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Three inflatable array antennas recently developed for spacecraft applications are a 3.3m x 1.0m L-band synthetic aperture radar (SAR) array, a 1.0m-diameter X-band telecom reflectarray, and a 3m-diameter Ka-band telecom reflectarray.
One important challenge in implementing inflatable structures technology for future space missions is the development and validation of anlaysis and simulation methodologies. This paper reviews selected topics previously addressed by various researchers in this area.
Inflatable structures have been identified as one of the enabling technologies to achieve low mass, high packaging efficiency, and reliable deployment for future NASA spaceborne synthetic aperture radar (SAR) array antennas.
A description is given of the hardware developed for the In- Space Technology Experiment Program (IN-STEP) flight experiment, which was flown to demonstrate the concept of large inflatable antennas in space.
Piezo induced deformations are proposed as a means of achieving a higher degree of on-orbit surface accuracy of inflatable antennas.
To help guide NASA and industry in the development and certification of crewed softgoods structures, this document details the fundamental testing, data, and documents recommended for the evaluation of a softgoods inflatable designed for crewed occupation in a space environment. This is not a requirements document but supports NASA-imposed standards used for certification. This document is intended to support and guide the development of programmatic requirements to demonstrate a design has followed a systematic and comprehensive design, fabrication, and test program.
The NASA TransHab project was a flight development program of a crewed inflatable habitat designed for in-space use. Through the course of the development, several novel technologies were developed and patented by NASA. One of these patents included information regarding a custom seam stitch that was used in the TransHab restraint layer design. As the patent protection has ended, the details of the custom seam stitch are being disclosed. The seam stitch developed during the TransHab program is known as the ‘tapered diamond stitch’ and includes both a ‘single’ and ‘double’ tapered diamond pattern for ‘end termination’ and ‘continuous’ webbing components respectively. It was designed for 1-in wide Kevlar webbings with load ratings of 6,000 lbf and 12,500 lbf. The stitch pattern was designed to gradually transfer load along the length of the seam using a tapered diamond geometry. The diamond stitch has been shown in tensile testing to provide greater than 85% load strength efficiency, compared to the pristine webbing.
NASA uses woven straps for restraint layers in inflatable structures. This work investigates the use of microwaves to measure low level loading in the woven straps. More specifically, microwaves from a linearly polarized antenna are used to investigate four straps composed of Vectran and Kevlar with ratings of 6,000 lbs and 12,000 lbs of force. The straps are all lightly loaded from 2kg to 10kg in 2kg increments. The spectral centroid (SC) technique has been used for the dimensionality reduction method to evaluate the microwave data. The SC method was used to reduce the data from 10001 points to a single point that corresponds to the amount of load on the strap.
Future NASA exploration plans call for lunar and Martian surface systems that form a base camp of multiple, pressurized elements. These discrete components, including habitats and pressurized rovers, require interoperability to meet the Artemis Accords and standard docking systems to physically connect elements together. A pressurized, articulating crew transfer tunnel can be used between a rover and habitat to enable shirt-sleeve transfer of crew and cargo, saving valuable crew time and resources. While transfer tunnels have been described in the past, this work details the design of a structural softgoods system that has compliant capability through a proposed docking range of motion. The inflatable softgoods design is based on a zero-hoop stress shape, known as a Taylor surface, that is stacked and truncated to form a unique and flexible configuration. Analytical, non-linear models have been developed to examine and predict the behavior of the structure, and material testing was used to determine the properties that were used in the model. Finally, a sub-scale test article was constructed using the baseline design and pressurized testing is in work. Additional full-scale testing is planned for future years to fully demonstrate the capability of the system.
Future NASA exploration plans call for lunar and Martian surface systems that form a base camp of multiple, pressurized elements. These discrete components, including habitats and pressurized rovers, require interoperability to meet the Artemis Accords and standard docking systems to physically connect elements together. A pressurized, articulating crew transfer tunnel can be used between a rover and habitat to enable shirt-sleeve transfer of crew and cargo, saving valuable crew time and resources. While transfer tunnels have been described in the past, this work details the design of a structural softgoods system that has compliant capability through a proposed docking range of motion. The inflatable softgoods design is based on a zero-hoop stress shape, known as a Taylor surface, that is stacked and truncated to form a unique and flexible configuration. Analytical, non-linear models have been developed to examine and predict the behavior of the structure, and material testing was used to determine the properties that were used in the model. Finally, a sub-scale test article was constructed using the baseline design and pressurized testing is in work. Additional full-scale testing is planned for future years to fully demonstrate the capability of the system.
This talk begins with an introduction to the structure and incentives within the recently passed U.S. Inflation Reduction Act (IRA) and moves to resulting LCOE implications.
The Inflation Reduction Act introduced or expanded a suite of federal tax credits for clean electricity generation and customer adoption of electric (and other highly efficient) end-use equipment. These incentives are expected to drive changes in both the electricity generation mix and demand for electricity (especially for space heating and light-duty vehicles), which are highly interconnected. In this session, Caitlin Murphy, Group Manager and Senior Analyst in NREL's Strategic Energy Analysis Center, will present findings from her team's recent state-level analysis on the combined effects of various IRA incentives on customer expenditures for electricity, natural gas, and gasoline. She will present and explain the regional variations observed in their analysis, based on interactions between end-use equipment cost and performance and projections for future energy prices.
A bstract Key to the simplicity of supergravity α -attractor models of inflation are Volkov-Akulov fermions, often in the form of nilpotent superfields. Here we explore the possibility of using the double-copy to construct theories of Dirac-Born-Infeld-Volkov-Akulov (DBIVA) coupled to supergravity. A color-dual bootstrap admits scattering amplitudes involving pions and vectors through five-point tree-level order by order in mass-dimension, but requires the introduction of a Tr( F 3 ) operator. Gauge theories with this operator were recently found to require a tower of higher-derivative operators to be compatible with the duality between color and kinematics. Adjoint-type double-copy construction at its most conservative seems to require the UV completion of DBIVA + pure Poincaré supergravity scattering amplitudes to a family of theories involving DBIVA-like particles coupled to Weyl-Einstein supergravity. We also point out an alternative solution to color-dual gauged pions that allows adjoint double-copy without a tower of higher derivative corrections but at the cost of exchange symmetry between scalars.
Simultaneous shape and topology optimization is used to design pressure-activated inflatable soft robots. The pressure loaded boundary is meshed conformingly and shape optimized, while the morphology of the robot is topology optimized. The design objective is to exert maximum force on an object, i.e. to produce soft “grippers”. The robot’s motion is modeled using nearly incompressible finite deformation hyperelasticity. To ensure stability of the robot, the buckling load factors obtained via linearized buckling analyses are constrained. The finite element method is used to evaluate the optimization cost and constraint functions and the adjoint method is employed to compute their sensitivities. The numerical examples produce pressure-driven soft robots with varying complexity. We also compare our simultaneous optimization results to those obtained via sequential topology and then shape optimization.
Abstract Although episodes of surface uplift and elevated seismicity precede many volcanic eruptions, their temporal evolution is often complex, and apparently in contradiction to simple trends predicted by mechanical deformation models. Here, we use continuous global positioning system and seismic data recorded at Sierra Negra volcano, Galápagos Islands, to show how the edifice responded to stress changes driven by magma accumulation in a shallow sill. The rate of uplift varied during the 13 years and 6.5 m of inflation before the 2018 eruption. The number of earthquakes per unit of uplift increased exponentially with total uplift as the differential stress increased. Accordingly, the temporal seismicity rate varied in time as a function of both the total uplift and the uplift rate. The Gutenberg‐Richter b ‐value decreased as a function of total uplift. In the final six months before the eruption, a sequence of large ( M > 4) earthquakes regulated the state of stress on the fault, each being followed by 2–3 days of postseismic quiescence, and retarding the increase in seismicity rate. These earthquakes did not affect the overall uplift rate. Subsidence of 8.5 m accompanied the 2‐month eruption. On resumption of uplift, the number of earthquakes per unit of uplift was very low, and the b ‐value high, reflecting the relaxed stress state of the fault system. These observations show that crustal deformation becomes increasingly brittle at higher stress states, and supports theoretical models based on elastic‐brittle mechanics. They suggest that joint interpretation of deformation and seismicity is key for forecasting future eruptions in similar volcanic settings.
