Patrick R. Chai

Reusable Lunar Transportation Architecture Utilizing Orbital Propellant Depots

To support a permanent human settlement on the Lunar surface, improvements to the current Lunar outpost architecture are investigated. A detailed analysis of architectures utilizing an orbital propellant depot and reusable vehicles is presented. Comparisons focus on cost, extensibility, performance, heritage, and reliability. An architecture utilizing a two stage reusable transit vehicle, a reusable Lunar lander, and a integrated orbital propellant depot is proposed. A 30% reduction in cost for payload delivered to the lunar surface is achieved with the proposed architecture when compared to the ESAS architecture. A detailed breakdown of the architecture is presented and recommendations are made regarding the direction of technology investments needed to enable permanent human settlement on the Lunar surface.

Plan B for U.S. Human Space Exploration Program

The Augustine Report recommended the use of commercial launch and propellant depots to improve Program sustainability. Plan A Apollo and Apollo programs provide a basis for sustainability where Apollo was quickly cancelled after the lunar landing but the Shuttle was sustained for 40 years. For an asteroid and lunar missions, commercial launch vehicles with depots showed significant cost improvements that are below current NASA exploration budgets with improvement of mission reliability over NASA baseline architectures and missions.

Permanent Manned Outpost with Commercial Launch and Propellant Depots

NASA has been developing a capability based space transportation framework for exploration evolution cis-lunar, lunar, asteroids, and Mars. With the recent discovery of water on the moon, research has been invigorated to establish a permanent manned outpost for in situ capture of water and transport support for in-space propellant. Using recent NASA studies of infrastructure needs for a permanent manned outpost, current and future launch vehicle and in-space transportation systems are evaluated based on performance, cost, and reliability. Because a constantly manned outpost requires astronaut replacement every six months and constant human and facility resupply, large yearly payloads are required. Present and planned expendable transportation systems may not meet reasonable cost and reliability expectations. Reusable systems may be acceptable if the high flight rates are sustained to cover the high development cost.

In-Space Assembly Capability Assessment for Potential Human Exploration and Science Applications

Human missions to Mars present several major challenges that must be overcome, including delivering multiple large mass and volume elements, keeping the crew safe and productive, meeting cost constraints, and ensuring a sustainable campaign. Traditional methods for executing human Mars missions minimize or eliminate in-space assembly, which provides a narrow range of options for addressing these challenges and limits the types of missions that can be performed. This paper discusses recent work to evaluate how the inclusion of in-space assembly in space mission architectural concepts could provide novel solutions to address these challenges by increasing operational flexibility, robustness, risk reduction, crew health and safety, and sustainability. A hierarchical framework is presented to characterize assembly strategies, assembly tasks, and the required capabilities to assemble mission systems in space. The framework is used to identify general mission system design considerations and assembly system characteristics by assembly strategy. These general approaches are then applied to identify potential in-space assembly applications to address each challenge. Through this process, several focus areas were identified where applications of in-space assembly could affect multiple challenges. Each focus area was developed to identify functions, potential assembly solutions and operations, key architectural trades, and potential considerations and implications of implementation. This paper helps to identify key areas to investigate were potentially significant gains in

Multigenerational Independent Colony for Extraterrestrial Habitation, Autonomy, and Behavior Health (MICEHAB): An Investigation of a Long Duration, Partial Gravity, Autonomous Rodent Colony

The path from Earth to Mars requires exploration missions to be increasingly Earth-independent as the foundation is laid for a sustained human presence in the following decades. NASA pioneering of Mars will expand the boundaries of human exploration, as a sustainable presence on the surface requires humans to successfully reproduce in a partial gravity environment independent from Earth intervention. Before significant investment is made in capabilities leading to such pioneering efforts, the challenges of multigenerational mammalian reproduction in a partial gravity environment need be investigated. The Multi-generational Independent Colony for Extraterrestrial Habitation, Autonomy, and Behavior health is designed to study these challenges. The proposed concept is a conceptual, long duration, autonomous habitat designed to house rodents in a partial gravity environment with the goal of understanding the effects of partial gravity on mammalian reproduction over multiple generations and how to effectively design such a facility to operate autonomously while keeping the rodents healthy in order to achieve multiple generations. All systems are designed to feed forward directly to full-scale human missions to Mars. This paper presents the baseline design concept formulated after considering challenges in the mission and vehicle architectures such as: vehicle automation, automated crew health management/medical care, unique automated waste disposal and hygiene, handling of deceased crew members, reliable long-duration crew support systems, and radiation protection. This concept was selected from an architectural trade space considering the balance between mission science return and robotic and autonomy capabilities. The baseline design is described in detail including: transportation and facility operation constraints, artificial gravity system design, habitat design, and a full-scale mock-up demonstration of autonomous rodent care facilities. The proposed concept has the potential to integrate into existing mission architectures in order to achieve exploration objectives, and to demonstrate and mature common capabilities that enable a range of destinations and missions.

