life Review Biologically-Based and Physiochemical Life Support and In Situ Resource Utilization for Exploration of the Solar System—Reviewing the Current State and Defining Future Development Needs Ryan J. Keller *, William Porter, Karthik Goli, Reece Rosenthal, Nicole Butler and Jeffrey A. Jones Center for Space Medicine, Baylor College of Medicine, Houston, TX 77030, USA; [email protected] (W.P.); [email protected] (K.G.); [email protected] (R.R.); [email protected] (N.B.); [email protected] (J.A.J.) * Correspondence: [email protected] Abstract: The future of long-duration spaceflight missions will place our vehicles and crew outside of the comfort of low-Earth orbit. Luxuries of quick resupply and frequent crew changes will not be available. Future missions will have to be adapted to low resource environments and be suited to use resources at their destinations to complete the latter parts of the mission. This includes the production of food, oxygen, and return fuel for human flight. In this chapter, we performed a review of the current literature, and offer a vision for the implementation of cyanobacteria-based bio-regenerative life support systems and in situ resource utilization during long duration expeditions, using the Moon and Mars for examples. Much work has been done to understand the nutritional benefits of Citation: Keller, R.J.; Porter, W.; Goli, cyanobacteria and their ability to survive in extreme environments like what is expected on other K.; Rosenthal, R.; Butler, N.; Jones, J.A. Biologically-Based and celestial objects. Fuel production is still in its infancy, but cyanobacterial production of methane is Physiochemical Life Support and In a promising front. In this chapter, we put forth a vision of a three-stage reactor system for regolith Situ Resource Utilization for processing, nutritional and atmospheric production, and biofuel production as well as diving into Exploration of the Solar System— what that system will look like during flight and a discussion on containment considerations. Reviewing the Current State and Defining Future Development Needs. Keywords: life support; atmospheric revitalization; in situ resource utilization; space exploration; Life 2021, 11, 844. https://doi.org/ planetary habitat; transfer vehicle; BLSS; ISRU; cyanobacteria; methane 10.3390/life11080844 Academic Editor: Daniela Billi 1. Introduction Received: 3 July 2021 When planning long-distance spaceflight missions, it becomes critical to create ways Accepted: 7 August 2021 Published: 18 August 2021 to reduce IMLEO (initial mass in low earth orbit) while also ensuring that the systems that increase IMLEO are reliable and have enough redundancies to ensure the success of the Publisher’s Note: MDPI stays neutral mission. Multiple probes and rovers have already been sent to Mars, but future missions with regard to jurisdictional claims in will add new complications in keeping humans alive and returning them home safely, published maps and institutional affil- requiring food, oxygen, carbon dioxide scrubbing, and propellants for the transit vehicle iations. and DAV (Descent/Ascent Vehicle). The current systems utilized on board spacecraft are physical-chemical, relying on both renewable and nonrenewable resources that are limited and require occasional resupply [1]. The current systems will not support a long-duration mission outside of LEO (Low Earth Orbit), and resupply to Mars, for example, will be both long and expensive. BLSS/ISRU (Bioregenerative Life Support System/In-Situ Resource Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Utilization) attempts to tackle these problems. This article is an open access article Lunar and Martian regolith contain many useful elements and compounds for survival, distributed under the terms and but at the moment, they do not exist in a form that satisfies our life support needs. The conditions of the Creative Commons Martian atmosphere contains 95% carbon dioxide and is very thin and inhospitable for Attribution (CC BY) license (https:// humans and broad forms of life. Cyanobacteria are ancient photosynthetic organisms on creativecommons.org/licenses/by/ Earth that are believed to be responsible for terraforming and oxygenating the planet to 4.0/). support higher orders of life. They are very effective sources of oxygen production, produce Life 2021, 11, 844. https://doi.org/10.3390/life11080844 https://www.mdpi.com/journal/life Life 2021, 11, 844 2 of 41 Life 2021, 11, x FOR PEER REVIEW 3 of 42 many useful compounds, and are used throughout the world as a nutritional supplement for their high protein content and wide resumé of vitamins, minerals, and antioxidants. 