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NASA NTRS1994

Design and simulation of EVA tools for first servicing mission of HST

The Hubble Space Telescope (HST) was launched into near-earth orbit by the Space Shuttle Discovery on April 24, 1990. The payload of two cameras, two spectrographs, and a high-speed photometer is supplemented by three fine-guidance sensors that can be used for astronomy as well as for star tracking. A widely reported spherical aberration in the primary mirror causes HST to produce images of much lower quality than intended. A Space Shuttle repair mission in January 1994 installed small corrective mirrors that restored the full intended optical capability of the HST. The First Servicing Mission (FSM) involved considerable Extra Vehicular Activity (EVA). Special EVA tools for the FSM were designed and developed for this specific purpose. In an earlier report, the details of the Data Acquisition System developed to test the performance of the various EVA tools in ambient as well as simulated space environment were presented. The general schematic of the test setup is reproduced in this report for continuity. Although the data acquisition system was used extensively to test a number of fasteners, only the results of one test each carried on various fasteners and the Power Ratchet Tool are included in this report.

Naik, Dipak↗

NASA NTRS1993

Hubble Space Telescope EVA Power Ratchet Tool redesign

The Power Ratchet Tool (PRT) is a self contained, power-driven, 3/8 inch drive ratchet wrench which will be used by astronauts during Extravehicular Activities (EVA). This battery-powered tool is controlled by a dedicated electonic controller. The PRT was flown during the Hubble Space Telescope (HST) Deployment Mission STS-31 to deploy the solar arrays if the automatic mechanisms failed. The PRT is currently intended for use during the first HST Servicing Mission STS-61 as a general purpose power tool. The PRT consists of three major components; the wrench, the controller, and the battery module. Fourteen discrete combinations of torque, turns, and speed may be programmed into the controller before the EVA. The crewmember selects the desired parameter profile by a switch mounted on the controller. The tool may also be used in the manual mode as a non-powered ratchet wrench. The power is provided by a silver-zinc battery module, which fits into the controller and is replaceable during an EVA. The original PRT did not meet the design specification of torque output and hours of operation. To increase efficiency and reliability the PRT underwent a redesign effort. The majority of this effort focused on the wrench. The original PRT drive train consisted of a low torque, high speed brushless DC motor, a face gear set, and a planocentric gear assembly. The total gear reduction was 300:1. The new PRT wrench consists of a low speed, high torque brushless DC motor, two planetary gear sets and a bevel gear set. The total gear reduction is now 75:1. A spline clutch has also been added to disengage the drive train in the manual mode. The design changes to the controller will consist of only those modifications necessary to accomodate the redesigned wrench. The battery design will be unaffected.

Richards, Paul W.↗

NASA NTRS1995

Emergency vehicle alert system (EVAS)

The Emergency Vehicle Alert System (EVAS) program is sponsored by the NASA/MSFC Technology Utilization (TU) office. The program was conceived to support the needs of hearing impaired drivers. The objective of the program is to develop a low-cost, small device which can be located in a personal vehicle and warn the driver, via a visual means, of the approach of an emergency vehicle. Many different technologies might be developed for this purpose and each has its own advantages and drawbacks. The requirements for an acoustic detection system, appear to be pretty stringent and may not allow the development of a reliable, low-cost device in the near future. The problems include variations in the sirens between various types of emergency vehicles, distortions due to wind and surrounding objects, competing background noise, sophisticated signal processing requirements, and omni-directional coverage requirements. Another approach is to use a Radio Frequency (RF) signal between the Emergency Vehicle (EV) and the Personal Vehicle (PV). This approach requires a transmitter on each EV and a receiver in each PV, however it is virtually assured that a system can be developed which works. With this approach, the real technology issue is how to make a system work as inexpensively as possible. This report gives a brief summary of the EVAS program from its inception and concentrates on describing the activities that occurred during Phase 4. References 1-3 describe activities under Phases 1-3. In the fourth phase of the program, the major effort to be expended was in development of the microcontroller system for the PV, refinement of some system elements and packaging for demonstration purposes. An EVAS system was developed and demonstrated which used standard spread spectrum modems with minor modifications.

