JSC FORM 151C (Rev Sept 86) NASA-JSC

JSC 39317 CREW AND THERMAL SYSTEMS DIVISION NASA–LYNDON B. JOHNSON SPACE CENTER HOUSTON, TEXAS

Advanced Life Support Systems Modeling and Analysis Project Baseline Values and Assumptions Document

Document Number CTSD-ADV-371 Date June 18, 1999

PREPARED BY: A. E. Drysdale Original signed by A. E. Drysdale PREPARED BY: A. J. Hanford Original signed by A. J. Hanford

APPROVED BY: M. K. Ewert Original signed by M. K. Ewert

APPROVED BY: C. H. Lin Original signed by C. H. Lin

APPROVED BY: D. L. Henninger Original signed by D. L. Henninger

APPROVED BY: A. F. Behrend, Jr. Original signed by A. F. Behrend, Jr.

Number of pages: ___40__ REVISIONS APPROVALS DATE AUTHOR SECTION BRANCH DIVISION REV. LETTER JSC FORM 151C (Rev Sept 86) NASA-JSC

Advanced Life Support Systems Modeling and Analysis Project Baseline Values and Assumptions Document

Alan E. Drysdale, Ph.D. The Boeing Company Kennedy Space Center, Florida 32815

Anthony J. Hanford, Ph.D. Lockheed Martin Space Operations Houston, Texas 77058

June 1999 Baseline Values and Assumptions Document, JSC 39317 June 1999

Contents

1 INTRODUCTION...... 1 1.1 PURPOSE AND PROCESS...... 1 1.2 ADVANTAGES...... 2 1.3 SYSTEMS MODELING AND ANALYSIS PROJECT...... 2 2 APPROACH...... 3 2.1 DEVELOPMENT...... 3 2.2 CONTEXT...... 3 2.3 DEFINITIONS OF TERMS AND UNITS...... 3 2.3.1 Equivalent System Mass...... 3 2.3.2 Infrastructure...... 3 2.3.3 Modeling...... 4 2.3.4 Units and Values...... 4 2.4 APPLICABLE DOCUMENTS...... 4 3 ASSUMPTIONS...... 5 3.1 MISSIONS...... 5 3.1.1 Design Reference Mission...... 5 3.1.2 Long-Term Mars Base...... 5 3.2 AIR REVITALIZATION OPTIONS...... 6 3.3 CLOTHING OPTIONS...... 8 3.4 CREW METABOLIC RATE...... 9 3.5 CREW TIME OPTIONS...... 9 3.6 FOOD SYSTEM OPTIONS...... 12 3.6.1 Flight System Options...... 12 3.6.2 Food System Options Based on Biomass Production Systems...... 15 3.7 FOOD PROCESSING OPTIONS...... 17 3.8 INFRASTRUCTURE COSTS/EQUIVALENCIES...... 18 3.9 IN SITU RESOURCE UTILIZATION OPTIONS...... 20 3.10 PLANT GROWTH CHAMBER OPTIONS...... 22 3.10.1 Lighting Assumptions...... 23 3.10.2 Other Lighting Data...... 24 3.10.3 Plant Growth Chamber Cost Factors...... 24 3.11 PLANTS...... 25 3.12 SENSOR OPTIONS...... 27 3.13 WASTE PROCESSING OPTIONS...... 27 3.14 WATER RECOVERY OPTIONS...... 29 4 REFERENCES...... 31 5 APPENDICES:...... 35 APPENDIX A: ACRONYMS AND ABBREVIATIONS...... 35 APPENDIX B: ABBREVIATIONS FOR UNITS...... 36

ii Baseline Values and Assumptions Document, JSC 39317 June 1999

Tables Table 3.1.1 Mission Assumptions...... 5 Table 3.2.1 Typical Static Values...... 6 Table 3.2.2 ALS Air Revitalization Technologies...... 7 Table 3.2.3 Air Regeneration System Options...... 7 Table 3.2.4 Gas Storage Options...... 8 Table 3.3.1 Clothing and Laundry Options...... 8 Table 3.3.2 Laundry Equipment Specifications...... 8 Table 3.4.1 Human Metabolic Rates...... 9 Table 3.5.1 Mars Surface Mission Time Allocation for a Nominal Crew Day...... 10 Table 3.5.2 Crew Time Allocation for Analysis...... 10 Table 3.5.3 Crew Time per Person per Week...... 11 Table 3.6.1 ISS Thermoelectric Freezer Properties...... 13 Table 3.6.2 Food Cold Storage Options on a Property per Frozen Food Mass Basis...... 13 Table 3.6.3 Food Quantity and Packaging...... 14 Table 3.6.4 Historical/Near-Term Food Masses...... 15 Table 3.6.5 20-Day Diet Using All Crops...... 16 Table 3.6.6 20-Day Diet Using Salad and Carbohydrate Crops...... 17 Table 3.8.1 Mars Mission Infrastructure Cost Options...... 18 Table 3.8.2 Mars Advanced Mission Power Cost Options...... 19 Table 3.8.3 Cost of Pressurized Volume Options...... 20 Table 3.8.4 Masses of TransHab Shell Components...... 20 Table 3.9.1 Nitrogen Gas Losses Associated with ISS Technology...... 21 Table 3.9.2 Nitrogen Gas Losses for the Mars DRM (One Mission) Using ISS Technologies...... 21 Table 3.9.3 Estimation of Cost Leverages from ISRU Options...... 22 Table 3.10.1 Lighting Data...... 23 Table 3.10.2 High Pressure Sodium Lighting Data...... 24 Table 3.10.3 Plant Growth Chamber Equivalent System Mass per Growing Area...... 25 Table 3.11.1 Plant Growth Rates...... 26 Table 3.11.2 Plant Growth and Support Requirements...... 26 Table 3.11.3 Mineral Mass Estimates...... 27 Table 3.11.4 Ion Estimates...... 27 Table 3.12.1 Sensor Mass Estimates...... 27 Table 3.13.1 Bioreactor Options...... 28 Table 3.13.2 Super Critical Wet Oxidation...... 28 Table 3.13.3 Incineration...... 29 Table 3.13.4 Dumping...... 29 Table 3.14.1 ALS Water Recovery Equipment Options...... 30 Table 3.14.2 ALS Water Recovery System Options...... 30

Baseline Values and Assumptions Document, JSC 39317 June 1999

1 Introduction The Advanced Life Support (ALS) Program Systems Modeling and Analysis Project (SMAP) Baseline Values and Assumptions Document (BVAD) provides analysts and modelers with a common set of initial values and assumptions, or baseline. This baseline in turn provides a common point of origin from which all SMAP studies will depart.

1.1 Purpose and Process The BVAD identifies specific physical quantities which define life support systems from an analysis and modeling perspective. For each physical quantity so identified, the BVAD provides a nominal or baseline value plus a range of possible or observed values. Finally, the BVAD documents each entry with a description of the quantity’s use, value selection rationale, and appropriate references. The baseline values found in the BVAD are designed to provide defaults for those quantities within each study which are not of particular interest for that study and may be adequately described by such defaults.

For example, the direct solar irradiation for vehicles orbiting around Luna varies between 1,323 W/m² and 1,414 W/m² with a mean value of 1,367 W/m² (K&K, 1998). Thus, the solar constant at Luna naturally varies by 91 W/m² (6.7 %). Williams (1997) lists a mean value of 1,380 W/m² for the solar constant at Luna. While any value from 1,323 W/m² to 1,414 W/m² might be selected for the solar constant in a study sited in Luna orbit, a mean value of 1,370 W/m² might be defined as the baseline solar flux at Luna. Thus, all studies would use a consistent value of 1,370 W/m² unless they were specifically exploring the effect of varying the solar constant.

This example is well bounded. Some life support assumptions are similarly well bounded. Others, such as the growth rate of plants, are not well bounded. For these, upper and lower values are given which are reasonable, although other values showing a greater range could be used.

Without an agreement, each researcher will generally select his/her baseline values using whatever sources are available and/or deemed most accurate. While values from one researcher to the next may be similar, variations in input values lead to further variations in results when one compares studies from multiple sources. As such, it is more difficult to assess the significance of variations in results between studies from different sources without conducting additional analyses to bring the multiple studies to a similar baseline. As part of the process of assigning values to each of the life support quantities, the researchers within SMAP generated a list of pertinent life support quantities with suggested baseline values and an acceptable range. Each submission was evaluated and debated within all of SMAP to produce a set of mutually agreeable baseline values with corresponding limits. To allow the BVAD to truly maintain its utility as a store of modeling and analysis information, the BVAD is a living document which will be updated annually or as necessary to reflect new technology and/or scientific discoveries. Note also that the current document does not include all possible current technologies so the technology listings are not all inclusive. Thus, additional entries describing current technologies will also provide updates for this document. The BVAD will be controlled by the SMAP project manager. After the baseline is released, subsequent releases will be made annually or as required. If sufficient comments are received, an interim update will be issued after six months. Please send comments to:

1 Baseline Values and Assumptions Document, JSC 39317 June 1999

M. K. Ewert Project Manager Systems Modeling and Analysis Project NASA Johnson Space Center Mail Code EC2 2101 NASA Road One Houston, TX 77058 E-mail: [email protected]

1.2 Advantages Aside from the advantages implied above, the BVAD provides several additional benefits.  The BVAD allows the life support analysis community to carefully review and evaluate input study assumptions. Such review will lead to greater confidence in and understanding of the studies.  Each study can now benefit from the “best” available input values and assumptions by drawing upon information collected by a group of researchers rather than just from one person’s files. Further, such values reflect the combined expertise of the group as a whole rather than just those from one individual.  The BVAD process identifies those quantities which are not well-defined by current information. Such quantities are primary candidates for parametric studies to determine their importance on modeling and analysis results. Further, this approach identifies values that may require additional experimental input to adequately quantify.  The BVAD allows researchers from multiple sites to efficiently and quickly compare results from multiple studies. Because each study uses the same baseline, the variations between studies arise from differences in models or the parameters varied rather than a complex combined effect which includes variations in the assumed baseline.  The BVAD will allow any researcher to conduct a follow-on study to any previous work because each study’s assumptions will be clearly available and carefully recorded. Further, researchers can reference the BVAD for their baseline parameter values except those which are unique to their specific study.

1.3 Systems Modeling and Analysis Project SMAP is a project within the ALS Program. It was established to encourage and improve communication between the various modelers within the ALS Program. The Project Management Plan (Hanford and Ewert, 1998) presents the project objectives and organization in detail.

2 Approach Assumptions arise from various sources and have been organized into sets of similar data. These assumptions relate to the scenarios, the mission infrastructure, and the various life support subsystems. References are documented where possible to provide traceability.

2.1 Development The baseline values and assumptions are based on experience in developing static and dynamic models of life support systems. Where numerical values are given (and an attempt has been made to focus on quantitative data), an attempt has been made to include upper and lower limits as well as a recommended value. In some cases, the upper and lower limits are definite values set by the physics or biology of the situation. For other cases, they are representative values which will not often be exceeded in a real system.

2.2 Context This assumptions document assumes a particular mission: going to Mars. There are other missions of interest, but this mission currently is of greatest interest to the ALS Program. Many of the data shown would be, most likely, unchanged by a different location. However, this gives a suitable focus, making the baseline values and assumptions more realistic.

