Author Topic: SpaceX fairing  (Read 37431 times)

Offline oldAtlas_Eguy

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Re: SpaceX fairing
« Reply #20 on: 02/12/2012 03:13 pm »
There is really no restriction on the number of panels the faring can be divided into as long as the number is divisible by 2. The reason for this is that the panels can be permanently connected to create two half shells after shipment to the launch site. A design like this means the faring would be heavier than just a half shell but it would be easier to ship if it was constrained to width-height-length so that use ground transport is not overly complex.

BTW the 13m length is at max of a box trailer. So a longer length means more panels say 8 where each is ~ 13m in length giving a total faring length of ~26m. This faring would be greater than 2 times the weight of the 13m faring probably closer to 3 times. All of this means more assembly at the launch site and a higher launch risk due to assembly errors (loose or missing fasteners) but if careful these risks can be mitigated.

Offline Antares

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Re: SpaceX fairing
« Reply #21 on: 02/13/2012 01:09 am »
There is really no restriction on the number of panels the faring can be divided into as long as the number is divisible by 2.

Coooool.  3 is divisible by 2.

http://commons.wikimedia.org/wiki/File:Titan_IV_fairing_after_jettison_test.JPG
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Offline Jim

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Re: SpaceX fairing
« Reply #22 on: 02/13/2012 01:11 am »
There is really no restriction on the number of panels the faring can be divided into as long as the number is divisible by 2.

Coooool.  3 is divisible by 2.

http://commons.wikimedia.org/wiki/File:Titan_IV_fairing_after_jettison_test.JPG

I believed that is applicable to all Titan III 10' dia fairings too

Offline starsilk

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Re: SpaceX fairing
« Reply #23 on: 02/13/2012 04:13 pm »
I'm intrigued with the FH GTO capacity. The 2011 FAA study on the commercial satellite market, stated that there would be a sort of stable demand for 20 GTO commercial satellite launches per year. Roughly 1/3 upto 3.5tonnes to GTO, between 3.5tonnes to 5.4tonnes, and 1/3 bigger (around 6.3tonnes max). There has also been an upward trend on weight.
The performance of the FH to GTO intrigues me. Maintly because they had stated a lot of times that it was 19.5tonnes to a 200x35,786km x 28.5 degrees. But now they have deleted that from the FH information page. Beside, I would say that even in the case of the biggest satellites, they could take about three!
That's too much for many reasons. First, there's the risk. What would be the insurance cost! From an insurance cost POV, three launches are safer than one. So up that goes. Second, what sort of dispenser system would they have to design, and at what weight. Third, even if they got 30% of the market, that's two FH launches per year, three at most. And we would be talking about taking 100% of the most heavy satellites, the most expensive one and the ones that pay quite a premium for reliability. What's more, at 80M to 120M, they can only compete with Ariane 5 if they dual manifest.
But, since this is the fairing thread. Currently, Soyuz-ST, Proton, Sea Launch and LM-3BE are restricted to 4.1 fairings. The available 5.2m fairings commercially are Ariane 5, Atlas V and H-IIA/B (might add Delta IV, if you really wanted). And the secondary satellite (the on in the SYLDA) with the Ariane 5 (and Delta IV, if ever), would be restricted to an equivalent 4m, anyways. So with doesn't seems to be a problem. In any case, Proton-M doesn't seems to have much problem competing with the Ariane 5, so I wouldn't say the fairing width is such a problem.
So, what FH needs is a dual manifest option. That would imply at least an extra 4m to 6m on the fairing length and some SYLDA's equivalent. I think that would be the truly interesting solutions.
Thus, if FH can do 13tonnes to GTO (1500m/s deficit)

presumably they could reduce the GTO deficit instead of carrying more weight, which would give the satellite much longer lifespan (less fuel used for GSO insertion).

that assumes the satellite is using the same fuel supply for GSO insertion and station keeping, of course.

Offline oldAtlas_Eguy

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Re: SpaceX fairing
« Reply #24 on: 02/13/2012 05:00 pm »
There is really no restriction on the number of panels the faring can be divided into as long as the number is divisible by 2.

Coooool.  3 is divisible by 2.

http://commons.wikimedia.org/wiki/File:Titan_IV_fairing_after_jettison_test.JPG

I believed that is applicable to all Titan III 10' dia fairings too

Divisible by two in this instance is that the result ends in an integer and not a fraction.

