Air Launch Vehicle Research Articles

Surrogate-Based Optimization Design for Air-Launched Vehicle Using Iterative Terminal Guidance

In recent years, the penetration of low-cost air-launched vehicles for nano/micro satellites has significantly increased worldwide. Conceptual design and overall parameters optimization of the air-launched vehicle has become an exigent task. In the present research, a modified surrogate-based sequential approximate optimization (SAO) framework with multidisciplinary simulation is proposed for overall design and parameters optimization of a solid air-launched vehicle system. In order to reduce the large computation costs of time-consuming simulation, a local density-based radial basis function is applied to build the surrogate model. In addition, an improved particle swarm algorithm with adaptive control parameters is proposed to ensure the efficiency and reliability of the optimization method. According to the LauncherOne air-launched vehicle, the overall optimization design problem aims to improve payload capacity with the same lift-off mass. Reasonable constraints are imposed to ensure the orbit injection accuracy and stability of the launch vehicle. The influences of the vehicle configuration, optimization method, and terminal guidance are considered and compared for eight different cases. Finally, the effect on the speed of optimization convergence of employing a terminal guidance module is investigated. The payload capability of the optimized configurations increased by 27.52% and 23.35%, respectively. The final estimated results and analysis show the significant efficiency of the proposed method. These results emphasize the ability of SAO to optimize the parameters of an air-launched vehicle at a lower computation cost.

Prediction and evaluation of the stage-separation compatibility of an internally carried air-launch vehicle

This work mainly predicts and evaluates the stage-separation compatibility of an internally carried air-launch vehicle by a multi-body separation wind-tunnel free-flight (WTFF) test without restraining the motional freedom. The Mach number is Ma=1.5, and the initial-launch angle of attack is considered to be α0=0° and α0=3°. The result shows that WTFF test is a feasible prediction and evaluation method for the stage-separation compatibility of an ICAL vehicle when the combined vehicle exhibits static stability. The launch-vehicle can be separated safely from the carrier-aircraft and has a good pitch-angle for ignition when α0=0°. However, the launch-vehicle exhibits a large pitch-angle when it separates completely from the carrier-aircraft when α0=3°, which is unacceptable. Different separation velocities have little influence on the stage-separation compatibility of the ICAL vehicle when α0=3°. The stage-separation compatibility of the ICAL vehicle is first investigated by a free-flight technique in a wind-tunnel, which provides a new research idea for interdisciplinary studies of the kinematics and aerodynamics of multi-body systems.

Multidisciplinary design and optimization of an innovative nano air launch vehicle with a twin-fuselage UAV as carrier aircraft

The population of nano satellites has increased dramatically in recent years, but there are few launch vehicles providing dedicated launch opportunities for them. This paper presents the conceptual design of an innovative nano air launch vehicle, dedicated to providing exclusive launch opportunity to nano satellites weighing 10 kg or less. This nano launcher is a three-stage launch vehicle carried by a twin-fuselage unmanned aerial vehicle and released at an altitude of 10 km from a velocity of 0.5Ma. The air launch vehicle is innovative in two senses: firstly, it adopts a novel air launch method. Before separation, the launch vehicle is adjusted to a large angle of attack by the carrier aircraft. The launch vehicle only needs to keep attitude stable after separation, and sequentially when first stage ignites, the orientation of the thrust is inclined upward so that the thrust can provide enough vertical force to pull up the flight path angle rapidly, without aid from large wings; secondly, a terminal lumped control unit is applied to undertake the flight control task on its own. The terminal lumped control unit is a combination of four thrusters that share the liquid propellant with the last stage's main engine. With the terminal lumped control unit, the air launch vehicle needs no movable attitude control instruments, including thrust vectoring gimbals and movable wings. This innovative flight control strategy makes the launch vehicle very simple in structure and light in weight. Multidisciplinary modeling of the nano launcher is performed and genetic algorithm is applied for optimization. Among all the disciplines, trajectory optimization is key in checking the feasibility of the design, for which the Radau pseudospectral method is successfully implemented to obtain the optimal ascent trajectory. The optimal nano launcher has a gross take-off weight of 1365 kg. Finally, a sensitivity analysis is performed to check the robustness of the result using Monte Carlo simulation method.

