Human Exploration of Mars Design Reference Architecture 5.0 Bret G. Drake NASA Lyndon B. Johnson Space Center Houston, Texas 77058 Stephen J. Hoffman Science Applications International Corporation Houston, Texas 77058 David W. Beaty Jet Propulsion Laboratory Pasadena, California 91109 This paper provides a summary of the 2007 Mars Design • Derive technology research and development plans Reference Architecture 5.0 (DRA 5.0) [1], which is the • Define and prioritize requirements for precursor robotic latest in a series of NASA Mars reference missions. It missions provides a vision of one potential approach to human Mars • Define and prioritize flight experiments and human exploration including how Constellation systems can be exploration mission elements, such as those involving used. The reference architecture provides a common the International Space Station (ISS), lunar surface framework for future planning of systems concepts, systems, and space transportation technology development, and operational testing as well as • Open a discussion with international partners in a Mars robotic missions, research that is conducted on the manner that allows identification of potential interests International Space Station, and future lunar exploration of the participants in specialized aspects of the missions missions. This summary the Mars DRA 5.0 provides an • Provide educational materials at all levels that can be overview of the overall mission approach, surface strategy used to explain various aspects of human interplanetary and exploration goals, as well as the key systems and exploration challenges for the first three human missions to Mars. • Describe to the public, media, other Federal Government organizations the feasible, long-term TABLE OF CONTENTS visions for space exploration 1. HISTORICAL BACKGROUND ..............................................1 2. GOALS AND OBJECTIVES ...................................................1 3. DRA 5.0 OVERVIEW ..........................................................7 Each of these previous architecture studies emphasized one 4. VEHICLE AND SYSTEMS OVERVIEW ................................11 or many aspects that are critical for human exploration to 5. KEY CHALLENGES ...........................................................21 determine basic feasibility and technology needs. Example 6. SUMMARY .......................................................................23 architectural areas of emphasis include the destination, ACKNOWLEDGEMENTS ........................................................24 system reusability, goals and objectives, surface mobility, REFERENCES........................................................................24 launch vehicles, transportation, LEO assembly, transit BIOGRAPHIES.......................................................................25 modes, surface power, and crew size to name a few. DRA 5.0 examined several of these aspects in an integrated manner. The strategy and results from this study have been reviewed and endorsed by the four NASA headquarters 1. HISTORICAL BACKGROUND mission directorates. A complete copy of this study During the past several years NASA has either conducted or including more details on the results can be found at: sponsored numerous studies of human exploration beyond http://www.nasa.gov/exploration/library/esmd_documents.html low-Earth Orbit (LEO) [2, 3, 4, 5, 6, 7, 8, 9]. These studies have been used to understand requirements for human exploration of the Moon and Mars in the context of other 2. GOALS AND OBJECTIVES space missions and research and development programs. The goals for the initial human exploration of Mars can best Each of these exploration architectures provides an end-to- end mission reference against which other mission and be organized under the following taxonomy: technology concepts can be compared. The results from the architecture studies are used by NASA to • Goals I-III: The traditional planetary science goals from the Mars Exploration Program Analysis Group (MEPAG) [10] for understanding Mars Life (Goal I), processes are likely to be partially complete. In addition to Climate (Goal II), and Geology/Geophysics (Goal III). continuing long-term observations, our scientific questions Goal IV: Preparation for the first human explorers, as seem likely to evolve in the following directions. Note in defined by MEPAG (revision in work). particular that if there is no robotic mission to one of the Goal IV+: Preparation for sustained human presence. polar caps, the priority of that science is likely to be Goal V (Ancillary Science): This includes all scientific significantly more important than it is today because of the objectives that are unrelated to Mars, including those influence of polar ice on the climate system. that are related to astrophysics, observations of the Sun, Earth, Moon, and the interplanetary environment. Note • Quantitative understanding of global atmospheric that these objectives may be important during the dynamics. transit phase for missions to and from Mars. • Understand microclimates – range of variation, how and why they exist. • Perform weather prediction. Goal I. Determine Whether Life Ever Arose on Mars • Understand the large-scale evolution of the polar caps including the modern energy balance, links with dust, The results of the robotic missions between now and 2025 carbon dioxide (CO2), and H2O cycles, changes in will answer some of the questions about Mars on our deposition and erosion patterns, flow, melting, age, and current horizon, which would therefore be removed and links between the two caps. would be replaced by new questions; this is the scientific process. Although our ability to predict the results of these future missions and the kinds of new questions that will Goal III: Determine the Evolution of the Surface and come up is partial, we do know the kinds of data that will be Interior of Mars collected and the kinds of questions that these data are capable of answering. Thus, we can make some general As of 2006, there were two primary objectives within this projections of the state of knowledge as of 2025. goal: (1) Determine the nature and evolution of the geologic processes that have created and modified the martian crust By 2025, our assessments of habitability potential will be and surface, and (2) characterize the structure, composition, well advanced for some environments, particularly those dynamics, and evolution of the martian interior. These are that have been visited by the Mars Sample Return (MSR) or broadly enough phrased that they are likely