B Survival on Mars: Radiation & Temperature Challenges

[GTOM]

Why do you expect a linear relationship between g on the surface and atmospheric pressure?

Without solar wind, the key quantity is the average kinetic energy of the molecules (in the upper atmosphere) compared to the energy necessary to escape from the planet. The escape velocity is about 5 km/s for Mars, for Earth it is 11.2 km/s.

Let's take Earth: T=2000 K, E=3/2 kT = 250 meV (the hot temperature is driven by solar radiation).
The necessary energy to escape for Helium is ##\frac{1}{2} m_{He} v^2_{esc} = 2.6 eV = 10.4 * 250 meV.
While it is rare, some helium atoms will get 10 times their average energy (and move upwards), and escape. Over geological timescales, most helium atoms escape.
Elementary nitrogen needs 3.5 times this energy, or ~35 times the average energy. That is really rare. Molecular nitrogen needs even more energy.

=> on Earth, helium escapes, but nitrogen does not (not including effects of solar wind).

Sorry, but still don't understand it fully. So escape speed is half on Mars (compared to Earth), kinetic energy is divided by four. But the rad dose from Sun is also about half (based on square of distance). That makes me think (of course i can be wrong), that chance to escape is twice that much, is that enough for such thin air?
Lighter elements also escape from Earth. Isnt it possible, that while lighter elements escaped from Mars, the heavier ones (nitrogen, molecules with oxygen) are rather frozen, captured by regolith?
How can we estimate the amount of ice on the caps?
About the speculation, what can be underground : https://www.nasaspaceflight.com/2015/09/nasa-confirms-salt-water-flows-mars/

 

[mfb]

The chance of thermal escape depends on the temperature, which depends on the solar radiation but not in a linear way. The temperature on Mars is more than half the temperature of Earth (absolute temperature of course). Yes, thermal escape is significantly easier on Mars. Which means helium escapes very quickly, but the heavier elements still stay around for a long time.

 

[GTOM]

The chance of thermal escape depends on the temperature, which depends on the solar radiation but not in a linear way. The temperature on Mars is more than half the temperature of Earth (absolute temperature of course). Yes, thermal escape is significantly easier on Mars. Which means helium escapes very quickly, but the heavier elements still stay around for a long time.

Thank you, but if you don't mind, i'd still like to ask.
Venus avarage temperature is 737 Kelvin, more than double of Earth, while gravity is smaller. Why doesn't it loose its atmosphere?

 

[mfb]

See the calculation I did in post 111. The temperature at the surface does not matter, the temperature is relevant at a place where atoms can escape without further collisions. The atmosphere of Earth is quite hot at that place, and still most elements cannot escape.

 

[GTOM]

See the calculation I did in post 111. The temperature at the surface does not matter, the temperature is relevant at a place where atoms can escape without further collisions. The atmosphere of Earth is quite hot at that place, and still most elements cannot escape.

Ok, thanks.

 

[GTOM]

https://www.nasa.gov/feature/jpl/mars-ice-deposit-holds-as-much-water-as-lake-superior

How could we extract that water from the regolith?

 

[DHF]

https://www.nasa.gov/feature/jpl/mars-ice-deposit-holds-as-much-water-as-lake-superior

How could we extract that water from the regolith?

Here is article on how they plan to mine water on the Moon. I expect similar methods would be used on Mars.

http://www.space.com/7350-nasa-hopes-water-moon.html

 

[mfb]

It should be easier on Mars as you directly have water ice. Maybe something like this: Dig or drill through the surface layer (1-10m) and put the material aside (can be used to cover habitats as radiation shielding). Continue excavating (now with >=50% water ice content), but this time put the material in a box, close the box once full. Heat it (concentrated sunlight, or worst case electricity).

(A) Let the water in the produced slush leave the chamber via a series of filters. Pressure can be provided by evaporation, some stirring looks useful but no pumps are needed. Dump the rest, clean the filters if necessary, repeat.

(B) Alternatively, use the vapor only: let it go to a box that is not heated, then just wait. Water/ice will accumulate there. Takes longer, even with a heat exchanger system, but the water will be very pure. Once the rate of water extracted gets too low, dump the rest, repeat.

