Author Topic: SpaceX fairing  (Read 37426 times)

Offline krytek

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SpaceX fairing
« on: 02/09/2012 05:38 pm »
There is some talk about the a SpaceX fairing which is needed to launch some commercial satellites, in connection with the asiasat contract.
I remember it was also discussed some time ago, can't find it now.


I would really appreciate a few details.

Offline dcporter

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Re: SpaceX fairing
« Reply #1 on: 02/09/2012 05:51 pm »
Here's corrodednut's original post on the asiasat thread:

I hope no one minds if I copy-and-paste this relevant tidbit, which has not been reported elsewhere:

"The commercial Falcon 9 missions require the development of the booster's 17-foot-diameter payload fairing... the company expects to fly the nose shroud on a Falcon 9 rocket later this year, according to Kirstin Brost, a SpaceX spokesperson."

http://spaceflightnow.com/news/n1202/08spacexasiasat/

The SpaceX website currently lists a 5.2 meter fairing for F9:

spacex.com/falcon9.php

Offline simonbp

Re: SpaceX fairing
« Reply #2 on: 02/09/2012 06:13 pm »
They do have at least one faring that they were going to use on the first flight (but opted for the Dragon STA instead).

http://www.spacex.com/photo_gallery.php

Offline baldusi

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Re: SpaceX fairing
« Reply #3 on: 02/09/2012 06:51 pm »
They still have to actually launch it. Orbital has had its fair share of trouble with the fairing, and, as of today, SPX has zero experience.

Online Robotbeat

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Re: SpaceX fairing
« Reply #4 on: 02/09/2012 06:58 pm »
They still have to actually launch it. Orbital has had its fair share of trouble with the fairing, and, as of today, SPX has zero experience.
Not true. Both of SpaceX's first two successful orbital flights had fairings which deployed successfully:

"The two halves of the fairing (nose cone) of the SpaceX Falcon 1 Flight 4 vehicle fall back towards Earth. As the vehicle now travels in the vacuum of space, it no longer requires the streamlining provided by the fairings."

"The fairing halves fall gracefully back towards Earth, to burn up as they reenter the atmosphere."

and for RAZAKSAT's successful launch to orbit:
"The fairing halves fall cleanly away from the vehicle."
« Last Edit: 02/09/2012 07:03 pm by Robotbeat »
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Offline baldusi

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Re: SpaceX fairing
« Reply #5 on: 02/09/2012 07:13 pm »
True, but those where 1.7m biconic metallic fairings and the 5.2m seems to be a von Kármán ogive composite.
« Last Edit: 02/09/2012 07:14 pm by baldusi »

Online Robotbeat

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Re: SpaceX fairing
« Reply #6 on: 02/09/2012 07:40 pm »
True, but those where 1.7m biconic metallic fairings and the 5.2m seems to be a von Kármán ogive composite.
You said "zero experience." ;)
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Offline Comga

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Re: SpaceX fairing
« Reply #7 on: 02/09/2012 08:36 pm »
They still have to actually launch it. Orbital has had its fair share of trouble with the fairing, and, as of today, SPX has zero experience.
Not true. Both of SpaceX's first two successful orbital flights had fairings which deployed successfully:

The fairing was also deployed successfuly on the second Falcon 1 launch.  I believe that the fairing halves were successfully ejected on the third Falcon 1 launch as the damaged second stage tumbled.  The fairing even came off on the first Falcon 1 launch.  :-P
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline baldusi

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Re: SpaceX fairing
« Reply #8 on: 02/09/2012 09:03 pm »
Clearly my words were not well chosen. I mean that it's a fairing with zero flight history. Even the flight environment of the Falcon isn't known (only simulated) with this fairing (which they could have know and demonstrated had they used it in the inaugural flight).
But, if I where them, I'd try to keep all six block 1 Falcon for CRS, and start the commercial service with block 2 (Merlin 1D), this way they would accumulate flight history for the same configuration.

