Habitat Commonality for Lunar and Martian Missions

A Thesis

Presented to the Faculty of the Department of Mechanical Engineering

University of Houston

In Partial Fulfillment

of the Requirements for the Degree

Master of Science

in Space Architecture

Abhinav Prakash

May 2019

Habitat Commonality for Lunar and Martian Missions

Abhinav Prakash

Approved:

Co- Chair of the Committee Olga Bannova, Director SICSA Department of Mechanical Engineering

Co- Chair of the Committee Larry S. Bell, Director Emeritus SICSA Department of Architecture and Design

Committee Members:

Kriss Kennedy, Adjunct Assistant Professor Department of Mechanical Engineering

Larry Toups, Exploration Mission Planning Office NASA, Johnson Space Center

Suresh K. Khator, Associate Dean, Pradeep Sharma, M.D. Anderson Chair Professor Cullen College of Engineering Department Chair of Mechanical Engineering

Acknowledgements

I would like to thank all my professors in this great endeavor. They have been the leading light to constantly encourage and motivate me to strive for better results which has culminated in this thesis. I would also like to thank my friends and my family for constantly standing by my side.

Habitat Commonality for Lunar and Martian Missions

An Abstract

Of a

Thesis

Presented to the Faculty of the Department of Mechanical Engineering

University of Houston

In Partial Fulfilment

of the Requirements for the Degree

Master of Science

in Space Architecture

Abhinav Prakash

May 2019

Abstract

Human missions to the Moon and Mars are the future of the human civilization. In the current scheme of things, space missions are very complex and costly. This study presents some common elements that can be used during both Lunar and Martian missions.

The various possible forms of a habitat are studied and the one best suiting the requirements is chosen. A mission statement for both missions is drafted to analyze the functional requirements of such a mission and their similarities and differences. Finally, subsystem commonality is studied i.e. the requirements for the adaptation of currently existing zero gravity systems to partial gravity. The structure system is studied in particular to develop a common structure that can ideally survive launch loads. An element for the delivery and installation of habitats is also developed.

