Settlement design

louis · 2021-04-10 06:15:53

I think it is important to define goals. Musk has talked about a million person city, but oddly he doesn't seem to be very goal orientated. He appears to have a laissez faire idea that the million people will be the right people and will wish to emigrate.

Until the Covid pandemic hit and we were jettisoned into a new kind of dystopia, I thought that was absolutely crazy - highly paid people on Earth with the right STEM skills, with settled family lives, lovely homes, and rich & varied lives full of lovely holidays, friends and family are not going to up roots and head off to Mars. The new dystopia has made Mars a little more inviting a prospect but still there is a lot of inertia built in.

I can now see there might be a few more takers but I remain sceptical about Musk whole approach of what I would call "moving California to Mars".

I think a sensible goal would be to aim for 100,000 people as the point at which Mars could probably become fully self-sufficient (if it wished) and continue human culture in all its aspects. Getting to that point will be extremely challenging in my view. There are a number of big hurdles:

1. Establishing that there are no long term negative health effects from living in 0.38 gravity.

2. Establishing that natural light farming can be undertaken successfully.

3. Attracting the people with the "right stuff" to move to Mars. There's no point in sending one million illiterate peasants to Mars. Their skills will not be required. Farming will be largely robotic and controlled through computer programs. What will be required are people with the right STEM skills but also highly creative people who can enrich the culture and make Mars an interesting place to be. The problem is that ideally you will want people to move there permanently.

4. Ensuring foetal development can proceed without risk and that we can safely reproduce on Mars.

My feeling is that it will be important to get people to live there on a long term basis, staying for maybe 4-6 years in the first instance.

Ideally we will early on have presitigious universities like MIT, Cambridge, Paris, Bologna establishing a presence on Mars. Here talented engineers and scientists will pursue post grad studies. They will meet and establish bonds with others. Relationships will develop. Happy time of youth will be associated with being on Mars. They will take up job opportunities on Mars...you can see how people will begin to put down roots as they move in together. The next step will obviously be starting a family...if it's safe to do so, then I think more will tempted to start their family on Mars.

Getting to a community of maybe 100,000 with perhaps 50% being permanent residents is going to take a lot of effort. I'd be surprised if you get there in under 50 years. But of course I don't have the Musk Optimism Implant!

So, for me, establishing Mars as a post-grad uni centre, a centre of technical excellence and cutting edge science is vital. It needs to be a place of high salaries and advanced skills.

Noah wrote:

I saw some misconceptions about the size, so I determined a goal:
https://i.imgur.com/lZabsed.png
The number of people is not fixed, it is only to create a rough framework.
The goal can and should change over time.

Noah · 2021-04-10 07:23:57

louis wrote:

I think a sensible goal would be to aim for 100,000 people as the point at which Mars could probably become fully self-sufficient (if it wished) and continue human culture in all its aspects. Getting to that point will be extremely challenging in my view. There are a number of big hurdles:

I would add that one of the most important points is an economic/financial incentive. For example, resources that can be sold to the earth. But this is not in our hands, we must hope to find such resources.

louis wrote:

I'm at the other end of the scale - 6.
(…)
My vision for Mission One is it would depend a lot on Rovers and robots. I don't envisage there being much EVA surface action. The key task will be to locate, mine and transport water ice. All that can be done using human controlled rovers and robots. You don't need more than a couple of people working on that once you have found a good source. They will basically be supervising from the comfort of their pressurised Rover the work of robot drillers, diggers, lifters and transporters, dislodging soil and ice.

I agree that many tasks can be done by rovers and robots.
Most concepts I have heard of involve 4 to 6 people. Of course, that doesn't mean they are correct, so Oldfart1939's approach of 17 people seems interesting.

louis wrote:

In 2024, two crew ships and two cargo ships would follow, setting up a production plant to make fuel from the thin Martian atmosphere and begin building a base for future residents.

Ahh okay! You are right Louis.

louis wrote:

1. The One Million Person city isn't Noah's target as far as understand it. That target comes from Musk and in my view is crazily over-optimistic on his timescale (I think it was within 30 years).

Exactly, Therefore I created the goal.

