031CES-312 Restraining Loose Equipment Aboard the International Space Station: The Payload Equipment Restraint System Kenneth A. Smith Raytheon Information Technology and Scientific Services, Marshall Space Flight Center, Alabama, USA David W. Reynolds National Aeronautics and Space Administration, Marshall Space Flight Center, Alabama, USA Copyright 0 2003 SAE International ABSTRACT As the International Space Station (ISS) grows, so do the supplies and equipment needed to support its daily operations. Each day many items must be unstowed and moved to various worksites so that they are readily available to the crew. Due to the lack of gravity, these items ,may become loose and float away if not restrained. The Payload Equipment Restraint System (PERS) was developed to meet the new and unique challenge of restraining loose equipment aboard the ISS. INTRODUCTION Figure 1. Expedition 4-Flight Engineer Daniel Bursch preparing for an The ISS is a tremendously growing facility in Earth’s extravehicular activity. orbit built to enhance the scientific, technological, and commercial use of the space environment. As the Station grows, so do the supplies and equipment needed to support its daily operations. Each day many items must be unstowed (Figure 1) and relocated to various THE BASIC CHALLENGE worksites so that they are readily available to the crewmembers as they perform their activities. On Earth, This challenge needs to be approached in a manner that this task is relatively simple: gravity allows the relocated allows the task to be as simple as it is on Earth. That is, equipment to stay where it is placed. Due to the lack of after relocating the equipment from the stowed location gravity in Earth orbit, this task is not so simple-items to the worksite, it stays where you put it. Since there is float away if not properly restrained. This condition is very low gravity (called microgravity) aboard the ISS, a well known in the space industry and has been handled restraint device or system is needed to provide this in many ways over the years. Dealing with this condition condition. This sounds simple but becomes more aboard the ISS offers a new and unique challenge. complex when stated with more detail: temporarily Unlike Skylab- and Shuttle-based labs that typically have restrain equipment of various sizes and shapes at the equipment needed to perform an activity stowed at random worksite locations within the ISS within arm’s that location, equipment aboard the ISS is stowed in reach of the crewmember with quick, easy attachment- many locations. As more elements are added to the ISS, and-removal capability of the relocated equipment. This such as the European Space Agency (ESA) Columbus minimizes crew time needed for handling loose Orbital Facility (COF) and the National Space equipment (described as loose because it floats away if Development Agency (NASDA) Japanese Experiment not restrained). The PERS was developed to accomplish Module (JEM), the more spread out these stowage this taskkhallenge for intravehicular activity aboard the locations will become. ISS and is documented in the Marshall Space Flight Center (MSFC) reference implementation plan, PERS-PLAN-0034. To best solve this problem it is important to understand Reduce the number of trips required to and from the the overall ISS internal configuration and the typical daily worksite and stowage. crew operations that involve loose equipment. As the Provide a hands-free transport for small items and Destiny lab was assembled to the ISS, the worksite tools. capability increased. The lab provides an interface for Provide a means to restrain equipment and tools in the several types of international standard payload a vareity of sizes and shapes at various worksite racks, such as EXPRESS (Expediting the Process of locations within the ISS. Experiments to Space Station), resupply stowage, and zero-g storage racks. These racks can be located within several of the 24 rack locations, providing a versatile, reconfigurable work environment throughout the lab, as seen in Figure 2. These racks are also equipped with a standard hardware mounting interface, called seat track, used for mounting structural devices, such as handrails, foot restraints, and camera mounts on the front outer face of each rack, as seen in Figure 2. As more of these racks are installed, this seat track interface becomes available throughout the lab in all axes. Therefore, the seat track is an ideal interface for the PERS and provides an enormous variety of mounting locations throughout the U.S. elements. This same interface will also be used in the COF and JEM modules. ON-ORBIT OPERATIONS Daily activities require handling loose equipment and may be executed differently by each crewmember. However, one of the most common aspects is the need to have a variety of equipment, mostly small items and tools, available at arm’s reach wherever a crewmember is working, as seen in Figure 2. A typical crew activity scenario is as follows: 1. Prepare worksite (install crew and equipment restraints). 2. Collect stowed items required to perform the task or procedure and transfer them to the worksite. This may require several trips. 3. Temporarily restrain these items and tools at the worksite. 