Going Solar...the best solution for Mars.

GW Johnson · 2018-06-18 09:03:46

Water running around loose underneath dirt cover wouldn't boil or sublime away any more that ice does. The polar lander saw this in action, uncovering slivers of ice that sublimed within 2-3 days. The cover of a few inches regolith stops that. That's why those slivers of ice were there in the first place.

Using a standard atmosphere table, 6 mbar ~ 114,000 feet; 7 mbar ~ 110,000 feet, and 8 mbar ~107,500 feet. That's based on the pressure ratio to sea level standard, not density.

GW

GW Johnson · 2018-06-18 09:56:10

From the Wikipedia article “Climate of Mars” 6-18-18

-------------------

Observation since the 1950s has shown that the chances of a planet-wide dust storm in a particular Martian year are approximately one in three.[59]

Ref 59 is: Zurek, Richard W.; Martin, Leonard J. (1993). "Interannual variability of planet-encircling dust storms on Mars". Journal of Geophysical Research. Journal of Geophysical Research. 98 (E2): 3247–3259. Bibcode:1993JGR....98.3247Z. doi:10.1029/92JE02936. Retrieved March 16, 2007.

--------------------

For a crew on Mars waiting for the orbits to be right for the trip home, the stay at Mars is about 1 Earth year, or half a Martian year. The probability of seeing a global dust storm is thus about half the cited 1/3 probability for 1 Martian year, or about 1/6 ~ 17%.

That’s 1: 6 odds, significant enough to be very important to planning.

OK, there you go, I looked up the data on big Martian dust storms, complete with a real supporting citation. That ought to put the kibosh on any petty objections.

The effect is big, it is real, and it is fairly probable to happen. So, deal with it.

You ain't gonna deal with it effectively using only PV panels and batteries. Use the nuclear base load and superpose solar PV on top of it. We can argue relative percentages of each, but you have to plan them about the prospect of coping with a planet-wide dust storm.

GW

Last edited by GW Johnson (2018-06-18 09:59:37)

louis · 2018-06-18 11:21:34

I don't think nuclear fission energy is a desirable energy system on Earth for a variety of reasons. It has more going for it on Mars in relation to Mission One, but my main objections are (a) that it will greatly add to the complexity of the mission (b) it will use up too much human crew time (c) the equipment has not yet been built, and so - unlike PV - is untried (d) the mass is bigger than the equivalent PV-battery-methane system and (e) there are issues over location and waste heat that have not yet been deal with.

RobertDyck wrote:

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?

louis · 2018-06-18 11:24:40

Briney water might not sublimate in the same way and water can be trapped under ground. It would be safer to say "We just don't know..." or maybe you should think in terms of keeping the reactors on board the BFS.

kbd512 wrote:

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.

kbd512 · 2018-06-18 11:52:23

GW / Rob / Louis / Elderflower,

1. Any water in close contact with something that's hot enough to melt brass will boil off, period. At less than 10 millibars, that'll happen rather quickly unless the reactor core is literally sitting on a block of ice. If you hit the water ice jackpot, then you don't need a fission reactor at night because a LOX/LH2 combustion engine can provide plenty of power.

The reactor core, the part that needs to be buried, is already fully enclosed in a 316L can. If you think the core needs more protection, then use another stainless steel liner can as a bore hole liner. If you really want to over-engineer this, then add radial fold-out steel arms to the top of the can or radiation shielding and stake the arms into the ground. The reactor's not going anywhere at that point.

2. Two guys with a 3kW core drill can bore a hole in the regolith. No electric bulldozer is required to drill an 18" diameter hole 24" deep. I don't care if the ground is sand, ice, or granite, the drill will still go through it. An 18" diameter 48" long Belltec rock bit with carbide tipped bullet teeth weighs 87kg on Earth and 33kg on Mars. A 3.3kW Husqvarna core drill motor is 14kg and their stand is 26kg. It's $2K for the drill bit, $3.4K for the drill, and $2K for the stand.

NASA can reinvent the rock drill for 100 times the price, but a NASA-fied rock drill is still more affordable than any non-existent electric bulldozer. The logistics tail for an electric drill is a bag of spare parts. Add more bits for different diameter holes for different purposes. A 10kph 1t payload capacity electric wagon that can transport two astronauts, solar panel canisters, truss canisters, truss fabrication robots, fission reactors, power cables, drills, hoists, and other tools to construction sites is all that's required.

3. The reason we need thin film solar is that the thin film technology has superb off-nominal photon conversion and 100m of paneling is mere kilograms. The composite truss structure is similarly light. That should be enough mass to keep it on the ground in a storm, but not so much mass that powerful electric motors are required to tilt the arrays. If there isn't enough mass, then sandbag it and it'll stay put.

4. Who cares about missing launch windows when you have tons of consumables instead of tons of batteries? Has anyone here ever eaten a battery? If not, then leave the batteries and take the food.

