Kevin R. Duda

Design and analysis of lunar lander manual control modes

All Apollo landings were performed by the crew, manually commanding the lunar module (LM) attitude and rate-of-descent (ROD). In future missions, the astronauts will again need manual control of the flight path and attitude. Crew interaction mechanisms have been proposed to re-designate a landing aimpoint during the approach phase. However, manual control modes, crew control capability, and resulting vehicle performance during terminal descent have not been thoroughly investigated. A rate-control attitude hold (RCAH) mode was ultimately used in the LM for lateral flight and descent rate was controlled incrementally (P66), although other modes were considered and evaluated. These modes, as well as others proposed during Apollo, are reviewed and discussed in terms of their applicability to Altair. The ALHAT guidance, navigation, and control (GNC) algorithms for autonomous precision lunar landing were modified to include two manual flight control modes: RCAH with incremental ROD (A66) and incremental lateral velocity control with incremental ROD (A68) using Altair LDAC1-Delta vehicle parameters. Crew interactions with the ALHAT GNC system are described throughout the mission phases from lunar orbit to touchdown, focusing on manual control of flight path and attitude during terminal descent. These ALHAT manual attitude control modes are described and vehicle performance is discussed in terms of its estimated impact on handling quality ratings.

Pilot Performance, Workload, and Situation Awareness During Lunar Landing Mode Transitions

Aircraft and spacecraft pilots frequently change their level of supervisory control between full autopilot and other modes, providing varying levels of manual control. Therefore, multimodal systems must transition “gracefully,” meaning without unsafe decreases in flight performance or unacceptable changes in workload or situation awareness. Thirteen subjects flew a fixed base simulation of the NASA Constellation Program Altair lunar lander that transitioned from full autopilot to one of three flight-director-guided rate-command attitude hold manual control modes. After training, each subject flew 24 approaches, half of which included a landing point redesignation at the time of the mode transition requiring the pilot to null additional guidance errors. Bedford subjective workload and two-choice embedded secondary task response times were used to quantify temporal changes in mental workload. Situation awareness transients were detected by analysis of a tertiary task, verbal callouts of altitude, fuel, and ...

Analysis of human spatial perception during lunar landing

Crewed lunar landings require astronauts to interact with automated systems to identify a location that is level and free of hazards and to guide the vehicle to the lunar surface through a controlled descent. However, vestibular limitations resulting from exposure to lunar gravity after short-term adaptation to weightlessness, combined with acceleration profiles unique to lunar landing trajectories may result in astronaut spatial disorientation. A quantitative mathematical model of human spatial orientation previously developed was adopted to analyze disorientation concerns during lunar landing conditions that cannot be reproduced experimentally. Vehicle acceleration and rotation rate profiles of lunar landing descent trajectories were compiled and entered as inputs to the orientation model to predict astronaut perceived orientations. Both fully automated trajectories and trajectories with pilot interaction were studied. The latter included both simulated landing point redesignation and direct manual control. The lunar descent trajectories contain acceleration and rotation rate profiles producing attitude perceptions that differ substantially from the actual vehicle state. In particular, a somatogravic illusion is predicted that causes the perceived orientation to be nearly upright compared to the actual vehicle state which is pitched back. Furthermore, astronaut head location within the vehicle is considered for different vehicle designs to determine the effect on perceived orientation. The effect was found to be small, but measureable (0.3-4.1 degrees), and larger for the new Altair vehicle design compared to the Apollo Lunar Module.

Next-Generation Maneuvering System with Control-Moment Gyroscopes for Extravehicular Activities Near Low-Gravity Objects

Looking ahead to the human exploration of Mars, NASA is planning for exploration of near-Earth asteroids and the Martian moons. Performing tasks near the surface of such low-gravity objects will likely require the use of an updated version of the Manned Maneuvering Unit (MMU) since the surface gravity is not high enough to allow astronauts to walk, or have sufficient resistance to counter reaction forces and torques during movements. The extravehicular activity (EVA) Jetpack device currently under development is based on the Simplified Aid for EVA Rescue (SAFER) unit and has maneuvering capabilities to assist EVA astronauts with their tasks. This maneuvering unit has gas thrusters for attitude control and translation. When EVA astronauts are performing tasks that require ne motor control such as sample collection and equipment placement, the current control system will re thrusters to compensate for the resulting changes in center-of-mass location and moments of inertia, adversely affecting task performance. The proposed design of a next-generation maneuvering and stability system incorporates control concepts optimized to support astronaut tasks and adds control-moment gyroscopes (CMGs) to the current Jetpack system. This design aims to reduce fuel consumption, as well as improve task performance for astronauts by providing a sti er work platform. The high-level control architecture for an EVA maneuvering system using both thrusters and CMGs considers an initial assessment of tasks to be performed by an astronaut and an evaluation of the corresponding human-system dynamics. For a scenario in which the astronaut orbits an asteroid, simulation results from the current EVA maneuvering system are compared to those from a simulation of the same system augmented with CMGs, demonstrating that the forces and torques on an astronaut can be significantly reduced with the new control system actuation while conserving onboard fuel.