4. Perform the task without leaving the worksite whenever possible. This scenario summarizes why a restraint system was needed. The main goal of PERS is to minimize the overhead required for the crew to handle loose equipment and tools. That is, allow an efficient and effective means for transferring and restraining loose equipment and tools within the microgravity environment. Crew time is critical to operations aboard the ISS. The number of activities the crew can perform in a given day is directly related to the amount of science accomplished. Therefore, it is essential that the crew be provided with the right support equipment to work efficiently. This is accomplished by the following: Figure 2. Robotic workstation (RWS) installation. All equipment is temporarily stowed on the PERS (a) H-Strap, then installed on the (b) seat track. , DEGIGN GOALS complicated items in -10 working days. The simpler items can be built in less than 5 working days. This allows for There were many goals in mind while developing the quick fabrication and delivery of the hardware. PERS equipment. One of those goals was to design a restraint system that was intuitive for the crew to Another cost-cutting step was the use of the seat track understand and operate with little or no training as well as stud. As mentioned earlier, seat track is the primary enable crewmembers to use their imaginations for its interface for mounting equipment in the U.S., ESA, and uses. NASDA modules. Utilizing an existing piece of Station support equipment as the mounting interface for the The crew was trained on the basic concept of how the hardware lowered design and fabrication time and cost, PERS equipment could be used as individual elements and it also streamlined the certification and verification and as a system. They were also shown how the process required for the ISS interface. The seat track equipment could be used with other ISS equipment. But stud, used with other ISS hardware, such as bungees and as the crew became more familiar with the hardware, it tethers, is part of the standard ISS flight crew equipment was obvious that they could see its potential uses in ways inventory. Since the crew is familiar with this interface and not previously considered. It was clear that having the its other uses, this reduced the time for the crew to crew participate early in the design and evaluate the become familiar with the hardware interface. Again, less equipment at various concept stages paid off. Although crew time required to understand and operate the the original purpose for building this equipment was to hardware means more time dedicated to the crew support operations for one specific payload, the concept activities themselves. quickly became a generic design that would support many types of Station activities. THE ELEMENTS OF PERS Several crewmembers were asked to evaluate the system The PERS is a five-element, modular system consisting of and provide comments regarding the overall design and the following: how they expected the hardware to perform in microgravity. There were differing comments of how each crewmember 1. Belly Pack would perform a given activity and use the hardware, but 2. Tool Pages there was a common theme in their comments: simplify the 3. Laptop Restraint Belt (LRB) design. Some of the original elements of the system had 4. Single Strap many configurations and multiple uses, and they still do. 5. H-Strap However, the overall design of the elements was simplified, which contributed to achieving the first goal of making the These elements are designed to allow cohesive crew equipment intuitive to use with lime training. In turn, this operations for handling loose equipment. Each of these is also simplified the fabrication process to build the described in the following paragraphs. equipment-another major goal of the project. The Belly Pack serves as a portable stowage volume and Another design goal was to ensure that PERS would be interfaces with a crewmember's waist to accommodate safe to use within the ISS environment. Proper material hands-free translation to the worksite or may be carried by selection for efficient use, nontoxic Contamination, and an adjustable strap. At the worksite, the Belly Pack can be flame resistance as well as the structural integrity of the attached to the H-Strap or ISS hook-and-pile fastener H-Strap and Single Strap were the primary items surfaces for ease of access. Figure 3 shows the Belly addressed. The requirements to achieve this goal are Pack in use aboard the IS. documented in the MSFC requirements document, PERS-RQMT-0035A. To ensure that all materials met the ISS requirements, several tests were conducted for both toxic off-gassing and flammability resistance. To ensure that the ISS requirements of structural integrrty were met for the Single Strap, several tests were conducted. The hardware is primarily composed of flame-resistant fabrics and mesh, various types of hook-and-pile fasteners, webbing, buckles, and other off-the-shelf items. By utilizing off -the-shelf materials and hardware, the entire certification, verification, and fabrication process was streamlined, allowing short fabrication times as well as lower overall cost. Since no special equipment is needed to fabricate the hardware, it can easily be done by existing personnel and facilities. Two full-time technicians can fabricate the most Figure 3. Expedaion 2-Flight Engineer Jim Voss (left) wearing the Belly Pack. The Tool Pages provide portable containment for The Single Strap provides temporary restraintlstowage restraining tools in an organized fashion and make them of equipment and tools at the worksite. The Single Strap readily available to the crew at the worksite. Three types interfaces to the standard ISS rack seat tracks via the of interfaces are used: hook-and-loop fastener patches, seat track stud. It may be located at a variety of elastic tabs, and standard socket holders. These