5. Power production will best power storage for the foreseeable future. Store power if you have to, but make it whenever you can with the most suitable means available. In daylight hours, that means gigantic but lightweight thin film solar arrays. At night, just make enough power to survive.

kbd512 · 2018-06-18 12:32:12

Louis,

A. It's not proven that nuclear reactors "greatly add to the complexity" of operations in space. Since nuclear reactors have operated in space a button puncher on the ground to turn them on or shut them off, I think a button puncher who is much closer to the reactor can do the same thing. I've yet to see any explanation for your assertion. I don't think you have one or you'd just say what complications you think would occur.

B. Monitoring the systems that keep you alive is not "using up too much crew time". Since you die if you run out of power, that actually makes a lot of sense, much like monitoring your life support equipment.

C. TOPAZ was built and a handful of copies are flying in space right now as I write this. The oldest reactor has been up there since 1986 and is still being monitored. It hasn't exploded or melted down. KiloPower is a simplification of the same core technologies.

D. The mass of a solar and fission reactor system is only bigger than a solar panel and battery system if you try to get all your power from the fission reactors.

E. What issues are there with the location of the fission reactors that don't exist with the solar array? Please describe it. You don't think you're going to put your solar array next to your rocket, do you? Why do you think NASA doesn't put Li-Ion batteries inside the ISS to keep them warm and has the packs located on opposite ends of the truss structure instead of all in one place? Incidentally, DoE and NASA have already tested the core without a cooling system by electrically heating a piece of DU7.5Mo, same chemical material as HEU7.5Mo. It didn't melt. Since what you obviously fear most was already tested and didn't occur, what else do you think will happen?

louis · 2018-06-18 12:55:51

My view is: why complicate the mission by introducing another energy technology that is not human friendly, that requires a lot of monitoring and management and which clocks in with more mass than PV-battery-methane? What is the gain? I see none.

There is more ambient light, proportionally, on Mars than on Earth. That's good as it evens out generation over the sol.

I think any Mission design has to assume there will be a major, worst-case dust storm experienced during the mission.

If you don't believe solar plus storage can provide the power, then you have to take along virtually a full nuclear power system. What could be 130 tonnes is going to end up being something like 250 tonnes. Looking at it the other way round, why wouldn't you take a 100% or let's say a 90% nuclear power system if you think that is the way forward.

Solar doesn't need nuclear. It needs batteries, air and water supplies and methane/oxygen electricity generation. It will do the job and come in with less mass than an equivalent nuclear power system.

GW Johnson wrote:

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

kbd512 · 2018-06-18 14:32:51

Louis,

Any technology that doesn't produce power when required is "not human friendly". Methane explodes, just like any other rocket fuel. Let me guess, you're willing to put people inside a conventional bomb more powerful than any used in war, but a nuclear reactor 5km away is unacceptably close.

There is not more insolation on Mars than on Earth. "Ambient light" is a meaningless term. MW class solar arrays don't work off of "ambient light". We don't build solar arrays in giant warehouses and "power them" with LED lighting.

Only by your logic must there be an all-or-nothing solution to the power provisioning problem. The inability to store megawatt hours of energy in batteries of acceptable tonnage has no bearing on how a mission can make opportunistic use of available power sources. Solar needs batteries with energy density values that simply don't exist. Rather than "blowing harder", which seems to be what you're advocating for, some of us just want to use power generation sources in an efficient manner so we don't have to resort to horribly inefficient power storage schemes.

louis · 2018-06-18 14:52:43

kbd512 wrote:

Louis,
Any technology that doesn't produce power when required is "not human friendly". Methane explodes, just like any other rocket fuel. Let me guess, you're willing to put people inside a conventional bomb more powerful than any used in war, but a nuclear reactor 5km away is unacceptably close.

A methane/oxygen generator doesn't have to be sited in the hab. And given the pioneers are travelling to Mars on the back of an explosive rocket I think such lesser risks can be handled.

There is not more insolation on Mars than on Earth. "Ambient light" is a meaningless term. MW class solar arrays don't work off of "ambient light". We don't build solar arrays in giant warehouses and "power them" with LED lighting.

I didn't claim there was more insolation on Mars, only that in terms of proportion there is more ambient, or if you prefer diffuse, non-direct light.

Only by your logic must there be an all-or-nothing solution to the power provisioning problem. The inability to store megawatt hours of energy in batteries of acceptable tonnage has no bearing on how a mission can make opportunistic use of available power sources. Solar needs batteries with energy density values that simply don't exist. Rather than "blowing harder", which seems to be what you're advocating for, some of us just want to use power generation sources in an efficient manner so we don't have to resort to horribly inefficient power storage schemes.

OK, you put together an energy system with no additional air and water supplies, for 1 MW average constant that comes in at less than 130 tonnes mass. How are you going to do it?

Oldfart1939 · 2018-06-18 14:56:39

louis wrote:

Briney water might not sublimate in the same way and water can be trapped under ground. It would be safer to say "We just don't know..." or maybe you should think in terms of keeping the reactors on board the BFS.

