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Digital Archive International History Declassified

May 03, 1961


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    Preliminary Report analyzing the results of the Vostok flight of Yuriy Gagarin, prepared by the design bureau in charge of the flight, OKB-1, based in Kaliningrad north of Moscow.
    "Preliminary Report on the Results of the Launch of the Third Vostok-3a Satellite-Ship with Pilot Yu. A. Gagarin on Board (Accomplished On April 12, 1961) ," May 03, 1961, History and Public Policy Program Digital Archive, Selected, edited, and annotated by Asif Siddiqi. Translated by Gary Goldberg and Angela Greenfield.
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New Sources on Yuri Gagarin (April 2021)


Preliminary Report analyzing the results of the Vostok flight of Yuriy Gagarin, prepared by the design bureau in charge of the flight, OKB-1, based in Kaliningrad north of Moscow. – Asif Siddiqi

May 3, 1961

(classification stamp)



(accomplished on April 12, 1961)


The launch of booster rocket 8K72 with the Vostok-3A object, on board of which was pilot YU. A. GAGARIN, was carried out on April 12 at 0906:59 Moscow time. The object was inserted into orbit and separated from the booster at 0918:28.

The parameters of the orbit:

- perigee 181 km,

- apogee 327 km,

- inclination of orbit 64 57’,

- period 89.44 minutes.

The object was oriented toward the Sun before the braking engine unit (TDU) was turned on.

The TDU was turned on at 1025:04.2 (IKN) [Izmeritel’ Kontsentratsii napriazhenii or “voltage sensor”] and turned off at 1025:48.2. The separation of the instrument compartment and reentry apparatus occurred at 1036 (evidently, from the emergency separation system, from temperature-sensitive elements).

The pilot and the reentry apparatus landed respectively at 1053 and 1048, south of the city of Engels.

The coordinates of the pilot’s landing are 51 16’ north latitude and 45 59’ east longitude.

The distance from the point of landing to the reentry vehicle was about 1.5 km.

The deviation of the landing point from the calculated lay within the limits of possible dispersion.

The pilot felt normal in all segments of the flight, and conducted transmissions through the channels of the Zarya system, and recorded the changes of the nature of the G-forces and vibrations well and of the transition segments of the booster rocket’s stages.

The pilot’s observations in the Vzor optical orientation device showed that the Vzor can be used by the pilot to orient the object under manual control (a clear horizon line and the “course” [beg] of the Earth’s surface were observed). The weightlessness which came on after the end of the active [boost] segment did not cause the pilot any unpleasant sensations. During the flight in orbit the pilot took food and water without experiencing any difficulties in so doing.

The pilot endured the G-forces during the descent segment and landing normally.

However, in GAGARIN’s words, at the moment of the passage of the area of the maximum G-forces, in his eyes the objects he was observing began to take on a gray color. He was in this condition for two or three seconds.

The main information is presented below about the operation of individual systems and assemblies of the craft obtained on the basis of:

- the preliminary processing of the telemetry recordings of the Tral-P1 systems made at tracking stations IP-1, IP-4, and IP-7,

- reports about the processing of telemetry information of the Tral-P1 systems on the Atlantic floating telemetry complex,

- the first report of YU. A. GAGARIN which he made at a meeting of the State Commission about the launches of the Vostok objects on April 13, 1961,

- the results of an external examination and inspection of the reentry apparatus and pilot’s seat,

- reports from ground instrumentation points about the operation of the radio equipment.

An examination of these materials showed that the design of the craft, its system, and assemblies ensured the performance of the assigned program of the first manned spaceflight and its safe return to the Earth’s surface.


1. The operation of the ASO, STR, ASTR, Granit-5V, automatic landing equipment, emergency separation system (according to temperature-sensitive elements), SAS, the Vzor optical orientation device, the pilot’s control panel, the Tral-P1 system, the Tral-T with Seliger cameras, the Peleng SA, the space suit, the air conditioning systems, the food and water supply systems, the Vega and Mikron apparatuses, the object’s separation system, the deployment of the antennas, the window shades control, the ejection hatches, the pilot ejection seat, and the SA [reentry apparatus] and pilot parachute systems– operated in accordance with the flight program and there are no comments about the operation of these systems.

2. Comments about the operation of individual systems:

a. The Rubin system. The first complement of the system operated and was received normally by ground stations. The second complement was not received by the IP-6D station, and it was received by the IP-3D station in the form of a weak signal.

A frequency drift in the second complement is a possible reason.

b. KRL. The KRL [kommandnaya radioliniya or “command radio-link”] was not used in accordance with the KRL program in the process of flight.

c. Signal. The system operated normally in flight although strong interference from external radio stations was heard at ground stations.

d. Raduga. The apparatus of the Raduga system placed in the NAZ [nosimyy avariynyy zapas or wearable emergency reserves] was not turned on as a consequence of a disconnection of the NAZ (see below).

e. Zarya. There were no communications via channel KV [high-frequency]-1 (the night frequency) (evidently because of unfavorable conditions of wave propagation).

