Dust storms - don't panic!

louis · 2017-06-03 06:53:53

I think sometimes there is a bit of hysteria about dust storms on Mars. This is a useful corrective:

http://www.uapress.arizona.edu/onlinebk … rces30.pdf

Go to page 860 and look at graph (a).

At 25 degree latitude north, with the most extreme optical depth of 6, we see a reduction in irradiance at the surface from about 550 watts per square metre to 180 watts. A reduction of about 68% - and that is the most extreme scenario. Dust scatters light as well as absorbing it.

The authors conclude (page 882) that solar power remains a viable and justifiable potential energy source for a human mission to Mars.

They consider that producing methane and oxygen using solar power is perfectly doable. They were considering the Mars Direct propellant scenario. I would be more interested in producing it for failsafe energy storage to ensure a less variable energy supply, to bolster energy supply for industrial uses and to provide back up in an emergency.

Oldfart1939 · 2017-06-03 10:14:24

The correct term is obscuration for dust storms reducing the light reaching the surface. I've been an amateur astronomer for 65 years, and the presence of dust storms in the Martian atmosphere is the single most annoying thing while attempting a surface observation of the planet. You are saying "What, me worry?" Well, I'm certain that NASA would be very worried, enough to make solar power the backup to nuclear. But for the initial missions, everything must be as fail safe as possible--hence the reliance on nuclear reactor technology. Both technologies will play a role; solar will provide some of the power for the rovers, power tools and construction equipment, nut the core source will undoubtedly be nuclear. I have made sketches of the rovers simply covered with solar PV panels, capable of self-charging the vehicle in an emergency. If we take the Tesla automobile as our model, there should be adequate range available for local expeditions without need for recharging. If there are panels on the vehicle roof and slabby sides, there would be some recharge occurring while the scientists are outside collecting samples and taking photos or making measurements.

louis · 2017-06-03 12:17:52

So you are taking batteries to Mars, you just don't want to use them for anything other than driving Rovers!

Oldfart1939 wrote:

The correct term is obscuration for dust storms reducing the light reaching the surface. I've been an amateur astronomer for 65 years, and the presence of dust storms in the Martian atmosphere is the single most annoying thing while attempting a surface observation of the planet. You are saying "What, me worry?" Well, I'm certain that NASA would be very worried, enough to make solar power the backup to nuclear. But for the initial missions, everything must be as fail safe as possible--hence the reliance on nuclear reactor technology. Both technologies will play a role; solar will provide some of the power for the rovers, power tools and construction equipment, nut the core source will undoubtedly be nuclear. I have made sketches of the rovers simply covered with solar PV panels, capable of self-charging the vehicle in an emergency. If we take the Tesla automobile as our model, there should be adequate range available for local expeditions without need for recharging. If there are panels on the vehicle roof and slabby sides, there would be some recharge occurring while the scientists are outside collecting samples and taking photos or making measurements.

SpaceNut · 2017-06-03 13:37:00

Batteries for Rovers would be connected to not only day recharge via solar but on the nuclear side during the night as well, so as to have back up batteries for use on the rovers or for extended trips every other day..

louis · 2017-06-03 18:41:33

That's your view but kbd appears to favour nuclear-only. If you are going to have nuclear plus batteries then obviously you are adding to mass.

SpaceNut wrote:

Batteries for Rovers would be connected to not only day recharge via solar but on the nuclear side during the night as well, so as to have back up batteries for use on the rovers or for extended trips every other day..

SpaceNut · 2017-06-03 19:26:32

The rover batteries have not changed only the methods to recharge them to which we should be able to go with both or nuclear only as solar can not charge them at night to which is when the nuclear reactor has a surplus of power unless we moderate the machine to something lower to save the units life cycle.

Oldfart1939 · 2017-06-03 20:29:05

If we are still on track with the Mars Direct model/architecture, much of the power will be needed for return flight to Earth, via production and liquefaction of Methane and Oxygen. That's when the day/night cycle will allow capture of CO2 when power requirements are lowest, other than for base heating.

kbd512 · 2017-06-04 05:07:24

Louis,

NASA can't plan a mission with humans involved when they don't know how much power they'll get from day to day. If I get 100% of rated power one day and 10% to 20% the next, that means I either need a lot more power production equipment to account for input variability or I need a power source with a more continuous output. If the time interval for reduced power availability was guaranteed to be short enough, as it is in orbit, then the use of PV panels to provide power is far less problematic.

