Author Topic: Fairing reuse  (Read 550709 times)

Offline Hauerg

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Re: Fairing reuse
« Reply #140 on: 03/07/2016 03:58 PM »
They only test with one half. The other is a point of reference.

Offline pippin

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Re: Fairing reuse
« Reply #141 on: 03/07/2016 04:08 PM »
If this is really a reuse experiment, are they trying to land the fairing without a parachute? I mean... Given the shape and lightness it _should_ be possible to use that thing as a wing if they find a way to get enough control authority

Offline Kabloona

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Re: Fairing reuse
« Reply #142 on: 03/07/2016 04:10 PM »
They only test with one half. The other is a point of reference.

Yes, logical explanation for why gas jet is visible from only one fairing half.
« Last Edit: 03/07/2016 04:15 PM by Kabloona »

Offline ugordan

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Re: Fairing reuse
« Reply #143 on: 03/07/2016 04:16 PM »
Another thing is that only one half of the fairing contains the gas bottles for the sep pushers. Easier to outfit that one with ACS than introduce gas bottles to the other half as well.

Offline Jim

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Re: Fairing reuse
« Reply #144 on: 03/07/2016 04:26 PM »
Another thing is that only one half of the fairing contains the gas bottles for the sep pushers. Easier to outfit that one with ACS than introduce gas bottles to the other half as well.

Or it is the only half that can leak gas, since the other doesn't have bottles.

Offline ugordan

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Re: Fairing reuse
« Reply #145 on: 03/07/2016 04:44 PM »
Another thing is that only one half of the fairing contains the gas bottles for the sep pushers. Easier to outfit that one with ACS than introduce gas bottles to the other half as well.

Or it is the only half that can leak gas, since the other doesn't have bottles.

http://forum.nasaspaceflight.com/index.php?topic=34077.msg1500497#msg1500497


Offline dorkmo

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Re: Fairing reuse
« Reply #146 on: 03/07/2016 07:09 PM »

I might be mistaken, but in a vacuum Nitrogen freezes and produces ice crystals (hence the name "Cold Gas Thrusters" on the first stage). Where as helium simply disperses invisibly.

No, nitrogen does not freeze nor does it contain any water.  Any gas venting in a vacuum would be visible

Then I am puzzled why most upper stage exhaust plumes are not visible?

im not an expert but i believe it has to do with the short amount of time it takes for the gas to dissipate in the vacuum.

Offline Nomadd

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Re: Fairing reuse
« Reply #147 on: 03/07/2016 07:14 PM »
 I don't believe that venting gas is visible. The liquid or ice that it turns into is visible.
« Last Edit: 03/07/2016 07:15 PM by Nomadd »

Online matthewkantar

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Re: Fairing reuse
« Reply #148 on: 03/07/2016 08:16 PM »
The exhaust plume from the second stage seems huge, maybe what is observed is the vented gas displacing the plume, not the gas itself.

Matthew

Offline llanitedave

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Re: Fairing reuse
« Reply #149 on: 03/07/2016 10:05 PM »
I guess what I'm asking is why do the fairings need to maintain a particular orienation at all? They aren't seperating much higher/faster than stage 1 MECO, and the fairings are both big and light, so I can't imagine they're all that thermally stressed on reentry. Why not let them tumble until parachute altitude?

Allowing something big, light and aerodynamically unstable to freely tumble in hypersonic wind is a good recipe for destructive mechanical stresses.


Is it possible that what we're seeing is fragmentation of some of the fairing internals, for instance, the softer insulation materials, under re-entry stresses?  Or is it too early in the sequence for that?


Edit: After reading the posts following the one I quoted I agree this is unlikely.
« Last Edit: 03/07/2016 10:13 PM by llanitedave »
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Offline Kabloona

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Re: Fairing reuse
« Reply #150 on: 03/07/2016 10:22 PM »
Support ships GO Quest and GO Searcher have returned to port, with no fairing pieces visible on deck. So I lost my dollar bet...