to still be valid by major in-situ rovers with life-related experiments. in 2025. These two objectives, for example, currently apply However, it is likely that the habitability of the martian to the study of the Earth, even after more than 200 years of subsurface will be almost completely unexplored other than geologic study by thousands of geologists. Given the by geophysical methods. The objective relating to carbon anticipated robotic missions leading up to the first human cycling is likely to be partially complete, but in particular as missions, the first objective is likely to evolve in the related to subsurface environments. For the purpose of this following direction: planning, we assume that the investigations through 2025 have made one or more discoveries that are hypothesized as • Quantitatively characterize the different components of being related to ancient life (by analogy with the Allen Hills the martian geologic system (at different parts of meteorite story, this is a particularly likely outcome of martian geologic history), and understand how these MSR). We should then be prepared for the following new components relate to each other. objectives: • Understand the field context of the various martian features of geologic interest at both regional and local Characterize the full suite of biosignatures for ancient scale. life to confirm the past presence of life. Interpret its life • Test specific hypotheses. processes and the origin of such life. • Perform comparative planetology. Assess protected environmental niches that may serve as refugia for extant life forms that may have survived to the present. Find the life, measure its life processes. Goal IV: Preparing for Human Exploration of Mars In earliest martian rocks, characterize the pre-biotic chemistry. Goal IV addresses the precursor measurements of Mars needed to reduce the risk of the first human mission to Mars. MEPAG is currently updating Goal IV objectives as Goal II: Understanding the Processes and History of derived from Mars DRA 5.0. Since this process in still Climate on Mars underway, the results of this reformulation cannot be discussed here. By 2025, our objectives related to characterization of the Mars atmosphere and its present and ancient climate Goal IV+: Preparing for Sustained Human Presence Initial Human Exploration of Mars Objectives Related to Goals I-III Goal IV+ specifically focuses on Mars human habitability, exploration systems development, and long-duration space Geology Scientific Objectives— Some of the most important mission operations necessary for sustained human presence. questions about Goals I through III involve the relationship Goal IV+ focuses on the objectives for the first three human of H2O to martian geologic and biologic processes as a Mars missions that would support the performance of function of geologic time. Mars has apparently evolved human Mars missions four through ten. The scope of the from a potentially “warm and wet” period in its early representative scenarios for missions four through ten Noachian history to the later “cold and dry” period of the includes developing the knowledge, capabilities, and Amazonian period. Since rocks of different age are exposed infrastructure that are required to live and work on Mars, in different places on Mars, understanding this geologic with a focus on developing sustainable human presence on history requires an exploration program that also involves Mars. spatial diversity. One of the realities of geology-related exploration is that samples and outcrops are typically Goal V: Ancillary Science representative only of a certain geologic environment, and that acquiring information about other environments Potential science objectives that are appropriate to the initial requires going to a different place. (A terrestrial analog human missions to Mars extend beyond those relating solely would be asking how much we could learn about to the scientific exploration of Mars as a planet or the Precambrian granite by doing field work in the sedimentary preparation for a sustained human presence on Mars. As a rocks of the Great Plains.) unique planetary specimen, Mars is relevant to the study of the entire solar system, including its evolution under the The absolute ages of surface units on Mars have been influence of the sun (Heliophysics), and to the study of the deciphered through indirect methods. Samples returned solar system as an important specimen of stellar evolution from the moon in the Apollo Program were used to provide (Astrophysics), as well as other science disciplines. In constraints on the crater-size frequency distribution of the addition, Mars may be a unique location from which to lunar surface [12, 13], and this has been applied to Mars, perform certain astrophysical observations. among other terrestrial planetary bodies [14, 15, 16]. While this has provided a general history of martian surface Taking advantage of the unique attributes of humans in processes, it does not allow for detailed study of specific scientific exploration martian periods, in particular the Hesperian and Amazonian periods when the impact flux greatly decreased. While It is important to consider the unique capabilities that martian meteorites have been analyzed and dated [17], not humans bring to the process of exploring Mars. As a result, knowing their geologic context makes their incorporation a common set of human traits emerged that apply to into the geologic history of Mars difficult. While an MSR exploration relating to the MEPAG science disciplines, mission could potentially yield surface samples with known which include geology, geophysics, life, and climate. These context, a robotic mission would not yield the array of characteristics include: speed and efficiency to optimize optimal samples that would address a wide range of field work; agility and dexterity to go places that are fundamental questions. A human mission might allow for difficult for robotic access and to exceed currently limited greater access to samples that a robotic rover might not get degrees-of-freedom robotic manipulation capabilities; and, to, and the capacity for real-time analysis and decision- most importantly, the innate intelligence, ingenuity, and making would ensure that the samples obtained that were adaptability to evaluate in real time and improvise to would be the optimal available samples. overcome surprises while ensuring that the correct sampling strategy is in place to acquire the appropriate sample set. Human explorers would also have greater access to the Real-time evaluation and