Browse Topic: Propellants
To investigate the effect of negative pressure environment on the aging behavior of solid propellants, a 60-day negative pressure accelerated aging test was carried out on SG-2 propellant with five working conditions: atmospheric pressure at room temperature, atmospheric pressure at 80°C, and negative pressure at 40°C/60°C/80°C. Combined with Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), the functional group evolution law and thermal decomposition kinetic characteristics of the periphery zone and core zone of the propellant were analyzed. The results show that the propellant exhibits significant inhomogeneous aging characteristics under negative pressure aging. The functional group structure in the periphery zone is more stable in the early aging stage; in the middle stage, components such as DNT and C2 in the core zone migrate to the periphery zone; in the late stage, the undegraded components in the core zone continuously supplement the periphery zone, making the functional group integrity of the periphery zone better than that of the core zone. DSC tests combined with Kissinger and Ozawa methods show that the thermal decomposition activation energy of the propellant decreases continuously with the increase of aging temperature under negative pressure environment, and the activation energy drops to 428.91 kJ/mol after aging at negative pressure 80°C. High temperature accelerates the volatilization of NG, the cross- linking of NC molecular chains and the consumption of stabilizer, leading to the easy breakage of O-NO₂ groups and the significant deterioration of thermal stability. This study clarifies that the aging mechanism of the propellant under negative pressure environment is the synergistic effect of component migration and diffusion, functional group decomposition and molecular chain cross-linking, which provides a theoretical basis for the storage and application of solid propellants in negative pressure service scenarios such as deep space exploration.
Multiphase compressible flow problems are widespread in aviation, aerospace, transportation, military, and industrial fields, for instance, in underwater explosion bubble dynamics, fuel injection for hypersonic vehicles, liquid sloshing in propellant tanks, and supercavitating underwater vehicles. This paper proposes an improved THINC (Tangent of Hyperbola for Interface Capturing) method for multiphase flow simulations, based on a selective reconstruction strategy for the dominant material. The core of the strategy is to apply the THINC reconstruction exclusively to the material with the largest volume fraction within a multiphase mixed cell, which numerically governs the local interface evolution. The volume fractions of non-dominant materials are then obtained through a proportional distribution that inherently ensures the summation (Σαk = 1) and boundedness (0 ≤ αk> ≤ 1) constraints are met without explicit corrections. This approach reduces the number of THINC reconstructions for each time step in a multiphase mixed cell from Nm (the number of materials) to one, significantly simplifying the algorithm and lowering computational cost. It thereby avoids the error accumulation and complex renormalization procedures associated with conventional schemes that reconstruct all materials. While strictly maintaining volume fraction conservation, the proposed method preserves interface sharpness through the underlying THINC framework. The method is implemented in a diffuse-interface, multiphase Eulerian framework and validated with a series of challenging benchmarks, including shock-helium bubble interaction, triple-point problem, gas impact, and the more complex modified gas impact. Numerical results show that, compared with conventional multiphase THINC approaches that reconstruct every material, the proposed scheme can reduce CPU time by about 40.0% without compromising the accuracy of key physical quantities.
To solve a problem that ignition anomaly can’t be detected in time, based on the thermal equilibrium equation, the space heat flow, heater heating, propellant combustion, and thermal radiation to cryogenic space are considered to build an accurate ignition temperature method for the 10 N thruster by using on-orbit true temperature. Further, considering the error of measuring the thermistor, an envelope model for the 10 N thruster ignition temperature is established. Based on the above, a detection method for the 10 N thruster ignition anomaly of on-orbit satellites is proposed. The accuracy of the method is relatively high, and the absolute error is less than 3 degrees Celsius. An anomaly can be quickly detected when the 10N thruster ignition temperature deviates from the normal trend by 3–5 degrees celsius. The method is applied to a DFH-3 satellite, and the maximum difference of 10 N thruster ignition temperature between the theoretical values calculated by the proposed method and the measured values is only 2.72 degrees celsius. It has been proven that the prediction accuracy of the proposed method is high. It plays an important role in discovering the 10N thruster ignition anomaly in time and ensuring the success of satellite orbit or attitude control.
