Author Topic: Fairing reuse  (Read 173531 times)

Online envy887

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Re: Fairing reuse
« Reply #640 on: 03/19/2017 11:58 PM »
They aren't intended for immersion. You'll have to get them w/o reaching the water.

Which means either airborne recovery e.g. snag them with a drone, not unlike with Smart recovery, or you fly them back to land, and somehow recover them.

Or land them on something floating on the water.

Offline meekGee

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Re: Fairing reuse
« Reply #641 on: 03/20/2017 12:43 AM »
They aren't intended for immersion. You'll have to get them w/o reaching the water.

Which means either airborne recovery e.g. snag them with a drone, not unlike with Smart recovery, or you fly them back to land, and somehow recover them.

Or land them on something floating on the water.

To the extent that they can remain "dry", in wave action, salt spray, etc.

And that bouncing around on the waves doesn't exceed structural limits, or that at least such issues can be identified afterwards.
« Last Edit: 03/21/2017 05:21 AM by meekGee »
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Offline Lars-J

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Re: Fairing reuse
« Reply #642 on: 03/20/2017 03:39 AM »
They aren't intended for immersion. You'll have to get them w/o reaching the water.

Which means either airborne recovery e.g. snag them with a drone, not unlike with Smart recovery, or you fly them back to land, and somehow recover them.

Or the third option (most likely IMO), precision land them on a barge or boat.

Offline ChrisWilson68

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Re: Fairing reuse
« Reply #643 on: 03/20/2017 07:21 AM »
They aren't intended for immersion. You'll have to get them w/o reaching the water.

Which means either airborne recovery e.g. snag them with a drone, not unlike with Smart recovery, or you fly them back to land, and somehow recover them.

Or the third option (most likely IMO), precision land them on a barge or boat.

Then, just refuel them and let them fly themselves back to the launch site.

Offline Kaputnik

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Re: Fairing reuse
« Reply #644 on: 03/20/2017 09:17 PM »
In the absence of better information we are going round and round in circles here. I think that every possibility has been suggested by somebody at some point. By way of recap, I think these are:
- mid air recovery by long range helo
- mid air recovery by short range ship based helo
- unmanned variant of the above
- mid air recovery by fixed wing aircraft with handover to helo for landing
- precision touchdown on ship/barge
- precision touchdown on inflatable raft
- modified PLF with aerodynamic control surfaces for flyback

The fascinating thing is that *all* of these options can be discounted as unworkable for various reasons.
Have I missed any off the list?
Waiting for joy and raptor

Offline Lars-J

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Re: Fairing reuse
« Reply #645 on: 03/20/2017 10:00 PM »
In the absence of better information we are going round and round in circles here. I think that every possibility has been suggested by somebody at some point. By way of recap, I think these are:
- mid air recovery by long range helo
- mid air recovery by short range ship based helo
- unmanned variant of the above
- mid air recovery by fixed wing aircraft with handover to helo for landing
- precision touchdown on ship/barge
- precision touchdown on inflatable raft
- modified PLF with aerodynamic control surfaces for flyback

The fascinating thing is that *all* of these options can be discounted as unworkable for various reasons.
Have I missed any off the list?

How in the world is precision touchdown on ship/barge/raft unworkable?

Online docmordrid

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Re: Fairing reuse
« Reply #646 on: 03/21/2017 12:44 AM »
In the absence of better information we are going round and round in circles here. I think that every possibility has been suggested by somebody at some point. By way of recap, I think these are:
- mid air recovery by long range helo
- mid air recovery by short range ship based helo
- unmanned variant of the above
- mid air recovery by fixed wing aircraft with handover to helo for landing
- precision touchdown on ship/barge
- precision touchdown on inflatable raft
- modified PLF with aerodynamic control surfaces for flyback

The fascinating thing is that *all* of these options can be discounted as unworkable for various reasons.
Have I missed any off the list?

How in the world is precision touchdown on ship/barge/raft unworkable?

Airborne Systems Dragonfly precision drop system, good for 10,000 lbs, only specs a 250m accuracy.

http://airborne-sys.com/wp-content/uploads/2016/08/ASG-DragonFly-20170206-English.pdf
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Offline ChrisC

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Re: Fairing reuse
« Reply #647 on: 03/21/2017 02:19 AM »
In the absence of better information we are going round and round in circles here. I think that every possibility has been suggested by somebody at some point.

