Papers by Cornelius Dennehy
AAS Annual Guidance and Control Conference, Feb 1, 2019
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AIAA Guidance, Navigation and Control Conference and Exhibit, 2007
This paper will briefly define the vision, mission, and purpose of the NESC organization. The rol... more This paper will briefly define the vision, mission, and purpose of the NESC organization. The role of the GN&C TDT will then be described in detail along with an overview of how this team operates and engages in its objective engineering and safety assessments of critical NASA projects. This paper will then describe key issues and findings from several of the recent GN&C-related independent assessments and consultations performed and/or supported by the NESC GN&C TDT. Among the examples of the GN&C TDT s work that will be addressed in this paper are the following: the Space Shuttle Orbiter Repair Maneuver (ORM) assessment, the ISS CMG failure root cause assessment, the Demonstration of Autonomous Rendezvous Technologies (DART) spacecraft mishap consultation, the Phoenix Mars lander thruster-based controllability consultation, the NASA in-house Crew Exploration Vehicle (CEV) Smart Buyer assessment and the assessment of key engineering considerations for the Design, Development, Test & Evaluation (DDT&E) of robust and reliable GN&C systems for human-rated spacecraft.
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Historically, engineers at the National Aeronautics and Space Administration (NASA) had few oppor... more Historically, engineers at the National Aeronautics and Space Administration (NASA) had few opportunities or incentives to share their technical expertise across the Agency. Its centerand projectfocused culture often meant that knowledge never left organizational and geographic boundaries. With increasingly complex missions, the closeout of the Shuttle Program, and a new generation entering the workforce, developing a knowledge sharing culture became critical. To address this need, the Office of the Chief Engineer established communities of practice on the NASA Engineering Network. These communities were strategically aligned with NASA’s core competencies in such disciplines as avionics, flight mechanics, life support, propulsion, structures, loads and dynamics, human factors, and guidance, navigation, and control. This paper describes the process used to identify and develop communities, from establishing simple websites that compiled discipline-specific resources to fostering a kn...
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The NASA Engineering and Safety Center (NESC) was established in 2003 (after the Columbia acciden... more The NASA Engineering and Safety Center (NESC) was established in 2003 (after the Columbia accident) to provide an independent technical resource for the resolution of challenging technical problems (through the use of studies, analysis, tests, etc.) for NASA programs and projects. Since its inception, NESC has completed nearly 1000 technical assessments for NASA’s Human Exploration and Operation Mission Directorate (HEOMD), Science Mission Directorate (SMD), Space Technology Mission Directorate (STMD), and Aeronautics Research Mission Directorate (ARMD). Of the SMD related assessments, several were for the resolution of technical problems, analysis, or studies related to NASA’s astrophysics missions in various phases of the project from design to operation. Some of the recent examples of NESC technical support for NASA astrophysics missions have been for: Hubble Space Telescope (HST), Chandra X-ray Observatory (CXO), Fermi Gamma-ray Space Telescope, Kepler Space Telescope, Transitin...
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This paper describes a new operational capability for fast attitude maneuvering that is being dev... more This paper describes a new operational capability for fast attitude maneuvering that is being developed for the Lunar Reconnaissance Orbiter (LRO). The LRO hosts seven scientific instruments. For some instruments, it is necessary to perform large off-nadir slews to collect scientific data. The accessibility of off-nadir science targets has been limited by slew rates and/or occultation, thermal and power constraints along the standard slew path. The new fast maneuver (FastMan) algorithm employs a slew path that autonomously avoids constraint violations while simultaneously minimizing the slew time. The FastMan algorithm will open regions of observation that were not previously feasible and improve the overall science return for LRO’s extended mission. The design of an example fast maneuver for LRO’s Lunar Orbiter Laser Altimeter that reduces the slew time by nearly 40% is presented. Pre-flight, ground-test, end-to-end tests are also presented to demonstrate the readiness of FastMan. ...
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Developed by the core community to describe our vision of an approach to ensure a sufficiently te... more Developed by the core community to describe our vision of an approach to ensure a sufficiently technically advanced and affordable AR&D technology base is available to support future NASA missions. The goal of this strategy is to create an environment exploiting reusable technology elements for an AR&D system design and development process which is: a) Lower-Risk. b) More Versatile/Scalable. c) Reliable & Crew-Safe. d) More Affordable.
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The intent of this Technical Consultation Report is to document the finding and recommendations o... more The intent of this Technical Consultation Report is to document the finding and recommendations of the NESC Orbiter Repair Maneuver (ORM) Peer Review conducted at NASA s Johnson Space Center (JSC) with the ORM Working Group (WG) over the period 8-10 June 2005.
