Engineering topics

Kennedy, Brian

Publications and source records attributed to Kennedy, Brian.

43 records · Page 3

NASA NTRS2010

Transport and Use of a Centaur Second Stage in Space

As nations continue to explore space, the desire to reduce costs will continue to grow. As a method of cost reduction, transporting and/or use of launch system components as integral components of missions may become more commonplace in the future. There have been numerous scenarios written for using launch vehicle components (primarily space shuttle used external tanks) as part of flight missions or future habitats. Future studies for possible uses of launch vehicle upper stages might include asteroid diverter using gravity orbital perturbation, orbiting station component, raw material at an outpost, and kinetic impactor. The LCROSS (Lunar CRater Observation and Sensing Satellite) mission was conceived as a low-cost means of determining whether water exists at the polar regions of the moon. Manifested as a secondary payload with the LRO (Lunar Reconnaissance Orbiter) spacecraft aboard an Atlas V launch vehicle, LCROSS guided its spent Centaur Earth Departure Upper Stage (EDUS) into the lunar crater Cabeu's, as a kinetic impactor. This paper describes some of the challenges that the LCROSS project encountered in planning, designing, launching with and carrying the Centaur upper stage to the moon.

Strong, James M.↗

NASA NTRS2007

Trajectory Design and Orbit Determination for the Lunar CRater Observation and Sensing Satellite (LCROSS)

The Lunar CRater Observation and Sensing Satellite (LCROSS) was competitively selected by the National Aeronautical and Space Administration (NASA) Exploration Systems Mission Directorate (ESMD) as a low-cost (< $80M) 1000 kg secondary payload to be launched with the Lunar Reconnaissance Orbiter (LRO) in October of 2008. LCROSS is a lunar impactor mission that will investigate the presence or absence of water in a permanently shadowed crater. Following launch, trans-lunar injection (TLI) and separation from LRO, LCROSS will remain attached to the launch vehicle's approximately 2300 kg spent Earth Departure Upper Stage (EDUS) and will guide it toward an impact of a permanently shadowed crater at the lunar South Pole. Hours prior to impact, LCROSS will separate from the EDUS and perform a braking maneuver that will allow the spacecraft to take measurements of the resulting EDUS impact ejecta cloud for several minutes, before impacting the crater as well. As a cost-capped secondary mission that must accommodate specific LRO launch dates, LCROSS faces unique challenges and constraints that must be carefully reconciled in order to satisfy an ambitious set of science observation requirements. This paper examines driving mission requirements and constraints and describes the trajectory design and navigation strategy that shape the LCROSS mission.

Galal, Ken↗

NASA NTRS2007

Architecting the Communication and Navigation Networks for NASA's Space Exploration Systems

NASA is planning a series of short and long duration human and robotic missions to explore the Moon and then Mars. A key objective of the missions is to grow, through a series of launches, a system of systems communication, navigation, and timing infrastructure at minimum cost while providing a network-centric infrastructure that maximizes the exploration capabilities and science return. There is a strong need to use architecting processes in the mission pre-formulation stage to describe the systems, interfaces, and interoperability needed to implement multiple space communication systems that are deployed over time, yet support interoperability with each deployment phase and with 20 years of legacy systems. In this paper we present a process for defining the architecture of the communications, navigation, and networks needed to support future space explorers with the best adaptable and evolable network-centric space exploration infrastructure. The process steps presented are: 1) Architecture decomposition, 2) Defining mission systems and their interfaces, 3) Developing the communication, navigation, networking architecture, and 4) Integrating systems, operational and technical views and viewpoints. We demonstrate the process through the architecture development of the communication network for upcoming NASA space exploration missions.

Bhassin, Kul B.↗

NASA NTRS2006

Tool for Statistical Analysis and Display of Landing Sites

MarsLS is a software tool for analyzing statistical dispersion of spacecraft-landing sites and displaying the results of its analyses. Originally intended for the Mars Explorer Rover (MER) mission, MarsLS is also applicable to landing sites on Earth and non-MER sites on Mars. MarsLS is a collection of interdependent MATLAB scripts that utilize the MATLAB graphical-user-interface software environment to display landing-site data (see figure) on calibrated image-maps of the Martian or other terrain. The landing-site data comprise latitude/longitude pairs generated by Monte Carlo runs of other computer programs that simulate entry, descent, and landing. Using these data, MarsLS can compute a landing-site ellipse a standard means of depicting the area within which the spacecraft can be expected to land with a given probability. MarsLS incorporates several features for the user s convenience, including capabilities for drawing lines and ellipses, overlaying kilometer or latitude/longitude grids, drawing and/or specifying lines and/or points, entering notes, defining and/or displaying polygons to indicate hazards or areas of interest, and evaluating hazardous and/or scientifically interesting areas. As part of such an evaluation, MarsLS can compute the probability of landing in a specified polygonal area.

Wawrzyniak, Geoffrey↗

NASA NTRS2006

AutoNav Mark3: Engineering the Next Generation of Autonomous Onboard Navigation and Guidance

The success of JPL's AutoNav system at comet Tempel-1 on July 4, 2005, demonstrated the power of autonomous navigation technology for the Deep Impact Mission. This software is being planned for use as the onboard navigation, tracking and rendezvous system for a Mars Sample Return Mission technology demonstration, and several mission proposals are evaluating its use for rendezvous with, and landing on asteroids. Before this however, extensive re-engineering of AutoNav will take place. This paper describes the AutoNav systems-engineering effort in several areas: extending the capabilities, improving operability, utilizing new hardware elements, and demonstrating the new possibilities of AutoNav in simulations.

navigation↗

NASA NTRS2006

On-Orbit Maneuver Calibrations for the Stardust Spacecraft

The Stardust spacecraft, launched February 7, 1999, successfully delivered its sample return capsule to the Utah Test and Training Range on January 15, 2006. The entry maneuver strategy included a trajectory correction at entry minus 10 days (TCM18) targeted to entry with the inclusion of a final biased fixed direction maneuver at entry minus 29 hours (TCM19). To meet the stringent entry targeting requirements necessary for human safety and capsule integrity, a campaign of maneuver calibrations were undertaken in summers of 2003 and 2005 to improve performance for both maneuvers. The results of the calibration program are reported here. The in-flight calibrations included a series of several turns to various final attitudes via deadband walks about each of the three spacecraft axes, as well as 12 in-place burns with magnitudes between 0.5 and 1.0 m/s, the range initially expected for TCM19. The turn and burn calibrations as well as the performance of TCM 17, 18 and 19 are discussed.

maneuver↗

NASA NTRS2004

Orbit determination of Stardust from the Annefrank asteroid fly-by through the Wild 2 Comet encounter

Stardust is a 3-axis stabilized spacecraft that maintains its attitude by firing a pair of its one sided- thrusters. this thruster arrangement causes Stardust to produce unbalanced torques at each thruster firing, which yields an undesired perturbing force and makes navigation a challenge. In addition to this perturbing force, Stardust Navigation contended with the problems caused by the contamination of the Navigation Camera and the experience of flying through 2 solar conjunctions during Stardust's inbound leg to the Wild 2 encounter. Both the contamination and the solar conjunctions were major challenges Navigation had to overcome.

Williams, Kenneth↗