Settlement design

SpaceNut · 2021-04-18 16:14:44

This gives the passive solar green areas

ya that's big 7.28 metres in diameter

https://en.wikipedia.org/wiki/Tunnel_boring_machine

http://media.metro.net/projects_studies … boring.pdf

5 Different Types of Tunnel Boring Machines (TBMs)

we need something for sure

http://www.microtunnelboringmachine.com … chine.html
R3db138e7c90457e70cff0f070d650124?rik=RNERoD8Kfykpuw&riu=http%3a%2f%2fwww.microtunnelboringmachine.com%2fuploads%2f202027311%2fsmall-tunnel-boring-machine57306000395.jpg&ehk=3HSZz5ecgLsxetLivL19TcjQUJ7x46fO9Y0PK3QVyr4%3d&risl=&pid=ImgRaw

louis · 2021-04-18 16:19:56

Agreed. Missed opportunities.

Calliban wrote:

It sounds like Zubrin is risk averse and was worried about the prject not working and damaging the Mars Society reputation. He also sounds a little possessive; like all of us he has an ego. None the less, from what Robert describes, the balloon mission must be considered a lost opportunity. The same with the wiki. There is little danger in allowing non-engineers to produce useful articles, as there are engineers available to guide them on technical facts. And the site owner can always withdraw articles that don't stand up to peer review, so I don't really understand the problem.

Calliban · 2021-04-18 16:25:15

Natural light is important for mental health if nothing else. Windows at the ends of tunnel areas could be constructed from segmented steel frames, with smaller glass panes within them. They could rely on friction with the tunnel wall to hold them in place. If they are slightly curved inwards, the shape would transfer compressive stress into the rock. So long as the weight of overburden is sufficient, then friction will hold the window in place without the need for any tensile forces.

I keep going back to the Expanse in these discussions. There is a scene showing a residential street on Ceres, which is clearly a tunnel with LED panels mounted on the roof. The sides of the tunnel have had spaces cut out for individual houses and commercial premises.
https://www.space.com/31584-dwarf-plane … panse.html

The panels simulate a blue sky, even with the occasional white patch representing clouds. So all living spaces and buildings, look out onto a street with a blue sky, albeit a fake one. I wonder how practical that would be in real life? Could we produce thin LED wallpaper, that we attach to the roof of a tunnel to simulate a real sky?

Regarding transportation. One of the interesting things about transportation in narrow tunnels, is that vehicles have comparatively few degrees of freedom. You can go backwards and forwards, but not too far from side to side without hitting the walls. This suggests to me that most motorised transportation should be able to use direct electric power drawn from a cable running under the roof, to which they would be connected via a pole. There would be no need for batteries. This is a huge advantage, as batteries have high embodied energy, low energy density and require a high mass of relatively rare components. If all vehicles are powered directly from the grid, they become much easier to produce using native resources.

If a tunnel is circular or parabolic in shape, then the rock forms a natural arch. This should avoid the need for supporting steelwork. The same for any other cavities dug into the side of the tunnels. It is a highly elegant solution, that neatly avoids the need for structural materials. Cast basalt pillars are possible in situations where a large flat area is desirable. Basalt typically melts at 1200°C, so could be cast into cast iron molds that have been lined with sand or clay.

Last edited by Calliban (2021-04-18 16:41:11)

louis · 2021-04-18 16:36:09

"steel would become brittle"

This reminds me of a discussion long ago...

Musk is planning to send at least one stainless steel craft to Mars that will then fly back to Earth after two years on the surface.

Are you saying Musk is so stupid as to not realise the steel will turn brittle?

Regarding natural light farming on Mars, a good compromise might be to create (low pressure/high CO2) "greenhouses" on terraced hillsides. Using reflectors as well, light can be increased and also thrown "into" the hillside. Small, shallow craters might work well. You could have the farm habs taking up maybe half of one side of the crater, reflectors (A) on the other side and also reflectors (B) on the remaining part of the farm hab side. So in the morning, if you're east facing, the farm hab is getting nicely illuminated by the rising sun, with supplementary lighting from reflectors B reflecting light on to reflectors A which then reflect the light on to the farm hab green houses. In the afternoon reflectors A would reflect light from the west-facing side of the crater on to the east facing side of the crater where the farm habs are positioned.

At night time, robots would activate heat reflecting blinds to help retain heat in the farm habs.

Calliban wrote:

According to this site, underground homes are 20-30% more expensive than the above ground equivalent, but have lower heating costs.
https://granitehistory.org/underground-houses/
One thing that turns economics on its head on Mars, is that any construction on the surface takes place in vacuum and faces huge diurnal and seasonal temperature swings. The cold would make work difficult at night and steel would become brittle. Underground, tunnels can be pressurised and digging can be carried out without space suits. Temperature is stable and controllable, allowing low-alloy carbon steels to be used to support roof structures without fear of embrittlement. After initial heating, total heating requirements should be modest thanks to the low rates of thermal conduction through many metres of rock. So this may turn out to be the easiest way of creating habitable volume on Mars.
Some things have to be located above ground of course. Farms and landing pads, come to mind. Large factories require a lot of 2D floor space, so above ground may make more sense in this case. Nuclear power plants would be much better located underground and this has been frequently discussed on Earth. If an underground nuclear power plant suffers fuel damage, then the radioactive materials are naturally entombed.
Food could be grown underground using artificial lighting, but that approach consumes a lot of electricity. In general, low grade heat is far cheaper than electric power. A consequence of the second law of thermodynamics.

