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#26 2017-03-27 17:50:58

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 13,342

Re: In-Situ Propellant Production, design a opensource demonstrator

Nice outline below of mission but cost of each may become an issue.

kbd512 wrote:

Oldfart1939,

Even with the eminently more affordable mission hardware architecture I've proposed, there's nothing about this mission that will be inexpensive.  It just won't be so expensive and complicated that NASA can't possibly afford to do it within our lifetimes, given existing and projected budgets.

The storable fuel is a non-negotiable line item for initial exploration missions.  There is no such technology, nor experience with said technology, for launching a spacecraft loaded with cryogenic propellants, flying them tens of millions of miles to another planet, and then having them sit for a couple years on that planet with zero boil-off of propellants prior to use.  Simply making and storing LOX in the oxidizer tank of the ascent stage is pushing our present technological capabilities to the limit.

Mission #1:
* Demonstrate production and storage of LOX from Martian CO2 using MOXIE and solid state cryocoolers.
* Experiment with collection and purification of the briny Martian ground water.
* Demonstrate the ability to grow a few common fruits, vegetables, cotton, and hemp on Mars.

Mission #2:
* Demonstrate ice mining on a scale suitable for use in a propellant plant and in agriculture.
* Demonstrate water electrolysis and storage of LOX and LH2.

Mission #3:
* Demonstrate LOX/LCH4 production in a propellant plant and fueling of a LOX/LCH4 powered ascent vehicle.  Demonstrate production of Martian concrete.

Mission #4:
* Demonstrate a nuclear fission surface power system.
* Demonstrate production of Martian steel.
* Demonstrate construction techniques using steel-reinforced Martian concrete.

Mission #5:
* Demonstrate mining equipment for production of metals required for aerospace alloys.
* Demonstrate fabrication of simple tools and spare parts using 3D printing.
* Demonstrate fabrication of microchips.

That's as ambitious an ISRU demonstration plan as I'm willing to entertain.  I think it's extraordinarily ambitious at that.  Each successive mission is intended as a logical progression of technology demonstrations to confirm that the general capabilities required for establishment of a permanent human presence on Mars are executed by NASA so that corporations can then refine those technologies to make them cost effective and suitable for use in Martian colonies.

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#28 2017-10-23 19:59:25

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,342

Re: In-Situ Propellant Production, design a opensource demonstrator

I really had a hard time finding this topic to add the links provided by :

kbd512 wrote:

SpaceNut,

University of Texas at Arlington devised a process to capture CO2 from combustion and to turn it into more liquid hydrocarbon fuels:

UTA researchers devise one-step process to convert carbon dioxide and water directly into renewable liquid hydrocarbon fuels

nice PDF document on the page but here is that link: Solar photothermochemical alkane reverse combustion
https://www.uta.edu/news/_downloads/pnas.201516945.pdf

A one-step, gas-phase photothermocatalytic process for the synthesis of hydrocarbons, including liquid alkanes, aromatics, and oxygenates, with carbon numbers (Cn)uptoC13,from CO2 and water is demonstrated in a flow photoreactor operating at elevated temperature (180–200 °C) and pressures (1–6 bar) using a 5% cobalt on TiO2 cata-lyst and under UV irradiation. A parametric study of temperature, pressure, and partial pressure ratio revealed that temperatures in excess of 160 °C are needed to obtain the higher Cn products in quantity and that the product distribution shifts toward higher C n products with increasing pressure. In the best run so far, over 13% by mass of the products were C5 + hydrocarbons and some of these, i.e., octane, are drop-in replacements for existing liquid hydrocarbons fuels. Dioxygen was detected in yields ranging between 64% and 150%.

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#29 2018-12-05 22:46:35

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,342

Re: In-Situ Propellant Production, design a opensource demonstrator

With the size of BFR the insitu will need a processing plant as large as this one. New Facility Aims to Convert 150 Tons of CO2 to Natural Gas Per Year

The articles is talking about pulling the co2 out of atmospheric levels which probably is about the same partial pressure that mars would have.

company-that-sucks-co2-from-air-announces-a-new-methane-producing-plant-1538765472.jpg?resize=768:*

A catalyst then combines the CO2 and the hydrogen into methane gas in a reactor built by a French company called Atmostat.

https://arstechnica.com/science/2018/10 … ing-plant/

The new Italian plant will be run for more than 4,000 hours over the next 17 months (that's just under eight hours a day) in order to demonstrate the viability of fuel production as a potential revenue source for carbon capture.

The plant consists of three air collectors that are more energy-efficient than Climeworks' first ambient air collector. "The plant will filter up to 150 tons of CO2 from ambient air per year," Climeworks said in a press statement. "Simultaneously, an alkaline electrolyser (1.2 MW) locally generates 240 cubic meters of renewable hydrogen per hour by making use of excess on-site photovoltaic energy."

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#30 2018-12-06 04:25:34

Terraformer
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From: Lancashire
Registered: 2007-08-27
Posts: 2,903
Website

Re: In-Situ Propellant Production, design a opensource demonstrator

I wonder what it's EROEI is...


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#31 2018-12-06 08:43:31

kbd512
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Registered: 2015-01-02
Posts: 2,213

Re: In-Situ Propellant Production, design a opensource demonstrator

EROEI = Energy Return On Energy Invested - a ratio dictating how much total energy must be invested into obtaining a particular energy resource per unit of usable energy resource returned.

