Advanced Life Support Research and Technology Development Metric – Initial Draft Introduction

Basic Metric Formulation

The Advanced Life Support Research and Technology Development Metric, or Metric, is one of several measurement devices, or metrics, which will be employed by the National Aeronautics and Space Administration (NASA) to measure the Advanced Life Support (ALS) Program’s progress. Because any measure must have a baseline, whether explicitly defined or implied, the Metric is a comparison between a selected advanced life support system (ALSS) and an equivalently detailed system based on technology from the Environmental Control and Life Support System (ECLSS) for the International Space Station (ISS). More specifically, the Metric is the ratio of the equivalent system mass (ESM) for a life support system using the ISS ECLSS technologies divided by the ESM for an equivalent life support system using the “best” ALS technologies. As defined, the Metric should increase in value as the ALS technologies become less massive, less power intensive, and less voluminous. Here “best” is defined as the ALSS which, at the time of the Metric evaluation, provides the Metric with the highest value. Also, the ALSS technologies used here are not flight-certified; rather, they are in many cases much less mature. The uncertainties associated with less mature equipment add additional complicating factors to the ALSS technology selection process. While this may seem arbitrary, this process actually encourages the ALS Program to research more than a single technology for each life support function and then select the most appropriate for a particular mission, which is similar to the actual process used by mission planners. Also implied in this Metric formulation is an underlying mission for which each life support system might be evaluated. Currently the Design Reference Mission (DRM) of the NASA Mars Exploration Study Team (Hoffman and Kaplan, 1997, and Drake, 1998) provides an appropriate mission scenario both because of its relevance and as an appropriate challenge for the ALS community. For those life support functions which a particular set of life support technologies cannot provide, an open loop approach is assumed. Future versions of the Metric will consider various life support approaches, including supply from Earth, physicochemical and biological regenerative technologies, and in situ resource utilization, on their own merits.

Description of 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. A form developed by Drysdale (1998) is used in this work. The definition of equivalent mass for a system is the sum of the equipment mass plus the power, volume, thermal control, and crew time as masses. Background

Mars Reference Baseline

As per the DRM (Hoffman and Kaplan, 1997, and Drake, 1998), a vehicle with a rigid shell, the Mars Transfer Vehicle (MTV), transports the crew from Earth orbit to the surface of Mars. The MTV, once on the surface of Mars, is incorporated into the surface habitat. In addition to the MTV, the surface habitat includes an additional dedicated lander which provides some additional living volume for the crew during the mission’s exploration phase. The additional pressurized volume used solely on the surface employs an inflatable structure, as proposed for the TransHab 2 program, as per the DRM. A separate Earth Return Vehicle (ERV), which is initially deployed ahead of the crew, transports the mission personnel back to Earth. Thus, two long-duration life support system hardware sets were assumed for each mission. The life support systems employed during descent to Mars, ascent from Mars, which uses a separate vehicle in the current DRM, and within the Earth-return capsule are omitted. Such systems, especially within the ascent vehicle and Earth-return capsule, are expected to operate for no longer than a few days and, therefore, are likely to use expendable, open-loop technologies. Alternate assumptions might be made, including use of a reusable transit vehicle, and a single shipset for the surface. However, the annual resupply mass (consumables) is about a third of the fixed mass, so this might not be economical. The DRM defines the overall mission as:

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 The TransHab is a concept to create an inflatable module with greater volume than a standard International Space Station (ISS) rigid module while using no more volume during launch than is currently available within the Space Transportation System (STS) Orbiter payload bay. Effectively the TransHab has a non-rigid outer structure which is inflated or deployed once the vehicle reaches orbit. Internal outfitting is accomplished by deploying folded structures and/or by moving appropriate equipment into the shell’s volume once it deployed. Drake (1998), page 43, provides a picture of a transfer vehicle with a TransHab crew compartment. Number of Crew per Mission 6 Transit Duration 180 days (nominal) Surface Duration 600 days (nominal) Number of Missions to One Site 3