Offline Jim

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Re: Fairing reuse
« Reply #151 on: 03/08/2016 01:20 AM »
I don't believe that venting gas is visible. The liquid or ice that it turns into is visible.

http://history.nasa.gov/SP-4206/ch12.htm
« Last Edit: 03/08/2016 01:20 AM by Jim »

Offline dorkmo

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Re: Fairing reuse
« Reply #152 on: 03/08/2016 01:37 AM »
just some "duh" thoughts...

since the latch mechanism has a pretty heavy duty gas supply, it seems like there would always be some gas left over as margin. adding thrusters could mean tapping into an existing infrastructure. for not much added weight they can play around till the gas is depleted.

Offline Jim

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Re: Fairing reuse
« Reply #153 on: 03/08/2016 01:44 AM »
just some "duh" thoughts...

since the latch mechanism has a pretty heavy duty gas supply,

it may be high pressure but it would be a small amount of gas

Offline intrepidpursuit

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Re: Fairing reuse
« Reply #154 on: 03/08/2016 04:37 AM »
If they are doing reentry control testing with the fairings, I highly doubt they would touch the existing fairing separation system. If something goes wrong with that the mission fails. They would put in a separate system for the reuse functions and not mess with the fairing sep that has worked perfectly every time. I also don't see why they would vent helium in this case. Once the fairing separates it is gone, why do they care if there is a half full helium tank on it?

The video looks very, very much like the nitrogen thrusters firing around the same time from the first stage. I doubt they would do this on just one fairing half though, they have plenty of data on the fairings falling. Seems odd too that they would separate in such an orientation that one fairing half is above the other, as opposed to jettisoning them side to side. Then one has to fall back through the plume and the other doesn't. Perhaps the plume is hitting the stage and causing it to tumble, so we see irregular plume interference based on the orientation of the fairing.

I hope it is fairing reuse, and the evidence is somewhat compelling. But I'm not yet convinced.

Offline rst

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Re: Fairing reuse
« Reply #155 on: 03/08/2016 08:30 PM »
If they are doing reentry control testing with the fairings, I highly doubt they would touch the existing fairing separation system. If something goes wrong with that the mission fails.

That depends, to some extent, on what modifications we're talking about.  If it involves changing the number or positioning of thrusters, that's risky.  If, on the other hand, it involves just giving the pre-existing thrusters bigger propellant tanks, perhaps less so...

Offline Chris_Pi

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Re: Fairing reuse
« Reply #156 on: 03/08/2016 09:11 PM »
That depends, to some extent, on what modifications we're talking about.  If it involves changing the number or positioning of thrusters, that's risky.  If, on the other hand, it involves just giving the pre-existing thrusters bigger propellant tanks, perhaps less so...

Separation is done with pushers - A few pages back there's video of a separation test where they can be seen. Any attitude control stuff would be additional to that. Could be entirely separate, Could be tied in to the gas supply and using whatever leftovers there after separation. That would allow limited tests with very little weight added.

Offline OxCartMark

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Re: Fairing reuse
« Reply #157 on: 03/09/2016 03:50 PM »
Separation is done with pushers

I've always known it was done with pushers and I think N gas pushers but I'm surprised by the technology path they've chosen. I always assumed that they used COTS nitrogen gas springs of the type used in automotive lift gates or the type used in stamping dies.  In my scenario the halves would be held together with electrically releasable latches such as on car trunks.  I guess those assumptions show the field that I've been working in.  But also now see that if they'd have chosen the path that I envision there'd be challenges in bringing the fairing halves together evenly against the multiple springs.

Offline sghill

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Re: Fairing reuse
« Reply #158 on: 03/10/2016 03:47 PM »
Why not develop a fairing that peels back like a banana peel and locks against the second stage skin? Kind of like the legs, but in reverse.

It could be used as a TPS for the second stage so the stage can be recovered.
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Offline Jim

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Re: Fairing reuse
« Reply #159 on: 03/10/2016 03:53 PM »
Why not develop a fairing that peels back like a banana peel and locks against the second stage skin? Kind of like the legs, but in reverse.

It could be used as a TPS for the second stage so the stage can be recovered.

No need to peel it back if it is taken to orbit.  It could be opened right before spacecraft deployment.  But the fairing would reduce payload mass.

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