SpaceX Falcon 9 historic landing thread (1st landing attempt & most recent missions)

It appears the solar cells are exposed during flight which begs the question, how are they protected?

Could be they don't have cells on that side of the trunk.

Peartree said:

No, they keep saying, "Out of family." Which is unfamiliar to me. Does that make sense to anyone else?

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As manixFan said, it relates to historical data. They will have a set of data on lots of things that they have logged over the course of launching over 50 Falcon 9 rockets. If you look at the set of graphs for a particular parameter (or group of related sensors) there will be a general pattern and spread range of data due to external variables. This is a "family" of graphs. If they see something that is really out of shape or out past the limits of existing data (or trending that way) the statistical outlier of the new launch possibly warrants investigation to make sure they don't have any nasty surprises.

Nytrunner said:

Definitely. The damaged interstage seems like it'd be terrible for lifting. Imagine lifting up a steel pipe by a cracked eggshell glued to the end



Eesh, the salt water will be doing a nasty job on things. The inner liner isn't just a smooth shell. It's got channels and subtle geometries which are purposeful, and I'm not looking forward to that cleaning job. I guess it depends on which erodes worse, cleaning off the crud or being fired nominally.

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Take it from a boat person. Salt water ruins everything. The only thing worse than regular salt water is warm salt water like you might find, say, just offshore in Florida.

'Out of Family' refers to being different that what is expected form historical data. For example, the max temperature of some device may be +90, but historical data shows that normally the part does not exceed 82. If it is at 87, it is within spec but 'out of family'.

I find it hard to believe that there wasn't a perfectly cromulent statistics word to embiggen for this role, but I could be wrong.

A bit of chemistry...

Most of us in rocketry know what oxygen is, and are familiar with the use of liquid oxygen as an oxidizer. Oxygen turns to liquid at about -183C (-297F), and freezes at about -219C (-362F). SpaceX "supercools" the liquid oxygen to right at its freezing point to increase its density so that more can be stored in the tank. Its viscosity doesn't change much as the liquid cools, but does become more viscous as solids build up at the freezing point (slush).

Kerosene, however, is a different story. Kerosene, like diesel and gasoline, are not names of single molecules. Kerosene is a mixture of hydrocarbons with from 10 to 16 carbon atoms per molecule. The molecules may be either straight, branched, or ring structures. Kerosene used for rocket propellant, usually referred to as RP-1, is highly refined to remove any sulfur and most of the straight-chain hydrocarbons, and is typically approximated with the formula C12H26 for oxygen reaction calculations. As it is a mixture of varied hydrocarbons, it does not have a specific freezing point, but will typically freeze below -40C (-40F). The big problem with kerosene is that its viscosity increases as it gets colder. At temps below about -30C, the thickness increases significantly. SpaceX chills their propellant fuel to -7 to -10C to gain the benefits of increased density, but not so cold as to run into problems with increased viscosity. Another thing to note is that rocket engines frequently go from full thrust to zero. Any excess or residual kerosene can polymerize or create carbon build-up (coking) from the high heat remaining in the combustion chamber or fuel delivery system. This problem can also exist in turbopumps where heat from the driving turbine is carried to the fuel turbine. This requires extra attention and care when rebuilding the engines. These problems do not exist in hydrogen or methane fueled rocket engines.

SpaceX scrubbed due to weather today.

That’s the last straw, temperature reading! You are OUT OF THE FAMILY! I have no son! You’re DEAD TO ME, temperature reading!!!

ThirstyBarbarian said:

That’s the last straw, temperature reading! You are OUT OF THE FAMILY! I have no son! You’re DEAD TO ME, temperature reading!!!

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If it were a Game of Thrones family it would probably be dead, and based on statistics, from a knife wound to the neck.

New launch attempt tomorrow (Saturday Dec 2nd), at 8:55 AM EST

"SpaceX is now targeting December 22nd for launch of the United States Air Force's first Global Positioning System III space vehicle (SV) from Space Launch Complex 40 (SLC-40) at Cape Canaveral Air Force Station, Florida. Weather is 80% favorable for the launch window which opens at 8:55 a.m. EST, 13:55 UTC."

Webcast:

RocketGeekInFL said:

It appears the solar cells are exposed during flight which begs the question, how are they protected?

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An epoxy layer is supposed to protect them. First orbital spacecraft to have solar cells exposed for launch. I presume when it flies up (uncrewed) to ISS, that the ISS crew will take crap-loads of closeup photos (out of ISS windows) of that area to verify how well it holds up (Spacewalk using a Canada RMS Arm would be cool but probably not). Greatest ascent heating loads are on the nose, not the sides (Will be some amount of supersonic shockwave extra heating at the stub fin areas, particularly near the roots).