I said I was not going to comment further on this topic, but the above quote compelled me to break my silence.

There are 2 constants at play here and they both deal with the Molality of the solution; one is the Molal Boiling point elevation constant, and the second being the Molal freezing point depression constant, (immaterial here). This is different than simple Molarity in chemistry. It's defined as moles of solute divided by the volume of Solvent, not of the solution. Therefore the "Briney water WILL sublimate the same way, but at an elevated temperature to that of pure water. So--a 1 Molal Sodium Chloride solution is made by dissolving one mole of solute in 1 liter of water.

Louis-

You've just about exhausted all the possible strawman arguments possible. I am only supportive of nuclear as it is obviously the only power source which is usable under all conditions of visibility. I don't have "any skin in the game," but your fear of anything nuclear is irrational.

I suggest you stop waving your arms around and railing about this topic, lest someone misidentify you as a windmill.

Basically, I've had enough.

louis · 2018-06-18 16:16:39

I think your comment would be fair if the lead exponent and implementer of a Mars colonisation project (Musk) was also persuaded by your argument. But since (as far as we can tell) he isn't, then I don't think your comment is fair. I've put together a perfectly practical package for delivering the required energy, with adequate back up and failsafeness. I am not sure why people want a package that requires more mass. That seems irrational to me! If nuclear power was unproblematic, then I could see why the extra mass might be justified. But it is very problematical, bringing additional levels of complexity and management challenges.

Oldfart1939 wrote:

louis wrote:
Briney water might not sublimate in the same way and water can be trapped under ground. It would be safer to say "We just don't know..." or maybe you should think in terms of keeping the reactors on board the BFS.
I said I was not going to comment further on this topic, but the above quote compelled me to break my silence.
There are 2 constants at play here and they both deal with the Molality of the solution; one is the Molal Boiling point elevation constant, and the second being the Molal freezing point depression constant, (immaterial here). This is different than simple Molarity in chemistry. It's defined as moles of solute divided by the volume of Solvent, not of the solution. Therefore the "Briney water WILL sublimate the same way, but at an elevated temperature to that of pure water. So--a 1 Molal Sodium Chloride solution is made by dissolving one mole of solute in 1 liter of water.
Louis-
You've just about exhausted all the possible strawman arguments possible. I am only supportive of nuclear as it is obviously the only power source which is usable under all conditions of visibility. I don't have "any skin in the game," but your fear of anything nuclear is irrational.
I suggest you stop waving your arms around and railing about this topic, lest someone misidentify you as a windmill.
Basically, I've had enough.

RobertDyck · 2018-06-18 16:32:18

kbd512 wrote:

NASA can reinvent the rock drill for 100 times the price, but a NASA-fied rock drill is still more affordable than any non-existent electric bulldozer. The logistics tail for an electric drill is a bag of spare parts. Add more bits for different diameter holes for different purposes. A 10kph 1t payload capacity electric wagon that can transport two astronauts, solar panel canisters, truss canisters, truss fabrication robots, fission reactors, power cables, drills, hoists, and other tools to construction sites is all that's required.

I posted several times about CanaDrill. That was a drill developed for the Canadian Space Agency in 2005. The contractor who developed it was NORCAT: Northern Centre for Advanced Technology, a mining research organization. Advantages of this over commercial drills was 1) no lubricant, a dry drill, 2) 1 metre long drill pipe segments, 3) electric, 4) completely autonomous. It was intended for a Canadian Mars rover, but Parliament didn't approve funding. NORCAT would certainly be willing to sell their drill to NASA, no need to reinvent the wheel.

I also posted video of a Bobcat converted to electric. It used an electric motor, and lithium-ion batteries. I have argued for a compact track loader (tracks) rather than skid-steer (rubber wheels) because tracks work better in very soft/loose soil and climb hills better when that hill has soft/loose soil. Besides, that side-steps the issue of inflated rubber tires in low pressure and temperature of Mars. How much do you really have to "NASA-fy" a Bobcat?

SpaceNut · 2018-06-18 18:06:28

This page has the dust storms:
https://mars.jpl.nasa.gov/gallery/duststorms/index.html

https://solarsystem.nasa.gov/news/469/1 … m-on-mars/

Updated frames from MRO looking at the rovers location

Mars Solar Power

Pg3 of the document covers Diurnal Profile of Solar Energy on a Horizontal Surface on Mars
Showing The Direct (Circles), Scattered (Triangles), and Total Isolation During the Course of a Martian Sol.

Now what is Tau it is a calculated and observed number:
The illumination of orbit as compared to the recieved value at the ground:

Yes this is for a smake stack but it works in the same manner.
The What, Why and How of Opacity Measurement

Now onto the BFR landers that have cargo on them...
Why not put 2 x 10kw reactor units on each with the batteries for solar configured for a tau of 5 on each with the same level of panels on each for a matching set for 100kwhr on each. Leave the batteries onboard to act as the shield for any radiation that might have a crew exposed to. The sabetier reactor, puimps should also stay on board to allow for temperature control and shorter plumbing to the onboard tanks for the fuel and oxygen to go into. Plumb the CO2, H2O, O2, H2 and other mixed gasses as collected to the ground level with quick disconnects for other uses as required. All that is moved out of the BFR is the solar panels and cargo for the crews habitat.

louis · 2018-06-18 18:20:30

Well the pics seem to show a clearly visible rover for most days...

