Author Topic: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3  (Read 723384 times)

Offline Kabloona

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #140 on: 03/18/2016 03:50 PM »
Nate_Trost reporting that a barge landing is still "Plan A" for CRS-8:

http://forum.nasaspaceflight.com/index.php?topic=39350.msg1505239#msg1505239

Offline Lar

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #141 on: 03/18/2016 04:14 PM »
The first stages with unspent fuel all fall back into the ocean normally anyway.  These just get smashed on a barge first.  And perhaps the ensuing explosion burns up many of the toxin that would normally get released into the ocean from a typical splashdown and breakup? 

You're being way too logical. :)
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"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline John Alan

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #142 on: 03/18/2016 04:39 PM »
Nate_Trost reporting that a barge landing is still "Plan A" for CRS-8:

http://forum.nasaspaceflight.com/index.php?topic=39350.msg1505239#msg1505239

I thought so... been saying RTLS will be rare for some time now...  ;)

Offline Hankelow8

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #143 on: 03/18/2016 04:52 PM »


I have just checked what the average American wage is and it comes in at 44K, if this is correct I cannot see any skilled welder working for 36K.

I would think (depending on damage) there could be support structure that will need to be replaced. Who knows  what is needed under the barge surface decking, we do not have Super Man eyes, but it does look like it's not just a patch and weld job.
« Last Edit: 03/18/2016 04:54 PM by Hankelow8 »

Offline Kabloona

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #144 on: 03/18/2016 04:56 PM »
Nate_Trost reporting that a barge landing is still "Plan A" for CRS-8:

http://forum.nasaspaceflight.com/index.php?topic=39350.msg1505239#msg1505239

Loren Grush says so, too:

Quote
James Stewart  ‏@JamesStewart97  2h2 hours ago United Kingdom
@lorengrush have @SpaceX confirmed that they're going for a first stage drone ship landing rather than a RTLS?
 
Loren GrushVerified account
‏@lorengrush
@JamesStewart97 Yep! Got confirmation this morning

Offline Ohsin

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #145 on: 03/18/2016 05:05 PM »
Just adding this old one to better illustrate my previous post on topic

A good look at beam that aligns with 'Bollard Boxes' on sides of barge. The hole is exactly on it and damages two compartments, also you can see it is one of the stronger portion on barge. Attached one is from 303 and not the same region.
Source: http://www.worldmarine.com/projects/barges

Octaweb is (was?) probably under the white tarp, I would think.

I think it is top of stage minus interstage. Didn't blow away possibly due to less pressure, crumpled and got stuck between wing and thruster mount.
« Last Edit: 03/18/2016 05:09 PM by Ohsin »
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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #146 on: 03/18/2016 06:24 PM »
Just want to add my two cents to this.

I'm currently building a 55 fot steel trawler yacht. All the steel and work on the entire hull with peripherals does not cost 250k.

If you can not patch a 10 feet hole for less, get a new contractor.

No way this is a 250K job. I would be surprised if it was anything more than 50k. Steel, even high quality stuff, is cheap this days. Transport is cheap. A welder for a weeks work is cheap. Welding steel plate an even repairing beams is not a complex task (I've built boats before) and doesn't require a lot of finesse. Just a good plan and a decent weld.


I agree this isn't average welding work and that all the stuff listed by OxCartMark raises costs.... I'm still thinking 250K is a reasonable estimate here...  we did our usual good job of ballparking this.... and that it was a good bet for SpaceX. SpaceX also know that even a direct hit can make a good hole but not sink the barge, right? How much worse could it be?

Let's not go TOO far down the hole of how much welders and steel cost, though, ok?
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Offline gadgetmind

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #147 on: 03/18/2016 06:27 PM »
And for another data point, it would cost ULA about $2.5 million to fix this.

Offline MarsInMyLifetime

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #148 on: 03/18/2016 07:08 PM »
Another metric for comparing costs is to compare this repair to the cost of a first stage. We know a full stack is priced to customers at about $60 million, so let me pull a WAG of a $20 million internal cost of a stage--this is just a guesstimate used for the sake of magnitude. Was the cost of fixing the hole close to the cost of a first stage? Not by a long shot. Was the risk worth accepting in order to recoup the ~$20 million cost of a successfully returned stage? By all means. Is some of the accounting for this work hidden in R&D or contingency funds rather than direct cost against the mission budget? Undoubtedly. So the way I look at it, whether this repair job cost $50K vs $250K is a moot point; in the bigger picture, costs of this nature are worth embracing repeatedly for the sake of getting to a sustained level of stage recovery and an improved amortization rate on launch costs. I happen to think they are very close to working out the systemic impedances.
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Offline CyndyC

OCISLY was listing away from the hole

Was it determined as fact that the ASDS came in listing away from the hole? I couldn't see the list then, and now what's obvious in the latest video is that there's a list towards the hole. Seems to me that means two things:

1) they didn't find any hull plate damage, or else they would be continuing to keep the hole's corner as far above the ocean surface as possible instead of letting it back down,

2) either they re-ballasted the hole's corner (after more obviously emptying the other corners) to stabilize the hole for work, OR, guess what, the dry weight of nine octaweb engines is 4.66 US tons.

My only question now is, why was the ASDS turned around to put the hole opposite the bulkhead? When it was first moored, the hole was on the same side as the bulkhead.
« Last Edit: 03/18/2016 07:28 PM by CyndyC »
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Online JamesH65

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #150 on: 03/18/2016 07:53 PM »
A second hand (preloved) 300ft barge costs about $2.5M (very quick google).

Repairs to same barge for a small hole, $250k? No, don't think so.

Offline leetdan

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #151 on: 03/18/2016 08:07 PM »
OR, guess what, the dry weight of nine octaweb engines is 4.66 US tons.

