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Space Science Coverage / Re: ESA - Gaia updates
« Last post by AegeanBlue on Today at 07:41 AM »
Another new Gaia discovery that popped up on twitter today: there is a gap in the HR main sequence stars. This seems to correspond to where dwarfs transition to partial to fully convective. The Gaia team members have weighed in on twitter and do not believe that this is a systematic error, rather a real effect.

arXiv paper:

A Gap in the Lower Main Sequence Revealed by Gaia Data Release 2

Synopsis: We present the discovery of a gap near MG≈10 in the main sequence on the Hertzsprung-Russell Diagram (HRD) based on measurements presented in Gaia Data Release 2 (DR2). Using an observational form of the HRD with MG representing luminosity and GBP−GRP representing temperature, the gap presents a diagonal feature that dips toward lower luminosities at redder colors. The gap is seen in samples extracted from DR2 with various distances, and is not unique to the {\it Gaia} photometry --- it also appears when using near-IR photometry (J−Ks vs MKs). The gap is very narrow (∼0.05 mag) and is near the luminosity-temperature regime where M dwarf stars transition from partially to fully convective, i.e., near spectral type M3.0V. This gap provides a new feature in the H-R Diagram that hints at an underlying astrophysical cause and we propose that it is linked to the onset of full convection in M dwarfs.
Space Science Coverage / Re: NASA - Voyager 1 and 2 updates
« Last post by AegeanBlue on Today at 07:21 AM »
A paper on arXiv: Measuring the Local ISM along the Sight Lines of the Two Voyager Spacecraft with HST/STIS

In 2012, Voyager 1 crossed the heliopause, becoming the first human-made object to exit the solar system. This milestone signifies the beginning of an important new era for local interstellar medium (LISM) exploration. We present measurements of the structure and composition of the LISM in the immediate path of the Voyager spacecraft by using high-resolution Hubble Space Telescope (HST) spectra of nearby stars that lie along the same lines of sight. We provide a comprehensive inventory of LISM absorption in the near-ultraviolet (2600-2800 Angstroms) and far-ultraviolet (1200-1500 Angstroms). The LISM absorption profiles are used to make comparisons between each pair of closely spaced (<15 deg) sight lines. With fits to several absorption lines, we make measurements of the physical properties of the LISM. We estimate electron density along the Voyager 2 sight line, and our values are consistent with recent measurements by Voyager 1. Excess absorption in the HI Ly-alpha line displays the presence of both the heliosphere and an astrosphere around GJ 780. This is only the 14th detection of an astrosphere, and the large mass-loss rate (M˙=10M˙⊙) is consistent with other subgiant stars. The heliospheric absorption matches the predicted strength for a sight line 58 deg from the upwind direction. As both HST and Voyager reach the end of their lifetimes, we have the opportunity to synthesize their respective observations, combining in situ measurements with the shortest possible line-of-sight measurements to study the Galactic ISM surrounding the Sun.

I am starting to think REL looking for investment from companies like Boeing is them with at least half an eye to hedging their bets against a hard Brexit. With Airbus’s latest threat to quit the UK it wouldn’t surprise me if REL have it in their forward plans on doing the same thing. That any manufacturer of the Skylon itself would be done outside the UK. It wouldn’t be too difficult to get Airbus or Boeing to manufacture it elsewhere. Once the development program is complete I can’t see there’s anything particularly holding them to the UK especially now with Mr Bond retired.

Oh not this silliness. It's bluster designed to pressure the PM into keeping the UK in the customs union (and single market by extension). They're saying these things now because the government recently defeated a Lords amendment in the Commons which would have made a no-deal Brexit impossible; a no-deal Brexit is *the* thing that they, the EU, need the UK to explicitly disclaim.

BAe and Rolls-Royce are both partially owned by the government and both own a not insignificant part of REL.

This government is more minded to a hard Brexit than anything else you only have to look at the proclamations of the foreign secretary or their recent behaviour in the various votes to see this. All these companies are doing is expressing their concerns as they are fill entitled to do.

