Survival on Mars: Radiation & Temperature Challenges

[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.