Going Solar...the best solution for Mars.

Oldfart1939 · 2018-06-17 11:09:27

Batteries PRODUCE nothing unless fully charged. What you have continued to ignore is that once a major sandstorm begins, the solar panels begin accumulating dust which impairs their efficiency in addition to lowered irradiance from all the garbage swirling. If power is hugely diminished, don't count on the battery powered robots to clean them off. This is exactly a graveyard spiral set of conditions that Zubrin sought to avoid by making Mars Direct 100% dependent on nuclear reactors.

louis · 2018-06-17 12:17:44

The batteries will leave Earth fully charged and will remain fully charged unless there is a critical need to discharge them. There is no need to use the charge unless an extremely serious dust storm scenario arises.

I have not ignored the issue of dust on PV panels. That can of course impact negatively on output. But I prefer the science to the assertion:

"It was observed that during its deposition on the solar panels, the Mars dust simulant formed dendrites and agglomerations, which can be explained by the bipolar nature of the charging process. These facts can explain that even at relatively large mass density values of dust deposited on the solar panels, the panels still generate power."

http://citeseerx.ist.psu.edu/viewdoc/do … 1&type=pdf

Since this amount of dust in the atmosphere varies, the degradation of array performance could be between 1 and 50% over a 30 day mission, and between 22 and 89% over a two-year mission.

https://www.sciencedirect.com/science/a … 6596000884

[And that appears to be with no dust removal.]

Remember Spirit and Opportunity have kept going for more than a decade, powered by solar, despite being designed for 90 day missions.

NASA got it wrong about the Space Shuttle. Musk and Space X will show they have got it wrong about the necessity for nuclear on Mars.

Oldfart1939 wrote:

Batteries PRODUCE nothing unless fully charged. What you have continued to ignore is that once a major sandstorm begins, the solar panels begin accumulating dust which impairs their efficiency in addition to lowered irradiance from all the garbage swirling. If power is hugely diminished, don't count on the battery powered robots to clean them off. This is exactly a graveyard spiral set of conditions that Zubrin sought to avoid by making Mars Direct 100% dependent on nuclear reactors.

Terraformer · 2018-06-17 13:18:40

louis, have you ever heard of the term "self-discharge"?

louis · 2018-06-17 13:40:59

I agree that many nuclear enthusiasts have moved away from "nuclear only" to "nuclear combined with PV", though not everyone seems to be defining the relevant proportions (some think it's "nuclear plus PV", others "PV with nuclear back-up").

What you do by taking both nuclear and PV is adding unnecessary complexity to the mission. Nuclear reactors create specific management issues that cannot simply be swept aside as trivial. Unloading, location and dealing with waste heat all become significant challenges in themselves.

A nuclear reactor beats batteries on mass and output over time, but not PV panels. Space rated PV panels give superior mass to output performance. A key point here as well is that nearly all the energy for a Space X style Mission One will go into propellant production. Now that does not require continuous operation so the intermittency of PV power is not an issue.

While you are making assertions about PV panels being blanked out by dust storms for substantial periods of time, you aren't linking to any scientific papers backing up those assertions.

All (and I mean all) the science papers I have seen stress that power production can continue through dust storms (and most of them are referencing robot missions, where there are no humans to direct panel cleaning).

I take the 1969 9 months storm as a reference point. You need an energy system that can cope with a storm of that duration.

I've already indicated I think you might need to build in over-capacity in relation to normal PV power to compensate for dust storm conditions during Mission One (I'm guessing around 30-40% over). This only applies to Mission One, and a situation where you arrive just before or during a worst case scenario dust storm. Thereafter you will have sufficient supplies of methane/oxygen to drive generators and maintain desired power levels. No need for chemical batteries en masse at that point, although they will I am sure be part of the energy solution.

On Earth nuclear power reactors are built well away from habitation. But for Mars you propose building them next to habitation - at least I presume you do. And how do you deal with waste heat from the reactors?

GW Johnson wrote:

Louis:
Your prejudices against nuclear power are irrational (so are the anti-nuclear prejudices of most of the world's brainwashed public). Besides, it's NOT either/or. Most of us are saying "take both".
A reactor of 100 KWe weighs less than batteries capable of 100 KWe, and will operate for many years, while tons upon tons upon tons of batteries are required to operate for weeks. It's that simple.
Your attitudes about the risks posed by Martian dust storms are also irrational. It is pointless to demand citations from scientific or engineering papers when you have the historical evidence right in front of your face.
You have not said one word about my example of the 1969 dust storm that blanketed the entire planet for 9+ months (it was already going on when Mariner 9 got there, and dissipated 9 months after the probe's arrival). I infer that you have nothing you can say about it. It does not take very many tiny particles per cubic meter to totally obscure all beam radiation, and most diffuse radiation, when the slant path length through them is 20+ km in length! Simple physics, man! OF COURSE it was almost totally blacked out down there! How could it NOT be?
I'm not an astronomer. I haven't kept up with dust storms on Mars. I don't know how many near-planet-wide obscuration events there have been since the 1969 event. But the current event seems to be falling into that category, so that's at least 2 in about 50 years. What that means is that the probability of having one during any particular 2 to 4 year stay on Mars is significantly nonzero! That's just statistical math, man! You cannot argue with it without making a complete fool of yourself!
All right, since the statistics are significantly larger than zero, you are ETHICALLY OBLIGATED to design-in adequate power for your crew on Mars in conditions of near total darkness for extended periods of time (approaching a year).
As for your fears of how unsafe nuclear power is, consider that since SSN-571 Nautilus was launched in 1954 (an event I personally remember, by the way), NOT ONE accident was ever experienced with a compact pressurized-water reactor on any ship or submarine in the US Navy, despite two sinkings (Thresher SSN-593 and Scorpion SSN-589) into the deep sea far beyond the crush depth of any of the pressure hulls. Such a compact pressurized water design is not identical to, but very similar to, what would be needed on Mars. As for isolation, bulldoze an earthen berm around it. Don't start the thing until you have it emplaced. Simple!
The ONLY blot on that US Navy record was the experimental sodium-cooled reactor installed in SSN-585 Seawolf. It leaked with radioactive sodium fires inside a pressure hull at sea. It was replaced with the pressurized-water design, and NEVER EVER had another problem! The ship served many, many years flawlessly after that.
Amazing what the safety record can be when safety is prioritized over cost by edict from the top. Hyman Rickover was a real SOB, but his insistence on safety and reliability FIRST above all really paid off.
Commercial power plants are built and operated by outfits for which the bottom line is the god they worship above all, and safety regulations are complied-with only under duress. This shows in the Three Mile Island incident, which released a very minor amount of radiation, and the Fukushima incident, which has released (and continues to release) a huge amount. Chernobyl was in a class by itself: no one in their right mind today would use a graphite pile reactor with no containment at all.
The point here is: TAKE BOTH! You're gonna need the nuke when the long darkness comes (and it will). You cannot ship enough batteries to get through that.
GW

