Author Topic: Fairing reuse  (Read 326170 times)

Offline georgegassaway

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Re: Fairing reuse
« Reply #440 on: 06/04/2016 07:12 PM »
DAZ,  what you say makes a lot of sense.

First they need to get one or two fairings back just to see what shape they are in after enduring re-entry and splashdown in the ocean with whatever type of chute is used (probably simple non-steerable).  Also, likely documentation with several GoPros (they did that with one GoPro years ago, for more serious testing they’d use several plus a likely small “black box” to record all sorts of sensor data including G sensors).  I also would suspect the fairings themselves do not tend to float (unless they have a honeycomb construction or some other fabrication method that adds buoyancy as a side benefit), so they may need to add some buoyancy to them such as foam (K.I.S.S.) or inflatable air bags (If they use a ballute to help with re-entry, that could do double duty as a “bouy” after landing)

If  the fairings are badly damaged by re-entry heating or aerodynamic loads, that would be a key upstream problem to work on , such as perhaps a “Ballute” system to cause enough high drag (and stability) during re-entry to make the heating effects gentler (and the fairings may not be practical to make them aerodynamically stable without some deployable system such as ballute or far more complex means).

So once they get 1-2 back and learn what needs to be done, and what is fine as-is, they can move on with upgrades and determine whether a parachute landing into the ocean is good enough, to refine the chute system, or if they have to try to snag it with a copter (To me the only good reason for copter air-snag would be if the fairings can't get soaked in saltwater).

I am 99%+ sure that an “airplane” based horizontal air-snag recovery is totally impractical.  The aerodynamic and mass forces of a small  Discoverer / Corona satellite being snagged horizontally, and the forces of the relatively HUGE fairing halves are orders of magnitude differences.  Indeed the fairings are also relatively flimsy once separated, they would tend to deform and rip due to the massive loads of the air-snag, as well as spin and wobble like crazy until ripping apart.  To “reel one inside” the fuselage, would require a cargo plane of about the size of a C-5 , and one heck of a method to stabilize the fairing half so it could be reeled inside the rear opening.  Actually I am not even sure a fairing would be small enough to fit thru the rear ramp door of a C-5, and it seems so unlikely that a horizontal air-snag by airplane could be practical that I’m not inclined to go look up the stats on fairing dimensions vs C-5 or other very large cargo aircraft.
« Last Edit: 06/04/2016 07:18 PM by georgegassaway »

Offline Kabloona

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Re: Fairing reuse
« Reply #441 on: 06/05/2016 12:03 AM »
Quote
  I also would suspect the fairings themselves do not tend to float (unless they have a honeycomb construction or some other fabrication method that adds buoyancy as a side benefit),

The fairings do have a honeycomb core and we've already seen at least one fairing half wash up on shore (the one from which the GoPro video of fairing descent was recovered). Additional flotation wouldn't hurt, of course, but the fairings are likely quite buoyant already.

Offline Bob Shaw

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Re: Fairing reuse
« Reply #442 on: 06/05/2016 12:35 AM »
'Buoyant' is pretty easy. Using the suckers again is hard.

Offline ppb

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Re: Fairing reuse
« Reply #443 on: 06/05/2016 12:52 AM »
Plus I really doubt a steerable chute could have the accuracy to get it down onto a boat anyway.
Military precision airdrop steerable parafoils ( Atair, MMIST, SPADES, Zodiac etc) had accuracy of about 50-200 meters ~8 years ago. Depending on payload size and drop altitude of course. Not hitting a barge with that, but i guess military never had a land on a dime requirement.
Maybe the boat can drive the last 50-100m to get under the fairing. It doesn't have to land on a droneship, since a fairing coming down under a chute isn't all that dangerous... mass in only ~2t, terminal velocity is probably a few m/s, and there's no explosives aboard. Land it on a airbag sitting on the deck.
I really like this idea if salt water immersion is an obstacle to reuse. After a few notable learning experiences (see e.g. F1 fuel slosh failure) Spacex has proven themselves to harbor a pretty good stable of controls engineers. I wouldn't be surprised if they could reduce parafoil CEP to the point where the ship catcher wouldn't have to move much at all (Yes, I know analysis without numbers is just an opinion, to quote another poster's byline)

