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The point of my post #15 above is that things like methane are NOT an energy source on Mars because there is NO oxygen to burn them with. Until you have oxygen to burn it with, methane on Mars is as inert as a piece of stone. It really is irrelevant as to how efficiently you might produce it. Without oxygen, it is utterly and completely useless.
Electrolysis to produce oxygen from local water is around 6% energy efficient. Period. Deal with it. I don't know much about "Moxie", but it cannot be much better than electrolysis, or we'd already be doing it here.
There's nothing at all wrong with solar except its immediacy and intermittency. The ONLY way around those is energy storage, and that means batteries. PERIOD!!! At something on the order of 1/100 of the energy per unit mass (or volume) of what we are used to with liquid fuels. And, especially with lithium, a short service life.
And then there is nuclear, which is both reliable and energy-dense, compared to these other sources, and it is unaffected by darkness and dust storms. In space, it needs big radiators to reject its waste heat, but that can be done with buried plumbing, to the cold Martian regolith as a heat sink.
EXCEPT, wearing those idiotic balloon suits, NO astronaut is capable of digging real pipe trenches, nor is he capable of doing real plumbing in pipe sizes under 2 inch diameter. And I'm not at all sure he can do plumbing in pipe sizes of 2.5 inch and up.
Solar PV is pre-packageable and self-contained, but it is intermittent, and it requires construction to set up the panels. Nuclear requires construction work for shielding and regolith heat rejection. We CANNOT do construction work for either type of energy using the space suits we have.
Does THAT tell you where the real shortfall is? Spacesuit design?
GW
Last edited by GW Johnson (2017-05-31 18:44:41)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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I've never said it will be impossible to build a nuclear reactor on Mars. I've said it will be beyond the capability of a small settlement, say 100 people. For every 100 Kw of additional power, you are going to want to import ten tonnes of nuclear reactor. That's a lot of tonnage denied to other purposes. If you are saying you can build a nuclear reactor on Mars in a small settlement, then the issue is how much labour time per Kw of output is required - that will be the main test (apart from usage suitability). I can only go by the incredibly high costs of nuclear reactor construction to assume there is a lot of complexity in the construction process.
We're not going to manufacture solar panels, gas turbines, or nuclear reactors on Mars. Power plants come from space ship Earth because that's where all the infrastructure exists to design, build, and test power plants of any kind.
The batteries required to store 1.2MWh (100kWh * 12 hours) weigh 6,000kg using Panasonic / Tesla 20700 Lithium-ion cells. That's the best commercial battery tech we have. It's been tested in just about every way imaginable and is as reliable as any battery technology available. That's more mass than a shadow-shielded SAFE-400, just for the batteries. Once Graphene-based batteries become comercially available, that mass drops to 1,500kg to store 1.2MWh. In another ten years or so, I expect Graphene-based batteries to store 2.5kWh/kg. If we wait about ten years, then the initial exploration missions can use thin film solar panels and Graphene batteries and deliver equivalent power to small nuclear reactors for less mass.
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I am not sure why you are quoting fright figures for batteries.
You will need batteries on Mars, whatever your basic energy source is. But chemical batteries are not the only form of storage. Also, please note batteries can also be manufactured on Mars with relative ease. Batteries are not that complex. Lastly, batteries can double up in use. Batteries that are used to power vehicles can also be used to provide emergency power if necessary.
Your assumption that solar panels cannot be constructed by a small Mars community endowed with the right machines is simply not tenable.
louis wrote:I've never said it will be impossible to build a nuclear reactor on Mars. I've said it will be beyond the capability of a small settlement, say 100 people. For every 100 Kw of additional power, you are going to want to import ten tonnes of nuclear reactor. That's a lot of tonnage denied to other purposes. If you are saying you can build a nuclear reactor on Mars in a small settlement, then the issue is how much labour time per Kw of output is required - that will be the main test (apart from usage suitability). I can only go by the incredibly high costs of nuclear reactor construction to assume there is a lot of complexity in the construction process.
We're not going to manufacture solar panels, gas turbines, or nuclear reactors on Mars. Power plants come from space ship Earth because that's where all the infrastructure exists to design, build, and test power plants of any kind.
The batteries required to store 1.2MWh (100kWh * 12 hours) weigh 6,000kg using Panasonic / Tesla 20700 Lithium-ion cells. That's the best commercial battery tech we have. It's been tested in just about every way imaginable and is as reliable as any battery technology available. That's more mass than a shadow-shielded SAFE-400, just for the batteries. Once Graphene-based batteries become comercially available, that mass drops to 1,500kg to store 1.2MWh. In another ten years or so, I expect Graphene-based batteries to store 2.5kWh/kg. If we wait about ten years, then the initial exploration missions can use thin film solar panels and Graphene batteries and deliver equivalent power to small nuclear reactors for less mass.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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I am not sure why you are quoting fright figures for batteries.
I quoted figures that correspond to the highest energy density actually achieved in mass-produced batteries made on Earth. I'm not trying to "scare" anyone with the battery mass figures I provided. I'm trying to inject some engineering reality into this discussion.
I already told you that if we improve the energy density of our batteries enough, then solar becomes competitive with nuclear. Presently, fission power sources provide more continuous power with less mass. You've attempted every re-direct (gas turbines), mis-representation (incorrect math regarding battery capacity or assumptions about how much power is required with no backing data to support your assertions), and glittering generality (we'll have better batteries when we need them) imaginable, but the numbers don't lie (the numbers don't support mathematically invalid arguments).
This is not an ideologically driven argument for me, although it clearly is for you. I know how to count and I know why it is that more than absolute minimum capacity is required. Basic math won't change to support ideological arguments from you, me, or anyone else.
You will need batteries on Mars, whatever your basic energy source is. But chemical batteries are not the only form of storage. Also, please note batteries can also be manufactured on Mars with relative ease. Batteries are not that complex. Lastly, batteries can double up in use. Batteries that are used to power vehicles can also be used to provide emergency power if necessary.
All the hand-waving in the world won't change engineering reality. If you think you can manufacture a 100kWh battery in your garage, then try it and see what you come up with. It's not impossible, but you'll be surprised at how non-trivial it becomes, how much it weighs, and what's required from a basic engineering standpoint.
Vehicle batteries can and should serve as backup power sources, but that doesn't remove the requirement to provide adequate capacity for operations to begin with.
Your assumption that solar panels cannot be constructed by a small Mars community endowed with the right machines is simply not tenable.
When you say "manufacture", do you mean print ink onto plastic using materials (plastic and ink) brought from Earth, or do you actually mean all materials locally sourced and fabricated using machinery brought from Earth?
The former is certainly doable while the latter requires a level of industrialization that won't be achievable for decades.
Last edited by kbd512 (2017-06-01 08:02:45)
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Thanks kbd512;
I think we've all been saying the same thing, over and over, and over again. My argument has been based on the system-concept useful in thermodynamics. But getting down to batteries: they are based on chemistry, and specifically the reduction-oxidation couple between the metal involved (Lead, Lithium, Cadmium, etc.) and it's ionic form. We are limited by the realities of this number, and no amount of wishful thinking can change the physical realities of the system. The power available from a battery is thus based on mass of the metal involved. Batteries. Weigh. a LOT.
Louis continues to overstate the mass of a SAFE-400 nuclear power plant in order to support his fanciful beliefs. Please, please, I'm not attacking Louis, but he needs to come to grips with the physical limitations of the chemical systems he's called upon to support his Solar concepts.
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"The SAFE-400 space fission reactor (Safe Affordable Fission Engine) is a 400 kWt HPS producing 100 kWe to power a space vehicle using two Brayton power systems – gas turbines driven directly by the hot gas from the reactor. Heat exchanger outlet temperature is 880°C. The reactor has 127 identical heatpipe modules made of molybdenum, or niobium with 1% zirconium. Each has three fuel pins 1 cm diameter, nesting together into a compact hexagonal core 25 cm across. The fuel pins are 70 cm long (fuelled length 56 cm), the total heatpipe length is 145 cm, extending 75 cm above the core, where they are coupled with the heat exchangers. The core with reflector has a 51 cm diameter. The mass of the core is about 512 kg and each heat exchanger is 72 kg."
http://www.world-nuclear.org/informatio … space.aspx
Well you tell me what the mass is...it looks like the core is 512 kg. But I can't find info on what the total heat exchanger mass is. Is it 72 Kgs x 127 ? Then we have to consider the deployment system, cabling and so on. Of course we don't have a real Safe 400 in existence to satisfy our curiosity.