If it took 2 gallons of fuel to refine and extract every gallon of fuel produced for consumption, it quickly makes little sense to continue using that energy source because you must input more energy into obtaining the energy resource than you get in return.

From Wikipedia:

Energy returned on energy invested

In energy economics and ecological energetics, energy returned on energy invested (EROEI or ERoEI), or energy return on investment (EROI), is the ratio of the amount of usable energy (the exergy) delivered from a particular energy resource to the amount of exergy used to obtain that energy resource.[1][2] It is a distinct measure from energy efficiency as it does not measure the primary energy inputs to the system, only usable energy.

When the EROEI of a source of energy is less than or equal to one, that energy source becomes a net "energy sink", and can no longer be used as a source of energy, but depending on the system might be useful for energy storage (for example a battery). A related measure Energy Store On Energy Invested (ESOEI) is used to analyse storage systems.[4][5]

To be considered viable as a prominent fuel or energy source a fuel or energy must have an EROEI ratio of at least 3:1.[6][3]

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#32 2018-12-06 09:48:12

louis
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From: UK
Registered: 2008-03-24
Posts: 4,031

Re: In-Situ Propellant Production, design a opensource demonstrator

An example of caged thinking...

We're into marginal cost theory here...

If you have the equipment that produces PV energy but say 35% is oversupply, then making hydrogen to then produce methane - is at, at least from the point of view of solar electric input, viable, since the cost of the energy input is effectively near zero (if it was previously going to waste)...Presumably your solar plant can also power the CO2 extraction.

I'm agnostic on how carbon emissions affect climate - I am not convinced we really know. But if you are convinced that carbon emissions are going to cause global catastrophe, then catastrophe is a cost and if you offset the cost through CO2 sequestration, that would be an economic gain.

It would be interesting to see some financial figures.

EROEI is of limited use. Nuclear power has a fantastic EROEI...until you start dealing with all the safety issues. EROEI is also bad at assessing human input (which is what drives up the price of nuclear and which makes solar and wind long term winners).

Ultimately if you had a solar plant in the desert that used robots to gather materials like silica, iron ore and so on and power robot factories that produced PV panels, robot mining rovers etc then your operation is effectively cost-free.




Terraformer wrote:

I wonder what it's EROEI is...

kbd512 wrote:

EROEI = Energy Return On Energy Invested - a ratio dictating how much total energy must be invested into obtaining a particular energy resource per unit of usable energy resource returned.

If it took 2 gallons of fuel to refine and extract every gallon of fuel produced for consumption, it quickly makes little sense to continue using that energy source because you must input more energy into obtaining the energy resource than you get in return.

From Wikipedia:

Energy returned on energy invested

In energy economics and ecological energetics, energy returned on energy invested (EROEI or ERoEI), or energy return on investment (EROI), is the ratio of the amount of usable energy (the exergy) delivered from a particular energy resource to the amount of exergy used to obtain that energy resource.[1][2] It is a distinct measure from energy efficiency as it does not measure the primary energy inputs to the system, only usable energy.

When the EROEI of a source of energy is less than or equal to one, that energy source becomes a net "energy sink", and can no longer be used as a source of energy, but depending on the system might be useful for energy storage (for example a battery). A related measure Energy Store On Energy Invested (ESOEI) is used to analyse storage systems.[4][5]

To be considered viable as a prominent fuel or energy source a fuel or energy must have an EROEI ratio of at least 3:1.[6][3]


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#33 2018-12-06 18:34:19

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,342

Re: In-Situ Propellant Production, design a opensource demonstrator

For delivered good to mars the is no EROEI as the up front energy and costs were to send it there and once there all that matters is does it work to the efficiency levels and is not needing constant repair to keep it running.

A solar driven system is sun light for free and all that matters are the results.

The company has built 3 of these I think so there must not be any issues on returns...

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#34 2018-12-06 21:04:54

kbd512
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Registered: 2015-01-02
Posts: 2,213

Re: In-Situ Propellant Production, design a opensource demonstrator

There is a term that people in psychology call "magical thinking".  It's a belief or faith in an idea with no tangible evidence backing it.  There is no relationship whatsoever between magical thinking ideas and math or science.  Rather unfortunately, through the deception of unscrupulous people with a giant megaphone (presently, collectivist politicians and media personalities who routinely flaunt their ignorance of math and science as virtuous), magical thinking has been weaponized into something more akin to religious zealotry that those proclaiming to believe in math and science use to attack other people who are capable of "doing the math" while they unwaveringly practice the very precepts that any independent observer would characterize as "religion".  Our climate change practitioners are just worshipping different types of equally absurd human brain derived ideas, like "safety" and "saving the planet".

Safety is by far the greatest self-inflicted self-delusion ever devised by humanity.  Safety has never existed anywhere else outside of a person's brain, nor could it ever exist anywhere else outside of the human brain, because it's a human brain construct or concept that we made up to describe ideas we're fearful of or not fearful of.  The concept of fear has no direct applicability to the real world, even if the human physiological response to their ideation is real.  There's no definable relationship between ideas we're fearful of and the danger they actually pose to a person or to a group of people.

