A Mission Design for International Manned Mars Mission:

(From the 1991 International Space University (ISU) Design Project)

Wendell W. Mendell,
Co-Director, ISU91 Design Project
Solar System Exploration Div.
NASA Johnson Space Center
Houston, TX 77058 USA

Abstract

The International Space University (ISU) conducted a study of an international program to support human exploration of Mars as its annual Design Project activity during its 1991 summer session in Toulouse, France. Although an ISU Design Project strives to produce an in-depth analysis during the intense 10-week summer session, the International Mars Mission (IMM) project was conducted in a manner designed to provide a learning experience for young professionals working in an unusual multidisciplinary and mulitnational environment. The breadth of the IMM study exceeds that of most Mars mission studies of the past, encompassing political organization for long-term commitment, multinational management structure, cost analysis, mission architecture, vehicle configuration, crew health, life support, Mars surface infrastructure, mission operations, technology evaluation, risk assessment, scientific planning, exploration, communication networks, and martian resource utilization. The IMM Final Report has particular value for those seeking insight into the choices made by a multinational group working in an apolitical environment on the problems of international cooperation in space.

Introduction

During its fourth annual summer session from June 25 to August 30 in Toulouse, France, hosted by the Ecole Nationale de l'Aviation Civile (ENAC) and Formation Internationale Aeronautique et Spatiale (FIAS), the International Space University (ISU) conducted a study of an International Mars Mission (IMM). The IMM study served as the 1991 ISU Design Project, a part of the standard curriculum wherein the student body works as a team on a program plan for a potential future space mission chosen by the ISU Board of Directors. ISU Design Project topics are deliberately structured as multinational, multidisciplinary endeavors set in the future, beyond the normal planning horizons of the world's space agencies. The Design Project activity is intended to expose young space professionals to complex group interactions and to decision-making in an environment where knowledge can be incomplete. Experiences in the Design Project often reflect circumstances encountered by space professionals in leadership and policy-making positions.

The problem statement was kept very general, forcing the students to deal with many "soft" issues such as defining goals and objectives and setting priorities among competing mission activities. They were commissioned to perform an interdisciplinary study on the establishment of a staffed international outpost on the surface of the planet Mars. The purpose of the martian facility was:

  1. to conduct scientific exploration of Mars and the martian system and
  2. to develop and/or validate technology enabling the eventual human settlement of the planet.

The plan for IMM was to structure the program as a long-term, multinational cooperative effort. Commercial return had only secondary importance as an objective of the plan. Participation of private entities as partners in IMM were allowed but not mandated.

The Design Project Context

The ISU summer sessions consist of 10 weeks of intense multidisciplinary information transfer spanning all aspects of space studies. Lectures, both introductory and advanced, are given by the academic faculty in 8 Departments: Space Policy and Law; Space Business and Management; Space Engineering; Space Architecture; Space Life Sciences; Space Physical Sciences; Space Resources and Manufacturing; and Satellite Applications.

The ISU attracts a multinational and multidisciplinary collection of young professionals, in the early stages of their careers, who want to gain insight into the complex decisions that will be facing the leaders of the world's space programs in the next generation. This year 137 students from 26 countries attended the ISU.

The curriculum has three components: Core (Introductory) Lectures, intended to acquaint all students with the basic ideas in each of the eight disciplines; Advanced Lectures, intended to provide students with current information on new research related to their specialties; and a Design Project, intended to provide an active, participatory process wherein students can exercise their technical skills and apply knowledge acquired in lectures.

Since the Design Project is one element of the academic experience at ISU, the students actually do not to work on the project for ten weeks. They are required to attend the Core Curriculum and the lectures directly related to the Design Project during the first 5 weeks from 9:00 a.m. to 6:00 p.m. Monday through Friday and from 9:00 a.m. to noon on Saturday. The technical design groups for the project are not formed until the third week of the ISU session, and they must find time outside the normal curriculum to meet and organize their work. In the Advanced Curriculum, the formal time allotted to the Project is only 50% of the academic schedule until the week the report is written.

In addition, the skill mix among students attending the ISU is not optimized to address the Design Project problem statement. In fact, many students come from countries where human exploration of Mars is hardly discussed.

Why formulate such an Herculean task? If the ISU is to develop leaders for tomorrow's space programs, then the young, highly trained but narrowly focussed specialist must become aware of the unstructured, multidimensional environment in which decisions are made. Some of these dimensions are technical, some are political, some are bureaucratic, and some are cultural. Currently, the ISU is unique in its ability to provide a milieu where the students must deal with Process as well as Product.

Process - The Design Project exercise is experiential as well as tutorial. Students are asked to work in a truly multidisciplinary environment where a policy analyst or a sociologist might have strong input to an engineering design problem. Also, the ISU will be the first encounter for many students with a multicultural workplace where the technical methodology may be unfamiliar. Students are involved for the first time in debates over the highest level program requirements and scope as opposed to being restricted to narrow technical design questions. These process issues are very significant in the Design Project experience.

