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Report on Alternative Devices to Pyrotechnics on Spacecraft
Abstract
Pyrotechnics accomplish many functions on today's spacecraft, possessing minimum volume/weight, providing instantaneous operation on demand, and requiring little input energy. However, functional shock, safety, and overall system cost issues, combined with emergence and availability of new technologies question their continued use on space missions. Upon request from the National Aeronautics and Space Administration's (NASA) Program Management Council (PMC), Langley Research Center (LaRC) conducted a survey to identify and evaluate state-of-the-art non-explosively actuated (NEA) alternatives to pyrotechnics, identify NEA devices planned for NASA use, and investigate potential interagency cooperative efforts. In this study, over 135 organizations were contacted, including NASA field centers, Department of Defense (DOD) and other government laboratories, universities, and American and European industrial sources resulting in further detailed discussions with over half, and 18 face-to-face briefings. Unlike their single use pyrotechnic predecessors, NEA mechanisms are typically reusable or refurbishable, allowing flight of actual tested units. NEAs surveyed include spool-based devices, thermal knife, Fast Acting Shockless Separation Nut (FASSN), paraffin actuators, and shape memory alloy (SMA) devices (e.g., Frangibolt). The electro-mechanical spool, paraffin actuator and thermal knife are mature, flight proven technologies, while SMA devices have a limited flight history. There is a relationship between shock, input energy requirements, and mechanism functioning rate. Some devices (e.g., Frangibolt and spool based mechanisms) produce significant levels of functional shock. Paraffin, thermal knife, and SMA devices can provide gentle, shock-free release but cannot perform critically timed, simultaneous functions. The FASSN flywheel-nut release device possesses significant potential for reducing functional shock while activating nearly instantaneously. Specific study recommendations include: (1) development of NEA standards, specifically in areas of material characterization, functioning rates, and test methods; (2) a systems level approach to assure successful NEA technology application; and (3) further investigations into user needs, along with industry/government system-level real spacecraft cost benefit trade studies to determine NEA application foci and performance requirements. Additional survey observations reveal an industry and government desire to establish partnerships to investigate remaining unknowns and formulate NEA standards, specifically those driven by SMAs. Finally, there is increased interest and need to investigate alternative devices for such functions as stage/shroud separation and high pressure valving. This paper summarizes results of the NASA-LaRC survey of pyrotechnic alternatives. State of-the-art devices with their associated weight and cost savings are presented. Additionally, a comparison of functional shock characteristics of several devices are shown, and potentially related technology developments are highlighted.
... Despite the intensive utilization of pyrotechnics, their application is often accompanied by reluctance due to inherent limitations, such as the lack of pre-use functional verification. In addition, safety concerns arise because of the use of explosive materials, leading to the production of contaminants [2,3]. Specifically, high levels of pyroshock can induce severe problems, becoming a significant hurdle for certain applications. ...
... This notably includes the development of nonexplosive separation and release devices, also known as nonexplosive actuators (NEAs). NEA devices are typically reusable, resettable, and cost-effective [2,12]. However, the separation reliability of NEA devices represents a notable drawback when compared with pyrotechnic release devices. ...
... An illustration of the electromechanical spool is provided in Fig. 12a. The linear motion of the plunger is constrained by spool halves that are wound with a restraining wire [2]. The application of an electric current causes the linkwire, a component of the restraining wire, to fail. ...
This review presents an in-depth examination of the advancements, current state, and future trends of separation and release devices in aeronautical and astronautical systems, focusing on their classification into one-point and linear devices as well as the move from pyrotechnic to nonexplosive methods. For one-point separation devices, this review discusses the evolution from traditional explosive bolts, which use high explosives to operate, to nonexplosive actuators such as shape memory alloy devices that offer resettable, low-shock options. It also highlights devices that rely on pyrotechnic initiators without using high explosives as key developments for reducing shock and increasing safety. In the section on linear separation devices, the review examines flexible linear shaped charges and mild-detonating fuses, which are crucial for precise separations such as stage and fairing detachments. Introducing expanding tubes as a new method to avoid the usual debris and damage from pyrotechnics is a big improvement. In addition, the use of clamp-band joint systems for satellite separation, secured by either pyrotechnic bolts or nonexplosive dual-initiator devices, is a common approach. The recent focus on developing pneumatic linear separation devices marks a shift toward systems that can be reused and reduce shock without explosives. Moreover, the emergence of nonexplosive satellite separation systems represents a shift toward safer and more adaptable deployment technologies. These fully mechanical actuation methods facilitate shock-free separations, which are crucial for the integrity of sensitive payloads. This review suggests that continuous innovation in nonexplosive separation technology will significantly change mission planning and system design in the aeronautics and astronautics fields.
