Mars radiation not so bad after all

[czokletmuss]

The risk of radiation exposure is not a show-stopper for a long-term manned mission to Mars, new results from NASA's Curiosity rover suggest.

A mission consisting of a 180-day cruise to Mars, a 500-day stay on the Red Planet and a 180-day return flight to Earth would expose astronauts to a cumulative radiation dose of about 1.01 sieverts, measurements by Curiosity's Radiation Assessment Detector (RAD) instrument indicate.

To put that in perspective: The European Space Agency generally limits its astronauts to a total career radiation dose of 1 sievert, which is associated with a 5-percent increase in lifetime fatal cancer risk. [Mars Radiation Threat to Astronauts Explained (Infographics)]

"It's certainly a manageable number," said RAD principal investigator Don Hassler of the Southwest Research Institute in Boulder, Colo., lead author of a study that reports the results today (Dec. 9) in the journal Science.

Source: http://www.huffingtonpost.com/2013/12/09/mars-radiation-manned-mission-curiosity-rover_n_4413351.html

[Scotius]

Huh. Now that's a piece of good news Wonder how much rads it will be when we'll add radiation shielding?

[Psycix]

For the trip you can't properly shield.

While you can shield against the sun's particles, you can't against cosmic rays.

For the stay, you might need to construct a base in a cave to properly shield yourself.

[jwenting]

idea has been postulated to embed the crew module in the middle of a large tank of water, which would shield against most radiation quite well, and on arrival give you reaction mass for braking (and drinking water of course).

[maccollo]

So on mars you would receive a radiation dose roughly a third that of in interplanetary space.

This means that the martian atmosphere blocks out one third of 50% of the radiation.

Given that most of the radiation will be coming from the top of the sky where the atmosphere is the thinnest this is where you would want most of the radiation shielding.

If the astronauts spend about half the time inside the hab, and the had is well shielded the radiation dose for one year would be just a bit over 120 millisieverts, and then the total dose for the round trip would drop well below the 1 sievert limit.

If they spend a third of the time outside the hab then it would be possible to get the radiation dose per year lower than the annual maximum dose allowed for a nuclear plant worker, which is 100millisieverts.

So then we just need to figure out a way to shield the hab it has landed. We could use a super powerful magnetic field. We could also drag the hab into a cave.

Or we could just make use of this tried and true techmology =D

Just bring a few 1000 sandbags and a few shovels, fill them up at mars and line the upper walls and roof of the hab.

As for whether the hab can support the weight, it better be able to do that given the fact that it's gonna have to live through quite a few earth Gs during EDL.

Edited December 15, 2013 by maccollo

[Nibb31]

When you spend $200 billion to send highly-trained astronauts to Mars for 500 days, you don't want them to waste 200 days filling sandbags.

[maccollo]

When you spend $200 billion to send highly-trained astronauts to Mars for 500 days, you don't want them to waste 200 days filling sandbags.

That would mean that the entire crew would be able to fill less than 10 sandbags per day. That would be truly astounding. The most highly trained explorers mankind has to offer take several hours to fill one sandbag.... DERP

Now the actual rate at which a regular person can fill sandbags with very light and simplistic equipment is around 100 per hour. Now obviously, it's gonna be more difficult to do when you have a space suit, let's assume they can only to 10 per person per hour.

Assuming a crew of 4 they could still fill 200 sandbags in 5 hours.

The diameter of the mars direct habitation module is supposed to be 7.5 meters in diameter, which means the roof has an area of just over 44 square meters, so we're gonna need around 230 standard sized sandbags for each layer.

I don't know what the halving thickness is for martian soil and sand, but if it's similar to dirt and sand here on earth (9 cm) then each layer would almost reduce the radiation by 75%, so they would only need 2 or 3 layers for substantial extra shielding... Which should only take 2-3 days. Or maybe it could take a week if half the team fills sandbags while the mechanics inspect everything to see that everything held together.

ANYWAY, my point is it is not something that should take 200 days. It should take a week at most.