SpaceNut · 2018-06-17 16:06:25

A set of batteries not connected to anything will hold charge unless it has an event that allows for self discharging which happens when pressures on the internals cause moisture wicking to happen and then they can explode and burn quite readily. This is one of the reasons for the flights on airplanes to limit such devices that hold them as to reduce risk. The internal temperature also if to excessive as well as to cold will cause the cell to be damaged as well.

http://batteryuniversity.com/learn/arti … ion_to_die

To charge a battery you need a voltage source of at least 1.5 volts approximate greater than the voltage of the battery to charge level with sufficient current at a minimum but that will need to be increased as the voltage on the battery increases for a single cell. That is where the 70% condition can not charge a battery unit its that high in order to be able to charge and can not charge a battery unit until its is that high for the voltage and its power level to make it happen.

This article is what we are doing for single cell charge and discharge use but is the method used for a cell bank that gets to higher voltages and power levels.
Proper Lithium-Ion battery charging and safety

The article is also written for single cell but that is the base level to which lithium cell batteries work.
https://www.techrepublic.com/blog/five- … tery-life/

http://www.electronicdesign.com/power/u … y-equation

https://www.gamry.com/application-notes … batteries/

Now making up a battery pack means trying to match cell performance and balance the charging circuits that make the battery work the way it does.

Charge-discharge studies of lithium-ion batteries

Guidelines on Lithium-ion Battery Use in Space

Lious wrote:

While you are making assertions about PV panels being blanked out by dust storms for substantial periods of time, you aren't linking to any scientific papers backing up those assertions.

I did give science papers that had nasa information in the DRM 5 but Nasa is not making a complete paper on that one subject as they know from the pheonix, spirit and so forth that just solar is not with out a risk and its one that humans can not take. Sure total isolation / obscurity does not happen everyday but a battery is dead once it can no longer be charged, when charging is continually blocked and useage is continued it will build up a barrier and the battery will fail. I would not think of trying to say a tau of 5 and greater will never happen and that is why solar is not a garrentee.

Luois wrote:

All (and I mean all) the science papers I have seen stress that power production can continue through dust storms (and most of them are referencing robot missions, where there are no humans to direct panel cleaning).

The dead rover is the proof that oscurity / isolation will in time kill when it falls below survival level and for a human mission that is not going below that minimum for any length of time. Humans will not survive once temperatuires reach prolonged freezing levels as water will not be available, Oxygen levels drop due to respiration scrubbers no longer working and backup oxygen is exhausted or can not be accessed due to no power, food can not be eaten as its frozen....

SpaceNut · 2018-06-17 16:21:49

Solar and Nuclear are equally part of any mission and a balance of both is required. When solar is to low the nuclear side can charge the batteries slowly and still keep them from being damaged. Also when solar is in the full ability the nuclear side and be set to moderate or be shut down as required. The nuclear is not just a backup but an intergral part of surviving for when solar is not operational or is so reduced that its not working.

Earth's surface solar insolation.

louis · 2018-06-17 16:44:51

SpaceNut wrote:

A set of batteries not connected to anything will hold charge unless it has an event that allows for self discharging which happens when pressures on the internals cause moisture wicking to happen and then they can explode and burn quite readily. This is one of the reasons for the flights on airplanes to limit such devices that hold them as to reduce risk. The internal temperature also if to excessive as well as to cold will cause the cell to be damaged as well.

Are you actually saying we can't get a charged battery from Earth to Mars? The ISS batteries seem to work perfectly well. I am sure there are all sorts of technical issues with battery storage that I am not qualified to discuss but I think the experience of the ISS and other missions suggests this is not going to be a problem. Airplane holds are basically unsupervised and unmonitored. I don't think that would apply on a BFS.

I did give science papers that had nasa information in the DRM 5 but Nasa is not making a complete paper on that one subject as they know from the pheonix, spirit and so forth that just solar is not with out a risk and its one that humans can not take. Sure total isolation / obscurity does not happen everyday but a battery is dead once it can no longer be charged, when charging is continually blocked and useage is continued it will build up a barrier and the battery will fail. I would not think of trying to say a tau of 5 and greater will never happen and that is why solar is not a garrentee.

Not sure how many times I have to say it - tau does not read across to insolation. Tau, as far as I can make out, is really a measure of direct insolation. It doesn't incorporate ambient light, which PV panels can convert into electricity.

