Browsing by Author "Akin, David L."
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Item EVA/Robotic Servicing in the Commercial Space Era(45th International Conference on Environmental Systems, 2015-07-12) Akin, David L.With the start of commercial crew flight to International Space Station (ISS) in 2017, US-supplied human access to low Earth orbit (LEO) will again be available upon need, ideally for significantly less than the cost of a shuttle flight. Besides performing crew rotation to the ISS, commercial crew vehicles may be capable of a wide variety of missions previously accomplished by the shuttle program. Chief among these is in-orbit spacecraft servicing, which was performed to great effect throughout the three decades of shuttle flight operations. This paper examines the requirements for EVA/robotic collaborative servicing in the commercial crew era, chosen from the three vehicles initially in the NASA Commercial Crew competition (Boeing CST100, SpaceX Dragon, and Sierra Nevada Dream Chaser). All these vehicles offer the basic ability to transport crew and some cargo to the target servicing site in LEO, performing rendezvous and proximity operations as part of their basic design requirements. Initial versions of these vehicles lack some of the features that made the shuttle an ideal servicing platform, including large internal and external payload capability (in terms of both size and volume), a grappling manipulator, and EVA support via an airlock and logistics for multiple EVA sessions per flight. For each vehicle under consideration, accommodations were conceptualized and implemented in a solid modeling program to verify dimensions, kinematics, reach envelopes, and other necessary metrics for operational feasibility. Since none of these vehicles are currently equipped with an airlock, options for adding an airlock module were assessed for each system. Similarly, robotic system concepts were developed for each vehicle, based on the constraints of unpressurized cargo capacity for each design. Although three vehicles were originally in contention, this paper focuses primarily on the SpaceX Dragon and the SNC Dream Chaser vehicles. The Boeing CST100 details available to date do not have sufficient detail in the spacecraft’s service/propulsion module to allow assessment of potential volumes for servicing-related systems, and the operational scenarios for the two capsule designs are similar enough to justify focusing on the better-documented Dragon. The Dream Chaser, while not picked for further development under the NASA Commercial Crew program, is an interesting counterpoint to the capsule designs due to the complications of developing EVA and robotic systems concepts compatible with the strict mold line restrictions of a high-lift aerodynamic vehicle. Both vehicles provide adequate, if challenging, volumes for unpressurized cargo. Dragon has the “trunk” adapter behind the entry vehicle, which was designed from the outset for unpressurized storage. While Dream Chaser did not have planned external accommodations, the launch vehicle interface structure (LVIS) provides sufficient volume and attach points for basing robotic systems internal to that structure. While the Dragon trunk provides a significantly larger and more accommodating launch volume for robotic systems, a grappling manipulator would be required to “walk out” of the internal volume of the trunk. The grappling manipulators for both vehicles require additional degrees of freedom to stow in the allotted volume, but unstow to produce a 5-6 m reach capability when deployed. The Dragon version has the additional advantage of direct visibility from the Dragon viewing windows, while Dream Chaser internal control will of necessity be based on video camera feeds. The paper considers various approaches to providing airlocks for each vehicle. Dream Chaser can accommodate an internal airlock, although intrusions into the nominal aft pressurized volume due to external systems and tankage severely limited internal airlock dimensions. A design was also developed for a rigid external airlock, which also served as a mounting location for one or two 5-6 m serving arms. Although there may be options for an internal airlock in Dragon, it was felt to impose too many restrictions on the internal layout, so all airlock options for that vehicle to date were based on an inflatable airlock module.Item Hard Suits/Soft Suits: Revisiting Technologies and Applications for a New Space Era(45th International Conference on Environmental Systems, 2015-07-12) Akin, David L.; Davis, KevinFor three decades, two major types of pressure suits were developed in parallel for potential flight applications. Suits flown through Apollo were “soft suits”, where the pressure garment was exactly that: a multilayer fabric garment that provided wearer motion while retaining atmospheric pressure for life support. Never flown, “hard suits” were rigid metal suits providing body articulation via multiple sealed rotary bearings around the body. This system produced a true constant-volume suit, eliminating the primary source of joint forces driving to a “neutral” position and creating the need for continual application of torque by the wearer. Hard suits were more flexible with lower biomechanical loads on the wearer than soft suits, but had operational implications due to their mass and limited ability to stow in restricted volumes. The shuttle extravehicular mobility unit (EMU) was a “hybrid” design, adopting a rigid upper torso as a convenient mounting point for the portable life support system, helmet, and fabric limb assemblies. This paper does not rehash the competitive aspect of “hard” vs. “soft” suits, but looks at the technologies, capabil- ities, and limitations of each in the context of upcoming space operations focused on planetary exploration. Over the next decades, there are potential requirements for extravehicular activities (EVAs) in various microgravity conditions, including geostationary orbit and at microgravity bodies such as asteroids, comets, or the moons of Mars. There are also potential requirements for extensive EVA exploration tasks on the lunar surface and Mars. The paper examines the requirements for each of these locations and their associated environments, including on human protection from radiation, micrometeoroids and orbital debris, shifting structures on low-gravity bodies, and dust intrusion and fall protection on the moon and Mars. Duration is also a critical issue: missions to Mars could involve surface stay times of up to 15 months, which could translate to hundreds of EVAs per crew in a highly challenging environment. As humans move farther away from Earth for longer durations, without the feasibility of logistics resupply, the need to maintain, repair, and replace suit components will become paramount for crew productivity and safety. Given mission requirements and logistics challenges, the paper examines current and upcoming fabrication tech- nologies to assess their potential impact on EVA systems design and operations. While the access to Earth or shorter duration missions may favor the use of a fabric-based solution, the specialized equipment and high levels of required technical skills make this design difficult to maintain and repair on extended missions. One potential mitigation for this is the use of state-of-the-art fabrication techniques, such as additive manufacturing, in conjunction with wider use of hard-suit components. Recent self-funded research at the University of Maryland has demonstrated the ability to use fused deposition manufacturing to produce components of a four-roll elbow assembly, including a single-build mono- lithic construction of an elbow bearing. The paper examines potential automated fabrication technologies to produce suit replacement components on need, and compares that scenario to the challenge of providing sufficient logistics to ensure adequate spares in all potentially replaceable suit components throughout the extent of an extended-duration surface stay, or in the eventual implementation of a permanently inhabited base on the moon, Mars, or both.Item Pneumatically Power Assisted Extra-Vehicular Activity Glove(45th International Conference on Environmental Systems, 2015-07-12) Pillsbury, Thomas E.; Kothera, Curt s.; Wereley, Norman M.; Akin, David L.The effectiveness of Extra-Vehicular Activity (EVA) systems is paramount for enabling humans to perform successful missions. This is particularly true for space suit pressure garment systems. As the bounds of human space exploration continue to expand, this need will become even more critical as the types of tasks necessary for humans to perform increases, as well. This includes maintenance and repair work on vehicles during long missions to erecting structures and dwellings on extra-terrestrial surfaces. A key to successfully achieving such mission operations is dexterous manipulation, and in terms of the EVA system, this need translates directly to the EVA glove. We are developing an innovative pneumatically powered EVA glove exoskeleton to augment the performance capability of the hand inside the EVA glove. The exoskeleton employs novel, miniature pneumatic artificial muscles to proportionally and controllably augment the finger motion in a natural manner to provide assistance in counteracting the loss of functionality when wearing the EVA glove. The technology exploits the high performance, lightweight, and scalability of Pneumatic Artificial Muscle (PAM) actuators to produce an exoskeleton glove with smaller form factor and higher assistive capability than existing electromechanical concepts. A detailed design study and experimental validation is presented, which evaluates the feasibility of this concept and its operational advantages and challenges.Item Random Access Frame (RAF) System Neutral Buoyancy Evaluations(45th International Conference on Environmental Systems, 2015-07-12) Howe, A. Scott; Polit-Casillas, Raul; Akin, David L.; McBryan, Katherine; Carlsen, ChristopherThe Random Access Frame (RAF) concept is a system for organizing internal layouts of space habitats, vehicles, and outposts. The RAF system is designed as a more efficient improvement over the current International Standard Payload Rack (ISPR) used on the International Space Station (ISS), which was originally designed to allow for swapping and resupply by the Space Shuttle. The RAF system is intended to be applied in variable gravity or microgravity environments. This paper discusses evaluations and results of testing the RAF system in a neutral buoyancy facility simulating low levels of gravity that might be encountered in a deep space environment.Item Suit Simulators for Analog Sites: Lessons Learned from HI-SEAS Testing(45th International Conference