NASA Particle Partition Challenge

For long duration habitation on extraterrestrial surfaces, habitats have to be efficient and self-sustaining, especially beyond low earth orbit where resupply of equipment and crew supplies becomes cost prohibitive.  This includes the processes used to maintain a breathable atmosphere in surface habitats. One potential way to recycle oxygen is through use of a Bosch reactor. In the Bosch reaction, one molecule of carbon dioxide is reacted with two molecules of hydrogen to yield two molecules of water and solid carbon.  Water is as important a resource for breathable air because water can be broken down by electrolysis to yield hydrogen and oxygen. The solid carbon particulates that are produced in a Bosch reactor are a nuisance byproduct. So much carbon is produced per day (1 Kg per crew of 4), that it must be regularly or continuously removed for the reactor to operate. And we don’t want a removal step to interfere with the continuously running process. 

This challenge seeks to identify novel ways that fine carbon particles can be safely and efficiently removed from a Bosch reactor, without impacting the reactor’s performance.  Your design concept could help future astronauts breathe easy by contributing to the development of improved life support systems for future extraterrestrial habitats.

Winners of this single phase challenge will share a total prize purse of $45,000.  Click over to the Guidelines Tab to learn more about the Bosch reactor and solution requirements.

If you are under 18 years of age, check out the junior challenge here.
 

Background

Astronauts living aboard the International Space Station (ISS) are sustained through a complex life support system that maintains a breathable atmosphere.  From 2011 to 2017, this state of the art system included a subsystem based on the Sabatier reaction.  It essentially converted waste carbon dioxide into methane and water.  In the Sabatier reaction, one molecule of carbon dioxide is reacted with four molecules of hydrogen to produce one molecule of methane and two molecules of water.  The water, which is an important resource itself, can be electrolyzed into oxygen (for breathing) and hydrogen (to be recycled back for reaction with carbon dioxide).

Astronaut Doug Wheelock installed the state of the art Sabatier CO₂ Reduction Assembly (CRA) on the ISS in 2011. The CRA was limited to about 50% recovery. No oxygen recovery capability is currently operational on the ISS. The CRA was returned to Earth in 2017.

Another way to generate oxygen from carbon dioxide is through the Bosch reaction.  In this reaction, one molecule of carbon dioxide is reacted with two molecules of hydrogen to produce solid carbon and two molecules of water. Carbon is produced as fine solid particles. The safe collection and removal of carbon particulates generated by this reaction, when run continuously, is the heart of this challenge.

The Challenge 

Currently under development at NASA, the Continuous Bosch Reactor leverages the Bosch reaction to recycle waste CO₂ into water vapor, which is condensed and used as a source of oxygen for the crew to breathe. A major issue that prevents the implementation of the reactor is the safe and efficient removal of its carbon byproduct. As much as 1 kg (2.2 lbs) is produced per day if all the crew’s CO₂ is processed. The carbon forms as fine particles, which can foul filters and downstream condensers. If effectively collected, there is potential for the carbon to be repurposed or prepared for disposal. 

 NASA has tried a simple approach to remove the carbon from the recirculating gas stream using a metallic frit or porous ceramic filter element, diverting the accumulating carbon via a side stream to a collection system - where the carbon is contained in a replaceable bag. Although this design is intended to remove carbon particulates from the main gas stream, the carbon builds up on the filter itself. This clogs the filter, which causes a large pressure drop. This pressure drop slows down the stream of gas recirculating through the system, reducing the reactor’s efficiency, eventually requiring shut down. NASA is looking for design concepts to capture and safely remove solid carbon particulates, either from the hot gas stream or a condensed phase without fouling.

For maximum efficiency, NASA envisions a continuous Bosch reactor that continually generates oxygen. However, removing carbon from a continuous process is more complex than removing it from a batch process.  Additionally, any design concept should require minimal or infrequent intervention and maintenance from inhabitants for normal operation.

The schematic below (Figure 1) shows the general layout of a continuous Bosch reactor. A stream of heated gas at a temperature in the range of 600-700 degrees Celsius is introduced into one end of the cylindrical reactor (1). The gas stream, composed mainly of hydrogen and carbon dioxide, reacts with the catalyst already in the reactor to produce water vapor and carbon particulates. The hot gas stream carrying the water vapor and solid carbon then exits the cylindrical reactor. NASA’s original design separated the carbon before the humid gas stream passed through a down-stream condenser, where water was collected. The gas stream is refortified with carbon dioxide and hydrogen before it flows back into the reactor as the process repeats itself. This is intended to be a continuous process.  Expected gas flow rates are in the range of 20 to 50 standard liters per minute. 