allow worksites in several configurations depending on the the crew to load the Tool Pages with several different operational requirements. It provides multiple interfaces tools as required for any particular task. The Tool Pages for restraining equipment and tools: hook-and-pile are designed to interface with the H-Strap. Figure 4 fasteners, elastic loops, D-rings for bungeeltether use, shows a typical way the Tool Pages are loaded with and integrated ties for cables. figure 6 shows the Single tools. Strap in use aboard the ISS. Figure 4. The PERS Tool Pages are used with the ISS tool kits for transporting and temporarily stowing specific tools at the worksite. The LRB provides a flat surface, which can be deployed on a crewmember’s waist and used as a laptop worksurface interface. In addition, the LRB provides bungee interfaces to restrain small tools and equipment. When the LRB is not worn by a crewmember, it can be attached to the H-Strap or other ISS hook-and-pile fastener interfaces and used as a worksurface (Figure 5). Figure 6. Expedition 2-Commander Yuty Usachev using the Single Strap shown in foreground to restrain cables and hoses. The H-Strap is a portable restraint surface that provides temporary restraintlstowage for equipment and tools at the worksite. The H-Strap also provides restraint interfaces for all of the other PERS elements. In addition to the integrated tool pouches, the H-Strap provides hook-and-pile fastener loops, elastic loops, D-rings, and integrated cable ties to interface with ISS cargo transfer bags (CTBs), bungeesltethers, and other loose equipment. The H-Strap interfaces to the standard ISS Figure 5. The LRB deployed with the Space Station laptop computer rack seat track via seat track studs. Figure 7 shows the attached to it. H-Strap in use aboard the ISS. when we had multiple objects strapped to a PERS strap and it looked like a tree. We even used them for semilong-term storage of bags when we didn't have a specific stowage location or when we were collecting things for return on an upcoming Shuttle flight. Tool Pages allowed carrying all your tools to a worksite and restrained them there. We used one of them as a permanent toolbox with our most commonly used tools in it, ready to go. Figure 7. Expedition 2-Right Engineer Jim Voss preparing to install one of the ISS RWSs. The PERS elements are also designed to work as an integral system. The Belly Pack, Tool Pages, and LRB interface directly with the H-Strap and Single Strap, as seen in Figure 8. CONCLUSION (USE ABOARD THE ISS) The success of the PERS aboard the ISS was immediate upon arrival. The Expedition 2 crew began using it for multiple tasks and found that it was so useful Figure 8. The PERS Belly Pack shown attached to the H-Strap for that some of the PERS items were never put away and additional temporarily stowage of various items. remained in constant use on Expeditions 3 and 4. This success is best stated by one of the on-orbit users, astronaut Jim Voss, during some of his debriefing comments: "I think the best thing about the PERS was that it just allowed you to work more efficiently in space. One of the big difficulties of zero-g is keeping everything tied down while you are working with things. PERS solves that problem by allowing you to have all the items ' close by that you need to work with. We used the PERS straps for everything: large 3.0 CTBs (Figure 9), contingency water containers (CWCs) (Figure lo), big pieces of equipment (Figure ll), hoses and cables (Figure 12), etc. Many of our assembly tasks involved installing multiple (5-1 5) cables, hoses, and pieces of equipment in bags. We could put all of them near the worksite and not have to make many time-consuming Figure 9. Expedition 2-Flight Engineer Susan Helms shown stowing trips back and forth to lockers. We often had what we various large items temporarily on straps. referred to as 'PERS trees' in the Station-that was Figure 10. The PERS Single Strap assists in temporarily stowing Figure 12. The PERS H-Strap temporarily restrains several cables cwcs. prior to being installed. We sometimes used PERS straps (using the strap center seat track stud) for holding a rack in a partially rotated position while we worked behind it (Figure 11). And we used it to hold our paper procedures while working (Figure 8). Though not designed for this, we often used the straps for handholds and to stop ourselves while moving through the node or lab. I kept my towel, book, and CD player on a strap while I used the CEVIS [Cycle Ergometer Vibration Isolation System] bicycle. Tool Pages were placed on straps near the worksite for ready access to your tools. I used it to hold all the IMAP accessories (lenses, cleaning kit, magazine, light meter, lights, cables) near the camera stowage location. I used the strap to restrain the Major Constituents Analyzer [MCA] dryout hose (about 154 long, 2.5-in diameter anaconda) when it was connected between vacuum and the MCA. Having a handy, easy- to-use restraint system that accommodates all kinds of equipment is a godsend.” These comments sum it up; the challenge was met. The task of restraining loose equipment aboard the ISS is now almost as easy as a similar task on Earth. That is, after relocating the equipment from the stowed location to the worksite, it stays where you put It. This has been accomplished by a simple, easy-to-use system called the PERS. Now almost any size and shape of materials, supplies, tools, and equipment can be easily used at Figure 11. The PERS Single Strap used to restrain a partially rotated almost any location within the ISS. rack.