Online kevin-rf

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Re: SpaceX fairing
« Reply #9 on: 02/09/2012 11:10 pm »
The group opinion at the time was the fairing was not far enough along and would have delayed the falcon 9 flight, so the boiler plate dragon was used instead. It was also the low risk option.
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Offline majormajor42

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Re: SpaceX fairing
« Reply #10 on: 02/11/2012 07:49 pm »
They do have at least one faring that they were going to use on the first flight (but opted for the Dragon STA instead).

http://www.spacex.com/photo_gallery.php

So is that fairing in the picture available as flight hardware? Is it ready to go now?
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Online ugordan

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Re: SpaceX fairing
« Reply #11 on: 02/11/2012 07:54 pm »
One half of that fairing could be seen sitting outside at LC-40 pad for months. So probably not exactly flightworthy...

Edit: actually, scratch that, it looks like both halves ended up outside at one point.
« Last Edit: 02/11/2012 08:01 pm by ugordan »

Offline krytek

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Re: SpaceX fairing
« Reply #12 on: 02/11/2012 08:47 pm »
Thank you guys.
Somehow I initially thought it was supposed to be some sort of hammerhead fairing, probably mixed it up with something from the advanced section...

So what are the considerations and trouble spots when someone goes to design a payload fairing like that?

Online Robotbeat

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Re: SpaceX fairing
« Reply #13 on: 02/11/2012 09:42 pm »
One half of that fairing could be seen sitting outside at LC-40 pad for months. So probably not exactly flightworthy...

Edit: actually, scratch that, it looks like both halves ended up outside at one point.
LOL, yeah. Probably was more of a mock-up anyway, though.
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Offline spectre9

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Re: SpaceX fairing
« Reply #14 on: 02/11/2012 10:32 pm »


First 35 seconds. Enjoy  8)

Offline Rhyshaelkan

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Re: SpaceX fairing
« Reply #15 on: 02/11/2012 10:36 pm »
I wonder what is the largest size one could conceivably make the fairing for a F9/FH without adding stupid aerodynamic loads. Do they increase at a 3:1 ratio? 4:1?

Heat shields for an aero-breaking OTV are large, even if you have a folding design concept. Bulky but not entirely heavy.
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Offline Zed_Noir

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Re: SpaceX fairing
« Reply #16 on: 02/11/2012 10:59 pm »
I wonder what is the largest size one could conceivably make the fairing for a F9/FH without adding stupid aerodynamic loads.

Probably about the same that you could fitted on the Atlas V. IIRC from the AV user guide about 7 meter diameter and lots of additional cost..

Offline Antares

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Re: SpaceX fairing
« Reply #17 on: 02/12/2012 12:38 am »
You could make a fairing so big you have no payload and/or are able to fly sideways. You need to specify more constraints.
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Offline baldusi

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Re: SpaceX fairing
« Reply #18 on: 02/12/2012 01:04 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)

Offline Zed_Noir

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Re: SpaceX fairing
« Reply #19 on: 02/12/2012 02:27 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?

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 »

Offline go4mars

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Re: SpaceX fairing
« Reply #40 on: 02/14/2012 04:41 pm »
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?
Yes.  IIRC, Shotwell mentioned it almost 2 years ago. 
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Offline baldusi

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Re: SpaceX fairing
« Reply #41 on: 02/14/2012 05:42 pm »
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.
I seriously doubt that developing a smaller fairing is very expensive. In fact, it might well be the cheapest part of the rocket. And it is quite commercial. Ariane 5, Vega, and Atlas V all use Ruag and Antares uses  fairings, I know Delta IV offered the SYLDA, so it seems to be a COTS piece of equipment. Please note that the separation mechanism, sound suppression inlay, connectors, etc. are mostly the same.
In any case, it might well be the cheapest upgrade available for the money. Remember that a 4m fairing has 38% less drag losses. That's a lot. So, in every 5.2m launch that would fit a 4m they are paying that cost. That also translates into strain on the thrust structure. Less strain allows for more aggressive ascent profiles. And since Falcon can fly with 3.6m Dragon, and 5.2m fairing, flying with 4m should be easy. An there's weight issues. In the case of the Atlas V, the 5m medium fairing is 1700kg heavier than the 4m. And the F9 separates the fairing while the US is firing, so it does adds an extra weight.
What's more, I think very few commercial satellites need 5m. If you need that you can only use Arian 5 (120M), Atlas V(180M) or H-IIA (I don't know how much). If you can use 4m, then you can use Proton (80M), Sea Launch (around 70M?), Soyuz-ST, LM-3BE. What do you think satellite operators usually chose? In particular, Atlas V and H-IIA/b have zero share in the commercial market. And only five satellites per year use the upper part of the Arian 5. So at most (and I guess is much less) there are five commercial satellites that might need 5m.
Look into the fairing sizes for DoD, too. Delta IV did 11 4m launches and 2 5m launches, plus the 5 heavies, of course. Atlas IV is 19 of 4m vs 9 of 5m. In just 3 (the two OTV plus one NROL) of the 11 launches (sans heavy) of 5m F9 could match the performance of the LV. So overall it would seem that they would rather get the extra performance
Quote
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?
I think it was proposed somewhere. But I'm stating that as an economist. The FH is too expensive unless you dual manifest for at least 80% of the GTO market (that's about 16 satellites/yr, btw). Without dual manifest it's too expensive. Will be dirty cheap if they do, though.

