Author Topic: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2  (Read 1873990 times)

Offline enzo

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The stage can hover not at all. Minimum thrust from one engine will be more than the weight of the stage, so an attempt to hover would see the stage gain altitude. The stage will have to cancel it's velocity at the same moment it touches the barge.
So then F9Rdev1 had some ballast? It was quite proficient at hovering.

edit: never mind, found this post http://forum.nasaspaceflight.com/index.php?topic=33892.msg1185402#msg1185402
New question, if there is only one shot at landing, does that mean the barge landing abort mode is to throttle up and fly away?
« Last Edit: 12/17/2014 04:00 AM by enzo »

Offline ChrisC

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anyone has the picture of the barge leaving  ?

See Spaceflightnow story linked earlier in this thread.
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thank you, you earn a forecast wave map :



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things are looking good ... calm weather
« Last Edit: 12/17/2014 04:36 AM by laika_fr »
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Offline Mader Levap

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During previous attempts, we could only expect a landing accuracy of within 10km.
Isn't that first time they said anything about accuracy of previous attempts?

For this attempt, we’re targeting a landing accuracy of within 10 meters."
From 10 km to 10 m... oh dear. This is three orders of magnitude. Can fins, upgraded software etc really make up that difference? Apparently, at least according to SpaceX simulations. Still, no wonder there is talk about 50:50 chances.

New question, if there is only one shot at landing, does that mean the barge landing abort mode is to throttle up and fly away?
I think they either hit barge exactly on the spot or miss it by wide margin. While your abort mode is probably possible, I doubt it will be used.
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Offline Hauerg

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From the email SpaceX sent yesterday:
"The concept of landing a rocket on an ocean platform has been around for decades but it has never been attempted."

Seems like a special greeting to Blue Origin.

Offline robertross

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With the Yellow wrap around low wall, maybe they plan to flood the deck 0.5m deep in sea water just before touchdown?

I posted a quote of my earlier comment on that low yellow wall.

That is, I believe, the underside I-beam structure of the fold-out extensions we are seeing.
So my guess now is that they aren't flooding it.
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Offline AnalogMan

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Just for fun I have attempted to remove the fisheye distortion from the photo and realigned the lower side of the platform to be horizontal (also cropped).  The painted targets are pretty good circles, so the image is amenable to dimensional analysis anyone cares to make.
« Last Edit: 12/17/2014 11:13 AM by AnalogMan »

Offline Llian Rhydderch

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Just for fun I have attempted to remove the fisheye distortion from the photo and realigned the lower side of the platform to be horizontal (also cropped).  The painted targets are pretty good circles, so the image is amenable to dimensional analysis anyone cares to make.

Great work!  Thanks for removing that distortion and giving us all this photo.

Now, anyone want to speculate on where the azimuth thruster booms are?  I would think they would be stowed horizontal while at the dock in port (and for transport while under tugboat power). I'm not seeing them. 

If we really are seeing bits of the barge and/or water through some sort of a deck grid, I would think we might be able to make out where the four large thrusters are in their stowed position.
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Offline Ohsin

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Just for fun I have attempted to remove the fisheye distortion from the photo and realigned the lower side of the platform to be horizontal (also cropped).  The painted targets are pretty good circles, so the image is amenable to dimensional analysis anyone cares to make.


Based on your image dimensions of barge if length is 300ft or 288ft

985 px Length
325 px Width
495 px Winged Width
550 px Winged width + work platform

985 * X = 300
X = 0.30456852791878172588832487309645

300.0  ft Length
98.98  ft Width
150.76 ft Winged Width
167.51 ft Winged width + work platform


985 * X = 288
X = 0.29238578680203045685279187817259

288.0  ft Length
95.02  ft Width
144.73 ft Winged Width
160.81 ft Winged width + work platform
« Last Edit: 12/17/2014 12:07 PM by Ohsin »
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Offline deruch

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Nice.  Another way to get good measurements on this thing might be to crosscheck against the dimensions on the power units for the thrusters (I think they're the white boxes, but maybe the blue ones).  That would give a good confirmation of all estimates.  Page 8 of their brochure (http://www.thrustmaster.net/wp-content/uploads/2013/12/Portable-Dyanmic-Positioning-System-Brochure-2014.pdf) has a table with the dimensions of their variously sized units: 

length x width x height (in inches) 
136 x 67 x 117
240 x 96 x 108
255 x 96 x 101
238 x 96 x 171
240 x 98 x 139
324 x 114 x 166
324 x 114 x 166

Which gives possible lengths to the hydraulic thruster unit boxes of:  11'4"; 20'; 21'3"; 19'10"; 27'

If anyone wants to try to find out for sure which model it is you can call Thrustmaster.  I found 2 phone numbers for them on the website(www.thrustmaster.net): (713)987-4265 or (713)937-6295.  No guarantee they'll tell you which model SpaceX used, though.
« Last Edit: 12/17/2014 02:57 PM by deruch »
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Offline Marams

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In reply from the mission section:
BTW,  what's the big divot in the deck near the "x", a burn mark from testing? It looks like a small impact crater!

Looks to me like a pipe coming up from under the deck at an angle, making an elliptical intersection with the deck. Maybe a drain, or maybe they will pump seawater onto the deck through the pipe.

I happened to read that comment then look at this pic:
http://spaceflightnow.com/wp-content/uploads/2014/12/barge03.jpg

They appear to be pumping something into it. I am guessing they want to use freshwater not seawater.

Or if it's a grid deck, they could fill the whole barge with freshwater. It's still a barge afterall. The extra weight would also stabilize the barge in heavy seas. The water would mostly absorb the blast. And the nearby containers would survive the landing.

If I look long enough at the images I almost see the slosh baffles through the grid deck :) .


Online sghill

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Just for fun I have attempted to remove the fisheye distortion from the photo and realigned the lower side of the platform to be horizontal (also cropped).  The painted targets are pretty good circles, so the image is amenable to dimensional analysis anyone cares to make.

Great work!  Thanks for removing that distortion and giving us all this photo.

Now, anyone want to speculate on where the azimuth thruster booms are?  I would think they would be stowed horizontal while at the dock in port (and for transport while under tugboat power). I'm not seeing them. 

If we really are seeing bits of the barge and/or water through some sort of a deck grid, I would think we might be able to make out where the four large thrusters are in their stowed position.

In the first thread, one of the NSF members more familiar with those types of thrusters stated that they are usually left in the down and locked position unless they need to raise them for maintenance.

You can see the 4 thrusters peaking out of the shadows at each corner.  The tops of them look like teeny tiny blue the same shade as the larger blue generators at each corner.  The thrusters are closer in to the middle of the barge than the generator units. The two at the front are easier to spot than the two at the rear, but you can see all 4.

I also noticed something from the photo about the height of the "service decks" where all the fore and aft equipment is stowed.  The service decks are NOT below the level of the flight deck.  They are level with it.

Take a look at the shadows on the aft cargo boxes, they fall right onto the flight deck with no "step" pattern you'd get if the boxes were at a lower height than the flight deck.  Also the safety railing continues unbroken along the port side (water facing side) with no difference in shadowing from the rail posts, and they don't continue to run along the flight deck, they run behind the service deck instead meaning the service and flight decks are the same height.  Finally, there is a red cherry picker stowed on the fore-deck that would have little value if they can't drive it onto the flight deck.

There are two guys standing on deck.  One appears to me to be the drone operator holding an RC transmitter.  The other is wearing a trench coat and glasses off to the side. ;)

There appears to be large loading ramps on the port and starboard sides about 10-12 wide.  The port side is stowed, and the starboard side ramp is lowered.  There's also a covered white gangway leading up to the deck from the dock (look at the shadows).

I don't think this is a grid deck at all.  It looks like a standard welded steel barge deck IMHO.

I've added captions to some of the details I noticed.

« Last Edit: 12/17/2014 02:02 PM by sghill »
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Offline Lar

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Trench coat and glasses? Your eyes are better than mine. :)
Nice work on the captions to identify bits.
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Online sghill

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Trench coat and glasses? Your eyes are better than mine. :)
Nice work on the captions to identify bits.