RobertDyck · 2021-04-18 16:49:53

Mars Homestead was a hillside. Dug into dirt using a compact track loader. Cut and cover. That means cut (dig) into the hillside, build pressure hull, then use a loader to push dirt down from the hill onto the habitat. Bury it. This means the primary construction device is a loader. (click on image for manufacturer website)

The reason for living underground is radiation shielding. Mars surface has on average half the radiation of ISS, but that's still a lot. (click image for JPL page on Mars radiation)

Light green areas have 22 REM per year. US nuclear reactor workers are limited to 5 REM per year. A settler on Mars can keep radiation exposure to 5 REM/year by limiting time outdoors to 40 hours per week (7 Mars solar days) on average. That's a work week, so not a restriction.

Mars Homestead image for a bachelor apartment: (click image for enlargement)

Mars Homestead image for atrium deep within hillside with light pipe for natural light: (click for enlargement)

A city could have something like this. Inside Portage Place, a mall in Winnipeg. This has a glass roof over the central atrium, but could light be reflected via mirrors? (click for enlargement)

Winnipeg Square, an underground mall. It's under two large downtown towers, between the towers there's a window for natural light. (click image to enlarge)

::Edit:: I should emphasize, the windows for Winnipeg Square are not a skylight. As you see from the picture, it's a "lean-to" configuration: roof is solid, window is a wall. I could grab an image from Google Maps; it shows a solid roof. I also said it's underground beneath 2 towers. Originally built in 1979, it was to be twin office towers. They did build one tower, and started construction of the second. They built the steel superstructure of the second to 5 stories, then dismantled it. Foundation for the second tower was completed, but the second tower itself wasn't there. Now they're expanding retail to ground level (above what you see here), and building a condominium building. Foundations were for a major tower building, right in the heart of downtown, so it only makes sense they're using those foundations now. Other office towers were built across the street, so there was demand, but what they're building now is condos. Whatever, my point was building into a hillside or cliffside on Mars is reasonable.

Last edited by RobertDyck (2021-04-19 02:55:01)

Calliban · 2021-04-18 17:02:41

louis wrote:

"steel would become brittle"
This reminds me of a discussion long ago...
Musk is planning to send at least one stainless steel craft to Mars that will then fly back to Earth after two years on the surface.
Are you saying Musk is so stupid as to not realise the steel will turn brittle?

No. But for steels to remain ductile at Martian nighttime temperatures, they require specific alloying elements that render them more expensive than ordinary structural steels. You can use austenitic stainless steels or you can add additional manganese to carbon steels. This retains pearlite microstructure and remains ductile at temperatures beneath -20°C.

I am sure that Musk is aware of this and I don't mean to suggest that he isn't. And I am sure that his design team have taken it into account in Starship design. But when you are building large steel civil engineering structures that weigh thousands of tonnes, the cost of high manganese steel will begin to add up. It may turn out to be cheaper building things underground than to have to rate them for huge thermal cycles. Or maybe it isn't. It is something that needs to be weighed in design considerations however.

louis · 2021-04-18 17:08:01

I've mentioned the idea of false skies here before now. To insert a blue gas predominantly with a smaller amount of white gas into double glazing so as to create the illusion of an Earth sky sounds possible to me. Over the years I've seen some pretty stunning theatrical effects - I am sure that skilled people could enhance the illusion with lighting. I think with use of natural vegetation mixed with artificial vegetation to disguise supportive columns (similar to how phone masts are disguised) and also illusion effects to suggest distance, one could create very pleasant Earth like environments for walking and cycling.

One could create artificial breezes and convection currents, even light showers perhaps.

Calliban wrote:

Natural light is important for mental health if nothing else. Windows at the ends of tunnel areas could be constructed from segmented steel frames, with smaller glass panes within them. They could rely on friction with the tunnel wall to hold them in place. If they are slightly curved inwards, the shape would transfer compressive stress into the rock. So long as the weight of overburden is sufficient, then friction will hold the window in place without the need for any tensile forces.
I keep going back to the Expanse in these discussions. There is a scene showing a residential street on Ceres, which is clearly a tunnel with LED panels mounted on the roof. The sides of the tunnel have had spaces cut out for individual houses and commercial premises.
https://www.space.com/31584-dwarf-plane … panse.html
The panels simulate a blue sky, even with the occasional white patch representing clouds. So all living spaces and buildings, look out onto a street with a blue sky, albeit a fake one. I wonder how practical that would be in real life? Could we produce thin LED wallpaper, that we attach to the roof of a tunnel to simulate a real sky?
Regarding transportation. One of the interesting things about transportation in narrow tunnels, is that vehicles have comparatively few degrees of freedom. You can go backwards and forwards, but not too far from side to side without hitting the walls. This suggests to me that most motorised transportation should be able to use direct electric power drawn from a cable running under the roof, to which they would be connected via a pole. There would be no need for batteries. This is a huge advantage, as batteries have high embodied energy, low energy density and require a high mass of relatively rare components. If all vehicles are powered directly from the grid, they become much easier to produce using native resources.
If a tunnel is circular or parabolic in shape, then the rock forms a natural arch. This should avoid the need for supporting steelwork. The same for any other cavities dug into the side of the tunnels. It is a highly elegant solution, that neatly avoids the need for structural materials. Cast basalt pillars are possible in situations where a large flat area is desirable. Basalt typically melts at 1200°C, so could be cast into cast iron molds that have been lined with sand or clay.

kbd512 · 2021-04-18 18:05:51

Noah,

Space Flight Qualified Long Duration Closed Loop Life Support

If we're talking about supporting a crew of 8 people with all of their food imported from Earth, then the Mars One estimates for life support are pretty much all that actually matters, since there are no other human space flight-qualified, long-duration closed-loop life support technologies available. All of the cutting edge technology developed for long duration closed-loop life support has been the exclusive domain of NASA's contractors.