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Re: SpaceX fairing
« Reply #42 on: 02/14/2012 05:54 pm »
Keep in mind drag losses are more significant for smaller rockets. Wouldn't make much of a difference for larger rockets (Falcon Heavy in particular).
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Offline baldusi

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Re: SpaceX fairing
« Reply #43 on: 02/14/2012 06:47 pm »
Keep in mind drag losses are more significant for smaller rockets. Wouldn't make much of a difference for larger rockets (Falcon Heavy in particular).
The Atlas V guide says that the GTO (1800m/s deficit) difference between a 400 and a 500 is almost 950kg. A 401 to a 501 is 700kg. Between a Delta IV (4,2) and a (5,2) is 1,076kg. I couldn't get the numbers on any other LV (the H-IIA didn't shows for same configuration, and the Ariane 5 doesn't offers 4m). Those are not trivial numbers. And going from 3.5tonnes to 4.5tonnes means reaching 35% vs 50% of the market.

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Re: SpaceX fairing
« Reply #44 on: 02/14/2012 06:53 pm »
Those are not trivial numbers.

Nor are they solely due to higher drag. A bigger fairing weighs more, there's also additional hardware for Atlas in the 5xx variant like the CFLR.

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Re: SpaceX fairing
« Reply #45 on: 02/14/2012 06:59 pm »
Keep in mind drag losses are more significant for smaller rockets. Wouldn't make much of a difference for larger rockets (Falcon Heavy in particular).
The Atlas V guide says that the GTO (1800m/s deficit) difference between a 400 and a 500 is almost 950kg. A 401 to a 501 is 700kg. Between a Delta IV (4,2) and a (5,2) is 1,076kg. I couldn't get the numbers on any other LV (the H-IIA didn't shows for same configuration, and the Ariane 5 doesn't offers 4m). Those are not trivial numbers. And going from 3.5tonnes to 4.5tonnes means reaching 35% vs 50% of the market.
The larger fairings are also pretty heavy. In the case of Atlas V, the larger fairing covers the entire second stage as well. Falcon 9 uses a carbon-fiber fairing which supposedly is very, very light (compared to the fairings on competing rockets... of course, the Falcon 9 hasn't flown, yet!).

My statement about how drag losses are less significant for larger rockets is supposed to be a general statement, anyway. Falcon 1 has far higher drag losses than Saturn V, for instance. Gravity losses tend to be a much bigger concern for larger rockets. In some ways, gravity losses and drag losses trade against each other... if your rocket has a relatively low T/W through the lower atmosphere, it will have lower drag losses but higher gravity losses. If it's a small solid-rocket-based launcher, you'll have high drag losses but low gravity losses.