I find the "moon crater" to be the most interesting bit of the image.  I wonder if they just came up with a blow torch to simulate a landing and see if the steel deck would hold up.
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Offline Almurray1958

Barge name = Marmac 300
Google search "Hull type Marmac 300"

results = http://boatdb.net/boat/marmac-300-1063184.htm 

pretty standard barge

MARMAC 300 (1063184)
USCG ID   1063184
Year   1998
Length   288 feet / 87.8 meters
Depth   19.8 feet / 6 meters
Breadth   100 feet / 30.5 meters
Gross Tonnage   4422
Net Tonnage   1326
Name   MARMAC 300
Service   FREIGHT BARGE
Trade   Coastwise Unrestricted, Registry
Hull Material   STEEL
Builder   GULF COAST FABRICATION
Port   NEW ORLEANS LA
Owner   MARMAC LLC
1750 CLEARVIEW PARKWAY
METAIRIE, LA 70001-2470
Previous Names   No Vessel Name Changes
Previous Owners   MARMAC LLC
Hull Number   
Imo   
Call Sign   
Date Issued   2014-03-24 04:00:00
Date Expires   2015-04-30 04:00:00
Owner Name   MARMAC LLC
- Al Murray

Offline Almurray1958

built 1998, not a cat just a barge
std ballast, standard anti-fouling paint

http://cfpub2.epa.gov/npdes/vessels/vesselsnoidetail.cfm?PermitId=131541&status=Active
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Online cscott

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The green support ship is the GO QUEST: http://www.marinetraffic.com/ais/details/ships/shipid:450521/mmsi:367564890/imo:1155515/vessel:GO_QUEST

I'm not sure we can tell about the deck grid status -- looking at the pictures at http://www.heligrid.com/ for comparison, every picture which is not a close up looking directly downward shows the deck as "solid".  There are pictures of executives wearing heels walking across it as well, so the grid holes must be pretty small (well, they are pretty chunky heels).

I'm not saying that it is a heligrid, or a more standard mesh, or not.  I'm just saying that I don't think our pictures have the right combination of resolution and angle to tell.  (My current vote would be "standard mesh", based on the comments of other commenters here to the effect that solid steel would buckle under rocket exhaust, but I'm not claiming photographic evidence.)

@sghill you should also look at http://spaceflightnow.com/2014/12/16/photos-spacexs-autonomous-spaceport-drone-ship/ which has different angles.

I'm not sure that the structures off the port and starboard edges are "loading ramps".  They look like extra "wings" to me, that would normally be angled slightly upward to catch an off-target (or toppling?) stage.  I think they are folded down in port to allow the gangway access.  If my guess is right, I'd guess that the stage would approach the barge in the port-starboard direction, so that overshoots or skids will take it into the "wings", not into the equipment containers.

There also seems to be a second "crater" on the deck just outside the white circle.
« Last Edit: 12/17/2014 02:41 PM by cscott »

Offline Ohsin

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From spaceflightnow.com photograph. We can see one of the thrusters ?

EDIT: 'Stowed platform' is just supporting beams for overhanging wings
« Last Edit: 12/21/2014 01:52 PM by Ohsin »
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Online sghill

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I'm not sure that the structures off the port and starboard edges are "loading ramps".  They look like extra "wings" to me, that would normally be angled slightly upward to catch an off-target (or toppling?) stage.  I think they are folded down in port to allow the gangway access.  If my guess is right, I'd guess that the stage would approach the barge in the port-starboard direction, so that overshoots or skids will take it into the "wings", not into the equipment containers.

Step back a sec and think about what this barge looks like in relation to how it has to function.  With all that service deck equipment- especially as it's the same the same height as the flight deck- they're either going to be dead on target, or they're going to ditch the booster the ocean.  A few feet more of extra wings isn't going to save it.  The white circle may be an "abort" line, where if they are outside of the white circle AT ALL, they splash it.

The side ramps may not be load bearing at all, they may just be foldable safety fencing that sticks out further, but drops down for side access to the barge.
« Last Edit: 12/17/2014 03:19 PM by sghill »
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Online cscott

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The side ramps may not be load bearing at all, they may just be foldable safety fencing that sticks out further, but drops down for side access to the barge.
Yup, exactly what I'm saying.  Safety fencing, wings, whatever.  Maybe it's for people's safety, maybe they think it could help catch a tipping rocket, who knows.  All I'm saying is that it doesn't look seriously load bearing to me, and we agree on that, and that I think its position during a landing will be "tipped up" rather than "stowed" or "down".  Perhaps we agree on that as well.

I agree that jumping from 10km accuracy to 10m accuracy means that if they miss *on this flight*, they probably will miss by a lot not a little.

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