Author Topic: Fairing reuse  (Read 435053 times)

Offline CyndyC

Re: Fairing reuse
« Reply #260 on: 04/02/2016 04:59 PM »
Along with the video Jim posted, this video of a SpaceX fairing separation test might help with the brainstorming:

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Offline D_Dom

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Re: Fairing reuse
« Reply #261 on: 04/02/2016 06:54 PM »
Thank you Jim and CyndyC! I really enjoy good high speed imagery, it helps me understand the forces involved. The Atlas fairing flex as it separates for example. The SpaceX chamber test demonstrates their fine tuned inertia absorbing system, just amazing.
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Offline chalz

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Re: Fairing reuse
« Reply #262 on: 04/04/2016 03:44 AM »
Suppose you wanted to add a parachute to try to make a fairing more survivable. Where on the fairing would you put it? Could the pushers handle the extra weight and would a change in CG affect the opening motion? I'm thinking they might have to attach a parachute halfway up the outside. Drill some holes in it and bolt it to it, maybe 100kg extra. Also perhaps a buoyancy aid will be necessary for the post splashdown procedure but SpaceX won't find that out until they can get one down in one piece.

Offline Stan-1967

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Re: Fairing reuse
« Reply #263 on: 04/04/2016 06:24 AM »
The problem of fairing reuse is really lacking a problem statement(s) to drive potential solutions.

Take for example the problem of precision landing hoverslams:
1.  Pioneer the work to execute hypersonic retropulsion
2.  Slow the stage to "x" meters/sec., +- some value "y", at elevation "A"
3.  perform #2 velocity change with "M1" kg's of fuel and oxidizer.
4.  perform #2 & #3 above with +- 15 meters accuracy to a predetermined latitude/longitude coordinate
5.  Do all the above, but don't land at an angle and tip over and explode, don't break a leg and tip over and explode, don't have horizontal velocity and hit the barge and explode, don't run out of fuel and explode, etc. etc.

My point being is that the hoverslam maneuver first defined the vehicle orientation, stability, velocity change requirements, navigation requirements, and load tolerance requirements before SpaceX added all the systems that adapted mass trade-offs against them. ( i.e grid fins, landing legs, ASDS vs. RTLS, etc. )

So for fairing reuse, what are the problems?   How do they limit ( or eliminate ) the possible solutions?

Here is what I can come up with:
1.  The fairing needs to be slowed to a speed that does not fracture the composite structure no matter the orientation at impact.  ( let imaginations flow if this is to be done with parachutes, active flight control surfaces deployed, sliding the fairing down the side of S1 prior to MECO, rocket retropropulsion aka Soyuz capsule etc.)

2.  Methods proposed in #1 cannot jeopardize the payload, or be less reliable than existing disposable fairings.

3.  Landing accuracy needs to occur in a specified landing ellipse or search grid that is a 100X smaller area than a ballistic reentry with unstable aerodynamics.  Want a bigger margin for area?  How will you search it before winds & currents expand the search area to unmanagable proportion?

4.  The fairings cannot be left in the ocean for extended search times in excess of 24-36 hours.  Again want more time? fine, how will you home in on the fairing when wind, current, weather, and search resources make recovery moot.

5.  Allowable extra mass is 1000kg per half.   This addition penalizes S1 about 9200 kg's of extra fuel that cannot be used for RTLS or DPL, not to mention less mass to orbit.  If you want a bigger mass budget, fine.  It comes at the expense of S1 reuse probability, and could be the difference between RTLS or DPL, not to mention success or failure of S1 reuse.  If you can propose some method using less mass, great! Better chance for S1 re-use.
« Last Edit: 04/05/2016 05:01 AM by Stan-1967 »

Offline bioelectromechanic

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Re: Fairing reuse
« Reply #264 on: 04/04/2016 12:58 PM »
How much does it weight? dimensions? surface area? how much additional mass would systems require? will it require a change in the F9 flight profile? what is dV cost of the flight profile change?
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Offline cambrianera

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Re: Fairing reuse
« Reply #265 on: 04/04/2016 08:06 PM »

So for fairing reuse, what are the problems?   How do they limit ( or eliminate ) the possible solutions?


