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HELSINKI — China’s foreign ministry acknowledged the imminent uncontrolled reentry of the Long March 5B Friday as the orbit of the first stage continued to lose altitude.
At a Foreign Ministry regular press conference May 7 spokesperson Wang Wenbin responded to a question from Bloomberg stating that it is “common practice across the world for upper stages of rockets to burn up while reentering the atmosphere.”
The second Long March 5B rocket successfully launched the Tianhe core module for China’s space station late April 28 Eastern. It soon became apparent, as reported by SpaceNews, that the first stage had also reached orbit and was slowly returning to Earth.
Latest orbital data from has the U.S. Space Force’s 18th Space Control Squadron reveals the roughly 30-meter-long, 21-metric-ton Long March 5B in a 154 by 241-kilometer altitude orbit.
The current US 18 SPCS prediction points to a reentry during a window between 10:13 a.m. Eastern Saturday, May 8 and 4:13 a.m. Sunday, May 9. EU Space Surveillance and Tracking (EU SST) estimates reentry between 2:00 p.m. May 8 and Sun 6:00 a.m. May 9.
The latest prediction from the Aerospace Corporation shows blue and yellow ground tracks over which the rocket body will pass during the predicted window.
Our latest prediction for CZ-5B rocket body reentry is:
🚀 09 May 2021 03:53 UTC ± 11 hours
Reentry will be along one of the ground tracks shown here. It is still too early to determine a meaningful debris footprint. Follow this page for updates: https://t.co/p2AU9zE3y2 pic.twitter.com/1depRKMk6f— The Aerospace Corporation (@AerospaceCorp) May 7, 2021
The large windows are due to uncertainties stemming from modeling challenges, including the non-spherical shape of the Earth, fluctuations in atmospheric density.
“China is following closely the upper stage’s reentry into the atmosphere. To my knowledge, the upper stage of this rocket has been deactivated, which means that most of its parts will burn up upon reentry, making the likelihood of damage to aviation or ground facilities and activities extremely low. The competent authority will release relevant information in a timely manner,” Wang said.
The “upper stage” referred to by Wang is also the first—typically the largest—stage of the Long March 5B. While most upper stages enter orbit and eventually reenter due to atmospheric drag, first stages of most expendable rockets do not reach orbital velocity and reenter the atmosphere and land in a pre-defined reentry zone.
Between 60 and 80 percent of the rocket stage is generally predicted to burn up during its high velocity reentry in the atmosphere, meaning some components consisting of heat resistant material are expected to reach the surface.
At a press conference a day earlier Wang responded to a question on the situation only by reiterating that “China is always committed to the peaceful use of outer space.”
Wang acknowledged there was risk associated with the reentry but that this was “extremely low,” an assessment shared by space debris modelling experts.
The Long March 5B core stage’s orbital inclination of 41.5 degrees means the rocket body passes a little farther north than New York, Madrid and Beijing and as far south as southern Chile and Wellington, New Zealand, and could make its reentry at any point within this area.
#EUSST keeps on monitoring the re-entry of object CZ-5B R/B. Latest autonomous predictions show that the re-entry window is 2021-05-09 01:27:13 UTC ±752 min. Estimations about location of re-entry will vary significantly until last hours. Read more: https://t.co/yTfN8XrT4d pic.twitter.com/mix1FO8oux
— EUSST (@EU_SST) May 6, 2021
Christopher Newman, professor of space law and policy at Northumbria University, told SpaceNews that there are no international laws which dictate how reentry of space objects, or parts thereof, is supposed to be accomplished.
“There are broad principles of safety that have been captured in the Long Term Sustainability (LTSG) of Outer Space Guidelines, but these are not legally binding. It is national regulators to authorise and supervise national space activities. According to Prof Hugh Lewis, there are numerous spent rocket bodies in orbit that will make an uncontrolled re-entry.”
Holger Krag, head of the Space Safety Programme Office for the European Space Agency, told SpaceNews last week that an average mass of about 100 tons is reentering in an uncontrolled way through 50-60 individual events per year.
In the case of damage, Newman says Article VII of the Outer Space Treaty makes States liable for the damage caused by a space object. “The Liability Convention of 1972 provides a little more clarity on this, with Article II of the 1972 convention making a State absolutely liable should a space object or part of a space object be shown to cause damage on Earth or to an aircraft in flight.”
The Liability Convention “operates on an international level between nation states, so individuals will not have recourse to this. They will have to seek a domestic remedy and look to the government to recover any costs from the other state. This works on a diplomatic level.”
Significantly, in practical terms, engaging the Liability Convention is as much a foreign policy decision as a legal one, says Newman. “The ‘victim’ state may be heavily dependent on the ‘liable’ state for infrastructure or investment and might not wish to rock the boat. So it is by no means certain that the 1972 Convention will be invoked.”
Brian Weeden of the Secure World Foundation, told SpaceNews via email that while there is an emerging international norm towards controlled de-orbiting of rocket stages, it’s definitely not universal.
“It’s not hard law that’s binding on countries, only a voluntary guideline, and that’s because countries like the United States did not want to create a binding law as they sometimes need to deviate from it themselves,” says Weeden.
Weeden also notes that what we are seeing now are the results of decisions, such as having a non-restartable Long March 5B first tage, taken a long time ago.
“I don’t know when that design decision was made, but it might have been quite a while ago. That’s a problem we have with orbital debris mitigation in general; lots of design decisions made decades ago that are still in play today because technological advancement is just not that fast. Once built, big rockets and satellites tend to get used for decades.”
China is planning two further Long March 5B launches in 2022 to send two experiment modules to join Tianhe in orbit. How China will respond to this situation, which has detracted from the successful Tianhe launch, remains to be seen.
Ultimately, Weeden says, mission requirements, in absence of hard law, may win out. “Who’s going to tell the Pentagon or CNSA they can’t put up a critical new military satellite or a politically important space station because the rocket might have a small chance of landing on someone?”