At the large end of the spectrum for mostly-cylindrical rockets, the taller your rocket (for the same propellant and chamber pressure), the larger your chamber throat must be in relation to your rocket's diameter, thus it's harder to get as much T/W (so will tend to have higher gravity losses), but a taller rocket also has a smaller frontal-area-to-total-mass ratio so its drag losses are less than for a shorter rocket. That's the general picture for largish rockets, at least.
« Last Edit: 02/14/2012 07:06 pm by Robotbeat »
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Offline pippin

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Re: SpaceX fairing
« Reply #46 on: 02/14/2012 07:07 pm »
Falcon 9 uses a carbon-fiber fairing which supposedly is very, very light (compared to the fairings on competing rockets... of course, the Falcon 9 hasn't flown, yet!).
Plus the "competing rockets" also use fairing that are mainly made from carbon. If you do it right, a carbon-composite structure can be just as light or even lighter than a purely carbon one, carbon fiber is good for tensile loads, need lots of filler for compression loads.

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Re: SpaceX fairing
« Reply #47 on: 02/14/2012 07:09 pm »
Falcon 9 uses a carbon-fiber fairing which supposedly is very, very light (compared to the fairings on competing rockets... of course, the Falcon 9 hasn't flown, yet!).
Plus the "competing rockets" also use fairing that are mainly made from carbon. If you do it right, a carbon-composite structure can be just as light or even lighter than a purely carbon one, carbon fiber is good for tensile loads, need lots of filler for compression loads.
To be honest, I'm not entirely sure whether Falcon 9's fairing is carbon fiber or carbon composite, just that it isn't plain aluminum alloy and is claimed (by Elon) to be lighter than competing ones.
« Last Edit: 02/14/2012 08:30 pm by Robotbeat »
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Offline pippin

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Re: SpaceX fairing
« Reply #48 on: 02/14/2012 07:13 pm »
To be honest, I'm not entirely sure whether Falcon 9's fairing is carbon fiber or carbon composite, just that it isn't aluminum and is claimed (by Elon) to be lighter than competing ones.

Well, the question is whether it's already in existence so one could tell at all :)
Ariane 5 and Atlas 5 use carbon composite, though, and RUAG (the maker of these fairings) has quite a position in the market and they didn't get it for their overly heavy designs.

Might well be that SpaceX has a prototype that's the lightest one around but then the next question is whether it meets the same requirements as the more heavy competing ones.
« Last Edit: 02/14/2012 07:15 pm by pippin »

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Re: SpaceX fairing
« Reply #49 on: 02/14/2012 07:16 pm »
Light, but strong enough to handle the loads at maxQ. That is the danger for any new light weight fairing design.
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Offline pippin

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Re: SpaceX fairing
« Reply #50 on: 02/14/2012 07:18 pm »
Plus all the vibration modes. Which might as well be an advantage for SpaceX since they don't use solids.

Offline baldusi

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Re: SpaceX fairing
« Reply #51 on: 02/14/2012 07:20 pm »
Originally I had stated that they could earn some extra 100kg to 200kg from a smaller fairing. Looking into those numbers, even if not so critical, I'm inclined to think that it's going to be more than that.
And let's remember that the F9 is supposed to have a T/W of 1.45, so the drag losses should have an impact. Of course, if the new F9 block II has a T/W of 1.19, as it briefly appeared on their site after the FH presentation, then it might be less critical. But it sure should weight less, that should give some saving.

Offline oldAtlas_Eguy

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Re: SpaceX fairing
« Reply #52 on: 02/14/2012 08:27 pm »
The interstage seems to be a carbon fiber aluminum core composite. So the faring would probably be somthing similar.

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Re: SpaceX fairing
« Reply #53 on: 02/15/2012 01:57 am »
To be honest, I'm not entirely sure whether Falcon 9's fairing is carbon fiber or carbon composite, just that it isn't plain aluminum alloy and is claimed (by Elon) to be lighter than competing ones.

I'd bet a steak dinner that SpaceX isn't entirely sure what it's made of either. ;)
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Re: SpaceX fairing
« Reply #54 on: 02/15/2012 09:21 am »
To be honest, I'm not entirely sure whether Falcon 9's fairing is carbon fiber or carbon composite, just that it isn't plain aluminum alloy and is claimed (by Elon) to be lighter than competing ones.

I'd bet a steak dinner that SpaceX isn't entirely sure what it's made of either. ;)

LOL. And after the Taurus debacle, one wonders if Orbital is sure what the Antares fairing is made of.

