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The surface solar is about 43% of the on orbit amount of 1K w/M^2 so a sm^2 will only get 430 w before conversion effiecency of the panels are figured in. The film panels while low mass are also low efficiency of the 10 to 15% while we can achieve lots better but these are more expensive and heavier that the film units are.
The spectra lab units are multi layer and get 35% plus.... so if you are going to want a power level of x you need to calculate in the number of hours that you are recieving versus how many hours that you are not for the batteries to not only charge but also for day time use. So if you need 12 hours during the night from the batteries you are going to need 2 to 3 times that from the panels from the day light hours to which are not 12 as the curve for light will only yield on an untracking system by far less, Which means we need say 4 to 5 times the quantity of panels to make the source for charging and use leave extra for the day time use which will be higher than the night time useage.
On earth the untrack system here in the north for NH only gets about 3.5 to 4 hours of time during the day while down near new mexico we are back up towards 6 hours at least. So location is a big factor for allignment of these panels to get the most out of them.
Batteries are rated in Ampere hour discharge rates not wattage and the voltage is cell voltage of 1.5v with a useable down to 0.9 v for a cell so not all power can come from the battery as the 1.5v is a full cell and the 0.9v is a fully discharged cell.
Charging rates are as well is dependant on the cell type and is typically only a quarter of the discharge levels so it is a time dependant charge rate to refill them.
So while we can design a system for the numbers the intendant use will yield less useable power under normal levels from it as you need to leave a level of reserve in the batteries for a lower charging rate from the panels.
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The spectra lab units are multi layer and get 35% plus....
Spectrolab current best multi-junction cell: 30.7% NeXt Triple Junction (XTJ) Prime Solar Cells
It produces 30.7% conversion of sunlight to electricity, beginning-of-life. 26.7% end-of-life.
Panels using their cells: Panels
(28°C, Beginning of life), Panel Area > 2.5 m²: 366 W/m²
Mass (add-on to substrate):
3 mil Ceria Doped Coverslide: 1.76 kg/m² (5.5 mil thick cell)
6 mil Ceria Doped Coverslide: 2.06 kg/m² (5.5 mil thick cell)
These figures are for Earth orbit. Then calculate Mars gets 47% as much sunlight as Earth orbit. Then if your panel is deployed on Mars surface, it will be dark at night.
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There is quite a difference between efficiencies reported in a lab test, and performance of a real production product "in the field".
I have very severe heartburn believing 30+% solar cell efficiencies for a deployable product.
Highest I ever heard of was ~20% for a multi-band item. Most are single-band and fall in the 6-12% range.
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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I have very severe heartburn believing 30+% solar cell efficiencies for a deployable product.
Yes and no. My last post included links directly to the website of Spectrolab. They make deployable solar panels for satellites. A number of years ago, Spectrolab was bought by Boeing Satellite Systems. But notice the efficiencies cited: 30.7% beginning-of-life, but only 26.7% end-of-life. The satellite has to operate at end-of-life of the solar panels, so satellite systems have to be designed to use no more than end-of-life power from the solar panels. They may have been able to produce higher efficiencies in a lab, but this is commercial product currently available for purchase and deployment.
Highest I ever heard of was ~20% for a multi-band item. Most are single-band and fall in the 6-12% range.
That was a number of years ago. Now they use multi-junction. That means multiple solar cells, stacked. Some solar cells are transparent to colours of light they do not convert into electricity. This allows solar cells to be stacked. The semiconductor diode junction is the critical part of the solar cell that makes it work, so they call this stacked thing "multi-juction". There are two American manufacturers of solar panels for use in space, Spectrolab is one of them. They've made triple junction cells for a number of years now. In the 1970s, silicon solar cells converted 4% of sunlight to electricity. When the Hubble Space Telescope was first launched, there was an amorphous solar panel that was flexible, could be rolled up. It converted about 12% to electricity, beginning-of-life. Now high quality silicon cells can convert 14%, such as the polycrystaline cells you can buy for your cottage. Panels for the dash of your car convert 6%. Since then researchers discovered multi-junction cells. They're rigid, but a lot more efficient. Spectrolab uses gallium-indium-phosphate on top, gallium-arsenide in the middle, and germanium on the bottom. Germanium is not transparent, so has to be on the bottom.