No other government-sponsored space flight agency, such as ESA or ROSCOSMOS, nor public / private corporation, has spent a quarter of a billion dollars to thoroughly test, evaluate, and qualify any comparable life support technologies aboard ISS. Apart from NASA's contractors, other corporations like SpaceX do not possess a single piece of flight-qualified long duration life support equipment, for example. From that, we can deduce that amongst all other competing alternatives, NASA is the singular space flight agency that is the most serious about providing an actual hardware-based solution for long duration life support. NASA and their contractors are therefore the most credible authorities pertaining to this topic, like it or not.

Daytime Power Provisioning for Mission One

To store determine the generating subsystem sizing for 8 people, we first take the Mars One estimate for a crew of 4 (356kWh per day) and multiply by 2 to obtain a total daily estimated power requirement of 712kWh per day. This is the power requirement for life support only, using CAMRAS and IWP, with ISRU replenishment of air and water to replace losses. CAMRAS and IWP are the only flight-qualified hardware set in current existence that has been tested and proven to work.

The Mars One body of work comes from professional aerospace engineers with decades of actual experience supporting actual human space flight missions for NASA, so we're taking their word over that of anyone else here, including mine, about how many Watt-hours of electrical power the human space flight rated systems that they actually developed and that NASA actually deployed into space, actually consume over the course of 24 hours. Their facts / figures / data are computed from real human space flight hardware with real human lives at stake, versus science fiction fantasies entertained by people with little to no relevant space flight engineering knowledge.

We're going to use SolAero's Silicon from the recent Mars Insight Lander as our NEW baseline for solar power on Mars, rather than the Silicon used in the Bhadla array, or CIGS, or any other array technology that is not currently space flight qualified to produce power on Mars.

I counted the individual Silicon wafers per gore using a very high resolution image of the actual Mars InSight Lander. The press brief states that SolAero provided their ZTJ triple-junction (InGaP-InGaAs-Ge) Silicon for the solar arrays, with the array contract awarded to Orbital ATK / O-ATK by Lockheed-Martin for use of O-ATK's UltraFlex array technology, with actual sub-contracted manufacturing work performed by EMCORE on behalf of O-ATK. The brief also states that SolAero's ZTJ Silicon represents the most efficient, in terms of Watts-per-kg, solar cells ever flown on any interplanetary mission to date (InSight was launched on May 5, 2018), at 29.5% BOL efficiency. They were designed to produce up to 700 Watts of peak power output, can withstand Martian winds of up to 75 meters per second, and are specially designed to work under LILT (Low Intensity / Low Temperature) conditions. LILT technology was developed by NASA's contractors, for NASA, for solar powered missions between Mars and Jupiter.

Row Number for the Cells on the Gore - Cell Count per Row Number - Running Total Number of Cells per Gore
1 - 1 - 1
2 - 2 - 3
3 - 3 - 6
4 - 4 - 10
5 - 5 - 15
6 - 6 - 21
7 - 7 - 28
8 - 6 - 34 <- pair of holes in each gore to accommodate the array deployment mechanism
9 - 9 - 43
10 - 10 - 53
11 - 11 - 64
12 = 12 - 76
13 - 4 - 80 <- last row is arranged "circumferentially" along the edge of each gore

80 - 30cm^2 SolAreo ZTJ wafers per gore on Mars InSight, 20 gores per array, 2 arrays on Mars Insight

80 * 20 * 2 = 3,200 wafers

Total active area = 30cm^2 per wafer * 3,200 wafers = 96,000cm^2 (9.6m^2).

On InSight's best day on Mars, it produced 4,588Watt-hours of electricity.

4,588Wh / 9.6m^2 = 477.92Wh/m^2

The scientific literature ("Scientific Observations With the InSight Solar Arrays: Dust, Clouds, and Eclipses on Mars") lists the total array active area as 10.28m^2, but I can't find the exact cell surface area reference for each wafer from SolAero. That said, the discrepancy is rather large, at 0.68m^2. I wonder if they've measured the total gore surface area and called that the "active area". SolAero lists the wafer surface area attainable from 4" diameter Silicon bar as ranging between 27cm^2 to 30cm^2 per wafer (two 30cm^2 wafers per slice, or a single 60cm^2 wafer per slice), yet the 10.28m^2 figure suggests that the actual wafer surface area is 32.125cm^2. The Chinese-made FullSuns wafers cut from 4" diameter Silicon bar are also listed as roughly 30cm^2, not 32cm^2.

I know what kind of cell it is and I know what SolAero says about the nominal surface area, but they give a variance of up to 3cm^2 per wafer. I don't understand why there's not an exact cell surface area, which would be required for mission planning). If we use the literature's figure for active array area:

4,588Wh / 10.28m^2 = 446.3Wh/m^2 <- ("Scientific Observations With the InSight Solar Arrays: Dust, Clouds, and Eclipses on Mars")

We can either use my own figures for "total active area", which agree with the manufacturer's own specification sheets, or we can use the figures from the scientific paper. For sake of argument about using actual scientific data, despite the conflicting information presented by SolAero, we'll use the figures from the science paper. Given that SolAero is already working on 30.5% efficient LILT cells, I think we'll round up to 450Wh/m^2 and call it good.

712,000Wh per day / 450Wh/m^2 = 1,582.2m^2 of total active area

I haven't found an actual reference for the total gore area, so we'll use the 85% fill factor. We wind up with 282 wafers per square meter using SolAero's reference or 266 using the science paper. No matter how you figure the actual active array area, 3,200 individual wafers produced 1.43375Wh/day on InSight's best day. When we consider the problem that way, we can simply divide the total power requirement by the power each wafer produced during a day on Mars.

