Sputnik 2 was the second spacecraft launched into Earth orbit and the first biological spacecraft. It was a 4-meter-high cone-shaped capsule with a base diameter of 2 meters. A separate sealed cabin contained the experimental dog Laika.

The first being to orbit the Earth was a female part-Samoyed terrier originally named Kudryavka (Little Curly) but later renamed Laika (Barker). She weighed about 6 kg. The pressurized cabin on Sputnik 2 provided enough room for her to lie down or stand and was padded. An air regeneration system supplied oxygen, while food and water were dispensed in a gelatinized form. Laika was fitted with a harness, a bag to collect waste, and electrodes to monitor vital signs. Early telemetry indicated that Laika was agitated but eating her food.

At that time, there was no capability to return a payload safely to Earth, so it was planned that Laika would run out of oxygen after about 10 days of orbiting. The mission provided scientists with the first data on the behavior of a living organism in the space environment.