Author Topic: Envisioning Amazing Martian Habitats  (Read 869857 times)

Offline LMT

  • Lake Matthew Team
  • Senior Member
  • *****
  • Posts: 2351
    • Lake Matthew
  • Liked: 424
  • Likes Given: 0
Re: Envisioning Amazing Martian Habitats
« Reply #520 on: 11/28/2016 05:22 pm »
Sabatier waste heat (which is optimally 300-400C)

Sabatier reaction is exothermic, but it can't run at a scale to heat Hew Thermopylae in winter because the energy input required to maintain the reaction is far too high, as I think you know.  It's more efficient to heat electrically, from PV, and skip intermediary processes.  But in winter the PV for tunnel heating just isn't there.

As you stated the Sabatier reaction is exothermic. It does not need any energy input to run except the initial energy to get it to operating temperature.

Needeed is hydrogen from water electrolysis, this indeed needs a lot of energy. You can produce the hydrogen during the day and keep the Sabatier reaction going all night.

The reaction needs hydrogen, heat and pressure, yes, and exothermy doesn't get us there, unfortunately.  As example, Zubrin's unit is predicted to output 1 kg/hr, while requiring 700 W electrical, continuous.

And his hydrogen comes from a bottle, gratis.
You are ignoring scale which is why Zubrin needed input power for a very exothermic reaction. If you're doing megawatts of Sabatier youll need to dump heat to keep your reactor from melting

A Sabatier reactor is not a nuclear reactor.  It's chemistry:  net useful energy output < electrical energy input.  Losses occur at each step, and no practical design catches all the waste heat at each step.  So we minimize steps, ideally down to just one:  convert PV electrical power directly to heat, for example in a tunnel heating wire. 

But of course PV itself is a problem in winter, because there doesn't seem to be nearly enough

Disagree?  Well, you can sum the energy inputs and outputs in a Sabatier/electrolysis system, and just see. 
« Last Edit: 12/14/2016 07:49 pm by LMT »

Online lamontagne

  • Senior Member
  • *****
  • Posts: 4269
  • Otterburn Park, Quebec,Canada
  • Liked: 3840
  • Likes Given: 716
Re: Envisioning Amazing Martian Habitats
« Reply #521 on: 11/28/2016 05:39 pm »
If we need 25 MW of installed solar power to run a 300 person base, and these are about 0,1 kw per m2 (summer), then we need 250 000 m2 of solar panels?  A bit more than 500m x 500m?  does that seem about right? And a 10 000 person base would be about 3 x 3 km?  And the 1 million people target city 30 km x 30 km?

Most likely spread out among a number of smaller communities, or will Mars generate a single big city and a number of mostly robotic outposts?







Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25240
  • Likes Given: 12115
Re: Envisioning Amazing Martian Habitats
« Reply #522 on: 11/28/2016 06:04 pm »
Sabatier waste heat (which is optimally 300-400C)

Sabatier reaction is exothermic, but it can't run at a scale to heat Hew Thermopylae in winter because the energy input required to maintain the reaction is far too high, as I think you know.  It's more efficient to heat electrically, from PV, and skip intermediary processes.  But in winter the PV for tunnel heating just isn't there.

As you stated the Sabatier reaction is exothermic. It does not need any energy input to run except the initial energy to get it to operating temperature.

Needeed is hydrogen from water electrolysis, this indeed needs a lot of energy. You can produce the hydrogen during the day and keep the Sabatier reaction going all night.

The reaction needs hydrogen, heat and pressure, yes, and exothermy doesn't get us there, unfortunately.  As example, Zubrin's unit is predicted to output 1 kg/hr, while requiring 700 W electrical, continuous.

And his hydrogen comes from a bottle, gratis.
You are ignoring scale which is why Zubrin needed input power for a very exothermic reaction. If you're doing megawatts of Sabatier youll need to dump heat to keep your reactor from melting

A Sabatier reactor is not a nuclear reactor.  It's chemistry:  net useful energy output < electrical energy input.  Losses occur at each step, and no practical design catches all the waste heat at each step.  So we minimize steps, ideally down to just one:  convert PV electrical power directly to heat, for example in a tunnel heating wire. 