2.3 Definitions of Terms and Units

2.3.1 Equivalent System Mass Equivalent system mass (ESM) is a technique by which several physical quantities which describe a system or subsystem may be reduced to a single physical parameter, mass. The primary advantage is to allow comparison of two life support systems with different parameters using a single scale. This is accomplished by determining appropriate mass penalties or conversion factors to convert the non-mass physical inputs to an equivalent mass. For systems which require power, for example, the power system can yield an appropriate power-mass penalty by dividing the average power plant output by the total mass of the generating power system. Thus, for a nuclear power system on an independent lander which, on average, delivers 100 kW of electrical power and has a overall mass of 8,708 kg (Mason, et al., 1992) 1 the power mass penalty is 11.48 W/kg. This power-mass penalty effectively assigns a fraction of the power system mass to a power-using subsystem in place of that subsystem’s power requirement. In like manner, mass penalties to account for heat rejection and volume within a pressurized shell are defined. Work is also in progress to define a crew-time-mass penalty to convert maintenance time to mass, but the derivation for this conversion factor is not as obvious, although a form is presented in this document based on Drysdale (1998b). The definition of equivalent mass for a system is the sum of the equipment and consumable commodity mass plus the power, volume, thermal control, and crew-time requirements as masses.

2.3.2 Infrastructure This is everything necessary for operation of the life support system with the exception of the transportation system. In short, it includes all necessary supplies and equipment for a power system to provide electrical power and a thermal control system to provide cooling, as delivered to the operating environment of interest. Other infrastructure is likely to be required, such as data and communications, but these systems are not expected to use significant resources for life support.

1 The actual mass quoted here has been adjusted slightly to account for some differences between the work listed in the reference and the desired system.

2.3.3 Modeling Modeling involves the simulation of the ALS system or some ALS component or subsystem to determine performance. Models might be quite simple, to calculate overall masses, for example, or quite complex, involving gas exchange at the molecular or plant growth levels. Initially, this document has been built to supply supporting values for the simpler models, but current plans are to expand the level of detail to encompass all ALS-unique models.

2.3.4 Units and Values All numerical assumptions are given in Sytème International (SI) units. This approach is consistent with the current philosophy within the Crew and Thermal Systems Division that all analysis tasks for advanced systems use SI units. A list of units is provided in the Appendices. Generally, lower, nominal, and upper values are provided. In all cases, the numbers are intended to represent average values under nominal conditions for different design cases. Short-term fluctuations are not considered, nor are emergency or contingency situations except as explicitly noted. Values assume a crew of six, unless otherwise stated.

2.4 Applicable Documents The BVAD is intended to provide values for analysis and modeling tasks. Analysis and modeling is charged with examining both off-nominal and diverse technology options. As a result, many studies may consider situations which differ from the accepted bounds listed in the various documents containing requirements. However, when applicable, the BVAD is intended to capture the individual extremes for inputs which are appropriate for human spaceflight. Further, while the nominal values throughout this document should be consistent with one another, off-nominal values may not be consistent with other values within this document. Thus, the validity of using off-nominal values should be independently verified by the user. As noted, the BVAD attempts to provide inputs for all quantities of importance for studies associated with life support systems. However, as research within the ALS Program is constantly changing, many studies will require inputs for quantities not listed here. In such situations, analysts should use whatever values are appropriate and available and so note and reference those values in their reports or documentation. Further, analysts are asked to report such omissions to SMAP and provide whatever information could be used to determine values for such omitted quantities. The following documents are important references for life support. The latest revision is noted below. Subsequent releases will be considered in updating this document. Lange, K. E., and Lin, C. H. (1998) “Advanced Life Support Program: Requirements Definition and Design Consideration,” JSC-38571 (CTSD-ADV-245, Rev. A) National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. http://peer1.idi.usra.edu/peer_review/prog/ALSREQ98.PDF

3 Assumptions

3.1 Missions The mission affects analyses and models by changing the weighting of the various pieces of the system in terms of time dependent items, equipment design, and infrastructure cost. It can also require different contingency planning for a mission with a short-term abort option (e.g., Low Earth Orbit (LEO), or Lunar missions) versus one without such an option (e.g., Mars missions).

3.1.1 Design Reference Mission The primary mission addressed is the current Mars Design Reference Mission (DRM), by Hoffman and Kaplan (1997). This document describes a three-trip mission architecture that covers transits to Mars, surface stays, and return trips. Assumptions are given in Table 3.1.1 for mission parameters from the current DRM documents. Other options have been identified elsewhere which are outside these ranges. The volume assumptions given are from the DRM documents, but more space could be available on the surface, particularly if a TransHab approach is used with a new TransHab being landed on Mars each time a human crew goes there, and if the new habitat is connected to the old ones. In practice, the volume limits might be applied to transit only, and possibly to the initial surface habitat.

Table 3.1.1 Mission Assumptions Assumptions Source Parameter lower nominal upper Document Section Crew Size 4 6 9 SMAP (1999a) Duration [days] transit 110 180 180 Hoffman & Kaplan (1997) 1.3.3.1 surface 540 600 619 Hoffman & Kaplan (1997) 1.3.3.2 Volume [m3/person] 18 NASA (1999) Fig 8.6.2.1-1 50 90 Hoffman & Kaplan (1997) P 6, 7 Visits to One Site 1 3 3 Hoffman & Kaplan (1997)

The DRM assumes a laboratory module would land before the crew arrives. If this module uses TransHab technology, and is counted as crew volume, the total volume per person would double. However, because this laboratory is presumably intended for experimental operations, it is not included here.

3.1.2 Long-Term Mars Base The Bioregenerative Planetary Life Support Systems Test Complex (BIO-Plex) is planned to be a closed-chamber facility comprised of five chambers and an airlock all connected by a tunnel. The BIO-Plex will provide integrated test facilities for technologies which will likely be used for an early human base on Mars. Each BIO-Plex module is 185.15 m3 in volume. The tunnel is 263.43 m3. The airlock volume is 48 m3. Thus the total volume is estimated to be 1,237 m3, or 309 m3 per person assuming the nominal crew of four people. Internal air pressure will be approximately ambient. While the BIO-Plex is nominally designed for four people, with overlaps for crew changeout, up to eight people may be supported for up to a week. While the planned duration for tests is under review, 120 through 400+ day missions have been mentioned most often by those working on the BIO-Plex. A facility similar to the BIO-Plex could be built on Mars, with a similar configuration and constraints. The most likely difference would be on mission duration, with a probable minimum duration of 540 days (as in Table 3.1.1) and an operational lifetime of perhaps ten to fifteen years.

3.2 Air Revitalization Options Air regeneration is one of the more time-critical life support functions. Typical control (static) values, are given in Table 3.2.2, together with technologies in Table 3.2.3 and systems in Table 3.2.4. Total pressure is an issue. Some generally prefer to use normal sea-level pressure, because that is the condition under which most of the data was collected, and because people can live satisfactorily for a long duration under these conditions. Others, however, prefer lower pressures, as this reduces the mass of gas required, the mass of the vehicle, and the requirement to pre-breathe with current extravehicular mobility units or “spacesuits.” Reduced pressure normally entails increasing the percentage of oxygen, relative to other gases, in the cabin atmosphere, which increases the risk of fire.

The accepted levels of partial pressure of carbon dioxide, p(CO2), for humans, are higher than desired for most plants. The generally accepted optimum for plants is 0.120 kPa (1,200 ppm). However, separate values could be used for the crew compartments and the plant chambers through regulating the transfer rates. Earth normal is 0.035 – 0.040 kPa (350 to 400 ppm).

Table 3.2.2 Typical Static Values 2 Assumptions Source Parameter Units lower nominal upper Reference Carbon Dioxide Generated kg/cd 3 0.998 Lange and Lin (1998) kg/cd 0.466 2.241 calculated 4 Oxygen Consumed kg/cd 0.835 Lange and Lin (1998) kg/cd 0.385 1.852 calculated Error: Reference source not found

p(CO2) for Crew kPa 0.4 Lin (1997a) p 3 kPa 0.031 0.71 Lange and Lin (1998) p 33

p(CO2) for Plants kPa 0.12 kPa 0.04 Earth normal kPa TBD

p(O2) for Crew kPa 17.76 Lin (1997a) p 12 kPa 19.5 – 23.1 23.1 Lange and Lin (1998) p 9 Total Cabin Pressure kPa 59.2 5 70.3 Lin (1997a) p 12 kPa 101.3 Lange and Lin (1998) Temperature °C 18.5 22.0 26.8 Lange and Lin (1998) p 33 Relative Humidity % 25 60 75 Lange and Lin (1998); NASA (1999)

A number of regenerative technologies have been suggested for air revitalization. The better- researched physicochemical (PC) regenerative technologies are listed below. The values presented assume a crew of six. In addition, plants can regenerate air, taking in carbon dioxide and releasing oxygen. These are addressed in the section below on plants. Note that the Sabatier reaction plus electrolysis requires

2 The values here are averages for nominal operation of the life support system. Degraded or emergency life support system values may be different. 3 In this report, crew time is expressed in “crew-hours,” ch, or “crew-days,” cd, where crew implies a single individual conducting a task for the appended time interval. In short, “crew” here is an abbreviation for “crew member.” 4 The lower and upper limits for this mass of gas per person per day are calculated based on metabolic rates. 5 An almost pure oxygen atmosphere, such as was utilized for early spacecraft (Mercury, Geminii, and Apollo), has a total pressure of 34.5 kPa. Skylab used an atmosphere at 258 millimeters of mercury, but the crew reported numerous ill effects.

6 Baseline Values and Assumptions Document, JSC 39317 June 1999 excess hydrogen, and that this is assumed to be available from excess water. This may be true with supplied food, but must be assessed at a system-level.

Table 3.2.3 ALS Air Revitalization Technologies 6

Components 7 Mass Volume Power Crew Time Logistics [kg] [m3] [kW] [ch/y] [kg/y] 4BMS (Z5A) 255 1.55 1 TBD 0 SAVD (HS-X) 257 TBD 0.22 TBD 0 Node 3 (ISS) Improved CDRA 176 0.45 8 0.365 TBD 0 (solid amine or carbon) CRS (Sabatier) 9 182 0.21 0.2 TBD 4.2 OGS (SPWE) 10 377 1.1 1.84 4.9 18 Node 3 Advanced TCCS 77 0.14 Error: 0.128 3.2 23 Reference source not found

The technologies identified in Table 3.2.3 may be combined into air revitalization systems (See Table 3.2.4). Note that all three systems have similar cost factors. Thus, as a first approximation, any of these systems can be considered equivalent.

Table 3.2.4 Air Regeneration System Options 11 Mass Volume Power Crew Time Logistics Systems [kg] [m³] [kW] [ch/y] [kg/y] 4BMS+CRS+OGS+TCCS 891 3.00 3.17 8.1 45.2 SAVD+CRS+OGS+TCCS 893 TBD 2.39 8.1 45.2 Improved CDRA+CRS+OGS+TCCS 812 1.90 2.53 8.1 45.2

Gas storage is necessary for any life support system. Gas can be stored in pressure vessels, as a cryogenic fluid, adsorbed, or chemically combined. The cost of storage depends on the gas, with the “permanent” gases such as nitrogen and oxygen requiring higher pressure and remaining in the gaseous state at normal temperatures, while the “non-permanent” gases like carbon dioxide can be stored as liquids under pressure. Cryogenic storage will either require continuous cooling or use of a small quantity of the gas to provide cooling by evaporation. Adsorption and chemical combination are very gas-specific, and vary in performance. See Table 3.2.5 for gas storage tankage mass.

