Multilayer Insulation Blankets Research Articles

Extendable origami multilayer insulation thermal characterization

Spacecraft commonly use multilayer insulation (MLI) for passive thermal control, however deployable structures such as telescoping booms impose the need to stow MLI preflight and extend with the structure for in flight operation. This paper investigates an octagonal origami folding pattern that allows predictable stowage and extension of multilayer insulation. Feasibility was demonstrated to fold, compress and extend a MLI blanket comprising 10 layers of aluminized Kapton, each separated by a layer of scrim cloth. Both folded and unfolded 10-layer MLI blankets were tested in thermal vacuum to characterize heat leak of deployed configurations. The 10-layer origami folded configuration increased thermal conductance and radiative heat transport relative to the unfolded configuration. Degradation factors for heat transport were empirically found to be Mk=2.5±0.3 and Me=1.3±0.2 for effective thermal conductance and emittance, respectively.

Addressing the Orbital Debris Threat Directionality for Enhanced Protection of Low-Earth-Orbit Robotic Spacecraft

This study conducts a detailed investigation into addressing the directionality of micrometeoroid and orbital debris (MMOD) threats, emphasizing the strategic placement of protective resources on a spacecraft. The research considers the conversion of the structural sandwich panel and the multilayer thermal blanket into multifunctional elements that provide MMOD protection without causing substantial weight gain or affecting operational parameters. The effectiveness of the reconfigured components, such as the foam core sandwich panel and multilayer insulation blanket toughened by Nextel fabrics, is evaluated using developed and validated numerical models and experimental methods. Their performance is demonstrated by meeting the protection needs of the Canadian robotic Radarsat Constellation Mission spacecraft.

Predicting high‐speed particle impact damage in spacecraft thermal protection systems

All spacecraft use some sort of thermal insulation, or thermal protection system (TPS), in their design. TPS materials vary, ranging from ceramic tiles or phenolic ablators for heatshields to lightweight multi-layer insulation (MLI) blankets. Since TPS is usually placed on the spacecraft's exterior, it is susceptible to impacts by meteoroids and orbital debris. These high-speed impacts can damage the TPS to a point where the protection it offers is below acceptable limits. As such, it is important to be able to characterize expected TPS damage levels stemming from such high-speed impacts. In this paper, we present the results of a study that sought to characterize the high-speed impact damage that would be sustained by two TPS materials that have recently gained attention for possible use in future interplanetary missions. Empirical equations were developed for TPS crater depths, as well as maximum and minimum crater mouth dimensions. In the event of TPS perforations, empirical equations were developed for the maximum and minimum through-hole dimensions. As part of the analyses performed, ballistic limit equations (BLEs) for these TPS configurations were also developed where possible. The validity of the equations developed was assessed by comparing their predictions against test data. In nearly all cases, the empirical equations developed herein were seen to adequately capture the magnitudes of the measured damage parameters.

Augmenting foam-core sandwich panel with toughened blanket for enhanced orbital debris protection

Experimental and numerical analyses have demonstrated that foam-core sandwich panels (FCSP) can serve as a practical substitute for conventional sandwich structures, offering both structural support and effective protection against micrometeoroid and orbital debris (MMOD) in space applications. This research aims to enhance further the MMOD protection level beyond the inherent capability of FCSP by augmenting the panel with the toughened thermal blanket. The study employs a numerical simulation approach validated with physical test data and investigates the effect of integrating Nextel fabrics into multilayer insulation blankets on the overall shielding performance of the system.

Fiber Bragg Grating Sensor Networks Enhance the In Situ Real-Time Monitoring Capabilities of MLI Thermal Blankets for Space Applications.

