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Aerospace
Special Issues
Innovation and Challenges in Hypersonic Propulsion
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Innovation and Challenges in Hypersonic Propulsion

A special issue of Aerospace (ISSN 2226-4310). This special issue belongs to the section "Aeronautics".

Deadline for manuscript submissions: 20 August 2025 | Viewed by 4241

Special Issue Editors

Prof. Dr. Kunyuan Zhang

E-Mail Website
Guest Editor
College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Interests: hypersonic propulsion; hypersonic inlet and nozzle design; internal flow
Dr. Yongzhou Li

E-Mail Website
Guest Editor
College of Aircraft Engineering, Nanchang Hangkong University, Nanchang 330063, China
Interests: hypersonic propulsion; hypersonic inlet and nozzle design; forebody-inlet integration design

Special Issue Information

Dear Colleagues,

Hypersonic propulsion, enabling flight at speeds exceeding Mach 5, has ignited a revolution in aerospace engineering, opening new frontiers in transportation, scientific exploration, and beyond. As research continues to push the boundaries of performance and efficiency, this Special Issue focuses on disseminating cutting-edge advancements and tackling critical challenges in this rapidly evolving field. We invite researchers and engineers from academia, industry, and government to submit original and high-quality manuscripts that explore innovative solutions and emerging frontiers related to hypersonic propulsion.

This Special Issue welcomes submissions on a broad spectrum of topics, including the following:

  • Air breathing propulsion system design;
  • Propulsion system and airframe integration;
  • Design and analysis of advanced inlets and nozzles;
  • Thermal management strategies and novel thermal protection materials;
  • Innovative combustion organization and advanced flame-stabilization techniques;
  • High-fidelity numerical simulations for hypersonic propulsion systems;
  • Advanced testing and experimental techniques;
  • Exploration of novel propulsion theories and technologies.

Prof. Dr. Kunyuan Zhang
Dr. Yongzhou Li
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Aerospace is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • hypersonic propulsion
  • propulsion/airframe integration
  • combined cycle engine
  • inlet design
  • supersonic combustion
  • nozzle design
  • flame stabilization
  • thermal management
  • aerothermodynamics
  • wind tunnel testing
  • numerical simulation

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Further information on MDPI's Special Issue policies can be found here.

Published Papers (6 papers)