6 From Hanford (1998a) except as noted. A crew size of six is assumed. 7 The acronyms is this table are: four bed molecular sieve (4BMS), solid amine vacuum desorbed (SAVD), International Space Station (ISS), carbon dioxide removal assembly (CDRA), carbon dioxide reduction subsystem (CRS), oxygen generation subsystem (OGS), solid polymer water electrolysis (SPWE), and trace contaminant control subsystem (TCCS). Z5A is a zeolite and HS-X is a solid amine. 8 From Carrasquillo, et al. (1997). 9 From Ham. Stand. (1998). 10 From Ham. Stand (1999). 11 To be truly regenerative, the carbon dioxide concentration equipment requires a vacuum pump to desorb carbon dioxide from the absorbent bed followed by a compressor to repressurize the carbon dioxide stream. The vacuum pump, compressor, and their associated costs are not included in these values.

Table 3.2.5 Gas Storage Options Performance [kg of gas/kg of tankage] Type of Storage Carbon Dioxide Nitrogen Oxygen Reference Pressure Vessel TBD 12 2.16 2.75 Ham. Stand. (1970) Cryogenic Storage TBD Error: 1.91 2.33 Ham. Stand. (1970) Reference source not found

3.3 Clothing Options Clothes are not traditionally part of a life support system. However, data are provided here because of the many interfaces and the significant influence of clothing on the crew support mass and the water and waste systems. The approach for International Space Station (ISS) is to resupply clothes as needed. The main interfaces between the life support system and a laundry would be the mass of water needed for a water-based washer and the corresponding water vapor load. The water vapor load would depend on the performance of the laundry system, but assuming that most of the wash water is removed mechanically, leaving a mass of water within the fabric equal to the mass of the clothes, the corresponding water-vapor load would be about 1.5 kg per person per day.

Table 3.3.6 Clothing and Laundry Options Mass Mass Volume Power [kg] [kg/cd] [m3/cd] [kW] Source Notes ISS Approach (clothes shipped, single use): 1.69 0.00135 Branch (1998) 1.47 0.00140 Reimers & McDonald (1992) Using a Laundry: clothes 0.267 0.000351 Reimers & McDonald (1992) laundry equipment 118 0.31 Reimers & McDonald (1992) interfaces (water) 12.47 Lange and Lin (1998) gray water

12 In the absence of data for carbon dioxide storage, the values for oxygen storage may be substituted in the interim.

Table 3.3.7 Laundry Equipment Specifications 13 Value Units Comments ISS Clothing Allowance 1.5 kg/cd Average of values from above. Washer Unit Value Units Comments Mass 118 kg Volume 0.66 m³ Capacity 2.7 kg/load Water Usage 49 kg/load Effluent is gray water. This unit does not release water vapor. Crew Time 0.33 ch/load Load, remove, fold and stow clothes. Energy 3.3 kWh/load Consumables (detergent) 0.0024 kg/load

3.4 Crew Metabolic Rate The metabolic load will affect air revitalization, food use, and heat production directly, and to a lesser extent will affect water use, waste production, and other functions. Lane, et al. (1996) give energy requirements as shown in Table 3.4.8. The average metabolic rate for a 70 kg crew member is given, based on this data, as 11,720 kJ/d as provided by Hall and Vodovotz (1999). Actual metabolic rate will vary with body size, sex, environment, and level of physical activity. Thus, a 95th percentile US male per NASA STD 3000 will have a body mass of 98.5 kg, compared to a 5th percentile Japanese female with a mass of 41 kg. Metabolism will be increased by physical exertion, and a heavy workload can reach more than 800 W. Few people can continue this level of exertion for long, and the total energy expenditure for an exceptionally active 70 kg male could be as high as 18 MJ/day. (Metabolic data from Muller and Tobin, 1980.) Thus, extravehicular activity (EVA) and exercise protocols can elevate metabolic rate. This data does not account for any metabolic effects due to low gravity. Data given in following sections are scaled for low and high levels of activity and for small and large people.

Table 3.4.8 Human Metabolic Rates

Gender Age [y] Metabolic Rate 14 [kJ/d] Male 18 – 30 1.7 (64.09•m + 2,844) 30 – 60 1.7 (48.59•m + 3,682) Female 18 – 30 1.6 (61.58•m + 2,278) 30 – 60 1.6 (36.44•m + 3,473)

3.5 Crew Time Options Crew time is an important commodity on any human mission. In fact, wise usage of the crew’s time is at the core of all exploration in which human beings take part. Historically, crew time for life support functions has been limited to monitoring equipment and infrequently replacing expendables. Support for plant systems, however, could easily consume a substantial fraction of the crew’s time if designed with inadequate automation. The information here is meant to outline the time available to a crew member during a standard work week. Hoffman and Kaplan (1997) propose a generic schedule and identify three phases in each

13 From Lunsford and Grounds (1993) with updates from material presented at Systems Workshop (1998). This information is based on the laundry originally under development for ISS. 14 The metabolic rate is the product of a basal rate and an activity factor. The basal rate, in parentheses, depends on crew mass [kg], m, and a second, weight-independent coefficient. The activity factor is gender-dependent while the other coefficients are both gender and age dependent.

9 Baseline Values and Assumptions Document, JSC 39317 June 1999 nominal crew day. These phases are personal time, overhead time, and production time. More specifically, the schedule is presented in Table 3.5.9.

Table 3.5.9 Mars Surface Mission Time Allocation for a Nominal Crew Day 15 Time Total Time Phase Activities [ch] [ch] Sleep, Sleep Preparation, Dress, Undress 8 Hygiene, Cleaning, Personal Communication 1 Personal Recreation, Exercise, Relaxation 1 14 One Day Off Per Week 3 Eating, Meal Preparation, Clean-up 1 Group Socialization, Meetings, Life Sciences, Health 1 Monitoring, Health Care Overhead Planning, Reporting, Documentation, Earth Communication 1 3 System Monitoring, Inspection Calibration, Maintenance, Repair 1 Production Exploration, Sample Collection, Analysis 7 7

The values in Table 3.5.9 are approximations. Individuals may use more or less time for each task listed, but on average, each person will have about 14 ch/d of personal time, 3 ch/d of overhead time, and provide 7 ch/d of production time. From the perspective of advanced life support system modeling and analysis, the crew time is that period each day which could be used to maintain, repair, and support life support functions. It is assumed that a portion of the crew day will be personal time which is not available to maintain the life support system. The other portion of the day will be allotted to mission activities and overhead. This latter segment, called mission production in Table 3.5.10, includes time to maintain the life support system. As life support here includes providing food, any time associated with food preparation, consumption, or clean-up should be included under mission production. Likewise, so should time devoted to laundry because clothing is also included under life support.

Table 3.5.10 Crew Time Allocation for Analysis Time Total Time Phase Activities [ch] [ch] Sleep, Sleep Preparation, Dress, Undress 8 Hygiene, Cleaning, Personal Communication 1 Personal Recreation, Exercise, Relaxation 1 14 One Day Off Per Week 3 Group Socialization, Meetings, Life Sciences, Health 1 Monitoring, Health Care Eating, Meal Preparation, Clean-up 1

Mission Planning, Reporting, Documentation, Earth Communication 1 10 Production System Monitoring, Inspection Calibration, Maintenance, Repair 1 Exploration, Sample Collection, Analysis 7 Total 24 24

15 From Hoffman and Kaplan (1997). Note: Time estimates are averaged over a nominal week and then reported on a daily basis per person.

Therefore, excluding time devoted to personal activities, each crew member has roughly 10 ch/d available, or about 70 ch/wk. Hoffman and Kaplan (1997) propose crew members will be allotted five weeks off during an 86 week stay on the surface of Mars. This is equivalent to about three weeks per every 52 weeks. Thus, averaging vacation time over the entire stay on the surface, crew members will have about 66 ch/wk available. On orbit, health care and/or exercising during long-term missions will probably use more time than the values assumed above for a planetary environment. As such, available crew time in microgravity will probably be an hour less per day, or 9 ch/d (63 ch/wk) or 59 ch/wk assuming three weeks of vacation are allotted every 52 weeks.

Table 3.5.11 Crew Time per Person per Week Assumptions [ch/wk] Mission Phase Source lower nominal upper 16 Transit/Microgravity 50 59 70 Estimated Surface/Hypogravity 50 66 77 Hoffman & Kaplan (1997)

To assess the cost associated with adding an operation which requires crew intervention, a crew time mass penalty is computed by dividing the total per capita life support mass by the crew time which is not devoted to personal activities. This penalty may be applied to determine the ESM associated with crew operations. Typical values might vary between 0.1 kg/ch and 10 kg/ch. Two philosophies are commonly employed by researchers to compute a crew-time-mass-penalty (CTMP). The first assumes that each hour of crew time which is required by the life support systems is equally valuable. The second, as forwarded by Vaccari and Levri (1999), assumes that each additional hour of time required by the life support system is more valuable than the previous hour. The first approach is consistent with the philosophy adopted to compute the other mass-equivalencies (See Section 3.8), while the second tends to penalize a life support system architecture which makes large demands on crew-time. In short, the second philosophy favors greater automation, especially for biomass production on site. Assuming each hour of crew-time is equally valuable, the CTMP is computed by dividing the life support system mass, excluding crew time, by the total available crew time which is not devoted to personal activities. This value is fixed once the crew time and life support system mass are determined. It does not depend on the crew-time required to service and maintain the life support system. Assuming each hour of crew-time is more valuable than the previous hours of crew time, Vaccari and Levri (1999) present an alternate formulation to account for crew-time. They define the following terms:

Symbol Units Physical Meaning

ESMw/o ch [kg] Equivalent system mass (ESM) for the life support system without accounting for crew-time.

ESMLSS [kg] Component of life support ESM to support crew-time involved in life support.

ESMTotal [kg] Total life support system ESM; ESMw/o ch + ESMLSS.

tLSS [ch/wk] Crew-time spent on the life support system.

tMP [ch/wk] Total crew-time per week not devoted to personal activities, or mission production crew time.

tMP-LSS [ch/wk] Crew-time per week not devoted to the life support system or to personal activities; tMP - tLSS.

16 The listed upper limit for crew time per week is seven hours above the values discussed in the text. Firm upper limits are not currently known.

Vaccari and Levri (1999) then assume that the overall ESM of the life support system, including the crew-time, is proportional to the total mission production time as the ESM of the life support system without crew-time is proportional to mission production time less the time for life support, or:

ESM ESMTotal  w/ o ch tMP tMPLSS

Or, the overall ESM of the life support system is:

tMP ESMTotal  ESM w/ o ch   tMPLSS

Using this approach, as crew-time for life support increases, the crew-time per week not devoted to life support or to personal activities, tMP-LSS, decreases, and the overall ESM for the life support system increases in a highly non-linear manner. In fact, as tMP-LSS approaches zero, the overall ESM for the life support system approaches infinity.