As a function of the total system mass required to provide a 10kWe continuous output at 1.5AU distances, small fission reactors like Kilopower require less mass to produce 10kWe continuous output. Since PV panel input power variability can be so substantial and for at least half of a sol you get no power whatsoever from PV panels, mission planners must account for that variability by increasing the mass of PV panels and batteries or you will run out of power and astronauts will die as a result.

I already demonstrated with simple math why it is that merely providing a continuous 10kWe requires double the mass of a fission reactor in PV panels alone. In addition to providing power during the day, the PV panels have to recharge a battery with sufficient capacity to store enough power to make it through the night.

Your claims about demand variability don't correlate with actual demand patterns aboard ISS. They don't shut off their life support or communications equipment. It's powered up 24/7.

Assuming MOXIE works as advertised, MOXIE alone requires 2,016We of continuous power to produce O2 for 6 astronauts who never EVA. Once you turn on a SOXE-based oxygen generator that operates at 800C, you leave it on if you're at all concerned about the operational life of the system.

Would PV panels and batteries require less mass than a 751kg 2.2kWe Kilopower reactor?

Let's do some math to find out.

Battery capacity required to provide 2kWh continuous:

2kWh * 12 = 24kWh

5kg/kWh for Panasonic / Tesla 20700 Lithium-ion cells

24kWh * 5kg/kWh = 120kg of batteries

The output of ATK's MegaFlex PV panels is 250We/kg at 1AU. 2.74 is the factor that determines how much output is required to produce the same power on the surface of Mars. Peak output is produced for 4 hours per sol, so a 6kW array should produce sufficient power to recharge the battery and we'll presume the rest of the output is used to produce input power for MOXIE during the rest of the daylight hours.

24kWh / 4hrs = 6kW

6kW * 2.74 = 16.44kW to provide 6kW on the surface of Mars

16.44kW * 7kg/kW = 115.08kg

Our total mass is thus 235kg to provide 2kWe continuous with PV panels when we receive 100% of the average solar irradiance. In this case, it makes sense to provide that continuous power with PV panels. If the solar irradiance received drops to 32% of what it normally is, then you need 51.375kW to produce the the same output and the PV panel mass becomes 360kg. Even at that point, we're still better off with solar than nuclear. On days when we receive 100% of input solar irradiance available we make 18.75kWe, which is substantially more than the reactor will ever be capable of producing.

Whereupon we make the jump from 2kWe continuous to 10kWe continuous, our PV panels alone weigh as much as a pair of 10kWe Kilopower reactors. On some days, we'd make far more power than we ever could with the nuclear reactors. On other days, we'd only make enough power to survive. Mission planners hope for the best, but prepare for the worst. As continuous output requirements increase, the problems inherent to using PV panels and batteries become substantially worse.

louis · 2017-06-04 05:16:41

I don't personally favour that. For one thing you have to produce a lot of fuel/propellant. I think in the new environment being created by Space X, we should be looking at landing fuel/propellant for the ascent vehicle.

I think you need something like 4 to 1 for propellant/fuel v. load. The Apollo ascent vehicle was just over 2 tonnes so maybe 3 tonnes for a three person Mars ascent vehicle. Implies 12 tonnes of propellant/fuel. Could we make it reusable? Perhaps...then we could refuel in LMO and the vehicle could return to carry another three people back up to the ITS. And of course if you had replacement personnel they would need to be brought to the surface. A vehicle that could be reused several times would be ideal.

Oldfart1939 wrote:

If we are still on track with the Mars Direct model/architecture, much of the power will be needed for return flight to Earth, via production and liquefaction of Methane and Oxygen. That's when the day/night cycle will allow capture of CO2 when power requirements are lowest, other than for base heating.

Oldfart1939 · 2017-06-04 08:13:04

Just a quick note re: space vehicle reusability; SpaceX yesterday, flew a "recycled" Dragon capsule loaded with 2,200 kg of science experiments on a mission to the ISS.

Here's the youtube SpaceX video of the launch and first stage flyback and recovery. : https://youtu.be/JuZBOUMsYws

louis · 2017-06-04 14:36:35

I don't think these calculations are right. Firstly I have seen a figure for Megaflex of 150 We per Kg, not 250. Do you have a link to your figure? However let's run with 250 We...

If it's 250 We per Kg divided by 2.74 for Mars, that gives 91 watts or 0.091 Kw per Kg being generated on the Mars surface.