Metric Baseline Assumptions

For both life support systems, a habitable volume of 50 m³ per person has been included. This is primarily a pressure-vessel cost, and there is a difference between ISS technology (0.015 m³/kg), and an inflatable structure such as TransHab, (0.43 m³/kg). An ISS pressure vessel is assumed for interplanetary transit while inflatable structures are assumed for the additional habitable volume provided on the surface. Makeup gas for leakage and the mass for filling the volume once have been included for ISS. For the advanced life support system (ALSS) case, all gas masses are assumed to be included in the mass of gas provided. Crew time is assumed to be 50 hrs of time devoted to mission goals per crew member per week. Additional time will be required for base operations. Assuming the most significant mission work is done on the surface of Mars, crew time here is only counted for days spent on Mars. Thus, a crew of six will provide 76,932 hours over three missions. No provision has been made for contingencies. Further, radiation shielding is omitted, as the requirement is ill-defined at present and the penalty is expected to be similar in both cases. Finally, support for extravehicular activities (EVA) and their associated airlock operations have also been omitted. While EVA loads on a life support system (LSS) are far from negligible, further study is necessary to define the actual EVA loads. Thus, while this is a useful estimate of technological capability, it does not directly represent a good estimate for the LSS initial mass in low Earth orbit (IMLEO). Waste disposition is limited to overboard jettison for the ALSS scenario. ISS returns waste to Earth, using either a soft landing on-board the Space Transportation System (STS, or Shuttle) or incineration during re-entry. However, this is believed to be a relatively small item, and is not addressed in these estimates.

International Space Station Environmental Control and Life Support System Technology Baseline

The numerator of the Metric is an ESM estimate of a LSS for a mission to Mars based on technology from the ISS ECLSS and the DRM. Background ISS ECLSS Technology Information The ISS ECLSS technology is defined in various documents (such as Carrasquillo, et al., 1997), often at a high level of detail The values here have been adjusted to remove any overcapacity as this is a form of contingency. EVA and airlock related items have also been removed. Appropriate duration and infrastructure equivalencies have also been applied. The assessment presented is based on the ECLSS of the U. S. On-Orbit Segment of the ISS (USOS). Fixed masses, mostly equipment, and time dependent masses, mostly consumables, are identified separately and applied as appropriate to the mission. Note that the ISS baseline for food is taken from Bourland (1998), though Hanford (1997) provides a similar value.

ISS ECLSS Mission Definition Data Number of Crew 4 USOS only Nominal Duration 3,650 days at the same site, or 10 Earth years. Location LEO

ISS ECLSS Infrastructure Costs Factor Value Units Comments Mass Delivery Factor 2 kg packaged For components requiring packaging /kg unpackaged (food and clothing) Pressurized Volume 0.015 m³/kg ISS common module; No shielding or secondary structures Power 11.4 W/kg Nuclear power; Based on SP100 Program Heat Rejection 25.4 W/kg Crew Time 2 person•hr/kg A rough estimate Derived Costs for Mission Energy 492.48 kWh/kg Heat Rejection 3,950.2 kWh/kg

References: Hanford (1997) and Hanford and Ewert (1996).

ISS Food and Clothing Components kg/(person•day) Required Food (hydrated) 1.955 Total Food Mass 3.910 Clothing 1.4 Packaged Clothing 2.8

From Bourland (1998) and ISS Laundry Package. The dry weight value for ISS food is 0.674 kg/(person•day) excluding packaging. The full mass of food includes moisture as ISS food is not completely dehydrated.