Nice post, I would like to add my comment.

Let me start with #2:
Would we discuss addition/tweaks to existing disposable fairings to avoid too many variables? This also not jeopardizes payload nor worsen reliability.

#1 Orientation is paramount, going convex first you can spread conveniently the shock wave at the atmospheric interface, then going concave first when subsonic you can slow down under 20 m/s of terminal velocity. I see deployable panels for convex first, and midsize drogues/parachutes for concave first.

#3 Radio beacons?

#4 Agree on search time, I think would be enough w radio beacon.

#5 I will start the "guesstimate" phase soon, but let me say 1000 kg is too much. Not more than 300 kg per half to avoid compounding effects on the fairing itself (more mass, more structure and so on)

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Offline Lars-J

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Re: Fairing reuse
« Reply #266 on: 04/04/2016 08:20 PM »
All this "fairing reuse" talk seems to be misleading. You don't want that. What you actually want - but somehow refuse to call it - is a payload bay with doors that can open and close. (like on Shuttle)

It's a certainly doable and a good idea for a reusable upper stage, but it will weigh significantly more and be a lot more complex. You need a lot of mass margin to pull it off.

(An upper stage with an integrated cargo bay is what I have been advocating for commercial BFR use, where margins would be plentiful)

But don't think of it is a "reused fairing". Think of it as a payload bay - it is a far more realistic approach.
« Last Edit: 04/04/2016 08:43 PM by Lars-J »

Offline OxCartMark

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Re: Fairing reuse
« Reply #267 on: 04/04/2016 09:25 PM »
All this "fairing reuse" talk seems to be misleading. You don't want that. What you actually want - but somehow refuse to call it - is a payload bay with doors that can open and close. (like on Shuttle)

It's a certainly doable and a good idea for a reusable upper stage, but it will weigh significantly more and be a lot more complex. You need a lot of mass margin to pull it off.

(An upper stage with an integrated cargo bay is what I have been advocating for commercial BFR use, where margins would be plentiful)

But don't think of it is a "reused fairing". Think of it as a payload bay - it is a far more realistic approach.

Then you'd be taking it all the way up and as has been hashed and re-hashed above won't work because taking the current fairing along for the whole ride cuts your payload to orbit in half and you're talking about making it weigh more and then taking it to orbit.  And not only do you pay the mass penalty once going up but you've also added more energy to the second stage that needs to be dissipated on the way down with thrust and with heating.  And, since under the scenario you propose it would have to survive re-entry at many times the speed that it currently hits at it would need to be made structurally stouter (heavier) to survive and would need a heat shield (more weight) if it is even possible to make a heat shield work on a piece of plastic.  My seat of the pants feel is that you'd reduce the payload to orbit to 1000 pounds but I may be off by a few thousand pounds and maybe it wouldn't be capable of going that fast.

Offline savuporo

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Re: Fairing reuse
« Reply #268 on: 04/04/2016 09:46 PM »
Not sure if this is feasible or buys you anything much, but one could envision a system where separated sides fairing will remain connected via a tether. Definitely would require extra pyrotechnics to make the separation clean - and separation is risky as it is.
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Offline Jdeshetler

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Re: Fairing reuse
« Reply #269 on: 04/05/2016 03:22 AM »
Speed up the slow motion of SpaceX fairing separation test back to "real time".
It moved faster than the test straps that is holding it.



This is how fast a fairing comes off
« Last Edit: 04/05/2016 03:23 AM by Jdeshetler »

Offline Stan-1967

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Re: Fairing reuse
« Reply #270 on: 04/05/2016 04:58 AM »
Not sure if this is feasible or buys you anything much, but one could envision a system where separated sides fairing will remain connected via a tether. Definitely would require extra pyrotechnics to make the separation clean - and separation is risky as it is.

Why is my brain having images of "Space Clackers"?