Noah · 2021-04-10 07:31:29

kbd512,

Regarding the energy issue: I read your comment, but I don't have enough experience to evaluate how realistic the calculations are. But I will look into it and then come back to your suggestions.

kbd512 wrote:

You won't see a city with a million people on Mars within your lifetime using current chemical rocket technology. You won't see it with nuclear thermal rocket technology, either. Neither are remotely close to being efficient enough for the stated purpose.

I agree that it is now very very difficult (almost impossible) to achieve such an ambitious plan. But I also would not say it is not possible in my lifetime! We should not underestimate what can invent/improve in 80+ years.

louis · 2021-04-10 07:42:53

How much PV array would you need to install for one million people ? And how much for 100,000 people?

kbd,

Right, apologies for misinterpreting your post.

So taking the smaller 500 sq km figure, that's 22360 x 22360 metres, which gives a per person figure of near enough 500 sq. metres per person which would produce 250 KwHes per sol (assuming you can get 0.5 KwH per sol per sq. metre of PV panel).

Lop off 25% for energy storage, and I make that 187.5 KwHes per sol, or a constant of 7.6 KwHes.

Still seems a bit excessive to me but I wouldn't rule it out necessarily.

I seemed to be working on the right figures for the daily roll-out of PV panels (ie 500 sq kms) in a previous post, so I think my calculation stands: a team of 40 robot rovers could handle the daily roll-out of PV panelling with support from another 20 robots delivering the PV panel rolls to the site where you are expanding your array.

Your assertions about dust are not proven. NASA's solar panels on Mars worked well, far beyond their stated lifetime. The only cleaning available was a perodic angled move to get the dust off. There are already autonomous cleaning systems for panels on Earth.

https://wonderfulengineering.com/how-to … r-of-sand/

I think something like the Eccopia system but maybe attached to autonomous robots would be OK. Daily cleaning completely removes dust-caused loss of power on Earth.

I have never been a proponent of a million people on Mars within 30 years, so I am only really saying it's possible to manage the energy demand with solar power but more realistically I think we will see a slower development. It's much more likely we'll be at 100,000 after 30 years.

I have never said that I believe we will meet energy demand 100% from solar power. There are other options:

1. If we discover concentrated sources of methane on Mars, we can use these in methane electricity generators. If these generators are placed in habs with vegetation the oxygen for combustion could be produced by the plants thriving under natural light conditions (ie using photosynthesis to power the process).

2. Sublimation engines, similar to steam engines on Earth, should definitely work on Mars.

https://www.weforum.org/agenda/2015/03/ … s-on-mars/

3. Various designs of differential heat engines might work well on Mars given the temperature range.

4. Although wind is a lot less powerful on Mars, it might be useful to develop some wind energy facilities as dust storms are associated with higher wind speeds.

5. As on Earth, energy from waste e.g. incineration will be an option.

Taking all the above into consideration that might provide 20% of your energy needs.

So, on my timeline you might need 3840 sq metres of PV panels to be installed per sol, to meet the needs of a 100,000 person community. If your PV panelling needs replacing after 20 years, all falls in efficiency over that period you could be looking at a larger figure - perhaps 6000 sq metres or thereabouts. But laying out an array of 77 metres x 77 metres every sol is definitely doable.

SpaceNut · 2021-04-10 08:49:31

On earth we are using the free solar energy of the sun accross the entire world and yet we still require the 7 to 10Kw a day per person so with Mars we are starting out with a smaller world and less energy per meter that means you will need more from the solar array to make up for the natural energy that has not been figured into the power needs.
That natural power is of the sun is stored and made to create food which must take place at an energy expense not figured out for mars.

Noah size goal appended in first post:

Size goal needs a time scale for the transition from one phase to the next as that tells man the number of flights needed to achieve the goal.

Oldfart1939 · 2021-04-10 09:21:42

The one great advantage the Martians will have is much easier access to the asteroid belt. A recent episode of The Angry Astronaut examined this in detail. These asteroids seem to be a real treasure trove of rare Earth elements and in a very pure state, and access to them will be at a lot lower deltaV than from either Earth or the Moon. This could actually become the greatest source of revenue for the Mars colony, harvesting Rhodium and other equally scarce elements, and then transshipment to Earth after purification and processing.

Here's the link: https://www.youtube.com/watch?v=tKkltnTqarY

GW Johnson · 2021-04-10 09:30:41

"1. If we discover concentrated sources of methane on Mars, we can use these in methane electricity generators. If these generators are placed in habs with vegetation the oxygen for combustion could be produced by the plants thriving under natural light conditions (ie using photosynthesis to power the process)."

