Cosmic radiation exposure and persistent cognitive dysfunction

https://www.nature.com/articles/srep34774?error=cookies_not_supported&code=01085646-d8e1-4d84-b74f-893382c8aeb5

by pwg • 9 years ago

64 36 9 years ago

QAPereo6• 9 years ago

Radiation shielding is either heavy, or difficult. Heavy is too expensive, and the quietly cold calculus of many seems to have been, “well these early explorers won’t live as long as us.” This however injects the possibility of mission failure, not just a bad end for early Mars colonists on slow boats from Earth.

nnfy• 9 years ago

I wonder how many of those with the qualifications to be selected for a trip to mars would make such a sacrifice.

If you knew you weren't coming back, would you still be willing to be the first person on mars?

throwawaylalala• 9 years ago

Yes. Not now, but soon.

T-A• 9 years ago

Immediate response: no way, why would I want to do that? Second thought: maybe if I were terminally ill and had nothing special left to do on Earth. Third thought: ... but given my usual luck, in that case a cure for my condition would be announced as soon as I had passed the point of no return. :P

jayd163• 9 years ago

Theoretically they could send the cure but they announce cancer cures every other week.

Razengan• 9 years ago

I for one would gladly volunteer for even a one-way trip out of the solar system.

I could keep myself occupied and entertained the same way I do now, with some personal computing devices and game consoles, and I should be able to steer my craft and make direct observations while maintaining communications with Earth as long as the distance allows.

It would be a privilege rather than a sacrifice, and it will help humans back here in understanding the cosmos better than unmanned probes would.

WalterBright3• 9 years ago

One possibility is to find an asteroid that moves between earth and mars orbits, and hitch a ride on it for the bulk of the journey. The asteroid's mass can serve as shielding, and also as a source of raw materials.

eref2• 9 years ago

I was wondering whether one could bring several asteroids in a regular orbit near Earth and Mars with minimal need for correction. Perhaps there exist orbits which might take significantly longer than a more direct trajectory (e.g. several years), but ultimately it might pay off in terms of reducing radiation exposure.

QAPereo6• 9 years ago

Who would you trust with control over that potential weapon?

curtis• 9 years ago

You don't even need a complete asteroid. You only need a few hundred or maybe a few thousand tons of shielding material. You could get that from any nearby (relatively speaking) asteroid-like body with a reasonable delta-v and a surface covered by loose regolith.

Mars's moon Deimos might be the best candidate -- delta-v between Deimos and Earth-Moon L4/L5 is about 3800m/s [1], and there's no need to move the bulk of your shielding lower into the gravity well on either end.

In this scenario, you'd want to use something like an Aldrin Cycler [2] to provide radiation shielded transport between Earth and Mars. This isn't exactly the same thing as hitching a ride on an asteroid, but it's the same basic principle.

You'd definitely need nuclear electric or maybe solar electric propulsion to make such a scheme work, though.

[1] https://en.wikipedia.org/wiki/Delta-v#Delta-vs_around_the_So...

[2] https://en.wikipedia.org/wiki/Mars_cycler

pocketstar• 9 years ago

Electromagnetic shielding with superconductors is probably better than a mass solution.

jayd163• 9 years ago

Hmm. How hard is it to get superconduction in space? Its not like it has to be room temperature.

WalterBright3• 9 years ago

A mass solution, once put into a transfer orbit, requires no further energy input and can be used again and again.

In fact, a large, heavy one can be created or moved into such an orbit, then Mars/Earth journeys only need small, light ships to dock with it at each end.

ScottBurson• 9 years ago

Except that magnets don't deflect neutrons or gamma rays. Seems like you would need some amount of mass shielding in any case.

WhatIsDukkha2• 9 years ago

It's a persistent and PERNICIOUS myth that mass is an effective shield for cosmic radiation.

To quote this page -

"""Manned missions to planets such as Mars require extended missions that will expose astronauts to harmful radiation in the form of energetic particles from solar and galatic sources. Traditional methods for protecting spacecraft and occupants from these forms of radiation involve some configuration of a massive material shield to absorb the energy of incoming particles. For the high energy galactic cosmic rays (GCRs) that astronauts will be exposed to, these so-called passive shields are too massive to be practical and will likely produce showers of secondary radiation that could be more harmful than the GCRs themselves."""

https://engineering.dartmouth.edu/~d76205x/research/Shieldin...

It's concerning that so many people that are interested in space exploration are unaware of this.

The primary enabler for actual space exploration is most likely superconducting magnetic fields but this is an unsolved problem, though the European Space Agency did complete some work in 2016 towards it by reusing technology from CERN

https://home.cern/about/updates/2015/08/superconducting-shie...

It's unfortunate that propulsion is where everyone seems to focus their attention when the shielding is so much more important to human settlement.

mikeytown2• 9 years ago

Getting there faster is one of the best ways to reduce the amount of radiation absorbed. Nuclear power is needed for faster rockets and powerful magnets; safe and reliable access to LEO is the first step to getting reactors in space.

WhatIsDukkha2• 9 years ago

"There" isn't safe either.

Mars has no magnetosphere.

Estimates are that people exploring Mars will have to spend 20 hours a day under 10+ meters of rock to protect from solar radiation alone. I don't believe this protects from the GCR.

Much of that time in the cave will be spent on the conical treadmill to make up for the .3g low gravity. The impact on human biology over longer term is unknown.

I think for actual work, living and use space is almost uninhabitable without the active shielding problem being solved. Risking cancer for a select few isn't the issue, its making space a place humans can live.