The main principle of the of the mars direct/design reference mission is to make use of the resources that are available. Sand and dirt is probably the most plentiful resource I can think of on Mars.

Alternatively there could just not be any extra protection, or to substantially increase the mass of the payload and thus the cost of the mission.

Edited December 16, 2013 by maccollo

[Nuke]

i dont think it would be that bad. it might take 2 people about a minute to fill a sandbag with one holding the bag and the other filling it. a simple light weight apparatus (a fold up aluminum hopper) can probibly accomplish the second man's job. of course with space suits (baring any spacesuit advancements in the near future) that might take 2 or 3 minutes. mission control would of course probibly want the crew to slow it down for safety and for energy/oxygen conservation to 5 minutes a bag. even then it would only take 83 man hours to fill a thousand bags. thats 2 weeks work plus overtime according to most labor standards. if a crew of 4 pitches in, 2 people shoveling, one putting new bags on the hopper and tying them closed when they are full, and a 4th man moving the bags to their intended destination, you could probibly do it in about 3 or 4 days, barring any accidents. you could also employ teams of 2 working in shifts for similar results.

finding a cave site would be very useful, but you may need to reinforce it because cave collapse is a concern. a sprayable concrete mixture with local aggregate would probibly work here, probibly with some light reinforcement (kevlar mesh?). the tools for this would be rather massive, and so probibly wouldn't be considered unless you were building a permanent base. if you were then you would probibly want to bring some airlocks, some cinder block forms for building walls, some sprayable epoxy for sealing in and possibly some sprayable foam insulation. you could hose out a habitat in no time. problem is its hard to find caves from orbit, and if you did find one you would probibly want to inspect the cave to make sure its fit for habitation so it would require a number of precursor missions. i dont think mission planners would want to go for this.

[maccollo]

To put it in a different way.

The cost to launch payload to the moon is usually said to be around 100 000 dollars per kg.

Mars has similar delta V requirements, so let's assume the same cost for a kg to mars.

Filled sandbags typically weight in at 20 kg.

Each sandbag they fill and use as radiation shielding saves 2 million dollars.

Each layer will save almost half a billion dollars minus the weight of the empty sandbags, which would be less than 10 kg for 230 sandbags.

Edited December 16, 2013 by maccollo

[Nibb31]

On Mars, you don't just pop on a suit, go outside, pick up a shovel, and dig away.

EVAs are serious business. You're in space, in a hazardous environment, with an atmospheric pressure of 2% of Earth, it's similar to being in a vacuum.

The ISS EMU suit typically weighs 140kg. Even on Mars with 0.4g, you would be carrying the equivalent of 60 kg. They are also stiff, because they are pressurized, so each movement requires more effort than if you were wearing a jump suit. Lunar EVAs were exhausting for the astronauts, despite the low gravity. Seriously I wish you good luck digging for hours with a shovel in an EMU suit.

And there will never be more than 2 people working outside at the same time. The other crew members will be busy monitoring the EVA. On Earth, you have entire teams of people doing the health monitoring and following the EVA procedures. On Mars, with the time delay, that work will have to be done by the other crew members on site.

And when you arrive, you want to prioritize your tasks so that you maximize the science return if the crew has to abort the mission early. You do the most valuable science work first, you don't waste time filling sandbags.

No, if you wanted to bury a Mars base, the best way to do it would be with robots before the crew arrives. You could either design your base to have a mobile arm like Canadarm or Dextre or you could have a bunch of robots that could do the excavation work autonomously. It would still take a long time.

[jwenting]

When you spend $200 billion to send highly-trained astronauts to Mars for 500 days, you don't want them to waste 200 days filling sandbags.

So send ahead an unmanned mission with an automated sandbag filler. Only needs to land a few days ahead of the crew to have a pile of sandbags large enough to cover the entire base

[SargeRho]

How about water? We already know that water is fairly abundant on Mars, much more so on the pole caps. Wouldn't it be viable to bury a large part under the surface, and then have a sort of "water floor" above that shields from the incoming radiation? Or making bricks of compressed regolith rather than sandbags. Hell, have the fresh-water tank be your radiation shield.

