Aerospace

Research

12 pages, 3618 KiB

Open AccessArticle

Experimental Investigation of Solid Rocket Scramjet Based on Central Strut

by Jia Zeng, Guohui Wang, Hui Huang, Jian Fan and Haosu Wang

Aerospace 2024, 11(5), 410; https://doi.org/10.3390/aerospace11050410 - 19 May 2024

Cited by 1 | Viewed by 990

Scramjet based on solid propellant has become a potential choice for the development of future hypersonic vehicles. In this paper, a boron-containing solid rocket scramjet based on the central strut injection was proposed, and the ground direct-connect experiment with the equivalence ratios of [...] Read more.

Scramjet based on solid propellant has become a potential choice for the development of future hypersonic vehicles. In this paper, a boron-containing solid rocket scramjet based on the central strut injection was proposed, and the ground direct-connect experiment with the equivalence ratios of 0.43 to 2.4 under the flight condition of Mach 6, 25 km was carried out. The pressure and flow rate over time were measured in the experiment. The results show that the engine can realize stable supersonic mode or subsonic mode combustion by changing the gas flow rate. The engine can effectively increase the combustor pressure, reduce the unstable combustion time, and advance the strong combustion position by increasing the gas flow rate. The engine achieved high combustion efficiency when the equivalence ratio was about 1, with a maximum of 88.28%. A numerical simulation analysis was also carried out in this paper. Compared to the experimental results, the pressure error obtained by numerical simulation was less than 4%, and the typical position error was less than 3%, suggesting that the simulation model can be used to predict the behavior of scramjet. Full article

(This article belongs to the Special Issue Advanced Chemical Propulsion and Electric Propulsion)

► Show Figures

Figure 1

24 pages, 7198 KiB

Open AccessArticle

A High Step-Down SiC-Based T-Type LLC Resonant Converter for Spacecraft Power Processing Unit

by Wenjie Ma and Hui Li

Aerospace 2024, 11(5), 396; https://doi.org/10.3390/aerospace11050396 - 15 May 2024

Viewed by 1184

Abstract

A spacecraft power processing unit (PPU) is utilized to convert power from solar arrays or electric batteries to the payload, including electric propulsion, communication equipment, and scientific instruments. Currently, a high-voltage converter is widely applied to the spacecraft PPU to improve power density [...] Read more.

A spacecraft power processing unit (PPU) is utilized to convert power from solar arrays or electric batteries to the payload, including electric propulsion, communication equipment, and scientific instruments. Currently, a high-voltage converter is widely applied to the spacecraft PPU to improve power density and save launch weight. However, the high voltage level poses challenges such as high step-down ratios and high power losses. To achieve less conduction loss, a SiC-based T-type three-level (TL)

L L C

resonant converter is proposed. To further broaden the gain range and achieve high step-down ratios, a variable frequency and adjustable phase-shift (VFAPS) modulation scheme is proposed. Meanwhile, the steady-state time-domain model is established to elaborate the operation principles and boundary conditions for soft switching. Furthermore, the optimal resonant element design considerations have been elaborated to achieve wider gain range and facilitate easier soft switching. Furthermore, the numerical solutions for switching frequency and phase shift (PS) angle under each specific input could be figured out. Finally, the effectiveness of this theoretical analysis is demonstrated via a 500-W experimental prototype with 650∼950-V input and constant output of 48-V/11-A. Full article

(This article belongs to the Special Issue Advanced Chemical Propulsion and Electric Propulsion)

► Show Figures

Figure 1

14 pages, 4514 KiB

Open AccessArticle

Experimental Study of the Effect of the Initial Droplet Diameter on the Evaporation Characteristics of Unsymmetrical Dimethylhydrazine Droplets in a Subcritical Environment

by Gangqiang Wu, Wansheng Nie, Congling Yang, Siyin Zhou and Hui Wang

Aerospace 2024, 11(4), 297; https://doi.org/10.3390/aerospace11040297 - 11 Apr 2024

Viewed by 981

Abstract

The evaporation characteristics of unsymmetrical dimethylhydrazine droplets with different initial diameters in a subcritical environment were experimentally investigated with the temperature–pressure separation technique. The evaporation processes of unsymmetrical dimethylhydrazine droplets with different initial diameters in this environment have the same general pattern. All [...] Read more.

