Author Topic: Fairing reuse  (Read 327653 times)

Re: Fairing reuse
« Reply #1040 on: 12/20/2017 01:56 AM »
The claws have hooks on the top of each, just pointing it out.
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Offline meekGee

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Re: Fairing reuse
« Reply #1041 on: 12/20/2017 01:57 AM »
Irrespective of the picture, just a data point, when the military uses net-captured drones, the drone basically fly into a net that is pretty steep - they don't land on a horizontal net.

Many differences between the two systems of course.
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Offline meekGee

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Re: Fairing reuse
« Reply #1042 on: 12/20/2017 02:00 AM »
My speculation:

The parachute system overtakes the boat, doing a fly-by maybe 10-20' overhead.

The precision act made by the parachute system is a timely release of the fairing to hit the net.

Seems easier to control timing then to control several flight parameters simultaneously.

The parachute system can trade speed for lift during the final flare, and the computer just needs to calculate a "dropping solution".

Also this way, parachute entanglement is pre-solved.

And yes, one ship per half-fairing, and only a single recovery this flight.
« Last Edit: 12/20/2017 04:24 AM by meekGee »
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Offline deruch

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Re: Fairing reuse
« Reply #1043 on: 12/20/2017 02:11 AM »
Fairing halves are very large, unwieldy, and heavy-ish equipment that I don't imagine would be easy to manhandle while on a moving ship at sea.  And also possibly at an elevated speed.  So, either this set up is capable of catching 2 halves without much deckhand intervention or there will eventually have to be 2 ships for any launch where SpaceX tries to catch both halves.  I have trouble imagining that they are ever going to try catching and unloading the first half like an F1 pit crew while still having enough time to reset the catching mechanism and pre-positioning the ship for the second run.  Even if the parachutes are capable of creating a few minutes of difference in landing time that's a lot to ask. 
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Offline garcianc

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Re: Fairing reuse
« Reply #1044 on: 12/20/2017 03:28 AM »
Ok, super crazy idea (perhaps wine-induced), so bear with me.

How feasible would it be to tether the fairing mid-flight to the boat and parasail the thing down to the cradle/claw basket by winching it down in a controlled fashion? Once tethered, the boat's speed could be used to raise altitude or keep the fairing from falling too fast until it is caught.

Presumably, all the equipment the fairing would need would be a [right type of] parachute system and a long enough tether to hang down so the boat can catch the tether before the fairing hits the water.

It sounds James Bond enough for SpaceX  ;D

Offline wannamoonbase

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Re: Fairing reuse
« Reply #1045 on: 12/20/2017 03:48 AM »
I think 1 ship per half. 

1 ship for both could work sometimes, but maybe not every time.

Very interesting concept, not what I was imaging.  I was thinking a catamaran with a net between the sides.
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Offline JamesH65

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Re: Fairing reuse
« Reply #1046 on: 12/20/2017 10:16 AM »
Could just use one ship, catch the first, lower the net a bit, pull another net over the top of it. Would be quick and easy, and simply automated.

Offline Comga

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Re: Fairing reuse
« Reply #1047 on: 12/20/2017 12:56 PM »
Those arms look solidly fixed to me. 
No hydraulically actuated elbows
Don’t look like pivoting bases
Hard to envision how they would attach winches to those fixed eyelets
Certainly no features for the fancier schemes described above
Don't see how they will get the fairing half out if the net other than to cruise home and use a crane
How would they even cover a fairing in a high, fixed net?

What’s the opposite of “Rube Goldberg” for excessive simplicity?
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Offline cscott

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Re: Fairing reuse
« Reply #1048 on: 12/20/2017 01:05 PM »


What’s the opposite of “Rube Goldberg” for excessive simplicity?

KISS?

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Re: Fairing reuse
« Reply #1049 on: 12/20/2017 01:17 PM »
It's pretty clear to me that the reason is to buy mass for the fairing recovery experiment, but @IridiumBoss isn't allowed to say that (or is just being polite by not spoiling SpaceX's announcement).  That explains his coy answers.

If it's pretty clear to you, perhaps you'd like to share your reasoning with the rest of us as that's the 2nd time you state this, in the updates thread nonetheless.

For example, your reasoning on why this fairing recovery experiment requires so much extra weight offload from S1 that SpaceX would have to go all the way from a rapid flip and boostback burn + reentry burn which they executed on the previous Iridium flight, to not only skipping at least a GTO-type reentry with no boostback burn, but going all the way and completely giving up on recovery altogether. Fact is the reentry energy trade space between these two reentry profiles alone is almost *guaranteed* to vastly outweigh any additional fairing recovery mass they might put on the vehicle. Or, for all we know, might have already *been* flying that same extra mass for several past flights.

I said it before and I'll say it again, I think you're vastly underestimating the performance reserve SpaceX have for this flight and the leeway in the recovery method they therefore could choose if the reserve is deemed insufficient for the recovery method using a boostback burn.

The answer given by Chris_G and others, that they're simply getting rid of block 3 hardware is a much more plausible answer.

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Re: Fairing reuse
« Reply #1051 on: 12/20/2017 01:34 PM »
Irrespective of the picture, just a data point, when the military uses net-captured drones, the drone basically fly into a net that is pretty steep - they don't land on a horizontal net.

Many differences between the two systems of course.