712,000Wh per day / 1.43375Wh per wafer per day = 496,600 total number of wafers

I think SolAero's own tech specifications regarding wafer size (a pair of 30cm^2 wafers per slice) is more likely to be correct than the science paper, so our total active area works out to be 14,898,000cm^2 (1,489.8m^2). If we divide the total number of wafers by 282, we get 1,761m^2 as our actual solar array surface area. That correlates with an actual array area of 42m^2 and 1,761 1m^2 panels to erect on the surface, which seems doable to me. It seems technologically feasible to me for a human, man or woman, in an Artemis program space suit to handle a 1m^2. If a total of 4 people working together while using a battery-operated hand-cart to carry the panels can each erect and connect a panel every 5 minutes, then that's 240 panels per hour, which means that the entire array could feasibly be built by humans in a day. It seems far more likely and practical that the array would be built over the course of 2 days, meaning a single 4 hour EVA per day with half the crew members emplacing and connecting the panels into an array, with the other half fabricating the wiring runs or assembling the CFRP panel supports to keep the panels away from the ground, so as not to attract more dust than usual. If each panel weighs 2kg, which is an ambitious but attainable mass target, and each panel support weighs 0.5kg, then the total array weighs 4,402.5kg. To save mass on wiring, we're obviously going to connect the panels in strings that generate some specific voltage multiple that an existing power inverter can work with. I'll have to hunt for info on the power inverters that NASA uses aboard ISS.

Nighttime Power Provisioning for Mission One

During any normal day at any place other than the equator of Mars, where there are no known large sub-surface deposits of ice to extract for water replenishment, you have around 8 hours of daylight and 16 hours of darkness / functionally unusable insolation. Apart from the slightly longer days and longer seasons of the year, the day / night cycle of Mars is remarkably similar to that of Earth.

To determine the battery pack sizing for the minimum power storage requirement of 16 hours of power per day for 8 people, we first take the Mars One estimate for a crew of 4 (356kWh per day) and multiply by 2 to obtain the total daily estimated power requirement of 712kWh per day, divide by the number of hours per day, and then multiply by 16. If we have to store that power in Lithium-ion batteries produced by Tesla, and they can approximately double achieved battery pack-level energy density from the 160Wh/kg demonstrated by Rolls Royce in an aircraft battery pack application that used existing Tesla batteries with most of the thermal regulation and safety features of Tesla's battery packs stripped away, then we arrive at 300Wh/kg. That 300Wh/kg figure is attributable to something Elon Musk has actually stated about the pack level energy density design goal behind Tesla's newest / larger battery cell format, the 4680 cells (46mm in diameter by 80mm long).

712,000 / 24 = 29,667 Watt-hours per hour

29,667 Watt-hours per hour * 16 hours of darkness = 474,672 Watt-hours

474,672 / 300 = 1,582kg

The 1,582kg figure is an absolute bare-minimum requirement, without which the crew will not survive until the next morning unless they stop replenishing their air and water losses, which is not long-term sustainable. That figure also presumes a 100% discharge rate, which would destroy the batteries in less than a year. For multi-year longevity, we're talking about 50% DoD (Depth-of-Discharge) or less. Therefore, a much more reasonable mass figure for the entire battery pack is 3,164kg.

Total mass allocation for solar and batteries, under optimal conditions:

4,402.5kg (solar array) + 3,164kg (batteries) = 7,566.5kg

Note: This mass estimate does not include the mass of the wiring or power inverters

KiloPower Alternative for Continuous Power Provisioning

The 10kWe KiloPower units that use LEU cores would weigh 2,106kg per unit and can produce 240,000Wh (240kWh) per day.

712,000Wh per day / 240,000Wh per KiloPower unit per day = 3 KiloPower reactors

2,106kg per 10kWe LEU KiloPower unit * 3 reactors = 6,318kg

Power Requirement Conclusions

I am presuming that the end goal is to merely keep these 8 crew members alive and capable of performing some minimal surface exploration activities around their Mars outpost. No power for agriculture or Earth-return propellant production is factored into these figures, as was the case with the Mars One ECLSS design requirements.

Even using an absolute "best case scenario" for solar power, current photovoltaic and battery technology still can't match nuclear power on a mass basis when the power requirement is only for 8 crew members who have been equipped with the best solar and battery technology that money can buy. If the power storage requirement increases or the solar insolation decreases for any substantial period of time, then the only long-term practical solution is to increase the mass of the photovoltaic array or batteries or both. If you must contend with a dust storm of any significant length, then there's no practical way (meaning, within reasonable mass constraints) to store enough power in batteries alone to account for the substantial power demands, which means you then need a fuel cell backup that adds more mass to your mission's life support-related power provisioning mass totals for the fuel cell itself, the oxidizer, and the fuel.

If money is no object, then a "million dollars per kiloWatt" solar array and battery solution will minimally be 20% heavier for equivalent time-averaged power than one of the most inefficient nuclear reactor designs currently in existence. The Mars InSight Lander touched down a mere 4.5 degrees north of the Martian equator, which means it's ideally sited for solar power production. If you move away from the equator towards the mid-latitudes, where all the subsurface ice deposits have been detected, then insolation drops off significantly and your array mass figures must increase accordingly, in order to produce the power demanded by the life support equipment. The Mars One mission architecture assumed ISRU water replenishment to keep total landed tonnage figures within the realm of feasibility. If you can import enough water from Earth to replenish all losses, then the power requirement goes down substantially and the mass figures favor the use of solar power under ideal conditions.

louis · 2021-04-18 18:57:41

Kbd.