Potential sites where carbon particulate capture can be introduced are either at (2) as the carbon is carried by the gas stream as it exits the reactor, or (3) at the condenser, if a condenser can be designed to collect carbon and condensed water vapor at the same time.

Figure 1: Schematic of the Continuous Bosch Reactor being developed by NASA

The carbon particulates produced by this process range in size from 1 to 500 microns, with an average particle size of 8.36 microns and an average diameter of 9.2 microns. It is largely amorphous carbon. Example particle morphologies are depicted in Figure 2 below.  The bulk density of dry collected carbon ranges from 0.65 - 0.76g/cc.  Figure 3 shows the distribution of particles by size versus percent volume.  Note that Figure 3 appears to underestimate the amount of fine carbon particulates that should be considered, since the size of larger particles disproportionately skews the area under the curve towards larger particles and a large amount of finer particles occupies a smaller volume. The amount of carbon particulates produced during a crewed mission is expected to have a mass of 250g per crew member per day, or 1kg for four crew members per day (a likely number for future missions). These particles pose a safety hazard to inhabitants, so any proposed solution should address their safe collection and removal from the reactor.

Figure 2: Example morphologies of carbon particulates formed in the Continuous Bosch Reactor

Figure 3: Graph showing the distribution of carbon particles by size versus percent volume. Note that this graph indicates quantity of particles in terms of volume percentage, not number of particles. There are likely more small particles than the graph indicates.

NASA is interested in compact, lightweight, and low power solutions that will easily integrate into a continuous Bosch reactor, effecting reliable and continuous separation of carbon particulates that are formed during the Bosch reaction. Solutions can be integrated into the reactor either prior to or during the condensation step. There are advantages and disadvantages to both locations. Design concepts that collect carbon from the hot gas flow will need to be robust to the ambient conditions, operating at a temperature high enough to avoid condensation of the water vapor present and in a manner that does not appreciably limit the gas flow rate. Components and fluid lines between the reactor and condenser must be maintained above 100°C to prevent condensation in these areas. This includes any containers that are present to contain the accumulating carbon.  Design concepts that collect carbon from the condenser location will likely need to account for potential fouling of the condenser from carbon particulates. These types of solutions would also need to be able to separate carbon from water and remove each material separately. 

Design concepts need to address the performance criteria and specifications listed below. In meeting the volume, mass, and power requirements, you should also consider things like integration, maintenance, and overall efficiency. Efficiency can be thought of in two different ways: energy and mass. Energy is a valuable resource in surface habitats and will likely be generated through solar panels, so something that requires a large amount of additional power above that required for operating the Bosch Reactor itself is less desirable. 

Minimizing mass is important because it’s expensive to launch mass off of Earth. Both the mass of the design concept and any consumables need to be considered. To calculate consumable mass, multiply the mass of the consumable items by the number required over the mission duration. For this competition we will consider the length of the mission to be 500 days. If the design concept required a replaceable filter or collection bag that is sized to be replaced every 10 days, there would need to be 50 change outs of the consumable over the duration of the mission. Total mass (equipment plus consumables) must be minimized.  Some solutions may have a higher equipment mass but lower consumable mass, while other solutions may have a lower equipment mass but higher consumable mass. 

Crews are busy and minimizing the amount of time spent on maintenance is important.  Ideal solutions will allow collected carbon to be removed less frequently (every 7-10 days instead of once a day).  Design concepts that have minimal maintenance or can go for longer periods without required maintenance are favored. This also ties into the comments about efficiency in the preceding paragraph - having fewer consumables, like filters that need to be replaced, means that maintenance will likely be faster and/or easier. In addition, maintenance should not interfere with reactor operation. For example, removal of captured carbon should be accommodated in such a way that the reactor’s operation is not disrupted. The same requirement exists for replacement of consumables. As an example, if a design concept has consumable components that need to be replaced periodically, there could be two assemblies, such that one is operating while the consumable in the other is being replaced.

In addition, the reactor and all plumbing will be operated at a pressure below the atmospheric pressure within the spacecraft. This is because we don’t want any release of hydrogen into the cabin if a leak occurs. Hydrogen is an explosive gas. This will impact design, because components for collection of the carbon must be able to withstand a delta pressure.

Finally, the ease with which a design concept can be integrated with the Bosch reactor should be considered. If significant modifications to the existing reactor are required, a solution may be considered less favorably.