You make it sound like nuclear precludes the need for batteries. I doubt that. I think batteries are probably going to be running most of the vehicles around base. There's no reason why they can't double up as an emergency power supply. But most power storage under a solar system would be as methane/oxygen or as short term heat in my view.
Thanks kbd512;
I think we've all been saying the same thing, over and over, and over again. My argument has been based on the system-concept useful in thermodynamics. But getting down to batteries: they are based on chemistry, and specifically the reduction-oxidation couple between the metal involved (Lead, Lithium, Cadmium, etc.) and it's ionic form. We are limited by the realities of this number, and no amount of wishful thinking can change the physical realities of the system. The power available from a battery is thus based on mass of the metal involved. Batteries. Weigh. a LOT.
Louis continues to overstate the mass of a SAFE-400 nuclear power plant in order to support his fanciful beliefs. Please, please, I'm not attacking Louis, but he needs to come to grips with the physical limitations of the chemical systems he's called upon to support his Solar concepts.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Louis-
I never said we wouldn't need any batteries, but the scale of vehicle and power tool operation is considerably less than the total energy requirement of the entire base, especially if there is a massive dust storm lasting for months at a time. The Safe-400 would seem to require a total mass of << 3000 kg, but the cables and support wiring are needed regardless of the power source utilized. Using regolith for shielding would be prudent.
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If we are looking at ISRU, I would point out that it should be possible to construct heat exchangers, boilers and crude steam generating systems on Mars, much as Louis has described for his solar power system. The bulk material needed is low carbon steel, which can be moulded into bulk components using the carbonyl process. Only the 512kg reactor core itself would need to be shipped from Earth under this scenario.
If we can manufacture steam engines sets that are 15% efficient, then a 400kWth reactor core would generate 60kWe. The power density of the from-Earth component would be 117W/kg. If uranium represents most of the weight of the core and burn-up is 10% say at end of life, then the core would produce 54million kWh over its lifetime. If it costs $2000/kg to ship stuff from Earth under colonisation phase, the cost of importing the reactor would add 1.87 cents to the cost of generating a unit of electric power on Mars. That really is lost in the noise.
I looked earlier at the possibility of building small Magnox reactors on Mars, using Martian natural uranium and reduced carbon as a moderator. Calder Hall took several years to build and the workforce ran into many hundreds of people. Each reactor weighed 33,000 tonnes (most of which was shielding) and produced 50MWe. So that's 660Kg/KWe, maybe ~100Kg/kWe without shielding. That compares to 8.53Kg/kWe for the SAFE-400 core. So, until the population on Mars reaches a level of thousands, it will make more sense importing fast reactor cores from Earth and building the secondary systems on Mars.
Last edited by Antius (2017-06-01 11:32:07)
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As best I can tell, information on the mass of a complete SAFE-400 design is very incomplete. There is the core at 512 kg, which includes those 127 heat pipe assemblies that are also the fuel rods. There is no weight published for the moderator or structural shell, although these would not be "large" numbers.
There are two heat exchanger assemblies at 72 kg each, which take heat from the heat pipes and dump it into a gas loop for the turbine-driven generators. I have not found anything about the weights of those turbogenerators, which each would have to include a turbine, a compressor, and an electric generator machine. The heat gets dumped into the gas stream between the compressor and the turbine, so that's where the heat exchangers physically have to be located.
The rejected heat is radiated to space from a large radiator panel or panels. There must be radiator fluid, pumps to circulate it, supply tanks from which the coolant comes, and of course the radiator panels themselves. I cannot find weights for any of these items.
The people developing these systems are playing it "cagey" with the numbers for marketing/funding purposes. They always compare only on the basis of core weight. The real system is much heavier, in its complete and operable form. In the ground tests of these things, not all the system has to be there. And it isn't, yet.
I dunno; a wild guess says 2 tons or thereabouts, without shielding. Shielding can be regolith piled up about a device mounted down in a small crater or other depression.
As for nuclear versus solar: that's angels on the head of a pin. I repeat: you need both. The only "argument" is over how much of each to send.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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You keep using words like "uneconomical" and "competitive" without defining what you mean by them. Are you really claiming that an Mars ISRU energy system that was 10% less energy dense than a nuclear reactor imported from Earth would be less "competitive" than a nuclear reactor, even though you are hauling your nuclear reactor all the way from Earth?
Energy density is no more a master concept than EROI. On Earth energy density is a matter of convenience and profitability. On Mars it is an irrelevance in comparison with labour requiments, reliability, health and safety, failsafe quality, and flexibility. Land on Mars is free. There is no commercial cost and in whether it's nuclear or solar it's being delivered to or built at the site.
I've accepted I made a calculation error on the batteries but in my defence, I couldn't really comprehend why you would be talking about such gigantic battery usage - 1 GwH...i.e. 1 million KWhs which would be enough for 3,400 sols at emergency power level (12Kws) for a six person mission! Why would you be talking about such huge battery usage? I made it quite clear that for emergency power I am envisaging methane plus oxygen being the main source - and that would be manufactured initially during the pre-landing period. For Mission One, I would think we would want probably a couple of tonnes of batteries or thereabouts, for powering a rover and industrial uses, which in an emergency situation could keep a six person mission power-supplied for a sol or more. But as already indicated, there would be a plentiful back up through methane and oxygen.
The mass of an ISRU battery on Mars is unlikely to be a key issue. I would envisage such a Mars ISRU battery would be built close to an industrial hab and would be a fixed installation.
I don't doubt this is a job for people who know what they are doing and having the right equipment available. But it looks very doable:
http://www.madehow.com/Volume-1/Battery.html
Potassium, manganese, carbon and zinc are all available on Mars.
louis wrote:I am not sure why you are quoting fright figures for batteries.
I quoted figures that correspond to the highest energy density actually achieved in mass-produced batteries made on Earth. I'm not trying to "scare" anyone with the battery mass figures I provided. I'm trying to inject some engineering reality into this discussion.
I already told you that if we improve the energy density of our batteries enough, then solar becomes competitive with nuclear. Presently, fission power sources provide more continuous power with less mass. You've attempted every re-direct (gas turbines), mis-representation (incorrect math regarding battery capacity or assumptions about how much power is required with no backing data to support your assertions), and glittering generality (we'll have better batteries when we need them) imaginable, but the numbers don't lie (the numbers don't support mathematically invalid arguments).
This is not an ideologically driven argument for me, although it clearly is for you. I know how to count and I know why it is that more than absolute minimum capacity is required. Basic math won't change to support ideological arguments from you, me, or anyone else.
louis wrote:You will need batteries on Mars, whatever your basic energy source is. But chemical batteries are not the only form of storage. Also, please note batteries can also be manufactured on Mars with relative ease. Batteries are not that complex. Lastly, batteries can double up in use. Batteries that are used to power vehicles can also be used to provide emergency power if necessary.
All the hand-waving in the world won't change engineering reality. If you think you can manufacture a 100kWh battery in your garage, then try it and see what you come up with. It's not impossible, but you'll be surprised at how non-trivial it becomes, how much it weighs, and what's required from a basic engineering standpoint.
Vehicle batteries can and should serve as backup power sources, but that doesn't remove the requirement to provide adequate capacity for operations to begin with.
louis wrote:Your assumption that solar panels cannot be constructed by a small Mars community endowed with the right machines is simply not tenable.
When you say "manufacture", do you mean print ink onto plastic using materials (plastic and ink) brought from Earth, or do you actually mean all materials locally sourced and fabricated using machinery brought from Earth?
