controlled by gyroscopic inertial reference; this type of guidance system was invented by Robert H. Goddard, who had partial success with it before World War II intervened. Roll control was by use of the turbopump exhaust to power reaction control system (RCS) jets on the fins. Compressed gas jets stabilized the vehicle after the main power cutoff. Similar devices are now extensively used in large, steerable rockets and in space vehicles. Another improvement was that initially the alcohol tank, and later the LOX tank also, were built integral with the outer skin, saving weight. The structure was also largely aluminum, as opposed to steel used in the V-2, thus shedding more weight. Vikings 1 through 7 were slightly longer (about ) than the V-2, but with a straight cylindrical body only in diameter, making the rocket quite slender. They had fairly large fins similar to those on the V-2. Vikings 8 through 14 were built with an enlarged airframe of improved design. The diameter was increased to , while the length was reduced to , altering the missile's "pencil shape". The fins were made much smaller and triangular. The added diameter meant more fuel and more weight, but the "mass ratio", of fueled to empty mass, was improved to about 5:1, a record for the time. Flight history First model (Vikings 1-7) On 3 May 1949, after two static firings (11 March and 25 April), the first Viking rocket took off from White Sands White Sands Missile Range in New Mexico. Its engine fired for 55 seconds, ten seconds short of the hoped-for maximum of 65, but the rocket flew on course and reached an altitude of —deemed a good start to the program. Viking 2, launched four months later, also suffered from premature engine cutoff and only made it to . Both had suffered from leaks in their turbines, the intense heat of the steam breaking the seal of the turbine casing. The solution was to weld the casing shut, there being no reason to access the turbine wheel again after a flight. The fix worked, and Viking 3, launched 9 February 1950 and incorporating an integrated (rather than discrete) oxygen tank, reached and could have gone higher. However, after 34 seconds of accurately guided flight, the rocket veered westward and threatened to leave the launch range. Range safety triggered charges in the rocket to separate the nose from