Review of Recent U.S. Human Space Exploration Plans Beyond Low Earth Orbit

In the wake of the Space Shuttle Columbia accident, NASA began to formulate post-shuttle human space exploration plans. A decade later, NASA is no closer to sending humans beyond low Earth orbit. During that time, NASA had adopted two major visions for the future of human space exploration: the 2004 Vision for Space Exploration, and the 2010 National Space Policy of the United States of America. Both of these visions led to studies intended to guide NASA’s path to far-reaching exploration destinations. However, the architectures developed in these studies failed to align with their corresponding visions. As a result of this rift and the steady budget decline over the past 20 years, NASA has neither met milestones outlined in the architecture, nor realized the visions that would return the United States to the forefront of human space exploration. This paper reviewed NASA’s space exploration plans beyond low Earth orbit, and identify the discontinuity between the exploration visions and the resulting architectures and programs. NASA’s current exploration planning process, from vision to program, has exhibited a cyclical pattern that hinders tangible progress to sending humans back beyond low Earth orbit. Additionally unrealistic fiscal assumption have contributed to inability to meet programmatic goals. For NASA to break the cycle and enable our astronauts to boldly go where no one has gone before, fundamental changes to the status quo are essential.

The Utilization of Launch Vehicles Core Stages and Propellant Depots for Human Space Exploration

A crewed mission to a near earth asteroid would yield both scientific and engineering advancements. Visiting one or several of these objects would not only validate technologies that could later be used to visit the Moon or Mars, but would also develop our scientific understanding of asteroids and the solar system. This study proposes an architecture that represents a paradigm shift in the way space exploration is conducted. By including the commercial space industry in this mission and encouraging competition, NASA can realize significant cost savings and schedule improvements. This architecture uses a commercial launch vehicle core stage, which can reach orbit if a rocket is launched with no payload, as the in space propulsion system for both outbound and inbound burns. Refueling the core stage with commercial launch systems separates the propellant from the mission-critical elements, and using multiple commercial partners shortens the mission life cycle time and increases mission reliability. Removing expensive and unnecessary systems and supplementing NASA hardware with existing commercial systems brings the program under the current human space exploration budget. Furthermore, this architecture is also extensible to other destinations of interest for human exploration.

Station Keeping for Earth-Moon Lagrangian Point Exploration Architectural Assets

The 2010 National Space Policy set wide reaching goals for the United States space program, however these milestones are in serious jeopardy due the economic down turn and budget restrictions. There is an increasing need to examine the current exploration architecture to determine if there are more economical, yet still technically feasible options. The Earth-Moon Lagrangian points in the cis-lunar space have long been proposed as staging points to enable lunar colonization and missions to Mars and other planetary bodies. The placement of an orbital propellant depot near Lagrangian points enables a more robust and economical way to accomplish NASA’s exploration goals. The primary technical challenge of placing assets near the L1 and L2 points is the inherent instability of orbits around the Lagrangian points. Trajectory simulation of in-plane Lyapunov orbit shows that near the Earth-Moon L1 point, the station keeping cost decreases as the orbital altitude decreases, however, the insertion cost increases as the altitude decreases. Similar trajectory simulation shows that a 9,000km altitude L2 Lyapunov orbit provides a minimum station keeping cost as well as low insertion cost. The phasing of the Earth-Moon orbital plane makes the departure orbit inclination a viable candidate for optimization as well.