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There is a heightened interest within NASA for the design, development, and flight implementation... more There is a heightened interest within NASA for the design, development, and flight implementation of mixed-actuator hybrid attitude control systems for science spacecraft that have less than three functional reaction wheel actuators. This interest is driven by a number of recent reaction wheel failures on aging, but what could be still scientifically productive, NASA spacecraft if a successful hybrid attitude control mode can be implemented. Over the years, hybrid (mixed-actuator) control has been employed for contingency attitude control purposes on several NASA science mission spacecraft. This paper provides a historical perspective of NASA's previous engineering work on spacecraft mixed-actuator hybrid control approaches. An update of the current situation will also be provided emphasizing why NASA is now so interested in hybrid control. The results of the NASA Spacecraft Hybrid Attitude Control Workshop, held in April of 2013, will be highlighted. In particular, the lessons ...
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Summary of the STORRM VNS Performance from Reference 9 To obtain information useful for assessing... more Summary of the STORRM VNS Performance from Reference 9 To obtain information useful for assessing the STORRM VNS’s performance as a navigation sensor, a number of post-processing steps were performed on the raw data stored on the STORRM data recording units (DRUs). First, a range calibration algorithm supplied by Ball Aerospace Technologies Corporation was applied to the raw VNS images, which resulted in the “range corrected” images. Then, centroiding and reflector identification algorithms were used to identify candidate reflectors within the VNS imagery. For the bulk of the rendezvous, this algorithm combined six consecutive VNS images (collected at 30 Hz) to produce centroid measurements to candidate reflectors at a rate of 5 Hz. These candidate reflectors were compared to what the VNS was expected to see based on the BET. Using this comparison information, each candidate reflector could then be matched to a known reflector or be identified as a spurious reflection. Finally, afte...
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The November 15, 1967, loss of X-15 Flight 3-65-97 (hereafter referred to as Flight 3-65) was a u... more The November 15, 1967, loss of X-15 Flight 3-65-97 (hereafter referred to as Flight 3-65) was a unique incident in that it was the first and only aerospace flight accident involving loss of crew on a vehicle with an adaptive flight control system (AFCS). In addition, Flight 3-65 remains the only incidence of a single-pilot departure from controlled flight of a manned entry vehicle in a hypersonic flight regime. To mitigate risk to emerging aerospace systems, the NASA Engineering and Safety Center (NESC) proposed a comprehensive review of this accident. The goal of the assessment was to resolve lingering questions regarding the failure modes of the aircraft systems (including the AFCS) and thoroughly analyze the interactions among the human agents and autonomous systems that contributed to the loss of the pilot and aircraft. This document contains the outcome of the accident review.
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At the request of the Science Mission Directorate Chief Engineer, the NASA Technical Fellow for G... more At the request of the Science Mission Directorate Chief Engineer, the NASA Technical Fellow for Guidance, Navigation & Control assembled and facilitated a workshop on Spacecraft Hybrid Attitude Control. This multi-Center, academic, and industry workshop, sponsored by the NASA Engineering and Safety Center (NESC), was held in April 2013 to unite nationwide experts to present and discuss the various innovative solutions, techniques, and lessons learned regarding the development and implementation of the various hybrid attitude control system solutions investigated or implemented. This report attempts to document these key lessons learned with the 16 findings and 9 NESC recommendations.
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The NASA Engineering and Safety Center (NESC) is an independently funded NASA Program whose dedic... more The NASA Engineering and Safety Center (NESC) is an independently funded NASA Program whose dedicated team of technical experts provides objective engineering and safety assessments of critical, high risk projects. NESC's strength is rooted in the diverse perspectives and broad knowledge base that add value to its products, affording customers a responsive, alternate path for assessing and preventing technical problems while protecting vital human and national resources. The Guidance Navigation and Control (GN&C) Technical Discipline Team (TDT) is one of fifteen such discipline-focused teams within the NESC organization. The TDT membership is composed of GN&C specialists from across NASA and its partner organizations in other government agencies, industry, national laboratories, and universities. This paper will briefly define the vision, mission, and purpose of the NESC organization. The role of the GN&C TDT will then be described in detail along with an overview of how this te...
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The National Aeronautics and Space Administration (NASA) Engineering and Safety Center was charte... more The National Aeronautics and Space Administration (NASA) Engineering and Safety Center was chartered to develop an alternate launch abort system (LAS) as risk mitigation for the Orion Project. Its successful flight test provided data for the design of future LAS vehicles. Design of the flight test vehicle (FTV) and pad abort trajectory relied heavily on modeling and simulation including computational fluid dynamics for vehicle aero modeling, 6-degree-of-freedom kinematics models for flight trajectory modeling, and 3-degree-of-freedom kinematics models for parachute force modeling. This paper highlights the simulation techniques and the interaction between the aerodynamics, flight mechanics, and aerodynamic decelerator disciplines during development of the Max Launch Abort System FTV.