3.6 Food System Options

3.6.1 Flight System Options Food, like clothing, is not traditionally part of life support, but has significant impacts on the cost of crew support. In particular, if food is grown locally, some air and water will be regenerated. If more than about 25% of the food is produced locally, all the required water can be regenerated by the same process. If approximately 50% or more of the food is produced locally, all the required air can be regenerated by the same process (Drysdale, et al., 1997). This latter number does, however, depend on the cropping scenario used and the overall harvest index. The food energy requirement of the crew will depend on the crew themselves, their lean body mass in particular, and the amount of physical work they are required to perform. Extravehicular activity (EVA), for example, requires additional food compared with crews conducting only intravehicular activities (IVA) because more physical work is typically associated with an EVA. This document assumes an average body mass of 70 kg, and a caloric requirement of 11.720 MJ/person day (Hall and Vodovotz, 1999). The mass of food required depends heavily on the lipid content and the degree of hydration. A 30% lipid content is generally recommended, by calories, though much lower levels of lipids have been suggested by some sources. Degree of hydration is largely a function of the type of food, and the method of storage. Fresh foods can have as much as 95% water content, while dry grains can be as low as 12%. Food quality is not addressed here, as SMAP does not have the necessary expertise and this is generally addressed in designing food systems. However, it is recognized that food quality can have a tremendous effect on the morale of a crew and the success of a long duration mission. The mass of food can also depend on the quality of the food, with more mass of protein required if it is of inferior quality, for example. Digestibility will vary, being lowest for vegetarian diets. Besides the mass of food itself, food requires packaging to protect it from degradation and contamination. This packaging includes wrapping the food itself (into individual servings, for example), stowage (e.g., within lockers), and provision of a suitable atmosphere, temperature (e.g., freezers for some foods) and other environmental conditions, and secondary structure to house the stowage and environmentally conditioned chambers. In total, these can easily add up to a mass factor of 100% of the original food mass for packaging and stowage. Historically packaging masses are available for two applicable food systems. Bourland (1999) reports an empty locker for food abroad Shuttle has a mass of 6.4 kg. Filled, this locker holds 36 to 40 individual meals for an overall mass of 24.5 kg. The Shuttle food system is a shelf-stable without any frozen components. The ISS thermoelectric freezer, which can hold 295 kg of packaged food, has the following characteristics:

Table 3.6.12 ISS Thermoelectric Freezer Properties 17 Crew Internal Mass Volume Power Time Logistics Volume [kg] [m³] [kW] [ch/y] [kg/y] [m³] ISS Thermoelectric Freezer 321 TBD 0.265 TBD TBD 0.654

The thermodynamic coefficient of performance (COP) for this unit is 0.5. The listed mass is the freezer alone, excluding any secondary structure mass, while the internal volume is the freezer drawer capacity. More generally, properties for frozen food storage on a per frozen food mass (ffm) basis are provided in Table 3.6.13. The ISS thermoelectric freezer provides values for the cases as noted.

Table 3.6.13 Food Cold Storage Options on a Property per Frozen Food Mass Basis 18

Assumptions Characteristic Units low nominal high comments 1/COP 0.5 0.66 2.0 19 Mass kg TBD 321 Error: Reference source not found

kg/kg ffm 1.28 Volume m³ TBD

m³/kg ffm Power kW 0.066 0.088 0.265 Error: Reference source not found

kW/kg ffm 0.00026 0.00035 0.00106 Cooling kW 0.066 0.088 0.265 Error: Reference source not found

kW/kg ffm 0.00026 0.00035 0.00106 Crew Time 0.0 TBD

ch/(y•kg ffm) Logistics kg/y 0.0 TBD

kg/(y•kg ffm)

Energy and packaging requirements will be technology specific. Crew time requirements will depend on the form in which food is shipped and its preparation requirements. Crew time required for food preparation during Space Transportation System (STS, or Shuttle) missions is 45 – 90 minutes per day for a crew of up to six (Lane, 1999). This approach uses individually packaged servings. Better cooking facilities would allow better quality food, with consequent morale advantages, but would take more resources and time.

17 From Ewert (1999). 18 From Ewert (1999). 19 Value associated with the ISS thermoelectric freezer unit.

Hunter (1999) provides another estimate of crew-time for food preparation. Hunter’s model assumes that each crewmember eats ten different food dishes per day. For a crew of six, each dish prepared using ingredients provided by bioregenerative methods requires 15 to 45 minutes each, while each dish taken from resupplied stocks requires an average of 6 minutes to prepare based on Lane (1999). Assuming that meals prepared using bioregenerative methods each require 30 minutes on average to prepare, a diet based on crops grown on-site would require 5.0 ch/d or 0.83 ch/cd assuming a crew of six. Daily meals prepared completely from resupplied foods would require 1.0 ch/d or 0.17 ch/cd. Assuming five dishes are prepared from crops grown on site and five dishes are prepared from resupplied stocks, daily meal preparation time would be 3.0 ch/d or 0.50 ch/cd. Kloeris, et al. (1998) report meal preparation time during the Lunar Mars Life Support Test Program (LMLSTP) Phase III test while using the 10-day BIO-Plex menu averaged 9 ch/d. Wastage will depend on the type of food and the type of preparation, but can be quite large. For example, during the 10-day BIO-Plex menu test conducted during the LMLSTP Phase III, total waste (including preparation, plate waste, and unused left-over food) was 42% (Kloeris, et al. ,1998). Typical values from the literature for food-related masses are shown in Table 3.6.14. However, the food mass values do not reflect as great a range as is shown in Table 3.2.2, which would require a range of 0.31 to 1.51 kg of food per person day.

Table 3.6.14 Food Quantity and Packaging 20

Assumptions Parameter lower nominal upper Source IVA (dw) 21 [kg/cd] 0.54 Lange and Lin (1998) 0.674 Bourland (1998) IVA Human Metabolic 0.335 derived, Lange and Lin (1998) Water Production [kg/cd] IVA [MJ/cd] 11.72 22 Hall and Vodovotz (1999) EVA added 23 [kg/ch] + 0.026 derived, Lange and Lin (1998) EVA added Error: + 0.016 derived, Lange and Lin (1998) Reference source not found Metabolic Water Production [kg/ch] EVA added Error: + 0.563 Lange and Lin (1998) Reference source not found [MJ/ch] Packaging 24 [kg/kg] 100% Hanford (1997a) Crew time [ch/d] 1 Lane (1999), from Shuttle 3 Hunter (1999); See above 9 Kloeris, et al. (1998) from LMLSTP Ph III

20 The listed food values are “as shipped” and before additional of any hydration fluid (water). 21 On a dry weight (dw) basis. 22 The value here is consistent with the diets presented in Section 3.6.2. 23 EVA requirements are in addition to any IVA requirements. 24 Packaging accounts for individual food packages, trays, food storage lockers, and other associated secondary structure.

Table 3.6.15 Historical/Near-Term Food Masses 25 Mass Volume Water Parameter [kg/cd] [m³/cd] Comments Content IVA Food, dw 0.674 0% STS Food 26 0.8 0.002558 Dehydrated 20% 1.818 0.004045 Packaged, with Water Content 0.227 Packaging Alone 1.591 Fresh Weight, No Packaging 58% ISS Food 27 2.3 0.006570 Packaged, with Water Content 1.955 Fresh Weight, No Packaging 66%

3.6.2 Food System Options Based on Biomass Production Systems Currently the ALS Program assumes that crops within a biomass production chamber will be grown and harvested on a bulk basis, rather than quasi-continuously. This assumption is designed to minimize crew time requirements by making crew activities more efficient, and may be revisited when more data is available. Two diets are presented below which assume differing availability of crops grown on-site. In both cases, the menus are designed to be used as a unit in order to maintain nutritional integrity. However, minor changes might include moving small amounts of crops from the list to be grown and into the resupplied mass, especially for those items like rice which are consumed as grown. Both diets are comparable in quality and acceptability to the International Space Station Assembly Complete food system.

25 From Bourland (1998) and Vodovotz (1999). 26 STS food systems are provided for reference only. They do not meet nutritional requirements for long-duration space flight. (For example, while this diet meets all minimum nutritional requirements, it exceeds the limit for sodium and iron for a microgravity diet.) This food system does not use any refrigeration. 27 International Space Station Assembly Complete food system. This food is provided as 50% frozen products. For a 540 cd (six crew for 90 d) food supply, 1.84 m³ of refrigerated storage is required.

The ALS Program defines a 20-day crew diet using crops specified as shown in Table 3.6.16. The edible masses of the main crops as harvested to support the 20-day diet are calculated per crew-day and for a crew of six people for a 20-day period. This menu averages roughly 11.72 MJ/cd, uses a wide variety of crops, and provides a high degree of closure. With respect to closure, the majority of the resupplied mass is oil which is necessary for nutritional purposes but is not produced efficiently from higher crops.

Table 3.6.16 20-Day Diet Using All Crops 28

Average Menu Consumption Consumption 29 Crop [kg/cd] [kg] Soybean 0.086 10.4 Wheat 0.24 28.8 White Potato 0.20 24.2 Sweet Potato 0.20 23.7 Rice 0.029 3.5 Peanut 0.013 1.5 Tomato 0.22 26.6 Carrot 0.041 5.0 Cabbage 0.0038 0.5 Lettuce 0.024 2.9 Dry Bean 0.013 1.5 Celery 0.013 1.5 Green Onion 0.048 5.7 Strawberry 0.016 2.0 Peppers 0.049 5.9 Pea 0.0075 0.9 Mushroom 0.0011 0.1 Snap Bean 0.010 1.2 Spinach 0.040 4.8 Crop Sub Total 1.25 150.7 Water 30 2.20 263.3 Resupplied Food Stuffs 31 0.37 44.6 Total 3.82 458.6

28 From Hall and Vodovotz (1999). 29 Basis: Six crew over twenty days. 30 Water for hydration, cooking, and food preparation only. Water for clean-up is not included. Water tankage is not included. 31 Oil is included as resupply. No frozen or refrigerated foods are assumed for this calculation. Packaging is not included. Resupplied food is about 20 percent moisture by mass.

A second 20-day crew diet is presented in Table 3.6.17. Again the edible masses of the main crops as harvested to support the 20-day diet are calculated per crew-day for a crew of six people for a 20- day period. This menu also averages 11.72 MJ/cd. Unlike the previous formulation, this diet grows only salad and carbohydrate crops on-site because they are the most efficient of the higher plants considered here. Most protein is resupplied primarily in the form of shelf-stable meat for this diet.

Table 3.6.17 20-Day Diet Using Salad and Carbohydrate Crops Error: Reference source not found

Average Menu Consumption Consumption Err Crop [kg/cd] or: Reference source not found [kg] Soybean n/a n/a Wheat 0.22 25.8 White Potato 0.17 19.8 Sweet Potato 0.18 21.5 Rice n/a n/a Peanut n/a n/a Tomato 0.21 24.6 Carrot 0.040 4.8 Cabbage 0.0025 0.3 Lettuce 0.021 2.6 Dry Bean 0.013 1.5 Celery 0.0075 0.9 Green Onion 0.034 4.1 Strawberry n/a n/a Peppers 0.031 3.8 Pea 0.0038 0.5 Mushroom 0.0013 0.2 Snap Bean 0.010 1.2 Spinach 0.040 4.8 Crop Sub Total 1.0 116.4 Water Error: Reference 2.1 253.7 source not found Resupplied Food Stuffs 32 0.5 57.5 Total 3.6 427.6

3.7 Food Processing Options Food processing takes the edible biomass produced by plant crops, either fresh or as prepared for storage, and produces food products such as pasta and flour. These food products may be stored or used immediately, together with ingredients supplied from the Earth (or, for the BIO-Plex, from outside the facility), and prepared to provide food.

32 Oil is included as resupply. No frozen or refrigerated foods are assumed for this calculation. Packaging is not included. Resupplied food is about 40 percent moisture by mass. Resupplied food includes meat.

BIO-Plex planning assumes that crops will be grown and processed on a bulk basis. Hunter and Drysdale (1996) estimated the equipment mass to perform food processing for a crew of four to be about 655 kg. However this is a very preliminary estimate.