Sensitivity Analysis and Optimization of Delta Wing Design Parameters using CFD-Based Response Surface Method

This paper explores the effect of design variables on the objective functions of clipped delta wing with a modified double-wedge airfoil section based on parametric analysis and CFD-based optimization using response surface method. This type of wing is used in air-launch-to-orbit vehicles. The thickness, wing-span, tip chord, leading edge radius, front diagonal edge and rear diagonal edge lengths are defined as design variables and aerodynamic efficiency, drag and lift coefficients as objective functions. The analysis was performed at Mach 0.85 and 1.2 and for several angle of attack (AOA). The optimization process is performed by numerical stimulation of the flow around the wing at different Mach numbers and AOAs for the deformed geometry at each step including 368 cases. Minimizing the drag force and maximizing both lift coefficient and aerodynamic efficiency have been selected as optimization goal. The evolutionary optimization technique of NSGA-II (Non-dominated Sorted Genetic Algorithm-II) in combination with the RSM has been used, which leads to distinct but very close candidates for each flight conditions. Defining the critical design point, it can be deduced the aerodynamic efficiency will be increased by 50% compared with base wing model. Finally, it is shown that the best point for optimizing the air-launched vehicle equipped with delta wing in the ascent trajectory, is the maximum angle of attack that occurs at Mach 1.2.

Ascent Trajectory Optimization for Air-Launched Launch Vehicle with Small Sun-Synchronous Orbit Satellite Based on Pseudo-spectral Method

Ascent Trajectory Optimization for Air-Launched Launch Vehicle with Small Sun-Synchronous Orbit Satellite Based on Pseudo-spectral Method

Effect of Varying Design Options on the Transient Behavior of a Hybrid Rocket Motor

Hybrid rockets provide compelling features for use in atmospheric and space rocket propulsion. One of the prominent applications of hybrid rockets which foster on its characteristics is the propulsion of micro air launch vehicles. In this paper, a set of design options of a hybrid rocket motor is evaluated for propulsion of micro air launch vehicles. In order to evaluate the various design options of a hybrid rocket, we developed design and performance simulation codes. A simulation code is based on a legacy interior ballistic model. MATLAB® environment was used to develop the design and performance analysis codes and to visualize the temporal variation of performance characteristics and grain geometry during burning. We employ the developed codes to assess the replacement of solid rocket motors which are typically used in Air Launch Vehicles by hybrid rocket motors. A typical Micro Air Launch Vehicle mission to launch a 20-kg payload into a 400-km circular polar orbit is assumed. The results show that a hybrid rocket is a suitable candidate for micro air launch vehicles. The performance is improved in terms of specific impulse and thrust with smaller size in the same mission. Several design parameters of hybrid rocket motors were also evaluated and analyzed, including different fuel port geometry, type of fuels and oxidizers, number of ports, nozzle design and initial mass flux. These design parameters bring a significant effect on hybrid rocket performance and size.

Design optimization of micro air launch vehicle using differential evolution

In this paper, we have used the differential evolution to optimize the design of a Micro Air Launch Vehicle and its launch trajectory. Since trajectory design of a launch vehicle requires prior knowledge of the masses and propulsion performance parameters of the Micro Air Launch Vehicle, whereas the vehicle design requires prior knowledge of the required velocity (ΔV) to insert the required payload into the target orbit, a two-step optimization cycle was adopted. A Micro Air Launch Vehicle was designed to launch a 20-kg payload into a 400-km circular polar orbit. The preliminary design of the Micro Air Launch Vehicle was conducted given the required (ΔV), which was obtained from trajectory optimization, and then applied in mission analysis to obtain the initial masses. These initial masses were used in the vehicle design to get the performance and geometry parameters. The objective function of the Micro Air Launch Vehicle design optimization is to minimize the initial mass under specified constraints on the insertion orbit. The objective of trajectory optimization is to maximize the payload mass under constraints on orbit specifications and design variables. For the 20-kg payload mass, the optimal initial mass is 1267.8 kg and optimal payload is 20.6 kg, which slightly exceeds the mission requirements.

Particle swarm optimization of a micro air-launch vehicle trajectory

The demand for submicrosatellites is growing rapidly. A new low-cost launching method is needed to launch these types of satellites. This can be done by launching from airplanes. By implementing air launching, there would be no restrictions on the launch site, the launch angle, and the launch direction. In this paper, trajectory optimization of the micro air-launch vehicle (MALV) is carried out using the particle swarm optimization method. The problem is treated as a parameter optimization problem, and it is formulated as a single objective constraint optimization problem with the explicit objective of maximizing the payload mass. The simulation results show the effectiveness of the proposed technique in solving the nonlinear optimal trajectory problem for MALV.