However with active shielding, approaches like L5 colonies and in deep space become viable. They could be made far more human habitable then any of the planets or moons.

njarboe3• 9 years ago

Hopefully this problem with radiation exposure when traveling to Mars can change the way people evaluate nuclear propulsion. One could offset a lot of radiation exposure from a nuclear power plant by getting to Mars in weeks instead of months. People traveling to Mars are not going to have a "safety first" philosophy that is dominant in the current US culture and would be able to understand and accept the trade-off.

Maybe someone will start working on nuclear rockets again. I think a large number quality people would come out of the woodwork to be able to be part of such a project.

nradov• 9 years ago

The trouble with nuclear propulsion is not the safety of the astronauts travelling to Mars, but rather the safety of people on Earth. If you launch a large reactor from Earth then a catastrophic launch vehicle failure could cause a radiological incident. Space agencies have launched RTGs before, but those are much smaller and more durable than the real reactors that would be needed to drive a useful propulsion system.

Maybe someday we'll be able to mine fissionable materials from asteroids and construct nuclear rockets in deep space with no risk to Earth. But that technology is firmly in the realm of science fiction today.

njarboe3• 9 years ago

If one gives this problem a bit of thought I think it is really political problem, not a safety issue. First, nuclear fuel is just pieces of metal or ceramic. If it blows up on launch these won't explode in a nuclear chain reaction like what happens in a nuclear weapon. They will just scatter and fall into the sea. They have not been activated yet so they have very low radioactivity at that point. Brand new nuclear fuel is basically harmless. The worry with nueclear fuel is after it is used it becomes very radioactive.

And, even if the fuel was a problem, reactors are going to be designed to be refueled. One could send up the reactor and fuel on different launches with the fuel sent in packaging the would survive any explosion (although the fuel itself already would)

RTGs are actually more of a radiological hazard, as the fuel for those are necessarily very radioactive.

In the end I do agree with your position that the safety of the people on Earth are likely to be a problem because safety is a feeling, not some well defined risk factor. Without some large generational educational project (or maybe change the name?), most people will think that nuclear power can never be safe, even when driving their gasoline powered car on a two lane road to work.

wolf550e• 9 years ago

Robert Zubrin, founder of the Mars Society and author of "The Case for Mars" and "Mars Direct", has a Ph.D. in Nuclear Engineering. In his review of a different article on the same topic, he writes [1]:

"On a Mars mission, astronauts would receive a dose of 1 rad per month during the 6 month outbound and return transfers, and about 0.5 rad per month during 18 months on Mars, for a total of 21 Rads. (1 Gray = 100 rads)".

In the paper, the animals were irradiated "at dose rates between 0.05 and 0.25 Gy/min".

Zubrin writes that the huge difference in dose rates (0.01 Gy per 60 * 24 * 30 = 43200 minutes vs. 0.05 Gy per minute) makes such studies completely useless because at the lower dose rate the body can self repair and at the higher dose rate it can't.

Quoting him again:

"For example, if an individual were to drink one shot of vodka per second for 100 seconds, he would die. But if the same person drank one shot of vodka a month for 100 months, he would experience no ill effects at all. This is about the same ratio of dose rates as... ".

1 - http://www.marssociety.org/r-zubrin-radiation-hucksters-stri...

Analemma_• 9 years ago

Zubrin writes that the huge difference in dose rates (0.01 Gy per 60 * 24 * 30 = 43200 minutes vs. 0.05 Gy per minute) makes such studies completely useless because at the lower dose rate the body can self repair and at the higher dose rate it can't.

I think it's worth pointing out his views, but I also think people should know Zubrin is going against the grain here. Most researchers, as well as nuclear regulatory agencies, use the Linear No-Threshold model for connecting radiation exposure and risk. This is exactly what it sounds like: the model assumes that risk accumulates as a linear function of dose. Whether the LNT is true at small doses is a matter of considerable debate (it's hard to study in humans because the purported effect size is small and it's hard to do such a study ethically), but Zubrin should not talk as though the matter is settled.

njarboe3• 9 years ago

Like most things where one cannot do repeated, controlled experiments, no one really knows where the truth lies apart from some vague notions. What is used as the "truth" will be a political decision.

I think in the case of going to Mars, building a ship that can get there, land, and come back is the hard part. Finding out how bad or not the radiation will be on people will be found out by the people who end up going. Inform them the best we can, so they can make their own decision, monitor their radiation doses, so we can learn more about long-length, high-level radiation exposure in humans, and let people decide if they want to risk it. As long as the radiation dose is not so high to make them sick in the first few years and ruin the mission, let people take the risk if they want to. I don't see why going to another planet should have to be less risky than taking a wagon on the Oregon Trail, to allow people to try it. A safety first philosophy will not get humans living off of Earth.

narrator2• 9 years ago

The future is already here. It's just not evenly distributed:

The polyhydroxylated fullerene derivative C60(OH)24 protects mice from ionizing-radiation-induced immune and mitochondrial dysfunction. : https://www.ncbi.nlm.nih.gov/pubmed/19914272

fsloth2• 9 years ago

What the... where did this idea of injecting hydrolyzed fullerenes come from? Fantastic that it works, but coming up with the idea in the first place sounds completely bonkers (in a good way).

narrator2• 9 years ago

They did a study a while back to see if fullerenes were toxic in mice and they doubled the mice life span. Lots of research outside of the U.S after that. http://www.sciencedirect.com/science/article/pii/S0142961212...

Nobody cares about this kind of research in the U.S because it's a synthetic substance that's not patentable.

Cosmic radiation exposure and persistent cognitive dysfunction

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