Author Topic: Fairing reuse  (Read 442556 times)

Offline matthewkantar

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Re: Fairing reuse
« Reply #1060 on: 12/20/2017 05:42 PM »
One way to catch both halves with one rig is to have one net deployed and lowerable with winches while the other net is furled and stretched between two of the masts. Line would go from each end of the furled net to the opposite mast on each side, through a pulley and to another winch. This would be similar to how a rubber-banded spinnaker is released on sail boat.

The first fairing hits and is lowered to the deck in maybe fifteen seconds. The second net is deployed by running the winches, in a minute or so, and the second half is caught. This would explain the height of the masts on Mr Steven.

Matthew

Offline rakaydos

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Re: Fairing reuse
« Reply #1061 on: 12/20/2017 07:53 PM »
One way to catch both halves with one rig is to have one net deployed and lowerable with winches while the other net is furled and stretched between two of the masts. Line would go from each end of the furled net to the opposite mast on each side, through a pulley and to another winch. This would be similar to how a rubber-banded spinnaker is released on sail boat.

The first fairing hits and is lowered to the deck in maybe fifteen seconds. The second net is deployed by running the winches, in a minute or so, and the second half is caught. This would explain the height of the masts on Mr Steven.

Matthew
For bonus points, have a 3rd net on the other side, to secure the top fairing for transport.

Offline Jcc

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Re: Fairing reuse
« Reply #1062 on: 12/20/2017 11:06 PM »
How's this arrangement to capture 2 fairing halves: two nets, one attached on the left side, with cables to pull it open to the right side. The other net attached on the right, with cables that pull it open to the left. Start with both nets folded, first pull the cables to stretch out the left net, capture one fairing half, then pull the cables back to fold the left net with the fairing half inside, and stow it to the left of the deck. Next open the right net, capture the other fairing half, then fold it back to stow the fairing.

Offline robert_d

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Re: Fairing reuse
« Reply #1063 on: 12/21/2017 12:28 AM »
How's this arrangement to capture 2 fairing halves: two nets, one attached on the left side, with cables to pull it open to the right side. The other net attached on the right, with cables that pull it open to the left. Start with both nets folded, first pull the cables to stretch out the left net, capture one fairing half, then pull the cables back to fold the left net with the fairing half inside, and stow it to the left of the deck. Next open the right net, capture the other fairing half, then fold it back to stow the fairing.

We may not be seeing everything yet by I like this idea better. I am thinking that lack of attach points may actually argue against a complicated net and winch system. It may possibly indicate 2 inflatable structures, port and starboard that would catch the fairings coming in from behind at say a 15 degree angle. They would slide to the center with a center cushion to prevent contact.

Offline IanThePineapple

Re: Fairing reuse
« Reply #1064 on: 12/21/2017 12:58 AM »
How's this arrangement to capture 2 fairing halves: two nets, one attached on the left side, with cables to pull it open to the right side. The other net attached on the right, with cables that pull it open to the left. Start with both nets folded, first pull the cables to stretch out the left net, capture one fairing half, then pull the cables back to fold the left net with the fairing half inside, and stow it to the left of the deck. Next open the right net, capture the other fairing half, then fold it back to stow the fairing.

We may not be seeing everything yet by I like this idea better. I am thinking that lack of attach points may actually argue against a complicated net and winch system. It may possibly indicate 2 inflatable structures, port and starboard that would catch the fairings coming in from behind at say a 15 degree angle. They would slide to the center with a center cushion to prevent contact.

The boat may not even be in its final form ( ;D ), it might not even be ready for this mission. There could still be quite a bit more work needed on it, like how 39A's TEL looked in one of our first glimpses of it (http://i.imgur.com/o64Whbk.jpg).
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Offline Lar

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Re: Fairing reuse
« Reply #1065 on: 12/21/2017 01:16 AM »
maybe but dubious. Why rush Mr. Steven over here when there are several missions on the other coast that will be ejecting pallets of cash, er fairings.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline cscott

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Re: Fairing reuse
« Reply #1066 on: 12/21/2017 01:24 AM »
I wonder if GO Mr. Steven can fit back through the Panama Canal with this superstructure on it?

Offline speedevil

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Re: Fairing reuse
« Reply #1067 on: 12/21/2017 01:40 AM »
I wonder if GO Mr. Steven can fit back through the Panama Canal with this superstructure on it?

Easily.
This is a 'tiny' ship - it is only 9m wide, and with the fairing support structure only ~15m wide.
The ASDS fit through the canal with only removal of the 'wings', and that's more 90m wide than 9.

Offline Lar

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Re: Fairing reuse
« Reply #1068 on: 12/21/2017 01:49 AM »
you think the fairing support arms are only 3M beyond the hull? I think someone would need to measure it but I'm dubious, more like almost the hull width again on each side. but I could be wrong.

That still easily fits through the canal but I see it as quite ungainly.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline speedevil

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Re: Fairing reuse
« Reply #1069 on: 12/21/2017 02:14 AM »
you think the fairing support arms are only 3M beyond the hull? I think someone would need to measure it but I'm dubious, more like almost the hull width again on each side. but I could be wrong.

That still easily fits through the canal but I see it as quite ungainly.
Hmm.

The ship is only 205 feet long, 65m or so.
The arms spacing fore-aft at the tips is around 1/2.2* the ships length, or 29m. I think I may have initially measured the bases, and then forgotten what I was measuring.

Measuring more carefully using:
 
gives around 26m from tip-tip.

This is consistent with a 25 or 26m square, about 13m off the deck.
for reference.

