HELSINKI — China is planning to greatly increase the number of launches of its Long March 5B rocket which has created a number of high-profile uncontrolled reentries of its large first stage.
Liu Bing, director of the general design department at the China Academy of Launch Vehicle Technology (CALT), told Chinese media that the the Long March 5B, designed for launches to low Earth orbit, would be used together with the Yuanzheng upper stage series to launch multiple satellites for constellations.
Though not clearly stated, the launcher and YZ-2 combination could be used to help deliver high numbers of satellites into orbit for the planned national “guowang” satellite internet megaconstellation.
SatNet, the company overseeing Guowang, is understood to be looking to contract companies from China’s nascent private sector to launch the small communication satellites, but the large Long March 5B could provide a route to launches more comparable to how SpaceX uses the Falcon 9 to launch its Starlink satellites.
“In the next few years, the Long March 5 series of rockets will be transferred to the high-density launch stage to meet the country’s needs for large-scale and rapid access to space,” Liu said.
The Long March 5B rocket has so far been used to launch modules for China’s now-completed Tiangong space station, as well as a test of a new generation crew spacecraft.
Notably however the four Long March 5B launches so far have seen the 30-meter-long, roughly 23-ton first stage of the rocket enter orbit and make uncontrolled reentries around a week later, sparking rebuke from NASA administrators and strong rebuttals from China’s foreign ministry.
However, future Long March 5B launches utilizing the YZ-2 upper stage might be able to avoid the issue of uncontrolled first stage reentries. The upper stage could provide the kick to carry the payloads into orbit without the need for the first stage itself to reach orbital velocity.
“It is plausible that it [the YZ-2 upper stage] will let the Long March 5B be mildly suborbital, as with Proton-M/Briz-M where the Proton stage, orbital on the earlier Blok DM version, is suborbital for Briz-M launches,” astronomer and spacecraft tracker Jonathan McDowell told SpaceNews.
McDowell notes however that it is unclear whether or not this will be the case, with much depending on how large the initial YZ-2 burn will be. Chinese space officials have not commented on the issue.
Other considerations, such as calculating safe drop zones for the rocket stage downrange from the Wenchang spaceport on Hainan island, or the possibility of making the rocket’s YF-77 hydrolox engines capable of restarting and thus controlling when and where the first stage reenters, could decide how these launches are planned. The value of the payload compared with multi-billion-dollar space station modules, could also be part of determining whether or not the future Long March 5B first stages go orbital and make uncontrolled reentries.
The danger of injury or property damage from an uncontrolled reentry of a Long March 5B first stage is very small, but much greater than a standard but still troublesome reentry of a rocket’s smaller second or upper stage.
Ted Muelhaupt of the Aerospace Corporation said in July that the odds of debris from the reentry following the launch of the Wentian module ranged from one in 230 to one in 1,000. This was more than an order of magnitude greater than internationally accepted casualty risk threshold for the uncontrolled reentry of rockets of one in 10,000, stated in a 2019 report issued by the U.S. Government Orbital Debris Mitigation Standard Practices.
China meanwhile has been dismissive of the risks, noting that it is “customary international practice for rockets’ upper stages to burn up in the Earth’s atmosphere,” Chinese foreign ministry spokesperson Zhao Lijian said during a July 27 press conference.
Exceptionally, the first and largest stage of the Long March 5B has also acted as the upper stage, inserting the payload into orbit.
Long March 5B reentries is a large and prominent symptom of a wider problem. A recent Nature Astronomy paper published earlier assesses that current international space practices mean there is a 10 percent chance of uncontrolled reentries causing one or more casualties over a decade.
The Long March 5B is next slated to launch Xuntian, a Hubble-class space telescope with a large field of view. It will co-orbit with the Tiangong space station and be able to dock with it for repairs, maintenance and possibly upgrades. That mission is expected no earlier than late 2023.