Six single-element injectors that systematically varied propellant spreading and mixing were compared using liquid oxygen and gaseous hydro¬gen in a 200-pound-thrust rocket engine. Characteristic velocity was measured over a range of oxidant-fuel weight ratios of approximately 2 to 7 at a total propellant flow of about 0.6 pound per second. Most of the experiments were made with propellants at an initial temperature of -320° F.nCharacteristic velocity efficiency for all the injectors, except the parallel jets, approached 94 to 97 percent at the extreme fuel-rich mixture ratio. Injectors that mixed and spread the propellants had ef¬ficiencies exceeding 93 percent over the entire mixture range. An in-crease in hydrogen temperature from -320° to 80° F increased efficiency about 20 percent . For similar propellant treatment the combustor length for oxygen-hydrogen was about 0.2 to 0.5 times that needed to obtain comparable efficiencies with oxygen-heptane.
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