"then the Mars One estimates for life support are pretty much all that actually matters"

I don't accept that at all.

Their estimates included allowances for daily showers. We know ISS participants use wet wipes to clean themselves, so it's not at all obvious that daily showers are necessary for Mars pioneers.

They also had large gas loss to frequent air lock usage to faciliate EVAs but really EVAs will not be necessary with a Space X style mission.

SpaceNut · 2021-04-18 19:02:13

The solar array for insight was made via Atk orbitals ultraflex build which is now owned by Northrop Grumman and it does not pivot but deploys flat not tracking or it would be producing even more power.

kbd512 · 2021-04-18 19:25:31

louis wrote:

Kbd.
"then the Mars One estimates for life support are pretty much all that actually matters"
I don't accept that at all.
Their estimates included allowances for daily showers. We know ISS participants use wet wipes to clean themselves, so it's not at all obvious that daily showers are necessary for Mars pioneers.
They also had large gas loss to frequent air lock usage to faciliate EVAs but really EVAs will not be necessary with a Space X style mission.

Louis,

Unless you're an aerospace engineer who has designed, built, tested, and operationally fielded long duration life support equipment used on a real human space flight mission, then we're going with mass and power estimates from aerospace engineers who design ECLSS for a living, not yours.

ISS uses wet wipes because they have no other option. If you gave astronauts a choice between a shower and wet wipes, I'm pretty sure every last person you interview would take a shower. If these crew members exercise everyday, then they're going to stink, and someone there is bound to object to the stench of their team mates, which means they're taking showers.

EVAs are part of actual exploration activities associated with human exploration of Mars. If the crew is not doing any EVAs, then there's no reason at all for them to be on Mars, because they're not exploring anything. American tax payers who are actually footing the bill for this mission expect to see some bunny hopping action. If the UK tax payers want to pay good money to watch a few guys slowly go nuts while cooped up inside a tin can, then you guys can pay Elon for a ride. Here in America, we expect to see astronauts in space suits doing astronaut stuff, like collecting strange looking rocks, hitting golf balls, drag racing dune buggies, and maybe some slam dunk contests. The fact that you've never considered the importance of a slam dunk contest demonstrates a profound lack of creativity. Heck, we're expecting to see some Mars football action before the end of the mission.

kbd512 · 2021-04-18 19:31:12

SpaceNut wrote:

The solar array for insight was made via Atk orbitals ultraflex build which is now owned by Northrop Grumman and it does not pivot but deploys flat not tracking or it would be producing even more power.

SpaceNut,

Given the extremely low power output per array unit area, even at the equator, we should evaluate the mass penalty associated with adding single-axis tracking mechanisms to improve array output. I'd bet almost anything that it's not nearly as significant as the power lost by not tracking the Sun. IIRC, Spirit and Opportunity had some limited form of single-axis tracking. It's needless added complexity for a stationary robotic mission, but for the size of array that we're talking about, and the fact that human lives depend upon its output, the additional power production potential starts to add up pretty fast.

Edit:

FIXED-TILT VS. AXIS TRACKER SOLAR PANELS

From the above linked Kiewit company website:

There are many design and financial evaluations that go into selecting the correct type of renewable resources in a region. One of these evaluations is choosing between fixed-tilt and axis tracking systems in PV solar fields. KED’s solar market partner, Stellavise, is sharing their experience in the thought processes in selecting a tracking system.
Solar photovoltaic (PV) power plants utilize three main types of racking systems: (i) fixed-tilt, (ii) single-axis tracker, and (iii) dual-axis tracker. A fixed-tilt system positions the modules at a “fixed” tilt and orientation, while solar tracker systems automatically adjust the positions of the PV array so that the PV modules consistently “track” the sun throughout the day. Compared to a fixed-tilt PV array, single- or dual-axis tracking systems will increase the energy production by 15-30% for the same size array.

Louis, dual-axis tracking is one way in which we could potentially make a solar solution more mass-competitive with a nuclear solution. This is purely a numbers and reliability proposition to me. If we can feasibly make a non-nuclear alternative work, then I have no objection whatsoever. If the math adds up, then it adds up, and vice versa. My bottom line is that power had better be available when demanded.

Kiewit is a company that provides engineering and construction resources / services for major projects in the US, Canada, and Mexico, with billions of dollars in yearly revenues. They've built more miles of interstate highway system than any other contractor, for example, as well as work on multiple dams in the US and Canada. You name it, they've done it, at least several times. They're even assisting with the cleanup at the Hanford site.

Last edited by kbd512 (2021-04-19 04:17:57)

tahanson43206 · 2021-04-18 19:37:22

As a follow up to discussion of solar panels .... A relative sent a link to an article about the Ingenuity helicopter.

A reader of the article then commented that it seemed surprising that NASA engineers have not found a way to dust off solar panels.

I would like to point out that ** if ** the helicopter can fly at all, then it certainly provide a solar panel cleaning service of some significance.

Unfortunately for the helicopter itself, it's blades are ** beneath ** the solar panel mounted to its frame. However, those fast spinning blades will most definitely be moving what Martian molecules it can reach with considerable force.

I asked Google how far Ingenuity is from Insight, and the distance is daunting...

about 3,452 kilometers
Perseverance will be landing in Jezero Crater, about 3,452 kilometers (2,145 miles) away from InSight's location in Elysium Planitia. But the landing of the rover won't be exactly what InSight will listen for.Feb 10, 2021

There seems little prospect of flying Ingenuity over to Insight to dust off the solar panels.

