Small “ullage” examples of these machines are used to ensure larger ones can operate in zero-g conditions. An equation describing these machines was derived by making an analogy to the “experiment of the boat.”The efficiency of these machines can be quantified by a parameter equal to “one over little g times SFC”, or by the ratio of “dry” and “wet” forms of a certain quantity. An equation named for these devices, which states (*) the log of the initial mass over final mass is proportional to delta-v, is credited to Konstantin Tsiolkovsky (10[1])[see-ul-KAWF-skee]. Wernher von Braun helped design several examples of these machines, such as the multistage Saturn V and V-2. For 10 points, name these machines that eject exhaust with no air intake to produce the thrust needed to propel spacecraft to space. ■END■