For a 3000 kg. PV unit that will be 273 Kwes averaged across the day (let's say we are working with days to keep this simple).

But that would imply an average for daylight hours of 546 Kwes (variable with the seasons of course).

[Nuclear and solar approach the problem in different ways. You are assuming, it seems, we have to replicate the nuclear constant power. We do not. ]

Let's assume an upper level for basic requirements of 2Kwe per person (12 Kwe constant required for a six person mission). I actually think that is too high for night time hours if we are doing a lot of the life support work during the day. But that was used in the MIT study, so let's stick with that.

So let's say we sought to provide 12 Kwe via a battery for say a 16 hour period - including dusk and dawn when the irradiance is not that strong. So that would be 192 KweHs. Assuming a loss of 20% that would mean we had to use up 240 KWehs of daytime PV electricity production, perhaps at a rate of 120 Kws over two hours, reducing the amount of available power by that amount. 240 KWehs could be stored in 1.2 tonnes of batteries.

The solar energy system with batteries at 4.2 tonnes would be producing 6552 KWehs per day. There would be some additional equipment - cabling and converters perhaps...let's assume the ratio is similar to on Earth, so add one third of the panel weight, that's another tonne. Brings it to 5.2 tonnes.

The 15 tonne 10x 10Kwe KiloPower nuclear reactors would be producing a miserly 2400 KWehs per day.

kbd512 wrote:

The output of ATK's MegaFlex PV panels is 250We/kg at 1AU. 2.74 is the factor that determines how much output is required to produce the same power on the surface of Mars. Peak output is produced for 4 hours per sol, so a 6kW array should produce sufficient power to recharge the battery and we'll presume the rest of the output is used to produce input power for MOXIE during the rest of the daylight hours.
24kWh / 4hrs = 6kW
6kW * 2.74 = 16.44kW to provide 6kW on the surface of Mars
16.44kW * 7kg/kW = 115.08kg
Our total mass is thus 235kg to provide 2kWe continuous with PV panels when we receive 100% of the average solar irradiance. In this case, it makes sense to provide that continuous power with PV panels. If the solar irradiance received drops to 32% of what it normally is, then you need 51.375kW to produce the the same output and the PV panel mass becomes 360kg. Even at that point, we're still better off with solar than nuclear. On days when we receive 100% of input solar irradiance available we make 18.75kWe, which is substantially more than the reactor will ever be capable of producing.
Whereupon we make the jump from 2kWe continuous to 10kWe continuous, our PV panels alone weigh as much as a pair of 10kWe Kilopower reactors. On some days, we'd make far more power than we ever could with the nuclear reactors. On other days, we'd only make enough power to survive. Mission planners hope for the best, but prepare for the worst. As continuous output requirements increase, the problems inherent to using PV panels and batteries become substantially worse.

kbd512 · 2017-06-05 02:07:16

louis wrote:

I don't think these calculations are right. Firstly I have seen a figure for Megaflex of 150 We per Kg, not 250. Do you have a link to your figure? However let's run with 250 We...

MegaFlex is intended to deliver 250We/kg at 1AU in space. We're running with that number because that's what both NASA and Orbital ATK say on this subject. Some variants of ATK's UltraFlex PV panels, on the other hand, are 150We/kg. In any event, you're debating the documentation from testing performed by numerous people at NASA and Orbital ATK and I'm done arguing this point.

louis wrote:

If it's 250 We per Kg divided by 2.74 for Mars, that gives 91 watts or 0.091 Kw per Kg being generated on the Mars surface.
For a 3000 kg. PV unit that will be 273 Kwes averaged across the day (let's say we are working with days to keep this simple).
But that would imply an average for daylight hours of 546 Kwes (variable with the seasons of course).

Beam irradiance at the top of the Martian atmosphere varies between 493W/m^2 at Aphelion and 718W/m^2 at Perihelion.

louis wrote:

Nuclear and solar approach the problem in different ways. You are assuming, it seems, we have to replicate the nuclear constant power. We do not.

You can't shut off life support equipment. It just doesn't work that way. I don't know what else to say about it. All human carrying spacecraft built to date have constant power requirements to keep the humans inside them alive. The next generation life support technologies currently in testing, namely CAMRAS and IWP, have dramatically lower power requirements than current generation life support technologies aboard ISS, but shutting them off is a non-starter.

