dding a newly designed kerosene/LOX second stage with an RD-120 engine made the booster into the "Zenit 2". The "Zenit 3" version added the Block-D third stage   to the booster with 8500 kg. thrust. In 1990, the "Zenit 3" was scheduled for testing for 1993 but it never came about due to low demand until the Sea Launch project adopted it. The "Zenit" is carried to the launch pad on a rail car/erector combination similar to the "Proton". The booster was designed to be assembled in 10 working days, to be storable in that configuration for up to a year, and payload integration took 10 days for the booster and 4.5 days for a standard payload. After 24 hours of preparation on the pad the booster is ready to launch. Booster is 3.9 m diameter, 57 m long, inside payload shroud diameter is 3.4 meters, length 8.37 or 7.3 m depending on upper stage. The "Zenit" booster was tested in at least four sub-orbital tests in 1985 (one on April 13). The first orbital launch of a "Zenit" was on June 21, 1985, and was the unintentional result of a sub-orbital test in which the upper stage exploded with some resulting pieces pushed into a 64.4° orbit, a characteristic of a launch from Baykonur. The Soviets were unaware of this and the pieces became the first unannounced launch in many years. The  second  orbital  test  was "Kosmos 1697",   the third was "Kosmos 1714". "Kosmos 1767" in July 30, 1986, and "Kosmos 1786" were the fourth and  fifth orbital   test flights.  The  next  tests  were  "Kosmos 1820" and  "Kosmos 1833". "Kosmos 1697" and "Kosmos 1714" were probably ELINT satellites (but "1714" was stranded in a low orbit after the upper stage failed to