New Mars Forums

Official discussion forum of The Mars Society and MarsNews.com

You are not logged in.

Announcement

Announcement: We've recently made changes to our user database and have removed inactive and spam users. If you can not login, please re-register.

#1 2017-04-21 19:27:49

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Moxie and only Moxie

Lets see if we can just talk technical here on what does it take to get Oxygen from Mars Co2.

https://mars.nasa.gov/mars2020/mission/ … nts/moxie/

POWER:300 watts, VOLUME:9.4 x 9.4 x 12.2 inches, (23.9 x 23.9 x 30.9 centimeters)
OXYGEN PRODUCTION RATE:About 10 grams per hour (About 0.022 pounds per hour)
TIME:To produce oxygen from the carbon-dioxide (CO2) gas of the Martian atmosphere:About 2 hours
Operating Temp: 1472 degrees Fahrenheit (800 degrees Celsius)

Going to the Red Planet
An MIT oxygen-creating instrument has been selected to fly on the upcoming Mars 2020 mission.

Maia Weinstock | MIT News Office
July 31, 2014

On Thursday, NASA announced the seven instruments that will accompany Mars 2020, a planned $1.9 billion roving laboratory similar to the Mars Curiosity rover currently cruising the Red Planet. MOXIE — short for Mars OXygen In situ resource utilization Experiment — was selected from 58 instrument proposals submitted by research teams around the world. The experiment, currently scheduled to launch in the summer of 2020, is a specialized reverse fuel cell whose primary function is to consume electricity in order to produce oxygen on Mars, where the atmosphere is 96 percent carbon dioxide. If proven to work on the Mars 2020 mission, a MOXIE-like system could later be used to produce oxygen on a larger scale, both for life-sustaining activities for human travelers and to provide liquid oxygen needed to burn the rocket fuel for a return trip to Earth. To do this, MOXIE will be designed and built as what Hecht calls a “fuel cell run in reverse.” In a normal fuel cell, fuel is heated together with an oxidizer — often oxygen — producing electricity. In this case, however, electricity produced by a separate machine would be combined with carbon dioxide from the Martian air to produce oxygen and carbon monoxide in a process called solid oxide electrolysis. “It’s a pretty exotic way to run a fuel cell on Earth,” Hecht says, “but on Mars if you want to run an engine, you don’t have oxygen. Over 75 percent of what you would have to carry to run an engine on Mars would be oxygen.”

https://www.hou.usra.edu/meetings/ipm2016/pdf/4130.pdf

https://en.wikipedia.org/wiki/Mars_Oxyg … Experiment

File:MOXIE_O2_generator.jpg

https://mars.jpl.nasa.gov/multimedia/im … vestigator

Offline

#2 2017-04-21 19:35:33

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,893

Re: Moxie and only Moxie

For any scale of production, this will require a SAFE-400 and plenty of power! This eliminates the need to find water for electrolysis, but then--no means of making methane. But--as you stated--Oxygen is 75% of the necessary propellant for Earth return.

Offline

#3 2017-04-21 19:52:22

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

I am putting all of the other insitu methane stuff in the other topic....

This gives a good view of the plate assembly for the fuel cell...

The Mars Oxygen ISRU Experiment (MOXIE)

index.php?action=dlattach;topic=38675.0;attach=1074201;sess=0

The ceramic plates https://www.coorstek.com/media/2786/mar … branes.pdf

index.php?action=dlattach;topic=38675.0;attach=1379143;sess=0

Offline

#4 2017-04-21 20:27:27

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

Air Squared Awarded Contract to Develop Scroll Compressor in NASA MOXIE Demonstration Unit for Mars 2020 Mission

https://airsquared.com/news/scroll-comp … ent/moxie/

https://airsquared.com/news/scroll-comp … mars-2020/

Design Specifications

    A mass flow rate of at least 100 grams per hour
    An outlet pressure of at least 760 Torr, with 7 Torr inlet pressure
    A compressor and motor not exceeding 175 mm in length
    Full compatibility with the working fluid: 95% CO2, 3% N, and 2% Ar
    A total mass of compressor, motor, and controller not exceeding 1.8 kg
    The ability to function in the Martian environment
    Further improvements in size, weight, and efficiency throughout the development of both units

Offline

#5 2017-04-22 00:55:32

kbd512
Administrator
Registered: 2015-01-02
Posts: 3,721

Re: Moxie and only Moxie

SpaceNut,

I've seen a variety of numbers for this unit.