ISS ECLSS Physical Quantities Translated to Equivalent System Mass (ESM) Equipment Resupply Assumed Resupply Average Average Crew Total Mass Mass Volume Volume Power Cooling Time Mass [kg ESM] [kg ESM] [kg ESM] [kg ESM] [kW] [kW] [kg ESM] [kg ESM] 2,031 119,808 18,059 6,641 621 269 457 147,886 1.4% 81.0% 12.2% 4.5% 0.4% 0.2% 0.3%

Physical mass (equipment/initial mass plus the resupply mass) equals 121,838 kg ESM and accounts for 82.4% of the total equivalent system mass. International Space Station Environmental Control and Life Support System (excluding equipment for Extravehicular Activities and Airlock operations) Average Assumed Resupply Average Average System Percentage Mass Volume Power USOS Mass Volume Mass Volume Power Cooling Crew Time ESM ESM of Total System / Item [kg] [m³] [kW] Num [kg] [m³] [kg] [m³] [kW] [kW] [per•hr/yr] [kg ESM] [kg ESM] ECLSS Air Revitalization System (ARS) 2,901.3 2.0% Carbon Dioxide Removal Assembly (CDRA) 201.0 0.39 0.860 1 201.0 0.86 0.86 2.7 323.8 Trace Contaminant Control Subsystem (TCCS) 78.2 0.175 1 78.2 163.0 0.340 0.18 0.18 4.4 1,979.0 Major Constituent Analyzer (MCA) 54.7 0.44 0.088 1 54.7 12.0 0.023 0.09 0.09 0.4 203.5 Oxygen Generation Assembly (OGA) 113.0 0.14 1.470 0.57 64.6 12.7 0.010 1.47 1.47 2.0 395.1 Temperature and Humidity Control System (THCS) 1,488.9 1.0% Common Cabin Air Assembly (CCAA) 112.0 0.40 0.468 3 336.0 1.200 1.66 1.66 627.0 Avionics Air Assembly (AAA) 12.4 0.03 0.083 3 37.2 0.102 0.25 0.25 75.8 Intermodule Ventilation (IMV) Fan 4.8 0.01 0.055 5 24.0 0.045 0.22 0.22 55.0 Intermodule Ventilation (IMV) Valve 5.1 0.01 0.006 15 76.5 0.149 0.01 0.01 87.2 High Efficiency Particle Atmosphere (HEPA) Filter 2.0 0.01 15 30.0 0.120 47.0 0.189 2.0 644.0 Fire Detection and Suppression 75.1 0.1% Smoke Detector 1.5 0.002 8 12.0 12.0 Portable Fire Extinguisher (PFE) 15.1 0.04 4 60.4 0.041 63.1 Crew Cabin 15,101.4 10.2% Volume: 50 m³/person 200.00 200.000 13,333.3 Air: 1 volume of gas 258.9 258.9 258.9 150.9 1,509.1 Leakage Rate: 83 kg/(module•yr) Vacuum System The largest item is 10 kg - negligible 0.0 Water Recovery and Management (WRM) and Waste Management (WM) 22,674.3 15.3% Water Processor (WP) 476.0 10.39 0.300 1 476.0 478.0 0.30 0.30 6.0 5,324.1 Process Control Water Quality Monitor (PCWQM) 38.0 0.51 0.030 1 38.0 0.03 0.03 1.0 46.8 Urine Processor (UP) 128.0 0.37 0.091 1 128.0 175.0 2.178 0.09 0.09 13.0 3,406.6 Fuel Cell Water Storage 21.0 0.10 4 84.0 684.0 6,924.0 Condensate Storage 21.0 0.10 1 21.0 21.0 Commode / Urinal 50.0 0.072 1 50.0 435.0 3.364 0.07 0.07 60.0 6,951.8 Other Miscellaneous 105,645.1 71.4% Food 5,708.6 1.61 1.61 57,290.7 Clothing 4,114.5 3.857 43,717.0 Miscellaneous Power 0.25 22.0 ECLSS Racks (10) 69.230 4,615.3 Total ISS ECLSS 1,593 212.9 2,031 270.89 11,981 9.96 7.1 6.8 91 147,886 Breakdown of ISS ECLSS Equivalent System Mass Components by System Assumed Resupply Assumed Resupply Average Average Crew Time Percentage Mass Mass Volume Volume Power Cooling [per•hr/yr] ESM of Total System [kg] [kg/yr] [m³] [m³/yr] [kW] [kW] [kg ESM] ECLSS Air 1,233.5 385.6 201.657 0.562 4.73 4.73 11.5 19,567 13.2% Clothing 0 4,114.5 0 3.857 0 0 0 43,717 29.6% Food 0 5,708.6 0 0 1.61 1.61 0 57,291 38.7% Waste 0% Water 797.0 1,772.0 0 5.542 0.49 0.49 80.0 22,674 15.3% Other 0 0 69.230 0 0.25 0 0 4,637 3.1%