And we will again in about two weeks.  Wash, rinse, repeat until more facts come in.  See you in April.
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Offline meekGee

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Re: Fairing reuse
« Reply #648 on: 03/21/2017 05:23 AM »
In the absence of better information we are going round and round in circles here. I think that every possibility has been suggested by somebody at some point. By way of recap, I think these are:
- mid air recovery by long range helo
- mid air recovery by short range ship based helo
- unmanned variant of the above
- mid air recovery by fixed wing aircraft with handover to helo for landing
- precision touchdown on ship/barge
- precision touchdown on inflatable raft
- modified PLF with aerodynamic control surfaces for flyback

The fascinating thing is that *all* of these options can be discounted as unworkable for various reasons.
Have I missed any off the list?
You can add long line dropoff from fixed wing aircraft. I don't think it was ever tried with something this big tho
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Offline JamesH65

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Re: Fairing reuse
« Reply #649 on: 03/21/2017 09:24 AM »
Anyone have any guesses on what the glide angle of a fairing is? Perhaps with fins/winglets? And how far downrange are they released, and how fast are they going at release?

Offline Kaputnik

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Re: Fairing reuse
« Reply #650 on: 03/21/2017 11:22 AM »
In the absence of better information we are going round and round in circles here. I think that every possibility has been suggested by somebody at some point. By way of recap, I think these are:
- mid air recovery by long range helo
- mid air recovery by short range ship based helo
- unmanned variant of the above
- mid air recovery by fixed wing aircraft with handover to helo for landing
- precision touchdown on ship/barge
- precision touchdown on inflatable raft
- modified PLF with aerodynamic control surfaces for flyback

The fascinating thing is that *all* of these options can be discounted as unworkable for various reasons.
Have I missed any off the list?
You can add long line dropoff from fixed wing aircraft. I don't think it was ever tried with something this big tho

How does that work? Do you reel it out realky fast, to negate airspeed, or do you fly a circle with a long tow?
Waiting for joy and raptor

Offline Kaputnik

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Re: Fairing reuse
« Reply #651 on: 03/21/2017 11:28 AM »
Anyone have any guesses on what the glide angle of a fairing is? Perhaps with fins/winglets? And how far downrange are they released, and how fast are they going at release?

I can't put any number to this right now (making it opinion rather than analysis) but I think the terminal velocity of a fairing half will be pretty low, making for a slow glide and a short range. Also, they are released ahortly after staging and will continue up on a ballistic trajectory alongside the first stage, making entry at a similar distance downrange (they are too high in the atmosphere, I think, to be able to make any aerodynamic manoeuvres).
So, if y are wondering whether the fairing halves would be able to glide back towards to the landing site for easier helo recovery, the answer is probably no.
Waiting for joy and raptor

Offline meekGee

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Re: Fairing reuse
« Reply #652 on: 03/21/2017 01:51 PM »
In the absence of better information we are going round and round in circles here. I think that every possibility has been suggested by somebody at some point. By way of recap, I think these are:
- mid air recovery by long range helo
- mid air recovery by short range ship based helo
- unmanned variant of the above
- mid air recovery by fixed wing aircraft with handover to helo for landing
- precision touchdown on ship/barge
- precision touchdown on inflatable raft
- modified PLF with aerodynamic control surfaces for flyback

The fascinating thing is that *all* of these options can be discounted as unworkable for various reasons.
Have I missed any off the list?
You can add long line dropoff from fixed wing aircraft. I don't think it was ever tried with something this big tho

How does that work? Do you reel it out realky fast, to negate airspeed, or do you fly a circle with a long tow?
The latter.

Long line, draggy device, fly in a circle.

Legend has it that you can hand pick mail that way, but legends are famously exaggerated....