A person can decide to be afraid of crystal clear and pure drinking water for completely irrational reasons, such as being told by some mathematically illiterate idiot on TV that some ridiculously trivial quantity of barely radioactive material is present in the water, but if they're so fearful of a bottle of water that they refuse to drink water, then they will die in a matter of days.  The fact that the idiot on TV neglected to mention that the food they eat contains an even greater concentration of the same radioactive particles or that they receive a substantially higher equivalent dose during their daily walk outside would be completely lost on someone who is so mathematically illiterate that they can't even begin to quantify the actual risk posed by drinking the water, eating the food, and walking around outside without wearing sunscreen.

Well, then.  Enough about how the ignorance-based fear of overly emotional and irrational humans can adversely affect their eating or drinking habits.  Let's see how ignorance of mathematics is used by those with agendas to deceive the mathematically illiterate in other ways.

For example, it does not make one bit of difference if some enterprising young lad gets the idea stuck in his head that he can light his farts to go to the moon.  He can eat beans until he pukes, but apart from blistering his rear end, not only is he not going to the moon, and apart from jumping into the air from the pain he experiences when he briefly sets fire to his hind parts, he'll never leave the ground if that's his chosen method of achieving flight.  The mathematics behind the physics required for his idea to work simply do not generate a result amenable to his ideation about what should happen.  His flatulence-lighting idea may very well take him places, but unfortunately for him the place where he ends up is most likely to be a minor emergency clinic.  If that young lad had enough knowledge of math and physics to compute how much force and therefore energy was required to simply leave the ground, one would hope that that would be enough to dissuade him from actually trying something that would never work, despite having watched a video made by some unscrupulous person on YouTube falsely claiming that such an inadvisable stunt would work.  Fortunately, YouTube is also a platform where mathematically literate people can express why such concepts don't work as desired in the real world.  That's the problem with information.  Unless you have context for the information and understand what it means in practical terms, it's not of much use to you.

So...

In real-world engineering, there's a concept known as a "cost-benefit analysis".  Whether or not someone chooses to believe otherwise, math-based physics dictates that certain implementations of ideas will work better than others.  Every possible idea that the human brain can concoct to try to solve a specific problem need not actually be tried by a mathematically literate person who has the faculties and tools required to estimate, calculate / model / simulate, and then test (to ensure observed data are in agreement with any calculations / models / simulations) to determine if an idea has merit (here I define "merit" to mean a practical solution to a given problem).  The fact that some people here refuse to acknowledge the wisdom of making such analyses indicates why it is that they should never be permitted to make such decisions.

Lord Monckton, scourge of climate change alarmists the world over, unequivocally demonstrated with mathematics, not personal belief based upon magical thinking or favored ideology, why virtually every wind turbine in existence that's part of a commercial generating station is an utter waste of resources in comparison to any other form of electrical power generation technology and will in fact have a negative effect on global warming due to the requirement to use gas turbines or coal power plants backing them up for as long as they are permitted to exist.

Lord Christopher Monckton – The Economics Behind Windmills

Sometimes you actually have to buckle down and crunch some numbers, even if the exercise doesn't agree with your magical thinking or favored political ideology, hurts your feelings for personal reasons, or hurts your head from thinking so hard.

I understand quite plainly from his commentary that Louis is deathly afraid of nuclear power.  From his past commentary about what was clearly a reference to the absurd "The China Syndrome" movie brought to us by the imaginative but technologically illiterate fruits and nuts from Hollyweird, I must assume that nuclear power is indistinguishable from "black magic" to him.  He doesn't know the first thing about it and from what little I gather from exchanges of information with him about the subject, he refuses to learn.  I would ask him if he knows a single person who has been killed by civil nuclear power production, but unless he's friends with some Ukrainians, he doesn't.  Nuclear power production means uses of nuclear power not directly related to nuclear weapons production and not related to being electrocuted or falling.  It turns out the producing nuclear weapons is quite dangerous, though incomparably less dangerous than production of conventional weapons that use explosives.  Who knew that nuclear weapons could be dangerous?  What a shocker.  The risk of being electrocuted or falling is a risk associated with all practical forms of electrical power production and therefore not a valid argument against the use of any specific power source, to include nuclear.

The only people who have ever died from civil nuclear power production in the US have died from trauma associated with electrocution and falling.  Those who have died from radiation were screwing around (not following nuclear materials handling protocols) with the pits of nuclear weapons or screwing around (not following maintenance protocols) with military test reactors intended to produce Plutonium for nuclear weapons.  Shockingly, most of the people who have died from nuclear weapons production have died from fires and explosions from chemical reactions.  Some of them would've died from radiation had they lived long enough, but the trauma or thermal burns from the explosions killed them before radiation could.  The nuclear submarines that were lost at sea were lost because the men in charge of the nuclear power plants decided to shut the reactors down while submerged.  If power is lost or intentionally disconnected in a dive, a submarine can rapidly exceed crush depth before the reactor can be brought back online.  That is obviously an absurdly bad idea and we've never permitted anyone to run that type of test ever since.  As deaths from nuclear power or nuclear weapons in the US goes, that pretty much covers the gamut of the nuclear accidents that resulted in death.

