Introduction

August 19, 1960, marked a historic date: a spacecraft successfully launched dogs Belka and Strelka into orbit. This flight represented the first successful return of living beings from an orbital journey back to Earth.

The Genesis of the Idea and Selection of Subjects

The initiative to study the reactions of highly organized organisms to space conditions originated with Sergei Korolev in late 1948. After extensive discussions, it was decided that dogs would be the most suitable «biological subjects» for the research. Physiologists already had vast experience working with these animals, understanding their behavior and anatomy well. Furthermore, dogs were known for their docile nature and ease of training.

Selecting the «Space Squad»

The initial candidates for space flights were ordinary stray dogs. Medics believed that such dogs, accustomed to surviving in challenging conditions, would be unpretentious and quickly adapt to personnel. Small animals were selected for experiments: weighing up to six kilograms, no taller than 35 centimeters, and aged between two and six years. Key criteria included robust health, resistance to diseases and external influences, as well as being cooperative and patient. Later, light-colored female dogs were preferred – for ease of tailoring special suits and better visibility on television screens. Their appearance was also considered, as these «space travelers» needed to look presentable in newspapers.

Flight Preparations

The direct preparation of the dogs took place at the Institute of Aviation and Space Medicine in Moscow, near Dynamo Stadium, in a red-brick mansion that had previously housed the «Mauritania» hotel before the revolution.

Scientific Training Program

A comprehensive scientific program was developed, including preparation for short suborbital and long orbital flights. The animals were accustomed to special clothing (restraining and waste-management), and to eating from an automatic feeder that dispensed food on schedule. Water was provided as part of the food, as drinking from a bowl was impossible in zero gravity. The dogs were also trained to calmly endure prolonged confinement in a small cabin (up to twenty days) and underwent intensive training: on a centrifuge, vibration stand, and for ejection. The final stage involved a comprehensive physiological experiment within a sealed capsule, simulating the conditions of the upcoming flight.

First Suborbital Flights

The first launch with dogs Tsygan and Dezik took place on July 22, 1951, at the Kapustin Yar range. This was a suborbital flight on the R-2A geophysical rocket. The dogs successfully returned to Earth after fifteen minutes in a parachute-equipped descent capsule. From July 1951 to September 1962, 29 suborbital flights to altitudes of 100-150 kilometers were carried out, eight of which ended tragically due to cabin depressurization, parachute system failure, or life support system malfunctions.

The Tragedy of Laika

The first dog to undertake an orbital flight was Laika. However, as technologies for returning spacecraft from orbit had not yet been developed, she perished from overheating a few hours after launch.

Development of a Returnable Spacecraft

In early 1960, a new returnable spacecraft equipped with full life-support systems was developed. Its initial launch attempt was unsuccessful.

Belka and Strelka`s Triumph: Flight Objectives

On August 19, 1960, at 3:44 PM from the Baikonur Cosmodrome, the second returnable spacecraft was successfully launched into Earth orbit. The primary objective of the mission was to refine the design and all systems ensuring human safety and life support during spaceflight and upon return to Earth. For medico-biological research, the satellite-ship`s cabin housed not only dogs Belka and Strelka but also mice, insects, and plants. Scientists aimed to determine the influence of the space environment on living organisms, concurrently with a program of scientific space research.

Spacecraft Design

The satellite-ship comprised two main sections: a descent module with a sealed cabin and an instrument compartment. Its exterior featured compressed gas tanks for attitude control, reaction engines, scientific equipment, autonomously driven solar panels for constant sun orientation, antennas, and thermal control louvers. During re-entry, the descent module separated from the instrument compartment, which would burn up in the dense layers of the atmosphere.

Contents of the Descent Module

Inside the sealed cabin of the descent module were animal life-support systems, equipment for biological experiments, part of the scientific apparatus, and an ejectable container with cages and receptacles for various biological subjects.

Biological Cargo and Dog Characteristics

The ejectable container housed Belka and Strelka, twelve laboratory mice (six black and six white), hundreds of fruit flies (Drosophila), two vessels with Tradescantia plants, seeds of various crops (onions, peas, wheat, corn, nigella), actinomycete fungi, and the single-celled alga Chlorella. Outside the container, the cabin also contained two more white laboratory rats and 28 mice. Belka and Strelka were light-colored, with Strelka having dark spots. Belka weighed 4.5 kilograms, was 30 centimeters tall, and 47 centimeters long. Strelka weighed 5.5 kilograms, was 32 centimeters tall, and 50 centimeters long. They wore special red and green suits and were secured with chains that restricted their movement but allowed them to stand, sit, lie down, and move slightly forward and backward.

Monitoring and Telemetry

The spacecraft was equipped with medico-biological apparatus to continuously record changes in the dogs` organisms throughout the flight. A radiotelemetric system transmitted service and scientific information. For visual observation of Belka and Strelka, a radiotelevision system with two cameras was installed, allowing Belka to be seen full-face and Strelka in profile.

Radiation Control and Additional Experiments

Sergei Korolev paid extraordinary attention to radiation measurements. Dosimeters were installed in the sealed cabin and on the dogs` clothing. Small samples of human and rabbit skin were also onboard the satellite-ship to investigate the potential effects of spaceflight factors on living organisms` cellular systems.

Landing Systems

Both the ejectable container and the descent module had their own parachute systems, ensuring landing speeds of 6-8 m/s and 10 m/s respectively. The descent module was equipped with heat-resistant portholes and rapidly opening hatches. The ejection of the animal container occurred through a jettisonable hatch, triggered by barometric sensors at an altitude of 7-8 kilometers.

Orbit and In-Flight Monitoring

The spacecraft was placed into a near-circular orbit with an altitude of 306-339 kilometers. During the flight, electrocardiograms (ECG) were recorded, arterial pressure, body temperature, and respiration rate were measured, and the motor activity of the dogs was analyzed.

Animal Behavior in Space

The animals felt normal. Television footage showed their calm demeanor in zero gravity. Belka barked, but as the microphone was located outside the sealed container, her «report» from space was not recorded.

Flight Completion and Landing

The flight lasted over 25 hours, during which the spacecraft completed 17 orbits around Earth. On August 20, 1960, at 10:15 AM, the command for descent was given. The descent module`s parachutes deployed at an altitude of eight kilometers. As it descended to five kilometers, the hatch cover jettisoned, and the container with the animals ejected from the descent module. The landing occurred in the designated area, only 10 kilometers from the calculated target point.

Experiment Results

Post-flight examinations of the «cosmonauts» revealed no negative changes. The experiment provided unique data on the impact of spaceflight factors on the physiological, genetic, and cytological systems of living organisms. This collected data assured scientists that human spaceflight was possible and did not pose an insurmountable danger to living organisms.

Life After Space

After their historic flight, Belka and Strelka became beloved public figures and continued to live at the Institute of Aviation and Space Medicine. Scientists continued their research to understand the long-term genetic impact of space on animals. Strelka gave birth to healthy offspring twice, and one of her puppies was gifted to the family of U.S. President John F. Kennedy. The dogs eventually died of natural causes, and their preserved remains are now exhibited at the Museum of Cosmonautics.