Advanced EVA Roadmaps and Requirements

A wide range of solutions can be theorized for the architectures, technologies and operations concepts of advanced EVA systems for future space and planetary applications. This paper reports on the status of the latest advanced EVA roadmaps and ongoing work to capture and refine an initial set of candidate requirements. A brief summary of related research and development is also presented. The end goal is a cost effective, safe and resource efficient integrated system that enables work in a diversity of environments at multiple destinations. A balance of cooperative efforts between humans and automated/robotic devices is envisioned to maximize productivity and safety in remote locations. The challenges ahead to be addressed will reflect past lessons learned and visionary new solutions. This information is intended to provide credible and useful guidance for those involved in the eventual implementation, validation and utilization of an advanced EVA system. INTRODUCTION – WHY HUMANS? The debate over the selection of human versus robotic means to accomplish space exploration is long standing and will surely continue. Each approach has pros and cons depending upon the intended application and the state of technology readiness. It is readily acknowledged that robotic missions are entirely appropriate for distant and hazardous new environments. At some point however, a combination of human and robotic resources provides leverage to enable more productive and timely efforts. This joint approach has numerous benefits that can be applied to a diversity of future exploration destinations and commercial ventures. Human intervention at a given site provides specific positive gains. • Productivity Use of creative cognitive abilities for rapid on scene decisions which overcome radio communication time delays and bandwidth limitations • Reliability – Additional capability for response to unforeseen situations and unique non-repetitive activities • Cost/Mass – Less need to expend resources upon complex, redundant and fully automated designs • Terrestrial Benefits – Human space activities engage public interest and advance new opportunities These human capabilities are further enhanced when appropriate tools are advantageously applied. Environmental protection, transportation vehicles, sensors, computerized information processing and mechanical handling aids typify classes of such aids. Interactive robotics also provide complementary strength, intelligence and extended duration external access. Direct teaming of the human brain and these aids has historically proven to be an effective means to enable difficult or otherwise impossible ventures. CURRENT EVA LIMITATIONS FIGURE 1. Russian Orlan-M and U.S. EMU One tool that enables humans to work productively and effectively in space is the extravehicular activity (EVA) suit. Its origins are rooted in high altitude flights where protection from extreme cold and low pressure was paramount. Work compatible designs have culminated in the U.S. extravehicular mobility unit (EMU) and in the Russian Orlan M suits. While these suits are proven and robust to meet near term applications such as the International Space Station, they have serious limitations, which need to be addressed. The current NASA EVA suit design baseline is over 24 years old (1977) and has evolved from Apollo, Skylab and Shuttle program applications. It is only compatible with low earth orbit and microgravity activities. It requires regular ground based maintenance, re-supply and monitoring. Obsolescence of materials and components is an ongoing challenge. It relies upon a rigid architectural platform that is not well suited for advanced technology upgrades. A synopsis of key issues with both U.S. and Russian EVA systems can be broken down into environmental, productivity and logistics induced factors : Environmental Issues 1. The mass, mobility and visibility of the current suits are not compatible with partial gravity planetary environments. Suited body control in zero gravity is also hampered by these factors. The current U.S. suit is twice as heavy as the Apollo suit and is not designed for kneeling, prolonged walking or inertia free handling. Arm/hand work envelope and foot visibility are severely degraded by chest-mounted controls. Physical comfort is not sustainable for high frequency work in partial gravity. 2. Suit protection from dust intrusion is inadequate. Even the Apollo suits would have been unable to support more than 3 days of lunar work due to highly abrasive minerals preventing rotation of mobility bearings. 3. Available thermal insulation materials either only work in vacuum conditions or are thick and impede suit mobility and glove dexterity. Even with active heating, touch temperatures are limited to short durations and narrow ranges (-140 to +240F or –96 to 116C). 4. Radiation environment definition, monitoring and protection are inadequate beyond earth’s ionosphere. 