3.8 Infrastructure Costs/Equivalencies Infrastructure costs (mass, volume, power, thermal control, and crew time, for example), are key factors in trade studies. It is far easier to decide on reasonable figures for these parameters before the study than try to objectively determine them at the end of the study. The mass factor reflects the different penalties associated with placing mass on the different segments of the mission. They are given relative to the cost in LEO, which is assigned a value of unity. This measure is quite specific to both the mission and the propulsion technology. The penalties provided below in Table 3.8.18 are estimated assuming nuclear thermal propulsion. Chemical propulsion would be significantly worse. Other options, such as solar thermal propulsion, might be similar. Advanced options, such as ion propulsion, could be significantly better. Infrastructure costs can vary according to the mission environments, such as the environmental temperature for thermal control devices, the technologies used, the mission duration, and other factors. For example, transit segments require a different volume equivalency because more shielding is required in transit, where the radiation environment is more severe, and where there is no convenient local source of shielding materials. On a planetary surface, the local atmosphere, if any, and the surface regolith may be used as radiation shielding. Selection of power systems for a near-term mission to Mars is an important issue with numerous political overtones. However, from an engineering perspective, nuclear propulsion and nuclear power for the surface may be essential to provide the required power at an acceptable cost. Solar propulsion would require very large and massive arrays, perhaps too large to be practical for the outer solar system. Solar power on Mars would also require very large arrays to provide adequate power during dust storms (Drake, 1998), and these would be costly and hard to keep clear of dust. Further, solar power generation would be much worse for sites located away from the equator. The nuclear power options presented in Table 3.8.18 and Table 3.8.19 below are based on technology developed for the SP100 program which should be typical of this approach.

Table 3.8.18 Mars Mission Infrastructure Cost Options Assumptions Parameter lower nominal upper Source Equivalencies (Transit) Mass Factor 3.6 (outbound) TBD 9.7 (return) Estimated Volume [kg/m3] 16.1 33 16.1 Error: 66.7 34 Drysdale (1998b) Reference source not found Power [kg/kW] 83.3 35 Drysdale (1998b) Thermal Control [kg/kW] 17.5 21.1 26.3 Drysdale (1998b) Equivalencies (Surface) Mass Factor 3 Volume [kg/m3] 2.08 36 2.08 Error: 66.7 Error: Drysdale (1998b) Reference source Reference not found source not found Power [kg/kW] 54 87 37 226 See Table 3.8.19 Thermal Control [kg/kW] 58.8 66.7 76.9 Drysdale (1998b)

Table 3.8.19 Mars Advanced Mission Power Cost Options 38 Power Cost Options (Surface) kg/kW(e) kW/kg Comments Solar Photovoltaic Power Generation with 175 0.0057 Spring; Northern Hemisphere at Regenerative Fuel Cell Power Storage the Equator Nuclear Reactor on a Mobile Cart with Shielding 226 0.0044 1 km from Base; SP100 Program Nuclear Reactor on Lander with Shielding 87 0.011 1 km from Base; SP100 Program Nuclear Reactor Emplaced in Excavated Hole 54 0.019 1 km from Base; SP100 Program; Excavation Equipment is Included. Nuclear Reactor Emplaced in Excavated Hole 29 0.035 1 km from Base; SP100 Program; Excavation Equipment is Included; Assumed to Generate 1 MW(e).

The issue to use nuclear power systems to support spaceflight is highly political. While power systems based on nuclear reactors offer the most economical performance, compared to other currently available technologies, especially for systems designed to generate a megawatt or more, under some mission scenarios only non-nuclear power options are permitted. In such situations, the values associated

33 This value is associated with an inflatable module (TransHab) with radiation shielding. 34 This value is associated with an International Space Station Standard Module. 35 This value assumes power generation in space using solar activated photovoltaic cells. 36 This value is associated with an inflatable module (TransHab) without radiation shielding. The planetary atmosphere and the planet itself provide the necessary radiation shielding. Regolith in bags can be used for additional shielding if necessary. 37 This value assumes nuclear power generation. The reactor arrives on an independent lander one kilometer from the base. 38 The systems used to develop these infrastructure estimates assume generation of 100 kW(electric) of user power continuously. Thus, for scenarios which will use one or more 100 kW(e) systems, these values are appropriate. Systems which deliver considerably less power will generally have higher power-mass-penalty values, while very large systems, such as a 1 MW nuclear power system will have a lower power-mass-penalty. References: Cataldo (1998) and Hanford and Ewert (1996).

19 Baseline Values and Assumptions Document, JSC 39317 June 1999 with solar photovoltaic power generation with regenerative fuel cells for energy storage should be used instead of the nominal value listed in Table 3.8.18. Estimates for thermal control systems assume lightweight, inflatable radiators for heat rejection (Lin, 1997b). Where possible, heat loads are cold-plated to allow heat to transfer directly to the thermal working fluid. For transit vehicles, body-mounted radiators would be used to eliminate or minimize any deployment mechanism mass. For surface applications, body-mounted radiators or deployed systems may be used. Life support equipment requires crew time for operations and maintenance. This time can be small for some systems and large for others. Notably for functions related to food – producing it, preparing food products, and preparing meals – the crew time may be very large. The cost of crew time must be derived from the life support system ESM and the crew time available. Typical equivalencies vary from about 0.1 to 10 crew-hours per kg of ESM. Section 3.5 provides additional details. Pressurized volume is important for the crew and for bioregenerative systems. Currently the United States uses the ISS common module to provide pressurized volume. However, this design is both more massive and more costly than it needs to be for some other uses. Inflatable modules have been suggested since the Apollo Program. TransHab is a robust inflatable, providing protection from micrometeoroids. Less substantial inflatable modules could be used on the surface, where regolith could be used for meteoroid shielding, or within caverns. Additional mass would be needed to provide radiation shielding for TransHab during transit. The baseline version of the radiation shielding is to provide a 0.19-m thick water tank around the crew sleeping quarters for protection in the event of a solar flare. This substantially increases the mass, but the volume equivalency is still lower than, for example, the ISS module (and that would require added shielding also). Leakage is technology dependent. The specification for ISS modules is 83 kg leakage per module per year (0.18% per day), but tests have shown that the actual leakage rate is significantly lower than this specification (Boeing, 199X).

Table 3.8.20 Cost of Pressurized Volume Options Assumptions Technology/Approach Units lower nominal upper Source ISS Module (shell only) kg/m3 63.0 Hanford (1997a), p. 11 TransHab kg/m3 2.078 39 16.08 40 28.25 41 Schneider (No Date)

Table 3.8.21 Masses of TransHab Shell Components Mass Item [kg] Assumed Shielding is 0.19 m of Water, Over 35 m2 Surface Area 42 6,650 Shielding Mass Rounded up to Account for Tankage 7,000 Primary Structure Mass (Core, Airlock, Shell) 1,039 Primary Structure and Shielding Mass 8,039 Total Mass (Including Secondary Structure and Systems) 14,118

39 Estimate based on only TransHab Primary Structure mass. Habitats sited on a planetary surface might use regolith in bags or a cavern for radiation shielding and so do not require dedicated shielding from Earth. Appropriate equipment may be required to construct such shielding, but the associated mass should be considerably less than the mass of shielding brought from Earth. The radiation environment on the surface of Mars, however, is not well-characterized yet, so the nature and thickness of any habitat shielding is not known. 40 Estimate based on TransHab Primary Structure plus Shielding mass. 41 Estimate based on complete TransHab module mass. 42 Some shielding might be provided by stores and/or systems.

3.9 In Situ Resource Utilization Options Significant quantities of local resources are available at Mars that can be used for life support. Sridhar, et al. (1998) identified some resources that might be needed. (See Table 3.9.22) Drysdale (1998a) estimated very roughly the masses required for each resource and the cost leverage that seemed credible from in situ resource utilization (ISRU) based on data from John Finn (NASA Ames Research Center). (See Table 3.9.24) Regolith may be used for radiation and meteoroid protection at a long-term base, and would be available for the cost of moving it and bagging it. Water would be a high leverage item, particularly if bioregeneration is used extensively. It could be available from the atmosphere, despite its dryness, from permafrost that is expected to be extensive a meter or two below the surface, from polar ice, or from subsurface water or ice deposits. It could also be made from atmospheric carbon dioxide, if a source of hydrogen is available. Even if hydrogen had to be shipped from Earth, this would still give a 5 to 1 cost advantage. The cost of acquisition would depend on the cost of extraction and purification. Currently, the abundance and location of water on Mars is undetermined. The atmosphere of Mars carries water vapor, but in minimal quantities. Likewise, large deposits of water exist at both Martian poles, but accessing that water is complicated by the seasonal deposition of frozen carbon dioxide on top of the ice deposits. Atmospheric carbon dioxide could support plant growth, particularly if a plant growth unit is set up and started remotely. It could be readily extracted from the atmosphere, which is 95% carbon dioxide, though at a low pressure. An inert gas would be needed to dilute the cabin oxygen, assuming the base air would not be pure oxygen. This could be extracted from the atmosphere by removing the carbon dioxide and water vapor. Finally, oxygen, for crew respiration, can be obtained from the atmosphere, either by removing the rest of the gases, or by reaction with the atmospheric carbon dioxide using either a Sabatier/electrolysis or zirconia cell reaction. The DRM (Hoffman and Kaplan, 1997) proposes to use local resources to make rocket propellant, liquid methane and liquid oxygen, for the Mars ascent vehicle from the Martian atmosphere. While oxygen is available as a product from splitting carbon dioxide, methane production requires a source of hydrogen. Water provides a readily used source of hydrogen, but as addressed above, it may not be readily available. The DRM avoids the issue of water availability by providing liquid hydrogen from Earth for ISRU propellant production. Similar propellants could be used for power storage, including propelling surface or aerial vehicles, especially if a local source of water is available. In addition, the same chemical processing plant could be used to make life support commodities, such as listed below in Table 3.9.24. Some of these, inert gases, for example, might be made available as by-products at minimal added cost. Note that shipped commodities will have a negative cost leverage to account for packaging. This can be a significant mass factor, as shown in Table 3.2.5 for permanent gases. This is in addition to any cost factor for the shipping location as identified in Table 3.8.18.

Table 3.9.22 Nitrogen Gas Losses Associated with ISS Technology 43

Mass Parameter [kg/y] Comments Nitrogen Resupplied 796 ISS Module Leakage 18 to 44 Airlock Losses 10% mass of nitrogen lost per cycle is 1 kg

43 From Sridhar, et al. (1998).

Table 3.9.23 Nitrogen Gas Losses for the Mars DRM (One Mission) Using ISS Technologies Error: Reference source not found

Mission Mass per Total Mass Lost Phase Event [kg] Event [kg] Calculation Basis Transit Module Leakage 0.1 day 26 260 days transit; both ways Surface Airlock Usage 1 cycle 1,200 2 cycles/day for 619 days Surface Module Leakage 0.1 day 62 619 days Total 1,288 Gas Mass Excluding Tanks

Table 3.9.24 Estimation of Cost Leverages from ISRU Options 44 Requirement Cost Comments / Assumptions Commodity [kg] Leverage Likelihood 45 Regolith 620,000 3,100 Assumes a Rover is Available Always Water 12,000 310 From Local Permafrost Unknown to Unlikely Water 12,000 390 From Local Atmosphere Unlikely Water 12,000 5 Produced Using Hydrogen from Earth Always Carbon Dioxide 528 47 For 30 days of Plant Growth; Using Local Always Atmosphere Inert Gas 508 1.6 From Local Atmosphere Always (Argon/Nitrogen) Oxygen 121 19 From Electrolysis of Local Water Unknown to Unlikely Hydrogen system 1.2 From Electrolysis of Local Water Depends on water dependent availability

3.10Plant Growth Chamber Options Plants offer the greatest opportunity for self-sufficiency and possibly cost reduction for long duration missions, but at the same time have some of the greatest unknowns. An attempt has been made to estimate the mass of a plant growth system on the surface of Mars. Two uncertainties are the cost of power, and the availability of water locally. The initial assumption, as shown in Table 3.10.25, is that natural lighting cannot be used, because Mars is farther from the sun than the Earth, significant quantities of dust are always in the atmosphere, and global dust storms occur almost every Martian spring that last for as long as 100 days during which the light levels are reduced by several orders of magnitude. However, these assessments assume water is readily available from local sources. In addition, fresh food is crucial to crew welfare, and can only be produced by growing plants. Fresh foods would be significantly heavier than dehydrated foods which could be shipped due to the water content. Thus, while plants will probably be grown on Mars, the question is what proportion of the food will be grown locally versus what proportion will be shipped.

