274 research outputs found
Phase Control and Eclipse Avoidance in Near Rectilinear Halo Orbits
The baseline trajectory proposed for the Gateway is a southern Earth-Moon L2 Near Rectilinear Halo Orbit (NRHO). Designed to avoid eclipses, the NRHO exhibits a resonance with the lunar synodic period. The current investigation details the eclipse behavior in the baseline NRHO. Then, phase control is added to the orbit maintenance algorithm to regulate perilune passage time and maintain the eclipse-free characteristics of the Gateway reference orbit. A targeting strategy is designed to periodically target back to the long-horizon virtual reference if the orbit diverges over time in the presence of additional perturbations
2007 Western States Fire Mission
A general overview of the Ikhana Uninhabited Air System (UAS) is presented. The contents include: 1) Ikhana UAS; 2) Ikhana UAS / Ground Control Station (GCS); 3) Ikhana UAS / Antennas; 4) Western States Fire Mission 2007 Partners; 5) FAA Certificate of Authorization (COA); 6) Western States Fire Missions (WSFM) 2007; 7) WSFM 1-4 2007; 8) California Wildfire Emergency Response 2007; 9) WSFM 5-8 Emergency Response 2007; 10) WSFM Achievements; and 11) WSFM Challenges
Access to Mars from Earth-Moon Libration Point Orbits:
This investigation is focused specifically on transfers from Earth-Moon L(sub 1)/L(sub 2) libration point orbits to Mars. Initially, the analysis is based in the circular restricted three-body problem to utilize the framework of the invariant manifolds. Various departure scenarios are compared, including arcs that leverage manifolds associated with the Sun-Earth L(sub 2) orbits as well as non-manifold trajectories. For the manifold options, ballistic transfers from Earth-Moon L(sub 2) libration point orbits to Sun-Earth L(sub 1)/L(sub 2) halo orbits are first computed. This autonomous procedure applies to both departure and arrival between the Earth-Moon and Sun-Earth systems. Departure times in the lunar cycle, amplitudes and types of libration point orbits, manifold selection, and the orientation/location of the surface of section all contribute to produce a variety of options. As the destination planet, the ephemeris position for Mars is employed throughout the analysis. The complete transfer is transitioned to the ephemeris model after the initial design phase. Results for multiple departure/arrival scenarios are compared
Incorporation of trajectory behaviors in the vicinities of different planetary moons using Finite-Time Lyapunov Exponent Maps
There is an increasing interest in future space missions devoted to the exploration of key moons in the Solar system. These many different missions may involve libration point orbits as well as trajectories that satisfy different endgames in the vicinities of the moons. To this end, an efficient design strategy to produce low-energy transfers between the vicinities of adjacent moons of a planetary system is introduced that leverages the dynamics in these multi-body systems. Such a design strategy is denoted as the moon-to-moon analytical transfer (MMAT) method. It consists of a general methodology for transfer design between the vicinities of the moons in any given system within the context of the circular restricted three-body problem, useful regardless of the orbital planes in which the moons reside. A simplified model enables analytical constraints to efficiently determine the feasibility of a transfer between two different moons moving in the vicinity of a common planet. Additionally, Finite-Time Lyapunov Exponent (FTLE) maps within the context of the MMAT scheme are incorporated to enable direct transfers between moons that offer a wide variety of trajectory patterns and endgames, such as temporary captures, transits, takeoffs and landings. The resulting technique is demonstrated to be applicable to several mission scenarios
Heliocentric Escape and Lunar Impact from Near Rectilinear Halo Orbits
Spacecraft departing from the Gateway in a Near Rectilinear Halo Orbit (NRHO) experience gravitational forces from the Moon, the Earth, and the Sun, all of which can be simultaneously significant. These complex dynamics influence the post-separation risk of recontact with the Gateway and the eventual destinations of the departing spacecraft. The current investigation examines the flow of objects leaving NRHOs in the Bicircular Restricted Four-Body Problem, and results are applied to heliocentric escape and lunar impact trajectories in a higher-fidelity ephemeris model. Separation maneuver magnitude, direction, and location are correlated with risk of recontact with the Gateway and successful departure to various destinations
Trajectory Design Leveraging Low-Thrust, Multi-Body Equilibria and Their Manifolds
A key challenge in low-thrust trajectory design is generating preliminary solutions that simultaneously specify the spacecraft position and velocity vectors, as well as the thrust history. To mitigate this difficulty, dynamical structures within a combined low-thrust circular restricted 3-body problem (CR3BP) are investigated as candidate solutions to seed initial low-thrust trajectory designs. The addition of low-thrust to the CR3BP modifies the locations and stability of the equilibria, offering novel geometries for mission applications. Transfers between these novel equilibria are constructed by leveraging the associated stable and unstable manifolds and insights from the low-thrust CR3BP
Ikhana MIZOPEX and Alaska Fire Missions
Discussion of the proposed operations of the Ikhana UAS over Alaska and the Beaufort Sea for melting ice studies and fire observation technology development
Transfers between moons with escape and capture patterns via Lyapunov exponent maps
This contribution focuses on the design of low-energy transfers between
planetary moons and presents an efficient technique to compute trajectories
characterized by desirable behaviors in the vicinities of the departure and
destination bodies. The method utilizes finite-time Lyapunov exponent maps in
combination with the Moon-to-Moon Analytical Transfer (MMAT) method previously
proposed by the authors. The integration of these two components facilitates
the design of direct transfers between moons within the context of the circular
restricted three-body problem, and allows the inclusion of a variety of
trajectory patterns, such as captures, landings, transits and takeoffs, at the
two ends of a transfer. The foundations and properties of the technique are
illustrated through an application based on impulsive direct transfers between
Ganymede and Europa. However, the methodology can be employed to assist in the
design of more complex mission scenarios, such as moon tours
Disposal Trajectories from Near Rectilinear Halo Orbits
After completion of a resupply mission to NASA's proposed Lunar Orbital Platform - Gateway, safe disposal of the Logistics Module is required. One potential option is disposal to heliocentric space. This investigation includes an exploration of the trajectory escape dynamics from an Earth-Moon Near Rectilinear Halo Orbit (NRHO) and applies these insights to the design of a low-cost heliocentric Logistics Module disposal option. The effects of the solar gravitational perturbations are assessed in both the bicircular restricted 4-body problem and in an ephemeris force model
An Earth-Moon System Trajectory Design Reference Catalog
As demonstrated by ongoing concept designs and the recent ARTEMIS mission, there is, currently, significant interest in exploiting three-body dynamics in the design of trajectories for both robotic and human missions within the Earth-Moon system. The concept of an interactive and 'dynamic' catalog of potential solutions in the Earth-Moon system is explored within this paper and analyzed as a framework to guide trajectory design. Characterizing and compiling periodic and quasi-periodic solutions that exist in the circular restricted three-body problem may offer faster and more efficient strategies for orbit design, while also delivering innovative mission design parameters for further examination
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