Author Topic: Developing the BFS - Phase 1 Big Falcon Hopper (BFH) Discussion - THREAD 2  (Read 495619 times)

Offline jpo234

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Something interesting in bocachicagal's latest image, looks like they put a ventilation fan on the manhole. Maybe the missing piece on the top dome serves the same function: ventilation.

There is already a BIG hole at the apex of the dome. I don't think they need a small secondary hole for ventilation.
« Last Edit: 01/25/2019 01:35 pm by jpo234 »
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Offline Cheapchips

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Something interesting in bocachicagal's latest image, looks like they put a ventilation fan on the manhole. Maybe the missing piece on the top dome serves the same function: ventilation.

There is already a BIG hole at the apex of the dome. I don't think they need a small secondary hole for ventilation.

They may if they're in the lower tank, but I'm not sure where the common bulkhead is in relation to the small hole.
« Last Edit: 01/25/2019 01:31 pm by Cheapchips »

Offline Lee Jay

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They didn't just leave it out in the wind - a mooring system was put in place.

Either it was under designed, or one of the components under performed.


Under performed is an understatement.  If this thing really blew over at 50mph, that's pretty sad.  I have to design to 140mph plus safety factor, and that's not that hard.  50mph is 1/8th of that strength.

The wind can be very insidious.  I had a mini-tornado rip rebar out of a 4,000 block of concrete and fling the other one 10 meters while simultaneously flipping over a 10 ton item strapped to two additional 8,750 pound blocks.  Caught it on video too.

But 50mph isn't much to design for.  They should be designing to at least 90mph plus a 1.4x dynamic load factor plus a safety factor of at least 1.4, and probably 2.  Failure at 50 means it was really designed for something like 30-35.

Offline Lar

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(mod) We probably need to cut back on the level of back and forth about whether SpaceX is entirely incompetent or that this is just a normal run of the mill testing result that has no impact whatever (the extremes I see are roughly there)....  as it's not that interesting. This is a fast moving thread. Unless you have something NEW to add about this incident's implications, it might be best not to say it.   IMHO.

Thanks.
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Offline su27k

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But 50mph isn't much to design for.  They should be designing to at least 90mph plus a 1.4x dynamic load factor plus a safety factor of at least 1.4, and probably 2.  Failure at 50 means it was really designed for something like 30-35.

Maybe that's exactly what they did? I don't know what's the best way to get wind data, but just causal browsing of weather underground for the past 3 years shows max wind speed for January is indeed around 30-35mph.

Offline Nomadd

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Something interesting in bocachicagal's latest image, looks like they put a ventilation fan on the manhole. Maybe the missing piece on the top dome serves the same function: ventilation.
They're not even close to being done inside. They're still lowering all kinds of stuff through that big hole in the top. Having that hole means there was no reason to wait to put the dome on. It
« Last Edit: 01/25/2019 03:32 pm by Nomadd »
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Offline strato1

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Something interesting in bocachicagal's latest image, looks like they put a ventilation fan on the manhole. Maybe the missing piece on the top dome serves the same function: ventilation.

There is already a BIG hole at the apex of the dome. I don't think they need a small secondary hole for ventilation.


The secondary hole at the joint line might give a slight bit of play to get everything aligned.  Nothing about this installation is precision.

Offline Nomadd

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But 50mph isn't much to design for.  They should be designing to at least 90mph plus a 1.4x dynamic load factor plus a safety factor of at least 1.4, and probably 2.  Failure at 50 means it was really designed for something like 30-35.

Maybe that's exactly what they did? I don't know what's the best way to get wind data, but just causal browsing of weather underground for the past 3 years shows max wind speed for January is indeed around 30-35mph.
At the airport, 20 miles inland maybe. Wind at the beach is a whole different story.
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Offline billh

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But 50mph isn't much to design for.  They should be designing to at least 90mph plus a 1.4x dynamic load factor plus a safety factor of at least 1.4, and probably 2.  Failure at 50 means it was really designed for something like 30-35.

Maybe that's exactly what they did? I don't know what's the best way to get wind data, but just causal browsing of weather underground for the past 3 years shows max wind speed for January is indeed around 30-35mph.
At the airport, 20 miles inland maybe. Wind at the beach is a whole different story.
Looking at the NWS 3 day record for Port Isabel (the nearest station I could find to Boca Chica - 5 miles north) you can see that the highest gust recorded in the past 72 hours was 51 mph. Over the 3 day period there were numerous hours when the sustained winds were in the mid 30s with gusts to the high 40s. Naturally, the gusts experienced by the hopper are influenced by the micro environment, but this gives you an indication of what was going on in the area.

Offline rsdavis9

Briefly read through everything since the test vehicle had a wind driven RUD. Maybe it is just me but I honestly don't see why this is a big deal or even a semi big deal.

The vehicle they built is barley even what you might quantify as a test article. It's not made of the materials the final vehicle will be, it does not include any real structures besides only the most basic ones, and the top half of the vehicle is basically a shiny nosecone/aero surface simulator. It's essentially a boilerplate that can hover.

