The concept of a metal-clad dirigible airships was again explored in the late 1800s by Russian rocket theorist Konstantin Eduardovich Tsiolkovsky. He wrote that since his teens (in the early 1870s) "the idea of the all-metal aerostat has never left my mind" and by 1891 he had produced detailed designs of a variable volume corrugated metal envelope airship that did not need ballonets. These were submitted to an Imperial department for aeronautics, which convened a conference to consider it. In 1891 they declined his request for a grant to produce a model, considering the idea "cannot have any considerable practical importance". In 1892 he published his designs as "Aerostat Metallitscheski" (the all-metal dirgible aerostat).