Sprint 3: Optimal Architecture for Return to the Moon Integrating Government and Commercial Interests

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Stakeholder Analysis

Stakeholder Value Network in Current State

File:3Current StakeholderValueNetwork.png

Stakeholder Value Network in a Mature Newspace Economy

File:Future StakeholderValueNetwork.png

Based on Stakeholder Analysis in Sprint 2 by John Hernandez

Stakeholder Stakeholder Type Need
MIT Support Acquire BAA Funding
U.S. Government Support/Funding Develop a plan viable to both the U.S. Government, international entities and the commercial sector
Foreign Governments Support/Funding Contribute to the efforts of achieving sustainable lunar surface operations.
U.S. Public Support Develop a cost effective and economically beneficial plan to achieve lunar surface operations.
National Pride
International Public Support Develop a cost effective and economically beneficial plan to achieve lunar surface operations.
Congress Support, Funding Develop a plan viable to both the U.S. Government, international entities and the commercial sector
Commercial Entities (e.g. Blue Origin, SpaceX, Draper) - Jeff and Javier Partner, Investor, Support Build the architecture to accommodate both NASA and the commercial space industry
Make money using lunar natural resources
Build a profitable cargo transport system
Build an architecture which demonstrates a private company owning the Gateway will be advantageous to both NASA and the commercial sector
NASA Sponsor Provide a cloud of architectures considered during your analysis
Independent Investors Funding Fund viable business models with breakeven point analysis and partnership opportunities
Scientific Community (U.S./International) User Provide both lunar samples and data
Astronauts User Develop safe systems used to travel to the lunar surface and establish sustained operations
Universities (U.S./International) User Provide both lunar samples and data or technical research

Based on Stakeholder Value Network in Cameron et al., 2011, Goals for space exploration based on stakeholder value network considerations

Also Based on Stakeholder Studies by Stella Tkatchova, 2018, Emerging Space Markets

Determining the optimal architecture for value producing exploration

Architecture Generation

The architecture generation process is driven by the morph matrix that was created at the beginning of sprint 1. However, as we progressed from sprint 1 to now sprint 3, the morph matrix has been updated to reflect the key decision points within the architecture. The morph matrix was thus simplified for this sprint, and focuses on trades such as where to launch from Earth to, whether or not to conduct Earth orbit rendezvous, whether or not to conduct Lunar Orbit Rendezvous, and other parameters as seen in the figure. The majority of the decisions will impact the overall trajectory taken to the lunar surface, and thus will impact the propellant requirements for various architectures.


Outside of trajectory decisions, the morph matrix also examines key trades that will take place on the lunar surface. These include the number of crew to bring to the surface, the number of surface days, and how much mobility the crew will have. The number of crew and surface days were assumed to range between the values listed in the figure, but moon mobility was driven by the type of rover used on the surface. For example, if no rover was brought to the lunar surface, then the max mobility would be about a mile. The larger the rover, the more range, but more mass delivered to the lunar surface.

From all of the key decision points, we are able to apply logical constraints from a trajectory point of view in order to minimize the architectures needed for evaluation. Utilizing full factorial enumeration, the total number of architectures generated from our morph matrix is 2,211,840. However, after applying the trajectory constraints, the number of "feasible" architectures reduces to 34,560. This is roughly 1.5% of all the architectures, and a much more reasonable set of architectures to work with.

Delta V Metric

One key component of the morph matrix is the Delta V requirement metric. Previously, the Delta V parameter has focused on an Apollo 11 style trajectory architecture. In this iteration we introduce trajectories established and implemented during the later Apollo missions. We deviate from a traditional free return trajectory in favor of a hybrid free return trajectory. This hybrid trajectory was implemented for Apollo 13 and later, and allows for a status check and initial free return trajectory before performing a midcourse correction that reduces time of flight and energy requirements. While this midcourse correction inherently eliminates a free return abort, we have observed in Apollo 13 that it is possible to burn back onto a free return trajectory.

Gateway has been more thoroughly explored in this iteration, and we believe that the best insertion into the NRHO is from the L2 point. We also explore using the NRHO to navigate into low lunar orbit either at an equatorial inclination, or at polar latitudes.