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Offline Bob Shaw

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Re: Fairing reuse
« Reply #444 on: 06/05/2016 01:10 AM »
Plus I really doubt a steerable chute could have the accuracy to get it down onto a boat anyway.
Military precision airdrop steerable parafoils ( Atair, MMIST, SPADES, Zodiac etc) had accuracy of about 50-200 meters ~8 years ago. Depending on payload size and drop altitude of course. Not hitting a barge with that, but i guess military never had a land on a dime requirement.
Maybe the boat can drive the last 50-100m to get under the fairing. It doesn't have to land on a droneship, since a fairing coming down under a chute isn't all that dangerous... mass in only ~2t, terminal velocity is probably a few m/s, and there's no explosives aboard. Land it on a airbag sitting on the deck.
I really like this idea if salt water immersion is an obstacle to reuse. After a few notable learning experiences (see e.g. F1 fuel slosh failure) Spacex has proven themselves to harbor a pretty good stable of controls engineers. I wouldn't be surprised if they could reduce parafoil CEP to the point where the ship catcher wouldn't have to move much at all (Yes, I know analysis without numbers is just an opinion, to quote another poster's byline)

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Look at the AI in quadcopter drones; give the latest commercially available examples a Lat/Long and they'll go there, or follow a signal. SpaceX doesn't need to re-invent the wheel, just to place a landing pad in the right place. Once the things hit the water they are probably useless anyway...

Offline meekGee

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Re: Fairing reuse
« Reply #445 on: 06/05/2016 03:57 AM »
Or use an airplane to recover them. Doesn't have to be a helicopter. Corona used airplanes. Seems like it'd be cheaper, faster, maybe safer. Airplanes are lower maintenance, can cover a much longer range, and SpaceX already uses them sometimes just for observing the booster recovery attempts.

Once a fairing halve is caught by the plane, however, I'm not entirely sure how it'd be gently placed on the ground.

There's a trick to that.

If the line is long, and the airplane flies in a tight circle, the bottom of the line remains stationary  (so the line describes a down-vertex cone.

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Offline pericynthion

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Re: Fairing reuse
« Reply #446 on: 06/05/2016 05:54 AM »
There's a trick to that.

If the line is long, and the airplane flies in a tight circle, the bottom of the line remains stationary  (so the line describes a down-vertex cone.

Unfortunately that doesn't work well if there's any wind.  But there are some tricks you can do.

Offline The Amazing Catstronaut

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Re: Fairing reuse
« Reply #447 on: 06/05/2016 06:02 AM »
Could it pop floatation bags and would it stay in one (well, two) piece(s) under wave action? I'm trying to think of ways a fairing half could reach the surface of the sea without being either totally inundated or lost under anything but the most ideal sea conditions, just as a counterpoint to air recovery. I'm not having very good ideas.
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Online AncientU

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Re: Fairing reuse
« Reply #448 on: 06/05/2016 01:44 PM »
When fairings are making a controlled descent, are there any more significant (dangerous) pieces planned to fall immediately downrange of the launch site?  (Second stages obviously deorbit in the Southern Sea or elsewhere.)

Will this either begin to shrink the NOTAM restrictions, or eventually eliminate them?
Can reusable rockets eventually be launched from interior (desert SouthWest, for instance) launch sites?

This could be a driver for fairing recovery, since the cost argument seems to be weak, and production capacity is trivial to scale.  If it is just cost, then someone is planning for really cheap launches.
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Offline Lar

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Re: Fairing reuse
« Reply #449 on: 06/05/2016 01:57 PM »
This could be a driver for fairing recovery, since the cost argument seems to be weak, and production capacity is trivial to scale.  If it is just cost, then someone is planning for really cheap launches.
Weak cost argument? If fairings really cost 5M a pair and you can recover/refurbish for 30% of that steady state (long term that's a generous number I GUESS (don't know)) it's a strong argument. even if it's only 3M or so you save a time.

As for scaling capacity, there's a step function there somewhere if you're already running parts of the process 24/7, they may want to avoid the cost of duplicating most or all of the line. 

Do we have hard numbers on the production process and timings?
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Offline cscott

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Re: Fairing reuse
« Reply #450 on: 06/05/2016 02:59 PM »
AIUI the production capacity is *not* trivial to scale.  The equipment is large, a lot of manual labor is involved; you'd need to build a new factory to hold the new equipment and train a new workforce.  And those are then ongoing fixed costs you incur even when you don't happen to need the excess capacity.

SpaceX has run the spreadsheets.

