David Willson - NASA Ames/KISS institute of Practical Robotics david.willson@nasa

1. Design Processes:A Moon Base Habitat Concept Design For Students and Arm Chair AstronautsA teacher’s guide for the study of ‘Design Processes’ for high school students and arm chair astronauts using a moon base Hab design as inspiration. David Willson - NASA Ames/KISS institute of Practical Robotics david.willson@nasa.gov Mark Gargano - Mars Society Australia, Education Officer Source: Wiley J Larson and Linda K Pranke, “Human Space Flight, Mission analysis and design”

2. Overview • Design Processes • Traditional Design Process and Concurrent Engineering Process • Concept Development Process & Team work • Generation of Ideas • Design Example: Design an Accommodation Hab for a Moon Base • Define the project aims, scope of work and technical specification • Define the Assumptions • Concept • Estimate the volume and define a geometry/shape Define the Structure • Estimate the supplies and equipment • Estimate the power needs. • Risk Assessment - Concept Design

3. Design Processes Develop a Rough Concept Various Design disciplines Finished Product (1) Traditional (sequential) Design Process Detailed Design process – long time & lots of errors Various Design disciplines Develop a Very Detailed Concept Finished Product War Room Detailed Design process – shorter time, less errors (2) Concurrent (parallel) Engineering Design Process (How the Japanese out-competed US and European Car Manufacturers: “Kim B.Clark, Takahiro Fujimoto “Product Development Performance” Harvard Business School)

4. Concept Design Process & Design Teams Concept Design Process Design Teams (1950’s-60’s & Today) Mission statement or general aim, Scope of work and technical specifications/data Various Technical Specialists Aims - Specification List Assumptions Drawing Board Develop Concept Vendor Equipment Marketing Information Assess risks & Check that Aims or general specification are satisfied Design Teams (1970’s & 80s) Aims - Specification Drawing Board Technical Specialist(s) or Manager(s) Detailed Concept Detailed Design Vendor Equipment Marketing Information

5. How do we generate new ideas?(Where do they come from?) • Understand the ‘core’ of the problem as best possible before developing a new idea. - One technique is to empty the mind of pre-conceived notions and sketch out thoughts and associations as they come regardless of their impracticality. A new idea can be generated from these thoughts. • Look at the work of artists and science fiction writers. Their ideas may not be workable but can inspire and generate new ones. • Bounce ideas of others. Allow others to add and change. Let the ‘team’ develop the idea. This requires good teamwork. An individual cannot know more than the team.

6. Design Example: Design a Moon Base Habitat (Hab) NASA is to build a moon base to be visited regularly during the moon’s daylight period. The construction will start late in 2018. The moon base will consist of an accommodation Hab, a science laboratory Hab and large airlock for rovers and moonwalkers. The accommodation Hab will be the first to land on the Moon. You have been given the contract to make the accommodation Hab! Contract: Provide an accommodation Hab that is to be located on the moon and lived in during the moon’s daylight period of 14 days. It must be at Cape Canaveral on 1st July 2018 for launching to the moon. The Hab is to have: - Provision for 6 people to sleep, exercise and relax; - The Hab must have capacity to be independent from the moon base; - A 500 kg, 5m³ emergency airlock; - A walk through docking port in one location to connect to other Habs; - Supplies and space for the 6 people suitable for a total of 30 days; - Solar cell power generator that will be erected on the moon by the first visiting astronauts - The Hab must fit in the ‘heavy lift rocket’ payload space that is a diameter of 7 metres and 20 metres long; - 50 Year life with capacity to be modified.

7. Concept Design Process – STEP 1 Define the project aims, scope of work and technical specification Concept Design Process Mission statement or general aim NASA is to build a moon base to be visited regularly during the moon’s daylight period. The construction will start late in 2018. The moon base will consist of an accommodation Hab, a science laboratory Hab and large airlock for rovers and moonwalkers. Scope of work Provide an accommodation Hab that is to be located on the moon and lived in during the moon’s daylight period of 14 days. It must be at Cape Canaveral on 1st July 2018 for launching to the moon. Technical specification: The Hab is to have: - Provision for 6 people to sleep, exercise and relax; - A 500 kg, 5m³ emergency airlock; - A walk through docking port in one location to connect to other modules; - Supplies and space for the 6 people for a total of 30 days; - Solar cell power generator that will be erected on the moon by the first visiting astronauts - The module must fit in the ‘heavy lift rocket’ payload space that is a diameter of 7 metres and 20 metres long; - 50 year life with capacity to be modified. Mission statement or general aim, Scope of work and technical specifications List Assumptions Develop Concept Assess risks & Check that Aims or general specification are satisfied Detailed Concept Detailed Design