So, the fairing can be ten meters off centre in port-starboard, or some five meters in fore-aft inaccuracy without coming off a hypothetical square net.
Or rather more than that in fore-aft if we consider  the ends poking over. There is a _lot_ of vertical space below the net, and forward of the net, meaning the first one could be slid off onto the deck rapidly while awaiting the next.
This is probably needless complexity for a first attempt.
« Last Edit: 12/21/2017 02:27 AM by speedevil »

Offline cppetrie

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Re: Fairing reuse
« Reply #1070 on: 12/21/2017 04:30 AM »
Iím not convinced that the arms arenít mounted on rotating bases that would allow the arms to Ďfoldí in and lie within the draft of the vessel. Itís unclear whether they would be hydraulically driven or just manual with locking pins. The latter is certainly simpler.

Offline speedevil

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Re: Fairing reuse
« Reply #1071 on: 12/21/2017 12:08 PM »
Iím not convinced that the arms arenít mounted on rotating bases that would allow the arms to Ďfoldí in and lie within the draft of the vessel. Itís unclear whether they would be hydraulically driven or just manual with locking pins. The latter is certainly simpler.

It would complicate the structure, and is only really needed to go under low bridges, (low in marine contexts anyway) and to lie directly next to a >8m tall structure or ship.
Many fishing boats have sticky-out bits protruding from their outline, and nearly all harbours do not have a tidal range this great.
If it was not welded in place to a beam, I would suspect that there would be some mechanism visible, but it's quite possible either way.

Offline Johnnyhinbos

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Fairing reuse
« Reply #1072 on: 12/21/2017 02:38 PM »
Yeah, I think itís 100% probable that the arms rotate aft. Thatís a solved problem that you can see on any derrick, davit, hoist, and crane.

Edit to add that fishing trawlers only run outriggers outboard once underway. I keep my 46í Saber Hardtop Express in New Bedford, MA amongst hundreds of 100í trawlers. Theyíre packed in like sardines, hull to hull.

Those arms 100% rig aft.
« Last Edit: 12/21/2017 02:43 PM by Johnnyhinbos »
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Offline dorkmo

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Re: Fairing reuse
« Reply #1073 on: 12/21/2017 03:49 PM »
to me it looked like there was a big hunky base sort the width and length of a shipping container that had short stands coming out from its corners that the arms appear to bolt to. if its not a rotating mechanism i'd guess it could at least be un bolted.

Offline RDMM2081

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Re: Fairing reuse
« Reply #1074 on: 12/21/2017 04:55 PM »
There might be a very obvious answer to this question but since it's not obvious to me I'll ask it.
      Why can't the two halves be caught in the same net despite contact. Would the damage be that great that would render the effort worthless? I don't know enough about the material and speed of landing to be able to discern the impact.
     Also seems to me that the first try is more about catching than using the fairings that were caught.

I am not sure about this at all, but my speculation is that Mr. Steven will be catching exactly one half of the fairing this attempt.  Any of the "multiple catch" scenarios (except maybe the double decker net) or offloading between catches treat these fairings much more robustly than I think they are built.  The cost estimates are currently somewhere between "pallet of cash" and the $6m neighborhood of comparable fairings.  To me, this means that these are complicated, expensive, and therefore fragile, delicate, high grade aerospace carbon composite structures that cannot be "slid" off nets, or moved by hand, or hastily moved by crane.  I think any contact between the halves would be an instant deal-breaker as well.  This is why I suspect that they will catch only one half this attempt.

Supposing that they do in fact catch only one half this time, will it be able to be re-used?  What I mean, is are the fairing halves built to be paired with a specific second half, or are they interchangeable, even in theory?  If they catch one half, or course it is good practice for future efforts and proof of concept, but without the second "matching" (I in no way claim to know that they need to be matched, but it seems possible to me at first thought) fairing half, is it potentially useless for reuse?

Offline cscott

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Re: Fairing reuse
« Reply #1075 on: 12/21/2017 05:01 PM »
They are built/cured one half at a time; I assume they could build a matching passive half if needed.

Offline cppetrie

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Re: Fairing reuse
« Reply #1076 on: 12/21/2017 05:10 PM »
Given what the fairing has to withstand during launch and max q, Iím not sure fragile is the right word. I do however think they are designed to handle only certain kinds of loads in a robust way. Contact between them is unlikely to be a mode for which they are designed. Contact would likely result in some level of cracking, chipping or delamination that would make it structurally unsound to fly again through max q.

Offline leetdan

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Re: Fairing reuse
« Reply #1077 on: 12/21/2017 05:14 PM »
An empty soda can is "fragile" if you squeeze the sides, but not if you stand on it.  Just because the joined fairing is strong against aero loads doesn't mean a separated fairing will survive rough handling or impacts.

Offline RDoc

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Re: Fairing reuse
« Reply #1078 on: 12/21/2017 05:28 PM »
I'd not be surprised if jcc was close https://forum.nasaspaceflight.com/index.php?topic=37727.msg1761981#msg1761981. Two large floating air cushions, port and starboard, one per half. One issue I see with nets is t some kind of shock absorbing mechanism the fairing half will decelerate pretty quickly.

Offline cppetrie

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Re: Fairing reuse
« Reply #1079 on: 12/21/2017 05:57 PM »
I'd not be surprised if jcc was close https://forum.nasaspaceflight.com/index.php?topic=37727.msg1761981#msg1761981. Two large floating air cushions, port and starboard, one per half. One issue I see with nets is t some kind of shock absorbing mechanism the fairing half will decelerate pretty quickly.
Pretty easy to add some shock absorbing to the net. Think trapeze safety net. Some springs at the mount points plus the tensioning cables and netting material will have some inherent stretch and thus shock absorption capacity.

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