Performance Criteria

A successful design concept must:

• Be at least 98% efficient in separation and capture of carbon (1.0kg per day) from the process stream.
• Include a process for collection of the captured carbon and a method for its safe and easy removal at periodic intervals.  
• Require removal of the collected carbon at intervals of no less than once a week.
• Allow for continuous operation of the Bosch reactor, even during maintenance, including when captured carbon is removed.  
• Be highly reliable and robust, able to operate for at least 500 days, and ideally for several years.
• Be easily accessed by the crew for maintenance and service.
• Be supported by a scientific rationale and preferably also by modeling or other data.

Performance specifications:

• The mass of the design concept and its supporting consumables needed for 500 days of continuous operation should be minimized as much as possible, but must not exceed 60 kg.  Consumables include things like disposable filters, collection bags, etc. 
• The volume of the design concept is to be minimized as much as possible, but must not be greater than 100 liters (0.1M³) when assembled as a system, including consumables. This volume includes both the separator and the volume that collects the accumulated carbon. For reference, the volume of 3 basketballs is roughly 22L.
• The design concept must integrate with the Bosch reactor at either points (2) or (3) in Figure 1.
• The design concept’s power consumption must be minimized but not exceed 500W. 
• Depending on where the solution is located, the design concept will have to be compatible with different temperature ranges:
  • Solutions integrated at the exit of  the reactor itself will experience temperatures close to the 600-700℃ range
  • Solutions integrated between the reactor and condenser will experience cooler temperatures but that are still in excess of 100℃
  • Solutions that are integrated as part of the condenser will experience ambient temperatures (nominally 25℃)
• The design concept must be able to operate at internal pressures below spacecraft cabin atmospheric pressure. 

Prize

$45,000 purse distributed through five prizes:

• One first place winner will receive $20,000 
• One second place winner will receive $10,000 
• Up to 3 third place winners will each receive $5000  

Timeline

Challenge launch: October 26, 2022

Submission deadline: January 12, 2023, 5pm Eastern Time (11 weeks)

Evaluation period: January 12 - March 9, 2023 (8 weeks)

Winners announced: March 16, 2023

Judging Criteria

Rules

Participation Eligibility:

The Prize is open to anyone age 18 or older participating as an individual or as a team. Individual competitors and teams may originate from any country, as long as United States federal sanctions do not prohibit participation (see: https://www.treasury.gov/resource-center/sanctions/Programs/Pages/Programs.aspx). If you are a NASA employee, a Government contractor, or employed by a Government Contractor, your participation in this challenge may be restricted.

Submissions must originate from either the U.S. or a designated country (see definition of designated country at https://www.acquisition.gov/far/part-25#FAR_25_003, OR have been substantially transformed in the US or designated country prior to prototype delivery pursuant to FAR 25.403(c). 

Submissions must be made in English. All challenge-related communication will be in English.

You are required to ensure that all releases or transfers of technical data to non-US persons comply with International Traffic in Arms Regulation (ITAR), 22 C.F.R. §§ 120.1 to 130.17.

No specific qualifications or expertise in the field of Bosch reactors or carbon separation is required. NASA encourages outside individuals and non-expert teams to compete and propose new solutions.

To be eligible to compete, you must comply with all the terms of the challenge as defined in the Challenge-Specific Agreement.

Intellectual Property

Innovators who are awarded a prize for their submission must agree to grant the United States Government  a royalty-free, non-exclusive, irrevocable, worldwide license in all Intellectual Property demonstrated by the winning/awarded submissions. See the Challenge-Specific Agreement for complete details.

You may be required to complete an additional form to document this license if you are selected as a winner.

Registration and Submissions:

Submissions must be made online (only), via upload to the HeroX.com website, on or before January 12, 2023 at 5pm ET. No late submissions will be accepted.

Selection of Winners:

Based on the winning criteria, prizes will be awarded per the weighted Judging Criteria section above.

Judging Panel:

The determination of the winners will be made by HeroX based on evaluation by relevant NASA specialists.

Additional Information

• By participating in the challenge, each competitor agrees to submit only their original idea. Any indication of "copying" amongst competitors is grounds for disqualification.
• All applications will go through a process of due diligence; any application found to be misrepresentative, plagiarized, or sharing an idea that is not their own will be automatically disqualified.
• All ineligible applicants will be automatically removed from the competition with no recourse or reimbursement.
• No purchase or payment of any kind is necessary to enter or win the competition.
• Void wherever restricted or prohibited by law.