Tianzhou-3 | Long March 7

Lift Off Time
September 20, 2021 – 07:10 UTC | 15:10 BJT
Mission Name
Tianzhou 3
Launch Provider
(What rocket company launched it?)
China Aerospace Science Corporation (CASC)
Customer
(Who payed for this?)
China National Space Administration (CNSA)
Rocket
Long March 7
Launch Location
LC-201, Wenchang Satellite Launch Center, Hainan Island, China
Payload mass
~5,600 kg (12,346 lb) of cargo
Where did the spacecraft go?
Low Earth orbit (LEO) – 370 km (230 mi), at a 41° inclination
Did they attempt to recover the first stage?
No, this is not a capability of the Long March 7
Where did the first stage land?
It crashed into the Pacific ocean
Did they attempt to recover the fairings?
No, this is not a capability of the Long March 7
Were these fairings new?
Yes
This was the:
2nd resupply mission for the Tiangong 3 Space Station
– 3rd launch of a Tianzhou spacecraft
– 6th mission of a Long March 7 rocket

– 91st orbital launch attempt in 2021 (84th successful)
Where to re-watch
Official replay

How did it go?

The China Aerospace Science Corporation (CASC) successfully launched its second cargo resupply mission, the Tianzhou 3, to the new Tiangong 3 Space Station, currently under construction in low Earth orbit (LEO). The rocket launched from LC-201, Wenchang Satellite Launch Center, in China on September 20, 2021. This mission marked the fourth of 11 launches needed for the construction phase of the China’s Space Station (CSS). 

The Long March 7, Tianzhou 3 mission
Lift off of the Tianzhou 3 mission (Credit: Hu Xujie/ Global Times)

Tianzhou-3 Mission

The Tianzhou 3 mission is the second cargo resupply mission to the Tianhe Core Crew module (CCM) of China’s new and developing Tiangong 3 Space Station. The first cargo resupply mission was successfully launched on May 29, 2021.

The mission delivered supplies for the upcoming Shenzhou-13 crewed mission, which is currently planned to launch in October. Among them were the replacement parts of the urine treatment system. This mission also provided the Tianhe CCM with enough propellant to maintain its orbital altitude. One of the most expensive items onboard the Tianzhou-3 was a spacesuit (90 kg) designed for spacewalk missions.

The spacecraft docked with the Tiangong 3 Space Station on September 21, 2021, at 14:08 UTC (22:08 BJT). The Tianzhou-3 cargo spacecraft executed a fast and automatic rendezvous and docking with the Tianhe core module, which took only seven hours after lift-off.

The Tianzhou Spacecraft

The Tianzhou (which means “heavenly boat”) is an automated cargo spacecraft that will function as the main resupply vehicle for the Tiangong 3 Space Station. The spacecraft was developed from China’s first prototype space station, the Tiangong 1. The first Tianzhou spacecraft, Tianzhou 1, launched on a Long March 7 rocket from Wenchang in April 2017.

Tianzhou 1 spacecraft, artist concept
An artist’s impression of the Tianzhou-1 spacecraft. (Credit: China Aerospace Science and Technology Corporation)

This spacecraft is 10.6 meters long and has a diameter of 3.35 meters. It consists of two main parts: a cargo cabin and a propulsion section.

The Tiangong 3 Space Station

The Tiangong 3 Space Station (meaning “heavenly palace”) is a space station currently under construction in LEO. When complete, the station will be roughly one-fifth the mass of the International Space Station. The Tiangong 3 Space Station will operate in orbit for at least ten years.

Construction began on April 29, 2021, when the core module, the Tianhe (“harmony of the heavens”), which is able to accommodate three crew members with a built-in life support system, was launched on a Long March 5B rocket. The Tianhe is 16.6 m long and has a diameter of 4.2 m. This module can also provide propulsion to maintain the orbital altitude of the station. Later, it will be joined by the two other modules, Mengtian and Wentian that will host Chinese and international science experiments.

The Tiangong 3 space station, the Tianhe core module
The Tianhe core module of the Tiangong 3 space station. (Credit: Global Times via Twitter)

China’s aim is to construct the three-module space station with 11 launches across 2021-2022, which will include three module launches, four cargo spacecraft, and four crewed missions. The station will be comprised of three modules, though it has the ability to expand to six, and it is expected to be operational for at least ten years.

The first crewed flight to the station took place on June 17, 2021. The three astronauts from that mission have already left the Tiangong 3 on September 16, 2021. They undocked from the station at 00:56 UTC. After that, they landed at the new Dongfeng landing site in northern China’s Inner Mongolia autonomous region, on September 17, 2021.

What is the Long March 7?

The Long March 7 is a three-stage medium-lift launch vehicle, capable of placing a 13,500 kg (~29,800 lb) payload into low earth orbit (LEO), or a 7,000 kg (~15,000 lb) payload into geostationary transfer orbit (GTO).

The basic version of the Long March 7 can be customized by varying the number of boosters, allowing it to be capable of reaching higher orbits or executing multiple orbital deployments.

Shao Yetao, chief designer of the Long March 7 carrier rocket, said that the rocket had some upgrades for the Tianzhou-3 mission. For example, its water- and moisture-proof function was improved to ensure a smooth launch in unfavourable weather conditions.

Long March 7, launch pad, Tianzhou 2
The Long March 7 (Credit: Xinhua News)

Boosters

The center core of the Long March 7 can be supported by either 0, 2, or 4 boosters, which use refined kerosene (RP-1) and liquid oxygen (LOx) propellant. The boosters are powered by an oxidizer-rich staged combustion YF-100 engine. At sea level, each booster provides 1,200 kN (270,000 lbf) of thrust. This increases to 1,340 kN (300,000 lbf) of thrust in a vacuum.

First Stage

The center core of the rocket is 3.35 meters in diameter and has two YF-100 engines. Like the boosters, this first stage uses refined kerosene (RP-1) and liquid oxygen (LOx). At sea level, this stage produces 2,400 kN (540,000 lbf) of thrust, increasing to 2,680 kN (600,000 lbf) in a vacuum.

Second Stage

Like the first stage, the second stage is also 3.35 meters in diameter and uses RP-1 and LOx. This stage is powered by four oxidizer-rich staged combustion YF-115 engines, two of which are fixed and two of which are able to gimble. The second stage offers 706 kN (159,000 lbf) of thrust in a vacuum.

Third Stage

The Long March 7 did not have a third stage in the basic configuration used for this mission, but the Long March 7A variant has an additional third stage powered by liquid hydrogen (LH2) and LOx. The stage uses 2 YF-75 engines, which produce 167 kN (37,580 lbf) of thrust and have an ISP of 438 s.

Article adapted from Claire Percival

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