# How can I make humans not negatively affected by radiation?

My people are traveling in a generation ship. For some reason they can't make the ship radiation-proof. Their solution: genetically modify their descendants to be radiation proof. How could one modify a cell to resist radiation? Is it plausible to modify our genetic structure to be radiation-proof?

Assume they have a level of tech about fifty to a hundred years ahead of our current level.

• "For this next test, we put nanoparticles in the gel. In layman's terms, that's a billion little gizmos that are gonna travel into your bloodstream and pump experimental genes and RNA molecules and so forth into your tumors." "Now, maybe you don't have any tumors. Well, don't worry. If you sat on a folding chair in the lobby and weren't wearing lead underpants, we took care of that too." - Cave Johnson – Cort Ammon Mar 11 '15 at 15:43
• You can't make anything radiation-proof. It's all a matter of degree. Get too close to a strong radiation source, say a gamma ray burst, and you and ship will become ionized vapor. At the other end, here on Earth we all live with a certain level of background radiation, and have since the origin of life. Indeed, our own bodies are radioactive. So the question depends on the exact level of radiation your ship experiences. – jamesqf Mar 11 '15 at 18:46
• I recall a short story by Charles Stross set after Saturn's Children. Even über-nanotech was overwhelmed when the shipmwas irradiated. They could not get enough uncontaminated elements, as radioactive isotopes continued to damage living/nanotechnological structures. – JDługosz Mar 11 '15 at 23:17

Use Checksums.

A Checksum is a computer science tool used to prevent storage or replication errors. In your case you would have some sort of algorithm that would translate a DNA sequence into a unique code. You'd then store this value. Then when the DNA replication step happens, it is first checked against the stored Checksum. If it's incorrect, the cell then needs to poll its neighbors for the "good" DNA value, and replace it.

Potential Issues:

1. This assumes a capability with genetic engineering that's iffy for your time frame. Beyond modifying genes, you're creating entirely new processes here from scratch. It might be possible with the computing resources we have 100 years from now, though.
2. This will almost entirely eliminate normal mutations. If your colonists lose their genetic technology, they will be "stuck" with their current genetic code until they re-develop it. This could be bad for the long-term (millions of years) survival of the species.
3. Sufficient radiation damage will overwhelm the system, as cells will be unable to retrieve a "good" version of the DNA sequence.
4. The corrective and check steps aren't free, so this will likely slightly increase the metabolic requirements of your colonists - they'll need slightly more food and oxygen. I doubt it will be significant though - probably less than 1% under normal circumstances, but increasing as they take more radiation damage.
• I'm guessing you're not a biologist. ;-) Living organisms already have the biochemical equivalent of checksums. The challenge is not to introduce them from scratch, but to make the existing ones better. See my answer for details. – Royal Canadian Bandit Mar 11 '15 at 16:13
• @RoyalCanadianBandit: Interesting... and yes, you're correct. Do you know offhand how effective current biological error correction is? I'd be interested in comparing the two. – Dan Smolinske Mar 11 '15 at 16:18
• Good question, but the answer is complicated and very much an open field of research. An introduction from a mathematical/compsci point of view is here: PDF link. Headline figure: Simple correction processes improve a baseline error rate of between 10^(-3) and 10^(-5) to a value of 10^(-10). – Royal Canadian Bandit Mar 11 '15 at 16:48
• @RoyalCanadianBandit: I just skimmed that for now, but I only see references to protecting against replication errors. Does DNA have error-correction against storage errors, or against mutations introduced by radiation? – Dan Smolinske Mar 11 '15 at 16:51
• The existing DNA storage-error correction based on a mirror copy is only so good, and cannot be extended. Introduing ECC checksum would only defend against the same thing but not against chunk corruption. Only viable solution: 3 copies of all DNA and active resyncing. – Joshua Mar 11 '15 at 18:35

Rip it off from something that worked millions of years to get it.

The bacterium deinococcus radiodurans is an extremophile. It can survive cold, dehydration, vacuum, acid, and ionizing radiation. It is, in fact, an organism with some of the highest radioresistance known. For instance, this guy can take an acute dose of 5,000 Gy. For a 50% chance of death a human can only take 4.5 Gy. To give it a 37% chance of life it has to be hit with 15,000 Gy.

How does it do this?

It has multiple copies of its genome and a unique rapid repair mechanism for its DNA.

It usually repairs breaks in its chromosomes within 12–24 hours through a 2-step process. First, D. radiodurans reconnects some chromosome fragments through a process called single-stranded annealing. In the second step, multiple proteins mend double-strand breaks through homologous recombination. This process does not introduce any more mutations than a normal round of replication would.

Not only that, but they can take DNA from other cells if theirs is too damaged, they'll even repair it first.

D. radiodurans is capable of genetic transformation, a process by which DNA derived from one cell can be taken up by another cell and integrated into the recipient genome by homologous recombination. When DNA damages (e.g. pyrimidine dimers) are introduced into donor DNA by UV irradiation, the recipient cells efficiently repair the damages in the transforming DNA as they do in cellular DNA when the cells themselves are irradiated.

