Starshade Technology Development: Deployment Accuracy & Thermoelastic Stability of Key Structures
No abstract provided
Willems, Phil↗
Engineering topics
Webb, David
Publications and source records attributed to Webb, David.
Origami-Inspired Optical Shield for a Starshade Inner Disk Testbed: Design, Fabrication, and Analysis
In 2019, a 10 m-diameter starshade inner disk test article was assembled; this test article demonstrated deployment accuracy sufficient for starshade mission concepts. Here, we describe the design, fabrication, and computational structural analysis of a key inner disk component realized for this effort: the origami-folded optical shield. The optical shield is a 10 m-diameter lightweight cover that makes the inner disk opaque. It stows within a 2.3 m-diameter volume by using an origami-inspired wrapping pattern, and is deployed passively by the inner disk perimeter truss. The fold pattern was generated by a custom algorithm based one existing generative design approaches. This prototype demonstrated critical functions: stowage in a compact volume, static equilibrium when stowed and deployed, and low strain when stowed. Four separate computational structural analysis models of the optical shield were de- veloped, at varying levels of fidelity and using a variety of software solutions: Abaqus, RAPID, and ADAMS. These models were intended to pathfind approaches for modeling the stowage and deployment of the inner disk, and to demonstrate that the optical shield is amenable existing structural modeling approaches. These models were found to adequately capture pertinent stowage and deployment behavior of the optical shield prototype.
Hoffman, Laura↗
Origami Inspired Optical Shield for a Starshade Inner DiskTestbed: Design, Fabrication, and Analysis
No abstract provided
Hoffman, Laura↗
Demonstration of Deployment Accuracy of the Starshade Inner Disk Subsystem
We present experimental results that demonstrate the required in-plane deployment accuracy of the starshade Inner Disk Subsystem (IDS). This effort was to address Milestone 7C of the Starshade Technology Activity S5, which requires that the in-plane deployment accuracy of the petal interfaces on the IDS be within +/-300um. A full-scale 10m-diameter IDS prototype was constructed. This prototype comprised a medium-fidelity perimeter truss, medium-fidelity spokes, and a low-fidelity optical shield (OS). The testbed also included gravity compensation systems and a laser tracker metrology system. The post-processed measurement uncertainties of the laser tracker were less than 30um at the 3 sigma level. Design, engineering and fabrication of these components was done by JPL, Tendeg, and Roccor. Testing was performed at the Tendeg facility in Louisville, Colorado. The IDS prototype was deployed 22 times and the locations of petal interfaces on the IDS were measured after each deployment. Based on this data, tolerance intervals were calculated that would contain 99.73% of future deployment accuracy errors with 90% confidence. These tolerance intervals are conservative estimates for 3 sigma bounds. The tolerance intervals for the three pertinent error components were found to be within the required allocations, with at least 19% margin.
Turse, Dana↗
Starshade Rendezvous Probe
The Starshade Rendezvous Probe Mission (https://smd-prod.s3.amazonaws.com/science-red/s3fs-public/atoms/files/Starshade2.pdf ) [1] will be the first space-based, high-contrast imaging mission with the potential to detect and characterize Earth-like planets in the habitable zone (HZ) around sunlike stars while at the same time exploring entire planetary systems about our nearest neighbors. Over the last two decades, astronomers have discovered and cataloged thousands of planets around other stars. Nevertheless, we have yet to find a planetary system like our own or to characterize discovered small planets to determine if they are similar to Earth. The next step in exploration is to image full planetary systems, including their HZs, and to obtain planetary spectra with enough sensitivity to determine if a planet is Earth-like. A space-based direct imaging mission to ultimately find and characterize other Earth-like planets is a long-term priority for space astrophysics [2, 3].
Seager, Sara↗
Development of Low-Scatter Optical Edges for Starshades
Starshades, combined with future space telescopes, provide the ability to detect Earth-like exoplanets in the habitable zone by producing high contrast ratios at small inner working angles. The primary function of a starshade is to suppress light from a target star such that its orbiting planets are revealed. In order to do so, the optical edges of the starshade must maintain their precise in-plane profile to produce the necessary apodization function. However, an equally important consideration is the interaction of these edges with light emanating from our own Sun as scattered and/or diffracted sunlight can significantly degrade the achievable contrast. This paper describes the technical efforts performed to obtain precision, low-scatter optical edges for future starshades. Trades between edge radius (i.e. sharpness) and surface reflectivity have been made and small-scale coupons have been produced using scalable manufacturing processes. A custom scattered light testbed has been developed to quantify the magnitude of scattered light over all sun angles. Models have also been developed to make predictions on the level of reflected and/or diffracted light for various edge architectures. The results of these studies have established a current baseline approach which implements photochemical etching techniques on thin metal foils.
Bradley, Christine↗
Advances in Starshade Technology Readiness for an Exoplanet Characterizing Science Mission in the 2020's
The discovery of thousands of exoplanets is generating increasing interest in the direct imaging and characterization of these planets. Starshade, and eternal occulter, could fly in formation between a telescope and distant star, blocking out the light from the star, and enabling us to focus on the light of any orbiting planets. Recent technology developments in coordination with system design, has added much needed detail to define the technology requirements for a science mission that could launch in the 2020's. This paper address the mechanical architecture, the successful efforts to date, the current state of design for the mechanical system, and upcoming technology efforts.
occulter↗
Precision Optical Edges for a Starshade External Occulter
The use of a starshade is one technique to perform high contrast imaging with space-based telescopes. The primary function of a starshade is to suppress light from a target star in order to image its orbiting planets. In order to provide the proper apodization function the edges of the starshade must follow a precise in-plane profile. However of equal importance is the issue of light from our own sun scattering off of the edges and entering the telescope. A method to alleviate this problem is to make the edges extremely sharp (< 1 µmterminal radius) such that the area available for scattering is minimized. The combination of these two requirements, along with the need to integrate the edges into a 30-40 m dia. deployable structure, present a number of significant engineering challenges. Substrate etching techniques are used to obtain both the intended profile as well as the edge sharpness. Current efforts implement an isotropic etching process on thin metal substrates. This paper discusses the progress towards producing a sharp optical edge at the coupon level. Samples have been characterized using scanning electron microscopy as well as a custom testbed to assess their scattered-light performance.
starshade↗
The effect of environmental initiatives on NASA specifications and standards activities
The NASA Operational Environment Team (NOET) has conducted a survey of NASA centers specifications and standards that require the use of Ozone Depleting Substances (ODS's) (Chlorofluorocarbons (CFCs), Halons, and chlorinated solvents). The results of this survey are presented here, along with a pathfinder approach utilized at Marshall Space Flight Center (MSFC) to eliminate the use of ODS's in targeted specifications and standards. Presented here are the lessons learned from a pathfinder effort to replace CFC-113 in a significant MSFC specification for cleaning and cleanliness verification methods for oxygen, fuel and pneumatic service, including Shuttle propulsion elements.
Griffin, Dennis↗