The Soviet Union inaugurated the Space Age on October 4, 1957, with the successful launch of Sputnik 1, the world’s first artificial satellite. The satellite was a polished metal sphere, measuring 58 centimeters in diameter and weighing 83.6 kilograms. It carried a simple radio transmitter whose primary function was to transmit a “beep-beep” signal on two radio frequencies, allowing observers globally to track its path.
The Orbital Decay of Sputnik 1
Sputnik 1 did not meet its end in a catastrophic crash, but rather gradually succumbed to orbital mechanics. Its initial orbit was deliberately low, meaning the satellite constantly experienced drag from the faint upper atmosphere. This atmospheric friction acted as a continuous brake, slowly pulling the sphere closer to Earth.
Sputnik 1 remained in orbit for approximately 92 days, circling the globe 1,440 times. Its mission officially ended on January 4, 1958, when it plunged deep enough into the atmosphere to be destroyed. Because this disintegration occurred at a high altitude over a vast, unpopulated area, there is no single, defined crash site. Its final moments were visible as a bright, man-made meteor streaking across the night sky, likely fragmenting above the Western United States.
The Separate Fate of Sputnik 2
The Soviets followed up with Sputnik 2 on November 3, 1957. This spacecraft was a four-meter-high, cone-shaped capsule weighing 508.3 kilograms, designed to carry a living organism. Its passenger was the dog Laika, who became the first living creature to orbit the Earth.
This satellite was not designed for a safe return and was intended to burn up upon re-entry, a fate Laika shared, as she died just a few hours after launch due to overheating. Sputnik 2 remained in orbit for 162 days, a longer duration than its predecessor. It finally met its demise on April 14, 1958, when its orbit decayed. Like Sputnik 1, it fragmented high above the Earth, with its final trajectory projected over a non-specific region including parts of the Caribbean and South America.
The Science of Atmospheric Re-entry
The reason neither satellite “crashed” is rooted in the physics of atmospheric entry, a process that converts orbital velocity into intense heat. When a satellite’s decaying orbit dips into the denser layers of the atmosphere, it is still traveling at high speeds, often exceeding 7.8 kilometers per second. This velocity causes the air molecules in front of the object to be compressed and superheated.
This rapid compression generates a shockwave, which is the primary source of aerodynamic heating that affects the satellite’s structure. The friction and heat can push temperatures on the spacecraft’s surface past 3,000 degrees Celsius, far exceeding the melting points of most metals. The process that follows is known as ablation, where the spacecraft’s materials are vaporized and stripped away layer by layer.
The satellite does not burn; it disintegrates, transforming into hot gases, metallic vapors, and microscopic particles. Components made of aluminum, titanium, and other structural materials are turned into fine aerosols and dust, which disperse across the upper atmosphere. This pulverization ensures that only the most dense, heat-resistant components—if any—survive to reach the ground. This physical mechanism explains why early satellites never result in a large impact crater.