### Author Topic: Fairing reuse  (Read 598435 times)

#### speedevil

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##### Re: Fairing reuse
« Reply #1640 on: 05/25/2018 03:26 pm »
The two main techniques for preventing seawater damage to an object, and the only two that are 100% effective, are a) keep the object out of the seawater and b) keep the seawater out of the object.
The fairings need to be porous (vented) to they can be brought from 1ATM or near 0ATM and back without bursting or collapsing, which is at odds with the need to seal them against seawater ingress. Keeping them out of the seawater in the first place is preferable to a complete fairing redesign to avoid internal pockets.

The internal pressure in vacuum is only 14PSI, or somewhere slightly over that due to heating.
14PSI, in the context of a CF honeycomb structure, may be entirely structurally irrelevant and containing it may be less work than venting it.

#### DistantTemple

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##### Re: Fairing reuse
« Reply #1641 on: 05/25/2018 07:27 pm »
The two main techniques for preventing seawater damage to an object, and the only two that are 100% effective, are a) keep the object out of the seawater and b) keep the seawater out of the object.
The fairings need to be porous (vented) to they can be brought from 1ATM or near 0ATM and back without bursting or collapsing, which is at odds with the need to seal them against seawater ingress. Keeping them out of the seawater in the first place is preferable to a complete fairing redesign to avoid internal pockets.

The internal pressure in vacuum is only 14PSI, or somewhere slightly over that due to heating.
14PSI, in the context of a CF honeycomb structure, may be entirely structurally irrelevant and containing it may be less work than venting it.
Do you know if the CF honeycomb is safe in vacuum. Your logic above, alone, is not valid. 14 psi = 10 tonnes/sqm. Which just as convincingly sounds like the sort of force (OK tonnes force is not SI unit) that would expand a honeycomb to destruction!
« Last Edit: 05/25/2018 07:28 pm by DistantTemple »
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#### speedevil

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##### Re: Fairing reuse
« Reply #1642 on: 05/25/2018 07:53 pm »
The two main techniques for preventing seawater damage to an object, and the only two that are 100% effective, are a) keep the object out of the seawater and b) keep the seawater out of the object.
The fairings need to be porous (vented) to they can be brought from 1ATM or near 0ATM and back without bursting or collapsing, which is at odds with the need to seal them against seawater ingress. Keeping them out of the seawater in the first place is preferable to a complete fairing redesign to avoid internal pockets.

The internal pressure in vacuum is only 14PSI, or somewhere slightly over that due to heating.
14PSI, in the context of a CF honeycomb structure, may be entirely structurally irrelevant and containing it may be less work than venting it.
Do you know if the CF honeycomb is safe in vacuum. Your logic above, alone, is not valid. 14 psi = 10 tonnes/sqm. Which just as convincingly sounds like the sort of force (OK tonnes force is not SI unit) that would expand a honeycomb to destruction!

14PSI is also 14 pounds per square inch. Or perhaps a couple of pounds per linear inch of aluminium honeycomb edge if that honeycomb has cells around 8mm. It would be quite hard to get a CF/Al joint that bad.

I have made considerably less advanced honeycomb than this, and the delamination strength would have been well over 140, rather than 14 PSI.
It is unclear if the honeycomb/CF they are using is structurally airtight to 14PSI without extra work - it is at least plausible.

If other loads are much larger than 14PSI in the structure, and they likely are, the ability to resist exploding in vacuum may be free.

#### DistantTemple

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##### Re: Fairing reuse
« Reply #1643 on: 05/25/2018 10:33 pm »
thanks Speedevil:
Quote from: speedevil
I have made considerably less advanced honeycomb than this, and the delamination strength would have been well over 140, rather than 14 PSI.
Ok good data. And I guess the exterior composite surface could be easily made waterproof with extra resin, gel-coat etc (I only have v limited boat experience!). However all the sound baffles, which I assume are naturally soft and absorbent, as well as internal equipment cannot be sealed, and would have to be stripped and replaced. Contamination and salt residue would collect behind every item and cable, and damp and salt, would seek ingress at every fastener.
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#### deruch

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##### Re: Fairing reuse
« Reply #1644 on: 05/26/2018 01:03 am »
The two main techniques for preventing seawater damage to an object, and the only two that are 100% effective, are a) keep the object out of the seawater and b) keep the seawater out of the object.
The fairings need to be porous (vented) to they can be brought from 1ATM or near 0ATM and back without bursting or collapsing, which is at odds with the need to seal them against seawater ingress. Keeping them out of the seawater in the first place is preferable to a complete fairing redesign to avoid internal pockets.