Advanced Life Support System Technology Baseline

The ALSS technology baseline is an example of an ALS Program LSS from Johnson Space Center (Lin, 1997), with additional components added for completeness and comparability to the ISS case. The selections presented in this particular baseline arose from a preliminary study of a life support configuration for a transit vehicle for a mission to Mars using a TransHab-style inflatable structure for the crew module. The underlying reference mission, which differs from the DRM and the reference mission for the Metric, assumed a single vehicle would transport the crew from Earth orbit to Mars and then back to Earth again. Separate vehicles would transfer the crew to the surface of Mars and provide a habitat once there. As such, the technology selection process did not consider surface operations. While systems designed to function in microgravity generally are not gravity sensitive and will function on a planetary surface, overall such an equipment selection may not be optimal. Finally, because the systems included are under development and not flight-ready, the physical attributes are less precise than the values for the USOS equipment. Thus, the ALSS baseline should be considered representative, but not necessarily optimal, for the reference mission. Thus, the ALSS case is extrapolated from ALS Program values developed at Johnson Space Center. The original ALSS values (Lin, 1997) have been updated with more recent values (Hanford, 1998) where possible. The ALSS here is primarily a physicochemical system with a biological primary water processor and very limited biological food production. The system is defined in detail in the tables below. It represents an advance over ISS technology, and is for a 400-day outbound and return transit. As noted above, similar technology should work on the surface, and should be independent of the mission scenario. This scenario does include a small plant growth chamber. The mass allocated is 120 kg. This is adequate for about a half square meter growing area. Half a square meter could produce as much as 1% of the food for the crew with a high productivity cereal crop, or as low as 0.1% for a low productivity crop. Food, clothes, and laundry are not covered by these references, and have been added. These masses are large compared to other equipment. Nevertheless, these items will be important issues when comparisons to bioregenerative options are eventually undertaken. Radiation protection could also be an issue when considering transit vehicles, but it can be ignored as a first approximation. Food cost is taken from Hanford (1997). This value is 12% lighter than the figure used for ISS technology case. This is reasonable assuming a greater use of dehydrated food for longer-duration trips and the availability of a small quantity of fresh food. For clothing, a laundry is assumed. This would be a non-critical item, but it may provide significant savings (ISS Laundry package).

ALSS Sizing Assumptions Physical Quantity Value Units Crew Size 6 people Mission Duration 400 days Cabin Atmosphere Total Cabin Pressure 59.2 kPa Partial Pressure – Oxygen 17.8 kPa Partial Pressure – Carbon Dioxide 0.4 kPa Leakage Rate 0.76 kPa Human Consumption Food 11.8 MJ/(person•day) Oxygen Consumption 0.835 kg/(person•day) Carbon Dioxide Production 0.998 kg/(person•day) Water Usage Water Consumption (Food & Drink) 3.52 kg/(person•day) Hygiene Water Usage 4.44 kg/(person•day) Shower Water Usage 2.72 kg/(person•day) Urinal Flush Usage 0.49 kg/(person•day) Dish Wash Usage 5.44 kg/(person•day) Clothing Wash Usage 12.47 kg/(person•day) Total Water Consumption / Usage 29.08 kg/(person•day)

ALSS Infrastructure Costs Factor Value Units Comments Mass Delivery Factor 2 kg packaged For components requiring packaging /kg unpackaged (food and clothing) Pressurized Volume 0.062 m³/kg TransHab inflatable module including 19 cm of water for “storm shelter” shielding Power 12.0 W/kg Solar power. Heat Rejection 25.4 W/kg Food 1.725 kg/(per•day) Clothes 0.267 kg/(per•day) Clothes are washed in a laundry. Spares & Expendables 15% An estimate in the absence of better data.