I definitely think that nuclear enthusiasts should look to keeping the reactors on the BFS cargo craft. That makes a lot more sense to me than offloading them (difficult at 1.5 tonnes a time - and you've got to do it ten times minimum) and then siting them somewhere the waste heat might destabilise the surface or release flood water.

SpaceNut wrote:

This page has the dust storms:
https://mars.jpl.nasa.gov/gallery/duststorms/index.html
https://solarsystem.nasa.gov/news/469/1 … m-on-mars/
Updated frames from MRO looking at the rovers location
https://www.nasa.gov/images/content/182 … 0b-516.jpg
Mars Solar Power
Pg3 of the document covers Diurnal Profile of Solar Energy on a Horizontal Surface on Mars
Showing The Direct (Circles), Scattered (Triangles), and Total Isolation During the Course of a Martian Sol.
Now what is Tau it is a calculated and observed number:
The illumination of orbit as compared to the recieved value at the ground:
Yes this is for a smake stack but it works in the same manner.
The What, Why and How of Opacity Measurement
https://insights.globalspec.com/images/ … k_Fig1.jpg
https://insights.globalspec.com/images/ … ormula.jpg
Now onto the BFR landers that have cargo on them...
Why not put 2 x 10kw reactor units on each with the batteries for solar configured for a tau of 5 on each with the same level of panels on each for a matching set for 100kwhr on each. Leave the batteries onboard to act as the shield for any radiation that might have a crew exposed to. The sabetier reactor, puimps should also stay on board to allow for temperature control and shorter plumbing to the onboard tanks for the fuel and oxygen to go into. Plumb the CO2, H2O, O2, H2 and other mixed gasses as collected to the ground level with quick disconnects for other uses as required. All that is moved out of the BFR is the solar panels and cargo for the crews habitat.

SpaceNut · 2018-06-18 18:58:57

The dot is an indicator place holder not of the actual rover and its the 2007 storm with a tau of 5...much like paint the dark colors will bleed through the lighter colors underneath.
The other colorized orange image was retouch to indicate the storms boundary....Nasa must think that we are stupid....
There has not been any further news releases or content images after last friday....

Something to keep in mind when comparing the power on orbit to that recieved on the ground is the amount of dust covering the reference cell will and does skew the tau value as the light recieved is reverse calculated back to what should be recieved from the wattage and efficiency of that cell use.

Now onto the battery. A battery that has been charged to full will need to be brought back down to the storage charge level of 75-80 of the working cell voltage range. examply of a single lithium voltage when full for a 3 volt cell is near 3.6v but a dead cell is near the 2.7v level. So a discharged battery readied for packaging will read about 3.1v for long term storage, to which they need a full 8 hours typically to recharge to full levels.
Lithium will not like a constant trickle charge as they will open internally from being overcharged if connected all the way to mars, to which they usually make a draw down circuit within the charger to be able to condition the cell for each use.
The story is about one or the other of the limits of use has been exceeded internally to the batteries normal operation. This is not only the stories vendor but all of the lithium battery types.
U.S. regulator to send observer for Tesla probe of Model S fire

This was the crash

This one happened while driving just before its parked
17008257_G.png?lastEditedDate=20180618213215

This one was whjile connected to the charger
519431992-Tesla-Catches-Fire-While-At-Supercharger-Autoblog.jpg

The power bank is an ac device storage and since mars is a dc world until an invertor is turned for the device to operate will not be storing any excess power.

louis · 2018-06-18 20:23:13

Yep, I've been trying to make that point about dust on panels. We have a lot of variables here, including:

Direct insolation, ambient light, amount of dust on PV panels, dust patterns on PV panels (it seems like the dust can clump, which is a positive for PV power), minimal power requirements, intensity of dust storms, length of dust storms, and ability of robot rovers or human controlled panels to clean themselves.

I never stated a trickle charge. But I think there must be some way of fully charging a battery en route from Earth to Mars using the PV wings of a BFS.