44 From Drysdale (1998a) using data from J. Finn (NASA/Ames Research Center). These estimates are very preliminary. 45 Likelihood assesses how likely a particular commodity might be available based on current knowledge of Mars for a typical site. Assessment scale: “Always” implies availability at all sites. “Likely” implies availability at most sites in unlimited quantities. “Unlikely” implies availability at some sites in unlimited quantities, or available at most sites in limited quantities. “Unknown” implies unknown availability.

Table 3.10.25 Lighting Data 46

Parameter [Units] low nominal 47 high Comments

Light Conversion Efficiency [Wradiation/Welectrical] 0.18 0.3 0.5 proportion of lighting system power turned into PPF

Light Delivery Efficiency [PPFdelivered/PPFemitted] 0.3 0.37 0.7 proportion of PPF at lamp surface delivered to canopy Overall Light Delivery Efficiency 0.11 Overall Light Delivery Efficiency [µmol/(m²•J)] 3.8 different format from above

3.10.1 Lighting Assumptions A key parameter for plant growth is lighting, and this might be provided by electrical lighting. The efficiency of electrical lighting depends on the efficiency of the conversion of electricity into radiant energy, and the direction of this energy onto the canopy. The conversion efficiency depends on the type of lamp, and must be considered for photosynthetically active radiation (PAR). Photosynthetic photon flux (PPF) is the light absorbed by the plants and used for photosynthesis, and is similar in extent to visible light, but has a different graph of absorption versus wavelength, peaking in the red and blue rather than in the yellow. Incandescent lamps are good in that they are red-rich, but the conversion efficiency is low. High pressure discharge lamps produce more light, but the spectrum is not as good photosynthetically. New lamp types, such as microwave lamps, have good efficiency and spectrum (Sager, 1999). Direction of the energy to the canopy depends on the geometry of the lamp, the distance from the lamp to the canopy, and the quality of the reflectors. The Biomass Production Chamber (BPC) at Kennedy Space Center used relatively unsophisticated reflectors, and only achieved a rating of about 30%. Much higher ratings can be achieved, but it is difficult to maintain these high ratings over long periods of time.

46 Data from Sager (1999). 47 Values from Lighting Test Stand at JSC (Ewert, 1998).

3.10.2 Other Lighting Data Additional assumptions can be made about specific lighting systems. Data for high pressure sodium lights (HPS) are shown below.

Table 3.10.26 High Pressure Sodium Lighting Data 48

Units low nominal high Lamp Power (not including ballast) kW 0.4 49 Lamp Mass kg 0.21 Error: Reference source not found Lamp Life h 20,000 24,000 Number of Lamps per Area to Give 1,000 mol/(m²•s) 1.98 50 TBD 5.56 51 Crew Time to Change Out Lamps ch 0.03 52 Hours of Lighting Usage per Day 10 24 Lamp Volume for Resupply m³ 0.000625 Ballast Power kW/lamp 0.03 0.06 Error: 0.08 Reference source not found Ballast Mass kg/lamp 4.76 TBD 9.52 Error : Reference source not found Ballast Life h TBD 20,000 Mass of Coldplate, Water Barrier, Condensing Heat kg/m² 4.43 54 7.02 55 25.83 56 Exchangers per Growing Area 53 Height of Lighting Assembly m 0.15 57 0.3 Lamp Resupply Mass Factor 1.5 Lamp Resupply Volume Factor 1.5

Resupply mass and volume factor account for the extra mass and volume required to package replacement lamps.

48 Data from or via A. Drysdale (The Boeing Company/Kennedy Space Center), except as noted. 49 From Hanford (1997a). 50 Data from J. Sager (NASA/Kennedy Space Center) using the BPC. 51 This is a calculated value assuming high efficiency lamps. 52 This value is a rough approximation from J. Hunter (Cornell) 53 From Ewert (1998). 54 This system uses only a bulb in a water jacket. Transmissivity, relative to the baseline case using a coldplate and no barrier, is 0.92. Note: This configuration provided the best overall performance in testing. 55 This system uses a bulb in a water jacket with a Teflon barrier. Transmissivity, relative to the baseline case using a coldplate and no barrier, is 0.846. 56 This system uses a coldplate with a glass barrier. Transmissivity, relative to the baseline case using a coldplate and no barrier, is 0.89. 57 From BIO-Plex drawings.

3.10.3 Plant Growth Chamber Cost Factors The cost factors for a plant growth chamber have been estimated on an square-meter basis. This addresses the plant growth chamber itself. If crew access is needed, and it generally will be, provision must be made for that access. A reasonable number might be 25 – 50% of the plant canopy area. Lower numbers might be adequate if extensive physical automation is planned. A higher number might be appropriate if most tasks are expected to be performed manually. Crew access space would not, however, require the equipment and other costs shown here. Crew height will be greater than the height of most plants that have been considered for ALS crops. Layout of the crops and crew space will depend on issues such as the type of plant lighting. Thus, if natural lighting is to be used, only a single layer of crops might be possible due to the diffuseness of light on Mars. In this case, the limiting height would be the taller of the crew and the plants. Table 3.10.27 (Drysdale, 1999) presents preliminary values for an optimized biomass production chamber based on projecting current NASA growth chambers to flight configurations.

Table 3.10.27 Plant Growth Chamber Equivalent System Mass per Growing Area 58 Mass Volume Power Cooling Crew Time Logistics Component [kg/m2] [m3/m2] [kW/m2] [kW/m2] [ch/(y•m2)] [kg/(y•m2)] Crops 20.0 ------13.0 Shoot Zone 3.6 0.67 0.3 0.3 -- -- Root Zone & Nutrients 36.8 0.11 0.14 0.14 TBD TBD Lamps 22.9 0.25 2.1 2.1 0.027 0.57 Ballasts 8.4 TBD 0.075 0.075 0.032 3.24 Mechanization Systems 4.1 TBD TBD TBD TBD TBD Secondary Structure 5.7 ------Total 101.5 1.03 2.6 2.6 13.1 3.81

3.11Plants Plant growth rates depend on the type of plant (species and cultivar) and the growth conditions. Typical growth rates are shown in Table 3.11.28 for candidate ALS Program plants. The growth rate is for edible biomass, in kilograms dry weight per square meter per day. Nominal and upper rates are given. (The lower rate would be zero.) The given upper limit is the highest rate recorded in the literature. These may not be the absolute maxima, however. For example, wheat may well produce higher growth rates with higher light intensities (Bugbee, 1998). These maximal rates are generally for small chambers under ideal conditions, and they might be difficult to achieve in larger chambers which have been optimized for spaceflight. The nominal rates are rates from the ALS Breadboard Facility at Kennedy Space Center. These rates are lower partly because of the lower light levels, but a less homogeneous environment, due to the larger scale, may also impact the growth rates. Plants require somewhat different environmental conditions from the crew. For example, the optimum partial pressure of carbon dioxide for plant growth is 0.120 kPa. The sensitivity may vary from species to species, but plants do appear to have reduced productivity at partial pressures of carbon dioxide that are considered within the normal range for crew (up to about 1.0 kPa). Similarly, plants require higher relative humidity – about 75% – to avoid water stress and minimize nutrient solution usage. Such humidity levels are at the high end for crew comfort. Further, some key plants, such as wheat and potatoes, are most productive at temperatures below the standard crew comfort zone. Finally, some evidence indicates that plants might grow better under atmospheres with partial pressures of oxygen below the values associated with nominal conditions on Earth. However, because humans live with plants on Earth, plants and crew can live in a single air loop. As such, what environmental modifications are cost effective for the plants? In Table 3.11.28, the harvest index is the ratio of edible biomass to total biomass. The growth rate of inedible biomass is also given. Area refers to the growing area devoted to that crop in the third cropping scenario for the BIO-Plex. Total inedible biomass is the mass of inedible biomass per day based on the

58 From Drysdale (1999).

25 Baseline Values and Assumptions Document, JSC 39317 June 1999 inedible growth rate and the crop areas. The rate of inedible biomass production could be important for sizing waste treatment options, as well as for the potential for recovery of resources from inedible biomass. These data are for dry weight. Plant material can be from 10% (dry grains) to 95% (lettuce) water content. In addition, plants contain a variety of minerals comprising about 10% of the biomass (dry weight).

Table 3.11.28 Plant Growth Rates Assumed Total Photosyn- Photo- Growth Rate Harvest Inedible Inedible Growth thetic Photon period [kg edible dw/(m²•d)] Index Biomass Area Biomass Period Flux Error: Length 59 Crop nominal 60 high 61 [kg/kg] [kg/(m²•d)] [m²] [kg/d] [d] Erro Reference [h] r: source not Referen found ce [µmol/(m²•s)] source not found Wheat 0.0177 0.0600 0.4 0.09 25.2 2.268 79 2,080 20 Potato 0.0195 0.0350 0.7 0.015 7.8 0.117 132 725 12 Sweet 0.012 0.0205 0.82 0.0045 7.8 0.035 Potato 62 Tomato TBD 0.0170 0.48 0.018 4 0.074 85 500 Rice TBD 0.0117 0.4 0.018 0 85 1,200 Carrot TBD 0.0100 0.9 0.0011 0 50 350 Peanut Err TBD 0.0090 0.27 0.024 0 104 600 or: Reference source not found Cabbage TBD 0.0090 0.9 0.001 0 29 350 Soybean 0.0057 0.0080 0.4 0.012 41.1 0.493 97 1,000 12 Lettuce 0.0058 0.0071 0.95 0.00037 4 0.001 60 314 16 Chard TBD 0.0050 0.9 0.00056 0 50 350 Total 2.988

Table 3.11.29 shows some details about plant growth with current hydroponic technology, showing light levels, water use, and other details necessary to keep the plants healthy. These growth conditions provided luxuriant nutrient levels. However, lower levels of nutrients might also suffice. The nutrient solution shown was formulated to require only acid addition for pH control. However, alternative formulations might require less active pH control (and thus less acid or base to maintain the pH).

59 From Wheeler, et al. (1994). 60 From Systems Workshop (1998). 61 From Hanford (1997a). 62 From Loretan (1998).

Table 3.11.29 Plant Growth and Support Requirements 63 Units Soy Wheat Potato Lettuce 2 Total Biomass g dw/(m •d) 14.3 35.3 26.4 6.2 PAR mol/(m2•d) 31 67 42 17 Water Usage L/(m2•d) 4.7 4.7 4 2.1 Stock Solution mL/(m2•d) 374 748 573 209 Acid mmol/(m2•d) 12 42 18 6 Water Usage per Dry Mass L/g 0.32 0.13 0.15 0.34 Stock Usage per Dry Mass L/g 0.026 0.021 0.022 0.034

Acid Usage per Dry Mass mmol acid/g 0.87 1.18 0.68 0.98

This data has been compared to the nutrient composition, to calculate masses of minerals required (See Table 3.11.30 and Table 3.11.31)

Table 3.11.30 Mineral Mass Estimates Units Soy Wheat Potato Lettuce Water Usage per Dry Weight g/g 320 130 150 340 Stock Usage per Dry Weight 64 g/g 0.00029 0.000234 0.000245 0.000379 Acid Usage per Dry Weight 65 g/g 0.05481 0.07434 0.04284 0.06174

Table 3.11.31 Ion Estimates Replenishment Concentration Molecular Content Component [mmol/L] Weight Valence g/L (element) g/L (ion) – Nitrate, NO3 75 62.00 -1 1.05 4.65 3– Phosphate, PO4 7.5 94.97 -3 0.6975 2.1375 Potassium, K + 68 39.10 +1 2.652 2.652 Calcium, Ca 2+ 7.5 40.08 +2 0.6 0.6 Magnesium, Mg 2+ 9.8 24.31 +2 0.4704 0.4704 2– Sulfate, SO4 9.8 96.06 -2 0.6272 0.6272 Total 11.1371

3.12Sensor Options Sensors are critical to life support system operation. However, based on current estimates from the ALS Systems Analysis Workshop of March 1998, the mass will not be significant compared to the overall life support system mass.