Product - The tangible product of an ISU Design Project is a report. The outside world judges the value of the ISU in terms of the technical content of that report. In fact, the students judge themselves by the same measure. Frequently, quality is equated with the level and wealth of detail, but the quality of the product lies as much with the conception of the plan as it does with any technical tour de force that might reside within the report. In practice, the final reports of the Design Projects have been thoughtful and remarkably complete because the students always mount an extraordinary effort to produce a high quality product despite the time constraints.

In the end, the success of the Design Project depends on access to adequate technical information, the imposition of the "right" amount of organizational structure on the project by the faculty without reducing the experience to solving homework assignments, and the constant monitoring of student task groups by the faculty and staff to mitigate destructive personal tensions. However, this year, as in other years, the most important component of the success of the Design Project was the dedication and ingenuity of the students themselves.

Organization of the IMM Design Project

The IMM study was directed by two full-time faculty and six half-time faculty, each of the latter being in residence for either the first half or the second half of the summer session. The faculty was supported by eight full-time Project Assistants, each of whom had been an ISU student. Additional support came from the academic ISU faculty, the academic Department Assistants, and various visiting lecturers who generally chose to stay a few days to work with the students.

Table 1. IMM Technical Task Groups
Program OrganizationMission DesignResearch Payloads
International Relations and Agreements
Organization and Management
Cost Analysis
Mission Architecture
Vehicle Configuration
Crew Health
Life Support
Surface Requirements
Communication
Mission Operations
Technology Evaluation
Risk Assessment
Science
Exploration
Resource Utilization

"Phase Zero"

For the first two weeks of the ISU session, every student was assigned to a Design Project Orientation Group. The groups were constructed from the student data base so that each consisted (as far as possible) of students of differing nationalities, disciplines, and gender. The groups were asked to discuss the relevance of exploration of Mars to their countries or to themselves, the significance of international participation in such a project, the technical challenges associated with sending humans to Mars, and the challenges to our institutions to maintain a long-term commitment to such a project. Each group prepared a short paper on their discussions and a ten-minute presentation to the student body. The presentations were interesting because half the groups chose to make more or less standard presentations and half chose to act out short sketches illustrating the important elements of their experience. Most groups spent the greater part of their meetings discussing differences in individual views on the relevance of human exploration of Mars.

The Orientation Group exercise accomplished three objectives. First, the discussions forced each student to decide whether working on such a futuristic scenario made sense. For many students, particularly those from developing countries, this is a serious issue. In past years, debates have erupted over what is realistic and what is "science fiction" after the technical work began and have been disruptive to the cohesiveness of the effort. In the 1991 session, these problems were worked out before initiation of the project .

Secondly, the technical task groups that ultimately perform the design study have to organize themselves. This method of self-organizing groups is disconcerting to students from some cultures where hierarchies and job functions are always strictly defined from the top. Since the group dynamic initially manifests itself through discussion and negotiation, students weak in English find themselves at a disadvantage in the development of group leadership, organization, and goal definition. The Orientation Groups provided a forum for working on the problem of domination by native English speakers in developing the group's position on issues.

Finally, many students arrive with little knowledge about Mars and very little understanding of the issues associated with human exploration of space. The Orientation Groups made students aware of the importance of these subjects to the project and allowed them to learn outside the lecture hall.

The IMM Project Structure

Task Groups. At the beginning of the third week of the ISU session, each student volunteered to join one of 13 Task Groups (Table 1). Each Task Group had responsibility for technical analysis and design for some aspect of the project. By the end of the project, two of the Task Groups had subdivided into independent subgroups.

The Task Groups can be classified into three major categories: Program Organization, Mission Design, and Research Payloads. Under Program Organization fall two Task Groups, one for developing the political structure of the international endeavor and another for developing the management organization as well as cost analysis. These analyses are unique to this study. Under Mission Design come nine Task Groups dealing with engineering design, mission architecture, crew, and operations. Included also was risk assessment, as topic rarely given weight in studies of this type. In the category of Research Payloads, two and a half groups worked on the science, exploration, and technology development experiments that would be carried to the martian surface.

Management Interface Group. In a project as complex as the IMM, each Task Group requires information from other Task Groups and, in turn, generates information required by others. In addition, a method of reporting progress and identifying choke points is necessary for the Design Faculty. These functions were performed by a Management Interface Group (MIG).

Each Task Group appointed a representative to the MIG. The MIG met twice a week to review progress and to document interface requirements. The membership of the MIG rotated so that no one person represented his/her group for more than two meetings. This arrangement gave more students the experience of the multidisciplinary interaction and helped to avoid dominance of decision-making within the project by strong personalities. In addition, it encouraged non-native English speakers to take responsibility for representing the views of their group. At the first MIG meeting were 12 North Americans and one French student, while the last meeting consisted predominantly of Asians and Europeans.

