Going Solar...the best solution for Mars.

SpaceNut · 2021-04-12 18:31:27

So the production rate which can barely fill one starship to go home if consumed due to dust storm must out live the storm since all the panels take up the size of 5 payloads which we already calculated. You are counting that the amount of fuel is a full ship and what happens if its not? You are counting on the unknown of how long did you get to make fuel to go home in hopes that the storm does not out last the fuel consumed to keep you alive....

kbd512 · 2021-04-12 18:52:26

Someone should take a look at the cost of manufacturing 30% efficient solar cells and then ask why it is that nobody uses them here on Earth when they can produce 10% more power. 45% efficient panels are still the stuff of university labs. They exist, which is to say someone can make them, but they're not mass manufactured the way 15% to 30% efficient panels are, and virtually all of the cells used in space applications are around 30% efficient, some slightly less and some slightly more (+/- 5%).

Hyundai's new Sonata Hybrid has a solar panel roof. They claim their 22.8% efficient roof-mounted panel can provide a 60% charge on the vehicle's 1.56kWh battery pack in a sunny locale over the course of a day. If you do the math, 1.56kWh * 0.60 = 0.936kWh, but let's round up to 1kWh for easy math. If we have a 3.7GWe constant power requirement, that works out to 59.2GWh over the course of 16 hours of darkness. That means we need a bare minimum of 59,200,000m^2 / 59.2km^2 of solar panel area to recharge that battery pack on Mars using 45.6% efficient panels, under ideal conditions, to produce the same amount of Watt-hours of power on Mars. The actual array size would be larger still, around 63.25km^2, not taking into account any electrical efficiency losses from thousands of kilometers of wiring or battery efficiency losses or less than ideal atmospheric conditions (dust and normal planetary cycles such as time of year, if the city isn't located on the equator, and Mars' eccentric orbit) that cause the panels to produce less power.

In terms of actual output per year, if you double the efficiency of the Bhadla array, you get Earth-equivalent performance on Mars, which means 25 Bhadlas to supply the power over the course of a year, still equivalent to covering the City of Houston in solar panels. Anyone who thinks they're going to build a photovoltaic array on Mars, 25 times larger than the largest solar array on Earth, for less or even comparable weight to a nuclear reactor, is basically pretending that empirically measured power output and simple multiplication don't exist. In short, they're denying basic math.

If we invoke the use of Lithium-ion batteries that achieve 150Wh/kg at the pack level with 70% DoD (this is what Rolls Royce achieved for their battery powered aircraft, which used Tesla battery cells with most of the packaging and pack protection features stripped away to reduce weight), in order to have any kind of acceptable cell life, we're talking about a truly enormous battery. That's 566,666,666kg, but we'll call it 567,000t. If you invoke the use of O2/CH4 SOXE fuel cells, at 3kW/kg (power density), then you can reduce the "battery" weight to 1,233,333t, and we'll call that 1234t, but that's just for the fuel cell itself. At 70% efficiency, daily Methane consumption for 16 hours of power at night is 6,084,275kg (13.9Wh/kg * 0.7 = 9.73Wh/kg; 59,200,000,000 / 9,730 = 6,084,275kg of Methane alone, which works out to 12,863m^3 if it's stored as LNG, at 473kg/m^3, so the storage vessel is about 23.43m per side if it had a cubic shape). That's enough LNG to refuel 3 Starships and their boosters, but that is what you have to produce EVERY SINGLE DAY to keep all the fans and pumps and electrical heating elements supplied with power.

There's another problem with this method, though, and that's the amount of power you need to make 6,084t of LNG and 21,801t of LOX to react it with. You'd be absolutely overjoyed if your complete process was 50% efficient, which means you need to supply a LOT more power. P2G efficiency sits around 45% to 55% in practical implementations, but that's just the power to make the Methane and compress it to 80 bar or so, but any more compression or liquefaction to save space and we're talking about even lower overall efficiency. If you capture the waste CO2 and H2O as part of a regenerative process, the overall efficiency is better for subsequent cycles but the mass requirement goes up accordingly.

The PV silicon itself is very nearly as heavy as the batteries, whereas the wiring and power transformation equipment could be substantially heavier. At peak power output, the array is producing considerably more power than nuclear reactors running at constant output, so more utility scale power transformers are required. These will be heavier than Earth-bound models, for either power source, because they need massive radiators to remove heat. The more of them you need to contend with power fluctuations, the worse your overall electrical efficiency. The quantity and variety of power inverters and transformers and wiring of the Bhadla array was a real eye-opener, all driven by the fact that output wildly overshoots constant power requirements. If we're being honest about it, the fewer of these massive power transformers that we require for normal operations, the better. It's possible that lighter wiring technology could reduce the weight considerably, but the containment is steel or cast resin, the cores are iron, they're filled with oil, and the conductors are very healthy chunks of Aluminum or Copper.