SpaceNut wrote:

The dot is an indicator place holder not of the actual rover and its the 2007 storm with a tau of 5...much like paint the dark colors will bleed through the lighter colors underneath.
The other colorized orange image was retouch to indicate the storms boundary....Nasa must think that we are stupid....
There has not been any further news releases or content images after last friday....
Something to keep in mind when comparing the power on orbit to that recieved on the ground is the amount of dust covering the reference cell will and does skew the tau value as the light recieved is reverse calculated back to what should be recieved from the wattage and efficiency of that cell use.
Now onto the battery. A battery that has been charged to full will need to be brought back down to the storage charge level of 75-80 of the working cell voltage range. examply of a single lithium voltage when full for a 3 volt cell is near 3.6v but a dead cell is near the 2.7v level. So a discharged battery readied for packaging will read about 3.1v for long term storage, to which they need a full 8 hours typically to recharge to full levels.
Lithium will not like a constant trickle charge as they will open internally from being overcharged if connected all the way to mars, to which they usually make a draw down circuit within the charger to be able to condition the cell for each use.
The story is about one or the other of the limits of use has been exceeded internally to the batteries normal operation. This is not only the stories vendor but all of the lithium battery types.
U.S. regulator to send observer for Tesla probe of Model S fire
This was the crash
https://s3.caradvice.com.au/thumb/1200/ … onfire.jpg
This one happened while driving just before its parked
http://meredith.images.worldnow.com/ima … 0618213215
This one was whjile connected to the charger
https://video.newsserve.net/700/v/20160 … toblog.jpg

The power bank is an ac device storage and since mars is a dc world until an invertor is turned for the device to operate will not be storing any excess power.

louis · 2018-06-19 05:04:10

Actually, I've been a bit stupid. If you take with you 10 tonnes of methane and 26.7 tonnes of oxygen, 36.7 tonnes in total, you have nearly 140,000 KwHs of power available. If we achieve 40% efficiency on conversion to electricity, that's 56,000 KwHes available (so much more than 75 tonnes of batteries were producing).

I think you could get a PV-methane-batteries system to come in at under 100 tonnes, even better.

kbd512 · 2018-06-19 05:07:35

louis wrote:

A methane/oxygen generator doesn't have to be sited in the hab. And given the pioneers are travelling to Mars on the back of an explosive rocket I think such lesser risks can be handled.

You're worried about a handful of fission reactors located 5 kilometers away from the rocket while the crew or colonists on Mars are living inside the rocket while it's being loaded with hundreds of tons of cryogenic propellants over the course of months using an as-yet unbuilt and untested cryogen plant. That's not what I'd call a "lesser risk" since there have been far more accidents and deaths from rockets, energetic chemical propellants, and batteries than all the RTG's and fission reactors ever built.

louis wrote:

I didn't claim there was more insolation on Mars, only that in terms of proportion there is more ambient, or if you prefer diffuse, non-direct light.

If there is less total insolation, then you get less power, not more. Scattered photons don't produce a greater photoelectric effect than when the photons are launched directly at the photovoltaic cell. This has been tested with all manner of photovoltaic arrays over the course of decades, but no doubt you'll dispute those results because they don't provide evidence backing what you wish to believe.

Effect of diffusion of light on thin-film photovoltaic laminates

louis wrote:

OK, you put together an energy system with no additional air and water supplies, for 1 MW average constant that comes in at less than 130 tonnes mass. How are you going to do it?

If you skipped the grid scale batteries entirely and just operated off of thin film solar arrays and LOX/LCH4 gas turbines, that'd be an infinitely more plausible plan than loading 75t to 150t of batteries into a BFS. Put the mass saved on batteries towards the construction of a solar array so powerful that it can overcome any output degradation from dust and produce enough LOX/LCH4 during the day to provide nightly backup power to keep the humans warm and the propellant cold.

The ground vehicles and robots necessary to construct the solar array can use batteries. It just so happens that batteries are a better fit for this specific application because Mars has one gas station, the vehicles require far less continuous power output than generators for life support, and vehicles see intermittent use. CH4 routinely fuels micro gas turbine engines to produce electrical power. The better designs use gas bearings so none of the rotating components actually touch each other.

All fuel cells that produce electrical power have average reliability and lifespans at best, but they're great when they work. Nobody has one that can run as long as jet engine without significant maintenance because all H2 fuel cells leak when the reactants eat through the seals and all CH4 fuel cells coke their anodes from impurities in the CH4. Therefore, fuel cells that provide electrical power are not viable long duration power provisioning technology.

Performance & Reliability of Fuel Cell Systems in the Field

If it's not perfectly clear what my point has been for some time now, it's that production is forever and always the name of the game.

I'm not laboring under the assumption that an unbuilt and untested LOX/LCH4 plant, that nobody on Earth can tell you the power requirement for or how much it weighs, since it's never been built, could ever be something that can be planned for. The Sabatier reactor is a scientific curiosity that might be useful on Mars if sucking hundreds of tons of CO2 out of an atmosphere loaded with dust works passably well. The high performance air pumps I've seen operated in the deserts of the Middle East look like someone sandblasted them. If SOXE works on Mars despite the dust, then we'll have an idea about how to obtain the oxidizer in the quantities required without spending every waking hour blowing down dust filters using the compressed CO2 that the system is supposed to collect to turn into O2. Fortunately for the Martians, SOXE fuel cells are a little more durable than other types, so long as thermal cycling is minimized. It should be noted that these cells operate above the temperature of the fission reactor at full power.