Offline go4mars

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Re: SpaceX fairing
« Reply #55 on: 02/15/2012 05:00 pm »
  JWST has also demonstrated just how problematic and elaborate folding TPS can be.
No, it hasn't.  Point out one problem.
Relative Price. 
http://forum.nasaspaceflight.com/index.php?topic=23637.msg677193#msg677193

Now that it's $8.5 billion instead of $6.5, it's an even bigger problem. 
« Last Edit: 02/15/2012 05:01 pm by go4mars »
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Offline baldusi

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Re: SpaceX fairing
« Reply #56 on: 02/15/2012 05:19 pm »
  JWST has also demonstrated just how problematic and elaborate folding TPS can be.
No, it hasn't.  Point out one problem.
Relative Price. 
http://forum.nasaspaceflight.com/index.php?topic=23637.msg677193#msg677193

Now that it's $8.5 billion instead of $6.5, it's an even bigger problem. 
Do you think that it went out of budget because of the opening system?
I really doubt it. They could have stated that they needed a bigger fairing. I'm sure Raug and Arianespace would gladly make a bigger fairing for less than 200M. Of course ULA could have pitched a Delta IV plus a bigger fairing. Both LV have 5m bodies, so they could go to 8.4m relatively easy. Again, somewhere between 100M to 500M extra cost.
But that was not the point. The JWST has specification so out of what's currently available, that they had to use small mirrors and active optics. They had to qualify everything for 20K working temperature (including sensors). They had to develop the shade.
When you look at all, the opening system wasn't that much extra complication, since they needed to be able to adjust all the mirrors due to thermal expansion. And as I said, going monolithic could have meant at most 500M in vehicle development. So it was not the cause. The problem was that every single piece was a couple of technology generation ahead of the state of the art. The folding mechanism was simply never done, not ahead of the technology curve. In fact, I would ask you how do they fit comm sats and spy sats within current fairings.

Offline go4mars

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Re: SpaceX fairing
« Reply #57 on: 02/15/2012 06:02 pm »
Do you think that it went out of budget because of the opening system?
NASA claim.  Not mine.   

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090043018_2009044057.pdf

"Ares V would enable the launch of a simpler 6-meter monolithic mirror with the same or better light-gathering power while producing a 30 per cent savings in overall mission development cost by reducing the need for stowage and deployment hardware and testing. "
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Offline baldusi

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Re: SpaceX fairing
« Reply #58 on: 02/15/2012 06:14 pm »
Do you think that it went out of budget because of the opening system?
NASA claim.  Not mine.   

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090043018_2009044057.pdf

"Ares V would enable the launch of a simpler 6-meter monolithic mirror with the same or better light-gathering power while producing a 30 per cent savings in overall mission development cost by reducing the need for stowage and deployment hardware and testing. "
NASA is big. That is the claim of the ones trying to save the sinking ship that was Ares V when it was clear it was going to be cancelled. Ask the actual engineers and scientist doing telescopes.

Offline go4mars

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Re: SpaceX fairing
« Reply #59 on: 02/15/2012 06:32 pm »
NASA is big. That is the claim of the ones trying to save the sinking ship that was Ares V when it was clear it was going to be cancelled. Ask the actual engineers and scientist doing telescopes.
Are you proposing that they made up the 30% number?   
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Re: SpaceX fairing
« Reply #60 on: 02/15/2012 06:34 pm »
I share baldusi’s point here.

First, the cost saving given in the paper referenced by go4mars [1] is not justified at all, no sources, no cost breakdown whatsoever. Also, this paper has been published by an ARES projects planning manager in October 2009, just when the Augustine commission recommended to toss it.

Second, a 6 m monolithic mirror is not just driving fairing size. If you want to avoid adaptive optics to have the cost benefit you need a very sturdy monolithic mirror. That has its weight. For comparison, the SOFIA telescope has a diameter of 2.7m and weighs 15.4 metric tons [2]. Scale that up gives you 15.4*(6/2.7)^2=76mT. Even if you divide by factor two (space-, not aircraft-HW) you’ll end up with 38 mT. Other reference, the largest monolithic mirror without adaptive optics has 4.2m diameter and weighs 16.5 mT [3], so factor two for 6 m diameter plus spacecraft and sunshield. Acc. to [1], fig. 6 this would have been within the P/L capability of ARES V to Sun-Earth-L2, but is definitely outside Ariane 5 and Falcon Heavy capabilities. So stop arguing about the fairing diameter as limiting factor using JWST as an example, esp. in a Falcon thread.
Folding mechanisms are state of the art, the telescope’s allowed mass is the limiting factor. This made the active mirror alignment necessary, even if it were monolithic, and that drove (drives) the cost.

