Author Topic: Envisioning Amazing Martian Habitats  (Read 869987 times)

Offline Lumina

Re: Envisioning Amazing Martian Habitats
« Reply #260 on: 10/30/2016 09:47 pm »
(i.e. Where it's hard to land anyway, like Mount Olympus). GCRs may be a consideration, but SPEs are not.

Citation needed. Propulsive landing isn't especially difficult at higher altitudes. It's easier to get research grants for fancy aerodynamic deceleration however.
It takes MUCH more propellant to land on Mount Olympus. I'm still talking about ITS-style EDL. If you want to land on the top of Mt. OLympus, you basically have to do the entire landing propulsively, like landing while moving at Mach 8, versus Mach 3 for supersonic retropropulsion. That's a huge difference and means far less landed mass for a given propellant.

Could a lifting body vehicle (not ITS) decelerate aerodynamically in the lower atmosphere with a high drag angle of attack and then gain altitude with a high lift/low drag attitude to land propulsively at high altitudes without burning too much propellant? Or is this too nutty to even contemplate?
« Last Edit: 10/30/2016 09:48 pm by Lumina »

Offline LMT

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Re: Envisioning Amazing Martian Habitats
« Reply #261 on: 10/30/2016 11:24 pm »
Storm vs. Flare

Look at the diagram I posted. That should answer your question. We're concerned here narrowly with solar storms and with reducing their level until they pose no acute risk. It doesn't have to block the entire spectrum, just the overall level. And even just 30g/cm^2 of aluminum can do that. Mars's atmosphere does even better.

A solar storm proton is not the same beast as a solar flare proton.  Up to 1000x the energy.  That's why the martian atmosphere doesn't protect from the flare, or from GCRs for that matter. 

And I don't know who the "we" is, but what studies if any have actually recommended a mere 30g/cm2 of aluminum shielding (11 cm) for a long-duration Mars hab?

wstewart, would (or could) colonists have advanced warning that a solar flare was coming?  If so, does that suggest that their 'normal' habs would not have to protect against them, but that they'd need some type of underground 'storm shelter' to scurry to in the (rare) event of a direct hit by a solar flare?

(Though that still leaves the ongoing, though lower dosage threat of GCRs, yes?)

Well sure.  Or the hab designers could do a real job.  What's your preference?  :)
« Last Edit: 12/14/2016 07:53 pm by LMT »

Offline GORDAP

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Re: Envisioning Amazing Martian Habitats
« Reply #262 on: 10/31/2016 12:02 am »
Storm vs. Flare

Look at the diagram I posted. That should answer your question. We're concerned here narrowly with solar storms and with reducing their level until they pose no acute risk. It doesn't have to block the entire spectrum, just the overall level. And even just 30g/cm^2 of aluminum can do that. Mars's atmosphere does even better.

A solar storm proton is not the same beast as a solar flare proton.  Up to 1000x the energy.  That's why the martian atmosphere doesn't protect from the flare, or from GCRs for that matter. 

And I don't know who the "we" is, but what studies if any have actually recommended a mere 30g/cm2 of aluminum shielding (11 cm) for a long-duration Mars hab?

wstewart, would (or could) colonists have advanced warning that a solar flare was coming?  If so, does that suggest that their 'normal' habs would not have to protect against them, but that they'd need some type of underground 'storm shelter' to scurry to in the (rare) event of a direct hit by a solar flare?

(Though that still leaves the ongoing, though lower dosage threat of GCRs, yes?)

Well sure.  Or the hab designers could do a real job.  What's your preference?  :)

That would depend upon the frequency and duration of the solar flares (of which I am completely ignorant).  If on Mars surface they are completely random, once a month-ish events, with only 15 minutes of warning, and they last for several hours, I'd want all habitats to be 'flare-proof' for their inhabitants.  If on the other hand, they are once a decade event, with hours of notice, and last only 30 minutes, I don't think it would make sense to drastically increase the cost and complexity of the habitats (and decrease their aesthetics and 'livability', such as burying everyone under meters of opaque regolith). In this case I think an adequate 'storm shelter' would make the most sense.

