Kosmos 27

Kosmos 27
Mission type	Venus impact probe
Operator	OKB-1
COSPAR ID	1964-014A
SATCAT no.	00770
Spacecraft properties
Spacecraft type	3MV-1
Manufacturer	OKB-1
Launch mass	6520 kg
Dry mass	948 kg; (including an impact; probe of 285 kg)
Start of mission
Launch date	27 March 1964, 03:24:43 GMT
Rocket	Molniya 8K78; s/n T15000-27
Launch site	Baikonur, Site 1/5
Contractor	OKB-1
End of mission
Decay date	28 March 1964
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Perigee altitude	167 km
Apogee altitude	198 km
Inclination	64.8°
Period	88.7 minutes
Epoch	27 March 1964
	Venera ← Venera 3MV-1 No.2 Venera 2 →

Kosmos 27 (Russian: Космос 27 meaning Cosmos 27), also known as Zond 3MV-1 No.3 was a space mission intended as a Venus impact probe. The spacecraft was launched by a Molniya 8K78 carrier rocket from Baikonur. The Blok L stage and probe reached Earth orbit successfully, but the attitude control system failed to operate.^[4]

Launch

Kosmos 27 was launched at 03:24:43 GMT on 27 March 1964, atop a Molniya 8K78 s/n T15000-27 carrier rocket flying from Site 1/5 at the Baikonur Cosmodrome.

Spacecraft

Kosmos 27 was a "third-generation" deep space planetary probes of the 3MV series of the Soviet Union. The Soviet engineers planned four types of the 3MV, the 3MV-1 (for Venus impact), 3MV-2 (for Venus flyby), 3MV-3 (for Mars impact), and 3MV-4 (for Mars flyby). The primary difference over the second-generation was vastly improved (and in many cases doubled) orientation system elements as well as improved onboard propulsion systems. While these four versions were meant to study Mars and Venus.^[2]

Mission

The probe was the first dedicated 3MV spacecraft that the Soviets launched (earlier missions had been of the test "Object-Probe" versions as Kosmos 21). It was designed to accomplish atmospheric entry into Venus followed by descent and impact. On 27 March 1964, it had a perigee of 167 kilometres (104 mi) and an apogee of 198 kilometres (123 mi), with an inclination of 64.8° and an orbital period of 88.7 minutes. The spacecraft successfully reached Earth orbit but failed to leave for Venus when the Blok L upper stage malfunctioned. The upper stage lost stable attitude due to a failure in the circuit of the power supply circuit that powered the valves for the attitude control system; hence, the stage remained uncontrollable and not ready to initiate a burn to leave Earth orbit. The problem was traced to a design error, the examination of telemetry data found that the failure was due to a design flaw in the circuitry of the BOZ unit, which resulted in power not being transferred to the attitude control jets on the Blok L stage, rather than one related to quality control. The spacecraft burned up in Earth's atmosphere the following day, on 28 March 1964. If successful, this mission would have been given a "Venera" designation.^[2]