In this iteration we also explored the options for inserting spacecraft into a polar lunar orbit. A polar orbit would allow for exploration of Shackleton crater and other polar areas of interest. Polar exploration requires significantly more energy than a descent from an equatorial latitude. The polar orbit insertion trajectory is initiated as part of the transfer burn from Earth, rather than a change in inclination burn from low lunar orbit. The maneuver conducted is a hybrid transfer burn with vectoring that changes inclination simultaneously. Circularization occurs at perilune, and follows the same procedure as equatorial circularization seen in the Apollo 16 flight log.

While an equatorial Low Earth Orbit (LEO EQ) was included in the figure, it is unrealistic to utilize this orbit. Both an inclination change maneuver and a launch j-hook maneuver are expensive in delta V. Rather, a translunar injection from LEO at the Kennedy Space Center latitude (~28 degrees) allows for a midcourse correction that is less costly and has been thoroughly tested on all later Apollo missions.

Finally, some additional assumptions need to be touched on. We assume that a geosynchronous orbit, as well as L3, and L4/L5 orbits are irrelevant given the scope of the mission. We assume that all burns use high impulse engines, with the goal of minimizing time in flight to the best of our ability.

Mass on Lunar Surface

One of the most important variables to consider for each architecture is the mass delivered to the lunar surface. This mass is a key variable, and an excellent one to trade on, because each decision point will greatly impact the mass delivered to the lunar surface. For this pre-phase A analysis, we made some key assumptions that allowed the analysis to be more straightforward and less dependent on other key design trades such as what type of lunar module to utilize, etc. We assumed that we only had to care about a few variables that make up the mass on the lunar surface, all of which are derivative of some of the decisions within the morph matrix.

The mass on the lunar surface was the summation of the consumables brought to the lunar surface, the mass of the rover brought to the lunar surface, and any additional ISRU infrastructure that needs to be deployed on the lunar surface. Obviously, there are other variables that must be brought to the lunar surface such as power systems, communication systems, etc., however these were not considered because as stated above, are highly dependent on the lunar architecture, as in lander design, that is chosen. Consumables brought to the lunar surface is directly related to the number of crew days on the lunar surface, or number of crew * number of days on surface. The mass of the rover is directly related to the lunar mobility defined in the morph matrix. ISRU capability and associated mass was analyzed for two different architectures as described in the next section.

Once the mass on the lunar surface is obtained, we can utilize the rocket equation to determine the mass of the system at Earth launch. This is an extremely important variable and will help us understand the differences in the architectures. The rocket equation was used for each staging point in the trajectory, and a wet mass was determined for each stage along the route. This does not look into more nuanced design trades such as the number of modules, etc., but simply assumes that if there is a change in trajectory, i.e. you go from LEO to Gateway to the Lunar surface, a different propulsive module will be used. This will give us a large final mass value, but this is a good thing at this point along the process.

Trade Studies

Figures of Merit

The following Figures of Merit (FOMs) were selected to evaluate the lunar missions.

  • Cargo delivered to lunar surface [kg]
  • Exploration Capability [kg * crew days]
  • Relative Exploration Capability [vs. Apollo 17]
  • Injected Mass into Low Earth Orbit [kg]
  • Return on Investment ROI or Net Present Value [%], [%]
  • Risk = Probability of Loss of Mission P(LOM), Loss of Crew P(LOC), Loss of Element P(LOE), Number of mission critical events (burns, docking etc)
  • Total Investment Cost [$]
  • Commercial Merit: cost / crew-days-on-surface
  • ISRU Production = Ultimate long term production mass capability (kg)
  • Overall Metric: mass_to_lunar_surface * number_of_crew / (delta_v * cost)

Each of these FOMs was weighted to deliver an overall preferred architecture. Exploration capability was the most weighted FOM it is the most representative of the stakeholder needs of both government and commercial interests.

ISRU on the Moon

Why ISRU?

In order to tackle the topic of lunar ISRU, we must first examine if the endeavor is worth pursuing. (All data and results in this section were excerpted from a publication written by a postdoc in Professor de Weck’s lab):

Ishimatsu, Takuto, Olivier L. de Weck, Jeffrey A. Hoffman, Yoshiaki Ohkami, and Robert Shishko. “Generalized Multicommodity Network Flow Model for the Earth–Moon–Mars Logistics System.” Journal of Spacecraft and Rockets 53, no. 1 (January 2016): 25–38.

Ishimatsu applied a Generalized Multi-Commodity Network Flow (GMCNF) Model to the Earth-Moon-Mars Logistics System to determine optimal logistical strategies for missions to Mars.

