Author Topic: Fairing reuse  (Read 509798 times)

Offline WBY1984

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Re: Fairing reuse
« Reply #120 on: 03/07/2016 12:39 PM »


They need thrusters to orient the fairings to come in at the correct orientation.



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?

Offline R7

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Re: Fairing reuse
« Reply #121 on: 03/07/2016 12:45 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.
AD·ASTRA·ASTRORVM·GRATIA

Offline WBY1984

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Re: Fairing reuse
« Reply #122 on: 03/07/2016 12:48 PM »
Thanks :)

Offline OxCartMark

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Re: Fairing reuse
« Reply #123 on: 03/07/2016 12:59 PM »
what I'm asking is why do the fairings need to maintain a particular orienation at all?...Why not let them tumble until parachute altitude?

Buncha speculations:
- Because they've modeled the re-entry and found that one orientation is better than others
- Because they want to expose the outside surface which is not very heat tolerant epoxy to the heat rather than the inside surface which has expanded foam which is even less heat tolerant.
- Because they fly a predictable stable path if you get them concave down rather than tumbling and producing a less predictable landing point otherwise
- Because their longer range plan if they can get through re-entry is to add control surfaces to "fly" them through the lower atmosphere to a designated point for collection and you need to get them to a stable orientation to start that process

Separate observation: I find it interesting that the fairings are so far separated considering that their separation speed isn't that great and there is little aerodynamic influence.

What cameras or other resources do we have available in Port Canaveral to see if they were successful?

Offline dorkmo

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Re: Fairing reuse
« Reply #124 on: 03/07/2016 12:59 PM »
Can't quite understand what you're getting at: If you zoom in *where*, we see a black round *what*?
https://imgur.com/lUPlvL9  ;)

not sure if its related but it looks like there is the top of a COPV with a pipe coming out right above the right shoulder of the guy on the right in blue jumpsuit.

Offline Jim

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Re: Fairing reuse
« Reply #125 on: 03/07/2016 01:29 PM »
seeing as how there aren't any known gas bottles on the fairings

There are and this could be the system breaching from aero affects

Offline WBY1984

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Re: Fairing reuse
« Reply #126 on: 03/07/2016 01:39 PM »
seeing as how there aren't any known gas bottles on the fairings

There are and this could be the system breaching from aero affects

Yeah, seems just as likely as RCS to me. Should be skeptical until we know more.

Offline ugordan

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Re: Fairing reuse
« Reply #127 on: 03/07/2016 01:42 PM »
seeing as how there aren't any known gas bottles on the fairings

There are and this could be the system breaching from aero affects

A mere 50 or so seconds after fairing sep? Unlikely. The thing was likely to still be way up above the atmosphere at that time.

Edit: trajectory analysis by Reddit user ianniss shows fairing sep at a velocity of around 2.5 km/s, velocity angle around 13 deg above horizontal. The vertical displacement from faring sep altitude is then:

sin(13 deg)*2500m/s*50s - 10m/s /2*50s*50s = 28 km upward - 12.5 km downward. So the fairing halves were, in fact, still coasting up at that point.

The gas might have been autonomously vented, but aeroloads it wasn't.
« Last Edit: 03/07/2016 02:08 PM by ugordan »

Offline thor1872

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Re: Fairing reuse
« Reply #128 on: 03/07/2016 01:44 PM »
Can't quite understand what you're getting at: If you zoom in *where*, we see a black round *what*?
https://imgur.com/lUPlvL9  ;)

not sure if its related but it looks like there is the top of a COPV with a pipe coming out right above the right shoulder of the guy on the right in blue jumpsuit.
well seen
https://imgur.com/aRsIuDm

Offline Jim

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Re: Fairing reuse
« Reply #129 on: 03/07/2016 02:09 PM »
seeing as how there aren't any known gas bottles on the fairings

There are and this could be the system breaching from aero affects

A mere 50 or so seconds after fairing sep? Unlikely. The thing was likely to still be way up above the atmosphere at that time.

Edit: trajectory analysis by Reddit user ianniss shows fairing sep at a velocity of around 2.5 km/s, velocity angle around 13 deg above horizontal. The vertical displacement from faring sep altitude is then:

sin(13 deg)*2500m/s*50s - 10m/s /2*50s*50s = 28 km upward - 12.5 km downward. So the fairing halves were, in fact, still coasting up at that point.

