NASASpaceFlight.com Forum
General Discussion => Q&A Section => Topic started by: kevin-rf on 04/12/2009 04:55 pm
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I've noticed fairing seperations on many vehicles usually occurs shortly after second stage seperation and ignition.
I understand the need to balance the protection of the payload verses the payload penalty from dragging the fairing along.
What I am wondering is, does keeping the fairing attached until shortly after second stage ignition provided any payload contamination protection during staging and engine startup? Or is it strickly a performance verses protection from the thin upper atmosphere trade.
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What I am wondering is, does keeping the fairing attached until shortly after second stage ignition provided any payload contamination protection during staging and engine startup? Or is it strickly a performance verses protection from the thin upper atmosphere trade.
Thev key constraint is free molecular heating level. Usually, the fairing jettison after this goes below a certain level and depending when this occurs, also after everything has settled down from staging
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There have been a few where the fairing came off during 1st stage, IIRC. Pluto? It had a high FMH constraint to allow it and shed the fairing sooner to eke out a little more performance.
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All the 5m Atlas have to have the fairings come off in first stage flight since the upperstage is encapsulated by the fairing
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Atlas V 5xx versions drop the fairing during Atlas boost phase (partly I guess due to the way the fairing encompasses the Centaur), but the heating constraint is the same as for 4xx as per the LV User Guide.
I guess 5xx flies a very lofted trajectory to exit the atmosphere sooner to allow for that, I know New Horizons certainly went straight up though it was the only 5 solid config up to now.
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There have been a few where the fairing came off during 1st stage, IIRC. Pluto? It had a high FMH constraint to allow it and shed the fairing sooner to eke out a little more performance.
New Horizons? True, it was designed for that. Using the big fairing, it had to do the jettison before staging anyway. Getting a drag racing start from 5 solids also helped - it was already ~66 miles high at fairing sep and still had around a minute to go until staging.
(just rewatched the launch video - a really obvious pitch change right after the solids jettisoned)
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(Chastises self). 5m early... Should have thought of that.
Pluto had a higher FMH constraint and it did NOT fly straight up, I can assure you. Details and rationale are probably proprietary.
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it did NOT fly straight up, I can assure you.
I know it didn't but it sure looked like that given how it just jumped off the pad and the Atlas V usually flying these lofted trajectories. As MKremer said, you could really see a large pitch-down (and probably a bit of a yaw steer) after SRB jettison, so large that it looked creepy during the live coverage.
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I know and understand that fairings are very necessary and that rockets would not be able to launch payloads without them.
But, how much orbital debris is atributed to fairings?
How about the interstage sections?
How many miles out were the Apollo spacecraft after TLI when the fairings covering the LEM's were seperated from the vehicle? I suppose these also are a part of the orbital debris that is present out there?
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1. But, how much orbital debris is atributed to fairings?
2. How about the interstage sections?
3. How many miles out were the Apollo spacecraft after TLI when the fairings covering the LEM's were seperated from the vehicle? I suppose these also are a part of the orbital debris that is present out there?
1. they aren't at orbital speed so they reentered
2. Only the Saturn V jettisoned interstages but see #1
3. They are most likely in solar orbit
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3. They are most likely in solar orbit
Weren't those jettisoned in second stage flight, once they'd achieved a stable Earth orbit? They hadn't done the TLI burn yet when the jettison took place, IIRC.
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Transposition and docking was done after the TLI burn and at that point the whole stack was travelling on a trajectory aimed to flyby the Moon. So the 4 panels protecting the LM and supporting the CM/SM were already on an Earth escape by the time they were jettisoned.
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1. But, how much orbital debris is atributed to fairings?
2. How about the interstage sections?
3. How many miles out were the Apollo spacecraft after TLI when the fairings covering the LEM's were seperated from the vehicle? I suppose these also are a part of the orbital debris that is present out there?
1. they aren't at orbital speed so they reentered
2. Only the Saturn V jettisoned interstages but see #1
3. They are most likely in solar orbit
I wonder if any of the SLA panels were on a free-return trajectory?
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Alright, I got a fair question... it's kind of a noob question but bear with me. What's the problem with large fairing diameter size (> 1.5 diameter of rocket)?
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Alright, I got a fair question... it's kind of a noob question but bear with me. What's the problem with large fairing diameter size (> 1.5 diameter of rocket)?
I'm an ordnance/propulsion guy, not an aerodynamicist, so I am speculating somewhat. That said, the larger your fairing, the more likely you are to run into flow separation, which can cause issues with stability. For some cases, you can get unstable oscillating vortices (http://upload.wikimedia.org/wikipedia/commons/b/b4/Vortex-street-animation.gif), which will rain havok down on your controllability.