Production rates are described as the amount of resource produced (in kg) per year per kilogram of system mass. Anything above 1.0 signifies that the ISRU system is producing more resources than its own weight, which means it is productive. The GMCNF modeling found that lunar ISRU becomes beneficial above a production rate above 1.9 kg/year/kg. Beyond that, the production rate generally increases, although the system mass fluctuates up and down in a zigzag manner. Above 3.6 kg/year/kg, lunar ISRU is strongly favored over Mars IRU. Therefore, engineers should aim to create a lunar ISRU system with at least these capabilities.

File:ISRUprod.png
ISRU resource production rates Lunar and Martian missions

Key findings:

  • Liquid Oxygen/Liquid Hydrogen (LOX/LH2) is much more compatible with ISRU water production than Nuclear Thermal Rocket (NTR) propulsion
  • Aerocapture significantly reduces Total Launch Mass to LEO (TLMLEO), development of lightweight aeroshell/thermal protection system should be encouraged
  • Lunar water ice is the most valuable resource for Mars missions. Production rates above 1.9kg/year/kg for lunar ISRU and 0.6kg/year/kg for Mars ISRU would make the lunar/Mars ISRU system benefit exceed the cost in terms of overall launch mass.

It is important to note that these results can vary greatly depending on the parameters and assumptions used in the model, as well as the figures of merit used for optimization. So far, the paper proves that the GMCNF model is useful as a preliminary guide for the logistics of lunar a lunar architecture with ISRU infrastructure.


(Data and results in this section excerpted from this Ph.D thesis written by a student in Professor de Weck’s lab:)
Ho, K. (June 2015). Dynamic Network Modeling for Spaceflight Logistics with Time-Expanded Networks (Doctoral dissertation). Retrieved from DSpace@MIT. (Identifier No. 920684579)

In his dissertation, Dr. Koki Ho developed a new dynamic time-expanded GMCNF model and applied it to several cases with lunar ISRU capability: an architecture for human exploration of Mars, an architecture for human exploration of Near Earth Objects (NEO), and an architecture for human exploration of both Mars and a NEO.

In his case study for human exploration of Mars, Ho found that as lunar ISRU capabilities increase, the required initial mass to LEO (IMLEO) decreases. When ISRU capability is 5 kg/kg plant/year, IMLEO is about 15.7% lower than the case without ISRU (511.5 MT to 431.3MT IMLEO reduction).

File:LunarISRU.png
Lunar ISRU provides decreased IMLEO requirement

Sensitivity analyses for all cases studies revealed that IMLEO values all decrease as lunar ISRU capability increases. The cost of ISRU pays off if its capability is large enough. The more capable the ISRU system is, the more efficient it will be to use a common space infrastructure for multiple missions, even those with different destinations. Developing lunar ISRU capability is critical for a lunar architecture, and Ho suggests that it would be very beneficial to design Mars and NEO missions together if ISRU technology can achieve and possibly exceed the range of 1-7 kg/kg plant/year. Ishimatsu showed that the target for resource generation should be above 3.6 kg/kg plant/year, and this value falls within Ho’s range.

How to do Lunar ISRU?

Previous research does suggest that lunar ISRU does bring plenty of benefits to human space exploration missions, especially in terms of IMLEO estimates. Now, it is important to examine if the technology is capable of achieving the capability goals set by Ishimatsu and Ho.

(Data and results in this section excerpted from a S.M thesis of a graduate student in Professor de Weck’s lab:)
Schreiner, S.S. (May 2015). Molten Regolith Electrolysis Reactor Modeling and Optimization of In-Situ Resource Utilization Systems (S.M. thesis). Retrieved from DSpace@MIT. (Identifier No. 921147148)

Schreiner focused on an oxygen production technique called Molten Regolith Electrolysis (MRE), in which molten lunar regolith is directly electrolyzed to produce oxygen gas and metals (iron and silicon).

File:RegElec.png
Schematic diagram of Molten Regolith Electrolysis Reactor producing oxygen gas at the anode and molten metals at the cathode.

The MRE reactor model used in the thesis predicts that an MRE reactor is able to produce oxygen with a specific mass on the order of ≈10 (kg O2/year)/(kg reactor) and ≈5 (W)/(kg O2/year). These values provide initial evidence that an MRE reactor can be a viable option for producing oxygen from lunar regolith to resupply ECLSS consumables and provide oxygen for chemical propulsion systems.

