Mars Beyond Human Landing Achievement?

[RuBisCO]

The radiation problem is overblown. 100 times background radiation is not going to make human life impossible, example: Ramsar, Iran. Ramsar is the most radioactive town on earth thanks to all the radon spewing hotsprings, people have been living there for generations with at present no obvious health effects despite radiation levels ranging from 10-80 times normal background.

The linear no-threshold model for radiation and cancer is based on atomic bomb survivors and one time exposure to huge radiation dosages and radiotoxins. There is a lot of evidence that it does not hold true for low chronic dosages of background radiation. Biology can compensate by upping genetic repair mechanism and thus low chronic dosages aren't as much of a threat as thee model would suggest. Anyway its a controversy.

[Borklund]

This data doesn't tell, that You cannot send people to mars - only that round trip to mars give you +5% to cancer risk (this is still small cancer risk compared to smoking cigarettes on earth).

In this case missions like mars fly-by is just ridiculous idea ,but for early mars missions you always find lot of astronauts willing to take the risk (and never fly into space again if they come back to earth, because of radiation limit).

Advocates of "mars to stay" received another argument for one way mission, because you get less radiation on proper outpost on mars than going back to earth in nearly unshielded ship... also for stay missions could go colonists after mid-age, so they risk much less of getting cancer before they elder and die.

I would rather don't count on some brand new propulsion (especially VASIMR aren't serious competitor of chemical and NTR rockets) who could get us to mars in 2 months (viable only for people, cargo can go 8 months anyway), but focus on new radiation shielding, there is promising idea based on carbon nanotubes composites as decent (and lightweight) radiation shielding.

It would be useful for both protection from space radiation and making nervas safer to use, not mention of application ($$) of carbon nanotubes on earth.

It's not about what astronauts will or won't do; NASA administrators decide that policy. With the 99.9% launch vehicle safety goalpost I don't know that they will move the radiation goalpost further to the right; NASA is super focused (some say unreasonably so) on safety. The 5% increase is for a round trip of 180 days using chemical propulsion. Solar electric propulsion/plasma could bring this down to weeks and it is way more technologically and politically feasible than sending a nuclear reactor to orbit Earth (nuclear propulsion is never going to happen). Solar electric propulsion exists already and has powered several small spacecraft. That tech will be scaled up to be able to be used in propelling humans across space in the decade to come. While radiation protection can be improved stuff like carbon nanotubes are way further out than solar electric propulsion which cuts down on the radiation just by the fact that it takes less time to get to Mars and back.

The radiation problem is overblown. 100 times background radiation is not going to make human life impossible, example: Ramsar, Iran. Ramsar is the most radioactive town on earth thanks to all the radon spewing hotsprings, people have been living there for generations with at present no obvious health effects despite radiation levels ranging from 10-80 times normal background.

The linear no-threshold model for radiation and cancer is based on atomic bomb survivors and one time exposure to huge radiation dosages and radiotoxins. There is a lot of evidence that it does not hold true for low chronic dosages of background radiation. Biology can compensate by upping genetic repair mechanism and thus low chronic dosages aren't as much of a threat as thee model would suggest. Anyway its a controversy.

Too much radiation too quickly will kill you and I'm pretty sure that there are radiation levels that you do not simply adapt to, or thousands of people would not have died or suffered illnesses from Chernobyl for instance.

[Fractal_UK]

The radiation problem is overblown. 100 times background radiation is not going to make human life impossible, example: Ramsar, Iran. Ramsar is the most radioactive town on earth thanks to all the radon spewing hotsprings, people have been living there for generations with at present no obvious health effects despite radiation levels ranging from 10-80 times normal background.

The linear no-threshold model for radiation and cancer is based on atomic bomb survivors and one time exposure to huge radiation dosages and radiotoxins. There is a lot of evidence that it does not hold true for low chronic dosages of background radiation. Biology can compensate by upping genetic repair mechanism and thus low chronic dosages aren't as much of a threat as thee model would suggest. Anyway its a controversy.

