Paul D. Wooster

Affordable Human Moon and Mars Exploration through Hardware Commonality

The Vision for Space Exploration calls for the safe, affordable, and sustainable human exploration of the Moon and Mars. In order to achieve exploration affordability and sustainability, the Mars -back approach was developed. The fundamental principle of the Mars -back approach is that the syste m elements used for lunar exploration are a subset (in terms of design) of those used for Mars exploration; thereby the lunar exploration hardware is directly relevant to the exploration of Mars. After systematic qualitative and quantitative analysis of ov er 1000 lunar and over 1000 Mars exploration architectures using a discrete event simulation tool, two architectures were chosen for further analysis based on overall mission mass, mission risk, and cost: a direct return architecture for lunar exploration, and an architecture similar in concept to the 1993 NASA Mars Design Reference Mission for conjunction -class Mars exploration. Employing the Mars -back approach, the Mars exploration hardware can enable a crewed lunar direct return architecture along with o ne way cargo -delivery capability, such as for a long -duration surface habitat, without the need for additional hardware development. Common system elements include the CEV for short term habitation and Earth entry, long -term in -space and planetary surface habitats, and propulsion stages for Earth departure, deep -space maneuvers, and planetary descent / ascent. Commonality was introduced through design for the most stressing case, typically Mars, when requirements were similar, and through modular, extensibl e solutions when requirements differed more widely. Based on the commonality concept, a hardware development roadmap was laid out for phased development of the hardware; each phase provides increasing mission capability. Hardware development with commonali ty eliminates the need for any significant “development gap” between lunar and Mars exploration missions. The development approach ensures that technology and hardware development for lunar missions is directly relevant to Mars exploration. Also, extensive testing of Mars hardware can be carried out during long -stay lunar missions, thereby increasing operational experience with the equipment to be used for Mars missions and reducing Mars mission risk. As identical hardware is used, lunar missions could stil l be executed during Mars exploration because the production and assembly lines would still be running. Most importantly, the overall lifecycle cost for exploration of the Moon and Mars is significantly reduced by limiting the amount of hardware that must be developed. The drawback of Mars -back commonality is a certain non -optimality in the common system design which leads to increased system dry and wet mass and therefore to a potential increase in recurring cost, mainly in launch and production. Quantitat ive analysis of this commonality penalty shows a modest growth of Initial Mass in LEO, which appears acceptable when set against the significant savings in overall lifecycle cost that would be achieved.

Selection and Technology Evaluation of Moon/Mars Transportation Architectures

Our purpose is to evaluate and select from a large family of Moon-Mars transportation architectures by integrating a general architecture network model with vehicle computational modules. A complete tradespace of 1162 unique transportation architectures for human missions to the Moon and to Mars provided by an Object Process Network based architecture generator has been interpreted and integrated with subsystem models. Three Mars and five lunar architectures are downselected based on total launch mass to LEO, risk, complexity and further criteria. Sensitivity analysis and trades of mass for dierent advanced propulsion types and in-situ propellant production availability are presented.

Trajectory options for human mars missions

This paper explores trajectory options for the huma n exploration of Mars, with an emphasis on conjunction-class missions. Conjunction-class missions are characterized by short in-space durations with long surface stays, a s opposed to the long in-space durations and short surface stays characteristic of oppositio n-class missions. Earth-Mars and Mars- Earth trajectories are presented across a series of mission opportunities and transfer times in order to explore the space of possible crew and cargo transfer trajectories. In the specific instance of crew transfer from Earth to Mars, the p otential for aborting the mission without capture into Mars orbit is also of interest. As suc h two additional classes of trajectories are considered: free-return trajectories, where the tra jectory would return the crew to Earth after a fixed period of time; and propulsive-abort trajectories, where the propulsive capability of the transfer vehicle is used to modif y the trajectory during a Mars swing-by. The propulsive requirements of a trajectory, due to their associated impact on spacecraft mass, are clearly of interest in assessing trajecto ries for human Mars missions. Beyond the propulsive requirements, trajectory selection can h ave a significant impact on the entry velocity and therefore the aeroassist system requir ements. The paper suggests potential constraints for entry velocities at Earth and Mars. Based upon Mars entry velocity, the 2- year period free-return abort trajectory is shown t o be less desirable than previously considered for many mission opportunities.

Analysis of Human Lunar Outpost Strategies and Architectures

Recently published plans for a human lunar exploration campaign as part of the Vision for Space Exploration focus on the establishment of an outpost at the lunar South Pole with the intent of permanent or near-permanent inhabitation. This paper investigates potential lunar exploration alternatives to this strategy based on a small number of so-called campaign elements which could be placed end-to-end to build a lunar exploration campaign. Results indicate that special consideration should be given to campaign strategies that include what we term “intermediate outpost” missions, as such missions can provide significant value for Mars preparation early in the campaign and under certain conditions may obviate the need for a long-term outpost altogether. The paper also includes conceptual design analysis for technical lunar surface architectures based either on a full-size habitat pre-integrated on Earth or on a habitat that is assembled on the lunar surface out of multiple modules. Comparison of campaign performance shows that the differences between the technical surface architectures are small compared to the differences in campaign strategy; technical architectures therefore need to be compared on cost and risk. Based on cost and risk considerations, a lunar surface architecture with a full-size habitat pre-integrated on Earth is preferred. In general, the lunar surface system architecture should be designed to support all or most of the campaign elements in order to provide flexibility and robustness to programmatic change over the next decade before the actual implementation of the campaign.

Extending NASA's Exploration Systems Architecture towards Long-term Crewed Moon and Mars Operations

This paper presents a baseline strategy for extending lunar crew transportation system operations as outlined in NASA’s Exploration Systems Architecture Study (ESAS) report towards longer-stay lunar surface operations and conjunction class Mars missions. The analysis of options for commonality between initial lunar sortie operations and later Moon and Mars exploration missions is essential for reducing life-cycle cost and providing lowinvestment / high-return options for extending exploration capabilities soon after the 7 human lunar landing. The analysis is also intended to inform the development of the human lunar lander and other exploration system elements by identifying enabling requirements for extension of the lunar crew transportation system. The baseline strategy outlined in this paper was generated using a three-step process: the analysis of exploration objectives and scenarios, identification of functional and operational extension options, and the conceptual design of a set of preferred extension options. Extension options include (but are not limited to) the use of the human lunar lander as outpost for extended stays, and Mars crew transportation using evolved Crew Exploration Vehicle (CEV) and human lander crew compartments. Although the results presented in this paper are based on the ESAS elements, the conclusions drawn in this paper are generally applicable provided the same lunar transportation mode (lunar orbit rendezvous) is used.

Opening Space for Humanity - Applying Open Source Concepts to Human Space Activities

With the open source paradigm gaining traction in a variety of fields, the question arises as to in what ways open source concepts can be applied towards space development endeavors. This paper examines the potential for applying open source towards human space activities. We find that open source holds much promise for benefiting space development endeavors. Open source can clearly be applied in the space software area, including modeling and design tools, testing, ground software, and flight software. The paradigm can, however, be extended beyond software, in areas such as system design, compilation of reference data, system verification & validation procedures and associated results, and relevant education and training materials. Many individuals around the world are highly motivated towards contributing to the expansion of humanity into space. Applying open source principles towards space activities can provide them with a means of doing so. A new organization, DevelopSpace, has been created to aid in the advancement of such activities, focused on building up the technical foundations for human space activities, and doing so in an open manner.

Interplanetary Transfer Vehicle Concepts for Near-Term Human Exploration Missions beyond Low Earth Orbit

This paper presents an analysis of architecture alternatives for carrying out near-term human missions beyond Low Earth Orbit (LEO), in particular missions to Near Earth Objects (NEOs). A minimalist approach to near-term human missions beyond LEO was identified based on the development of an Orion-like vehicle providing Earth entry and deep space propulsion (development could be either lead by government or by a commercial entity), a human-rated heavy-lift launch vehicle capable of launching 72 mt or more to LEO and accommodating payloads of up to 35 m height and up to 5 m diameter, a habitation module similar in size to a lunar lander crew compartment, and an adapted Centaur V1 upper stages from existing commercial launch vehicles. This minimalist architecture would enable lunar flyby, lunar orbit, and Sun-Earth Lagrange point missions with a single launch, and missions to Geostationary Earth Orbit (GEO) and to NEOs with two launches. Based on publicly available estimates of development schedules and cost, for example for shuttlederived launch vehicles (as provided to the Augustine Committee in 2009), such a minimalist architecture should be available 5-7 years after start of development at current funding levels. While being minimalist with regard to near-term availability, this approach would also provide important elements which are forward-extensible to human Mars missions, such as the Orion crew module, the human-rated heavy-lift launch vehicle, and possibly the habitation module.

Mars Gravity Biosatellite: International Student Training and Public Outreach

Designed by students and other volunteers from three universities in the U.S. and Australia, the Mars Gravity Biosatellite Program plans a launch of a small, unmanned research platform to support ground-breaking investigations in partial gravity physiology. This spinning spacecraft will provide artificial gravity at 0.38-g, the surface gravity of Mars. Onboard life support systems will support a payload of fifteen mice for a total mission duration of five weeks, culminating in reentry at the Woomera Protected Area in Australia. We present this international, multi-disciplinary, multi-institute program as a new model for both aerospace workforce development and public outreach.