The former is certainly doable while the latter requires a level of industrialization that won't be achievable for decades.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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You keep using words like "uneconomical" and "competitive" without defining what you mean by them. Are you really claiming that an Mars ISRU energy system that was 10% less energy dense than a nuclear reactor imported from Earth would be less "competitive" than a nuclear reactor, even though you are hauling your nuclear reactor all the way from Earth?
I'm talking about power plant mass required to achieve a given level of electrical output on the order of what NASA projects for their exploration missions. Increasing human presence and capabilities only exacerbates energy problems. The notion that solar is only 10% less energy dense than a fission reactor is absurd and the proof is all around us here on Earth. Even with 1950's nuclear reactor technology, the mass of steel and concrete is still less than it is for PV panel solar power plants and we're 50% closer to the Sun than Mars is.
Adding up the mass of the PV panels themselves and saying "Oh, look how great my PV panels are compared to coal / oil / nuclear" is being ridiculously naive. The only reason we can afford to use PV panels here on Earth is due to the mass exploitation of coal and oil reserves that don't exist on Mars. There's nothing to stop us form turning the water there into fuel, but only if far more mass is thrown at the problem. There are no super tankers, tanker trucks, refineries, or manufacturing plants on Mars. Stop and think about how much mass is devoted to providing electrical power here on Earth when the Sun don't shine and the wind don't blow.
We're hauling something to produce power all the way from Earth to the surface of Mars. That "something" can either provide the best electrical output per unit mass of power plant or it can be decidedly sub-optimal. Right now, as in today, fission reactors provide the best output per unit mass of power plant. In the future, it may very well be solar panels and batteries. On account of PV panels not working in darkness and current battery technology weighing what it weighs, as opposed to what we'd like it to weigh, the fission reactor comes out ahead at 1.5AU with 12 hours of darkness (in other words, the surface of Mars).
As nuclear power plants scale up and fissile material burnup rates increase using Thorium-fueled molten salt reactors instead of ridiculously inefficient solid Uranium fuel, the energy density is so far ahead of every competing technology that it makes me wonder whether or not we're really serious about providing electrical power for everyone here on Earth.
Energy density is no more a master concept than EROI. On Earth energy density is a matter of convenience and profitability. On Mars it is an irrelevance in comparison with labour requiments, reliability, health and safety, failsafe quality, and flexibility. Land on Mars is free. There is no commercial cost and in whether it's nuclear or solar it's being delivered to or built at the site.
Energy density is paramount if it costs $50,000/kg to ship whatever you want to ship. That's what it costs right now. Even if it was only $25,000/kg, that's still more than half as much as a kilogram of Gold. No matter claims to the contrary, energy density matters greatly for this application.
Small fission reactors of the type NASA wishes to use require the least amount of labor (unattended, just like any PV array and battery will be on the surface of Mars), are the most reliable (produce the same amount of power 24/7, irrespective of what local weather conditions are like, distance from the sun, etc), and are less costly than competing solar technologies (because NASA told DOE to use what they have on hand to build what they want and the only development items are the electric generators and control electronics, which have been subcontracted to people who specialize in these sorts of things). The ATK solar panels alone, for one mission, will cost more than the development program for the Kilopower reactors. DOE doesn't have unlimited budgets and since no cost-plus contracts involved, DOE and their contractors either deliver what was requested on time and within budget or they don't get funded by NASA.
I've accepted I made a calculation error on the batteries but in my defence, I couldn't really comprehend why you would be talking about such gigantic battery usage - 1 GwH...i.e. 1 million KWhs which would be enough for 3,400 sols at emergency power level (12Kws) for a six person mission! Why would you be talking about such huge battery usage? I made it quite clear that for emergency power I am envisaging methane plus oxygen being the main source - and that would be manufactured initially during the pre-landing period. For Mission One, I would think we would want probably a couple of tonnes of batteries or thereabouts, for powering a rover and industrial uses, which in an emergency situation could keep a six person mission power-supplied for a sol or more. But as already indicated, there would be a plentiful back up through methane and oxygen.
We have Lithium-ion batteries, PV panels, RTG's, and small fission reactors. There is no active development program for robotic methalox plants. Obviously it could be done, but the development funding and rockets to ship the mass to Mars have to come from somewhere. If you think the solar panels, batteries, and methalox plants (and all the mass required to extract water from Mars or to ship Hydrogen from Earth) would weigh less than a fission reactor, then you're not dealing with reality.
The mass of an ISRU battery on Mars is unlikely to be a key issue. I would envisage such a Mars ISRU battery would be built close to an industrial hab and would be a fixed installation.
Mass is a key issue for pretty much everything sent to into space. We're not on Mars right now largely as a function of what it costs. If we could afford to be inefficient and still get the job done, we'd have done that a long time ago. The only reason the NTR program existed was because we simply couldn't afford to ship enough mass using Saturn V. NASA wanted to send humans to Mars decades ago, but chemical rockets couldn't get the job done even with their massive budget.
I don't doubt this is a job for people who know what they are doing and having the right equipment available. But it looks very doable:
Potassium, manganese, carbon and zinc are all available on Mars.
Just about anything is possible, but what's practical to do with the types of technologies we can affordably ship to Mars?
How much power do you think we'll need to use to mine and refine those materials?
You also realize there's a difference between a lab experiment and something you're betting your life on, right?
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Energy payback time / EROI is doubly important on Mars, especially if ISRU is being used to expand the energy supply. Moving to Mars does not obviate energy economics, if anything it accentuates it.
You have paid billions of dollars to ship infrastructure and people to Mars with the objective of building native energy sources. You need to pay those people while they are there. If EROI is 80, then those people and assets are generating 20 times more output than if EROI is 4. But it gets worse. Remember, a quarter of that EROI must be reinvested just to maintain the energy supply. So an EROI of 4 actually provides 3 units of surplus energy.
That is a problem because even in a non-growing economy, there is still non-energy infrastructure that must be operated and maintained using energy. If the EROI is only 4, there is very little surplus to build anything else or expand the energy supply. This makes basic living very expensive and growth very difficult.
If EROI is 80, it is clearly very easy to spare enough energy to maintain the energy supply and there is likely to be a huge surplus available after maintaining and operating existing systems, a surplus that can be invested in new growth. If it takes 1 unit to maintain the energy supply, 2 units to run and maintain non-energy infrastructure, then an EROI of 80 gives 77 surplus units that can be reinvested in new infrastructure, energy sources, research into new technology, etc, or just consumer products to be enjoyed. If just 10 of those units are invested in expanding energy supply at an EROI of 80, then at the next iteration there will be 880 units of energy available, 11 of which must be reinvested to maintain the energy supply.
If EROI is 4, and 1 unit is reinvested in maintaining energy supply, 2 units are invested in running and maintaining non-energy infrastructure, then only 1 unit is left for both reinvestment and consumer products. If 10% of that unit is invested in new energy at EROI of 4, then at the next iteration there will be 4.4 units available, 1.1 of which must be reinvested to maintain the existing energy supply.
This is why human living standards did not improve on Earth until we started mining high EROI fossil fuels. High EROI means both high wealth per capita and the potential for high rates of growth. It will be very difficult to achieve high EROI on either Earth or Mars using diffuse renewable energy sources. The declining EROI of Earth bound energy sources is the primary reason behind the huge debt bubble, financial crisis and squeeze on living standards in recent years.
Last edited by Antius (2017-06-01 16:49:27)
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I'm talking about power plant mass required to achieve a given level of electrical output on the order of what NASA projects for their exploration missions. Increasing human presence and capabilities only exacerbates energy problems. The notion that solar is only 10% less energy dense than a fission reactor is absurd and the proof is all around us here on Earth. Even with 1950's nuclear reactor technology, the mass of steel and concrete is still less than it is for PV panel solar power plants and we're 50% closer to the Sun than Mars is.
Adding up the mass of the PV panels themselves and saying "Oh, look how great my PV panels are compared to coal / oil / nuclear" is being ridiculously naive. The only reason we can afford to use PV panels here on Earth is due to the mass exploitation of coal and oil reserves that don't exist on Mars. There's nothing to stop us form turning the water there into fuel, but only if far more mass is thrown at the problem. There are no super tankers, tanker trucks, refineries, or manufacturing plants on Mars. Stop and think about how much mass is devoted to providing electrical power here on Earth when the Sun don't shine and the wind don't blow.