adaptability especially would be a near-subsurface of Mars, which would yield insights into significant new tool that humans on Mars would bring to climate and surface evolution, geophysics, and, potentially, surface exploration. There are limitations to the autonomous life. Humans would be able to navigate more effectively operations that are possible with current robotic systems, through blocky ejecta deposits, which would provide with fundamental limitations to direct commanding from samples that were excavated from great depth and provide a Earth being the time difference imposed by the 6- to 20- window into the deeper subsurface. Humans could trench in minute communications transit time and the small number dozens of targeted locations and operate sophisticated of daily uplink and downlink communications passes. The drilling equipment that could drill to a depth of 500 to 1,000 scientific exploration of Mars by humans would presumably meters below the surface. Our current understanding of the be performed as a synergistic partnership between humans crust of Mars is limited to the top meter of the surface, so and robotic probes – a partnership that is controlled by the drilling experiments would yield unprecedented and human explorers on the surface of Mars [1 1]. immediate data. Drilling in areas of gully formation could also test the groundwater model by searching for a confined aquifer at depth. We have analyzed three different exploration sites in detail stations, one at each landing site. At regional scales (tens to as reference missions for the first program of human Mars thousands of kilometers), characterizing crustal structure, exploration. The sites, which span the geologic history of magnetism, and other objectives requires mobility to em- Mars (one site for each period of martian history), allow for place local networks around a landing site. Finally, at local exploration traverses that would examine a variety of scales (10 km), mobility is key to performing traverse surface morphologies, textures, and mineralogy to address geophysics, and in carrying out investigations (such as the fundamental questions posed by the MEPAG. seismic or electromagnetic sounding) at specific stations along a traverse. The central geophysics stations and the Geophysics Scientific Objectives— Mars geophysics science regional scale networks would be emplaced and left to objectives fall into two broad categories: planetary scale operate autonomously after the human crew departs. geophysics (thousands of kilometers), and what might be Traverse and station geophysics would be carried out only called “exploration geophysics,” which addresses regional during the human mission, unless this could be done (tens to hundreds of kilometers) or local scales (<10 km). robotically after completion of the human mission. The first category involves characterizing the structure, composition, dynamics, and evolution of the martian Central geophysical stations at each landing site would interior, while the second category addresses the structure, include passive broadband seismic, heat flow, precision composition, and state of the crust, cryosphere, hydrologic geodesy, and passive low-frequency electromagnetic systems, and upper mantle. Here we describe how these instrumentation. Satellite geophysics stations would include objectives might be met through investigations carried out the nodes of a regional seismic array and vector on human missions. We assume here that no robotic magnetometers. Along the traverses, experiments would be missions to Mars before 2025 address the science issues in a performed at sites of interest. These would include active complete way. For example, we assume that no network electromagnetic (EM) sounding for subsurface aquifers, missions (National Research Council [18]) will be flown. In active seismic profiling to establish structure with depth, general, Mars geophysics will be well served by the and gravity measurements. Ground-penetrating radar and diversity of landing sites needed to pursue the geological neutron spectroscopy along the traverse track help map out and life-related objectives. subsurface structure and hydration state/ice content for the near-subsurface. To characterize the structure and dynamics of Mars’ interior band, we must determine the chemical and thermal Atmoshphere/Climate Scientific Objectives— In the human evolution of the planet, including physical quantities such as era of exploration, atmospheric measurements at all sites density and temperature with depth, composition and phase would be seen as important not only to understanding Mars’ changes within the mantle, the core/mantle boundary atmosphere and climate and to planning human surface location, thermal conductivity profile and the 3-dimensional operations, but also as an environmental characterization mass distribution of the planet. To determine the origin and that is essential to the interpretation of many life and history of the planet’s magnetic field, we must discover the geology objectives. The trend towards system science called mineralogy responsible for today’s observed remnant out in MEPAG [10] as a “ground-to-exosphere approach to magnetization, and understand how and when the rocks monitoring the martian atmospheric structure and bearing these minerals were emplaced. A key driver is the dynamics” will continue with more emphasis on the mass, need to instrument the planet at appropriate scales: e.g., heat, and momentum fluxes between the three Mars climate global seismic studies rely on widely separated stations so components: atmosphere, cryosphere, and planetary surface. that seismic ray paths passing through the deep mantle and core can be observed. This need translates into multiple, Understanding Mars’ past climate will benefit from widely separated landing sites for the first human missions. anticipated new knowledge of current atmospheric escape If only a single landing site is selected and revisited, far less rates that will be gained from the 2013 Mars Aeronomy information about Mars’ interior will be obtained. A wide Scout. However, a significant advancement in the key area variety of exploration geophysics techniques could be of access to the polar stratigraphic record is not expected in brought to bear, including sounding for aquifers through the decades before human exploration. In 2030, this will electromagnetic techniques and reflection seismology to therefore remain one of the highest priorities for MEPAG. determine local structure. Magnetic surveys that are carried On the other hand, the study of the paleoclimatic