The more panels that are jettisoned as separate entities the more possibilities that the jettison will fail. KISS. Titan using 3 shells was actually a foolish thing to do unless it had a very specific and necessary reason, which I believe it did for only a few of the sats that it launched for the others it was overkill. Two shells are going to be the best from a standpoint of jettison reliability and complexity. How many individually manufactured and shipped panels to the launch site that is then used to create these two shells has little to do with the jettison except in dynamic bending/warping during jettison that can cause problems.

Offline baldusi

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Re: SpaceX fairing
« Reply #25 on: 02/13/2012 05:16 pm »
presumably they could reduce the GTO deficit instead of carrying more weight, which would give the satellite much longer lifespan (less fuel used for GSO insertion).

that assumes the satellite is using the same fuel supply for GSO insertion and station keeping, of course.
I'm expecting the FH to have a GTO (1500m/s deficit)  performance of around 12 to 13 tonnes. Quite similar to the Ariane 5 ME, in fact. The great difference is explained both by the launch pad distance to equator and the low isp of the RP-1 GG Merlin Vac compared to the HM7-B or Vinci.
But I also think its price will be around 120M, not less than that (probably more). At that price if dual manifested is very cheap and can get lot's of cargo. But single manifested looses to both Proton and Ariane 5. And dual manifest needs longer fairing.

Offline spacejulien

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Re: SpaceX fairing
« Reply #26 on: 02/13/2012 06:13 pm »
Anyone got any guesses to how many components the future Falcon fairing will have?

Recall from old you-tube video that Elon Musk said the F9 PLF will have 4 panels. Is that still the plan?

Just to make things more complex: Segments are not necessarily equal separation planes. I.e. the Ariane 5 fairings are made of 4 panels (in cross section), but then pairwise riveted together, so in the end you have two half fairings with one separation plane.

And I'll hazard a guess that Falcon 9 and F9H will also have just 1 separation plane. The reasoning being as follows:

The usable (net) diameter of 15 ft (4.57 m) of the shuttle cargo bay has since become an industry standard. But only really large satcoms need this width, the small and middle class need only 4.0 m diameter.

I.e. Ariane 5 uses the SYLDA system (which offers the lower P/L only 4.0 m diameter) instead of the SPELTRA system (which would offer both passengers 4.57 m diameter, but weighs more).

Also, as pointed out above, the F9H would loft

[...] They had stated a lot of times that it was 19.5tonnes to a 200x35,786km x 28.5 degrees. [...] Thus, if FH can do 13tonnes to GTO (1500m/s deficit) [...]

which is maybe a metric ton more to GTO than the Ariane 5 evolution currently under development. It is planned to lengthen fairing + SYLDA for Ariane 5 ME, but keep the diameter.

So technically there seems to be no need to increase the fairing diameter in the foreseeable future.

Also, no satellte manufacturer/customer would build a comsat that would fit onto one launcher only (would be a bad negotiation strategy for launch costs).

Thus net 4.57 m diameter (gross 5.X m) can safely be assumed sufficient for the years to come.

And thus as one separation plane is proven feasible and simplest I expect also the F9H fairing to be 5.2 m (as F9) in two half shells with one separation plane.

But, there might be interest to have a reduced size fairing for F9 to improve it's performance due to reduced drag and reduced fairing mass. But on the other hand cost reduction is best achieved by commonality and high quantity production, so there'll probably be no dedicated F9 small fairing.
« Last Edit: 02/13/2012 06:16 pm by spacejulien »
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Offline simonbp

Re: SpaceX fairing
« Reply #27 on: 02/13/2012 06:30 pm »
The usable (net) diameter of 15 ft (4.57 m) of the shuttle cargo bay has since become an industry standard.

That is a really interesting point; I wonder how long it will last? Standards like that can have very long lives; e.g. Roman cart tracks roughly determined the railway gauge initially used in Britain, and therefore most of Europe and North America today. I wonder if 100 years from now Shuttle will be mainly remembered as the vehicle that set the "15-ft standard payload width"...
« Last Edit: 02/13/2012 06:31 pm by simonbp »

Offline baldusi

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Re: SpaceX fairing
« Reply #28 on: 02/13/2012 09:43 pm »
The usable (net) diameter of 15 ft (4.57 m) of the shuttle cargo bay has since become an industry standard.

