Daniel D. Mazanek

Simulation and Shuttle Hitchhiker validation of passive satellite aerostabilization

The Passive Aerodynamically Stabilized Magnetically Damped Satellite experiment will characterize and demonstrate passive aerodynamic stabilization and passive magnetic hysteresis damping of attitude rates. It is currently scheduled to be deployed on a Shuttle Hitchhiker flight. Although theoretically feasible, aerodynamically induced passive attitude stability represents a technology that has never been substantiated through actual flight experience. The two-week experiment will serve to validate overall performance predictions by the high-fidelity free-molecularflow simulation code developed at the Langley Research Center of NASA. The code can simulate with high fidelity the flight characteristics of a satellite in low Earth orbit. Aerostabilization, if proved, is highly desirable for future missions such as the Gravity and Magnetic Earth Surveyor. This paper describes the simulator, simulation results, and the Hitchhiker experiment in the context of the Gravity and Magnetic Earth Surveyor subsatellite aerostabilization requirements.

Asteroid Redirect Robotic Mission: Robotic Boulder Capture Option Overview

The National Aeronautics and Space Administration (NASA) is currently studying an option for the Asteroid Redirect Robotic Mission (ARRM) that would capture a multi-ton boulder (typically 2-4 meters in size) from the surface of a large (is approximately 100+ meter) Near-Earth Asteroid (NEA) and return it to cislunar space for subsequent human and robotic exploration. This alternative mission approach, designated the Robotic Boulder Capture Option (Option B), has been investigated to determine the mission feasibility and identify potential differences from the initial ARRM concept of capturing an entire small NEA (4-10 meters in size), which has been designated the Small Asteroid Capture Option (Option A). Compared to the initial ARRM concept, Option B allows for centimeter-level characterization over an entire large NEA, the certainty of target NEA composition type, the ability to select the boulder that is captured, numerous opportunities for mission enhancements to support science objectives, additional experience operating at a low-gravity planetary body including extended surface contact, and the ability to demonstrate future planetary defense strategies on a hazardous-size NEA. Option B can leverage precursor missions and existing Agency capabilities to help ensure mission success by targeting wellcharacterized asteroids and can accommodate uncertain programmatic schedules by tailoring the return mass.

Mission Functionality for Deflecting Earth-Crossing Asteroids/Comets

Using astrometric interferometry on near-Earth objects (NEOs) poses many interesting and difficult challenges. Poor reflectance properties and potentially no significant active emissions lead to NEOs having intrinsically low visual magnitudes. Using worst case estimates for signal reflection properties leads to NEOs having visual magnitudes of 27 and higher. Today the most sensitive interferometers in operation have limiting magnitudes of 20 or less. The main reason for this limit is due to the atmosphere, where turbulence affects the light coming from the target, limiting the sensitivity of the interferometer. In this analysis, the interferometer designs assume no atmosphere, meaning they would be placed at a location somewhere in space. Interferometer configurations and operational uncertainties are looked at in order to parameterize the requirements necessary to achieve measurements of low visual magnitude NEOs. This analysis provides a preliminary estimate of what will be required in order to take high resolution measurements of these objects using interferometry techniques.

Parametric and classical resonance in passive satellite aerostabilization

Purely passive aerostabilization of satellites has never been flight demonstrated. The Shuttle hitchhiker passive aerodynamically stabilized magnetically damped satellite experiment would be the first flight experiment of its kind that, in conjunction with results from a high-fidelity computer simulator, would corroborate attitude stability. Pure aerostabilization, with no gravity gradient restoring torques, if proved, is highly desirable for future missions such as the gravity and magnetic Earth surveyor. High-fidelity nonlinear simulation results indicate interesting attitude behavior, such as cone angle transients that provoke the need for sound theoretical justification. A wind vane in a wind field model is used to derive simple analogous Mathieu-Hill equations of motion, the stability properties of which are predicted via Floquet theory. Parametric resonance caused by higher order of the once per orbit density harmonics, varying natural frequency of oscillation as a result of altitude decay, and varying wind magnitude due to global winds are studied in detail. The simple time-varying linear wind vane analogy captures the essence of the observations made with the complex nonlinear simulation. Classical resonance because of step changes in the solar torques as a result of Earth occultation is also discussed. Based on insight obtained from the stability properties observed for the wind vane analogy, an optimal satellite is designed that provides best attitude performance while maintaining sufficient lifetime and other mission constraints. Nomenclature : area of analogous wind vane, m2 = average ballistic coefficient of subsat, kg/m2 = moment of inertia about an axis of rotation, kg-m2 : aerodynamic moment stiffness, N-m/rad = length of back shell, cm : length of front shell, cm : mass of subsat, kg = center-of-pres sure to center-of-mas s offset, m = inner radius of front shell, cm : aerodynamic torque, N-m : thickness of back shell, cm : thickness of front shell, cm = velocity magnitude of wind, m/s = cone angle of the satellite, rad : damping ratio = coefficient of damping, N-m-s/rad = angle of rotation of wind vane from reference wind direction, rad = density of air, kg/m3 = amplitude of once/orbit harmonic of Q, kg/m3 = density of back shell, kg/m3 = bias component of density of air profile over one orbit, kg/m3 = density of front shell, kg/m3 = accommodation coefficients = natural frequency of oscillation of wind vane, rad/s = once per orbit frequency, rad/s