This is one of the best single resources I've found on the net for our power transformers and load switching equipment:

Power Transformer Dimensions, Weights, and Efficiency Ratings

louis · 2021-04-12 18:53:34

I'm not sure anyone here ever reads my posts!

I have stated clearly that with a solar power energy system you have to budget for a larger propellant production facility than would otherwise be the case on the "make hay while the sun shines" principle. But nukie fanatics also have to allow for potential downtime, depending on their solution.

I have done all the calculations before and came up with a figure of something like 120-150 tons for a system based on solar power (including emergency methox supply, methox generators, chemical batteries, inverters, cabling and so on). That's a failsafe system. The only failing would be if the sun stopped shining and that's a lot less likely than a nuclear power station going into meltdown.

I suggest you research dust storms on Mars and then I think you might realise they are not the terrifying beastie of your nightmare imagination. They are just periods of low insolation. Big deal. It's like a cloudy day in Kansas.

SpaceNut wrote:

So the production rate which can barely fill one starship to go home if consumed due to dust storm must out live the storm since all the panels take up the size of 5 payloads which we already calculated. You are counting that the amount of fuel is a full ship and what happens if its not? You are counting on the unknown of how long did you get to make fuel to go home in hopes that the storm does not out last the fuel consumed to keep you alive....

louis · 2021-04-12 19:05:51

I have been clear: 25% efficiency is a reasonable assumption for a Mars Mission led by Space X. All my calculations are based on 25%. So, as far as my proposals go, what you say about systems with efficiency in excess of 25% are irrelevant.

It's ludicrous to think you've won some sort of argument by working on Earth assumptions then applying Mars constraints and pointing out the difference. We all know Mars receive 43% or thereabouts insolation compared with Earth. I might point out, since you never do, that Mars's insolation - excepting dust storm periods - is much more reliable on a day-to-day basis and the seasonal variation in mid latitudes is far less, which is helpful.

See my other posts re methox production.

I very much doubt we will actually need to resort to Mars ISRU methox production for electric power. Chemical batteries will be able to store enough energy to see the pioneers through the worst period of a major dust storm. Insolation never approaches zero in even the worst dust storm and over weeks your production is unlikely to fall below 40% of normal. So all we are really talking about is scaling back on methox propellant production while the dust storm is doing its worst .

kbd512 wrote:

Someone should take a look at the cost of manufacturing 30% efficient solar cells and then ask why it is that nobody uses them here on Earth when they can produce 10% more power. 45% efficient panels are still the stuff of university labs. They exist, which is to say someone can make them, but they're not mass manufactured the way 15% to 30% efficient panels are, and virtually all of the cells used in space applications are around 30% efficient, some slightly less and some slightly more (+/- 5%).
Hyundai's new Sonata Hybrid has a solar panel roof. They claim their 22.8% efficient roof-mounted panel can provide a 60% charge on the vehicle's 1.56kWh battery pack in a sunny locale over the course of a day. If you do the math, 1.56kWh * 0.60 = 0.936kWh, but let's round up to 1kWh for easy math. If we have a 3.7GWe constant power requirement, that works out to 59.2GWh over the course of 16 hours of darkness. That means we need a bare minimum of 59,200,000m^2 / 59.2km^2 of solar panel area to recharge that battery pack on Mars using 45.6% efficient panels, under ideal conditions, to produce the same amount of Watt-hours of power on Mars. The actual array size would be larger still, around 63.25km^2, not taking into account any electrical efficiency losses from thousands of kilometers of wiring or battery efficiency losses or less than ideal atmospheric conditions (dust and normal planetary cycles such as time of year, if the city isn't located on the equator, and Mars' eccentric orbit) that cause the panels to produce less power.
In terms of actual output per year, if you double the efficiency of the Bhadla array, you get Earth-equivalent performance on Mars, which means 25 Bhadlas to supply the power over the course of a year, still equivalent to covering the City of Houston in solar panels. Anyone who thinks they're going to build a photovoltaic array on Mars, 25 times larger than the largest solar array on Earth, for less or even comparable weight to a nuclear reactor, is basically pretending that empirically measured power output and simple multiplication don't exist. In short, they're denying basic math.
If we invoke the use of Lithium-ion batteries that achieve 150Wh/kg at the pack level with 70% DoD (this is what Rolls Royce achieved for their battery powered aircraft, which used Tesla battery cells with most of the packaging and pack protection features stripped away to reduce weight), in order to have any kind of acceptable cell life, we're talking about a truly enormous battery. That's 566,666,666kg, but we'll call it 567,000t. If you invoke the use of O2/CH4 SOXE fuel cells, at 3kW/kg (power density), then you can reduce the "battery" weight to 1,233,333t, and we'll call that 1234t, but that's just for the fuel cell itself. At 70% efficiency, daily Methane consumption for 16 hours of power at night is 6,084,275kg (13.9Wh/kg * 0.7 = 9.73Wh/kg; 59,200,000,000 / 9,730 = 6,084,275kg of Methane alone, which works out to 12,863m^3 if it's stored as LNG, at 473kg/m^3, so the storage vessel is about 23.43m per side if it had a cubic shape). That's enough LNG to refuel 3 Starships and their boosters, but that is what you have to produce EVERY SINGLE DAY to keep all the fans and pumps and electrical heating elements supplied with power.
There's another problem with this method, though, and that's the amount of power you need to make 6,084t of LNG and 21,801t of LOX to react it with. You'd be absolutely overjoyed if your complete process was 50% efficient, which means you need to supply a LOT more power. P2G efficiency sits around 45% to 55% in practical implementations, but that's just the power to make the Methane and compress it to 80 bar or so, but any more compression or liquefaction to save space and we're talking about even lower overall efficiency. If you capture the waste CO2 and H2O as part of a regenerative process, the overall efficiency is better for subsequent cycles but the mass requirement goes up accordingly.
The PV silicon itself is very nearly as heavy as the batteries, whereas the wiring and power transformation equipment could be substantially heavier. At peak power output, the array is producing considerably more power than nuclear reactors running at constant output, so more utility scale power transformers are required. These will be heavier than Earth-bound models, for either power source, because they need massive radiators to remove heat. The more of them you need to contend with power fluctuations, the worse your overall electrical efficiency. The quantity and variety of power inverters and transformers and wiring of the Bhadla array was a real eye-opener, all driven by the fact that output wildly overshoots constant power requirements. If we're being honest about it, the fewer of these massive power transformers that we require for normal operations, the better. It's possible that lighter wiring technology could reduce the weight considerably, but the containment is steel or cast resin, the cores are iron, they're filled with oil, and the conductors are very healthy chunks of Aluminum or Copper.
This is one of the best single resources I've found on the net for our power transformers and load switching equipment:
Power Transformer Dimensions, Weights, and Efficiency Ratings