That's why I said the upper stage must use LOX/LH2. Water is available anywhere humans can live. If it's not, then humans can't live there. H2 is not fun to work with, but most tests of cryogen tanks, fuel cells, and gas turbines use H2 because it's the devil we know. All of our most advanced chemical power and propulsion technologies use H2.

SpaceX or anyone else can walk into Proton OnSite / NEL Hydrogen's facilities, drop $26M, and walk out with a M400 O2/H2 plant with unrivaled reliability and longevity. Every technical specification you could ask for is in the PDF that I've posted at least twice now. If we can't run water through a PEM fuel cell to produce O2 and H2, then anything more complicated than that is immediately suspect. Furthermore, scientists have recently doubled the efficiency of water electrolysis.

Trying to produce 1MWe 24/7 is an utter waste of time with the new thin film solar panels and M400 since the H2 plant can go from cold start to maximum output in less than 5 minutes and was specifically designed to do that on a daily basis using power from photovoltaic arrays. Produce more Hydrogen during the day to make more propellant during the day.

When you first proposed that idea yourself, only UltraFlex had ever flown in space or been to Mars, thin film arrays were just something NASA scientists were tinkering with and had not completed ground testing, never mind long duration space testing, and the ATK fans' output and deployment methods were so woefully insufficient that the idea was a non-starter. Years later, Lithium-Ion battery technology is still grossly insufficient to even consider using them for backup power storage.

There is no need to produce 1MWe all the time if you can produce more MW's during the day. The solution is to massively increase power output during the day when solar power is available. What you get in peak power output is all but meaningless. We want 1MWe from the time the Sun peeks over the horizon till the time it sets. There's only one way to do that.

Finally, the more I consider the implications of this plan to vertically land giant spaceships to Mars, the dumber it looks. The entire point of the giant spaceship is to send serious tonnage to Mars, but only a purpose built ITV can do that and then a nominal quantity of propellant is required to actually land on Mars. If throwing away a couple of fabric HIAD's is too expensive to consider, then launching six times to send anything to Mars is just absurd.

Use RL-10's to land on Mars. LOX/LH2 expanders are far less complicated than reusable full flow staged combustion LOX/LCH4 engines attached to the largest composite propellant tanks ever built. Lest we forget, RL-10's are the only engines that have successfully sent anything to Mars more than once or twice. Aerojet-Rocketdyne is rapidly killing the cost of RL-10's using 3D printed components. The stock of RL-10's on the surface will serve as feedstock for partially reusable landers that use fresh HIAD's from orbiting ITV's.

The entire purpose of landing things on Mars is to build things on Mars to establish a permanent human presence there. The BFS is a ridiculous design for the delivery of the machinery required to do that. There's no way to exit the craft without a multi-story ladder or crane and any substantial load on the crane will simply bring the rocket crashing down with the cargo. Wrong design, plain and simple.

I want to send 25t electric TBM's to Mars to dig the tunnels required for permanent residence. Unfortunately, there's no way that device could leave the BFS cargo compartment without toppling the rocket as a function of the BFS CG location above the landing gear. Once we send people to Mars, I don't want them anywhere near a fueled rocket or propellant depot unless they're going somewhere.

I've learned some things:

1. BFR is the lower stage that SLS should have had.
2. RS-25's are the engines BFS should use.
3. BFS should go to and from Earth orbit and be the reusable space truck that Space Shuttle was supposed to be, but never was.
4. RL-10's and HIAD's are the landing technology we need. Incidentally, SpaceX is going to try to bring back an upper stage using HIAD.
5. ITV's are the only suitable transport technology for extended duration space flight.

All extreme performance requirements are removed using this mission architecture and it works just as well for exploration as it does for colonization. After real launch pads are built on Mars, then BFS can land passengers on Mars by the hundreds.

kbd512 · 2018-06-19 05:57:52

louis wrote:

Actually, I've been a bit stupid. If you take with you 10 tonnes of methane and 26.7 tonnes of oxygen, 36.7 tonnes in total, you have nearly 140,000 KwHs of power available. If we achieve 40% efficiency on conversion to electricity, that's 56,000 KwHes available (so much more than 75 tonnes of batteries were producing).
I think you could get a PV-methane-batteries system to come in at under 100 tonnes, even better.

It's almost like you're beginning to understand what I've been trying to say about this class of problem. If you have a propellant plant, then you burn a little propellant to keep the lights on at night. IVF has proven it can carry the heat away from the cryogenic propellants through gas expansion, pressurize propellant, and provide more electrical power than is actually required. That's why ULA is working on it. It drastically simplifies the design of a spacecraft to something wrench turners and stick actuators can maintain. All operations boil down to propellant math. If you made enough propellant on Earth to sink a battleship just to get to Mars, then you obviously don't care much about efficiency. Burn a little gas on Mars. There's no EPA there. Like Dr. Z said, it's the best reason to go there.

Forget about the batteries and the fuel cells. It might work one day, but today is not that day. Since it doesn't work well on Earth, it definitely won't work well in a mass constrained hostile environment like Mars. Take more propellant and gas turbines. The gas turbines are featherweights compared to the batteries and fuel cells.