The more oxygen the ISRU system produces annually, the more the total system mass is expected to increase. For a system that produces 10,000kg oxygen/year processing Highlands regolith, the largest system mass breakdowns are given below (in relation to total system mass):

  • Oxygen liquefaction/storage system (Designed to hold 6 months of oxygen production - can be relaxed depending on system needs): 30%
  • Reactor: 30%
  • Power System: 25%
File:Annualox.png
Resource requirement breakdown for 10t peak O2 production

Optimized models predict that:

  • 400kg, 14kW MRE-based ISRU system can produce 1,000kg oxygen per year from lunar Highlands regolith.
  • 1593kg, 56.5kW system can produce 10,000kg oxygen per year

Note that the optimal design of an MRE-based ISRU system does not vary significantly with regolith type, which gives flexibility in landing site designation.

As seen in this paper, Ishimatsu’s 3.6 kg/kg plant/year capability and Ho’s 1-7 kg/kg plant/year capability range can easily be met using an MRE-based ISRU system.

What is the optimum lunar ISRU architecture?

Now that lunar ISRU seems beneficial and is a feasible endeavor worth pursuing, we need to look into the details of an ISRU architecture and conduct a preliminary trade study to determine preliminary IMLEO estimates.

(Data and results in this section excerpted from a S.M thesis of a visiting student that Professor de Weck sponsored:)
Schrenk, Lukas, “Development of an In-Situ Resource Utilization (ISRU) Module for the Analysis Environment HabNet”, Visiting Student from TU Munich, December 2015

For a soil-based ISRU on Moon and Mars, a soil processor for water extraction and a water electrolysis unit has been implemented. The figure below depicts the design configuration of a water extraction system enhanced with additional subsystems (heat exchanger, filter, condenser, heater, and auger heater)

File:Schemsoiloven.png
Interbartolo, M. A., Sanders, G. B., Oryshchyn, L. et al. (2013), ‘Prototype Development of an Integrated Mars Atmosphere and Soil-Processing System’, Journal of Aerospace Engineering, 26.


Soil processing requires water extraction and water electrolysis(split water into oxygen and hydrogen, which is then provided as fuel at EML fuel depot where it is stored as liquids to refuel spacecraft)

Water Extraction Model

Currently available data suggest adapting water extraction sizing models by applying a sizing uncertainty factor to undetermined mass, volume, and power results:

  • Mass: 1.8 x calculated mass
  • Volume: 11 x calculated volume
  • Power: 1 x calculated power

The maximum size of the water extraction oven is constrained by various factors:

  • Chemical process inefficiencies in drying process due to large oven volume can decrease productivity rate at a certain point
  • Module size and assembly strategy can limit the maximum possible volume of the water extraction plant

Analysis conducted for three different water abundances (Minimum [0.5%], Mean [2.7%], Maximum [6.5%]) from Lunar Environmental Description Model (EDM) water map within +60 degree and -60 degree latitude.



File:Waterproduction3.png
Productivity for the water extraction process, for 3 different water contents in martian soil. Specific system mass for the water extraction process, for 3 different water contents in Martian soil. Specific mass of a water electrolysis system, for different hydrogen production rates.



Performance of water extraction system strongly depends on water availability at the target site.

Water Electrolysis Model

Not enough data on electrolysis units for space applications to draw a final conclusion. Sizing uncertainty parameters for mass, volume, and power:

  • Mass: 4 x calculated mass (mean value)
  • Volume: 1.64 x calculated volume
  • Power: 1 x calculated power


The thesis looked at producing LOX/LH2 propellant using lunar surface water ice found in shadowed craters. The production process is detailed in the figure below:

File:Propellantproductprocess.png
Overview of propellant production process from excavation to storage