Since the membership of the MIG changed each week, maintaining the continuity of the project was a concern. Therefore, with each voting representative from a Task Group came the next week's representative as a nonvoting observer (and to serve as an alternate). In addition, the meeting was chaired by a Faculty Director to maintain a consistent format and decision methodology.

I chose this project decision process to be "parliamentary" rather than "executive" as in the usual Project Manager system. Decisions were reached by consensus of the MIG, leading often to very long meetings. Despite my colleagues' predictions of disaster without a Project Manager to make decisions, the process worked satisfactorily. On the other hand, progress in establishing requirements was not always as "crisp" as one would like.

When we identified technical issues which had to be resolved by more than one group, a "tiger team" composed of members from affected groups was formed to generate a report on the optional solutions to the problem and to report back to the MIG. Time constraints in the study required these tiger teams to complete their work between meetings.

Schedule. The Task Groups worked for three weeks during the Core Curriculum. Although their days were taken up by lectures, they found enough time to flesh out the issues associated with human missions to Mars and to produce a preliminary set of conclusions. Following a five-day break at the end of July, the ISU reconvened on August 1; and the Design Project Preliminary Review was held on August 3. On August 17, the Final Technical Review was held, after two weeks during which the Design Project shared time with the Advanced Curriculum lectures. The next week was devoted to cleaning up the final technical details and writing the report. Inputs from the 137 students were coordinated by a Report Committee and a (almost) complete draft of the Final Report was in the computers by midnight, Friday, August 23. Following a weekend of editing, attempts to print the final copy of the report began early in the morning of Monday, August 26, and succeeded some 30 hours later. The report was reproduced rapidly and handed to students on August 31, graduation day.

The International Mars Mission

Program Organization

International Relations and Agreements To manage and coordinate the International Mars Mission (IMM) the students propose an International Space Exploration Organization (ISEO). The ISEO is a non-profit, international and intergovernmental organization with the primary purpose to establish, maintain, and utilize the benefits of international cooperation and collaboration in space exploration activities. The founding goal of the ISEO is to carry out the IMM and to accomplish the international scientific and exploratory missions for the establishment of a permanent international human outpost on Mars.

The development of an organizational structure is carried out in progressive phases, beginning by convening a Forum. The Forum is composed of experts from space-related fields, convened by a non-governmental organization such as the International Academy of Astronautics. The Forum generates a set of models for organizing international cooperation as well as an analysis of the technical challenges of human missions to Mars.

The countries which would have expressed an intent to create such a multinational collaboration form a Commission to establish a consensus on the principles of international cooperation for a mission to Mars. That consensus leads to the establishment of the International Space Exploration Organization. This phased approach ensures the stability required for this long-term international program.

Org Structure

Figure 1. The International Space Exploration Organization Structure Chart

A suggested organization of the ISEO is given in Figure 1. The Assembly of Contracting Parties constitutes the member participants and ensures the general political outlines of the ISEO and its long-term objectives. Each Contracting Party is allocated one equal vote in the Assembly, independent of the financial and in-kind contributions given to the ISEO. In the case of procedural decisions, a simple majority is required. A two-thirds majority is required for all decisions of substance. In the event of a conflict between contracting parties, an Ad Hoc Arbitration Court is established.

The Assembly of Contracting Parties is also responsible for the approval of the overall budget for the different project phases and the phase time lines. If at some point the budget exceeds 120%, then it remains between the Assembly of Contracting Parties and the Board of Governors to renegotiate the budget.

The Board of Governors has the responsibility for the design, development, construction, establishment, operation, and maintenance of the programs approved by the Assembly of Contracting Parties. It implements the general political outlines and long-term objectives developed by the Assembly of Contracting Parties. The Board is composed of one Governor representing each Contracting Party whose total overall contribution is not less than 9% of the overall ISEO contributions; or one Governor representing each group of any two or more Contracting Parties having together not less than 9% of the overall contributions. In any case, a single Contracting Party cannot compose more than 33.2% of the overall weighted amount of all votes allocated to all Contracting Parties in proportion to their contribution to the Organization.

The Director General (DG) is the chief executive and the legal representative of the ISEO and is directly responsible to the Board of Governors for the performance of all management functions. He/she is appointed by the Board of Governors for a five year period, and is subject to confirmation by the Assembly of Contracting Parties. After this period, reappointment is possible only twice.

The DG is responsible for the negotiating and signing international agreements and contracts on behalf of the Organization. All international agreements and contracts of substance are subject to approval by the Board of Governors prior to signature. Within the management structure of the ISEO, the DG may take all necessary decisions to ensure that technical activities are in accord with the policies and directives of the Board of Governors.

