After three previous failures, the Soviets finally got a probe on its way to Mars on I November L962, although not without the spacecraft radio failing en route. Launches of probes to Venus were likewise dogged by failures. Although Venera I, launched in February 1961, became the first interplanetary probe to escape from the Earth, five years were to pass before Venera 3 became the first probe to reach the surface of another planet.

BY TIMOTHY VARFOLOMEYEV St Petersburg, Russia

THREE four-stage carrier vehicles 8K78 and three Mars probes, Object MI, were originally planned by Korolyov for the first Mars shots but only two of these were hurriedly readied for launches scheduled in late September - early October 1960. After a few delays the first attempt came on 10 October 1960. During the second stage burning, resonance vibra-tions of the third stage arose and pitch control malfunctioned. When the veering in pitch had exceeded the permitted limit, - 7 degree - at T+309s, the control system failed. The launcher went out of control and the AVD command was given, i.e. the engine of Stage 3 was cut off. A study of the telemetry data showed the possible cause of failure - strong vibrations caused a break of contact in the command potentiometer of the gyrohorizon [1]. During the next attempt on 14 October 1960 the third stage engine, 8D715K, •failed to ignite at T+290s. The unpowered upper stage, i.e. the combined Blocks I/L with the payload, came back into the at-mosphere and broke up. Post flight analysis revealed that the cause of the failure *AVD in Russian stands for Avarijnoye Vykiyucheniye Dvigatelei or in English for Emergency Cut-off of Engines. was a non-hermetic seal on an oxygen separation valve. The LOX leak had frozen kerosene in the fuel inlet to the pump from the time that it was on the launch pad. Three launches of the 8K78 vehicle with Venus probes Object 1VA were scheduled for late January-early February 1961 [2], and again only two attempts took place. After two delays on 4 February 1961, the 8K78's three stages put into orbit the escape stage block L with the first Venues probe 1VA. After 60 minutes of unpowered coast in Earth orbit, the BOZ unit was put into operation. But a direct current transformer of the Block L power system failed and the timer was left unpowered. The spacecraft attached to the fourth stage remained in Earth orbit On 12 February 1961 when the second Object 1VA was sent to Venus the 8K78 launch was at first successful, but shortly after injection into an interplanetary trajec-tory the spacecraft's thermal control sys-tem failed and on 17 February 1961 con-tact with the probe was lost at a distance of 1.7 million km from the Earth. During 1962 the launch vehicle 8K78 was modified. In order to .place a more massive and larger spacecraft, Object 2MV (Mars-Venera), on the forward end of the fourth stage it was nec Jssary to in-crease the volume under the nose shroud. Therefore a new cylindrical section was put between third stage airframe Launch vebide 8K78 with a Venus probe of the 2MV-series before lift off from Tyuxa-Tam in September 1962. FROM THE AUTHOR'S PAPERS and the fairing, the latter being raised up by 2.3 m. The central sustainer Block A was powered by the first version of the uprated RD-108 engine designated 8D727K. Pressure in the main combustion chambers was upgraded by 5 per cent As a result its total thrust and specific impulse also increased. The first modified 8K78 was launched carrying the Venus landing spacecraft 2MV-1 on 25 August 1962. The escape stage with the probe was first placed in a parking orbit After 60 minutes of orbital flight the small solid motors of the BOZ unit were to be ignited, but only three motors of the four fired. Due to an asymmetric torque the stage lost its pre-set correct position and began to turn slightly. Nevertheless the sequencer con-tinued to give out the next commands and the main engine S1.5400A1 was ignited. But 3 seconds after firing the stage be-gan to somersault The motor burnt for 45 seconds and then cut off early as slosh-ing of fuel in the tanks interrupted propel-lant flow into the chamber. The stage with payload did not leave Earth orbit During the next two Venus attempts on •1 and 12 September -1962 the escape stage came down again. (See the Table opposite). On 24 October 1962, the 8K78 launcher was to send the fly-by space-craft 2MV-4 towards Mars. The fourth stage's main engine fired but blew up af-ter 16 seconds of burning. Post flight study revealed that a lubricant leak led to heating up and jamming of a cog shaft in the turbopump gear-box with the result that the turbine broke up and the engine exploded. The launch on 1 November 1962 was successful. The second probe 2MV-4, called Mars-1, was put on a trajectory to Mars, but shortly after the launch the spacecraft's system of attitude control and stabilisation failed because pressurised nitrogen leaked out from a faulty valve of a gas-storage bottle into space. It was a fatal failure. Firstly the probe could not point it's high-gain antenna in the direction of the Earth and secondly it became impossible to make mid-course corrections. Links with the Earth were maintained only by the low-powered omnt-direction antenna. The next attempt on 4 November 1962 was unsuccessful again. During the ascent phase, strong vibrations of the upper stages shook loose a fuse support from its mount in the main chamber and the pyrotechnic igniter popped out from the nozzle. Although the Block L stage with the Mars landing spacecraft 2MV-3 was placed into a parking orbit, the engine could not be fired. During 1962 to 1965, the launcher 8K78 of 1962 was flown 20 times with nine Mars/Venus probes of the 2MV and 3MV series, seven lunar landing space-craft E-6 and four communication satel-lites Molniya (product 11F67). Eleven at-tempts ended in failures. In 1963 the modified launch vehicle 8K78L tried to launch a new Korolyov lu-nar spacecraft, designated Object E-6, which was intended to soft land on the Moon. The first attempt came on 4 Janu-ary 1963. After being placed in parking orbit. Block L's direct current transformer failed much like it did during the first Venus probe shot of 4 February 1961. On 4 June 1964 the first Soviet communication satellite Molniya was to be put into a high elliptic orbit by the 8K78 launcher. At T+104s the fuel delivery system of the central sustainer failed because the controlling servo-motored throttle jammed and the motor circuit broke off, leading to abnormal operation of the engine unit and a break in the burning cycle. The launcher fell to the ground. To be continued in 'Part 6: The Improved Four-Slage Vehicle, 1964-1972', in a forthcoming issue.