Offline joek

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Re: Fairing reuse
« Reply #451 on: 06/05/2016 03:08 PM »
...
This could be a driver for fairing recovery, since the cost argument seems to be weak, and production capacity is trivial to scale.  If it is just cost, then someone is planning for really cheap launches.

If they save $1 in all-up costs, they are ahead.  That they are seriously pursuing fairing recovery-reuse at this time suggests that it is high on the list of potential cost saving measures.

Online AncientU

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Re: Fairing reuse
« Reply #452 on: 06/05/2016 04:23 PM »
...
This could be a driver for fairing recovery, since the cost argument seems to be weak, and production capacity is trivial to scale.  If it is just cost, then someone is planning for really cheap launches.

If they save $1 in all-up costs, they are ahead.  That they are seriously pursuing fairing recovery-reuse at this time suggests that it is high on the list of potential cost saving measures.

I agree that the cost argument is most likely -- though I doubt they'd do all of this capability augmentation for your $1 net per launch (did you mean $1M?).  If fairing pairs are $5M as Lar speculates (my guess would be half or less of that), they would have to save a substantial portion of that to avoid locking in that $5M into the base price.  If they can save a substantial portion, say 75% or more, then baseline cost improvement is relevant.

Going back to the circa $43M price for reused booster, a couple million dollars saved on fairing recovery is less than 5%... never getting to the ultimate price range that way.  But, that said, if they see $2-3M as significant cost factor down the road, then this could actually be a harbinger of something incredible.
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Offline guckyfan

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Re: Fairing reuse
« Reply #453 on: 06/05/2016 05:13 PM »
Production capacity may not be trivial to scale. It seems they are limited in space at the Hawthorne site. They may have to transfer the whole fairing production to another location to increase capacity. They may not want to do that.

Plus Elon Musks just likes reuse as long as the cost balance is positive.

Offline Lar

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Re: Fairing reuse
« Reply #454 on: 06/05/2016 05:17 PM »
I think they'd do it for positive 1.00 USD per fairing. Because it's a way to learn about stuff, and just because it was barely marginal on this ship, it might be hugely positive on the next one.

I don't think it's barely marginal, I think it's a big win but even if it was.... The 5M isn't from me, I read it somewhere but I forget where. I think Musk said it was in the millions...
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Offline MP99

Re: Fairing reuse
« Reply #455 on: 06/05/2016 07:14 PM »
For FH, which obviously stages the centre core later, could the fairing be retained on the core, and recovered as part of the core landing?

It would obviously imply a larger fairing which would also encapsulate the upper stage. Could imagine this causing various issues, including loss of commonality with F9 fairing.

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Offline oiorionsbelt

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Re: Fairing reuse
« Reply #456 on: 06/06/2016 12:00 AM »
It appears as though the fairings end up as flotsam.
Get it in the water gently, pick it up quickly, design for salt water and see if it's any good to use again.

Offline joek

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Re: Fairing reuse
« Reply #457 on: 06/06/2016 03:30 AM »
I agree that the cost argument is most likely -- though I doubt they'd do all of this capability augmentation for your $1 net per launch (did you mean $1M?).
...

Meant $1.00.  That SpaceX is pursuing fairing reuse at this point suggests that it is potentially low-hanging fruit.  That is, if you put recovery-reuse-cost-benefit on a Pareto chart, it would probably be near the top.  In any case, that savings from any single effort must be large in order to justify pursuit is a disease that SpaceX does not seem to be afflicted with.

Offline wannamoonbase

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Re: Fairing reuse
« Reply #458 on: 06/06/2016 04:58 AM »
I agree that the cost argument is most likely -- though I doubt they'd do all of this capability augmentation for your $1 net per launch (did you mean $1M?).
...

Meant $1.00.  That SpaceX is pursuing fairing reuse at this point suggests that it is potentially low-hanging fruit.  That is, if you put recovery-reuse-cost-benefit on a Pareto chart, it would probably be near the top.  In any case, that savings from any single effort must be large in order to justify pursuit is a disease that SpaceX does not seem to be afflicted with.

I think it could also mean that upper stage recovery is some distance down the road.   Falcon 9 replacement type stuff.
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Offline S.Paulissen

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Re: Fairing reuse
« Reply #459 on: 06/06/2016 05:25 AM »
It could also mean they need fairings as much as they need reused cores to launch satellites.
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