When I came to Delft in 2003 I had a vision. It was to radically overturn contemporary aerospace design practice. To start afresh and come up with an aircraft design that was low-noise, zero-emission, super-efficient and ultra-comfortable. In short, this aircraft of the future would have to be completely green.

To achieve this, I quickly realised, we had to look to the young, to our MSc and PhD students. Why the young? Because at no other point in life than in youth can one be so unencumbered, free of spirit and full of wild new ideas. It is these ideas I wished to harvest.

At the same time, this was an excellent opportunity to bring together all the disciplines within our renowned Faculty of Aerospace Engineering in one great collaborative effort. Therefore, every chair was invited to select one PhD candidate to dedicate his or her efforts to the undertaking.

The outcome was the CleanEra project, a group of young (prospective) engineers and scientists from a varied international background, ready to take on the challenge, share the dream and create something new. To maximise the usefulness beyond academic output, Dutch industry and research institutes were also invited to take part. Among others, this led to the appointment of a project director from an such a background. But the journey from vision to reality takes years of meticulous research and design. That our radically new plane has not arrived (yet) was not caused by lack of effort. Nor by lack of inspiration, for our CleanEra participants surprised us and the outside world with their ideas and unconventionality.

The need for sustainable solutions is now greater than ever, not only from an environmental point of view, but also from perspectives of cost-efficiency, image, and ultimately survival. This book offers you just that: a set of technological solutions aimed at making aviation low-noise, zero-emission, super-efficient and ultra-comfortable. In other words: truly sustainable. Individually, they can be applied to existing aircraft. But this book is more; it is also a presentation of the work of a group of young scientists fuelled by the same ambition. I hope this publication will inspire industry, government and the scientific community to continue that ambition and help aviation enter a new, clean era.

- Ben Droste

Founding partner of the Space Expedition Corporation (SXC)