Case study of two architecture ideas that provide in-situ fuel for a depot at EML:
  • Architecture A -(Decentralized Complexity) Fuel produced on orbit and shuttle transports water ice to fuel depot. Water electrolysis unit attached to EML fuel depot and a shuttle transports water ice from lunar surface to depot
    • Advantages
      • Water can be provided at fuel depot in addition to LOX/LH2
      • Water electrolysis unit at EML allows flexibility with regard to changing demand
    • Disadvantages
      • Ice transport: Common LOX/LH2 ratios are 5:1, and water has a ratio of 8:1. Therefore, more oxygen than hydrogen is transported (fixed oxidizer to fuel ratios)
      • Two electrolysis systems needed since shuttle cannot be refueled at the depot (shuttle propellant budget analysis showed that it uses more propellant on the whole trip than it can transport), one at lunar surface is needed for shuttle propellant production
  • Architecture B -(Centralized Complexity) Water electrolysis unit deployed with water extraction oven at lunar surface and shuttle carries LOX and LH2 to orbit. Produces propellant for both shuttle and fuel depot
    • Advantages
      • Oxygen and hydrogen can be transported independently of each other
      • Single electrolysis system on the surface can supply both shuttle and depot
      • Maintenance of the system can be checked with a single mission
    • Disadvantages
      • Delayed response to demand changes since production and transport are from lunar surface
      • Multiple cryogenic storage tanks: EML, Lunar surface, Shuttle
      • Cannot provide water without major changes
      • Everything is on Moon, which is more expensive to get to than Lagrange points

This conceptual design figure shows the major lunar surface systems necessary to produce LOX/LH2


File:Fueldepot.png
Source: Charania, A. C., and DePasquale, D. (2007), ‘Economic Analysis of a Lunar In-Situ Resource Utilization (USRU) Propellant Services Market’, 58th International Astronautical Congress


Full factorial search was applied to find the combination with minimum initial mass in LEO (IMLEO). Feasibility check used a time step analysis of the fuel demand scenario, preventing fuel depot tanks from dropping below zero (which would regard configuration infeasible). Optimum IMLEO determined by the mass of systems and propellant required to transport them to the surface or EML

Assumptions:
  • Demand evaluation function considers boil off (depends on tank size and location) and different launch strategies
    • EML tank exposed to space and solar radiation
    • Lunar surface tank assumed to be in shadowed areas and only exposed to thermal radiation from the surface and thermal radiation to space
  • Transportation evaluation constrained by the maximum number of launches during the demand scenario. Assumed that a round-trip to/from the lunar surface and EML fuel depot takes 8 days.
  • Use shuttle for transport: Estimated Delta-V required for a shuttle from surface → EML fuel depot: 2.64km/s, 2km/s necessary to reach LLO


Mass Comparison of Architecture A and B for combined NEO and Mars propellant demand scenario
A B
IMLEO 19844 (100%) 23988 (121%)
ISRU Systems 2383 (100%) 2644 (111%)
ISRU Mass to EML 428 (100%) 0 (0%)
ISRU Mass to Moon 1955 (100%) 2644 (135%)
Shuttle, Structural Mass to Moon 884 (100%) 1065 (121%)
Maximum Payload 6031 (100%) 5290 (88%)
Maximum O2 5361 (100%) 4513 (84%)
Maximum H2 670 (100%) 777 (116%)


Architecture B has a significantly higher IMLEO than Architecture A. This is because:

  • Mass to lunar surface is larger and more propellant is required for transportation
  • Due to nonconstrained Hydrogen and Oxygen relation, Architecture B transports less oxygen due to demand scenario
  • Due to higher boil-off losses (during surface storage and transport), more hydrogen has to be transported than Architecture A
  • Shuttle mass is higher because cryogenic storage tanks are heavier than a water ice tank due to insulation and higher internal pressure
  • Heavier shuttle for B leads to higher propellant production demand and therefore heavier ISRU system

Conclusion: Architecture A is the better solution to the lunar ISRU supported fuel depot

Advantages:

  • Provides more flexible fuel depot that can also supply manned missions with water and excess oxygen

Disadvantages:

  • Development of an additional electrolysis system for zero gravity operations at the fuel depot
  • Heavier fuel depot, which requires more propellant for station keeping

Muramoto (talk) Ferrous (talk) 21:30, 19 March 2019 (UTC)