What is the object of that history lesson?  Producing nuclear weapons is an inherently dangerous activity (applies to all explosive weapons, but especially when you don't follow material handling protocols) and diving into the ocean when your submarine has no power (deciding to turn your reactor off while you're diving a submarine) is an unrecoverable mistake.  If you don't do those things, then nuclear power is one of the very best forms of energy production that humanity has ever devised.  The fact that the US Navy operates approximately 100 nuclear powered vessels and the government or civil electric power utility sectors operate approximately 100 reactors and haven't killed anyone from radiation in a human lifetime is NOT an accident.  That kind of track record is not accidental.  With all that said, we could decide to design and operate nuclear reactors that were impossible to melt down without deliberate human actions specifically intended to accomplish that task, since we already did that decades ago when the engineering tool of choice was the slide rule.

If all deaths from electrical power generation are accounted for, then worldwide use of nuclear power remains the absolute safest in terms of numbers of deaths per terawatt-hour of electricity produced.  That is a fact, I don't care if it's a bitter pill to swallow for those who advocate for other forms of electrical power generation, and I will continue to respond with facts and numbers to any person who posts here stating something that is mathematically false.

If someone does have any "safety" questions, and I will arbitrarily choose to define the human brain construct we call "safety" as adverse consequences of issues arising from improper operation of a nuclear power generating source since someone's personal feelings or beliefs about nuclear power have nothing whatsoever to do with actual adverse consequences of nuclear accidents, then post those here and I'll respond or "phone an expert", if need be.

Now then, where were we?

Oh, right, we were discussing why it is that extracting more energy from your chosen energy source than what you have to put into the process is a beneficial thing to have for technologically advanced societies.

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#35 2018-12-07 11:02:47

tahanson43206
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Registered: 2018-04-27
Posts: 74

Re: In-Situ Propellant Production, design a opensource demonstrator

kbd512 wrote:

There is a term that people in psychology call "magical thinking".  It's a belief or faith in an idea with no tangible evidence backing it.

kbd512 .... This is offered as a brief counterpoint. For your presentation on one view of "magical thinking" there are few who will surpass it.

However, after thinking about the point of view you are so effectively supporting, I decided to remind readers that this concept in English has more than one interpretation.  English (and probably all languages) has the multiple interpretation option built in as a feature.

"Magical Thinking" is what Einstein was doing when he imagined flying along with a light beam.

"Magical Thinking" is what the PhD's and undergraduates are doing when they try to think of a way to confirm the validity of String Theory with observations.

The interpretation I am offering, as distinct from your perfectly valid one, is that "Magical Thinking" is indistinguishable from "Creative Thinking".

I would argue that ALL scientific progress has come about as a result of a combination of observation of the natural world and creative thinking, which (I argue) was indistinguishable from "magical thinking" at the time it occurred.

Your presentation (while most assuredly valid) has the unfortunate effect of casting a wet blanket of implied criticism over the field of creative thinking.

The vision of humans living on Mars, most recently articulated by Louis in this forum, is going to come about through vast amounts of creative thinking, harnessed and guided by knowledge of the understood universe. 

While I agree that Louis does appear to engage in magical thinking from time to time, of the kind that you point out correctly does not match the understood universe, I find in Louis' imaginings inspiration for renewed effort to help him realize those parts of his vision which can be guided to match reality.

(th)

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#36 2018-12-07 12:11:27

louis
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From: UK
Registered: 2008-03-24
Posts: 4,031

Re: In-Situ Propellant Production, design a opensource demonstrator

It's a matter of fact that all nuclear power generation of electricity in all places around the world  involves elaborate safety procedures. It's not so much the danger arising from day to day operation that is the issue but rather the dangers involved if there is a catastrophic systems failure of the type we saw in Chernobyl and Fukuyama or if terrorists were to gain control of such a station. None of that is magical thinking.



kbd512 wrote:

There is a term that people in psychology call "magical thinking". 

Oh, right, we were discussing why it is that extracting more energy from your chosen energy source than what you have to put into the process is a beneficial thing to have for technologically advanced societies.

Last edited by SpaceNut (2018-12-07 19:08:15)


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#37 2018-12-07 19:13:17

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,342

Re: In-Situ Propellant Production, design a opensource demonstrator

Repost for solar capability of the fan panels...
aHR0cDovL3d3dy5zcGFjZS5jb20vaW1hZ2VzL2kvMDAwLzA4MS8zOTEvb3JpZ2luYWwvaW5zaWdodC1tYXJzLWxhbmRlci1zb2xhci1hcnJheXMuSlBH

"The 4,588 watt-hours we produced during sol 1 means we currently have more than enough juice to perform these tasks and move forward with our science mission."

The 4,588 watt-hours InSight generated on its first sol, or Martian day, from solar power is well over the 2,806 watt-hours generated in a day by NASA's Curiosity rover, which runs on a nuclear system called a radioisotope thermoelectric generator. Coming in third was the solar-powered Phoenix lander, which generated around 1,800 watt-hours in a day, according to NASA officials.

After sending back its first photo of the landing site and extending its two solar arrays, each of which is about 7 feet in diameter (2.2 meters),

So this lander type will have plenty of power to make methane with an inflateable bladder for the methane to go into.

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#38 2018-12-08 05:32:25

elderflower
Member
Registered: 2016-06-19
Posts: 960

Re: In-Situ Propellant Production, design a opensource demonstrator

To store a respectable amount of methane it will need to be liquefied. Density of the gas is quite low- indeed it offers a fair amount of lift for a balloon, since CO2 is considerably more dense.