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The Marshall Space Flight Center (MSFC) Flight Mechanics and Analysis Division developed an adapt... more The Marshall Space Flight Center (MSFC) Flight Mechanics and Analysis Division developed an adaptive augmenting control (AAC) algorithm for launch vehicles that improves robustness and performance on an as-needed basis by adapting a classical control algorithm to unexpected environments or variations in vehicle dynamics. This was baselined as part of the Space Launch System (SLS) flight control system. The NASA Engineering and Safety Center (NESC) was asked to partner with the SLS Program and the Space Technology Mission Directorate (STMD) Game Changing Development Program (GCDP) to flight test the AAC algorithm on a manned aircraft that can achieve a high level of dynamic similarity to a launch vehicle and raise the technology readiness of the algorithm early in the program. This document reports the outcome of the NESC assessment.
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This final report summarizes the results of a comparative assessment of the fault tolerance and r... more This final report summarizes the results of a comparative assessment of the fault tolerance and reliability of different Guidance, Navigation and Control (GN&C) architectural approaches. This study was proactively performed by a combined Massachusetts Institute of Technology (MIT) and Draper Laboratory team as a GN&C "Discipline-Advancing" activity sponsored by the NASA Engineering and Safety Center (NESC). This systematic comparative assessment of GN&C system architectural approaches was undertaken as a fundamental step towards understanding the opportunities for, and limitations of, architecting highly reliable and fault tolerant GN&C systems composed of common avionic components. The primary goal of this study was to obtain architectural 'rules of thumb' that could positively influence future designs in the direction of an optimized (i.e., most reliable and cost-efficient) GN&C system. A secondary goal was to demonstrate the application and the utility of a syst...
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Predicting, managing, controlling, and testing spacecraft Line-of-Sight (LoS) jitter due to on-bo... more Predicting, managing, controlling, and testing spacecraft Line-of-Sight (LoS) jitter due to on-board internal disturbance sources is a challenging multidisciplinary systems engineering problem, especially for those observatories hosting extremely sensitive optical sensor payloads with stringent requirements on allowable LoS jitter. Some specific spacecraft jitter engineering challenges will be introduced and described in this survey paper. Illustrative examples of missions where dynamic interactions have to be addressed to satisfy demanding payload instrument LoS jitter requirements will be provided. Some lessons learned and a set of recommended rules of thumb are also presented to provide guidance for analysts on where to initiate and how to approach a new spacecraft jitter design problem. These experience-based spacecraft jitter lessons learned and rules of thumb are provided in the hope they can be leveraged on new space system development projects to help overcome unfamiliarity ...
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The NESC conducted an abridged independent examination of available information and personnel int... more The NESC conducted an abridged independent examination of available information and personnel interviews to evaluate the current and anticipated state of the spacecraft subsystems and the parameters that describe the HST's health. These examinations included the projected timeliness of a robotic SM and whether the GSFC baseline concept is likely to provide the capability to extend the useful scientific life of the HST by an additional 5 years. The NESC team collected a broad spectrum of pertinent HST Program analyses, reports, briefings, and the results of the IPAO and the Aerospace Corporation AOA assessments as they relate to the degradation of the HST s health. This review included the state of the HST subsystems having the potential to impact the viability of the HST, but will not be serviced under the baseline robotic SM.
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The National Aeronautics and Space Administration (NASA) and European Space Agency (ESA) are plan... more The National Aeronautics and Space Administration (NASA) and European Space Agency (ESA) are planning spaceflight missions that will operate highperformance optical payloads with highly vibrationsensitive scientific instruments for Space Science and Earth Science observations. Accurately predicting spacecraft jitter (i.e., micro-vibrations) due to on-board internal disturbance sources is a formidable multidisciplinary engineering challenge. This is especially true for observatories hosting sensitive optical instrument payloads with stringent requirements on allowable line-of-sight (LoS) jitter. Mechanisms mounted on the observatory’s spacecraft bus are typically the source of jitter-producing disturbances. Historically, reaction wheels (RWs) have been the principal sources of spacecraft on-board disturbances on NASA and ESA missions. It is well-known that RWs can export undesirable torque and force disturbances into the spacecraft’s flexible structure, perturbing an instrument’s LoS...
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The Guidance, Navigation, and Control (GN&C) Technical Discipline Team (TDT) sponsored Dr. J. Rus... more The Guidance, Navigation, and Control (GN&C) Technical Discipline Team (TDT) sponsored Dr. J. Russell Carpenter, a Navigation and Rendezvous Subject Matter Expert (SME) from NASA's Goddard Space Flight Center (GSFC), to provide support to the Defense Advanced Research Project Agency (DARPA) Orbital Express (OE) rendezvous and docking flight test that was conducted in 2007. When that DARPA OE mission was completed, Mr. Neil Dennehy, NASA Technical Fellow for GN&C, requested Dr. Carpenter document his findings (lessons learned) and recommendations for future rendezvous missions resulting from his OE support experience. This report captures lessons specifically from anomalies that occurred during one of OE's unmated operations.
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Papers by Cornelius Dennehy