Ballistic representation for kinematic access

This work uses simple two-body orbital dynamics to initially determine the kinematic access for a ballistic vehicle. Primarily this analysis was developed to assess when a rocket body might conjunct with an orbiting satellite platform. A family of access opportunities can be represented as a volume for a specific rocket relative to its launch platform. Alternately, the opportunities can be represented as a geographical footprint relative to aircraft or satellite position that encompasses all possible launcher locations for a specific rocket. A thrusting rocket is treated as a ballistic vehicle that receives all its energy at launch and follows a coasting trajectory. To do so, the rocket’s burnout energy is used to find its equivalent initial velocity for a given launcher’s altitude. Three kinematic access solutions are then found that account for spherical Earth rotation. One solution finds the maximum range for an ascent-only trajectory while another solution accommodates a descending trajectory. In addition, the ascent engagement for the descending trajectory is used to depict a rapid access scenario. These preliminary solutions are formulated to address ground-, sea-, or air-launched vehicles.

Optimal air-launching rocket design using system trades and a multi-disciplinary optimization approach

Compared with the conventional ground rocket launching, air-launching has many advantages. However, a comprehensive and integrated system design approach is required because the physical geometry of air launch vehicle is quite dependent on the installation limitation of the mother plane. For the selection of the best system alternative, a trade study for the first stage engine type and launching speeds is performed using a sequential optimization technique, confirming the feasibility of the baseline air-launching rocket. Then, a system design has been performed using the multi-disciplinary feasible (MDF) design optimization method. Analysis modules include mission analysis, staging, propulsion analysis, configuration, weight analysis, aerodynamics analysis and trajectory analysis. As a result of multi-disciplinary system optimization, a supersonic air launching rocket with total mass of 1244.9 kg, total length of 6.36 m, outer diameter of 0.60 m has been successfully designed to launch a satellite of 7.5 kg to the 700 km circular orbit.

Optimal design for hybrid rocket engine for air launch vehicle

A feasibility study and the optimal design was conducted for the application of a hybrid motor with HTPB/LOX combination to the first stage of an air launch system. The feasibility analysis showed that the hybrid motor could successfully be used as a substitute for the solid rocket motor of the first stage of the Pegasus XL if the average specific impulse (I sp ) of the hybrid motor could be approximately 350sec. And the optimal design of the hybrid motor was carried out for a given mission requirement with selected design variables: number of ports, initial oxidizer flux, combustion chamber pressure, and nozzle expansion ratio. The design results show the hybrid motor can be successfully applicable to the air launching vehicle. And, the optimal design can meet physical constraints of length and diameter imposed by the mother plane installation for a 3.5kg nano-sat to the orbit located on the 200×1500km elliptic orbit plane. Also, it was found that the design results would provide nearly the same design configurations regardless of the selection of objective functions: either mass or length of the engine.

A comparative analysis of methods for air-launching vehicles from earth to sub-orbit or orbit

A variety of air-launched sub-orbital and orbital vehicles are demonstrated and others have been proposed recently by different organizations. The purpose of this article is three-fold: (a) to identify benefits of air-launching vehicles for space missions; (b) to categorize airlaunched vehicles with respect to how they are integrated to their carrier vehicle; (c) to identify benefits and shortcomings of these methods. Our analysis study shows that air-launching provides mobility and deployment advantages over surface launching. It can also provide performance advantages over surface launching. However, many air-launch concepts proposed require advance technologies that are currently not available.

다분야 최적화 기법을 이용한 공중발사 로켓 최적설계

공중발사 방식은 일반적인 지상발사와 비교해 볼 때 많은 장점을 지니고 있다. 그러나 공중발사 로켓의 형상은 모선에 장착 시 많은 제한이 따르기 때문에 여러 해석분야를 통합한 시스템 설계가 필요하다. 시스템 설계는 순차적 최적화와 MDF 기법을 이용하여 수행되었다. 해석 모듈은 임무분석, 단배분, 추진해석, 형상, 중량해석, 공력해석, 궤적해석을 포함한다. 두 가지 기법 중 MDF 기법을 이용하였을 때 더 좋은 결과를 도출하였다. 시스템 최적화 결과 총 중량 1244.91kg, 위성중량 7.5kg, 총 길이 6.36 m, 지름 0.60m을 지닌 초음속 공중발사 로켓이 설계되었다. Compared with the conventional ground rocket launching, air-launching has many advantages. However, a comprehensive and integrated system design approach is required because the physical geometry of air launch vehicle is quite dependent on the installation limitation of the mother plane. The system design has been performed using two different approaches: the sequential optimization and the multidisciplinary feasible(MDF) optimization method. Analysis modules include mission analysis, staging, propulsion analysis, configuration, weight analysis, aerodynamics analysis and trajectory analysis. MDF optimization shows better results than the sequential optimization. As a result of system optimization, a supersonic air launching rocket with total mass of 1244.91kg, total length of 6.36m, outer diameter of 0.60m and the payload mass of 7.5kg has been successfully designed.