Management and Organization. The students decided to make the ISEO a coordinating body, meaning that the ISEO itself does not directly contract for mission related hardware and software but instead coordinates the efforts of the different member countries. This model was chosen because the other option, an organization to which funds are allocated by governments and from which funds are paid to contracting parties, was not considered possible within the present or foreseeable political and economic framework. Problems with an international organization that administers direct funding are: 1) developing common contracting methods with entities (corporations or state agencies) from all countries and 2) transferring of large quantities of funds between countries with rival economic and political interests.

The choice of a coordinating organization was made with full consideration of the unsuccessful experience of the European Launcher Development Organization (ELDO). The management structure that is presented here has been structured to facilitate oversight of the program element designs in order to maintain proper technical interfaces.

Under the DG of the ISEO, there is the IMM Program Manager's office and the Offices of the Directors of Administration, Technology & Standards, and Operations. In addition, an office of future programs has been added to allow for the possibility of the continuation of the organization if its structure should prove useful for future space exploration initiatives. Offices for public relations and staff positions, directly reporting to the DG have also been established.

The management role of the Director General is the Chief Executive Officer of the ISEO. However, the technical management role of the DG office shall be limited to the technical issues that intersect the political direction handed to the DG by the Board of Governors. Procedures have been instituted to allow for review of disputes between the DG and the Program Manager, who has authority over purely technical decisions. The DG reports directly to the Board of Governors on the status of the IMM.

The Administration Director is responsible for the support of the organization for the IMM. This directorate has the responsibility for Finance, Contracts (in support of the IMM organization), Personnel, International Relationships and Legal Affairs, and General Services (purchasing, facilities maintenance, etc.) The administrative function of the organization, including salaries, shall be directly funded by the organization in proportion to the voting weight of the member states.

The Technology and Standards Director is responsible for identification of the technology development needs of the specific program elements and maintenance of standards to facilitate interfaces of program elements. The ISEO organization does not develop its own technology nor impose given methods or procedures on participating countries and the design organizations within them.

The Operations Director is responsible for overall mission operations through the Main Mission Control Center and the Main Science Control Center. These centers will require direct funding, like the administration, for their operation but rely on the facilities and capabilities of the member states. Contracting of member state's facilities may take place but within the framework of treaties developed by the Board of Governors. The Mission Control and Science Control Centers are responsible for operational requirements and planning, personnel training and IMM crew training, and coordination of other control centers.

The role of the Program Manager (PM) and the Program Management Office is the technical coordination of all hardware and software elements of the IMM, including precursor missions. The office shall: 1) implement the technical aspects of the political decisions of the Board of Governors; 2) define top level requirements of each program element and control interfaces between each program element; 3) monitor schedule, compliance with requirements, and quality of the IMM elements; and 4) report to the DG the status of the overall technical program. Divisions within the PM office established to carry out these duties are System Engineering, Program Control, Quality, and Science. All of these divisions have direct interfaces with the Element Monitors. The Element Monitors are the direct interface between ISEO and the Agencies of the member states. This interface shall be with the Program Element Managers who are employees of the member states and have direct control of the respective country's or agency's elements.

World Funding

Figure 2. World Funding Availability for the IMM

Cost. Costing human exploration missions is a very sensitive subject because the numbers integrated over long time frames appear to have unattainable magnitudes. The cost analyst finds himself trapped between the task of discovering substantial long-term funding sources and the temptation to invoke "new business practices" to reduce the funding needs. Although the students had received lectures identifying cost-escalating attributes of the management culture in manned space programs, they chose not to emphasize reforms that might bias the cost models downward lest such manipulation appear to be a deus ex machina for solving the cost conundrum.

For the IMM study the students estimated costs of the components of the program as described by the technical groups. The estimating tools were simplified versions of those used in aerospace industry. The students then made a deliberately conservative estimate (see below) of the possible contributions from participating members of the ISEO over time. The mismatch between the two curves was more evident in the time-phasing of the costs than in any overall shortfall of funds. A closer match between funding and cost would have been possible with iterations of the technical scenarios.

To estimate the available funds the Cost Task Group analyzed the expenditures on space within the budgets of countries most likely to participate in the IMM, as identified by the International Relations Task Group. Expenditures were characterized in terms of percentage of Gross National Product (GNP), and real growth in GNP was estimated for the period out to 2025. Detailed analysis was done only for four major participants: the European Space Agency (ESA), Japan, the United States, and the Soviet Union (U.S.S.R). In each case an estimate was made as to what percentage of the participant's space expenditures might be devoted to IMM in the future. (The coup attempt in the Soviet Union occurred near the end of the study, and a caveat was added to the analysis for the U.S.S.R.) From this approach a smooth curve of funding versus time could be generated. The total was augmented by 4% to represent the contributions from smaller nations. The result is depicted in Figure 2. A comparison with projected costs is given in Figure 3.

