It has been more than two months since the Shenzhou-17 spacecraft was launched and put into orbit, and the Tianzhou-7 cargo spacecraft has not yet been launched.
Previously, before each Shenzhou spacecraft launch, it was common to launch a Tianzhou cargo spacecraft to send supplies to the space station, and then choose the right time to launch the Shenzhou spacecraft to send astronauts to the space station. This time, however, a different story has arisen.
The reason is that the carrying capacity of the Tianzhou-7 cargo spacecraft has been greatly improved. Compared with the Tianzhou-2 to 5 cargo spacecraft, the Tianzhou-6 cargo spacecraft and its subsequent upgraded versions of the cargo spacecraft have been greatly upgraded, and their cargo capacity has been greatly improved, and they can carry more materials.
The length of time an astronaut travels in orbit is closely related to the replenishment capacity of the cargo spacecraft.
In the early stage of manned spaceflight, the space station had not yet been established, and the materials needed for the astronauts' life and work in space could only rely on the manned spacecraft itself.
It's going to be too long. After the completion of the space station, the astronauts' time in orbit has increased from a few days in the past to a year, and they can even be continuously stationed. This is because the space inside the space station is much larger than the spaceship and can be replenished by cargo ships.
China's Tianzhou cargo spacecraft and Russia's Progress cargo spacecraft are carrying out precisely such tasks. Thanks to the upgrade of the Tianzhou-6 cargo spacecraft and carrying more supplies than before, it will be able to support the space station for a longer period of time.
Why didn't the Tianzhou-7 cargo spacecraft be launched ahead of schedule before the Shenzhou-17 spacecraft was prepared?This is because although the cargo capacity of the Tianzhou-6 cargo spacecraft has been improved, it is still unable to meet the materials required for subsequent missions.
Therefore, the Tianzhou-7 cargo spacecraft will need to support subsequent missions. In addition, the Tianzhou-7 cargo spacecraft and the Long March-7 Yao-8 launch vehicle have arrived at the Wenchang launch site and are scheduled to be launched in January next year. So why hasn't the space station run out of oxygen yet?
Currently, our space station maintains a permanent presence of three astronauts, each of whom typically stays in orbit for six months. During such a long mission, these astronauts will need to consume at least 300,000 liters of oxygen.
However, because the space station, the Tianzhou cargo spacecraft, and the Shenzhou spacecraft are all very limited, it is impossible to store such a large amount of oxygen. Therefore, the oxygen in the space station does not come from space, but is obtained by other means. So, what is the best thing about so much oxygen?
As mentioned earlier, the supplies in the space station are mainly replenished through the Tianzhou cargo spacecraft. However, not all oxygen is transported directly from the cargo spacecraft to the space station due to the limited internal space that cannot carry large quantities of supplies.
This mode of transportation is not only unrealistic, but also has safety risks. If oxygen tanks are used to compress oxygen and transport it to the space station, there are serious safety risks during both transport and use.
In 1969, the Apollo 13 spacecraft encountered an oxygen tank** on its way to the moon, which led to the cancellation of the mission.
Today, although the Tianzhou cargo spacecraft does not directly deliver oxygen to the space station, it provides oxygen to the space station in a safer and more reliable way. This way is to prepare oxygen by electrolysis of water, as water molecules are made up of hydrogen and oxygen.
Transporting water into space is clearly safer and more practical than transporting oxygen. Scientists have calculated that less than 500 liters of water are needed to produce 620 liters of oxygen, enough for three astronauts to fly in orbit for six months.
Transporting 500 litres of water is much simpler than sending 300,000 litres of oxygen into space. In addition, the water inside the space station can be recycled, including the sewage produced by astronauts on a daily basis.
This advanced oxygen preparation method is not only safer and more reliable, but also more in line with practical needs.