BFR Developments

Elon said yesterday (Tuesday May 21) that the Watertower's first flight should be in about 10 days.

I'm growing increasingly skeptical, since the engine still isn't there. That's not something that they can just quickly bolt on as long as it's pointed down. If they plan to control the massive Watertower with the engine's throttle and with vectored thrust, there's going to be an elaborate gimbaled mounting for the engine to fit into and all kinds of control lines and actuators, along with plumbing for fuel, oxidizer and pressurization. Plus all kinds electronic spaghetti for control and telemetry. Then they will have to test the hugely complex system integration.

Or maybe not. Maybe they will just slap it on and pass around a bottle of Jack.

A couple of days ago, somebody wrote on twitter: "On our next episode of Junkyard Empire, the boys decide to build themselves a spaceship and fly to Mars!" Pure Texas. (Except that NASA's in Texas and it isn't like that. At least not any more.)
I might believe anything if they finally get the Starlink satellites launched tomorrow from that other place without another cancellation.
Successful liftoff. Booster B1049 was flying for the third time and obviously has learned the routine, and is safely back down on its 'droneship' in the Atlantic. The 60 Starlinks are said to be deployed. I express a small bit of doubt because they came free from the second stage in one big 'stack' that split into two with a couple of individual satellites coming free. SpaceX says that they weren't launched with a dispenser system and that they will drift away from each other and that what we saw was expected. I was kind of speculating that they might spin them up so that they would separate centrifugally, but we didn't seem to see that. No springs to spring them free either.

(A clump just isn't a mumuration.)

Edit: Talk is that once it comes free, each Starlink will deploy a big solar panel (that might serve as a little solar sail) and will carry a small ion thruster of the sort found in some small cubesats. So that might enable the clump to disperse.

SpaceX photo of the clump of 60 Starlinks immediately after deployment from the second stage:

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A little video of them starting to 'deploy':

SpaceX photo of B1049 back for the third time:

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Boca Chica beach closures for May 28, 29 and 30 have been cancelled. Apparently there's a possibility of closures in the week of June 3, but that's TBA.

As of today, Friday May 24, there's still no sign of the Raptor engine. (The Watertower ain't gonna fly anywhere without its engine.)

There has been some activity concerning the Watertower. Several liquid nitrogen tankers have arrived in the last few days and yesterday the Hopper was venting white vapor. So they are apparently doing tanking and pressurization tests and looking for leaks after the two months of so of work that they've done since the first test series in early April.
(May 24, 2019 05:06 AM)Yazata Wrote: Edit: Talk is that once it comes free, each Starlink will deploy a big solar panel (that might serve as a little solar sail) and will carry a small ion thruster of the sort found in some small cubesats. So that might enable the clump to disperse.

That Dutch skywatcher who made a video of them passing overhead like a string of pearls almost sounded a tad alarmed: "I do worry a bit what this will do to the night sky when there are thousands of them. I wonder if SpaceX has realised how bright they are. Of course they will manoeuvre some 100 km higher, but still, they are bright."

Sometimes a reflective antenna on the older members of the Iridium satellite constellation will generate a so-called Iridium flare "where the satellite momentarily appears as one of the brightest objects in the night sky and can be seen even during daylight". But like the newer Iridium sats, surely SpaceX designed the Starlink bunch to have minimal reflectivity, so that "satellite constellation" doesn't acquire a secondary, almost quasi-literal meaning of new "star" configurations appearing in the night heavens.
Here's a very detailed video of the Junkyard Empire filmed by local resident Luis (who runs the 'Labpadre' site in South Padre Island). This was recorded on May 21. It shows all of the many mods made to the Watertower over the last two months and all the cryptic things that they've stuck to it, in surprising close-up. (The engineers love looking at these kind of photos and identifying what they see and how it's all connected.) Apparently the consensus is that it's mostly the control system from a Falcon 9. Red COPVs on top, thrusters below. The quick-disconnect that he shows is interesting, it's where the fuel and oxidizer lines connect to the vehicle and disconnect all at once when it leaves.

The video shows tankers delivering liquid nitrogen (for the tanking and plumbing tests over the last few days) and an endless succession of trucks delivering gravel. The site is largely a tidal wetland and my guess is that they want to expand the area of their facility and are doing some landfill. They may also need to prepare the underlying soil before they pour concrete for more formal and sightly launch and landing pads. There's been lots of construction of new buildings as well, but not at this beachfront site but about a mile west where the second vehicle is being constructed. One big warehousy thing has already gotten its roof.

Here's the Labpadre Youtube channel. It's the best live-feed when the Boca Chica testing is underway. Luis is currently trying get SpaceX to allow him to set up a closer live-cam for closeup live coverage of the Hopper tests.