Other Uses

These bacteria are so good at repairing their DNA that they have been considered for long term information storage, capable of surviving a nuclear holocaust.

In 2003, U.S. scientists demonstrated D. radiodurans could be used as a means of information storage that might survive a nuclear catastrophe. They translated the song "It's a Small World" into a series of DNA segments 150 base pairs long, inserted these into the bacteria, and were able to retrieve them without errors 100 bacterial generations later.

How to rip it off?

The DNA repair mechanism from this bacteria has been replicated to assemble DNA fragments into chromosomes, the ultimate goal is to assemble a synthetic lifeform by the Craig Venter Institute. It would not be impossible then, that engineered humans could include these mechanisms in their own cells.

• Amazing! I got you right that the part with the storage medium was real and nto fiction, didn't I? I'm not a native speaker and have some times trouble to seperate sarkasm and such kinds of talking styl. – Zaibis Mar 12 '15 at 12:34
• @Zaibis: Using DNA for digital data storage is completely real. Another example is in this article: ebi.ac.uk/about/news/press-releases/DNA-storage – Royal Canadian Bandit Mar 12 '15 at 13:55

If your starship encounters a very strong source of radiation such as a gamma-ray burst, game over. ("The crew are dead, killed by a radiation leak. The only survivors are Dave Lister, who was in suspended animation at the time of the disaster, and his pregnant cat...")

Otherwise, the crew will undergo long-term exposure to moderate levels of radiation. The main danger from this is errors in DNA replication, which can cause cancer and/or birth defects in the following generation.

The human body already has elaborate mechanisms to ensure DNA replication fidelity, destroy tumours when they appear, and stop a non-viable embryo from being implanted and carried to term. If you could make these mechanisms better, you would have a cure for cancer; so they are a very active field of research.

Unfortunately for us, it turns out that curing cancer is hard; but in a science-fiction scenario, you could postulate some amazing breakthroughs in cancer prevention. These would serve to protect your starship crew from the worst effects of background radiation.

## Repairing DNA

As I wrote in my answer to Radiation sudden stop the key to surviving radiation is to efficiently repair DNA as @bowlturner has mentioned as well.

The most notable example of this ability is Deinococcus radiodurans. You might be aware that there is already bacterial DNA in the human genome so it's quite likely humans could be genetically engineered to gain deinococcus radiodurans' radiation-resistance.

Edit:

Luckily, I just had another idea regarding your problem so I can contribute some more beside just citing my self.

Here we go:

## Why would you need a generation ship?

If the generation ship is not part of your plot you could also have an automated ship with robots on stand-by. Instead of humans you transport only their DNA in small radiation-proof container. After an automatic landing on your target planet the robots will get activated and create your population by in vitro fertilization in artifical wombs and raise them to adolescence.

This way you only have to conserve the DNA plus ova&spermatozoa – or build them artificially.

You will not need a circular economy on your ship, i.e. no complex infrastructure and no resources to fuel the infrastructure so that your space-requirements and maintenance costs are very, very low.

Of course the premise of the whole idea is mind uploading / transhumanism is not technically feasible or still to scary compared to letting humanity cease to exist only temporarily ;-)

• Interesting idea. Sounds original too as I don't think I have ever heard anything like it. I don't see how humans could be educated unless you could upload and download skill sets into the human mind from the robots. As it turns out, computers by themselves are crappy teachers. – JDSweetBeat Mar 11 '15 at 18:54
• A major problem with this is that DNA isn't really the complete specification of an organism. That is, it's a set of instructions that tell an existing organism how to go about building a new organism. To create a new human from DNA alone would be like giving the Aztecs the complete blueprints for a car. Without existing automobile factories & other infrastructure, could they actually build one? – jamesqf Mar 11 '15 at 22:01
• This is a well-established theme. On wikipedia it is referred to as en.wikipedia.org/wiki/Embryo_space_colonization – Martin Serrano Mar 11 '15 at 23:26
• @MartinSerrano +1 Great finding. – Søren D. Ptæus Mar 12 '15 at 7:56
• @jamesqf Good point. However, that was not what I meant. I think this is going somewhat off-topic. I will write a question up about this concept in a few hours. – Søren D. Ptæus Mar 12 '15 at 7:57

There are two things you could do about the radiation, reduce it or reduce its effects.

The reduce approach depends on the type of radiation and the energy of the radiation. The basic idea is cladding the human's surface with a material which has a very high reduction such as lead or even a composite.

+----------------------+------------------------+----------------------+
| Material             | Halving Thickness [cm] | Halving Mass [g/cm²] |
+----------------------+------------------------+----------------------+
| Lead                 | 1                      | 12                   |
| Steel                | 2.5                    | 20                   |
| Concrete             | 6.1                    | 20                   |
| Packed soil          | 9.1                    | 18                   |
| Water                | 18                     | 18                   |
| Lumber or other wood | 29                     | 16                   |
| Air                  | 15 000                 | 18                   |
+----------------------+------------------------+----------------------+


The problem with cladding your human is that he gets very heavy very quick. Even with composite materials and a thin layer you will see this problem arise. An average male has a surface area of 1.9 square meters, this times the mass of lead would result in 22.8 kilos to halve the radiation once.