The dead rover is the proof that oscurity / isolation will in time kill when it falls below survival level and for a human mission that is not going below that minimum for any length of time. Humans will not survive once temperatuires reach prolonged freezing levels as water will not be available, Oxygen levels drop due to respiration scrubbers no longer working and backup oxygen is exhausted or can not be accessed due to no power, food can not be eaten as its frozen....

These rovers are tiny, tiny. They have to close down in certain conditions, because the PV panel and the robot are really one machine.

You cannot possibly use their history as an indicator of how an 800 tonne mission will handle energy demand. But if you try to, then at least acknowledge that their solar power energy system was only designed to last 90 days and has kept going for up to 14 years.

In an 800 tonne PV-orientated mission as proposed by Musk and Space X there is simply no question of people freezing to death, or dying from lack of oxygen. It ain't gonna happen! As I have already explained you can take 50 tonnes of air and water which will keep six humans alive for 500 sols.

GW Johnson · 2018-06-17 17:13:54

Louis:

I've taken you to task before about requiring citations when it isn't necessary. You do this the same way Trump quotes falsehoods from Fox and Friends as if they were facts. It's nothing but a sop to your emotions: trying to discredit other's information that you don't want to believe. Stop doing that. It really discredits you.

There are now batteries many times better than the old lead acid battery in your car. They all self discharge as a function ONLY of time, just at different rates for the different types. But they DO self-discharge, even when connected to nothing. So, yes, batteries shipped to Mars will self-discharge during the trip, to one extent or another!

Your car has circuits you cannot turn off these days, which is why if you leave it parked without use for a single handful of months, or less, the battery will be very nearly discharged, if not fully discharged. On the other hand, if you go to the trouble of disconnecting at least the ground strap, the car battery will retain a decent charge far longer.

This shows up when you buy one off the shelf at the auto store as a battery that will start the car, but shows low on charge if you actually bother to test it with a real battery tester. It has been sitting on the shelf, unconnected to anything, self discharging, for a double or triple handful of months. Typically, if it was manufactured more than a year or so before its got sold, it really will require at least some recharge before it will start the car.

I don't need any "scientific paper" citations for that. It is simple human experience with batteries in cars (and other things) over more than a century now. And deep down somewhere, you KNOW I am speaking the truth.

Batteries also have a finite life, in the sense of only a fixed number of discharge-recharge cycles. It varies from type to type, and sharply with manufacturing quality. This is why most 2 year car batteries fail in just about 24 months. The better-built, more expensive 5-year batteries generally fail about 60 months into their installed service. The people who make these things know very well just about how long they really will last, which is why a warranty replacement for full value is so rare.

My own experience with rechargeable lithium-ion batteries makes the ancient lead-acid technology look really good. The rechargeables in my flashlights and in my solar-powered yard lights are usually crap in a year or less. It shows up as ever-reducing capacity until it won't take a charge at all. The same goes for the lithium-ion battery packs they sell in your laptop computers. I have never seen one that functions adequately for over a year, and they are usually quite dead in 2 years.

THIS is what you want to bet lives on, on Mars? With no backup? THAT is unethical in the extreme.

Again, take both solar and nuclear. We can debate how much of each. But arguing for one without the other is insanely unethical!

GW

Last edited by GW Johnson (2018-06-17 17:18:02)

RobertDyck · 2018-06-17 17:19:12

louis wrote:

The ISS batteries seem to work perfectly well. I am sure there are all sorts of technical issues with battery storage that I am not qualified to discuss but I think the experience of the ISS and other missions suggests this is not going to be a problem.

No system of batteries will ever last 9 months. Or 3 months. Batteries on ISS will not last that long. ISS experiences 45 minutes of direct sunlight, then 45 minutes of dark. Batteries are intended to last during that period of dark. I'm sure there's a large safety margin, but they certainly won't last 9 months of dark.
EVA-39: Spacewalkers complete the upgrading of ISS batteries

Last edited by RobertDyck (2018-06-17 17:21:15)

SpaceNut · 2018-06-17 17:45:56

Sleep mode or off in modern electrenic devices does not mean off totally as there is what is known as phantom circuit draw as you are sampling and running code in a none displayed manner still even in off which will make a battery dead the next time months later that you want it. Try it on a laptop, cellphone, tablet ect and you will see a dead battery. A full battery is only going to happen when totally disconnected and isolated from the contact ends that can draw a current or if there is some sort of trickle charging circuit.

Mars Rovers Weather Worst of Dust Storms

A tau of five means that less than one percent of direct sunlight is reaching the Mars surface, but the rovers have been successful drawing power from scattered sunlight.

A Tau measured value of 5 of indirect sunlight wattage given a page back.
This is why Insight is going to mars with larger panels...as its not because it needs more power...

NASA_video_848x480_1224973891937.jpg?w=670&quality=70&strip=all

This was the 2007 storm, intensified over a months time and longer

plot of tau and power for that 2007 storm

Tau value of 1.00 is about 765 whrs
Tau value of 3.30 is about 402 whrs
Tau value of 4.00 is about 270 whrs
Tau value of 5.00 is about 148 whrs

Tau value of 10.8 is about 22 whrs

This being the summer and having eight radioisotope heater units (RHU) in its body providing about 8 watts of thermal energy may make it able to survive the storm.
Dust is lifted into the atmosphere by winds of around 70 mph, and as the storm spreads, additional dust raising areas form as well, filling the sky with haze that can encircle the entire planet. Understanding how these storms start, and predicting them in advance, will be critical to supporting future missions to Mars—especially any that involve people on the surface.

louis · 2018-06-17 18:24:06

It's wrong to require citations if you refuse to produce them yourself. I, however, have produced a number of citations suggesting that PV electricity generation can continue through Mars dust storms at a reduced rate. No one else has produced a citation showing the opposite to be true.