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#39 2018-12-08 09:49:28

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,342

Re: In-Situ Propellant Production, design a opensource demonstrator

That said when we would want to liquify the methane we would simply pump the balloons content out, then cool and liquify it into the stronger metal tank for transfer into the return vehicle or for other uses. In fact save the extra mass to mars just pump it into the return ships tank from the bladder as its cooled and compressed.

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#40 2018-12-09 20:29:09

kbd512
Member
Registered: 2015-01-02
Posts: 2,213

Re: In-Situ Propellant Production, design a opensource demonstrator

tahanson43206,

There's nothing wrong with thinking creatively, but math and physics still apply to any prospective solution.  Science clearly says that batteries are still a poor means to store mass quantities of electrical power and don't last nearly as long as a fission reactor.  I'm going to go through this exercise with numbers using ISS equipment that actually exists and is in orbit as I write this, rather than beliefs or science fiction equipment that only exists in someone's head.

Terminology:
BoL - Beginning-of-Life - refers to the characteristics of a rechargeable battery cell when brand new

EoL - End-of-Life - refers to the expected life span of a rechargeable battery when the cell is only capable of storing 80% as much power as it did at BoL

DoD - Depth-of-Discharge, not Department of Defense, in this use case; virtually all rechargeable cells are life-span rated (rated for a specific number of charge/discharge cycles) to EoL based upon an 80% DoD (80% of a battery cell's capacity is drained during a single use); discharging a cell to 100% DoD is VERY hard on the cell and the number of charge/discharge cycles that a cell is capable of falls off a cliff as a result

NiMH - Nickel Metal Hydride - a type of cell chemistry used in rechargeable batteries

LCO - Lithium Cobalt Oxide - a newer type of cell chemistry used in rechargeable batteries; colloquially known as Lithium-ion, even though that covers a very broad range of different cell chemistries

ORU - Orbital Replacement Unit - a suite of modular on-orbit replaceable equipment produced for ISS, covering everything from life support equipment such as pumps and battery packs to scientific instruments

BCDU - Battery Charge / Discharge Unit - a type of ORU that contains batteries (previously NiMH batteries, now LCO Lithium-ion batteries); I will refer to BCDU's as ORU's for brevity, but realize that ORU is a catch-all term for modular swappable equipment

DCSU - Direct Current Switch Unit - a charge controller for BCDU's; just another type of ORU

MBSU - Main Bus Switch Unit - a power management and distribution controller; just another type of ORU

LSE134-101 - the product model number for a type of LCO cell chemistry rechargeable Lithium-ion battery, produced by GS-Yuasa, that was incorporated into redesigned BCDU's (battery pack ORU's) by Boeing and NASA to replace the previously used rechargeable NiMH BCDU's used aboard ISS when the NiMH BCDU's deteriorated with age and use; the new LCO cells are expected to last for 60,000 charge / discharge cycles before EOL

Numerology (System Masses):
1 ORU Pack - 435lbs (197kg)
1 ORU Heater Plate - 85lbs (38.6kg)
1 ORU contains 30 GS-Yuasa LSE134-101's - 77.8lbs (35.3kg)
1 ORU Pack and Heater Plate combo - 15kWh of electrical energy storage
1 LSE134-101 battery cell - 7.8lbs (3.53kg)

Louis says we need 122kWe continuous power to produce 1,100t of propellant over 700 sols.  I'm not sure how he arrived at that figure since nobody has a working LOX/LCH4 plant, nor if he did the math correctly in his estimation.  Even so, let's just use his estimation.

Recall that 80% DoD is the standard for measurement of achievable cycle life for rechargeable batteries to 80% of original capacity.  The cell doesn't magically quit working after reaching whatever that number of cycles that happens to be, but to retain stored capacity for most use cases you must add fresh cells or entirely new battery packs.  The individual cells in the ISS ORU's hardware can be replaced, if desired.  Fortuitously, 80% of 150kWh is 120kWh and thus we'll use that approximation.  If you discharge more than 80% of the capacity of a cell in all Lithium-ion cell chemistries I'm aware of, it rapidly degrades cell life.  You'd be lucky to achieve a 1,000 cycles at rated capacity and could do a lot worse.  Each ISS ORU (BCDU) stores 15kWh, therefore a minimum of 15 packs are required to stored 150kWh.  That means each hour of power storage has a mass of 7,800lbs or 3,538kg.  For 12 hours of storage, that's 93,600lbs or 42,456kg.  I've not included the mass of the DCSU's that serve as the charge controllers.  That's just the batteries and we're already up to 42t.

Now let's look at what an equivalent solution using the grossly inefficient KiloPower units would weigh.  Each 10kWe reactor weighs 1,544kg.  We're going to assume that each reactor is run at 75% of it's maximum rated output.  That means 16 reactors are required to produce 120kWe of continuous power.  If the remaining units are run at 100% of maximum rated output, which only increases fuel burn-up rate, then 4 of the reactors can be lost due to system casualty of one sort or another and there is still sufficient power to meet demand.  16 of the KiloPower reactors weigh 24,704kg.

