The first show was a success! The large-scale solar directional device on the space station is very eye-catching

On July 28, 2022, four days after the launch of the Wentian experimental module, my country's first large-scale solar orientation device, which was carried on board the module, officially debuted and successfully completed a series of in-orbit performance tests. All indicators performed well. my country's space station successfully achieved dual-degree-of-freedom solar orientation.

What is the "solar orientation device"? Simply put, it is mainly responsible for driving the rotation of the solar panels and the transmission of energy inside and outside the cabin. It is one of the key technologies that was first put on the agenda at the beginning of the Chinese space station project. After the construction of the future space station is completed, the various scientific instruments and payloads in the cabin, including the electricity required for important equipment to maintain the life system of astronauts, will rely on the large-scale solar orientation device to transmit efficiently and reliably from outside the cabin to inside the cabin. It can be said that it is a veritable "energy guardian" of the space station .

Strong and able to turn

In order to ensure the power demand of the space station, the large flexible solar wing equipped on the Wentian experimental module is 27 meters long and has an effective power generation area of ​​about 110 square meters, which can ensure a steady supply of energy to the space station. But it is not easy to drive these two flexible solar wings to "circle" smoothly in space so that they can receive sunlight around the clock. If you imagine that we hold a 27-meter-long "banana fan" in one hand and rotate it 360° with the wrist as the center of the circle, this requires our wrist to have a strong load-bearing capacity and rotational force. The solar orientation device on the experimental module is equivalent to our wrist, which needs to drive the solar wing to rotate continuously and stably face the sun.

The solar orientation device of the space station provides inexhaustible energy for the entire cabin, but the space environment faced by long-term stationing outside the cabin will put severe tests on large rotating mechanisms. How to ensure that the solar orientation device drives the solar wing transmission accurately without causing motion jamming is a huge challenge for the development team. To this end, the development team brainstormed and designed a new set of "distributed slewing support drive transmission scheme" that is the first of its kind in China . It can ensure that the large guide rail can still support the smooth rotation of the drive mechanism when it is deformed by thermal expansion and contraction at high and low temperatures, and drive the two giant solar wings to track the sun in real time. At the same time, the team also added a layer of "temperature control jacket" to the solar orientation device to ensure that the solar orientation device is always in a suitable temperature range under long-term extreme high and low temperature external environments.

High efficiency and fast transmission

The electricity we use in our daily lives is delivered to thousands of households through the huge power grid system of power plants, and in the solar system, the sun is a natural "large power plant." But how can we transmit the tens of thousands of watts of electricity generated by large flexible wings to the space station, build a stable and efficient "energy lifeline", and make the space station truly "worry-free" in electricity use?

Generally speaking, most spacecraft use the traditional slip ring conductive transmission method. In simple terms, the slip ring is a "rotating joint" used to connect and transmit energy. However, due to sliding wear in this method, it is generally suitable for spacecraft with kilowatt-level transmission power. The power transmission demand of the space station is more than 20 times that of ordinary spacecraft, and the design life requirement is high. In the face of the huge power consumption caused by sliding wear, the space station expresses "zero tolerance"! To this end, the research and development team pioneered a super-power and super-long-life rolling ring electrical transmission mechanism, realizing the first high-power transmission in China by replacing sliding contact with rolling. In order to verify the high reliability, high efficiency and long life of the rolling ring, the research and development team conducted 200,000 circles of accelerated life test assessment on the ground, which is equivalent to 34 years of work in orbit, and ensures the efficient and smooth energy path of the space station with 100% product reliability.

Be accurate and controllable

How to keep the solar panels pointing to the sun during the space station's in-orbit flight? The solar orientation device is equipped with a rotary transformer that can collect information on the sun's rotation angle in real time . After receiving the motion mode requirements issued by the attitude control system, the solar orientation device can accurately adjust its own state through autonomous motion planning, so that the solar panels can be stably pointed to the sun like a "sunflower".

"In addition to accurate alignment, the more difficult thing is how to control such a large and soft solar wing smoothly." This is the common consideration and worry of the research and development team during the design. The total effective power generation area of ​​the solar wing is about 220 square meters, and the entire wing is 55 meters long , but it is only as soft as printing paper, and any slight vibration can make it sway. If the solar wing rotates unsteadily, it will cause difficulties in the attitude control of the space station. Therefore, the "high-flexibility and high-stability servo control system" came into being. This control solution tailored for the solar directional device allows the solar wing to "dance with long sleeves" and achieve stable tracking control of the sun.

What’s even more amazing is that when the solar panels are shaken by external interference, the control system of the solar orientation device can detect it very sensitively and "quickly soothe" it, just like "Tai Chi Push Hands" that turns the tangible into the intangible. In less than 30 seconds, the elastic vibration energy of the solar panels can be dissipated in time, giving the space station "stable happiness."

High reliability, but also strong

The "transportation train" that the Wentian Experimental Module took this time was the Long March 5B carrier rocket tailored for the construction of the space station. It is safe, accurate and reliable, and is dedicated to providing preferential services to the "big customers" of the space station. However, during the flight phase of the rocket, the Wentian Experimental Module will inevitably bear a large ascent load, especially the solar directional device installed on the resource module at the end of the experimental module. After entering the rocket fairing, it is at the top and is subject to the brunt of the huge pressure. "There are thousands of roads, but safety is the first." In order to avoid overloading the "little heart" of the solar directional device during the rocket launch phase, the design team adopted a new type of W-shaped strap , that is, to fasten a "seat belt" with multiple protections for the solar directional device, so that it can feel more at ease during the flight. After the experimental module successfully entered orbit, the "seat belt" received the command and was released, so that the solar directional device could freely drive its small motor and start its journey to the sun.

This in-orbit test is the "first show" of the large-scale Sun-directed directional device in the process of building my country's space station. The complete success of the test will lay a solid foundation for the subsequent space station construction and in-orbit operation.

(Shanghai Institute of Technology)