Spectrolab has a multi-decade plan to slowly improve their space solar cells. They intend to increase performance from 24% beginning-of-life to 45% beginning-of-life, gouging their customers for each fraction of a percent increase. They have been working this plan since year 2000; their current best produces 30.7% beginning-of-life. To get into the 40% range, they intend to go to 4-junction. At least according to published announcements.
I could talk about the best photovoltaic cell ever studied in a lab. But this is available for deployment now.
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Louis,
Will a solar flare fry the electronics that regulate power or the thin film arrays themselves?
Do thin film solar arrays require any heating at night to prevent damage from the frigid Martian nights? If so, can the panels be rolled back up to heat them in insulated cylinders without damaging them? For example, if I have 10kg rolls, can a robot carefully re-roll the panels at dusk, store them under the habitat module in heated cylinders at night, and then re-deploy them at dawn. I presume a robot can also use a simple brush to wipe off the dust while re-rolling them.
You say you're worried about micro meteoroids damaging the reactor. What's easier to hit, a buried reactor that's half the diameter of a 55 gallon drum with a 150m^3 worth of radiator panels or 1850m^3 worth of solar panels? A micro meteoroid wouldn't even dent the reactor's thick Be reflector / containment vessel nor its W / LiH shadow shield. However, it'll put a hole in virtually any solar panel or radiator panel. Even if it put a hole through a Molybdenum heat pipe, the heat from the reactor core is propagated across the core material to the other heat pipes. The SAFE-400 reactors are designed so that they can loose some of their 127 heat pipes, since each pipe is an independent coolant loop, and still remain operational. There's no real argument for or against either solar or nuclear here.
Will the battery be separated from the habitat module? If so, I assume it could be stored in a Red Dragon lander to contend with this micro meteoroid problem. How much power is required to keep the batteries warm?
Apart from the electric generators, a 100kWe fission reactor has one set of moving components, which would be the control drums. There's no reason why a completely mechanical reactor control system can't be designed. If the reactor's temperature exceeds design specifications, a mechanical system can automatically actuate the control drums to reduce output or effect a complete shutdown. It would not be subject to any significant degradation from radiation. Mechanical systems to actuate valves are already in use in nuclear reactors. There's no difference between actuating a valve and turning a control drum inward.
I think it's abundantly clear that roll-up solar panels currently available are suitable for stationary power applications. How much is output reduced by in the event of a dust storm?
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My suggestion did have double redundancy - by the time humans land on Mars you have huge storage of power through methane or combustible iron, or both and you will of course have charged batteries.
So, really any comment based on lack of back up is irrelevant.
Regarding heating, my understand is that heat is not easily transferred out of a building in the v. low pressure atmosphere on Mars. Furthermore, we would underdoubtedly be using materials like aerogel to further slow down heat loss. Add to that, you will have electric equipment and human bodies in quite a confined space, which will be generating heat. Air con might be more of an issue!
Louis-
I really appreciate your thoughts. I'm not ruling out or belittling solar panels, but we need to have systems in double redundancy. I was around an operational nuclear reactor many times during my grad school days, since the University of Wyoming had a critical mass Thorium reactor on the University Campus. My first 2 years of grad school, I was a teaching assistant for Dr. Victor Ryan, who was the Nuclear Chemist and University Safety Officer. After he passed on some years later, the University had the reactor decommissioned and subsequently dismantled. There were really no safety issues that ever arose, but the cost of insurance became excessive during the 1980s. In several of my previous posts, I suggest that we send at least 2 small nukes in these Red Dragon experimental landers, but certainly NOT on the first one!
The numbers you've stated seem pretty minimal when all energy requirements are taken into account; I'd personally at least double them. I own and operate a small cattle ranch (or I DID before I fully retired just 4 years ago), and a minimum rate of power consumption for cold weather seemed to be in the 8KWe to 13KWe, depending on the severity of weather. This includes heating the home (all electric except for hot water and cooking), keeping water tanks thawed for cattle (that's 5-7 KWE right there), and lighting.