THAT is one of the more ridiculous statements I have ever seen. What oxygen a greenhouse of plants can produce is measured in grams per day. What oxygen a 1-HP lawnmower engine burns at idle is dozens of grams per second. NOT EVEN CLOSE to the same ballpark!

GW

tahanson43206 · 2021-04-10 10:04:01

For GW Johnson re #82

Thanks for your taking that on! Louis sometimes gets carried away in his enthusiasm.

Louis, thanks for all your contributions over the years, including the ones that inspire kbd512, GW Johnson and others to create some of their very best writing to deal with the situations that occur.

(th)

Oldfart1939 · 2021-04-10 11:04:25

GW-
Your comment is dead on the mark, and Louis ignores the enormous amount of energy required to manufacture CH4 and compress it.
Energy is what defines the state of a society, and energy consumption/production is the benchmark for measurement. All of these ideas are based on a preexisting massive and efficient infrastucture as an industrial society. Then--what happens if the dust storm lasts more than several months and the premanufactured methane is depleted and the same for Oxygen? Everybody dies. That's the bottom line in all of these proposals.
These arguments suggesting otherwise are, unfortunately, wishful thinking.

Noah · 2021-04-10 13:19:39

SpaceNut wrote:

Noah size goal appended in first post:
Size goal needs a time scale for the transition from one phase to the next as that tells man the number of flights needed to achieve the goal.

Good idea to pin the post, thanks!

I intentionally left out the timetable. Hypothetically, if I had the opportunity to build a Mars building, I would still have no influence on how the rocket sector develops and thus almost no influence on the timetable. Maybe in the future, when things become clearer, I would create a timetable.
I could create a timetable for after the first touchdown of humans, but that would also be highly speculative. For now, I want to focus on the first step: Home for the settlers.

louis · 2021-04-10 13:23:54

I think your "7 to 10 Kw" figure on Earth should be 7 to 10 Kwhs per day, and is not a constant energy - also it is not per person but per household. Kbd's figure suggest energy usage of 187.5 KwHs per person on Mars. For an average sort of household of 2.5 people that would be 455 KwHes per household per sol! Of course, I accept that not all the energy will be used directly in the household, especially in a Mars colony but, even so, that is a huge amount of energy for a household equivalent and I doubt anything like that much will be needed.

SpaceNut wrote:

On earth we are using the free solar energy of the sun accross the entire world and yet we still require the 7 to 10Kw a day per person so with Mars we are starting out with a smaller world and less energy per meter that means you will need more from the solar array to make up for the natural energy that has not been figured into the power needs.
That natural power is of the sun is stored and made to create food which must take place at an energy expense not figured out for mars.
Noah size goal appended in first post:
Size goal needs a time scale for the transition from one phase to the next as that tells man the number of flights needed to achieve the goal.

Last edited by louis (2021-04-10 13:25:11)

Noah · 2021-04-10 13:29:26

RobertDyck,
regarding the Hillside Settlement 1:
Sounds great your concept and very nice pictures for 2005. I can't open the file type unfortunately, maybe you have another type? I would like to have a closer look.

Noah · 2021-04-10 13:58:36

SpaceNut wrote:

I think its time to slow down so that Noah can get caught up and give insight into what might not be of concern in his proposal to enter the forum....

For me, every comment is valuable, related to the topics in post #1. I would like (and it is my responsibility) to provide a source for all settlement design topics. Therefore, all comments with a source are optimal for me.

RobertDyck · 2021-04-10 15:03:25

Noah wrote:

RobertDyck,
regarding the Hillside Settlement 1:
Sounds great your concept and very nice pictures for 2005. I can't open the file type unfortunately, maybe you have another type? I would like to have a closer look.

