China successfully launched its Tianzhou-1 space station cargo resupply spacecraft today. If all goes according to plan, it will rendezvous and dock with the Tiangong-2 space station three times and demonstrate in-orbit refueling. With such a capability, China could maintain a space station in Earth orbit for many years like the International Space Station (ISS). [UPDATE, April 22: Tianzhou-1 successfully docked to Tiangong-2 at 12:23 am EDT (04:23 GMT] today as planned per Xinhua.]

The Soviet Union was the first country to demonstrate cargo resupply and in-orbit refueling in 1978 with the Progress spacecraft and Salyut 6 space station. Progress spacecraft are still used today to refuel the ISS station-keeping engines and take other cargo to the facility. Three other cargo spacecraft resupply ISS (Japan’s HTV and the U.S. Dragon and Cygnus), but they do not refuel it.

China’s human spaceflight program is proceeding at a measured pace. After four uncrewed test flights from 1999-2002, China launched its first astronaut (sometimes called a taikonaut in the West) in 2003 on Shenzhou-5. The next crewed flight, with two astronauts, flew in 2005 (Shenzhou-6) and three astronauts were launched on Shenzhou-7 in 2008. In 2011, China launched its first small space station, Tiangong-1, to which three spacecraft were sent: an uncrewed Shenzhou-8 as a test flight, then Shenzhou-9 and Shenzhou-10 in 2012 and 2013 respectively, each with three astronauts (two men and one woman). Tiangong-2 was launched in 2016 and one two-person crew (Shenzhou-11) spent 30 days onboard last fall, the longest Chinese spaceflight to date (a total of 33 days including the trip to and from Tiangong-2).

By comparison, Russian cosmonaut Valeriy Polyakov holds the record for the longest continuous spaceflight — 438 days (14 months) in 1994-1995. Scott Kelly holds the record for the longest continuous spaceflight by a U.S. astronaut — 340 days in 2015-2016. (On Monday, NASA astronaut Peggy Whitson will break the U.S. record for cumulative time in space — 534 days — but that was acquired over three spaceflights, not a continuous mission. She is currently in command of the ISS. President Trump will phone her on Monday to congratulate her on her record-breaking mission.)

Chinese officials describe the launch of Tianzhou-1 as the last step of the second phase of its human spaceflight program. The first phase was the initial launches of astronauts. The second phase includes demonstration of extravehicular activity (EVA, also know as a spacewalk), which was accomplished on Shenzhou-7, and the initial space station flights. If Tianzhou-1 is successful in its refueling task, that will complete phase 2 and phase 3 — launch and operation of a multi-modular space station for 10 years — will be next. China plans to launch the new space station’s core module in 2018 and complete construction of the three-module, 60 metric ton (MT) facility by 2022. By comparison, ISS has a mass of about 400 MT. It has been continuously occupied by international crews rotating typically on 4-6 month shifts since November 2000.

No one is aboard Tiangong-2 or Tianzhou-1; the refueling tests are all automated.



Launch of Tianzhou-1 space station cargo resupply spacecraft on Long March 7 from Wenchang Satellite Launch Center, China, April 20, 2017. Photo credit: CGTN.com

Tianzhou-1 is the heaviest spacecraft ever launched by China — 13 MT. It can carry 6.5 MT of cargo, slightly more than Japan’s HTV (Kounotori) cargo ship that resupplies ISS. HTV can transport 6 MT of cargo and is the largest of the ISS resupply ships.

The new Long March 7 rocket boosted Tianzhou-1 into orbit from the Wenchang Satellite Launch Center on Hainan Island, which became operational last year. Long March 7 is one of several new rockets China is introducing to replace its older models (Long March 2, 3 and 4). The new rockets use more environmentally friendly fuel – liquid oxygen and kerosene. The largest is the Long March 5, which can place 25 MT into low Earth orbit (LEO), slightly less than the largest U.S. rocket, Delta IV Heavy, which can lift 28 MT to LEO. Long March 5 had its first, and to date only, launch from Wenchang last year, but China has plans to use it for many missions, including launching the three 20-MT space station modules and robotic lunar and planetary exploration spacecraft. Between now and 2020, China plans to send a sample return mission to the Moon, a probe to land on the far side of the Moon, and an orbiter/lander/rover to Mars.

The ISS partners — the United States, Russia, Japan, Canada, and 11 European countries working through the European Space Agency — have agreed to continue operating ISS until at least 2024. NASA officials often speak of extending it to 2028, 30 years after the first modules were launched, but there is no agreement on that timeline. China has picked up on the 2024 date and routinely points out that with the ISS “set to retire” in 2024, it will have the only space station in Earth orbit thereafter.

NASA is hoping that the U.S. private sector will pick up the gauntlet and build their own space stations to follow-on from ISS that NASA and other customers could use instead of the government building future Earth orbiting facilities. Section 303 of the recently enacted NASA Transition Authorization Act of 2017 requires NASA to submit a report to Congress by December 1, 2017 and biennially thereafter until 2023 to show how to transition from the current NASA-reliant regime to one where NASA is only one of many customers of a non-governmental LEO human space flight enterprise. The goal is for NASA itself to focus on sending astronauts beyond LEO to the distance of the Moon and Mars.