Reusable Launch Vehicle Research Articles

Анализ основных проектных параметров малого разгонного блока

The contemporary space market is in need of small upper stages for performing operations for the delivery of small spacecraft to a working orbit and for solving other problems of interorbital operations. Based on materials that are publicly available, an overview of upper stages of spacecraft is given, including the concepts of small upper stages that are under study. An analysis of the design parameters of a small upper stage was carried out, the tasks of which are to deliver a payload of 500 kg to a geostationary orbit from a low Earth orbit, refuel and return to low Earth orbit. The obtained results are compared with the parameters of the operating upper stages. The design and development of small upper stages is at the development stage and is a promising area of research. The application of a reusable upper stage will allow it to be returned to Earth employing reusable launch vehicles.

Computational Fluid Dynamics analysis on the Reusable Launch Vehicle

Computational fluid dynamics and Additive manufacturing are the two important and recently used technique in the reusable launch vehicle. In this article the design and flow simulation of the re-entry capsule has been performed using Computational Fluid Dynamics in order to optimize the suitable re-entry capsule design. Computational fluid dynamics can be used to simulate the real time supersonic flow during re-entry which helps in predicting the important characteristics during the formation of shock waves. The study considered Mach 5 conditions and an altitude of 5km. In addition, the formation of shock waves was delayed in the present studies compared to previous work. It should be noted that the current aerospace industry uses the advantage of additive production in prototyping to test re-entry launch vehicles.

Adaptive finite-time prescribed performance attitude tracking control for reusable launch vehicle during reentry phase: An event-triggered case

This paper is devoted to address the attitude tracking problem for reusable launch vehicle (RLV) with uncertain aerodynamic parameters, input saturation and limited transmission resources. Based on the framework of the backstepping technique, a novel event-triggered adaptive prescribed performance control protocol is presented. Firstly, an extended state observer is used to provide the estimation for the whole system uncertainties. Then, an event-triggered mechanism is applied to exactly determine when control signals should be updated, which successfully eliminates the unnecessary periodic/continuous sampling in time-triggered researches and creates less waste of transmission resources. To compensate the negative effects induced by the aperiodic updating of control signals in event-triggered mechanism, an appointed-time prescribed performance controller is devised. In this way, the stability and tracking performance for the attitude system of the RLV can be guaranteed simultaneously. Moreover, the detailed theoretical analysis confirms that Zeno-free triggering is completely guaranteed along with stability. Finally, extensive simulations are carried out to validate the effectiveness of the proposed control protocol.

Anti-Windup Robust Backstepping Control for an Underactuated Reusable Launch Vehicle

The attitude control of an underactuated reusable launch vehicle (RLV) in the reentry phase involving nonminimum phase problem and control input constraints is investigated in this article. To address the nonminimum phase problem, an approach combining output redefinition and robust backstepping is proposed, where a synthetic output is constructed using the combination of the original output and the internal states to obtain stable zero dynamics, and then robust backstepping is performed on the new output. Besides, the ideal internal dynamics are obtained by using optimal bounded inversion, which are incorporated into the controller as the reference trajectories for the internal states to improve the output tracking accuracy. To cope with the control input constraints, a simple and useful anti-windup strategy is proposed by using feedback error clipping, which is shown to be very effective in mitigating control input saturation. Numerical simulations are given to validate the effectiveness of the proposed method.

The solar shield concept: Current status and future possibilities

The concept of deploying a large solar shield, or sunshade, near the Sun-Earth L1 Lagrange equilibrium point was first proposed in 1989. The purpose of such a solar shade would be to reduce the quantity of solar radiation impinging on planet Earth, thus lowering the average global surface temperature and countering, to some extent, global warming. This form of solar radiation management seems to be one of the safest and most efficient methods proposed to date but also seems to be extremely expensive and perhaps too difficult to implement in a timely manner. The near-term arrival of cheap, re-useable launch vehicles may be able to address both of these concerns. Depending on the assumptions made, deploying a solar shield near the Sun-Earth L1 point might actually be feasible in the near term and would be able to slow, stop, or even reverse Earth's global warming, even in the face of increasing levels of greenhouse gases in Earth's atmosphere. Solar radiation management doesn't address other environmental issues, such as the acidification of the world's oceans, but it does address the more urgent issue of impending global warming and the resulting climate change, thus buying time for the World's economies to transition to more sustainable, carbon-free energy sources. The infrastructure necessary to construct and deploy a large solar shield will probably be space-based and could be useful for many other purposes after deployment of the solar shield.