And make greenhouses from things like polyethylene, or better yet, have polyethylene in everything. IIRC that is a rather efficient light-weight radiation shield, shielding against a whole lot of radiation types.

[Nibb31]

So send ahead an unmanned mission with an automated sandbag filler. Only needs to land a few days ahead of the crew to have a pile of sandbags large enough to cover the entire base

It would need more than a few days, and if it failed, you would need a backup solution or it would be shortened mission. You would probably want to send it with the base module on the previous launch window, ie. 2 years before the manned mission arrives. This gives you time to check out systems before you launch your crew.

How about water? We already know that water is fairly abundant on Mars, much more so on the pole caps. Wouldn't it be viable to bury a large part under the surface, and then have a sort of "water floor" above that shields from the incoming radiation? Or making bricks of compressed regolith rather than sandbags. Hell, have the fresh-water tank be your radiation shield.

And make greenhouses from things like polyethylene, or better yet, have polyethylene in everything. IIRC that is a rather efficient light-weight radiation shield, shielding against a whole lot of radiation types.

I don't think you'd want to send a manned mission to the poles. The temperatures would be too extreme and you would have trouble getting through the winter. Phoenix was crushed by the ice caps and even on Earth, Antarctic bases are a tough design challenge.

Again, any sort of excavation or digging equipment is going to be complicated. It has to be autonomous, reliable, low-maintenance, with few moving parts, few consumables, capable of working at low temperatures for long periods of time and with no human intervention, and light enough to put several of them on a Mars lander... That's a pretty tough set of requirements, and even on Earth, it's not easy to do.

But yes, I think that if we ever want to land humans on Mars, we will have to land a whole lot of robots to prepare the ground for them first.

The problem is, what is the point of landing humans if you can do the same work with robots? If you can send robots that are smart enough to build a base for humans, then you can build robots that are smart enough to do the same science work as the humans without the hassle of building the base in the first place.

Edited December 16, 2013 by Nibb31

[Scotius]

I love this site It started with a piece of optimistic news about radiation levels - and now we are discussing the logistics of filling hundreds of sandbags by astronauts. What we need is: a sturdy rover with a backhoe loader, and a collapsible belt conveyor. Pile sand on the conveyor, then it will be transported over the top of the base and simply dropped down until we get layer thick enough. Sure, it will weight more than couple of shovels and a bunch of sandbags. Not to mention it will require fairly powerful source of energy. But rover will be useful for other things, and if we'll go for semi-permanent base that will be used for more then one expedition, we'll have to bring more stuff along anyway.

Or we can drop this issue entirely, build Fusion Pulse Drive and cut down both travel time and dirtside stay to safe lenghts.

[SargeRho]

The problem is, what is the point of landing humans if you can do the same work with robots? If you can send robots that are smart enough to build a base for humans, then you can build robots that are smart enough to do the same science work as the humans without the hassle of building the base in the first place.

Telling a robot to dig a hole is relatively easy. You'd probably need nuclear powered excavators on Mars, using small nuclear reactors, not RTGs.

Getting a robot to do science as well as a Human could, that'd a little harder. On the moon it's workable, there the signal only takes what, 2.5 seconds to get from Earth to the Moon, and then Back?

On Mars, it takes anywhere from I think 14 minutes to half an hour or so. And last time I checked, our AIs are still Artificial Stupidities, nowhere near a Human's capacity.

And lastly, there's an emotional/political reason behind putting humans on Mars: It satisfies our need to explore. Sure, a robot on Mars is nice and all...but it doesn't quite do it. And landing a Human on Mars and returning him safely - or hell, colonising Mars - would unambiguously win you the "Most powerful nation in the Solar System" badge.

[maccollo]

The problem is, what is the point of landing humans if you can do the same work with robots? If you can send robots that are smart enough to build a base for humans, then you can build robots that are smart enough to do the same science work as the humans without the hassle of building the base in the first place.