The evaporation characteristics of unsymmetrical dimethylhydrazine droplets with different initial diameters in a subcritical environment were experimentally investigated with the temperature–pressure separation technique. The evaporation processes of unsymmetrical dimethylhydrazine droplets with different initial diameters in this environment have the same general pattern. All the studied droplets exhibit a short transient heating phase and a steady-state evaporation phase obeying

d^{2}

. Notably, the expansion of the transient heating phase gradually increases with increasing ambient pressure. The change in diameter squared

{(∆ d^{2})}_{m a x}

increases from 1.03% at 1 MPa to 12.48% at 5 MPa. Under subcritical conditions, the evaporation rate decreases linearly with decreasing droplet diameter, and the droplet evaporation lifetime increases linearly. Changes in the initial droplet diameter may still have a large effect on droplets smaller than those studied here. When the ambient pressure is not greater than 3 MPa, the change in the steady-state evaporation time for both medium- and large-diameter droplets accounts for more than 70% of the variation in the droplet evaporation lifetime. As the ambient pressure increases to 4 MPa and 5 MPa, the percentage of the change in the transient heating time contributing to the variation in the droplet evaporation lifetime gradually increases to more than 45%. Full article

(This article belongs to the Special Issue Advanced Chemical Propulsion and Electric Propulsion)

► Show Figures

Figure 1

13 pages, 5178 KiB

Open AccessArticle

Analysis of Wave Propagation with Different Magnetic Configurations in Helicon Plasmas

by Bin Tian, Kan Xie, Bingchen An, Jing Wang, Su-Lan Yang and Yong Cao

Aerospace 2024, 11(4), 277; https://doi.org/10.3390/aerospace11040277 - 31 Mar 2024

Viewed by 1306

Abstract

A two-dimensional plasma–wave interaction model, which is based on the cold collisional plasma dielectric tensor, is applied to investigate the wave propagation and power depositions under different magnetic configurations in helicon plasmas. The varied magnetic configurations are formed by changing the radius of [...] Read more.

A two-dimensional plasma–wave interaction model, which is based on the cold collisional plasma dielectric tensor, is applied to investigate the wave propagation and power depositions under different magnetic configurations in helicon plasmas. The varied magnetic configurations are formed by changing the radius of the magnetic coil. When the magnetic coil was positioned closer to the plasma, the magnetic field within the plasma became stronger and more curved. Consequently, the simulation results show that the wave propagation and power deposition in plasmas follow the curved magnetic field lines. In the axial direction, the periodic distribution of wave fields and power deposition are clearly observed and keep consistency in helicon plasmas due to the eigenmodes of helicon waves. Furthermore, a concave dark area where the wave cannot propagate is observed in the closest magnetic coil case and leads to limited power deposition. Full article

(This article belongs to the Special Issue Advanced Chemical Propulsion and Electric Propulsion)

► Show Figures

Figure 1

20 pages, 11084 KiB

Open AccessArticle

Transient Characteristics of Fluidic Pintle Nozzle in a Solid Rocket Motor

by Dongfeng Yan, Zehang Zhao, Anchen Song, Fengming Li, Lu Ye, Ganchao Zhao and Shan Ma

Aerospace 2024, 11(3), 243; https://doi.org/10.3390/aerospace11030243 - 20 Mar 2024

Cited by 1 | Viewed by 1425

Abstract

The fluidic pintle nozzle, a new method to control the thrust of a solid rocket motor, has been proposed in recent years by combining the pintle with the aerodynamic throat (fluidic throat). The study of static characteristics has proved that it has a [...] Read more.

