Tianzhou 1 completed first on-orbit refuelling with Tiangong 2

Tianzhou 1 approaching Tiangong 2 in its first rendezvous docking

Chinese space authority announced on Thursday (27 April) that Tianzhou 1 cargo ship had successfully completed its first on-orbit propellant refuelling demonstration with the Tiangong 2 space laboratory module, marking a major milestone in the country’s 30-year quest to establish a permanent human presence in Earth Orbit.

The Tianzhou 1 cargo resupply ship was launched from the Wenchang Space Launch Centre at 19:41 CST (11:41 UTC) on Thursday 20 April. After entering an initial 200 x 380 km parking orbit, the cargo spacecraft, carrying nearly 6 tonnes of equipment and supplies including 2 tonnes of liquid propellants, performed a number of orbit elevation and refinement burns to meet the space laboratory module on a 400 km orbit. Tianzhou 1 then performed an automated rendezvous docking with the unoccupied Tiangong 2 module, and the two vehicle were fully docked at 12:23 CST (04:23 UTC) on Saturday 22 April.

Tianzhou 1 mission 5

Tianzhou 1 mission 1

Once having berthed at the space laboratory module, Tianzhou 1 switched off its docking system and propulsions. The spacecraft complex, under the control of Tiangong 2, then performed a 180° turn in azimuth direction, so that Tiangong 2 could resume its ‘normal’ flying position, with the docked Tianzhou 1 vehicle at front and the space laboratory’s engine thrusters towards back.

Tianzhou 1 carried over 100 bags of equipment and supplies, including a dummy EVA suit. However, the hatches on the docking port of both vehicles were not opened and no transfer of solid cargo was demonstrated, given that these tasks would need to be performed by a human crew. Instead, the cargo spacecraft was readied for the first demonstration of in-orbit propellant transfer.

Tianzhou 1 mission 3

The entire refuelling procedure took about five days to complete. Mission control first performed standard checkouts to ensure the integrity of the refuelling mechanism and detect any leakage. In order to create a difference in pressure between the supply and receiver tanks, the propellant tanks on Tianzhou 1 were maintained at a level of sufficient pressure, while receiver tanks on Tiangong 2 were maintained at a lower pressure to allow the transfer of liquid propellants. The propellants were transferred via the four fuelling nozzles (2 for fuel and 2 for oxidiser) on the docking port.

The transfer of propellants in low gravity condition is a highly complex and risky process, posing a number of technical challenges, including ensuring minimum of fluid loss in the propellant transfer line, difficulty in fluid management and vapour distributions in a tank in low gravity, the venting of large amount of vapour during the transfer of cryogenic liquid. To help understand the characteristics of liquid propellants in low gravity, a ‘glass box’ device containing liquid propellants was launched aboard the first Long March 7 test flight in June 2016, so that aerospace engineers could observe their behaviours in orbit remotely via a video link.

The first on-orbit refuelling demonstration was completed without a hitch at 19:07 CST (11:07 UTC) on Thursday 27 April. The mission has been hailed by Chinese media as a great accomplishment and major milestone, which marks the successful conclusion of the second phase of China’s human spaceflight programme (Project 921) and paves the way for the construction of a permanent space station on Low Earth Orbit (LEO) in the third and final phase of the programme by 2022.

Tianzhou 1 rollout 3

According to its mission schedule, Tianzhou 1 will remain docked with Tiangong 2 over the next two months, with a second refuelling demonstration scheduled for late June, after which the cargo spacecraft will undock with the space laboratory module. Tianzhou 1 will then fully autonomously for at least three months, during which it will perform a number of sophisticated orbital manoeuvres and also carrying out scientific experiments with its onboard applications packages.

Then towards the end of its six-month mission, Tianzhou 1 will demonstrate a fast docking procedure with Tiangong 2, which will allow future crew and cargo spacecraft to dock with the orbital space station in 6 hours after launch. After this it will perform the third and final on-orbit refuelling demonstration. The cargo spacecraft will then undock with the space laboratory for the final time, before performing a controlled de-orbit to be burned up in the atmosphere.

1 Comment on Tianzhou 1 completed first on-orbit refuelling with Tiangong 2

  1. Whilst the 2 failures of the Chinese heavy launcher, would have been heartbreaking, China has been enormously successful lately, resupply of the second temporarily manned space station, with a resupply vessel, that weighs more than, the temporary space station itself. Launched atop a new medium lift launcher, from a new launch pad, the long term space station core module, already awaiting launch. Work underway on the larger manned capsules, to be launched from Long March 7s, from the new launch pad, the super heavy launcher rocket engine tests and intellectual property talks, for the Russian RD 180 rocket engines, going well.

    With Russia Europe and the US, having agreed, to a joint Moon orbit station and base program, soon we will see robust Chinese missions, like the long term space station, visited by the new capsule, 6 crew, but to fit them all, the station would have to be empty. The crew would then have to halve, 3 going into the large capsule, a shenzou capsule docking, station crew at 6, three more crew going to the large capsule, station crew at 3, for long term operations. No wonder the resupply vessel, requires a medium lift launcher, with 9 crew shuffling through, the long term space station and prolonged 6 month long missions, for 3 crew.

    The first Chinese Moon missions will be standalone, but with the super heavy launcher, a lunar orbit station, as big as the long term space station, could be put in place, I suspect, that this will happen, before 2030, because of the large capital flows from Clean Disruption. I believe that a once a century, peak decade, of industrial revolution, another roaring twenties, is coming and that capital uplift, will accelerate, all space programs. As government and private financial reserves build, due to decade temporarily low unemployment, low energy prices, low transportation prices (electric vehicles,) low food prices (high rise agriculture.) This lift in disposable income, to the middle class, during the construction and manufacturing phase, of the change to cheap solar power, electric vehicles and vertical farming, will bring about lower government expenditure and higher government tax revenues. Before the inevitable market saturation of the 2030’s, possible Grand Depression, companies, will also have lower input costs and higher demand during the construction and manufacturing phase prior to the Grand Depression.

    Higher company tax revenues and lower company subsidies, during the construction and manufacturing phase, prior to the market saturation, will create a virtuous circle, for governments, before a negative circle, first during Clean Disruption, then during the Grand Depression. The way to offset the Grand Depression, would be to have an age of exploration, in space and magnetic levitation train tunnel, network construction (as is happening in Japan,) for example, on the Belt Road network. Thus somewhat offsetting the market saturation, as consumers have all the electric vehicles they want, construction of solar power plants, vertical farming, is completed and the effects of automation (artificial intelligence, robotics,) causes higher unemployment.

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