I'm not saying take no batteries at all, just that it's not worth wasting precious cargo tonnage on in some misguided attempt to construct a multi-megawatt electrical power storage system. A dozen micro gas turbines and a propellant plant are better than a 100t of batteries. The propellant plant can always produce more fuel. The battery capacity is only as good as what it starts out as and never increases without shipping in more from Earth. After a propellant depot is established, only spare parts are required. The spares are workable.

I told you before that I'm agnostic about the power sources, but I'm not agnostic about not having power available. I don't care where the power comes from, but it better be reliable and available. If you want solar panels and gas turbines instead of nukes, I can get behind that. Those things actually work within feasible mass constraints. My only concern is keeping everyone alive.

If the giant supposedly reusable rocket ever takes off again, then great. If not, I wouldn't be too surprised. The BFS carrying the propellant depot is never coming back because there's nowhere else to store that much gas. Exxon's not on Mars... yet. As long as we can keep delivering consumables, and with the ITV we could, then nobody is going to die. We can figure out how to get people back later. Anyone who thinks it's not a one-way trip is only fooling themselves. No air, water, food, or power are the deal breakers for me. No proposals that stand an excellent chance of killing people for want of those things.

elderflower · 2018-06-19 07:22:13

Where does the propellant plant get it's input power from?

louis · 2018-06-19 08:37:19

From the PV power plant would be my view. In order to account for a worst case dust storm scenario - say 9 months at 20% of normal PV generation (I don't think there has ever been a storm like that but one has to go to the extreme - there have been long duration storms but I think the insolation reduction was not as great) - you'd probably need to go 40% over capacity (ie 40% over he normal expected generation capacity). So if you would normally need 6000 sq. metres for that, you would go to 8400 sq ms. That will allow you to raise production after a dust storm has abated and increases what 20% of normal delivers.

elderflower wrote:

Where does the propellant plant get it's input power from?

louis · 2018-06-19 08:54:07

Lol! Confucius say : Better to travel on foot and arrive at the destination by one's own efforts than to be carried there in someone else's limousine.

I think I'd still see a role for batteries. They can provide a big power boost over a short period of time, should that be required at some point. But, yes, most of the emergency power could be in the form of methane/oxygen to drive an electricity generator. I'd favour it being separate from the rocket propellant system itself.

Just a thought, but do you really need to "store" methane on Mars? Couldn't you just have it in a pit stored as clathrates and covered in regolith - it's not going anywhere in that cold is it (as long as you choose a nice shaded location).

But assuming you have got to store it all, 1000 tonnes of fuel/propellant might require a couple of hundred tonnes of storage tanks.

Out of the 800 tonnes allowance...

Maybe 100 tonnes is going on the PV-methane-battery system

Maybe 200 tonnes on propellant storage. Or maybe you just store it in our BFS directly?

50 tonnes for habs and rovers...

How much would the propellant plant mass? Maybe 50 tonnes?

Maybe 100 tonnes of emergency supplies of air and water, so that the crew could if necessary live on for another two years should there be a failure in the return launch?

Still seems an awful lot of tonnage left over...

Maybe Space X want to begin food production immediately? Or put up a number of habs?

kbd512 wrote:

louis wrote:
Actually, I've been a bit stupid. If you take with you 10 tonnes of methane and 26.7 tonnes of oxygen, 36.7 tonnes in total, you have nearly 140,000 KwHs of power available. If we achieve 40% efficiency on conversion to electricity, that's 56,000 KwHes available (so much more than 75 tonnes of batteries were producing).
I think you could get a PV-methane-batteries system to come in at under 100 tonnes, even better.
It's almost like you're beginning to understand what I've been trying to say about this class of problem. If you have a propellant plant, then you burn a little propellant to keep the lights on at night. IVF has proven it can carry the heat away from the cryogenic propellants through gas expansion, pressurize propellant, and provide more electrical power than is actually required. That's why ULA is working on it. It drastically simplifies the design of a spacecraft to something wrench turners and stick actuators can maintain. All operations boil down to propellant math. If you made enough propellant on Earth to sink a battleship just to get to Mars, then you obviously don't care much about efficiency. Burn a little gas on Mars. There's no EPA there. Like Dr. Z said, it's the best reason to go there.
Forget about the batteries and the fuel cells. It might work one day, but today is not that day. Since it doesn't work well on Earth, it definitely won't work well in a mass constrained hostile environment like Mars. Take more propellant and gas turbines. The gas turbines are featherweights compared to the batteries and fuel cells.
I'm not saying take no batteries at all, just that it's not worth wasting precious cargo tonnage on in some misguided attempt to construct a multi-megawatt electrical power storage system. A dozen micro gas turbines and a propellant plant are better than a 100t of batteries. The propellant plant can always produce more fuel. The battery capacity is only as good as what it starts out as and never increases without shipping in more from Earth. After a propellant depot is established, only spare parts are required. The spares are workable.
I told you before that I'm agnostic about the power sources, but I'm not agnostic about not having power available. I don't care where the power comes from, but it better be reliable and available. If you want solar panels and gas turbines instead of nukes, I can get behind that. Those things actually work within feasible mass constraints. My only concern is keeping everyone alive.
If the giant supposedly reusable rocket ever takes off again, then great. If not, I wouldn't be too surprised. The BFS carrying the propellant depot is never coming back because there's nowhere else to store that much gas. Exxon's not on Mars... yet. As long as we can keep delivering consumables, and with the ITV we could, then nobody is going to die. We can figure out how to get people back later. Anyone who thinks it's not a one-way trip is only fooling themselves. No air, water, food, or power are the deal breakers for me. No proposals that stand an excellent chance of killing people for want of those things.

Last edited by louis (2018-06-19 08:54:45)

kbd512 · 2018-06-19 16:23:56

Elderflower,

* solar array provides daylight power (habitat / robot / vehicle / power tool battery recharging, LOX/LH2 production)
* Proton OnSite M400 for Martian ground water electrolysis (daylight only LOX/LH2 production)
* fresnel lens heated stainless steel regolith roasters for Martian ground water extraction
* O2/H2 micro gas turbines for propellant refrigeration and backup habitat power

It's a daylight only operation to save mass. Some of the propellant generated on the previous day is burned at night to produce electrical power. M400 can produce 902kg of LH2 in 24hrs at maximum capacity, but we're operating the plant for about 8 hours per day. The gas expansion from combustion cools the propellants. H2 has sufficient heat carrying capacity to retain all of the LOX. I've already posted ULA's Integrated Vehicle Fluids (IVF) documentation that explains how this works, but here's some more links to read.

Launch Services for the Moon

Numerical Modeling of an Integrated Vehicle Fluids System Loop for Pressurizing a Cryogenic Tank

On Orbit Refueling: Supporting a Robust Cislunar Space Economy

ULA Human Spaceflight Update

Innovation at ULA

ULA Briefing to National Research Council - In-Space Propulsion Roadmap

ACES Stage Concept: Higher Performance, New Capabilities, at a Lower Recurring Cost

Development Status of an Integrated Propulsion and Power System for Long Duration Cryogenic Spaceflight

A STUDY OF CRYOGENIC PROPULSIVE STAGES FOR HUMAN EXPLORATION BEYOND LOW EARTH ORBIT

Integrated Vehicle Fluids A Combined Propulsion & Power System for Long Duration Spaceflight

An Integrated Vehicle Propulsion and Power System for Long Duration Cryogenic Spaceflight

* electromagnetic cryocooler for active refrigeration could be used here (no, I didn't make that up - certain types of magnetic materials warm or cool when a magnetic field is applied; supposedly ~30% more efficient than normal heat pumps)
* regolith sifted into vacuum insulated stainless steel vessels enclosed with fresnel lens lids, vessel heats up to vaporize the water, the water collected and pumped into storage tanks for subsequent electrolysis
* when someone actually builds a multi-megawatt Sabatier reactor, then we can talk about how that process might vary
* available down-mass from the ITV is allocated to other important necessities like food and water
* keeping propellant cold for 12 hours during the cold Martian night is not an insurmountable challenge with reasonably good MLI insulation

kbd512 · 2018-06-19 16:55:30

Louis,

There is a battery technology that I would be willing to live with inside a pressure vessel. The cell chemistry is called Sodium Nickel Chloride, or sometimes "SoNick" for short. It's gravimetric energy density is not as impressive as current Lithium-Ion cells, but it has none of their nastier characteristics and capacity is still adequate.

SoNick Battery Comparisons

FIAMM model "48TL200" 10kWh Sodium Nickel Chloride backup battery pack characteristics
Voltage: 48VDC
Amp-Hour Rating: 200Ah
Mass: 105kg
Gravimetric Energy Density: 91Wh/kg
Volumetric Energy Density: 108Wh/L
Dimensions: 558mm (L) x 496mm (W) x 320mm (H)

* no adverse reactions from cell rupture or exposure to oxygen and water
* retains 100% of original capacity after 10 years of daily charge/discharge cycles
* -20C to +60C operating temperature range
* physically smaller that competing batteries
* peak output capability above other types of batteries with equivalent A-h ratings

Put 6 of these things inside the habitat module and it'll service all habitation power requirements.

SpaceNut · 2018-06-19 19:44:22

Moisture of any amount in the sodium Nickle Chloride battery compartment is its enemy.

Battery types and current curves pg8 and on 9 is li-poly from MIAAION THt did not happen yet.
MARVIN- Near Surface Methane Detection on Mars

Contains mass power for levels of water and processing on pg7
An ISRU Propellant Production System to Fully Fuel a Mars Ascent Vehicle

Something I have indicated before with a waste truck for the journey to mars to be sent down to the surface for recycling pg2 gives content numbers but that may be even higher for some mission plans
Creating Methane from Plastic: Recycling at a Lunar Outpost

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