### Author Topic: Fairing reuse  (Read 565387 times)

#### cambrianera

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##### Re: Fairing reuse
« Reply #200 on: 03/21/2016 07:09 PM »

If the mounting hoop that the fairing halves are hinged to has a larger inner diameter than the outer diameter of the second/final stage, you could slide the entire opened up fairing & mounting hoop down the side of the stage and jettison it at the rear of the rocket, into the plume of the accelerating stage.  It would have to have clearance of the payload pedestal & payloads, as well as any exterior plumbing on the side of the rocket.

You don't need a full clamshell opening to slide your fairing back.
And making the cylindrical part of the fairing in a single piece, without joints, you can save a good amount of mass.
"Small" problem: sliding the fairing into the plume of the accelerating stage you are likely going to shred it in pieces smaller than those previously recovered.
I did this animation to look at the concept some month ago, then I realized the "small" problem .
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#### Stan-1967

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##### Re: Fairing reuse
« Reply #201 on: 03/21/2016 11:19 PM »

If the mounting hoop that the fairing halves are hinged to has a larger inner diameter than the outer diameter of the second/final stage, you could slide the entire opened up fairing & mounting hoop down the side of the stage and jettison it at the rear of the rocket, into the plume of the accelerating stage.  It would have to have clearance of the payload pedestal & payloads, as well as any exterior plumbing on the side of the rocket.

You don't need a full clamshell opening to slide your fairing back.
And making the cylindrical part of the fairing in a single piece, without joints, you can save a good amount of mass.
"Small" problem: sliding the fairing into the plume of the accelerating stage you are likely going to shred it in pieces smaller than those previously recovered.
I did this animation to look at the concept some month ago, then I realized the "small" problem .

Nice animation!  Captures the concept exactly.  I wonder if the "small" problem of the exhaust plume could be avoided if the rocket flew a more highly lofted trajectory and jettison the fairing right after MECO and before second stage ignition, using smaller ullage rockets?  Alternately throttle down the S2 engine as far as possible during jettison.   My first thoughts was that the potential to tear apart the fairing would look like the Saturn V second stage interstage in this clip.  ( it survived a bit scorched apparently )

#### Chris_Pi

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##### Re: Fairing reuse
« Reply #202 on: 03/22/2016 02:00 AM »
That Saturn interstage started to tumble pretty quick. I think having the engine running at all when the longer Falcon fairing drops down the whole length of the second stage might be a problem. Jettisoning or folding out the rear bevel on the fairing would increase the clearance quite a bit but it still has to come off very straight and preferably fast so the second stage can get started.

More than a few degrees rotation during separation and the fairing starts bumping into important parts. It could probably work but fairing separation would definitely not be boring for a while. More like a second really long interstage.

#### dorkmo

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##### Re: Fairing reuse
« Reply #203 on: 03/22/2016 02:31 AM »
im not really following, but for an idea, perhaps following seperation using thrusters the two halves could quickly dock with one another to become one again.

#### hrissan

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##### Re: Fairing reuse
« Reply #204 on: 03/22/2016 10:12 AM »
Might the future fairing be attached to the first stage and return together with it?

#### rpapo

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##### Re: Fairing reuse
« Reply #205 on: 03/22/2016 10:51 AM »
Might the future fairing be attached to the first stage and return together with it?
To do that, it would probably have to (1) cover the entire second stage, (2) be able to open very quickly at staging time and (3) survive the starting of the second stage motors.