But that is the point of sending humans. Robots are amazingly clumsy and slow. If it is impossible for humans to do this stuff then they would just have to tough it out during the first expeditions like champs.

Sending heavier equipment to deal with this wouldn't be worth it until we've been there a few times, and 1 sievert over the course of the mission is something NASA is apparently willing to work with.

I would assume the astronauts would be slightly better shielded in the habitation than what curiosity is.

But if a rover could be devised that would be capable of performing this task that would be pretty cool, not to mention cute in a wall-e kind of way.

It would have like a magazine of sandbags that would be loaded into a cavity, then it would shove sand and dirt in there and throw out the sandbags behind it.

The main problem with such a contraption would be how to avoid the problem getting stuck in the sand it's trying to excavate. Mars rovers haven't been to lucky with sand dunes.

Edited December 16, 2013 by maccollo

[Nibb31]

But that is the point of sending humans. Robots are amazingly clumsy and slow. If it is impossible for humans to do this stuff then they would just have to tough it out during the first expeditions like champs.

I really would call Curiosity or the MERs "clumsy", but humans are also amazingly clumsy and slow. Look at how long it takes to do most EVA activities on the ISS. The Apollo astronauts could only venture 7 km from the LM because they were limited by life-support. Mars astronauts would also be limited to a range around their landing site. On the other hand, you can drop dozens of automatic rovers all over the planet to get a much wider variety of data, and they can keep going for months or years without having to go back to the landing site. So effectively you can cover a much wider area with multiple automatic rovers than with a single manned mission.

Getting a robot to do science as well as a Human could, that'd a little harder. On the moon it's workable, there the signal only takes what, 2.5 seconds to get from Earth to the Moon, and then Back?

I disagree. The "science" that humans would be doing on Mars is basically an extension of what the Apollo or ISS astronauts do: they tend to experiments, make observations, and pick up samples. The actual analysis and research work is still done on Earth. The science equipment and experiments are designed on Earth to minimize astronaut interaction. Most of the work done by astronauts on the ISS is maintaining the equipment that allows them to stay alive, running the experiments and transmitting the results to the labs on the ground who actually analyze it.

A Mars expedition would be similar. A part of their work day would be picking up samples in a limited radius around their base/lander, running predefined experiments with the equipment they have, following instructions from the ground, and transmitting the results back. However, the major part of their time will be spent running the base, maintaining equipment, and keeping themselves alive, including all those human inefficiencies like sleeping, eating, cleaning, and performing other bodily functions. The equipment just to perform those bodily functions represents more than 80% of the mass of the mission. That's a major inefficiency that trumps any gain that you might have from having an human on-site.

Robots are getting smarter and more mobile everyday. There is no reason a robot couldn't be designed to perform the exact same sample gathering and science mission or to return soil samples from much wider locations than a manned mission ever could. In addition, a robot doesn't get tired, it doesn't get sick, it doesn't need to eat or go to the toilet. It can cover a much wider observation area for a much longer observation period, which is important for siesmic or climate research. It doesn't need rescuing if something goes wrong and it doesn't need bringing back. A robot is only limited by the actual experiments and instruments that you add to it, but then so is a manned mission.

And lastly, there's an emotional/political reason behind putting humans on Mars: It satisfies our need to explore. Sure, a robot on Mars is nice and all...but it doesn't quite do it. And landing a Human on Mars and returning him safely - or hell, colonising Mars - would unambiguously win you the "Most powerful nation in the Solar System" badge.

Sure, it's a nice dream, but it's an expensive dream that's pretty much out of our reach for now. There will probably be a time when it is techically feasible, but the technology simply isn't ready yet, so I'd rather see us use the technology that we do have to reach goals that are actually achievable now. Achieving smaller goals today will help us reach the milestones that will make manned interplanetary expeditions possible tomorrow.