I'm with Dr. Zubrin on this issue; there can never be TOO MUCH electric power available.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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The Press tends to sensationalize any Nuclear accident--especially the Fukushima disaster which resulted from the combination of earthquake and tsunami. Three Mile Island was another one, but the problems there never resulted in deaths or radiation illness. The granddaddy of all was Chernobyl, in Russia. These were all isolated incidents, and after considering how much nuclear power is currently used in Europe, the 2 earlier day accidents fade into near insignificance. As kbd512 has already pointed out, micrometeorite damage to a buried reactor is statistically far lower risk than that to solar panels. Dislike of nuclear power is rooted in hysteria generated by the media. Some of your other concepts such as storing cryogenic fuels have merit. As does having both nuclear and solar operating in parallel. a nuclear powerplant which is self-propelled and robotically controlled is far easier to deploy remotely than a massive solar farm. Collecting and oxidizing Fe isn't that great an idea, since it involves finding adequate metallic iron for starters.
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The rolling up of the thin film solar panels is cracking and damage due to the enbrittlement from cold as it will be cold when the warm panel in unrolled and when it near night its will be a cold panel being rolled up to keep it warmer.
If they are the fan style as made by ATk then they do not have this issue of enbrittlement but we have the motor wear issue for opening and closing of the fan panels.
Nuclear only has the radiator filling with a cooling mass issue to its overall empty mass and size for send it to mars....
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On ISS, the batteries are stored on the truss structure, which is outside of the warm pressure vessels. NASA did not want to contend with thermal events from powerful batteries. The batteries are made by GS Yuasa. The cells are variants of the cells the company makes for the Boeing 787, with additional over-voltage and thermal protections built into the packs. The development effort took 6 years, from start to implementation.
Initial capacity is 12kWh per pack (3.7v / 148Ah / 113.2Wh/kg cells per pack, each cell 3.53kg, 3 banks of 10 cells), 288kWh total installed capacity. Each battery pack weighs 197kg and replaces two 166kg Ni-H2 battery packs previously used. The new pack's storage capacity is 1.5 times the capacity of the old pack's storage capacity, so 24 of the new packs will replace 48 of the old packs. The packs are rated for 60,000 charge/discharge cycles for an expected operating life time of 10 years and 48Ah EOL storage capacity. These packs should last a lot longer on Mars with lower temperature deltas, fewer cycles per day, and longer charge/discharge cycles. I'm still trying to find out how much power the battery pack heater plates consume.
Our state-of-the-art 250Wh/kg cells have more than double the capacity, which means a 25kWh pack would only weigh 100kg, not including all the support equipment, so perhaps 125kg for a complete 25kWh pack using a composite container, MMOD protection, heater plate, and BCDU computer built in.
If a 100kWh pack only weighs 500kg, then there's no comparable nuclear solution that would weigh less. I presume ATK's 250W/kg MegaFlex arrays will be the front runner solar panel technology. The thin film arrays sound great, but not if they're destroyed by the temperature extremes or solar flares. ATK's panels are flight proven technology. So we need approximately 1400kg worth of solar arrays, corresponding to an array 50% larger than an Earth array to provide equivalent power output using MegaFlex's ~7kg/kw actual mass, which includes support structure, deployment servos, and power management equipment.
Since every system requires a backup, these means 3.8t for a completely redundant 100kWh power solution. This is approximately what a one adequately shielded reactor, power cabling, and power distribution equipment would weigh. After it's successfully tested on Mars, I'll remove my objections to an all-solar power provisioning approach. It should be noted, however, that a properly designed reactor will provide 100kWe nearly 100% of the time. If there are any significant events that degrade the panel output or battery storage capacity, my objection remains.
As I've previously stated numerous times, I'm not opposed to any practical approach that provides reliable electrical power. Running out of electrical power is a 100% fatal, show-stopping event and that is the only thing I object to.
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Very silly comment. If you've been driven out of your home by a nuclear accident as in Chernobyl or Fukushima, that isn't "hysteria" it's fact. The requirement that nuclear power facilities be located far from population centres tells everything you need to know.
It's silly to talk about burying a nuclear reactor on Mars as a trivial exercise for an early mission. This is a major undertaking.
If you can't find iron ore on Mars you really shouldn't be in the business of planetary exploration.