63 From Wheeler, et al. (1999). 64 1 ℓ of stock solution contains 0.011137 g of solutes. 65 1 mmol of nitric acid (HNO3) contains 0.063 g of solutes.

Table 3.12.32 Sensor Mass Estimates Assumptions [kg] Parameter lower nominal upper Source low tech 221 TBD 680 Jan (1998) high tech 71 TBD 165 Jan (1998) highest tech 39 TBD 106 Jan (1998)

3.13Waste Processing Options Waste tends to be less compact than the stowed item it came from. It can be inert or biologically active. It can be hazardous or not. Shuttle stores most waste for return to Earth. Waste processing for Shuttle does, however, include extensive dumping, particularly of excess water. Waste processing for ISS is planned to depend on storage and return to Earth, either controlled re-entry aboard the Shuttle or burning up in re-entering Progress modules. During transit to Mars, dumping might be acceptable, though waste could also be used for radiation shielding. However, waste dumping on Mars will likely be constrained by an exploration protocol which will require that Mars is not biologically contaminated. Note that both organic materials as well as microbial contamination could pose such a threat to the Martian environment. Waste is a good source of materials for closing the life support loop. In general, extraction of needed materials from waste is likely to be more cost effective than extraction from in-situ resources. However, there may be cases where this is not true. Oxidation of waste is the obvious disposal mechanism in a completely closed space. However, this does require oxygen and produces carbon dioxide. Regenerating this oxygen will require additional processing, whether using physicochemical processes, bioregeneration, and/or ISRU. In a partially closed system, it would be more appropriate to dump excess waste – in an equal mass to the mass of supplied food – if this can be done within other constraints. Table 3.13.33 through Table 3.13.36 present information on several waste disposal technologies.

Table 3.13.33 Bioreactor Options 66

Crew Mineral Feed Solids Time Mass Volume Power Cooling Time Logistics Recovery Solids Degradation System [d] [kg] [m³] [kW] [kW] [ch/y] [kg/y] [kg/kg] [kg/kg] [kg/kg] CSTR 67 8 703 0.6 minor 0.59 3,285 5 85% 2% 50% Rapid Cycle 1 101 0.1 minor 0.25 3,285 5 TBD 2% Bioreactor Composter 68 21 231 0.46 minor 0.59 1,095 1.5 TBD 40% 50% Biofilter 69 22 0.014 minor minor 91 0.05

Bioreactors rely on micro-organisms to degrade waste materials. They typically degrade organic products such as inedible biomass, though feed streams can include processed biomass such as paper also. Bioreactors can operate aerobically. In this mode they require oxygen and produce heat, water vapor, carbon dioxide, and ash. Bioreactors can also operate anaerobically. In this mode they require a source of

66 From Atkinson (1998). Sizing for these systems assumes a feedrate of 1.0 kg (dry weight) per crew member per day of waste which is 10% minerals. The assumed crew size is six. The bioreactors recover 85% of the input minerals on average per pass. Recovery of individual mineral species varies. The sizing parameters and performance noted below are based on current capabilities. 67 The sizing for the Continuous Stirred Tank Reactor (CSTR) assumes the feed contains 2% solids with a retention time between 6 hours and 48 days. 68 The sizing for the Composter assumes the feed contains 40% solids and degrades the solids by 50% on a carbon basis. The composter will pasteurize its product. 69 The biofilter is designed for treating air streams.

28 Baseline Values and Assumptions Document, JSC 39317 June 1999 nitrogen, produce less waste heat, and use no oxygen. However, anaerobic bioreactors produce somewhat toxic organic compounds such as volatile fatty acids, and carbon dioxide. Generally, to work rapidly, bioreactors require satisfactory ratios of carbon to nitrogen. Different approaches have been investigated, including dilute aqueous reactors and composters. Dilute reactors require large volumes of water, and would not be applicable unless water is readily available locally. Bioreactors can extract significant masses of minerals from waste in a form that is compatible for use with growing plants. Different waste materials degrade at different rates. Cellulose typically degrades readily, while lignin is quite resistant to breakdown. The recalcitrant materials can have other uses, such as a planting medium, soil modifier, and for air filtration.

Table 3.13.34 Super Critical Wet Oxidation 70

Crew Mineral Feed Solids Time Mass Volume Power Cooling Time Logistics Recovery Solids Degradation Technology [d] [kg] [m³] [kW] [kW] [ch/y] [kg/y] [kg/kg] [kg/kg] [kg/kg] Existing 500 2.8 2.7 3.7 3 Flight Ready 200 1.4 0.5 1.5 0.2 Theoretical 100 0.57 0 1 0

Table 3.13.35 Incineration Error: Reference source not found Crew Mineral Feed Solids Time Mass Volume Power Cooling Time Logistics Recovery Solids Degradation Technology [d] [kg] [m³] [kW] [kW] [ch/y] [kg/y] [kg/kg] [kg/kg] [kg/kg] Existing 500 5.7 2.7 3.7 3 120 Flight Ready 200 1.4 0.3 1.3 0.2 10 Theoretical 50 0.57 0 1 0 0

Typical physicochemical (PC) approaches also oxidize the waste. Some, such as super critical wet oxidation (SCWO), breakdown the feedstock quite completely, resulting in water vapor, carbon dioxide, nitrogen, and salts. Others are likely to produce toxic materials, such as carbon monoxide and oxides of nitrogen, unless carefully controlled. If organic solids are heated in the absence of oxygen, water is driven off and volatile organic compounds such as methanol are released, leaving a tarry or cindery residue. This approach could be useful in recovering some mass from the waste while leaving the residue biologically inert, but this approach does not completely oxidize the waste.

Table 3.13.36 Dumping

Crew Mineral Feed Solids Time Mass Volume Power Cooling Time Logistics Recovery Solids Degradation Technology [d] [kg] [m³] [kW] [kW] [ch/y] [kg/y] [kg/kg] [kg/kg] [kg/kg] Existing TBD Flight Ready TBD Theoretical TBD

3.14Water Recovery Options Water may not be the most time-critical life support commodity, but it requires processing of the greatest mass of material. Water quality is also of great concern with respect to crew safety. No single technology has proven adequate for water regeneration, and five combinations of technologies are

70 From Fisher (1998).

29 Baseline Values and Assumptions Document, JSC 39317 June 1999 presented below. In the past, power use has driven water regeneration. However, other infrastructure costs also need to be traded against power. Water loop closure is a measure of the completeness of regeneration, and unless the closure approaches 100%, or water is readily available locally, makeup water is a significant system cost. However, total system costs must be considered. The ISS system is quite good at water loop closure, but requires significant resupply: about 1 kg of resupply for every 60 kg of water regenerated (a specific cost – mass processed /ESM – of 60). ALS approaches look much more promising. (See Table 3.14.37)

Table 3.14.37 ALS Water Recovery Equipment Options 71

Percent Crew Water Mass Volume Power Time Logistics Technology Recovery [kg] [m³] [kW] [ch/y] [kg/y] Air Evaporation Subsystem (AES) >99% 45 0.3 1.00 TBD 14 Aqueous Phase Catalytic Oxidation 45 TBD 1.07 TBD 5 Subsystem (APCOS) Biological Water Processor (BWP) 100% 80 TBD 0.30 TBD 55 Milli-Q Post Processor (MilliQ) 11 0.06 0.23 TBD 46 Multifiltration/Volatile Removal Assembly 100% 510 TBD 0.85 TBD 1,660 (MF/VRA) Reverse Osmosis (RO) 85% 50 0.3 0.15 TBD 18 Ultrafiltration/Reverse Osmosis (UF/RO) 91% 90 TBD 0.35 TBD 18 Vapor Compression Distillation (VCD) 91% 128 TBD 0.14 TBD 263

Clearly, the fifth option shown in Table 3.14.38, biological water processor, reverse osmosis, air evaporation, and a Milli-Q post processor, gives the lowest overall cost assuming mass equivalencies on the order of those noted in Table 3.10.27.

Table 3.14.38 ALS Water Recovery System Options 72 Crew Makeup Mass Volume Power Time Logistics Water 73 System [kg] [m³] [kW] [ch/y] [kg/y] [kg/y] VCD+UF/RO+APCOS 263 TBD 1.56 TBD 286 4,663 VCD+UF/RO+MilliQ 229 TBD 0.72 TBD 327 4,663 VCD+MF+VRA 638 TBD 0.99 TBD 1,923 576 BWP+RO+MilliQ 141 TBD 0.68 TBD 119 13,907 BWP+RO+AES+MilliQ 186 TBD 1.68 TBD 133 0

Water can also be regenerated using plants. The quality of the product depends mainly on the system’s construction materials, especially the heat exchangers, condensers, piping, and tankage. Some trace organic compounds may be absorbed from the air, but most of the trace organic compounds released by plants, such as ethylene, are quite insoluble. Relatively minor cleanup suffices to make this water potable. There might be some issues related to microbiology, but ongoing work at Kennedy Space Center has shown that hygiene water can be processed by plants without detectable reduction in productivity or the quality of the product.

71 From Hanford (1998b). Sizing criteria for these pieces of equipment assume six people generating a total of 174 kg/d of waste water. 72 From Hanford (1998b). Sizing criteria for these systems assume six people generating a total of 174 kg/d of waste water for 400 days. Further, this analysis does not address disposal costs for any associated brine streams. 73 Mass of makeup water plus tankage. Tankage mass is based on 46% of the corresponding water mass.

The rate of water production varies tremendously according to the species of plant and the growth environment and stage of development. Reasonable average figures are about 5 ℓ of water per m2 of plant canopy per day, for typical crop plants. This figure can be at least doubled by reducing the humidity and increasing the airflow rate. The rate cannot be reduced appreciably without mineral deficiencies – particularly calcium – appearing in the plants. Calculations have shown that water closure will typically occur with about 25% food closure (Drysdale, et al., 1997).