Which of these two extremes best characterizes the flares?

(And again, I acknowledge this completely ignores the GCR issue.)

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #263 on: 10/31/2016 12:56 am »
View from inside a Martian dome.

Offline Robotbeat

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Re: Envisioning Amazing Martian Habitats
« Reply #264 on: 10/31/2016 01:04 am »
Storm vs. Flare

Look at the diagram I posted. That should answer your question. We're concerned here narrowly with solar storms and with reducing their level until they pose no acute risk. It doesn't have to block the entire spectrum, just the overall level. And even just 30g/cm^2 of aluminum can do that. Mars's atmosphere does even better.

A solar storm proton is not the same beast as a solar flare proton.  Up to 1000x the energy.  That's why the martian atmosphere doesn't protect from the flare
It sure does.

Quote
And I don't know who the "we" is, but what studies if any have actually recommended a mere 30g/cm2 of aluminum shielding (11 cm) for a long-duration Mars hab?
You missed the point. The Martian atmosphere is a better shield than that 11cm of aluminum would be. No shielding is necessary on Mars (unless you're at high altitude) for solar particle events. It's not something to bother considering in your habitat design.

GCR might be (though that's actually debatable), but that's about limiting your total time, not about being "caught out" during a solar particle event.

EDIT:And of course I'm not talking about the relatively slow particles in the solar wind.
« Last Edit: 10/31/2016 01:10 am by Robotbeat »
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Offline LMT

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Re: Envisioning Amazing Martian Habitats
« Reply #265 on: 10/31/2016 05:44 am »
Staying Alive, with Aesthetics

wstewart, would (or could) colonists have advanced warning that a solar flare was coming?  If so, does that suggest that their 'normal' habs would not have to protect against them, but that they'd need some type of underground 'storm shelter' to scurry to in the (rare) event of a direct hit by a solar flare?

(Though that still leaves the ongoing, though lower dosage threat of GCRs, yes?)

Well sure.  Or the hab designers could do a real job.  What's your preference?  :)

That would depend upon the frequency and duration of the solar flares (of which I am completely ignorant).  If on Mars surface they are completely random, once a month-ish events, with only 15 minutes of warning, and they last for several hours, I'd want all habitats to be 'flare-proof' for their inhabitants.  If on the other hand, they are once a decade event, with hours of notice, and last only 30 minutes, I don't think it would make sense to drastically increase the cost and complexity of the habitats (and decrease their aesthetics and 'livability', such as burying everyone under meters of opaque regolith). In this case I think an adequate 'storm shelter' would make the most sense.

Which of these two extremes best characterizes the flares?

(And again, I acknowledge this completely ignores the GCR issue.)

Actually I don't know that shielding has to force a "dramatic increase in cost and complexity" of habitats.  Not on Mars, anyway.  Now in flight, mass is precious and shielding is measured by the centimeter in every dimension, with some complexity.  On Mars however, shielding is readily available and essentially free.  Just fill the space, by any means.  It would be dirty work, but all potentially external to the habitat, and therefore not necessarily requiring an increase in habitat cost or complexity.

And I think that shielding work is required, if Mars habitats are going to house multi-synod crews or permanent settlers, and not just single-synod visitors.  Consider for example McGirl et al. 2016:  "Crew Radiation Exposure Estimates from GCR and SPE Environments During a Hypothetical Mars Mission".  The study long and short:  female crew members under 40 approach their lifetime 3% risk limit, even on a single-synod mission with 500-day stay.  That's at -7000 m elevation, beneath 15 cm of aluminum shielding. 

Add also the extra risk of poorly-understood HZE particle effects, and it's quite possible that most crew members will approach the 3% limit.  Inference being, most crew members would be restricted to one single-synod mission (500 days on the surface).  A two-synod mission (1300 days on the surface) would put all well beyond the 3% limit.