4.66 tons is just over 4 cubic meters of water displacement.  The barge hull is 91 * 30 meters.  That ain't it.

Offline CyndyC

OR, guess what, the dry weight of nine octaweb engines is 4.66 US tons.

4.66 tons is just over 4 cubic meters of water displacement.  The barge hull is 91 * 30 meters. That ain't it.

I was talking about only one corner, and even smaller, only the ballast tanks underneath that one corner. That more confined area is still probably larger than 4 cubic meters though, I presume. Have to admit I wasn't quite motivated enough on top of everything else to look up the weight of water. So does that imply you agree that corner was re-ballasted to stabilize it for the work, or what else could be weighing it down more than all 3 other corners? Surely not just the equipment & supplies on the deck?

BTW, I reviewed some images and can answer one of my own questions, asking if the list first being away from the hole was fact. In the video of the ASDS coming in, the list is toward the corner opposite the hole but on the same end, and the corner with the hole is obviously up -- I don't know if that end is the bow or stern, but I mark it by a small white metal "bubble" sticking up from one of the large white containers, something that isn't duplicated on the other end. 
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Offline leetdan

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #153 on: 03/18/2016 09:34 PM »
I don't really have an opinion on how or where or why it was ballasted.  But with all the recent talk of the ASDS moving out of the way of a falling rocket, or FTS somehow being used to prevent crash damage, etc. I thought it would be helpful to remind people of just how light aerospace hardware is on the relative scale of an oceangoing barge.
« Last Edit: 03/18/2016 09:34 PM by leetdan »

Offline OxCartMark

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #154 on: 03/19/2016 03:08 AM »
I reviewed some images and can answer one of my own questions, asking if the list first being away from the hole was fact. In the video of the ASDS coming in, the list is toward the corner opposite the hole but on the same end, and the corner with the hole is obviously up -- I don't know if that end is the bow or stern, but
Too tired to think much maybe you've got this or maybe not - It came in bow first (of course) but then did a U turn before parking.  Bow now pointing out towards ocean.

Offline CyndyC

It came in bow first (of course) but then did a U turn before parking.  Bow now pointing out towards ocean.

Thanks for the heads up on which end is the bow, but there wasn't a U turn before mooring when she first came in, as can be seen in this picture from that day March 8th. Probably not much to chew on though, I thought later, maybe just how they had to turn to eject the ballast water into the sea instead of into the street, or whatever that is behind the bulkhead. Also could have something to do with the levels of the other corners relative to the bulkhead while the hole corner is weighed down, and getting machinery & supplies onboard more easily.

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Offline CJ

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #156 on: 03/20/2016 08:07 AM »
It came in bow first (of course) but then did a U turn before parking.  Bow now pointing out towards ocean.

Thanks for the heads up on which end is the bow, but there wasn't a U turn before mooring when she first came in, as can be seen in this picture from that day March 8th. Probably not much to chew on though, I thought later, maybe just how they had to turn to eject the ballast water into the sea instead of into the street, or whatever that is behind the bulkhead. Also could have something to do with the levels of the other corners relative to the bulkhead while the hole corner is weighed down, and getting machinery & supplies onboard more easily.



There seems to be some confusion here (though I may be the one confused - if I'm wrong, I'd appreciate being corrected).

In that picture you posted, the bow is to the right. An easy way to determine it is the ASDSs name is on the port (left) side. The ASDS appears to be in the same orientation in later pictures.

The list seen was, as I recall, toward the forward starboard quarter (which was a bit lower in the water than the rest), so away from the hole, which is in the aft port quarter.


Offline Kabloona

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #157 on: 03/20/2016 12:07 PM »
Quote
There seems to be some confusion here (though I may be the one confused - if I'm wrong, I'd appreciate being corrected).

In that picture you posted, the bow is to the right. An easy way to determine it is the ASDSs name is on the port (left) side. The ASDS appears to be in the same orientation in later pictures.

The list seen was, as I recall, toward the forward starboard quarter (which was a bit lower in the water than the rest), so away from the hole, which is in the aft port quarter.

You (and Ohsin) are correct. Bow is now on right side of photo, pointing towards open sea, which means she did a U-turn before docking.

Also, this screen shot from the Port Canaveral webcam shows the list towards the bow (left side of photo) as she entered port. To my eye the bow port corner is lowest to the water, but maybe the perspective is fooling my eye.

« Last Edit: 03/20/2016 12:11 PM by Kabloona »

Offline Kabloona

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #158 on: 03/20/2016 12:17 PM »
And for help with perspective on the orientation, here's a shot from before SES-9, with bow facing left as it would be during tow-in (in opposite direction of her current orientation). Port entrance is to the right.

« Last Edit: 03/20/2016 12:40 PM by Kabloona »

Offline the_other_Doug

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #159 on: 03/20/2016 12:51 PM »
A couple of points...

Recall that the ASDS operates with its "bollard boxes" partially flooded.  This lets it ride lower in the water and gives it great stability in an ocean-wave environment.

The list seen as OCISLY came back from SES-9 duty was down in the opposite corner of the barge from the holed compartment.  This means that OCISLY wasn't listing because of complete flooding of the compartment(s) under the hole -- it was listing because the compartment(s) under the hole had been pumped as dry as possible.

So, for the sake of illustration, if the various "bollard box" compartments normally operate half-flooded, for stability, OCISLY's list was caused by pumping water out of the affected compartment(s) and having them providing a higher level of flotation than the rest of the barge.

This speaks to the likelihood that the hull plating beneath the hole was likely not damaged (at least not holed), and the list was due the compartment(s) under the hole being emptied of their normal level of water. The opposite of the list being caused by one or more compartments being breached to the sea and flooded.
-Doug  (With my shield, not yet upon it)

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