 

[GTOM]

How much delta-V could be saved by aerobreaking when descend to Mars? 1-2km/s?

What could be the daily routine to sustain a small colony with local resources?
Cleanse solar panels? Filter the dust for peroxides, water, dry ice? Is it something like dewfall on Mars?
Fergitilize plants, check everything, whether maintenance needed?

 

[mfb]

How much delta-V could be saved by aerobreaking when descend to Mars? 1-2km/s?

Coming from Earth, you enter the atmosphere at about 6 km/s. A heat shield followed by a parachute can slow you down to less than 1 km/s, which leads to about 5km/s delta_v from the atmosphere.

Take care of food production, fix things that break (preferably remotely if outside), produce new things and install them.

The atmosphere has a little bit of water vapor, but extracting ice from the ground looks much more interesting.

 

[GTOM]

Isnt terribly new, but i found that one now.

https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html

Does it sound something realistic in next hundred years for example?

 

[Al_]

Spending a long time in cramped quarters is not fun and provokes enduring psychological issues. A mission to Mars would land a menagerie of psychologically impaired people in a hostile. alien environmnet. That is a recipe for disaaster, IMO.

Exactly. I think that we should concentrate on building large, comfortable free-flying space stations (perhaps with spinning to create artificial gravity) and build and sustain them with robot mining, so they have freely available resources. Then we can head off to Mars in comfort and safety, using plenty of shielding, using the large amounts of fuel available, having lots of know-how about growing our own food, and with off-the-shelf mining robots and virtual reality controllers to operate them. We stop at Deimos to find easily available resources, and send robots down to prospect for a good landing site. Or just to prospect.

 

[mfb]

Magnetic fields are irrelevant on timescales interesting for humans. Sure, if you install such a magnetic field and wait for a few million years, Mars will have a slightly thicker atmosphere. But who wants to wait that long? And who wants to use 21st century technology for a multi-million-year project? People in 3000, assuming humans are still around, will laugh at our attempts, long before the artificial magnetic field would have any notable effect.

Similarly: If we find a way to give Mars an atmosphere, just do it and don't worry about the magnetic field. It doesn't make a difference if we add it in 2100 or in the year 210,000.

 

[nikkkom]

Exactly. I think that we should concentrate on building large, comfortable free-flying space stations (perhaps with spinning to create artificial gravity) and build and sustain them with robot mining, so they have freely available resources. Then we can head off to Mars in comfort and safety, using plenty of shielding

...and meet children of those who dared to endure "cramped quarters".

 

[GTOM]

Magnetic fields are irrelevant on timescales interesting for humans. Sure, if you install such a magnetic field and wait for a few million years, Mars will have a slightly thicker atmosphere. But who wants to wait that long? And who wants to use 21st century technology for a multi-million-year project? People in 3000, assuming humans are still around, will laugh at our attempts, long before the artificial magnetic field would have any notable effect.

Similarly: If we find a way to give Mars an atmosphere, just do it and don't worry about the magnetic field. It doesn't make a difference if we add it in 2100 or in the year 210,000.

What about the other issue, radiation protection? (As far as i know, high speed charged particles are a significant percent of radiation hazard) Simply pack another layer to houses easier, however, glass houses are better for plants, they also need rad protection.
Also if we build in a space station in orbit (to eventually convert it to a big mothership for travel) than thicker walls require more material, and launch from surface is expensive.

 

[mfb]

The proposed magnetic field is irrelevant for galactic cosmic rays, and probably doesn't much against strong solar flares. People on Mars will need radiation shielding anyway - either an atmosphere or some solid material.

Also if we build in a space station in orbit (to eventually convert it to a big mothership for travel) than thicker walls require more material, and launch from surface is expensive.

How is that related to the discussed magnetic field?

 

[GTOM]

The proposed magnetic field is irrelevant for galactic cosmic rays, and probably doesn't much against strong solar flares. People on Mars will need radiation shielding anyway - either an atmosphere or some solid material.How is that related to the discussed magnetic field?

So, a strong magnetic field doesn't seem to be an easier way for rad protection, than simply lift more mass (whether on a planet, or during the trip to Mars).