Spot on, and an important enough point that I think it is worth reiterating. Far too many people appear to judge radiation hazards based on the linear no-threshold model despite abundant and increasing evidence that it simply doesn't hold up to scrutiny.

[Charzy]

A hundred years ago, people thought that landing on the Moon was impossible. They've been proved wrong.

[MBobrik]

The linear no-threshold model for radiation and cancer is based on atomic bomb survivors and one time exposure to huge radiation dosages and radiotoxins. There is a lot of evidence that it does not hold true for low chronic dosages of background radiation. Biology can compensate by upping genetic repair mechanism and thus low chronic dosages aren't as much of a threat as thee model would suggest. Anyway its a controversy.

.

Record levels were found in a house where the effective radiation dose due to external radiation was 131 mSv/a, and the committed dose from radon was 72 mSv/a.[5] This unique case is over 80 times higher than the world average background radiation.

The prevailing model of radiation-induced cancer posits that the risk rises linearly with dose at a rate of 5% per Sv. If this linear no-threshold model is correct, it should be possible to observe an increased incidence of cancer in Ramsar through careful long-term studies currently underway.[4] Early anecdotal evidence from local doctors and preliminary cytogenetic studies suggested that there may be no such harmful effect, and possibly even a radioadaptive effect.[6] More recent epidemiological data show a slightly reduced lung cancer rate[7] and non-significantly elevated morbidity, but the small size of the population (only 1800 inhabitants in the high-background areas) will require a longer monitoring period to draw definitive conclusions.[8] Furthermore, there are questions regarding possible non-cancer effects of the radiation background.

nuf said

[xandski]

A hundred years ago, people thought that landing on the Moon was impossible. They've been proved wrong.

^^ This. When it comes to space exploration I'm forever the optimist and most of the people at NASA are as well. We seem to forget that there are teams of people far smarter that the majority of us working on these problems and the earliest planned manned mission to Mars is, as far as I know, Mars One which won't launch for at least 10 years. Even in the past few years science has discovered some amazing things (graphene and the Higgs being two off the top of my head) so I have no doubt that in that 10 years there will be solutions to the problems with radiation and propulsion along with any others that might arise in the future.

Although it is not directly related to Mars travel I think this video is a bit of an eye opener, particularly Chris Hadfield's comments in relation to the question asked at 51:20

Slightly OT: I've personally singed up for Mars One and would love to travel to Mars... Even if it is a one way trip.

[Britpoint]

I wonder what will come first: development of a suitable radiation shield to protect astronauts from the increased cancer risk, or a cure for cancer to make such a thing obsolete? Hopefully the latter, maybe NASA should invest some of their research $$$ in that direction

[Kerbface]

I wonder what will come first: development of a suitable radiation shield to protect astronauts from the increased cancer risk, or a cure for cancer to make such a thing obsolete? Hopefully the latter, maybe NASA should invest some of their research $$$ in that direction

I believe there's a bit more to radiation exposure than JUST getting cancer.

[NeoMorph]

I believe there's a bit more to radiation exposure than JUST getting cancer.

This times a thousand. Cancer is only one of the risks. It also affects the brain (turns you into Homer Simpson after a while). It may sound like something from a cartoon but it's the truth. If you don't believe me, just read this... http://www.space.com/19082-space-radiation-astronauts-alzheimers.html

People say "Oh yeah, we can overcome the cancer or just ignore it" but what happens when you forget the right sequence to recharge the air processing. What happens when you forget the door to outside isn't a nice sunny day on Earth? THESE are the problems that could face the Mars explorers.

[Kerbface]

This times a thousand. Cancer is only one of the risks. It also affects the brain (turns you into Homer Simpson after a while). It may sound like something from a cartoon but it's the truth. If you don't believe me, just read this... http://www.space.com/19082-space-radiation-astronauts-alzheimers.html

People say "Oh yeah, we can overcome the cancer or just ignore it" but what happens when you forget the right sequence to recharge the air processing. What happens when you forget the door to outside isn't a nice sunny day on Earth? THESE are the problems that could face the Mars explorers.