We're hauling something to produce power all the way from Earth to the surface of Mars. That "something" can either provide the best electrical output per unit mass of power plant or it can be decidedly sub-optimal. Right now, as in today, fission reactors provide the best output per unit mass of power plant. In the future, it may very well be solar panels and batteries. On account of PV panels not working in darkness and current battery technology weighing what it weighs, as opposed to what we'd like it to weigh, the fission reactor comes out ahead at 1.5AU with 12 hours of darkness (in other words, the surface of Mars).
As nuclear power plants scale up and fissile material burnup rates increase using Thorium-fueled molten salt reactors instead of ridiculously inefficient solid Uranium fuel, the energy density is so far ahead of every competing technology that it makes me wonder whether or not we're really serious about providing electrical power for everyone here on Earth.
I note you haven't defined what you mean by competitive in a Mars context...
A nuclear reactor has advantages that I have never denied but I think you are overstating them.
Firstly, night time will be a natural time or rest and recuperation - on Mars as much as on Earth. There is a natural rythm to activity which will see a huge dip in nighttime demand. Furthermore much of the night time life support work can be done during the day (e.g. oxygen production and heat production which can then be saved in night storage heaters or in lagged hot water). Electricity usage can further be biased towards the day in various ways e.g. using washing machines during the day, using slow cookers during the day and microwave ovens at night. Night time electricity usage will come down to pumps, fans, and comms. For a six person mission, I doubt they will be using much more than 1 Kw average constant overnight if the mission is designed properly.
Secondly, a nuclear reactor is an unwieldy beast. It will be OK for a static Apollo 11 style mission. But not very good if you are serious about exploring the surrounding area and beginning the process of gathering raw materials for processing and use at the base.
Third, I don't accept (and many others here I think don't accept) that you can go with one reactor alone for Mission One. You will need failsafe back up if you are sending people to another planet 100million kms away.
Finally, the SAFE 400 has not been built as far as I know and it seems counterintuitive that it will be monitoring and maintenance free - when every other nuclear reactor on Earth needs constant attendance.
Energy density is paramount if it costs $50,000/kg to ship whatever you want to ship. That's what it costs right now. Even if it was only $25,000/kg, that's still more than half as much as a kilogram of Gold. No matter claims to the contrary, energy density matters greatly for this application.
Small fission reactors of the type NASA wishes to use require the least amount of labor (unattended, just like any PV array and battery will be on the surface of Mars), are the most reliable (produce the same amount of power 24/7, irrespective of what local weather conditions are like, distance from the sun, etc), and are less costly than competing solar technologies (because NASA told DOE to use what they have on hand to build what they want and the only development items are the electric generators and control electronics, which have been subcontracted to people who specialize in these sorts of things). The ATK solar panels alone, for one mission, will cost more than the development program for the Kilopower reactors. DOE doesn't have unlimited budgets and since no cost-plus contracts involved, DOE and their contractors either deliver what was requested on time and within budget or they don't get funded by NASA.
The SAFE 400 has not yet been built or tested in Mars conditions as far as I know. We haven't yet established what he mass difference between a PV based system and a nuclear power system will be. I can't even get a fix on the SAFE 400 mass. What do you think it is?
If we assume (only an assumption at this stage)the mass comparison is, say, 4 tonnes in nuclear's favour, that will be $100 million if we take your figure of $25,000 per kg (bit on the high side I think). Sounds a lot but in the context of a mission costing probably around $15 billion it isn't anything close to a deal breaker.
We have Lithium-ion batteries, PV panels, RTG's, and small fission reactors. There is no active development program for robotic methalox plants. Obviously it could be done, but the development funding and rockets to ship the mass to Mars have to come from somewhere. If you think the solar panels, batteries, and methalox plants (and all the mass required to extract water from Mars or to ship Hydrogen from Earth) would weigh less than a fission reactor, then you're not dealing with reality.
This is partly a matter of mission architecture choice. I favour a lot of pre-landing activity. If you don't favour such activity I think you are going to pay the penalty in terms of having to over-design your lander which will then be carrying a lot of equipment. I don't think any novel technologies would be involved in a robotic methalox plant, but I accept there will be a significant development cost because you have to test in Mars like conditions and ensure it is a robust system. In a context where NASA wasted hundreds of millions on developing landing systems for Curiosity, I don't think we are talking about vast amounts.
Mass is a key issue for pretty much everything sent to into space. We're not on Mars right now largely as a function of what it costs. If we could afford to be inefficient and still get the job done, we'd have done that a long time ago. The only reason the NTR program existed was because we simply couldn't afford to ship enough mass using Saturn V. NASA wanted to send humans to Mars decades ago, but chemical rockets couldn't get the job done even with their massive budget.
I don't believe NASA has wanted to send people to Mars in any meaningful sense (i.e. other than as a vague desire) since about 1970!
NASA has a diffuse and unfocussed range of objectives. It could have got to Mars by the mid 80s had it really wanted to.
The only serious Mars player, Elon Musk, is not proposing an NTR nor, as far as I know, a nuclear power based energy system (though to be fair I haven't heard him say it will be solar power either).
Just about anything is possible, but what's practical to do with the types of technologies we can affordably ship to Mars?
How much power do you think we'll need to use to mine and refine those materials?
You also realize there's a difference between a lab experiment and something you're betting your life on, right?
Mining on Mars in the early settlement will not be the vast enterprise it is on Earth.
Mining will be undertaken by vehicles more like this sort of mini digger:
https://www.aplant.com/products/021010- … -excavator
This has an energy usage of 2.25 litres of deisel per hour. I read that there is 10 KwH of power in one litre of diesel. So that would be
22.5 KwHs per hour. A Tesla style battery could get you to a mining site a few kms away and work for a couple of hours. You could also have PV panelling at the site to recharge the batteries. Alternatively you could have a methane generator powering the vehicle. I would assume that less power would be needed on Mars to do the digging and lifting, although on the other hand you might need to use a microwave add on to help loosen regolith. Swings and roundabouts... perhaps a figure of 30 Kwhs per hour would be a reasonable guide.
In terms of mining, initially we will not need huge amounts of materials. We are talking perhaps of 10s or 100s of kgs a week rather than tonnes for Mission One. I expect water mining will be the biggest area of demand for Mission One.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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I note you haven't defined what you mean by competitive in a Mars context...
Advantages of a Nuclear Reactor in a "Mars context"
1. Weighs less than equivalent PV panels and batteries if 10+ kilowatts of continuous, key word being "continuous", electrical power is required.
Orbital ATK solar panels weigh 7kg/kW (not including ground mounts or tracking motors)
Panasonic / Tesla batteries weigh 5kg/kW (not including packaging or charge controller electronics)
5kg * 10kW = 50kg to store 10kWh
50kg * 12hrs = 600kg for 1.2MWh of capacity (this is the absolute minimum requirement at the equator due to the day/night cycle)
600kWh/4hrs = 150kW for 4 hours (we'll assume the other half of the storage requirement is met during the rest of the day)
7kg/kW * 150kW = 1,050kg
1,050kg + 600kg = 1650kg
Kilopower, the most inefficient fission reactor in active development as a function of its design, weighs 1,545kg complete (everything but the power cable going back to the habitat module). The PV panel + batteries solution has already exceeded the mass of the reactor and no packaging (Lithium-ion batteries require insulation and heat or they cease to function), ground mounts (something to put the solar panels on so they can track the Sun to maximize output), or other electronics (charge controllers) have been included.
A mere 300kg difference is $15,000,000.
2. Produces continuous output
What happens if there is a dust storm that reduces PV panel output by 25% for a week or a month, never mind the month-long 99% insolation drops that Spirit and Opportunity have actually experienced?