 

[_PJ_]

I really feel that any permanent residency on Mars is reallistically a LONG way off.
Sure we could (technology and determination, not budget/psychology)establish some form of habitat that could sustain life within 50 years - however, so few people would be there and a single 'disaster' could threaten everything.
For maybe 6 month, 2 maybe even 5 year extended trials - an equivalent kind of research station (As is found in Arctic, Antartic, now the ISS) seems to be a tried and tested foray into remote and dangerous locations.

The real benefits, I feel, will come from enhanced automation capabilities of robots and AI in establishing and generally maintaining such a station until such occasions as human lives are absolutely required.

LONG term I see a larger scale terraforming (habitat, unlikely to be the entire world) endeavour to ensure a more sustainable, ' comfortable' and safer environs for people

 

[nikkkom]

I really feel that any permanent residency on Mars is reallistically a LONG way off.
Sure we could (technology and determination, not budget/psychology)establish some form of habitat that could sustain life within 50 years - however, so few people would be there and a single 'disaster' could threaten everything.
For maybe 6 month, 2 maybe even 5 year extended trials - an equivalent kind of research station (As is found in Arctic, Antartic, now the ISS) seems to be a tried and tested foray into remote and dangerous locations.

Antarctic is not developed/colonized due to treaties prohibiting that.
ISS is a tried and tested foray how to NOT go about expanding into space.

I suggest we try something new, which is also a rather old method: after we have initial tech working reasonably well, send people to Mars who volunteer to go there intending to stay. Colonies on Earth were not generally planned as 5-year stints. _That_ method often worked remarkably better than ISS or our Moon program.
And if you don't like cramped spaces, please reread carefully: "volunteer". Nobody will force _you_ to go.

 

[rootone]

intending to stay.

That's the problem really.

 

[Al_]

...and meet children of those who dared to endure "cramped quarters".

- as they head in the opposite direction!

 

[Ryan_m_b]

I suggest we try something new, which is also a rather old method: after we have initial tech working reasonably well, send people to Mars who volunteer to go there intending to stay. Colonies on Earth were not generally planned as 5-year stints. _That_ method often worked remarkably better than ISS or our Moon program.
And if you don't like cramped spaces, please reread carefully: "volunteer". Nobody will force _you_ to go.

We'd get a better return on investment by setting up closed ecosystems on Earth. For the price (and risk) of shipping infrastructure, an ecosystem and a nascent local economy to Mars we could try out multiple parallel tests on Earth. Iteratively grow increasingly self sufficient cities in the world's deserts.

 

[Chronos]

A desert without any readily avaivable air, water or organic resources would make that scenario more realistic.

 

[mfb]

Colonies on Earth were not generally planned as 5-year stints. _That_ method often worked remarkably better than ISS or our Moon program.

Colonies on Earth were built with different motivations, and in different places.
You might not like the ISS, but it is still our longest-running and most successful project to learn more about life in space (plus all the other experiments done there).

A desert without any readily avaivable air, water or organic resources would make that scenario more realistic.

Water ice is quite readily available in places interesting for humans, and CO2 is available everywhere.

 

[stefan r]

...and meet children of those who dared to endure "cramped quarters".

Why not have children in the "large, comfortable free-flying space" maternity ward station? If people want to visit Mar's surface they could still go when they are adults and not pregnant.

 

[GTOM]

Maybe self sufficient colonies on Antarctica?
Solar power ok, ice ok, extreme cold ok.

 

[stefan r]

Maybe self sufficient colonies on Antarctica?
Solar power ok, ice ok, extreme cold ok.

Equatorial Mars gets more sun than Antarctica. The sun is up every 24 hours. 6 month battery supply is painful.

It often feels colder at -1°C in damp weather than a dry -15 °C. Low pressure argon is an excellent insulator. The measured temperatures on Antarctica and in Gail crater are comparable. Heat loss would be more serious in Antarctica.

There is a lot of spare room available in the equatorial mid pacific. There is no ice yet but you could make it with a solar powered freezer.

Saskatchewan has a large tar sands area. The Canadians are already tearing the face off the surface and then replacing it. You could bury a lot of colony habitats under the sand. SpaceX wants to charge $500k for tickets to the Mars colony. That price includes $millions per colonist in subsidies which could be lowered or even removed for a Saskatchewan colony. People willing to pay the $500k dollars will get a cramped space in a hole under the tundra and tunnel access to a sealed greenhouse where they can compost their own wastes. If the colonist's children grow up and decide they do not like living in a hole in Saskatchewan they could be evacuated by bus.

