building units. On 14 June 1956, Korolev decided to adapt the R-7 rocket to the 'Object D' (Sputnik 3), that would later be replaced by the much lighter 'Object PS' (Sputnik 1). The first launch of an R-7 rocket (8K71 No.5L) occurred on 15 May 1957. A fire began in the Blok D strap-on almost immediately at liftoff, but the booster continued flying until 98 seconds after launch when the strap-on broke away and the vehicle crashed some downrange. Three attempts to launch the second rocket (8K71 No.6) were made on 10–11 June, but an assembly defect prevented launch. The unsuccessful launch of the third R-7 rocket (8K71 No.7) took place on 12 July. An electrical short caused the vernier engines to put the missile into an uncontrolled roll which resulted in all of the strap-ons separating 33 seconds into the launch. The R-7 crashed about from the pad. The launch of the fourth rocket (8K71 No.8), on 21 August at 15:25 Moscow Time, was successful. The rocket's core boosted the dummy warhead to the target altitude and velocity, reentered the atmosphere, and broke apart at a height of after traveling . On 27 August, the TASS issued a statement on the successful launch of a long-distance multistage ICBM. The launch of the fifth R-7 rocket (8K71 No.9), on 7 September, was also successful, but the dummy was also destroyed on atmospheric re-entry, and hence needed a redesign to completely fulfill its military purpose. The rocket, however, was deemed suitable for satellite launches, and Korolev was able to convince the State Commission to allow the use of the next R-7 to launch PS-1, allowing the delay in the rocket's military exploitation to launch the PS-1 and PS-2 satellites. On 22 September a modified R-7 rocket, named Sputnik and indexed as 8K71PS, arrived at the proving ground and preparations for the launch of PS-1 began. Compared to the military R-7 test vehicles, the mass of 8K71PS was reduced from 280 t to 272 t, its length with PS-1 was and the thrust at liftoff was . Observation complex PS-1 was not designed to be controlled; it could only be observed. Initial data at the launch site would be collected at six separate observatories and telegraphed to NII-4. Located back in Moscow (at Bolshevo), NII-4 was a scientific research arm of the Ministry of Defence that was dedicated to missile development. The