File type is .ppt which is Microsoft PowerPoint. It's not .pptx which is the newer format, for Microsoft Office 2007 and later. Remember, the Mars Homestead Project is from 2005. However, all versions of PowerPoint can open the older format. You can download a PowerPoint Viewer free directly from Microsoft. The free viewer can view only, you would have to buy the full version to create content. US version is here: PPTX Viewer

Or you could use LibreOffice. The full version is entirely free. They operate on donations only. LibreOffice has equivalent programs to everything in Microsoft Office. There are some differences, and content written for Microsoft PowerPoint may look a little different when viewed with LibreOffice Impress. Eg, fonts may be a little different, table alignment, etc. But differences are small. LibreOffice was originally written for Linux, but has been ported to both OS-X for Apple Macintosh, and Microsoft Windows. LibreOffice on Windows takes a little more memory than Microsoft Office, but has the advantage that the full version is entirely free. LibreOffice includes Writer (word processor), Calc (spreadsheet), Impress (presentation), Base (database), as well as Math and Draw. Download here: LibreOffice Download

I gave a number of links, including a link directly to Document Library. Go through it, there are several documents. One is a presentation made to SAE. That presentation is different, includes useful things such as an image of a construction tent used for construction of the habitat. It's format is PDF, so you shouldn't have trouble. You could go to the SAE website and pay $33 US funds, or download free from the Mars Homestead website here: Mars Homestead Architecture Presentation

Also look at the directory of images. There are more than those embedded in my post. Images by architect Georgi Petrov: Hillside Settlement 1

Artwork by Phil Smith: Commissioned or MF Owned Artwork

louis · 2021-04-10 16:11:47

Feel free to join in. Kbd has arrived at a situation where he thinks a figure of 455 KwHes usage per household per sol of 2.5 people is a reasonable figure for a mature Mars colony. That's nearly half a MwH!

People seem to forget it's Musk, far more than me, who must be getting "carried away in his enthusiasm" since he's the one who wants to build a city of one million with solar power.

So far, all we've had is "it's going to be a very big PV farm" and "it won't look nice" and some rather inflated energy usage figures.

tahanson43206 wrote:

For GW Johnson re #82
Thanks for your taking that on! Louis sometimes gets carried away in his enthusiasm.
Louis, thanks for all your contributions over the years, including the ones that inspire kbd512, GW Johnson and others to create some of their very best writing to deal with the situations that occur.
(th)

louis · 2021-04-10 16:31:22

The one thing we have a lot of on Mars for sure is land.

I'm not sure your scepticism is well placed.

https://www.theconsciouschallenge.org/e … l-overview

The above link states 7.5 trees produce enough oxygen for one human being to breathe.

There are estimated to be over 3,000 billion trees on planet Earth.

Is it really such an outlandish idea that you might have 7.5 million trees on Mars to produce the oxygen for a million people?

I'm using trees as shorthand - it could be grass, other plants or algae - anything that can get on and use photosynthesis to create oxygen without much human intervention.

Of course, this would be predicated on us developing suitable low cost farm habs/forest habs, probably plastic housing and using concentrated CO2. It might require use of thermogenic plants to raise temperatures at night. It's not my area of expertise but others have said this sort of set up is feasible on Mars.

I accept there are many challenges but getting nature to produce the oxygen could be a lot less energy intensive than the alternatives. If we can produce it for ourselves, then there is no reason we can't produce oxygen for fuel burning (not just methane - can also be used with metals, another alternative).

I never said methane-oxygen generation would provide 100% of the energy. But it might make say a 5% contribution.

GW Johnson wrote:

"1. If we discover concentrated sources of methane on Mars, we can use these in methane electricity generators. If these generators are placed in habs with vegetation the oxygen for combustion could be produced by the plants thriving under natural light conditions (ie using photosynthesis to power the process)."
THAT is one of the more ridiculous statements I have ever seen. What oxygen a greenhouse of plants can produce is measured in grams per day. What oxygen a 1-HP lawnmower engine burns at idle is dozens of grams per second. NOT EVEN CLOSE to the same ballpark!
GW

Last edited by louis (2021-04-10 16:32:04)

louis · 2021-04-10 16:35:50

If people here are saying Space X will not be able to build a colony on Mars with solar power they really need to be clear about that. They are saying Space X will fail.

But at what point? On Mission One? Ten years in? Thirty years in?

I'd like some clarity on that.

