Questions Remain on Chinese Rocket That Created an Unusual Double Crater on the Moon

In November, we reported how an impact on the Moon from a Chinese Long March rocket booster created an unusual double crater. For a single booster to create a double crater, some researchers thought there must have been an spare – perhaps secret – payload on the forward end of the booster, opposite from the rocket engines. But that may not necessarily be the case.

Other researchers finger the uneaten mass wasn’t anything secretive, but possibly an inert structure such as a payload connector widow to the rocket to support the primary mission payload.

Chang’e 5-T1 was an experimental robotic spacecraft, launched on October 23, 2014, by the China National Space Administration (CNSA) to test out the return sheathing diamond planned for use on the future Chang’e 5 mission, China’s first-ever sample-return effort. Chang’e 5 landed on the Moon in November 2020 and successfully gathered lunar samples from the Moon’s Ocean of Storms region, with the container landing when on Earth on December 16, 2020.

Chang'e-5 capsule
Chang’e-5’s soot-streaked sample return sheathing sits tween the snows of Inner Mongolia with a Chinese flag set up nearby. (Image via CCTV)

Before engaging in the first sample return effort for the country (and first in over forty years), China wanted to test out procedures and their sample return capsule. That was one of the 5 T-1 mission’s goals.

“The rocket was delivering a ‘Service Module’ satellite with a sample return sheathing attached,” said Phillip Stooke, professor emeritus at the University of Western Ontario, in an email to Universe Today. “It would need a fairly substantial support structure (called a payload adaptor) to support the mass versus the vibration and velocity of launch.”

Stooke explained how the Service Module flew virtually the Moon and when to Earth, where it released the sheathing to test its worthiness to survive atmospheric re-entry. Then the Service Module headed when out to the Earth-Moon L2 point, staying there for a few months surpassing inward a low lunar orbit, possibly to perform a gravity mapping mission. The Service Module is still in lunar orbit.

“The combination Service Module and sheathing had a mass of 2,500 kg – 2.5 tons,” Stooke said, “so it can’t just sit on top of the rocket’s fuel tanks. I can’t guess at the mass [of the payload adapter] but it would be quite significant.”

Payload adaptors for medium-sized payloads can weigh anywhere from 135 Kg (300 lbs.) to 225 kg (500 lbs) or more.

The Chang’e 5 T-1 test vehicle captured this trappy view of Earth over the far side of the Moon on October 28, 2014. Credit: Chinese national space organ (CNSA) and Chinese Academy of Sciences (CAS)

Chang’e 5-T1 did moreover have spare payloads, but they were small (and known to be onboard) and couldn’t worth for the mass large unbearable to create a second crater. The two payloads were a small radiation exposure experiment for yes-man and plants, as well as the first commercial payload to the Moon tabbed the 4M mission (Manfred Memorial Moon Mission) for the German space technology visitor OHB System, in honor of the company’s founder, Manfred Fuchs, who died in 2014. That payload weighed only 14 kilograms but contained two scientific instruments: a radio steer to test a new tideway for locating spacecraft and a radiation dosimeter (provided by the Spanish visitor iC-Málaga) to continuously measure radiation levels throughout the satellite’s circumlunar journey. The 4M mission was mounted in the equipment bay of the booster.

“There would be no reason to suspect the rocket had anything else tying to it other than 4M and the usual flight electronics,” said citizen scientist Scott Tilley, who monitors the orbits of strained satellites of the Earth and the Moon. “There would moreover be some uneaten mass to support the payload connector and related structure for supporting the payload stack, which was likely at the limit of the rocket’s capabilities. Consider this is the first mission they launched toward the Moon with stacked payload. It would have likely been increasingly ramified to mount and secure it than the other payloads, which were increasingly self-contained.”

