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Vostok-1K No. 5

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First Vostok lifts off

On May 15, 1960, the Soviet Union announced the launch the first unpiloted prototype of the spacecraft designed to pave the way to human missions. However, the May 19 attempt to deorbit the vehicle revealed a nightmare scenario for future cosmonauts.

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Assembly of early Vostok spacecraft at OKB-1 in Podlipki near Moscow. A capsule for drop tests can be seen at the center of the photo. The assembly of the instrument module is on the left.

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Vostok-1KP mission at a glance:

Spacecraft designation Perviy Kosmichesky Korabl-Sputnik (public), 1KP, Vostok-1P, Sputnik-4
Launch vehicle 8K72K No. L1-11 (Vostok)
Spacecraft mass 4,540 kilograms
Payload mass 1,477 kilograms
Spacecraft dimensions 4.4 meters (length without antennas), 2.43 meters (diameter)
Launch Site Tyuratam, Site 1
Launch date and time 1960 May 15, 03:00:05.6 Moscow Time
Orbit parameters 312 by 369 km, 65 degrees, 91.2 minutes
Flight duration - days
Reentry 1962 Sept. 5 (instrument module), 1965 Oct. 15 (Descent Module)
Crew No

Behind the scene, the first prototype of the Vostok spacecraft had the designation 1KP, where "P" stood for the "prosteishiy" (simplest) variant of the 1K experimental series. The production batch included a total of seven vehicles and was designed to prepare the operational flights of automated and piloted reconnaissance satellites.

The Descent Module of the 1KP vehicle was not intended for the return to Earth and, therefore, it had no thermal protection shielding, no life-support system and none of the landing systems intended for the piloted vehicle, such as parachutes and or an ejection seat.

Starting with the writings of Korolev's Soviet-era biographer, Yaroslav Golovanov, the popular literature on the Soviet space flight said that the first Vostok had lacked a heat shield because it was still in development at the time. (229) However, original documents made public in subsequent years revealed that officials had been concerned about the reliable operation of the flight control system and wanted to prevent the survival of the Descent Vehicle in case of an unplanned descent of the capsule over foreign territory. (509) Vostok's leading architect Konstantin Feoktistov mostly confirmed that explanation in his memoirs, adding that he had proposed stripping the first Vostok of its reentry and landing equipment very late in the development process when a typical Soviet-era paranoia set in around the possibility of "military secrets" falling into the wrong hands. Feoktistov apparently proposed the idea for the first two Vostoks as an alternative to the demands for equipping the vehicle with a self-destruct mechanism, whose development would require postponing the politically important missions. (196)

Thus, the main goal of the 1KP flight was to test the capability of the spacecraft to fire its TDU braking engine in a precise direction and duration, initiating the critical reentry into the Earth's atmosphere. During the piloted mission, the cosmonaut would have no alternative to the TDU engine for a controlled return to Earth. The operation of the motion control and attitude control systems would also be tested, allowing the rehearsal of all key phases of the flight but the landing. (229)

Although later Vostoks carried live animals, there was apparently no plans to put a live dog or other large animal on the one-way mission, possibly, because of the backlash over the death of Laika aboard Sputnik-2 a year and half earlier.

The 1KP spacecraft was expected to stay in orbit for four or five days, before being commanded to reenter for a breakup over the Pacific Ocean. (509)

In order to boost the mass of the experimental payload to that of an operational vehicle with a cosmonaut onboard (2), Vostok-1KP carried some kind of ballast. According to Feoktistov, it consisted of metal bricks, loaded into the capsule.

The main nerve center of the mission was located at the NII-4 military research institute in Bolshevo, near Moscow.

Preparations for launch

Even the stripped-down Vostok put huge workload on the engineering team with its unprecedented complexity. The TDU braking engine for the mission was apparently only delivered from Aleksei Isaev's OKB-2 on April 25, 1960, or less than three weeks before the actual launch. Ground tests of the first Soviet orbital maneuvering engine started on September 27, 1959, and it performed 15 firings, including one failure during its fifth test, due to a missing pyrotechnic valve on the fuel line. (18)

The State Commission led by Konstantin Rudnev oversaw the preparations and all phases of the flight. It was largely the same group of officials who were previously responsible for flight testing of the R-7A (8K74) missile. (52)

In a top-secret memo to the Soviet of Ministers submitted on April 23, 1960, Georgy Pashkov, Deputy Chairman of the Commission on Military-Industrial Issues, wrote that the launch of the first simplified Vostok was planned for April or May 1960, but, at the time, the spacecraft was undergoing integrated testing at OKB-1 and its rollout was planned for the end of April. The second simplified vehicle and a fully equipped Vostok with thermal shielding were still in assembly at OKB-1, but all the hardware for the latter vehicle had been delivered. The fully operational spacecraft could be sent to the launch site no earlier than the end of May 1960, Pashkov wrote.