Cost Compare

Figure 3. Funding and Cost Comparison

Mission Design

Overview. The design of piloted missions to Mars is driven by the requirements placed on the performance of the systems and the crew. However, those requirements are rarely derived by an objective, logical process. Many of the priorities depend on the aggressiveness of the groups with competing requirements and on the quality of competing technical analyses.

In the IMM study, the Crew Health Group stated very early strong requirements for a large crew (based on psychological studies) - all of whom go to the martian surface - and artificial gravity (as a conservative approach to physiological countermeasures). The Vehicle Configuration Group was unable to produce detailed analyses until late in the study to characterize the impact of these requirements. A decision to design the interplanetary rotating spacecraft with a truss (rather than tethers), coupled with the large crew, resulted in a massive vehicle. Nuclear propulsion was chosen to minimize the number of Earth-to-orbit launches for assembly of the vehicle. Use of nuclear thermal propulsion was rejected in favor of nuclear electric propulsion (NEP) because of difficulties in maintaining proper mass balance in a rotating vehicle as propellant was expended. The low-thrust vehicle spirals out of low Earth orbit (LEO) through the Van Allen Belts without the crew onboard to minimize radiation exposure. The crew is launched from Earth by a chemical rocket and docks with the interplanetary vehicle in high Earth orbit just prior to trans-Mars injection.

The large mass requirements to support the crew on the martian surface and to perform robotic exploration led to a decision to launch an unmanned cargo mission to Mars at the launch opportunity preceding the first human mission. The cargo mission would serve also as a flight test for the nuclear vehicle, albeit not in a rotating mode. A part of the cargo would be devoted to a technology demonstration for utilization of martian resources to support subsequent missions.

Mission Architecture. The students produced a reference mission architecture which would allow humans to land on Mars in the year 2016, establish a base, and initiate a permanent program of human exploration of the solar system. The guiding objective for the mission architecture design was to construct an interplanetary transportation system which would enable continued piloted missions, with the possibility of the future settlement of Mars, using the world's existing space infrastructure to the greatest extent possible. The design project itself focussed on the precursors, cargo missions, and first two piloted missions necessary to begin long duration stays.

The first piloted mission launches on an opposition-class trajectory, and the crew stays on the martian surface approximately 40 days. The first mission was chosen to be a short time on the surface to provide an evaluation of the crew performance before committing to a long duration mission. Assuming that the first mission succeeds, the second mission follows a conjunction-class trajectory with a crew stay-time of approximately 400 days.

The students proposed construction of an artificial gravity prototype vehicle (AGPV), initially to be used for life sciences research and the development and test of artificial gravity vehicle components. Later it could be used (in a non-spinning mode) to support the assembly of the NEP vehicles. The NEP vehicles would be assembled in 400-km altitude low Earth orbit, but the nuclear reactor would not be used until the vehicle was raised to 900-km altitude nuclear safe orbit.

Precursor missions to Mars were identified to satisfy many objectives including: science, exploration and landing site selection, the return of Mars samples for scientific and engineering evaluations, the installation of communications and solar flare warning systems, and the test and validation of the NEP interplanetary vehicle and the lander/ascent vehicles.

NEP vehicle

Figure 4. Artificial Gravity Vehicle with Nuclear Electric Propulsion

Vehicle configuration. The basic design is an artificial gravity spacecraft, which is 200 m long and is capable of rotating at 2 rpm to provide a level of artificial gravity of 0.4 g (Figure 4). It is propelled by a nuclear electric system for most of its time of flight. Two habitat modules are located at one end, one housing 8 crew, one for work. At the other end is the nuclear reactor, the radiation shield, and the power conditioning system. An aluminium square truss, running the length of the craft, acts as the backbone for the radiators which dissipate waste heat from the reactor. Because the shield is a shadow shield to conserve mass, the radiators are triangular, hiding in the shadow, so as not to backscatter any radiation into the habitats. The propellant is stored in eight tanks, four at each end. The ship is stable and controllable, and final mass balancing can be performed with a robot arm next to the habitat.

The Mars landers were designed as biconic vehicles which can deliver 40 tonnes to the Mars surface. A cargo vehicle, using the same structure and propulsion as the crewed vehicle was also designed. A Crew Transfer Capsule would be utilized to launch the crew from the Earth to dock with the interplanetary vehicle, and it would be combined with an Earth Return Capsule for when they return.

Crew A crew size of eight (4 men and 4 women) was picked as a compromise between the Crew Health Group, which wanted as many as twelve, and the Vehicle Configuration Group, which wanted to limit crew to four. Psychologists and psychiatrists in the student body argued forcefully that mission success would depend on the group dynamics, which could be unpredictable with small numbers. Other Task Groups preferred larger numbers in order to increase the work output on Mars. The skills and responsibilities of the crew are given in Table 2. Individuals will need to have overlap in knowledge to ensure that all mission objectives are met and that there is redundancy in case some crew members are incapacitated.

