Saturday, 5 September 2020

China launches a 'Reusable Experimental Spacecraft' - a Space Plane? [UPDATED MULTIPLE TIMES]

Early September 2020, the space tracking community was in nervous anticipation of a rather mysterious Chinese launch. Amidst tight security measures, a Changzeng-2F (CZ-2F) rocket was readied at SLS-1 of Jiuquan's Launch Area 4. Chinese tracking ships were taking up positions near South America and in the Arabian Sea. Two NOTAM's appeared suggesting a launch between 5:20 and 6:00 UT on September 4. Something was afoot! Speculation was, that this was the long anticipated inaugural launch of a robottic Space Plane, a version of the Shenlong, China's answer to the American Air Force's X-37B robottic Space Plane.

Then, on September 4th, the Chinese news agency Xinhua published a very brief news item announcing that a CZ-2F from Jiuquan had launched a 'Reusable Experimental Spacecraft' earlier that day. 

The bulletin was scarce in information but stated that "after a period of in-orbit operation, the spacecraft will return to the scheduled landing site in China. It will test reusable technologies during its flight, providing technological support for the peaceful use of space".

No further details were given on launch time, orbit or character of the spacecraft. The description of the spacecraft is a bit ambiguous. Instead of a space plane, a 'reusable spacecraft' could in theory also be some sort of capsule (e.g. like the SpaceX Dragon): but most analysts think this indeed refers to the long rumoured space plane, China's answer to the US X-37B.

Pre-launch, and based on the positions of the hazard zones from the two NOTAM's, I calculated a launch into an orbital inclination of ~45 degrees, incidentally similar to the orbital inclination of the X-37B OTV 6 mission currently on-orbit. What's more, the launch window given (the NOTAM windows were from 5:23 to 6:05 UT) indicated the possibility of a launch into the orbital plane of OTV 6! The orbital plane of OTV 6 passed over Jiuquan at 6:00 UT - near the end of the launch window.

I published the following expected track for a launch into a 45 degree inclined orbit (which we now know is wrong):

Initial pre-launch trajectory guess. Click map to enlarge

When later that day the first orbital elements by the US military tracking network appeared on the CSpOC portal, it turned out that the orbital inclination was not ~45 degrees, but 50.2 degrees, 5 degrees higher than I anticipated. The reason for the mismatch, is that the rocket apparently did a dog-leg manoeuvre during ascend. This is very clear when we plot the orbital ground track in relation to the launch site and hazard zones from the two NOTAM's: it passes obliquely between them rather than lining up.

Actual orbital track. Click map to enlarge

 A 'dog-leg' manoeuvre is usually done for safety reasons, to avoid overflying a particular area downrange (e.g. a city or a foreign nation), but can also be done to insert the spacecraft into an orbital inclination that otherwise cannot be reached from the launch site. The latter is however not the case here - [editted] the orbital inclination is higher than the launch site latitude (you cannot reach an orbital inclination that is lower than your launch site latitude without a dog-leg, but higher you can.). So the reason must be range safety.

It is clear that the launch occurred well outside the NOTAM time window (why, is not clear). My analysis, based on a proximity analysis using the orbits of the spacecraft, the upper stage of the CZ-2F rocket, and that of four engine covers ejected upon spacecraft separation, indicate spacecraft separation and insertion into orbit around 7:41 UT on September 4th, over the Chinese coast with the orbital plane lining up with Jiuquan (see image below which depicts the orbital position at orbit insertion). The launch itself then should have occured some 8-10 minutes earlier i.e. around 7:30 UT, give or take a few minutes.