The 1% scale demonstrator is supposed to produce 22g/hr of O2 using 168We input power.  An average human, whatever that is, supposedly requires 35g/hr or .84kg/day of O2.  That means a 2% scale device is required for every human, which would produce 44g/hr or 1.056kg/day of O2.  The electrolysis plates for the 2% scale unit would require 336We and the pump to compress the O2 would supposedly require 22We, for a total input power requirement of 358We.

The mass flow requirement for the 1% scale demonstrator unit provided to JPL is 100g/hr and the maximum mass target is 1.8kg for the pump / motor / motor controller, but I believe the unit actually supplied weighs 2kg.  Some development is obviously required to hit the mass target, but hopefully not too much.  The scroll compressor boosts Mars atmospheric CO2 pressure from 7 torr at the inlet to 760 torr or 1atm at the outlet.  I would love to know what the input wattage differential is between the single stage and two stage designs.

The denser the CO2, the higher the O2 output.  I wonder if a more powerful compressor to compress the CO2 to 2atm would be useful.

We need to figure out how to implement this stack in a canister format, such that the plates provide more surface area in a smaller, lighter package.

I think this company has the right idea:

FCO Power - Next-Generation Printed SOFC: Printed Fuel Cell

If we can heat a smaller volume of electrolysis plates with a larger surface area and ensure that the stack is properly insulated, wouldn't that lower the input wattage requirement to maintain the temperature to sustain the reaction?

I would think that the demonstrator unit would place greater emphasis on what is easy to manufacture and use, rather than what the most efficient design geometry is for a unit intended for use by humans, but I could be wrong.

Offline

#6 2017-04-22 08:20:55

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,893

Re: Moxie and only Moxie

SpaceNut-

I like the concept, but have concerns about the lifetime of such units, since they have electric motors and a host of other moving parts. Any application, such as maintenance of the atmosphere of the Mars Habitat would seem to require multiple redundancy of units. Anything driven by an electric motor with a scroll -type compressor is subject to wearing out when operated continuously for years. If, for example, one of these can be demonstrated to run continuously for 3 years, that would remove some of my concerns. If for example, it would take a full scale unit to provide adequate habitat Oxygen for a crew of 12, I'd expect there to be at least a second "standby" unit in place for automatic startup, should the primary unit take a dump. In addition, having at least a 3rd unit held in reserve, if not a fourth unit.  I'm thinking not just fail-safe, but fail-safe-safe-safe. This unit and the scroll-type compressor would be a candidate for a 3D printer project here on Earth before this unit is flown in a real-time life support mission.

Offline

#7 2017-04-22 14:17:49

elderflower
Member
Registered: 2016-06-19
Posts: 1,260

Re: Moxie and only Moxie

Redundancy should not just apply to machinery and equipment items. We should have more than one technique for each critical sytem. eg you can get Oxygen by electrolysis of CO2 and you can also get it by electrolysis of H2O. The people should have both systems so that unforeseen upsets are not fatal. Same goes for power supplies , storage units, refrigeration etc. We should not depend solely on nuclear reactors, but should have solar units as well, and big batteries and fuel cells.

Offline

#8 2017-04-22 15:19:24

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

I agree kbd512 that a square simple plate design is a better choice for lowering the cost of the design as for the comparison of compressor I think this page will help : https://airsquared.com/products/scroll-compressors

I agree Oldfart1939 motor assembly replacement should be in the spare parts replacement list and or a secondary unit supplied as part of a standby unit and just because its not used we should still keep sending these as if they had so that there is a build up of parts or units for espansion of breathable air and oxygen surplus.

I agree elderflower the ISS different methods has proven to be just that for being able to be turned on as a back up as well.

But all the redundancy also adds to the expense and payload deliverables to which we are struggling with currently so we will need to temper the risk adversion with some sort of priority list to justify which back up will and should be done.