But of course PV itself is a problem in winter, because there doesn't seem to be nearly enough

Disagree?  Well, you can sum the energy inputs and outputs in a Sabatier/electrolysis system, and just see.
Youre not getting it.   You need to make the methane anyway and you get waste heat as a byproduct
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25240
  • Likes Given: 12115
Re: Envisioning Amazing Martian Habitats
« Reply #523 on: 11/28/2016 06:13 pm »
Where do the losses go? Waste heat. Which we can use.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25240
  • Likes Given: 12115
Re: Envisioning Amazing Martian Habitats
« Reply #524 on: 11/28/2016 06:26 pm »
Also build on the equator melas  and use lighter weight PV
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline LMT

  • Lake Matthew Team
  • Senior Member
  • *****
  • Posts: 2351
    • Lake Matthew
  • Liked: 424
  • Likes Given: 0
Re: Envisioning Amazing Martian Habitats
« Reply #525 on: 11/28/2016 08:01 pm »

...you can sum the energy inputs and outputs in a Sabatier/electrolysis system, and just see [net heat recovered for Hew Thermopylae].
 

Youre not getting it.   You need to make the methane anyway and you get waste heat as a byproduct


Just try to sum the energies into and out of the Sabatier/electrolysis system (including heat lost and recovered), and then I think you'll ballpark the fraction of tunnel heat you get from Sabatier PV, relative to what direct PV heating can give.  Which itself isn't enough, but still.
« Last Edit: 12/14/2016 07:49 pm by LMT »

Offline sghill

  • Full Member
  • ****
  • Posts: 1682
  • United States
  • Liked: 2092
  • Likes Given: 3200
Re: Envisioning Amazing Martian Habitats
« Reply #526 on: 11/28/2016 08:11 pm »
We've been off-topic for a while.  We have a thread for power source discussions.

http://forum.nasaspaceflight.com/index.php?topic=34836.420
Bring the thunder!

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25240
  • Likes Given: 12115
Re: Envisioning Amazing Martian Habitats
« Reply #527 on: 11/28/2016 08:28 pm »

...you can sum the energy inputs and outputs in a Sabatier/electrolysis system, and just see [net heat recovered for Hew Thermopylae].
 

Youre not getting it.   You need to make the methane anyway and you get waste heat as a byproduct


Just try to sum the energies into and out of the Sabatier/electrolysis system (including heat lost and recovered), and then I think you'll ballpark the fraction of tunnel heat you get from Sabatier PV, relative to what direct PV heating can give.  Which itself isn't enough, but still.
You still are attacking something I'm not saying.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25240
  • Likes Given: 12115
Re: Envisioning Amazing Martian Habitats
« Reply #528 on: 11/28/2016 08:32 pm »
We've been off-topic for a while.  We have a thread for power source discussions.

http://forum.nasaspaceflight.com/index.php?topic=34836.420
Sabatier isn't a power source.  it produces waste heat
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline JasonAW3

  • Senior Member
  • *****
  • Posts: 2443
  • Claremore, Ok.
  • Liked: 410
  • Likes Given: 14
Re: Envisioning Amazing Martian Habitats
« Reply #529 on: 11/28/2016 08:46 pm »
We've been off-topic for a while.  We have a thread for power source discussions.

http://forum.nasaspaceflight.com/index.php?topic=34836.420
Sabatier isn't a power source.  it produces waste heat

Waste heat is still usable.  If it can be redirected as actual heat for the colony, that is.

      What seems to escape many peoples' notice, Mars is VERY, very cold.  Every bit of heat that can be scavenged, from whatever source available, should be scavenged.

      Obviously, some heat sources are so low in thermal production, or too far or mobile, to be of use, but all fixed sources, putting out significant amounts of waste heat, should be utilized, if at all possible or practical.
My God!  It's full of universes!

Offline LMT

  • Lake Matthew Team
  • Senior Member
  • *****
  • Posts: 2351
    • Lake Matthew
  • Liked: 424
  • Likes Given: 0
Re: Envisioning Amazing Martian Habitats
« Reply #530 on: 11/28/2016 08:47 pm »
Isn't 15 kW x 3600s x 6 hrs = 324 million joules?  so 2000 tonnes rather than 40 000 tonnes?