Fractional-order sliding mode control with a predefined-time observer for VTVL reusable launch vehicles under actuator faults and saturation constraints

For vertical takeoff vertical landing (VTVL) reusable launch vehicle (RLV) with actuator faults and saturation constraints, this paper presents a composite control system including a high-order predefined-time extended state observer (HO-PTESO), a predefined-time anti-saturation compensator (PTASC), and a fractional-order practical predefined-time sliding mode control law (FO-PPTSMC). The HO-PTESO accomplishes the precise estimation of disturbance in a time interval predefined by only one design parameter, resulting in a simple and weakly conservative parameter tuning process for temporal demands. Moreover, the peaking value problem is well addressed. The PTASC serves to ensure the stability of the saturated system. Auxiliary variables of the PTASC remain bounded during the saturation process and vanish within the predefined time interval after the saturation process ends, avoiding long-term impacts on the attitude tracking that are common concerns for existing ASCs. Using the estimated disturbance, the FO-PPTSMC enforces unsaturated system states to a predefined residual set of the origin in a chattering-alleviated manner within the predefined time interval. Two parameters respectively predefine the convergence range and time, resulting in a considerably simplified synthesis procedure. Ultimately, numerical simulations on the double integrator system and VTVL RLV model validate the efficiency of the proposed control system.

Drag and Heat Flux Reduction on Hypersonic Re-entry Vehicles in Combination with Different Aerospikes

Hypersonic re-entry space vehicles, reusable launch vehicles and intercontinental ballistic missiles all use a blunt body as its fore body to decelerate the re-entry vehicle with aerodynamic heating as the result. Blunt bodies produce more wave drag due to strong detached bow shock wave formation in front of the body. To overcome this, wave drag aerospike has been introduced in front of the blunt body. This aerospike weakens the strong detached bow shock into a weaker oblique shock. It also creates a re-circulation zone (due to the adverse pressure gradient) in front of the body which greatly reduces the high pressure on the front portion of the body. Hence, aerospike is used in front of the blunt body to reduce the wave drag. This aerospike concept was first conceived in the 1950s as a means of reducing the heat transfer rates and aerodynamic drag on axis-symmetric blunt bodies. Many researchers have carried experiments out on the aerospike concept. In this study, computational investigations were carried out on blunt bodies with and without spikes, to know the flow behaviour at different Mach numbers with the help of computational fluid dynamics software. Experimental validations were compared. The effects on the coefficient of drag due to changing the spike tips, such as different aerospikes and spikes, were studied. The effect of the heat flux of the spike was also studied. Finally, conclusions on the optimum tip portion spike were chosen.

Fin actuation, thrust vector control and landing leg mechanisms design for the RETALT VTVL launcher

To foster the competitiveness of the European industry in the global launcher market, the need arose to build up the necessary know-how on state-of-the-art vertical take-off vertical landing (VTVL) concepts and corresponding technologies. In the EU Horizon 2020 project RETALT (RETro propulsion Assisted Landing Technologies), the VTVL approach applying retro propulsion is investigated for two-stage-to-orbit (TSTO) and single-stage-to-orbit (SSTO) reusable launch vehicles, these configurations are named RETALT1 and RETALT2. In the project framework investigation of both reference configurations is performed in several areas: aerodynamics, aerothermodynamics, flight dynamics and guidance, navigation, and control (GNC), as well as thermal protection and structures and mechanisms. Focusing on solutions for the RETALT 1 launch vehicle, Almatech contributes with the design of mechanisms to actuate the aerodynamic controls surfaces, retain and deploy the landing legs and provide means to dissipate energy during touch-down. Demonstrators of these mechanism are also built during the project. In addition to the above activities, Almatech proposes thrust vectoring solutions. This paper presents an overview of these activities and results obtained so far.

RETALT_TPS design and manufacturing

The present document discusses the development of a new trowelable Thermal Protection System (TPS), able of being mixed, applied and cured directly onto the vehicle structure, with the aim to fulfill the requirements of the thermal properties for the re-usable launch vehicle studied in the Retro Propulsion Landing Technology (RETALT) project. During the development of this TPS, several formula optimizations were made to improve or eliminate cracks in the char surface, increase char stiffness, rheological adjustments, and adhesion improvement to different substrates. The most promising material developed is composed by cork and epoxy resin, together with a set of rheological and thermal resistance additives, that makes it possible to be applied with a spatula, while at the same time it is able to withstand the demanding environmental conditions during atmospheric reentry. In terms of thermal properties, the developed material has a higher thermal conductivity than the current P50 TPS commercialized by Amorim Cork Composites (ACC), but it has a better behavior when exposed to flame conditions. It is expected that the absence of cracks improves its structure and resistance to demanding conditions. The development work included a detailed study of the composition and processes required for the development of a TPS material, which were evaluated by several types of flame characterization tests and thermal properties analysis.