Communications were satisfactory via channel KV-2, better via the craft-ground line and worse via the ground-craft line. A fading of the signal was observed, evidently connected with the rotation of the object. A consideration part of the information received on the Earth came at the level of noise.

To improve communications via the KV-channels of the Zarya system it is advisable:

- to analyze to correctness of the choice of the communications frequencies and, if necessary, to change them,

- to introduce a retouching of the carrier frequency with tonal impulses to make tracking of the on-board transmitter easier at the ground stations when there is no transmission from the craft,

- transmit from the Earth with greater power and with the aid of directional antennas.

The UKV [VHF]-channel operated normally although a dropping out of individual words was observed on the active segment, possibly connected with low pressure of the “UKV transmission” button (when there are G-forces).

The tape recorder system operated normally. However, during the flight, it hit the limit switches - the capacity of the tape recorder was used up. It was necessary to ensure a complete rewind of the tape recorder before starting.

f. The control system in the segment of the TDU’s operation.

Stabilization in the segment of the TDU’s operation was accomplished normally.

There were two anomalies [zamechaniia]:

- Switching off the TDU occurred not from the integrator, but from the timer of the SU TDU [braking engine unit’s control system] 44.0 seconds after the IKN [voltage sensor],

- after the separation command was passed an overspinning was observed of the object on the pitch channel up to six degrees per second.

The shutdown of the TDU from the timer is explained by incomplete processing of the TDU pulse (see below).

The overspinning of the object is explained by the following reasons.

Inasmuch as the TDU shut down from the timer, a command to cancel the separation was issued. In this event according to the command for separation a deactivation of the SU [control system] of the TDU occurred, but the separation did not take place.

According to the telemetry data after passing this command, the pitch channel throttle seized, which could occur naturally since the drives were disconnected. This, in turn, (because of the escape of gasses through the nozzle) led to an overspinning of the object.

When the engine is normally shut down from the integrator, overspinning of the object should not occur, i.e., a separation of the object should occur. In order to avoid overspinning of the object in the event that the TDU is shut down from the timer, the SU TDU shutdown command needs to be shifted to a later time (for example, to marker 76 minutes of cycle Nº 4, to 66 minutes of cycle Nº 5, [or] to 20 minutes of cycle Nº 6 of system Granit-5V).

g. The braking engine unit (TDU).

The TDU was turned on at 1025:4.2 seconds (the “pressurize” command). The “launch” command followed 2.2 seconds after this command. The engine went to [operating] mode 1.5 seconds after the “launch” command.

A fall of the fuel pressure occurred 42.2 seconds after the IKN after the pump and [a fall of the] gas pressure after TNA [turbonasosnyy agregat or “turbopump assembly”]. The main command to turn on the TDU came 44 seconds after the IKN [voltage sensor].

The value of the braking pulse determined through the axial overload and the precise contact of the integrators was close to the estimated one.

At the present time the causes of the described operation of the TDU have not been identified.

h. Mir

[The following] was detected during inspection of the instrument:

- the magnetic tape at the receiving cassette was torn off;

- there is no record that the tape wound on the receiving cassette;

- five or six meters of crumpled magnetic tape which jammed the drive shaft are wound on the drive shaft of the instrument;

- a positioning washer [baziruyushchaya shayba] which ensures the clearance between the cassette and the bottom of the armored body did not end up on the spindle of the receiving cassette (three washers which were manually cut from thick white paper were covered instead of the base washer on the shaft of the receiving cassette).

i. The pilot’s seat and the NAZ.

The ejection system, the injection of pilot parachute systems, and the ejection of the pilot from the seat went normally. However, after the separation of the NAZ from the pilot, the NAZ was destroyed and lost.

An activation of powder booster and the destruction of the seat upon impacting the Earth was recorded.

j. The pilot’s parachute systems.

After operation and filling of the primary canopy, the reserve canopy was automatically jettisoned. In this flight an inflation of the reserve canopy occurred and a subsequent descent occurred on two canopies.

According to a statement of YU. A. GAGARIN he was not able to control the flight on parachutes and he descended almost to the very ground facing the wind.

The reason for this was:

- the constraint of the pilot’s movements while in the space suit;

- the insufficient training of the pilots to control the regular parachute system installed on the seat during descent.

k. The P57 direction finder container.

The short wave of the P57 direction finder worked normally. However, the search group at the landing site noticed that the rubber balloon of the container was in a poorly-inflated condition. The cause for this was damage to the fabric of the rubber balloon during the placement of the cover of the container.

l. The fan of the 1K.1320-0 parachute container.

The search group at the landing site noticed that the fan of the parachute container did not work.







Archival source: Central Archive of RKK Energiya. Arkh. 13029, op. 1/70.

[1] Sergey Pavlovich Korolev (1907-1966) was chief designer of OKB-1.

[2] Konstantin Davydovich Bushuyev (1914-1978) was deputy chief designer of OKB-1.

[3] Mikhail Klavdiyevich Tikhonravov (1900-1974) was chief of Department No. 9 at OKB-1.


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