Okay, well I'm pretty certain doors to outside would be airlocks and wouldn't be as simple to open as turning the handle and pushing lightly.

[Thaniel]

Well, the question about radiation during the transfer between earth and mars is only an economic one. We can build a ship that shields the astronauts adequately for the trip. That is not questioned realy. The whole discussion is realy a question of engineering, since we would like to launch a small and light a ship as possible, so it can go faster, or be cheaper to launch. The whole discussion about radiation boils down to "Do we bring 50 ton of water? Or only 10 tons?"

As for the outpost on Mars, send the parts in advance, use remotecontrolled dozers to cover them, and roll out the carpet (might need some dusting off when the crew arrive).

[Kerbface]

I've heard liquid hydrogen is a very effective method of shielding. Any comments on this?

[karolus10]

Red carpet on red planet, that would be something .

Shielding, fuel and consumables placing was essential for NTR rockets designs to limit exposure risk from engines, tanks full of liquid hydrogen can be good (fuel must go with us anyway) radiation protection, also water would be very good addition, because it can be useful later, unlike heavy shield made only for radiation protection.

Edited June 4, 2013 by karolus10

[Thaniel]

Water is a molecule made up of 2 hydrogen atoms and one oxygen atom. Neither of them are known for producing highenergy ionizing particles when struck by high energy radiation (secondary radiation). It also have the added benefit of not needing cryogenic and/or high pressure storagecontainers as hydrogen would require to be of a sufficiently high density to provide good protection (or build a ginormous inflatable zepelin around the vehicle). Water also don't leak as easily as hydrogen does. And it can be used for most anything during the journey. It will in spacetravel be very valuable sine it can also be reused.

So while hydrogen might be a good shielding material on it's own, water is also an excelent material, is easier and safer to handle, and it can be used for a lot of things along the way.

Edit: addition:

I did some rough calculations, if they where to launch 50 tons worth of water to act as radiationshielding for the crew of an expedition to mars, it would, if deciding n a 40 cm thick layer of water, mean a tubular section with around 5 meter diameter, 8 meter length would be available, with most likely a backgroundradiation of less than in most peoples gardens. If that size was reduced a bit, to say, 4 meter interior diameter, reduce the thickness to 20 cm, and add food and other provisions, parts and systems and fuel as efficient shielding, *oohh, new idea, need to do some more calculations* but think rotating donut.....

Sarcasm warning: But, we must also remember that it is currently far beyond our current capability to launch as much as 50 tons of anything into space, even if it can be divided into smaller cargos, it would most likely break the space-time continuum and lead to unspeakable horrors in faraway places, not to mention ruin small countries economy.

Edited June 4, 2013 by Thaniel

[Mr Shifty]

Cosmic radiation is different than any of the radiation we're familiar with working around in Earth-based facilities. I've worked around nuclear facilities (both fission and fusion) for 12 years and am well aware of the risks and mitigation strategies we currently employ for these systems. Two radiation sources we worry about are alpha particles -- helium nuclei consisting of two protons and two neutrons with a +2e charge -- and neutrons, which have no charge. Charged massive particles like alphas on earth are easy to mitigate against; they're typically not super high energy, because it is hard to accelerate them, and shielding can be done easily with, for instance, your skin. They pose a hazard to mucous membranes like your eyes, and they can damage your stomach and lungs if breathed or swallowed, but generally aren't a worry externally. Neutrons, on the other hand, because they have no charge and thus are hard to stop, are difficult to shield against. Materials with many hydrogen atoms in them, like plastics and water (and humans!) tend to be pretty good neutron shields because the hydrogen atom nuclei have close to the same mass as a neutron and are able to deflect it. But, it takes, for instance, about 2 feet thick of water shielding to mitigate neutron radiation by 1/10.

