Dr Sabatier's Appurtenances

By IonMars

Last edited June 25, 2014

Paul Sabatier died in 1941 at the outbreak of WWII, but as far as we know he was unaware of the advances in missiles achieved by Nazi Germany, in fact he had no expertise in rocketry.  Nor did he live to see the space race of the 1960s that realized the Saturn V moon rocket.  Nor did he have any inkling of a future International Space Station or a Mars Colonial Transport.  Yet every Mars pioneer will depend on the devices of Dr. Sabatier that make his or her life on Mars possible. 

Dr, SabatierThe Royal Society of London recognizes the achievement of notable international figures by granting them the title of Fellow of the Royal Society.  Among these honored Fellows are Albert Einstein, Alan Turing, and Paul Sabatier.  In his obituary of Dr. Sabatier, Eric Rideal1 noted that he was born in 1859, entered the Ecole Normale in 1874 and presented for the degree of Doctor of Science at Lycée of Vimes in 1880.  His thesis concerned the metallic sulfides.  In 1882 he entered the University Toulouse where he settled into a lifetime career in physical chemistry, initially addressing the nature of sulfur dioxide and a number of metallic nitrides.  It was only after fifteen years of study into inorganic chemistry that he began the remarkable series of investigations into the action of catalysts in the chemistry of organic compounds.  At that time the current theory proposed that the rate of chemical change in organic gases exposed to a catalyst was to be explained by gas molecules absorbed into the pores of a solid catalyst, which under increased temperature and pressure accelerated the change.  Sabatier, on the other hand, observed a number of anomalies that contradicted this view.  He formulated a new theory of catalysis that postulated the formation of intermediate chemical compounds.  It was the characteristics of these intermediates that determined the rates and directions of chemical changes.  For twenty years he and his associates carried out extensive testing of catalytic hydrogenation, especially involving nickel as a catalyst.  This investigation is considered to be the most comprehensive ever undertaken for a new method and a new reaction.  According to Rideal1 the merit of Sabatier’s work is that it demonstrated the potential of a simple and elegant methodology in the field of preparative organic chemistry.  For his work he was awarded the Nobel Prize in Chemistry in 1912.

For a Mars pioneer the importance of Dr. Sabatier’s methodology lies not in its elegance but in the practical outputs of his device.  It so happens that the chemical reaction named after him2 produces water, a necessity for human life, and methane, a rocket fuel.  It involves the reaction of hydrogen with carbon dioxide at elevated temperatures and pressures in the presence of a nickel catalyst to produce these products.  We have discovered that the atmosphere of Mars (what little there is) consists largely of carbon dioxide, one of the two inputs to the reaction.  These facts have led to the employment of the Sabatier process into every practical NASA plan for Mars colonization.  It makes feasible the In-Situ Resource Utilization (ISRU) strategy or “living off the land.” 

Before practicality there was the “90-day Study” in 1989 that proposed to spend about $500 billion over a period of 30 years to send people to Mars.  The reaction in Congress was to cancel every NASA project concerning the manned exploration of Mars.  After this political disaster, NASA engineers Mark Zubrin and David Baker proposed an alternate method for Mars exploration, called Mars Direct 4  In this scenario, the manned vehicle sent to Mars would only carry enough fuel to get there.  Getting back would rely on fuel and oxygen generated on Mars itself.  This strategy was found to drop the cost of human exploration dramatically.  It employed ISRU, which was centered on the Sabatier reaction to create fuel from CO2 in the Martian air and hydrogen imported from Earth or from the hydrolysis of Martian water.  The fuel product would be stored over a period of time to accumulate sufficient amounts for a return trip to Earth.  This approach was adopted by NASA and has continued to be the basis for Mars exploration in every NASA plan to date albeit with refinements, variations and improvements.5ISS Astrounaut Wheellock installing the Sabatier system

At the present time the only Sabatier system currently in routine operation by NASA is a device on the International Space Station (ISS).  This appurtenance is used to produce drinking water from by-products from other systems, namely CO2 and H2, which were previously dumped to outer space as waste.6 Of the two products produced by the Sabatier system, the water is consumed, but the CH4 is now dumped to outer space.  This small scale application is useful in reducing the amount of water that must be ferried to the ISS, but it is a far cry from the larger scale system needed to produce fuel on the planet Mars. 

