Gherman Titov had suffered
space sickness during his record-breaking one-day mission aboard
Vostok 2. This condition was unknown at the time, leading Soviet scientists to devote efforts to study the
effect of spaceflight on the human body. In 1961, Soviet rocket engineer
Sergei Korolev pushed for a three-day spaceflight as a follow-up to Vostok 2. Such a mission was opposed by the head of cosmonaut training
Nikolai Kamanin and the cosmonauts themselves, who were concerned about unforeseen health effects that might result from extending space flights too quickly. Plans for a three-day mission only went forward when the approval of Soviet Premier
Nikita Khrushchev was obtained; in the end, Vostok 3 would last nearly four days. One objective of the missions of Vostok 3 and Vostok 4 was the study of how the reactions of Nikolayev and
Pavel Popovich might differ during a series of tests under similar circumstances. The close orbits of the two spacecraft would keep the number of variables to a minimum, allowing the measurement of individual differences in adaptation to spaceflight. The
Vostok spacecraft were upgraded to increase the volume of information collected about the flight conditions and the crew. Training was expanded to condition cosmonauts against space sickness and select those candidate spacefarers deemed least susceptible. Informed by Titov's experience in Vostok 2, Nikolayev and Popovich thoroughly rehearsed their spacecraft maneuvers and other planned activities in a simulator. The Vostok 3/4 flights were originally scheduled for November 1961, which would have had the propaganda value of the Soviet program having flown four men in space along with a dual mission in the same calendar year when the United States had yet to orbit a single man, but Korolev's plans were frustrated by the
Zenit photo
reconnaissance satellite program which needed to use the R-7 pads at Baikonur. He then suggested launching at the end of December or the start of January, but Chief of Cosmonaut Training
Nikolai Kamanin and the State Planning Commission opposed launching in the wintertime due to harsh weather conditions and instead suggested waiting until March. The first Zenit launch took place on 11 December, but the Blok E stage malfunctioned and the satellite was destroyed. Since this was the same model of booster used by the Vostok (8K72K), it was a concern for the program. While engineers attempted to resolve the problem, Vostok 3/4's mission was pushed back a month to April. However, further delays happened when the second Zenit satellite (
Kosmos 4) experienced problems with its orientation system, necessitating another test and further delays. On 1 June, an attempted launch of a
Zenit photo reconnaissance satellite ended with the booster crashing near the pad. One of the strap-ons had also fallen back onto LC-1 and burned, resulting in extensive damage that took over a month to repair. By mid-July, the pad had been restored to use, but another delay occurred when the United States carried out a
high-altitude nuclear test on 9 July known as
Starfish Prime. The test had unexpected consequences in that it released high levels of radiation into the upper atmosphere and space, knocking out several satellites and making any crewed space launch unsafe for at least a month. By the second week of August, radiation levels had diminished enough that the Vostok 3/4 mission could go ahead. The Zenit launch accident had occurred in a new, uprated version of the R-7
launch vehicle (the 8A92) while the Vostok used the older 8K72K booster, so it was not a direct concern for the program. However, just to be cautious, it was decided to fly an additional Zenit satellite to verify the reliability of the R-7. In addition, since the Zenit satellite was essentially a modified Vostok, the flight doubled as an engineering test of certain Vostok components. This was done successfully on July 28, after which preparations at LC-1 began for Vostok 3. ==Mission highlights==