Cosmic radiation consists mostly of protons, i.e. particles with the mass of neutrons but also with charge like alphas. However, cosmic radiation particles have on the order of 1000 times more energy (GeV instead of MeV) than terrestrial radiation sources, which means they can penetrate metal, water, anything. The fact that they have charge means that as they pass through you, they'll do more damage. It's sort of like a neutron is a bullet that passes right through you, with a small exit wound. Potentially deadly, but survivable if it doesn't hit anything vital. Alphas are like a shotgun blast from far away. You might have a few small penetrating wounds, but it's unlikely to be fatal. Cosmic radiation is like a shotgun blast at point blank range. The mitigating factor is that cosmic radiation is pretty low background, except that during a solar flare, they can increase to 10-3000 times normal flux (July 11-13, 1982 had a 10MeV flux of 2900 pfu; the current 10MeV flux is 0.18pfu), which would kill astronauts in hours.

The problem isn't trivial. The effects of cosmic radiation on biology haven't been well studied (because how would you?) Passive shielding is going to be heavy and not very effective. Active shielding (using electric or magnetic fields to repel or deflect the proton flux) is complicated, heavy, untested, and has unknown effects on humans.

Add to this the complications that proton (and neutron) radiation has on electronics. (Neutron radiation is a major headache in my job as an electrical engineer at a fusion research facility.) Neutrons are just the right size to cause random bit errors in memories and cause latch-up and outright failure in microprocessors and other smart electronics (FPGA's, etc.) Space vehicle electronics (and nuclear facility electronics) typically look like they're 30 years out of date because we use large, simple components that are less likely to fail and can be easily replaced when they do.

Edited June 4, 2013 by Mr Shifty
Corrected misspelling of helium

[Thaniel]

So with that in mind, the safest way to get to mars is by building ginormous engines on earth and move the whole planet into a hohman trajectory that will get us safely to mars.

Or build a vessel with 6 meter of water in the walls.

[karolus10]

What about feasibility of using mars cyclers at some point of mars exploration ?.

It would be heavy shielded space station, providing habitats with artificial gravity (that would be more like ship cruise rather than traveling in cramped family car), so crew space of actual spaceships could be limited to capsule and will not be used when docked with cycler.

[Borklund]

Artificial gravity is not high up on the technological readiness scale.

[karolus10]

Artificial gravity is not high up on the technological readiness scale.

Artificial gravity could be quite feasible, especially if we use large enough centrifuge or put spacecraft into rotation.

We could get even better results by using long tether:

Version for people with steel nerves ;P.

[Borklund]

Artificial gravity could be quite feasible, especially if we use large enough centrifuge or put spacecraft into rotation.

That's not what I meant. The technology doesn't exist yet, and has never been tried, and it hasn't even been shown to be absolutely critical to space exploration. It's a waste of time and resources, because time and resources are scarce in number when it comes to developing new space exploration hardware and missions.

[GJames]

That's not what I meant. The technology doesn't exist yet, and has never been tried, and it hasn't even been shown to be absolutely critical to space exploration. It's a waste of time and resources, because time and resources are scarce in number when it comes to developing new space exploration hardware and missions.

It's hardly "technology" in the traditional sense. Just stick a rope* between the spent upper stage of a craft and the crew module and then spin it round at a couple of rpm. Voila, artificial gravity.

All it needs is someone to actually do it and we're gold.

*Not actual rope

[Borklund]

It's hardly "technology" in the traditional sense. Just stick a rope* between the spent upper stage of a craft and the crew module and then spin it round at a couple of rpm. Voila, artificial gravity.

All it needs is someone to actually do it and we're gold.

*Not actual rope

That is a crude oversimplification at best. It's not just a matter of "just doing it". Science fiction fluff like this, along with space elevators, nuclear engines and warp drives do nothing but distract from getting actual progress made. We can do it with proven hardware and technology. We can go to the Moon and Mars but there's no political will and a general lack of long term planning.

Edited June 4, 2013 by Borklund

[karolus10]

Putting NERVA engines at same shelf with warp drives and space elevators is an misunderstanding at least. NTR rocket are proven feasible (and able to bee re-used many times, unlike chemical engines) and possible to build...