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Research

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25 pages, 7114 KiB  
Article
Identification and Assessment of Scramjet Isolator Unstart and Operability Metrics
by Ragini Acharya
Aerospace 2025, 12(6), 503; https://doi.org/10.3390/aerospace12060503 - 2 Jun 2025
Viewed by 276
Abstract
Computational fluid dynamics (CFD) simulations play a strong role in the design and development of aerospace and defense vehicles, including high-speed applications where testing under the correct operational conditions is not yet viable. In this study, metrics for the onset of isolator unstart [...] Read more.
Computational fluid dynamics (CFD) simulations play a strong role in the design and development of aerospace and defense vehicles, including high-speed applications where testing under the correct operational conditions is not yet viable. In this study, metrics for the onset of isolator unstart are identified. An assessment of the variance of operating variables and their impact on metrics for the onset of isolator unstart and operability metrics was performed, utilizing a nozzle–isolator assembly from NASA Langley Research Center as a demonstration case. The effects of increasing backpressure ratio and decreasing inflow Mach number on these metrics and the underlying contributions of shock physics were investigated in detail. A major conclusion from this study is that both inflow Mach number and backpressure ratio can strongly impact pseudo shock train and shock–boundary layer interactions inside the isolator, but inflow Mach number has a stronger impact than the backpressure ratio. The research presented in this paper demonstrates that the isolator performance can shift from start to unstarted and operable to inoperable with a small variance in operating conditions. Another important insight presented in this research is that the length of the pseudo shock train and the Mach stem height change discontinuously with both the backpressure ratio and the inflow Mach number. Therefore, the length of the pseudo shock train and height of the Mach stem are strong indicators of the onset of unstart, which is an important consequence for instrumentation and closed-loop adaptive feedback control system design for scramjet flight operations. Full article
(This article belongs to the Special Issue Innovation and Challenges in Hypersonic Propulsion)
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20 pages, 5673 KiB  
Article
Unsteady Numerical Investigation into the Impact of Isolator Motion on High-Mach-Number Inlet Restart via Throat Adjustment
by Hongyu Tang, Yuan Liu, Yongfei Cao, Liangjie Gao and Zhansen Qian
Aerospace 2025, 12(5), 450; https://doi.org/10.3390/aerospace12050450 - 21 May 2025
Viewed by 148
Abstract
This paper focuses on exploring the variable throat-assisted restart method for high-Mach-number inlets. A two-dimensional adjustable throat hypersonic inlet was designed, and unsteady numerical simulations were carried out on its restart process, which was triggered by unstart induced by excessive back pressure and [...] Read more.
This paper focuses on exploring the variable throat-assisted restart method for high-Mach-number inlets. A two-dimensional adjustable throat hypersonic inlet was designed, and unsteady numerical simulations were carried out on its restart process, which was triggered by unstart induced by excessive back pressure and assisted by throat adjustment. The Chimera grid technique was used for grid generation, and the simulations were performed on the ARI_CFD platform. Results show that during the throat adjustment restart process, different flow states emerged with an increase in adjustment height. Specifically, when the adjustment height was too low, an unstarted flow state existed; within a specific height range (with lower and upper critical heights of 1.190 and 1.196, respectively, in this study), a fully restarted flow state occurred; and when the height was too high, an off-design flow state induced by the separation region in the internal contraction section occurred. The geometric adjustment time and throat adjustment angle also had a significant impact on the restart process. Shorter adjustment times and larger adjustment angles expanded the adjustment interval for full restart, as the rotation of the isolator helps reduce the resistance of the separation bubble’s downstream movement on the compression surface, thereby facilitating the full restart of the inlet. Full article
(This article belongs to the Special Issue Innovation and Challenges in Hypersonic Propulsion)
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14 pages, 7735 KiB  
Article
Numerical Investigation of a Supersonic Wind Tunnel Diffuser Optimization
by Riccardo Nicoletti, Francesco Margani, Luca Armani, Antonella Ingenito, Chihiro Fujio, Hideaki Ogawa, Seoeum Han and Bok Jik Lee
Aerospace 2025, 12(5), 366; https://doi.org/10.3390/aerospace12050366 - 23 Apr 2025
Viewed by 511
Abstract
The objective of this study is to enhance the methodology for the design of a supersonic wind tunnel, improving the process with advanced computational techniques. The supersonic wind tunnel is intended to operate within a flight envelope of Mach 2.5 to 4 and [...] Read more.
The objective of this study is to enhance the methodology for the design of a supersonic wind tunnel, improving the process with advanced computational techniques. The supersonic wind tunnel is intended to operate within a flight envelope of Mach 2.5 to 4 and altitudes between 18 and 20 km; this study focuses on the operative condition of Mach 3.5. The research is based on computational fluid dynamics, enabling a deeper understanding of fluid flow phenomena that can deteriorate the operability of the wind tunnel. Additionally, a detailed mesh independence study has been conducted to ensure the reliability and robustness of the computational results. These new analyses allowed for a more comprehensive optimization in the state of the art of tunnel geometry and operational conditions, further enhancing the ability to sustain supersonic flow for extended durations. Particular attention was given to the second throat, which plays a crucial role in the overall performance of the facility, especially during the start-up process. Its design has been refined to improve efficiency by reducing the minimum starting pressure. Full article
(This article belongs to the Special Issue Innovation and Challenges in Hypersonic Propulsion)
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20 pages, 5727 KiB  
Article
Study on the Characteristics of a Composite Power System with a Tip-Jet-Driven Rotor
by Yifei Wu, Yun Wang, Jinwu Wu and Jianxiang Tang
Aerospace 2025, 12(2), 109; https://doi.org/10.3390/aerospace12020109 - 31 Jan 2025
Viewed by 718
Abstract
Tip-jet helicopters operate by utilizing the reaction force generated by a high-speed tip jet, offering advantages such as a simplified and compact fuselage design and a reduction in empty weight by eliminating anti-torque balancing equipment. In tip-jet helicopter research, the composite power system [...] Read more.
Tip-jet helicopters operate by utilizing the reaction force generated by a high-speed tip jet, offering advantages such as a simplified and compact fuselage design and a reduction in empty weight by eliminating anti-torque balancing equipment. In tip-jet helicopter research, the composite power system is regarded as a crucial and bottleneck element. This study employs numerical simulations to comprehensively analyze the internal flow characteristics of the gas generator and tip-jet-driven rotor within the composite power system. Specifically, an in-depth investigation has been conducted on the influence laws of various parameters on the system characteristics. These parameters encompass the tip-jet-driven rotor speed, which takes on values of 50 rad/s, 80 rad/s, 100 rad/s, 120 rad/s, and 150 rad/s, the tip-jet-driven rotor length, measured at 1585 mm, 1785 mm, 1985 mm, 2185 mm, 2385 mm, 2585 mm, and 2785 mm, and the tip-jet-driven rotor nozzle area, which is specified by six values corresponding to multiples of the straight section area of the rotor’s internal channel, namely 0.25 times, 0.5 times, 0.75 times, 1 times, 1.25 times, and 1.5 times. The analysis of the obtained results indicates several significant relationships. Firstly, it is observed that the available moment exhibits a linear decrease as the tip-jet-driven rotor speed increases. Secondly, the maximum available moment is attained when the tip-jet-driven rotor length (L) satisfies the relationship L = Vr/2ω. Additionally, the maximum available power is achieved when the transport velocity of the tip-jet-driven rotor nozzle is precisely half of the relative velocity of the nozzle. Moreover, under the condition that the mass flow rate of the tip-jet-driven rotor nozzle remains constant, a positive correlation between the available moment and the reduction in the tip-jet-driven rotor nozzle area is noted. Full article
(This article belongs to the Special Issue Innovation and Challenges in Hypersonic Propulsion)
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14 pages, 2917 KiB  
Article
Numerical Investigation of Non-Equilibrium Condensation in a Supersonic Nozzle Based on Spontaneous Nucleation
by Saman Javadi Kouchaksaraei and Mohammad Akrami
Aerospace 2024, 11(12), 1032; https://doi.org/10.3390/aerospace11121032 - 17 Dec 2024
Cited by 3 | Viewed by 999
Abstract
Non-equilibrium condensation involves intricate physics, making it crucial to thoroughly investigate the factors that influence it. Understanding these factors is essential for optimizing the system performance and minimizing the negative effects associated with non-equilibrium condensation. This study focused on examining the impact of [...] Read more.
Non-equilibrium condensation involves intricate physics, making it crucial to thoroughly investigate the factors that influence it. Understanding these factors is essential for optimizing the system performance and minimizing the negative effects associated with non-equilibrium condensation. This study focused on examining the impact of various operational conditions in a saturated mode on non-equilibrium condensation within a supersonic nozzle. The operation conditions under investigation involved pressures of 25 kPa, 50 kPa, 75 kPa, and 100 kPa. Each saturation state was examined to assess its effect on various parameters, such as temperature, pressure, liquid mass fraction, droplet radius, nucleation rate, Mach number, and droplet count. A consistent pattern emerged across all samples. As the gas accelerated through the converging section of the nozzle, both pressure and temperature gradually decreased. However, upon reaching the throat and entering the divergent section, a phenomenon known as condensation shock occurred. This shock wave caused a sudden and significant spike in both pressure and temperature. Following the shock, both parameters resumed their downward trend along the remaining length of the nozzle. Interestingly, increasing the initial pressure of the gas led to a less intense condensation shock. Additionally, raising the saturation pressure at the nozzle inlet resulted in larger droplets and a higher concentration of liquid within the gas flow. By quadrupling the inlet saturation pressure from 25 to 100 kPa, a substantial 106.9% increase in droplet radius and a 9.65% increase in liquid mass fraction were observed at the nozzle outlet. Full article
(This article belongs to the Special Issue Innovation and Challenges in Hypersonic Propulsion)
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Review