Business Perspective

Commercial, Government Partnership Considerations The fuel depot business case (excel file attached) provides the basis for a sustainable presence on the moon. We can’t start from the moon – doing so assumes an unrealistic time and monetary investment up front without proof of return on investment. Our team proposes two fuel depots established in LEO, which can serve to propel government(s) sanctioned lunar exploration and jump start the commercial space economy (e.g. tourism, in-space manufacturing). Moon Missions The fuel depots serve as a staging point for optimizing the mass transported to the lunar surface. This can be materials for surveying, materials for infrastructure buildup, etc. As infrastructure is built up on the lunar surface, ISRU processing and storage becomes a potential revenue stream. An L2 fuel depot could represent the next staging point for deep-space missions. Space Economy The fuel depot provides a life source from which to develop a space economy. Fuel Depot The cost to develop and operate the fuel depot(s) is almost prohibitively expensive for one entity to should the amount. Partners will be required to get this project completed. In our initial business case, we propose government entities provide 70% of the cost for DDTE up to deployment and commercial entities provide 30% of the cost. Long-term, government entities enjoy a heavy discount on LEO fuel costs and the depots help stimulate space commerce in their respective countries. Strategic Resource To prevent one country from holding the project hostage, we recommend each country (government) contribute a percentage of their GDP (TBD) up front. This significant up-front investment anchors the country to the project. If they elect to leave the project, they agree to (initial contract) abandon their contribution to date. This mechanism incentivizes government entities from threatening to leave the project, possibly hampering progress. The biggest economic strategic resource in this project will the fuel depot interface. If an agreement can be made to provide one country exclusive rights to manufacture and produce this interface, essentially setting the industry standard, this entity will control everything. In particular, costs of fuel for this specific project. Since the most significant barrier to entry is up front and sustained capital investment, a very long-term strategic horizon it afforded this entity. Our team brings this point up as a topic of discussion for ownership and control of project assets and rights for long-term bargaining.



Fuel Depot Analysis Media:Fuel_Depot_Business_Case.png


  • Key Assumptions and Requirements


File:ISRU Processing Requirements 2.png
Source: NASA (2019), ‘NASA In-Situ Resource Utilization (ISRU) Development & Incorporation Plans’


  • Tanker and Propellant Launch from Earth to Cis-lunar Aggregation Point
    • Architecture 1: SLS
    • Architecture 2: Commercial Launch Vehicles


File:Concepts of Operations 1.png
Source: NASA Langley (2019), ‘Cost Breakeven Analysis of Cis-lunar ISRU for Propellant’


  • All-Up Architectures: All ISRU Infrastructure Deployed Using Earth-launched Capabilities Prior to the Start of Lunar Propellant Production
    • Architecture 3: Single Reusable Lunar Lander Delivered Propellant Directly from the Lunar Surface to the Cis-lunar Aggregation Point
    • Architecture 4: Reusable Lunar Lander Delivered Propellant from the Lunar Surface to a Reusable In-space Stage in LLO, In-space Stage Delivered Propellant from LLO to the Cis-lunar Aggregation Point


File:Concepts of Operations 2.png
Source: NASA Langley (2019), ‘Cost Breakeven Analysis of Cis-lunar ISRU for Propellant’


  • Alternative All-Up/Bootstrapping Architectures: Smaller Initial ISRU System is Deployed from Earth
    • Architecture 5: Initial ISRU System Produced Propellant from Lunar Resources to Enable the Lander to Return to the Cis-Lunar Aggregation Point to Retrieve Additional ISRU Systems and Deliver them to the Lunar Surface
    • Architecture 6: Initial ISRU System Produced Propellant from Lunar Resources to Enable the Lander and the In-space Stage to Return to the Cis-Lunar Aggregation Point to Retrieve Additional ISRU Systems and Deliver them to the Lunar Surface


File:Concepts of Operations 3.png
Source: NASA Langley (2019), ‘Cost Breakeven Analysis of Cis-lunar ISRU for Propellant’


  • Resulting Costs Per Kilogram of Each of the Six Architectures
    • The metric for evaluating the architectures was the cost per kilogram of propellant delivered to cis-lunar space, calculated as the total architecture cost divided by the total propellant delivered to meet annual demand over the time horizon
    • The most cost effective architecture overall was Architecture 2 (commercial delivery from Earth) at $40,000/kg followed by Architecture 1 (SLS Delivered Propellant) at $46,000/kg
    • The least expensive lunar ISRU architecture was Architecture 5 (Bootstrapping with single reusable lander) at a cost of $78,000/kg
    • Lunar ISRU propellant was found to be 97% more expensive than Earth-based propellant
    • The high cost per kilogram of Architecture 6 resulted from the large number of additional ISRU systems that were retrieved and delivered, the time it took to produce sufficient propellant using the existing capability to retrieve additional plants, and the number of spares required to support the growing lunar infrastructure during that time
      • 262 additional plants were needed (each producing less than 6 t/yr of propellant) to meet the annual demand of 59 t/yr in cis-lunar space (which corresponds with a production rate on the lunar surface of 594 t/yr)
      • Architecture 6 required 63 years from the initial delivery of an ISRU capability to reach full production
      • 31 SLS flights were required to deliver the spares to meet the sparing rate