Yeah, the fairing would essentially need to stall just before the net in order to land on a horizontal net without sliding right off.
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Offline meekGee

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Re: Fairing reuse
« Reply #1052 on: 12/20/2017 01:38 PM »
Irrespective of the picture, just a data point, when the military uses net-captured drones, the drone basically fly into a net that is pretty steep - they don't land on a horizontal net.

Many differences between the two systems of course.

Yeah, the fairing would essentially need to stall just before the net in order to land on a horizontal net without sliding right off.
Hence the "cut loose" idea.

Even a 15' drop would add enough vertical velocity so the line of flight is near 45 degrees.

A 30' (10 m) drop might be better.

The wind won't have enough time to ruin the targeting - about 1 second in free fall.
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Offline scdavis

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Re: Fairing reuse
« Reply #1053 on: 12/20/2017 02:22 PM »
I have trouble imagining that they are ever going to try catching and unloading the first half like an F1 pit crew while still having enough time to reset the catching mechanism and pre-positioning the ship for the second run.

I agree with you about the difficulty of quickly unloading all the way to the deck. But -- those arms are quite high. They might be able to simply lower the first net almost to the deck (fully automatic, nothing fancy, just lower the net straight down). Then attach another net *on top* and bring it tight. If the lines are taut enough, it could conceivable catch the second fairing without the second faring sagging down to touch the first fairing.

If this is confusing, just picture a double-decker net with a fairing in each net as the configuration after they have been caught.

Tricky bit will be for the crew to quickly attach the second net after the first fairing has been caught. Otherwise, nothing fancy required.

Online AncientU

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Re: Fairing reuse
« Reply #1054 on: 12/20/2017 02:43 PM »
Could be wide enough to have separate halves, left and right. 
A ridge in the middle could keep the pair of landings separate and enable either fairing half to be recovered first.
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Offline cscott

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Re: Fairing reuse
« Reply #1055 on: 12/20/2017 03:04 PM »
It's pretty clear to me that the reason is to buy mass for the fairing recovery experiment, but @IridiumBoss isn't allowed to say that (or is just being polite by not spoiling SpaceX's announcement).  That explains his coy answers.

I said it before and I'll say it again, I think you're vastly underestimating the performance reserve SpaceX have for this flight and the leeway in the recovery method they therefore could choose if the reserve is deemed insufficient for the recovery method using a boostback burn.

Perhaps.  There is L2 info re: the re-entry profile, maybe we'll discuss that further there.  My post was stating a cause-and-effect: @IridiumBoss' coy response, which seems to hint at the key factor being something he can't directly disclose, was making me more certain. I should have written "It's becoming more clear to me" instead of just "It's pretty clear to me" to make the point clearer. As you mention, the actual reasoning is in other posts, I didn't feel I had to repeat that.

And I'm not claiming the fairing experiment is the *only* factor.  Just that it's one piece which, combined with the other issues discussed here (block 3, lack of space, etc), may have pushed the decision over the edge into expendibility.
« Last Edit: 12/20/2017 03:05 PM by cscott »

Offline Stefan.Christoff.19

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Re: Fairing reuse
« Reply #1056 on: 12/20/2017 03:48 PM »
There might be a very obvious answer to this question but since it's not obvious to me I'll ask it.
      Why can't the two halves be caught in the same net despite contact. Would the damage be that great that would render the effort worthless? I don't know enough about the material and speed of landing to be able to discern the impact.
     Also seems to me that the first try is more about catching than using the fairings that were caught.

Offline geoffc

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Re: Fairing reuse
« Reply #1057 on: 12/20/2017 04:39 PM »

- If it was from the stern then you'd think they would be trying to catch the fairing while the boat was in motion. If so they that implies communications between the boat and the parachute system so that they can be cooperative in the landing.

Will this violate the Blue Origin patent?  Or did that get thrown out after 20 successful SpaceX landings?

Offline nacnud

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Re: Fairing reuse
« Reply #1058 on: 12/20/2017 04:47 PM »

Offline the_other_Doug

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Re: Fairing reuse
« Reply #1059 on: 12/20/2017 04:52 PM »
It's pretty clear to me that the reason is to buy mass for the fairing recovery experiment, but @IridiumBoss isn't allowed to say that (or is just being polite by not spoiling SpaceX's announcement).  That explains his coy answers.

I said it before and I'll say it again, I think you're vastly underestimating the performance reserve SpaceX have for this flight and the leeway in the recovery method they therefore could choose if the reserve is deemed insufficient for the recovery method using a boostback burn.

Perhaps.  There is L2 info re: the re-entry profile, maybe we'll discuss that further there.  My post was stating a cause-and-effect: @IridiumBoss' coy response, which seems to hint at the key factor being something he can't directly disclose, was making me more certain. I should have written "It's becoming more clear to me" instead of just "It's pretty clear to me" to make the point clearer. As you mention, the actual reasoning is in other posts, I didn't feel I had to repeat that.

And I'm not claiming the fairing experiment is the *only* factor.  Just that it's one piece which, combined with the other issues discussed here (block 3, lack of space, etc), may have pushed the decision over the edge into expendibility.

Seeing as what is now the Zuma booster (definitely *not* a Block 5) was going to launch this Iridium flight, and that it was going to perform the first Vandenberg RTLS recovery, I would have to think that a Block 3 is way more than capable of any number of ASDS recovery trajectories, even with a few hundred extra pounds of fairing recovery gear aboard, with so much energy to spare they could experiment with ASDS touch-and-go's... :)
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