... Restraints keep the deployable from moving during launch and then allow deployment to initiate on command. In addition to the references here, we would like to draw the readers' attention to two key review papers on nonpyrotechnic restraint approaches 48,49 . ...
... Pin puller or pusher This restraint actuates a pin inward or outwards, often powered by a Shape Memory Alloy (SMA) 48,57,58 , electromagnet 59 or paraffin wax 48 , triggering a release. The magnetometer booms on the CINEMA 1-5 CubeSats were released by a pin puller mechanism 44,60 . ...
... Pin puller or pusher This restraint actuates a pin inward or outwards, often powered by a Shape Memory Alloy (SMA) 48,57,58 , electromagnet 59 or paraffin wax 48 , triggering a release. The magnetometer booms on the CINEMA 1-5 CubeSats were released by a pin puller mechanism 44,60 . ...
Because of the miniaturization of small satellites, most of them have deployables to expand effective areas. However, Small Satellites are not only required to miniaturize systems, but often have a reduced budget, timeline, and employ teams with less experience. The goal of this paper is to provide a starting point for those new to deloyables, and working on small satellites, to understand the approaches available for deployable mechanisms and provide design practices which can improve success rates. To do so, this paper develops a framework for small satellite deployable structures, categorizing them into distinct deployment stages. It investigates the approaches that can be utilized for each stage, focusing on the stow, restrain, actuate, and locate stages. This review paper discusses the advantages and disadvantages of each approach, supported by examples provided in the references. It then highlights best practices for deployable mechanisms, and describes key challenges and future directions. By offering a comprehensive analysis of small deployable systems, this paper aims to guide engineers and researchers in implementing successful design practices for small satellite deployable structures.
... For example, during the release process, there will be violent vibrations, which will cause an impact on the spacecraft, leading to damage or misoperations on the surrounding parts. 245,246 Moreover, since the pyrotechnic release devices cannot be reused, the reliability of the devices cannot be verified on the ground in advance. With the rapid development of space technology, the applications of pyrotechnic nuts and explosive bolts are decreasing, while non-impact and non-pyrotechnic release devices attract much attention. ...
Shape memory polymer (SMP) and SMP composites (SMPC) can memorize the permanent shape and recover from the temporary shape to the permanent shape when stimulated by the appropriate stimuli. Because of the unique shape memory effect, coupled with its low cost, low density, high specific strength, biodegradability, biocompatibility, and other characteristics, SMP and SMPC have become possible materials to solve the problems currently faced by space deployable structures, biomedical devices, mold manufacturing, release devices, etc. This work reviews the research and developments of SMP and SMPC, including the achievements in constitutive theory, the applications, and prospects in aerospace, biomedical medicine, intelligent mold, and release devices. Published under an exclusive license by AIP Publishing. https://doi.
... .15 mm diameter activated with Joule-effect heating. A similar design at a miniature scale has been implemented by Liu et al. (2019) (see Figure 6A) for medical applications, by Khan et al. (2016) for robotics applications and Basaeri et al. (2014) for aeronautic applications. Design with coil form torsional SMAs with passive spring are studied in Lucy and Center. (1996), Redmond et al. (2010), Song (2007) (see Figure 6B); shear strain-driven actuators are presented in Tobushi et al. (2010), Takeda et al. (2012), Prahlad and Frontiers in Robotics and AI | www.frontiersin.org ...
Shape memory alloys (SMAs) are a group of metallic alloys capable of sustaining large inelastic strains that can be recovered when subjected to a specific process between two distinct phases. Regarding their unique and outstanding properties, SMAs have drawn considerable attention in various domains and recently became appropriate candidates for origami robots, that require bi-directional rotational motion actuation with limited operational space. However, longitudinal motion-driven actuators are frequently investigated and commonly mentioned, whereas studies in SMA-based rotational motion actuation is still very limited in the literature. This work provides a review of different research efforts related to SMA-based actuators for bi-directional rotational motion (BRM), thus provides a survey and classification of current approaches and design tools that can be applied to origami robots in order to achieve shape-changing. For this purpose, analytical tools for description of actuator behaviour are presented, followed by characterisation and performance prediction. Afterward, the actuators’ design methods, sensing, and controlling strategies are discussed. Finally, open challenges are discussed.
... Initiators are widely used in the military [1,2], aerospace [3,4], and automotive applications [5][6][7][8] as pin pullers [9][10][11], valves [12][13][14][15], and airbag inflators [16][17][18][19], respectively. Due to the fast triggering property, an initiator is primarily used to ignite more difficult-to-ignite materials, e.g., solid propellants and thermites. ...