The internal pressure in vacuum is only 14PSI, or somewhere slightly over that due to heating.
14PSI, in the context of a CF honeycomb structure, may be entirely structurally irrelevant and containing it may be less work than venting it.

How many satellites are designed to experience a sudden, catastrophic depressurization of 14 PSI when you explosively jettison the fairings?  Surviving the shock of fairing jettison is already a S/C design driver.  And that's with fairings that are vented to reduce the pressure differential.

#### Swedish chef

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##### Re: Fairing reuse
« Reply #1645 on: 05/26/2018 05:16 am »
The two main techniques for preventing seawater damage to an object, and the only two that are 100% effective, are a) keep the object out of the seawater and b) keep the seawater out of the object.

I am wondering, are there any technique that the fairings could be washed clean if they where to be subjected to seawater? I'm thinking of submersion in distilled water until no trace of sodium chloride could be detected? If that is the case one could skip the chase boat and personnel and probably get a even cheaper solution to faring reuse.

#### john smith 19

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##### Re: Fairing reuse
« Reply #1646 on: 05/26/2018 06:18 am »
The two main techniques for preventing seawater damage to an object, and the only two that are 100% effective, are a) keep the object out of the seawater and b) keep the seawater out of the object.
The fairings need to be porous (vented) to they can be brought from 1ATM or near 0ATM and back without bursting or collapsing, which is at odds with the need to seal them against seawater ingress. Keeping them out of the seawater in the first place is preferable to a complete fairing redesign to avoid internal pockets.

The internal pressure in vacuum is only 14PSI, or somewhere slightly over that due to heating.
14PSI, in the context of a CF honeycomb structure, may be entirely structurally irrelevant and containing it may be less work than venting it.
Do you know if the CF honeycomb is safe in vacuum. Your logic above, alone, is not valid. 14 psi = 10 tonnes/sqm. Which just as convincingly sounds like the sort of force (OK tonnes force is not SI unit) that would expand a honeycomb to destruction!

14PSI is also 14 pounds per square inch. Or perhaps a couple of pounds per linear inch of aluminium honeycomb edge if that honeycomb has cells around 8mm. It would be quite hard to get a CF/Al joint that bad.

I have made considerably less advanced honeycomb than this, and the delamination strength would have been well over 140, rather than 14 PSI.
It is unclear if the honeycomb/CF they are using is structurally airtight to 14PSI without extra work - it is at least plausible.

If other loads are much larger than 14PSI in the structure, and they likely are, the ability to resist exploding in vacuum may be free.
I'm getting the impression you're talking at cross purposes to each other.

One of you seems concerned about the pressure between the inside and outside surfaces of the fairing. The other (it seems) is more concerned about the cells bursting. These are completely different effects.

Vented honeycomb has certainly been made (pin holes in the walls of the cells or little bits "chewed" out of the edges of each end of the wall material) but I'm not sure if air tightness is a design requirement. With a peel strength of 140psi that should certainly resist any internal expansion blowing the end caps off the cells.

The 2 fairing parts do look kind of like boats but boats with no stern. I suspect the it is more a problem of sea water soaking inside the shell and all the stuff attached to it. If the acoustic blankets need to be open cell to be effective at their thickness then sealing them doesn't seem to be an option.

OTOH I expect fairing recovery to be a much simpler task than recovery of the rest of the upper stage.
« Last Edit: 05/29/2018 06:22 am by john smith 19 »
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#### RDMM2081

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##### Re: Fairing reuse
« Reply #1647 on: 05/27/2018 06:12 pm »
The two main techniques for preventing seawater damage to an object, and the only two that are 100% effective, are a) keep the object out of the seawater and b) keep the seawater out of the object.

I am wondering, are there any technique that the fairings could be washed clean if they where to be subjected to seawater? I'm thinking of submersion in distilled water until no trace of sodium chloride could be detected? If that is the case one could skip the chase boat and personnel and probably get a even cheaper solution to faring reuse.

Not trying to be obtuse, but SpaceX are the actual rocket engineers here and they have obviously decided that immersion and then rinsing is not the path to recovery and reuse of the fairings.  There is no middle ground of designing for immersion, they are designing for dry recovery.  I doubt very much that any of us here are qualified to second guess this decision.