Reed, Bill↗

NASA NTRS1999

In Vivo Noninvasive Analysis of Human Forearm Muscle Function and Fatigue: Applications to EVA Operations and Training Maneuvers

Forearm muscle fatigue is one of the major limiting factors affecting endurance during performance of deep-space extravehicular activity (EVA) by crew members. Magnetic resonance (MR) provides in vivo noninvasive analysis of tissue level metabolism and fluid exchange dynamics in exercised forearm muscles through the monitoring of proton magnetic resonance imaging (MRI) and phosphorus magnetic resonance spectroscopy (P-31-MRS) parameter variations. Using a space glove box and EVA simulation protocols, we conducted a preliminary MRS/MRI study in a small group of human test subjects during submaximal exercise and recovery and following exhaustive exercise. In assessing simulated EVA-related muscle fatigue and function, this pilot study revealed substantial changes in the MR image longitudinal relaxation times (T2) as an indicator of specific muscle activation and proton flux as well as changes in spectral phosphocreatine-to-phosphate (PCr/Pi) levels as a function of tissue bioenergetic potential.

Fotedar, L. K.↗

NASA NTRS2000

STS-101 / Atlantis EVA briefing

The primary mission objective for STS-101 was to deliver supplies to the International Space Station, perform a space walk, and reboost the station from 230 statute miles to 250 statute miles. The commander of this mission was James D. Halsell. The crew was Scott J. Horowitz, the pilot, and mission specialists Mary Ellen Weber, Jeffrey N. Williams, James S. Voss, Susan J. Helms, and Yuri Vladimirovich Usachev. This videotape is a press briefing by Scott Bleisath, STS-101 Lead EVA Officer, about the planned Extravehicular Activity planned for the fourth day of the mission. The work that this EVA is to accomplish is the repair of a crane and the installation of a beam on Unity. The astronauts will also replace antennae and install hand rails and cables. The astronauts who are scheduled to perform the EVA activities are Williams and Voss. They will be assisted by Weber, who will operate the Shuttle's robotic arm, and Scott Horowitz. The spacewalk is scheduled to take 6 hours. The videotape includes some views of the astronauts training in an underwater environment. Mr. Bleisath answered questions from the press after he completed the briefing.

Source record↗

NASA NTRS2001

Evidence-Based Approach to the Analysis of Serious Decompression Sickness with Application to EVA Astronauts

It is important to understand the risk of serious hypobaric decompression sickness (DCS) in order to develop procedures and treatment responses to mitigate the risk. Since it is not ethical to conduct prospective tests about serious DCS with humans, the necessary information was gathered from 73 published reports. We hypothesize that a 4-hr 100% oxygen (O2) prebreathe results in a very low risk of serious DCS, and test this through analysis. We evaluated 258 tests containing information from 79,366 exposures in attitude chambers. Serious DCS was documented in 918 men during the tests. Serious DCS are signs and symptoms broadly classified as Type II DCS. A risk function analysis with maximum likelihood optimization was performed to identify significant explanatory variables, and to create a predictive model for the probability of serious DCS [P(serious DCS)]. Useful variables were Tissue Ratio, the planned time spent at altitude (T(sub alt)), and whether or not repetitive exercise was performed at altitude. Tissue Ratio is P1N2/P2, where P1N2 is calculated nitrogen (N2) pressure in a compartment with a 180-min half-time for N2 pressure just before ascent, and P2 is ambient pressure after ascent. A prebreathe and decompression profile Shuttle astronauts use for extravehicular activity (EVA) includes a 4-hr prebreathe with 100% O2, an ascent to P2 = 4.3 lb per sq. in. absolute, and a T(sub alt) = 6 hr. The P(serious DCS) is: 0.0014 (0.00096 - 0.00196, 95% confidence interval) with exercise and 0.00025 (0.00016 - 0.00035) without exercise. Given 100 Shuttle EVAs to date and no report of serious DCS, the true risk is less than 0.03 with 95% confidence (Binomial Theorem). It is problematic to estimate the risk of serious DCS since it appears infrequently, even if the estimate is based on thousands of altitude chamber exposures. The true risk to astronauts may lie between the extremes of the confidence intervals (0.00016 - 0.00196) since the contribution of other factors, particularly exercise, to the risk of serious DCS during EVA is unknown. A simple model that only accounts for four important variables in retrospective data is still helpful to increase our understanding about the risk of serious DCS.