Surface buildup scenarios and outpost architectures for Lunar Exploration

The Constellation Program Architecture Team and the Lunar Surface Systems Project Office have developed an initial set of lunar surface buildup scenarios and associated polar outpost architectures, along with preliminary supporting element and system designs in support of NASAs Exploration Strategy. The surface scenarios are structured in such a way that outpost assembly can be suspended at any time to accommodate delivery contingencies or changes in mission emphasis. The modular nature of the architectures mitigates the impact of the loss of any one element and enhances the ability of international and commercial partners to contribute elements and systems. Additionally, the core lunar surface system technologies and outpost operations concepts are applicable to future Mars exploration. These buildup scenarios provide a point of departure for future trades and assessments of alternative architectures and surface elements.

A Flexible Path for Human and Robotic Space Exploration

During the summer of 2009, a flexible path scenario for human and robotic space exploration was developed that enables frequent, measured, and publicly notable human exploration of space beyond low-Earth orbit (LEO). The formulation of this scenario was in support of the Exploration Beyond LEO subcommittee of the Review of U.S. Human Space Flight Plans Committee that was commissioned by President Obama. Exploration mission sequences that allow humans to visit a wide number of inner solar system destinations were investigated. The scope of destinations included the Earth-Moon and Earth-Sun Lagrange points, near-Earth objects (NEOs), the Moon, and Mars and its moons. The missions examined assumed the use of Constellation Program elements along with existing launch vehicles and proposed augmentations. Additionally, robotic missions were envisioned as complements to human exploration through precursor missions, as crew emplaced scientific investigations, and as sample gathering assistants to the human crews. The focus of the flexible path approach was to gain ever-increasing operational experience through human exploration missions ranging from a few weeks to several years in duration, beginning in deep space beyond LEO and evolving to landings on the Moon and eventually Mars.

Lunar Lander Structural Design Studies at NASA Langley

The National Aeronautics and Space Administration is currently developing mission architectures, vehicle concepts and flight hardware to support the planned human return to the Moon. During Phase II of the 2006 Lunar Lander Preparatory Study, a team from the Langley Research Center was tasked with developing and refining two proposed Lander concepts. The Descent-Assisted, Split Habitat Lander concept uses a disposable braking stage to perform the lunar orbit insertion maneuver and most of the descent from lunar orbit to the surface. The second concept, the Cargo Star Horizontal Lander, carries ascent loads along its longitudinal axis, and is then rotated in flight so that its main engines (mounted perpendicular to the vehicle longitudinal axis) are correctly oriented for lunar orbit insertion and a horizontal landing. Both Landers have separate crew transport volumes and habitats for surface operations, and allow placement of large cargo elements very close to the lunar surface. As part of this study, lightweight, efficient structural configurations for these spacecraft were proposed and evaluated. Vehicle structural configurations were first developed, and preliminary structural sizing was then performed using finite element-based methods. Results of selected structural design and trade studies performed during this activity are presented and discussed.

Comet/Asteroid Protection System (CAPS): A Space-Based System Concept for Revolutionizing Earth Protection and Utilization of Near-Earth Objects

Abstract There exists an infrequent, but significant hazard to life and property due to impacting asteroids and comets. There is currently no specific search for long-period comets, smaller near-Earth asteroids, or smaller short-period comets. These objects represent a threat with potentially little or no warning time using conventional ground-based telescopes. These planetary bodies also represent a significant resource for commercial exploitation, long-term sustained space exploration, and scientific research. The Comet/Asteroid Protection System (CAPS) would expand the current detection effort to include long-period comets, as well as small asteroids and short-period comets capable of regional destruction. A space-based detection system, despite being more costly and complex than Earth-based initiatives, is the most promising way of expanding the range of detectable objects, and surveying the entire celestial sky on a regular basis. CAPS is a future space-based system concept that provides permanent, continuous asteroid and comet monitoring, and rapid, controlled modification of the orbital trajectories of selected bodies. CAPS would provide an orbit modification system capable of diverting kilometer class objects, and modifying the orbits of smaller asteroids for impact defense and resource utilization. This paper provides a summary of CAPS and discusses several key areas and technologies that are being investigated.

Descent Assisted Split Habitat Lunar Lander Concept

The descent assisted split habitat (DASH) lunar lander concept utilizes a disposable braking stage for descent and a minimally sized pressurized volume for crew transport to and from the lunar surface. The lander can also be configured to perform autonomous cargo missions. Although a braking-stage approach represents a significantly different operational concept compared with a traditional two-stage lander, the DASH lander offers many important benefits. These benefits include improved crew egress/ingress and large-cargo unloading; excellent surface visibility during landing; elimination of the need for deep-throttling descent engines; potentially reduced plume-surface interactions and lower vertical touchdown velocity; and reduced lander gross mass through efficient mass staging and volume segmentation. This paper documents the conceptual study on various aspects of the design, including development of sortie and outpost lander configurations and a mission concept of operations; the initial descent trajectory design; the initial spacecraft sizing estimates and subsystem design; and the identification of technology needs.