NASA intends to send five of these units to Mars per mission.  That's 900kWh of power per day.  , but that means 17 KiloPower reactors would be required if all are run at 75% of rated power.  There's no technical reason why all reactors can't be run at 100% of rated power, apart from a higher fuel burn-up rate, so as many as 4 of the 17 reactors could fail and there's still sufficient power to produce the fuel.  17 reactors would have a combined mass of 26,248kg.

If we merely wanted to match the system mass of the batteries alone for the solar plus battery backup solution, then we could include an additional 11 reactors and power cables for those reactors.

Then there's one other problem we've never attempted to solve for.  We haven't included the mass of the solar panels.  If the mass of the solar hardware is zero, then that solar solution still weighs more than the nuclear solution.

Want to use more solar panels with a gas turbine to provide propellant thermal stabilization at night?  That could actually work.  If you run 4 of the Generac 60kWe natural gas generators at half load, they consume a combined 20gph (no idea how many gallons of LOX would be required) to provide the 120kWe continuous.

In any event, I hope that example illustrates how much nonsense the battery backup idea is.  It's impossible to achievable mass-parity with horribly inefficient nuclear reactors by using current battery technology.  I'd rather combine the nuclear reactors with the remaining tonnage in solar panels and I'll have plenty of LOX/LCH4 for both Earth return and to power ground vehicles or backup gas turbine generators.

Backup:

BCDU / ORU System Masses:

International Space Station Lithium-Ion Battery

GS-Yuasa LSE134-101 Cell Specifications:

Assessment of International Space Station (ISS) Lithium-ion Battery Thermal Runaway (TR)

GS-Yuasa LSE Gen III Series Cell Characteristics (Cycle Life and Related Info):

Lithium Ion Cells For Satellites– Power Optimized

Note: Longer useful cell lifetimes are achieved principally by limiting DoD to between 40% and 60%, along with thermal control, in which case you can get up to 60,000 cycles in the case of ISS (somewhere between 40% and 60%- look it up if you're curious).  The only problem with that is what it does to the number of BCDU's / ORU's.  You need an increasing number of ORU's to achieve that sort of cycle life, even though it's doable.

Louis,

There are also elaborate "safety" procedures involved in rocketry.  That doesn't stop us from using rocketry.  If we applied your reasoning as to why it is that we shouldn't develop and use nuclear power to why we shouldn't develop and use rockets, then humanity would still be staring up at the stars and wondering what was really out there.

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#41 2018-12-09 22:10:43

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 13,342

Re: In-Situ Propellant Production, design a opensource demonstrator

A key element of equipment seems to be a Ramgen as posted by kbd512.

So here are a few links to what it is.

http://www.ramgen.com/apps_comp_unique.html

https://www.nist.gov/sites/default/file … proved.PDF

http://conference.co2geonet.com/media/1 … kuzdal.pdf

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#42 2018-12-10 08:40:12

kbd512
Member
Registered: 2015-01-02
Posts: 2,213

Re: In-Situ Propellant Production, design a opensource demonstrator

tahanson43206,

Strike the paragraph that talks about using 17 versus 16 KiloPower reactors in my Post #40 where I also talked about the 5 KiloPower units NASA intends to send to Mars for their mission architecture using SLS.  17 reactors would provide the full 122kWe at 75% rated output, but I rounded the notional energy requirement to 120kWe and used that figure to calculate the power requirements for both the batteries and reactors.  If you do the math, though, it doesn't improve the argument in favor of using batteries as a night time power source since the number of batteries must also increase to meet 122kWe continuous at 80% DoD.

One other thing I forgot to mention is that you have to charge the Lithium-ion batteries during the trip to Mars or they'll be unrecoverable when you arrive, assuming it takes 6 months to reach Mars, so you need to allocate additional power aboard BFS to charge them during transit or any significant on-orbit storage period (full charging is not required, just trickle charging, but you have to do it).  The batteries should survive for 3 months without power, but 4 or 5 is pushing it and at 6 the batteries will most likely be unrecoverable.  Anything longer than 6 guarantees that you just shipped the world's most expensive brick to Mars.

A second thing I neglected to mention is replacement interval for delivered power equipment.  The KiloPower units have been designed to guarantee 15 years of operation at full rated output, but the fuel in the reactor can produce that level of output for about a century or so before fuel burn-up and cracking of the fuel element becomes an issue that mandates replacement.  At 80% DoD, the batteries are sufficient for two mission at most.  The solar panels are good for at least 10 years, possibly 15 to 20 years, although in actual practice a decade seems to be about as long as the solar panels last.

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#43 2018-12-10 09:54:12

kbd512
Member
Registered: 2015-01-02
Posts: 2,213

Re: In-Situ Propellant Production, design a opensource demonstrator

SpaceNut,

This has nothing to do with RamGen.  It's a straight-up comparison of solar and battery power versus nuclear power.  Solar loses the argument convincingly because the mass of the batteries is substantially more than the mass of the reactors if continuous output is required.  If the mass figure associated with the solar panels is zero, then the argument about delivered tonnage per unit of output is already lost.

Assuming no global dust storm, 24t of solar panels instead of 24t of KiloPower reactors would greatly exceed the output of the 16 miniature fission reactors in the day time.  Unfortunately, there are at least 12 hours of the day when those solar panels deliver nothing.  Equally unfortunately, there are global dust storms on Mars that can reduce solar panel output to between 1% to 10% of nominal output.

If batteries are out, then what about a gas turbine backup for the photovoltaics?