SpaceNut · 2021-04-12 19:08:51

last dust storm seen by the nuclear rover curiosity june 2018 ....How often are global dust storms in 1971, 1977, 1982, 1994, 2001 and 2007 2018, 2019 https://agupubs.onlinelibrary.wiley.com … 17JE005255 https://www.nature.com/articles/s41467-020-14510-x
Once every three Mars years (about 5 ½ Earth years), on average, normal storms grow into planet-encircling dust storms

This dust is an especially big problem for solar panels. Even dust devils of only a few feet across -- which are much smaller than traditional storms -- can move enough dust to cover the equipment and decrease the amount of sunlight hitting the panels. Less sunlight means less energy created.

1183_Animated_GIF_of_dust_thickening_in_the_skies_of_Mars..gif

Looking at the sun after the first 2 segments its not producing anything out of a panel
1169

Forecasting Dust Storms on Mars

DUST STORM IMPACTS ON HUMAN MARS MISSION EQUIPMENT AND OPERATIONS

louis · 2021-04-12 19:42:55

Odd isn't it?...you can post doctored photos and all sorts of flim flam but you can't post any verifiable evidence that insolation at the surface on Mars ever dips below 20% in a dust storm.

What you're doing here SpaceNut is "creating a narrative". It's not science.

As for telling me "less sunlight means less energy created" that's actually not a new thought for me!

We have PV facilities in sandy deserts and we have dust storms on Earth. It's all a lot more manageable than you want to think.

SpaceNut wrote:

last dust storm seen by the nuclear rover curiosity june 2018 ....How often are global dust storms in 1971, 1977, 1982, 1994, 2001 and 2007 2018, 2019 https://agupubs.onlinelibrary.wiley.com … 17JE005255 https://www.nature.com/articles/s41467-020-14510-x
Once every three Mars years (about 5 ½ Earth years), on average, normal storms grow into planet-encircling dust storms
This dust is an especially big problem for solar panels. Even dust devils of only a few feet across -- which are much smaller than traditional storms -- can move enough dust to cover the equipment and decrease the amount of sunlight hitting the panels. Less sunlight means less energy created.

https://solarsystem.nasa.gov/system/int … _Mars..gif
Looking at the sun after the first 2 segments its not producing anything out of a panel
https://solarsystem.nasa.gov/internal_resources/1169/

Forecasting Dust Storms on Mars

DUST STORM IMPACTS ON HUMAN MARS MISSION EQUIPMENT AND OPERATIONS

kbd512 · 2021-04-12 20:31:52

Louis,

louis wrote:

I have been clear: 25% efficiency is a reasonable assumption for a Mars Mission led by Space X. All my calculations are based on 25%. So, as far as my proposals go, what you say about systems with efficiency in excess of 25% are irrelevant.

None of your calculations use power requirements associated with any actual physical flight-qualified ECLSS hardware.

louis wrote:

It's ludicrous to think you've won some sort of argument by working on Earth assumptions then applying Mars constraints and pointing out the difference. We all know Mars receive 43% or thereabouts insolation compared with Earth. I might point out, since you never do, that Mars's insolation - excepting dust storm periods - is much more reliable on a day-to-day basis and the seasonal variation in mid latitudes is far less, which is helpful.