If it could do all that, and close on its own, then it would probably help the aerodynamics of stage return by pushing the center of drag even higher on the stage.  That said, that would reduce the effectiveness of the grid fins unless they were moved even higher than they already are.
« Last Edit: 03/22/2016 10:52 AM by rpapo »
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#### cambrianera

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##### Re: Fairing reuse
« Reply #206 on: 03/22/2016 10:59 AM »
@Stan:
Sliding the fairing before MECO you can lock it on the upper part of the interstage, and get a free ride back to earth (what hrissan wrote): I remember Jim said spacecrafts need protection also after MECO, therefore this should be carefully balanced.
Throttling down second stage engine to minimum during sliding may be ok (but not a given).
@Chris:
A sliding fairing should have rails, therefore a straighter path & no lateral jerks on separation.
@dorkmo:
This means add to them complete navigation & RCS....
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#### Stan-1967

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##### Re: Fairing reuse
« Reply #207 on: 03/23/2016 02:53 PM »
@Stan:
Sliding the fairing before MECO you can lock it on the upper part of the interstage, and get a free ride back to earth (what hrissan wrote): I remember Jim said spacecrafts need protection also after MECO, therefore this should be carefully balanced.
Throttling down second stage engine to minimum during sliding may be ok (but not a given).
@Chris:
A sliding fairing should have rails, therefore a straighter path & no lateral jerks on separation.
@dorkmo:
This means add to them complete navigation & RCS....

I like the idea of sliding the fairing all the way onto S1 for the return ride, but I think this concept would then be limited to rockets with a S1 that delivers S2 & payload at very high altitudes where the exposed payload would not be damaged.  In reading the SpaceX F9 users manual, fairing jettison is predicated on the dyanamic pressure on the fairing falling to a specified amount.   The vehicle does not reach this until well into the burn of S2 and the rocket is only around 50km up at MECO. ( hence the lofted trajectory idea )

The Atlas V S1 on the other hand, is likely around 100km high at MECO.  I would note that the Atlas V sequence after MECO is to start S2 and immediately jettison the fairing once S2 thrust is nominal.   The Atlas V vehicle has other problems with this concept that make it less interesting to consider.   The concept of the sliding fairing might work on the FH center core, since it will be throttled down and have a longer burn time, plus the side cores will be giving extra push to get it to a high altitude at center core MECO.

I agree that some type of rail, plus bearings, would be needed to guide the fairing as it slides.   A stuck fairing in the wrong position would be loss of mission for the rocket.

#### Stan-1967

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##### Re: Fairing reuse
« Reply #208 on: 03/23/2016 03:01 PM »
im not really following, but for an idea, perhaps following seperation using thrusters the two halves could quickly dock with one another to become one again.

Watch the animation from cambrianera in reply#200.   How would separate halves autonomously dock after jettison?  You will need more than thrusters. You would need to install a separate docking mechanisms, avionics & special software, laser/radar rangefinding gear?  I think it would be a long list of very complicated stuff.

#### spacenut

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##### Re: Fairing reuse
« Reply #209 on: 03/23/2016 03:48 PM »
Fairing could also be attached to the second stage to protect the engine during reentry if and when a second stage is reused.

#### Comga

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##### Re: Fairing reuse
« Reply #210 on: 03/23/2016 05:26 PM »
[sarcasm]They could just have Scotty beam them back to the HIF.[/sarcasm]

If fairings are not ejected, their mass takes away from the payload, possibly driving it negative.
We have seen payloads launched into "hydrosynchronous orbits" when fairings don't eject.

SpaceX is staging earlier than optimum to recover the first stage.  They are not going to stage later than optimum to be out of the atmosphere and try to include the fairing in the first stage recovery. edit: IMO

Fairing halves will stay separate once separated.  As Stan-1967 said, rejoining would be of overwhelming complexity.

How about we not come up with more Rube Goldberg systems and wait to see what SpaceX actually does?
« Last Edit: 03/23/2016 05:27 PM by Comga »
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

#### Lar

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##### Re: Fairing reuse
« Reply #211 on: 03/23/2016 06:01 PM »
We tried the second stage as ship with cargo bay thing... didn't work that well... all of these fairing slides up and down ideas smack of that.