Over 700 days, using the solar plus gas turbine generator night time / backup solution requires an additional 240 gallons of LCH4 to be produced per day.  That equates to an additional 168,000 gallons over 700 days.  168,000 gallons of LCH4 is 270,480kg.  CH4 requires at least an equal amount of O2 in order to achieve an efficient burn, although in practice you need slightly more O2.  So we need an additional 540t of LOX/LCH4 to produce 120kWe continuous power for 12 hours per day.  For every gallon of propellant you produce for the BFS / Starship, you need another (Edit: "half gallon", not "gallon") gallon to run the propellant plant through the night.  There is a way to recuperate some of the thermal energy from the the gas turbine combustion products, perhaps as much as 25% or so, but at best any solution that involves using an internal combustion engine is a very resource-intensive operation.  In simple terms, our propellant plant needs at least double its original production capacity without requiring any more power, else more mass must be devoted to power and propellant production.

Does gas turbine backup still seem like a good solution to you, even though the water and carbon dioxide are essentially free when you have the equipment to use them?

The attraction to the solution, at least from my perspective, is that the delivered tonnage is low because solar panels and gas turbines are very light for the power they produce.  I would expect that the solar plus gas turbine solution would require the same or slightly more delivered tonnage as the all-nuclear solution.  It's workable, provided that enough H2O and CO2 can be sourced.

Is it becoming apparent why NASA thinks that nuclear energy is required to produce sufficient continuous power with a reasonable mass figure attached to that capability?

Last edited by kbd512 (2018-12-10 09:57:12)

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#44 2018-12-10 17:58:12

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 13,342

Re: In-Situ Propellant Production, design a opensource demonstrator

Power is only 1 part in the equation to make methane and while its not totally decided as to what type or the mix the issue for power is its not insitu made or created. I think we can move on as we do not even have a working from end to end solution for the remaining part of the process to do so. To which we are not even close to being able to land one to begin the process.

http://www.climeworks.com/climeworks-la … -in-italy/

This project will demonstrate the viability of large-volume energy storage through Power-to-Fuel technology in real life applications and will be operated for 4,000 hours over the next 17 months.

Hinwil. http://www.climeworks.com/world-first-c … ure-plant/

The plant will filter up to 150 tons of CO2 from ambient air per year. Simultaneously, an alkaline electrolyser (1.2 MW) locally generates 240 cubic meters of renewable hydrogen per hour by making use of excess on-site photovoltaic energy.

One method for collection is to use a fan to blow the mars air into the chamber and then use a chemical obsorbent to strip the co2 allowing the remaining to flow through before closint the chamber to heat the collection to be able to collect it.

6a00d8341c4fbe53ef01b8d28b0963970c-600wi

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#45 2018-12-10 18:12:47

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 13,342

Re: In-Situ Propellant Production, design a opensource demonstrator

Here are values for the site meantioned
Climeworks-process-and-facts.png

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#46 2018-12-10 18:28:43

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 13,342

Re: In-Situ Propellant Production, design a opensource demonstrator

This is the direct air removal of co2 content that is in the area of 0.04 %
carbon-air-capture-2.jpg?auto=format%2Ccompress&ch=Width%2CDPR&fit=crop&h=347&q=60&rect=0%2C0%2C1918%2C1078&w=616&s=a987f4ec67a158201f5dadb129625c1b

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#47 Yesterday 20:35:48

kbd512
Member
Registered: 2015-01-02
Posts: 2,213

Re: In-Situ Propellant Production, design a opensource demonstrator

SpaceNut,

Valuing Mathematics Over Fear and Ideology

The solution is nuclear energy if the goal is to minimize both delivered tonnage and processed tonnage of CO2 and H2O to obtain LOX/LCH4 rocket fuel because simple math says it is.  Simple math is agnostic about anyone's personal feelings or beliefs.  If solar and batteries provided the better solution in terms of the required delivered tonnage to produce a specific level of output and someone came here arguing for using nuclear power, then I would present the same sort of math indicating why solar and battery power was better.  I don't dictate how physics work or the mathematics behind it.  The anti-nuclear crowd doesn't, either.  Perceptions of nuclear power also have very little to do with physical reality.  This isn't ideological to me, it's just about the cost and capability provided by whatever system is used.  A fission reactor happens to be the cheapest and most suitable option if sustainment of an exploration or colonization campaign is desirable.  The amount of money spent on KiloPower thus far wouldn't purchase a solar power system suitable for ISS.

Thoughts on Flight Safety

The only arguments for using any other forms of power come in the form of "safety" arguments, which are not directly quantifiable because they're not based on things that are measurable.  Fear of something bad happening has no correlation with its probability nor its actual effects if the feared event is actualized.

Some people might consider the small single piston-engine aircraft that some of us like to fly to be "unsafe" because they rely more heavily on the good judgement of the pilot than systems redundancy and sophistication.  However, every pilot on the planet learned how to fly using one.  Apart from joy rides with a qualified pilot, they don't let anyone fly a jet until they've had about 1,500 hours of experience in smaller and less capable aircraft.  Why?  Speed kills.  The faster you go, the faster things go wrong.  Some might say those "less capable" aircraft are "less safe", but again, "safety" is all in your head and prudent piloting procedures are actually quantifiable (making sure you have enough fuel and oil, looking for obvious damage, knowing the performance limits of your airframe, keeping your airspeed above stall speed, performing appropriate pre-flight checks to ensure all systems are ready for flight, etc).

