Behind The Black – Robert Zimmerman

China launches two GPS-style satellites

October 15, 2018 8:43 am Robert Zimmerman

In launching two more GPS-style satellites with its Long March 3B rocket, China today also did their first test of equipment to be used in a parachute system designed to recover the rocket’s first stage.

The China Aerospace Science and Technology Corporation (CASC) confirmed the mission to be a success four hours later, following direct insertion of the Beidou-3 satellites into their intended medium Earth orbits (MEO).

The China Academy of Launch Vehicle Technology (CALT) which developed the Long March 3B rocket reported that data logging and active tracking equipment was placed aboard for tests to determine to altitude and timing for future parachute landings for boosters.

The trial phase of parachute booster landings is expected in 2019. Expended rocket boosters frequently land in or near populated areas downrange of Xichang.

It is about time. The article also included a short video showing the booster wreakage that landed near a town during a previous launch. For any nation to allow rocket stages crashing near habitable areas speaks poorly of that nation.

The leaders in the 2018 launch race:

28 China
17 SpaceX
8 Russia
7 ULA
6 Europe (Arianespace)

In the national rankings China leads the U.S. now 28 to 25. I must add that with every launch China is setting a new record for itself in its annual totals. Previously its highest total of launches in a year had been 20.

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Giant planets around young star defy model predictions

October 15, 2018 8:21 am Robert Zimmerman

The uncertainty of science: The recent discovery of four Saturn/Jupiter-sized planets orbiting a star only about two million years old throws a wrench into all existing solar system formation theories.

The star, CI Tau, is located about 500 light years away in a highly-productive stellar ‘nursery’ region of the galaxy. Its four planets differ greatly in their orbits: the closest (the hot Jupiter) is within the equivalent of the orbit of Mercury, while the farthest orbits at a distance more than three times greater than that of Neptune. The two outer planets are about the mass of Saturn, while the two inner planets are respectively around one and 10 times the mass of Jupiter.

The discovery raises many questions for astronomers. Around 1% of stars host hot Jupiters, but most of the known hot Jupiters are hundreds of times older than CI Tau. “It is currently impossible to say whether the extreme planetary architecture seen in CI Tau is common in hot Jupiter systems because the way that these sibling planets were detected – through their effect on the protoplanetary disc – would not work in older systems which no longer have a protoplanetary disc,” said Professor Cathie Clarke from Cambridge’s Institute of Astronomy, the study’s first author.

According to the researchers, it is also unclear whether the sibling planets played a role in driving the innermost planet into its ultra-close orbit, and whether this is a mechanism that works in making hot Jupiters in general. And a further mystery is how the outer two planets formed at all.

“Planet formation models tend to focus on being able to make the types of planets that have been observed already, so new discoveries don’t necessarily fit the models,” said Clarke. “Saturn mass planets are supposed to form by first accumulating a solid core and then pulling in a layer of gas on top, but these processes are supposed to be very slow at large distances from the star. Most models will struggle to make planets of this mass at this distance.” [emphasis mine]

In other words, the present models are absurdly premature. We simply don’t know enough to formulate any theory that can be taken seriously.

This is not to say that models shouldn’t be formulated, only to emphasize that no one should consider them predictive of any part of reality. They give astronomers some guidance on what to look for, but if they take them too seriously they might not look in the right places.

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Hayabusa-2 will do two touchdown rehearsals prior to landing in January

October 14, 2018 9:37 am Robert Zimmerman

In order to test whether they can bring Hayabusa-2 down to the surface within a circle only 20 meters (65 feet) across (the largest smooth landing area they have found so far on Ryugu), their engineering team has decided to first do two more touchdown rehearsals in October.

In the area where the spacecraft will touchdown, it is dangerous to have boulders with a height greater than about 50cm. Since the length of the sampler horn is about 1m and the spacecraft will be to be slightly inclined during the touchdown, there is a possibility that if a boulder with a height above about 50cm is present, it will strike the main body of the spacecraft or the solar panels. Viewed from the position in Figure 2, there is no boulder larger than 50cm in the area L08-B. L08-B is the widest part within all the candidate sites without a boulder larger than 50cm.

The difficulty is that area L08-B is only about 20m in diameter. Originally, it was assumed that a safe region for touchdown would be a flat area with a radius of about 50m (100m in diameter). This has now become a radius of just 10m; a fairly severe constraint. On the other hand, during the descent to an altitude of about 50m during the MINERVA-II1 and MASCOT separation operations, we were able to confirm that the spacecraft can be guided within a position accuracy of about 10m for a height 50m above the surface of Ryugu (Figure 3). This is a promising feature for touchdown.

Although the spacecraft can be controlled with a position error of 10m at an altitude down to 50m, there remains the question of whether this accuracy can be retained as the spacecraft descends to the surface. This must be confirmed before touchdown operations. Therefore, the touchdown itself will be postponed until next year, during which time we will have two touchdown rehearsals; TD1-R1-A and TD1-R3.

After the rehearsals in October they must wait until January to do the landing because in November and December the sun will be in-between the Earth and the spacecraft, making operations more difficult. They want to also use this time to review the results of the rehearsals to better prepare for the January landing.

Winner of the 2003 Eugene M. Emme Award of the American Astronautical Society.