Author Topic: Where will BFR launch from?  (Read 156673 times)

Offline docmordrid

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Re: Where will BFR launch from?
« Reply #340 on: 06/25/2016 06:38 pm »
And yet Shotwell hinted the BFR will have to be built on the pad...perhaps because they're making it without a mono tank? 
>

Or - mono or not, she simply misspoke. 
« Last Edit: 06/25/2016 06:39 pm by docmordrid »
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Offline Robotbeat

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Re: Where will BFR launch from?
« Reply #341 on: 06/25/2016 06:46 pm »
And yet Shotwell hinted the BFR will have to be built on the pad......
...citation needed.

She said it would be built at (or near) the launch site.
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Offline llanitedave

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Re: Where will BFR launch from?
« Reply #342 on: 06/25/2016 07:33 pm »
Building on the pad really doesn't seem compatible with a fast launch cadence.
"I've just abducted an alien -- now what?"

Offline cuddihy

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Re: Where will BFR launch from?
« Reply #343 on: 06/25/2016 08:33 pm »
I wonder... Could BFR be so big that it wouldn't need an erector/ launcher by it?

I'm sure it'd still be processed horizontally--even if it's 20m wide, it's easier to reach a 20m height than a 50m height. And odds seem to be on 15-17m wide. But once erected, it's probably massive enough even empty to not need a TEL providing stability in wind. Only a service gantry/ arm would be needed, probably about the size of the current F9 TEL. In that case, there may be no need for a permanent vertical structure near the pad, so if the BFR was able to orient correctly, it could land back on the launch pad.
 I know, crazy right?
« Last Edit: 06/25/2016 08:35 pm by cuddihy »

Online Bob Shaw

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Re: Where will BFR launch from?
« Reply #344 on: 06/25/2016 08:52 pm »
No. The bigger it gets, the more surface area to be blown about by the wind, and when empty it will be pretty light.

Offline cuddihy

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Re: Where will BFR launch from?
« Reply #345 on: 06/25/2016 08:58 pm »
The current TEL isn't there to ensure the F9 stays in one place but to provide strenthening in the wind so that it doesn't see rediculous bending loads. But would a much squatter, thicker skinned stage (which it has to be anyway due to circumference), still need external support for bending loads?

As a data point, the F9 first stage is just fine without a TEL post-landing.
« Last Edit: 06/25/2016 09:00 pm by cuddihy »

Offline the_other_Doug

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Re: Where will BFR launch from?
« Reply #346 on: 06/26/2016 01:49 am »
The current TEL isn't there to ensure the F9 stays in one place but to provide strenthening in the wind so that it doesn't see rediculous bending loads. But would a much squatter, thicker skinned stage (which it has to be anyway due to circumference), still need external support for bending loads?

As a data point, the F9 first stage is just fine without a TEL post-landing.

I know that the von Braun team (i.e. MSFC) in the early '60s decided to stack the Saturn V vertically and transport it vertically out to the pad in great measure to avoid bending loads.  Of course, with their solid Teutonic engineering, with everything overbuilt, I imagine there were more deltas between the mass of the thrust structures and that of the tanking, especially in the first stage.  I would think that would make bending loads worse.

Of course, it is always pointed out that the Soviets didn't seem to think bending loads an issue when they designed the N-1 to be built and transported to the pad horizontally and then erected once it reached the pad, just like the R-7 was.  Maybe they just had more familiarity with the bending loads on relatively larger, heavier structures, as deduced from R-7 behaviors, that led them to design their N-1 system that way.

(And yeah, the N-1 never flew successfully -- but I've never seen anything to even hint that any of the problems with it had anything to do with bending loads during construction or erection...)
-Doug  (With my shield, not yet upon it)

Offline guckyfan

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Re: Where will BFR launch from?
« Reply #347 on: 06/26/2016 04:12 am »
Just thinking of bending loads, when seeing a Falcon 9 first stage transported. Long and slender, very lightweight. They just put wheels under both ends and transport it over the highway.

Offline envy887

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Re: Where will BFR launch from?
« Reply #348 on: 06/26/2016 04:27 am »
Transport is easier than standing in terms of bending, because the supports are very far apart. On the pad, the supports are close together, and the moment arm twice as long.