ISS presently uses between 75kWe and 90kWe, every hour of every day its in operation. NASA projects a continuous electrical power requirement for their Mars surface exploration missions of 40kWe. In other words, NASA thinks that every hour of every day they need a minimum of 40kWe.

louis wrote:

Let's assume an upper level for basic requirements of 2Kwe per person (12 Kwe constant required for a six person mission). I actually think that is too high for night time hours if we are doing a lot of the life support work during the day. But that was used in the MIT study, so let's stick with that.
So let's say we sought to provide 12 Kwe via a battery for say a 16 hour period - including dusk and dawn when the irradiance is not that strong. So that would be 192 KweHs. Assuming a loss of 20% that would mean we had to use up 240 KWehs of daytime PV electricity production, perhaps at a rate of 120 Kws over two hours, reducing the amount of available power by that amount. 240 KWehs could be stored in 1.2 tonnes of batteries.

You can use 5kg/kW to compute the mass of 20700 cells required to store a given amount of power. Alternatively, you can use the flight qualified batteries aboard ISS to determine what the ISS batteries weigh. It's 435lbs (198kg) for each 122V 48AH (15kWh) pack. 106kg's of the 198kg total are batteries. The other 92kg is mostly packaging and protection, but also includes charge/discharge controller electronics.

192kWh / 15kW/pack = 12.8 battery packs

13packs * 435lbs/pack = 5,655lbs (2,570kg)

20700 batteries with 15kWh capacity would weigh 75kg, or 31kg less than the GS Yuasa LSE 134 cells aboard ISS, so 15kWh packs would weigh 167kg. The ORU adapter plate, the component that the heater plate is affixed to, weighs 85lbs (38.6kg).

(167kg ORU + 36.8kg ORU) * 13 = 2,672.8kg

I keep saying 20700, but the Tesla 2170 cells are actually 21mm in diameter, same 70mm length as the 20700 cells. We should determine how many 20700 cells we can cram in one of these ORU's to reduce the number of packs, therefore packaging mass, but we should ensure that we still have sufficient volume for the radiant barrier separators between cells to preclude cell ruptures from destroying other cells in the pack. There has to be some way to get rid of some of the mass of that heater plate, too. Since we determined that packaged batteries weigh more than what you budgeted, let's go through that cramming exercise to see how many 2170 or 20700 cells we can stuff into one of those ISS ORU's. I'm relatively certain that the heater plate can be incorporated into the pack since the adapter plate exists to affix the ORU to the truss structure aboard ISS. 63kg (Mars weight for the ORU, less heater / adapter plate) is still far too heavy for a single astronaut to move, so we must shed some packaging mass.

louis wrote:

The solar energy system with batteries at 4.2 tonnes would be producing 6552 KWehs per day. There would be some additional equipment - cabling and converters perhaps...let's assume the ratio is similar to on Earth, so add one third of the panel weight, that's another tonne. Brings it to 5.2 tonnes.
The 15 tonne 10x 10Kwe KiloPower nuclear reactors would be producing a miserly 2400 KWehs per day.

6552kWh in the base case scenario, Louis. That level of output is not guaranteed. The solar arrays could be far smaller and lighter if minimum required output was easier to achieve. NASA is working on LILT arrays. We're just not there, yet.

If you had 10kWe of power from a fission reactor to provide most of the base load, then you could use the battery from a vehicle to provide supplementary or backup power, reduce both battery and PV panel mass, and convert most of the packaging mass associated with the ORU's into vehicle mass.

louis · 2017-06-05 08:18:46

Thanks for the clarification on Megaflex. I think for the moment I will stick with the 150 Kwe per kg for my solar-based design (see other thread). I took the 150 W figure from a referenced presentation. ATK don't give a figure on their website that I can find.

I meant replicate the constant power rate achievable through nuclear.

It's all a question of how you design a system. As you will see from the other thread, solar has no difficulty covering life support at all times, with energy storage.

ISS as I understand it has some pretty big power storage requirements owing to the nature of its flight. On Mars we can produce power more in line with the natural circadian cycle of human beings.