The "trunk" has solar cells on one side (180 degrees) and radiators (white) for cooling fluids on the other side. Apollo SM had radiators, and Shuttle orbiter had radiators inside the bay doors. Oh, Gemini also had radiators on the adapter module that also served as a Service Module.



For those who do not recall or wonder, the stub fins are to help keep the Dragon-2 and Trunk aerodynamically stable in case of an abort.

The trunk section is slightly smaller diameter than the Dragon capsule. I guess that means any shocks set up on the trailing edge of the Dragon during the atmospheric portion of flight are weak expansion shocks. Somebody will have run a lot of CFD on that I assume. Great way to simplify the design

Will Trump's partial government shutdown impact the launch?

Marc_G said:

Will Trump's partial government shutdown impact the launch?

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I'm pretty sure rockets are ESSENTIAL... [emoji12]

I seem to remember some other launch last shutdown was postponed because the range clearance folks (Maybe coast guard ?) were not allowed to operate.

From what I've read today, If the shutdown happens it will have NO EFFECT on the launch scheduled for tomorrow morning.

Rescheduled for Sunday morning 8:51 am due to high level winds. The hold hit at T minus 0:29.

Successful launch and satellite deployment. Booster expended as planned.



21 launches for 2018.

Next is Iridium NEXT 8, NET January 8th from Vandy.

Meanwhile, a new funky Water Tower is being assembled at the SpaceX site at Boca Chica, TX:



OK, it's apparently not a water tower. It's the low altitude test "Hopper" for BFS/Starship (second stage of BFR). Info a bit sketchy, but apparently it is going be stubby, not full length, to focus mostly on low altitude test hops (It is 30 feet in diameter as the real thing is planned to be).

Photo by Maria Porter:


I am somewhat surprised it's not full length, with canards and fins, as the flip-around and tail-first descent steering (aerodynamically, not thrust) seems to me like a huge unproven design element they should be testing. But it may take too long to develop the design that far, and indeed the design KEEPS changing. So at least they can get a "crude" Hopper flying, and get some experience actually flying and throttling the new Raptor engines (Methane fuel, not RP-1. More efficient and Methane can be made on Mars).

Being built relatively crudely. Probably more analogous to SpaceX's Grasshopper 1 with its fixed legs, used for doing vertical landing tests. Indeed if that "tank" looking part does fly, it might actually have been built using common curved steel used for water tanks. Because for a rocket design that's supposed to weigh about 100,000 pounds when it lands, and this being much shorter and without the crew cabin and all that entails, might as well build it out of common thick normal steel and be super-strong to withstand possible hard landings better (I mean hard landings in the real world sense of a hard landing that might be repairable, not the Elon Musk total obliteration of Kamikaze booster crashing into barge "hard landing", as he described it before video was later released to show otherwise). If it needs "ballast" to reach a desired mass of around 100,000 pounds, might as well increase the mass by using thick (and relatively cheap) common steel to beef up the structure. Musk is talking about flying this in THE SPRING. Of course, any timelines he posts have to be taken with a grain of salt, but... maybe. In any case to claim to be able to fly this that soon, this is a far faster way to go about it. The "real" BFS stage parts will be fabricated in California and barged to Boca Chica. But he has said the prototype would be built in Texas.

Very cool stuff.

Scott Manley's take:

This is apples and kumquats but LNG tanks for marine use are often large stainless steel pressure vessels that look an awful lot like an overgrown propane tank. They are typically double walled with insulation between the shells. Matching up with what Scott Manley said, the marine world vaporizes LNG before burning it in an engine, and they do have heat exchangers to warm the LNG slightly to keep the internal pressure between 5 and 10 bar. One nice side effect of using LNG is that you don’t need helium pressurization of the fuel tanks. The LNG takes care of that itself.

I believe the LOX tanks are He pressurized. That’s what blew the second stage, isn’t it?

If LOX needs extra pressurization, then LNG will.

Charles_McG said:

I believe the LOX tanks are He pressurized. That’s what blew the second stage, isn’t it?

If LOX needs extra pressurization, then LNG will.

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That’s a really good point. The fine folks at Blue Origin say that LNG can be used to pressurize the tanks. https://www.blueorigin.com/engines

That said, I agree that it seems like here shouldn’t be a difference between LOX and LNG for tank pressurization. They are both liquids over a temperature range of about 100C and 40-50 bar of pressure. I don’t know why self-pressurization would work for LNG and not for LOX. Are there big density shifts that would mess up mixture ratios?