Even in the absence of flow separation, a large fairing will act as a wing, pushing the Center of Pressure (http://exploration.grc.nasa.gov/education/rocket/rktstab.html) of the rocket forward. For a statically stable rocket, the Cp should be aft of the center of gravity. The closer it is, the less stability margin. If it goes above the CG, it's statically unstable. Most modern rockets are statically unstable, and depend on TVC to counteract that. However, the further forward your Cp, the more unstable you are, and the more your control system has to work to counteract that instability.
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Exactly. The main issue is controllability in the lower atmosphere
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I'm an ordnance/propulsion guy, not an aerodynamicist, so I am speculating somewhat. That said, the larger your fairing, the more likely you are to run into flow separation, which can cause issues with stability. For some cases, you can get unstable oscillating vortices (http://upload.wikimedia.org/wikipedia/commons/b/b4/Vortex-street-animation.gif), which will rain havok down on your controllability.
Even in the absence of flow separation, a large fairing will act as a wing, pushing the Center of Pressure (http://exploration.grc.nasa.gov/education/rocket/rktstab.html) of the rocket forward. For a statically stable rocket, the Cp should be aft of the center of gravity. The closer it is, the less stability margin. If it goes above the CG, it's statically unstable. Most modern rockets are statically unstable, and depend on TVC to counteract that. However, the further forward your Cp, the more unstable you are, and the more your control system has to work to counteract that instability.
Thanks.
So here's an idea, that probably would never work; could you make a fairing for the whole rocket to widen the diameter? You'd obviously suffer a major performance hit, but if you wanted to launch a large heatshield, would this work?
Ah... the answer will be probably if you had the money. Just wondering if this seemed feasible to anyone else...
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So here's an idea, that probably would never work; could you make a fairing for the whole rocket to widen the diameter? You'd obviously suffer a major performance hit, but if you wanted to launch a large heatshield, would this work?
Ah... the answer will be probably if you had the money. Just wondering if this seemed feasible to anyone else...
No need. There was a study in large asymmetric PLF.
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Here's a thread discussing large and/or asymmetric fairings: http://forum.nasaspaceflight.com/index.php?topic=29319.0 . It also discusses the ~5m limitation of US satellite infrastructure.
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Some fishermen cauhgt an so far unindentified object near the village Båtsfjord in Norway.
https://www.facebook.com/photo.php?fbid=10152906657502267&set=pcb.10152906658102267&type=1&theater
Any suggestions what that can be ?
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Some fishermen cauhgt an so far unindentified object near the village Båtsfjord in Norway.
https://www.facebook.com/photo.php?fbid=10152906657502267&set=pcb.10152906658102267&type=1&theater
Any suggestions what that can be ?
Given that it's near the top of Europe it's almost certainly a Russian fairing from one of the launches out of Plesetsk Cosmodrome. Two Soyuz rockets have flew out of there this month and it could be from either of them:
http://forum.nasaspaceflight.com/index.php?topic=37430.0 (http://forum.nasaspaceflight.com/index.php?topic=37430.0)
http://forum.nasaspaceflight.com/index.php?topic=37770.0 (http://forum.nasaspaceflight.com/index.php?topic=37770.0)
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Some fishermen cauhgt an so far unindentified object near the village Båtsfjord in Norway.
https://www.facebook.com/photo.php?fbid=10152906657502267&set=pcb.10152906658102267&type=1&theater
Any suggestions what that can be ?
This one:-
Half of the fairing ended up in Norway, again (did so the last time also), and again they have know idea what it is.
http://www.nrk.no/finnmark/fant-mystisk-vrakdel-i-havet-_-politiet-aner-ikke-hva-det-kan-vaere-1.12427576
Previous one:-
The 14С738 fairing ended up in Norway
http://www.theaviationist.com/2013/07/08/mysterious-russian-debris/
http://www.tv2.no/nyheter/ekspertene-er-uenige-om-de-mystiske-vrakdelene-4082313.html
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Although the Taurus rocket was rebranded with Minotaur avionics, could the fairing still fail to separate? Skybox does not want an OCO or Glory-like failure to occur.
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Although the Taurus rocket was rebranded with Minotaur avionics, could the fairing still fail to separate? Skybox does not want an OCO or Glory-like failure to occur.
The root cause took something like three years of research but it was found. It was a lack of process control for a secondary characteristic on the aluminum plates used to machine the frangible joints.
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Thanks a lot. I appreciate your optimism.