Anyway, see the Going Solar thread for my detailed proposals.

kbd512 wrote:

louis wrote:
I don't think these calculations are right. Firstly I have seen a figure for Megaflex of 150 We per Kg, not 250. Do you have a link to your figure? However let's run with 250 We...
MegaFlex is intended to deliver 250We/kg at 1AU in space. We're running with that number because that's what both NASA and Orbital ATK say on this subject. Some variants of ATK's UltraFlex PV panels, on the other hand, are 150We/kg. In any event, you're debating the documentation from testing performed by numerous people at NASA and Orbital ATK and I'm done arguing this point.
louis wrote:
If it's 250 We per Kg divided by 2.74 for Mars, that gives 91 watts or 0.091 Kw per Kg being generated on the Mars surface.
For a 3000 kg. PV unit that will be 273 Kwes averaged across the day (let's say we are working with days to keep this simple).
But that would imply an average for daylight hours of 546 Kwes (variable with the seasons of course).
Beam irradiance at the top of the Martian atmosphere varies between 493W/m^2 at Aphelion and 718W/m^2 at Perihelion.
louis wrote:
Nuclear and solar approach the problem in different ways. You are assuming, it seems, we have to replicate the nuclear constant power. We do not.
You can't shut off life support equipment. It just doesn't work that way. I don't know what else to say about it. All human carrying spacecraft built to date have constant power requirements to keep the humans inside them alive. The next generation life support technologies currently in testing, namely CAMRAS and IWP, have dramatically lower power requirements than current generation life support technologies aboard ISS, but shutting them off is a non-starter.
ISS presently uses between 75kWe and 90kWe, every hour of every day its in operation. NASA projects a continuous electrical power requirement for their Mars surface exploration missions of 40kWe. In other words, NASA thinks that every hour of every day they need a minimum of 40kWe.
louis wrote:
Let's assume an upper level for basic requirements of 2Kwe per person (12 Kwe constant required for a six person mission). I actually think that is too high for night time hours if we are doing a lot of the life support work during the day. But that was used in the MIT study, so let's stick with that.
So let's say we sought to provide 12 Kwe via a battery for say a 16 hour period - including dusk and dawn when the irradiance is not that strong. So that would be 192 KweHs. Assuming a loss of 20% that would mean we had to use up 240 KWehs of daytime PV electricity production, perhaps at a rate of 120 Kws over two hours, reducing the amount of available power by that amount. 240 KWehs could be stored in 1.2 tonnes of batteries.
You can use 5kg/kW to compute the mass of 20700 cells required to store a given amount of power. Alternatively, you can use the flight qualified batteries aboard ISS to determine what the ISS batteries weigh. It's 435lbs (198kg) for each 122V 48AH (15kWh) pack. 106kg's of the 198kg total are batteries. The other 92kg is mostly packaging and protection, but also includes charge/discharge controller electronics.
192kWh / 15kW/pack = 12.8 battery packs
13packs * 435lbs/pack = 5,655lbs (2,570kg)
20700 batteries with 15kWh capacity would weigh 75kg, or 31kg less than the GS Yuasa LSE 134 cells aboard ISS, so 15kWh packs would weigh 167kg. The ORU adapter plate, the component that the heater plate is affixed to, weighs 85lbs (38.6kg).
(167kg ORU + 36.8kg ORU) * 13 = 2,672.8kg
I keep saying 20700, but the Tesla 2170 cells are actually 21mm in diameter, same 70mm length as the 20700 cells. We should determine how many 20700 cells we can cram in one of these ORU's to reduce the number of packs, therefore packaging mass, but we should ensure that we still have sufficient volume for the radiant barrier separators between cells to preclude cell ruptures from destroying other cells in the pack. There has to be some way to get rid of some of the mass of that heater plate, too. Since we determined that packaged batteries weigh more than what you budgeted, let's go through that cramming exercise to see how many 2170 or 20700 cells we can stuff into one of those ISS ORU's. I'm relatively certain that the heater plate can be incorporated into the pack since the adapter plate exists to affix the ORU to the truss structure aboard ISS. 63kg (Mars weight for the ORU, less heater / adapter plate) is still far too heavy for a single astronaut to move, so we must shed some packaging mass.
louis wrote:
The solar energy system with batteries at 4.2 tonnes would be producing 6552 KWehs per day. There would be some additional equipment - cabling and converters perhaps...let's assume the ratio is similar to on Earth, so add one third of the panel weight, that's another tonne. Brings it to 5.2 tonnes.
The 15 tonne 10x 10Kwe KiloPower nuclear reactors would be producing a miserly 2400 KWehs per day.
6552kWh in the base case scenario, Louis. That level of output is not guaranteed. The solar arrays could be far smaller and lighter if minimum required output was easier to achieve. NASA is working on LILT arrays. We're just not there, yet.
If you had 10kWe of power from a fission reactor to provide most of the base load, then you could use the battery from a vehicle to provide supplementary or backup power, reduce both battery and PV panel mass, and convert most of the packaging mass associated with the ORU's into vehicle mass.