File:Cost per mass.png
Source: NASA Langley (2019), ‘Cost Breakeven Analysis of Cis-lunar ISRU for Propellant’


  • Additional Metrics: Propellant Efficiency, Total Number of SLS Launches (14-year Time Horizon), 0% Sparing Requirement
    • Propellant efficiency is defined as the ratio of usable propellant delivered to cis-lunar space to the total propellant produced on the Moon
    • The number shows how much propellant is required by the reusable lunar lander (and reusable in-space stage in Architecture 4 and Architecture 6) to meet the propellant demand
    • Based on the performance of the lander and the trajectory requirements, the efficiency varies from 10% to 19%
    • Earth-based propellant was still less expensive than any of the four lunar ISRU architectures with a 0% sparing requirement
    • The addition of spares costs would lead Earth-based propellant to trade even more favorably vs lunar produced propellant
    • Including spares costs was identified as a priority for future work


File:Propellant Efficiency SLS Sparing.png
Source: NASA Langley (2019), ‘Cost Breakeven Analysis of Cis-lunar ISRU for Propellant’


  • Sensitivity Results
    • Figure 5 shows the changes in the cost per kilogram metric as a function of changes in the reusable lunar lander Inert Mass Fraction (IMF: total mass of the stage minus the mass of the propellant and the mass of the payload divided by the total mass of the stage)
    • Even significant improvements in lander performance relative to the baseline IMF value of 0.26 only lead to one architecture, Architecture 5 (Bootstrapping with only the reusable lander), reaching cost parity with Earth launch, at an IMF of 0.21


File:0.png
Source: NASA Langley (2019), ‘Cost Breakeven Analysis of Cis-lunar ISRU for Propellant’


    • Figure 6 shows the sensitivity of the architecture costs relative to the nuclear power system performance
    • The baseline specific power assumed in this study of 75 kg/kW is more efficient than more recent, lower power designs, which exceed 125 kg/kW
    • A factor of 3 improvement beyond this high-performing baseline in power system specific mass is required for the lunar-supplied propellant architecture to reach cost parity with Earth-launched propellant


File:00.png
Source: NASA Langley (2019), ‘Cost Breakeven Analysis of Cis-lunar ISRU for Propellant’


    • Figure 7 shows that the lunar ISRU architectures were highly sensitive to the mass efficiency of the propellant production plant
    • The baseline value of 109 kg plant mass per ton per year of propellant produced represents the mass efficiency of a molten regolith electrolysis system
    • Lunar ice ISRU system would need to be 2-3 times more efficient than this baseline for lunar-based propellant to become competitive with Earth-launched propellant
      • Lunar ice ISRU system would need to be better than 50 kg/(t/yr) to reach cost parity


File:1.png
Source: NASA Langley (2019), ‘Cost Breakeven Analysis of Cis-lunar ISRU for Propellant’


    • Figure 8 shows that the specific power of the ISRU system has a significant impact on the cost per kilogram of the lunar ISRU architectures
    • The specific power would need to improve by 2-5 times (<20 kW/tISRU) relative to the molten-regolith-electrolysis-derived value for lunar based propellant to compare favorably with Earth-launched propellant


File:2.png
Source: NASA Langley (2019), ‘Cost Breakeven Analysis of Cis-lunar ISRU for Propellant’


    • Figure 6 shows that the breakeven point occurs at 35 years of an annual propellant demand of 59 t/r


File:3.png
Source: NASA Langley (2019), ‘Cost Breakeven Analysis of Cis-lunar ISRU for Propellant’


Rover selection and exploration capability

Bringing a rover to the lunar surface is one of the most critical ways that the exploration value of a manned lunar mission can be increased. Having a rover allows for greater mobility on the lunar surface, and allows astronauts to potentially access different areas of scientific interest located away from the original landing location.