And come to think of it, if those crew members had cis-lunar experience, or any mission experience beyond LEO, their cumulative prior dosage could use up their "margin", and disqualify them for any Mars mission at all. 

Moreover flare events aren't the worst of it.  In the study, GCR doses are 7-18x as great as flare doses, depending on elevation.  (GCRs with nasty HZE wildcards.)   So to win more time on the surface, the crew would need to slash GCR exposure drastically, day-in, day-out.  Flare shelters wouldn't do the job.  They'd have to lay on the hab shielding.

I think.



Each Lake Matthew dome has a notional 5 m water/ice shield.   That seemed... adequate.  ( ? )  That shield would admit ~60% of incident light, at least in summer.  With blue skies.  In winter the ice would capture only a little light.  Reading light, I guess.   

Question:  Could such shielding give adequate "aesthetics and livability"?  Or what aesthetic goals would you prefer to shoot for?
« Last Edit: 12/14/2016 07:53 pm by LMT »

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #266 on: 10/31/2016 10:52 am »
A busy day at Mars Alpha. A few synods after the first flights.

The mostly underground base (not quite a city yet) has just received a new influx of colonists. 
The solar panel farm is just outside the frame of the pictures.  A glacier a few km away provides the water for the base and fuel production.

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #267 on: 10/31/2016 11:00 am »
Close up of the ITS-SS.

Offline The Amazing Catstronaut

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Re: Envisioning Amazing Martian Habitats
« Reply #268 on: 10/31/2016 11:43 am »
Gorgeous rendering - and possibly quite realistic.

How ballistics resistant/anchored/thermally/vibro resistant would the dome have to be without being prohibitive, to situate the domes closer to the landing zone? There isn't a distance problem as-is; you're going to need good rover capacity anyway.

The domes would be much easier to construct if they were manufactured with local glass. Perhaps with additives brought from earth.
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Offline Robotbeat

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Re: Envisioning Amazing Martian Habitats
« Reply #269 on: 10/31/2016 12:20 pm »
The plastic PVB layer used in safety glass could be made on Mars from the air and water. It needs H, CO, ethanol, ethylene and propylene (both made from methane), and ascetic acid. There are fancy ways of making ethanol and ascetic acid using catalysts and electrolysis.

You could make the plastic layer extra thick for strength, thermal insulation, toughness, and even some residual radiation shielding (although it'd have to be very thick, like a foot or a meter or so, to make any significant difference in radiation shielding). The thin glass layers could be shipped (carefully!) from Earth.
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Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #270 on: 10/31/2016 12:21 pm »
Gorgeous rendering - and possibly quite realistic.

How ballistics resistant/anchored/thermally/vibro resistant would the dome have to be without being prohibitive, to situate the domes closer to the landing zone? There isn't a distance problem as-is; you're going to need good rover capacity anyway.

The domes would be much easier to construct if they were manufactured with local glass. Perhaps with additives brought from earth.
The location illustrated is supposed to be the edge of a volcanic plateau, or the edge of a crater where the rock was properly mixed and melted.  Ideally the rock would need to be hard, but not too hard, so less SiO2, if possible.  If the base could be located near a SiO2 source, ideally sand, to reduce mining energy, that would help with local production of glass.  Hematite spheres could provide iron, but removing the Oxygen would be energy intensive, perhaps there are enough nickel iron asteroids on the surface to provide revenue for roving miners?
I expect the main structural design requirement will be anchoring of the domes due to atmospheric pressure.  Other forces should be minor.  As the ships land pretty much empty of fuel, landing may not be that much of a vibration source.  Take off requires a lot more power, and there is the risk of fuel explosion, so I put the take off pad a bit further away.  There would be a need for some kind of crawler from one pad to the other, perhaps a multiwheel vehicle rather than a caterpillar type vehicle?
I have no idea what is the sound power from a landing, so some of the design elements for airports may not apply.  In the present design I just eyeballed distances based on airports that I have seen over the years.  The underground structure comes from subway projects I have been involved with.  It's basically a big subway station ;-)
« Last Edit: 10/31/2016 12:23 pm by lamontagne »