Larger scale systems are being developed and put to use in Germany as part of the national effort to use solar and wind energies to produce electricity for the national grid.  During high wind days some wind farms may be closed due to a lack of a reservoir to store the extra energy being generated.  One strategy uses excess electrical energy for the electrolysis of water to produce hydrogen and oxygen.   The hydrogen is inserted into the natural gas network up to a limit of 2 percent H2 in the pipelines.  An example of this process is the H2 injection system that was installed for the gas pipeline network in Frankfurt, Germany.  The equipment is shown in the adjacent photo from a 2013 news article.7 Hydrogen injection is workable in an area where a natural gas pipeline is already established to provide a large reservoir of fuel that can be supplemented by H2. 

To utilize even more of the excess energy the Sabtier process will be employed in Germany.  The H2 input to the process will come from the electrolysis of water and the CO2 will come from the air.  The output, “synthetic” CH4, will be injected into a gas pipeline and the output O2 will be stored for later use.  When the electrical grid needs an additional boost, this stored O2 will be used to burn CH4 to generate additional electricity.  Thus the overall system not only stores energy, but also exploits it for a short-term supplement to the electrical grid as required.  This is a type of process that needs to be built into a portable unit on a scale suitable for use on Mars. 

The Sabatier electrolysis process does not produces enough oxygen for the combustion of all the CH4 that it produces.  This has led to a suggestion that either the excess methane must be dumped (tongue in cheek?) or that additional O2 must be produced (7).  An alternative procedure would employ a reverse water gas shift (RWGS) process integrated into the Sabatier reaction.  The object is to produce more oxygen using CO2 as an input.  The result is a closer balance between the fuel and oxygen required for a return trip from Mars to Earth. The proposed device is called the Integrated Mars In-Situ Propellant Production System (IMISPPS).  The term propellant is stated rather than methane because the resulting fuel is a blend of CO and CH4.  This requires an additional component to complete the work.  Either 1) the rocket motors to be employed must be readjusted to use this blend or 2) the CO must be removed so that the propellant can be utilized by methane rocket motors.  The authors found that cryogenic distillation is effective in removing excess CO from the fuel blend (7)

 

Exploiting the Cryosphere

A chilling prospect for a Mars pioneer is that Mars’ surface temperature is extremely low, -50 to -80 degrees C (193 to 223 degrees Kelvin) depending on latitude and season.   The deeper subsurface layer has not been measured directly but is indirectly estimated to exhibit extremely low temperatures, hence the term “cryosphere.”  However, the principal chemicals that are required for life and civilization on the planet are best kept at low or cryogenic temperatures.  These chemicals include H2O, O2, H2, CO2, and CH4 

Kelvin ChartMost of these chemicals can take advantage of the low surface or subsurface temperatures of Mars by simply passing the gaseous form of the chemical into the ground through small tubes.  The object will be to utilize the cryosphere to dissipate heat by radiation and conduction.  A device using this method would be analogous to a radiator on Earth that dissipates heat to the air (which also can be used on Mars).  The device will work best if used intermittently so that the ground that receives the heat will have time to cool off and regain the usual cold temperature.  The exact design would depend on the actual temperature gradients beneath the surface in the locality and the conductivity of the subsurface rocks and regolith found there.  The low temperature to be reached may not be sufficient to bring the chemical below its boiling point but it will be a pretreatment to a refrigeration unit that will complete the job.  The object of the device will be to greatly reduce the energy required to liquefy (or solidify) the chemical. 