This is not an expensive robotic toy for college kids to play with, we're talking about irreplaceable people we've spent tens of millions of dollars training. Forget about their families or basic human morality. I can't walk down to the astronaut depot and pick up another trained astronaut, no matter how much money I have in my bank account. We're talking about burying six of them if the power ever runs out.
Do you understand what will, not "may" but "will", happen if the power runs out? The "sleep mode" for humans is quite unlike that of Spirit or Opportunity and goes by a different name with a markedly different connotation. It's called death. Unlike the rovers, astronauts won't come back to life when the Sun starts shining again.
How much additional capacity is required to prevent loss of power?
3. Has a design life measured in decades
Ultimate durability and longevity are pretty important at current delivery prices.
A nuclear reactor has advantages that I have never denied but I think you are overstating them.
I stated what the actual conditions on Mars can be like above along with actual mass figures.
Firstly, night time will be a natural time or rest and recuperation - on Mars as much as on Earth. There is a natural rythm to activity which will see a huge dip in nighttime demand. Furthermore much of the night time life support work can be done during the day (e.g. oxygen production and heat production which can then be saved in night storage heaters or in lagged hot water). Electricity usage can further be biased towards the day in various ways e.g. using washing machines during the day, using slow cookers during the day and microwave ovens at night. Night time electricity usage will come down to pumps, fans, and comms. For a six person mission, I doubt they will be using much more than 1 Kw average constant overnight if the mission is designed properly.
Given improvements in life support technology, I'd say 1kWe continuous per person is a realistic figure.
Secondly, a nuclear reactor is an unwieldy beast. It will be OK for a static Apollo 11 style mission. But not very good if you are serious about exploring the surrounding area and beginning the process of gathering raw materials for processing and use at the base.
Your mobility in a small rover can be and hopefully is better with PV panels and batteries. If not, then Orion 11 it is.
Third, I don't accept (and many others here I think don't accept) that you can go with one reactor alone for Mission One. You will need failsafe back up if you are sending people to another planet 100million kms away.
Agreed. The same applies to PV panels and batteries. There are no robotic methalox plants and no funding or plans to build one. So, what's your backup plan? More PV panels and batteries?
Finally, the SAFE 400 has not been built as far as I know and it seems counterintuitive that it will be monitoring and maintenance free - when every other nuclear reactor on Earth needs constant attendance.
Is anyone on Earth monitoring a nuclear reactor with a core the size of a 5 gallon bucket?
The SAFE 400 has not yet been built or tested in Mars conditions as far as I know. We haven't yet established what he mass difference between a PV based system and a nuclear power system will be. I can't even get a fix on the SAFE 400 mass. What do you think it is?
Kilopower's mass is 1,545kg. Let's stick with 10kWe continuous and forget about systems producing more kW/kg, like SAFE-400. I don't even have to make the jump to 100kWe continuous to demonstrate that fission reactors weigh less and therefore cost less to deliver.
If we assume (only an assumption at this stage)the mass comparison is, say, 4 tonnes in nuclear's favour, that will be $100 million if we take your figure of $25,000 per kg (bit on the high side I think). Sounds a lot but in the context of a mission costing probably around $15 billion it isn't anything close to a deal breaker.
$50,000/kg is what it actually costs. If we could cut that figure in half, it'd be a minor miracle unto itself.
This is partly a matter of mission architecture choice. I favour a lot of pre-landing activity. If you don't favour such activity I think you are going to pay the penalty in terms of having to over-design your lander which will then be carrying a lot of equipment. I don't think any novel technologies would be involved in a robotic methalox plant, but I accept there will be a significant development cost because you have to test in Mars like conditions and ensure it is a robust system. In a context where NASA wasted hundreds of millions on developing landing systems for Curiosity, I don't think we are talking about vast amounts.
It's a matter of basic math and funding allocation.
I don't believe NASA has wanted to send people to Mars in any meaningful sense (i.e. other than as a vague desire) since about 1970!
NASA has a diffuse and unfocussed range of objectives. It could have got to Mars by the mid 80s had it really wanted to.
Maybe, but we'll never know.
The only serious Mars player, Elon Musk, is not proposing an NTR nor, as far as I know, a nuclear power based energy system (though to be fair I haven't heard him say it will be solar power either).
Elon Musk proposed detonating hundreds of nuclear weapons at the poles of Mars to warm the planet. Just because he had an idea doesn't necessarily mean it's a good one. He doesn't walk backwards on water. He's human and makes mistakes like everyone else.
Mining on Mars in the early settlement will not be the vast enterprise it is on Earth.
Mining will be undertaken by vehicles more like this sort of mini digger:
https://www.aplant.com/products/021010- … -excavator
This has an energy usage of 2.25 litres of deisel per hour. I read that there is 10 KwH of power in one litre of diesel. So that would be
22.5 KwHs per hour. A Tesla style battery could get you to a mining site a few kms away and work for a couple of hours. You could also have PV panelling at the site to recharge the batteries. Alternatively you could have a methane generator powering the vehicle. I would assume that less power would be needed on Mars to do the digging and lifting, although on the other hand you might need to use a microwave add on to help loosen regolith. Swings and roundabouts... perhaps a figure of 30 Kwhs per hour would be a reasonable guide.In terms of mining, initially we will not need huge amounts of materials. We are talking perhaps of 10s or 100s of kgs a week rather than tonnes for Mission One. I expect water mining will be the biggest area of demand for Mission One.
Yes, mining on Mars will not be like mining on Earth. There are no liquid hydrocarbon fuels on Mars that we know of and no roads or other infrastructure of any kind. Hundreds of kilograms per week for fuel? What about the oxidizer? This is starting to sound heavy (expensive).
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night time will be a natural time or rest and recuperation
True the crew is at rest but all the life support and recharging of batteries will be happening while they do.
This would also be the time to up certain pumping operations such as to store more CO2 for processing or turning on the dry ice frost plate to capture it as other have suggested.
Things that can be automated such as the building of solar panels would use that time to cycle up to peak processing....
I am sure that the ISS works on shifts so some crew will be active while others sleep.
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Night time would also be ideal for mining regolith for ice. Mine it during dark hours, and allow to melt inside habitats during light hours.
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You may end up with a habfull of bleach solution, Oldfart.
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Recharging of batteries at night would only take place on a nuclear power scenario, I think. With nuclear you have a flat line power output. You need more power during the day, so it makes sense to charge up batteries at night, otherwise you end up with a vast over supply of energy overall if you want to meet peak daylight demand.
Is 100Kwe all we will ever need during daylight hours? I doubt - not if you are doing some serious ISRU experimentation.
That is where the solar scenario wins out. With a combination of daylight PV, solar reflectors and concentrators, batteries and methane/oxygen facilities it can deliver some serious power - the kind need to smelt metals and so on.
Under the solar option daylight is when you do your serious work on life support - ice melting, oxygen production, gas separation etc.
They are just two entirely different approaches. As long as they can both deliver the necessary life support and other power requirements, they are both contenders.
louis wrote:night time will be a natural time or rest and recuperation
True the crew is at rest but all the life support and recharging of batteries will be happening while they do.
This would also be the time to up certain pumping operations such as to store more CO2 for processing or turning on the dry ice frost plate to capture it as other have suggested.
Things that can be automated such as the building of solar panels would use that time to cycle up to peak processing....
I am sure that the ISS works on shifts so some crew will be active while others sleep.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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I don't know about other places, but in the UK, power consumption at the lowest point of night is about 35% lower than the peak value in day-time. Many service industries may work 9-5, and loads will be lower outside of working hours. Domestic consumption is lower (though by no means zero) at night. Most industries and a good chunk of services, work 24/7, so their power consumption is flat. The reason is simple: if you have invested in capital intensive equipment, you don't want it sitting idle for half or two-thirds of the time. Anything that you ship to Mars is capital intensive. The mugs back home are paying for it, but there is a limit to what they are capable of paying for.