 

[nikkkom]

You might not like the ISS, but it is still our longest-running and most successful project to learn more about life in space (plus all the other experiments done there).

I completely agree with you. ISS is a valuable project. Its main lesson: whatever you do, do not let government bureaucrats run your space project.
For those not convinced yet, we also run a duplicate experiment called "SLS". Elon Musk just wrote its death note by launching Falcon Heavy.

 

[nikkkom]

Why not have children in the "large, comfortable free-flying space" maternity ward station? If people want to visit Mar's surface they could still go when they are adults and not pregnant.

I still prefer "If people want to visit Mar's surface they should be allowed to, _whenever they want_, not when someone else allows them to". But then, I'm this dangerous "classical liberal", with his outdated ideas of "freedom" and "limited government"...

 

[stefan r]

I still prefer "If people want to visit Mar's surface they should be allowed to, _whenever they want_, not when someone else allows them to". But then, I'm this dangerous "classical liberal", with his outdated ideas of "freedom" and "limited government"...

I was assuming that fetuses grown in odd gravity might turn into odd children or come out sick and dying.

I have no idea how childbirth itself would feel on Earth or anywhere else. Some midwives claim it is easier to give birth upright because gravity assists. In a space station you could adjust rpms or radius to get an ideal gravity setting.

It occurred to me that you could test birth under various gravitational conditions using the vomit comet. With in flight refueling the plane could keep flying for a long duration. You could set the autopilot to increase g-force during contractions and switch to low-g in between. This might be the worst idea I have had in a long time so I thought I should share it.

 

[GTOM]

I completely agree with you. ISS is a valuable project. Its main lesson: whatever you do, do not let government bureaucrats run your space project.
For those not convinced yet, we also run a duplicate experiment called "SLS". Elon Musk just wrote its death note by launching Falcon Heavy.

I fear i don't understand that, why Falcon Heavy is a death note?

 

[stefan r]

I fear i don't understand that, why Falcon Heavy is a death note?

link. Falcon heavy is not the death note of SLS. Boeing spreads jobs around a lot of congressional districts.

 

[nikkkom]

I fear i don't understand that, why Falcon Heavy is a death note?

Let's see.

Falcon Heavy: exists right now, costs $100m per launch, lifts 64t to LEO.

SLS: first launch NET December 2019 (in "SLS 1" configuration),
next one 2022 (in "SLS 1B" configuration),
first flight of "SLS 2" config: 2029 (LOL),
projected to cost $1000m per launch, planned launch rate 1/2 launch per year (aka "once in 2 years"),
mass to LEO: "SLS 1": 70t, "SLS 1B": 105t, "SLS 2": 130t.

Hmmm. Help me choose.

 

[mfb]

It occurred to me that you could test birth under various gravitational conditions using the vomit comet.

You can't give birth in 20-30 seconds. Higher gravity for a longer time is possible in a centrifuge, but lower gravity for more than 30 seconds needs a rocket.

Falcon Heavy: exists right now, costs $100m per launch, lifts 64t to LEO.

$150 million if you want the expendable version that can lift 64 tons. For $100 million you get the partially reusable version with a much lower payload.

[SLS] projected to cost $1000m per launch

More like $2 billion, or $3-4 billion if you include development costs.

The conclusion is right, FH is significantly cheaper than SLS, but don't misrepresent the numbers please.

 

[stefan r]

You can't give birth in 20-30 seconds. Higher gravity for a longer time is possible in a centrifuge, but lower gravity for more than 30 seconds needs a rocket.

20 to 30 seconds is typical for training on NASA's vomit comet. 04g could be sustained longer. 737 is rated for -1.0g to 2.5g. It could maintain close to 2g's in a circle or climb.

Contractions in humans last 30 to 70 seconds. I assumed you would want higher g during contractions. But I really do not know.

None of the rats of cosmos 1129 got pregnant.

 

[rootone]

I still prefer "If people want to visit Mar's surface they should be allowed to, _whenever they want_, not when someone else allows them to". But then, I'm this dangerous "classical liberal", with his outdated ideas of "freedom" and "limited government"...