Gain Scheduled Finite Horizon LQR for Approach and Landing Phase of a Reusable Launch Vehicle

Gain Scheduled Finite Horizon LQR for Approach and Landing Phase of a Reusable Launch Vehicle

Aerothermal databases and load predictions for Retro Propulsion-Assisted Launch Vehicles (RETALT)

The assessment of thermal loads occurring on reusable launch vehicles during the entire trajectory is essential for the correct dimensioning of the thermal protection system. Due to the costs and limitations of ground-based testing for large-scale vehicles, these predictions rely intensively on numerical simulations (CFD). The need of aero-thermal databases, as a fast-response surrogate model for the aero-thermodynamic heating, arises from the practical impossibility of performing unsteady CFD analysis over the entire trajectory due to the large disparity of fluid mechanical and structural time scales. The construction of these databases is based on a representative set of CFD simulations which cover, at a minimum, the flight regimes with significant thermal loads. The aim of this paper is to analyse the results of these representative CFD simulations during both the ascent flight and atmospheric entry for the RETALT1 vehicle to show typical flow field phenomena occurring during these phases and the resulting heating patterns.

Terminal Phase Descent Trajectory Optimization of Reusable Launch Vehicle

Optimization of terminal phase descent trajectory of winged reusable launch vehicle is studied in this paper. This trajectory consists of ‘Terminal Area Energy Management (TAEM)’ phase and ‘Approach and Landing (AL)’ phase. Three dimensional dynamics of an unpowered winged launch vehicle over a rotating Earth and an oblate gravitational field, is considered. The objective of the trajectory optimization is to land the vehicle horizontally on a predefined runway, using angle of attack and bank angle command, satisfying the path constraints of dynamic pressure, load factor and control limits, and terminal constraints of position, horizontal velocity, sink rate and heading. Trajectory is optimized using Chebyshev pseudospectral knotting method, wherein the state and control variables are discretized at Chebyshev-Gauss-Lobatto (CGL) points and the problem is converted to a nonlinear programming problem. The versatility of the formulation is demonstrated by obtaining optimum trajectories for a variety of initial conditions and cost functions and the analysis of the optimum trajectories are presented.

Hydrogen sensor for application in reusable launch vehicles

Hydrogen sensor for application in reusable launch vehicles

Hydrogen sensor for application in reusable launch vehicles

Hydrogen sensor for application in reusable launch vehicles

Thermo-mechanical characterization of carbon-based ceramic foams for high temperature space application

The successful development of aerospace reusable launch vehicles (RLV) require to realize effective thermal protection systems (TPS) for preserving spacecraft integrity from the severe thermal loads during re-entry phase. To such an aim, due to the need of reducing payload transportation costs, applied research is driven towards lightweight materials with advanced thermo-mechanical properties. Space TPS are often based on sandwich structures, where the core material has the main function of thermal insulation. Ceramic porous materials, as carbon (C) and silicon carbide (SiC) foams, represent ideal candidates for application as structural TPS component, thanks to both low density and significant thermal stability at very high temperatures. The paper presents a joint experimental study of carbon-based ceramic foams proposed as sandwich’s core for TPS design. A full thermal characterization of commercial C- and SiC-foam materials is reported, including measurements of thermo-mechanical combined stress, temperature-induced outgassing behavior and heat transfer properties. These latter, in particular, are studied by means of a robust numerical technique, known as the inverse method, which allows to evaluate materials thermal conductivity and heat capacity over a wide range of temperatures, thus establishing the required material behavior for potential use in spacecraft TPS.

Constrained state feedback pole placement of coupled lateral plant dynamics of RLV during the reentry phase

Stability and dynamic behaviour of a linear multivariable system mainly depend on the pole locations of the plant in the complex s plane. For general linear time-invariant multi-input multi-output (MIMO) systems, static (constant gain) output feedback pole-placement is an open nondeterministic polynomial time (NP) hard problem. This problem has attracted much attention from the control community for the last four decades. Even today, the general problem has not been solved analytically because of its highly nonlinear nature. In this paper, we have addressed the issue of finding gains without using the procedure of sequential loop closure. We have proposed an iterative numerical algorithm to solve the pole placement problem with a minimum number of feedback gains. The proposed method is used to compute the state feedback gain matrix for coupled yaw-roll dynamics of a typical reusable launch vehicle (RLV) during the reentry phase.

