Journal of Propulsion and Power, Volume 39, Issue 1, Page 1-2, January 2023.

Journal of Propulsion and Power, Ahead of Print.

Ammonium dinitramide (ADN)-based energetic ionic liquid propellants (ADN-EILPs) present considerable potential as monopropellants due to high energy density, high thermal/chemical stability, and low toxicity. Consequently, a chemical thruster system based on ADN-EILPs can be employed in the development of high-performance ultrasmall/small satellites. However, the characteristics of the ADN-EILPs present various problems in their ignition during the thruster development. To solve this problem, the authors have previously achieved the continuous-wave (CW) laser ignition of ADN-EILPs using laser absorbers composed of carbon wools. However, the conventional propellant injection of ADN-EILPs with carbon wool using high-pressure gas faces several limitations. Therefore, a propellant feed system suited for the ignition method is proposed here, as well as a conceptual model of a 0.5 U/0.5 N-class thruster operated by the CW laser ignition of ADN-EILPs (1U=100×100×100 mm). Additionally, an attempt is made to manufacture a laboratory model (LM) thruster, and its fundamental operation properties are determined. The future research implications of this study include the further observation of the combustion of the decomposed gas before its emission from the throat of the LM thruster, along with the further development of the propellant feeding system proposed in this study and the hot-fire tests performed for the feeding systems.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

Two algorithms aimed at the optimal design of bare electrodynamic tethers in the active mode, including reboost and stationkeeping scenarios in low Earth orbit, are presented. By assuming a quasi-circular orbit evolution with constant environmental values at each altitude, the algorithms construct figures of merit as a function of the tether dimensions and the input power and look for their optimum values while satisfying other mission constraints like duration and safety. In the case of reboost scenarios, the figures of merit are the tether system-to-satellite mass ratio and the reboost time. Two separate subcases are studied: a nonautonomous tether system that receives power from the satellite, and an autonomous case where the power source is part of the tether system. Regarding stationkeeping scenarios, the design algorithm minimizes the tether system-to-satellite mass ratio while ensuring that the thrust provided by the Lorentz force compensates for the aerodynamic drag. A map of performances of the tether system in the altitude–inclination plane is presented. The optimal tether sizing and power obtained with the two algorithms were used as input to run simulations with the BETsMA Version 2.0 software. They confirmed that, although based on some simplifying hypotheses, the algorithms provide acceptable values of the design parameters in a preliminary design phase. The extension of the algorithms to bare-photovoltaic tethers and low work-function tethers is briefly discussed.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

An ethylene-fueled scramjet operating at Mach 10 was experimentally tested in the JF-24 shock tunnel and modeled using improved delayed detached eddy simulation based on up to 368.34 million cells. An in-depth analysis of the effects of thermal and chemical nonequilibrium on combustion characteristics and engine performance was conducted. The contrary effects of nonequilibrium heating and nonequilibrium cooling that occur in different sections of a scramjet were revealed. The underlying mechanism can be attributed to the delayed relaxation of thermal nonequilibrium under energy addition or deduction. The nonequilibrium case has better mixing, while the equilibrium case has higher combustion efficiency. The synchronous reductions in thrust and drag counteract each other and lead to a higher final net thrust under nonequilibrium. The net thrust increases with the global equivalence ratio, whereas the specific impulse decreases. The evolution of flamelets and reaction paths were analyzed to reveal the effect of chemical nonequilibrium, which produces an abundance of O, OH, and NO radicals through endothermic dissociation reactions and significantly alters the rate-limiting reaction paths.

The ignition and extinction characteristics of perchlorate-based electrically controlled solid propellants (ECSPs) that can achieve multiple ignition and produce controllable thrusts were investigated. We examined the multiple-ignition and combustion behaviors of ECSPs and identified the basic ignition-model parameters for these materials. Single-frame photography and a schlieren imaging system were used to determine the ignition, combustion, and extinction properties of two different ECSP formulations at various voltages, pressures, and initial temperatures. The results revealed that increasing the voltage, pressure, and initial temperature reduced the ignition delay; whereas increasing the number of ignitions decreased the ignition delay and ignition energy but increased the extinction delay and smoldering time. Furthermore, under the same experimental conditions, the voltage, pressure, and initial temperature produced a larger effect on a nonmetallic ECSP than on an ECSP containing 5% aluminum (Al) powder. The nonmetallic ECSP exhibited a longer ignition delay, higher ignition energy, and better extinguishing performance than the Al-containing ECSP. Moreover, four distinct stages of the ECSP ignition process were identified. The findings of this study demonstrated that the electrical energy consumed during condensed phase heating plays a critical role in propellant ignition.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

A variably premixed rotating detonation engine using gaseous hydrogen and air reactants is introduced to enable investigation of key cycle processes while varying the homogeneity of the reactant inlet conditions. Two chamber configurations are investigated, the first with reactants filling the entire span of a straight annular channel and the second with a slightly larger channel and a backward-facing step. The first configuration permits both premixed and non-premixed fuel injection, enabling mixing quality modulation. The second configuration is operated only at fully premixed conditions. Operating modes and detonation wave speeds are characterized using exhaust-plume imaging, while the chamber heat release field is captured by transverse imaging through a transparent outer body. Tests using the first configuration were characterized by unstable counterpropagating modes with low detonation wave speeds regardless of the state of premixing, while the second configuration rendered single-wave behavior with wave speeds up to 86% of the Chapman–Jouguet velocity. Comparisons with a simple computational fluid dynamics model of the second configuration indicate that reactant preheating significantly influences the detonation wave topology, highlighting the potential utility of the test platform for isolating key physics associated with the effects of reactant premixing, preheating, and chamber geometry on rotating detonation engine operation.

Journal of Propulsion and Power, Ahead of Print.