I must refer the reader to the IMM report for extensive discussions of crew selection, crew training, health maintenance, and human factors design considerations.

Table 2. Responsibilities and Duties of Mars Mission Crew
BackgroundSpacecraft SkillsMars Habitat Skills
EngineerSpacecraft maintenance
Spacecraft pilot
Communications
Habitat maintenance
Communications
Rover maintenance
Rover driver
EngineerSpacecraft maintenance
Computer operations
Spacecraft pilot
Habitat maintenance
Rover maintenance
Computer operations
EngineerLife support
EVA suit maintenance
Life support
EVA suit maintenance
EngineerLife support
Astrophysics
Life support
Geology/Geophysics
Rover maintenance
Rover driver
EngineerCommunications
Computer operations
Communications
Computer operations
ScientistPhysics
MD Assistant
Geology/Geophysics
MD Assistant
Medical DoctorCrew medical and mental health (medicine)
Life science research
Crew medical and mental health (medicine)
Life science research
Medical DoctorCrew medical and mental health (surgery)
Life science research
Crew medical and mental health (surgery)
Life science research

Mars Surface Base. The habitats and laboratories of the surface base consist of inflatable modules. A construction rover prepares a site and drag the modules there. The crew, temporarily living in their lander, connect the modules and erect the inflatable structure. The initial power system is composed of photovoltaic arrays, providing 40 kW of electricity during the day, and regenerable fuel cells, providing 25 kW at night.

The surface habitats are pressurized to 10.2 psi. Airlocks are designed to mitigate both forward and backward contamination. A safe haven is provided for crew protection during solar flares.

Life Support The life support system aboard the interplanetary vehicle and on the surface of Mars features closed loop processing of air and water. However, food is brought from Earth. Although plants are utilized in the waste water treatment system, a fully bioregenerative life support system was judged to be an immature technology for the first missions. Technology demonstrations were included in the payload in anticipation of using bioregenerative systems eventually.

Extravehicular activity (EVA) presents two classes of problems. In transit between Earth and Mars, the astronaut going EVA feels a varying "gravity" at different places on the structure of the rotating spacecraft. Any object breaking loose from the spacecraft is supplied with a certain amount of linear momentum, causing it to be rapidly lost. On the martian surface, the weight of the spacesuit is very critical to crew performance. Current spacesuit technology cannot provide an adequate work suit in the 0.4 g environment.

Communication. The communication network carries science and exploration data, voice, video images, navigation, tracking, and control and command. For the human missions, the communication network is required to provide continuous service. During the first precursor mission, the Mars-Earth communication link is provided onboard a remote sensing satellite in Mars-stationary orbit. A dedicated communication satellite is placed in Mars-stationary orbit during the second precursor mission. The complete network of three communication satellites is finalized during the third precursor mission to be fully tested before the first human mission. Also deployed before the first human mission are the two communication relay satellites in the Earth-Sun Trojan points.

The Mars-Earth link uses multiple frequencies to achieve redundancy. The three communication satellites in the Mars-stationary orbit provide not only an excellent coverage of the Mars surface and overcome the problem of occultation due to the rotation of Mars, which could interrupt the required continuous communications to Earth. In the event of any single satellite failure, the Mars surface coverage is reduced but the Mars-Earth link still is operational.

The two Trojan relay satellites overcome the problem of communication blackouts when the Earth-Sun-Mars conjunction occurs. Although a single Trojan relay satellite suffices, the second satellite is proposed to provide a redundant link. These two satellites are also used for solar particle event detection and warning.

On Earth, the three NASA Deep Space Network (DSN) stations are proposed as the main communication nodes. Their capability, however, needs to be upgraded to operate in the proposed higher frequency band (Ka-band) and each of the stations must be equipped with an array of four 34-m dish antennas. Additional receiving stations are also required to provide spatial diversity to overcome the problem of rain attenuation at Ka-band.

Mission Operations. The students realized that systems designed with operations in mind cost less over the lifetime of the program and potentially deliver better overall performance. They favored development of facilities that are free of commitments to space programs other than the IMM. They discuss in some detail the in-flight training program that is required to maintain crew proficiency levels.

Launch vehicle processing and launch control center operations involve three facilities in three different continents. These centers are joined by three different mission control centers, all six of which are responsible for various phases of activity. Conceptual plans for how these centers work together to share mission control responsibility are discussed.

The Mars Transfer Vehicle is so large that it may take nearly two years to launch and assemble all the elements. Mission control centers control the assembly, checkout, and operation of the vehicle until the crew boards it. During the flights, the crews have greater autonomy than exists currently for near-Earth operations.

A main science control center networked to multiple supporting science centers manages all science activities (coordinating this with the mission control center). These centers distribute the science data to world-wide users. Both the mission and the science control centers provide long range planning, engineering, and science support to the mission.