vii

Table of Contents

Acknowledgements…………………………………………………………………v

Abstract…………………………………………………………………………….vii

Table of Contents…………………………………………………………………..viii

List of Figures………………………………………………………………………ix

List of Tables………………………………………………………………………..x

Nomenclature………………………………………………………………………..xi

Chapter I

I. Introduction………………………………………………………………….1

II. Case for Commonality………………………………………………………2

III. Design Philosophy…………………………………………………………..3

IV. Environment Study………………………………………………………….4

Chapter II

I. Mission Scenario……………………………………………………………7

II. Mission Outline……………………………………………………………..8

III. Design commonality………………………………………………………..9

Chapter III

I. Habitat Design…………………………………………………………….12

II. Multi Utility Vehicle………………………………………………………20

Conclusion…………………………………………………………………………25

References…………………………………………………………………………27

Appendix…………………………………………………………………………..28

viii

List of Figures

1. Mission Outline for cargo delivery to landing site ……...... 8

2. Architecture elements developed as part of Mars architecture……………..10

3. Modified Architecture elements utilizing common habitat………………...11

4. Cost Comparison of architecture with and without commonality………….11

5. Different vertical and horizontal habitat forms……………………………..14

6. The two different end effectors on the MUV with the storage area………...22

7. The MUV offloading from the decent vehicle……………………………...23

8. The MUV using its excavator to load regolith into the storage…………….24

9. The MUV latching onto a habitat and moving it from lander to base site….29

10. The different iterations of the habitat structure and their stress analysis…...30

List of Tables

1. A comparison of subsystem requirements and possible

modifications……..…………………………………………………………18

2. A comparison of the various environmental conditions on Moon and

Mars…………………………………………………………………………28

Nomenclature

ISS = International Space Station

ConOps = Concept of operations

SPE = Solar particle event

GCR = Galactic cosmic radiation

TCS = Thermal control system

ECLSS = Environmental control and life support system

Chapter I

I. Introduction

Commonality is a buzz word in the space sector. Commonality is the ability to utilize a single element of a system to perform multiple functions. It is a much- required characteristic amongst various space systems. It leads to multiple advantages such as reduction in cost and complexity, reduction in mass and less training for crew to acquaint themselves to diverse components. The International Space Station (ISS) also exhibits some form of commonality which was imposed on it due to the space shuttle. The ISS has a common form for most of its modules. This is because of the size of the space shuttle cargo bay. However, the functional arrangement of systems inside is very diverse. Due to form commonality in the ISS there were benefits in the form of universal installation and assembly procedures in Low-Earth Orbit (LEO) as well as easier manufacturing resulting in the formation of the ISS heritage systems which is commonly cited in literature as a premise for elements based on it.

Apart from the ISS there have been efforts in the past to instill commonality between zero gravity and partial gravity systems such as the creation of a common element that can be used to perform different functions in the Earth-Moon-Mars system. A study develops a common habitat that is integrated with different infrastructure based on the requirements of the vehicle. For example, the habitat is integrated with an ascent vehicle to function as a Mars ascent vehicle but, the same habitat can also be couple to a surface chassis to form a Mars surface rover. However, this requires the pre-integration of the developed habitat to the additional elements.

II. Case for Commonality

The multiple advantages for commonality are:

 Interchangeable – In case of an emergency a module destined for one

destination may be easily replaced due to the availability multiple spare

modules already produced.

 Reduced Cost – Since a single habitat can be used for both Lunar and Martian

missions, the development cost reduces by almost half since only one module

development phase is required.

 Empirical Contingency Procedures – In case of an on-surface emergency or

malfunction the crew does not need to be trained on different elements. Their

training on a single module can be universal irrespective of whether they are

assigned to a Lunar crew or Mars crew.

 Simpler Manufacturing – Space habitats require a long time and high precision

to be manufactured due to their critical nature. Ensuring manufacturing of only

one type of product increases experience as well as reduces cost.

 Less Spares – If two different habitats are to be made, they would require a

different set of spares leading to manufacturing and inventory management. If

a common habitat is developed such efforts are reduced.

 Easier Troubleshooting – A single habitat can be widely tested to find all

failure modes. If all failure modes are known, dedicated staff and training

required for troubleshooting is reduced.

 Common Training – As indicated above, crew and support staff don’t have to

be accustomed to multiple elements and can utilize their common training to

develop other solutions that might work in both environments.

III. Design Philosophy

To start the design, process a set of high-level guidelines were developed to

assist in the design process. These guidelines are stated below.

A. Vision

To reduce the cost of space missions to build widespread colonies on the Moon

and Mars.

B. Mission

Develop a set of elements that can be used on the Moon and Mars based on their

varied environmental and mission parameters.

C. Goals

1) Should define form and configuration of given habitats.

2) Should define functional distribution of base.

3) Should design subsystems that can be used in both environments.

D. Objectives

1) Identify different habitat forms and compare them.

2) Identify different habitat configurations.

3) Identify variety of functions required on the base.

4) Find subsystems required for providing given functions and modify them to

function in both environments.

5) Integrate modified subsystems with designed habitat.

6) Assess feasibility of designed habitat to be adapted to zero gravity.

E. Requirements

1) Shall be capable of supporting four crew for mission duration.

2) Shall be capable of resisting high temperature variations.

3) Shall have internal systems capable of self-adjusting to different gravity

environments.

4) Structure should be able to support launch and landing loads.

5) Shall be able to shield humans from high radiation environment.

F. Assumptions

1) Shorter duration sortie missions have been conducted.

2) All technologies used are matured by mission launch.

3) Mars and Moon present same radiation environment.

4) Suitable quality control standards exist for all elements.

G. Risks

1) Different partial gravity environments present a big difference.

2) Lunar systems are overdesigned resulting in higher cost.

IV. Environment Study

The Lunar and Martian environment have a set of common entities and different

entities. The degree of commonality or difference however, depends on a personal

perspective. In very high order general terms they are exactly the same because they

have similar pressure, temperature, dust, wind and radiation. But, on careful

breakdown there are certain differences that are critical towards design.