I'm seeing figures of 20% charge loss over one year for lithium ion batteries. If that is the figure, you lose 10% over a six month journey to Mars. Ok, so make it 82.5 tonnes instead of 75 tonnes or recharge them from the BFS PV "wings" in transit. Once you are on Mars you can recharge them from your PV system, keeping them topped up ready for any emergency.

The Tesla automobile battery is covered by an 8 year warranty. Are you sure your claims are credible? If they were all Tesla cars would stop running after a max of 2 years.

https://www.tesla.com/support/vehicle-warranty-ms-mx

GW Johnson wrote:

Louis:
I've taken you to task before about requiring citations when it isn't necessary. You do this the same way Trump quotes falsehoods from Fox and Friends as if they were facts. It's nothing but a sop to your emotions: trying to discredit other's information that you don't want to believe. Stop doing that. It really discredits you.
There are now batteries many times better than the old lead acid battery in your car. They all self discharge as a function ONLY of time, just at different rates for the different types. But they DO self-discharge, even when connected to nothing. So, yes, batteries shipped to Mars will self-discharge during the trip, to one extent or another!
Your car has circuits you cannot turn off these days, which is why if you leave it parked without use for a single handful of months, or less, the battery will be very nearly discharged, if not fully discharged. On the other hand, if you go to the trouble of disconnecting at least the ground strap, the car battery will retain a decent charge far longer.
This shows up when you buy one off the shelf at the auto store as a battery that will start the car, but shows low on charge if you actually bother to test it with a real battery tester. It has been sitting on the shelf, unconnected to anything, self discharging, for a double or triple handful of months. Typically, if it was manufactured more than a year or so before its got sold, it really will require at least some recharge before it will start the car.
I don't need any "scientific paper" citations for that. It is simple human experience with batteries in cars (and other things) over more than a century now. And deep down somewhere, you KNOW I am speaking the truth.
Batteries also have a finite life, in the sense of only a fixed number of discharge-recharge cycles. It varies from type to type, and sharply with manufacturing quality. This is why most 2 year car batteries fail in just about 24 months. The better-built, more expensive 5-year batteries generally fail about 60 months into their installed service. The people who make these things know very well just about how long they really will last, which is why a warranty replacement for full value is so rare.
My own experience with rechargeable lithium-ion batteries makes the ancient lead-acid technology look really good. The rechargeables in my flashlights and in my solar-powered yard lights are usually crap in a year or less. It shows up as ever-reducing capacity until it won't take a charge at all. The same goes for the lithium-ion battery packs they sell in your laptop computers. I have never seen one that functions adequately for over a year, and they are usually quite dead in 2 years.
THIS is what you want to bet lives on, on Mars? With no backup? THAT is unethical in the extreme.
Again, take both solar and nuclear. We can debate how much of each. But arguing for one without the other is insanely unethical!
GW

Oldfart1939 · 2018-06-17 18:34:11

It ultimately boils down to "follow the money." Musk is heavily invested in Solar City, as well as Tesla. It's in his business interest to promote solar power, not that it is the best and most logical path forward for Mars. On the other hand NASA is working with the DOE in the development of the Kilopower nuclear reactors. As much as I have in past posts disparaged NASA, this is one area in which they are adamantly working for safe, deep space power. And they essentially have an open checkbook to draw upon. I am confident that when the BFS finally goes to the Red Planet, NASA will INSIST on a major nuclear power component's inclusion.

And with this statement, I'm retiring from this specific thread and Louis' not quite circular arguments (but they are pretty elliptical). Those Angels on pinheads are already exhausted from tap dancing there.

louis · 2018-06-17 18:37:44

Some points:

1. The tau figure is being ESTIMATED. Remember that, estimated. We've no idea whether NASA have got it right or not. There may be an observational bias going on here. NASA don't want to be proved wrong yet again, in opting for nuclear power in the same way they opted for a white elephant spaceplane in the 70s.

2. Tau and dust on solar panels are not the same thing. If it's getting v. dusty, the panels might well be functioning poorly. But that doesn't mean that a human mission with large arrays and robots constantly cleaning panels would be recording the same sorts of figures per sq. metre of panel.

3. The tiny rover could just be in a particularly bad spot where its panel is getting covered in dust really badly. It really is a v. tiny machine, so, it can't give you any real evidence for what the prevailing conditions are in the local say 4 sq. kms.

4. If the tau value of 10.8 is correct, it is the highest ever recorded on Mars. But then the question is - does it persist? For how many sols? If it's just one and it then goes down to 5, it's a phenomenon of virtually no interest. If it's 10.8 for 3 sols and then goes down to 5, that's also of little relevance. If it's staying up there for 10 sols well, yes, that's of greater interest. I think a relevant figure would be an average over 100 sols. If that ever approached a tau of 10 that might be cause for concern. As far as I know, we have never ever been even remotely close to that scenario.

