of 10s of kilometers, and send electrical current through them. This will generate magnetic fields of hundreds of kilometers diameter, and that radius should allow sufficient bending of GCR charged primary particulate radiation away from the hulls of the crewed spaceships to steeply drop dosage from GCRs.

  • Steve Burrows

    One trip to and back Mars in a career/lifetime, works for me.

  • Lee S

    @ Tom…. Errrm…. Send your research to Elon…. Or at least NASA…

    @ Steve….. Exactly!!! Who genuinely wouldn’t take 60% of their working career “safe” radiation dose for a trip to Mars and back? ( Perhaps young pups planning a family… But they shouldn’t be going anyway!)
    My first thought was ” is that it???”
    NASA, and SpaceX can rest assured, that dispute this information, I am still available, should the call ever come… ;-)

  • wayne

    With the complete caveat: I have only watched 1/2 of this so far…
    (what I’ve seen so far appears to be a fair presentation of the Problem, I haven’t gotten to his solutions yet.)

    “Manned Mars Mission Radiation Analysis”
    Feb 2018

    This guy is saying a Mars Mission (680 days) would net you about 1.5 sieverts (1,500 milisieverts) at a minimum, assuming the Sun remained stable, etc.

  • Tom Billings

    “@ Tom…. Errrm…. Send your research to Elon…. Or at least NASA…”

    NASA already has the basic work Dr. Winglee did at Un. of Washington, at the NIAC archives, since they paid for it. He claimed back then that his work demonstrated you should be able to build plasma sheaths 10s to 100s miles in length, and that these could then be used to generate even larger magnetic fields, which would be used as magnetic sails. This also, of course, suits them for bending charged particulate radiation away from a volume enclosed by these plasma sheaths.

  • If you take no measures whatsoever, you will be exposed to 60% of your career limit. Yeah, but no one’s planning on a mission without any thought to shielding. So, have the crew spend their sedentary time in a place where their water-bearing provisions (and waste) surround then and that 60% goes down to about 35%. So, what’s the issue? Why not recognize that the radiation issue on a Mars mission can be reasonably mitigated and not always start from

  • wodun

    Dr Doug, what does an astronaut’s career exposure limit actually mean in terms of getting cancer or some other health complication? At that level of exposure during that time frame, what is their chance of getting cancer?

    I could look it up but I’m lazy. I seem to recall that it is not that big of a risk but memory is faulty here.

  • Edward

    The video linked by wayne, above, talks a bit about radiation, showing that the big problem is the Galactic Cosmic Radiation (GCR), which is not easily stopped by shielding.

    The next three minutes of the presentation discusses this shielding problem:

    The paper to which you had linked suggests (Figure 6) that about 5 cm (2 in) of water would reduce CGR radiation to the annual limit, but wayne’s video seems to disagree that this is a likely solution.

    Your recommendation seems to be that the sleeping areas be the same as the solar flare shelter area, tightly packed in the center of the ship (perhaps a 2-meter diameter “tube”), surrounded by the most shielding. This reduces the shielding mass by, perhaps, a factor of four over shielding the outside diameter (9m) of the BFR passenger spacecraft.

  • wayne


    Thanks for watching that video! It is filled with great factoids.

    –It’s from a Conference earlier in the year called “Observing the Frontier.” The presenter is definitely pro-mars and his solutions mainly involve advanced-materials. (for which he does research at Caltech I believe it is.)

    Lithium + Boron infused polyethylene appear to offer a bit of protection, but as you note— it’s the galactic cosmic rays we have to really worry about, and that’s not a matter of a few inches of water.

    It’s not just the people that have to be protected— all the electronics have to be hardened and shielded as well.

  • Edward

    Fortunately, we have figured out not only how to protect the electronics, but we have contingencies built into the electronics and software to handle many of the radiation problems that still happen. These protections are not perfect, and we can and do still lose satellites due to radiation, but these protections have done well at keeping many satellites and probes working, sometimes for decades.

    People are larger, somewhat more delicate, and we do not consider it as acceptable to lose one and move on to his backup person as we do for electronics.

  • Warren Platts

    If you had refueling capability at L2, and a reusable, single-stage spacecraft with a delta v of 11 km/sec (cf. the Mars transit vehicle once proposed by ULA), using a gravity assist around the Earth, you could probably cut the transit time to Mars to about 3 months, and thus halve the radiation exposure over the conventional Hohmann transfer time.

  • wayne

    NASA Talk – Spacecraft, Habitats and Radiation Protection

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