[1] http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090043018_2009044057.pdf
[2] http://www.nasa.gov/pdf/503322main_SOFIA%20_QuickFacts2.pdf
[3] http://en.wikipedia.org/wiki/William_Herschel_Telescope
« Last Edit: 02/15/2012 06:43 pm by spacejulien »
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Re: SpaceX fairing
« Reply #61 on: 02/15/2012 06:47 pm »
a 6 m monolithic mirror is not just driving fairing size. If you want to avoid adaptive optics to have the cost benefit you need a very sturdy monolithic mirror. That has its weight. For comparison, the SOFIA telescope has a diameter of 2.7m and weighs 15.4 metric tons [2]. Scale that up gives you 15.4*(6/2.7)^2=76mT. Even if you divide by factor two (space-, not aircraft-HW) you’ll end up with 38 mT. Other reference, the largest monolithic mirror without adaptive optics has 4.2m diameter and weighs 16.5 mT [3], so factor two for 6 m diameter plus spacecraft and sunshield. Acc. to [1], fig. 6 this would have been within the P/L capability of ARES V to EML2, but is definitely outside Ariane 5 and Falcon Heavy capabilities. So stop arguing about the fairing diameter as limiting factor using JWST as an example, esp. in a Falcon thread.  Folding mechanisms are state of the art, the telescope’s allowed mass is the limiting factor. This made the active mirror alignment necessary, even if it were monolithic, and that drove (drives) the cost.
Thank you spacejulien.  That returns us to the point on the linked thread: That the savings on a monolith JWST could have been used to develop something like F-XX (Elon's guaranteed $2.5 billion 150 tonne launcher) for an equal or better, lower-risk telescope (because it would have the mass capacity while hammerhead EELV's presumably do not).   That assumes that 30% is in the ball-park.  We will probably never know for sure if 30% is exactly accurate, but it's the only number we have been given. 
« Last Edit: 02/15/2012 06:48 pm by go4mars »
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Re: SpaceX fairing
« Reply #62 on: 02/15/2012 06:55 pm »
  That returns us to the point on the linked thread: That the savings on a monolith JWST could have been used to develop something like F-XX (Elon's guaranteed $2.5 billion 150 tonne launcher) for an equal or better, lower-risk telescope (because it would have the mass capacity while hammerhead EELV's presumably do not).   That assumes that 30% is in the ball-park.  We will probably never know for sure if 30% is exactly accurate, but it's the only number we have been given. 

Wrong, that is just fantasy, there are no savings.  No one would take that offer.  Elon's guarantee is meaningless.   



Offline spacejulien

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Re: SpaceX fairing
« Reply #63 on: 02/15/2012 07:03 pm »
go4mars, there are a lot of ifs implied in your statement:
If Elon could develop a Falcon XX incl. Merlin 2 for 2.5 B$ (which I severely doubt),
if he could accomplish that until 2018 (which I doubt),
if one would have known at the outset of JWST that the launch would slip to 2018+,
if it would have been known at the beginning that the cost would be 8.5 B$,
if the political environment at that time would NOT have permitted to embark on such a large-scale commercial development (remember FY2011 rollout),
if it is really 30% of the JWST total (which I doubt, reasons given in post #60),
if you can really be sure you can definitely avoit adaptive optics (which I doubt, as the mirror is used under completely different environmental conditions than it was manufactured).

Three ifs are retroactive and unchangeable, you can't do anything about them, the other ifs are numerous enough not to go down that track. Too risky project management, more so than JWST itself.

But now, back to F9 and FH fairings...
« Last Edit: 02/15/2012 07:13 pm by spacejulien »
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Online kevin-rf

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Re: SpaceX fairing
« Reply #64 on: 02/15/2012 09:12 pm »
Elon's guarantee is meaningless.   