5. The effects of planetary unique gases (such as argon) on EVA physiology are undefined. 6. Sensitive environments and science devices are contaminated from suit by-products (water, particulates, atmosphere leakage). Productivity Issues 1. EVA information processing is limited to suit/medical telemetry and is based on old technology that is not inflight reprogrammable. Radio communication is the sole means of information exchange for science interaction, worksite unique data and navigation/tracking status. Imagery is only captured by standard photography and video. Reference information is paper based because no environment compatible display yet exists. Hands free interaction is needed to avoid fatiguing manual efforts and obstructed work volumes. 2. Medical monitoring and treatment of EVA crew is minimal. Cannot yet quantitatively track fatigue or decompression sickness symptoms. Non-intrusive, 100% O2 compatible and wireless devices are lacking. There is no effective insuit treatment capability for injury or illness. 3. Robotic EVA aids in use are primarily large arms with limited mobility and dexterous capability. Human capable wheeled rovers are not in development. Highly mobile and dexterous robotics get limited attention. None are yet fully developed for autonomous inspections, cargo handling, worksite setup, crew tracking or self charging/storage/maintenance. Most are too reliant upon unique visual and handling aids. 4. Tools are limited to manual force/torque reaction & zeroG transport/restraint. Limited environmental & mechanical analysis devices. No drills. Few true repair options. Delicate materials not easily handled. Logistics Issues 1. EVA overhead penalties are high in terms of mass, volume and time. Historically, less than 20% of crew time related to EVA is spent on productive external work. 2600 lbs and 90 ft3 (1182 kg and 2.6m) were manifested for suits, tools, carriers and consumables on STS-103 for Hubble Space Telescope servicing (1470 lbs and 60 ft3 or 668 kg and 1.7 m for 4 suits). The 300 lb mass and 13 ft3 (136 kg and 0.4 m) stowage volume of the current U.S. suit is not compatible with the restricted delivery capacity of remote exploration. 2. Suit consumables are wastefully expended and require frequent replenishment or considerable time/power to recharge. Heavy cooling water is vented. CO2 scrubbing canisters require wholesale replacement or time/power consuming bakeout between sorties. No insitu resource utilization is possible. 3. No real suit maintenance capability exists beyond limited resizing and consumables replacement. Spares change out is only done via large integrated assemblies. Many intricate parts are not crew serviceable. 4. Airlock designs have remained static. Depress/repress gas is still vented or pumped with large power penalties. Existing designs are not compatible with dust/biologic isolation or hyperbaric treatment. 5. Separate self rescue and emergency life support limits return range and adds to suit mass/volume IMPLEMENTATION GOALS AND REQUIREMENTS To enable the human and robotic aspects of efficient and effective space ventures, a visionary yet practical approach is planned. By documenting and maintaining a collection of the best known requirements from a broad set of sources, technology research and development will proceed with real targets in sight. Because past programs have suffered from late and incomplete collections of requirements, the hope is that a detailed and early capturing of this information will lead to success in future EVA implementation. Rather than wait for a specific destination to be named, a wide range of relevant and accessible environments will be targeted. The resulting products will be compatible with multiple destinations and provide an open architecture to enable a diversity of opportunities. Unlike the limited flexibility of the current technologies, a well thought out integrated system will be a readily adaptable and cost effective enhancement to human capabilities. As shown in the roadmap of Appendix A, an initial design can be fully implemented within 10 years and can improve as time and resources are further invested. Investing in a more efficient system will also save resources in the mid to long term. A draft document of the necessary requirements has been compiled from the best of numerous existing sources (individual experts, reports and past programs). To avoid painful and costly iterations, the mistakes and successes of the past will be heeded in future designs. This information will provide planners, designers and fabricators with a standard reference of the desired end products and uses. All significant EVA operations and hardware elements are considered. These include operations guidelines and hardware systems such as suits, airlocks, robotics, tools and ground infrastructure. Guiding priorities and principals include safety, simplicity, reliability, low mass, low cost, resource frugality, comfort, time efficiency and commonality. To m