References: Hanford and Ewert (1996), and ISS Laundry Package.

ALSS Equivalent System Mass Calculations [kg ESM] Mass Resupply Volume Power Cooling Total Equivalent System Mass 12,739 272 5,269 598 283 19,161 Percentage of Total ESM 66.5% 1.4% 27.5% 3.1% 1.5% Breakdown of Equivalent System Mass Components Mass Resupply Volume Power Cooling Total Fixed Costs [kg] 3,062.0 5,115.1 598.2 282.6 9,057.9 Time Dependent Costs [kg/mission] 9,677.4 271.8 154.2 10,103.4 Time Dependent Costs [kg/day] 24.2 0.7 0.4 25.3 An Advanced Life Support System (based on physicochemical technologies and estimates for TransHab) Air Revitalization System Technology Assumed [Program] / Notes Mass [kg] Resupply [kg] Volume [m³] Power [kW] Cooling [kW] Air Pressure ARPCS [X-38] 74.0 11.1 0.41 0.100 0.100 Oxygen/Nitrogen Storage high pressure [Space Transportation System (STS)] 284.0 0 1.21 0.008 0.008 Humidity Control anti-microbial condensing heat exchanger [LMLSTP Ph IIA] 46.0 6.9 0.26 0.400 0.400 Air Temperature Control anti-microbial condensing heat exchanger [LMLSTP Ph IIA] 99.0 14.9 0.74 0.370 0.370 Carbon Dioxide Removal [Node 3] 176.0 13.8 0.45 0.365 0.365 Carbon Dioxide Reduction (a) Sabatier 31.0 4.2 0.44 0.130 0.130 Oxygen Production (a) Solid Polymer Water Electrolysis (SPWE) 120.9 18.0 1.12 1.840 1.840 CO2 Reduction/O2 Production (b) Salad Machine / This item is carried in food production. Trace Contaminant Control [Node 3] 77.0 5.6 0.14 0.128 0.128 Particulate and Microbe Control reusable filters 7.0 1.1 0.08 0 0 Air Pressure Monitoring sensors [International Space Station (ISS)] 2.0 0.3 0 0.005 0.005 Air Composition Monitoring [Space Transportation System (STS)] 6.0 0.9 0 0.015 0.015 Fire Detection and Suppression smoke detector and halon 19.0 2.9 0.05 0.050 0.050 Crew Cabin Volume [TransHab] / The mass of gas is assumed to be elsewhere. 300.00 Water Recovery System Technology Assumed [Program] / Notes Mass [kg] Resupply [kg] Volume [m³] Power [kW] Cooling [kW] Urine Pretreatment flush + solid agent / This item is included in water storage. Urine Processing Bioreactor + Reverse Osmosis + Air Evaporative Subsystem 175.0 87.0 0.60 1.450 1.450 Hygiene Waste Storage Bladder-less tanks 203.0 0.64 Hygiene Waste Processing Bioreactor + Reverse Osmosis + Air Evaporative Subsystem 76.0 6.9 0.99 0.200 0.200 Hygiene Waste Post Processing Milli-Q + ammonia removal 56.0 8.0 0.55 0.540 0.540 Microbial Control iodine microbial check valve 10.0 1.5 0.012 0.012 Water Quality Monitoring Water Quality Monitoring (WQM) [ISS] 39.0 5.9 0.08 0.100 0.100 Potable Water Storage bladder-less tanks 950.0 1.61 0.020 0.020 Waste Handling & Processing Technology Assumed [Program] / Notes Mass [kg] Resupply [kg] Volume [m³] Power [kW] Cooling [kW] Urine Collection Waste Management Subsystem [ISS] / This item is included with feces collection. Urine Storage bladder-less tanks 49.0 0.32 Feces Collection and Storage Waste Management Subsystem [ISS] 103.0 15.5 1.28 0.340 0.340 Other Solid Wastes trash compactor [International Space Station (ISS)] 27.0 4.1 0.09 0.060 0.060 Solid Waste Processing stabilization + disposal and incineration 225.0 33.8 2.38 0.265 0.265 Solid Waste Disposal overboard jettison [International Space Station (ISS)] 59.0 8.9 1.77 0.130 0.130 Miscellaneous Technology Assumed [Program] / Notes Mass [kg] Resupply [kg] Volume [m³] Power [kW] Cooling [kW] Food Supply storage [ISS] and on-board production / This item is included in Crew Accommodations; 100% food provided. Regenerative Food Production Salad Machine / Less than 10% production. 120.0 18.0 1.94 0.650 0.650 System Monitoring and Control intelligent monitoring and control (M&C) 20.0 3.0 System Operations Planning artificial intelligence (AI) expert system / Included in M&C Crew Accommodation System Technology Assumed [Program] / Notes Mass [kg] Resupply [kg] Volume [m³] Power [kW] Cooling [kW] Food 1.725 kg/(person•day) 8,280.0 8.28 Clothes 0.267 kg/(person•day) 1,279.2 1.28 Laundry 118.2 Totals 12,739.4 271.8 326.70 7.178 7.178 Advanced Life Support Research and Technology Development Metric