Markov analysis of human-in-the-loop system performance

Pilot interaction with complex vehicles involves information perception and understanding, as well as decision making to select and execute the desired action. These decisions and actions are often time-critical and require an accurate response. When designing a complex system, the analysis of human-in-the-loop system performance is important during early-stage system design to assess the impact of varying levels of automation, redundancy, and task allocation. We have integrated several human performance models with a model of a piloted vehicle to analyze human-in-the-loop performance using Draper Laboratorys Performance and Reliability Analysis via Dynamic Modeling (PARADyM) toolkit. This approach provides a framework for understanding the effects of a vehicle component failure or human error as it propagates through a complex system. Vehicle and human performance models, which include a model of the Space Shuttle Orbiter lateral flight dynamics, visual and vestibular perception, rule-based judgment and decision making, and pilot action, were implemented using MATLAB/Simulink?. Trajectory scenarios were simulated for analysis with and without instrumentation failures, and with and without human errors. The resulting pilot-vehicle performance during scenarios with a component failure was compared to a baseline (no failure) trajectory. Performance thresholds were specified to determine whether the resulting vehicle trajectory represented degraded performance that was within the specified bounds (operational) or outside the bounds (resulting in system loss). At the present stage, this analysis methodology is viable as an early-stage design tool. However, if associated with experimentally validated models for both the human performance and vehicle dynamics, this approach has the potential for a mission and configuration design analysis tool.

The Variable Vector Countermeasure Suit (V2Suit) for space habitation and exploration.

The “Variable Vector Countermeasure Suit (V2Suit) for Space Habitation and Exploration” is a novel system concept that provides a platform for integrating sensors and actuators with daily astronaut intravehicular activities to improve health and performance, while reducing the mass and volume of the physiologic adaptation countermeasure systems, as well as the required exercise time during long-duration space exploration missions. The V2Suit system leverages wearable kinematic monitoring technology and uses inertial measurement units (IMUs) and control moment gyroscopes (CMGs) within miniaturized modules placed on body segments to provide a “viscous resistance” during movements against a specified direction of “down”—initially as a countermeasure to the sensorimotor adaptation performance decrements that manifest themselves while living and working in microgravity and during gravitational transitions during long-duration spaceflight, including post-flight recovery and rehabilitation. Several aspects of the V2Suit system concept were explored and simulated prior to developing a brassboard prototype for technology demonstration. This included a system architecture for identifying the key components and their interconnects, initial identification of key human-system integration challenges, development of a simulation architecture for CMG selection and parameter sizing, and the detailed mechanical design and fabrication of a module. The brassboard prototype demonstrates closed-loop control from “down” initialization through CMG actuation, and provides a research platform for human performance evaluations to mitigate sensorimotor adaptation, as well as a tool for determining the performance requirements when used as a musculoskeletal deconditioning countermeasure. This type of countermeasure system also has Earth benefits, particularly in gait or movement stabilization and rehabilitation.

Developing a prototype ALHAT Human System Interface for landing

NASAs Autonomous Landing and Hazard Avoidance Technology (ALHAT) project is developing technologies for safe landing anytime/anywhere on planetary surfaces. Minimizing time, thus minimizing fuel consumption, is critical during landing, so ALHAT displays must convey information efficiently to operators. The ALHAT Human System Interface (HSI) team developed prototype displays, explored methods of providing situation awareness, and modeled the cognitive task and information requirement for landing site selection. Input from NASA astronauts and mission controllers was solicited to refine ALHAT display concepts in a series of evaluations. This paper discusses the evolution of ALHAT displays and future plans for ALHAT HSI.1,2

Development of an integrated simulation platform for real-time task performance assessment

A re-configurable, portable test station was developed for integrating and testing real-time performance metrics for continuously assessing operator effectiveness in operationally-relevant spaceflight piloting tasks. The test station includes a single computer for hosting the vehicle simulation, rendering both graphical flight displays and a 3-D out-the-window view, and computing the performance metrics in real-time. The pilot interacts with the simulation using four displays (two piloting displays, one out-the-window display, and a mission summary display), a rotational hand controller, a translational hand controller, and a microphone. A fifth display provides a system status / engineering view for the experimenter. A key component of the simulation station is the real-time metrics engine and algorithms, which estimates pilot workload, situation awareness, and flight performance without interfering with the piloting task, or adding equipment or infrastructure to the flight deck. Workload and flight performance are estimated based on an analysis of the vehicle state (e.g., attitude, altitude, % fuel) and the pilot commands (e.g., hand controller movement), whereas situation awareness is estimated based on the comparison of the actual vehicle state and that spoken (and converted to text through an automatic speech recognition algorithm) by the flying pilot. This real-time simulation station development is discussed in the context of four operationally-relevant spaceflight tasks: piloted lunar landing, Orion/MPCV docking operations with the International Space Station (ISS), and manual control of the spacewalking Simplified Aid for EVA Rescue (SAFER) jet pack near the ISS.

A new spin on space suits

An astronaut uses the thrusters on her space suit to propel herself toward a nearby asteroid. With great care, she gets as close and as steady as she can in preparation for knocking a few samples off the surface. But with very little gravity to anchor her, the strike of her hammer throws her backward in an uncontrolled tumble.

Variable Vector Countermeasure Suit (V2Suit) for Space Exploration

The “Variable Vector Countermeasure Suit (V2Suit) for Space Exploration” is an integrated countermeasure platform to mitigate the spaceflight-induced physiologic adaptation and de-conditioning that manifests during long-duration spaceflight and gravitational transitions. The V2Suit integrates flywheel gyroscopes and inertial measurement units within a wearable module that can be placed on the body segments, and when commanded in a coordinated manner provides a “viscous resistance” during movements. The system architecture, human-system integration, and three six degree-of-freedom simulations are presented which describe the magnitude and direction of the gyroscopic torque and resulting force within the module during representative arm movements. The results demonstrate of the ability of the V2Suit module design to generate a reaction force along a specified direction and reject perturbations due to body kinematics - collectively illustrating the feasibility of the concept.