NASA's Centennial Challenge for 3D-Printed Habitat: Phase II Outcomes and Phase III Competition Overview

The 3D-Printed Habitat Challenge is part of NASA's Centennial Challenges Program. NASA's Centennial Challenges seek to accelerate innovation in aerospace technology development through public competitions. The 3D-Printed Habitat Challenge, launched in 2015, is part of the Centennial Challenges portfolio and focuses on habitat design and development of large-scale additive construction systems capable of fabricating structures from in situ materials and/or mission recyclables. The challenge is a partnership between NASA, Caterpillar (primary sponsor), Bechtel, Brick and Mortar Ventures, and Bradley University. Phase I of the challenge was an architectural concept competition in which participants generated conceptual renderings of habitats on Mars which could be constructed using locally available resources. Phase II asked teams to develop the printing systems and material formulations needed to translate these designs into reality. Work under the phase II competition, which concluded in August 2017 with a head to head competition at Caterpillar's Edward Demonstration Facility in Peoria, Illinois, is discussed, including the key technology development outcomes resulting from this portion of the competition. The phase III competition consists of both virtual and construction subcompetitions. Virtual construction asks teams to render high fidelity architectural models of a habitat and all the accompanying information required for construction of the pressure retaining and load bearing portions of the structure. In construction phase III, teams are asked to scale up their printing systems to produce a 1/3 scale habitat on-site at Caterpillar. The levels of the phase III construction competition (which include printing of a foundation and printing and hydrostatic testing of a habitat element) are discussed. Phase III construction also has an increased focus on autonomy, as these systems are envisioned for robotic precursor missions which would buildup infrastructure prior to the arrival of crew. Results of the phase III competition through July 2017 (which includes virtual construction level 1) are discussed. This Centennial Challenge enables an assessment of the scaleability and efficacy of various processes, material systems, and designs for planetary construction. There are also near-term terrestrial applications, from disaster response to affordable housing and infrastructure refurbishment, for these technologies

Cytoskeletal Changes During Adhesion and Release: A Comparison of Human and Nonhuman Primate Platelets

The organization of cytoskeletal proteins in whole-mount adherent platelets from African green monkeys and normal human volunteers has been studied by SEM, high vacuum electron microscopy (HVEM) and conventional (120 kV) electron microscopy. We describe three distinct organizational zones, the Central Matrix, the Trabecular Zone and the Peripheral Web in spread platelets from both sources. The Central Matrix is an ill-defined superstructure of 80-100 Å filaments of short length which enshrouded the granules, dense bodies, mitochondria and elements of the open-channel and dense-tubular systems. The latter, identified through the use of peroxidase cytochemistry with the whole mounts, is an anastomosing network of elongate saccules having diameters of 600-1200 Å. The Trabecular Zone, which encircles the Central Matrix, contains 165, 80-100 and 30-50 Å filaments in an open lattice of irregular lattice spacing. The outermost region of the cells, the Peripheral Web, is comprised of 70 Å filaments organized in a honeycomb lattice with center to center spacing in the range 150-300 Å. This pattern for the spread cells is not consistently observed in cells during the early stages of adhesion; therefore, correlations of SEM and TEM observations are made for the various stages of adhesion/activation

Neoclassical tearing modes in DIII-D and calculations of the stabilizing effects of localized electron cyclotron current drive

Neoclassical tearing modes are found to limit the achievable beta in many high performance discharges in DIII-D. Electron cyclotron current drive within the magnetic islands formed as the tearing mode grows has been proposed as a means of stabilizing these modes or reducing their amplitude, thereby increasing the beta limit by a factor around 1.5. Some experimental success has been obtained previously on Asdex-U. Here the authors examine the parameter range in DIII-C in which this effect can best be studied

Study of UV Degradation on Plastic (PET) Aerosols

The present study was aimed to explore the impact of UV radiation, from ‘real world’ environmental exposure, on the degradation of plastic PET aerosol containers. Additionally, the intent was to correlate the ‘real world’ environmental exposure to artificial sunlight, using a Xenon-Arc lamp, to develop a simulated test. The standardized methodology could then be used to evaluate the integrity of the plastic aerosol container and product, without the complexity of using ‘real world’ exposure. Through this study, a lab method was developed and validated that would simulate the effect of UV radiation using the Xenon-Arc. Moreover, a correlation was made for conditions inside the Xenon-Arc chamber that were conducive to testing a plastic pressurized container

