Reusable Launch Vehicle Research Articles

Additive manufacturing of ceramic multi-material heating and ignition elements for a sustainable space access

The continuous advancement in the space industry and in space access has opened the doors to greater global participation and exploration, with numerous nations, institutes and companies now actively engaged in space exploration. This expansion owes much to the progress in commercial space technologies, such as reusable launch vehicles and micro satellites, which have significantly reduced the overall costs associated with space missions, thereby enhancing space accessibility.Nevertheless, to foster further growth, it is necessary to look at further options of making space access more sustainable and cost-effective. For that, it is important to investigate and identify the cost drivers. An example is the use of traditional manufacturing techniques and materials, which come with inherent limitations, notably in terms of design flexibility and performance efficiency. This results in solutions that are not only time-consuming to manufacture but also not the most effective, making it a costly process.To address these challenges, increasing emphasis is being placed on utilising alternative manufacturing methods, such as additive manufacturing technologies combined with high-performance ceramic materials. This aims to reduce the overall number of manufacturing steps for producing a component and to optimise complex and functional parts reducing the overall costs of mass-produced or individually manufactured components, as evident in current studies.The primary objective of this study is to enhance space accessibility through the development, production and optimisation of electrically functional, all-ceramic and multi-material components (heating/ignition elements). For that, the AM technology “CerAM MMJ” in combination with high performance ceramic material are utilised and discussed. Subsequently, these components undergo electrical measurements and tests, and the resulting data is presented and analysed in the following sections.The findings aim to shed light on the current state of the art and whether the additively manufactured, fully ceramic and electrically functional components could represent a more cost-effective alternative to conventionally manufactured components in the future.

Enhancing the landing guidance of a reusable launch vehicle by improving genetic algorithm-based deep reinforcement learning using Hybrid Deterministic-Stochastic algorithm.

The PbGA-DDPG algorithm, which uses a potential-based GA-optimized reward shaping function, is a versatiledeep reinforcement learning/DRLagent that can control a vehicle in a complex environment without prior knowledge. However, when compared to an established deterministic controller, it consistently falls short in terms of landing distance accuracy. To address this issue, the HYDESTOC Hybrid Deterministic-Stochastic (a combination of DDPG/deep deterministic policy gradient and PID/proportional-integral-derivative) algorithm was introduced to improve terminal distance accuracy while keeping propellant consumption low. Results from extensive cross-validated Monte Carlo simulations show that a miss distance of less than 0.02 meters, landing speed of less than 0.4 m/s, settling time of 20 seconds or fewer, and a constant crash-free performance is achievable using this method.

Multibody modelling of tether and capture system for dynamic simulations of In-Air Capturing

The launcher recovery method known as ‘In-Air Capturing’ is an innovative approach where a winged rocket stage is captured mid-air by an aircraft and subsequently towed back to the launch site. To achieve this, a capturing device attached to a tether is released from the towing aircraft. This device autonomously connects the reusable launch vehicle to the aircraft, while the two vehicles are in proximity. The tether’s flexible dynamics have a strong influence on the maneuverability of the capturing device. Thus, it is critical to model the dynamics of the tether to get a realistic understanding and to evaluate feasibility of the concept. However, precise modelling and control of highly flexible systems with large deformations is both challenging and computationally intensive. For engineering applications which involve closed-loop simulations, finding a trade-off between accuracy and computational effort is crucial. In this paper, the tether is modelled as a discretized chain of rigid bodies connected by rotational springs at the joints. The tether along with the capture system is integrated in a simulation model and open loop tests are performed to analyse the system characteristics. The tether properties are studied to find a suited configuration for ‘In-Air Capturing’.

UDE-based adaptive dynamic surface control for attitude-constrained reusable launch vehicle

UDE-based adaptive dynamic surface control for attitude-constrained reusable launch vehicle

Design and Implementation of Continuous Bounded Finite-Time Attitude Control of Reusable Launch Vehicle

In this paper, a novel continuous bounded finite-time control algorithm is proposed for reusable launch vehicle (RLV) attitude control system with mismatched disturbances and unknown control coefficients. The remarkable feature of the developed algorithm is to ensure the finite-time stability of RLV attitude system with uniformly continuous bounded control torque signal. Meanwhile, a multivariable finite-time observer is designed to estimate the unknown mismatched disturbances, and the combination of the developed controller and observer could offer better robustness without losing control boundedness. Finally, numerical simulations and experimental results based on three-axis turntable are provided to verify the effectiveness and advantages of the proposed continuous bounded finite-time control method.