Many people have predicted Musk's failure in many fields, but in nearly all cases he's proven the critics wrong. I personally think this will be another example of disproving the critics.

kbd512 · 2021-04-10 16:37:35

Noah wrote:

kbd512,
Regarding the energy issue: I read your comment, but I don't have enough experience to evaluate how realistic the calculations are. But I will look into it and then come back to your suggestions.
kbd512 wrote:
You won't see a city with a million people on Mars within your lifetime using current chemical rocket technology. You won't see it with nuclear thermal rocket technology, either. Neither are remotely close to being efficient enough for the stated purpose.
I agree that it is now very very difficult (almost impossible) to achieve such an ambitious plan. But I also would not say it is not possible in my lifetime! We should not underestimate what can invent/improve in 80+ years.

Noah,

I'm trying to infuse a little engineering reality into the goal of operating a city on another planet. If the practical capabilities of the technology you want to use can't support that goal, and it becomes increasingly unlikely to do so as the scale of your goal increases, then the solution is to pursue a different technology that can. I never said that we shouldn't start solving the problems, but we need to accept the realistic limits of every potential technology used to achieve that goal. If you pursue technology that at least has the possibility of making the dream a physical reality, then you're already on the path to achieving that dream.

The goal is to start a self-sustaining city on another planet. The major problems are that we're literally starting from scratch, most of our power and propulsion technologies are incredibly inefficient, Mars is very far away from both Earth and the Sun, and all sustainable cities are ultimately logistics equations to solve, which require given inputs of energy, materials, labor, and capital to produce a given output- such as the ability to transport and feed another 1,000 people who want to live in the city. When it comes to energy density and efficiency, power laws / orders of magnitude are incredibly important. If a new technology is 10 times more efficient at converting energy into mechanical power, or 10 times lighter / faster than what it replaced (for a given energy input), that makes applications that were previously completely infeasible an actual possibility.

The Raptor engine that SpaceX is planning to use to power Starship has a vacuum Specific Impulse of 380 seconds. That dictates how much fuel they burn to accelerate Starship to a given velocity, thus how much fuel vs payload that Starship can carry to a given destination. The RS-25s and RL-10s that NASA uses are only a little better at 450 seconds. A solid core nuclear thermal rocket, that only consumes LH2 fuel like the RS-25s and RL-10s, but no LOX since the nuclear reactor is supplying all of the heat to accelerate the Hydrogen gas, instead of combustion, is around 900 seconds.

At 380 seconds, more than 99% of everything you ship is propellant, not payload. It takes 3,600t of propellant to get 100t of payload into Low Earth Orbit (LEO). It then takes an additional 21,600t of propellant to refuel that Starship 6 times so it can then leave LEO for Mars. Every 1t of payload sent to the surface of Mars requires 252t of fuel to get it there. Around 1,000t of propellant for each fully fueled rocket is LNG / LCH4, the remainder is LOX, and you're going to launch 7 times for each 1 cargo flight to Mars. The payload fraction is 0.4%. If the propulsion system has double the specific impulse as nuclear thermal does (it's utterly impossible to actually takeoff from the surface of the Earth and achieve orbit using a solid core nuclear thermal rocket, by the way), then 151t of fuel are required for each ton of delivered payload. Even if you ignore money completely, which you can't since someone has to pay for this, there's an enormous energy cost to doing that, and that energy has to come from somewhere.

In terms of actual energy expenditure using electricity, every kilogram of payload "only" requires about 28kWh to achieve orbit around the Earth, so 28MWh per ton. In terms of a practical combustion engine, such as a gas turbine at 60% efficiency, that would equate to burning around 3,357kg, or about 3.3t of Methane, to electromagnetically accelerate 1t of payload to orbital velocity. There are many other reasons why that's not practical and some propellant would still have to be expended to achieve orbit, but maybe that gives you a better idea of why chemical rocket engines alone won't likely be used to colonize another planet, especially when the average person living on Earth is consuming 14.28t of manufactured goods per year (and you should presume that many more tons of machinery were required to make all of those manufactured goods).