Sealing systems in space applications must perform reliably under demanding conditions in engineering: cryogenic temperatures, vibration, leakage control, ultra-high vacuum, ionizing radiation, abrasive particulates, and repeated thermal cycling. Each factor strains conventional sealing technologies. In combination, they can rapidly cause failure in systems where margins are unforgiving and maintenance is impossible. As spacecraft architectures evolve toward longer operational lifetimes and broader mission profiles, sealing requirements continue to tighten. Launch vehicles, satellites, and exploration platforms now operate across wider temperature ranges and in contact with more aggressive propellants and media. As a result, both metal seals and engineered polymer alternatives are evaluated-and selected-against increasingly specific, measurable performance criteria.
Much like baking the perfect cake involves following a list of ingredients and instructions, manufacturing energetic materials — explosives, pyrotechnics and propellants — requires precise formulations, conditions and procedures to ensure they are safe and perform as intended.
Plastic materials are used for a wide variety of spacecraft applications including seals, bearings, fasteners, electrical insulators, thermal isolators, and radomes. Selecting plastics for use in space is complex due to wide operating temperature ranges, vacuum conditions, and exposure to radiation and atomic oxygen. Additionally, some spacecraft applications require sealing flammable propellants such as hydrogen and oxygen. This article will present some design considerations when selecting plastics for use in spacecraft. It will provide rich data on the performance characteristics of plastics as well as examples of successful spacecraft applications.
The race is on for leadership in cislunar space, considered a gateway to the future of space exploration. Yet operating in this domain introduces unique challenges for propulsion systems. In contrast to low-Earth orbit (LEO), the cislunar environment requires higher precision propulsion solutions; these are necessary to enable rapid and accurate maneuvering of spacecraft and long-term sustainability. Propellants like hydrazine and nitrogen tetroxide offer the high energy density required for cislunar missions, but they must be handled very differently from the inert, non-reactive gases at play in LEO systems.
Engineers at NASAs Stennis Space Center have developed the HYdrocarbon Propellants Enabling Reproduction of Flows in Rocket Engines (HYPERFIRE), a sub-scale, non-reacting flow test system. HYPERFIRE uses heated ethane to enable physical simulation of rocket engines powered by a broad range of propellants in an inexpensive, accurate, and simple fashion.
As NASA plans for manned missions to Mars, efforts are being made to identify technologies that must be improved to make such trips feasible. Without improvements in valve technologies, propellant and commodity losses will likely make long-duration space missions infeasible. Engineers at NASA's Marshall Space Flight Center have developed a self-aligning poppet for low leakage valves a seat alignment technology that eliminates the need to precisely control interfaces between poppet sealing surfaces and the valve seat seal.
Researchers have used the ancient Japanese art of paper folding to possibly solve a key challenge for outer space travel: how to store and move fuel to rocket engines. They developed an origami-inspired, folded plastic fuel bladder that doesn’t crack at super-cold temperatures and could someday be used to store and pump fuel.
NASA Goddard developed the Cooperative Service Valve (CSV) to facilitate the resupply of media, such as propellants and pressurants, to satellites. The CSV replaces a standard spacecraft fill and drain valve.
Strategies to control solid rocket propellant regression rate require a robust throttling technique applicable to high performance propellant formulations. Currently, several methods to control and throttle either motors or subscale propellant strands exist, including chamber pressure control (e.g. pintle nozzles or rapid depressurization quench), infrared laser irradiation of the burning surface to increase burning rates, development of inherently unstable combustion chamber geometries (producing either local pressure or velocity perturbations), and electrically sensitive hydroxylammonium nitrate (HAN)-based formulations in which burning rate is controlled by a voltage potential. However, these techniques are limited in that they either can only be used with low flame temperature (low specific impulse) propellants, result in low propulsion system mass fraction (pintle), are only capable of producing a single perturbation, or are formulation specific.
Researchers have developed a new propulsion concept for swimming robots that exploits temperature fluctuations in the water for propulsion without the need for an engine, propellant, or power supply.