A novel cable-net buffer device for recovering reusable launch vehicle: Design, dynamic modeling, and performance analysis

At present, reusable launch vehicle technology (RLV) has become a research hotspot in the aerospace field and one of the major development trends in this industry. With reference to the aircraft carrier’s arresting cable technology, this paper puts forward a novel cable-net buffer device for recovering the first stage of launch vehicle. The device can transfer load through a cable-pulley mechanism, and then complete the first stage recovery by losing the kinetic energy and gravitational potential energy of the first stage through hydraulic dampers and preloaded counterweights. In order to analyze the performance of this cable-net buffer device, the finite element software ABAQUS is adopted to establish a rigid-flexible coupling dynamic model. In this model, the cable-pulley mechanism is simulated by connector and shell elements, the damping force of the hydraulic dampers by VUAMP subroutine, and the preloaded counterweights by mass point. And then, performance evaluation indexes of this buffer device are proposed in this paper. Meanwhile, the dynamic simulation, using the established dynamic model, is carried out under different device design parameters and working condition parameters. On the one hand, the simulation results show that the tower span and damping force have remarkable effects on the buffer performance. On the other hand, among all working condition parameters, only the fall point deviation has a significant effect on the buffer performance, but this effect is less than that of the design parameters. Finally, combing the dynamic model and the surrogate model technique, this paper obtains feasible boundaries of design parameters of the device for the subsequent detailed design of it. Researches in this paper will provide new ideas for the development of RLV.

Adaptive multivariate reusable launch vehicles reentry attitude control with pre-specified performance in the presence of unmatched disturbances

This paper introduces a novel adaptive multivariable attitude control method for a reusable launch vehicle (RLV) to track desired attitude trajectories in the presence of unknown external disturbances and uncertainties. Unlike most existing designs that overlook mismatched disturbances, this method employs an adaptive finite-time observer (AFO) to estimate the unknown states. Based on the outputs of the AFO and the prescribed performance function, a time-varying adaptive gain that is not overestimated is designed to establish the adaptive multivariable attitude control for the RLV system. The simulations demonstrate that the proposed approach successfully guides the RLV to follow desired attitude signals despite the presence of unmatched disturbances and uncertainties.

Экономика космоса: глобальный контекст и опыт Франции

Various approaches to the space economy are considered, its components are highlighted. Space and the knowledge about it, being the bedrock of the space economy, are considered as a public good. The space economy as a factor of geopolitics and realization of sustainable development goals is an area of competition and cooperation for global actors. On the one hand, the leading role of the State and its expenditures now and next in space exploration and development is emphasized, on the other hand, the growing role of public and private companies’ partnership is gaining momentum, including commercial projects for launching people into space not only for research, but also for recreational purposes by reusable launch vehicles. The gap between the USA as a leader of the space economy and its competitors exploring and using space for civil and military purposes has been statistically proven. The traditional disparity between spending on civilian and military projects in space is shrinking, and the parity may be set by 2030. The key role of France – the leading country of the EU and of the countries of the ESA – in the genesis and development of the space economy in the West European part of the continent is revealed. Such an important role of France is largely due to the attention that has historically been paid to this sphere of the national economy, based on the use of nuclear technologies by the only nuclear power in the EU. The dynamics of the space economy is not in favor of France and Europe, largely due to insufficient financing (both public and private), with a great difference between European space budget and that of the USA and China. The conclusion is made that it is unlikely for France (and the EU) to bridge the gap with these leaders in the foreseeable future, despite the planned increase in investments for this innovative sector of the economy.