8. Concept Design Process – STEP 2 List Assumptions Assumptions • The moon environment is: • A vacuum and Habs must be pressurized; • An average temperaturer of 253ºK during daytime. Habs must have insulation and radiators to dump wast heat. • The module must be re-supplied with 14 days supplies when the crew arrive for their 14 day stay. • The emergency airlock can be used for other things as it will be rarely used. • The module must have a shower, toilet and 6 bunks/rooms; -The solar cells can be cleaned by the astronauts in moonwalks and are operational 90% of the time. Concept Design Process Mission statement or general aim, Scope of work and technical specifications List Assumptions Develop Concept Assess risks & Check that Aims or general specification are satisfied Detailed Concept Detailed Design

9. Concept Design Process – STEP 3-1 Develop Concept : Estimate the volume and define a geometry/shape - 1 Consider the graph above (NASA-STD-3000) It shows the ‘free’ space per person considered as ‘accepted’ over given time periods. If a person has less than the accepted ‘free’ space then it is considered as ‘intolerable’ for the person. Remember the graph is for spacecraft in orbit with crew in 0 G conditions where ‘free’ space is more easily usable. Our Hab is on the moon. We are to design ‘free’ space for 30 days or 1 month. This translates to a minimum of 4 m³ but better with 10 m³ free space. We will use 10 m³ free space as our minimum bench mark. This is not much – a cube 2.15 metres per side!

10. Concept Design Process – STEP 3-2 Develop Concept : Estimate the volume and define a geometry/shape - 2 Now consider the graph above (NASA, 1995) It shows the history of total space per person over given time periods for various spacecraft. Thisincludes space for ‘free space’ and ‘space for equipment and supplies’ for time durations. Again remember the graph is for spacecraft in orbit with crew in 0 G conditions where space is more easily usable. Our Hab is on the moon. We are to design space 30 days or 1 month. This translates to a 20 m³ space per person. This is still not much space!

11. Concept Design Process – STEP 3-3 Develop Concept : Estimate the volume and define a geometry/shape - 3 Volume and find a ‘first pass’ mass Estimate Volume: The previous slide suggested we use a total space of 20 m³ per person. Thus for 6 people, Volume = 6 people x 20 m³/person = 120 m³ ‘First pass’ Mass Estimate: Design history of manned spacecraft show that the mass of the spacecraft habitation space is a function of Volume, Number of crew and Endurance time. We use the algorithm Mass = 592 x ( Volume (m) x number of crew x Endurance (days))^0.342 = 592 x (120 m³ x 6 crew x 14 days)^0.342 = 13,850 kg Geometry and shapes Note: The shapes must have rounded corners to minimize the bending stresses when pressurized. Sphere Most mass efficient shape. Has the least surface area for volume enclosed The walls can be half as thick as a cylinder to carry the same load. Volume = 4/3 (PI) R³ Surface area = 4 (PI) R² Cylinder Is easy to move around and bury under regolith. Nice shape to fit together. Volume = (PI) R²/2 x L Surface area = 2x (PI) R²/2 (ends) + (PI) x D x L Tuna Can More mass efficient shape Good as a stable landing platform Volume = (PI) R²/2 x L Surface area = 2x (PI) R²/2 (ends) + (PI) x D x L

12. Concept Design Process – STEP 4 Develop Concept Geometry and Structure We choose a cylinder as our geometry as it is more useful to for connecting to other HABs. - Adopt 4.2 m diameter as it can be cheaply manufactured and transported on Earth. - Adopt 9.5 m in length as this provides a volume of 120 m³ . Item Mass/m² Thickness Description Outer shell 22 kg/m² 80 mm Double walled aluminum shell including insulation Internal walls 8 kg/m² 50mm Double walled carbon composite incl insulation Internal floors 15 kg/m 150mm Double walled carbon composite incl insulation Item Area Mass Volume Monocoque structure Outer shell 140 4,200 kg 120 m³ Isogrid strucure Walls 70 560 kg 3.5 m³ Graphite/epoxy composites Floors 33 500 kg 4 m³ TOTAL 5260kg Note: For spherical structures use outer shell 17 kg/m