A numerical model describing the ballistic behavior of a commercially used initiator is presented in this article. This model was built on the principle of conservation of mass and energy in the multi-phase framework incorporated with multi-loaded conditions. After obtaining the information about the grain size distribution in each composite, a fixing factor was proposed based on the surface area ratio of the composites. Thus, the solid propellant burning process based on distributed grain size was described, and the burn rate parameters of the applied pyrotechnic compositions were re-evaluated for different preconditioned temperature levels according to Vieille’s law. The influence of bridge wire and initiator metal cap was further modeled concerning their characteristic properties according to the observed measurements. The validation of the entire initiator model in the closed bomb test showed quantitative agreement with the measured pressure evolution, while the parameter study for evaluating the ballistic sensitivity of each component delivered some insights into the product development process. Furthermore, the configuration of a cold gas inflator was utilized to evaluate the initiator impact for a realistic application, where the shock wave intensity during deployment serves the main function in the inflator design. Incorporated with CFD simulations to capture the shock wave propagation, 0D-3D coupling strategy for initiator ballistics to inflator configuration was realized. Besides, the simulation results reflected the physical conditions in a proper manner. In particular, the parameter study led to a better understanding of interactions between inflator components, which were barely possible to be quantified through the measurements. The proposed initiator model could also be used in combination with other mechanical principles as a component of pyrotechnic devices such as pin-puller, electric line cutters, or airbag inflators. The detailed information gained in describing the physical properties enabled us to assess the existing design quantitatively and to have better control of the product quality.
Stage separation system in a launch vehicle helps to physically separate the burnt stage of the vehicle from the subsequent live stage located towards the fore end. There are several stage separation systems and they differ from their principle of operation, construction, generated impulse or the shock levels, the type of mechanism and the operational duration. This paper provides a brief review of several stage separation systems being adopted in launch vehicles. It explores the adopted methods, design specifications, and identifies the problems and challenges.KeywordsSeparation systemActuatorsRelease devicesSeparationImpulse devicesPyrotechnics
To solve the problem of large operating noise of existing pyrotechnic separation devices, a new low-noise pyrotechnic separation device is designed by changing the utilisation mode of pyrotechnic separation, using micro gas pyrotechnic as heat sources, and shape memory alloy material to convert heat energy into mechanical energy. The results showed that the separation time was 1.526 s when the preload was 20 kN, and the maximum shock response was 319 G (2268 Hz) for 100 Hz–100 kHz. When used underwater, the maximum sound pressure level is 106.9 dB at 12,698 Hz and 98.5 dB from 10 Hz–5 kHz. Compared with a conventional separation nut, the frequency band sound pressure level can be reduced by more than 70 dB, realising underwater low-noise separation.
Space missions have become diversified in recent years, where connection and separation devices play a crucial role as key components of various spacecraft. Traditional pyrotechnic devices have the advantages of large carrying capacity, rapid motion and functional reliability. However, their shortcomings such as great release shock, poor safety, unrepeatability and other prominent defects make them unsuitable for new generation spacecraft such as microsatellites to separate at low shock or lock repeatedly, etc. Therefore, it is necessary to develop space non-pyrotechnic low-shock connection and separation devices (SNLD) which are required for advanced aerospace missions. In this paper, the progress of the research on space non-pyrotechnic low-shock connection and separation technology (SNLT) is summarized and reviewed. Proceed from the principle of reducing shock for non-pyrotechnic devices, present studies are classified from the perspective of actuating technology and systematic designing methods. For non-pyrotechnic actuating techniques, according to different driving sources, the separation devices are classified into several main categories: electric, magnetic, gas and thermal actuating devices. The actuation principle and application prospect of separation techniques are introduced and the working process, dimension and mechanical properties of typical devices are compared and evaluated. For the systematic designing method, the common mechanism types of SNLDs are summarized according to the designing concept of reducing shock. Then connection configurations are classified according to the structural forms of connection devices, of which the principles, bearing capacities and general applications are discussed. This paper systematically summarizes the key problems, puts forward the future development trend of SNLT, and points out the breakthrough direction for related scholars.
A piecewise linear vibration isolator used to isolate the rocket launch vibration is proposed and investigated in this paper. The dynamic characteristics of the piecewise linear vibration isolator are analyzed theoretically and experimentally. Assuming base excitation from the rocket, the dynamic equation is established and the response is solved by using averaging method. The influence of the system parameters such as stiffness ratio and clearance distance on the system performance is discussed. The jumping phenomenon and frequency shift are observed. The vibration isolation performance of the isolator is tested by using vibration table to simulate the launch vibration loads according to certain criterion. The theoretical and experimental results are compared and are in good accordance. The results show that the piecewise linear vibration isolation system can lower the response for large amplitude vibration excitation at launch. The results present here can be a useful guideline when design such kind of vibration isolator.
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