The utilization of Fiber Bragg Grating (FBG) sensors in innovative optical sensor networks has displayed remarkable potential in providing precise and dependable thermal measurements in hostile environments on Earth. Multi-Layer Insulation (MLI) blankets serve as critical components of spacecraft and are employed to regulate the temperature of sensitive components by reflecting or absorbing thermal radiation. To enable accurate and continuous monitoring of temperature along the length of the insulative barrier without compromising its flexibility and low weight, FBG sensors can be embedded within the thermal blanket, thereby enabling distributed temperature sensing. This capability can aid in optimizing the thermal regulation of the spacecraft and ensuring the reliable and safe operation of vital components. Furthermore, FBG sensors offer sev eral advantages over traditional temperature sensors, including high sensitivity, immunity to electromagnetic interference, and the ability to operate in harsh environments. These properties make FBG sensors an excellent option for thermal blankets in space applications, where precise temperature regulation is crucial for mission success. Nevertheless, the calibration of temperature sensors in vacuum conditions poses a significant challenge due to the lack of an appropriate calibration reference. Therefore, this paper aimed to investigate innovative solutions for calibrating temperature sensors in vacuum conditions. The proposed solutions have the potential to enhance the accuracy and reliability of temperature measurements in space applications, which can enable engineers to develop more resilient and dependable spacecraft systems.

Surface Modification of Space Exposed Materials Induced by Low Energetic Proton Irradiation

The aim of this paper is to verify if commonly occurring space debris materials change their reflectivity and morphology after being exposed to low energy protons. Therefore, a set of six different materials frequently used in spacecraft engineering was irradiated with low energy (100 keV) protons to simulate the aging of their surfaces due to space radiation in low Earth orbit (LEO). A microscopic and spectroscopic analysis of the irradiated samples reveals that the tested materials containing organic polymers (Polytetrafluoroethylene (PTFE) and carbon fiber reinforced plastic (CFRP)) show changes in surface morphology. Metallic surfaces did not show surface modifications but we found changes in the reflectivity of coated polyimide sheets, like used in Multi Layer Insulation blankets, during and after proton irradiation. Our results show that space materials exhibit significant changes after irradiation equivalent to the dose accumulated after 100 years in LEO. This knowledge is highly relevant for the interpretation of optical data related to the observation of space debris as well as to studies about laser-matter interaction for laser-based debris removal.

Extendable Origami Multilayer Insulation Design and Thermal Performance Characterization

Spacecraft commonly use multilayer insulation (MLI) on fixed panels and bodies to assist with thermal management of the system. This paper describes the design of an origami pattern that allows MLI to be used on deployable structures, specifically telescoping booms. Origami patterns have well-defined fold lines that provide predictable compression and extension of the MLI, which allows for high compression ratios from the deployed to the extended state with predictable thermal performance. Two four-layer MLI blankets were tested in thermal vacuum, one in its original unfolded state and the other folded using an octagonal origami pattern to characterize heat leak. The origami folds decreased thermal conductance and increased radiative heat transport through the MLI blanket with degradation factors empirically found to be and , for the effective thermal conductance and emittance, respectively.

Implementation of a Cryogenic Facility for Space Debris Analysis

This paper has resulted from a continued study of spacecraft material degradation and space debris formation. The design and implementation of a thermal vacuum cycling cryogenic facility for the evaluation of space debris generation at a low Earth orbit (LEO) is presented. The facility used for spacecraft external material evaluation is described, and some of the obtained results are presented. The infrastructure was developed in the framework of a study for the European Space Agency (ESA). The main purpose of the cryogenic facility is to simulate the LEO spacecraft environment, namely thermal cycling and vacuum ultraviolet (VUV) irradiation to simulate the spacecraft material degradation and the generation of space debris. In a previous work, some results under LEO test conditions showed the effectiveness of the cryogenic facility for material evaluation, namely: the degradation of satellite paints with a change in their thermo-optical properties, leading to the emission of cover flakes; the degradation of the pressure-sensitive adhesive (PSA) used to glue Velcro’s to the spacecraft, and to glue multilayer insulation (MLI) to the spacecraft’s. The paint flakes generated are space debris. Hence, in a scenario of space missions where a spacecraft has lost the thermal shielding capability, the failure of PSA tape and the loss of Velcro properties may contribute to the release of the full MLI blanket, contributing to the generation of space debris that presents a growing threat to space missions in the main Earth orbits.