Two general categories of rover architecture were considered: pressurized rovers (such as the Space Exploration Vehicle) and unpressurized rovers (such as the rover that was used in the Apollo missions).

File:Example.jpg
Space Exploration Vehicle
File:LRV.jpg
Apollo Lunar Rover

While the pressurized rovers are generally heavier, they allow for a much greater range of travel and are self-contained, which supports more complex and longer duration field work. The unpressurized rovers are lighter and may save on costs, however their exploration value is lower since their range must be limited for safety to the distance an astronaut can reasonably be expected to walk in an emergency.

The table below shows mass values of a few different rover options. The “updated” Apollo rover assumes the same general design as the original Apollo rover, but constructed with lighter, modern materials and onboard equipment. The extended versions of the rovers are based on calculations that take into account what percentage of the mass of a car is generally due to passenger area. Those values are scaled to 4 person rovers.

Rover Mass (kg) Capacity (people) Capacity (equipment, kg) Maximum range (km) Pressurized Costs Notes
Apollo Rover 210 2 490 7.6 No Manufacturing Range limited by how far astronauts would be expected to walk back to lander
Space Exploration Vehicle 2994 2 998 201 Yes Manufacturing Rover developed (but never used) by NASA
Upgraded Apollo Rover 157.5 2 490 7.6 No Manufacturing Mass reduction based on studies that showed that cars had an average reduction in weight of 25% from the beginning of the 1970's due to upgraded technology and materials
Upgraded, extended Apollo Rover 189 4 490 7.6 No Design + Manufacturing Scaled up mass based on the percentage of weight that a car usually has for the passenger cabin
Extended Space Exploration Vehicle 3900 4 1100 201 Yes Design + Manufacturing Based on scaled up passenger cabin
(Also look at the option of bringing 2 regular space exploration vehicles) Manufacturing

References: [1] Determinants of U.S. passenger car weight http://faculty.washington.edu/dwhm/wp-content/uploads/2016/02/authorFinalVersion.pdf

Extensibilities for Mars Missions

Per business owner request, we focused on the lander element and its potential extensibility for Mars. This includes the commonality of elements within the lunar architecture (e.g. ascent element share the same fuel type) or commonality between Moon and Mars element that enable the same function in the architecture (e.g. Moon descent element vs. Mars descent element).

Architecture Element Lunar Architecture Earth-Moon-Mars Architecture Earth-Mars Architecture Commonalities
Lander
Ascent to Orbit ΔV to lunar orbit ~1 km/s ΔV to lunar orbit ~1 km/s ΔV to low Mars orbit 3.3 km/s None. Significant increase in ΔV required to reach stable orbit
Command and Service Module Larger to accommodate larger crew Similar
Launch Vehicle Two LV launches: first with cargo; second with crew Two LV launches: first with cargo; second with crew Requires greater capacity: send two LV cargo and 1 LV with crew Lunar and EMM could be similar with refueling at Moon, but Earth-Mars likely different since rocket capacity would need to be greater
Life Support Systems Human habitation needs for crew of 4 Human habitation needs for crew of 4 Increased cargo and habitation resources (e.g. longer duration suits) for crew of 6 Given that cargo will increase per architecture, if direct to Mars, similar attributes would include mass of caloric intakes etc.
ISRU Production Tools Methane: carbon monoxide on surface could be used to create fuel Methane: would need a system that could work on both Moon and Mars, which have different in-situ resources Methane: would have to bring hydrogen, then use CO2 in the atmosphere If using methane, may require different structures to ensure ISRU on both Moon and Mars
Entry, Descent and Landing Martian atmosphere ranges from 30 Pa to 1.1 kPa Martian atmosphere ranges from 30 Pa to 1.1 kPa Requires atmospheric interface hardware, such as heat shield, or significant ΔV margin to slow before entry to minimize heating
Power Systems Solar irradiance is ~ 1000 W/m2 on Earth surface Solar irradiance on Mars is ~ 590 W/m2 Solar irradiance on Mars is ~ 590 W/m2 None. Requires larger solar panels, alternate power generation capability, or significantly lower power usage
Communication and Navigation Systems Uses the Deep Space Network Mars system requires greater range and power Mars system requires greater range, power and laser communications Increase communications system power and mass budgets, use antennas ranged for the distance and pointing needs seen in a Mars mission profile


Partially based on:


Sse_studentx (talk) 18:55, 17 March 2019 (UTC)