I don't know, I put them a little more credible than Boeing management on 787 deliveries ;)
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Offline krytek

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Re: SpaceX fairing
« Reply #65 on: 02/15/2012 09:20 pm »
Falcon 9 uses a carbon-fiber fairing which supposedly is very, very light (compared to the fairings on competing rockets... of course, the Falcon 9 hasn't flown, yet!).
Plus the "competing rockets" also use fairing that are mainly made from carbon. If you do it right, a carbon-composite structure can be just as light or even lighter than a purely carbon one, carbon fiber is good for tensile loads, need lots of filler for compression loads.
To be honest, I'm not entirely sure whether Falcon 9's fairing is carbon fiber or carbon composite, just that it isn't plain aluminum alloy and is claimed (by Elon) to be lighter than competing ones.

this is from RUAG's official site
Quote
The fairings are built in composite technology based on aluminum honeycomb cores with carbon fiber reinforced plastic face sheets

Can you please explain the difference between "carbon fiber" and "carbon composite", not sure I understand the terminology.


Offline peter-b

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Re: SpaceX fairing
« Reply #66 on: 02/15/2012 09:26 pm »
Quote
The fairings are built in composite technology based on aluminum honeycomb cores with carbon fiber reinforced plastic face sheets

Can you please explain the difference between "carbon fiber" and "carbon composite", not sure I understand the terminology.

As I understand it, "carbon fibre" is a term usually used as shorthand for "carbon fibre reinforced polymer", which is most commonly a composite material made by binding layers of graphite fibres into a matrix of epoxy resin.

"Carbon composite" is an even vaguer term, which basically just indicates some composite material that uses "carbon" (probably in the form of graphite fibres).  I suspect that in this case it indicates some sort of composite material combining graphite fibres, polymers, and lightweight metal elements.
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Offline spacejulien

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Re: SpaceX fairing
« Reply #67 on: 02/15/2012 09:37 pm »
Quote
The fairings are built in composite technology based on aluminum honeycomb cores with carbon fiber reinforced plastic face sheets

Can you please explain the difference between "carbon fiber" and "carbon composite", not sure I understand the terminology.

As I understand it, "carbon fibre" is a term usually used as shorthand for "carbon fibre reinforced polymer", which is most commonly a composite material made by binding layers of graphite fibres into a matrix of epoxy resin.

"Carbon composite" is an even vaguer term, which basically just indicates some composite material that uses "carbon" (probably in the form of graphite fibres).  I suspect that in this case it indicates some sort of composite material combining graphite fibres, polymers, and lightweight metal elements.

For the latter (usually) some sort of core material is used, honeycomb cores are very popular in aerospace [1]. Then the two surfaces are covered by some sort of CFRP lay-up [2], then called face-sheets. Gives very light structures with good buckling performance. As launchers are usually under compression loads between drag, inertia and the trust of the engine and thus susceptible to buckling such "sandwich" is very popular for interstages, fairings, skirts, intertank structures, thrust frames, payload adapters, etc.

[1] http://en.wikipedia.org/wiki/Honeycomb_structure
[2] http://en.wikipedia.org/wiki/Carbon_fiber-reinforced_polymer
« Last Edit: 02/15/2012 09:38 pm by spacejulien »
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Offline beancounter

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Re: SpaceX fairing
« Reply #68 on: 02/16/2012 02:09 am »
Quote
The fairings are built in composite technology based on aluminum honeycomb cores with carbon fiber reinforced plastic face sheets

Can you please explain the difference between "carbon fiber" and "carbon composite", not sure I understand the terminology.

As I understand it, "carbon fibre" is a term usually used as shorthand for "carbon fibre reinforced polymer", which is most commonly a composite material made by binding layers of graphite fibres into a matrix of epoxy resin.

"Carbon composite" is an even vaguer term, which basically just indicates some composite material that uses "carbon" (probably in the form of graphite fibres).  I suspect that in this case it indicates some sort of composite material combining graphite fibres, polymers, and lightweight metal elements.