That is a really interesting point; I wonder how long it will last? Standards like that can have very long lives; e.g. Roman cart tracks roughly determined the railway gauge initially used in Britain, and therefore most of Europe and North America today. I wonder if 100 years from now Shuttle will be mainly remembered as the vehicle that set the "15-ft standard payload width"...
Actually, I think the 15ft was a previous standard (like Titan) for the NROL payloads.
But current 4.57m is sort of restricted by modes of transport. The AN-124 has a 4.4m x 6.4m bay. You can usually ship the solar panels separately and have enough clearance for the shipping container and GSE. But going over that size, would basically mean vessel transport. I know about the Airbus Beluga and the Boeing Dreamlifter. But you have to think of all the production chain.
The factory high bays can probably take it. But then you need an anechoic chamber, an environmental test chamber, an acoustic test chamber. Most of them are designed for 3.9m or 4.55m standard. And you have to transport from the factory to each test site.
As always, the only reason I would expect this to change is for some military or intelligence requirement that would pay top dollar. Which wouldn't seem like a possibility for the next five years.

Offline A_M_Swallow

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Re: SpaceX fairing
« Reply #29 on: 02/13/2012 09:55 pm »
Actually, I think the 15ft was a previous standard (like Titan) for the NROL payloads.
But current 4.57m is sort of restricted by modes of transport. The AN-124 has a 4.4m x 6.4m bay. You can usually ship the solar panels separately and have enough clearance for the shipping container and GSE. But going over that size, would basically mean vessel transport. I know about the Airbus Beluga and the Boeing Dreamlifter. But you have to think of all the production chain.
The factory high bays can probably take it. But then you need an anechoic chamber, an environmental test chamber, an acoustic test chamber. Most of them are designed for 3.9m or 4.55m standard. And you have to transport from the factory to each test site.
As always, the only reason I would expect this to change is for some military or intelligence requirement that would pay top dollar. Which wouldn't seem like a possibility for the next five years.

The SLS may introduce a new fairing size, possibly to contain large lunar landers.

Offline pippin

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Re: SpaceX fairing
« Reply #30 on: 02/13/2012 10:15 pm »
Which of course are the real bread-and-butter market for satcom manufacturers.

Offline ChefPat

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Re: SpaceX fairing
« Reply #31 on: 02/14/2012 10:56 am »

The SLS may introduce a new fairing size, possibly to contain large lunar landers.
I have zero faith SLS will be anything but a pork money pit.
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Offline Ben the Space Brit

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Re: SpaceX fairing
« Reply #32 on: 02/14/2012 11:04 am »
Purely FWIW, actual and probable demand seems to leave a requirement for two 'families' of fairing sizes: Approximately 5m for commercial satellite launch and approximately 7-8m for HSF cargo launch.
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Offline baldusi

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Re: SpaceX fairing
« Reply #33 on: 02/14/2012 11:24 am »
Purely FWIW, actual and probable demand seems to leave a requirement for two 'families' of fairing sizes: Approximately 5m for commercial satellite launch and approximately 7-8m for HSF cargo launch.
And which payload would require the big fairing? I don't see any funded project. Everything is in studies. Nothing will get done before the SLS. And, at least until 2021, it will fly Orion. Let's not kid ourselves.
SpaceX might use a 4.1m fairing for the Falcon 9 to get extra performance to GTO. Or a longer 5m with dual manifest capability for the FH. Nothing more for the foreseeable future. Let's remember that even most missions on EELV use the 4m fairing.

Offline Ben the Space Brit

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Re: SpaceX fairing
« Reply #34 on: 02/14/2012 11:39 am »
Purely FWIW, actual and probable demand seems to leave a requirement for two 'families' of fairing sizes: Approximately 5m for commercial satellite launch and approximately 7-8m for HSF cargo launch.
And which payload would require the big fairing? I don't see any funded project. Everything is in studies.

That's why I said "probable".

Still, you have to admit that a large HSF module, say a lander, would require a large fairing.  If your plans include HSF exploration (which SpaceX's apparently do), then you need to be planning a large fairing.  It's a long way off but I'd be surprised if there isn't a 6-7m fairing option for FH at least being studied.
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Offline Blackjax

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Re: SpaceX fairing
« Reply #35 on: 02/14/2012 02:31 pm »
Still, you have to admit that a large HSF module, say a lander, would require a large fairing.  If your plans include HSF exploration (which SpaceX's apparently do), then you need to be planning a large fairing.  It's a long way off but I'd be surprised if there isn't a 6-7m fairing option for FH at least being studied.

