Korolev's team knew that in order to get a satellite up before the Americans, it would have to be small and uncomplicated. A heavier satellite would require further advances in rocketry to achieve the speeds necessary to attain orbit. The Soviets had to create a simpler device that didn't weigh as much.
Sputnik had a diameter of 22.8 inches (58 cm) and weighed 183.9 pounds (83.6 kg). Korolev's team built the orb out of two aluminum hemispheres, each only 2 millimeters thick. They attached two antennas to the satellite. They polished the surface of the satellite to make it easier to detect using optical telescopes.
Inside the satellite was a simple radio transmitter and a silver-zinc battery pack. The radio broadcast a repeated series of beeps. The purpose of this transmission was to provide proof to the rest of the world that the Soviet Union had succeeded in launching the first manmade satellite. Many radio operators wondered if the beeps had any further significance, and theories ranged from simple navigational readings to more sinister applications, such as spy information. In reality, the radio transmissions could only give listeners on Earth an indication of the temperature inside the satellite.
The satellite also had several other simple mechanisms inside of it. There was a fan that would turn on automatically if the temperature inside the satellite went above 86 degrees Fahrenheit (30 degrees Celsius). The engineers filled the satellite with nitrogen until it had an internal pressure of 1.3 atmospheres. They installed various switches that activated depending on changes in pressure or temperature. When activated, the switches altered the signals sent by Sputnik, giving Soviet ground control an idea of what was going on inside the satellite.
The engineers attached Sputnik to a special R-7 launch vehicle. Sputnik's systems activated upon detaching from the vehicle. The R-7 rocket had two stages and weighed more than 272 tons before launch (without fuel it weighed only 22 tons). It used kerosene T-1 as a fuel and liquid oxygen as an oxidizer. The Sputnik satellite sat at the top of the rocket, housed in a special casing that the rocket jettisoned upon attaining orbit.
The rocket was a stripped down version of a military ICBM. It had no remote control system, and operated solely using calibrated gyroscopes. The gyroscopes helped the rocket make adjustments in flight to maintain its course. There was no way for ground control to affect the rocket's flight path. In fact, there were no active tracking systems onboard the rocket -- the Soviet Union had to track Sputnik's progress by radar and ground telescopes.
How did the launch of Sputnik change the world? Find out in the next section.