parameters out at landing sites tell us about the spatial scales of crustal that are imprinted in the ancient geological record (e.g., magnetization, and tie in to local and regional geology for Noachian to Amazonian periods) also concerns the high context. priorities of the MEPAG, which directly relates to unlocking the ancient climatic conditions of Mars through a Geophysics measurement requirements span three disparate physical (e.g., geomorphic and/or sedimentary), spatial scales, depending on the science that is to be done. petrological, mineral, and geochemical (including isotopic) At the largest scales (thousands of kilometers), material characterization. characterizing the interior of Mars requires a widely spaced network of at least three emplaced central geophysics The emphasis of atmospheric science measurements by continue to be, based on a search for H O, since all life on 2 human missions would likely focus on processes within the Earth requires H O for survival. Abundant evidence on the 2 planetary boundary layer (PBL), which is surface to 2 km, martian surface of past H O activity (e.g., rivers, lakes, 2 where surface-atmosphere interactions impart fundamental groundwater discharge) has led to Mars becoming a strong influences on the dynamical, chemical, and aerosol candidate as a second planet in our solar system with a characters of the global Mars atmosphere. For the PBL, all history of life. With our increasing knowledge of the spatial scales are important in turbulent exchange, from extremes under which organisms can survive on Earth, centimeters to kilometers, in both horizontal and vertical especially in the deep subsurface, whether martian life is dimensions. Human atmospheric observations could provide still present today has become a compelling and legitimate optimum in-situ and remote access to the PBL and, in turn, scientific question. characterize local environmental conditions in support of human operations. As pointed out by the NRC [21 ], the search for life on Mars requires a very broad understanding of Mars as an • Atmospheric dynamics. This is important because it integrated planetary system. Such an integrated determines the basic thermal structure of the martian understanding requires investigation of the following: atmosphere, the global transport of volatiles (CO , H O, 2 2 dust), and the maintenance of the martian polar ice • The geological and geophysical evolution of Mars; caps, all of which vary on seasonal and inter-annual • The history of Mars’ volatiles and climate; timescales. • The nature of the surface and the subsurface martian • Atmospheric Dust. Atmospheric heating that is environments; associated with atmospheric dust intensifies global • The temporal and geographical distribution of H O; 2 atmospheric circulation and near-surface winds, which • The availability of other resources (e.g., energy) that in turn increases lifting of surface dust into the are necessary to support life; and atmosphere. • An understanding of the processes that control each of • Atmospheric Water: Atmospheric H2O, in the form of the factors listed above. vapor and ice clouds, plays significant roles in atmospheric chemistry, dust radiative forcing, and climate balance. The search for extant life—The NRC [21] suggests a • Atmospheric Chemistry: The trace chemical number of high-priority targets based on evidence for composition of the current martian atmosphere reflects present-day or geologically recent H O near the surface. 2 the photochemical cycles that are associated with the These targets are major atmospheric constituents CO , H O, and nitrogen 2 2 (N2); and perhaps non-equilibrium chemistry that is The surface, interior, and margins of the polar caps; associated with potential subsurface sources – sinks of Cold, warm, or hot springs or underground methane (CH ), sulfur dioxide (SO ) and hydrogen 4 2 hydrothermal systems; and peroxide (H O ) [19; 20]. 2 2 Source or outflow regions that are associated with near- • Electrical Effects: Experimental and theoretical surface aquifers that might be responsible for the investigations of frictional charging mechanisms in “gullies” that have been observed on the martian both small and large-scale meteorological phenomena surface. suggest that Mars very likely possesses an electrically active atmosphere as a result of dust-lifting processes of all scales, including dust devils and dust storms. The MEPAG Special Regions Science Analysis Group [10] Electrical effects impact human exploration and the noted that the sites where recent H O may have occurred 2 environment of Mars as a source of both continual and might also include some mid-latitude deposits that are episodic energy. indicative of shallow ground ice. Conditions in the top 5 m of the martian surface are considered extremely limiting for life. Limiting conditions include high levels of ultraviolet Biology/Life Scientific Objectives —Human-enabled radiation and purported oxidants as well as most of the biological investigations on Mars would focus on taking surface being below the limits of H O activity and 2 samples and making measurements to determine whether temperature for life on Earth. For these reasons, finding life ever arose on Mars. This goal is consistent with the evidence of extant life near the martian surface will likely 2006 MEPAG goals and priorities, and we do not see this be difficult, and the search will almost certainly require goal changing within the next 30 years. subsurface access. This was also a key recommendation of the National Research Council [21]. The search for life on Mars can be generally broken into two broad categories: (1) the search for evidence of past life on Mars, which may or may not still be alive; and (2) the search for present (extant) life. Both have been, and will The search for past life—The NRC [21] lists sites that are disturbances of the martian atmosphere and ionosphere. pertinent to geologically ancient H2O (and, by association, Mars also represents an important key instance of the possibility of past life), including the following: fundamental Heliophysical processes that influence the habitability of planets. Because the space environment Source or outflow regions for the catastrophic flood matters to the safety and productivity of humans and their channels; technological systems both at Mars and in transit, it is Ancient highlands that formed at a time when surface essential that we monitor Heliophysical conditions between H2O might have been widespread (e.g., in the Earth and Mars and understand solar effects on the martian