Cruiser-Feeder

Successful Mid-Term review of the RECREATE project

Summary

Good progress of the European REsearch on a Cruiser-Enabled Air Transport Environment (RECREATE) has been achieved within the first reporting period.

The RECREATE collaborative research is all about the introduction and airworthiness of cruiser-feeder operations for civil aircraft. Cruiser-feeder operations are investigated as a promising pioneering idea for the air transport of the future. The soundness of the concept of cruiser-feeder operations for civil aircraft fuel burn reduction is further underpinned during the first reporting period, taking air-to-air refuelling operations as an example. The comprehensive estimate showing a fuel burn reduction potential and a CO2 emission reduction of 31% for a typical 6000 nautical miles flight with a payload of 250 passengers is reconfirmed. This reduction potential is known to be large by any standard.

The top level objective of the RECREATE project is to demonstrate on a preliminary design level that cruiser-feeder operations (as a concept to reduce fuel burn and CO2 emission levels) can be shown to comply with the airworthiness requirements for civil aircraft. Good progress has been made regarding this important objective, showing routes to create identified missing regulations and new technology in order to achieve airworthiness in the future. A first iteration of identifying cruiser-feeder concepts of operation has been made, taking the requirement of reaching airworthiness in the future into account. The benefits in terms of CO2 emission reduction have been derived and quantified for this first iterate. A conceptual and preliminary design study of the cruiser and feeder aircraft required has been made, and a first version of automatic flight control concepts necessary to achieve airworthiness and to reduce the workload of the pilots has been identified and studied. Concepts to transfer payload and consumables have been studied as well. Finally, preparations of flight simulations to investigate the initial cruiser-feeder concept of operations have been started. Dissemination of RECREATE project results to the general public, to advisory groups and to the aeronautical sciences community has been started. At mid-term it can be concluded that seeding by the RECREATE consortium has already led to an increased attention for the cruiser-feeder concept of operation in the media and at universities.

This research on the cruiser-feeder concept of operation as a promising pioneering idea for energy efficient air transport in the second half of this century has been conducted since August 2011. A design space of different cruiser-feeder concepts has been explored, with divergence and convergence in the number of concepts considered. Due to the pioneering character of the cruiser-feeder concept, it finally was not possible to downselect all concepts into one concept. Consequently, two RECREATE concepts have been retained for further investigation in the project. One RECREATE cruiser-feeder concept is based on transfer of consumables only (e.g. fuel for propulsion). Realisation of this civil air-to-air refuelling concept can be projected in the not too distant future. Cruiser top level aircraft requirements have been specified as a 250 passenger aircraft with a nominal range of 2500 to 3000 nm, to be extended to long ranges with aerial refuelling. The corresponding tanker aircraft has to be capable to deliver 35.000 lb fuel and to loiter for a period of 4 hours along with a number of requirements concerning the refuelling process. The other RECREATE cruiser-feeder concept is an ultra-long range cruiser with a propulsion system independent of consumables (nuclear), and transfer of payload by means of interchangeable, preloaded containers including a life-support system. Cruiser top level aircraft requirements have been specified for a 1000 passenger aircraft.



System for transfer of payload between feeder and cruiser by means of interchangeable, preloaded containers (blue and red) including a passenger life-support system

Conceptual design of ultra-long range cruiser with a propulsion system independent of consumables (nuclear), and transfer of payload by means of interchangeable, preloaded containers including a passenger life-support system

Cruiser-feeder airworthiness requirements have been studied for the first iteration concepts. Critical airworthiness, continued airworthiness, flight crew licencing and operations regulations for cruiser–feeder civil air transport operations have been identified and analysed, taking into account the identified systems requirements and design characteristics, and leading to identification of topics which could require specific new regulations and means of compliance for cruiser-feeder operations. A full evaluation of the civil European regulations CS-25 and in addition the military guidelines MIL-HDBK 516B and JSSG-2009 has also been performed. The main results are that for the non-nuclear propulsion related hazards, risk mitigating measures are judged to be feasible. For the nuclear propulsion related hazards on the other hand, an exception has been made. It has been decided to consider for the nuclear propulsion related hazards only long term feasibility, anticipating future technology to ensure equivalent levels of safety in the second half of this century. This approach has been confirmed during the RECREATE review meeting on January 31, 2013.

A first qualitative assessment of the benefits of the two RECREATE concepts retained for further study has been made. The assessment is made in comparison to the defined baseline concept of operation without cruiser-feeder operations. The main activities in this work package have been devoted to the establishment and clear definition of the methods to evaluate environmental, operational and cost benefits for cruiser-feeder concepts.

The conceptual and preliminary design study of the aircraft required for both RECREATE initial concepts has delivered first conceptual and preliminary designs for both feeder, cruiser and boom. Three cruiser aircraft configurations have been developed at preliminary design level and are being evaluated. A conceptual study of a nuclear propelled blended wing body aircraft has also been initiated.

A family of feeder aircraft for one of the RECREATE cruiser-feeder concepts

A prerequisite for future airworthiness of the cruiser-feeder concept of operations is automation of the hazardous mid-air docking manoeuvre. Good progress has been made in the first reporting period of the RECREATE project. Based on detailed aircraft simulation models, redundant sensors and relative position measuring systems have been developed and added to the aircraft models. A boom model has been developed as well. The integrated simulation model of cruiser, feeder and boom has been designed and implemented for the development of the automatic docking control systems, based on open-loop control authority and controllability investigations. In the second reporting period, these models will also be used for flight simulation experiments, with a full simulation of cruiser, feeder, exchange mechanism (boom) and automated docking control systems. The coupled simulator setup for cruiser and feeder aircraft and a selection of evaluation scenarios have been written as a first version of the test plan for the upcoming simulator experiments.

The project with its objectives as well as promising intermediate results has been presented to the general public as well as to peers by issuing several articles in the newspaper, press releases, presentations and scientific papers. Furthermore a video featuring an animated artist’s impression of the cruiser-feeder concept has been produced and is publicly accessible as well as the public homepage of the RECREATE project (www.cruiser-feeder.eu). More papers are in preparation.

In the first reporting period, an important step has been taken towards creation of impact on the aeronautical community, by promoting research that can bring civil cruiser-feeder operations one step closer to realisation. Progress beyond state of the art on for instance the question how to comply with airworthiness requirements for civil aircraft performing cruiser-feeder operations will boost the interest of the aeronautical community and industry to conduct research on civil air-to-air refuelling as a means of greening the air transport in the second half of this century. Results becoming available during the second reporting period will reinforce this effect. Very good progress beyond the state of the art is expected regarding automated flight control algorithms and technology, which is required to reach equivalent levels of safety for cruiser-feeder operations such that airworthiness comes within reach. New knowledge is being generated regarding environmental, operational and economic benefits, and regarding human factors of cruiser-feeder operations. Relevant progress beyond state of the art is being made for design choices as basic as the most beneficial relative cruiser-feeder position. Finally, a modest part of the study is devoted to the airworthiness perspective of nuclear propulsion for the cruise, offering a real step change beyond state of the art. However, the consortium realizes that such a concept will remain unacceptable for society for many years to come, and is awaiting future technological discoveries to ensure equivalent levels of safety of nuclear propulsion in the second half of this century.