Offline

#9 2017-04-22 15:27:26

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,893

Re: Moxie and only Moxie

SpaceNut:

That's easy: Food, water, and air. These items inside a habitat and we're good to go.

Offline

#10 2019-03-10 20:34:39

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

A predecessor to MOXIE, called MIP (Mars In-situ propellant production Precursor), was intended as one of the first direct attempts to prepare for future manned missions. But the Mars Surveyor 2001 Lander mission, aboard which MIP was slated to fly, was canceled, meaning MIP was never put into use.

MOXIE is a 1% scale model of an oxygen processing plant that might support a human expedi- tion sometime in the 2030s. MOXIE will produce 22g/hr of O. 2 on Mars with >99.6% purity !during 50 sols.

https://ssed.gsfc.nasa.gov/IPM/PDF/1134.pdf

https://www.earthmagazine.org/article/m … ygen-moxie

Full-scale oxygen generators to support human missions on Mars would need to be roughly 100 times larger by volume than MOXIE, so about the size of a standard home air conditioning unit closer to 25 kilowatts.

Offline

#11 2019-04-13 18:15:08

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

Repost discription is right on for build of a Moxie unit,

kbd512 wrote:

SpaceNut,

Assembly of the stack components of a fuel cell is simple, if repetitive.  Actually fabricating the separator membranes and gaskets would be exceptionally difficult for an individual to do without very expensive equipment that loads the catalysts into the membrane material.  In the same way that there's a lot of electro-chemical engineering going on in operation, there's quite a bit of that in the fabrication processes as well.  The Balance-of-Plant (BoP) can be fairly sophisticated or fairly simplistic.  A lot of that depends on power density and size.  However, there are generally mass / volume / power benefits to integrated BoP.

From a mechanically standpoint, fuel cells are pretty simple.  From an electrical standpoint, they're no more complex than a battery.  From an electro-chemistry standpoint, there's a little bit of "magic" going on with that exchange membrane.  That said, engineers and scientists have already "figured that out" for us. 

What we actually need is for a major manufacturer, like GM or Toyota or GE or Siemens, to take some of their talent pool and determine how to scale up and automate the fabrication process to make fuel cells ubiquitous and therefore cheap.

Of course while I would not be building any units for the purpose of sales we must learn how to repair with what we have on hand as parts will not be coming for at least a mars cycle if not 2 as to when they can be loaded onto the next rocket.

Offline

#12 2019-08-11 16:42:13

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

The talk of using compressors have gotten me back to how Moxie will work as it is using a scrol compressor design.

https://www.compressedairchallenge.org/ … cebook.pdf

The big issue for the compression is the volume or in this case the final pressure level that will require a given level of energy to be used to obtain it.

Of course for Moxie this is step one to making oxygen.

The atmosphere of Mars is the layer of gases surrounding Mars. The atmospheric pressure on the Martian surface averages 600 pascals (0.087 psi), about 0.6% of Earth's mean sea level pressure of 101.3 kilopascals (14.69 psi)...

Offline

#13 2019-08-14 21:18:36

kbd512
Administrator
Registered: 2015-01-02
Posts: 3,721

Re: Moxie and only Moxie

That Stirling generator that NASA has, the prototype for KiloPower, has been running continuously for more than 12 years.  I would think that the right combination of materials and fabrication techniques could produce an air compressor that would last that long, since the Stirling engine runs on gas bearings.

Apart from pumps and electronic sensors, the "repair parts" for a fuel cell are typically limited to sealing gaskets and catalyst membranes, which are exceptionally light and compact.  Apart from the pumps, even for a MW-class fuel cell we're talking about things you can easily carry in your hands.

I also think that Elderflower's assertion that we should diversify the critical life support equipment is a sound approach to inhibiting absolute reliance on a single type of system to function properly for years at a time.  We already do that with the power generation equipment used here on Earth, even if we use more of certain types of equipment than others.

Offline

#14 2019-12-29 21:51:54

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

moxie will soon be launching for its questions to be answered for longevity and quantity that it will produce.

Mars 2020 is a Mars rover mission by NASA's Mars Exploration Program with a planned launch on 17 July 2020, and touch down in Jezero crater on Mars on 18 February 2021.