But seriously, to what effect would the tether do anything useful?  What benefit is derived from this?   What do you want to do with two fairing halves connected with a tether?

Offline Stan-1967

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Re: Fairing reuse
« Reply #271 on: 04/05/2016 06:01 AM »

snip...

#1 Orientation is paramount, going convex first you can spread conveniently the shock wave at the atmospheric interface, then going concave first when subsonic you can slow down under 20 m/s of terminal velocity. I see deployable panels for convex first, and midsize drogues/parachutes for concave first.

#3 Radio beacons

 snip...


As to radio beacons, I think that not only could the fairings be instrumented with either radio beacons, but also sono emitters that could be picked up and triangulated with prepositioned sonobouys in the landing zone.  The tough part is still getting to a landing zone.

I get the convex/concave choices for managing shock and drag, but I am not sure a fairing (half) can maintain attitude control during re-entry, or during decent at terminal velocity.   Are you certain of the stability?  I do not know.   

It looks like it would have dynamic instability and tumble, roll, & spin all over the place.  Indeed I think figuring out the existing stability characteristics is a good starting point.  At the simple end of the spectrum, maybe a drogue chute can fix it, if that doesn't do the job, move on to deployable passive control surfaces, then active surfaces. 


I had another idea for stability.   Imagine the inside of each fairing to have a bladder ( thin rubber/plastic/composite?) lightly adhered ( think 3M yellow stick notes type of adhesion) to the inside surface of the composite fairing shell.   All the anechoic foams,insulation, & active sonic devices are layered on top of this bladder, and continue to perform the functions needed for the fairing environment.   The fairing can look and work just as the existing items currently do.

When the fairing is jettisoned, a COPV attached inside the fairing half will inflate the bladder, and the pressure of the gas will peel the bladder away from the inside of the fairing and inflate to a form that mirrors the composite fairing half, and once inflated the fairing will have virtually the same shape as a full fairing.  Most of the anechoic foams/insulation will pop off during this event.

What next?   I might want to try and spin it up for some stability, or I might try to have some passive aero surfaces spin it.   Whatever the method ( passive surfaces or drogue chute ) it takes to impart stability, that is what I want to solve.  The reason is so that it follows a stable ballistic trajectory, no tumbling, surfing, or gliding all over the downrange ocean.    This minimizes the area of the landing zone, and enables location and recovery.   At some point, maybe 2000'-3000' above sea level, it would deploy a chute for a soft landing at some angle on it's side, and preferably with the gas bladder impacting the ocean first. (like an airbag softening the impact)


Offline JamesH65

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Re: Fairing reuse
« Reply #272 on: 04/05/2016 09:13 AM »

snip...

#1 Orientation is paramount, going convex first you can spread conveniently the shock wave at the atmospheric interface, then going concave first when subsonic you can slow down under 20 m/s of terminal velocity. I see deployable panels for convex first, and midsize drogues/parachutes for concave first.

#3 Radio beacons

 snip...


As to radio beacons, I think that not only could the fairings be instrumented with either radio beacons, but also sono emitters that could be picked up and triangulated with prepositioned sonobouys in the landing zone.  The tough part is still getting to a landing zone.


Isn't the obvious route for location to simple have a GPS + satellite link on board that transmits its exact location in real time? Cost and weight minimal, accuracy within 1m.

Offline Jim

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Re: Fairing reuse
« Reply #273 on: 04/05/2016 11:33 AM »

When the fairing is jettisoned, a COPV attached inside the fairing half will inflate the bladder, and the pressure of the gas will peel the bladder away from the inside of the fairing


How are you going to keep it in place and yet make inflation "peel" it off.

Offline Stan-1967

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Re: Fairing reuse
« Reply #274 on: 04/05/2016 01:54 PM »

When the fairing is jettisoned, a COPV attached inside the fairing half will inflate the bladder, and the pressure of the gas will peel the bladder away from the inside of the fairing


How are you going to keep it in place and yet make inflation "peel" it off.

