Object D

The 149-88ss decree and its design requirements

The Council of Ministers decree No. 149-88ss of 30 January 1956 called for developing a satellite without an attitude control system over the period 1957-1958. The spacecraft's mass was limited to 1,000-1,400 kg to match the R-7's capability, with 200-300 kg allocated to scientific instruments. The decree divided responsibilities: general scientific management went to the USSR Academy of Sciences, satellite bus development to OKB-1 under the Ministry of Defense Industry, and radio and telemetry systems to the Ministry of Radio Industry.

The decree also authorized reusing hardware developed for other R-7 payloads on Object D to save time and resources. It further approved preliminary work on Object OD, an attitude-controlled vehicle that later became the foundation for a spacecraft capable of returning from orbit, and thus for the first crewed ship.

Twelve instruments, one orbital laboratory

Object D was planned as a multi-functional laboratory to measure atmospheric density and ion composition, magnetic fields, solar radiation, and cosmic rays. The decree assigned the Academy of Sciences research in four disciplines: geophysics, physics, biology, and astronomy. Twelve scientific instruments flew aboard, their operating sequence controlled by a program timer. To record telemetry on orbital segments out of range of ground tracking stations, engineers intended to use an onboard tape recorder for the first time; a fault was detected immediately before launch, and the recorder flew inoperative.

The turn to PS-1

The project began slipping badly from mid-1956. Subcontractors delivered late, and some parts did not match specifications. In late November 1956, with R-7 engine tests showing lower than calculated specific impulse and with pressure from the prospect of an American launch, Korolev decided to simplify. That same month Mikhail Tikhonravov proposed a lighter satellite; Keldysh at first opposed the idea but eventually yielded. In January 1957 Korolev submitted a revised plan for two small satellites of 40-50 kg to be launched just before the International Geophysical Year, and on 15 February the Council of Ministers approved it, pushing Object D's launch back to April 1958.

The immediate trigger came from outside: in July 1955 the Eisenhower administration announced it would orbit a satellite during the IGY, and in August 1955 Academician Leonid Sedov answered publicly at Copenhagen that a Soviet satellite could be launched within two years. Weighing the R-7's test schedule against the IGY calendar, Korolev chose the simplest satellite, PS-1, to secure the first-launch record.

Four attempts

The first three R-7 test flights failed; the fourth, on 21 August 1957, succeeded, and PS-1 reached orbit on 4 October that year. Object D's first launch attempt on 27 April 1958 failed when the booster was destroyed after 120 seconds by pressure oscillations in the oxidizer line, a phenomenon not explained until that summer. The backup vehicle and satellite flew successfully on 15 May 1958, putting Object D into orbit as Sputnik 3.

On orbit and its results

Sputnik 3 drew power from silver-zinc batteries and solar cells; the cells ran a small radio beacon and kept transmitting after the main batteries were exhausted on 3 June 1958. The satellite remained in orbit for 692 days, reentering the atmosphere on 6 April 1960.

Seven development groups built its instruments, which measured the composition of the upper atmosphere, charged particles, protons and cosmic rays, magnetic and electrostatic fields, and encounters with micrometeorites. Its most important scientific result was the first observation, outside the Earth's atmosphere, of a solar cosmic-ray burst from the solar flare of 7 July 1958. Its highly elliptical orbit, with an apogee of 1,881 km and a perigee of 226 km, had already established safe altitude ranges for human spaceflight by 1958.

Discrepancies in the record

Reported masses differ between sources: the decree set a limit of 1,000-1,400 kg, the 1956 preliminary design came in at 570 kg, and Russian accounts give a launch mass of 1,327 kg. Accounts also vary on the timing and cause of the first launch failure and on the booster's designation (the improved 8A91 derived from the 8K71). This entry therefore presents the figures as each published source gives them.