I’ve already talked about the first two artificial satellites in history, Sputnik 1 and Sputnik 2, both launched by the Soviet Union in 1957. But what about the Soviets’ Cold War rivals, the United States? Their first successful satellite, Explorer 1, was launched on 31st January 1958 – so today, on the 60th anniversary of its launch, here are some fun facts about it!
1. In 1955, the US Navy was given the task of launching the first US satellite with Project Vanguard. Their rivals, the US Army, boasted a team of very experienced rocket engineers, led by Dr Wernher von Braun, transported from Germany after the Second World War. But the Eisenhower administration didn’t want the first American satellite to be built by Germans – particularly as the missiles they were responsible for creating were based on the design of the V-2, which had been used to bomb Allied targets during the war. When the Soviets beat the Americans by launching Sputnik 1 in October 1957, however, there was a panicked rush to get an American equivalent off the ground, and the Army were given permission to launch their own satellite. The Navy did still get to try first, on 6th December 1957, but their rocket barely made it off the launchpad before crashing and exploding. “Kaputnik”, as one newspaper described it.
2. Constructed by the Jet Propulsion Laboratory in Pasadena, California, the Army’s satellite – Explorer 1 – would be a cylinder weighing 13.4 kilograms, considerably smaller than Sputnik 1. Unlike Sputnik, however, it carried scientific instruments, including detectors for measuring cosmic rays and micrometeorite impacts.
3. The launch vehicle for Explorer 1 was the Juno I rocket, a modification of another rocket called the Jupiter-C, with an extra engine on top to boost the satellite into orbit. The US Army had been using the Jupiter-C for testing the re-entry properties of missile nose cones since September 1956; indeed, had they been given permission, they could have used one to launch a satellite well before the Soviets. In 1961, a rocket from the same family, the Mercury-Redstone, would be used to launch the first manned American spaceflights.
4. A three-day launch window was given for Explorer 1, beginning on 29th January 1958. Bad weather caused delays, and it wasn’t until 10:48pm on 31st January that the Juno I rocket was launched from Cape Canaveral in Florida. To make things especially tense, the signal from the satellite only came through several minutes after the expected time: Explorer had entered a higher orbit than anticipated. Its highly elliptical orbit had a maximum altitude (apogee) of 1,580 miles, and a much lower perigee of 222 miles.
5. The overall levels of cosmic rays detected by Explorer 1 were lower than expected – one of the designers, Dr James van Allen, theorised that this was because the detector was being saturated by concentrated radiation whenever the satellite reached higher altitudes on its orbit. This would eventually lead to the confirmation that there is a belt of charged particles surrounding the Earth, held in place by the planet’s magnetic field; it would become known as the Van Allen radiation belt.
6. Explorer 1 fell silent when its batteries died on 23rd May 1958, almost four months after its launch, but it remained in orbit much longer than the first two Sputniks. It had completed over 58,000 orbits when it finally re-entered the atmosphere in March 1970 – by which time, the world had gone as far as putting men on the Moon.
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