Offline the_other_Doug

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Re: Where will BFR launch from?
« Reply #349 on: 06/26/2016 04:37 am »
Just thinking of bending loads, when seeing a Falcon 9 first stage transported. Long and slender, very lightweight. They just put wheels under both ends and transport it over the highway.

Well, to be honest, they connect the wheel trucks to handling rings (in the case of the road trucks, there are two sets of claw-like rings at each wheel truck, integral to the trucks), which are strategically connected to specially reinforced sections of the long, slender, lightweight stages, and I bet there are longitudinal stiffeners that run up and down the stages from those attach points.

In other words, it's not that simple rolled tubes of the aluminum-lithium alloy SpaceX uses for the Falcons are so strong they wouldn't show bending deformations without stiffeners.  Such stiffeners do add to the mass of the stage, but they also add strength and longitudinal stability, not just during transport and erection on the pad, but also in flight.  I'd be willing to bet that pretty much every airframe, for every type of aerospace vehicle, has such attach points connected to strengthened or reinforced sections of the airframe.

Besides, I seem to recall that SpaceX uses a chemically milled integral stiffening on the interiors of their vehicles, and tries to reclaim the material milled away from the etching chemicals.  Which means they can pattern the stiffeners and the attach points, both external and internal, into the metal using the milling process.  I believe the overall stiffening pattern is the grid pattern we can see in the internal views of the tanks.

I know that things like the Saturns had big metal stiffeners welded into their structures, though they became thinner and less massive the higher you got on the stack -- that staged rocket equation.  Maybe it was just an engineering intuition that was ultimately faulty, but back then, they worried about bending effects on rockets the size of the Saturn V, Nova -- and in this case, the BFR.  I figure that SpaceX thinks they have such things figured out, and aren't too worried about such effects with either FH or BFR, at this point.
-Doug  (With my shield, not yet upon it)

Offline guckyfan

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Re: Where will BFR launch from?
« Reply #350 on: 06/26/2016 07:58 am »
Just thinking of bending loads, when seeing a Falcon 9 first stage transported. Long and slender, very lightweight. They just put wheels under both ends and transport it over the highway.

Well, to be honest, they connect the wheel trucks to handling rings (in the case of the road trucks, there are two sets of claw-like rings at each wheel truck, integral to the trucks), which are strategically connected to specially reinforced sections of the long, slender, lightweight stages, and I bet there are longitudinal stiffeners that run up and down the stages from those attach points.

That does not change the fact that an ultralight cylinder takes all the bending load it experiences during road transport. There is no intermediate support.

Offline BobHk

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Re: Where will BFR launch from?
« Reply #351 on: 06/27/2016 04:25 am »
And yet Shotwell hinted the BFR will have to be built on the pad......
...citation needed.

She said it would be built at (or near) the launch site.

https://www.youtube.com/watch?v=EoCDLUHb0y4&feature=youtu.be

3:40 to 4:05

How far from the pad do you think they'll build it when she says its not going to go over roads...
« Last Edit: 06/27/2016 04:37 am by BobHk »

Offline Robotbeat

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Re: Where will BFR launch from?
« Reply #352 on: 06/27/2016 04:34 am »
And yet Shotwell hinted the BFR will have to be built on the pad......
...citation needed.

She said it would be built at (or near) the launch site.

https://www.youtube.com/watch?v=EoCDLUHb0y4&feature=youtu.be

3:40 to 4:05
So in other words, /exactly/ what I said.
"the Mars Colonial Transporter ...we're going to have to build that rocket at the launch site"

This is NOT the same thing as being built on the pad.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline BobHk

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Re: Where will BFR launch from?
« Reply #353 on: 06/27/2016 04:38 am »
And yet Shotwell hinted the BFR will have to be built on the pad......
...citation needed.

She said it would be built at (or near) the launch site.

https://www.youtube.com/watch?v=EoCDLUHb0y4&feature=youtu.be

3:40 to 4:05
So in other words, /exactly/ what I said.
"the Mars Colonial Transporter ...we're going to have to build that rocket at the launch site"

This is NOT the same thing as being built on the pad.

and how far do you think shell build it from the pad if shes not intending to send it/parts of it over roadways?  a building a few miles from the pad might as well be the bloody pad.