Offline Robotbeat

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Re: Envisioning Amazing Martian Habitats
« Reply #271 on: 10/31/2016 12:40 pm »
How about a tunnel from the main dome to the landing/launch pads? You could keep the domes several kilometers away.
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Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #272 on: 10/31/2016 12:53 pm »
How about a tunnel from the main dome to the landing/launch pads? You could keep the domes several kilometers away.
As a transportation infrastructure, I expect a surface road and rovers is less expensive than a tunnel.  The pad won't be used all that much after all, so low traffic.  The pads might be further away, but then they wouldn't fit into the illustration any more.  A little artistic licence there, perhaps. At least I'm not landing Petawatt class spaceships in the middle of cities with km tall towers ;-) 

Offline kenny008

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Re: Envisioning Amazing Martian Habitats
« Reply #273 on: 10/31/2016 01:04 pm »
Might be best to just put the landing pads "around the corner" from the domes.  The domes would be shielded from direct impact from landing / launch debris by an intervening hill, yet still within a reasonable distance.  No real reason for the domes to face directly at the launch site.  Just drive the rovers from the domes, around the corner of the hill, and out to the launch site.

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #274 on: 10/31/2016 01:39 pm »
Might be best to just put the landing pads "around the corner" from the domes.  The domes would be shielded from direct impact from landing / launch debris by an intervening hill, yet still within a reasonable distance.  No real reason for the domes to face directly at the launch site.  Just drive the rovers from the domes, around the corner of the hill, and out to the launch site.
Would be fun to see the ships land though, I expect it would be quite an event.  There shouldn't be any debris from a normal landing.  A crash might be another matter though, wouldn't want to compound a catastrophe.  If the vehicle has little fuel and is down to a few hundred m/s, will it be a kaboom or a crumple?

Offline kenny008

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Re: Envisioning Amazing Martian Habitats
« Reply #275 on: 10/31/2016 02:22 pm »
Even well-engineered concrete may pretty quickly degrade after a few landings.  Even LZ-1 showed a little damage from the first landing.  I probably wouldn't want to risk a chunk of pad material being flung through my dome.
But yeah, it would look really cool.

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #276 on: 10/31/2016 02:31 pm »
Even well-engineered concrete may pretty quickly degrade after a few landings.  Even LZ-1 showed a little damage from the first landing.  I probably wouldn't want to risk a chunk of pad material being flung through my dome.
But yeah, it would look really cool.
Could there be a layer of water added to the pad just before a landing?  How quickly would it sublimate, or would it turn to ice and add the danger of flying ice blocks to the danger of flying concrete bits?

If the landing is as precise as on Earth, might just put in a thick mild steel plate at the center of the pad?
Guess it would be logical to just put the landing field further away.  There's no romance in safety.  Sigh.

Offline jpo234

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Re: Envisioning Amazing Martian Habitats
« Reply #277 on: 10/31/2016 02:45 pm »
If the landing is as precise as on Earth, might just put in a thick mild steel plate at the center of the pad?
Guess it would be logical to just put the landing field further away.  There's no romance in safety.  Sigh.

Hide the domes from the landing field. Only a utility entrance needs to face the pads.
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Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #278 on: 10/31/2016 03:05 pm »
If the landing is as precise as on Earth, might just put in a thick mild steel plate at the center of the pad?
Guess it would be logical to just put the landing field further away.  There's no romance in safety.  Sigh.

Hide the domes from the landing field. Only a utility entrance needs to face the pads.
Don't forget, these are the Amazing Martian Habitats.  Got to stretch the limits a little.  It should feel and look impressive, but be reasonably safe.  What is the likelihood of a chunk of concrete flying off and hitting the dome fast enough to break the glass?  There are a lot of safe angles, and the domes are 500 m away in the illustration.

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #279 on: 11/01/2016 12:54 am »
My new ellipsoid version of the domes.

Simpler to build.  Less risk.  Now needs an inside, unless someone convinces me these don't look good or will not work  :-)

 

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