Design of the first artificial satellite of the Earth

Previous chapter: Object D project


Exploded view of the PS-1 (Sputnik-1) satellite. Copyright © 2012 Anatoly Zak

Sputnik design

Main components of the PS-1 (Sputnik-1) and its interface with with the launch vehicle:

1 Switch of the DTK-34 thermal control system 12 Heat shield
2 Radio transmitter D-200 13 Jet nozzle
3 Control thermal switch and barometric switch 14 Transfer section
4 Sealed cable entrance 15 Satellite
5 Antenna 16 Satellite
6 Power supply batteries 17 Pyrotechnic devices
7 Interface outlet 18 Pyrotechnic interface
8 Switch interface 19 Valve
9 Fan 20 EPK system
10 Diffuser 21 Drossel interface
11 Remote switch 22 Receiver

Shortcut to a Simplest Satellite

By the end of 1956, it became clear that problems with the development of scientific instruments for Object D, coupled with lower then expected specific impulse of the R-7 rocket (304 seconds, instead of projected 309-310 seconds) threatened to derail the schedule. (84) As a result, the launch date of Object D slipped to April 1958. (52) In the meantime, the International Geophysical Year, IGY, officially starting on July 1, 1957, was officially targeted by the United States as the launch window of the first American satellite. To meet politically important window, OKB-1 proposed the Soviet government to precede Object D with a real "simplest satellite"or "prosteishy sputnik," or also known by Russian abbreviation as PS. With the launch mass of "only" 80-100 kilograms, and with only the most essential equipment onboard, it could be launched in April-May 1957, OKB-1 promised. (52)

One source dates OKB-1 proposal to "bypass" Object D with a simple satellite to November 1956. (248) Korolev's biographer, Yaroslav Golovanov attributes the first proposal to build "lighter, simpler satellite" to Mikhail Tikhonravov and also dates it by November 1956. Tikhonravov reportedly suggested building a satellite with the mass of "some 30 kilograms or less," which would carry minimum scientific gear, with little dependency on contractors outside Korolev's OKB-1.

On Nov. 25, 1956, engineer OKB-1 Nikolai Kutyrkin received an assignment to design the simple satellite. Soon thereafter, future cosmonaut Georgy Grechko was assigned to calculate launch trajectory for the satellite. This work was conducted on a recently inaugurated computer of the Academy of Sciences. (18, 256)

Keldysh and other scientists at the Academy of Sciences were reportedly against the idea of the simplest satellite, since their stakes were in Object D and they would have no involvement in the PS project, and therefore could not claim credit with the Soviet government in case of its success. (18) Nevertheless, Korolev had prevailed.

On January 5, 1957, Korolev sent an official request to Ustinov for the launch of the simplest satellite before the opening of the IGY. (84)

On Feb. 15, 1957,** the Soviet government issued a decree entitled "Insertion of the simplest unoriented satellite of the Earth (Object PS) into orbit, the testing of the simplest satellite tracking in orbit and the reception of signals transmitted from Object PS. (248) A total of two PS satellites could be launched, but only after the R-7 rocket completes two successful flights. (52)

Sputnik's technical description


Assembly of the aft hemisphere for the PS-1 satellite.

According to recollections of OKB-1 veteran Vakhtang Vachnadze recorded in 2010s, Korolev was first shown a design for a cylinder-shaped satellite, however the Chief Designer refused even to look at blueprints and demanded a planet-looking body.

The Simplest Satellite was designed as a sealed ball-shaped container with the diameter of 580 millimeters. Its main body was made out of two hemispheres two millimeters thick and connected by 36 bolts. Resin O-rings ensured sealed interface between hemispheres. The top hemisphere carried two antennas with two beams each. One antenna had 2.4-meter beams, another 3.9 meter beams. A special spring mechanism was designed to deploy antennas to the angle of 35 degrees toward the main axis of the container, immediately after the spacecraft had separated from the rocket. (84) A laboratory at OKB-1 led by M. V. Krauyshkin, developed the antennas. (52)

On the exterior, the top hemisphere was covered by a thermal protective shield one millimeter thick. On its internal side it carried an attachment for the radio transmitter. The surface of both hemispheres was thoroughly polished to enable better reflection of the sunlight, which could help in optical tracking of the satellite from the ground.

The PS satellite carried following internal components:

  • Radio transmitter developed by V. I. Lappo at the NII-885 institute led by M. S. Ryazansky;
  • Power supply system made out of three silver-zinc batteries developed at the Institute of Electrical Sources led by N. S. Lidorenko;
  • Remote switch
  • Thermal system fan
  • Dual sequencer switch of the thermal control system
  • Control thermal switch and
  • Barometric switch

At OKB-1, Mikhail Khomyakov was a leading designer of the satellite; (254) Maksim Khramov was a chief designer of the PS-1 satellite bus; (250) Oleg Ivanovskiy was in charge of pre-flight testing. (254)

After its final assembly, the satellite would be filled with nitrogen, achieving internal pressure of 1.3 atmospheres. Power supply to the radio transmitter and the thermal control system onboard the satellite would be activated by a remote switch. It would be triggered by a sensor at the moment of separation of the launch vehicle and the satellite.

A one-watt radio transmitter emitted signals lasting 0.4 seconds on the wavelength of 7 and 15 meters. If temperature onboard the satellite would exceed 50 degrees C or fall below 0 degrees C, or if the pressure inside fell below 0.35 kilograms per square centimeter, thermal and barometric switches would be activated changing the length of the radio signal sent by the satellite.


A fan assembly for the PS-1 satellite.

To maintain the normal temperature inside the satellite, a special fan would be activated, when the interior temperature would increase above 30 degrees C. If the temperature fell below 20-23 degrees C, the fan would be turned off. A dual thermal switch was responsible for turning the fan on and off. (84) Batteries were designed to function for two weeks. (52)

The total mass of the satellite reached 83.6 kilograms. A special transfer section was developed to connect the rocket with the satellite. A separation system was designed to jettison the payload fairing and the satellite from the core stage of the R-7 rocket.

Despite its limited payload, the satellite was expected to achieve following scientific goals:

  • Rate of decay of its orbit would allow to determine the density of the upper atmosphere;
  • Property of radio wave distribution throughout the ionosphere;
  • Theoretical calculations and technical solutions associated with delivering satellites into orbit would be tested; (51)

All tracking of the rocket in flight had to be conducted passively by means of radar, without onboard response, and with the help of ground telescopes.

**According to another source, the decree was issued on February 7, 1957. (84)

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Mikhail Khomyakov worked as the leading designer of the first satellite.


Early draft of the first Sputnik.


Final design of the PS-1 satellite. Credit: RGANTD




Actual blueprints of the PS-1 (Sptunik-1) satellite.

Sputnik's front hemisphere

1) Sputnik's front hemisphere; 2) Radio transmitter; 3) Antenna interface. Credit: RGANTD

Sputnik's batteries

Sputnik's electric batteries served as the source of power for all onboard systems. Credit: RGANTD

Sputnik semisphere

The front hemisphere of Sputnik-1 with antenna attachments and other system interfaces clearly visible. (Anatoly Zak's archive)


Internal view of Sputnik from the side of a cooling fan. Credit: Roskosmos


The D-200 transmitter for the PS-1 satellite. (Anatoly Zak's archive)



The aft section of the satellite shows the interface of the rocket separation mechanism. Cosmonautics Memorial Museum, Moscow, Russia. Click to enlarge Copyright © 2005 Anatoly Zak


A payload fairing of the PS-1 satellite (Sputnik-1). Copyright © 2011 Anatoly Zak


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