Since you're still arguing against basic math, clearly no argument has been won. BTW, it's even more ludicrous to make assertions about the power requirements of equipment that doesn't exist. My estimates are based upon the work done by actual aerospace engineers who design long duration ECLSS for NASA. Professionals don't plan for "best case" scenarios. That kind of thinking is what gets people killed. Every time the professionals are ignored, people die as a result. That's a recurring theme for humanity.

louis wrote:

See my other posts re methox production.
I very much doubt we will actually need to resort to Mars ISRU methox production for electric power. Chemical batteries will be able to store enough energy to see the pioneers through the worst period of a major dust storm. Insolation never approaches zero in even the worst dust storm and over weeks your production is unlikely to fall below 40% of normal. So all we are really talking about is scaling back on methox propellant production while the dust storm is doing its worst .

I very much doubt such hubris will pay off.

Effects of the MY34/2018 Global Dust Storm as Measured by MSL REMS in Gale Crater

UV A / B / C is only one component of sunlight, but it dropped by 95% during the dust storm.

NASA’s Opportunity rover is fighting for its life in a Martian dust storm

From the article:

For the solar-powered robot, the dust is not as dangerous as the darkness. Since the storm began two weeks ago, the amount of light the spacecraft receives has dropped to less than 1 percent of normal levels. Energy production has fallen from hundreds of watt-hours a day to almost nothing. NASA has not heard from the rover since Tuesday.
This is a “spacecraft emergency,” Mars Exploration Rover project manager John Callas said Wednesday. His team is operating under the assumption that the charge in Opportunity’s batteries has dipped below 24 volts and that the rover has entered a low-power fault mode, when all subsystems except the mission clock are turned off.
The clock is programmed to rouse the rover at periodic intervals to check whether light levels are sufficient to wake up -- a state called “solar groovy.” But the storm is still growing and should encircle the planet in a matter of days. NASA expects that it will be weeks, if not months, before the dust clears enough to allow the spacecraft to turn back on.

Mars Dust Storm 2018: How It Grew & Killed the Opportunity Rover

Use your eyeballs:

Opportunity Power vs Mars Dust Storm

Calliban · 2021-04-13 02:08:41

Louis, regarding strictly the use of solar PV power, with stored propellant used as backup during early SpaceX Mars missions.

There is a heavy burden of proof on this proposal, because the consequences of failure are not trivial. A single mission failure resulting in crew death, would halt the programme effectively forever. In theory, if you assume Elon Musk's pockets are deep enough, it will always be possible to send to Mars as many solar panels and whatever sized propellant manufacturing and storage facility are needed to produce a power system of any required reliability. Essentially, the more mass you are prepared to add, the greater the reliability. But the higher the cost.

What is really needed here is a complete peer reviewed engineering study of the concept that moves beyond back of the envelope calculations. Hunches, educated guesses and optimism cannot come into it. It needs to be clear about system mass, reliability and what it allows in terms of mission performance, using commercially available and backed up by references that stand up to peer review. The closer we get to actually needing such a system, the less tolerable uncertainty becomes.

For the longer term goal of powering a settlement that grows into a city, you cannot rely on any pocket being deep enough to sustain the cost of manufacturing and shipping to Mars the required power supply. As Kbd512 has shown, the required mass for a city of 1 million people exceeds 1 million tonnes. And manufacturing costs become less trivial as transportation costs decline. There needs to be a way of making this equipment on Mars.

As I explained previously, ERoEI, and conversely ECoE, matters a great deal. I don't think you remotely understand why. You have to invest energy in building, maintaining and replacing an energy source as one of many energy investments in a society. The lower ERoEI, the less energy remains for other things, including building and repairing other infrastructure and meeting essential needs. It is simple accountancy really. In a situation where energy supply and infrastructure need to expand rapidly, poor ERoEI isn't going to work for very obvious reasons. For some reason, discussions on economics seem to confuse you about this. You are familiar I take it, with the first law of thermodynamics, the conservation of energy? You also know that making things requires the use of energy to rework matter? The second law tells us that using energy to carry out work, always involves an increase in total entropy. It sets limits on the efficiency of processes and introduces the concept of energy quality. I think you should read up on this.

GW Johnson · 2021-04-13 08:21:15

Periodically, we keep going down this same road, arguing over solar-only. Again and again. I see a lot of numbers quoted, especially to support Louis's position that dust storms be damned, no nuclear. And I see selective choice of data in those arguments. His 20% min insolation figure is just plain wrong.

Go to http://exrocketman.blogspot.com to see where I posted some NASA data from Opportunity, and more. It includes a link to the NASA report itself. That 2018 dust storm starved the rover of PV-generable power (near 5% not Louis's 20%), and it died in the cold for lack of power to run its heaters. So says NASA, not me. Click on year 2019, then click on month October, then click on the title "A Note on Solar vs Dust Storms on Mars". There are NASA's own photos, too, to show just how dark it got during the day.