Offline

#15 2020-02-15 09:51:14

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

fast approaching launch and trial creation of oxygen at mars

Edit adding repost
The conversion of air which can be processed for the co2 there is an energy required to process a given volume at the parts per million rate with in the volume of air process which will give us a net mass of co2 at gas level and then at a liquid volume pressure for temperature.

That said how do we compute some of this?

How much volume does 1 kg of CO2 occupy at room temperature and standard pressure?

CO2 has a molecular weight of 44 g/mol
1 kg CO2 = 1000 g × (1 mol/44 g) = 22.7 mol CO2

V=nRT/P, V=(22.7)(0.0821)(300)/1 = 559 L CO2 at 27°C (300K), 1 atm

This is a little more than half a cubic meter approximately equal to the volume of two bathtubs or the trunk of a large car.

So using the formular we need to suck in since carbon is 12 and oxygen is 16 for a mole mass of 12+32 = 44

1 kg o2 = 1000 g x (1 mol/32 g) = 31.25 mol o2

https://techport.nasa.gov/view/33080
Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE)

producing at least 6 grams of O2 per hour

A scroll pump delivers up to 50 g/hour of atmosphere to the SOXE subsystem.

The Mars atmosphere is processed as follows: the SOXE is warmed to 800 C; the pump is started and the filtered air will flow continuously at >1 torr to the SOXE. The O2 and CO are separated and the flow rate is measured.

Mars 2020 is a Mars rover mission by NASA's Mars Exploration Program with a planned launch on 17 July 2020, and touch down in Jezero crater on Mars on 18 February 2021.

Offline

#16 2020-02-15 17:18:14

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

Mars is not a total co2 but has a mix at 0.15 psi that is below the the Armstrong limit of 0.87 psi. from co2 greenhouse topic
The atmospheric pressure on the Martian surface averages 600 pascals (0.087 psi), post 12 above seems to not be the same....
so for sake of a common point lets use 0.100 psi or xxx in millibars and if you want grams cvcvc

https://www.digikey.com/en/resources/co … r-pressure
https://www.convert-me.com/en/convert/p … ?u=psi&v=1

MOXIE will produce 22g/hr or 0.550 kg/day from a single device and we need 35g/hr or .875 kg/day of O2. That said what is this in psi or ppm as that is where we are for other uses.
Note: this must be per sq cm

https://sciencing.com/calculate-air-volume-5146908.html
https://sciencing.com/convert-volume-pe … 40558.html

2 x 16 is 32g for oxygen for mole mass

https://socratic.org/questions/what-is- … iner-at-30-
What is the pressure exerted by 32.00 g of Oxygen gas in a 20. L container at 30.00 C? Use R = 0.0821 L atm/mol k?

https://socratic.org/questions/what-vol … re-of-52-7-
What volume will 12.0 g of oxygen gas (O2) occupy at 25°C and a pressure of 52.7 kPa?

https://www.grc.nasa.gov/www/k-12/airplane/airprop.html
Liquid oxygen has a density of 1.141 g/cm3 but we have a gas to start with and one once its processed.

http://ww2010.atmos.uiuc.edu/(Gh)/guide … s/def.rxml

def2.gif

metric equivalent of pounds per square inch (psi). 1 kg/cm2 equals 98,066.5 pascals.

The digikey calculator allows for entry of any value and a quick conversion

Offline

#17 2020-02-16 15:52:08

Ancient Mars
Member
From: Canada
Registered: 2020-02-01
Posts: 8

Re: Moxie and only Moxie

Why don't we just use plants? All the colonists have to do is introduce some of the CO2 into the greenhouse and the plants will do the rest, right? This seems much simpler to me.

Offline

#18 2020-02-16 16:02:46

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

Actually not true with the mars level atmosphere as we must compress a level to allow for the plants to take root as they need oxygen and nitrogen to at a comparible level and you can find that in the other topic. The moxie system is used to convert co2 for our breathing and other uses.

Agriculture Study Mars Pure CO2 Greenhouse
Optimal air pressures.. - Which is best? More O2 or more pressure?