Mars_B4_Moon · 2022-05-09 02:09:51

Mars rover spots gusty weather blowing across the Martian desert
https://www.aol.com/mars-rover-spots-gu … 30497.html

Perseverance Rover Arrives At A Dry River Delta
http://spaceref.com/mars/perseverance-r … delta.html

Will dust be the Death of Mars colonies, while not as dangerous and toxic as Lunar dust it seems it will get everywhere into circuits, go into tubes, get inside filters, it will cover Solar Planes, China claimed to have a Rover that would fight dust, a non-stick surface, it could tilt its panel or shake it off like a dog but now their Rover is also covered in 'Mars dust'. The little JPL NASA Mars helicopter has seen power levels drop because of 'Dust'

Mars_B4_Moon · 2022-06-02 08:42:34

Scientists Think They Know What Causes Mars's Planet-Encompassing Dust Storms

https://www.thesciverse.com/2022/05/sci … auses.html

SpaceNut · 2022-06-02 21:35:40

These storms are why solar is going to need backups and a means to be cleaned in order to keep them at peak performance. Comparing earth which stores solar in the green plants to a barren mars is why its released after a quite winter.

Mars_B4_Moon · 2022-06-05 13:36:31

Possibly Mars related

NASA Funds R&D into Mitigating Dust for Future Lunar Explorers
http://www.parabolicarc.com/2022/05/31/ … explorers/

Mars_B4_Moon · 2022-10-09 20:22:22

NASA’s InSight Waits Out Dust Storm. InSight’s team is taking steps to help the solar-powered lander continue operating for as long as possible.

https://mars.nasa.gov/news/9191/nasas-i … -diminish/

Last edited by Mars_B4_Moon (2022-10-09 20:22:33)

Calliban · 2022-10-09 20:43:00

An old Louis topic. He has been gone for a while now. He had a lot of pet obsessions about renewable energy. Sacred cows involving things like solar power. After a global dust storm killed a NASA rover stone dead, he even adapted the idea to include using solar power to make methane to burned in an engine for backup during dust storms.

Unfortunately, Kbd512 and I routinely turned those sacred cows into burgers. The mass budget for any durable solar powered solution looks terrible. Especially if you need enough to power a growing base with manufacturing capabilities. It didn't seem to matter to him. The elegance and aesthetics of certain ideas were more important to him than their practicality. A strange character. I honestly think he would rather have seen Mars colonisation fail than see it happen in a way that wasn't 100% solar powered.

Last edited by Calliban (2022-10-09 20:44:15)

kbd512 · 2022-10-10 10:18:59

Calliban,

The reality of living on a place like Mars is very stark and completely unforgiving of both human error and ideology. The planet is forever and always trying to kill you. Earth is little different in practice, but all life still in existence has adapted to it over significant timescales. Given the fact that more than 90% of all species that ever lived have gone extinct, it should be obvious how well that went. Over enough time, survival rates for nearly all species drop to zero. Are humans so very different than all those other species? I can't say because I don't know.

Obsession is perfectly normal human behavior, BTW. It's a survival mechanism. It's not very useful when applied to engineering, though, since none of the physical laws that govern how the universe works were put in place to agree with human brain constructs such as aesthetics.

Louis is not strange in the slightest to favor the aesthetics of specific ideas. That's normal for most people. You seem to think that because we see the world in terms of cold hard numbers that we're the norm. Most people don't think that way. We may as well be space aliens compared to him. That is not how the vast majority people perceive or relate to their place in the world- at all or ever, to include many people who are also engineer or scientists. Most people favor ideas that they find beautiful to imagine. Whether or not reality correlates well with their "beautiful ideas", is another story.

Speaking of sacrificing sacred cows, we're the oddballs here, not Louis. Louis is much more "normal" than you or I have ever been. We're only "similar" in that we all think other people do or should think the same way we do. Making that assumption is laughably wrong, even though we all do it to one degree or another.