SpaceNut wrote:

Sleep mode or off in modern electrenic devices does not mean off totally as there is what is known as phantom circuit draw as you are sampling and running code in a none displayed manner still even in off which will make a battery dead the next time months later that you want it. Try it on a laptop, cellphone, tablet ect and you will see a dead battery. A full battery is only going to happen when totally disconnected and isolated from the contact ends that can draw a current or if there is some sort of trickle charging circuit.
Mars Rovers Weather Worst of Dust Storms
A tau of five means that less than one percent of direct sunlight is reaching the Mars surface, but the rovers have been successful drawing power from scattered sunlight.
A Tau measured value of 5 of indirect sunlight wattage given a page back.
This is why Insight is going to mars with larger panels...as its not because it needs more power...
https://i0.wp.com/media.globalnews.ca/v … &strip=all
This was the 2007 storm, intensified over a months time and longer
http://planetary.s3.amazonaws.com/image … ed_med.gif
plot of tau and power for that 2007 storm
http://planetary.s3.amazonaws.com/image … ug_med.jpg
Tau value of 1.00 is about 765 whrs
Tau value of 3.30 is about 402 whrs
Tau value of 4.00 is about 270 whrs
Tau value of 5.00 is about 148 whrs
Tau value of 10.8 is about 22 whrs
This being the summer and having eight radioisotope heater units (RHU) in its body providing about 8 watts of thermal energy may make it able to survive the storm.
Dust is lifted into the atmosphere by winds of around 70 mph, and as the storm spreads, additional dust raising areas form as well, filling the sky with haze that can encircle the entire planet. Understanding how these storms start, and predicting them in advance, will be critical to supporting future missions to Mars—especially any that involve people on the surface.

Last edited by louis (2018-06-17 18:39:23)

louis · 2018-06-17 18:45:11

I agree. Musk has a vested interest in promoting solar - I've said the same myself before. It's all of a piece with Musk. He's way smarter than most people realise I think. Everything supports everything else: solar supports batteries supports Tesla supports Boring supports hyperloop supports solar supports Mars supports rockets supports satellites supports internet in the sky supports orbital tourism supports lunar tourism supports Mars again...

Oldfart1939 wrote:

It ultimately boils down to "follow the money." Musk is heavily invested in Solar City, as well as Tesla. It's in his business interest to promote solar power, not that it is the best and most logical path forward for Mars. On the other hand NASA is working with the DOE in the development of the Kilopower nuclear reactors. As much as I have in past posts disparaged NASA, this is one area in which they are adamantly working for safe, deep space power. And they essentially have an open checkbook to draw upon. I am confident that when the BFS finally goes to the Red Planet, NASA will INSIST on a major nuclear power component's inclusion.
And with this statement, I'm retiring from this specific thread and Louis' not quite circular arguments (but they are pretty elliptical). Those Angels on pinheads are already exhausted from tap dancing there.

kbd512 · 2018-06-17 19:21:07

Louis,

* Tesla bakes in more capacity to their batteries than the nameplate capacity on the battery pack. This is well-documented and proven with the Tesla PowerWall and electric vehicles. That's why their batteries last longer. Li-Ion battery life is directly related to depth of discharge (DoD). At a higher DoD, battery life is much lower. At a lower DoD, batteries can last for many years. This is not a major problem on Earth because no vehicle has to take the batteries to another planet. At 30% to 50% DoD in a room temperature environment, a Li-Ion battery can last through daily charge/discharge cycle for 8 to 10 years. One might note that that corresponds quite nicely with Tesla's claimed battery life and actual results prove exactly what I just stated and what Tesla claimed.

* Operating KiloPower is in no way comparable to operating a multi-gigawatt commercial nuclear generating station on Earth, so stop with the hyperbole already. It's plug-and-play. KiloPower has one control rod that controls the reactor's thermal power output. That's the only control to operate. The entire device is twice the heigh of a suited astronaut and about the same width with the radiator panels folded.

1. astronaut digs a hole two to four feed deep and uses a manually operated crane or winch to put the reactor in the hole
2. astronaut packs in the regolith like potting a plant
3. astronaut unfurls the radiator panels
4. astronaut connects a power cable
5. astronaut walks away and sends a command to gradually remove the control rod

That's it. Over the course of an hour or two, the reactor heats up and thermal output builds and gradually stabilizes. This procedure can be done in a day by two astronauts. In real life, you'd repeat steps 1 through 4 several times before turning the reactors on.

Poston said that DoE and NASA built and completed ground testing of KiloPower from scratch for less than $20M. This was possible because the US government has a stockpile of thousands of tons of HEU that is F-R-E-E. DoE simply has it sitting in a bunker collecting dust and no other uses planned for it.

* Nobody needs to produce a citation showing that Opportunity is dead. NASA said the dust storm on Mars killed it and they're not making things up just to prove or disprove anybody's talking points on electrical energy production on Mars. That's an actual solar powered victim that died on Mars from lack of power that was directly related to the dust storms. That's more "proof" than any research paper ever written. Spirit died the same death. Opportunity isn't affected by how much dust is in the atmosphere. It'll keep going till the wheels fall off, which will happen prematurely because of lack of testing and understanding about how the terrain would degrade aluminum alloy wheels. Something else will invariably kill the Mars 2020 rover from lack of understanding since the problem with the wheels was fixed.

I don't trust any technology to provide all the power. I want solar, nuclear, fuel cells, and internal combustion engines. After all, we can land the mass, so why not? There is no "best" or "right" answer. There are only probabilities of failure, demonstrated or known failure modes, and the certainty of death and destruction that comes from a lack of electrical power. PV is known to die from cell degradation when exposed to radiation. Batteries die when they get too cold or melt / explode if internally short circuited. Fission reactors die when they get too hot and subsequently melt. Fuel cells explode when their membranes rupture. ICE's run out of fuel, explode, or suffer from mechanical failures in operation. Bringing and using a little bit of everything is a means of mixing complementary power provisioning technologies as part of a comprehensive survival strategy.

louis · 2018-06-17 20:20:04

kbd512 wrote:

Louis,
* Tesla bakes in more capacity to their batteries than the nameplate capacity on the battery pack. This is well-documented and proven with the Tesla PowerWall and electric vehicles. That's why their batteries last longer. Li-Ion battery life is directly related to depth of discharge (DoD). At a higher DoD, battery life is much lower. At a lower DoD, batteries can last for many years. This is not a major problem on Earth because no vehicle has to take the batteries to another planet. At 30% to 50% DoD in a room temperature environment, a Li-Ion battery can last through daily charge/discharge cycle for 8 to 10 years. One might note that that corresponds quite nicely with Tesla's claimed battery life and actual results prove exactly what I just stated and what Tesla claimed.

