Space News: Chinese rocket stage predicted to reenter atmosphere around May 8

by Andrew Jones

Rollout of the first Long March 5B to the pad at Wenchang, South China in April 2020.

HELSINKI — A large rocket stage which launched China’s first space station last week is likely to reenter the atmosphere around May 8 according to early space tracking predictions. 

U.S. Department of Defense Spokesperson Mike Howard in a statement May 4 said that “U.S. Space Command is aware of and tracking the location of the Chinese Long March 5B in space, but its exact entry point into the Earth’s atmosphere cannot be pinpointed until within hours of its reentry, which is expected around May 8.”   

“Until then, the 18th Space Control Squadron will be offering daily updates to the rocket body’s location on www.space-track-org beginning May 4. We will provide additional information as it becomes available,” the statement read.

The launch of the Long March 5B late April 28 Eastern successfully placed the 22.5-metric-ton Tianhe core module into orbit. However the roughly 30-meter-long, 5-meter-diameter Long March 5B first stage also reached orbital velocity rather than fall with a predetermined area downrange.

The empty rocket body is now in a 162 by 306-kilometer altitude orbit according to U.S. 18th Space Control Squadron space tracking, down from an initial 170 by 372-kilometer orbit.

Without the ability to restart its engines the core stage will be dragged towards Earth by increasing collisions with molecules in the Earth’s atmosphere. Atmospheric fluctuations and other variables and the high velocity of the stage mean that accurate predictions of when and where the stage will reenter are not possible until a few hours before the event.

An May 4 update from the Aerospace Corporation predicts reentry will occur May 9 at 12:37 a.m. Eastern (04:37 Universal time), with a margin of error of plus or minus 28 hours.

Russian space agency Roscosmos also stated May 4 that its Automated Warning System on Hazardous Situations in Outer Space (ASPOS OKP) indicated that the Long March 5B was set for an uncontrolled reentry. 

Calculations by Russian experts indicate a reentry window of 9:00 p.m. May 7 to 4:00 p.m. May 9 Eastern, with more refined predictions to follow in the coming days.

China has yet to comment on the status of the Long March 5B. The country is planning 10 further launches of various spacecraft and launch vehicles to construct its three-module space station across 2021-22. 

China is currently preparing to send the Tianzhou-2 cargo spacecraft to Tianhe in the next few weeks using a Long March 7 rocket. A first crewed mission, Shenzhou-12, is expected to send three astronauts to the new orbital outpost in June.

Notably two further launches of the Long March 5B are expected in 2022 to send the Wentian and Mengtian experiment modules to join Tianhe in orbit. 

It is unknown if the China Academy of Launch Vehicle Technology (CALT) which designed and manufactures the Long March 5B, is or has planned alterations to the rocket or launch profile which would allow the core stage to either deorbit or fall to Earth on a ballistic trajectory.

The Long March 5B was designed specifically for launching modules for the Chinese space station into low Earth orbit. A test flight in 2020 also saw the core stage reach orbital velocity. That incident saw the stage reenter over the Atlantic Ocean with local reports suggesting debris from that 20-ton stage appears to have survived reentry and landed in the African nation of Côte d’Ivoire.

Components of the Long March 5B (Y2) to launch the Chinese space station core module at a facility in Tianjin.
Components of the Long March 5B (Y2) to launch the Chinese space station core module at a facility in Tianjin. Credit: CMSA

Holger Krag, head of the Space Safety Programme Office for the European Space Agency, Told SpaceNews that an average mass of about 100 tons reenters the atmosphere in an uncontrolled way per year. 

“It is always difficult to assess the amount of surviving mass and number of fragments without knowing the design of the object, but a reasonable “rule-of-thumb” is about 20-40% of the original dry mass,” Krag said.

Unlike older Long March series rockets the Long March 5B core stage uses liquid hydrogen and liquid oxygen for fuel. Older-generation Long March 2, 3 and 4 series rockets use a toxic hypergolic propellant combination of hydrazine and nitrogen tetroxide, which would make debris surviving reentry potentially hazardous to anyone approaching the wreckage.

Debris from Chinese rocket launches from inland spaceports occasionally falls within inhabited areas. China is understood to take precautions against causing injury through safety notices, evacuations and calculation of rocket stage drop zones, as well as experimenting with technologies including grid fins and parafoils.

While much attention is paid to the threat to people on the ground and aircraft in flight from satellite and rocket components reentering, the Aerospace Corporation last year raised the issue of pollution from reentry.

SpaceNews



from SpaceNews https://ift.tt/2QT5Rf2

Popular posts from this blog

APOD:

Image
Sometimes lightning occurs out near space. One such lightning type is red sprite lightning, which has only been photographed and studied on Earth over the past 25 years. The origins of all types of lightning remain topics for research, and scientists are still trying to figure out why red sprite lightning occurs at all. Research has shown that following a powerful positive cloud-to-ground lightning strike, red sprites may start as 100-meter balls of ionized air that shoot down from about 80-km high at 10 percent the speed of light. They are quickly followed by a group of upward streaking ionized balls. Featured here is an extraordinarily high-resolution image of a group of red sprites. This image is a single frame lasting only 1/25th of a second from a video taken above Castelnaud Castle in Dordogne, France, about three weeks ago. The sprites quickly vanished -- no sprites were visible even on the very next video frame. via NASA https://ift.tt/sQvWMF0
Read more

APOD: M15: Dense Globular Star Cluster

Image
Messier 15 is an immense swarm of over 100,000 stars. A 13 billion year old relic of the early formative years of our galaxy it's one of about 170 globular star clusters that still roam the halo of the Milky Way. Centered in this sharp reprocessed Hubble image, M15 lies some 35,000 light-years away toward the constellation Pegasus. Its diameter is about 200 light-years, but more than half its stars are packed into the central 10 light-years or so, making one of the densest concentrations of stars known. Hubble-based measurements of the increasing velocities of M15's central stars are evidence that a massive black hole resides at the center of the dense cluster. M15 is also known to harbour a planetary nebula. Called Pease 1 (aka PN Ps 1), it can be seen in this image as a small blue blob below and just right of center. via NASA https://ift.tt/aQoCO61
Read more

Space News: MEV-2 servicer closing in on Intelsat-10-02 docking attempt

Image
by Jason Rainbow TAMPA, Fla. — Northrop Grumman’s MEV-2 satellite servicer is performing close proximity operations with Intelsat’s in-orbit 10-02 spacecraft ahead of a docking attempt, SpaceNews has learned. Both spacecraft remain healthy after being in close quarters to calibrate and test systems before MEV-2 backed off, according to a Northrop Grumman official. The company intends to release an update once it completes the docking. It is understood the satellite servicer’s predecessor MEV-1 made several close proximity operations maneuvers and approaches before successfully attaching to Intelsat-901 last year , enabling the 19-year-old satellite to resume services from April 2. MEV-2 has a similar design to MEV-1, but the two missions have distinct differences. While Intelsat-901 was no longer functioning as it languished in a graveyard orbit, Intelsat-10-02 has been active in geosynchronous orbit since 2004 and is carrying communications traffic.  The two companies a...
Read more