Moment of orbital insertion. click to enlarge

The spacecraft was inserted into a 50.2 degree inclined, initially 332 x 348 km orbit. During the hours after launch, the spacecraft made small orbital manoeuvres (see diagram below). At the time of writing (5 September 20:45 UT) it is in a 331 x 347 km orbit.

click diagram to enlarge

The later than initially expected launch time and, through a dog-leg manoeuvre, insertion into a 50.2 degree inclined orbit moved the orbital plane away from that of the X-37B OTV 6, although the two orbital planes are still near. Igor Lissov has pointed out some resemblance to the orbital plane of another US classified payload, USA 276, which has a similar orbital inclination to the Chinese spacecraft (but 50 km higher orbital altitude). The RAAN difference is 8 degrees:

click to enlarge

Based on the current orbits of all three spacecraft, there will be no close approaches of the Chinese spacecraft to either of these classified US payloads over the coming two weeks.

OTV 6 is currently in a 383 x 391, 45.0 degree inclined orbit. The difference in RAAN with respect to the Chinese spacecraft is 13.4 degrees, with a 5.2 degree difference in inclination and about 40-50 km difference in orbital altitude.

USA 276, the mysterious spacecraft that made a close approach to the ISS in May 2017 (see my July 2017 article in The Space Review), is currently in a 397 x 395, 50.0 degree inclined orbit. The difference in RAAN with respect to the Chinese spacecraft is 7.9 degrees, with a 0.2 degree difference in inclination and about 50-60 km difference in orbital altitude.

The Chinese 'reusable' spacecraft was launched from SLS-1, one of two launch platforms at Launch Area 4 of the Jiuquan Space Launch Center. Below is a Copernicus Sentinel 2B image of the launch complex, taken on September 2nd, two days before the launch. The two launch platforms are indicated: the southernmost one is the platform used for this launch.

click image to enlarge

It will be interesting to see where the 'reusable spacecraft' will eventually land. One likely candidate is a military airfield, the Dingxin Test and Training Base, that is located some 75 km southwest of the launch site. I have indicated both the launch site (A) and the potential landing site (B) in the Copernicus Sentinel 2B image below. The second image gives a more detailed look on the airbase.

Click image to enlarge

Click image to enlarge

We have no clue how long the spacecraft will stay in orbit. It will be interesting to see when and where it lands.

The 'reusable spacecraft' has the CSpOC catalogue entry #46389 (COSPAR ID 2020-063A). The CZ-2F upper stage is object #46390 (2020-063B). The four ejected engine covers (with apogees in the 458 to 566 km range), have numbers 46391-46394 (2020-063A to 202-063F).

UPDATE 6 Sept 2020 8:45 UT:

Xinhua reports on Sept 6 that the spacecraft has landed after 2 days on-orbit. Depending on the landing site, landing should have been (based on orbital overpass) either around 1:55 UT at Lop Nor (an alternative landing site suggested), or 6:45 UT at Dingxin Airbase.

UPDATE 2, 9:30 UT:
As the Chinese version of the Xinhua bulletin dates to an hour after the first option (1:55 UT), it seems that the landing was near 1:55 UT near Lop Nur in the Taklamakan desert (HT to Jonathan McDowell).

UPDATE 3, 10:30 UT:
This is the potential landing site, a triangular arrangement of 5 km long landing strips in the Taklamakan Desert. The orbital track of the spacecraft passed some 42.5 km northwest of it around 1:54 UT, more or less parallel to what appears to be the main landing strip:

Click image to enlarge

Click image to enlarge

UPDATE  4, 14:00 UT:
This is an updated diagram of the orbital evolution over the test flight. It seems no large manoeuvers were tried during this flight.

Click diagram to enlarge

UPDATE 5, 16:00 UT:

Jonathan McDowell noted that a new object related to the launch has been catalogued, object 2020-063G, #46395. My analysis suggests it was ejected from the experimental spacecraft near 22:25 UT on the 5th, two revolutions before landing. It likely is a cubesat of some sort. It is in a  332 x 348 km, 50.2 degree inclined orbit. (Update 8 Sept: on Twitter, Bob Christy has suggested that it might be a small inspector satellite, used to inspect the outside of the experimental spacecraft prior to deorbit)

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