China is supersizing its rocket industry – and it’s coming for Starlink
South China Morning Post
25/05/2023
- Pulse assembly line will nearly double rocket launch capacity to deploy a 'giant satellite constellation' above Starlink sats
- Mega rocket factory is part of a larger space centre on track for its first launch next year
China's rocket industry is about to receive some massive thrust.
The country is constructing an unprecedented rocket assembly plant capable of producing 50 Long March 8 rockets a year, according to scientists involved in the project.
Once completed next year, the mega factory on the tropical island Hainan will nearly double China's annual launch capacity - already one of the world's largest.
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No other existing facility can manufacture rockets at that rate, according to openly available information. Last year, Elon Musk's SpaceX recorded 61 launches, most of them with reusable Falcon rockets.
The Long March 8 is a low-cost, non-reusable rocket that can house more than 20 Starlink-sized communication satellites. China intends to use the medium-sized launch vehicle, which has seen two successful test launches, to send more than 1,000 satellites into space every year, comparable to the current pace of SpaceX.
But the new rocket is also designed to put satellites in a higher orbit than the Starlink satellites. The more advantageous altitude would allow Chinese satellites to monitor or even suppress their American rivals.
The race to "build a giant satellite constellation is driving China's space industry into a new age", said Song Zhengyu, a senior rocket scientist with the China Academy of Launch Vehicle Technology (CALT), who is leading the Long March 8 team, in a paper published in the Chinese Journal of Astronautics last month.
Production with a pulse
In a bid to catch up with SpaceX's Starlink programme, China plans to launch nearly 13,000 satellites, in addition to the more than 4,000 satellites it currently has in orbit.
The project - code-named "GW" - is specifically aimed at suppressing Starlink's global services in the event of war, according to some PLA scientists.
But China's current line-up of rockets is not up to the task, according to Song and his colleagues. Existing Long March rockets are either too small or too big, they said.
The Long March 8 is designed to fill the gap, with unprecedented efficiency.
It "can meet more than 90 per cent of China's follow-up launch mission requirements for medium- and low-Earth orbits", Song said.
At the same time, China's existing rocket production methods cannot achieve the pace required by project GW, according to the rocket scientists.
Traditional rocket production involves workers assembling different components and then attaching them to the rocket at a fixed location. The rocket itself does not move down the line, but rather stays in one place while workers move around it to complete their tasks.
Some modern rocket manufacturers have started to adopt pulse assembly line techniques - similar to those used in fighter jet production - to speed up assembly and reduce costs.
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SpaceX has developed an automated system called the "Falcon 9 Integrated Assembly Line" that uses synchronised pulses to move rocket components through the assembly process quickly and efficiently. The method allows SpaceX to produce more rockets at a lower cost than traditional methods.
The Long March 8 factory in Wenchang, Hainan will be similar to that of SpaceX but it will also have some unique advantages, according to Song's team.
For a pulse assembly line to be effective, it must have a steady supply of high-quality components that can be quickly assembled into the final product.
In China, such a task can be relatively easy to achieve at a competitive cost, as the country has the world's largest manufacturing capability for many industrial products, including those that require high degrees of precision and consistency.
Bringing down the Long March price tag
It costs about US$3,000 to put 1kg (2.2 pounds) of cargo into low-Earth orbit (LEO) using the existing Long March rockets, similar to that of SpaceX's reusable Falcon 9 rockets, according to a recent report by researchers at the China Aerospace Science and Technology Corporation, the nation's largest rocket manufacturer.
Song's team said they had found methods to further reduce the costs of the Long March 8, some of which have never been attempted before.
Modal testing is a painstaking process that measures a structure's natural frequencies and mode shapes, which can help engineers understand how the structure will behave under different loads and conditions. Historically, rockets that have not undergone modal testing have experienced major failures.
The Long March 8 was the first rocket in the world to successfully fly without the need for full-scale modal testing. Instead, scientists used simulations to obtain dynamic parameters that allowed for successful launches, even after cancelling boosters and replacing fairings.
By using the latest digital design and simulation tools, "the development cycle was shortened by 12 months, and a large amount of test funds were saved", the team said in the paper.
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A Long March 8 rocket carrying 22 satellites blasts off from a Wenchang launch site in 2022. Photo Xinhua
The Chinese scientists also developed a new method to guide and control the rocket during flight, which involves alternating powered flight and gliding to optimise the rocket's trajectory.
Specifically, during the first part of the second stage of flight, the rocket glides along a suborbital path to a specific target. Then, during the second part of the second stage, it switches to powered flight to reach its final target orbit.
The method allows for more precise control over the rocket's trajectory and can help it adapt to deviations from its intended path. It is difficult to achieve because it requires precise timing and coordination between different stages of the rocket's flight.
Gliding in space is difficult since there is no air resistance to help control the rocket's movement. The new method is a key advancement in rocket technology that could improve the accuracy and efficiency of space missions, according to Song's team.
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To reduce costs even more, the Long March 8 no longer requires a triple redundant inertial measurement unit (IMU) configuration. Instead, it uses a simplified dual IMU configuration. This requires new technology to improve flight reliability and intelligence, and uses alternative methods to address potential failures.
Gaining altitude
Long's team said that the Long March 8 rocket is optimised to send satellites to the sun-synchronous orbit (SSO) at an altitude of 700km (435 miles), higher than most Starlink satellites, which operate at about 550km.
At present, the SSO is used mainly by Earth observation satellites. It is called "sun-synchronous" because the satellite passes over any given point on Earth at the same local time each day, which makes it easier to take consistent measurements of things like temperature, vegetation growth and ocean currents.
SSO has advantages and disadvantages compared to the LEO used by most Starlink satellites. One advantage is that it allows for more consistent and accurate data collection, since the satellite passes over the same area at the same time of day.
Because they are higher up, SSO satellites are also easier to communicate with since they have a clearer line of sight to ground stations.
Still, SSO does have drawbacks. More energy is required to achieve this type of orbit, and because satellites in SSO are further from Earth than those in LEO, they can be less responsive and slower to transmit data.
Some of the communication satellites intended for project GW will be equipped with sensors and other equipment for observation or other purposes, according to Chinese military scientists.
If China were able to use its SSO satellites to track Starlink satellites and gather data about their movements and activities, it could use the information to interfere with or disrupt Starlink's operations, according to the scientists.
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That, however, would be a tall order. Such a complex and challenging task would require significant resources and expertise, and any attempt by China to interfere with or disrupt Starlink could have serious consequences for international relations and space policy, according to critics.
Countdown has begun
China's new rocket factory is part of a larger commercial space centre under construction in Wenchang that is expected to see its first launch by June next year.
According to a statement by CALT released on social media this month, workers and engineers are working overtime to meet the deadline.
The main structure of the first launch pad was completed 20 days ahead of schedule, at the rate of "one floor every 10 days", the statement said.
According to the Wenchang city government, the approaching rainy season and typhoon season in Hainan could slow construction progress.
The local authorities said they were taking the initiative to provide "door-to-door" services to support the project - handling various tasks, including paperwork and approvals - to help speed up administrative work for the project command centre.
"Everything revolves around the project, everything is done around the project," the Wenchang government said on its website.
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