The document also said that VNII-380 was completing the development of a TV system for transmitting images of the Earth's surface from Vostok with a deadline in April (1960), but its manufacturing could be completed in May or June.

Early signs of political troubles

Interestingly, as an apparent indication of early skepticism of the military and scientific community toward piloted spacecraft, Pashkov's letter noted that the issues with the production of antennas for receiving TV signals from orbit were still in discussions between the Ministry of Defense and the State Committee for Radio-electronics, GKRE. Moreover, the proposals for the development and launches of subsequent Vostok spacecraft during 1960, which were to have been submitted by the State Committee for Defense Technology, the Academy of Sciences and the Ministry of Defense by December 1959, had still not been provided.

The letter apparently produced some action, because on May 6, 1960, the Central Committee received a memo signed by military, industrial and scientific leaders, proposing systematic flight testing of Vostok vehicles starting in May 1960 and including seven launches before the end of the year. The document did confirm that not one but two simplified Vostok spacecraft were planned for launch before the end of May 1960.

Moreover, by August 1960, two or even three Vostok-1 were scheduled to fly, testing equipment for imaging and electronic intelligence from space. They would pave the way for an operational Vostok-2 reconnaissance satellite.

Next, from September to December 1960, two Vostok-3 vehicles would be launched testing the equipment for life support and the emergency escape of a pilot in case of launch vehicle failure. To implement this ambitious plan, the letter requested converting eight R-7 ICBMs from the stockpile of the Ministry of Defense into space launch vehicles for piloted and planetary missions. This plan was re-confirmed in a draft of an official decree signed on June 4, 1960. (509)

At the launch site

The first Vostok spacecraft, accompanied by several hundred engineers, but still lacking many of its key components, was delivered to the Tyuratam launch site aboard an An-12 transport plane on April 29, 1960, followed on May 2 by the 8K72K No. L1-11 rocket assigned to launch the mission.

In parallel with the processing of the spacecraft and its rocket, the new project required deploying and tuning up a great deal of new testing hardware, cabling network, communications and tracking equipment at various facilities of the launch site. The newly developed, but still inadequately tested hardware for the Chaika motion control system, only flew to the launch site on May 3. (51) Its trip to Tyuratam started several days earlier with a bumpy ride on a truck driven by a drunk driver who managed to smash into a tree on the way to the airport.

After its installation aboard the Vostok, the autonomous tests of the motion control system started at midnight on May 5, 1960. By May 9, the spacecraft had all its systems installed and ready for powering up, but integrated testing began on May 12 only, due to various glitches. The next day, the spacecraft was fully assembled and suspended by a crane on a flexible tether. As engineers tried to manually spin the vehicle, the small thrusters came to life indicating that the attitude control system was performing well. The following 20 hours were spent on the integration of the spacecraft with its rocket, instead of the allocated nine hours, due to broken cables and mismatch in support hardware. Finally, the rollout of the launch vehicle from the assembly building at Site 2 to the launch pad at Site 1 took place during the night of May 13 to May 14, instead of the originally planned May 12, 1960.

On the launch pad, personnel used the newly installed gantry with an elevator for the cosmonaut to access the top section of the rocket. At 23:00 Moscow Time, Marshall Mitrofan Nedelin, the Commander of the Strategic Rocket Forces, opened the final pre-launch meeting of the State Commission, which cleared the Vostok-1K for liftoff. (466)

First Vostok lifts off

An 8K72K launch vehicle, carrying the Vostok-1KP spacecraft, lifted off on May 15, 1960, at 03:00:05.6 Moscow Time, as the first signs of dawn appeared in the sky over Tyuratam, which is two time zones east of Moscow.

