Despite these setbacks Zeppelin's organization had refined his idea: a rigid aluminium framework covered in a fabric envelope; separate multiple internal gas cells, each free to expand and contract thus obviating the need for ballonets; modular frame allowing addition of sections and gas cells; controls, engines and gondola rigidly attached. After publishing the idea in March 1892 he hired the engineer Theodor Kober who started work testing and further refining the design. Zeppelin submitted Kober's 1893 detailed designs to the Prussian Airship Service, whose committee reviewed it in 1894. In June 1895 this committee recommended minimum funds be granted, but withdrew this offer and rejected the design in July.