The Press tends to sensationalize any Nuclear accident--especially the Fukushima disaster which resulted from the combination of earthquake and tsunami. Three Mile Island was another one, but the problems there never resulted in deaths or radiation illness. The granddaddy of all was Chernobyl, in Russia. These were all isolated incidents, and after considering how much nuclear power is currently used in Europe, the 2 earlier day accidents fade into near insignificance. As kbd512 has already pointed out, micrometeorite damage to a buried reactor is statistically far lower risk than that to solar panels. Dislike of nuclear power is rooted in hysteria generated by the media. Some of your other concepts such as storing cryogenic fuels have merit. As does having both nuclear and solar operating in parallel. a nuclear powerplant which is self-propelled and robotically controlled is far easier to deploy remotely than a massive solar farm. Collecting and oxidizing Fe isn't that great an idea, since it involves finding adequate metallic iron for starters.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Lots of interesting detail there, but I assume you accept that a nuclear power plant that fails is a 100% failure, whereas the likelihood of a 100% failure with PV panels is close to zero. Risk is a matter of judgement.
On ISS, the batteries are stored on the truss structure, which is outside of the warm pressure vessels. NASA did not want to contend with thermal events from powerful batteries. The batteries are made by GS Yuasa. The cells are variants of the cells the company makes for the Boeing 787, with additional over-voltage and thermal protections built into the packs. The development effort took 6 years, from start to implementation.
Initial capacity is 12kWh per pack (3.7v / 148Ah / 113.2Wh/kg cells per pack, each cell 3.53kg, 3 banks of 10 cells), 288kWh total installed capacity. Each battery pack weighs 197kg and replaces two 166kg Ni-H2 battery packs previously used. The new pack's storage capacity is 1.5 times the capacity of the old pack's storage capacity, so 24 of the new packs will replace 48 of the old packs. The packs are rated for 60,000 charge/discharge cycles for an expected operating life time of 10 years and 48Ah EOL storage capacity. These packs should last a lot longer on Mars with lower temperature deltas, fewer cycles per day, and longer charge/discharge cycles. I'm still trying to find out how much power the battery pack heater plates consume.
Our state-of-the-art 250Wh/kg cells have more than double the capacity, which means a 25kWh pack would only weigh 100kg, not including all the support equipment, so perhaps 125kg for a complete 25kWh pack using a composite container, MMOD protection, heater plate, and BCDU computer built in.
If a 100kWh pack only weighs 500kg, then there's no comparable nuclear solution that would weigh less. I presume ATK's 250W/kg MegaFlex arrays will be the front runner solar panel technology. The thin film arrays sound great, but not if they're destroyed by the temperature extremes or solar flares. ATK's panels are flight proven technology. So we need approximately 1400kg worth of solar arrays, corresponding to an array 50% larger than an Earth array to provide equivalent power output using MegaFlex's ~7kg/kw actual mass, which includes support structure, deployment servos, and power management equipment.
Since every system requires a backup, these means 3.8t for a completely redundant 100kWh power solution. This is approximately what a one adequately shielded reactor, power cabling, and power distribution equipment would weigh. After it's successfully tested on Mars, I'll remove my objections to an all-solar power provisioning approach. It should be noted, however, that a properly designed reactor will provide 100kWe nearly 100% of the time. If there are any significant events that degrade the panel output or battery storage capacity, my objection remains.
As I've previously stated numerous times, I'm not opposed to any practical approach that provides reliable electrical power. Running out of electrical power is a 100% fatal, show-stopping event and that is the only thing I object to.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Not sure why you are pretending there aren't a host of potential problems with nuclear power plants. They are complex beasts. If they malfunction, you are jeopardising the whole colony. No way will all PV panels fail at the same time.
We know PV panels have worked brilliantly on Mars for several years at a time so let's not get hysterical about the issue of cold temperatures. I am sensing a will to failure which is absurd.
The rolling up of the thin film solar panels is cracking and damage due to the enbrittlement from cold as it will be cold when the warm panel in unrolled and when it near night its will be a cold panel being rolled up to keep it warmer.
If they are the fan style as made by ATk then they do not have this issue of enbrittlement but we have the motor wear issue for opening and closing of the fan panels.
Nuclear only has the radiator filling with a cooling mass issue to its overall empty mass and size for send it to mars....
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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It's very difficult to rationally discuss nuclear power with dedicated True Believer" in the danger of such. However, I'm probably the only member of this forum who has ever sat at the controls of a nuclear reactor. I was the TA for second semester physical chemistry laboratory where we neutron-irradiated some silver dimes in order to do an experiment in which the half life of the decaying radioisotope was to be measured, and Professor Ryan instructed me in operation of the Thorium reactor to do so. The reactor accidents we've heard of had many contributing causes, but Fukushima was simply built in the WRONG PLACE! On a fault line and too near a seacoast exposed to Tsunami flooding. Not. Smart. Chernobyl was even more disgraceful. That was a failure of the political system, which allowed substitution of poor materials incorporated in construction through systemic graft. My knowledge of 3 Mile Island is incomplete so I won't make any acidic comments about that scenario. Here on Earth, I've generally disliked the nuclear power option on the basis of waste radioactive by products disposal. The advent of Thorium based systems has removed my objections. Mars: that's a whole new ball game. Initially, we need the most compact and reliable source of power, and that IS nuclear.
My objection to total reliance on PV panels isn't based on a simple dislike; I dislike the weight of all the associated batteries we have to haul to mars, and the exhaustion/depletion of the cells with time. Solar should be THE backup for the nuclear system.
Last edited by Oldfart1939 (2017-04-09 18:56:49)
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You are talking as though no other facilities apart from Fukushima have been built in the wrong place. But we know there is every chance of a tsunami in the Eastern Atlantic which could deluge the French and UK nuclear power stations in that area (particularly the Channel where any tsunami effect would be amplified by the topography).
We do not need the most "compact" energy source on Mars. We need an energy source that is proven, reliable and flexible. For me that's PV.
I don't know why you are pretending I am requiring 100% dependence on PV panels. I have made it completely clear we need back up - e.g. methane.
The mission cycle on Mars will be around 2 years. There will be no significant loss of PV conversion. Within a couple of missions, around 4 years, there is no reason why the nascent Mars colony won't be moving to solar reflector technology to meet their energy needs.
It's very difficult to rationally discuss nuclear power with dedicated True Believer" in the danger of such. However, I'm probably the only member of this forum who has ever sat at the controls of a nuclear reactor. I was the TA for second semester physical chemistry laboratory where we neutron-irradiated some silver dimes in order to do an experiment in which the half life of the decaying radioisotope was to be measured, and Professor Ryan instructed me in operation of the Thorium reactor to do so. The reactor accidents we've heard of had many contributing causes, but Fukushima was simply built in the WRONG PLACE! On a fault line and too near a seacoast exposed to Tsunami flooding. Not. Smart. Chernobyl was even more disgraceful. That was a failure of the political system, which allowed substitution of poor materials incorporated in construction through systemic graft. My knowledge of 3 Mile Island is incomplete so I won't make any acidic comments about that scenario. Here on Earth, I've generally disliked the nuclear power option on the basis of waste radioactive by products disposal. The advent of Thorium based systems has removed my objections. Mars: that's a whole new ball game. Initially, we need the most compact and reliable source of power, and that IS nuclear.
My objection to total reliance on PV panels isn't based on a simple dislike; I dislike the weight of all the associated batteries we have to haul to mars, and the exhaustion/depletion of the cells with time. Solar should be THE backup for the nuclear system.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Louis-
Initial production of methane and Oxygen will undoubtedly be dedicated to the Earth Return Vehicle, and there will probably be NO excess if it's produced by the available PV power. PV power is available for only a half Sol, as there is a dark cycle to consider. I'm sorry that I don't have available to me any energy requirement data on the yet-to-be-built Methane production system, nor do I have any thermodynamic data for the yet to be field-trialed Moxie unit, nor do I have any idea of how much power will be consumed by compression/liquefaction of these two components. I'm sorry, but your faith in "PV solves all problems" seems misguided. The energy requirements are going to be HUGE in order to accomplish these tasks simultaneously. Before continuing this discussion, we need the spreadsheet of power required versus power available from different potential sources.
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I agree we need more detail.
I don't think PV solves "all" problems. But we know it has powered a number of robot rovers on Mars over several years. That's my starting point.
I think you need to recalibrate your assumptions.
If Space X can get launch-to-LEO costs down to $1000 per kg (as seems more and more likely now they have mastered the return of stages) then this argument over PV v Nuclear is becoming pretty irrelevant in terms of cost. If the cost differential between PV and nuclear is only $2 million either way then that is irrelevant to a huge Humans to Mars project.
Louis-
Initial production of methane and Oxygen will undoubtedly be dedicated to the Earth Return Vehicle, and there will probably be NO excess if it's produced by the available PV power. PV power is available for only a half Sol, as there is a dark cycle to consider. I'm sorry that I don't have available to me any energy requirement data on the yet-to-be-built Methane production system, nor do I have any thermodynamic data for the yet to be field-trialed Moxie unit, nor do I have any idea of how much power will be consumed by compression/liquefaction of these two components. I'm sorry, but your faith in "PV solves all problems" seems misguided. The energy requirements are going to be HUGE in order to accomplish these tasks simultaneously. Before continuing this discussion, we need the spreadsheet of power required versus power available from different potential sources.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Louis,
Your proposed methalox plant is many times more complicated than a nuclear reactor of the the type NASA wants to send to Mars. Your false equivalency with the Fukushima plant is not applicable. You're comparing something with thousands of moving parts to something simpler than a 1950's internal combustion engine. Since nobody here has proposed sending a 1950's tech nuclear reactor to Mars, it's a safe bet that there won't be any 1950's nuclear accidents on Mars. Nuclear reactors of the 1950's were originally designed to power things sitting in their coolant supply, namely naval vessels.
Your "starting point" for solar power ignores the fact that solar arrays were insufficient to power a rover half the weight of a compact car. Regarding re-calibration of assumptions, I think you need to assume that getting anything to Mars won't be nearly as inexpensive as you assume it will be, now or for the foreseeable future. That $1000/kg figure you cited is the projected cost to get something to LEO, not Mars, assuming Falcon 9 reusability is everything it's cracked up to be.
You still haven't addressed what a solar flare would do to all those sensitive electronics that are no longer protected by the magnetosphere. A nuclear reactor can be an entirely mechanical device, not subject to any sort of electronics failure. PV arrays and batteries require charge controllers and are, by definition, far more sensitive to the effects of electromagnetic radiation. You also spoke of reactors as being single points of failure while ignoring what happens when electronics get fried, frozen, or damaged. That sounds a lot like a single point of failure to me.
Thus far, you've mostly offered logical fallacies, non-issues, non-applicable issues, and issues that affect both solar and nuclear power production technologies as reasons not to use nuclear power. You might be able to get away with that in an echo chamber, but you'll have to do better than that on this forum. The only valid point I've seen thus far is that if the nuclear reactor quits working, then you lose power. The same also applies to the electronics controlling the solar panels and battery chargers.
Here are some simple truths that aren't going away:
1. Mars and deep space are extreme environments that are not particularly amenable to sensitive electronics. No integrated circuits or batteries would survive in the temperatures and radiation environment without ample insulation, heating, and radiation shielding. There is nothing easy, simple, or inexpensive about designing electronics or electrical power storage equipment to survive the deep space environment.
2. Mars has a day/night cycle and is 50% further from the Sun than Earth is. If Mars was closer to the Sun, warmer, or had an atmosphere more like that found on Earth, then it'd be a lot easier to make solar panels or internal combustion engines work there. From a practical standpoint, that means that the most powerful and capable vehicle presently on Mars is a nuclear powered rover. Even the solar powered rovers required radioisotope heaters to prevent their electronics from freezing at night, as the electrical power that their batteries could provide was insufficient for the task. There have been improvements in battery technology along the way, but not an order of magnitude improvement, and human missions to Mars will require an order of magnitude more power than the small robots we've sent thus far.
3. Any power provisioning technology must take account of the fact that Mars is tens of millions of miles from Earth and we can only go there every two years, at extreme cost. All technologies selected must be rigorously tested and any deficiencies identified and corrected, or there is a very good chance that anyone we send there won't be coming back.
It seems unwise to completely rely on one technology and foolish to rely on technologies that have never been used for space power applications. Apart from rocket engines using storable chemical propellants, we've never run any other type of internal combustion engine on another planet. That leaves solar and nuclear technologies as the candidate technologies to use for human exploration of Mars. I think a mix of both is likely required. I'm not entirely opposed to using one or the other, provided that the technology selected is thoroughly tested.
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Initial in situ fuel production of the type proposed relies on the discovery of an adequate and easily accessed water source. We haven't found and proved accessibility yet, although there are good indications of large amounts of ice near the surface in some regions. We cannot have manned craft dependent on this until it has been proven. I think that for initial couple of manned missions, if they depend on local fuel production, we should be using oxygen and CO as the ingredients are available just by compressing and separating the atmospheric gasses then reducing CO2 to O2 and CO. They have still to be refrigerated and stored for long periods as well.