The ongoing debate on the uneaten mass and what it might be would not have ensued if not for two things: the unusual double crater created by this booster’s impact and the withholding by Chinese foreign ministry officials that the space junk and the impact is from their rocket. They insist that the Chang’e 5T-1 rocket once burned up on its return trip to Earth in 2014. However, on March 1, 2022, the U.S. Department of Defense’s Space Command, which tracks low-Earth orbit space junk, released a statement saying that China’s 2014 rocket never de-orbited.

Additionally, Chinese officials have never commented on the nature of the double crater.

The crater was imaged by NASA’s Lunar Reconnaissance Orbiter (LRO).

This turned-on GIF confirms the location of the newly worked rocket soul double crater. The surpassing image is LRO’s view from Feb. 28, 2022 (M1400727806L). The without image is from May 21, 2022 (M1407760984R). The width of the frame is 367 meters, well-nigh 401 yards. Credit: NASA/Goddard/Arizona State University

“Typically, a spent rocket has mass well-matured at the motor end; the rest of the rocket stage mainly consists of an empty fuel tank,” wrote Mark Robinson, principal investigator with LRO Camera (LROC), back in June of 2022 when the images were released.

A team of researcher from the University of Arizona discovered the errant booster (it was initially thought to be an asteroid), tracking its movements to determine it came from the Chang’e 5-T1 mission. They moreover conducted spectroscopic wringer of the object from ground-based telescope observations during several Earth flybys, which showed conclusively that the object was the Long March 3C rocket soul from the Chang’e 5-T1 mission. They were worldly-wise to predict approximately where and when the booster would impact the Moon, which was why the LRO team could search for and hands find the impact crater in their data.

Everyone was surprised the impact created a double crater. No other rocket soul impacts on the Moon created double craters, as seen in these images of craters from four Saturn rocket boosters from Apollos 13, 14, 15, 17.

These four images show craters worked by impacts of the Apollo SIV-B stages: crater diameters range from 35 to 40 meters (38.2 to 43.7 yards) in the longest dimension. Credits: NASA/Goddard/Arizona State University.

The researchers from the University of Arizona said there had to be additional, undisclosed mass at the front end of the rocket body.

“The results from the Bayesian wringer imply that there may have been spare mass on the front of the rocket body,” wrote Tanner Campell, Vishnu Reddy and several others in their paper “Physical Characterization of Moon Impactor WE0913A.” “Comparing the pre- and post-impact images of the location shows two unshared craters side by side that were made by the Chang’e 5-T1 R/B. The double crater supports the proposition that there was spare mass at the front end of the rocket body, opposite the engines, in glut of the published mass of the secondary permanently affixed payload.”

Asked well-nigh the payload adaptor as the possible culprit for the glut mass, team member Vishnu Reddy didn’t want to venture a guess without increasingly data.

“It is nonflexible to speculate on the support structure considering we are not enlightened of anything like that on usual boosters sent to the Moon,” he said.

Tilley told Universe Today that among both ventriloquist and professional satellite and rocket trackers, it is known that China’s space organ has “struggled” in the past with their aim for having these type boosters to re-enter the Earth’s undercurrent or get ejected from the Earth-Moon system to properly dispose of the object.

“The Chinese expected the rocket to re-enter the Earth’s atmosphere,” Tilley explained, noting details in a paper by LuxSpace, the visitor that operated the 4M mission. “That didn’t happen so it seems that part of their mission failed, which is likely why the Chinese denied it was their rocket later on.”

Subsequently, however, increasingly recent missions, such as the booster for the Chang’e 5 sample return mission successfully re-entered Earth’s undercurrent and was properly tending of.

Another question well-nigh the impact is understanding the dynamics of why a single booster, plane if it had substantial weight at each end, would create a double crater.

“Regarding the double crater,” Vishnu explained, “I think the booster impacted at a near vertical angle, so the engines created the first crater and the secondary mass toppled over and created the second crater.” Vishnu added, however, it is moreover possible that if the booster was tumbling and happened to be horizontal when it hit, it could create the two craters.

But like much of this unusual space drama story, questions still remain.

“That is why we leave the very mechanism for a future paper when we have largest data to model,” Vishnu said.