on Environmental Systems, 2015-07-12) Swarmer, Tiffany; Akin, David L.; Davis, Kevin P.As the U.S. space program turns to focus on planetary surface exploration, there will be an increasingly important role for extended simulations at analog field sites. Field testing and training date back to the Apollo program, and have been pursued with increasing scope and concerns of fidelity during the past decade. These recent tests have included considerations of exploration for minor bodies, but in the whole have been more applicable to lunar and Mars missions. In simulating extravehicular activities (EVAs), a variety of pressure suit analogs have been adopted in the past, ranging from a full pressure suit to no special garments at all. Simulating an EVA on Mars or, more challenging, the moon realistically in the field on Earth is an effectively impossible task. The “gold standard” would be a pressurized suit, but even without life support equipment, the suited subject weighs substantially more than they would on a mission, massively increasing physiological workload and incurring increased physical risks to the subject. To attempt to improve Earth-based fidelity while supporting field testing, the University of Maryland has developed three successive series of suit simulators using garment design and interstitial padding to represent the bulk and joint limits of a pressure suit without pressurization. This allows the use of a lighter-weight suit, more representative of the on-back weight for a suit system for the moon or Mars, without incurring the training and safety monitoring requirements of a pressurized system. Helmets of these suits are totally enclosed with ventilation fans to provide fresh air to the wearer, simulating the aural environment of a pressurized suit with vent air noise in the helmet. Since the suit garment very effectively insulates the subject, these systems also had to be designed to incorporate a liquid cooling garment and ice reservoir in the backpack assembly. These suits were used in a series of field tests in Arizona in collaboration with Arizona State University, where professional geologists performed field research while in the suits in simulation of lunar or Mars scientific exploration. In the last two years, the UMd suit simulators have become an integral part of operations at the HI-SEAS field site in Hawaii. These tests are isolation studies, requiring the six-person crews to operate without any physical or visual interactions outside of the simulation, and requiring environmental isolation whenever an EVA simulation takes place. To date, two MX-C suit simulators have accumulated over six months of operational use in support of three successive missions. During the HI-SEAS tests, EVA operations are conducted in either MX-C suit simulators or in off-the-shelf hazardous material handling (HAZMAT) suits. The HAZMAT suits are lighter in weight, not overly restrictive of limb motion, and allow unrealistic capabilities such as pulling the arms inside and using a tablet inside the suit. The paper focuses on the lessons learned from EVA simulations performed in the second and third HI-SEAS missions using the MX-C suit simulators. Critical issues with the MX-C suits, including the need for assistance in doffing and donning the suits, and inability for self-rescue in the event of overheating or trauma. Desirable design revisions for the next generation suit simulators based on lessons learned are presented and prioritized.Item The Gravity Kit: A Modular Approach to Affordable Artificial Gravity(2024 International Conference on Environmnetal Systems, 2024-07-21) Akin, David L.One of the greatest unknowns for human space exploration is the effect of lunar or Mars gravity levels on the long-term health of the human body. Given the current lack of detail in human Mars program plans, it is entirely possible that we will commit humans to a Mars mission without any data on the effect of Mars gravity on biological processes, and with minimal long-term experience from lunar exploration. While the obvious solution would be to create a rotating habitat to simulate different gravitation levels for research, the size and concomitant expense of such a system have always made it a non-starter in the program planning process. This paper discusses the concept of a "Gravity Kit" — a modular system similar to an ESPA ring that launches between a payload and the upper stage, and creates artificial gravity through rotation and the use of cables to adjust radius of rotation and rotation rate. In this way, it should be possible to create artificial gravity spacecraft across a variety of scales for investigation of gravitation biology prior to committing humans to extended missions to Mars or beyond. The Gravity Kit module provides necessary utilities which need to be located on the spin axis, including spin thrusters, power generation, communications, and docking fixtures. By using six cables in a Stewart-platform configuration attached to both the payload and the upper stage (used as a counterweight) and providing active control of cable lengths, the system will adjust for motions of the center of gravity in the payload and provide active damping for spin perturbations. Conceptual designs are presented to show the feasibility of the concept at a variety of scales, from a cubesat-based proof of concept to animal facilities to human-scale habitats.