And NO, today nobody is capable to go to the moon or mars (hell, USA can't even launch own people to orbit !). There are technologies developed trough last half century of spaceflight, but toady nobody had ANY hardware and there is massive amount of engineering to do, before we go anywhere.

[Borklund]

Putting NERVA engines at same shelf with warp drives and space elevators is an misunderstanding at least. NTR rocket are proven feasible (and able to bee re-used many times, unlike chemical engines) and possible to build...

And NO, today nobody is capable to go to the moon or mars (hell, USA can't even launch own people to orbit !). There are technologies developed trough last half century of spaceflight, but toady nobody had ANY hardware and there is massive amount of engineering to do, before we go anywhere.

You're not going to see a nuclear reactor in orbit around the Earth. The NERVA engine may have made sense in the time of putting nuclear reactors on airplanes and using nukes to create harbour areas, but not today. However feasible it is technically you have to account for the political aspect and also the immense costs of R&D and testing before that tech would go on a spacecraft. It has not been shown that we need nuclear engines over say solar electric propulsion, which already exists on many a spacecraft and only needs upscaling for human needs.

When I say that we can go to the Moon and Mars today I don't mean that there is hardware sitting on the VAB at Cape Canaveral, but there are plans and know-how. NASA and ESA have sent many payloads to the Moon and Mars. The EDL problem on Mars has been tackled in many different ways with all the rovers sent there in the past two decades; it's not a huge problem. You don't need new technology to get a heavier payload to the Moon or Mars, you just need a bigger rocket, something that isn't being built (at least not fast enough in the case of SLS). That and the fact that there are no solid plans. Literally, there are NO missions for the SLS, NO payloads on the manifest. Long gone are the days of Gemini, Mercury and Apollo or even STS (Space Shuttle) that had years and years of missions and payload scheduled far out into the future. NASA is in the wilderness politically and funding-wise; not in terms of technology.

[Thaniel]

So you're saying that we can go to mars, fast, using nuclear engines, but it's not possible because of politics.

Please, if you're going to mix in politics into technical why-nots, say so to begin with. And besides, you're point isn't even valid, because of NTR's.

About there not being cargo ready for the SLS lined up, ofcourse there isn´t. The largest payload we, the puny humans, have been able to launch into orbit have been capped at 25-30 tonns since the 70´s. So, noone have built larger pieces since then. When SLS is confirmed actualy ready, even at it´s intermediate 70 (or so) ton capability, larger payloads can again be designed.

If there is a goal that requires the ability to launch heavy payloads, and that goal is important enough, then such vehicles will be developed, as with the race to the moon.

Even though the Apollo project could have been realised using multiple launches and docking in LEO, they opted for a single launch.

Interestingly, this is the first heavylift vehicle built that is not earmarked for a certain mission. It´s kinda like the spaceshuttle. They had an idea for a way of doing orbital activities that the shuttle would fill. Wether or not that worked out as intended is besides the point, but they developed and built the vehicle before there where any realy good reasons waiting in line. So, that point isn´t realy valid either.

The developement of the SLS is an investement, that I hope NASA will follow all the way through, and I realy do believe they will do that. Since without it, they won´t have much else to launch decent cargoes. The flexilibity of having a modern heavy lift vehicle not bound up to a single program will mean new possibilities in interesting areas. It can lift large modules for the ISS, stacks for interplanetary missions with decently-sized lannders. So we´ll see how it will be utilized, but being able to launch a cargo when it is ready beats having to wait another couple of decades for a vehicle able to launch the cargo, or having to divide it up into smaller pieces.

As for artificial gravity, there´s been numerous tests and experiments on this topic over the years. Tehtering where tried during Gemini 11, using the agena stage in the oposite end of the tether. And it worked. It´s just not been done a lot since. The concept was proved in reality using available hardware. There´s no reason it can´t be done "today".

Edited June 5, 2013 by Thaniel