#### jpo234

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##### Re: Fairing reuse
« Reply #1648 on: 05/31/2018 07:43 am »
From Recticel maakt cruciale onderdelen voor raketbedrijf Elon Musk

Quote
The company is already working on a successor for the black panels that it used at the Tesla launch. 'We are working on a hydrophobic version, to keep the pieces afloat when they fall into the sea. Reuse is one of the hobbies of SpaceX. '
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#### deruch

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##### Re: Fairing reuse
« Reply #1649 on: 05/31/2018 03:21 pm »
From Recticel maakt cruciale onderdelen voor raketbedrijf Elon Musk

Quote
The company is already working on a successor for the black panels that it used at the Tesla launch. 'We are working on a hydrophobic version, to keep the pieces afloat when they fall into the sea. Reuse is one of the hobbies of SpaceX. '

Cool find, thanks.

Just a note, this company makes the blocks/panels that get fixed on the interior face of the fairing to absorb acoustic vibrations.  Even though it mentions "fall[ing] into the sea," I would be surprised if this was related to plans that would allow actual immersion of the fairings as opposed to protecting them from spray/wetting after they are caught.  Also, due to the fall through the atmosphere as an open halfshell, I wouldn't be surprised to learn that there was enough water getting condensed on the inner surface to potentially be a concern.

#### dglow

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##### Re: Fairing reuse
« Reply #1650 on: 05/31/2018 07:25 pm »
Quote from: SpaceX
Falcon 9 fairing halves deployed their parafoils and splashed down in the Pacific Ocean last week after the launch of Iridium-6/GRACE-FO. Closest half was ~50m from SpaceX’s recovery ship, Mr. Steven.

#### deruch

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##### Re: Fairing reuse
« Reply #1651 on: 05/31/2018 07:38 pm »
Quote from: SpaceX
Falcon 9 fairing halves deployed their parafoils and splashed down in the Pacific Ocean last week after the launch of Iridium-6/GRACE-FO. Closest half was ~50m from SpaceX’s recovery ship, Mr. Steven.

Included 3 pics at original resolution.

edit: ninja'd by FST, but my attached pics are the higher resolution ones.
« Last Edit: 05/31/2018 07:40 pm by deruch »

#### dglow

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##### Re: Fairing reuse
« Reply #1652 on: 05/31/2018 08:07 pm »
Those brown stripes on the second pic... that's a well-toasted marshmallow.

#### Helodriver

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##### Re: Fairing reuse
« Reply #1653 on: 05/31/2018 08:25 pm »
In the image under chute, some damage can be seen to the left side trailing edge.

#### wannamoonbase

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##### Re: Fairing reuse
« Reply #1654 on: 05/31/2018 08:33 pm »
Very close and super cool.  Great pictures.  Video would be amazing.

Do we know for certain if they are trying to steer the fairing to the boat being stationary, or if they have the boat moving and moving toward the most probable location.

Flying to a fixed point with a fairing and para-foil seems possible but not reliable.

In my head I had just assumed that the boat would be moving slowly and just behind a predicted location determined by radar and speed etc.

Edit: my crude hand drawing, sorry.

« Last Edit: 05/31/2018 08:34 pm by wannamoonbase »
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##### Re: Fairing reuse
« Reply #1655 on: 05/31/2018 08:36 pm »
Given the tiny possibilties of tiny amounts of contamination that's delayed launches, I can see being hesitant to use fairings that have been immersed in seawater, no matter how well you think you've cleaned them. Seawater has a lot of things besides salt in it and some of them don't just rinse off. Electrical and mechanical problems  from contamination can lurk for years before causing trouble. Even the cleaning of incidental spray if they do manage to net them won't be that easy.
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#### matthewkantar

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##### Re: Fairing reuse
« Reply #1656 on: 05/31/2018 09:09 pm »
In the image under chute, some damage can be seen to the left side trailing edge.

I don't see that, could you please circle it for me?

#### virnin

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##### Re: Fairing reuse
« Reply #1657 on: 05/31/2018 10:10 pm »
In the image under chute, some damage can be seen to the left side trailing edge.

I don't see that, could you please circle it for me?

I think the reference was to damage to the chute, not the fairing.  It might be a big enough hole to adversely affect steering the para-foil.

#### cferreir

##### Re: Fairing reuse
« Reply #1658 on: 05/31/2018 10:35 pm »
Those brown stripes on the second pic... that's a well-toasted marshmallow.

No kidding...Lots of burn marks outside and it looks like inside too. Can that be re-used even if caught dry?? Uggh.

#### JJB

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##### Re: Fairing reuse
« Reply #1659 on: 05/31/2018 10:45 pm »
In the image under chute, some damage can be seen to the left side trailing edge.
Also, in the second shot, one of the lines on the right hand riser is broken.
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