A. Pressure

The Moon does not have any atmosphere. Years of solar wind have

eroded the atmosphere it used to have. Therefore, the vacuum of space is also

found on the lunar surface. However, Mars does have very little atmosphere.

The density of Martian atmosphere is 1/100th of the Earth atmosphere. The

resultant difference on common design is the structure/ pressure vessel must

be designed such that it can withstand vacuum while maintain an earth

atmosphere inside. For crew a direct effect is the design of EVA suits as

motion might be slightly easier on Mars.

B. Temperature

The moon due to lack of atmosphere presents a variation of almost 400

K between the highest temperature during the Lunar day and lunar night. Mars

however shows only a difference of about 80 K. This is a drastic difference in

temperatures. The thermal load on the Thermal Control System (TCS) is

massively different. So, for a common TCS it must account for Lunar

temperatures as well. From a human perspective, a wide temperature gap

changes the EVA frequency as suits might not be able to work against very

high lunar noon temperatures.

C. Dust

On the moon dust is very fine as well as electromagnetic. It tends to

stick to surfaces. On Mars, dust is very fine but not electromagnetic. Although,

it too does tend to settle on surfaces but sometimes wind helps in blowing off

settled dust. This is as much a system challenge as a human challenge. Systems

should have to be resilient to dust storms and coated or covered appropriately.

The systems should be agnostic to nature of dust i.e. electromagnetic or not.

For humans this poses a risk while EVA as when coming from an external

environment to an internal environment care has to be taken to not contaminate

internal systems with dust.

D. Wind

The moon due to a lack of atmosphere does not have any wind. Mars

has winds but due to the low density of air the wind does not result in high

loading. A direct result of wind is massive dust storms. Systems must be

resilient to dust as mentioned above.

E. Radiation

The moon is a high radiation risk. It is subject to solar particle events

(SPE) and galactic cosmic radiation (GCR). It is necessary to shield both

systems and humans. Even though Mars has an atmosphere it tends to provide

very little protection from radiation. So, systems as well as humans have to be

shielded from radiation.

F. Gravity

The gravity on the moon is one-sixth earth gravity. We have very little

experience with partial gravity and that too during the Apollo missions.

However, the gravity on Mars is one-third of earth gravity. At present, we have

insufficient data to gauge the difference between one-sixth and one-third

gravity. However, this variation affects primarily the humans as well as the

system.

G. Day/Night Cycle

The moon has a four-week day/night cycle. That is two weeks of

continuous day and two weeks of continuous night. However, this factor on

Mars is very similar to Earth. Mars has a 24.5-hour day/night cycle. So, it

would be easier to acclimatize to that. This factor primarily affects the human

and care should be taken during design to relieve psychological stressors due

to that.

CHAPTER II

I. Mission Scenario

The mission is designed to be able to work on Mars and Moon. So, it was tried that the set of mission parameters chosen for both missions remain similar. However, this was not possible as the variation of mission parameters on Moon and Mars are very different. For example, a Martian mission would practically take about 500 days, but the lunar mission could be shorter ranging from sortie mission durations to permanent occupancy. Hence, to start the design process the following mission parameters were chosen.

Mars

Plan a 600+ day mission on Martian surface that utilizes the Long Stay- Fast

Transit concept. The proposed design should be adaptable to shorter mission durations. The majority of activities during this mission are focused on science and

Martian environment investigation.

Moon

The Moon is a much closer destination for humans as compared to Mars. Hence, the frequency and duration of human missions will vary leading to many missions conducted in a relatively short time span. Humans return to the moon in the near future and during successive missions study the lunar environment and test high TRL technology in a real-world scenario. Hence, Initial missions to the moon may be very short resembling Apollo era missions. But as we build experience we start functioning in a more sophisticated manner which is useful in to future missions. Therefore, the mission duration would increase to about a week. For these missions a lander-based infrastructure should be sufficient. Following these steps, a long mission to the moon

can be conducted. The infrastructure required for a 100-day mission is investigated.