The Airbus threat is probably real since the French and indirectly the German governments are the biggest shareholders. France thinks Brexit is a great opportunity to grab all of Britain;s jobs and contracts.

This will happen gradually, I suspect. The French in particular simply dislike Britain and will do all they can to undermine us. The moral of this story is to never sell strategic assets; the Labour government of 1997-2010 should have intervened by buying BAe's share of Airbus.

This is just plain silly. If France ever disliked GB, as far as aerospace goes, it is because of their multiple "betrayals": while they were locked into Concorde (LMAO: no escape clause in the 1962 agreement !), they threw Airbus under a bus (RB-207) in favor of the Tristar RB-211; same for space, ELDO and the case of the Blue Streak.

GB had a nasty habit of starting aerospace projects, then goes to Europe for funding, then, if the project looked like failing, they retired;  then if the project survived, and thrieved, then and only then they come back. Typical of this is the Airbus story.

As of 1960 the French were willing to cooperate with the British rather than Germany, to get a strategic, major aerospace partner on the world scene. A string of major aerospace ventures followed, with mixed successes followed by a string of betrayals. By 1975 the French were baffled by British attitude and simply found that Germany is a far more reliable ally. It is as simple as that.

The moral of this story is to never sell strategic assets; the Labour government of 1997-2010 should have intervened by buying BAe's share of Airbus.

Hell yes, but Madame Thatcher just couldn't stand the words "government" or "public spending".  ::)  What is really a shame is that Tony Blair, supposedly from the opposite side, did not really contested that dogma when he came to power.

By 1945 or 1960 Great Britain had a wonderful aerospace industry, it is a crying shame it was dismantled and sold like this.

France thinks Brexit is a great opportunity to grab all of Britain's jobs and contracts.

Please don't paint the French as the story villain. If Great Britain has been stupid enough to commit the Brexit sepukku, well, it is hardly the fault of the French. Internal politics, my dear: its their own crazy decision to get away. Now they have to assume the consequences of their decision, including the bad side effects.

"You don't make an omelette without breaking some eggs".
I'm starting to read Leviathan Wakes now.
Google translate:
"The Greek University can and build microservices from start to finish. At the moment, four Greek universities join forces, Greece in one and a half to two years from now will have its own array of micro-satellites, "said Pappas, adding that" the two satellites that are already in space , Hellas Sat 3, and Hellas Sat 4 to be launched at the end of the year, will allow Greece to have many transponders. Some of them are also used for the needs of the Greek Armed Forces. "

The official confirmation from Arabsat:

...The award was handed by the President of Cyprus to Mr. Khalid Balkheyour, President and CEO of Arabsat who stated the following: “ARABSAT accepts with great honour the CIPA award and came to Cyprus to stay for a long time.  The business environment and the strategic geographic position of Cyprus are the main factors for our successful operations. Since Hellas Sat became member of ARABSAT group we expanded our operations with the launch of HS3 satellite and the procurement HS4 which is expected to be launch at the end of 2018.”

Report on first advisory group meeting:

Space council’s “think tank” starts work
by Jeff Foust — June 20, 2018

WASHINGTON — An advisory group dubbed the “think tank” for the National Space Council formally kicked off its work June 19 with a broad but vague mandate to study space policy issues.

The Users’ Advisory Group (UAG) of the National Space Council held its first meeting at NASA Headquarters, a five-hour “inaugural and, quite frankly, organizational session” of the committee, in the words of its chairman, retired U.S. Navy Adm. James Ellis.
NASA Kennedy LV images
A selection of payload images from NASA Kennedy
SpaceX BFR - Earth to Deep Space / Re: Building BFR
« Last post by RobLynn on Today at 05:06 AM »
Filament winding over convex formers with tension likely diminishes the need for any autoclave consolidation substantially.  You can get near perfect fiber fill fraction and eliminate almost all voids this way.
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