2.2.Such Food a versatile organism has the potential to revolutionize the way we operate life support systemsFor this in space. reference Inflight astronaut, BLSS would da needily to food provide is estimated oxygen and to food measur for thee crew at 0.80 for kg dry mass before interplanetary travel, thereby reducing dependence on foodstuffs and oxygen stores taken thefrom addition Earth. For of Planetarypreparatory ISRU, water. a three-stage According system isto being the FDA, proposed. the Stage average 1 will human be adult requires approximatelyresponsible for bioweathering 2000 kcal/day regolith made by siderophilicup of approximately cyanobacteria to78 free g of up fat non-organic (with 20 g of saturated fats andelements 300 mg and of create cholesterol), organic compounds 275 g of for carbohydrate photobioreactors, growth.2300 mg Stage of 2sodium, will involve 28 g of fiber, and 50 g a photobioreactor with species of cyanobacteria that will be responsible for production of ofprotein oxygen, [4]. fixation These of numbers carbon dioxide, are different and accumulation depending of biomass on the for source use in used human and vary to a certain degreeconsumption depending and fuel on for the subsequent size and operations. sex of the Stage person 3 will involvein question. a third bioreactorAstronauts performing sig- nificantresponsible physical for the activity creation of such biofuels as (methane)exercise forcountermeasures use in the DAV. and planetary surface EVA (ap- proximately2. Human Living 8 h EVA, Requirements 8 h IVS, and 8 h of sleep) will have additional caloric demands to main- tain boneThe introductionhealth, muscle of the mass, human et elementc., of an to theadditional mission is 500–1000 the basis for kcal/day. research into this field and establishes the need for generation of consumables and fuel during the 2.3.mission. Water While we have developed technology and food packaging for efficient long-term storage and use of foodstuffs, oxygen reserves, and carbon dioxide scrubbing, using these for aThe mission reference duration astronaut longer than thatis also of an expected ISS expedition to requireshave a a daily look into requirement a more of 2.79 kg of drinkingcyclical process. water Instead in addition of letting to material the 0.50 fall kg into needed a sink of inertfor food material, preparation BLSS systems and the 0.76 kg that can complete the circle to reorganize human waste, combined with harvested materials, alreadyinto usable exists consumables. in the Tofood. set a baseThis for water this discussion, is then we expected must discuss to the leave expected the astronaut in the amountsconsumable of 3.04 requirement kg from of the perspiration human body inand space. respiratory Ewert and Stromgrenwater, 1.40 conducted kg in the urine, and 0.09 kga in review feces. of experimentsSome flight and surgeons literature and advocate constructed up ato frame 3 L/day/crewmember for the metabolic mass to reduce the risk balance for an 82 kg reference astronaut during long-duration missions. These values ofwould urolithiasis vary with theduring size of theprolonged crewmember periods as well as of the hypogravity exercise regimen ofexposure. the day with It is not clear how muchsome bone days only mineral completing preservation the required exercises occurs with with the 0. potential16 or of0.3 other g exposure days requiring on the surface of the Moonsubstantial or Mars, movement so it andis not lifting clear while what setting the up risk experiments of calciuria and SHAB associated duties [1]. with For bone loss will be. specific effects of increased activity among the crew, the 41 node METMAN model should be consulted.Water is This provided is a model for that missions divides the humanthrough body direct into ten transportation, cylindrical elements byproducts of fuel combustion,each composed and of four reclamation compartments of (core, carbon muscle, dioxide fat, and through skin), and thethe heat Sabatier generation reaction [1]. Current theoreticalof each element estimates is calculated posit [2]. that Increased about heat 5.33 generation kg of willwater result can in the be need recycled for more and made available kcal, necessitating more food, oxygen, and a larger reactor. This is one reason that would forjustify use deployingwhile the a largerhuman reactor requirement than would be is thought only 5.03 necessary. kg [1]. In total,However, a 3–4-person Ewert and Stromgren statecrew that is expected with the to process potential 17.22–22.96 for loss kg ofthrough consumables processes a day. The including NASA DRA towels 5.0 for hygiene and disposedprovides awipes, great illustration the margin of the metabolicis too small requirements for comfort. and products of a 4 person crew in Figure1[3]. Figure 1. Inputs and outputs for a four-person crew [3]. Figure 1. Inputs and outputs for a four-person crew [3]. 3. History of Life Support System Designs 3.1. Lunar-Mars Life Support Test Project With a discussion of the future of life support systems, it becomes necessary to dis- cuss the developmental history of these regenerative systems. The first development that we will review is The Lunar-Mars Life Support Test Project (LMLSTP), which was a multi- phase experiment conducted from 1995–1997 designed to evaluate the efficacy of human- in-the-loop, closed-environment life support systems in supporting crew habitation.