Surface activities consist of science and exploration investigations.

The number of crew for both missions is maintained constant at four. Both cases should present the possibility for future base growth, it was also seen that apart from habitats a mission of this nature would also require other elements.

II. Mission Outline

The timeline for this mission remains uncertain, as it depends on the completion of earlier missions being successful. Once other missions are successful, and experience is gained the first launch takes place.

Figure -1 – Mission Outline for cargo delivery to landing site

The first launch is a cargo launch. It carries a set of three rovers to the lunar/Martian surface. Deliberate care is taken to insure elements remain location agnostic. The rovers scout the base site and send back data in the form of images and maps. Based on this data it is decided if the chosen site is feasible or not. If the site is not feasible another prospective site is already chosen as backup for scouting.

The landing site on being decided leads to a launch of a cargo vehicle from earth.

The launch vehicle may be an SLS block 2, Falcon Heavy or BFR based on the

delivery requirement in terms of mass. The first launch vehicle has ISRU related

hardware. It also contains a power source which is Kilopower. Kilopower can supply

at least 10 kW of power for up to ten years. Once the ISRU elements are landed,

system checks are run and on successful confirmation a second launch is planned.

This phase has two major launches back to back. Since, launch opportunities to

the Moon are much more than Mars, the exact time difference between launches is not

critical for a lunar mission but is critical for a Martian mission. So, the two successive

launches deliver the Multi-Utility Vehicle (MUV) which are mounted on a custom-

built lander. Once these are launched confirmed functional, the next phase begins.

In the next phase, the same launch vehicle is used but other items such as

backup equipment, food, water, logistics equipment etc. are also launched.

The last phase is the habitat launch and landing. The habitat launch takes place

such that all habitat elements are consecutively launched during the same launch

window as one ladder can only accommodate one habitat. Hence the total number of

launches is a direct function of number of habitat elements.

III. Design Commonality

Commonality has certain benefits when it is designed into systems. As per a

study conducted in 2015 commonality plays a huge part in decreasing costs and

simplifying mission architecture. In this study 1.Griffin et. Al. looked at different

elements that were designed as part of a Mars architecture. Each element had a

separate role. But some functions of the elements were similar such as mission

requirements in terms of duration of use, crew capacity and reusability. The elements

for this mission were a combination of crew and cargo vehicles. The study developed

a habitation element which could function as a habitat as well as a cargo element.

They integrated the new designed habitat with some parts of the old design. The new elements performed the desired functions by using the common habitat element. As a result, it was concluded that trying to incorporate commonality into a new design is easier as compared to designing elements and trying to find common functions or uses.

Commonality also provides the unique advantage of cost savings. In this case the cost saving was approximately $1.5 billion which is about 8% of the current NASA budget.

If these funds were available, they could be diverted to other studies which in turn could lead to technology development for other missions.

Figure -2 – Architecture elements developed as part of Mars architecture

Figure -3 – Modified Architecture elements utilizing common habitat

Hence, this study tries to introduce commonality as part of the design process from the beginning. When on Moon/Mars several elements are going to be used if all the functions needed are listed in the sign phase then it can be explored that how these functions can be performed by similar elements. For example in this case some elements that would be common were the habitat, transportation elements, power elements and rovers. Some of these elements are already in mid TRL levels such as the chariot rover.

Figure -4 – Cost Comparison of architecture with and without commonality

Chapter III

I. Habitat Design

When designing a habitat for any mission, some factors are number of crew, mission duration, nature of activities etc. But apart from that, factors such as mass and volume of the habitat also play a role. So, to start the habitat design process it was broken down into three primary parts.