I think you are trying to say you agree with me but don't particularly want to say that, so let me put it this way: I agree with you.

* Operating KiloPower is in no way comparable to operating a multi-gigawatt commercial nuclear generating station on Earth, so stop with the hyperbole already. It's plug-and-play. KiloPower has one control rod that controls the reactor's thermal power output. That's the only control to operate. The entire device is twice the heigh of a suited astronaut and about the same width with the radiator panels folded.

Well this is all a lovely fantasy...only problem is - no one has actually built one of these KiloPower units yet. Let me know when they do, then we can discuss how they deal with issues like waste heat in a Mars environment.

SpaceNut · 2018-06-17 21:59:09

https://www.reddit.com/r/SpaceXLounge/c … vers_dust/
Data average:
http://www.lpl.arizona.edu/~lemmon/mars-tau-b.html
http://www-mars.lmd.jussieu.fr/mars/dust_climatology/

Effect of Shading on the Performance of Solar PV Panel

https://ntrs.nasa.gov/archive/nasa/casi … 010752.pdf
[url=https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1998JE900017]Opacity of the Martian atmosphere measured
by the Imager for Mars Pathfinder[/url]

Atmospheric Effects on the Utility of Solar Power on Mars
NASA/TM-1999-209288 Solar Electric Power System Analyses for Mars Surface Missions
NASA/TM-2004-213367 Mars Solar Power
Solar Electric Power System for the Exploration of Mars
Telescopic Martian Dust Storms (British Astronomical Association)
Photovoltaics for Mars (NASA Glenn)
Statistical Analysis of Dust Storm data

dust accumilation being removed
https://www.newscientist.com/article/dn … -rolls-on/

Li-Ion Rechargeable Batteries on Mars Exploration Rovers

kbd512 · 2018-06-17 22:43:04

Louis,

I'm saying that I'd rather use 20t of thin film solar panels to make propellant during the day and then use 20t of small fission reactors to provide power at night instead of wasting an entire BFS landing delivering batteries. Since you agree that that's a better use of available tonnage, which is not unlimited, then we're in agreement.

I would limit the use of heavy batteries to applications where their characteristics are desirable, like power storage for vehicles. The space-rated thin film arrays are between 1,125kW/kg to 1,400kW/kg. If we add in the truss structures, electric motors for single axis Sun trackers, and the robots to construct the arrays on Mars, let's just call it ~1,000W/kg. Divide that number by two to arrive at a realistic peak output on Mars at the equator with little to no dust in the atmosphere. The Sun tracker can also tilt the panels to use gravity to remove excess dust. That is the best operational reason for why the truss structure and single axis tracker mechanisms are required.

I don't include PMAD because that's required for any power provisioning scheme and there's no way around it.

* 20t thin film solar arrays (~10MWe peak output, but 1MWe more or less guaranteed)
* 20t for a baker's dozen of the 10kWe fission reactors (100kWe of power for night operations at 75% constant rated output)
* batteries limited to vehicles and emergency power associated with PMAD failures
* 38.525t per LOX/LH2 plant (see notes below)

This is what a real portable chemical plant looks like (CONEX box), what it weighs (38,525kg), how much power it consumes (2.2MWe), and what it costs ($26M):

M Series PEM Electrolysers

M Series Technical Specifications

Nel/Proton is Proud to have Provided the M Series PEM Electrolyzer Stack Supplying Hydrogen for the First Biomethanation Reactor System Operating in the United States

Proton OnSite M Series PEM Megawatt Electrolyzer Achieves Over 500,000 Cell Hours With Zero Failures and No Loss in Efficiency

For 20t, we can have an array that can power a LOX/LH2 plant during daylight hours. At night, we can use nuclear power to limit propellant boil-off and keep the lights on.

DoE has already built and tested a 1kW KiloPower at full rated output power. The basic design has passed every single test thrown at it and for good reason. It's based upon existing flight rated hardware from the 1980's. DoE and NASA did that at a cost to the American tax payer of less than $20M. There aren't any aerospace contractors involved whose names start with "B" / "NG" / "L", which is why it cost so little and why testing was completed on schedule. The reactor deals with heat in any environment by radiating it, same as ISS and every other spacecraft ever built. If KiloPower's cooling system is totally removed, it won't melt down. That was actually tested using DU-Mo slugs machined to the same shape and size as the HEU core under test right now. That's what a high surface area to volume ratio provides.

Over the course of the next 5 years, approximately $100M to $200M will be spent flying KiloPower in space. Most of that cost is directly related to launch services. Rockets are still just that expensive.

Here's a picture of one that was "being built" a few months back (the same one that was run at full power):

Business Insider - NASA built and tested a 'truly astounding' nuclear reactor that may help astronauts travel longer, farther, and faster in space by Dave Mosher

It's already happening, whether you agree with it or not. Your opinions regarding what has already happened are quaint, but have nothing to do with reality. Put your fingers in your ears and scream "la la la" if it pleases you, but KiloPower is still happening because it's necessary. Do your best impression of a horse while real engineers demonstrate what a modicum of ingenuity can produce using existing flight proven nuclear fission reactor design.