Despite some spotty telemetry signal at T+460 seconds (during the operation of the third stage), the rocket successfully delivered the 4,540-kilogram spacecraft into a 312 by 369-kilometer orbit with an inclination 65 degrees toward the Equator. In the top-secret communications of the Soviet government, the newly launched spacecraft was identified as Vostok-1P. (509)

In its official announcement about the launch (which was made in the early hours of May 16 and appeared in the Soviet press the same morning, but was actually drafted in the first week of May and approved for publication on May 12), the Soviet government made no secret about the real purpose of the flight, identifying the newly launched payload as "Perviy Sovetsky Kosmichesky Korabl-Sputnik," which can be translated as the First Soviet Spacecraft-Satellite. (The name Vostok would not be disclosed until the launch of Gagarin almost a year later.) The announcement opened with a statement that the USSR was pursuing the research and development preparing the launch of a human in space and that this particular mission marked the beginning of flight testing aimed at long-duration piloted flights.

The announcement also said that the 4,450-kilogram spacecraft had a pressurized cabin containing a cargo simulating the mass of the human and various equipment with a total mass of 1,477 kilograms including power sources.

Even more surprisingly, the statement provided plenty of details about the upcoming flight program.

It disclosed that "after gathering necessary information, the 2.5-ton pressurized cabin would be separated from the spacecraft-satellite" and that there were no plans to return the capsule in this particular flight, therefore both, the cabin and the spacecraft-satellite would disintegrate during reentry.

The report went on to list the Signal transmitter, operating at 19,995 MHz in telephone and telegraph mode, as well as the transmitter for telemetry downlink and for precise measurement of orbital parameters, as payloads aboard the spacecraft. The power supply for the payloads and measurement equipment was provided via chemical batteries and solar panels, the statement said.

Last-minute additions to the pre-approved statement said that at 06:38 Moscow Time, the spacecraft had flown over Moscow and at 07:38 over Paris (where the Soviet leader Nikita Khrushchev was paying a visit at the time.) Passes over Leningrad and New York City had taken place at 07:43 and 10:36 Moscow Time, the report said. (52)

Reentry attempt

Because the first Vostok had entered a stable orbit, the flight control specialists had several days for thorough tests of the new complex flight control system. For the in-depth analysis of the flight data, the operational flight control team was split into two teams: Group M, deployed near Moscow and led by Korolev and Group T in Tyuratam under Boris Chertok. Group M had a broad picture of the situation in orbit based on reports from the entire Soviet ground station network, but Group T had access to live telemetry from the IP-1 ground station, during direct passes of the spacecraft over Tyuratam. That team also included the best analysts among all stations and it also had many actual developers of key systems at hand.

After initial trials of communications sessions with the spacecraft, members of Group T detected a potential issue with the Primary Attitude-control System, OSO, which relied on the infra-red sensor, IKV, to determine the orientation of the ship in space. The rotating sensor scanned the space, detecting the border between the Earth and space. The information from the IKV sensor was processed by the flight control system, which then commanded the ship's thrusters to point one axis of the spacecraft toward the center of the Earth. In order to prevent the rotation of the spacecraft around that axis, a special gyroscopic instrument determined the flight direction, while three angular velocity sensors, DUS, helped negating all other deviations.

After several passes of the spacecraft over Tyuratam, telemetry experts at Group T saw a progressively lower spin rate of the IKV scanner, until it seemingly stopped its rotation, possibly due to a failure of its electric motor. (466) Yet, all the data coming to Group M consistently (and suspiciously) showed zero deviation of the instrument from its center-of-Earth axis and there was no other evidence of any problems with the OSO system. No surprisingly, the leading developer of the instrument Yevgeny Bashkin insisted that "zero" readings were indicators of the absolutely perfect functioning of the attitude control system. (463)

Most specialists in Tyuratam urged a switch to the backup solar orientation system, ASO, which gave no doubts in its performance and Chertok claims in his memoirs that he had made multiple attempts in phone conversations with Korolev to convince him to switch to ASO.

However, after hot debates between Moscow and Tyuratam, Korolev sided with the Moscow team, pressing for the continuous use of the primary attitude control mode, probably seeing its real-life testing as absolutely crucial even with the high risk of failure during the deorbiting maneuver.

On May 19, 1960, at 02:52 Moscow Time, one orbit before landing, the NIP-12 ground station (51) in Kolpachevo in Western Siberia radioed the spacecraft a command to initiate the landing sequence, culminating with a braking maneuver over Africa and the subsequent separation of the Descent Module. (52) If everything went as planned, the ship would reenter and break communications with the ground as its antennas were melted by the heat of reentry. Ground radar would then expect to detect its flaming debris.