A Concept of Guidance for an Air-Launch Vehicle with Compensation of Initial Downrange and Launch Time Errors at Direct Insertion into a Rendezvous Point in the Orbit

A flying launcher (airplane carrier) can generate initial errors in position and time of launch. In order to compensate for these errors, one should have two control parameters in addition to those that provide for a spacecraft's injection into a preset orbit. We suggest the concept of controlling the trajectory of injection by choosing thrust values (within allowable regions of control) of second-stage engines or/and of a space booster of the Polyot carrier launcher. As an example, a rendezvous of the spacecraft at the end of its boost phase with the International Space Station (ISS) is considered. The methodology of the suggested approach can be extended to other mobile systems of launch to rendezvous orbits.

공중발사체를 위한 HTPB/LOX 하이브리드 모터의 최적설계

F-4E를 모선으로 하는 초소형 위성을 탑재할 수 있는 공중발사체 1단 부스터용 하이브리드 모터의 최적설계를 실시하였다. 설계변수는 포트개수, 초기 산화제 플럭스, 연소실 압력, 그리고 노즐 팽창비 등을 사용하였다. 또한 서로 다른 최적화 알고리듬의 적용 가능성을 검증하기 위하여 구배법 (GBM)과 유전자 알고리듬 (GA) 방법을 각각 사용하였으며, 목적함수의 선택에 따른 최적화 결과의 변화를 살펴보기 위하여 두 가지 종류의 목적함수 (모터 중량과 모터 길이)를 사용하여 그 결과를 상호 비교하였다. 최적화 알고리듬, 그리고 목적함수의 선택과 무관하게 거의 같은 설계결과로 수렴함을 확인하였다. 최적화결과로 설계요구조건을 만족하는 총중량 704.74kg, 1단 길이 3.74m의 하이브리드 모터를 설계 할 수 있었다. Optimal design of the hybrid motor has been performed for the first stage of nanosat air launch vehicle using F-4E Phantom as mother plane. Selected design variables are number of ports, the initial oxidizer flux, the combustion chamber pressure, and the nozzle expansion ratio. GBM(Gradient Based Method) and GA(Genetic Algorithm) are simultaneously used to compare the versatility of each algorithm for optimal design in this problem. Also, two objective functions of motor weight, and length are treated separatedly in the optimization to study how the objective function can affect the optimal design. The design results show that the optimal design can be successfully achieved either using GBM or GA regardless of the choice of the objective function; motor weight or length. And nanosat air launch vehicle which has total mass of 704.74kg, and length of first stage 3.74m is designed.

공중발사체 기술 개발동향 및 전망

공중발사체 기술 개발동향 및 전망

The Determination of Maximum Range for an Unpowered Atmospheric Vehicle

SummaryThe problem of maximising the range of a given unpowered, air-launched vehicle is formed as one of Mayer type in the calculus of variations. Eulers’ necessary conditions for the existence of an extremal are stated together with the natural end conditions. The problem reduces to finding the incidence programme which will give the greatest range.The vehicle is assumed to be an air-to-ground, winged unpowered vehicle flying in an isothermal atmosphere above a flat earth. It is also assumed to be a point mass acted upon by the forces of lift, drag and weight. The acceleration due to gravity is assumed constant.The fundamental constraints of the problem and the Euler-Lagrange equations are programmed for an automatic digital computer. By considering the Lagrange multipliers involved in the problem a method of search is devised based on finding flight paths with maximum range for specified final velocities. It is shown that this method leads to trajectories which are sufficiently close to the “best” trajectory for most practical purposes.It is concluded that such a method is practical and is particularly useful in obtaining the optimum incidence programme during the initial portion of the flight path.