Dale Arney

Orbital Propellant Depots Enabling Lunar Architectures Without Heavy-Lift Launch Vehicles

Many human lunar exploration architectures, both flown and conceptual, use at least one heavy-lift launch vehicle to deliver flight hardware to low Earth orbit. There exists a technology, however, that allows these large exploration missions to be performed without the use of a heavy-lift launch vehicle: propellant transfer. This study presents a methodology to incorporate propellant transfer into conceptual design of lunar architectures through the use of a low-Earth-orbit propellant depot. This technology is then applied to a two-launch human lunar architecture without a heavy-lift launch vehicle. The results show that not only is a lunar architecture without a heavy-lift launch vehicle feasible with a propellant depot, but it can also improve the capability to deliver payload to the surface over an architecture that includes a heavy-lift launch vehicle without a propellant depot. The optimal lunar lander for this architecture is a hypergolic lander with a deck height of only 1.53meters that performs only a portion of the descent burn, while the trans-lunar injection stage performs the other portion. The hypergolic propellant allows for a simpler, less expensive propulsion system, a volumetrically smaller lander, and enables the use of the existing hypergolic propellant transfer technology.

Modeling Space System Architectures with Graph Theory

Current space system architecture modeling frameworks use a variety of methods to generate their architecture definitions and system models but are either too manual or too limited in scope to effectively explore the architecture-level design space exploration. This paper outlines a method to mathematically model space system architectures using graph theory, which provides a simple mathematical framework that is flexible enough to model many different system architecture options, such as lunar, asteroid, and Mars missions. Multiple lunar system architectures were considered in NASA’s Exploration System Architecture Study mission modes comparison. These system architectures are modeled within this framework to demonstrate the ability to rapidly compare the performance of different system architectures within a single framework. This capability is crucial in order to explore the system architecture-level design space and make informed decisions on the future of a human space exploration program.

Sustaining Human Presence on Mars Using ISRU and a Reusable Lander

This paper presents an analysis of the impact of ISRU (In-Site Resource Utilization), reusability, and automation on sustaining a human presence on Mars, requiring a transition from Earth dependence to Earth independence. The study analyzes the surface and transportation architectures and compared campaigns that revealed the importance of ISRU and reusability. A reusable Mars lander, Hercules, eliminates the need to deliver a new descent and ascent stage with each cargo and crew delivery to Mars, reducing the mass delivered from Earth. As part of an evolvable transportation architecture, this investment is key to enabling continuous human presence on Mars. The extensive use of ISRU reduces the logistics supply chain from Earth in order to support population growth at Mars. Reliable and autonomous systems, in conjunction with robotics, are required to enable ISRU architectures as systems must operate and maintain themselves while the crew is not present. A comparison of Mars campaigns is presented to show the impact of adding these investments and their ability to contribute to sustaining a human presence on Mars.

Rapid Cost Estimation for Space Exploration Systems

Incorporating cost estimation into the space system architecture design space exploration process enables decision-makers to qualitatively assess the cost impact of architecture decisions. By creating simple, system-level cost estimating relationships (CERs) derived from bottoms-up estimates of mass, this information can be incorporated in the decisionmaking process. The research presented in this paper develops these relationships for various system types based on a baseline configuration for each system type. The capability of these CERs are demonstrated by using them within a graph theory system architecture modeling framework to explore the options identified within the Exploration System Architecture Study (ESAS) mission modes comparison. These options, along with a commercial architecture that is significantly different than any of the options identified in ESAS are compared based on cost, and the overall system architecture comparison that includes all of the figures of merit used in ESAS are discussed.

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.

A Modeling Environment for the Optimization of Space Architectures

The selection of a space system architecture to perform a human space mission is the most important decision in the development process. This decision provides the greatest impact on the cost and performance of the mission. However, decisions not only affect the current mission, but also subsequent missions in the overall exploration program. This paper presents a means of selecting system architectures during the architecture-level design space exploration. Decision making in commercial industry uses Net Present Value (NPV) as a selection criterion because it normalizes the return on investment to the current value. This paper extends NPV to space systems architecture selection. Within the evolutionary exploration program in place at NASA, NPV could be used to make decisions that not only affect the current mission, but also subsequent missions in the sequence. Finally, this exploration and selection methodology is used to compare human Mars system architectures.

Modeling Space Architectures through Graph Theory

*† This paper outlines a methodology to mathematically model space architectures by using graph theory. An overview of previous Mars architecture design studies is given, from the early studies in the Apollo era to the Space Exploration Initiative to the latest Design Reference Architecture 5.0. Utilizing graph theo ry to model architectures provides a simple mathematical framework that is flexible enough to model any of these given architectures. Developing the matrices that define a graph—the adjacency and incidence matrices—are easily developed by user-specified nodes and edge options. An example architecture is modeled from beginning to end to show the capability of this framework, which also lends itself to stochastic optimization methods, such as genetic algorithm and particle swarm, among others. There is ongoing work to improve the autonomy of this framework as well as generation of the vehicle sizing hierarchy.

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

High Altitude Venus Operational Concept (HAVOC): An Exploration Strategy for Venus

Humans are on their way to becoming a spacefaring civilization, and Venus presents an intriguing destination for expanding humanity’s journey beyond Earth. The atmosphere of Venus is a suitable environment for both further scientific study and future human exploration. Fifty kilometers above the Venusian surface is one of the most hospitable, Earthlike locations in the Solar System; the pressure, density, gravity, and radiation protection are all similar to Earth surface conditions. A recent internal NASA study of a High Altitude Venus Operational Concept (HAVOC) led to the development of an evolutionary program for the exploration of Venus, with a focus on the mission architecture and vehicle concepts for robotic missions and 30-day crewed missions into the Venusian atmosphere. Initial analysis has shown that both robotic and human exploration of the Venusian atmosphere is feasible contingent on the development of key capabilities: human-scale aeroentry vehicles, high dynamic pressure supersonic decelerators, long-duration cryogenic storage, Venus and Earth aerocapture, and rapid airship inflation (during the descent). Many of these capabilities are complementary to previously and currently considered Mars architectures, and their development would be enabling to voyages to either planet. Ultimately, with its relatively hospitable upper atmosphere, Venus can play a role in humanity’s future in space.

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.