How to design a space station?

The International Space Station is currently the largest space platform operating in orbit. It is a space laboratory with modern scientific research equipment that can carry out large-scale, multidisciplinary basic and applied scientific research. It provides a large number of experiments for scientific experimental research in a microgravity environment. Loads and resources. The International Space Station is a miracle of modern engineering, but the process of designing this miracle has gone through many twists and turns, which is comparable to a nightmare, even under the best conditions.

Many scientific researches and major projects can be regarded as the most difficult tasks in human history, but when a task involves three US presidents, 15 countries, hundreds of US congressmen, thousands of engineers, and more than 150 billion U.S. dollars The level of difficulty seems to be unreasonable when the public fund is established. The construction of the International Space Station is such a task. It took 30 years for the National Aeronautics and Space Administration (NASA) to build such a space station, but it still failed to meet the initial expectations of the agency’s staff.

“Space Base”
Soon after Neil Armstrong and Buzz Aldrin succeeded in taking a big human step on the moon, NASA set out to make humans exist forever in space. At that time, they wanted to build a “space base” that could accommodate 100 people. Through this base, it would be more convenient to send astronauts and supplies to the moon base. In order to build this “base” space station orbiting around the low-Earth orbit, the necessary construction materials must be transported from the earth to orbit one by one, and NASA soon realized that the cost of transporting with a disposable rocket far exceeds the space station In itself, so they chose reusable transport vehicles, such as the space shuttle. From then on, they can start building space stations like “stacking wood”.

The first space station in the United States was the “Sky Lab”. Three groups of astronauts visited the space station from 1973 to 1974 to conduct experiments. The three waves survived for a total of 6 months. Two years later, the space shuttle is ready, and NASA engineers are also considering the next step-allowing astronauts to be permanently stationed on the space station. In early 1982, NASA established a space station mission team to study this issue. They issued funds to eight top aerospace contractors, each with 1 million U.S. dollars, and required these eight companies to provide a space station design plan that could allow permanent residents.

In early 1983, these contractors provided NASA with their designs. Although each concept is unique, they are all composed of some common design elements to meet NASA’s requirements. First of all, each space station can accommodate up to 12 astronauts at a time, which is greatly reduced compared to the large base of 100 people originally envisioned by NASA. Most of the submitted designs also envisage the space station as a “space dock” or “space harbor” to repair spacecraft and satellites in orbit.

“Power Tower”
In 1984, about a year after the contractor submitted the design, US President Ronald Reagan formally instructed NASA to build a space station in his State of the Union address, which he later named the space station “Freedom.”

Reagan’s State of the Union address marked the beginning of a turbulent period in NASA’s ambition to build a space station. Between 1984 and 1993, in order to balance the budget and engineering priorities, the official design of the Freedom went through seven major revisions. Within a few months after the president’s order was issued, NASA had a basic design plan for the space station, but it was completely different from the design proposed by the contractor a year ago. This new design, commonly known as the “Power Tower”, consists of 5 modules-2 laboratories, 1 logistics center and 2 crew cabins-concentrated at the end of a 120-meter-long truss. The module is located at the bottom of the truss (the closest location to the earth), and at the other end of the truss structure is a solar cell array and several antennas.

The pendulum design of the “power tower” is designed to allow astronauts to observe the earth, the sun and space at the same time, which will help carry out scientific experiments and reduce the number of propeller firings required to keep the space station stable in orbit. But with the continuous improvement of the design plan, the concept of the power tower has been criticized by scientists who want to use the space station for research in other fields.

These scientists believe that the living cabin should be located at the center of gravity of the space station, not at the bottom. They believe that the power tower has serious structural problems. Due to oscillation and vibration, the design of placing the laboratory module at the bottom of the structure may be the worst. Most importantly, the design of the space station reflects the needs of users, and users need to reduce the movement of the space station to a minimum.

This means that NASA has to start from scratch.

“Revision of the baseline configuration”
In 1987, NASA released a new design for the Liberty Space Station, the “Revised Reference Configuration”, which is now the prototype of the International Space Station. In this plan, all the modules that make up the space station are concentrated in the center of a long truss with rows of solar panels on both sides. These modules come from international support, Europe and Japan provided laboratory parts, and Canada provided a spacecraft repair center.

The “revised reference configuration” is actually a compromise of the “double keel” design that NASA has been exploring since 1985. Although this design concept is also based on a long horizontal axis, there is a large rectangular structure in its center, the “double keel”, which can accommodate the docking station of the space shuttle and other logistic modules. However, it is estimated that the cost of this design is almost twice the space station construction cost originally estimated by NASA, so the “double keel” was abandoned and a cheaper “revised reference configuration” was used.

Although the revised baseline configuration later became the basis for the final design of the space station, NASA is still constantly adjusting the design to meet evolving budget constraints and technical requirements. Generally speaking, each design iteration will result in a decrease in the capacity of the space station and delay the launch plan.

However, an indisputable fact is that if the space station is to become a reality, it must fundamentally become the result of international cooperation. The United States clearly does not have enough political will to accomplish this task on its own. Therefore, after Clinton entered the White House in 1993, he officially announced that the Liberty plan was changed from being built solely by the United States to being built in international cooperation; after that, the United States began to cooperate with allies to build the International Space Station. With the end of the Cold War, Russia was also invited to cooperate with the United States on this unprecedented project.

The final design of the International Space Station relied heavily on the “revised reference configuration”. Later, NASA enriched the space station, but adopted a simpler design. For example, the main horizontal truss of the space station uses prefabricated components instead of being assembled by astronauts in orbit. This simplified space station configuration consists of a group of laboratories and living cabins, located in the center of a long horizontal truss, with 4 solar cell arrays on each side.

In 1998, the United States launched the first component to the space station-the “Unity” node module as an astronaut dining room. Thirteen years later, the last flight of the Space Shuttle Discovery delivered a multi-purpose pressurized cabin to the space station. At this point, the construction of the space station has officially ended, and the unremitting efforts of NASA and the world’s multinational space agencies have finally paid off. Since then, human beings have been able to work and live in space for 20 years, from the zero-gravity vegetable garden to the coldest known universe. The refrigerator has a unique platform for scientific experiments.