(th)

tahanson43206 · 2021-04-18 19:39:27

For kbd512 re #233

Thank you for a tour-de-force in coverage of requirements for power for an 8 person mission!

SearchTerm:power for 8 person mission thorough review kbd512 Post #233

Edit#1: It seems to me that covering both bases makes the most sense. The nuclear backbone can be supplemented by the solar panel arrays, and when those are working well the combined power supply should be sufficient to build up some reserves in addition to meeting mission requirements.

(th)

kbd512 · 2021-04-18 21:43:09

tahanson43206,

Production, Not Storage: Double or Nothing

If it was up to me, I would focus on power production strategies, rather than power storage. Power storage is always a losing game, even here on Earth. If power is plentiful, then we can use an inordinate amount of power to synthesize oxidizers and fuels from scratch, but those are generally reserved for high-energy activities related to transportation. As such, I would take 6 KiloPower reactors, double the size of the solar array, and double the size of the battery bank to ensure that we never run out of power.

Reality Check, Please

If the mission can't tolerate 12,636kg for the reactors, 8,805kg for the solar panels, and 6,638kg for the batteries, for a total of 28,079kg devoted to power, perhaps 30t for the power inverters / wiring, then the mass margins are way too tight. I know that if I was the mission director, I would not be prepared to tell the widows that their loved one died because we were a little too optimistic about power consumption.

Stop Complaining About the Numbers

Louis is here balking at supplying everyone with a hot shower while expecting to make 1,200t of propellants in 730 days to send the Starship back to Earth for reusability. That kind of argumentation is pure absurdity. If you can't supply the minuscule amount of fresh water to replenish losses and provide the crew with the comfort of a 5 minute Navy shower, then sourcing hundreds of tons of H2O and CO2 for propellant production is well beyond your power generation capabilities. Nobody here is talking about Hollywood showers or watering the grass on Mars to see if it grows. I'm tired of the incessant complaining about power requirements. They are what they are, given present technology. They don't exist to make one power provisioning technology look better or worse than the next. All of that is down to simple and unassailable physics, so deal with it by programming in realistic mass margins for power production and storage.

Pre-Stage or Cache Equipment and Supplies on the Surface

NASA's DRM called for landing at least 40t of cargo delivery prior to the arrival of humans on Mars, if only to prove that the lander wouldn't explode on impact. With the possible exception of the batteries, the power production hardware is the best kind of hardware to send ahead of the humans. We have little to no idea what issues will ultimately transpire, but we also know with certainty that running out of power brings the mission to an immediate and very ugly end.

Thriving in a Hostile Environment

The availability of backups is an essential part of the survival strategy. These people are tens of millions of miles away from home and we don't get a second shot at making the mission successful. We either prove to the entire world that we've come fully prepared to deal with all hardships or we admit that we're not ready to go and stay home. We're not sending 8 astronauts to another planet, only to kill them by being stingy with the power production and storage equipment. The entire point of going to Mars was to learn how to live and work there, forever.

Calliban · 2021-04-19 00:52:35

The amount of useful science carried out will be proportional to the number of EVA hours. It can be leveraged further by maximising mobility and increasing the amount of equipment available to support exploration. For example, pressurised rovers with IC engines; IC powered drills to allow the team to drill into subsurface water courses, small distributed fuel manufacturing facilities to extend the rover range, ground penetrative sonar and radar, etc. The more equipment you can bring along, the better the mission capabilities. If you're going to send these people to another planet and commiting to the expense that entails, then you want the best return on your investment possible. That means the most data gathered. And crew productivity will be a function of crew morale. So they need to be able to access as much water as they want and have good food and plenty of luxury items. They will need the discretion to carry out EVA for recreation and escape from confinement as well as for work. In for a penny, in for a pound. Better to pay twice as much for four times the return in terms of the total knowledge that the mission brings back. Value for money is important for whoever is paying for this. We aren't in it for laughs.

We are going to want to land the hab in the safest location. But the useful scientific sites are going to be scattered all around the planet. I would suggest that mobility really matters to how much value the mission returns. If we were dealing with a planet with a thicker atmosphere, then I would suggest the use of a helicopter to get the crew about. As it is, we need to make the best use of surface vehicles. Range is proportional to average speed. So ideally, the rover should be driving 24/7 between stops. Speed is a function of average power. We need a lot of excess propellant to support EVA.

I also wonder about mission duration. The longer the crew can remain on the surface, the better. It is more cost effective to extend mission stay time than it is to mount two missions. To do that whilst keeping total mission mass within tolerable limits means giving the crew the ability to stretch their rations. That means a heated greenhouse, supplemented with LED lights to extend the growing season as long as possible. That increases mission duration and capabilities, but also increases power requirements. The more power the mission has, the better return you get overall. A lightweight 24/7 power supply that returns plenty of process heat will boost mission capability, reliability and endurance.

Last edited by Calliban (2021-04-19 01:51:18)

tahanson43206 · 2021-04-19 06:35:15

For kbd512 re #240

SearchTerm:Power double for safety and quality of life kbd512 Post #240

If others have suggestions for how to find this post quickly please post them.

I agree that the idea of denying a crew a proper shower for two years is pure 1500's. However, there ** was ** a time when no European took a bath.

Perhaps that ancient practice still continues in some regions.

(th)

Calliban · 2021-04-19 06:46:03

tahanson43206 wrote:

For kbd512 re #240
SearchTerm:Power double for safety and quality of life kbd512 Post #240
If others have suggestions for how to find this post quickly please post them.
I agree that the idea of denying a crew a proper shower for two years is pure 1500's. However, there ** was ** a time when no European took a bath.
Perhaps that ancient practice still continues in some regions.
(th)

France, I would suspect :-) All that over-expensive perfume has got to covering something awful! And then there's the garlic to consider :-)

I nominate that Louis's mission should be carried out by French, who are used to that sort of thing.