Conkin, Johnny↗

NASA NTRS2004

Fuel Oxidizer Reaction Products (FORP) Contamination of Service Module (SM) and Release of N-nitrosodimethylamine(NDMA)in a Humid Environment from Crew EVA Suits Contaminated with FORP

The Service Module (SM) is an element of the Russian Segment of the International Space Station (ISS). One of the functions of the SM is to provide attitude control for the ISS using thrusters when the U.S. Control Moment Gyros (CMG's) must be desaturated. Prior to an Extravehicular Activity (EVA) on the Russian Segment, the Docking Compartment (DC1) is depressurized, as it is used as an airlock. When the DC1 is depressurized, the CMG's margin of momentum is insufficient and the SM attitude control thrusters need to fire to desaturate the CMG's. SM roll thruster firings induce contamination onto adjacent surfaces with Fuel Oxidizer Reaction Products (FORP). FORP is composed of both volatile and non-volatile components. One of the components of FORP is the potent carcinogen N-nitrosdimethylamine (NDMA). Since the EVA crewmembers often enter the area surrounding the thrusters for tasks on the aft end of the SM and when translating to other areas of the Russian Segment, the presence of FORP is a concern. This paper will discuss FORP contamination of the SM surfaces, the release of NDMA in a humid environment from crew EVA suits, if they happen to be contaminated with FORP, and the toxicological risk associated with the NDMA release.

Schmidl, William↗

NASA NTRS2004

Human-Centric Teaming in a Multi-Agent EVA Assembly Task

NASA's Human Space Flight program depends heavily on spacewalks performed by pairs of suited human astronauts. These Extra-Vehicular Activities (EVAs) are severely restricted in both duration and scope by consumables and available manpower.An expanded multi-agent EVA team combining the information-gathering and problem-solving skills of human astronauts with the survivability and physical capabilities of highly dexterous space robots is proposed. A 1-g test featuring two NASA/DARPA Robonaut systems working side-by-side with a suited human subject is conducted to evaluate human-robot teaming strategies in the context of a simulated EVA assembly task based on the STS-61B ACCESS flight experiment.

Rehnmark, Fredrik↗

NASA NTRS2007

Risk Reduction and Measures of Injury for EVA Associated Upper Extremity Medical Issues: Extended Vent Tube Study

During Neutral Buoyancy Lab (NBL) training sessions, a large amount of moisture accumulates in the EVA gloves. The glove design restricts the extension of the EVA suit s ventilation/cooling system to the hand. Subungual redness and fingernail pain develops for many astronauts following their NBL training sessions with subsequent oncholysis occurring over succeeding weeks. Various attempts have been made to reduce or avoid this problem. The causal role of moisture has yet to be defined. Methods: To determine the contribution that moisture plays in the injury to the fingers and fingernails during EVA training operations in NBL, the current Extravehicular Mobility Unit (EMU), with a Portable Life Support System (PLSS) was configured with a ventilation tube that extended down a single arm of the crewmember during the test and compared with the unventilated contralateral arm; with the ventilated hand serving as the experimental condition (E) and the opposite arm as the control (C). A cross-over design was used with opposite handedness for the vent tube on a subsequent NBL training run. Moisture content measures were conducted at six points on each hand with three types of moisture meters. A questionnaire was administered to determine subjective thermal hand discomfort, skin moisture perception, and hand and nail discomfort. Photographs and video were recorded. Measures were applied to six astronauts pre- and post-run in the NBL. Results: The consistent trends in relative hydration ratios at the dorsum, from 3.34 for C to 2.11 for E, and first ring finger joint locations, from 2.46 for C to 1.96 for E, indicated the extended vent tube promoted skin drying. The experimental treatment appeared to be more effective on the left hand versus the right hand, implying an interaction with hand anthropometry and glove fit. Video analyses differentiated fine and gross motor training tasks during runs and will be discussed. Conclusions: This potential countermeasure was effective in reducing the risks of hand and nail discomfort symptoms from moderate to low in two of six subjects. Improved design in the ventilation pattern of such a countermeasure is expected to improve the countermeasure s efficiency.