Just to throw you further into a fit, realize that the Soviets flew 150kWt / 5kWe (3 times higher thermal output than 40kWt/10kWe KiloPower) in space for their GEO spy satellites starting in 1986 and they're still orbiting above our heads in GEO. Furthermore, Russian nuclear scientists were first invited to Los Alamos in 1958 during the Cold War. By 1959, nuclear scientists in the US had created thermionic energy conversion devices and Russia followed suit in 1961. Russia created the TOPAZ series of space nuclear reactors (150kWt/5kWe) for space nuclear electric propulsion. Those reactors, some of which are still orbiting in GEO, weighed 320kg and contained 12kg of UO2. The 1061kg TOPAZ-II (100kWt/5kWe - using 25kg of U-Mo and NaK cooled, just like KiloPower) was extensively ground tested by American, British, French, and Russian nuclear scientists at Los Alamos, but never flew in space. KiloPower weighs more because it's an extraordinarily conservative and properly shielded (in one direction only, since the intent is to bury the rest of the core in the regolith) design.

Edit:

Here's the link for TOPAZ: History of Soviet Topaz Reactors

Since I provided a link to the picture of the already built KiloPower test reactor and since other models with the same basic core design (TOPAZ) are still flying around in space above our heads as I write this, do you want to discuss how the reactor deals with waste heat on Mars?

Last edited by kbd512 (2018-06-17 22:46:00)

elderflower · 2018-06-18 04:29:57

I suspect it won't work the way kbd512 thinks it will. Reactor in hole has waste heat which melts the water content of the regolith around it. Reactor is now sitting in a muddy puddle. Muddy puddle is extremely corrosive to reactor materials so heat pipes are breached and only the cable and its own buoyancy are supporting it. Without the cooling panels the reactor overheats (shutdown reactors continue to produce a lot of heat whilst short half life species decay). Astronauts dare not approach it to attempt any fixes.
I do think that reactors will have to be installed above ground (at least initially, until ground water/ice is a lot better understood than it is now), Radiation shielding will involve large berms, but free circulation around reactors will have to be maintained to prevent contact of berm material with warm surfaces.

Last edited by elderflower (2018-06-18 04:31:26)

louis · 2018-06-18 05:14:16

Yes, that was what I was coming to. What works in space might not work on the ground on Mars. It might be you could leave the reactors on the BFS. But then I don't know if that raises its own problems.

elderflower wrote:

I suspect it won't work the way kbd512 thinks it will. Reactor in hole has waste heat which melts the water content of the regolith around it. Reactor is now sitting in a muddy puddle. Muddy puddle is extremely corrosive to reactor materials so heat pipes are breached and only the cable and its own buoyancy are supporting it. Without the cooling panels the reactor overheats (shutdown reactors continue to produce a lot of heat whilst short half life species decay). Astronauts dare not approach it to attempt any fixes.
I do think that reactors will have to be installed above ground (at least initially, until ground water/ice is a lot better understood than it is now), Radiation shielding will involve large berms, but free circulation around reactors will have to be maintained to prevent contact of berm material with warm surfaces.

louis · 2018-06-18 05:52:56

Regarding the self-discharge issue, it looks like losses on a six month voyage to Mars would be between 20-25%. Taking the upper figure, that would be a loss of 3750 KwHs on a load of 75 tonnes of lithium-ion batteries. That would amount to under 21 KwHs per day or just under 1 Kw constant. I think the BFR solar power system could cope with that and top up the batteries en route to Mars.

A. Emergency storage.

75 tonnes of lithium-ion batteries having 200Whs per Kg of storage, which equates to 15000 KwHs in total. . Topped up en route to Mars and thereafter used immediately if the mission begins in the middle of a worst case dust storm or is again topped up by the Mars-based PV system.

B. PV energy on Mars.

We haven't bottomed out yet how much power is required to run the propellant production facility but if it is something like 1MW, the Mars-based configuration might be:

10,000 sq. metres of PV (light weight encapsulated film) (ie 100 metres by 100 metres). This would produce about 35000 KwHs of electricity per sol, an average constant of 1.428 Mws. Most propellant production would take place during the strong insolation period of about 5 hours. The 400 Kws excess would be used to feed night storage chemical batteries, power life support, make good any power losses during dust storms and also create an additional stock of methane/oxygen for back up during dust storms. In a severe prolonged dust storm the system should still produce a minimum of 285 KWes - more than enough to cover the base's life support needs.

Using Flisom style rolled PV thin film, the mass would be about 5 tonnes.

C. PMAD (Power Management and Distribution).

I usually add on 30% for PMAD equipment as a rough guesstimate but let's make it 2 tonnes to be on the safe side.

D. Additional air and water supplies to offset life support energy use in an emergency.

To cover 87 kgs of water and air per sol for a crew of six that would be 35 tonnes to provide cover for 400 sols. [Edited to add 10 tonnes for tanks and cylinders.]

E. Methane/oxygen electricity generator.

For additional energy security one might take along a generator powered by methane and oxygen. Let's put that at 1 tonne.

So the whole PV-battery-methane non-nuclear system would come in at under 130 tonnes .

The Kilopower nuclear reactors would have a mass of something like 150 tonnes (without any redundancy - if you added on 10% for back up, that would give you 165 tonnes).

Last edited by louis (2018-06-18 11:15:07)

RobertDyck · 2018-06-18 07:51:50

I find this discussion bizarre. If you want to go into space, you can't be afraid of technology. And that includes nuclear technology. We have a problem with some claiming we need nuclear propulsion to get to Mars, and no plans for a human mission to Mars can even begin until some form of nuclear propulsion is operational. Obviously that isn't required. But we have someone who is afraid of nuclear power?