Offline Robotbeat

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Re: Where will BFR launch from?
« Reply #354 on: 06/27/2016 04:45 am »
No, it's significantly different operationally. Delta II was/is basically built on the pad. Building on the pad itself dramatically slows operations, obviously, since the pad can't be used for launching.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline docmordrid

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Re: Where will BFR launch from?
« Reply #355 on: 06/27/2016 05:08 am »
>
and how far do you think shell build it from the pad if shes not intending to send it/parts of it over roadways?  a building a few miles from the pad might as well be the bloody pad.

Brownsville has a world class harbor and there's a shipping channel which can handle aircraft carries, and Musk testified before the TX legislature a factory for large cores could be part of this deal. They could build anywhere along that channel, which enters the Gulf 4.7 miles north of the pad.

The question is if they could  unload on an improved  Rte. 4 at the launch site using a shallow draft barge crane.
« Last Edit: 06/27/2016 05:13 am by docmordrid »
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Offline darkenfast

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Re: Where will BFR launch from?
« Reply #356 on: 06/27/2016 09:18 am »
While they might build pieces of the BFR in Brownsville, getting the rocket to the pad would be difficult.  The shipping channel is separated from the launch site by several miles of wetlands.  Dredging a channel and building a dock and roadway to the pad would have to get past an awful lot of environmental and political hurdles.  Then there's the other big issue: where are you going to test-fire this thing?  McGregor can't do it.  SpaceX has already said that they will make hearing protection available for Boca Chica residents during Falcon launches.  I seriously doubt that a full-duration test of a BFR is going to be allowed there.  The only water-accessible place that can test-fire something this big is Stennis.  The only place that can launch something this big is (at the moment), KSC (maybe).  Unless SpaceX surprises us with dancing unicorns, there simply aren't a lot of places with that kind of buffer zone, access and (in the case of launches) safe downrange areas.
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Offline docmordrid

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Re: Where will BFR launch from?
« Reply #357 on: 06/27/2016 09:51 am »
While they might build pieces of the BFR in Brownsville, getting the rocket to the pad would be difficult.  The shipping channel is separated from the launch site by several miles of wetlands.  Dredging a channel and building a dock and roadway to the pad would have to get past an awful lot of environmental and political hurdles.


Its 4.7 miles from the outlet, straight down the coast. IF they could get approval for a ramp or pier from the end of Rte 4 they could unload it from a crane barge.

Quote
Then there's the other big issue: where are you going to test-fire this thing?  McGregor can't do it. 
>

You could blow a 5 kiloton nuke over the pad and maybe have enough overpressure to break windows at the village (~1.5 psi.) NASA rated Saturn V at about half a kiloton, an order of magnitude less, and explosive effects do not scale linearly at a distance. Others here have estimated BFRs blast as about 1.4x that of a Falcon Heavy going boom. A test fire would be far less than either, and pointed out at sea.
« Last Edit: 06/27/2016 09:58 am by docmordrid »
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Offline Nomadd

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Re: Where will BFR launch from?
« Reply #358 on: 06/27/2016 03:36 pm »
 I've eliminated the biggest obstacle for building a BFR size assembly hangar near the pad by checking the angles from my living room window and determining it won't block my view of the rocket. Everything else is details.
« Last Edit: 06/27/2016 03:36 pm by Nomadd »
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Offline envy887

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Re: Where will BFR launch from?
« Reply #359 on: 06/27/2016 04:51 pm »
While they might build pieces of the BFR in Brownsville, getting the rocket to the pad would be difficult.  The shipping channel is separated from the launch site by several miles of wetlands.  Dredging a channel and building a dock and roadway to the pad would have to get past an awful lot of environmental and political hurdles.


Its 4.7 miles from the outlet, straight down the coast. IF they could get approval for a ramp or pier from the end of Rte 4 they could unload it from a crane barge.

Why would they build stages in Brownsville and then barge them to Boca Chica? If they are only going about 16 miles down Route 4 to the pad, road transport is straightforward.

Testing is a bit of a issue, but I wonder if BFR will even do full duration firings once they start flying often. If they can just test individual engines at McGregor and do a short static firing on the pad then they may not need a huge test stand.

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