Solar Electric Propulsion for Primitive Body Science Missions

This paper describes work that assesses the performance of solar electric propulsion (SEP) for three different primitive body science missions: 1) Comet Rendezvous 2) Comet Surface Sample Return (CSSR), and 3) a Trojan asteroid/Centaur object Reconnaissance Flyby. Each of these missions launches from Earth between 2010 and 2016. Beginning-of-life (BOL) solar array power (referenced at 1 A.U.) varies from 10 to 18 kW. Launch vehicle selections range from a Delta II to a Delta IV medium-class. The primary figure of merit (FOM) is net delivered mass (NDM). This analysis considers the effects of imposing various mission constraints on the Comet Rendezvous and CSSR missions. Specifically, the Comet Rendezvous mission analysis examines an arrival date constraint with a launch year variation, whereas the CSSR mission analysis investigates an Earth entry velocity constraint commensurate with past and current missions. Additionally, the CSSR mission analysis establishes NASA's New Frontiers (NF) Design Reference Mission (DRM) in order to evaluate current and future SEP technologies. The results show that transfer times range from 5 to 9 years (depending on the mission). More importantly, the spacecraft's primary propulsion system performs an average 5-degree plane change on the return leg of the CSSR mission to meet the previously mentioned Earth entry velocity constraint. Consequently, these analyses show that SEP technologies that have higher thrust-to-power ratios can: 1) reduce flight time, and 2) change planes more efficiently

Paradigm Changes Related to TSAS Viewed Through the Perspective of the FAA/NASA Operational Integration Assessment

In May 2015, NASA and the FAA conducted the Operational Integration Assessment (OIA) at the FAAs William J. Hughes Technical Center (referred to here as the Tech Center). The OIA was an operational assessment of a NASA-developed prototype technology, Terminal Sequencing and Spacing (TSAS, formerly known as TSS), planned for operational deployment in April 2019. The main objective was to identify risks that need to be addressed prior to transitioning TSAS from the laboratory to the National Airspace System (NAS). Key to the OIA was integrating TSAS with recently deployed Next Generation Air Transportation System (NextGen) technologies that the FAA expects TSAS to interoperate with when it becomes operational, such as the En Route Automation Modernization (ERAM) platform and newer Time Based Flow Management (TBFM) capabilities such as Extended Metering and Ground-based Interval Management for Spacing (GIM-S). The National Air Traffic Controllers Association (NATCA) controllers and traffic management coordinators (TMCs) from several Air Route Traffic Control Centers (en route) and Terminal Radar Approach Control (terminal) facilities participated in the OIA, and are critical to identifying risks when transitioning TSAS to an operational system. We discuss the OIA, including expected paradigm changes necessary to realize the full benefits of TSAS. Two of the paradigm changes are operational and one relates to testing and evaluation. We start by briefly discussing the impetus for TSAS, followed by its main background components. Next, we discuss the motivation for the OIA, its objective, and key attributes. We then proceed with a section discussing three important and expected paradigm shifts related to TSAS. We end by briefly discussing some representative observations and feedback from the OIA related to the paradigm shifts

Performance of Solar Electric Powered Deep Space Missions Using Hall Thruster Propulsion

Power limited, low-thrust trajectories were assessed for missions to Jupiter, Saturn, and Neptune utilizing a single Venus Gravity Assist (VGA) and a primary propulsion system based on either a 3-kW high voltage Hall thruster, of the type being developed by the NASA In-Space Propulsion Technology Program, or an 8-kW variant of this thruster. These Hall thrusters operate with specific impulses below 3,000 seconds. A trade study was conducted to examine mission parameters that include: net delivered mass (NDM), beginning-of-life (BOL) solar array power, heliocentric transfer time, required launch vehicle, number of operating thrusters, and throttle profile. The top performing spacecraft configuration was defined to be the one that delivered the highest mass for a range of transfer times. In order to evaluate the potential future benefit of using next generation Hall thrusters as the primary propulsion system, comparisons were made with the advanced state-of-the-art (ASOA), 7-kW, 4,100 second NASA's Evolutionary Xenon Thruster (NEXT) for the same mission scenarios. For the BOL array powers considered in this study (less than 30 kW), the results show that the performance of the Hall thrusters, relative to NEXT, is largely dependant on the performance capability of the launch vehicle, and that at least a 10 percent performance gain, equating to at least an additional 200 kg dry mass at each target planet, is achieved over the higher specific impulse NEXT when launched on an Atlas 551

Direct Method Transcription for a Human-Class Translunar Injection Trajectory Optimization

This paper presents a new trajectory optimization software package developed in the framework of a low-to-high fidelity 3 degrees-of-freedom (DOF)/6-DOF vehicle simulation program named Mission Analysis Simulation Tool in Fortran (MASTIF) and its application to a translunar trajectory optimization problem. The functionality of the developed optimization package is implemented as a new "mode" in generalized settings to make it applicable for a general trajectory optimization problem. In doing so, a direct optimization method using collocation is employed for solving the problem. Trajectory optimization problems in MASTIF are transcribed to a constrained nonlinear programming (NLP) problem and solved with SNOPT, a commercially available NLP solver. A detailed description of the optimization software developed is provided as well as the transcription specifics for the translunar injection (TLI) problem. The analysis includes a 3-DOF trajectory TLI optimization and a 3-DOF vehicle TLI simulation using closed-loop guidance