This is the Mars Society. This is a refuge from anti-technology activists. At the Mars Society convention in Chicago in 2004, we had one guy give a presentation where he called for establishing large areas as nature preserves. I don't remember the exact word he used, but an area that no one would be allowed to touch. I stood and asked "If we did what you're asking, why would anyone want to go to Mars? There are people willing to spend their entire life saving, sell their house and car, liquidate their pension and life insurance, just for a ticket. The reason is explicitly to get away from the excessive, unreasonable, overbearing regulation we have on Earth today. If you duplicate all that excessive, unreasonable, overbearing regulation on Mars before anyone has even set foot on the Red Planet, then why would anyone ever want to go?" I could go on. My response was about 10 minutes.

louis, most of what you posted here makes a lot of sense. I'm sure everyone here respects you. So why this irrational fear of nuclear?

kbd512 · 2018-06-18 08:00:35

Elderflower,

Mars Sea Level is roughly Earth 90,000 ft. Water boils at -38C at that altitude. The core's operating temperature ranges between 800C to 900C and it's almost a solid block of metal. How long do you imagine water near the reactor would remain liquid before it sublimates into the 6 millibar atmosphere? Why do you imagine your scenario would work like some sort of mud hole at Earth sea level where you have 1,013 millibars of pressure?

There's an image labeled "core containment can" in some of the technical descriptions of KiloPower that's made from AISI 316L. The heat pipes are made of Haynes 230. Both alloys are pretty tough stuff.

HAYNES® 230® alloy product brochure

If having just one stainless steel bucket around the core really bothers you, then use two stainless steel buckets. Problem solved.

Louis,

Nice try with the straw man argument. I didn't propose using 100% nuclear power. I said use opportunistic solar power in the day to maximize power production, then use nuclear power at night to keep the propellant cold and the humans warm. As an emergency backup to the fission reactors, IVF LOX/LH2 ICE's aboard BFS can keep the propellant cold or humans supplied with electrical power.

I get far more available power than your setup does during the day with 20t of thin film panels. Even if I have a lot less Sun, I can still make a lot more power. I skip the battery backup entirely and use fission reactors for limited demands of propellant refrigeration and life support at night. My power provisioning scheme is focused on making power, rather than storing power.

GW Johnson · 2018-06-18 08:35:04

I would suggest that if the regolith is wet enough at any particular site to become a mudhole, then don't bury the reactor for shielding, set it on a stable pad, and just bulldoze a berm around it. What could be simpler?

I think Kbd512 is quite right to suggest production not storage is the answer for electricity production. Use the nuclear for base load day-night around, and add more power-draw activities during the height of day when the solar works well. More-or-less the same as here. A big house here draws 1-2 KW at night when everything but the ac/heat is off and people are asleep. During the day when everybody is awake and all the stuff is turned on, that same house draws 4-6 KW.

Despite the differences between Earth and Mars, you will find that solar doesn't work well, if at all, at low sun angles. That's why you count most on it during only the height of the day, when sun angles are closer to 45 degrees or more above local horizon. Further, most photocells don't make much use of diffuse (scattered, low-energy) light, only direct beam radiation. It is solar THERMAL, not solar photovoltaic, that makes any real use of the diffuse radiation. That's been the experience with it here on Earth.

For the nuclear reactor, waste heat rejection by panel radiation is an option on Mars, yes, and is utterly required in space. But on Mars, there is the regolith, and it is very cold. Why not consider sinking a pipe field into the regolith and using it as your heat sink instead? The efficiency of heat rejection can be very much greater that way. Wet regolith turning into a mudhole actually makes the heat rejection even more efficient that way.

If the ground is too rocky to easily bury the pipes, then lay them on the surface, and bulldoze cover over them instead. It still works.

There. I've just given you two applications for an electric bulldozer on Mars. There are many more, including road-building. Can't be diesel, not in a super-thin CO2 atmosphere. Gotta be electric. That means batteries. And you must recharge them for the next day's use. Probably during the night, so your nuclear base load power is not just habitation heat.

When the bad dust storm comes, your solar isn't going to work much, if at all (that "diffuse radiation is ineffective" thing for solar PV). You must suspend all activities that your nuclear base load system cannot supply. If you are making propellant to come home, that has to get suspended, too, unless you upsize your nuclear component to cover it, too, as an around-the-clock day/night activity. If you don't upsize the nuke component for that, you may miss your return date, because you don't have enough propellant yet to actually go fly.

I don't know how many planet-wide, or near-planet-wide, dust storms have been seen since 1969, but there have been at least two over that 50-year interval: the 1969 event and the one right now. So the probability is at least 4% at any given time. Over a 2 year stay on Mars waiting for the orbits to be "right", that translates to at least an 8% expectation of seeing such a thing happen (multiple months of darkness or very dim light when your solar doesn't work well, or maybe not at all).

Small odds, but not vanishing. It would be unethical in the extreme not to plan for it.

Real life can get a tad complicated, can't it?

GW

Last edited by GW Johnson (2018-06-18 08:50:41)

RobertDyck · 2018-06-18 08:50:57

kbd512, I agree with the principles, but dispute some details. Mars pressure at Pathfinder varied from 6.77 to 7.08 millibar. That's why we say 7. Curiosity rover is at a lower altitude were pressure is usually a touch over 8. Any location where pressure is over 6.12, the triple point of water, boiling temperature is above zero. It's just a couple degrees above, exact temperature depends on pressure.

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