13. Concept Design Process – STEP 5 Supply and recycling CO2 Removal LiHO 4 Bed Molecular Oxygen sieve (4-BMS) Storage Mass 7kg/4p/day 30 kg/p 1 kg/p/d Volume 0.005 m³/Cartridge 0.15m³/p 0.07m³/p Power 12 W 0.3 kW/p - 4-BMS: 4 beds of synthetic zeolites or aluminum-silicate metal, two beds for CO2 obsorption and another two for water vapor material. The beds are heated to expel the CO2 overboard and water vapor collected. The Russian Mir space station used KCLO4 Potassium Perchlorate, where 1 kg KCLO4 provides 0.46 kg/p/d. A person requires nominally: • 30 kg supplies/person/day • This consists of: • 27kg water per day for drinking and washing. • 2 kg, food including 2/3 mass water per day. • 1 kg Oxygen per day We can recycle 24 kg water via the air conditioning, filtering washwater and distilling urine As such each day a person wastes nominally 6 kg in the form of CO2 some urine, faces and Brine. The supply mass budget per day per person = 6 kg/day/person

14. Concept Design Process – STEP 6-1 Develop Concept : Equipment and supplies

15. Concept Design Process – STEP 6-2 Develop Concept : Equipment and supplies Total Mass and Volume, Consumables + Fixed = 5850 kg & 34.5 m3

16. The Solar Generator Design Assumptions Concept Design Process – STEP 7: Power [i] The Cambridge Encyclopedia of Space, Cambridge University Press, Cambridge, p137 [ii] Clawson, “AG-Pod – The Integration of Existing Technologies for Efficient, Affordable Space Flight Agriculture.” 29th International Conference on Environmental Systems Denver, Colorado July 12-15 ,1999. We are using a solar cells power generator The Moon has continuous sunlight for 14 days The solar energy flux in Earth orbit/Moon = 1370 kW/m² We can assume solar cell efficiency for long term life = 15% but can be higher Also adopt and mass per Watt = 55 Watts/kg Suggest to allow an additional 50% to allow for the twilight period. For the concept allow 3 kW per person. This covers the environmental system radiators, stoves fridges etc. As such we require 27 kW mass = 490 Kg solar panels

17. Concept Design Process – STEP 7: Concept Questions: Are the rooms placed well for: -dealing with sound? • dealing with dust if the airlock is used? • connecting to other moon base ‘Habs? • Is the airlock practical in terms of entrance and exit?

18. Concept Design Process – STEP 7: Concept We are using a solar cells power generator Item Mass Volume Structural Mass 4,200 kg 120 m³ Fixed resources 2,800 kg 18.5 m³ Expendable Supplies 3,050 kg 16.4 m³ Airlock 500 kg 5 m³ Solar Generator Power 460 kg Margin (25%) 2,750 kg TOTAL 13,760 kg. Our original guess was 13,800 kg Free Volume 82 m³ This is 13.6 m³ per person and is > than our minimum 10m³/person

19. Concept Design Process – STEP 8: Risk Assessment For the exercise you need to consider the risks and select a matching ‘Likelihood’, ‘Consequence’ and ‘Rank’ An acceptable rank is ‘L’ or low to ‘M’ or medium. If it is not ‘L’ or ‘M’ then we need a ‘ design’ or ‘procedure’ solution in place to make it L or M You need to consider the solution or procedure and write it in the column above

20. Exercise: : Undertake a Risk Assessment on NASA’s Proto- type Manned Luna Rover: Forward your answers to NASA! Note the ‘Port Suits’. Astronauts climb into them through a door in the rear of the rover compartment. Suggested Issues to Consider: • How reliable do you think it would be in off road terrain compared to a ‘Land Rover’ vehicle? • What happens if it collides with a boulder or drives into a ditch? - Do you think it will be stable with the moons low gravity? • Do you think it is safe to climb on and off the rover in the suits? - How much maintenance do you think would the rover need compared to a ‘Land Rover’ vehicle?