The same article brings up the observations made during Mariner 9 from orbit in 1969. While there is no ground truth (no landers had ever made it that far back), you can calibrate the orbital observations by the fact that the volcanoes on Tharsis were obscured in the dust layer. We have never seen one that bad since. Mariner-9 observed 9 months to a clear atmosphere, but remember, it found Mars already obscured when it arrived.

So insolation really can approach zero %, and it really can be that way for many months on end. There is no way to survive that on solar alone. Not with batteries, not with propellant-fired engine generators, nothing. Nuclear is the ONLY option we have, at this time in history.

Sorry Louis, but them's the facts you so studiously ignore. Not mine, NASA's. Documented. Arguing about 20 vs 40% PV cell efficiency is arguing angels on the head of a pin, compared to those incontrovertible facts.

GW

Last edited by GW Johnson (2021-04-13 08:23:50)

Oldfart1939 · 2021-04-13 10:07:20

Louis-
We all appreciate your ideas and contributions here, but most of the scientific professionals have poked enough holes in your fanciful concept of a Solar Only colony to convince almost anyone else. You can't simply wave your hand and dismiss the thoughts of GW, kbd512, Calliban, Quaorar, Dr. Zubrin in his writings, and even myself, as not being based on factual analysis.

This undertaking is entirely TOO IMPORTANT TO MANKIND for any failure to occur. We can't lose our fellow man due to someone's wishful thinking.

kbd512 · 2021-04-13 11:52:28

GW,

Stop exaggerating. Surface insolation on Mars was never "close to zero". It was a whopping 1% for a month or so. It had a whole 0.9999999999% to go before it was "close to zero". If we had 50 Bhadlas on Mars, we'd still be making 890MWh per day. We only need 500 Bhadlas to produce enough life support power during that solar storm for life support energy production to continue on as normal. If we just shipped 564,000,000t of silicon to Mars, 500,000,000t of CFRP backer board, and who knows how much wiring and how many transformers, then there'd be no issue with using solar power to support a city of a million people during a global dust storm. On that note, I'm really starting to wonder how Bhadly things have to go before it dawns on some of us that this is not a game.

Edit: Should be 56,400,000t, not 564,000,000t. Brain... Broken... No more religion... Need... Engineering. Ugh!

Last edited by kbd512 (2021-04-13 12:42:03)

Calliban · 2021-04-13 12:20:26

kbd512 wrote:

GW,
Stop exaggerating. Surface insolation on Mars was never "close to zero". It was a whopping 1% for a month or so. It had a whole 0.9999999999% to go before it was "close to zero". If we had 50 Bhadlas on Mars, we'd still be making 890MWh per day. We only need 500 Bhadlas to produce enough life support power during that solar storm for life support energy production to continue on as normal. If we just shipped 564,000,000t of silicon to Mars, 500,000,000t of CFRP backer board, and who knows how much wiring and how many transformers, then there'd be no issue with using solar power to support a city of a million people during a global dust storm. On that note, I'm really starting to wonder how Bhadly things have to go before it dawns on some of us that this is not a game.

564Mtonnes of silicon? Should be a synch. We can use an Orion nuclear pulse engine to deliver that kind of mass! Oh wait...

kbd512 · 2021-04-13 12:40:42

Calliban,

My internal calculator is broken. I've been going blind on these numbers for too long. It's only 56,400,000t (100X the 564,000t of Silicon for the 50 Bhadlas, not 1,000X). That's what I get for doing this stuff in my head. That makes everything 10 times easier, right? At least I'm honest enough to correct my own mistakes. One of our members still won't accept the empirical power output figure from the world's largest solar array. I think it's power output is incredibly impressive. 1.3TWh per year is a LOT of power. The only problem is that we need a multiple of that. Anyway, the total tonnage of propellant and everything else will be wildly over 564,000,000t. Seriously, though, this is getting tedious and I just don't care enough to put more effort into it. This is about dogma for some people, not engineering. I'm not interested in joining any religious groups. I don't know why exactly, but it's never appealed to me, not even when I was 7 (probably why they asked me to leave the Catholic Church, which I was more than happy to do- they can't have inquisitive 7 year olds questioning stammering 50 year olds with masters and PhDs in front of the other kids). I know some people who are quite happy with their religion, but it's not for me.

That said, I know my numbers for the rest of this stuff are correct, because they're based upon empirical data that I've checked and re-checked at least a couple dozen times now. I checked so many times because I also have a hard time wrapping my head around how much power we need. It's nuts, but McMurdo Station is also using 32MWh per person in the winter. A city on Mars certainly won't be using any less energy than a place where the air and water are free.

louis · 2021-04-13 14:16:32

Kbd,

Regarding the document -

https://agupubs.onlinelibrary.wiley.com … 19JE005985

There are a number of things to say about this:

1. Gale Crater is a dust bowl. Whatever else is going to happen, no Starship is going to land with humans in a dustbowl. One of the criteria used by NASA/JPL in choosing the landing zone is to find somewhere with relatively low dust levels. So, Gale Crater is very much a worst case scenario.