The MOA team developed several important philosophies that guided the operations concepts presented in the report. Flight crew time is a limited resource which should be scheduled wisely. This implies that crew EVA time required for vehicle assembly should be minimized. Spacecraft systems should be designed for minimum planned maintenance and systems monitoring. Due to the extended length of the mission and the long communication time, the day-to-day planning of flight crew activities is an on-board responsibility.

Science, Exploration, Technology Validation

Science. The Science Task Group was asked to assume the role of the international scientific community within the Design Project. Their assignment was to characterize the opportunities for basic research within the IMM environment. They were not limited only to experiments supporting mission goals and objectives. The funding for basic science was assumed to be largely independent of the IMM project structure.

The Science Task Group formulated a general Science Mission Statement, "Did Mars ever sustain a similar evolution to Earth, physically, chemically or biologically, and is it capable of supporting a similar biological evolution in the future?" Their strategy for selecting experiments was weighted heavily toward support of the Mission Statement and, in addition, support of the achievement of long-term settlement of Mars. Thus, their approach was not quite as independent of the context of the project as it might have been.

Research was divided into several categories: Mars solid body studies (geology, geochemistry, and geophysics); Mars atmosphere; exobiology; life sciences (with emphasis on martian agriculture as well as crew physiology and psychology); and plasma and solar physics (data taken and analyzed in transit with emphasis on solar flare forecasting). The Science Group tried to work their experiments into the mission design rather than asking for independent spacecraft. They worked particularly closely with the Exploration Task Group with respect to robotic precursor missions.

Exploration. The Exploration Task Group took as their primary goal preparation for human settlement of Mars. They planned both precursor mission strategy as well as human exploration activities. The precursor strategy was based on two mission objectives: (a) identification of potential landing sites and (b) performance of basic scientific and technical investigations, including identification of areas in the martian system requiring further long-term study.

As part of their mission set they assumed successful completion of the U.S. Mars Observer mission and the Soviet Mars '94 and Mars '96 missions. These would be followed by a polar sun-synchronous satellite, a Mars-stationary satellite, and a ground station. The polar sun-synchronous satellite is used for mapping, with progressive resolution changes to obtain more detail in areas of interest such as potential landing sites. The Mars-stationary satellite, primarily used for meteorology, provides continuous coverage of selected regions. It has the capability to reposition its orbit to shift target areas. Finally, a ground station is sent to perform surface studies, to take meteorological data, and to verify and calibrate results from analysis of satellite data.

The data provided by the remote sensing phase of studies is used to select three potential landing sites. Multiple missions are sent to evaluate these three areas and select the best landing site. Three successive waves of 2000 microrobots perform basic surface analysis to provide ground truth for the remote sensing data. These are followed by robotic landers (i.e. semi-hard landers and/or penetrators). The robotic landers are sent in pairs to the potential sites and the martian poles. In the next wave of precursors are three autonomous rovers, again distributed to the three potential landing sites. These carry science and exploration packages as well as beacons to be deployed for navigation and lander guidance. In addition to travelling autonomously, they are able to deploy insect rovers to risky or difficult areas. Information from these phases will be used to select a landing site.

To verify the safety of the landing site a sample return and cargo mission are sent to it. The sample return mission is used for definitive verification of the precursor data and landing tests. With this mission, another Mars-stationary satellite and polar orbiter is sent, allowing repositioning of the old Mars-stationary satellite to another area of interest. The primary function of the new polar orbiters is navigation with some continuing planetary remote sensing. The cargo lander brings supplies for the manned mission as well as a strato-rover and a construction rover. The strato-rover is deployed and autonomously proceed to a predetermined site of interest where it will await human arrival. Finally, the construction rover works to prepare the landing site for human arrival.

Resource Utilization. Among the many architectures that have been proposed for piloted mission to Mars, there exists a class of schemes that proposes utilization of martian resources to produce propellant at Mars for use in the return trip to Earth. The advantage of such an approach is a sizeable decrease in the mass required in LEO to support flights to Mars with chemical propulsion. The philosophy, howver, flies in the face of orthodox approaches to space flight, which mandate carrying all necessary resources for completing the mission. Reliance on supplies at Mars is particularly sensitive when human beings are part of the payload to be returned.

The plan for the IMM Design Project was not formulated in such a way to ensure explicitly the consideration of resource utilization architectures. However, students from the ISU Resources and Manufacturing academic department pursued this topic through their academic studies and worked their results into the Surface Requirements Task Group.

Although resource utilization was not adopted as part of the baseline mission architecture for IMM, demonstration experiments were included in the surface activities. The students proposed extraction of essential resources from the martian atmosphere. This is a comparatively simple approach, using existing technology and processes which are easily automated. They designed an in-situ resource processing facility to provide materials needed for the second human mission. The pilot plant is designed to convert 4 tonnes of hydrogen - which are carried from Earth as cargo - into 12.7 tonnes of methane, 43.2 tonnes of liquid oxygen, and 4 tonnes of water. The plant theoretically functions on 10 kW of power supplied by the surface habitat solar power system and requires 2 years to complete one cycle.