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To show it's not just me:
https://www.universetoday.com/21293/des … -colonies/
A team from MIT have also concluded that PV power offers a quick and ready solution.
In summary:
"According to Hofstetter, a Mars mission should be able to transport several 2 metre-wide rolls of thin-film solar panel arrays. Rolling out an array of these thin-film rolls could supply ample energy to a colony. For example, if the array is positioned at 25° north, measuring 100×100 metres, 100 kilowatts can be generated. The MIT researchers even calculated it would take two astronauts 17 hours to construct the array (alternatively they could get a robot to do it)."
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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1. Experience on Mars has shown that, leaving aside the ultra-extreme polar regions, PV powered electronics perform well in robots,
without the advantage of on site human maintenance.
2. The reduction in insolation on Mars compared with Earth is greatly mitigated by the generally clear skies.
3. PV has been radically tested on Mars already. Nuclear reactors have not. The MIT research shows that PV is a perfectly adequate power source:
https://www.universetoday.com/21293/des … -colonies/
PV also has thea great advantage of flexibility - making it ideal for carrying on expeditions which will be an important feature of the early missions.
I very much doubt that methane manufacture is going to be any more challenging than the other life support technologies we must put in place. It's doable and the benefits of having a methane/oxygen power store will give even greater flexibility.
Louis,
Your proposed methalox plant is many times more complicated than a nuclear reactor of the the type NASA wants to send to Mars. Your false equivalency with the Fukushima plant is not applicable. You're comparing something with thousands of moving parts to something simpler than a 1950's internal combustion engine. Since nobody here has proposed sending a 1950's tech nuclear reactor to Mars, it's a safe bet that there won't be any 1950's nuclear accidents on Mars. Nuclear reactors of the 1950's were originally designed to power things sitting in their coolant supply, namely naval vessels.
Your "starting point" for solar power ignores the fact that solar arrays were insufficient to power a rover half the weight of a compact car. Regarding re-calibration of assumptions, I think you need to assume that getting anything to Mars won't be nearly as inexpensive as you assume it will be, now or for the foreseeable future. That $1000/kg figure you cited is the projected cost to get something to LEO, not Mars, assuming Falcon 9 reusability is everything it's cracked up to be.
You still haven't addressed what a solar flare would do to all those sensitive electronics that are no longer protected by the magnetosphere. A nuclear reactor can be an entirely mechanical device, not subject to any sort of electronics failure. PV arrays and batteries require charge controllers and are, by definition, far more sensitive to the effects of electromagnetic radiation. You also spoke of reactors as being single points of failure while ignoring what happens when electronics get fried, frozen, or damaged. That sounds a lot like a single point of failure to me.
Thus far, you've mostly offered logical fallacies, non-issues, non-applicable issues, and issues that affect both solar and nuclear power production technologies as reasons not to use nuclear power. You might be able to get away with that in an echo chamber, but you'll have to do better than that on this forum. The only valid point I've seen thus far is that if the nuclear reactor quits working, then you lose power. The same also applies to the electronics controlling the solar panels and battery chargers.
Here are some simple truths that aren't going away:
1. Mars and deep space are extreme environments that are not particularly amenable to sensitive electronics. No integrated circuits or batteries would survive in the temperatures and radiation environment without ample insulation, heating, and radiation shielding. There is nothing easy, simple, or inexpensive about designing electronics or electrical power storage equipment to survive the deep space environment.
2. Mars has a day/night cycle and is 50% further from the Sun than Earth is. If Mars was closer to the Sun, warmer, or had an atmosphere more like that found on Earth, then it'd be a lot easier to make solar panels or internal combustion engines work there. From a practical standpoint, that means that the most powerful and capable vehicle presently on Mars is a nuclear powered rover. Even the solar powered rovers required radioisotope heaters to prevent their electronics from freezing at night, as the electrical power that their batteries could provide was insufficient for the task. There have been improvements in battery technology along the way, but not an order of magnitude improvement, and human missions to Mars will require an order of magnitude more power than the small robots we've sent thus far.