Storing large amounts of power in synthetic fuels from a PV system to cover night time loads is very inefficient. For a non-tracking PV system, that means storing at least two-thirds of what you use for a base load system. Storage efficiency is about 25%. So to produce 2400kWh across the entire day (i.e. a constant 100KWe) some 7200kWh of power must be gathered by the PV system. Average power during the day is the RMS of a sine wave (0.707), multiplied by peak power. So a system that gathers 7200kWe over 12 hours has average power of 600kWe during daylight hours and a peak power of 0.85MWe. That would be equal to a 2MWe-peak system here on Earth, to produce a baseload power of 100KWe on Mars, using methane oxygen storage.
Last edited by Antius (2017-06-02 06:31:16)
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Louis,
Apologies, I made a mistake in my math on the PV panels. The 250W/kg figure I quoted is for 1AU distances in space, not 1.5AU on the surface of a planet with an atmosphere. If it's not clear, my numbers are for the new MegaFlex technology, not the older UltraFlex technology. When ATK quotes kW/kg figures, those figures are representative of the mass of the PV panels themselves (a measure of conversion efficiency), not the total mass for a usable array. That is why the 7kW/kg figure appears in the fine print of their product literature. Stiffeners or backing materials are required to assure the arrays survive launch and reentry loads.
Solar irradiance at Earth is 1,350W/m^2. Solar irradiance on the surface of Mars varies between 493W/m^2 and 717W/m^2, but the mean is 590W/m^2. So irradiance is 43.7% of what Earth receives, on average, but can be as low as 36.5% of what Earth receives. In order to produce 10kWe continuous, even when solar irradiance is at its minimum, multiply the required output by 2.74 (1 / .365 = 2.74) and then you know the mass of the PV array required to produce enough electricity at solar minimum to have 10kWe continuous. This still doesn't account for the irradiance nose dives associated with dust storms, but at least it produces the power required during normal weather conditions.
150kW * 2.74 = 411kW
411kW * 7kw/kg = 2,877kg
2,877kg + 600kg = 3,477kg
3,477kg / 2 = 1,738.5kg
If the same mass was allocated to a pair of 10kWe Kilopower fission reactors, then we just bought ourselves redundancy for the mass associated with a single PV panel system that can produce 10kWe continuous, year-round, in ideal weather conditions. If the required output must scale up to 100kWe, it only gets worse for PV panels. Now we're talking about 34,770kg of our best PV panels. That type of mass accounts for at least several SAFE-400 fission reactors, power cables, and emplacement equipment.
Using PV panels for high continuous output on the surface of Mars just doesn't work from a basic math perspective. That's probably why NASA has tasked DOE with producing a fission reactor to provide continuous power.
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You are talking about a completely different system when it comes to general electric supply in the UK. There is lots of night time electricity use because it's cheaper then. There is a substantial night shift population, of around one million. Lots of people watch electricity guzzling TVs at night. They cook their meals in the evening. They leave lights on unnecessarily. Obviously most of the 35% usage will be industry-related.
In terms of an early Mars settlement, there is simply no need to operate industrial services at night, to cook at night, or to watch big TVs. Oxygen can be produced during the day. Water can be heated during the day. Food can be cooked during the day.
Where exactly is all this energy use going to be at night time? Why will we need 100Kwe constant in the middle of the night?
Of course some storage will be required. But I think you are exaggerating the amount. There isn't a 75% energy loss in heating water during the day or making oxygen. The amount of storage will probably be more of the order of 100 KweH. You can still have boiling water in the morning from the day before.
Can you explain why you need 100 Kwe constant at night for Mission One?
Take a look at aerogel spec:
http://www.johnsavesenergy.com/PipeInsu … TGPD9y1uM8
Imagine if the hot water tank is lagged with aerogel...minimal heat loss, will stay hot for days at a time...
My vision of a great start for the Mars settlement is v. low energy use at night and plenty of experimentation and energy use during daylight hours.
I don't know about other places, but in the UK, power consumption at the lowest point of night is about 35% lower than the peak value in day-time. Many service industries may work 9-5, and loads will be lower outside of working hours. Domestic consumption is lower (though by no means zero) at night. Most industries and a good chunk of services, work 24/7, so their power consumption is flat. The reason is simple: if you have invested in capital intensive equipment, you don't want it sitting idle for half or two-thirds of the time. Anything that you ship to Mars is capital intensive. The mugs back home are paying for it, but there is a limit to what they are capable of paying for.
Storing large amounts of power in synthetic fuels from a PV system to cover night time loads is very inefficient. For a non-tracking PV system, that means storing at least two-thirds of what you use for a base load system. Storage efficiency is about 25%. So to produce 2400kWh across the entire day (i.e. a constant 100KWe) some 7200kWh of power must be gathered by the PV system. Average power during the day is the RMS of a sine wave (0.707), multiplied by peak power. So a system that gathers 7200kWe over 12 hours has average power of 600kWe during daylight hours and a peak power of 0.85MWe. That would be equal to a 2MWe-peak system here on Earth, to produce a baseload power of 100KWe on Mars, using methane oxygen storage.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Some questions arising from your post:
1. Are you assuming energy usage will be constant?
2. If the answer to Q1 is no then are you providing a storage mechanism or are you simply going to put the surplus energy in the ground? And how are you going to provide additional energy for activities like smelting? If the answer is yes, then why do you make that assumption.
3. Why are you referencing rigid orbital panels in relation to Mars. Do you not accept that flexible panels could be laid out on the Mars surface? Or that rigid panels could likewise be laid out with v. minimal support.
4. Why do we need to store more than 140 KwHs overnight for a six person mission? What energy will they be using over say a 16 hour dusk-night-early morning period that will require more than that?
5. Do you have a reference for the your claimed month-long "99% insolation drops that Spirit and Opportunity have actually experienced"? The worst I have seen are v. temporary 90% drops. You might be confusing hibernation with a drop in insolation.
6. Do you have a reference for the mass of the KiloPower units? I couldn't find a reference.
7. $50,000 kg for mass from Earth to Mars surface seems a bit high to me, when Space X are expected to get launch costs down to $2,500 per kg or lower. $20,000 would be tops for me. Why do you choose $50,000 per kg? Are you sure you are not including development costs of previous missions?
8. Accepting your figure of $50,000 per kg the differential on your calculated requirements (which I don't accept, since I don't accept the constant energy requirement) is for a 100 Kwe output $150 million. That is 1% of the total mission cost, if the total cost is $15 billion. 1%! Do you accept that is not a figure that can preclude all other considerations, like flexibility?
9. The solar option will also provide continuous power, sufficient to ensure the settlement's survival. If there are no dust storms it will provide enough peak power to actually undertake some useful activities in a range of industrial experiments. Do you not accept that energy demand will vary during the sol?
I will answer some outstanding questions you had for me later.
louis wrote:I note you haven't defined what you mean by competitive in a Mars context...
Advantages of a Nuclear Reactor in a "Mars context"
1. Weighs less than equivalent PV panels and batteries if 10+ kilowatts of continuous, key word being "continuous", electrical power is required.
Orbital ATK solar panels weigh 7kg/kW (not including ground mounts or tracking motors)
Panasonic / Tesla batteries weigh 5kg/kW (not including packaging or charge controller electronics)
5kg * 10kW = 50kg to store 10kWh
50kg * 12hrs = 600kg for 1.2MWh of capacity (this is the absolute minimum requirement at the equator due to the day/night cycle)
600kWh/4hrs = 150kW for 4 hours (we'll assume the other half of the storage requirement is met during the rest of the day)
7kg/kW * 150kW = 1,050kg
1,050kg + 600kg = 1650kg
Kilopower, the most inefficient fission reactor in active development as a function of its design, weighs 1,545kg complete (everything but the power cable going back to the habitat module). The PV panel + batteries solution has already exceeded the mass of the reactor and no packaging (Lithium-ion batteries require insulation and heat or they cease to function), ground mounts (something to put the solar panels on so they can track the Sun to maximize output), or other electronics (charge controllers) have been included.
A mere 300kg difference is $15,000,000.
2. Produces continuous output
What happens if there is a dust storm that reduces PV panel output by 25% for a week or a month, never mind the month-long 99% insolation drops that Spirit and Opportunity have actually experienced?
