Progress in Aerospace Sciences is an international review journal designed to be of broad interest and use to all those concerned with research in aerospace sciences and their applications in research establishments, industry and universities. The journal is devoted primarily to the publication of specially commissioned review articles designed to bring together under one cover current advances in the ever-broadening field of aerospace sciences. No artificial limits are imposed on the length of papers and authors are encouraged to provide specialist readers with an orderly and concise summary of recent work, including sufficient detail for more general aerospace readers to be informed of recent developments in fields other than their own.