  1.  H2O.  Water is a key ingredient to a successful Mars colony.  An article on this website, “A New Priority for NASA,” recommends that a site for a colony should be near a “large” source of water.  The article “Ice Mining” shows how water can be mined from a large source such as a glacier or from underground as in well mining.  Water mined from such sources can be stored in tanks constructed by the same techniques as described in “Pioneer House Building.”  It is a necessary ingredient for everyday life and a necessary component for growing food as in the article “Farmland.”  It is also the ingredient for producing hydrogen and oxygen by electrolysis.   Water is easily stored as ice since most of the time the surface temperature will be well below its freezing point.
  2. O2.  Oxygen is an obvious necessity of life and will be produced in a Mars colony by electrolysis.  It is a requirement for the combustion of methane fuel in a rocket returning to Earth.  Likewise it will be required for combustion of methane engines (See the article “Mars Village Vehicles”) and methane torches, among other uses.  It must be stored and loaded into an ascent vehicle as a cryogenic liquid. It can be stored cryogenically if maintained below its boiling point of 90 degrees kelvin (-183 degrees C) with rhe assistance of a supplementary refrigeration unit..
  3.  H2.  Hydrogen is the second product of hydrolysis and an input to the Sabatier reaction.  It has a very low boiling point of 20 degrees Kelvin, uncomfortably close to absolute zero.  Of all the strategic chemicals hydrogen is the most difficult to maintain as a liquid.   This can be accomplished on Earth where high efficiency refrigeration is available.  It would be difficult on Mars and may be more readily stored as a compressed gas.  If this is found to be necessary, the gas will be stored in a steel pressure vessel imported from earth and not one of the storage tanks built from stone and regolith as described on this website.
  4.  CO2.  Carbon dioxide can be readily stored in a stone tank covered with regolith insulation because the temperature of the surface is frequently lower than the boiling point of CO2 (-57 degrees C).  It may or may not require any additional refrigeration to maintain its solid form.  (It is now known that CO2 accumulates as a solid at the polar region of Mars during the cold season.)
  5. CH4.  Methane and oxygen will be employed together whenever methane combustion is the source of energy.  At -164 degrees C the boiling point of CH4 is only a little higher than that of O2 so it can be cooled and stored in a similar manner with a refrigeration unit..  A stone storage tank will work well in this case.

 

Strategic Storage

On Earth, when we need some #8 fine thread screws we can run over to the Ace Hardware store and get them and if the fuel gage light on our pickup is flashing we can fill up at the local Exxon station at the same time.  On Mars, we will order the items we need on Amazon but the FedEx inter-planetary delivery vehicle will take a little longer, say 4 to 12 months.  Of course if the #8 screw is critical to the only ECLSS system available, then Amazon should send a Hallmark card instead. 

As shown in the article “Pioneer Ice Mining,” we will have the ability to build stone storage tanks so let us build abundantly.  The following schematic shows the intermediate steps in our miniature chemical industry where storage of chemicals can logically take place.  In the sketch called “Chemical Storage 1” the electrolysis process and the Sabatier Reaction are shown as two different boxes even though they may be integrated into the same physical unit in actual operation.  They are separated in the diagram to show the opportunities for storage of intermediate chemicals as well as the inputs and outputs.  On the left side is a symbol that looks like a Revlon lipstick tube but is actually a square stone tank with an arched roof.  It contains ice that has been mined Chemical Storage 1from an ice source near the Mars village and accumulated in sufficient quantity to run through the process, it will be heated to a liquid state and pumped through the electrolysis process.  Of the products of electrolysis, oxygen is stored in a Mars stone tank and hydrogen is stored in a pressurized vessel (indicated by the pressure gage on top). Two benefits are realized by having these intermediate products in storage.  First, the system as a whole will likely run on electricity derived from photoelectric panels and can only be produced during daylight hours.  If H2 and O2 can be produced in excess during daylight hours and stored for the next day then the Sabatier process can run intermittently at times when other demands for electricity require that some part of the system be shut down.  This is a strategy for running the overall system.  If the colony employs a nuclear power facility then the use of two power sources will need to be coordinated. Second, if the electrolysis process were to break down then a vital chemical, oxygen, will still be available to the colonists while the unit is being repaired.  This is a safety measure.  If the Sabatier unit were to break down then the electrolysis unit could continue to operate and accumulate H2 and O2.  Storage of H2O at the beginning of the process is also a safety measure for the village.  A CH4 storage tank at the end of the process is obviously required to accumulate sufficient fuel for the Earth-bound rocket to ascend to orbit and for trans-Earth injection.  CH4 is the first export product of Mars and will be the only one during the initial stage of development. 

A Mars pioneer will live in constant need of items that he requires but doesn’t have.  Being a Mark Watney 10 kind of guy/girl, he can improvise, reuse or reinvent whenever necessary.  But even Mark Watney will need some tools, some supplies, and some backup equipment for his improvising.  When planning the colonization of Mars we should provide extra tools to compensate for the dust storm that loses the 6-way screwdriver.  We should have backup ECLSS and Sabatier systems as well as extra parts.  And all the strategic chemicals should be produced in surplus and stored for that rainy day— scratch that — for the wayward dust storm.  And as pioneers we will take a solemn oath to never, never, never throw anything away. 