Let's say we needed to deliver 1,000,000t of cargo to Mars to provide some initial supplies to a city of a million people. In America, our annual food consumption is ~906kg, so that's basically enough cargo to supply the people living there with food until the greenhouses are built and operating at full capacity. That's 10,000 flights, means 70,000,000t of LNG. The global LNG market in 2019 was 358,000,000t, so 19.6% of the global LNG market would've been tied up merely trying to feed a million of our people living on Mars. While it's doubtful that we'd send colonists there until we could feed them using locally produced food, we will have to import all of the machinery to make that possible, and nothing about that machinery is "lightweight". However, that should adequately illustrate why a significant improvement on rocket engine fuel economy is required, mostly through electrification of launch and in-space propulsion, such as solar-electric propulsion that uses high-powered ion engines. The use of solar is a lot more feasible in space where you receive full Sun 24/7/365, and the panels don't require protection from weather or abrasives there. Bringing in 1 million tons of machinery to start constructing a city is almost nothing at all. It's chicken scratch. No city on Earth has such a low tonnage of machinery and materials used to construct it here on Earth, where we don't require pressurized living spaces. You should start thinking in terms of billions of tons of constructions materials and tens of millions of tons of machinery to wrap your brain around the magnitude of the problem.

tahanson43206 · 2021-04-10 17:05:53

For kbd512 re #93

SearchTerm:Scope of challenge of supplying 1,000,000 with supplies to set up shop on Mars and sustain life there

If anyone else has suggestions for SearchTerms to properly categorize kbd512's essay please do not hesitate to provide them.

(th)

kbd512 · 2021-04-10 17:40:34

louis wrote:

Feel free to join in. Kbd has arrived at a situation where he thinks a figure of 455 KwHes usage per household per sol of 2.5 people is a reasonable figure for a mature Mars colony. That's nearly half a MwH!

Louis,

Our summer time energy usage is 27.5kWh per day. Our daily electricity usage is 5.5kWh per person. If you divide by 24, we're using 229.2Wh/hr. I go through your make-believe energy allotment in two weeks.

When you live in a ship or a submarine, you're living in a wind tunnel. Those fans that move the air to keep you alive require a LOT of power, much more than the waste water treatment in point of fact, though not as much as the flash evaporators that provide drinking water from brine.

If we lived on Mars instead of Earth, 229W of continuous power is NOT ENOUGH to power CAMRAS and IWP.

Please let us know when that sinks in.

louis · 2021-04-10 17:55:21

Kbd -

That figure you give for average per capita food intake in the USA - 906 Kgs sounds way over the top to me. That works out at 2482 grams per person per day. That's an enormous amount of food!!! The UK Health authorities for instance recommend a daily intake of only 70 grams of meat. Meat and cheese are probably the densest foods we eat every day.

I think that is probably a figure for food and drink. Also I think that Americans being large consumers of milk probably skews things a bit from world averages. But that 906 Kgs probably includes all the litre bottles of coke as well.

The reason I am labouring this point is that the figure probably includes liquids and water can be recycled both in transit and on Mars.

Moreover, there is no reason not to use dehydrated foods. They formed a large part of the diet in WW2 in the UK. If you make your food supply 30% dehydrated that hugely reduces the tonnage requirements. Likewise, if you also skew your diet towards some highly calorific foodstuffs like olive oil, you can greatly reduce the tonnage.

The upshot is that your figure for the huge tonnages of food requiring to be lifted into orbit is grossly inflated.

In fact all the figures for transit to Mars are really a diversion from the matter in hand. That really comes down to cost because there is no shortage of either methane, oxygen or the infrastructure to produce them on Earth. Essentially all that comes down to money, and it's pretty clear that Musk currently has no shortage of money. I really don't think the world's methane producers will have a problem upping production 20% in relation to new demand on Earth.

The only really important figure, in terms of transit, is how much fuel you need to produce on Mars. On the Musk plan, such as it is, you might need to fuel 600 Starships to return to Mars every two years - so that would require constant energy production of around 600 Mws. A lot but not impossible.

I am not sure why you think you need millions of tons of machinery on Mars to build a city. That doesn't ring true to me.

Producing millions of tons of Mars cement to be applied robotically to create the settlement seems one of the most straightforward approaches. In the UK the average house might weigh 40 tons. That will give a benchmark figure of 16 milllion tons of material for a one million person city (with 2.5 people per house). However that would be a gross overestimate for a city on Mars I would suggest. People are more likely to be living in the equivalent of apartments with partition walls. On the other hand, your will need strong structures to withstand pressurisation. So maybe halve that to 8 million tons as a guesstimate. Over 30 (Earth) years that would be about 270,000 tons of material per annum. Most of that would probably be cement or concrete. We wouldn't need millions of tons of machinery to produce that much material per annum. Total guess but a 10,000 ton industrial facility could probably produce that much material every year.