SpaceX was able to build this in a very small amount of time in a tent in the middle of nowhere. Should be no problem to fix it or build another one. In fact it would be entirely normal if they blow a few of these up or more of them fall over ect.

Trying to say this is somehow a failure or a sloppy project seems really silly at least to me. This is basically an STA/ half an DTA. Shouldn't try to compare these things to real hardware. Grasshopper two exploded and crashed and ARES 1-X had topspin and the booster also smashed into the ocean. Test articles are meant to be broken.

Yes test articles ARE meant to be broken, but while they are under test where you could determine margins and learn how to improve the design.  I did this for a living for 45 years so this really hits home.  The value of this test article and the short period of to time recover is really not the issue.  The Big Deal is this was avoidable, should never have happened, it is a waste of money and does reflect poorly on those responsible.  If in my former life I was involved and had taken a caviler attitude to this failure on my watch, I would have been relieved of my leadership role and very justifiably so.

The "hat" isn't a test article. What could they possibly test with it? It's an aesthetic non-functional or at most minimally-functional accessory.  The construction is non remotely similar to the real vehicle, and the hopper won't go fast enough for the shape to be relevant. They could just as easily use a pointy cone like grasshopper, but Elon wanted this to look like the real test vehicle.
The hopper will be developing and testing their control systems. Wouldn't you think they'd like to prove out its handling with wind pushing against a lightweight nose? True, they won't need it for the first few mini-hops.

Yes given that they will probably be adding the 10 tonne gaseous thrusters and probably want to practice landing on a mount(for SH). This version will probably not have the RCS system. Doesn't mean that future versions of the hopper are a ideal platform to test these things. Cheap, easy to make, easy to modify. Easy to crash.
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Offline Nehkara

Anyone have any theories what these guys are doing?

Credit: 

Offline Nomadd

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Anyone have any theories what these guys are doing?

Methane flare.
« Last Edit: 01/25/2019 04:56 pm by Nomadd »
Those who danced were thought to be quite insane by those who couldn't hear the music.

Offline cuddihy

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First steps to building the Big Crane for the launch tower? If so, it’s further Southwest than I thought.

I guess the berms to the East are to manage sound/ erosion then?

Offline cuddihy

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Anyone have any theories what these guys are doing?

Methane flare.

Hmm, that makes a lot more sense.

Offline kdhilliard

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Caught some deliveries being made inside the Hopper. The last pic is the missing panel being installed.
Seems strange to pass that missing panel upside down, but I'll trust they know what they are doing.

The main portion of the dome looks much like the steel (presumably mill finish stainless steel) panels of the lower, cylindrical hopper section (before it was clad with the polished stainless sheet metal), but the lowest portion of the dome is constructed of darker panels.  What's up with that?
« Last Edit: 01/25/2019 06:02 pm by kdhilliard »

Offline georgegassaway

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Regarding wind, while this incident seems to be simple (?) straight line winds, microbursts from storms can produce VERY intense straight line winds (airliners have crashed when flying into them).

https://en.wikipedia.org/wiki/Microburst

Note, I am not saying a microburst caused this. I am saying that extreme winds from microbursts are something  worth designing for.

Neighborhood I used to live in, three houses in a row had large trees blown onto them over the years. Each due to storm microbursts - not tornados, not windstorms. Each of those three incidents the wind was well over 50 mph, one was over 80 mph IIRC.

This was an oversight. They'll need to learn and do better for the future. 
« Last Edit: 01/25/2019 06:06 pm by georgegassaway »
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Offline Nomadd

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 Know why people have mobile homes in hurricane country?
  Because when it blows away, you can get another mobile home and install it for about 1/4th the money in 1/10th the time of a stick built house.
 If making and securing the shiny hopper nose against hurricanes cost 4 times as much and took 4 times as long, it really wouldn't have made much sense. And it could be months before there's any reason, other than looking pretty, before they need it.
 
« Last Edit: 01/25/2019 07:16 pm by Nomadd »
Those who danced were thought to be quite insane by those who couldn't hear the music.

Offline Nomadd

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Anyone have any theories what these guys are doing?

Methane flare.

Hmm, that makes a lot more sense.
You can always tell who the guy is that climbs the pipe and manually lights the flare when the ignitor goes out. He looks like Jeff Bezos.
Those who danced were thought to be quite insane by those who couldn't hear the music.

Offline guckyfan

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Yes given that they will probably be adding the 10 tonne gaseous thrusters and probably want to practice landing on a mount(for SH). This version will probably not have the RCS system. Doesn't mean that future versions of the hopper are a ideal platform to test these things. Cheap, easy to make, easy to modify. Easy to crash.

The 10t thrusters were part of the 2016 version of MCT. Also at that tíme the concept was that the thrusters do what the aerosurfaces do now. They may use very much smaller thrusters in the present version.

Offline strato1

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Then why did they build it?

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