After the initial landing of colonists, a subsequent delivery transporter will bring additional supplies and equipment.  Among these will be additional process units and additional scaffolds for building stone storage tanks.  The following chart, “Strategic Storage,” shows some additional storage tanks that will further the safety of the village and add flexibility to the production of CH4.  On the left side of the chart is an additional water (ice) storage tank at a remote location from the village.  In this scenario, a nearby tank will be one that is close enough to be connected to the village chemical system through a liquid-carrying pipeline.  A remote location will be further away where the practical means of delivery to the village will be by an ice truck or its Mars equivalent.  For example, ice mining could be conducted at a glacier, up to 10 km away.

Strategic Storage In addition to the electrolysis unit, an Integrated Mars In-Situ Propellant Production System (IMISPPS) is shown as a separate unit for the purpose of displaying the opportunities for strategic storage.  The inputs are CO2 and H2, and the output propellant (CH4/CO) is delivered to a cryogenic distillation unit.  From this unit the refined CH4 is pumped into an additional storage tank and the potentially hazardous CO component is vented to the Martian atmosphere.  Such a venting could be seen as a waste of fuel, but it is also a precaution since there is already a surfeit of safety problems in the village. 

Also added to the storage scheme is an additional pressurized hydrogen storage tank that is intended to prevent H2 from becoming a bottleneck in processing.  Such a pressurized tank is likely to be derived from a fuel or LOX tank that come from a landing rocket vehicle.  As such there will be no flexibility in the size of the tank because it is engineered for the interplanetary mission of the vehicle.  A Mars-built stone tank, on the other hand, will be built in different sizes as needed. 

The Strategic Storage sketch also shows an extra tank for the use of the colony.  This is to acknowledge the multiple uses of the methane product and does not preclude interconnections between storage tanks so that product can be stored and delivered in different ways as required.   Other tanks, such as for oxygen, could also be added. 

Another strategic chemical for a Mars colony is nitrogen.  It is not part of the CH4 production system so is treated separately as its own mining and production system on Mars.  It is an inert gas that comprises a large portion of Earth’s atmosphere and a desirable component of a normal breathing environment on Mars, such as inside a Mars house. Nitrogen is expected to be found on Mars as nitrate salts and as fixed ammonium bound to aluminosilicate minerals 9.   An early objective of exploration should be to discover a significant source of nitrogen that can be exploited.  As an alternative, the inert gas argon could be used, but it is experimental.  The production of nitrogen on Mars will be necessary to maintain a self-sufficient colony in the long run. 

 

Summary

Dr. Sabatier had no way of knowing that his chemical process that yields methane would become important in the life of a colony on a faraway world.  The Sabatier reaction will be a central feature of a rudimentary chemical processing facility on Mars. Inputs, outputs, and intermediate chemicals of this process will be strategically stored in tanks built on Mars.  The production process will generate methane fuel for a return trip from that world to Earth and for the principal fuel of the Mars colony. 

 

References

 

  1. Erick Rideal, “Paul Sabatier, 1859-1941,” Biographical Memoirs of the Fellows of the Royal Society. November 1, 1942 4 11 63-66; doi: 10.1098/rsbm.19420006.
  2. “Sabatier Reaction”, http://en.wikipedia.org/wiki/Sabatier_reaction Accessed 5-4-2014.
  3. “Space Exploration Initiative” (Undated) Retrieved 5-4-2014 from http://en.wikipedia.org/wiki/Space_Exploration_Initiative
  4. Mars Direct, (Undated) Retrieved 5-4-2014 from http://en.wikipedia.org/wiki/Mars_Direct .
  5. National Aeronautics and Space Administration, “Human Exploration of Mars Design Reference Architecture 5.0 Addendum” July 2009, NASA-SP-2009-566-ADD.
  6. Jessica Nimon, “The Sabatier System: Producing Water on the Space Station,” http://www.nasa.gov/mission_pages/station/research/news/sabatier.html, May 12, 2011.
  7. http://www.itm-power.com/news-item/injection-of-hydrogen-into-the-german-gas-distribution-grid/ Retrieved 5-12-2014.
  8. Zubrin, R., Muscatello, and Berggren (2012) “Integrated Mars In-Situ Propellant Production System,” Journal of Aerospace Engineering 26:43-56. ISSN 1943-55254 December 15, 2012.
  9. Rocco Mancinelli and Amos Banin, “Where is the Nitrogen on Mars?”  http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=191609
  10.  Andy Weir, The Martian (a Novel), Self-published 2011, eBook ISBN: 9780804139038.