Noachian); and atmosphere, which are relevant for vehicles in Mars orbit or Deposits of minerals associated with surface or traveling through the atmosphere to the surface subsurface H2O or with ancient hydrothermal systems environment. An important supporting objective is to or cold, warm, or hot springs. understand the influence of planetary plasmas and magnetic fields and their interaction with the solar wind plasma. Objectives Related to Preparation for Sustained Human Space weather— The sun and interplanetary medium Presence (Goal IV+) permeating our solar system, as well as the universe at large, consist primarily of plasmas. This leads to a rich set MEPAG’s Goal IV is interpreted to be related to of interacting physical processes and regimes, including preparation for the first human explorers, so by definition, it intricate exchanges with the neutral gas environments of will be complete before the initial set of human missions planets. In preparation for travel through this environment, has been attempted or the activity will have been shown not human explorers must anticipate and prepare for encounters to be necessary. We refer to Goal IV+ as the preparation for with hazardous conditions stemming from ionizing the sustained human presence on Mars beyond that of the radiation. Among the many questions to be answered, the DRA 5.0 mission set. Specific objectives within Goal IV+ following are perhaps the most significant: What are the could be carried out either within the context of the DRA mean conditions, variability, and extremes of the radiation 5.0 missions, or by the preceding robotic program. The and space environment for exploration of Mars? How does scope of the representative scenarios includes developing the radiation environment vary in space and time, and how the knowledge, capabilities, and infrastructure that are should it be monitored and predicted for situational required to live and work on Mars, with a focus on awareness during exploration? What is the relative developing sustainable human presence on Mars. contribution from solar energetic particles and cosmic radiation behind the various shielding materials that are used and encountered, and how does this vary? • Habitability: Includes the capability (1) of providing crew needs from local resources, (2) of extracting Laser ranging for astrophysics— While observations from power and propulsion consumables from local free space offer the most promise for significant progress in resources, and (3) for in-situ fabrication and repair. broad areas of astrophysics, some investigations could be • Systems Development: Includes objectives which relate uniquely enabled by the infrastructure and capabilities of a to the establishment of reliable and robust space human mission to Mars. Among the most promising in this systems that would enable gradual and safe growth of respect are laser ranging experiments to test a certain class capabilities. of alternative theories (to general relativity) of gravity. Such • Self-sufficiency: The level of self-sufficiency of experiments become even more valuable when considered operations for Mars missions also must increase and, in the context of a humans-to-Mars architecture. The long hence, is the objective in the Operational Capabilities baseline measurements that are afforded by laser ranging area. from Mars provides a unique capability that would • Other Objectives: Which address planetary protection otherwise not be enabled by free space implementations or concerns, partnerships, and public engagement, insofar via a lunar architecture. as these are concerned. Goals and Objectives Summary Implications Objectives Related to Ancillary Science (Goal V) During the development of the Mars Design Reference Architecture 5.0, options were developed to provide a better Heliophysics of Mars' environment—The martian system, as understanding of the relationship between the various an archive of solar system evolution (space climate) and a exploration goals and objectives and resulting case of planetary interfaces responding to immediate solar implementation approaches of meeting those goals. influences (space weather), is of great interest to the science Deliberations resulted in the following summary of Heliophysics. These influences range from solar implications: irradiance and high-energy particles irradiating the planet’s surface, to solar wind and magnetic fields driving Explore the Same Site or Different Sites? — Over the last Instruments that operate after humans leave— Several decade, exploration of Mars by robotic orbiters, landers, and types of monitoring stations should be configured so that rovers has shown Mars to be a planet of great diversity and they can continue operating after the astronauts leave. This complexity. This diversity and complexity offers a unique would specifically include network stations for seismic opportunity for humans on the surface of Mars to obtain monitoring and long-duration climate monitoring. data and measurements that could not be obtained by robotic probes alone. To use human explorers effectively in Planetary protection— The impact of human explorers and addressing these scientific questions, the first three human potential “human contamination” of the martian missions to Mars should be to three different geographic environment in the search for present-day life on Mars is a sites. The Goal IV+ objectives lend themselves best to problem that requires more study and evaluation, and that repeated visits to a specific site on Mars, however. Repeated must be solved prior to the first human landing on Mars. site visits would enable a buildup of infrastructure that would benefit the longer-term missions of the Goal IV+ Given that the engineering of missions to Mars are objectives. This buildup would provide more systems for constrained to be either “short stay” or “long stay” and use by the crews such as habitable volume, mobility aids, assuming that the initial human exploration of Mars consists and science equipment. These systems and the potential for of a program of three missions, a key tradeoff is mission spares could also potentially reduce the amount of logistics duration and whether the missions are sent to the same or to required for the long-term missions. different sites. From the perspective of our scientific goals, it is clear that our progress would be optimized b y visiting Short Stay or Long Stay? — It is clear that productivity of multiple sites and by maximizing the stay time at those the missions is amplified many-fold in a 500-day scenario sites. The same argument regarding