NB. Joking of course :-) A French crew would bring a nuclear reactor with them and would have plenty of hot water. The lack of bathing would be strictly voluntary.

Last edited by Calliban (2021-04-19 06:58:32)

tahanson43206 · 2021-04-19 07:18:25

Mais Oui! Nous avon lave depuis 1500! Une fois, n'est pas?

Google version:

mon oui! nous nous baignons depuis 1500. Une fois! n'est-ce pas?

Not bad, for being out of practice.

Noah is a native German speaker, with command of English and a nodding acquaintance with Latin.

My Latin is negligible ... Centurian ... Et Tu, Brute? ... Tempest Fugit ... (Google version: tempus Fugit)

However, Noah is also a diplomat, so I would expect his views on who bathes in Europe to be circumspect.

I've noticed that Louis is one who is happy to advocate privation for others, but I suspect that he uses paper products in his daily life.

I also suspect that Louis uses coal as the source of heating and electric power for his place of abode.

In my own case, I am totally dependent upon fossil fuels, and greatly appreciate the labors and attention to detail of my neighbors who supply all those fuels and their conveyance. Nonetheless, I ** would ** prefer we (the region) had ** more ** nuclear power than we do, and a ** lot ** more renewable energy.

Since this discussion is about Settlement on Mars, I note that the ONLY stored resource Nature appears willing to provide there is nuclear fission power. Otherwise, Louis will be in his element with solar power as the only renewable resource for centuries to come.

With any luck, (and progress in life extension), Louis ** will ** live to see those centuries of solar power panels all over Mars.

(th)

Calliban · 2021-04-19 07:46:19

The possible abundance of subsurface liquid CO2 is a wild card that could make solar electric power more practical on Mars. It would mean that low grade solar heat could be converted efficiently into mechanical power. The LCO2 is both working fluid and cold source in a compact power generation open cycle. If it exists at a temperature of -50C, say, under many metres of regolith, then low grade solar heat at 300K could provide the energy source for open cycle, CO2 gas turbines. Efficiency would be about 10%, which doesn't sound good until you realise that the embodied energy of flat plate collectors on Mars would be substantially lower than a PV panel and heat can be stored in large quantities in a rock mass under regolith. Definitely something we could use, if the LCO2 is there and we have no better options.

RobertDyck · 2021-04-19 13:18:47

Um, what? You seriously expect liquid CO2 on Mars? You suggest -50°C, which is a reasonable temperature. At any location, subsurface temperature will be the average of that spot over time: day/night, summer/winter. So Ok, let's assume -50°C. This is the full triple point chart for CO2: (yes, click image for reference)

So below -56.6°C it's not possible to get liquid CO2; but you said -50. Pressure will have to be a little higher than 0.51 MPa (510 kPa = 74 psi = 5.0 atmospheres). Too much pressure will convert CO2 into solid dry ice. I don't believe we'll find liquid CO2 on Mars.

You want more references? Note pressure on this one is logarithmic, and temperature is Kelvin.

louis · 2021-04-19 16:56:10

Thanks for those images and explanations Robert.

I think the central atrium with the window roof is the sort of thing we should be aiming for (using cut and cover methods) and yes we should use reflectors - maybe mylar style reflectors would be cheaper than mirrors. The benign weather and low G on Mars means we should be able to can put up effective reflectors much more easily on Mars than on Earth. So we might be able to octuple the amount of light coming through the glass roof. So if it's 5 metres wide it would be delivering the equivalent of something like a 17.5 metres wide glass roof on Earth. You supplement that with some artificial natural light spectrum lights up on the roof area.

RobertDyck wrote:

Mars Homestead was a hillside. Dug into dirt using a compact track loader. Cut and cover. That means cut (dig) into the hillside, build pressure hull, then use a loader to push dirt down from the hill onto the habitat. Bury it. This means the primary construction device is a loader. (click on image for manufacturer website)
https://assets.bobcat.com/loaders/nav/bobcat-t64-bucket-2l4a0223-19c3-fc-ko-238x200_pm_list.jpg
The reason for living underground is radiation shielding. Mars surface has on average half the radiation of ISS, but that's still a lot. (click image for JPL page on Mars radiation)
https://mepag.jpl.nasa.gov/goals/tmp_clip_image004.gif
Light green areas have 22 REM per year. US nuclear reactor workers are limited to 5 REM per year. A settler on Mars can keep radiation exposure to 5 REM/year by limiting time outdoors to 40 hours per week (7 Mars solar days) on average. That's a work week, so not a restriction.
Mars Homestead image for a bachelor apartment: (click image for enlargement)
http://www.marshome.org/images2/albums/Mars%20Homestead%20Project%20Effort/Commissioned%20or%20MF%20Owned%20Artwork/thumb_MHP-4FC-Image026.jpg
Mars Homestead image for atrium deep within hillside with light pipe for natural light: (click for enlargement)
http://www.marshome.org/images2/albums/Mars%20Homestead%20Project%20Effort/Commissioned%20or%20MF%20Owned%20Artwork/thumb_MHP-4FC-Image029.jpg
A city could have something like this. Inside Portage Place, a mall in Winnipeg. This has a glass roof over the central atrium, but could light be reflected via mirrors? (click for enlargement)
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQZilw7KZtOT3kXTKmP8dJs7F1V9ujWjxEZHw&usqp=CAU https://encrypted-tbn0.gstatic.com/imag … A&usqp=CAU
Winnipeg Square, an underground mall. It's under two large downtown towers, between the towers there's a window for natural light. (click image to enlarge)
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSYEH2fHtaHNRxbS6Rgf0iSdzwC-0X2as50FQBPr623NCIluT8I2Sv5QP0Ufuj3GCaOlG0&usqp=CAU https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQu2FSONfbxUWqNND2ND5UyutSQ91MEaGrG6TIpB_j8AWlkSzuqsYEIx4uqS8fACxoCmLk&usqp=CAU
::Edit:: I should emphasize, the windows for Winnipeg Square are not a skylight. As you see from the picture, it's a "lean-to" configuration: roof is solid, window is a wall. I could grab an image from Google Maps; it shows a solid roof. I also said it's underground beneath 2 towers. Originally built in 1979, it was to be twin office towers. They did build one tower, and started construction of the second. They built the steel superstructure of the second to 5 stories, then dismantled it. Foundation for the second tower was completed, but the second tower itself wasn't there. Now they're expanding retail to ground level (above what you see here), and building a condominium building. Foundations were for a major tower building, right in the heart of downtown, so it only makes sense they're using those foundations now. Other office towers were built across the street, so there was demand, but what they're building now is condos. Whatever, my point was building into a hillside or cliffside on Mars is reasonable.