Experimental and numerical analyses of thermal performance of a thin-film multi-layer insulation for satellite application

Multi-layer insulation (MLI) blankets are one of the main components of satellite thermal control system. The past studies have considered infinite heat transfer coefficient in modeling the MLI shields due to the use of reflective thin films such as aluminized Kapton (Polyimide Film Developed by DuPont Company) or aluminized PET (Polyethylene Terephthalate) in MLI shields. Therefore, equal temperature was considered on two sides of a shield and the effect of thermal resistance has been ignored in the total thermal resistance. In the present study, the effects of thermal conductivity of thin film and shield thickness are analyzed. For this purpose, numerical analyses are performed on three types of blankets that are made of Kapton, PET and null shields. The results indicate that the difference in effective emittance of Kapton and PET blanket is 17% to 2% from the thinnest film to the thickest film, respectively. In order to confirm the numerical results, the effective emittance of two types of MLI blankets made of Kapton and PET films is measured under identical conditions. It is concluded that the Kapton blanket has lower effective emittance than PET.

Development of a new MLI for orbital cryogenic propulsion systems -thermal performance under one atmosphere to a vacuum

The efficient storage of cryogenic propellants is among the key technologies for long-duration space exploration missions. For the orbital transfer vehicle, the required thermal insulation performance is more than ten times higher than that of conventional spray-on foam insulation. Conventional multi-layer insulation blankets are used as excellent insulation for spacecraft in the vacuum environment, but are not usable in the atmospheric environment. A new type of insulation-a load-bearing, non-interlayer-contact spacer MLI (LB-NICS MLI)-has been developed. The insulation performance in both air and vacuum environments is measured with a boil-off calorimeter. According to the test results, LB-NICS MLI is about 3 times superior under 1 atmosphere and 13 times superior under a vacuum, compared to foam insulation.

Enhanced RF Behavior Multi-Layer Thermal Insulation

This paper shows that it is possible to exploit the modulated metasurface concept to control the unwanted coupling between antennas that are installed on the same satellite. The metasurface is combined with a Multi-Layer thermal Insulation blanket to reduce its specular reflection by spreading the energy incoherently in the surrounding space. In the design, sub-wavelength radiating elements printed on thin substrate have been used to make the metasurface response azimuthally independent, and to keep the weight of blanket down. The comparison between simulations and measurements confirms the validity of the idea.

Repeatability of Cryogenic Multilayer Insulation

Due to the variety of requirements across aerospace platforms, and one off projects, the repeatability of cryogenic multilayer insulation (MLI) has never been fully established. The objective of this test program is to provide a more basic understanding of the thermal performance repeatability of MLI systems that are applicable to large scale tanks. There are several different types of repeatability that can be accounted for: these include repeatability between identical blankets, repeatability of installation of the same blanket, and repeatability of a test apparatus. The focus of the work in this report is on the first two types of repeatability. Statistically, repeatability can mean many different things. In simplest form, it refers to the range of performance that a population exhibits and the average of the population. However, as more and more identical components are made (i.e. the population of concern grows), the simple range morphs into a standard deviation from an average performance. Initial repeatability testing on MLI blankets has been completed at Florida State University. Repeatability of five Glenn Research Center (GRC) provided coupons with 25 layers was shown to be +/- 8.4% whereas repeatability of repeatedly installing a single coupon was shown to be +/- 8.0%. A second group of 10 coupons has been fabricated by Yetispace and tested by Florida State University, the repeatability between coupons has been shown to be +/- 15-25%. Based on detailed statistical analysis, the data has been shown to be statistically significant.