diversity of sites was as compared to a 30-day scenario. This is particularly true raised, and followed, during the Apollo Program. The of scientific objectives that are related to geology and the longer stay time is needed because the geology of Mars at search for life, for which we need to maximize the amount many sites has complexities that would take a significant of time that the astronauts spend examining the rocks and amount of time to resolve. If we are to bring the unique the diversity of the samples that are collected. Longer stays attributes of human explorers to bear, we would need to allow for a more comprehensive characterization of certain give them enough time on the outcrops. environmental parameters and a longer baseline of measurements. This specific and long-duration knowledge will be essential in the development of health monitoring 3. DRA 5.0 OVERVIEW and hazard mitigation strategies for both the crew and infrastructure elements. The systems required for long stays The NASA Design Reference Architecture 5.0 envisions are also more supportive of the eventual longer term sending six crewmembers to Mars on a minimum of three missions that would achieve sustained human presence consecutive opportunities. The rationale for a crew of this size has been judged to be a reasonable compromise Degree of Mobility— Achieving these scientific objectives between the skill mix and level of effort for missions of this would require mobility. Although different possible landing complexity and duration balanced with the magnitude of the sites have different spatial relationships, it is possible to systems and infrastructure needed to support the crew. One estimate that the capability of traveling a radial distance of of the primary objectives for future human exploration of several hundred kilometers would allow a full range of Mars is to understand the global context of the history of landing site options. Mars, and thus each mission would visit a different unique location on Mars. The science and exploration rationale for visiting three different sites recognizes that a planet that is Subsurface access— It is possible that drilling depths in the range of 100 to 1000 m would be necessary, depending on as diverse as Mars is not likely to be adequately explored the drilling site and the goal of the drilling. and understood from the activities that could take place at a single site. However, this three-site assumption does not preclude returning to any of the sites should there be a Returned sample science— Since human missions to Mars compelling need to do so. This approach was endorsed by have a round-trip component to them, they naturally lend the Human Exploration of Mars Science Advisory Group, themselves to returned sample science. To maximize the which is an independent science team sponsored by value of the returned sample collection, it would be MEPAG [22]. necessary to have a habitat laboratory for two purposes: (1) to help guide them on-Mars field strategies and (2) to ensure the high grade of the samples to be returned. Sample Each of the three missions would use conjunction class (long-stay) trajectories combined with a “forward deploy” conditioning and preservation will be essential. The cargo strategy. A portion of each mission’s assets would be minimum mass of samples to be returned to Earth is to be sent to Mars one opportunity prior to the crew. This forward determined, but it could be as much as 250 kg. deploy strategy would allow lower energy trajectories to be used for these pre-deployed assets, which allows more useful payload mass to be delivered to Mars for the Mars orbit. The SHAB would remain in Mars orbit in a propellant available. The decision to pre-position some of semi-dormant mode, waiting for arrival of the crew 2 years the mission assets also better accommodates the strategy to later. The DAV would be captured into a temporary Mars make part of the ascent propellant at Mars, using the orbit from which it would autonomously perform the entry, martian atmosphere as the raw material source for this descent, and landing on the surface of Mars at the desired ascent propellant. This use of in-situ resources and the landing site. After landing, the vehicle would be checked equipment to process these resources into useful out and its systems verified to be operational. The surface commodities results in a net decrease in the total mass that fission reactor would be deployed, and production of the is needed to complete a mission as well as a significant ascent propellant and other commodities that are needed by reduction in the size of the landers. A surface nuclear power the crew would be completed before committing to the crew source would be utilized for producing this ascent phase of the mission. propellant as well as for providing power for the surface systems once the crew arrives. Splitting the mission A key feature of the long-stay mission architecture is the elements between pre-deployed cargo and crew vehicles autonomous deployment of a portion of the surface allows the crew to fly on faster, higher-energy trajectories, infrastructure before the crew arrives, such as the surface thus minimizing their exposure to the hazards associated power system. This strategy includes the capability for these with deep-space inter-planetary travel. infrastructure elements to be unloaded, moved significant distances, and operated for significant periods of time Getting Ready, Getting to Mars, and Getting Back without humans present. In fact, the successful completion of these various activities would be part of the decision Due to the significant amount of mass required for a human criteria for launch of the first crew from Earth. mission to Mars, numerous heavy-lift launches would be required. The reference launch vehicle that would be used is The second phase of this architecture begins during the next the Ares V launch vehicle. Using the same launch vehicle injection opportunity with the launch, assembly, and currently envisioned for lunar missions would greatly checkout of the crew Mars transfer vehicle (MTV). The improve the overall mission risk due to the improved MTV would serve as the interplanetary support vehicle for maturity of the launch vehicle by the time the Mars missions the crew for a round-trip mission to Mars orbit and back to commence. Current estimates of the mission manifest Earth. Prior to departure of the flight crew, a separate indicate that at least seven heavy-lift cargo launches would checkout crew may be delivered to the MTV to perform be required, but the number of launches