There is a second problem. Thin layers of material will scatter high energy rays into multiple rays causing quite the opposite of what you want, they would cause even more ionization than when they were a single ray.

Instead of radiation 'proof', use that advanced technology to 'repair' the damage radiation does to genes. Most immediately dangerous radiation that will kill you in a short period of time can be blocked (at least down to tolerable levels) fairly easily. The rest of it is dangerous when dealing with causes of cancer (mostly). Especially in cells that reside in the body for a long time, such as the eggs in women's ovaries.

If you can design a retro-virus that would correct damage to the DNA it could prevent a lot of the problems caused by radiation. It would also be able to dramatically reduce aging as a side benefit.

http://www.ultramet.com/chemical_vapor_deposition.html

some years back I read an article on atom by atom materials .

with nano materials one could make reflective and refracting materials ,

metal objects shinny as copper in Discovery magazine yet with ceramic or glass like

properties ie will shatter.

X or Gama-rays in refract and reflect some of it away from ship, and or absorb and

re-radiative it. IE Infrared , or as light. or other more desirable wavelength.

one could have translucent nano glass shielding for plants and with cosmic rays have

light radiate on them instead. let desirable light in , else have it converted to light plants can use. on a long space flight capturing energies that are freely available is a need. so phosphor or other impregnated nano materials that protect your hydroponic bay and recycle unwanted energies ie x-rays to plant lighting etc useful.

also conceivably one could make better space suits and lightweight/flexible radiation shielding materials

"TONS of Lead shielding" yet light as silk and wearable, soft nano fabrics that reactor techs could ware like any other clothing.

We yet do not have this but someday soon someone will find a means of adding some micro-crystalline miracle compound and make your Levi Jeans very radiation prof.

Point being materials research can make things we cant even conceive of. some today tech below that's mind blowing.

comments I'm simply stating with new Materials , we dont have yet radiation could be mitigated and or absorbed and transformed to useful energies. and I tried to provide some current examples.

while not a biological solution having radiation resistant clothing via new material be the metamaterials and nano or combination of them.

some of the new materials made from atom by atom deposition have odd or unique properties , ie a sheet of copper that shatters like glass,

point being if someone found a light weight metal composition for radiation armor that is lightweight like aircraft aluminum but blocks more radiation than pounds of lead 3-4 times as thick and at 1.100th or less the weight would make a starship all that more survivable.

bio-radiation repair will be needed tech,

however if one can avoid or mitigate it not having to absorb as much radiation due to new materials also good.

there is nano particle treatments that makes cotton waterproof. it seems 10-100 years down the like that being able to treat cotton to be as protective to radiation exposure isn't all that inconceivable, not only useful to spaceflight personnel but first responders or even xray techs , or nuclear response personnel as well.

(also so used to html.... and there is no common markdown from sight to sight ie stack exchange github etc good old html , kinda markdown challenged)

and forgive my haste on the original section there isnt a post as a draft answer option, I was thinking kinda rapidly for what new wonder materials is likely possible in the near future that would help..

A:absorb & Change radiation to something useful IE electricity , or recovered as photons of light IE special nano-glass , ie a hydroponics bay designed to use a suns light in planetary orbits or take as much starlight/radiation in and convert it to plant light.

B: Enhanced radiation shielding with new types of metals or forced atomic structuring of the crystalline structures. a ship needs to be light weight , however a material with 6 feet? of lead mitigation/refraction/reflection/re-radiation as heat/etc. or etc but yet extremely light, would be a boon. CVD or similar tech is in it's infancy now, but also not inconceivable. some newer radiation armoring of the hull would be useful esp light weight and great protection.

C: new clothing or treatments for clothing , comfortable clothing ie cotton or other comfortable materials , that provides shielding or converts cosmic rays etc to light we can sea etc. when possible , having some enhanced protections without a radion suit which is bulky and not terribly comfortable in "normal" conditions , that would provide a great deal of protection if an event occurred, which could buy time to get into a radiation shield area, IE spacewalk etc. normal everyday treated clothing should provide comfort and high amount of radiation protection without users having to be as concerned.
IE if you had normal fabrics that offered a lead apron's worth of protection yet the same as your t-shirt or sweatshirt ie lightweight , and comfortable as daily wares that would help offer good protection , most would hardly notice.

• Could you do a little editing? The first half of your answer is hard to read and I'm not sure how to edit it myself to make it say what you want. – bowlturner Mar 11 '15 at 19:54
• I'm simply stating with new Materials , we dont have yet radiation could be mitigated and or absorbed and transformed to useful energies. and I tried to provide some current examples. while not a biological solution having radiation resistant clothing via new material be the metamaterials and nano or combination of them, – Necrose99 Mar 23 '15 at 21:41