This is not an expensive robotic toy for college kids to play with, we're talking about irreplaceable people we've spent tens of millions of dollars training. Forget about their families or basic human morality. I can't walk down to the astronaut depot and pick up another trained astronaut, no matter how much money I have in my bank account. We're talking about burying six of them if the power ever runs out.
Do you understand what will, not "may" but "will", happen if the power runs out? The "sleep mode" for humans is quite unlike that of Spirit or Opportunity and goes by a different name with a markedly different connotation. It's called death. Unlike the rovers, astronauts won't come back to life when the Sun starts shining again.
How much additional capacity is required to prevent loss of power?
3. Has a design life measured in decades
Ultimate durability and longevity are pretty important at current delivery prices.
louis wrote:A nuclear reactor has advantages that I have never denied but I think you are overstating them.
I stated what the actual conditions on Mars can be like above along with actual mass figures.
louis wrote:Firstly, night time will be a natural time or rest and recuperation - on Mars as much as on Earth. There is a natural rythm to activity which will see a huge dip in nighttime demand. Furthermore much of the night time life support work can be done during the day (e.g. oxygen production and heat production which can then be saved in night storage heaters or in lagged hot water). Electricity usage can further be biased towards the day in various ways e.g. using washing machines during the day, using slow cookers during the day and microwave ovens at night. Night time electricity usage will come down to pumps, fans, and comms. For a six person mission, I doubt they will be using much more than 1 Kw average constant overnight if the mission is designed properly.
Given improvements in life support technology, I'd say 1kWe continuous per person is a realistic figure.
louis wrote:Secondly, a nuclear reactor is an unwieldy beast. It will be OK for a static Apollo 11 style mission. But not very good if you are serious about exploring the surrounding area and beginning the process of gathering raw materials for processing and use at the base.
Your mobility in a small rover can be and hopefully is better with PV panels and batteries. If not, then Orion 11 it is.
louis wrote:Third, I don't accept (and many others here I think don't accept) that you can go with one reactor alone for Mission One. You will need failsafe back up if you are sending people to another planet 100million kms away.
Agreed. The same applies to PV panels and batteries. There are no robotic methalox plants and no funding or plans to build one. So, what's your backup plan? More PV panels and batteries?
louis wrote:Finally, the SAFE 400 has not been built as far as I know and it seems counterintuitive that it will be monitoring and maintenance free - when every other nuclear reactor on Earth needs constant attendance.
Is anyone on Earth monitoring a nuclear reactor with a core the size of a 5 gallon bucket?
louis wrote:The SAFE 400 has not yet been built or tested in Mars conditions as far as I know. We haven't yet established what he mass difference between a PV based system and a nuclear power system will be. I can't even get a fix on the SAFE 400 mass. What do you think it is?
Kilopower's mass is 1,545kg. Let's stick with 10kWe continuous and forget about systems producing more kW/kg, like SAFE-400. I don't even have to make the jump to 100kWe continuous to demonstrate that fission reactors weigh less and therefore cost less to deliver.
louis wrote:If we assume (only an assumption at this stage)the mass comparison is, say, 4 tonnes in nuclear's favour, that will be $100 million if we take your figure of $25,000 per kg (bit on the high side I think). Sounds a lot but in the context of a mission costing probably around $15 billion it isn't anything close to a deal breaker.
$50,000/kg is what it actually costs. If we could cut that figure in half, it'd be a minor miracle unto itself.
louis wrote:This is partly a matter of mission architecture choice. I favour a lot of pre-landing activity. If you don't favour such activity I think you are going to pay the penalty in terms of having to over-design your lander which will then be carrying a lot of equipment. I don't think any novel technologies would be involved in a robotic methalox plant, but I accept there will be a significant development cost because you have to test in Mars like conditions and ensure it is a robust system. In a context where NASA wasted hundreds of millions on developing landing systems for Curiosity, I don't think we are talking about vast amounts.
It's a matter of basic math and funding allocation.
louis wrote:I don't believe NASA has wanted to send people to Mars in any meaningful sense (i.e. other than as a vague desire) since about 1970!
NASA has a diffuse and unfocussed range of objectives. It could have got to Mars by the mid 80s had it really wanted to.Maybe, but we'll never know.
louis wrote:The only serious Mars player, Elon Musk, is not proposing an NTR nor, as far as I know, a nuclear power based energy system (though to be fair I haven't heard him say it will be solar power either).
Elon Musk proposed detonating hundreds of nuclear weapons at the poles of Mars to warm the planet. Just because he had an idea doesn't necessarily mean it's a good one. He doesn't walk backwards on water. He's human and makes mistakes like everyone else.
louis wrote:Mining on Mars in the early settlement will not be the vast enterprise it is on Earth.
Mining will be undertaken by vehicles more like this sort of mini digger:
https://www.aplant.com/products/021010- … -excavator
This has an energy usage of 2.25 litres of deisel per hour. I read that there is 10 KwH of power in one litre of diesel. So that would be
22.5 KwHs per hour. A Tesla style battery could get you to a mining site a few kms away and work for a couple of hours. You could also have PV panelling at the site to recharge the batteries. Alternatively you could have a methane generator powering the vehicle. I would assume that less power would be needed on Mars to do the digging and lifting, although on the other hand you might need to use a microwave add on to help loosen regolith. Swings and roundabouts... perhaps a figure of 30 Kwhs per hour would be a reasonable guide.In terms of mining, initially we will not need huge amounts of materials. We are talking perhaps of 10s or 100s of kgs a week rather than tonnes for Mission One. I expect water mining will be the biggest area of demand for Mission One.
Yes, mining on Mars will not be like mining on Earth. There are no liquid hydrocarbon fuels on Mars that we know of and no roads or other infrastructure of any kind. Hundreds of kilograms per week for fuel? What about the oxidizer? This is starting to sound heavy (expensive).
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Some questions arising from your post:
1. Are you assuming energy usage will be constant?
There will be a more or less constant base load from life support equipment. There will be load variances caused by charging batteries and using communications systems or scientific instruments.
2. If the answer to Q1 is no then are you providing a storage mechanism or are you simply going to put the surplus energy in the ground? And how are you going to provide additional energy for activities like smelting? If the answer is yes, then why do you make that assumption.
If the output from the reactor needs to be transmitted to ground, then we can do that. If there are extended periods of peak demand, then you vary the output of the reactor.
3. Why are you referencing rigid orbital panels in relation to Mars. Do you not accept that flexible panels could be laid out on the Mars surface? Or that rigid panels could likewise be laid out with v. minimal support.
I accept that rigid panels and flexible panels could be laid out on the surface of Mars. The rigid panels are real spacecraft technology that has been to Mars multiple times. Take a wild guess at which panels NASA will send first.
4. Why do we need to store more than 140 KwHs overnight for a six person mission? What energy will they be using over say a 16 hour dusk-night-early morning period that will require more than that?
I really thought I already explained the 99% irradiance drops, but maybe you missed that. That's the most important reason why. If the astronauts never leave the habitat module for EVA's, never operate a battery powered vehicle, never use personal electronics, and minimize communications, then maybe 140kWh is sufficient for six people.
5. Do you have a reference for the your claimed month-long "99% insolation drops that Spirit and Opportunity have actually experienced"? The worst I have seen are v. temporary 90% drops. You might be confusing hibernation with a drop in insolation.
Apart from the documents from NASA and science-related news articles, Google "Exploring the Solar System" by Peter Bond. You might be confusing the difference between a small multi-hundred million dollar rover being completely immobilized with what will happen if the astronauts can't get power for their life support equipment.
6. Do you have a reference for the mass of the KiloPower units? I couldn't find a reference.
Development of NASA’s Small Fission Power System for Science and Human Exploration
Solar Power and Energy Storage for Planetary Missions
7. $50,000 kg for mass from Earth to Mars surface seems a bit high to me, when Space X are expected to get launch costs down to $2,500 per kg or lower. $20,000 would be tops for me. Why do you choose $50,000 per kg? Are you sure you are not including development costs of previous missions?