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30 pages, 8617 KiB  
Review
Progress and Development of Solid-Fuel Scramjet Technologies
by Wenfeng Yu, Yun Hu, Shenghai Zhao and Rongqiao Wang
Aerospace 2025, 12(4), 351; https://doi.org/10.3390/aerospace12040351 - 16 Apr 2025
Viewed by 831
Abstract
The solid-fuel scramjet has become a potential power device for hypersonic missiles in the future and has important military application prospects due to its advantages in gas flow regulation, flame stability, and blended combustion efficiency. This paper summarizes the research progress of three [...] Read more.
The solid-fuel scramjet has become a potential power device for hypersonic missiles in the future and has important military application prospects due to its advantages in gas flow regulation, flame stability, and blended combustion efficiency. This paper summarizes the research progress of three types of solid-fuel scramjet, including a large number of landmark numerical and experimental results. At the same time, the research progress of supersonic steady combustion and combustion enhancement technology, thermal protection technology, and the improvement of solid-fuel and combustion performance are reviewed. On this basis, the key technologies of the solid solid-fueled scramjet are summarized, and several internal scientific problems are summarized, such as the combustion organization strategy of the wide velocity domain solid rocket scramjet, efficient combustion chamber loading and thermal bulking technology, combustion instability, etc. Finally, some suggestions for the future development of the solid-fuel scramjet are put forward. Full article
(This article belongs to the Special Issue Innovation and Challenges in Hypersonic Propulsion)
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