Summary Report on Phase I Results from the 3D Printing in Zero G Technology Demonstration Mission, Volume I

Human space exploration to date has been confined to low-Earth orbit and the Moon. The International Space Station (ISS) provides a unique opportunity for researchers to prove out the technologies that will enable humans to safely live and work in space for longer periods of time and venture beyond the Earth/Moon system. The ability to manufacture parts in-space rather than launch them from Earth represents a fundamental shift in the current risk and logistics paradigm for human spaceflight. In September 2014, NASA, in partnership with Made In Space, Inc., launched the 3D Printing in Zero-G technology demonstration mission to explore the potential of additive manufacturing for in-space applications and demonstrate the capability to manufacture parts and tools on orbit using fused deposition modeling. This Technical Publication summarizes the results of testing to date of the ground control and flight prints from the first phase of this ISS payload

Observation of discrete, vortex light bullets

We report the first experimental observation of vortex light bullets that are discrete, spatiotemporal, solitary waves with orbital angular momentum. We analyze conditions for their existence and investigate their rich properties and dynamics. Vortex light bullets are excited in fiber arrays with spatially shaped femtosecond pulses and analyzed with a spatiotemporal cross correlator. Most importantly, we find that they have entirely new stability properties, being robust against considerable degrees of perturbation in a limited range of energies. All experimental findings are backed up by rigorous simulations, giving further insight into the rich dynamics of vortex light bullets

The DIII-D 3 MW, 110 GHz ECH System

Three 110 GHz gyrotrons with nominal output power of 1 MW each have been installed and are operational on the DIII-D tokamak. One gyrotron is built by Gycom and has a nominal rating of 1 MW and a 2 s pulse length, with the pulse length being determined by the maximum temperature allowed on the edge cooled Boron Nitride window. The second and third gyrotrons were built by Communications and Power Industries (CPI). The first CPI gyrotron uses a double disc FC-75 cooled sapphire window which has a pulse length rating of 0.8 s at 1 MW, 2s at 0.5 MW and 10s at 0.35 MW. The second CPI gyrotron, utilizes a single disc chemical-vapor-deposition diamond window, that employs water cooling around the edge of the disc. Calculation predict that the diamond window should be capable of full 1 MW cw operation. All gyrotrons are connected to the tokamak by a low-loss-windowless evacuated transmission line using circular corrugated waveguide for propagation in the HEl 1 mode. Each waveguide system incorporates a two mirror launcher which can steer the rf beam poloidally from the center to the outer edge of the plasma. Central current drive experiments with the two gyrotrons with 1.5 MW of injected power drove about 0.17 MA. Results from using the three gyrotron systems will be reported as well as the plans to upgrade the system to 6 MW

THE 110 GHz MICROWAVE HEATING SYSTEM ON THE DIII-D TOKAMAK

OAK-B135 Six 110 GHz gyrotrons in the 1 MW class are operational on DIII-D. Source power is > 4.0 MW for pulse lengths {le} 2.1 s and {approx} 2.8 MW for 5.0 s. The rf beams can be steered poloidally across the tokamak upper half plane at off-perpendicular injection angles in the toroidal direction up to {+-} 20{sup o}. measured transmission line loss is about -1 dB for the longest line, which is 92 m long with 11 miter bends. Coupling efficiency into the waveguide is {approx} 93% for the Gaussian rf beams. The transmission lines are evacuated and windowless except for the gyrotron output window and include flexible control of the elliptical polarization of the injected rf beam with remote controlled grooved mirrors in two of the miter bends on each line. The injected power can be modulated according to a predetermined program or controlled by the DIII-D plasma control system using real time feedback based on diagnostic signals obtained during the plasma pulse. Three gyrotrons have operated at 1.0 MW output power for 5.0 s. Peak central temperatures of the artificially grown diamond gyrotron output windows are < 180 C at equilibrium