could be higher, vital systems verification and any necessary repairs prior to depending on the architecture-wide technology options departure of the flight crew. After all vehicles and systems, inserted. This large number of launches necessitates a including the Mars DAV (on the surface of Mars), SHAB launch campaign that must begin several months prior to the (in Mars orbit), and the MTV (in LEO) are verified opening of the Mars departure window. The reference operational, the flight crew would be injected on the strategy that is adopted eliminates on-orbit assembly of the appropriate fast-transit trajectory towards Mars. The length mission elements by segmenting the systems into discrete of this outbound transfer to Mars is dependent on the packages and using automated rendezvous and docking mission date, and ranges from 175 to 225 days. Upon (AR&D) of the major elements in LEO. Launches would arrival at Mars, the crew members perform a rendezvous occur 30 days apart and would be completed several months with the SHAB, which would serve as their transportation before the opening of the Mars departure window to leg to the surface of Mars. provide a margin for technical delays and other unforeseen problems. This strategy requires that the in space Current human health and support data indicate that it may transportation systems and payloads loiter in LEO for take the crew a few weeks to acclimate to the partial gravity several months prior to departure for Mars. The overall of Mars after landing. After the crew has acclimated, the launch and flight sequence for the first two missions is initial surface activities would focus on transitioning from a depicted in figure 1. “lander mode” to a fully functional surface habitat. This would include performing all remaining setup and checkout The first phase of the mission architecture would begin with that could not be performed prior to landing, as well as the pre-deployment of the first two cargo elements, the transfer of hardware and critical items from the pre- descent/ascent vehicle (DAV) and the surface habitat deployed DAV. (SHAB). These two vehicle sets would be first launched, assembled (via rendezvous and docking), and checked out The long-stay mission architecture lends itself to a very in LEO. After all of the systems have been verified and are robust surface exploration strategy. The crew would have operational, the vehicles loiter in Earth orbit until the Earth- approximately 18 months in which to perform the necessary Mars departure window opens when they would be injected surface exploration. Ample time would be provided to plan into minimum energy transfers from Earth orbit to Mars just and re-plan the surface activities, respond to problems, and over 2 years prior to the launch of the crew. Upon arrival at readdress the scientific questions posed throughout the Mars, the vehicles would be captured into a highly elliptical useful payload mass to be delivered to Mars for the Mars orbit. The SHAB would remain in Mars orbit in a propellant available. The decision to pre-position some of semi-dormant mode, waiting for arrival of the crew 2 years the mission assets also better accommodates the strategy to later. The DAV would be captured into a temporary Mars make part of the ascent propellant at Mars, using the orbit from which it would autonomously perform the entry, martian atmosphere as the raw material source for this descent, and landing on the surface of Mars at the desired ascent propellant. This use of in-situ resources and the landing site. After landing, the vehicle would be checked equipment to process these resources into useful out and its systems verified to be operational. The surface commodities results in a net decrease in the total mass that fission reactor would be deployed, and production of the is needed to complete a mission as well as a significant ascent propellant and other commodities that are needed by reduction in the size of the landers. A surface nuclear power the crew would be completed before committing to the crew source would be utilized for producing this ascent phase of the mission. propellant as well as for providing power for the surface systems once the crew arrives. Splitting the mission A key feature of the long-stay mission architecture is the elements between pre-deployed cargo and crew vehicles autonomous deployment of a portion of the surface allows the crew to fly on faster, higher-energy trajectories, infrastructure before the crew arrives, such as the surface thus minimizing their exposure to the hazards associated power system. This strategy includes the capability for these with deep-space inter-planetary travel. infrastructure elements to be unloaded, moved significant distances, and operated for significant periods of time Getting Ready, Getting to Mars, and Getting Back without humans present. In fact, the successful completion of these various activities would be part of the decision Due to the significant amount of mass required for a human criteria for launch of the first crew from Earth. mission to Mars, numerous heavy-lift launches would be required. The reference launch vehicle that would be used is The second phase of this architecture begins during the next the Ares V launch vehicle. Using the same launch vehicle injection opportunity with the launch, assembly, and currently envisioned for lunar missions would greatly checkout of the crew Mars transfer vehicle (MTV). The improve the overall mission risk due to the improved MTV would serve as the interplanetary support vehicle for maturity of the launch vehicle by the time the Mars missions the crew for a round-trip mission to Mars orbit and back to commence. Current estimates of the mission manifest Earth. Prior to departure of the flight crew, a separate indicate that at least seven heavy-lift cargo launches would checkout crew may be delivered to the MTV to perform be required, but the number of launches could be higher, vital systems verification and any necessary repairs prior to depending on the architecture-wide technology options departure of the flight crew. After all vehicles and systems, inserted. This large number of launches necessitates a including the Mars DAV (on the surface of Mars), SHAB launch campaign that must begin several months prior to the (in Mars orbit), and the MTV (in LEO) are verified opening of the Mars departure window. The reference operational, the flight crew would be injected on the strategy that is adopted eliminates on-orbit assembly of the appropriate fast-transit trajectory towards Mars. The length mission elements