I wonder, maybe it is time to create a split-off thread devoted to BFS/Starship/Mars Rocket, and keep this one related to the Falcon-9.


In any case, two articles on Teslatrati.com, effectively a Fanboi of all-things-Musk website:

Some info on the "Hopper" prototype, now being called Starship "Alpha", and design changes using stainless steel rather than composite as planned:

SpaceX CEO Elon Musk says Starship (BFS) hop tests could start in early 2019
https://www.teslarati.com/spacex-ceo-elon-musk-starship-bfs-hop-tests-early-2019/

More details:

SpaceX CEO Elon Musk: Starship prototype to have 3 Raptors and “mirror finish”
https://www.teslarati.com/spacex-elon-musk-starship-prototype-three-raptors-mirror-finish/

To backtrack, on NASA SpaceFlight Forum, a thread about SpaceX's Boca Chica TX facility had this post on December 14th by a local resident (Bocachicagal), which included this photo: https://forum.nasaspaceflight.com/index.php?topic=46406.msg1888125#msg1888125

" pic of the control center area."

One member (Nomadd) suggested right away it could be related to the planned hopper (though as a mock-up, not flying). But he got swatted down, and this became a "water tank", or "observaton tower" being built.

I saw that photo but didn't check into that thread again until the news broke that it really was for the Hopper

Then it got three holes cut into at where the three legs/fins would be.


Some began to come around to the idea, including the "crazy" one that this might be for the actual flying prototype and not a mock-up (one night SpaceX has a crew with thee cranes LATE at night working on this "water tower"/Observation Tower/Mock-up). With no viable reason as to why put so much effort into it when up to now Boca Chica progress has been very SLOW - nothing NEEDING a Water Tower or Observation Tower that fast.

A longtime "expert" with over 8700 posts responded to the idea that this really was the prototype hopper:

A Starship hopper that is literally bolted to a concrete foundation is unlikely to do any hopping at all.
As usual, you guys and girls are over-analyzing this.

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Another said:

Seriously, other than a water tower, what else could it be? A base for another tracking antenna? It's a foundation for a structure, not a play spaceship.

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WHOOPS.

Musk had tweeted a few weeks ago that he would post photos of the prototype "Hopper" in 6 weeks (by Mid-January), and he said it would be built in Texas. He should have expected that if you built something like that in the open a few hundred feet from a public road, that photos would show up on Space websites (many many photos of the Boca Chica facilities have been posted the last few years. One fan even bought a house to specifically move there. SpaceX is totally aware of such photos being taken and posted, maybe Musk isn't). So eventually those stating that this was for the Hopper , pointed to the expected mid-January photos of the Hopper to explain that with no other Hopper work visible elsewhere (no "big" enclosed building yet to assemble it inside of), this probably WAS the Hopper. And also a more logical explanation for the "rush" (Rush to build a water tank, or rush to build the Hopper?).

Of course it did require some brain-twisting to realize that for such a basic (and now clearly crude) prototype, it didn't need to be built fancy or as light since it NEEDS to be heavy like the real thing will be at landing - for the basic takeoff and low altitude landings it'll be testing with three Raptor engines. The thick steel (apparently water tank type fabrication) does put a totally different and unique literal twist to the terms "boilerplate", and "Iron Bird" (Iron Birds are non-flyable prototypes used for ground testing)

I still think it looks like a farm silo.

That's what went through my mind.

Well, more has been happening at Boca Chica. Poster "Bocachicagal" on NSF posted pics after the "water tank" was moved off of the concrete ring it was assembled on. https://forum.nasaspaceflight.com/index.php?topic=47022.msg1894673#msg1894673

After setting it down, and apparently cutting away or removing the lowest steel ring, three things poke out of the bottom (Apparently were installed some time ago, not added after it was moved overnight) . Those are the size of Raptor engine nozzles. MIGHT be mock-ups or non-flying prototypes, but might be real since this is supposed to fly in a few months.




Also, a new shiny metal section is being built, cylindrical. Believed that will be a mid-section between this and the nose section. Still expected to be shorter than the planned BFS/Starship, but not as "stubby" as it had seemed like it would be.

This is a speculative composite of what it may look like once all assembled (and if the leg struts are filled in to look like fins), by Jdeshetler on NSF: https://forum.nasaspaceflight.com/index.php?topic=47001.msg1894836#msg1894836

This is just beyond cool looking. The walkway is very retro futuristic, like out of an older Alien movie.