The gas might have been autonomously vented, but aeroloads it wasn't.

Or the actual separation event.


Offline obsever

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Re: Fairing reuse
« Reply #130 on: 03/07/2016 02:16 PM »
seeing as how there aren't any known gas bottles on the fairings

There are and this could be the system breaching from aero affects

A mere 50 or so seconds after fairing sep? Unlikely. The thing was likely to still be way up above the atmosphere at that time.

Edit: trajectory analysis by Reddit user ianniss shows fairing sep at a velocity of around 2.5 km/s, velocity angle around 13 deg above horizontal. The vertical displacement from faring sep altitude is then:

sin(13 deg)*2500m/s*50s - 10m/s /2*50s*50s = 28 km upward - 12.5 km downward. So the fairing halves were, in fact, still coasting up at that point.

The gas might have been autonomously vented, but aeroloads it wasn't.

Or the actual separation event.

...

Wouldn't it be a lot less violent on F9 compared to Atlas, since they are using a non-pyrotechnic method (pushers) on F9 ?

Edit: in the video from the test the separation event looks more smooth than the Atlas one you linked above:

« Last Edit: 03/07/2016 02:26 PM by obsever »

Offline Flying Beaver

Re: Fairing reuse
« Reply #131 on: 03/07/2016 02:46 PM »
The Helium bottles used for pneumatic fairing sep are pictured here (from Nov 2012):

https://www.flickr.com/photos/jurvetson/8233306859/
Watched B1019 land in person 21/12/2015.

Offline Ilikeboosterrockets

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Re: Fairing reuse
« Reply #132 on: 03/07/2016 02:53 PM »
I'm wondering if it was those helium bottles leaking instead of thrusters. Is there any difference in the visibility of helium outgassing vs. something like nitrogen?

Offline Flying Beaver

Re: Fairing reuse
« Reply #133 on: 03/07/2016 03:05 PM »
I'm wondering if it was those helium bottles leaking instead of thrusters. Is there any difference in the visibility of helium outgassing vs. something like nitrogen?

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.
Watched B1019 land in person 21/12/2015.

Offline Robotbeat

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Re: Fairing reuse
« Reply #134 on: 03/07/2016 03:17 PM »
I'm wondering if it was those helium bottles leaking instead of thrusters. Is there any difference in the visibility of helium outgassing vs. something like nitrogen?
Although helium does not condense, I wouldn't expect a visible sign from helium venting, but... That is the best alternative explanation I've heard so far.

But it might not even be contradictory. They may be venting what's left in the bottles out through a nozzle to test some aspect of fairing recovery hardware.

Do we know for a fact the pushers use helium and not nitrogen?
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Offline Jim

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Re: Fairing reuse
« Reply #135 on: 03/07/2016 03:25 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

Offline Saabstory88

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Re: Fairing reuse
« Reply #136 on: 03/07/2016 03:45 PM »
Maybe this is a stupid question, but wouldn't the fairing half passing through the second stage plume also create an effect like this?

Offline ugordan

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Re: Fairing reuse
« Reply #137 on: 03/07/2016 03:48 PM »
Maybe this is a stupid question, but wouldn't the fairing half passing through the second stage plume also create an effect like this?

There would be around 10 km distance between the fairing and engine around 50 seconds after fairing sep. Highly unlikely.

Offline AS-503

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Re: Fairing reuse
« Reply #138 on: 03/07/2016 03:51 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?

Offline Saabstory88

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Re: Fairing reuse
« Reply #139 on: 03/07/2016 03:57 PM »
Maybe this is a stupid question, but wouldn't the fairing half passing through the second stage plume also create an effect like this?

There would be around 10 km distance between the fairing and engine around 50 seconds after fairing sep. Highly unlikely.

I mention this because we only see the "thrusts" from the fairing half which appears to be trailing in the second stage exhaust plumes. I mean, of course, this is SpaceX we are talking about, but I'm just trying to remain skeptical. What's more likely, that only one of the fairings needs to complete maneuvers, or that the fairing caught in the plume redirects some gas as it spins in free fall?

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