Heat Loads Due To Small Penetrations In Multilayer Insulation Blankets

The main penetrations (supports and piping) through multilayer insulation systems for cryogenic tanks have been previously addressed by heat flow measurements. Smaller penetrations due to fasteners and attachments are now experimentally investigated. The use of small pins or plastic garment tag fasteners to ease the handling and construction of multilayer insulation (MLI) blankets goes back many years. While it has long been understood that penetrations and other discontinuities degrade the performance of the MLI blanket, quantification of this degradation has generally been lumped into gross performance multipliers (often called degradation factors or scale factors). Small penetrations contribute both solid conduction and radiation heat transfer paths through the blanket. The conduction is down the stem of the structural element itself while the radiation is through the hole formed during installation of the pin or fastener. Analytical models were developed in conjunction with MLI perforation theory and Fourier’s Law. Results of the analytical models are compared to experimental testing performed on a 10 layer MLI blanket with approximately 50 small plastic pins penetrating the test specimen. The pins were installed at ∼76-mm spacing inches in both directions to minimize the compounding of thermal effects due to localized compression or lateral heat transfer. The testing was performed using a liquid nitrogen boil-off calorimeter (Cryostat-100) with the standard boundary temperatures of 293 K and 78 K. Results show that the added radiation through the holes is much more significant than the conduction down the fastener. The results are shown to be in agreement with radiation theory for perforated films.

Numerical modeling of self-pressurization and pressure control by a thermodynamic vent system in a cryogenic tank

This paper presents a numerical model of a system-level test bed—the multipurpose hydrogen test bed (MHTB) using the Generalized Fluid System Simulation Program (GFSSP). MHTB is representative in size and shape of a space transportation vehicle liquid hydrogen propellant tank, and ground-based testing was performed at NASA Marshall Space Flight Center (MSFC) to generate data for cryogenic storage. GFSSP is a finite volume-based network flow analysis software developed at MSFC and used for thermofluid analysis of propulsion systems. GFSSP has been used to model the self-pressurization and ullage pressure control by the Thermodynamic Vent System (TVS). A TVS typically includes a Joule–Thompson (J–T) expansion device, a two-phase heat exchanger (HEX), and a mixing pump and liquid injector to extract thermal energy from the tank without significant loss of liquid propellant. For the MHTB tank, the HEX and liquid injector are combined into a vertical spray bar assembly. Two GFSSP models (Self-Pressurization and TVS) were separately developed and tested and then integrated to simulate the entire system. The Self-Pressurization model consists of multiple ullage nodes, a propellant node, and solid nodes; it computes the heat transfer through multilayer insulation blankets and calculates heat and mass transfer between the ullage and liquid propellant and the ullage and tank wall. A TVS model calculates the flow through a J–T valve, HEX, and spray and vent systems. Two models are integrated by exchanging data through User Subroutines of both models. Results of the integrated models have been compared with MHTB test data at a 50% fill level. Satisfactory comparison was observed between tests and numerical predictions.

Quantifying MLI Thermal Conduction in Cryogenic Applications from Experimental Data

Multilayer Insulation (MLI) uses stacks of low-emittance metalized sheets combined with low-conduction spacer features to greatly reduce the heat transfer to cryogenic applications from higher temperature surrounds. However, as the hot-side temperature decreases from room temperature to cryogenic temperatures, the level of radiant heat transfer drops as the fourth power of the temperature, while the heat transfer by conduction only falls off linearly. This results in cryogenic MLI being dominated by conduction, a quantity that is extremely sensitive to MLI blanket construction and very poorly quantified in the literature. To develop useful quantitative data on cryogenic blanket conduction, multilayer nonlinear heat transfer models are used to analyze extensive heat transfer data measured by Lockheed Palo Alto on their cryogenic dewar MLI and measured by JPL on their spacecraft MLI. The data-fitting aspect of the modeling allows the radiative and conductive thermal properties of the tested blankets to be explicitly quantified. Results are presented showing that MLI conductance varies by a factor of 600 between spacecraft MLI and Lockheed's best cryogenic MLI.

Experiment research on heat-transfer capability of the multi-layer insulation blankets under different vacuum degrees

The high-speed reentry capsule of lunar spacecraft will face a weak vacuum environment long-term on orbit, thus the difference of heat-transfer capability of the multi-layer insulation blankets under different vacuum degrees should be evaluated in thermal design. In this article, an one-dimensional method of mesurement with adiabatic boundary condition was constucted to test the heat tranfer performance of multi-layer insulation blankets with 5, 10, 15 and 20 under 0.001-10000 Pa. Based on the test data, equivalent thermal conductivities of different vacuum degrees were calculated. The proper equivalent thermal conductivity is selected in the entire spacecraft thermal analyses, and this method is proved to be correct through thermal balance test and on orbit temperature telemetry. This work achieves not only basic data for reentry capsule, but also important fundation of thermal design and thermal analyse with multi-layer insultaion blankets in different vacuum degree.