Advanced sandwich structures for thermal protection systems in hypersonic vehicles: A review

A heat shield called the thermal protection system (TPS) is an important structure in hypersonic vehicles as it prevents hot air from entering vehicles and potential impacts from space debris. With the increase in demand for low-cost reusable launch vehicles as well as for searching and exploration of new planets in both unmanned and manned missions, the need for developing an effective TPS has increased across many countries. The structural design of TPSs has become more prominent in the early stage of hypersonic vehicle development. Sandwich structures that have the advantages of low density and high performance are integrated into the structural design of an effective TPS. This paper provides a comprehensive review of recent research efforts on sandwich structures for TPSs. The topics discussed in this paper include aspects of structural and material design, mechanical and thermomechanical performances, and manufacturing methods. In particular, we review and discuss the structural design as well as the material design of sandwich structures for different TPS types with various configurations, including corrugated cores, lattice cores, multilayer cores, foams, honeycomb cores, bio-inspired cores. The materials used for the sandwich structures, such as various types of laminated composite, ceramic matrix composite, and metals, are included. We also discuss the performance of the TPS sandwich structures in terms of temperature gradients, deformation limits, and mechanical strengths and provide a discussion on the manufacturing methods of TPS sandwich structures for hypersonic vehicles. Finally, further research directions and challenges of sandwich structures for TPSs are presented.

Semi-globally smooth control for VTVL reusable launch vehicle under actuator faults and attitude constraints

The present paper deals with the control problem of vertical takeoff vertical landing (VTVL) reusable launch vehicle (RLV) under actuator faults and multi-type attitude constraints (unilateral constraints, symmetric/asymmetric bilateral constraints, or without constraints). A semi-globally smooth control system is proposed based on a novel barrier function (BF) to realize the finite-time convergence of attitude tracking errors into a small neighborhood of the origin. Moreover, the attitude constraints unviolated under multiple disturbances are guaranteed. To further enhance the disturbance rejection ability, a BF-based adaptive disturbance observer (DO) is derived and incorporated into the control system, which is responsible for reconstructing the disturbance in finite time. The proposed control systems are characterized by the following four points. One is to ensure the finite-time convergence of attitude tracking errors and guarantee the non-violation of constraints without requiring any prior information regarding the Lipschitz constant and upper bound of the disturbance. The second is to provide a unified instrument for control problems with the aforementioned multi-type state constraints. The third is the smoothness property contributing to the chattering-free convergence of attitude tracking errors. The high performance and robustness concerning non-Lipschitz disturbance (such as the sudden actuator faults) are the fourth. Ultimately, the effectiveness of the proposed control systems was demonstrated by the numerical simulation results.

Single-stage to orbit ascent trajectory optimisation with reliable evolutionary initial guess

In this paper, the ascent trajectory optimization of a lifting body Single-Stage To Orbit (SSTO) reusable launch vehicle is investigated. The work is carried out using a Direct Multiple Shooting method to solve the Optimal Control problem. The crucial initialisation of the optimisation process is performed by using a combination of two evolutionary algorithms, namely a Multi-Objective Parzen-based Estimation of Distribution (MOPED) algorithm and a Multi-Population Adaptive Inflationary Differential Evolution Algorithm (MP-AIDEA). Multi-Objective Parzen-based Estimation of Distribution (MOPED) belongs to the class of Estimation of Distribution Algorithms (EDAs) and it is used in the first phase of the initial guess research to explore the search space, then Multi-Population Adaptive Inflationary Differential Evolution Algorithm (MP-AIDEA) is used to refine the obtained results, and better fulfill the imposed constraints. The initial guesses obtained with this evolutionary framework were tested on different multiple shooting configurations. The importance of the continuity properties of the employed mathematical models was also quantitatively addressed.

Performance improvement-oriented reentry attitude control for reusable launch vehicles with overload constraint

This paper investigates the issue of reentry attitude control for reusable launch vehicles with overload constraint, and proposes a performance improvement-oriented control scheme. Incorporating the overload constraint into the performance functions, the presented control law proves to guarantee the overload limitation not violating throughout the reentry phase. Compared with traditional performance-guaranteed methods, the presented control introduces a special performance function to achieve better transient performance. Moreover, the attitude control model is reduced to a first-order system with disturbances, leading to a significant reduction of the sophisticated structure by the standard backstepping based approaches. The implementation of the control scheme in the practical engineering is also discussed including the control moment allocation. Simulation results verify the effectiveness of the proposed control approach.