Table 3. Major Categories of Risk and Contributing Factors
Risk CategoryMajor Contributing Factors
Loss of All LifeMainly due to explosion, rapid decompressions of the vehicle or habitat, and a mission length which outlasts the consumables
Loss of One LifeEVA related - based on the probability of failure of the EVA suit.
Loss of ScienceMainly due to equipment failures
Loss of FundingLoss of funding is always an issue in an uncertain political environment. (The probabilities have a large magnitude of uncertainty because political processes are unpredictable.) Best case scenarios are used.
Excessive Schedule DelaysResearch and technology development programs will be especially sensitive to the issue of schedule delays, but the key technologies are relatively well understood. However, failures during key mission phases (e.g., launch) will most certainly cause schedule delays.

Technology Evaluation and Risk Assessment

Introduction. Two Task Groups were formed to follow the entire project to check for self-consistency and to evaluate the quality of the design work. One of the most useful products of a study like IMM is the identification of key technologies which must be developed in the near term to enable such mission. The Technology Evaluation Group collected this information and also checked to make sure that technologies being invoked in the design would indeed be ready in the time frame of the proposed flight. The Risk Assessment Group made independent judgements on design trade-offs in terms of the threat to mission success from various alternatives. They also evaluated the probability of mission failure in the baseline scenario, and they helped to formulate specific statements of mission objectives and of mission success. Not all of their conclusions were popular.

Technology Evaluation. The Technology Evaluation Group identified the following key technologies and evaluated their state of readiness for application in a piloted Mars mission:

Risk Analysis. Throughout the conceptual design phase, the Risk Analysis Task Group maintained close collaboration with the design task groups, and acted as a driver for the project, by assessing risk to different aspects of the mission. One way that this was done was by subjective judgements. Another tool used to assess risk was the fault tree. Two types of fault trees were constructed - functional and mission-phased.

Functional Fault Trees were used to point out what are considered the greatest risks to the success of the IMM project as a whole. Table 3 illustrates the six main categories of risk to mission success and their principal contributing factors.

The other type of fault trees constructed were called Mission Phase Fault Trees. For each mission phase, a Functional Fault Tree was created. These trees were used to show when during the IMM project the greatest risks would occur. Mission Phase Fault Trees were constructed for the preparation, precursor, and the crew/cargo phases of the IMM. They showed that the largest risks to both the mission objectives and the crew occur during departing the Earth and the other propulsive phases of the mission. During normal Mars operations, only a life support system failure or explosive decompression of the habitat are likely to kill the entire crew.

Conclusions

The 1991 Design Project for the International Space University was carried out in an unusual multidisciplinary, multinational environment. The student participants, although not specialists in program planning, were a cross-section of bright young professionals who represent the future leadership of the world's space efforts. These students were aided by experienced space professionals from North America, Europe, the Soviet Union, and Japan. The Design Project was directed in such a way as to provide the students access to participation in the decision processes. In some ways, this worked to the detriment of the final product in the sense that decisions were not always made efficiently. The very short time frame of the study also placed severe constraints on in-depth consideration of some issues and precluded iterations that would have improved the consistency of the program plan.

On the other hand, the diversity of the disciplinary backgrounds of the participants provided an unusually broad analysis of the issues. In particular, the political analyses are unique to this study. The risk analyses are unusually candid. Human performance professionals had an unusual level of influence on the design. Finally, the student body displayed a high sensitivity to the preservation and study of Mars prior to the human incursions.

Studies of piloted missions to Mars have been done in the U.S. and in the U.S.S.R. It would be difficult to argue that the IMM project from the International Space University is superior in some way to those professional efforts. However, this study is unique in that it is the product of a multinational group, attempting to characterize a truly international program. It is therefore free of a number of constraints that are automatically imposed on studies from national agencies. The conclusions reached and the reasoning processes from the ISU student body may give some insights into the views of space exploration from the world community, into the acceptability of applications of technology, and into the institutional mechanisms required for true international cooperation in space.

Acknowledgement

In the section entitled "International Mars Mission", this paper borrows heavily from the IMM Final Report 1, which (except for the Faculty Preface) was written entirely by the students of the 1991 ISU session. In particular, most of the tables and all the figures have been extracted from the Final Report. Although I was one of the two full-time faculty for the Design Project, I wish to emphasize that I am reporting on the work of others.


References

1. International Space University (1991) International Mars Mission, Final Report of the 1991 ISU Design Project, W. W. Mendell and V. Legostaev, Co-Directors. International Space University, Cambridge, MA, USA, 697pp.