NASA's 2004 In-Space Propulsion Refocus Studies for New Frontiers Class Missions

The New Frontiers (NF) program is designed to provide opportunities to fulfill the science objectives for top priority, medium class missions identified in the Decadal Solar System Exploration Survey. This paper assesses the applicability of the In-Space Propulsion s (ISP) Solar Electric Propulsion (SEP) technologies for representative NF class missions that include a Jupiter Polar Orbiter with Probes (JPOP), Comet Surface Sample Return (CSSR), and two different Titan missions. The SEP technologies evaluated include the 7-kW, 4,100-second NASA's Evolutionary Xenon Thruster (NEXT), the 3-kW, 2,700-second Hall thruster, and two different NASA Solar Electric Propulsion Technology Readiness (NSTAR) thrusters that are variants of the Deep Space 1 (DS1) thruster. One type of NSTAR, a 2.6-kW, 3,100-second thruster, will be the primary propulsion system for the DAWN mission that is scheduled to launch in 2006; the other is an "enhanced", higher power variant (3.8-kW, 4,100-second) and is so-called because it uses NEXT system components such as the NEXT power processing unit (PPU). The results show that SEP is applicable for the CSSR mission and a Titan Lander mission. In addition, NEXT has improved its applicability for these types of missions by modifying its thruster performance relative to its performance at the beginning of this study

Status of Transferring NASA's Terminal Sequencing and Spacing Technologies to the FAA

This paper provides a brief overview of the Air Traffic Management Technology Demonstration 1 (ATD-1) technologies. These technologies are comprised of ground-based automation tools and airborne automation tools. The ground-based automation tools are referred to as terminal sequencing and spacing (TSS). NASA is currently maturing TSS prior to transfeering it to the FAA. This paper discusses the status of the transfer

ATD-1 Operational Integration Assessment Final Report

The FAA and NASA conducted an Operational Integration Assessment (OIA) of a prototype Terminal Sequencing and Spacing (formerly TSS, now TSAS) system at the FAA's William J. Hughes Technical Center (WJHTC). The OIA took approximately one year to plan and execute, culminating in a formal data collection, referred to as the Run for Record, from May 12-21, 2015. This report presents quantitative and qualitative results from the Run for Record

Evaluation of the Controller-Managed Spacing Tools, Flight-Deck Interval Management and Terminal Area Metering Capabilities for the ATM Technology Demonstration #1

NASA has developed a suite of advanced arrival management technologies combining time-based scheduling with controller- and flight deck-based precision spacing capabilities that allow fuel-efficient arrival operations during periods of high throughput. An operational demonstration of these integrated technologies, i.e., the ATM Technology Demonstration #1 (ATD-1), is slated for 2016. Human-in-the-loop simulations were conducted to evaluate the performance of the ATD-1 system and validate operational feasibility. The ATD-1 system was found to be robust to scenarios with saturated demand levels and high levels of system delay. High throughput, 10 above baseline demand levels, and schedule conformance less than 20 seconds at the 75th percentile were achievable. The flight-deck interval management capabilities also improved the median schedule conformance at the final approach fix from 5 to 3 seconds with less variance

Application of direct method transcription for a human-class translunar injection trajectory optimization

This thesis presents a new trajectory optimization software package developed in the framework of a low-to-high fidelity three degree-of-freedom (3-DOF)/6-DOF vehicle simulation program named Mission Analysis Simulation Tool in Fortran (MASTIF) and its application to a translunar trajectory optimization problem. The functionality of the developed optimization package is implemented as a new ``mode" in generalized settings to make it applicable for a general trajectory optimization problem. In doing so, a direct optimization method using collocation is employed for solving the problem. Trajectory optimization problems in MASTIF are transcribed to a constrained nonlinear programming (NLP) problem and solved with SNOPT, a commercially available NLP solver. A detailed description of the optimization software developed is provided as well as the transcription specifics for the translunar injection (TLI) problem. This assessment of the final results is formulated via a metric given as the minimization of the TLI main engine burn time, which is equivalent to the maximization of the mass at main engine cutoff (MECO). Key design parameters include the initial values for three orbital angles (right ascension of ascending node, argument of perigee, and true anomaly) and three Euler angles for steering during the main engine burn. To do so, the solution starts by modeling the entire trajectory into three distinct phases. The first two phases are based on a collocation method whereas the third phase appears with a high order Runge-Kutta integration. The next part of assessing the TLI trajectory utilizes MASTIF's vehicle simulation capabilities (the other "mode" within MASTIF). This includes the ability to design and test new and existing guidance, navigation, and control (GN\&C) algorithms. As a demonstration of MASTIF's versatility, results from the trajectory optimization (the open-loop solution) in the form of a set of initial states and specific orbital target parameters at MECO are used in a new preliminary assessment of a variant of the Space Shuttle's flight-proven closed-loop guidance algorithm named Powered Explicit Guidance (PEG). Main engine burn times and the LVLH Euler angles from the open-loop and closed-loop solutions are compared to show approximate agreement and efficacy of MASTIF's two distinct "modes''. (Published By University of Alabama Libraries