A significant number of hypervelocity stars with velocities between 1500 − 2500 km s −1 have recently been observed. The only plausible explanation so far is that they were produced through thermonuclear supernovae in white dwarf binaries. Since these stars are thought to be surviving donors of Type Ia supernovae, a surprising finding was that these stars are inflated, with radii an order of magnitude higher than expected for Roche-lobe-filling donors. Recent attempts at explaining them have combined 3D hydrodynamical supernova explosion simulations with 1D stellar modelling to explain the impact of supernova shocks on runaway white dwarfs. However, only the hottest and most compact of those runaway stars can so far marginally be reproduced by detailed models of runaways from supernova explosions. In this and a companion paper, we introduce a new AREPO simulation of two massive CO white dwarfs that explode via a violent merger. During the merger, the primary white dwarf ignites when the secondary is on its last orbit and plunging towards the primary. In the corresponding aftermath, the core of the secondary white dwarf of 0.16 M ⊙ remains bound, moving at a velocity of ∼2800 km s −1 . We mapped this object into MESA and show that this runaway star can explain the observations of two hypervelocity stars that were dubbed D6-1 and D6-3 based on their original discovery motivated by the D6 scenario, though the violent merger scenario presented here is somewhat distinct from the D6 scenario.
We develop a string-inspired model for particle cosmology, based on a flipped SU(5)×U(1) gauge group formulated in a no-scale supergravity framework. The model realizes Starobinsky-like inflation, which we assume to be followed by strong reheating, with the GUT symmetry being broken subsequently by a light ‘flaton’ field whose decay generates a second stage of reheating. We discuss the production of gravitinos and the non-thermal contribution made by their decays to the density of cold dark matter, which is assumed to be provided by the lightest neutralino. We also discuss the masses of light and heavy neutrinos and leptogenesis. As discussed previously, a key rôle is played by a superpotential coupling between the inflaton, matter and GUT Higgs fields, called λ 6 . We scan over possible values of λ 6 , exploring the correlations between the possible values of observables. We emphasize that the release of entropy during the GUT transition allows large regions of supersymmetry-breaking parameter space that would otherwise lead to severe overdensity of dark matter. Furthermore, we find that the Big Bang nucleosynthesis lower limit on the reheating temperature of ~ 1 MeV restricts the supersymmetry-breaking scale to a range O(10) TeV that is consistent with the absence of supersymmetric particles at the LHC.
We calculate the curvature power spectrum sourced by spectator fields that are excited repeatedly and non-adiabatically during inflation. In the absence of detailed information of the nature of spectator field interactions, we consider an ensemble of models with intervals between the repeated interactions and interaction strengths drawn from simple probabilistic distributions. We show that the curvature power spectra of each member of the ensemble shows rich structure with many features, and there is a large variability between different realizations of the same ensemble. Such features can be probed by the cosmic microwave background (CMB) and large scale structure observations. They can also have implications for primordial black hole formation and CMB spectral distortions. The geometric random walk behavior of the spectator field allows us to calculate the ensembleaveraged power spectrum of curvature perturbations semi-analytically. For sufficiently large stochastic sourcing, the ensemble averaged power spectrum shows a scale dependence arising from the time spent by modes outside the horizon during the period of particle production, in spite of there being no preferred scale in the underlying model. We find that the magnitude of the ensemble-averaged power spectrum overestimates the typical power spectra in the ensemble because the ensemble distribution of the power spectra is highly non-Gaussian with fat tails.