Practical Method of Control Allocation of Jets and Aerosurfaces for Reusable Launch Vehicle at Entry Phase

Practical Method of Control Allocation of Jets and Aerosurfaces for Reusable Launch Vehicle at Entry Phase

Zero Dynamic Active Suppression Control for Underactuated Reusable Launch Vehicles With Nonminimum Phase Property

Zero Dynamic Active Suppression Control for Underactuated Reusable Launch Vehicles With Nonminimum Phase Property

Numerical analysis on thermal environment of reusable launch vehicle during supersonic retropropulsion

Developing reusable launch vehicles (RLV) is an effective way to significantly reduce space transportation costs. However, in the return stage of the vehicle, especially the supersonic retropropulsion (SRP), the first stage is partially submerged in the hot exhaust plume and faces severe convective heating at the base plate and sidewalls. As a rule of thumb, the layout of nozzles at the rocket base significantly affects the heat load. In order to evaluate the influence of heat load under different nozzle configurations during SRP (33 km–22 km), the thermal environment of RLV was studied through numerical investigation for three typical nozzle configurations. Using Reynolds-averaged Navier–Stokes equations (RANS)-based computational methods and the k−ω SST turbulence model, the flowfield is characterized at different trajectory points during retropropulsion. Results showed that the high heat flux is mainly concentrated in the baseplate's center area and the sidewall's near base area during SRP. In general, activating engines in the radial position is beneficial for the thermal protection system of a reusable launch vehicle while the thrust is identical. Base heating primarily results from high-temperature counterflows due to plume interactions, while sidewall heating is predominantly a result of high-temperature recirculation zones generated by plume-induced flow separation. During the supersonic retropropulsion phase, the 3-nozzle-180°, a non-closed nozzle configuration, has significantly lower heat loads on the baseplate and the sidewall than that of the 4-nozzle-90° and the 3-nozzle-120°. In addition, reducing the number of engines is also an effective solution under the same conditions of thrust. Studying the layout of the working engine without changing the original layout has important guiding significance for improving the reusability and safety factor of the RLV.

Mission Performance Assessment of the Recovery and Vertical Landing of a Reusable Launch Vehicle

This paper focuses on the mission analysis of the return trajectory of a Vertical Landing Reusable Launch Vehicle, both for Return-to-Launch-Site (RTLS) and DownRange Landing (DRL) recovery strategies. The main objective is to assess the mission performance of propellant-optimal re-entry and landing trajectories from the Main Engine Cut-Off (MECO) while considering propellant budget and peak entry conditions constraints. As a result, performance envelopes and feasibility regions are built to comprehensively assess the required propellant and compare recovery strategies across a broad spectrum of MECO conditions. The results show that the DRL strategy achieves higher efficiency concerning the propellant consumption and a larger robustness regarding the dispersed MECO conditions.

Flame structure of GCH4/GOX pintle model combustor with wall confinement

The pintle injector is a representative option for designing a throttleable rocket engine that can be applied for various applications, including the vertical soft landing of reusable launch vehicles. Although the most direct research method to investigate the characteristics of pintle injectors experimentally is the high-pressure combustion test, it is often limited due to its cost and operational hazards. Consequently, atmospheric combustion or cold flow tests are frequently applied in the rocket injector field to simulate and study the fundamental combustion or spray characteristics. However, previous works, including such simulated experiments under atmospheric conditions, involved an unrealistically wide combustor or open condition. Since only a single pintle injector is typically used per engine, the combustor wall may significantly influence the fundamental characteristics. Thus, in this study, a pintle injector combustor with adequate wall confinement is designed, and its flame structure is investigated across a wide range of total volume flow rates and mixture ratio conditions, incorporating several geometries with varying gaseous oxygen injection areas. This research primarily focuses on the flame structure and its angle. Under specific experimental conditions, the unreported unstable flame was newly observed. The overall experimental results, supported by numerical methods, indicate that wall confinement has substantial importance in simulating a realistic flame structure and internal flow field within the combustor.

