Goddard, on an assistant professor's salary of US$ 1,000 per year, had used up his savings in rocket research. He wrote to the Smithsonian Institution, asking for research grant. When asked for supporting documentation, he submitted the draft of 'A Method of Reaching Extreme Altitudes', which proposed using multi-stage smokeless powder cartridge rockets to achieve altitudes of hundreds of miles. The cartridge rocket consisted essentially of a gun-like thrust chamber, into which a series of smokeless power cartridges would be automatically loaded and fired to produce thrust..