That doesn't make us "right" or "better", either. The people with an eye for aesthetics are the ones who sell "the big idea" to other people, and without them you have very little in the way of creativity. For example, it's highly likely that you first learned about the idea of colonizing Mars from a book or a movie, and then someone convinced you it was a good idea. I lack that sort of creativity, but Louis has it in spades. For you, at least from what I've read of what you post, it's more like a "big ideas" person (Void, Louis, tahanson43206) posts something about a topic you find interesting, and then you do some preliminary work to evaluate the feasibility of the idea. Many if not most ideas will turn out to be impractical, if not impossible, but every so often there's a stroke of genius mixed in with all the other ideas.

GW Johnson · 2022-10-10 12:50:57

Louis was an interesting correspondent on these forums, but he has been missing for some months now. I wish he would return.

The hardest part of dealing with him was his tendency to support what to him was a beautiful concept, in the face of actual data that contradicted him. Concepts are great, but one cannot deny real data, and not expect to get called out for it.

Like multiple others on these forums, I think nuclear power is the right base load power for Mars. I don't really know about the small reactors being built and proposed for Mars, but the big pressurized water units here on Earth do not respond at all quickly to changes in load demand. That's why they are base load units here. The rapid demand changes are handled by natural gas plants specifically designed for rapid response.

While one can make methane fuel on Mars, unlike here, you cannot burn it with Mars's "air". You must make many tons of oxygen for each ton of methane fuel you make, and that is just not an easy, efficient, or effective thing to do on Mars.

The obvious choice for rapidly-changing demand over and above base load, during the day on Mars, really is Louis's favorite, solar power. But for it to respond effectively to changing demand, you really need a battery of some size to draw surge power from, on a short-time basis, then recharge slowly after the demand transient has passed.

If you have enough panels making voltage, you can always not draw full current, when panel capacity exceeds demand. But if demand exceeds panel capacity, you have to have batteries to draw upon. There has to be some "optimum" proportioning of panels and batteries, but I don't know what it is. It is quite likely not what applies here on Earth. Mars is different.

So, for Mars, I think you need both nuclear and solar. Making the nuclear respond to variable demand is a whole lot more difficult and expensive than a near-constant output nuclear system.

Now, generating electricity from heat is at most about 45% efficient, so there's a lot of waste heat to "dump", of value more (maybe a lot more) than the value of the electricity produced. That's just thermodynamics. Most of the designs for small nuclear electricity generators seem to rely on waste heat radiators for use in the vacuum of space. Those will operate a high material temperatures, and they will be quite large.

There are no bodies of water we could use as cooling ponds on Mars. But the dirt under the surface is quite cold there. How about burying a field of coolant pipes in the cold dirt well below the surface, and let it be the heat sink? Sort of geothermal-in-reverse.

Waste heat radiator panels will suffer similar difficulties on Mars as solar panels: a dust covering messes them up. Pipefitters and some electric back hoes could well be the easier and more practical thing to do.

GW

SpaceNut · 2022-10-10 15:05:44

Dust we know is a problem for solar, but we have an example of a standing landing that refuses to die even when the amount of solar has become so low due to the caked-on dust panels. Understanding this rare occurrence means we can go with solar but with other power sources as a backup.

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'Continent-size' dust storm takes out NASA's seismic station on Mars

Its pair of 7-foot solar panels produce 5,000 watt-hours each Martian day. NASA says this is equivalent to powering an elective oven for an hour and 40 minutes. It has since dwindled to 500 watt-hours per day.
InSight, the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, landed on Mars on Nov. 26, 2018.
The dust storm was first observed on Sept. 21, and space officials say that by last week, the storm had grown large enough to increase dust by nearly 40% in the Martian atmosphere.
Most storms of this size happen during fall and winter. Winds can reach up to 60 mph and toss dust high into the atmosphere, which takes weeks to come down.
With the hazy atmosphere obstructing light to the lander's solar panels, NASA's InSight Mars lander's energy fell from 425 watt-hours per Martian day, or sol, to just 275 watt-hours per sol.
The battery continued to deteriorate, and mission scientists were forced to turn off InSight's seismometer for the next two weeks.

yet years later its still making use of the Seismic unit to explore mars.

Calliban · 2022-10-10 15:07:18

You are both right of course. We need a mix of energy sources in real life. It is not usually practical to load follow using a nuclear reactor. There are lots of reasons why. Capital amortization. Power transients leading to thermal gradients and thermal fatigue of components. Perhaps most of all, operating at variable load means altering control rod positions to control reactivity. This distorts the neutron flux profile in the core and will lead to uneven burnup. This means that you still have to replace all the fuel at the same interval as you would have if operating at 100% power. So reducing power doesn't save you very much in costs.