Jones, Jeffrey A.↗

NASA NTRS2007

Collaborative Human Engineering Work in Space Exploration Extravehicular Activities (EVA)

A viewgraph presentation on extravehicular activities in space exploration in collaboration with other NASA centers, industries, and universities is shown. The topics include: 1) Concept of Operations for Future EVA activities; 2) Desert Research and Technology Studies (RATS); 3) Advanced EVA Walkback Test; 4) Walkback Subjective Results; 5) Integrated Suit Test 1; 6) Portable Life Support Subsystem (PLSS); 7) Flex PLSS Design Process; and 8) EVA Information System; 9)

DeSantis, Lena↗

NASA NTRS2009

A Glimpse from the Inside of a Space Suit: What Is It Really Like to Train for an EVA?

The beauty of the view from the office of a spacewalking astronaut gives the impression of simplicity, but few beyond the astronauts, and those who train them, know what it really takes to get there. Extravehicular Activity (EVA) training is an intense process that utilizes NASA's Neutral Buoyancy Laboratory (NBL) to develop a very specific skill set needed to safely construct and maintain the orbiting International Space Station. To qualify for flight assignments, astronauts must demonstrate the ability to work safely and efficiently in the physically demanding environment of the spacesuit, possess an acute ability to resolve unforeseen problems, and implement proper tool protocols to ensure no tools will be lost in space. Through the insights and the lessons learned by actual EVA astronauts and EVA instructors, this paper twill take you on a journey through an astronaut's earliest experiences working in the spacesuit. termed the Extravehicular Mobility Unit (EMU), in the underwater training environment of the NBL. This work details an actual Suit Qualification NBL training event, outlines the numerous challenges the astronauts face throughout their initial training, and the various ways they adapt their own abilities to overcome them. The goal of this paper is to give everyone a small glimpse into what it is really like to work in a spacesuit.

Gast, Matthew A.↗

NASA NTRS2010

Climbing the Extravehicular Activity (EVA) Wall - Safely

The success of the EVA team, that includes the EVA project office, Crew Office, Mission Operations, Engineering and Safety, is assured by the full integration of all necessary disciplines. Safety participation in all activities from hardware development concepts, certification and crew training, provides for a strong partnership within the team. Early involvement of Safety on the EVA team has mitigated risk and produced a high degree of mission success.

Fuentes, Jose↗

NASA NTRS2012

Maturing Pump Technology for EVA Applications in a Collaborative Environment

The transition from low earth orbit Extravehicular Activity (EVA) for construction and maintenance activities to planetary surface EVA on asteroids, moons, and, ultimately, Mars demands a new spacesuit system. NASA's development of that system has resulted in dramatically different pumping requirements from those in the current spacesuit system. Hamilton Sundstrand, Cascon, and NASA are collaborating to develop and mature a pump that will reliably meet those new requirements in space environments and within the design constraints imposed by spacesuit system integration. That collaboration, which began in the NASA purchase of a pump prototype for test evaluation, is now entering a new phase of development. A second generation pump reflecting the lessons learned in NASA's testing of the original prototype will be developed under Hamilton Sundstrand internal research funding and ultimately tested in an integrated Advanced Portable Life Support System (APLSS) in NASA laboratories at the Johnson Space Center. This partnership is providing benefit to both industry and NASA by supplying a custom component for EVA integrated testing at no cost to the government while providing test data for industry that would otherwise be difficult or impossible to duplicate in industry laboratories. This paper discusses the evolving collaborative process, component requirements and design development based on early NASA test experience, component stand alone test results, and near term plans for integrated testing at JSCs.