Peeling it off is going to be an important trick.   I think adhesives engineered like this one would be candidates.

http://solutions.3m.com/wps/portal/3M/en_US/Adhesives/Tapes/Products/~/3M-Repositionable-75-Spray-Adhesive-Net-Wt-10-25-oz-12-per-case?N=5396314+4294924311&rt=rud

This class of adhesives have a storied past regarding the 3M Post-it-notes, however the adhesive can be engineered to adjust the strength/holding properties, but more importantly, the peel strength properties.   It needs to be strong enough to hold all the inner linings materials and insulation of the fairing to the bladder.   If you look at the mass of the fairing materials, and the very large surface area of the inside of the composite fairing shell, the holding strength is not very large in terms of Newtons/cm^2.   The peel strength probably the more critical property.   You need to get the inside of the bladder lifted from a small corner or edge, and then "unzip" the entire length of the assembly.
« Last Edit: 04/05/2016 01:58 PM by Stan-1967 »

Offline savuporo

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Re: Fairing reuse
« Reply #275 on: 04/05/2016 03:43 PM »
But seriously, to what effect would the tether do anything useful?  What benefit is derived from this?   What do you want to do with two fairing halves connected with a tether?
You could have the tether reel in a few seconds after clean separation, pulling the sides together. This might make the reentry tumble more survivable, or worse. No idea - just an idle thought
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Offline cambrianera

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Re: Fairing reuse
« Reply #276 on: 04/05/2016 07:00 PM »
But seriously, to what effect would the tether do anything useful?  What benefit is derived from this?   What do you want to do with two fairing halves connected with a tether?
You could have the tether reel in a few seconds after clean separation, pulling the sides together. This might make the reentry tumble more survivable, or worse. No idea - just an idle thought
I thought to that. Fishing reels are reliable, small mass, small friction devices that can be modified on purpose.
Still remaining important issues:
-risk of tangling into payload (or between tethers, if more than one);
-rejoining of halves to be completed by other devices (hooks, clamps or similar);
-terminal velocity probably too high to survive sea impact (need some other device).

Assuming the same mass, obviously separate halves have smaller mass/surface ratio.

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Offline llanitedave

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Re: Fairing reuse
« Reply #277 on: 04/05/2016 07:02 PM »
The fairing is not that heavy, and it's already relatively robust as it is.  I think it might not need anything more than a small drogue chute and a homing device, at least for starters.
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Offline cambrianera

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Re: Fairing reuse
« Reply #278 on: 04/05/2016 07:11 PM »

I had another idea for stability.   Imagine the inside of each fairing to have a bladder ( thin rubber/plastic/composite?) lightly adhered ( think 3M yellow stick notes type of adhesion) to the inside surface of the composite fairing shell.   All the anechoic foams,insulation, & active sonic devices are layered on top of this bladder, and continue to perform the functions needed for the fairing environment.   The fairing can look and work just as the existing items currently do.

When the fairing is jettisoned, a COPV attached inside the fairing half will inflate the bladder, and the pressure of the gas will peel the bladder away from the inside of the fairing and inflate to a form that mirrors the composite fairing half, and once inflated the fairing will have virtually the same shape as a full fairing.  Most of the anechoic foams/insulation will pop off during this event.


Intriguing idea, but I see a couple of important drawbacks:
-mass. The bladder should have some structural integrity, otherwise should not stand the stresses of peeling, mantaining a pressure enough to stabilize against airflow and finally splashdown; this having the same surface as a fairing half.
-reusability. You basically throw away all the internal parts of the fairing, moreover you have to reapply the bladder to the half fairing (assuming the bladder itself can be reused).
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Offline savuporo

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Re: Fairing reuse
« Reply #279 on: 04/05/2016 07:20 PM »
-risk of tangling into payload (or between tethers, if more than one);
If you had three sided fairing, tangling potential could be maybe smaller, if there are three tethers connecting the corners. Hard to clear the rocket with two-halve clamshell fairing, would need extra pyro gear or something
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