louis · 2021-04-19 17:10:51

Lol! And that's how myths start.

That said, I do recall some years ago staying in French hotel where it was advertised there was a shower. But you had to pay for it...quite a large, punitive sum. The look of horror on the manager's face when I asked to use it was like something out of a farce.

Calliban wrote:

tahanson43206 wrote:
For kbd512 re #240
SearchTerm:Power double for safety and quality of life kbd512 Post #240
If others have suggestions for how to find this post quickly please post them.
I agree that the idea of denying a crew a proper shower for two years is pure 1500's. However, there ** was ** a time when no European took a bath.
Perhaps that ancient practice still continues in some regions.
(th)
France, I would suspect :-) All that over-expensive perfume has got to covering something awful! And then there's the garlic to consider :-)
I nominate that Louis's mission should be carried out by French, who are used to that sort of thing.
NB. Joking of course :-) A French crew would bring a nuclear reactor with them and would have plenty of hot water. The lack of bathing would be strictly voluntary.

Calliban · 2021-04-19 17:48:26

They are different to us. In fact culturally, I think the French are very different from other Europeans. I can remember as a ten year old boy in the late 1980s, having to use a toilet in the south of France. It was intended for No 2's and consisted of two foot pads and a hole in the ground. As a boy, it horrified me and I have never forgotten it. Even in post-Franco Spain, things were more civilised than that.

Back around 2005, I went to a French restaurant in Knightsbridge with my girlfriend. The whole meal for two people, cost something like £150. Most of the things on the menu put me in mind of the dinner scene from Indiana Jones and the Temple of Doom. There was jelly-like goose liver that didn't appear to be cooked, steak ta ta, tripe, sheeps brains, and a whole load of other stuff that I don't even want to think about. I bet I could have found chilled monkey brain on the menu if I had searched for it. Probably eye ball soup as well. The worst thing about it was that my girlfriend, now wife, is a vegetarian. Suffice to say, I won't be taking her to an expensive French restaurant again. She got more out of the pizza place at Victoria Station, which cost about £7 for each of us. Cheap date.

I have never understood how France could have developed a reputation for having the best food in Europe. In my opinion, the Italians beat them hands down when it comes to producing things that most people want to eat. I don't mean to run them down. They make great wine and their beer is passable. Some of their cities are good too. I just can't do the whole undercooked internal organ based food thing. Or the pad toilets. Or the open air pisseries. Yuck yuck yuck! What is it with those people?

Last edited by Calliban (2021-04-19 17:50:05)

louis · 2021-04-19 18:06:09

PHASES OF URBAN SETTLEMENT ON MARS

I think there are likely to be successive phases of development on Mars before we arrive at a fairly permanent city settlement.

Phase 1 - "Import-based"

In the initial phase we will see a lot of imported habs. They will likely be inflatable Bigelow style habs in the first place. We might also see those followed by larger assembly habs brought in in parts that the pioneers then assemble on site. Sealants will also be imported.

The habs will be relatively small.

Phase 2 - "Tunnels and Cut and Cover"

This is the phase where we start to create space out of the Mars regolith.

Imported tunnel-boring equipment will be used to create spaces in hillsides. Window frames, glass windows and sealants will still be imported as might steel supports.

Also diggers will be used to create cut and cover units.

This sort of construction will be used to quickly expand farm hab and industrial hab space, to allow for a large expansion in population.

Phase 3 - "ISRU Building Materials in Use"

In this phase Mars ISRU materials will be in general use. These will include Mars-produced steel, compressed or fired Mars bricks, Mars concrete with basalt rebar reinforcement, Mars cement, ISRU glass, basalt tiles and basalt blocks. Many of these materials will be deployed robotically.

By this phase architecture won't be purely functional but will be making statements about the community and the purpose of the human presence on Mars. Statues and other art works using ISRU materials will be much in evidence.

Phase 4 - "Mature Phase"

The last phase will resemble more Earth-type construction, with steel girder construction more in evidence.

Glass or plastic domes will be a feature of this phase. These will house large public spaces.

Farm habs will be using natural light now and so plastic low pressure, concentrated CO2 greenhouses will be a familiar site.

The Mars colonists will be capable of creating large enclosed pressurised spaces using "canyon" construction to replicate Earth like environments, with vegetation, some wildlife and running water. This will be interconnected by tunnels so allowing the people of Mars to exercise over many miles through a complex of paths, rope bridges and so on.

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