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Tim Dodd the Everyday Astronaut has a youtube video explaining rocket engines. It's an hour long but entertaining and fun to watch. It's technical without being technical, if you know what I mean. A few seconds long explanation of what various technical terms and variables mean and where they fit into the big picture, without all the math. Good graphics. There's discussion of various difficulties and trade-offs (there's no one best rocket engine design) and how each rocket engine performs with regards to each desired variable. Elon Musk watched the video and likes it, adding some comments of his own in the twitter thread below.

It's Rocket Science, in about the most painless form possible. You will come away knowing what preburners are and what staged combustion is. You will also be able to say something intelligent about the relative pros and cons of RP1/rocket-grade kerosine, methane/natural-gas and hydrogen as rocket fuels, what the downside of running RP-1 in fuel-rich preburners is and why oxygen-rich preburners are hard. They're so hot that for years the US thought they were impossible because they would melt the turbines... until we learned after the end of the Cold War that the Russians had been doing it for years. The Russians sold some of their engines to us to test and even today the US buys many of its rocket engines from Russia, they are that good. You will know a little about the histories of some of these rocket engines, their relative efficiencies and costs. You will even know what that little flare of low pressure flame coming from the base of Falcon 9 boosters along with the expected rocket blast is. (It's preburner exhaust from the kerosine-burning Merlin engine's fuel-rich open-cycle preburner.)

You can find a link to the video and read the text in written form here
(May 25, 2019 07:10 AM)C C Wrote: That Dutch skywatcher who made a video of them passing overhead like a string of pearls almost sounded a tad alarmed: "I do worry a bit what this will do to the night sky when there are thousands of them. I wonder if SpaceX has realised how bright they are. Of course they will manoeuvre some 100 km higher, but still, they are bright."

I just saw the video of the flock of Starlinks passing in train over the Netherlands here:

They do look bright. And I do worry about putting tens of thousands of them up.

Another video showing the train of Starlinks over Japan.

Jonathan McDowell (who is a Harvard/Smithsonian astronomer, so he should know) says:


This apparently assuming the deployment of all the thousands of Starlinks that Elon proposes.

On the other hand...

He's not very hopeful about painting the Starlinks flat black or something so as to be less reflective, since their thermal characteristics would probably change too much.

There definitely seems to be a growing internet battle brewing between the astronomers and the Elon fanboys. I'm personally inclined to think that the former might be exaggerating, while the latter might be cheering something that could be irresponsible.

Starlink has its own website, separate from SpaceX's.

Later edit: Here's the Starlinks passing over Chicago:
Here's a very good article on the Starship and Starhopper developments, based in part on inside information.

The new news concerns the Raptor engines and what the timeframe is for the Hopper to receive the one it's been waiting for while it received its control system upgrades.

The first Boca Chica Hopper tests in early April used engine SN2. (SN1 had earlier been damaged in testing at McGregor.) SN2 fired very short burns a couple of times, then was removed from the Hopper and trucked off to parts unknown. It's now revealed that it was returned to Hawthorne California for inspections. (Elon insisted in a tweet that there wasn't anything the matter with it.) SN3 was already at McGregor for a full-scale test series. It's unknown (to me, anyway) why it isn't being sent to the Hopper. (I can speculate though. Perhaps the testing was testing-to-destruction, where they crank it up until it breaks, so that they learn what its limits are. But maybe SN1 had already done that, if it happened at all.)  

SN4 will go to the Hopper. So where is SN4 right now and what has it been doing? Last week it was at McGregor undergoing acceptance testing. Every rocket engine SpaceX builds is test-fired at McGregor before it is installed on a vehicle where it's test-fired again in a static test, before actually flying. (The article above includes a great photograph of SN4 on the McGregor test stand.) SN4 should be arriving in Boca Chica very soon for installation later this week.

Meanwhile, methane tankers were arriving yesterday and the flare stack is once again lit.

The plan seems to be to run methane and LOX tanking tests, then igniter and pre-burner tests (spinning up the turbopumps without lighting the main combustion chamber in other words), then probably a short static fire like we saw in early April. All leading up to a first-flight, vertical to about 20 meters altitude. (About as high as the thing is tall.) That may come as early as next week. (Of course that's aspirational "Elon-time", what they would like to do, and things may well slip.)

Edit: Still no sign of the engine on Tuesday 5-28. (Lots of trucks arrive and leave, so it could already be there. But it hasn't been installed on the Hopper where people can see it.) But Cameron County has announced new Boca Chica road and beach closures for June 2, 3 and 4.

Still no FAA Temporary Flight Restrictions, which we would expect to see prior to testing, even if the vehicle doesn't fly, if there's an explosion danger that could hurl shrapnel at low-flying aircraft.

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