For the Metric, the following infrastructure costs are assumed:

Infrastructure Costs Transit Surface Units Pressurized Volume 0.015 0.48 m³/kg Power 12 18 W/kg Heat Rejection 47.5 15 W/kg

The infrastructure costs here represent the incremental costs for pressurized volume, power, and heat rejection. Additionally, a crew time cost is presented based on each case. For the transit mission segment, the MTV and ERV use modules with rigid shells. Power is provided by converting solar energy to electricity using photovoltaic cells. On the surface, any additional volume above and beyond what is provided by the MTV is provided by an inflatable structure. Power is provided by Brayton conversion from a nuclear power plant of the SP100 class sized to generate 100 kW continuously. In both cases, lightweight, inflatable systems are used for heat rejection. The differences in heat rejection costs reflect differences in the thermal environment on the surface of Mars compared to that of interplanetary space.

Equivalent System Mass for ISS ECLSS Technology Baseline

In the tables which follow, the ISS ECLSS technology LSS have been resized for a crew of six versus the four crew in the baseline for the LSS of the USOS. Appropriate duration and infrastructure equivalencies have also been applied.

ISS ECLSS Baseline Crew 4 people Duration 3,650 days

Resupply Resupply Mass Volume Power Cooling Crew Time Mass Volume [kg] [m³] [kW] [kW] [per•hr/kg] [kg/yr] [m³/yr] Fixed Values 2,031 271 7.08 6.83 Time Dependent 91 9,922 9.96 Values

ISS ECLSS Baseline modified for Mars Design Reference Mission Crew 6 people Duration 2340 days

Resupply Resupply Mass Volume Power Cooling Crew Time Mass Volume [kg] [m³] [kW] [kW] [per•hr/kg] [kg/yr] [m³/yr] Fixed Values 3,046.5 406.5 10.6 10.2 Time Dependent 136.5 14,883.0 14.9 Values Once the total physical requirements of the LSS using the ISS ECLSS technology are determined, an overall ESM may be determined by applying the infrastructure costs. Note that the crew time cost is determined iteratively in this computation because it depends on the ESM of the LSS for the remaining cost factors.

ALS Metric Equivalent System Mass Calculations for ISS ECLSS Technology [kg ESM] Mars Transfer Vehicle Mass Volume Power Cooling Crew Time Total ESM (MTV) Transit Out 10,386 27,591 885 216 277 39,355 Surface Operations 24,465 51 590 683 922 26,712 MTV Total 66,066 Earth Return Vehicle (ERV) Mass Volume Power Cooling Crew Time Total ESM Transit Back 10,386 27,591 885 216 277 39,355 Single Mission Totals 45,237 55,234 2,360 1,114 1,476 105,421 Three Mission Totals 135,712 165,701 7,080 3,343 4,427 316,262

The total for all three missions is 316 metric tons. Dividing the crew mission time by the ESM yields a crew time equivalency of 0.243 person•hr/kg. This marginal cost is used for estimating LSS crew time costs, though the impact in this case is negligible.