4 References

Atkinson, C. F. (1998) “Bioreactors,” National Aeronautics and Space Administration, Kennedy Space Center, Florida. Presentation to the Advanced Life Support Systems Analysis Workshop, 26 March 1998. Boeing (199X) “Some Report,” Some Report Number, The Boeing Company, Kennedy Space Center, Florida. Bourland, C. T. (1998) National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. Personal communication, 9 December 1998. Bourland, C. T. (1999) National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. Personal communication, 25 May 1999. Branch, G. (1998) “International Space Station Clothing Subsystem,” National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. Presentation to the Advanced Life Support Systems Analysis Workshop, 27 March 1998. Bugbee, B. (1998) Plants, Soils, and Biometeorology Department, Utah State University, Logan, Utah. Personal communication. Carrasquillo, R. L., Reuter, J. L., and Philistine, C. L. (1997) “Summary of Resources for the ISS ECLSS,” SAE paper 972332, 27th International Conference on Environmental Systems, Society of Automotive Engineers, Warrendale, Pennsylvania. Cataldo, R. L. (1998) “Comparison of Solar Photovoltaic and Nuclear Power Systems for Human Missions to Mars,” Mars Exploration Forum, Lunar and Planetary Institute, Houston, Texas, 4-5 May 1998. Drake, B. G. (1998) “Reference Mission Version 3.0, Addendum to the Human Exploration of Mars: The Reference Mission of the NASA Mars Exploration Study Team,” EX13-98-036, National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. http://exploration.jsc.nasa.gov/explore/addendum/index.htm Drysdale, A. E. (1999) “Biomass Production System – Optimized from State-of-Art,” The Boeing Company, Kennedy Space Center, Florida. Draft presentation for Systems Modeling and Analysis Project management, 7 June 1999. Drysdale, A. E. (1998a) “KSC Systems Analysis,” The Boeing Company, Kennedy Space Center, Florida. Presentation to the Advanced Life Support Systems Analysis Workshop, 26 March 1998. Drysdale, A. E. (1998b) “Metrics and System Analysis,” SAE paper 981746, 28th International Conference on Environmental Systems, Society of Automotive Engineers, Warrendale, Pennsylvania. Drysdale, A. E., Beavers, D., and Posada, V. (1997) “KSC Life Sciences Project Annual Report for January to December, 1997,” The Boeing Company, Kennedy Space Center, Florida, June, 1998. Drysdale, A. E., Grysikiewicz, M., and Musgrove, V. (1996) “Life Sciences Project Annual Report for January to December, 1996,” McDonnell Douglas Space and Defense Systems, KSC Division, Kennedy Space Center, Florida, April, 1997. Ewert, M. K. (1998) National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Personal communication based on data from internal Biomass Production Chamber Lighting System Trade Study, October, 1998. Ewert, M. K. (1999) National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Personal communication, 28 May 1999. Fisher, J. W. (1998) “Supercritical Water Oxidation in Life Support Systems,” Advanced Life Support Status Telecon, 5 November 1998. Hall, P., and Vodovotz, Y. (1999) National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Personal communication, 10 May 1999.

Ham. Stand. (1970) “Trade-off Study and Conceptual Designs of Regenerative Advanced Integrated Life Support Systems (AILSS), February 1968 – January 1970,” NASA-CR-1458, Hamilton Standard, Windsor Locks, Connecticut. Ham. Stand. (1998) "Sabatier Reactor Subsystem (SRS) Preliminary Requirements Review (PRR) Technical Interchange Meeting (TIM)," Hamilton Standard, Windsor Locks, Connecticut, 24 June 1998 at National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Ham. Stand. (1999) "Regenerative Environmental Control and Life Support System (ECLSS) Integrated Rack and Urine Processor Assembly (UPA) Preliminary Design Review," Hamilton Standard, Windsor Locks, Connecticut, 14-15 April 1999 at National Aeronautics and Space Administration, Marshall Space Flight Center, Huntsville, Alabama. Hanford, A. J. (1997a) “Advanced Regenerative Life Support System Study,” JSC-38672 (CTSD-ADV-287), National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Hanford, A. J. (1997b) “Advanced Regenerative Life Support System Study Update,” LMSMSS-32447, Lockheed Martin Space Mission Systems and Services, Houston, Texas. This document is an update to JSC-38672. Hanford, A. J. (1998a) “Advanced Life Support System (ALSS) Study Air Revitalization System,” Lockheed Martin Space Mission Systems and Services, Houston, Texas. Presentation to the Advanced Life Support Systems Analysis Workshop, 27 March 1998. Note: The data in this presentation come from inputs by K. Lange, C. Lin, and J. Graf. Hanford, A. J. (1998b) “Advanced Life Support System (ALSS) Study Water Recovery System,” Lockheed Martin Space Mission Systems and Services, Houston, Texas. Presentation to the Advanced Life Support Systems Analysis Workshop, 27 March 1998. Note: The data in this presentation come from inputs by K. Lange and C. Lin. Hanford, A. J., and Drysdale, A. E. (1999) “Advanced Life Support Research and Technology Development Metric – Initial Draft,” LMSMSS-33045, Lockheed Martin Space Mission Systems and Services, Houston, Texas. Hanford, A. J., and Ewert, M. K. (1996) “Advanced Active Thermal Control Systems Architecture Study Report,” NASA-TM-104822, National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Hanford, A. J., and Ewert, M. K. (1998) “Advanced Life Support Program Systems Modeling and Analysis Project Management Plan,” JSC-39149 (CTAD-ADV-343), National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Hoffman, S. J., and Kaplan, D. L. (1997) “Human Exploration of Mars: The Reference Mission of the NASA Mars Exploration Study Team,” NASA-SP-6107, National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. http://exploration.jsc.nasa.gov/marsref/contents.html Hunter, J. (1999) Department of Agricultural and Biological Engineering, Cornell University, Ithaca, New York. Personal communication, 24 May 1999. Hunter, J. and Drysdale, A. E. (1996) “Concepts for Food Processing for Lunar and Planetary Stations,” SAE paper 961415, 26th International Conference on Environmental Systems, Society of Automotive Engineers, Warrendale, Pennsylvania. Jan, D. (1998) “Monitoring and Control Mass Estimate Issues,” National Aeronautics and Space Administration, Headquarters, Washington, D. C. Presentation to the Advanced Life Support Systems Analysis Workshop, 27 March 1998.

K&K (1998) “Luna's (Earth's Moon) Thermal Environment,” K & K Associates, Westminster, Colorado. Note: Material extracted from “Thermal Environments,” JPL D-8160. http://www.csn.net/~takinfo/planets/luna.htm Kloeris, V., et al. (1998) “Design and Implementation of a Vegetarian Food System for a Closed Chamber Test,” Life Support & Biosphere Science, 5, pp. 231-242. Lane, H. W. (1999) National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. Personal communication via J. Hunter dated 24 May 1999. Lane, H. W., Bourland, C. T., Pierson, D., Grigorov, E., Agureev, A., and Dobrovolsky, V. (1996) “Nutritional Requirements for ISS Missions up to 360 days,” JSC 28038, National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. Lange, K. E., and Lin, C. H. (1998) “Advanced Life Support Program: Requirements Definition and Design Consideration,” JSC-38571 (CTSD-ADV-245, Rev. A) National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. http://peer1.idi.usra.edu/peer_review/prog/ALSREQ98.PDF Lin, C. H. (1997a) “Mars Transit Habitat ECLSS,” National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. Internal NASA presentation package from Crew and Thermal Systems Division dated April 1997. Lin, C. H. (1997b) “Mars Transit Habitat ECLSS, Initial Baseline and Trade Studies,” National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. Internal NASA presentation package from Crew and Thermal Systems Division dated 9 December 1997. Loretan, P. (1998) NASA Center for Food and Environmental Systems for Human Exploration of Space, Tuskegee University, Tuskegee, Alabama. Personal communication. Lunsford, T., and Grounds, P. (1993) “Single Phase Laundry System Development,” SAE paper 932092, Society of Automotive Engineers, Warrendale, Pennsylvania. Muller, H. G. and Tobin, G. (1980) Nutrition and Food Processing, AVI Publishing Company, Westport, Connecticut. NASA (1999) “Man-Systems Integration Standards,” NASA-STD-3000, National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. http://www-sa.jsc.nasa.gov/FCSD/crewstationbranch/msis/online.htm Reimers and McDonald (1992) ISS Laundry decision package, National Aeronautics and Space Administration. Internal NASA presentation dated 23 January 1992. Sager, J. (1999) National Aeronautics and Space Administration, Kennedy Space Center, Florida. Personal communication. Schneider, W. C. (No Date) “Mars TransHab Design Study Team Presentation,” Internal Presentation, National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. SMAP (1999a) Systems Modeling and Analysis Project, National Aeronautics and Space Administration, Johnson Space Center, Advanced Life Support Program, Houston, Texas. Presented at the SMAP Telecon on 11 March 1999. Sridhar, K. R., Finn, J., and Kliss, M. (1998) “ISRU Technologies for Mars Life Support,” The University of Arizona in Tucson, Arizona, and the National Aeronautics and Space Administration, Ames Research Center, Moffett Field, California. Presentation to the Advanced Life Support Systems Analysis Workshop, 27 March 1998. Systems Workshop (1998) National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. Presentation to the Systems Workshop, March 1998.

Vaccari, D. A., and Levri, J. (1999), NASA Specialized Center of Research and Training in New Jersey, Steven Institute of Technology, Hoboken, New Jersey. Personal communication, 14 May 1999. Vodovotz, Y. (1999) National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Personal communication, May 1999. Wheeler, R. M., Mackowiak, C. L., Berry, W. L., Stutte, G. W., Yorio, N. C., Ruffe, L. M., and Sager, J. C. (1999) “Nutrient, acid, and water budgets of hydroponically grown crops,” Acta Horticulturae, 481, pp. 655-661. Wheeler, R. M., Mackowiak, C. L., Sager, J. C., Knott, W. M., and Berry, W. L. (1994) “Proximate nutritional composition of CELSS crops grown at different CO2 partial pressures,” Advances in Space Research, 14, 11, pp. 171-176. Williams, D. R. (1997) National Space Science Data Center, National Aeronautics and Space Administration, Goddard Space Flight Center, Greenbelt, Maryland, 19 June 1997. http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html

5 Appendices:

Appendix A: Acronyms and Abbreviations 4BMS four bed molecular sieve AES air evaporation subsystem ALS Advanced Life Support APCOS aqueous phase catalytic oxidation subsystem BIO-Plex Bioregenerative Planetary Life Support Systems Test Complex BVAD Basic Values and Assumptions Document (This Document) BWP biological water processor CDRA carbon dioxide removal assembly

CO2 carbon dioxide COP (thermodynamic) coefficient of performance CRS carbon dioxide removal subsystem CTMP crew-time-mass-penalty [kg/ch] CTSD Crew and Thermal Systems Division (at NASA JSC) DRM design reference mission dw dry weight ESM equivalent system mass EVA extravehicular activity ffm frozen food mass HPS high pressure sodium, a type of lamp HS-X type of solid amine ISRU in situ resource utilization ISS International Space Station IVA intra vehicular activity LEO Low Earth Orbit LMLSTP Lunar Mars Life Support Test Program MF multifiltration MilliQ MilliQ water post processing subsystem n/a not applicable

O2 oxygen OGS oxygen generation subsystem p(gas) partial pressure exerted by gas PAR photosynthetically active radiation PC physicochemical PPF photosynthetic photon flux RO reverse osmosis SAVD solid amine vacuum desorbed SCWO super critical wet oxidation SI Système International, or International System of Units SMAP Systems Modeling and Analysis Project SP100 type of nuclear reactor SPWE solid polymer water electrolysis STD standard STS space transportation system TBD to be determined TCCS trace contaminant control subsystem UF ultrafiltration VCD vapor compression distillation VRA volatile removal assembly Z5A a type of zeolite

Appendix B: Abbreviations for Units Symbol Actual Unit Physical Correspondence cd crew-day crew time ch crew-hour crew time d day time g gram mass h hour time J Joule energy k kilo- prefix L liter volume M mega- prefix m meter length m² square meter area m3 cubic meter volume m milli- prefix mol mole mole Pa Pascal pressure ppm parts per million concentration wk week time W Watt power y year time µ micro- prefix