The $50K figure comes from what it presently costs, but you're correct about SpaceX substantially improving upon that figure. Falcon Heavy can TMI 16.8t and can probably deliver 8.4t to the surface using HIAD and retro-propulsion, so yeah, that figure's a little high. That works out to $16K/kg. Falcon Heavy is currently listed at $135M per flight. Assuming all hardware that actually delivers the payload only costs $25M, then it's $19K/kg.
8. Accepting your figure of $50,000 per kg the differential on your calculated requirements (which I don't accept, since I don't accept the constant energy requirement) is for a 100 Kwe output $150 million. That is 1% of the total mission cost, if the total cost is $15 billion. 1%! Do you accept that is not a figure that can preclude all other considerations, like flexibility?
I made a mistake in what the mass of the system would be. It's 34,770kg just for the solar panels to provide 100kWe continuous, never mind the 72,000kg battery. That's $2,028,630,000 just to deliver the solar panels and batteries, never mind the cost of the PV panels and batteries.
9. The solar option will also provide continuous power, sufficient to ensure the settlement's survival. If there are no dust storms it will provide enough peak power to actually undertake some useful activities in a range of industrial experiments. Do you not accept that energy demand will vary during the sol?
Do you accept that to provide 100kWe continuous you just consumed most of the human space flight budget for a year if you insist on solar panels?
It's not about what I want or you want, it's about what NASA can afford. The "correct" solution is very nearly always the solution with the lowest mass and least cost. Solar is not mass-competitive and therefore not cost-competitive with Kilopower, never mind SAFE-400. If solar can't provide 10kWe for less mass than nuclear, the problem only gets worse for solar as the power requirement goes up. Make an argument based in math, not wishful thinking or technologies that don't exist, and then we can discuss it.
I don't have to resort to wild speculation or magical thinking because I have basic math (I can and do make mistakes, but I correct them as I find them) and the actual masses and outputs of things that are in active development. Both MegaFlex and Kilopower are in advanced active development, and both systems are based on thoroughly proven technologies (triple-junction solar cells or Uranium fissioning), and both will serve as the basis for the next generation of space power systems.
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There will be a more or less constant base load from life support equipment. There will be load variances caused by charging batteries and using communications systems or scientific instruments.
You mean a base load requirement for life support? I don't accept the life support requirement is necessarily constant at all. To take oxygen for example, I think we will probably make that in loads, to ensure we have an ongoing emergency surplus and we will be using it for other purposes, as well in any case. In terms of heat, well yes you can have a constant, but on Earth that is rare - it is more normal to heat your water that is then stored in a lagged container and heating is normally thermostatically controlled so it goes on and off. Fresh water can be produced at any time of day. There is probably a very small baseload requirement for fans, venting and so on but that will easily be covered by batteries.
If the output from the reactor needs to be transmitted to ground, then we can do that. If there are extended periods of peak demand, then you vary the output of the reactor.
I wasn't aware that the reactors were capable of produce more than their rated capacity e.g. 10Kwe for a KiloPower unit. Are you saying they can? Do you have any link to back that up?
I accept that rigid panels and flexible panels could be laid out on the surface of Mars. The rigid panels are real spacecraft technology that has been to Mars multiple times. Take a wild guess at which panels NASA will send first.
I very much doubt it will be NASA who get humans to Mars. The jury is still out on the weight of panels that will be used on Mars but (a) tecnological progress is being made towards panels that are durable (UV protected), lightweight and flexible. My view is there will probably be a mix. However it all depends on technical developments. The weather on Mars is at least benign - no hurricanes, no rain, no snow, no floods and there are no herds of animals to go trampling over your panels either.
NASA are working on roll out flexible ultra lightweight PV panelling.
https://www.nasa.gov/content/solar-cell … ray-design
I really thought I already explained the 99% irradiance drops, but maybe you missed that. That's the most important reason why. If the astronauts never leave the habitat module for EVA's, never operate a battery powered vehicle, never use personal electronics, and minimize communications, then maybe 140kWh is sufficient for six people.
Apart from the documents from NASA and science-related news articles, Google "Exploring the Solar System" by Peter Bond. You might be confusing the difference between a small multi-hundred million dollar rover being completely immobilized with what will happen if the astronauts can't get power for their life support equipment.
It appears you have no link to the 99% irradiance drop claim (beyond asking me to google a book). Under a solar energy system, there will be plenty of back up in the form of methane/oxygen. I have never seen any evidence of a dust storm causing more than a 90% drop in insolation on the surface (and even then only for a few days IIRC). With a system that delivers 2450 KWhes in normal weather conditions, that will mean you have a minimum of 245 KWhes available even in those extreme conditions, without back-up.
When someone asks for a citation for a claimed figure, they don't normally expect to be given generalised links, and asked to do their own research, wading through pages and pages of presentations...
The $50K figure comes from what it presently costs, but you're correct about SpaceX substantially improving upon that figure. Falcon Heavy can TMI 16.8t and can probably deliver 8.4t to the surface using HIAD and retro-propulsion, so yeah, that figure's a little high. That works out to $16K/kg. Falcon Heavy is currently listed at $135M per flight. Assuming all hardware that actually delivers the payload only costs $25M, then it's $19K/kg.
I made a mistake in what the mass of the system would be. It's 34,770kg just for the solar panels to provide 100kWe continuous, never mind the 72,000kg battery. That's $2,028,630,000 just to deliver the solar panels and batteries, never mind the cost of the PV panels and batteries.
Well if it is a "little" high as you know seem to accept it affects the comparison of course.
I don't accept your figure of nearly 106 tonnes for a solar energy system. It's patently absurd.
I need to go over the figures again, but I think probably 5 tonnes for the panels, using current technology, 1.6 tonnes for associated electrical equipment, 2 tonnes for batteries (doubling up on use, as Rover and other batteries), maybe 1.5 tonnes for a methane/oxygen plant, 2.5 tonnes for gas storage and 500 kgs for two 20 Kw generators. Around 13 tonnes in total out of budget of perhaps 70 tonnes.
Of course if we see ultra lightweight UV resistant PV panelling emerge, the total will be substantially less. Likewise with improved battery storage. Likewise if we can find a way of storing methane and oxygen in a less mass intensive way. That's quite possible as well. THere are lightweight storage solutions.
So with a solar energy system, it's basically a balancing act between PV panels, batteries,generators, and methane storage. We might also have a solar reflector system added to the overall mix.
Do you accept that to provide 100kWe continuous you just consumed most of the human space flight budget for a year if you insist on solar panels?
It's not about what I want or you want, it's about what NASA can afford. The "correct" solution is very nearly always the solution with the lowest mass and least cost. Solar is not mass-competitive and therefore not cost-competitive with Kilopower, never mind SAFE-400. If solar can't provide 10kWe for less mass than nuclear, the problem only gets worse for solar as the power requirement goes up. Make an argument based in math, not wishful thinking or technologies that don't exist, and then we can discuss it.
I don't have to resort to wild speculation or magical thinking because I have basic math (I can and do make mistakes, but I correct them as I find them) and the actual masses and outputs of things that are in active development. Both MegaFlex and Kilopower are in advanced active development, and both systems are based on thoroughly proven technologies (triple-junction solar cells or Uranium fissioning), and both will serve as the basis for the next generation of space power systems.
As indicated before, I don't think NASA will get humans to Mars. It will be Space X. As far as I know, they haven't specified their early energy system yet.
I don't think you've established a nuclear solution would have the lower mass (especially if you are going to take some batteries - are you?). You invented a crazy figure for solar and then compared it with a "nuclear only" option.
I am not engaging in magical thinking.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Louis-
Your dedication to the concept of Solar-only on Mars is commendable, but in my opinion--misguided. I envision a combination of nuclear , supplemented by Solar. The massive infrastructure requirement you propose is NOT GOING TO HAPPEN! A small nuclear reactor, as in the original Mars Direct proposal will lead the way, and solar backup will be available some 40% of the time. The reality is food and research equipment will compose a large portion of the early mass landed on the surface, not batteries and other equipment for manufacture of solar panels, turbines, and excess methane or Oxygen to power the colony. Everything you suggest always involves massive infrastructure investments.
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