Equivalent System Mass for ALSS Technology Baseline

In the tables which follow, the ALSS technology, detailed earlier, has been resized using appropriate duration and infrastructure equivalencies.

ALS Baseline Crew 6 people Duration 400 days

Resupply Resupply Mass Volume Power Cooling Crew Time Mass Volume [kg] [m³] [kW] [kW] [per•hr/kg] [kg/yr] [m³/yr] Fixed Values 3,062 317 7.18 7.18 Time Dependent 136.5 10,103 9.6 Values

ALS Metric Equivalent System Mass (ESM) Calculations for ALSS Technology [kg ESM] Mars Transfer Vehicle Mass Volume Power Cooling Crew Time Total ESM (MTV) Transit Out 7,609 21,429 598 151 183 29,971 Surface Operations 15,155 30 399 479 612 16,674 MTV Total 46,645 Earth Return Vehicle (ERV) Mass Volume Power Cooling Crew Time Total ESM Transit Back 7,609 21,429 598 151 183 29,971 Single Mission Totals 30,372 42,889 1,595 781 979 76,615 Three Mission Totals 91,116 128,666 4,785 2,342 2,936 229,846

The total cost for all three missions would be 230 metric tons. Using the same approach for crew time as above, the crew time equivalency is 0.335 person•hr/kg. The ALSS technologies yield significantly less massive system than do the ISS ECLSS technologies. The Metric is defined as the ratio of the ESM for a LSS using ISS ECLSS technologies divided by the ESM for a LSS using ALSS technologies. Or ESM of LSS using ISS ECLSS technologies The Metric = ESM of LSS using ALSS technologies

316,262 kg The Metric = = 1.38 229,846 kg

Thus, the ALSS technologies are 27% less massive than the corresponding ISS ECLSS technologies and yield a Metric value of 1.38 based on current estimates. Cautions and Disclaimers

These system level equivalent mass estimates are preliminary, and somewhat heterogeneous. The level of detail is about comparable, but the data are not classified exactly the same. In the interests of time, simplifications have been made. However, the approach is clearly defined, and presents an approach that can be refined. As stated above, these estimates intentionally do not include contingency. A valid and acceptable contingency plan will be needed that can be applied to both approaches in order to adequately identify the real mission masses. References

Bourland, C. T. (1998) Flight Crew Support Division, National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Personal communication. Carrasquillo, R. L., Reuter, J. L., and Philistine, C. L. (1997) “Summary of Resources for the International Space Station Environmental Control and Life Support System,” SAE 972332, 27th International Conference on Environmental Systems, Lake Tahoe, Nevada, July 14-17, 1997, Society of Automotive Engineers, Inc., Warrendale, Pennsylvania. 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, Exploration Office, National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas, June, 1998. This document may be found on the Internet at: http://exploration.jsc.nasa.gov/explore/explore.htm Drysdale, A. E. (1998) The Boeing Company, Kennedy Space Center, Florida. Personal communication. Hanford, A. J. (1997) “Advanced Regenerative Life Support System Study,” JSC-38672, National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Hanford, A. J. (1998) Lockheed Martin, Houston, Texas. Workshop presentation, March 1998 (Unpublished work). Hanford, A. J., and Ewert, M. K. (1996) “Advanced Active Thermal Control Systems Architecture Study,” NASA-TM-104822, 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,” Exploration Office, National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas, July, 1997. This is version 1.0. This document may be found on the Internet at: http://exploration.jsc.nasa.gov/explore/explore.htm ISS Laundry Package (199x) Unpublished work. Lin, C. H. (1997) Crew and Thermal Systems Division, National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, Houston, Texas. Personal communication. Mason, L. S., Rodriguez, C. D., McKissock, B. I., Hanlon, J. C., and Mansfield, B. C. (1992) "SP-100 Reactor with Brayton Conversion for Lunar Surface Applications," NASA-TM-105637, National Aeronautics and Space Administration, Lewis Research Center, Cleveland, Ohio.