Purpose

The aim of the research is to conduct a study into a configuration of an aircraft system with a focus on aerodynamics. In addition, trim condition and static stability constraints were included. The main application of this system is suborbital space flights. The presented concept of a modular airplane system (MAS) consists of two vehicles: a Rocket Plane and a Carrier. Both are designed in tailless configurations but coupled formed a classic tail aircraft configuration, where the Rocket Plane works as the empennage. The most important challenge is to define the mutual position of those two tailless vehicles under the assumption that each vehicle will be operating alone in different flight conditions while joined in one object create a conventional aircraft. Each vehicle configuration (separated and coupled) must fulfil static stability and trim requirements.

Design/methodology/approach

Aircrafts’ aerodynamic characteristics were obtained using the MGAERO software which is a commercial computing fluid dynamics tool created by AMI Aero. This software uses the Euler flow model. Results from this software were used in the static stability and trim condition analysis.

Findings

The main outcome of this investigation is a mutual position of the Rocket Plane and the Carrier that fulfils project requirements. Also, the final configuration of both separated vehicles (Rocket Plane and Carrier) and the complete MAS were defined. In addition, it was observed that in the case of classic aircraft configuration which is created by connecting two tailless vehicles increasing horizontal tail arm reduces static stability. This is related to a significantly higher mass ratio of the horizontal tail (the Rocket Plane) with respect to the whole system. Moving backward, the Rocket Plane has a notable effect on a position of a centre of gravity of the whole system static stability. Moreover, the impact of the mutual vehicles’ position (horizontal tail arm) and inclination angle on the coupled vehicle lift to drag ratio was analysed.

Research limitations/implications

In terms of aerodynamic computation, MGAERO software using an inviscid flow model, therefore, both a friction drag and breakdown of vortex are not considered. But the presented research is for the computation stage of the design, and the MGAERO software guarantees satisfactory accuracy with respect to the relatively low time of computations. The second limitation is that the presented results are for the conceptual stage of the design and dynamic stability constraints were not taken into account.

Practical implications

The ultimate goal of the coupled aircraft project is to conduct flying tests and the presented result is one of the milestones to achieve this goal.

Originality/value

A design process for a conventional aircraft configuration is well known however, there are not many examples of vehicles that consist of two coupled aircrafts where both vehicles have similar mass. The unique part of this paper includes results of the investigation of the mutual position of the vehicles that can fly alone, as well as in coupled form. The impact of the position of the centre of gravity on trim conditions and static stability of the coupled configuration was investigated.

中文翻译：

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飞机耦合系统与亚轨道太空飞行的空气动力学和静态稳定性研究

目的

该研究的目的是对以空气动力学为重点的飞机系统的配置进行研究。此外，还包括修整条件和静态稳定性约束。该系统的主要应用是亚轨道太空飞行。提出的模块化飞机系统（MAS）的概念包括两架飞机：火箭飞机和舰载机。两者都设计成无尾翼配置，但结合起来形成了经典的尾翼飞机配置，其中火箭飞机用作尾翼。最重要的挑战是在以下假设下定义这两个无尾翼飞行器的相互位置：假设每辆飞行器将在不同的飞行条件下单独运行，而在一个对象中结合在一起便形成了传统的飞机。

设计/方法/方法

使用MGAERO软件获得了飞机的空气动力学特性，该软件是由AMI Aero开发的商业计算流体动力学工具。该软件使用欧拉流量模型。该软件的结果用于静态稳定性和修整条件分析。

发现

这项调查的主要成果是满足飞机项目要求的火箭飞机和舰载机的相互定位。此外，还定义了两种分离的车辆（火箭飞机和运载工具）和完整的MAS的最终配置。另外，观察到，在经典飞机配置的情况下，通过连接两个无尾飞行器来创建，增加水平尾臂会降低静态稳定性。这与水平尾翼（火箭飞机）相对于整个系统的质量比明显更高有关。向后移动，火箭平面对整个系统静态稳定性的重心位置具有显着影响。此外，分析了相互车辆位置（水平尾臂）和倾斜角度对耦合车辆升阻比的影响。

研究局限/意义

在空气动力学计算方面，使用无粘性流模型的MGAERO软件因此不考虑摩擦阻力和涡流破坏。但是，本文提出的研究仅针对设计的计算阶段，而MGAERO软件相对于较短的计算时间就可以保证令人满意的精度。第二个限制是，所给出的结果仅用于设计的概念阶段，没有考虑动态稳定性约束。

实际影响

耦合飞机项目的最终目标是进行飞行测试，而提出的结果是实现这一目标的里程碑之一。

创意/价值

传统飞机配置的设计过程是众所周知的，但是，没有太多的例子由两架耦合的飞机组成的飞机，其中两架飞机的质量相似。本文的独特部分包括对可以单独飞行以及以耦合形式飞行的车辆相互位置的调查结果。研究了重心位置对配平条件和耦合配置的静态稳定性的影响。