Edited December 16, 2013 by Nibb31

[SargeRho]

I think we should rather work towards a manned mission. Rather than sending one mission after another, saying "It'll pave the way for a human mission". Well, perhaps it will, if you're willing to wait another century before landing on Mars. I'm certainly not. I don't see anyone actively working on trying to solve the life support issue. As for space suits: Several suits are being developed to solve that. At least one of them uses mechanical compression rather than air pressure. It's also a lot more mobile than the suits used on the ISS and on the Moon.

It's only economically out of reach. If NASA, or the Chinese, were to dedicate themselves to land Humans on Mars in the next 10 years, and bring them Back, I'd say it's doable. Fuel production for the retun? Not an issue. Sending things there? Well, we might need the SLS, else Proton M will do if you're going with 2 launches for each lander, and nuclear engines. Radiation? As we learned thanks to Curiosity, an acceptable risk. Robotic mining/earth-moving isn't a thing of science fiction. It's something that's been done for years. We'd need much more light-weight equipment than we currently have.

The technological issues then run down to two major things. Building the Landers, and Life-Support. And those aren't as hard to overcome as the political-economic problem of getting someone to actually fund this.

[Duxwing]

... the political-economic problem of getting someone to actually fund this.

It almost makes you miss the days when the US and USSR were racing to space.

-Duxwing

[SargeRho]

I kinda hope China sparks a new space race, to Mars.

[NASAFanboy]

I care little for science output.

Is our goal to build a spacefaring civilization, or to look at pretty pictures of other galaxies?

Is it to spread our race to new sancutaries from the void, or is it to look at dirt?

A manned Mission would pave the way for colonization. That is all.

[Albert VDS]

Science isn't looking at pretty pictures or dirt.

It's away to understand the everything around us and use this knowledge.

It is the most important tool for any civilization.

To think you can become a space-faring civilization without it is ridiculous.

[NASAFanboy]

There is no need to learn the science we do not need. We already have gathered enough knowledge of Mars to launch a manned expedition. I find no need to send more rovers, nor any need to send probes. Humans can do the science.

[Albert VDS]

I'm not saying we need to send more rover.

But you post seemed to me like you think science is just sending pictures and looking at dirt.

When in fact it's more than that, it's the reason why we have medicine, can talk over long distances, send rockets in to space, etc.

The reason why we learn more about the universe around us is because people stick their noses into places where we thought it wasn't needed.

[Nibb31]

I care little for science output.

Is our goal to build a spacefaring civilization, or to look at pretty pictures of other galaxies?

Is it to spread our race to new sancutaries from the void, or is it to look at dirt?

A manned Mission would pave the way for colonization. That is all.

You're getting all worked up again. Time to sit back and look at the real world instead of watching Star Trek. From all your messages, the feeling I get is that your goal in life is to live a science fiction adventure in your lifetime. That's nice, but you've got to remember that science fiction universes are pure fiction, in exactly the same way the Hobbit universe does not reflect real medieval times. It's entertainment, not a prophecy.

You are just a kid that has been raised on sci-fi movies and TV shows in one of the richest countries in the world. Your fantasy goal does not reflect the aspirations of all 8 billion of us on Earth. Humanity is a diverse group with many backgrounds, cultures, religions, and desires. You can ask Native Americans, Indigenous Australians, Africans, Indians, Philipinos, Lost amazonian tribes, Tibetan monks, Christians, Buddhists, Jews, Muslims, Atheists, Scientists, Criminals, Artists, etc... All of these groups have different ideas of what the goal of Humanity is, and none knows better than the other, because there simply is no universal goal or destiny that unites all Humanity.

It is nobody's goal to build a spacefaring civilization. There is no political party on Earth, no organization, no government agency, not even a cult, that has that goal. It is just your fantasy, which I suspect only comes from watching too much Star Trek. Building colonies on other planets or emigrating off-world is in nobody's interest. It might be a romantic idea and an entertaining background for a good book, but it's not going to happen that way, and not now.

Our goal, if there is one, is to expand human knowledge and - I guess - to survive as a species. That's it, and neither of those goals require space colonies and interstellar empires.

Edited December 16, 2013 by Nibb31