3. Any power provisioning technology must take account of the fact that Mars is tens of millions of miles from Earth and we can only go there every two years, at extreme cost. All technologies selected must be rigorously tested and any deficiencies identified and corrected, or there is a very good chance that anyone we send there won't be coming back.
It seems unwise to completely rely on one technology and foolish to rely on technologies that have never been used for space power applications. Apart from rocket engines using storable chemical propellants, we've never run any other type of internal combustion engine on another planet. That leaves solar and nuclear technologies as the candidate technologies to use for human exploration of Mars. I think a mix of both is likely required. I'm not entirely opposed to using one or the other, provided that the technology selected is thoroughly tested.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Interesting but I can't find any reference to using carbon monoxide by itself as a fuel. Don't you still need hydrogen?
Initial in situ fuel production of the type proposed relies on the discovery of an adequate and easily accessed water source. We haven't found and proved accessibility yet, although there are good indications of large amounts of ice near the surface in some regions. We cannot have manned craft dependent on this until it has been proven. I think that for initial couple of manned missions, if they depend on local fuel production, we should be using oxygen and CO as the ingredients are available just by compressing and separating the atmospheric gasses then reducing CO2 to O2 and CO. They have still to be refrigerated and stored for long periods as well.
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Interesting but I can't find any reference to using carbon monoxide by itself as a fuel. Don't you still need hydrogen?
No. The reaction discussed here is:
2 CO + O2 --------------> CO2
One of the mission models I've seen now requires only Oxygen production, and a stored Earth made hydrocarbon fuel type; possibly MMH or Aerozine 50. Oxygen makes up 75% of the combustion mass in any rocket motor, bringing along the fuel doesn't overwhelm the balance sheet for a Mars mission. If the ERV is only bound for Mars orbit, not that much mass would be required. Obviously, Methane production makes for a better option. But--this is one of the reasons NASA wants to send an experimental Moxie unit on the 2020 mars rover mission.
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Louis-
You seem to have forgotten that the Mars rovers all shut down to hibernate during the Martian Winters? And, as kbd512 has also pointed out, the rovers all have supplementary heating systems using RTG systems? Your analysis and enthusiasm has tended to overlook the drawbacks associated with Solar cells, such as seasonal variability of radiant energy, sensitive electronics, vulnerability to damage, obscuration by accumulated dust, etc., etc., etc. Then you continue spouting about nuclear systems which are by today's standards, hopelessly obsolete. We certainly could get solar power to work, but with a LOT more effort and mass involved than you are willing to acknowledge. I really don't think the Mars base will want to turn down the heat in the Hab during the winter season, either. What is required is constant energy supply 24+/7. No seasonal energy output need apply. No diurnal lapses in production. No massive battery banks need apply.
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No. The reaction discussed here is:
2 CO + O2 --------------> CO2
NASA considered that for ISPP long ago. The problem is carbon monoxide is an extremely poor fuel. Dr. Zubrin dramatically improved that by proposing a Sabatier Reactor to produce methane instead. Each unit mass of hydrogen brought from Earth becomes 18 units of mass of LCH4 and LOX. And Paul Sabatier invented it in the 1910s, he received the Nobel Prize in 1912. It was used for industrial production of "synthetic natural gas".
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The Rovers weren't designed for long term survival.
I don't think I am being over optimistic - rather robustly realistic. Take a look at the MIT paper:
http://systemarchitect.mit.edu/docs/cooper10.pdf
That was from 8 years ago. There will have been further technological improvements since. The lightweight PV panel option is clearly practical.
We can put in place back up with RTGs, chemical batteries, methane/CO production, and nano iron production for combustion.
Louis-
You seem to have forgotten that the Mars rovers all shut down to hibernate during the Martian Winters? And, as kbd512 has also pointed out, the rovers all have supplementary heating systems using RTG systems? Your analysis and enthusiasm has tended to overlook the drawbacks associated with Solar cells, such as seasonal variability of radiant energy, sensitive electronics, vulnerability to damage, obscuration by accumulated dust, etc., etc., etc. Then you continue spouting about nuclear systems which are by today's standards, hopelessly obsolete. We certainly could get solar power to work, but with a LOT more effort and mass involved than you are willing to acknowledge. I really don't think the Mars base will want to turn down the heat in the Hab during the winter season, either. What is required is constant energy supply 24+/7. No seasonal energy output need apply. No diurnal lapses in production. No massive battery banks need apply.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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