For the latter (usually) some sort of core material is used, honeycomb cores are very popular in aerospace [1]. Then the two surfaces are covered by some sort of CFRP lay-up [2], then called face-sheets. Gives very light structures with good buckling performance. As launchers are usually under compression loads between drag, inertia and the trust of the engine and thus susceptible to buckling such "sandwich" is very popular for interstages, fairings, skirts, intertank structures, thrust frames, payload adapters, etc.

[1] http://en.wikipedia.org/wiki/Honeycomb_structure
[2] http://en.wikipedia.org/wiki/Carbon_fiber-reinforced_polymer


Carbon fibre and expoxy composite's have been used in boat building for at least a decade probably several.  Commonly together with foam of various densities for different structures but also with timber.  Carbon fibre on it's own has been used for masts, booms, etc.  It's hardly a new material and it's properties are well understood.

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Offline krytek

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Re: SpaceX fairing
« Reply #69 on: 02/16/2012 09:36 am »
Again that what's confusing, I've played around some with carbon fiber and epoxy, which isn't all too difficult to work with.
Can't imagine what carbon fiber "on it's own" would make though, unless it's compressed or made into some sort of complex weave.

Offline Crispy

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Re: SpaceX fairing
« Reply #70 on: 02/16/2012 10:17 am »
The shuttle component max size may have been set by rail tunnel size, but that's a pretty generous 'standard.'
Not to mention that USA tunnel clearances are much larger than British ones. There are no double-decker passenger trains in the UK for this reason.

Hang on this isn't the railways forum... :D

Offline corrodedNut

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Re: SpaceX fairing
« Reply #71 on: 03/14/2012 04:19 pm »
Looks like confirmation the fairing's inagural flight will be out of Vandenberg.

From SFN:

"The upgraded Falcon 9 launcher should arrive at the Vandenberg launch site in late 2012, according to Shotwell...The new version of the Falcon 9 rocket will also feature modified propellant tanks and a 5.2-meter, or 17-foot, diameter payload fairing."


Offline go4mars

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Re: SpaceX fairing
« Reply #72 on: 03/14/2012 04:23 pm »
"The new version of the Falcon 9 rocket will also feature modified propellant tanks"
Does that imply stretched tanks?  Is this the tall version?
« Last Edit: 03/14/2012 04:23 pm by go4mars »
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Offline corrodedNut

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Re: SpaceX fairing
« Reply #73 on: 03/14/2012 04:33 pm »
"The new version of the Falcon 9 rocket will also feature modified propellant tanks"
Does that imply stretched tanks?  Is this the tall version?

Conventional wisdom says yes.

Offline oldAtlas_Eguy

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Re: SpaceX fairing
« Reply #74 on: 03/14/2012 04:38 pm »
"The new version of the Falcon 9 rocket will also feature modified propellant tanks"
Does that imply stretched tanks?  Is this the tall version?

Makes sense. The less supported configurations the less GSE and the costs associated with it. If VAFB is set to launch only stretched vehicles (as opposed to the F9's current length) then they only need one set of F9 support equipment (strongback).

Even if this is overkill for some of the VAFB payloads there will not be much of a cost difference between the manufacture of the stretched vehicle and the non-stretched. Plus it gives then the capability to prove out the stretched F9 prior to its use at the cape and the pad mods there as well to support it.

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Re: SpaceX fairing
« Reply #75 on: 03/14/2012 04:44 pm »
Playing devil's advocate for a second, but couldn't "modified propellant tanks" mean simply structural changes to handle the significantly higher thrust of M1d?

Offline Confusador

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Re: SpaceX fairing
« Reply #76 on: 03/14/2012 10:08 pm »
Playing devil's advocate for a second, but couldn't "modified propellant tanks" mean simply structural changes to handle the significantly higher thrust of M1d?
Could be, but if you're going to do that why wouldn't you do the stretch at the same time?  As OAE said, the fewer configurations you're working with, the simpler your operations become.

Now given that they're talking about the first flight with these changes being with CASSIOPE, I suppose there's an argument to be made for making as few changes as possible in order to mitigate risk, but I figure as long as you're doing it you might as well go all the way.  Unless there's something I'm missing about the amount of risk introduced by the core stretch?

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