As NASA exploration moves beyond earth's orbit, the need exists for long duration space systems that are resilient to events that compromise safety and performance. Fortunately, technology advances in autonomy, robotic manipulators, and modular plug-and-play architectures over the past two decades have made in-space vehicle assembly and servicing possible at acceptable cost and risk. This study evaluates future space systems needed to support scientific observatories and human/robotic Mars exploration to assess key structural design considerations. The impact of in-space assembly is discussed to identify gaps in structural technology and opportunities for new vehicle designs to support NASA's future long duration missions.

/pdf/in-space-structural-assembly-applications-and-technology-1qsuvkk38x.pdf

In-Space Structural Assembly: Applications and Technology

Laser surface nanostructuring for reliable Si3N4/Si3N4 and Si3N4/Invar joined components

The James Webb Space Telescope (JWST) is a large, infrared-optimized space telescope consisting of the following elements: (1) Optical telescope element (OTE) (2) Integrated science instrument module (ISIM) (3) Spacecraft (4) Sunshield The Integrated Science Instrument Module (ISIM) consists of the JWST science instruments (NIRCam, MIRI, NIRSpec), a fine guidance sensor (FGS), the ISIM Structure, and thermal and electrical subsystems. JWST's instruments are designed to work primarily in the infrared range of the electromagnetic spectrum, and the instruments and telescope operate at cryogenic temperatures (approximately 35 K for the instruments). The development and validation of a thermal distortion modeling and analysis capability for the JWST ISIM Structure was successfully completed. The modeling and analysis approach was grounded in initial constituent materials testing and benchmarked to test results at the composite bonded joint, subassembly, and fullscale flight hardware levels. Comparison of analysis predictions and test results from this series of incremental cryogenic thermal distortion tests demonstrates that the model validation goals are achieved.

/pdf/an-overview-of-thermal-distortion-modeling-analysis-and-4db9y7ckv1.pdf

An Overview of Thermal Distortion Modeling, Analysis, and Model Validation for the JWST ISIM Structure

The paper presents a semi-analytical model aiming to study the thermomechanical behavior of the insulation/metallic shell assembly of cryogenic reservoirs during the fueling step. The proposed model is applied to explore the influences of material properties and insulation dimensions on the stress distributions, and the ranges of applicability of the classical design formula. The present parametric study shows that the Poisson’s ratio strains have significant effects on stress fields in the insulation. The through-thickness shear deformation in the insulation must be taken into account for avoiding erroneous failure prediction. The maximum normal and shear stresses occur respectively at the center and close to free borders of the insulating panel. The failure of the assembly will occur in the insulating foam component or at least at the foam/adhesive interface due to the higher stiffness and strength of cryogenic adhesive layer than the foam. In addition, the adhesive layer can be neglected in the modeling by assuming the insulation putted in direct contact with the metallic shell. The applicability ranges of classical simple formula often used to dimension reservoir insulation are summarized in Table 2 . When one of these conditions is not fulfilled, the proposed semi-analytical or more complex approaches should be used.

On the thermomechanical behavior of two-dimensional foam/metal joints with shear-deformable adherends - Parametric study

/pdf/axisymmetric-finite-element-modeling-for-the-design-and-17ozubrz7w.pdf

Axisymmetric finite element modeling for the design and analysis of cylindrical adhesive joints based on dimensional stability

A major design and analysis challenge for the JWST ISIM structure is thermal survivability of metal/composite adhesively bonded joints at the cryogenic temperature of 30K (-405°F). Current bonded joint concepts include internal invar plug fittings, external saddle titanium/invar fittings and composite gusset/clip joints all bonded to hybrid composite tubes (75mm square) made with M55J/954-6 and T300/954-6 prepregs. Analytical experience and design work done on metal/composite bonded joints at temperatures below that of liquid nitrogen are limited and important analysis tools, material properties, and failure criteria for composites at cryogenic temperatures are sparse in the literature. Increasing this challenge is the difficulty in testing for these required tools and properties at cryogenic temperatures. To gain confidence in analyzing and designing the ISIM joints, a comprehensive joint development test program has been planned and is currently running. The test program is designed to produce required analytical tools and develop a composite failure criterion for bonded joint strengths at cryogenic temperatures. Finite element analysis is used to design simple test coupons that simulate anticipated stress states in the flight joints; subsequently, the test results are used to correlate the analysis technique for the final design of the bonded joints. In this work, we present an overview of the analysis and test methodology, current results, and working joint designs based on developed techniques and properties.

/pdf/design-analysis-of-the-jwst-isim-bonded-joints-for-46j2hw14q1.pdf

Design/analysis of the JWST ISIM bonded joints for survivability at cryogenic temperatures

- The Double Asteroid Redirection Test (DART) mission is NASA's first planetary defense mission to demonstrate the viability of kinetically impacting an asteroid and deflecting its trajectory. The DART spacecraft successfully launched on November 24, 2021 from the Vandenberg Space Force Base and successfully made impact on Dimorphos, the smaller asteroid in the Didymos system, on September 26, 2022. The DART spacecraft has one instrument called Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO). DRACO is an imaging telescope that, in conjunction with the SMART Navigation algorithm, autonomously guided the DART spacecraft to the asteroid. Because DRACO is a mission critical and light sensitive instrument, the DRACO Door mechanism was designed as the protective cover. The door functions to shield DRACO from stray light during launch, to deploy in space once when commanded, and to stay 180 degrees open for the duration of the mission. The DRACO Door went through several iterations during the design phase with decisions on various components such as Frangibolts ®, torsion springs, hardstops, and latches. After fabrication and assembly, the door went through a rigorous environmental testing plan, which included deployment testing, vibration testing, and thermal vacuum testing. After successful qualification of the mechanism, the door was installed and integrated into the DART spacecraft. It should be noted that during the fabrication of the mechanism piece-parts, the COVID-19 pandemic began, and the effects of the pandemic were seen in the challenges faced during the DRACO door assembly and testing. Under the constraints of the pandemic, the DART spacecraft was successfully built, tested, and launched, and the DRACO door was successfully deployed on December 7, 2021. The door has continued to function as intended. This paper will discuss the design choices behind the door components, the environmental qualification test program, and the installation of the door onto the DART spacecraft. In addition, this paper will discuss the lessons learned and the challenges of fabricating and testing the flight hardware.

The DRACO Door: Design, Test, and Integration of the Mechanism on the DART Spacecraft

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Design/analysis of the JWST ISIM bonded joints for survivability at cryogenic temperatures

The DRACO Door: Design, Test, and Integration of the Mechanism on the DART Spacecraft