“Design an unmanned containerised cargo freighter that can reduce the cost of shipping by air
and the time required for inter-modal transfers and transport on the ground”, was the objective for a concluding part of aerospace engineering bachelor’s curriculum at Delft University of Technology, called the the design synthesis exercise (DSE).
The DSE gives students the opportunity to obtain design experience in a multidisciplinary design project. In the DSE, realistic and holistic design challenges are posed that require knowledge from multiple disciplines. These challenges are solved by ten students, working as a team. The aim of the project is not to attain a flawless final result, because the design can only be partially developed within the limited time-frame. The aim is to demonstrate skills and knowledge acquired during the bachelor’s programme and accomplish a successful design of an aerospace system. The DSE can be divided into four phases: a planning phase, a requirements phase, a concept phase and a final design phase.
This report is submitted to Paul Roling (Researcher/lecturer at Delft University of Technology), Giuseppe Caridi (PhD candidate at Delft University of Technology), Jaco Brandsen (PhD candidate at Delft University of Technology) and Hans Heerkens (Assistant professor at University of Twente).
From the first cargo flight in 1911, cargo air transportation is recognised as one of the most time efficient means of transportation over long distances for over 100 years. However, for the past 100 years aircraft design has stagnated.
New technology is already available and the markets are in need of a more time and cost efficient way to transport cargo. The substantially lower cost, due to both fuel savings and the reduction of crew cost, will make the air cargo transportation more attractive. Furthermore, using cross modality containers and unmanned, moderate capacity vehicles, the total transportation time and total operating cost can be signicantly reduced.
To offer a knowledge-based solution to this problem, the following project objective statement, to design an unmanned containerised cargo freighter that can reduce the cost of shipping by air and the time required for inter-modal transfers and transport on the ground, is set. Using a system engineering approach this resulted in an innovative design solution, named ATLAS.
The ATLAS is a blended wing body design, consisting of a composite structure and skin. The lift generating body of the design helps to make it more fuel-efficient compared to a conventional design. For each subsystem, a sustainability strategy is proposed.
The main purpose of ATLAS is to transport cargo. For that an inside-out approach is taken. This means that the design of ATLAS is based on the size of containers that have to fit in the cargo bay. New containers are designed to fit in the ATLAS, which are compatible with trucks and current airport operations. However, to be compatible with the current market, ULD’s can also be used.
It is chosen to fly at high altitudes due to aerodynamic eciency. This means pressurisation becomes a concern when transporting goods at this altitude. It is chosen to pressurise the cargo bay instead of the whole fuselage. In order to design a cargo bay for a non-circular centre body, a multibubble design is applied.
To evaluate the design of ATLAS, the concurrent engineering approach is used. This approach focuses on the ability for simultaneous activities in the modules of performance analysis, aerodynamic characteristics, structural analysis, stability and control characteristics and financial analysis. A MATLAB computing environment was created to allow iterations through these modules in order to meet all the requirements. The individual modules have been veried and sensitivity analysis has been performed.
Through Roskam’s first class weight estimation method, aerodynamic sizing via XFLR5 software and Torenbeek’s second class weight estimation method a nal design has been iterated. The final design includes an inherently stable blended wing body with a T-tail and two CFM International Leap 1A engines. The direct operation cost, fuel consumption and produced emissions compared to a Boeing 747-400 have been reduced with 75%, 50% and 46% respectively.
Also, the noise production has been reduced with 78,5% compared to an Airbus A320. The carbon fibre composite structure of the ATLAS is able to cope with a maximum Von Mises stress of 625MPa and a maximum buckling load 85MN.
In order to let the unmanned design comply with the regulations from CS25, mitigation strategies for all possible failure modes have been provided. These failure modes are split in aviational, navigational, communication and mitigation failures. Aircraft modes are designed to make sure that all these failures can be dealt with. The sensors and subsystems to control the aircraft are designed to be redundant to ensure safe flight.
Through Project Evaluation and Review Technique (PERT) and critical chain analysis the critical chain in the loading and unloading process has been improved. This resulted in a turn around time (TAT) of 24.4 minutes for unsimultaneous loading and 12.6 minutes for simultaneous loading, compared to an average of 30-50 minutes for current freighters.
Furthermore, while keeping an eye on sustainability, a reliability, availability and maintainability analysis has been performed, a data and electrical block diagram is sketched and a production plan has been proposed.
In summary, ATLAS satises almost all requirements and it also performs signicantly better than any aircraft flying today. In the context of increasing fuel prices and high consideration for the environment, ATLAS is a sustainable choice due to its low fuel use and low noise contour.
In order to satisfy with the fuel reduction requirement of 75% compared to a Boeing 747-400 it is recommended to investigate the possibility of flying even higher than the current cruising altitude of 12,500m. This would be beneficial for the fuel use and operating cost, but would make it harder to have stable eigenmotions. It is also recommended to use CFD to investigate the aerodynamic properties of the aircraft more accurately.