I do think you tend to exaggerate the demands and the difficulties.

louis · 2021-04-10 18:30:01

Not sure you read my post correctly.

So you've reference a daily electricity use figure of 5.5KwH average for the USA - one of the most profligate energy usage nations on Earth. But your PV array figures for Mars give a usage of 187.5 KwHs per sol per person.

Now that is a huge, huge disparity (183 KwHs per sol/day!) - which you haven't explained. You can explain a lot of it away through extra energy for life support, gas used for heating, and energy used for industry, transport, the private sector and the public sector (ie non residential). But then as explained previously there is no need on Mars to have huge amounts of energy devoted to railways, airports, metalled roads, street lighting , private automobiles, paper production, pollution control or indeed fossil fuel production.

kbd512 wrote:

louis wrote:
Feel free to join in. Kbd has arrived at a situation where he thinks a figure of 455 KwHes usage per household per sol of 2.5 people is a reasonable figure for a mature Mars colony. That's nearly half a MwH!
Louis,
Our summer time energy usage is 27.5kWh per day. Our daily electricity usage is 5.5kWh per person. If you divide by 24, we're using 229.2Wh/hr. I go through your make-believe energy allotment in two weeks.
When you live in a ship or a submarine, you're living in a wind tunnel. Those fans that move the air to keep you alive require a LOT of power, much more than the waste water treatment in point of fact, though not as much as the flash evaporators that provide drinking water from brine.
If we lived on Mars instead of Earth, 229W of continuous power is NOT ENOUGH to power CAMRAS and IWP.
Please let us know when that sinks in.

SpaceNut · 2021-04-10 19:53:20

Kbd512 energy use does not account for the food growing needs so for Mars its going to be higher.

kbd512 · 2021-04-10 20:06:24

louis wrote:

The one thing we have a lot of on Mars for sure is land.
I'm not sure your scepticism is well placed.
https://www.theconsciouschallenge.org/e … l-overview
The above link states 7.5 trees produce enough oxygen for one human being to breathe.
There are estimated to be over 3,000 billion trees on planet Earth.
Is it really such an outlandish idea that you might have 7.5 million trees on Mars to produce the oxygen for a million people?
I'm using trees as shorthand - it could be grass, other plants or algae - anything that can get on and use photosynthesis to create oxygen without much human intervention.
Of course, this would be predicated on us developing suitable low cost farm habs/forest habs, probably plastic housing and using concentrated CO2. It might require use of thermogenic plants to raise temperatures at night. It's not my area of expertise but others have said this sort of set up is feasible on Mars.
I accept there are many challenges but getting nature to produce the oxygen could be a lot less energy intensive than the alternatives. If we can produce it for ourselves, then there is no reason we can't produce oxygen for fuel burning (not just methane - can also be used with metals, another alternative).
I never said methane-oxygen generation would provide 100% of the energy. But it might make say a 5% contribution.

Louis,

The more you keep talking about what you want to do, the more the internal calculator in my brain keeps adding up all the energy and material input requirements to do what you say you want to do. That's what an engineer thinks about when people like you come to them and start saying stuff like this. There's no issue with saying that you want to put a few million trees on Mars. Actually doing that is another matter entirely.

All of those plants require a certain number of cubic meters of pressurized space to exist in, because they can't live outside of that pressurized space. Those cubic meters of pressurized space then require many more cubic meters of concrete and a pressure membrane of an advanced fiber like CNT and plastic to contain the pressure. Fans and pumps that consume millions of kilowatt-hours of electricity then have to pressurize and circulate the atmosphere inside that space. The plants also require many thousands of liters of water per day, so even more power to provide that. If you actually want to eat them, then the water also has to be free of contaminants, as well as anything that would kill the plants, so even more power.

Remember those "energy-intensive" indoor greenhouses I spoke about?

There seems to be some fundamental misunderstanding on your part about why plants produce Oxygen. Leafy green plants generate Oxygen through Carbon fixation to create glucose that is then polymerized into cellulose, that allows them to grow, or they convert it into starch to store energy for later use. If the plant isn't growing, then it doesn't need glucose or starch, so it's not producing Oxygen.

