On this date in 1957 the Soviet Union launched Sputnik 1 (Простейший Спутник-1, “Elementary Satellite 1”) into a low Earth orbit, becoming the first artificial Earth satellite. It was a 58 cm (23 in) diameter polished metal sphere, with four external radio antennas to broadcast radio pulses. Its radio signal was easily detectable even by radio amateurs, and the 65° inclination and duration of its orbit made its flight path cover virtually the entire inhabited Earth. This surprise success precipitated the American Sputnik Crisis and triggered the Space Race, a part of the Cold War. Tracking and studying Sputnik 1 from Earth provided scientists with valuable information. The density of the upper atmosphere could be deduced from its drag on the orbit, and the propagation of its radio signals gave data about the ionosphere.
Sputnik 1 was launched during the International Geophysical Year from Site No.1/5, at the 5th Tyuratam range, in the Kazakh SSR (now known as the Baikonur Cosmodrome). The satellite travelled at about 29,000 kilometers per hour (18,000 mph; 8,100 m/s), taking 96.2 minutes to complete each orbit. It transmitted on 20.005 and 40.002 MHz, which were monitored by radio operators throughout the world. The signals continued for 21 days until the transmitter batteries ran out on 26th October 1957. Sputnik burned up on 4th January 1958 while re-entering Earth’s atmosphere, after three months, 1440 completed orbits of the Earth, and a distance traveled of about 70 million km (43 million mi).
I was 6 years old when Sputnik was launched and remember the sensation it caused very well even though it had no great meaning for me at the time. I do remember adults making a big fuss about it, however, and as I grew older I got interested in the Space Race, even though its accomplishments paled in comparison with the science fiction stories I became addicted to. I do remember a mixed sense of awe and fear as the news spread: awe that the Space Age had arrived, and fear at that this portended in the context of nuclear weapons and the Cold War.
The chief constructor of Sputnik 1 was Mikhail S. Khomyakov. The satellite was a 585-millimetre (23.0 in) diameter sphere, assembled from two hemispheres that were hermetically sealed with O-rings and connected by 36 bolts. It had a mass of 83.6 kilograms (184 lb). The hemispheres were 2 mm thick, and were covered with a highly polished 1 mm-thick heat shield made of aluminium-magnesium-titanium AMG6T alloy. The alloy is 6% magnesium and 0.2% titanium). The satellite carried two pairs of antennas designed by the Antenna Laboratory of OKB-1 led by Mikhail V. Krayushkin. Each antenna was made up of two whip-like parts: 2.4 and 2.9 meters (7.9 and 9.5 ft) in length, and had an almost spherical radiation pattern, so that the satellite beeps were transmitted with equal power in all directions, making reception of the transmitted signal independent of the satellite’s rotation.
The power supply, with a mass of 51 kg (112 lb), was in the shape of an octagonal nut with the radio transmitter in its hole. It consisted of three silver-zinc batteries, developed at the All-Union Research Institute of Current Sources (VNIIT) under the leadership of Nikolai S. Lidorenko. Two of these batteries powered the radio transmitter and one powered the temperature regulation system. The batteries had an expected lifetime of two weeks, and operated for 22 days. The power supply was turned on automatically at the moment of the satellite’s separation from the second stage of the rocket.
The satellite had a one-watt, 3.5 kg (7.7 lb) radio transmitting unit inside, developed by Vyacheslav I. Lappo from NII-885, the Moscow Electronics Research Institute, that worked on two frequencies, 20.005 and 40.002 MHz. Signals on the first frequency were transmitted in 0.3 sec pulses (under normal temperature and pressure conditions on-board), with pauses of the same duration filled by pulses on the second frequency. Analysis of the radio signals was used to gather information about the electron density of the ionosphere. Temperature and pressure were encoded in the duration of radio beeps. A temperature regulation system contained a fan, a dual thermal switch, and a control thermal switch. If the temperature inside the satellite exceeded 36 °C (97 °F) the fan was turned on and when it fell below 20 °C (68 °F) the fan was turned off by the dual thermal switch. If the temperature exceeded 50 °C (122 °F) or fell below 0 °C (32 °F), another control thermal switch was activated, changing the duration of the radio signal pulses. Sputnik 1 was filled with dry nitrogen, pressurized to 1.3 atm. The satellite had a barometric switch, activated if the pressure inside the satellite fell below 130 kPa, which would have indicated failure of the pressure vessel or puncture by a meteor, and would have changed the duration of radio signal impulse.