This is only true if you have a strong bias against higher flight rates and assembling things in space.  NASA has traditionally viewed things this way but I think it is not prudent to assume as a foregone conclusion that SpaceX would approach things with the same attitude.

Offline cuddihy

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Re: SpaceX fairing
« Reply #36 on: 02/14/2012 03:33 pm »
The usable (net) diameter of 15 ft (4.57 m) of the shuttle cargo bay has since become an industry standard.

That is a really interesting point; I wonder how long it will last? Standards like that can have very long lives; e.g. Roman cart tracks roughly determined the railway gauge initially used in Britain, and therefore most of Europe and North America today. I wonder if 100 years from now Shuttle will be mainly remembered as the vehicle that set the "15-ft standard payload width"...

Urban Legend Historicism alert!  The reality of RR gauge size is that several different widths started out in Britain but the one that won out won out for a variety of engineering and economic reasons, among them that that width was narrow enough to permit reasonable turn radii and wide enough to minimize derailing. Like other engineering decisions, it was the best economic tradeoff that meets at the intersection of two curves going in opposite directions, along with dominance of the most widespread. (simplicity of track construction vs limiting de-railing). The similarity to roman cart track widths, if it exists, is coincidental. (the main question being...which Roman carts? The 2nd century BC Pompeii ones? The 1st century Britain? The 3rd century Aquileia? Standard is not as standard as legend indicates... Although they are all reasonably close for obvious engineering reasons.)

The shuttle component max size may have been set by rail tunnel size, but that's a pretty generous 'standard.'
« Last Edit: 02/14/2012 03:38 pm by cuddihy »

Offline baldusi

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Re: SpaceX fairing
« Reply #37 on: 02/14/2012 03:42 pm »
Upto now I have been saying:
SpaceX has to demonstrate the 5m fairing but:
1) A 4.1m fairing for F9 is more in line with the needs of the commercial market (GTO to 3.6tonnes). The extra weight and drag could make a difference in the 100kg order, which might mean being able to tackle an order or not.
2) The current 5m is not enough to make the FH dual manifested, and thus, is too expensive. FH would need an option of a longer fairing with a dual deployment system.
Those are actual and current needs of the market. The rest is fanboy wet dreams.

Offline Ben the Space Brit

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Re: SpaceX fairing
« Reply #38 on: 02/14/2012 04:22 pm »
Still, you have to admit that a large HSF module, say a lander, would require a large fairing.  If your plans include HSF exploration (which SpaceX's apparently do), then you need to be planning a large fairing.  It's a long way off but I'd be surprised if there isn't a 6-7m fairing option for FH at least being studied.

This is only true if you have a strong bias against higher flight rates and assembling things in space.  NASA has traditionally viewed things this way but I think it is not prudent to assume as a foregone conclusion that SpaceX would approach things with the same attitude.

I don't want the thread to go OT, so I'll just make one technical point - the width of the fairing has little to do with on-orbit assembly.  It is simply the alternative to building a narrow, high or narrow, long vehicle.  JWST has also demonstrated just how problematic and elaborate folding TPS can be.


@ baldusi,

The real issue is cost.  If you can really only afford one fairing size right now, a 5m-class one is the one you want because you can handle wider payloads, should any come your way.  Also building a 4m-class PLF would be an extra cost that isn't really a necessity.  Not all companies have pockets as deep as ULA.

Regarding the PLF length, I read somewhere that SpaceX is claiming a variable-length PLF, should there be customer interest to justify its development.  Additionally, has SpaceX ever claimed it wishes to do Ariane-5-style dual launches or is this just a forum assumption of what they will do with FH?
« Last Edit: 02/14/2012 04:25 pm by Ben the Space Brit »
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Offline Jim

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Re: SpaceX fairing
« Reply #39 on: 02/14/2012 04:39 pm »
  JWST has also demonstrated just how problematic and elaborate folding TPS can be.


No, it hasn't.  Point out one problem.
« Last Edit: 02/14/2012 04:39 pm by Jim »

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