2. This paper does not state that insolation drops by 95% "during the dust storm" as you claim. It states that during the "highly dusty phase" of the storm values drop by more than 90%. However two important points:

(a) the "highly dusty" phase lasts for a mere 15 sols.

(b) after the peak period there was a dramatic recovery:

"However, after the peak, then values dropped to 60% of pre storm level but these were in keeping with the seasonal trend:
the UV ABC‐channel increased its signal from <10% (during the highly dusty phase) to ~60% of the values measured prior to onset. These irradiances are in fact only slightly below typical values for this time of year (see Figure 2), and given that Mastcam reported typical seasonal values by this point..."

So the insolation was "only slightly below" the norm for most of this dust storm.

My claim of getting around 40% of normal power during a dust storm appears very cautious if anything.

3. There is something opaque itself about the paper Firstly, there's this:

"...it is likely that the increase in dust deposition on the sensor photodiodes during the storm (Figure 1) attenuated the UV signal in its aftermath, rather than higher‐than‐normal atmospheric dust loading continuing to exist. "

And there's this:

"As stated above, the apparent attenuation observed during the highly dusty phase was 95% (Table 2), although additional dust deposition on the photodiodes (Figure 1) during the storm may also have slightly affected this value. "

Not sure what to make of that. One interpretation is that the 90-95% figures are over-inflated. They are certainly the highest I have ever seen quoted.

4. So, overall, this is really the worst of the worst: a dust bowl measurement during one of the worst dust storms on record and with the insolaton values further reduced by dust accumulation.

But let's assume we had an average 92.5% reduction over 15 sols (the paper indicates it was between 90 and 95%) - what then? That would mean if the Mission One base would on average be producing 1Mwe constant, we would be reduced to 75 KwHes constant during those 15 sols. That is probably more than enough to keep the base running. But if not you might look to your chemical battery reserve. I've recommended taking at least 30 tons of batteries. Some of these will of course be found in vehicles. Anyway, with 30,000 Kgs at 250 Whs per Kg that would give you 7,500 KwHes allowing you an additional 20Kwhes constant - so taking you up to 95 KwHes. Still not enough? Well then you starting using your methane and oxygen supply. If it's some way into the mission you will awash with it. Even on arrival there will be plenty sloshing around in the Starship tanks and you can bring with you a dedicated supply. 10 tons of methane could produce 13600 KwHs of energy converting to maybe 7480 KwEs or another 20KwHes constant - so taking you up to 115 KwHes constant . If you still feel that doesn't cut the mustard, then take more methane and more batteries.

A solar powered base can easily ride out even this worst case dust storm. However, the Starships won't be landing in areas with large dust accumulations.

Last edited by louis (2021-04-13 14:17:00)

Oldfart1939 · 2021-04-13 14:28:25

louis wrote:

Kbd,
A solar powered base can easily ride out even this worst case dust storm. However, the Starships won't be landing in areas with large dust accumulations.

Louis-I'm getting really tired of this BS. I'm a retired Physical Chemist and specialized--once upon a time--in Thermodynamics, and Molecular Photochemistry. You are simply grasping at straws now, trying to discredit the careful calculations and research of some professionals. OK, Solar Power is YOUR RELIGION. It isn't mine and it isn't kdb512's, nor is it GW's.

My bottom line is that if there isn't a strong nuclear system in place as the primary power source--I AIN'T GOIN'! I never argued that is should be the only power source, as I'm too eclectic to make that sort of demand.

If we follow your plan--people DIE.

Quaoar · 2021-04-13 14:49:13

Louis,

I may understand your aversion for nuclear on Earth, where an accident can contaminate a region and make a lot of damage like in Fukushima, but on Mars, where there is no air to pollute there is no problem: you just need to put your reactor far from the habitat and the buried glacier you use as a source of water.
If you want to colonize the space, we cannot go too far with chemical rockets: we need NTRs and we need to evolve them from the solid core to the more advanced gas core, so in a future we can go to the asteroid belt and the moons of Jupiter.

Last edited by Quaoar (2021-04-13 14:50:05)

kbd512 · 2021-04-13 14:51:15

Louis,

1. Starship will land wherever there's ice nearby and a low probability of tipping over.

2A. That doesn't matter if you need to consume 6,000t of Methane per day to power a city of a million people. You're not going to store 90,000t of LNG without the mother of all cryogen tanks.
2B. There will only be a dramatic recovery if people are still alive at the end of two weeks, no matter what the insolation levels do.

3. If there's higher than normal dust left on the PV panels, then it has to be cleaned off prior to resuming normal operations, right?

4. Do we have any measurements from other places to "know" that the conditions at Gale Crater were the "worst of the worst"? I have another news article that says Gale Crater was spared some of the worst dust accumulation from that storm. You could still be correct, but other source indicate that it wasn't as bad there as it was where Opportunity bit the dust.