If the food crops are growing 24/7/365, as they would be in an indoor greenhouse, guess what else is also happening?

kbd512 · 2021-04-10 21:40:01

Louis,

louis wrote:

Kbd -
That figure you give for average per capita food intake in the USA - 906 Kgs sounds way over the top to me. That works out at 2482 grams per person per day. That's an enormous amount of food!!! The UK Health authorities for instance recommend a daily intake of only 70 grams of meat. Meat and cheese are probably the densest foods we eat every day.
I think that is probably a figure for food and drink. Also I think that Americans being large consumers of milk probably skews things a bit from world averages. But that 906 Kgs probably includes all the litre bottles of coke as well.

How do you think tens of millions of people became morbidly obese?

It wasn't just the liter Colas, Favre!

Have you ever seen all the food thrown out in a cafeteria style operation after a meal?

louis wrote:

The reason I am labouring this point is that the figure probably includes liquids and water can be recycled both in transit and on Mars.

No, you're belaboring the point because you steadfastly refuse to admit to reality when it comes to energy consumption.

louis wrote:

Moreover, there is no reason not to use dehydrated foods. They formed a large part of the diet in WW2 in the UK. If you make your food supply 30% dehydrated that hugely reduces the tonnage requirements. Likewise, if you also skew your diet towards some highly calorific foodstuffs like olive oil, you can greatly reduce the tonnage.

This isn't WWII. See if you can find a million people who both have the money and want to live on another planet so they can live the way we did before industrialization. Good luck.

louis wrote:

The upshot is that your figure for the huge tonnages of food requiring to be lifted into orbit is grossly inflated.

The downshot is that you still refuse to admit to reality.

louis wrote:

In fact all the figures for transit to Mars are really a diversion from the matter in hand. That really comes down to cost because there is no shortage of either methane, oxygen or the infrastructure to produce them on Earth. Essentially all that comes down to money, and it's pretty clear that Musk currently has no shortage of money. I really don't think the world's methane producers will have a problem upping production 20% in relation to new demand on Earth.

He doesn't have nearly enough.

louis wrote:

The only really important figure, in terms of transit, is how much fuel you need to produce on Mars. On the Musk plan, such as it is, you might need to fuel 600 Starships to return to Mars every two years - so that would require constant energy production of around 600 Mws. A lot but not impossible.

Here you are talking about building 8 Bhadlas on Mars to supply the energy to refuel the ships, but bickering over the extra 50 to keep everyone alive.

Unbelievable.

louis wrote:

I am not sure why you think you need millions of tons of machinery on Mars to build a city. That doesn't ring true to me.

Do you want to see the city built in a human lifetime, or across five or more generations?

louis wrote:

Producing millions of tons of Mars cement to be applied robotically to create the settlement seems one of the most straightforward approaches. In the UK the average house might weigh 40 tons. That will give a benchmark figure of 16 milllion tons of material for a one million person city (with 2.5 people per house). However that would be a gross overestimate for a city on Mars I would suggest. People are more likely to be living in the equivalent of apartments with partition walls. On the other hand, your will need strong structures to withstand pressurisation. So maybe halve that to 8 million tons as a guesstimate. Over 30 (Earth) years that would be about 270,000 tons of material per annum. Most of that would probably be cement or concrete. We wouldn't need millions of tons of machinery to produce that much material per annum. Total guess but a 10,000 ton industrial facility could probably produce that much material every year.

A semi-truck weighs about 36t.

A 90,000 gallon Propane tank weighs about 78t. You'll probably need a few of those for hundreds of Starships coming and going.

A land drilling rig weighs about 100t.

A 1,000t hydraulic press weighs 150t to 200t.

A 100t crane weighs about 200t.

A mining dump truck weighs about 250t.

A 160MVA OLTC for on-load switching weighs about 700t. The Bhadla array literally had hundreds of power transformers, but you want to build something 50 times larger, assuming you think breathing and drinking water are important things for people to do.

A tunnel boring machine weighs 2,500t to 5,000t.

A million people who weigh 50kg weigh about 50,000t.

A real transport ship weighs 25,000t to 100,000t.

Doesn't really take too much in the way of vehicles and machinery for all that weight to really add up, does it?

louis wrote:

I do think you tend to exaggerate the demands and the difficulties.

I think you tend to ignore engineering reality in favor of fanciful ideas. I take no issue with that if you're writing a sci fi novel, but have an entirely different opinion when you're talking about endangering peoples' lives.

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