by segmenting the systems into discrete of this outbound transfer to Mars is dependent on the packages and using automated rendezvous and docking mission date, and ranges from 175 to 225 days. Upon (AR&D) of the major elements in LEO. Launches would arrival at Mars, the crew members perform a rendezvous occur 30 days apart and would be completed several months with the SHAB, which would serve as their transportation before the opening of the Mars departure window to leg to the surface of Mars. provide a margin for technical delays and other unforeseen problems. This strategy requires that the in space Current human health and support data indicate that it may transportation systems and payloads loiter in LEO for take the crew a few weeks to acclimate to the partial gravity several months prior to departure for Mars. The overall of Mars after landing. After the crew has acclimated, the launch and flight sequence for the first two missions is initial surface activities would focus on transitioning from a depicted in figure 1. “lander mode” to a fully functional surface habitat. This would include performing all remaining setup and checkout The first phase of the mission architecture would begin with that could not be performed prior to landing, as well as the pre-deployment of the first two cargo elements, the transfer of hardware and critical items from the pre- descent/ascent vehicle (DAV) and the surface habitat deployed DAV. (SHAB). These two vehicle sets would be first launched, assembled (via rendezvous and docking), and checked out The long-stay mission architecture lends itself to a very in LEO. After all of the systems have been verified and are robust surface exploration strategy. The crew would have operational, the vehicles loiter in Earth orbit until the Earth- approximately 18 months in which to perform the necessary Mars departure window opens when they would be injected surface exploration. Ample time would be provided to plan into minimum energy transfers from Earth orbit to Mars just and re-plan the surface activities, respond to problems, and over 2 years prior to the launch of the crew. Upon arrival at readdress the scientific questions posed throughout the Mars, the vehicles would be captured into a highly elliptical Peak Dust Storm Season Solar Conjunction Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 J FMAMJJASONDJFMAMJJASONDJ FMAM JJASONDJFMAM JJASONDJFMAMJJASONDJ FM AMJ JASONDJFMAM JJASON D Mission #1 Cargo (SHAB) Cargo (DAV) Depart Arrive Crew (MTV) A' Depart Arrive Depart Arrive Mission #2 r Cargo (DAV) Cargo (SHAB) Depart Arrive Crew (MTV) 0 Q Depart Arrive Launch Campaign Cargo Outbound _ Unoccupied Wait ® Crew Transits Surface Mission = Overlapping Elements Figure 1 Mars Mission Sequence mission. The focus during this phase of the mission would This vehicle would be used to return the crew from Mars, be on the primary science and exploration activities that ending with a direct entry at Earth in a modified Orion crew would change over time to accommodate early discoveries. vehicle. The nuclear thermal rocket version of the DRA, A general outline of crew activities would be established also known as a “bat chart”, is shown in figure 2. before the launch, but would be updated throughout the mission. This outline would contain detailed activities to Exploring the Surface ensure initial crew safety, make basic assumptions as to initial science activities, schedule periodic vehicle and Candidate surface sites would be chosen based on the best system checkouts, and plan for a certain number of sorties. possible data available at the time of the selection, the operational difficulties associated with that site, and the Much of the detailed activity planning while on the surface collective merit of the science and exploration questions would be based on initial findings and, therefore, could not that could be addressed at the site. Information available for be accomplished before landing on Mars. The crew would site selection would include remotely gathered data sets plus play a vital role in planning specific activities as derived data from any landed mission(s) in the vicinity plus from more general objectives defined by colleagues on interpretive analyses based on these data. Earth. Alternative approaches for exploring the surface are still under discussion and are expected to be examined Several different surface architectures were assessed during further, including maximizing commonality with lunar the formulation of the Mars DRA 5.0, each of which systems. One of the approaches that most closely follows emphasized different exploration strategies that were previous DRAs, referred to as the “Commuter” scenario, embodied in the combination of duration of in the field, was selected as the nominal approach and is described in the range of exploration reach, and depth of subsurface access. next section. The nominal surface mission scenario adopted for DRA 5.0 is the so-called “Commuter” reference architecture, which Before committing the crew to Mars ascent and return to would have a centrally located, monolithic habitat, two Earth, full systems checkout of the ascent vehicle and the small pressurized rovers, and two unpressurized rovers MTV would be required. Because both vehicles are critical (roughly equivalent to the lunar rover vehicle (LRV) that to crew survival, sufficient time must be provided prior to was used in the Apollo missions to the moon). This ascent to verify systems and troubleshoot any anomalies combination of habitation and surface mobility capability prior to crew use. In addition, the surface systems would be would allow the mission assets to land in relatively flat and placed in a dormant mode for potential reuse by future safe locations, yet provides the exploration range that would crews by stowing any nonessential hardware, safing critical be necessary to reach nearby regions of greater scientific systems and their backups, and performing general diversity. Power for these systems would be supplied by a housekeeping duties. Lastly, some surface elements would nuclear power plant that was previously deployed with the be placed in an automated operations mode for Earth-based DAV and used to make a portion of the ascent propellant. control so that scientific observations could be continued Traverses would be a significant feature of the exploration after the crew has departed. The crew would then ascend in strategy that would be used in this scenario, but these the DAV and performs a rendezvous with the waiting MTV. traverses would be constrained by the capability of the