At the IP-1 tracking station in Tyuratam, a group of communications officers let by Sr. Lieutenant Vladimir Poroshkov was conducting early tests of the Signal-Yupiter high-gain tracking antennas designed to receive and record telemetry from the new spacecraft not only in direct view, but also below the horizon, thanks to the reflection of radio waves from the ionosphere. During the tests, the operators discovered that the needle of the telemetry recorder was spraying ink all over the place, leaving their hands splattered with black spots up to their elbows. Still, with the help of guidance from the ballistics calculation center, the IP-1 station was able to track the spacecraft with their antennas and continue recording the first and secondary echo of the signal bouncing from the ionosphere. Further registering of the signal all the way to the other side of the planet proved impossible at the time.

As the reentry approached, the IP-1 station received guidance coordinates for both a nominal descent trajectory and a continuing orbital flight. At the time of the braking maneuver, Poroshkov's specialists looking at the live data almost instantly recognized the nominal engine firing and the separation of the Descent and Instrument modules. However, as the antenna began following the predicted descent path of the mission, the signal weakened. The IP-1 repositioned the antenna to a predicted orbital trajectory and the signal became stronger. It was clear that the deorbiting had failed and officers at IP-1 immediately reported that fact to the main control center in Moscow. (51)

The subsequent measurements of orbital parameters indicated that the spacecraft actually transitioned to a higher orbit, even though the Descent Module separated from the Instrument Module. According to estimates made by the Soviet specialists, the object would not decay from its new orbit for about a year. (Obviously, it would be a nightmare scenario for a hypothetical pilot, because the capsule would be stranded in space months or years after its vital supplies run out). Still, the onboard transmitters (limited by the life span of their batteries) were expected to operate for around a year.

It was obvious that the faulty attitude control system had pointed the spacecraft with its braking engine not against the direction of the flight, but in the opposite direction, turning the firing into an orbit-raising maneuver. As a silver lining, the exercise did confirm that the new propulsion system worked.

Contrary to the expectations of key engineers, who perceived the mission as a major failure, Korolev was reportedly happy enough not to go into one of his famous outbursts, according to the recollections of his deputy Konstantin Bushuev. Looking beyond this particular mission, Korolev saw it as the first orbit correction in space, paving the way to maneuvering in orbit. (229)

Indeed, the 1KP flight was apparently considered successful enough to cancel the second launch of a simplified spacecraft and to transition to the flights of the fully operational, though still pilotless capsules.

A few days after the 1KP mission, Korolev reportedly made a trip to the Institute of Aviation Medicine, IAM, where he met a group of military pilots who had just been recruited for the Vostok project. (18)

Given the original public disclosure about the planned landing of the first Vostok, Soviet officials drafted an official statement disclosing a problem "in one of the instruments of the attitude control system." The statement also said that after the unplanned maneuver, the spacecraft entered an elliptical orbit with an increased apogee, but almost unchanged orbital inclination. The statement also announced that the pressurized capsule had separated, and its stabilization system had worked as planned.

The draft of the statement listed the following orbital parameters of the first Vostok after its unplanned maneuver:

Orbital period 94.25 minutes
Perigee 307 kilometers
Apogee 690 kilometers
Orbital inclination 65 degrees toward the Equator

Ultimate reentry

Ironically, the initial fears about an uncontrolled reentry of the first Vostok were realized on September 5, 1962, when the Instrument Module decayed from orbit over Milwaukee, Wisconsin, where witnesses saw the flaming meteor appearing at 4:49 a.m. along the predicted path and heard a sonic boom. Several surviving fragments of the spacecraft reached the ground and were later recovered. One of them fell right in the middle of the street in Manitowoc, WI, and soon made it to the negotiations at the United Nations on the use of space.

Apparently due to its smooth shape, providing less resistance in the rarified atmosphere, the Descent Module remained in orbit for another three years and reentered only on October 15, 1965. (904)

Page author: Anatoly Zak; Last update: March 25, 2021

Page editor: Alain Chabot; Last edit: May 18, 2020

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insider content



An early version of the Vostok spacecraft. Copyright © 2011 Anatoly Zak


A demo version of the TDU braking engine for the Vostok spacecraft. Copyright © 2000 Anatoly Zak


A Soviet-era depiction of the 1K variant of the Vostok spacecraft in orbit.


A Soviet stamp dedicated to the 1KP mission.





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