Design Processes:A Moon Base Habitat Concept Design For Students and Arm Chair Astronauts

A 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

Source:Wiley J Larson and Linda K Pranke, “Human Space Flight, Mission analysis and design”

Mark Gargano - Mars Society Australia, Education Officer

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

Design Processes

Detailed Design process – long time & lots of errors

Develop aVeryDetailed Concept

(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)

(1) Traditional (sequential) Design Process

Develop a Rough Concept Various Design disciplines

Detailed Design process – shorter time, less errors

Fini

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War Room

Various Design disciplines

Concept Design Process & Design Teams

Various TechnicalSpecialists

Concept Design Process

Detailed ConceptDetailed Design

Mission statement or general aim, Scope of work and technical specifications/data

List Assumptions

Develop Concept

Assess risks & Check that Aims or general specification are satisfied

Design Teams (1950’s-60’s & Today)

Drawing Board

Aims - Specification

MarketingInformation

VendorEquipment

Design Teams (1970’s & 80s)

Technical Specialist(s)

or Manager(s)

DrawingBoard

Aims - Specification

VendorEquipment Marketing

Information

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.

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.

Concept Design Process – STEP 1Define the project aims, scope of work and technical specification

Mission statement or general aimNASA 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 workProvide 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.

Concept Design Process

Detailed ConceptDetailed Design

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

Concept Design Process – STEP 2List 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

Detailed ConceptDetailed Design

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

Concept Design Process – STEP 3-1Develop 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!

Concept Design Process – STEP 3-2Develop 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!

Concept Design Process – STEP 3-3Develop Concept : Estimate the volume and define a geometry/shape - 3

Volume and find a ‘first pass’ mass EstimateVolume: 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

SphereMost mass efficient shape.Has the least surface area for volume enclosedThe walls can be half as thick as a cylinder to carry the same load.

Volume = 4/3 (PI) R³Surface area = 4 (PI) R²

CylinderIs 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 CanMore mass efficient shapeGood as a stable landing platform

Volume = (PI) R²/2 x L

Surface area = 2x (PI) R²/2 (ends) + (PI) x D x L

Geometry and shapes

Note:The shapes must have rounded corners to minimize the bending stresses when pressurized.

Concept Design Process – STEP 4Develop 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 DescriptionOuter shell 22 kg/m² 80 mm Double walled aluminum shell including insulationInternal walls 8 kg/m² 50mm Double walled carbon composite incl insulationInternal floors 15 kg/m 150mm Double walled carbon composite incl insulationItem Area MassVolume Monocoque structureOuter shell 140 4,200 kg 120 m³ Isogrid strucureWalls 70 560 kg 3.5 m³ Graphite/epoxy compositesFloors 33 500 kg 4 m³TOTAL 5260kg

Note: For spherical structures use outer shell 17 kg/m

CO2 RemovalLiHO 4 Bed Molecular Oxygen

sieve (4-BMS) StorageMass7kg/4p/day 30 kg/p 1 kg/p/dVolume 0.005 m³/Cartridge 0.15m³/p 0.07m³/pPower 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

Concept Design Process – STEP 5Supply and recycling

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Number of Crew 6 Mass unit Mass kgVolumes unit Volume m^3

Number of days 30 allowance   subtotal     subtotalConsumables (/person, /day or /person per day)    Food (including 2/3 water)   2.30 kg/p/d 414 0.008 m3/p/d 1.44

Water   2.86 kg/p/d 513.90.00285

5 m3/p/d 0.51O2   0.84 kg/p/d 151.2 0.0007 m3/p/d 0.13

         Gas leakage - water kg/day   0.05 kg/d 1.5 0.00005 m3/d 0.00Gas leakage - O2 kg/day   1.2 kg/d 36 0.001 m3/d 0.03

Gas leakage - N2 kg/day   3.75 kg/d 112.50.00462

96 m3/d 0.14         

kitchen cleaning supplies   0.25 kg/d 7.5 0.0018 m3/d 0.054cooking utensiles   5 kg/p 30 0.014 m3/p 0.084