I agree with Comga, rather than doing what-if, why not try to figure out what SpaceX is doing and why and what things they are going to try next.  Some of the best threads on the site are those kind (the barge threads in many cases are like that)
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#### sevenperforce

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##### Re: Fairing reuse
« Reply #212 on: 03/23/2016 07:59 PM »
Last I heard, FH will use FT side boosters but a v1.1 core. So SpaceX isn't averse to retaining multiple versions of the same stage for different purposes.

To that end, might SpaceX consider two versions of the upper stage -- one that is expendable with the current breakaway fairing, and one that is reusable with a clamshell PICA-X-covered fairing that opens around 30 degrees to release the payload, then locks? It's a payload cut, but it might be worthwhile for lower-mass payloads to LEO.

With the fairing locked out at 30 degrees, the upper stage would passively orient into a retrograde attitude, and the PICA-X layer on the locked fairing would absorb the brunt of the compressive heating. It would also result in a significantly lower terminal velocity, which is good for landing. Higher center of gravity, though, which is less good for landing.

#### Lar

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##### Re: Fairing reuse
« Reply #213 on: 03/23/2016 08:50 PM »
Last I heard, FH will use FT side boosters but a v1.1 core. So SpaceX isn't averse to retaining multiple versions of the same stage for different purposes.

Do you have a cite for that.. I doubt they are building v1.1 cores any more.

As to the rest, I think it much more interesting to try to figure out what SpaceX actually are up to near term. But that's just me.
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#### spacenut

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##### Re: Fairing reuse
« Reply #214 on: 03/23/2016 08:59 PM »
Sorry, when I posted, I was thinking about the interstage between first and second stage, not the nose fairing.  What is wrong with dumping the fairings?  You can't save everything yet.

#### sevenperforce

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##### Re: Fairing reuse
« Reply #215 on: 03/23/2016 09:01 PM »
Sorry, when I posted, I was thinking about the interstage between first and second stage, not the nose fairing.  What is wrong with dumping the fairings?  You can't save everything yet.
The fairings are hella expensive.

#### robert_d

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##### Re: Fairing reuse
« Reply #216 on: 03/23/2016 09:05 PM »
Has anyone considered going the other way with the Faring? By that I mean make it super cheap like the wrapping on a candy bar? I know there are aerodynamic loads and all that but just wondering if a dry nitrogen pressurized gas bag made out of some tough material could be used. After all NASA is investigating inflatables for potential reentry use, so maybe not so crazy? Just wondering.

#### mme

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##### Re: Fairing reuse
« Reply #217 on: 03/23/2016 09:32 PM »
Sorry, when I posted, I was thinking about the interstage between first and second stage, not the nose fairing.  What is wrong with dumping the fairings?  You can't save everything yet.
The fairings are hella expensive.
My understanding is that they take a long time to make, are big to store and it's hard to ramp up production.
Space is not Highlander.  There can, and will, be more than one.

#### Jim

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##### Re: Fairing reuse
« Reply #218 on: 03/23/2016 09:38 PM »
Has anyone considered going the other way with the Faring? By that I mean make it super cheap like the wrapping on a candy bar? I know there are aerodynamic loads and all that but just wondering if a dry nitrogen pressurized gas bag made out of some tough material could be used. After all NASA is investigating inflatables for potential reentry use, so maybe not so crazy? Just wondering.

there is a thread on this and reasons that it is not feasible.

#### Stan-1967

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##### Re: Fairing reuse
« Reply #219 on: 03/24/2016 03:42 AM »
Has anyone considered going the other way with the Faring? By that I mean make it super cheap like the wrapping on a candy bar? I know there are aerodynamic loads and all that but just wondering if a dry nitrogen pressurized gas bag made out of some tough material could be used. After all NASA is investigating inflatables for potential reentry use, so maybe not so crazy? Just wondering.

It's not just aero loads.   The fairing shroud also provides an acoustic, thermal, chemical, & EMI environment that keeps the payload safe while waiting for launch as well as during ascent to orbit.  No cheap bag of gas is going to work for all those requirements.

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