And it's a hypothetical, I don't think that's really in the plan.
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Online LouScheffer

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Re: Fairing reuse
« Reply #653 on: 03/21/2017 02:48 PM »
In the absence of better information we are going round and round in circles here. I think that every possibility has been suggested by somebody at some point. By way of recap, I think these are:
- mid air recovery by long range helo
- mid air recovery by short range ship based helo
- unmanned variant of the above
- mid air recovery by fixed wing aircraft with handover to helo for landing
- precision touchdown on ship/barge
- precision touchdown on inflatable raft
- modified PLF with aerodynamic control surfaces for flyback

The fascinating thing is that *all* of these options can be discounted as unworkable for various reasons.
Have I missed any off the list?
How in the world is precision touchdown on ship/barge/raft unworkable?
Airborne Systems Dragonfly precision drop system, good for 10,000 lbs, only specs a 250m accuracy.
http://airborne-sys.com/wp-content/uploads/2016/08/ASG-DragonFly-20170206-English.pdf
But parachutes can be much more accurate. Parachute landing competitions have accuracies in the low cm range (they don't even record above 16cm, which is considered a complete miss).  So I would not rule this one out, if SpaceX cares to put some work into landing accuracy.

Offline Swoopert

Re: Fairing reuse
« Reply #654 on: 03/21/2017 04:19 PM »
But parachutes can be much more accurate. Parachute landing competitions have accuracies in the low cm range (they don't even record above 16cm, which is considered a complete miss).  So I would not rule this one out, if SpaceX cares to put some work into landing accuracy.

The types of parachute used for accuracy landing competitions are distinctly unsuited to these purposes. They are designed to open at very low speed, come in at an extremely steep glide angle, and require a very small range of wind conditions (usually less than 10-15kts and steady) to achieve that level of accuracy, which you're unlikely to see in the middle of the ocean where the fairings will end up due to the poor glide angle.

Swoopert.

2-time British Collegiate Parachute Accuracy champion

Offline Kaputnik

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Re: Fairing reuse
« Reply #655 on: 03/21/2017 04:55 PM »
Another one to suggest and instantly dismiss:
Steerable foil landing on a moving platform (the idea being that the moving platform, e.g. a ship with a cushion on its aft deck, or towing an inflatable raft) can compensate somewhat for the inaccuracy of the incoming fairing.
Having seen an episode of Top Gear where they tried landing a parachutist in the back of a moving car, it seems that moving the landing target only makes things much harder...
Waiting for joy and raptor

Online LouScheffer

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Re: Fairing reuse
« Reply #656 on: 03/21/2017 04:59 PM »
But parachutes can be much more accurate. Parachute landing competitions have accuracies in the low cm range (they don't even record above 16cm, which is considered a complete miss).  So I would not rule this one out, if SpaceX cares to put some work into landing accuracy.

The types of parachute used for accuracy landing competitions are distinctly unsuited to these purposes. They are designed to open at very low speed, come in at an extremely steep glide angle, and require a very small range of wind conditions (usually less than 10-15kts and steady) to achieve that level of accuracy, which you're unlikely to see in the middle of the ocean where the fairings will end up due to the poor glide angle.

Swoopert.

2-time British Collegiate Parachute Accuracy champion
I certainly agree you could not use the type of parachute used in accuracy contests, but you don't need cm class accuracy either.  If you could do only two orders of magnitude worse than humans with special parachutes, you'd have meter class accuracy, which would be plenty good enough to hit a ship/barge/raft.

In 1958, using parachutes certainly not optimized for accuracy, parachutists were achieving 4 meter accuracy.  Surely with modern parachute technology, we can do at least as well...

Offline dwheeler

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Re: Fairing reuse
« Reply #657 on: 03/21/2017 06:06 PM »
Another one to suggest and instantly dismiss:
Steerable foil landing on a moving platform (the idea being that the moving platform, e.g. a ship with a cushion on its aft deck, or towing an inflatable raft) can compensate somewhat for the inaccuracy of the incoming fairing.
Having seen an episode of Top Gear where they tried landing a parachutist in the back of a moving car, it seems that moving the landing target only makes things much harder...

Yeah, if the blokes at Top Gear found it difficult I'm sure the hardware/software/aero engineers at SpaceX wouldn't stand a chance...  ::) :P

Offline RoboGoofers

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Re: Fairing reuse
« Reply #658 on: 03/21/2017 06:57 PM »
The catch idea seems a bit crazy to me because if you could catch a fairing, why not a second stage?

Offline Comga

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Re: Fairing reuse
« Reply #659 on: 03/21/2017 07:09 PM »
The catch idea seems a bit crazy to me because if you could catch a fairing, why not a second stage?
If you have to ask, you need to do more research
The fairings don't re-enter from orbital speed, come in not too far from the launch site, have low ballistic coefficients and terminal velocity, have much lower mass, and detract from payload at well below the 1:1 ratio of the second stage.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

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