In terms of making renewable energy a practical supplementary energy source on Earth and Mars, Kris DeDecker provides some interesting suggestions in this article.
https://www.lowtechmagazine.com/2017/09 … ather.html

The key to reducing lifetime costs and energy payback time is to avoid storage and balance load to supply. We can do this with solar power on Mars by operating equipment when solar power is available and shutting it down when it is not. For example, a freight railway could draw energy directly from solar panels which power third rails. The speed of the trains would vary with sunlight intensity as current levels rise and fall.

Last edited by Calliban (2022-10-10 15:08:43)

kbd512 · 2022-10-10 16:13:43

GW,

Naval nuclear power plants respond very rapidly to load changes, but those also use HEU fuel and are significantly different in design, but I think governments are the only entities with the wealth required to transport those "nuclear spark plugs" to jump-start the creation of a Mars colony. There are some LEU designs that also respond rapidly to load changes, but those are uncommon. The naval PWRs are by far the most common designs purpose-built for frequent and large load changes. Power failure was the one type of casualty we never experienced aboard nuclear powered warships, unless it was related to equipment not directly connected to the reactor, which meant power distribution substations scattered around the ship.

I would opine that super capacitors are the absolute best option for very rapid load changes, followed by batteries. You need perhaps 2 minutes of load capacity on the super cap bank, 2 hours of battery backup at most, and redundant base load power supplied by multiple nuclear reactors. In a real shipboard casualty, we re-routed power around damaged equipment using power cables and used backup diesel generators, rather than batteries or super capacitors. That took anywhere between 10 and 30 minutes to accomplish, with proper training. However, Mars has no diesel fuel. A 2n/3rd/4th reactor would function as the "spinning reserve" that normally makes fuel or powers other loads that can be dropped, if need be. If primary life support (airflow, O2 production, pressurization) is ever threatened, then you automatically drop the other load and instantly re-route power to make up for equipment casualties associated with a reactor scram or power distribution failure.

I think you want banks of both types of devices. The super caps can truly "load-follow" without significant degradation, the batteries can supply supplemental or emergency backup power for minutes to hours, and then vastly more energy density from the power source is required after that. We can support Rube Goldberg power solutions (solar / wind / batteries / gas turbines / geothermal / nuclear, all on the same grid) here on Earth because our environment and established technology base supports having a multitude of different power provisioning solutions in so many other ways. That doesn't work on Mars. Mass and volume are subject to extreme restrictions. Solar and batteries works on ISS because full-Sun every 45 minutes, into perpetuity, the total power requirement is very low, gobs of excess capacity are provided, and there's an escape plan if all of that fails. That won't work on Mars. Your "escape plan" is to "fix the problem", immediately.

Calliban · 2022-10-10 20:24:20

Naval reactors as you have described, need a lot of excess reactivity to burn off xenon peaks.
https://www.nuclear-power.com/nuclear-p … odine-pit/

This explains the need for HEU fuel. In a battle situation, you don't want to be waiting around 9 hours for half of the xenon to decay. Another option that avoids the need for HEU is fluid fueled reactors like AHRs. Gaseous fission products like xenon bubble out of the fuel solution and have no effect on reactivity.

The Chernobyl accident was caused by a poorly trained operator attempting to burn off a xenon peak. They deactivated reactor trip settings and withdrew all control rods to 100%. They were succesful in burning off the xenon. But as it burned off, the positive void coefficient of the reactor amplified the positive reactivity increase. The reactor became super prompt critical, meaning it was critical on prompt neutrons, with have a short average lifetime. Power surged to 100s of times the rated maximum in just a few seconds. RBMK reactors have operating rules and trip settings to prevent precisely this dangerous situation. Unfortunately, operating rules are only effective so long as operators follow them. If they do idiotic things like deliberately sabotaging trip settings, then there is no protection against this dangerous condition.

Last edited by Calliban (2022-10-10 20:40:57)

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Dust storms - don't panic!

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Re: Dust storms - don't panic!

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Re: Dust storms - don't panic!

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Re: Dust storms - don't panic!

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Re: Dust storms - don't panic!

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Re: Dust storms - don't panic!

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Re: Dust storms - don't panic!

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Re: Dust storms - don't panic!

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