         Contingency fecal & urine collection bags   0.23 kg/p/d 41.4 0.0008 m3/p/d 0.144WCS suppies (toilet paper, cleaning, filters etc)   0.05 kg/p/d 9 0.0013 m3/p/d 0.234

         Hygiene supplies   0.075 kg/p/d 13.5 0.0015 m3/p/d 0.27Personal hygiene kit   1.8 kg/p 10.8 0.005 m3/p 0.03Clothing   99 kg/p 594 0.336 m3/p 2.016Personal stowage/closet space   50 kg/p 300 0.75 m3/p 4.5Disposable wipes   0.1 kg/p/d 18 0.002 m3/p/d 0.36Trash bags   0.05 kg/p/d 9 0.001 m3/p/d 0.18Operational Supplies (diskettees,ziplocks,velcro,tape) 20 kg/p 120 0.002 m3/p 0.012Sleep provisions   9 kg/p 54 0.1 m3/p 0.6Subtotals     2436.3   10.73 TOTAL :25% on mass+50% volume

  3045.4     16.10

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Number of Crew 4 Mass unit Mass kg Volumes unit Volume m^3Number of days 30 allowance   subtotal     subtotal

         Fixed Resources          Freezers   0 0 0 m3 0Conventional oven   50 kg 50 0.25 m3 0.25Microwave oven 2 ea   70 kg 70 0.3 m3 0.3Sink, spigot for food hydration and Drinking water   15 kg 15 0.0135 m3 0.0135Dishwasher   40 kg 40 0.56 m3 0.56Waste collection system 2 off   90 kg 90 4.36 m3 4.36Shower   75 kg 75 1.41 m3 1.41Handwash/mouthwash faucet   8 kg 8 0.01 m3 0.01Washing machine   100 kg 400 0.75 m3 0.75Clothes dryer   60 kg 60 0.75 m3 0.75Restraints and mobility aids   100 kg 100 0.54 m3 0.54Vacuum (prine + 2 spares)   13 kg 13 0.07 m3 0.07Trash compactor/trash lock   150 kg 150 0.3 m3 0.3Hand tools and accessories   300 kg 300 1 m3 1Spare parts/equipment & consumables   0 0 0 0Test equipment (oscilloscopes, gauges etc)   100 kg 100 0.3 m3 0.3Fixtures, large machine tools, Goveboxes, etc   250 kg 250 0 m3 0Equipment (still & vidio cameras, Lenses, etc)   120 kg 120 0.5 m3 0.5Film (assume digital)   0 0    Exercise equipment   145 kg 145 0.19 m3 0.19Medical/surgical/dental suite   200 kg 200 0.8 m3 0.8Medical/surgical/dental consumables   50 kg 50 0.25 m3 0.25Fixed resources Subtotals 2236 12.35Total incl 25% on mass+50% volume

2795     18.53Total Mass and Volume, Consumables + Fixed = 5850 kg & 34.5 m3

Concept Design Process – STEP 7: Power

We are using a solar cells power generatorThe Moon has continuous sunlight for 14 days

The solar energy flux in Earth orbit/Moon = 1370 kW/m²We can assume solar cell efficiency for long term life = 15% but can be higherAlso 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

The Solar Generator Design Assumptions

[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.

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?

Concept Design Process – STEP 7: Concept

We are using a solar cells power generator

Item Mass VolumeStructural Mass 4,200 kg 120 m³Fixed resources 2,800 kg 18.5 m³Expendable Supplies3,050 kg 16.4 m³Airlock 500 kg 5 m³Solar 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

Concept Design Process – STEP 8: Risk AssessmentRisk Likelihood Consequence Rank SolutionReturn ship may fail and Astronauts may stay longer than 14 days

E 5 M No solutionReturn ship cannot fail

Environmental system fails A 5 A Provide back up environmental system

Astronauts Become ill D 3 M Medical supplies and automated return ship

Solar Storm E 4 M Provide moon base with radiation shelter.

Structure punctured by meteorite

E 5 M Retreat to airlock & provide space suits in airlock.

Cosmic Rays A 1 M Cover base with regolith in long term

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

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 througha 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?