Test Apparatus Utilizing a Gifford-McMahon Cryocooler to Measure the Thermal Performance of Multilayer Insulation

A vertical cylindrical calorimeter for measuring the thermal performance of multilayer insulation (MLI) has been developed. Two concentric oxygen-free high-conductivity copper drums are wrapped with sample MLI blankets, and are cooled using a two-stage Gifford-McMahon cryocooler. As the drums are vertically supported, the layer density of the MLI sample is unaffected by gravity. The inner drum is cooled by the 2nd stage of the cooler and is maintained at a temperature of about 6K. The outer drum is maintained at a temperature of about 65K by connecting it to the first stage of the cooler. The heat transfer through the blanket is determined by measuring the temperature difference across the stainless steel thermal resistance tube in a heat-flow meter placed between the drum and the cold finger of the cryocooler. The structure of the calorimeter, the calibration procedure, and results for heat flow through the MLI sample are reported.

Development of a new multi-layer insulation blanket with non-interlayer-contact spacer for space cryogenic mission

For conventional Multi-Layer Insulation (MLI) blankets, it is difficult to control the layer density and the thermal insulation performance degrades due to the increase in conductive heat leak through interlayer contacts. At low temperatures, the proportion of conductive heat transfer through MLI blankets is large compared to that of radiative heat transfer, hence the decline in thermal insulation performance is significant. A new type of MLI blanket using new spacers; the Non-Interlayer-Contact Spacer MLI (NICS MLI) has been developed. This new MLI blanket uses small discrete spacers and can exclude uncertain interlayer contact between films. It is made of polyetheretherketone (PEEK) making it suitable for space use. The cross-sectional area to length ratio of the spacer is 1.0×10−5m with a 10mm diameter and 4mm height. The insulation performance is measured with a boil-off calorimeter. Because the NICS MLI blanket can exclude uncertain interlayer contact, the test results showed good agreement with estimations. Furthermore, the NICS MLI blanket shows significantly good insulation performance (effective emissivity is 0.0046 at ordinary temperature), particularly at low temperatures, due to the high thermal resistance of this spacer.

Influence of Processing on Thermal Performance of Space Use Multilayer Insulation

Most spacecrafts flown today are covered with multilayer insulation blankets as the most efficient thermal control element. This study was performed to investigate the influence of various processing methods for space use multilayer insulation on thermal performance. The latter was measured by the calorimetric method using a liquid nitrogen cryostat and it was verified that the thermal performance of the multilayer insulation blankets that were processed in the most conventional manner for space use was found to be deteriorated considerably by hem processing such as overlap, seam, and patch. An estimation of the deterioration of the thermal performance of processed multilayer insulation blankets is given in this report.

Effect of Size on Thermal Performance of Limited Size Multilayer Insulation

Multilayer insulation blankets are used in various sizes for thermal control of space systems. These multilayer insulation blankets are processed, usually by being seamed and patched. It is qualitatively understood that the thermal performance of small size multilayer insulation is more or less deteriorated. The effects of size of space use multilayer insulation blankets on thermal performance are known qualitatively, but not quantitatively. In this study, the thermal performance of limited size multilayer insulation blankets was measured by using the boil-off calorimeter method with liquid nitrogen. The temperature distribution on a rectangular multilayer insulation was also measured in order to investigate the nonuniformity of the local heat flux across the rectangular multilayer insulation. Thermal performance declines with the decrease of multilayer insulation area. This is because the local heat flux drastically increases in the hem region and the gap between the edge of blanket and base plate. Based on these measurement results, an equation to predict the thermal performance of multilayer insulation blankets of limited size was proposed.