It'd be ~15 kW at high noon, but it drops off after.  And I see I got the drop-off wrong.  Correction:  more like 160 million Joules/day, for 130 million Joules of useful heat at 80% conversion.  So maybe 5400 tons of PV.  All just ballpark.  Corrected above.

If you had sun tracking solar panels, you could probably do better than these numbers; less mass or more energy.

Actually I've read that stationary panels are doing well now at capturing off-axis light, without sun tracking hw.  So I just assumed that, and didn't allocate any mass for sun trackers.

... the lower grade losses can be used to heat the base...

Was wondering about that low-grade waste heat.  If it heats exchange-loop water to, say, room temperature, is that enough to prevent freeze-burst as the loop conducts heat into the cold rock?  Wouldn't we want water near boiling point in the loops?  But am unsure what temperature range you had in mind.

[Or maybe these things lead to sghill's other thread.]

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25240
  • Likes Given: 12115
Re: Envisioning Amazing Martian Habitats
« Reply #531 on: 11/28/2016 09:05 pm »
We've been off-topic for a while.  We have a thread for power source discussions.

http://forum.nasaspaceflight.com/index.php?topic=34836.420
Sabatier isn't a power source.  it produces waste heat

Waste heat is still usable.  If it can be redirected as actual heat for the colony, that is.

      What seems to escape many peoples' notice, Mars is VERY, very cold.  Every bit of heat that can be scavenged, from whatever source available, should be scavenged.

      Obviously, some heat sources are so low in thermal production, or too far or mobile, to be of use, but all fixed sources, putting out significant amounts of waste heat, should be utilized, if at all possible or practical.
Meh, average temperatures even during winter are no worse than Earth South Pole during winter night. And Mars is near vacuum so lower thermal transfer rates
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline LMT

  • Lake Matthew Team
  • Senior Member
  • *****
  • Posts: 2351
    • Lake Matthew
  • Liked: 424
  • Likes Given: 0
Re: Envisioning Amazing Martian Habitats
« Reply #532 on: 11/28/2016 09:14 pm »
Yurt?  Dirt?

We've been off-topic for a while.  We have a thread for power source discussions.

http://forum.nasaspaceflight.com/index.php?topic=34836.420
Sabatier isn't a power source.  it produces waste heat

Waste heat is still usable.  If it can be redirected as actual heat for the colony, that is.

      What seems to escape many peoples' notice, Mars is VERY, very cold.  Every bit of heat that can be scavenged, from whatever source available, should be scavenged.

      Obviously, some heat sources are so low in thermal production, or too far or mobile, to be of use, but all fixed sources, putting out significant amounts of waste heat, should be utilized, if at all possible or practical.

Cold sure enough.  And yes, you'd scavenge heat wherever practical, sure. 

Actually I'm wondering if maybe the heating problem is so bad that it renders this tunnel-hab concept more trouble than it's worth.  "By an order of magnitude," even.   :)   -60 C rock is just such an excellent heat conductor, and when it surrounds the crew on nearly every side, day and night... 

Well, maybe Hew Thermopylae is just an exercise in "problems of Xtreme hab design," without a ready solution. 

Question:  Anybody vote to exit the mesa now, and apply our painful knowin' to more forgiving hab designs, outside?


Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13463
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 11864
  • Likes Given: 11086
Re: Envisioning Amazing Martian Habitats
« Reply #533 on: 11/28/2016 09:14 pm »
Enough about heat and power production. Don't do an offtopic post and link to another thread, just post in the other thread.

Thanks.

Edit: Heat is fine, agreed, heat rejection/generation/storage is important and doesn't have other homes at present. But any of the usual Nuclear/Solar is better/worse cheaper/costlier safer/dangerous-er stuff? Right Out.

Thanks
« Last Edit: 11/29/2016 08:32 pm by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Lumina

Re: Envisioning Amazing Martian Habitats
« Reply #534 on: 11/29/2016 03:57 am »
Enough about heat and power production. Don't do an offtopic post and link to another thread, just post in the other thread.

Thanks.

Thank you. Proposals for amazing habitat concepts - especially when paired with a specific proposed location on Mars - would be great additions to this thread.