Hodgson, Edward↗

NASA NTRS2012

EVA Development and Verification Testing at NASA's Neutral Buoyancy Laboratory

As an early step in the preparation for future Extravehicular Activities (EVAs), astronauts perform neutral buoyancy testing to develop and verify EVA hardware and operations. Neutral buoyancy demonstrations at NASA Johnson Space Center's Sonny Carter Training Facility to date have primarily evaluated assembly and maintenance tasks associated with several elements of the International Space Station (ISS). With the retirement of the Shuttle, completion of ISS assembly, and introduction of commercial players for human transportation to space, evaluations at the Neutral Buoyancy Laboratory (NBL) will take on a new focus. Test objectives are selected for their criticality, lack of previous testing, or design changes that justify retesting. Assembly tasks investigated are performed using procedures developed by the flight hardware providers and the Mission Operations Directorate (MOD). Orbital Replacement Unit (ORU) maintenance tasks are performed using a more systematic set of procedures, EVA Concept of Operations for the International Space Station (JSC-33408), also developed by the MOD. This paper describes the requirements and process for performing a neutral buoyancy test, including typical hardware and support equipment requirements, personnel and administrative resource requirements, examples of ISS systems and operations that are evaluated, and typical operational objectives that are evaluated.

Jairala, Juniper C.↗

NASA NTRS2014

Asteroid Redirect Crewed Mission Space Suit and EVA System Architecture Trade Study

The Asteroid Redirect Crewed Mission (ARCM) requires a Launch/Entry/Abort (LEA) suit capability and short duration Extra Vehicular Activity (EVA) capability from the Orion spacecraft. For this mission, the pressure garment selected for both functions is the Modified Advanced Crew Escape Suit (MACES) with EVA enhancements and the life support option that was selected is the Exploration Portable Life Support System (PLSS) currently under development for Advanced Exploration Systems (AES). The proposed architecture meets the ARCM constraints, but much more work is required to determine the details of the suit upgrades, the integration with the PLSS, and the tools and equipment necessary to accomplish the mission. This work has continued over the last year to better define the operations and hardware maturation of these systems. EVA simulations were completed in the Neutral Buoyancy Lab (NBL) and interfacing options were prototyped and analyzed with testing planned for late 2014. This paper discusses the work done over the last year on the MACES enhancements, the use of tools while using the suit, and the integration of the PLSS with the MACES.

Bowie, Jonathan↗

NASA NTRS2015

Asteroid Redirect Crewed Mission Space Suit and EVA System Maturation

Bowie, Jonathan↗

NASA NTRS2015

Next Generation Life Support: High Performance EVA Glove

The objectives of the High Performance EVA Glove task are to develop advanced EVA gloves for future human space exploration missions and generate corresponding standards by which progress may be quantitatively assessed. New technologies and manufacturing techniques will be incorporated into the new gloves to address finger and hand mobility, injury reduction and durability in nonpristine environments. Three prototypes will be developed, each focusing on different technological advances. A robotic assist glove will integrate a powered grasping system into the current EVA glove design to reduce astronaut hand fatigue and hand injuries. A mechanical counter pressure (MCP) glove will be developed to further explore the potential of MCP technology and assess its capability for countering the effects of vacuum or low pressure environments on the body by using compression fabrics or materials to apply the necessary pressure. A gas pressurized glove, incorporating new technologies, will be the most flight-like of the three prototypes. Advancements include the development and integration of aerogel insulation, damage sensing components, dust-repellant coatings, and dust tolerant bearings.

Walsh, Sarah K.↗

NASA NTRS2015

Extravehicular Activity (EVA) Microbial Swab Tool

When we send humans to search for life on Mars, we'll need to know what we brought with us versus what may already be there. To ensure our crewed spacecraft meet planetary protection requirements--and to protect our science from human contamination--we'll need to know whether micro-organisms are leaking/venting from our ships and spacesuits. This is easily done by swabbing external vents and surfaces for analysis, but there was no US EVA tool for that job. NASA engineers developed an EVA-compatible swab tool that can be used to collect data on current hardware, which will influence eventual Mars life support and EVA hardware designs.

Rucker, Michelle↗