The fluidic pintle nozzle, a new method to control the thrust of a solid rocket motor, has been proposed in recent years by combining the pintle with the aerodynamic throat (fluidic throat). The study of static characteristics has proved that it has a remarkable effect on thrust control. To study the transient characteristics of the fluidic pintle nozzle, 2D transient simulations of a fluidic pintle nozzle propulsion system were conducted, employing dynamic meshing techniques. The Reynolds-averaged Navier–Stokes equations were meticulously solved, implementing a k–ω SST turbulence model. The thrust control principle of the fluid pintle nozzle was studied, and the wave structure was summarized. The transient characteristics of the secondary flow opening, secondary flow closing, pintle moving forward (pressure rise), and pintle moving backward (pressure drop) were obtained, and the effects of the injection angle and injection port position were studied. The response process after injection can be roughly divided into three stages: pressure propagation, pressure oscillation, and equilibrium stability, with time distributions of 0.4%, 5.39%, and 94.21%, respectively. In the process of the pintle moving forward, the rate of combustion chamber pressure increases and thrust decreases gradually because of the arc wall of the nozzle throat upstream, and the process of throats moving backward is just the opposite. Compared with the condition with a maximum throat opening and no secondary flow, the thrust of the condition with a minimum throat opening and a 0.3-flow-ratio secondary flow is increased by 80.95%. Under conditions of constrained flow ratio, the injection angle of the secondary flow ostensibly exerts negligible influence on the dynamic modulation of thrust. Nevertheless, it remains evident that a reduction in throat opening accentuates the impact of reverse injection. Furthermore, the proximity of the injection port to the head of the pintle is directly proportional to the efficacy of thrust control. Full article

(This article belongs to the Special Issue Advanced Chemical Propulsion and Electric Propulsion)

► Show Figures

Figure 1

26 pages, 10630 KiB

Open AccessArticle

Modelling of Cryopumps for Space Electric Propulsion Usage

by Andreas Neumann and Michaela Brchnelova

Aerospace 2024, 11(3), 177; https://doi.org/10.3390/aerospace11030177 - 23 Feb 2024

Viewed by 1556

Abstract

Electric space propulsion is a technology that is used in a continuously increasing number of spacecrafts. The qualification of these propulsion systems has to run in ground-based test facilities which requires long testing times and powerful pumping systems. In these usually large test [...] Read more.

Electric space propulsion is a technology that is used in a continuously increasing number of spacecrafts. The qualification of these propulsion systems has to run in ground-based test facilities which requires long testing times and powerful pumping systems. In these usually large test facilities, high pumping speeds are achieved with cryopumps. Cryopump operation is very expensive with respect to electrical energy and cooling water consumption. Therefore, being able to optimize pump shape, cold plate material, and pump placement in a chamber is beneficial. Pump design and tuned operating strategies can reduce costs and increase intervals between regeneration. Testing different pump configuration setups in a large facility is mostly prohibitive due to high costs and long testing times. Optimization via modelling is a better choice for design and also, later, for operation. Therefore, having a numerical model and proven guidelines at hand for optimization is very helpful. This paper describes a new model developed at DLR for the optimization of cryopump layout and operation. Model results are compared with cryopump operational and warm-up data. This validation is the basis for further optimization actions like multi-layer insulation layouts and pump cold plate upgrades, and helps in understanding and mitigating the detrimental effect of water condensates on the cryopump cold plates. Full article

(This article belongs to the Special Issue Advanced Chemical Propulsion and Electric Propulsion)

► Show Figures

Figure 1

12 pages, 4775 KiB

Open AccessArticle

Enhancing RDX Thermal Decomposition in Al@RDX Composites with Co Transition Metal Interfacial Layer

by Su-Lan Yang, Kan Xie, Jing Wang, Bingchen An, Bin Tian, Hongqi Nie, Jie-Yao Lyu and Qi-Long Yan

Aerospace 2024, 11(1), 81; https://doi.org/10.3390/aerospace11010081 - 16 Jan 2024

Cited by 1 | Viewed by 1917

Abstract

In this study, an Al/Co@RDX composite was meticulously prepared through a combination of planetary high-energy ball-milling and a spray-drying technique. The thermal reactivity of these Al/Co@RDX composites was comprehensively investigated and compared using the TG/DSC technique. It is shown that the initial decomposition [...] Read more.