(Edit: this thread should not concern itself with energy and heat sources. There are many options and degrees of freedom to solve any energy supply or thermal balance problem on Mars. For the purposes of this thread let's assume that energy/heat are solved and just go ahead to propose amazing hab concepts)
« Last Edit: 11/29/2016 04:04 am by Lumina »

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25240
  • Likes Given: 12115
Re: Envisioning Amazing Martian Habitats
« Reply #535 on: 11/29/2016 04:29 am »
There are no threads that concern chiefly with heat. This is the only one that really focused on it. Makes sense as heat management is one of the chief constraints of habitat design. I challenge the idea that it's off-topic here! Power, on the other hand, has like a billion cajillion threads devoted to it and isn't so directly coupled to habitat design (solar makes the most sense in vast fields and nuclear would be placed a safe distance from the habitat).

By the way. My keyboard was broken, so I wasn't able to properly respond. So let me do it now.

Musk has mentioned three habitats.
1) The ITS itself (clearly off-topic here)
2) Glass domes (has its own thread)
3) Tunnels (which seems to be the focus of this thread)

In reference to the last one, Musk mentioned that the tunnels would be used for industrial equipment. Even though this thread has had a lot of speculation about living in tunnels, it seems like Musk is implying people would live in the glass dome with tunnels for industry.

What do we know about industrial equipment on Mars? The biggest (besides the off-topic power production) are:
1) Electrolysis of water
2) Sabatier reaction of water with CO2
3) possibly extraction of water from the soil, although it seems to me this is best done out on the surface

Any kind of energy-intense industrial process is going to have waste heat. And the easiest place to dump it is not the thin Martian air but the air of the pressurized industrial tunnels, even though they'll be at higher temperature than the outside air. Filling up the ITS in a synod is going to take about half to a full Megawatt of electricity. Most of that is losses and doesn't end up as methane chemical energy. So if you have a thousand ITSes refueled every synod, that's hundreds of megawatts of heat you get automatically for free. No extra power required. It's already needed.

In Minnesota, we sometimes get a week where it doesn't get above zero. And the wind is brutal, carrying any heat quickly from your body. But the Mall of America was designed entirely without a heating system. It relies entirely on waste heat from sunlight coming in the massive skylights, artificial lighting, internal equipment, and warm bodies. I think a Mars settlement would be similar.


I like the Sabatier reaction as an example because it operates at high temperatures and so you have more options about what you do with the waste heat. You can, for instance, put it deep within the regolith underlying the settlement. So deep that the heat pulse produced by summer's excess electrical capacity (dumped still in the Sabatier process) doesn't reach the surface until the middle of winter when it's needed most. So the regolith itself is acting as a reservoir of heat and a sort of delay buffer to even out the heat flow.

And you don't need to really worry about pipes freezing. It's likely you'd use ethylene glycol or propylene glycol for the heat loop. Both are fairly easy to make via ISRU. Or even methanol. And the deep soil is already naturally at a high enough temperature to prevent freezing in that case. And even more so once you've dumped any kind of significant amount of heat into the soil. The ground will stay relatively warm for years.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline TripD

  • Full Member
  • ****
  • Posts: 872
  • Peace
  • Liked: 851
  • Likes Given: 677
Re: Envisioning Amazing Martian Habitats
« Reply #536 on: 11/29/2016 05:13 am »
Quote
In reference to the last one, Musk mentioned that the tunnels would be used for industrial equipment. Even though this thread has had a lot of speculation about living in tunnels, it seems like Musk is implying people would live in the glass dome with tunnels for industry.

I have experienced first hand how just a spring melt can cause an otherwise relatively safe mine to become active and worthy of concern.  Even several hundred feet below a mountain, water finds it way into the mine and can cause minor to major cave ins.  Granted water will not be the issue on mars, but changes caused by heat may well be.  If your plan is to constantly pump heat into tunnels, I hope you aren't planning on making those places habitats.

Offline LMT

  • Lake Matthew Team
  • Senior Member
  • *****
  • Posts: 2351
    • Lake Matthew
  • Liked: 424
  • Likes Given: 0
Re: Envisioning Amazing Martian Habitats
« Reply #537 on: 11/29/2016 07:14 am »
Siting Industrial Equipment For Habs

Quote
In reference to the last one, Musk mentioned that the tunnels would be used for industrial equipment. Even though this thread has had a lot of speculation about living in tunnels, it seems like Musk is implying people would live in the glass dome with tunnels for industry.

I have experienced first hand how just a spring melt can cause an otherwise relatively safe mine to become active and worthy of concern.  Even several hundred feet below a mountain, water finds it way into the mine and can cause minor to major cave ins.  Granted water will not be the issue on mars, but changes caused by heat may well be.  If your plan is to constantly pump heat into tunnels, I hope you aren't planning on making those places habitats.

Tunnel-hab is not my preference, no.  You wouldn't have spring melt, but I imagine the walls might "sweat" when heated.  Could get messy -- or messier.   :o

If these pressurized tunnels aren't used as habs, but only as equipment bays, why build them?  Why not just design the industrial machines to work on the surface, perhaps in a pressurized cargo module, perhaps under a loose protective tent?  What could justify the great expense and difficulty of the dig, if inhabitation isn't the goal?
« Last Edit: 12/14/2016 06:30 pm by LMT »

Online lamontagne

  • Senior Member
  • *****
  • Posts: 4269
  • Otterburn Park, Quebec,Canada
  • Liked: 3840
  • Likes Given: 716
Re: Envisioning Amazing Martian Habitats
« Reply #538 on: 11/29/2016 09:52 am »
Don't want to live in holes?  Here is Megatower!

1 km high.  Self supporting through air pressure, megatower has an external pykrete skeleton made up of 3 free standing columns than serves as backup if the internal pressure is lost. Internal arrangement is independent from the outer shell.

Megatower is protected from radiation by a minimagnetosphere that cover about 10 km2.  The little white smudge besides the tower is an ITS spaceship.  The slightly larger shape is a pickle type tower.

Each core is 60m in diameter and weighs 25000 tonnes.  It is supported by the air pressure exerted on the dome at the top of the tower.  The windows are light polycarbonate, the structure composite.

The pykrete columns are water and sand, reinforced with basalt fiber rods.  Wind loading is negligeable despite the structure's size.  As the columns are exterior to the habitat, they do not melt.
« Last Edit: 11/29/2016 01:17 pm by lamontagne »

Offline LMT

  • Lake Matthew Team
  • Senior Member
  • *****
  • Posts: 2351
    • Lake Matthew
  • Liked: 424
  • Likes Given: 0
Re: Envisioning Amazing Martian Habitats
« Reply #539 on: 11/29/2016 01:33 pm »
Oz Beneath the Magnetic Cloud of Protection

Don't want to live in holes?  Here is Megatower!

1 km high.  Self supporting through air pressure, megatower has an external pykrete skeleton made up of 3 free standing columns than serves as backup if the internal pressure is lost. Internal arrangement is independent from the outer shell.

Megatower is protected from radiation by a minimagnetosphere that cover about 10 km2.  The little white smudge besides the tower is an ITS spaceship.  The slightly larger shape is a pickle type tower.

Each core is 60m in diameter and weighs 25000 tonnes.  It is supported by the air pressure exerted on the dome at the top of the tower.  The windows are light polycarbonate, the structure composite.

The pykrete columns are water and sand, reinforced with basalt fiber rods.  Wind loading is negligeable despite the structure's size.  As they are exterior to the habitat, they do not melt.

Pykrete, it's not just for aircraft carriers now?  :)  And the facility is a lovely form, very Oz!  8)

As I understand it, pykrete gets its essential strength and low thermal conductivity from wood pulp fiber.  And I can understand why you might not want to ship pulp, and reinforce instead with ISRU basaltic fiber rods.  But why replace pulp with sand?  Wouldn't sand raise thermal conductivity significantly, without strength benefit?  Summertime seems challenging, with sand forcing measurable ice melt / sublimation on the columns, on those days when the surface regolith (sand) can exceed 20 C.

As for the magnetosphere, are you considering the notional balloon-encapsulated variant on Bamford et al., or something else?  If you go with an encapsulated form, can you add such a form to the illustration?  Should be a conversation-piece:  "Oz Beneath the Magnetic Cloud of Protection".   ;)
« Last Edit: 12/14/2016 06:30 pm by LMT »

 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0