A novel re-entry trajectory design strategy enforcing inequality and terminal constraints in height-velocity plane

A novel re-entry trajectory design approach for a winged reusable launch vehicle that satisfies path and terminal state constraints in the height velocity plane is proposed in this paper. A two-phase re-entry trajectory is proposed. A height-velocity plane entry corridor is designed using all path and quasi-equilibrium glide constraints. The proposed method creates the reference trajectory inside the re-entry corridor using three piecewise polynomials, such as linear and logarithmic. A two-parameter search optimization problem minimizes terminal range-to-go error for this reference trajectory generation problem. Improved Search Space Reduction solves this optimization problem. The Improved Search Space Reduction algorithm is compared to the Grey Wolf Optimizer and Particle Swarm Optimisation algorithms to prove its efficacy and superiority. The reference bank angle is modified using feedback linearization and bank reversal logic to create an entry trajectory that meets all path and terminal constraints. The effectiveness of the proposed method has been validated through Monte Carlo simulations that incorporate uncertainties such as variations in initial state, uncertainties in aerodynamics, and atmospheric perturbations. The controller OPAL-RT OP4510 provides bank angle command at every instant based on the current state of the vehicle parameters associated with real-time simulator OP4510. The real-time hardware-in-loop simulation results show that the obtained re-entry trajectory satisfies all path and terminal constraints.

Improved Analytical Model for the Magnetic Drag of a Dual-Conductor Plate Parallel Electric Suspension and Guiding Mechanism

The Maglev launch assist system (MLAS) has been adopted as part of a reusable launch vehicle system to lower launch costs. In this paper, a dual-conductor plate parallel electric suspension and guiding mechanism (DPESGM) serving the suspension and guidance function of the MLAS is proposed. First, the MLAS and the structure of the DPESGM are introduced. Then, a DPESGM magnetic drag analysis model is established based on the multilayer theory for the fast calculation of the magnetic drag. However, its accuracy is poor at high speed. To solve this problem, an improved analytical model suitable for the full speed range is developed, which takes the equivalent conductivity replacement approach to consider the skin effect. Finally, the improved analysis model is verified by the finite element method (FEM) and prototype experiments. The results show that the improved analytical model is highly accurate in the evaluation of the DPESGM magnetic drag from low speed to high speed. As the improved analytical model takes less computational time than 3D FEM, it is an efficient tool for the DPESGM magnetic drag calculations to complete the preliminary design of the propulsion and braking systems.

Estimation of the Thermophysical Properties of C/C Plates with Ceramic Nanocoating at Different SiO2 Filling for Aerospace Applications

In aerospace industrial and commercial scenario, the reusable launch vehicles (RLV) evolution works constantly toward the lowering of payload conveyance expenses. The thermal protection system (TPS) preserves the integrity of the space vehicle surfaces exposed to huge thermal shock during the re-entry phase: its advanced design and manufacturing, aimed at both reusing and withstanding harsh space environment, result in increasing the production and maintenance charges. The present study introduces a cost-saving concept of TPS component made of carbon/carbon (C/C) tiles coated by a commercial refractory varnish reinforced with ceramic nanoparticles. Using a reliable computing method, known as inverse method, the thermophysical properties such as heat capacity and thermal conductivity of the manufactured materials are assessed in a broad range of temperatures, with the input aid of an in-house developed experimental setup. The described technique is especially suited for approaching such kind of issues, thanks to the capability of taking into account several physical variables simultaneously, with the aim of gaining a robust knowledge of materials’ thermal behavior for potential use in spacecraft TPS.

Development of a Controlled Dynamics Simulator for Reusable Launcher Descent and Precise Landing

This paper introduces a Reusable Launch Vehicle (RLV) descent dynamics simulator coupled with closed-loop guidance and control (G&C) integration. The studied vehicle’s first-stage booster, evolving in the terrestrial atmosphere, is steered by a Thrust Vector Control (TVC) system and planar fins through gain-scheduled Proportional–Integral–Derivative controllers, correcting the trajectory deviations until precise landing from the reference profile computed in real time by a successive convex optimisation algorithm. Environmental and aerodynamic models that reproduce realistic atmospheric conditions are integrated into the simulator for enhanced assessment. Comparative performance results were achieved in terms of control configuration (TVC-only, fins-only, and both) for nominal conditions as well as with external disturbances such as wind gusts or multiple uncertainties through a Monte Carlo analysis to assess the G&C system. These studies demonstrated that the configuration combining TVC and steerable planar fins has sufficient control authority to provide stable flight and adequate uncertainties and disturbance rejection. The developed simulator provides a preliminary assessment of G&C techniques for the RLV descent and landing phase, along with examining the interactions that occur. In particular, it paves the way towards the development and assessment of more advanced and robust algorithms.