One of the first things you learn about jets in the Navy is that all of them leak fuel, oil, and hydraulic fluid, no matter how new or old or fancy or simple.  The mere presence of leaks aren't an indication that something is terribly wrong.  The rate of leakage and where it's leaking from is what actually matters.  If it's not leaking, that's generally a reasonably good indication that something is terribly wrong.  I'm sure that seems absolutely crazy to some, but once you understand how those jets work it's not nearly as scary as it looks.  It's normal.

Things That Will Kill Before Radiation

I can tell you this much with certainty.  If you don't have sufficient power generating capacity, then you're not coming back to Earth if your transportation system relies upon propellants made through application of prodigious amounts of power and a host of other mechanical equipment that's quantifiably less reliable than a small fission reactor.  If your solar generating system doesn't produce enough energy, then you can forget about coming back to Earth and start thinking about whether or not you have enough power to live to see the next day.  Running out of power only has one possible outcome since unlike robots, the "sleep mode" for humans is called "death".

In any event, if deployment of 16 fission reactors with a single control rod is too complicated, then setting up a multi-megawatt solar array to contend with the dramatic power reduction from Martian dust storms is absurdly overly-complicated.  The reactors can be set atop stainless steel vacuum thermos dishes or dog bowls to prevent the dreaded but entirely fictional "China Syndrome" that Louis is so afraid of.  Lastly, it doesn't really matter what orientation the reactor winds up in if the reactor is in a crater, natural or man-made.

Thoughts on DAC-3

Regarding DAC-3, their website says they need 497kJ of energy to filter, compress, and store 1kg of CO2.  We need to process about 943kg per day just to make the LOX.  That equates to about 130kWh per day.  If that much energy is required at Earth sea level STP, then the energy required for Mars is even higher, even though the atmosphere is mostly CO2.  Apart from being massive and likely ill-suited to development into space-rated hardware, using the technology in DAC-3 would require more than double the amount of power needed to simply run a vacuum pump to collect the CO2.

The figure Dr. Zubrin's team came up with for the NIMF was 25kWe for an electrically-powered vacuum pump that would consume 80kWh of electricity per metric ton of CO2 collected and compressed to LCO2.  At 80kWe, that's a little less than 13 days.  The NIMF's 100kWe of power was to be provided by a bi-modal NTR to fill the NIMF's 301,700kg LCO2 tank in just 12 days.  The LCO2 was stored in the NIMF's 8m diameter spherical tank.  However, a series of smaller tanks could also be utilized for BFS / Starship (perhaps one that stays on Mars and never returns, only to be used as a source of spare parts and the LOX/LCH4 plant).  16 of the KiloPower reactors run at 75% of rated output would produce that much LCO2 in just over 8 days.  By comparison, the electrical power required to mine regolith and the thermal power required to melt the ice trapped in the regolith will be far more energy-intensive.  It might make sense to use a special derivative of KiloPower that just melts ice since the reactor thermal power is 43.3kWt for the 10kWe model.  Conceptually, if we collected, purified, and stored the CO2 and H2O prior to the first human landing in a purpose-built BFS, then the ingredients for the propellant would already be available before the humans land.

Use of Ionic Liquids for Low-Energy-Cost CO2 Capture

Here's a possibility that NASA previously considered, but thought too immature 5 years ago.  The use of ionic liquids could selectively capture pure CO2, not that NASA's own parametric chemistry modeling of the Sabatier reaction found any energy usage benefits to using pure CO2 versus Mars standard atmosphere in the Sabatier reaction.  Apparently the little bit of N2 and Ar in the atmosphere helped get rid of some heat from the reaction or something like that.  My takeaway is that adiabatic requires no thermal management

Oldfart1939,

Please tell us what the hieroglyphics in the document linked below actually means (I was never any good at chemistry):

State-of-the-Art of CO2 Capture with Ionic Liquids

SpaceNut or Oldfart1939,

I have other docs from NASA that I could post about the MAV design and ISPP from NASA, just in case someone didn't post the links elsewhere, if you or Oldfart1939 are interested.  It deals directly with parametric modeling of the chemistry of the reactions involved, plant design, and trade space for the various uses of ISRU.  I thought it was interesting, but maybe everyone here has already read it.  I normally only post docs to provide backup for assertions, but this would just be a mini-dump.  Anyway, just some more food-for-thought.  The folks at NASA are clearly working on this since there are so many papers, but it's not a simple problem to solve.

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#48 Today 04:08:05

elderflower
Member
Registered: 2016-06-19
Posts: 960

Re: In-Situ Propellant Production, design a opensource demonstrator

Amine solutions have been favoured for capture of acid gases, including CO2 for a long time. The CO2 is absorbed by the amine which is pumped to another chamber at higher temperature and/or  lower pressure, where the acid gas is liberated. Used for removal of SO2 as well as CO2, for instance. Unfortunately, exposing the amine solution to Mars atmosphere would result in it's evaporating away so the atmosphere would require considerable compression to make this work.
There may be mileage in using a solid adsorbent which wouldn't be lost to atmosphere, but you would still need to compress the CO2 to get the adsorption/desorption cycle to work.

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