How do you get to determine where the Starship lands? If there's tons of ice under the dust, do they simply ignore that and land elsewhere, merely to appease your beliefs about solar power?

Do you have any idea how many rules and stipulations you've set for where Starship can land, who can go, what they can do when they get there, what they can eat, etc, all in an attempt to prove that solar power is merely feasible?

GW Johnson · 2021-04-13 16:41:58

I am still seeing the "selective data" monster operating here.

What happened in Gale crater is only one report about only one dust storm. What I posted on "exrocketman" (and called out in post 384 above) is another NASA report (link given on "exrocketman") about the dust storm that "killed" the Opportunity rover. That's a different storm, in a different place, at a different time. NASA estimated solar PV power production at 5-10% of clear-day nominal, not enough to run the heaters. So the electronics "froze to death".

So also would people freeze to death in conditions like that.

And that is NOT the worst dust storm we have ever observed on Mars!

The worst we ever observed was long before we ever had any rovers there to get ground truth. That was the total obscuration of the entire planet in a dust layer more than 15 km deep, that lasted for over 9 months before the atmosphere was entirely cleared. That was the Mariner-9 orbiter in 1969. The "exrocketman" article I posted discusses the implications of that event, too.

Louis obviously has not visited the "exrocketman" site, has not seen what I posted, and has not followed the cited link to the published NASA report on-line about Opportunity's "death".

Or else he chooses not to, for purposes of selective data to bolster his position. There is no other possible conclusion here.

GW

kbd512 · 2021-04-13 16:44:50

GW,

It's ideology, plain and simple. Whenever ideology doesn't correlate with objective reality, ideologues double-down on ideology.

Calliban · 2021-04-13 16:49:41

Quaoar wrote:

Louis,
I may understand your aversion for nuclear on Earth, where an accident can contaminate a region and make a lot of damage like in Fukushima, but on Mars, where there is no air to pollute there is no problem: you just need to put your reactor far from the habitat and the buried glacier you use as a source of water.
If you want to colonize the space, we cannot go too far with chemical rockets: we need NTRs and we need to evolve them from the solid core to the more advanced gas core, so in a future we can go to the asteroid belt and the moons of Jupiter.

Background radiation dose rates on Mars are about 200mSv per year. I worked out a while back that a 2000 hour per year exposure to that radiation for 40 years, would reduce average life expectancy by the same amount as air pollution does for the average person on Earth. This is a factor of 10 higher than the exclusion zone limits for Fukushima.

With a modern power reactor, there is something like a 1 in 10 million chance of a fuel damage event leading to a pollution hazard for an area of a few tens of square km, that is about equivalent to what we all face due to air pollution anyway. The risk is extremely small because the frequency is small and the realistic consequences aren't that scary when you put them into context. Even on Earth, nuclear power is the best way of generating power from a safety viewpoint.

On Mars, the environment is already screaming with radiation from cosmic rays. The reality of a nuclear accident is that it would increase background dose rates marginally over what is there already. Would the radiation spread further without a functioning hydrosphere? Probably. But the more the radiation spreads out, the less concentrated the effect would be.

Last edited by Calliban (2021-04-13 16:51:13)

Calliban · 2021-04-13 17:12:19

kbd512 wrote:

GW,
It's ideology, plain and simple. Whenever ideology doesn't correlate with objective reality, ideologues double-down on ideology.

My own boiling point over this nonsense occurred a couple of weeks back after researching the case for a solar powered aeroplane. I used the 747 as a case study and discovered that solar panels lining the entire upper surface and wings produced about 1000 times too little power to generate the requisite lift at the reported lift-drag ratio. Louis suggested towing a solar array behind the plane to boost power supply. I explained the need to maximise lift-drag ratio in a plane running at such low power, but Louis was having none of it. I gave up in the end. The man isn't here to develop practical suggestions, he just wants his pet ideas accepted unconditionally because they are emotionally important to him. Which is why this sort of exercise runs in endless circles. It is not an honest search for truth. He wants you to accept his ideals as a matter of faith. It may seem odd that anyone can have a religious level of belief in a power source. But apparently they can.

I wish him well, but I find his pet discussions soul destroying because nothing ever gets resolved. He refuses to concede points even when the evidence leaves him with no leg to stand on. It ends up looking pathetic.

From my own point of view, the solar power debate has been useful in focusing my attention on concepts for nuclear reactors that we could actually build on Mars. Not entirely wasted and I doubt that I would have done it otherwise.

Last edited by Calliban (2021-04-13 17:25:55)

kbd512 · 2021-04-13 17:37:08

Calliban,

I wouldn't get too worked up over it. Many of the ideas were throw around here are impractical in nature, if not fanciful. I honestly don't care about the power source selected, so long as we can feasibly deliver it and it works reliably. It should be clear that I like solar panels for what we can realistically use them for, which is why I have so many of them on my roof. I'm realistic about what they can do, though, as is the company that installed them. I can never power the AC unit, nor even all of the lights in the house, which is why they power a few critical items like the refrigerator and kitchen lights. I simply find dogmatic adherence to ideology to be unhelpful to a Mars mission. If someone invents a reliable fusion reactor tomorrow, then I'm not going to support the use of nuclear fission for a Mars mission when a power source that consumes even less material and produces less radiation is readily available.