In this study, an Al/Co@RDX composite was meticulously prepared through a combination of planetary high-energy ball-milling and a spray-drying technique. The thermal reactivity of these Al/Co@RDX composites was comprehensively investigated and compared using the TG/DSC technique. It is shown that the initial decomposition temperature of RDX in the DSC curve was decreased by 26.3 °C in the presence of Al/Co, which could be attributed to the nano-sized Co transition metal catalyzing the decomposition reaction of nitrogen oxides in RDX decomposition products. The decomposition peak temperature of RDX and the heat released by the thermal decomposition of RDX in the Al/Co@RDX composite were decreased by 26.3 °C and increased by 74.5 J·g⁻¹, respectively, in comparison with those of pure RDX. The types of major gaseous products released from Al/Co@RDX were found to be identical to those of pure RDX, encompassing N₂O, CH₂O, CO₂ and HCN. However, the concentrations of those gaseous products for Al/Co@RDX were higher than those observed for pure RDX, which may owe to the fact that the Al/Co composite can interact with the –CH₂ and –NO₂ within RDX molecules, which leads to the weakening of the C-N and N-N bonds. In addition, the decomposition of RDX in the Al/Co@RDX composite was observed as a one-step process with an apparent activation energy (E_a) of 115.6 kJ·cm⁻³. The decomposition mechanism of the RDX in the Al/Co@RDX composite was identified to follow the chain scission model (L2), whereas the two-step decomposition physical models observed for pure RDX were found to closely resemble the L2 and autocatalytic models. Full article

(This article belongs to the Special Issue Advanced Chemical Propulsion and Electric Propulsion)

► Show Figures

Figure 1

13 pages, 3618 KiB

Open AccessArticle

A Novel Transversal-Feed Electron Cyclotron Resonance Plasma Thruster: Design and Plasma Characteristics Analysis

by Yajie Han, Guangqing Xia, Bin Sun, Junjun Zhang, Liuwei Chen and Chang Lu

Aerospace 2023, 10(10), 865; https://doi.org/10.3390/aerospace10100865 - 1 Oct 2023

Cited by 1 | Viewed by 1425

Abstract

This paper presents the development, analysis, and performance evaluation of a novel transversal-feed Electron Cyclotron Resonance Plasma Thruster (ECRPT). The ECRPT operates based on the transversal-feed principle and incorporates optimized structural design. Through extensive simulation of the S-parameters of the [...] Read more.

This paper presents the development, analysis, and performance evaluation of a novel transversal-feed Electron Cyclotron Resonance Plasma Thruster (ECRPT). The ECRPT operates based on the transversal-feed principle and incorporates optimized structural design. Through extensive simulation of the S-parameters of the antenna, optimal antenna sizes are determined for both coaxial and transversal-feed configurations. Additionally, the electric field intensity of the antenna is simulated for both feed structures, revealing higher electric field intensity in the transversal structure, thereby promoting discharge. We employ the drift-diffusion model to calculate the number density of electrons in the discharge chamber and ascertain that the number density can reach an order of magnitude of 10¹⁸ m⁻³. Experimental discharge tests are conducted under various microwave power conditions, demonstrating that the thruster can initiate and cease operation with an incident power as low as 5 W, significantly lower than that of traditional coaxial feed structures. At a power level of 20 W, the ion current density can attain 3 A/m². Moreover, the transversal-feed thruster exhibits exceptional performance when the power exceeds 10 W, and the propellant flow rate ranges from 0.5 SCCM to 5 SCCM. The superior performance characteristics of the proposed thruster configuration make it a promising candidate for applications demanding efficient and low-power plasma propulsion systems. Full article

(This article belongs to the Special Issue Advanced Chemical Propulsion and Electric Propulsion)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Advanced Chemical Propulsion and Electric Propulsion

Share This Special Issue

Special Issue Editor

Special Issue Information

Benefits of Publishing in a Special Issue

Published Papers (8 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI