Author Topic: 9m ITS Development Updates and Discussion Thread  (Read 124077 times)

Offline cambrianera

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #760 on: 09/30/2017 01:19 PM »
There are problems with the Saturn I approach. 

There is a lot of empty space between the tubes that could hold fuel or lox. 

There is a lot of metal in the 3.7m tubes that add weight that a single large diameter cylinder would not. 

The Saturn I was quickly cobbled together due to the need to beat the Russians to the moon and test Apollo.  SpaceX has no need to do this, they already have a capsule to fit F9 and F9 is as powerful as Saturn IB as far as payload to LEO. 

The extra weight of the tubes will take away from payload.  Also, switching to Raptor methane engines requires more fuel than kerosene.  A single 9m core can hold more fuel than a clustered group of F9 cores.  7 F9 cores probably could only supply 14 Raptor engines.  A 9m core can supply probably 19-21 engines for more power and payload mass.

The booster rocket will not be as hard to make as the ITS spacecraft which goes to orbit, then lands back on Earth.  Compared to ITS spaceship, the booster will be easy.  They already know how to land a booster.  So making a 9m core with engines and landing it will be very similar to F9.

Multiple smaller vessels can have the same mass of a single bigger vessel.
Looking at Barlow's formula it's easy to realize that mass of a vessel (at same internal pressure) grows linearly with volume, therefore with mass of content.
It follows that many small, thinner vessels can have the same mass of a single, big & thicker vessel for the same total volume.
Personally I think that a bundled construction has some advantages, specially for a second stage.
Oh to be young again. . .

Offline launchwatcher

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #761 on: 09/30/2017 01:51 PM »
.... the delta wing control surfaces that are completely missing in all the renders.
you can see what appear to be control surfaces in the rear view slide here:

http://forum.nasaspaceflight.com/index.php?topic=43839.msg1728253#msg1728253

which shows that the wings are open to the rear, with the split-flap control surfaces only on the ventral face of the wing.

I don't think we see the belly side of the BFS in any of the animations..

Offline cscott

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #762 on: 09/30/2017 02:42 PM »


So I really wouldn't take any these CGI renders for more than they are. They cannot seriously be depicting an actual design that is going to start construction in 6 months.

Worth noting that promo-quality CGI models are fundamentally different from engineering drawings.  The details on one imply very little about the presence/absence/completeness of the other; one would naively expect that, for efficiency's sake, details would only be added to the CGI models if they were needed to illustrate some particular point in the story told by the animation.
  --scott

Offline Nibb31

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #763 on: 09/30/2017 03:52 PM »


So I really wouldn't take any these CGI renders for more than they are. They cannot seriously be depicting an actual design that is going to start construction in 6 months.

Worth noting that promo-quality CGI models are fundamentally different from engineering drawings.  The details on one imply very little about the presence/absence/completeness of the other; one would naively expect that, for efficiency's sake, details would only be added to the CGI models if they were needed to illustrate some particular point in the story told by the animation.
  --scott

Which is basically what I said: the CGI renders differ from the actual design that Musk claims will be going into production in 6 months. Landing gear, solar panels, or control surfaces aren't "details". They are fundamental parts of the design that have been left out from these renders, so we shouldn't be reading too much into them.

At least we aren't getting the ridiculous windows and the 50 cm nozzle ground clearance from last years' presentation.

Online Lars-J

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #764 on: 09/30/2017 04:40 PM »


So I really wouldn't take any these CGI renders for more than they are. They cannot seriously be depicting an actual design that is going to start construction in 6 months.

Worth noting that promo-quality CGI models are fundamentally different from engineering drawings.  The details on one imply very little about the presence/absence/completeness of the other; one would naively expect that, for efficiency's sake, details would only be added to the CGI models if they were needed to illustrate some particular point in the story told by the animation.
  --scott

Yep. And it is also worth noting that these renderings of the updated design are actually *less detailed* then the ones we saw last year of the old design. I think they were deliberate about not revealing as much.

Offline ZachF

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #765 on: 09/30/2017 05:19 PM »


So I really wouldn't take any these CGI renders for more than they are. They cannot seriously be depicting an actual design that is going to start construction in 6 months.

Worth noting that promo-quality CGI models are fundamentally different from engineering drawings.  The details on one imply very little about the presence/absence/completeness of the other; one would naively expect that, for efficiency's sake, details would only be added to the CGI models if they were needed to illustrate some particular point in the story told by the animation.
  --scott

Yep. And it is also worth noting that these renderings of the updated design are actually *less detailed* then the ones we saw last year of the old design. I think they were deliberate about not revealing as much.

They don't want nefarious pixel-measurers going over their plans...  ;)

Offline Norm38

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #766 on: 09/30/2017 05:51 PM »
But yet last year Musk said that the 12m renderings came directly from the engineering CAD models. And I bet the same is true of 9m. That doesn't mean that every detail is present, but that all the dimensions and major features align.

Online speedevil

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #767 on: 09/30/2017 09:00 PM »
Anyone seen a diagram of the BFS and the Shuttle side-by-side? Too early?

Not at all, let's paint BFS in Shuttle color scheme with NASA logo too, I bet there're still Shuttle lovers in NASA.

From 2030 wikipedia. "It turned out that the key to cancelling SLS and funding BFR by congress was the shuttle-derived artwork".

Offline su27k

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #768 on: 10/01/2017 07:10 AM »
Anyone seen a diagram of the BFS and the Shuttle side-by-side? Too early?

Not at all, let's paint BFS in Shuttle color scheme with NASA logo too, I bet there're still Shuttle lovers in NASA.

From 2030 wikipedia. "It turned out that the key to cancelling SLS and funding BFR by congress was the shuttle-derived artwork".

LOL, SpaceX is pretty far behind in terms of using arkwork to impress congress, they need to catch up.

Offline lamontagne

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #769 on: 10/07/2017 04:12 PM »
Has there been any mention of radiators on the BFS?

I've always expected them to be behind the solar panels, but are there other solutions?  And dos it make sense to pipe the coolant all the way down to where the solar panels are?

The space shuttle had large radiators in the doors, but that will not be the case for the BFR spaceship.
So where are the radiators going to be?


Offline John Alan

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #770 on: 10/07/2017 04:22 PM »
Has there been any mention of radiators on the BFS?

I've always expected them to be behind the solar panels, but are there other solutions?  And dos it make sense to pipe the coolant all the way down to where the solar panels are?

The space shuttle had large radiators in the doors, but that will not be the case for the BFR spaceship.
So where are the radiators going to be?

I have seen no mention myself...

Myself... I have wondered about conformal radiators mounted to the ship top surface (180* from the heat shield centerline)
If made tough enough to take some FOD and ground handing impacts... would that be a workable solution?
If you are running hot... turn the ship to deep space... reorient the solar panels to sun...
Just my two cents ...  ;)

Offline Kaputnik

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #771 on: 10/07/2017 04:45 PM »
Can't help thinking that the massive propellant tanks have to be part of the cooling system somehow. You could dump heat there and then compress the boiloff down to put it into the header tanks.
Which means that the 'F' in BFR/BFS stands for 'fridge'.
Waiting for joy and raptor

Offline lamontagne

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Re: 9m ITS Development Updates and Discussion Thread
« Reply #772 on: 10/07/2017 06:24 PM »
Can't help thinking that the massive propellant tanks have to be part of the cooling system somehow. You could dump heat there and then compress the boiloff down to put it into the header tanks.
Which means that the 'F' in BFR/BFS stands for 'fridge'.
Nope, too much compression work.  Compression creates heat, and you need to radiate away the compression work as well and high pressure compression is incredibly inefficient as far as processes go.

AFAIK no one has used compression cooling on space vehicles.  The shuttle and ISS both use/used fluid circulation and fairly cool radiators, taking advantage of low radiative temperatures in space.  The shuttle also used direct evaporation to space while it was launching and until the radiators deployed.

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