A highly miniaturized, MR-143, green monopropellant thruster was developed for 1N thrust. Testing indicated the initial catalyst bed heater was insufficient. In subsequent development, the thruster was equipped with a more efficient catalyst bed heater. For reliable ignition of the advanced, non-toxic, AF-M315E monopropellant, the catalyst needs to be preheated. This preheat temperature is much higher than what hydrazine thrusters require. Moreover, the combustion temperature of hydroxyl ammonium nitrate (HAN)-based monopropellants is higher than hydrazine, so the catalyst bed heater must be able to withstand repeated soak-back temperatures.
The scope of this SAE Information Report is to provide general information relative to the nature and use of infrared techniques for nondestructive testing. The document is not intended to provide detailed technical information, but will serve as an introduction to the theory and capabilities of infrared testing and as a guide to more extensive references.
Putting a satellite into low Earth orbit requires a lot of energy, with ground-launched rockets expending two-thirds of their propellant fighting to get through the atmosphere. Researchers at NASA’s Armstrong Flight Research Center have developed an innovative approach to launching satellites into space from an airborne platform. As with other air-launch approaches, it provides significant flexibility in the location and direction of the launch vehicle. Furthermore, unlike other air-based launch techniques, this system avoids the significant drawbacks related to expensive and complex design/development efforts, difficult maneuvering, risks to crew, and inefficient flight performance.
Structural analysis of solid rocket motors is challenging for several reasons, but the most important of these is the complex behavior of the propellant. The mechanical response of a solid propellant is time and temperature dependent. The complexity of the mathematical analysis of the propellant depends on the loading conditions, but for some loading situations, the linear viscoelasticity assumption is reasonable. In particular, linear viscoelasticity is perhaps the most appropriate material behavior description for use in the simulations of stresses related to storage conditions. Typically, simulations use a viscoelastic model in the form of a Prony series and a Williams–Landel–Ferry (WLF) equation. The parameters in these models are derived from stress relaxation experiments, making the stress relaxation experiment a key viscoelastic test, analogous to the tensile test for linear elastic materials.
In the study of combustion characteristics of liquid rocket fuels, it is customary to either study the combustion of liquid fuel droplets or the combustion of fuel sprays. However, the two are closely related to each other, because in a typical rocket combustion chamber, the burning of droplets, droplet clusters, and fuel sprays occur simultaneously.
Test methodology allows analysis of combustion dynamics for subscale rocket injectors under super critical conditions. Air Force Research Laboratory (AFMC), Edwards Air Force Base, California In the study of combustion characteristics of liquid rocket fuels, it is customary to either study the combustion of liquid fuel droplets or the combustion of fuel sprays. However, the two are closely related to each other, because in a typical rocket combustion chamber, the burning of droplets, droplet clusters, and fuel sprays occur simultaneously. The study of droplet burning is mostly focused either on single suspended droplets or free droplets, usually in a free fall. In either case, the conditions regarding the combustion of a single fuel droplet deviates from what is expected in typical liquid rocket engines (LREs). This not only concerns the chamber pressure and the temperature that is usually much lower in a typical droplet study, but also the droplet ignition process and the related transient effects such as temperature ramp up that is much slower than what takes place in LREs. As a result, reported values of combustion parameters such as the burning rate constant and the ignition delay time obtained under typical experimental conditions may not entirely represent the combustion processes in LREs.
Humans have been using rocket propulsion for almost a millennium, starting with Chinese rockets and “fire arrows” in the 13th century and continuing to the modern era's powerful Space Shuttle and Falcon rockets. For most of that history, rockets have been chemically fueled, but in the past century scientists and engineers have also experimented with electric rockets, also known as ion engines or ion propulsion systems. Rather than using chemical reactions to create heat and accelerate a propellant, electric rockets use electromagnetic or electrostatic fields acting on charged ions of propellant, speeding them up and shooting them out, away from the vehicle, producing thrust. The electrical energy to generate these fields comes from the sun, from batteries, or both.
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