SpaceNut · 2021-04-13 19:57:23

How SpaceX will Refuel on the Surface of Mars refueling is In-Situ Propellant Production (ISPP)

1*X2YyUhgFTOO3KzF-5MIVTw.jpeg

Refueling is a big one. The mission profile for a Starship traveling to Mars consists of the following phases:
Launch from Earth with Mars-bound payload, arriving in orbit with dry tanks
Refuel in orbit with multiple Starship tanker launches and rendezvous, topping off the tanks
Transfer orbit to Mars and land on Mars without orbital insertion.
MISSION
Refuel on the surface of Mars.
Launch from Mars and transfer orbit to Earth.
Land on Earth without orbital insertion.
Methane is CH4 — four hydrogen atoms and a carbon atom.
The hydrogen is roughly 25% the molecular mass of methane, so this amounts to bringing one fourth the mass of the total fuel along. Breaking this down:
Starship methane fuel mass: 240,000kg
Hydrogen portion of fuel mass: 240,000kg * .25 = 60,000kg
Starship Payload to Mars: 100,000kg

Bringing the hydrogen along would consume two-thirds of the payload capacity, but is doable but thats only half insitu

1*lDefPdCymjIJXom9g8R0kQ.png

ministarship.png?w=720

The Earth-Mars launch window opens for a few months every 2.2 years. One Starship can perform the Earth-Mars-Earth round trip during this time, provided it can refuel immediately upon landing and unloading cargo. If it has to wait for the next launch window to return, it can only launch from Earth every other window, roughly every 4.3 years.

Mars is only close to Earth every 22 months so a Mars mission would need to be able to stay on the surface for 22 months before they can return to Earth.

despite InSight detecting hundreds of passing dust devils, none has been close enough to clean off those dinner-table-size panels since they unfurled on Mars in November 2018.

Today, InSight’s solar arrays are producing just 27% of their dust-free capacity. That power has to be shared between science instruments, a robotic arm, the spacecraft’s radio, and a variety of heaters that keep everything in working order despite subfreezing temperatures. Since the windiest season of the Martian year has just ended, the team isn’t counting on a cleaning event in the coming months.

Thats with the huge fan solar arrays getting badly coated from dust that never gets removed getting thicker by the day.

Solar Power is Never Going to Work on Mars, and Everybody Knows It

If we look at a 2031 reference mission, departing on February 22, it arrives at Mars about nine months later on November 7th, 2031. The next departure date for Earth is February 5th, 2033, leaving only 456 days to generate the return fuel, assuming that we’re generating the fuel on-demand in real time). If we leave a fifty day safety zone, this means we must produce about 2,500kg of propellant per day.
Pioneer Astronautics created a prototype ISPP (In-Situ Propellant Production) plant which produces 1kg/day of propellant using 700 watts of power. If we take that number and multiply it by 2500, we get 1.75 Megawatts of power.
To calculate the area of solar panels needed, we’ll use a simplified equation:
Area = Total Energy Needed / Peak Solar Irradiance on Martian surface / efficiency of solar panels / Solar Irradiance ratio
Terms explained:
Peak Solar Irradiance on Martian surface
This is the solar energy (in watts per square meter) that reaches the Martian surface, at the equator at noon on a cloudless, duststorm-less day. That figure is 593 watts / sq. m.
Efficiency of Solar Panels
This is the engineering efficiency of the panels — their capability to transform solar irradiance into electricity. Highly efficient panels currently in development are at around 44% — I’m assuming some engineering trade offs and stipulating a still-impressive 35%.
Solar Irradiance ratio
The sun doesn’t shine at night, it doesn’t shine the same at 4PM as it does at noon, and it doesn’t shine as brightly way up north or south as it does at the equator. This number is a guess without knowing precisely where the landing site is, but 20% is a number commonly used for Earthbound panels used in northern European latitudes.
Looking at our equation again:
Area = Total Energy Needed / Peak Solar Irradiance on Martian surface / efficiency of solar panels / Solar Irradiance ratio
If we plug in our numbers:
Area = 1,750,000w / 593w / 35% / 20%
Area = ~42,000 sq meters (10 acres)

Even worse, the Pioneer Astronautics prototype relies on hydrogen feedstock.

https://ntrs.nasa.gov/archive/nasa/casi … 018252.pdf

20131231_tau_2007_dust_storm_graph_doug.jpg.webp

Oldfart1939 · 2021-04-14 10:01:56

Everyone needs to read the article linked by SpaceNut:

https://medium.com/swlh/solar-power-is- … fb221722b1

tahanson43206 · 2021-04-14 11:09:53

For Oldfart1939 re #399

Thanks for the encouragement to read the article ...

For SpaceNut ... thanks for finding it!

(th)

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