If there is ever a human exploration of Mars, I doubt that political philosophy will be much to do with the agenda.

 

[mfb]

04g could be sustained longer.

Not much. Relative to the ground you have to fall down at 0.6 g instead of 1 g. A naive scaling would suggest a factor sqrt(1/0.6)=1.29 for the time. 32 seconds instead of 25 seconds, or 39 seconds if you really push it.

 

[256bits]

None of the rats of cosmos 1129 got pregnant.

There you go - conception in zero g may be problematic.
Some other factor could be at play also for an animal in captivity, ( which is a known for certain animals in zoos ).
Development from embryo to a viable fetus is completely unknown for a human - translation from animal to human can have no direct correlation.
Birthing centres that simulate a zero g environment seem to have no problems AFAIK - ie underwater birth, at least for the pelvis area.

 

[ISamson]

Some everyday things might get really complicated...

 

[GTOM]

Lets suppose in not near future, hundred million people would live on Mars.

Would it make sense to import nitrogen from Venus? Is there any place closer than Jupiter, that so lacks nitrogen, that a dedicated nitrogen mine is necessary?

 

[mfb]

Mars has nitrogen in its atmosphere, about 2%. Why would you want to import nitrogen?

 

[GTOM]

Mars has nitrogen in its atmosphere, about 2%. Why would you want to import nitrogen?

They proposed Venus as a nitrogen mine in a Facebook science group, I also found that strange. Although maybe Mercury don't have nitrogen? (Sorry for bit off)

 

[mfb]

Mercury doesn't have much nitrogen (in traces in solid compounds) but I don't see any reason to bring nitrogen there.

 

[GTOM]

And if there is a mining city on Mercury with considerable amount of people?

 

[mfb]

A low-pressure pure oxygen atmosphere works well for humans. Apart from that, I would expect the mining to produce a bit of nitrogen as waste product.

Can we go back to Mars?

 

[GTOM]

A low-pressure pure oxygen atmosphere works well for humans. Apart from that, I would expect the mining to produce a bit of nitrogen as waste product.

Can we go back to Mars?

Ok, no more Mercury in this thread. But last post made me wonder, what experiments showed we don't nitrogen in martian or whatever habitats? I mean isn't it any problem that pressure is lower, but with lack of nitrogen, things ignite easily?

 

[mfb]

Things ignite easily in a pure oxygen atmosphere at atmospheric pressure (Earth, sea level, of course).

A pure oxygen atmosphere at 20% atmospheric pressure has the same partial pressure as our atmosphere. It has a lower heat capacity so fires are a bit more dangerous, but the difference is not that large. The Apollo missions used this to save mass (both from the gas itself and from thinner walls to contain the pressure).

 

[cjameshuff]

Things ignite easily in a pure oxygen atmosphere at atmospheric pressure (Earth, sea level, of course).

A pure oxygen atmosphere at 20% atmospheric pressure has the same partial pressure as our atmosphere. It has a lower heat capacity so fires are a bit more dangerous, but the difference is not that large. The Apollo missions used this to save mass (both from the gas itself and from thinner walls to contain the pressure).

Note that Apollo was initially pressurized with an Earthlike mix and had to be built to withstand 1 atm. The mass savings was largely from not having to carry replacement N2. It's not something that anyone has bothered with for spacecraft since, though reduced pressure O2 is still used for EVA suits.

Another issue is how combustion products change the composition. Assume a typical carbohydrate is burning, 3 O2 -> 1 CO2 + 2 H2O in pure oxygen, 3 O2 + 12 N2 -> 1 CO2 + 2 H2O + 12 N2 in Earthlike atmosphere. The pure oxygen case involves larger relative changes in density, leading to stronger convection currents that feed the flames better, and in an enclosed system, larger pressure changes even after things have cooled down (especially once the water condenses). And in low gravity/microgravity where the oxygen supply is largely by diffusion, all that nitrogen in the way slows things down.

So while it's not a huge deal, you would prefer to have some inert fill gas. Fortunately Mars has plenty of nitrogen, and also argon which should serve just as well as far as people are concerned. And another issue is that a lot of electronics and machines are designed to be air cooled...this won't work as well in 20% O2.