Physical modeling and simulation of electro-mechanical actuator-based TVC systems for reusable launch vehicles

This paper presents the high-fidelity physical modeling of a Thrust Vector Control (TVC) system operated by Electro-Mechanical Actuators (EMAs) for Reusable Launch Vehicles (RLVs). In contrast to simplified, often linear, models, high-fidelity physical models enable a better assessment of the actual system performance and a deeper verification of the on-board software robustness against disturbances, unmodeled dynamics or degradation. This aspect is essential to enable the reusability concept as driven by long-term reliability requirements. Moreover, critical systems like Fault Detection, Isolation and Recovery (FDIR) logic, whose robustness and efficacy are often difficult to prove, can be thoroughly tested without requiring hardware experiments with eventual invasive modifications for fault injections. This work captures the whole dynamics of the EMA and TVC components, including the power drive electronics, the electrical motor, and the mechanical transmission for the EMA, as well as the mechanical properties of the engine nozzle acting as a load. The resulting differential algebraic equation system is modeled in the Modelica acausal object-oriented modeling language. An ad-hoc framework is implemented to guarantee flexibility and modularity, which allows models with different fidelity levels to be easily exchanged to achieve the simulation objectives and needed accuracy level. The impact of the different models on the closed-loop TVC dynamics is analyzed in both the frequency and time domain, and then benchmarked with a realistic RLV mission. The results show that the high-fidelity physical models provide a better understanding of the more complex effects governing the TVC dynamics and can, in turn, effectively improve its requirement definition process.

A Real-Time and Optimal Hypersonic Entry Guidance Method Using Inverse Reinforcement Learning

The mission of hypersonic vehicles faces the problem of highly nonlinear dynamics and complex environments, which presents challenges to the intelligent level and real-time performance of onboard guidance algorithms. In this paper, inverse reinforcement learning is used to address the hypersonic entry guidance problem. The state-control sample pairs and state-rewards sample pairs obtained by interacting with hypersonic entry dynamics are used to train the neural network by applying the distributed proximal policy optimization method. To overcome the sparse reward problem in the hypersonic entry problem, a novel reward function combined with a sophisticated discriminator network is designed to generate dense optimal rewards continuously, which is the main contribution of this paper. The optimized guidance methodology can achieve good terminal accuracy and high success rates with a small number of trajectories as datasets while satisfying heating rate, overload, and dynamic pressure constraints. The proposed guidance method is employed for two typical hypersonic entry vehicles (Common Aero Vehicle-Hypersonic and Reusable Launch Vehicle) to demonstrate the feasibility and potential. Numerical simulation results validate the real-time performance and optimality of the proposed method and indicate its suitability for onboard applications in the hypersonic entry flight.

Unsteady investigation on parallel separation for spiked two-stage reusable launch vehicle

Two stage to orbit vehicles can reduce weight and improve propulsion efficiency, reducing launch cycle costs. For the safety of two-stage parallel separation, a spiked Two-Stage-To-Orbit (TSTO) configuration for parallel separation was proposed, which is consisted of a waverider liked booster and a wing-body configuration. An aerospike was placed at the head of the second stage. The unsteady simulation of the TSTO interstage separation at Mach 6 was investigated using the self-developed code, CMA. The pressure contours, pitch angle and displacement variation of the two models were compared. Under the interference of the aerospike, the flow field of the blunt body exhibited significant asymmetry at the angle of attack. The oblique shock wave on the leeward side was weaker than that on the windward side, and the area affected by the shock wave on the windward side gradually moved toward the stagnation point as the angle of attack increased, thereby improving the safety of the separation process of the two stages that originally collided by changing the flow field structure. In addition, the aerospike reduces the aerodynamic interference between the two stages without changing the aerodynamic shape of the aircraft, thereby reducing the drag.