A. Form and Configuration Commonality

B. Function Commonality

C. Subsystem Commonality

A. Form and Configuration Commonality

The habitat design needs to start by deciding if the nature of the habitat

is going to be vertical or horizontal. To study that different habitats were

studied starting from a 5m diameter,2 level habitat and a horizontal habitat

with the same volume. Over design iterations it was seen that a larger hatch

size needed to be incorporated in the system. The earlier systems used a

standard CBM with a diameter of about 1m. But this size would be

insufficient for even crew to pass through. Hence, the size of the hatch was

increased to a 2m diameter. After this iteration it was realized the habitats that

would be a result of this design would be too heavy to launch and land as their

masses were of the order of 50mT. The habitat was modified so that the mass

of each element is reduced. To do that the vertical habitat was scaled to a

single level habitat. Similarly, the horizontal habitat was scaled such that it

had the same volume as the vertical habitat. On looking at the resulting design

it was seen that the vertical habitat poses a greater advantage as it provides a

lower ratio of circulation volume to total pressurized volume. This means that when internal functions in the habitat are assigned there would be more space available. In the horizontal habitat the total volume was almost equivalent to the circulation volume which was not compatible with the desired design.

Most of the space on the circumference were taken up by hatches. However, a unique advantage of the horizontal habitat was that it could be divided into two sections

a) Circulation region- This is the region through which circulation volume passes. There is some space still available on the boundary and smaller functions such as storage and galley region could be accommodated.

b) Functional Region- This is the region that is marginalized to one sie of the module such that the circulation volume does not interfere with it. This functional region can be dedicated to any function and could serve as a specialized area. For example – It could support the ECLSS racks of a module or be used as the science area. This could be separated using small plug n play partitions. However, since the mass was too large for designs matching requirements and no functional area was available in the smaller, lighter habitats, this design was not chosen. Hence the final design chosen was the vertical habitat considering its mass and volume advantages.

Figure -5 – Different vertical and horizontal habitat forms

Another study that was conducted was to study different hatch

orientations in the habitat. Some of the hatch angles that were looked at were

180deg, 120deg, 60deg and 50 deg. Since the volume of the habitat is already

fixed the hatch angle manipulates the circulation volume and the growth

design for the base. Of all the available angles for hatch alignment, hatches

at 120 deg were chosen because they naturally divide the habitat into two

sections which serve a major and a minor section. Another advantage of this

orientation is that it is compatible to use with habitats with different number

of hatches. For example – if the habitat were to have 3 hatches certain

orientations such as 180deg can’t be used. Hence the current objective is to

design variants which are two hatch and three hatch modules. Two different

orientations are chosen because the three hatch modules could act as the

command control and interface module which would only act as a central

node and enable connection with other habitats and keep open hatches for

future expansion. Hence final system of 120 deg hatches fitted into two

modules of three hatches and two hatches is used. Due to this the two-hatch

module acts as a specialized functional module. The larger area of the habitat

is used for the larger functions such as exercise or medical whereas the smaller

area can be used for storage and medical activities. Hence as the base grows

the nodes become the central parts. Based on functions that need to be carried

out in certain base regions, the offshoot from the node arm can be used for

functional categorization. However, the current habitat is not designed for

functional specialization and is used to perform all functions in general.

Different functions share the same general habitat area.

B. Function Commonality

The base needs to be able to provide basic functions for the crew to

survive and perform mission tasks. The functions on a preliminary base like

this one is common amongst all bases. The base needs to have power, ECLSS,

storage, galley, crew quarters, medical area, command and control as well as

science areas. This would be common to any habitat designed for any mission.

The difference would be that some functions might be added based on the

specific mission design requirements. This can be proven by making the

argument that all these functions are present on the ISS and for any planetary

base where humans were to survive these were the basic things that would be

required. Hence, for both these environments the list reads: Medical,

Recreation, Dining, Hygiene, Exercise, Sleep, Trash Disposal, EVA,

Functionality for Daily Work Activities and Storage. These being general

functions which would mostly remain common.

However, the nature of some functions could differ due to the location.

The exercise systems are designed to keep astronauts fit during the mission and avoid harmful effects of absence of gravity. In zero gravity, on the ISS each astronaut is tasked to 2.5 hours of rigorous exercise per day. However, if gravity is introduced in the system, the stress due to gravity increases (which is desirable) and in partial gravity the need to exercise would not be as much as on the ISS. However, this requires further research into conditioning of the human body to different gravity conditions. It might be possible that on Mars since gravity is comparatively, stronger (one-third G) the physical deconditioning would be less fierce as compared to the moon (one-sixth G).

So, to conclude due to the different possible effects of different partial gravity values on the human body the duration of exercise might change. So, to keep in calibration with that, the sophistication and hence volume devoted to exercise may decrease as the partial gravity increases.

Another factor that shares a similar location dependent function is storage. The nature of redundancy on any mission is directly proportional to the level of autonomy required and travel time to destination from earth.

During a lunar mission, resupply is possible. With the onset of commercial launch capabilities this could even be done on a commercial contract. So, lunar resupply would mean a smaller storage inventory would be required.

Also, since the moon is very close to earth the communication lag is very small and hence mission control is always available on standby. So, a large inventory of redundant parts isn’t completely necessary. However, on a

Martian mission both of these factors would be different. Any resupply from earth is not an option as the mars launch window which requires minimum

expenditure in terms of cost and delta v is available every two and a half years.

So, this would mean that resupply from earth is not a feasible option. The

most feasible nature of resupply could be from a pre-positioned orbital asset

supported by a reusable ascent-descent vehicle to the Martian surface. But this

means that the base has to be capable of handling a larger inventory which

would mean a larger storage volume. Autonomy also has a role to play in this

discussion. On a Martian mission due to a large communication delay the total

transmission and reception lag could be as large as forty minutes. To account

for this eventuality an extra layer of redundancy is required and hence a larger

area for storage.

C. Subsystem Commonality

The subsystems on a habitat are indispensable when considering

commonality. The different systems that are part of the habitat must be

customized to be able to maintain ambient conditions inside. This is a very

common phenomenon which is also observed on earth. The types of houses

depend largely on the geography. Which means that the climate of the region

is one of the major design drivers amongst many others in building design.

The following table shows a comparison of the different subsystems

that would be part of a habitat and the major challenges encountered in

communalizing them.

Table 1- A comparison of subsystem requirements and possible modifications

One important factor to pay attention to is the interaction of human and

environment. This interaction can be classified into two categories.

1. Primary interaction – A primary interaction may be defined

as direct contact or direct interaction between two systems.

Space architecture or systems engineering is the study of

including the human as part of the system when designing the

system. However, between a factor like the day/night cycle

and humans the interaction is primary that is the variation in

the daylight time acts as a direct stressor to human in terms

of psychology. Therefore, the human is one of the important

factors that influence design.

2. Secondary Interaction – A secondary interaction is

interaction of two elements via a medium or another system.

For example- The existing temperature condition is handled

by the Thermal Control System (TCS). So, the external

stimuli is high temperature variation which is negated by the

TCS which in turn shields the human keeps the environment

suitable for them. However, a human would always interact

with the temperature condition through any other system such

as TCS or EVA systems. If there were a direct interaction the

human would be physically harmed. That is why even though

the human is part of the system,the effect on the human is not

direct. Hence, this would be a secondary interaction. Systems

that share a secondary interaction don’t affect each other

directly and sometimes may not contribute in a large margin

to design.

Structure

Subsystem commonality is an important aspect of commonality. So, of the many systems possible this study focuses specifically on the structure to aim to get a common structure for the habitat systems.

Once the geometry and size of the habitat is finalized a study was conducted to see how the structure for such a system would look. The initial notion of the structure approximated the final structure. The structure design commenced in an iterative manner. The first element that was designed were the structural rings. The structural rings were 7m in diameter and spaced by longerons 0.75m long. For all structure studies the load was kept constant at 10G’s to simulate launch loads. Launch loads however have a complex interaction of different loads including vibration loads and aerodynamic loads. The first structure did not fail and was suitable for use. However, it posed a challenge for the hatches. The initial structure could not support hatches as

the structure was too small to accommodate hatches. Therefore, the size of the structural rings and longerons were increased to accommodate the hatches. Once the modified hatches were integrated and a stress test was run it was found that the support for the hatch was failing due to immense stress. The member supporting the hatch was very small and hence would buckle under high load. Therefore, the hatch structure was modified to be supported by a continuous contoured base as compared to normal stress elements earlier. The stress test showed that the structure held up under this stress. The next step was to add domes to the habitat. The domes were made of 8 structural elements arching from the top ring to the first structural ring. This structure did hold up to the immense stress but had high stress concentrations n some regions.

This was basically due to the high loads on some regions of the rings due to the dome element. The dome elements were actually positioned between longerons and hence there was a possibility of the ring bending. To eliminate this problem the number of elements in the dome were increased to 12 such that each element from the dome lines up with the longerons. This also gives the added advantage of symmetry. This was the final structure since it showed the potential to survive high load environments. The final mass of the structure was 14.7 mt and made of Aluminum 6061. The factor of safety for this structure was 1.9 and according to NASA standards for primary structures, the desired factor of safety is 1.5. Therefore since 1.9>1.5 the structure satisfies this criterion. However, the structure can now be optimized to decrease the factor of safety to 1.5 thus reducing mass.

II. Multi Utility Vehicle

The Multi Utility Vehicle (MUV) is a result of trying to accumulate different functions into one element. In this case the functions were –

1. moving other elements such as a habitat ,

2. supporting ISRU operations

3. Transporting smaller equipment.

Because of the listed functions the objective was to either design or identify systems that could fulfill these requirements. The Multi-utility vehicle is a hybrid in the sense that it consists of newly designed parts and integration of already existing parts.

The first part to be identified was the chariot chassis. It was chosen to act as the base of the vehicle. The chariot was designed to be able to accommodate two people on a regular basis and in emergency scenarios a total of four people. However, the MUV does not have such a requirement and can be smaller. The chassis is sized to be able to ferry elements up to 20mT. hence, the modified chassis has only four wheels but all of them are able to rotate about their own axis to efficiently maneuver in all directions.

Once the chassis was finalized the attachment to the chassis was to be designed.

The modified chassis can have multiple attachments which are rotated based on the function required. However, this case focuses on a single attachment that is capable of transporting elements and assisting ISRU operations. The attachment is such that it has a storage cavity in the center. The storage cavity is flanked by end effectors on both sides. On one side of the end effector is an excavator. This is basically used to pick up and load regolith into the storage area of the vehicle. The arm is designed such that the claw can pass through the arm and is capable of dropping regolith into its own storage area.

The other end effector is a forklift mechanism. The forklift is used to attach and lift heavier elements by latching onto to them. The forklift arm is foldable that is it pivots about a point to rotate onto the top the MUV in a stowed position to be done when the vehicle is being transported. Another constraint while designing this vehicle

was the lander size. The lander size was driven by the SLS launch vehicle payload fairing due to which the total length of the lander is 8.5m. The MUV is designed to fit onto the lander such that each lander can transport one MUV to the surface.

Figure -6 – The two different end effectors on the MUV with the storage area

The MUV latches onto an adaptor when moving elements. The adaptor is custom designed to fit beneath each element. For example- the adaptor has a contour that matches the contour of the habitat dome. The habitat rests on this contour. The adaptor is a truss structure which has the base element shaped like a hexagon. The base of the adaptor has pre-drilled and threaded slots for screws.

Once the MUV lands it has to get off the lander. The lander has a stowed ramp which is a multi-element structure with each element hinged at the end. The ramp unfolds in an element by element fashion. The ramp unfolds to create a path from the top of the lander to the surface. Once the ramp unfolds the MUV drives down the ramp.

Figure -7 – The MUV offloading from the decent vehicle

The MUV is mostly moving regolith from the regolith production site to the

ISRU processing site. Once the MUV loads the regolith, it is unloaded using a dual- conveyor mechanism. The first conveyor is positioned in an inclined position inside the storage area of the MUV. The second conveyor acts as a door at the back of MUV.

The door opens to unload regolith. The second conveyor is coupled with the first conveyor. The conveyors together push out the regolith for it to accumulate for further use.

Figure -8 – The MUV using its excavator to load regolith into the storage area

When a habitat arrives the MUV works in pairs to offload and move the habitat.

Two MUV’s approach the lander from opposite sides. They already have regolith filled up in the storage area to act as counterweight for lifting operations. The MUV’s then move close to the lander and the forklift teeth rise to match the level of the lander.

Then the forklift teeth move under the adaptor to support the habitat during motion.

The forklift teeth have a dual clamping mechanism to latch onto the habitat. The clamps move near the adaptor walls and the screws move into the threaded holes in the adaptor to clasp the adaptor. The second mechanism is a suspension supported mechanism hinged on the forklift side. The second mechanism rotates and attaches itself to the leg support structure for the habitat. Once both MUV’s have attached to the habitat, they rotate their wheel by 90deg in the same direction. And start moving laterally. After clearing the lander, the wheels are again rotated by 90 deg and the forklift teeth are lowered such that the habitat center of gravity is as close to the MUV center of gravity as possible. Now, the MUV’s together move the habitat to the desired

location and set the habitat down. Once the habitat assembly is resting on the surface it is supported by the adaptor. The MUV moves slightly away and the habitat legs unfold and raise the habitat to clear it from the adaptor. The MUV then moves in to pick up the adaptor. This action can be completed by a single MUV. The adaptor is then deposited at a given distance from the habitat. The adaptor can be cannibalized in a later stage to be used for other equipment or as spare parts. The MUV’s then return to their task of assisting in ISRU operations. The MUV can also be used as a semi-truck such that cargo is put into the storage area and transported from one location to another.

Some other attachments that could work for the MUV would be an attachment for an unpressurised rover which would result in a rover that looks similar to the

Apollo Lunar rovers. Another possible option for the attachment could be a scientific payload which would result in the MUV working as a science rover.

Conclusion

The study aimed at developing common elements that can be used during Lunar and Martian missions. The essence was to develop elements which would reduce cost and promote incorporation of commonality in the design and development phase. The elements developed were a common habitat which satisfies the functional requirements for both locations.

A brief study was conducted to look at possible common subsystems and an initial structure was developed that would be capable of serving launch loads on earth.

A transportation element was developed that assists in ISRU activities and can move large elements. The future prospects could be to fully develop different subsystems which can be used across locations. Also, other attachments for the MUV can be developed as per mission need to promote further commonality.

References

[1] Brand N. Griffin, Robert Howard, Scott Howe, Roger Lepsch, John

Martin, Natalie Mary, Carey M. McCleskey, Philip Nerren, Michelle A.

Rucker, Edgar Zapata, and Tara Polsgrove. “Small Habitat Commonality Reduces

Human Mars Mission Costs” AIAA SPACE 2015 Conference and Exposition, AIAA

SPACE Forum, (AIAA 2015-4455)

[2] Palac, Don. (2016) “Nuclear Systems Kilopower Overview”

[3] Eckart, P. (2006). The Lunar Base Handbook. New York: McGraw-Hill.

[4] Ruess, F., Schaenzlin, J. and Benaroya, H. (2006). Structural Design of a Lunar

Habitat. Journal of Aerospace Engineering, 19(3), pp.133-157.Vatistas, G. H., Lin, S., and Kwok, C. K., “Reverse Flow Radius in Vortex Chambers,” AIAA

[5] Cohen, M. (2015). First Mars Habitat Architecture. AIAA SPACE 2015

Conference and Exposition.

[6] Alexandra Whitmire, Lauren Leveton, Hugh Broughton, Mathias Basner, Anne

Kearney, Laura Ikuma, Michael Morris. “Minimum Acceptable Net Habitable

Volume for Long-Duration Exploration Missions”

Appendix

Table 2 – A comparison of the various environmental conditions on Moon and Mars.

Figure -9– The MUV latching onto a habitat and moving it from lander to base site.

Figure -10 – The different iterations of the habitat structure and their stress analysis.