Offline

#19 2020-02-16 16:53:42

kbd512
Administrator
Registered: 2015-01-02
Posts: 3,721

Re: Moxie and only Moxie

Ancient Mars,

If only it was that simple...

As a Mars Society contributor famously noted, "just" is another one of those dirty four-letter words in the realm of real engineering.

Offline

#20 2020-02-16 22:57:25

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

https://mars.nasa.gov/mars2020/mission/ … nts/moxie/

https://ssed.gsfc.nasa.gov/IPM/PDF/1134.pdf

Accordingly, MOXIE proposed a straightforward but technically less mature direct-compression system that continuously feeds CO2 to the electrolytic conversion system at a pressure of ~0.1 bar.

https://sites.nationalacademies.org/cs/ … 183746.pdf
Mars 2020 Mission Objectives

1 Mars year (669 sols, 689 Earth days)

https://www.hou.usra.edu/meetings/ipm2016/pdf/4130.pdf

Offline

#21 2020-02-17 10:25:19

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

https://isruinfo.com/public/docs/srr18_ … -Hecht.pdf
Essential subsystems of the Mars Oxygen ISRU Experiment (MOXIE)

https://www.europhysicsnews.org/article … 493p15.pdf
LIVING ON MARS: HOW TO PRODUCE OXYGEN AND FUEL TO GET HOME

https://ttu-ir.tdl.org/bitstream/handle … sAllowed=y
MOXIE Development Driven Prospects for ISRU and Atmosphere Revitalization

The CO2 delivery rate from the CAC system is a function of atmospheric density and is expected to vary from 30 g/h to 80 g/h.

Documents indicate limited soxe use is in 1,000 hours and not years for what we need...

2Co2 = o2 + 2co

Offline

#22 2020-02-17 18:21:57

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

The gram rate on the inlet is a function of temperature of day and night for the levels with the high level benefiting the output side of the process. This also explains the psi difference in the co2 greenhouse topic.

nasaspaceforum MOXIE payload

https://www.coorstek.com/media/2786/mar … branes.pdf

Some of this will relate from ADVANCED SYSTEM CONCEPT FOR TOTAL ISRU BASED PROPULSION AND POWER SYSTEMS FOR UNMANNED AND MANNED EXPLORATION
http://www.niac.usra.edu/files/studies/ … 40Rice.pdf

http://www.hou.usra.edu/meetings/lpsc20 … r/2410.pdf

Offline

#23 2020-02-17 21:31:58

Ancient Mars
Member
From: Canada
Registered: 2020-02-01
Posts: 8

Re: Moxie and only Moxie

kbd512 wrote:

Ancient Mars,

If only it was that simple...

As a Mars Society contributor famously noted, "just" is another one of those dirty four-letter words in the realm of real engineering.

Yes, just opening the airlock and hoping some of the CO2 will just waft in over the plants would be a horrible idea. big_smile But perhaps the idea of bringing in CO2 from the outside and letting the plants "process" it might be an attractive alternative to the Moxie. (But maybe I'm missing something?) Of course, your plants could die, and then you'd be wishing you brought a Moxie instead.

Offline

#24 2020-02-17 21:37:13

kbd512
Administrator
Registered: 2015-01-02
Posts: 3,721

Re: Moxie and only Moxie

Ancient Mars,

That part about everyone and everything dying if Biosphere 3 doesn't work is usually where the conversation stops.

That said, if we could just bring enough plants and everything they require to thrive, then it just might work.

See what I did there?

Offline

#25 2020-02-17 21:50:27

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,686

Re: Moxie and only Moxie

Ancient Mars,
you do know why we have airlocks as its about the air pressure from one area to the other and what wemust do to equalize the chamber to. Mars is sub 100mb and the chamber for plants will be at 400mb possibly or more so men can enter it safely. That said once the airlock chamber is equalized for exit there is nothing of mars air within it to allow in as its replaced with greenhouse habitat air pressure once we are to comeback in...
Also plants die at those low presssures that mars has on its surface....in addition plants need oxygen and nitrogen as well as water inside the greenhouse area.

This topic is about the moxie unit and not greenhouse, plant growth as pointed out earlier...

Offline

Board footer

Powered by FluxBB