While attached to the rocket that launched it, Sputnik 1 was protected by a cone-shaped payload fairing, with a height of 80 cm (31.5 in). The fairing separated from both Sputnik and the spent R-7 second stage at the same time as the satellite was ejected.
The rocket that carried Sputnik was launched on 4th October 1957 at 19:28:34 UTC (5 October at the launch site) from Site No.1 at NIIP-5 in Kazakhstan. Telemetry indicated that the strap-on booster rockets separated 116 seconds into the flight and the core stage engine shut down 295.4 seconds into the flight. At shut down, the 7.5 tonne core stage with PS-1 attached had attained an altitude of 223 km (139 mi) above sea level, a velocity of 7,780 m/s (25,500 ft/s) and velocity vector inclination to the local horizon of 0 degrees 24 minutes. This resulted in an initial orbit of 223 km (139 mi) by 950 km (590 mi), with an apogee approximately 500 km (310 mi) lower than intended, and an inclination of 65.1 degrees and a period of 96.2 minutes.
The launch came very close to failure—a postflight examination of telemetry data found that the Blok G strap-on booster had not attained full power at ignition and the resulting imbalanced thrust caused the booster to pitch over by about 2° six seconds after liftoff. Two seconds later, the flight control system tried to compensate by rapidly moving the vernier engines and stabilizer fins. The Blok G strap-on finally reached 100% thrust only one second before the pitch angle would have been great enough to trigger an automatic shutdown command, which would have terminated the launch and sent the R-7 rocket and Sputnik 1 crashing to the ground in a fireball only a short distance from the pad.
A fuel regulator in the booster also failed around 16 seconds into launch, which resulted in excessive RP-1 fuel consumption for most of powered flight and engine thrust 4% above nominal. Core stage cutoff was intended for T+296 seconds, but the premature propellant depletion caused thrust termination to occur one second earlier when a sensor detected overspeed of the empty RP-1 turbopump. There were 375 kilograms (827 lb) of liquid oxygen fuel remaining at cutoff.
At 19.9 seconds after engine cut-off, PS-1 separated from the second stage and the satellite’s transmitter was activated. These signals were detected at the IP-1 station by Junior Engineer-Lieutenant V.G. Borisov, where reception of Sputnik 1’s “beep-beep-beep” tones confirmed the satellite’s successful deployment. Reception lasted for two minutes, until PS-1 fell below the horizon. The Tral telemetry system on the R-7 core stage continued to transmit and was detected on its second orbit.
The Soviets provided details of Sputnik 1 before the launch but few outside the Soviet Union noticed. Organized through the citizen science project Operation Moonwatch, teams of visual observers at 150 stations in the United States and other countries were alerted during the night to watch for the Soviet sphere at dawn and during the evening twilight through binoculars or telescopes as it passed overhead. The USSR asked radio amateurs and commercial stations to record the sound of the satellite on magnetic tape.
Listeners were both thrilled and terrified to hear Sputnik 1’s steady beep. News reports at the time pointed out that “anyone possessing a short wave receiver can hear the new Russian earth satellite as it hurtles over this area of the globe”. Directions, provided by the American Radio Relay League were to “Tune in 20 megacycles sharply, by the time signals, given on that frequency. Then tune to slightly higher frequencies. The ‘beep, beep’ sound of the satellite can be heard each time it rounds the globe.” The first recording of Sputnik 1’s signal was made by RCA engineers near Riverhead, Long Island. They then drove the tape recording into Manhattan for broadcast to the public over NBC radio. However, as Sputnik rose higher over the East Coast, its signal was picked up by W2AEE, the ham radio station of Columbia University. Students working in the university’s FM station, WKCR, made a tape of this, and were the first to rebroadcast the Sputnik signal to the US public (or whoever could receive the FM station).
Given that Sputnik was launched from Kazakhstan, a Kazakh recipe is in order. I’ve already given a recipe for beshbarmak, the national dish that I was able to sample last month when I was in Almaty. I also had baursak, a fried yeast dough. Here’s a video, mostly in English: