Solar panels: a protective umbrella for space exploration

Just like a close couple would celebrate their love anniversary, this May marks the first anniversary of China's space exploration and Mars "intimate encounter". Today, the Zhurong rover has traveled nearly 2 kilometers on Mars, sent back a large amount of observation data, and encountered many interesting things, igniting the "spark" of China's space exploration of Mars and even other planets.

As the successor of Tianwen-1, Tianwen-2 asteroid probe has entered the prototype development stage and is undergoing comprehensive testing. It is expected to be launched in 2025. Small body exploration is a field that China's space program has not yet deeply involved in. With the help of the flexible solar wing, a "protective umbrella" for deep space exploration, Tianwen-2 will fly with near-Earth asteroids and return samples. The mission may take up to 10 years. It can be said that the flexible solar wing will contribute to improving the global competitiveness of my country's aerospace technology.

Solar panels installed on the Chinese space station (Photo credit: China Manned Spaceflight Office)

According to public information, the Tianwen-2 probe consists of a main probe and a return capsule. The main power supply system of the main probe is a uniquely constructed circular flexible solar wing that resembles an open umbrella. Researchers chose this special configuration of "protective umbrella" to reduce the risk of traditional solar wings touching the ground during the probe's soft landing.

Tianwen-2 adopts a double-wing structure, with a single wing area of ​​17 square meters. One of the reasons why it carries such a large solar wing is that the mission goal is ambitious - after Tianwen-2 completes the asteroid sampling and return mission, the main probe is likely to continue flying into deep space. In this process, the sunlight obtained will become less and less, so the solar wing needs to be specially enlarged.

The solar wing is a veritable "protective umbrella" that continuously converts solar energy into electricity for continuous use by the aircraft during the deep space exploration journey. As we all know, a large amount of uninterrupted solar energy diffuses in the space environment, just like a WiFi wireless charger, which is most popular with spacecraft.

Since a single solar cell generally cannot meet the demand, a power generation device composed of solar cells and related structures connected in series and parallel is called a solar cell array. It is like a "nutritionist" for the spacecraft, constantly "cooking" solar energy into a "nutritional package" that can be directly consumed by various equipment.

Due to limitations such as rocket size, researchers must fold or compress the solar panels before launching the spacecraft. In space, the solar panels are stretched out and constantly adjusted during the flight of the spacecraft, aiming at the sun as much as possible to provide the most efficient sunlight. Some people describe it as a bird folding its wings when taking a nap on a branch and spreading its wings to break through the sky when flying high.

Unfolding is a standard action for the solar panels to be put into service. The new solar panels on the International Space Station unfold like a scroll, which is amazing. In fact, the number, shape and unfolding method of the solar panels are all determined in advance according to the preset functions.

The substrate of the flexible solar wing is very flexible and thin, generally not exceeding 0.5 mm. Its biggest advantage is that it is smaller and lighter when folded. Of course, the technology and structure are also more complicated.

At present, the cost of launching a 1-kilogram payload by a domestic rocket is about RMB 50,000 to 100,000. Flexible solar wings of the same area are more than 20% lighter than rigid solar wings. With the development of aerospace technology, it is even expected to reduce weight by more than 40%, which can significantly reduce launch costs.

Chinese rocket launches into space (Photo: Wang Jiangbo)

In the future, as costs decrease and technology breakthroughs increase, the functional positioning of the solar wing "umbrella" will become increasingly clear, providing greater imagination and development space for the exploration of distant extraterrestrial planets.