Author Topic: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3  (Read 807131 times)

Offline meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #800 on: 05/02/2016 07:10 PM »
Quote
So as I remembered (see picture), a sonic boom is only heard behind the vehicle, along a cone whose angle depends on the speed of the vehicle (and the speed of sound).   So for every speed you get a different angle, but it's always backwards of the vehicle.

That is true only for a body which continues on at M>1 or M=1.  cscott is correct above that if the vehicle is decelerating, the shock waves it created at supersonic speed *can* pass ahead of it. So the sonic boom *can* be heard directly "ahead" of a body decelerating below supersonic.

This is analogous to your M>1 diagram in which the point source (the center of the circles) suddenly slows below M=1 and stops creating more shock "circles." But the existing shock "circles" continue to propagate outward in all directions, including "ahead" of the last point where the body was supersonic.

This is why the sonic boom could be heard right on the landing pad, directly "ahead" of the incoming, now-subsonic stage...if only there were someone on the pad to actually hear it...  :)

Right - I'm aware of that - which is why it is interesting...

Let's assume the vehicle is decelerating along a straight line.

In all the "cone" section, the wavefronts at each point are moving at different directions (each originating from the vehicle when it was at a different position) and so the shock doesn't "move".  There's just "wave group" information there.

But in the front of the vehicle, at mach 1.0, all those shocks are moving in the same direction - forward.  And at the same velocity...  Which means that there is a real propagating "boom" just along the axis.

I want to use this to estimate the amount of slam in the hoverslam.  It's a really good data point.
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Offline OxCartMark

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #801 on: 05/02/2016 08:06 PM »
What is the yellow apparatus at the starboard rear of OCISLY? Seems like it has two vertical bars in back, a cylinder inside, and perhaps a ladder on the deck side? It seems to be overhanging the stern slightly.

I noticed that thing too, I think it may be new. Got good screen shots of it, but don't think I can post them for IP reasons. On the other hand, it is not an angle we usually see Ocisly from.

Matthew

I couldn't see departure so all I have are these still frames...anyway.

http://www.portfever.com/webcam_player_pcw.php?date=20160430&start=1141&end=1200

Frame 1159 onwards. Yes a ladder and guard rails on top. What could be its function?
A similar feature has appeared on the back of Go Quest in the last set of images I saw.  I'll leave that to you as an exercise to look it up  ;)   My first thought was that the ladder on the stern of GQ would be butted up against the ladder on the stern of OCISLY and they would form a continuous ladder but on second thought that doesn't make much sense as the ladder on OCISLY starts at deck level and goes up to a useless height.  So here is my current thought for bunking or debunking as you prefer:  Both are commercial off the shelf ladders that have the ladder inset from two stout vertical bumpers so that the person on the ladder has some protection from being pinched between two hulls.  There is a fixed portion and a vertically displaceable portion.  That displaceable portion would go up in the case of the one on GQ to get to the deck height of OCISLY (forming a ladder twice the collapsed height) and the displaceable portion would go down in the case of the one on OCISLY to reach (approximately) the deck of GQ.  Either ladder would get the job done, no need for both simultaneously.

EDIT: Using Doesitfloat's search term below here you can see the how the bumper protection works:
« Last Edit: 05/03/2016 02:41 AM by OxCartMark »

Offline Doesitfloat

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #802 on: 05/02/2016 08:21 PM »
off shore crew transfer

Offline CameronD

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #803 on: 05/03/2016 04:43 AM »
off shore crew transfer

IMHO, it's a bit soppy really.  What's wrong with using a rope ladder?  Either that or they should learn to jump just like everyone else..  ::)

;D
« Last Edit: 05/03/2016 04:44 AM by CameronD »
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline Lar

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #804 on: 05/03/2016 05:11 AM »
If it was hard to land on, it should be hard to board???
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Offline CameronD

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #805 on: 05/03/2016 05:15 AM »
If it was hard to land on, it should be hard to board???

Not at all.. but it seems likely that some well-meaning Health & Safety Rep may have paid a visit to poor unloved OCISLY during recent deck repairs and.. well... made a few suggestions.
« Last Edit: 05/03/2016 05:16 AM by CameronD »
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline llanitedave

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #806 on: 05/03/2016 05:34 AM »
The most important question for OCISLY is, have they renewed the 4-leaf clover?
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Offline Ohsin

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #807 on: 05/03/2016 10:54 AM »
off shore crew transfer

From that video Mark posted it really looks like it but I doubt this is to board the Droneship for accessing deck as after climbing that they would have to go over the guard rails and then clumsily hop to deck it has some other specific purpose. It is also not high enough to have a good view of deck and far from HPU to have anything to do with it.

They board the Droneship from stern where generators are as we saw when OCISLY arrived with trophy and was being berthed. Perimeter fence there is also chained not wired.

The most important question for OCISLY is, have they renewed the 4-leaf clover?

Yup it is there :)
« Last Edit: 05/03/2016 10:56 AM by Ohsin »
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Offline Kabloona

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #808 on: 05/03/2016 11:20 AM »
Sitting on deck, the ladder and bumpers are too high to do any good. Looks like they just put it on board temporarily and didn't have time to weld it into final position before leaving port.

It may go here when they have time to weld it on. Don't know if that's their usual boarding point, but it looks like there's a removeable safety chain there for crew boarding, suspended between the stanchions.
« Last Edit: 05/03/2016 11:31 AM by Kabloona »

Offline Ohsin

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #809 on: 05/03/2016 12:42 PM »
Yes those are the chains I mentioned and yes that crew transfer thing is very last moment addition as it is not there on instagram image and the bumpers should rest against fendering like what Elsbeth III has on front (tyre stack). For Go Quest it would be metal vs metal pinching situation and its fendering is sparse so this isn't for GQ.

On a separate note  according to latest Terraserver imagery JRTI isn't at Long Beach at its usual location, not near Island Freeman where I expected it (but there is hole in imagery there) or where INTL Freedom is at the moment..

Edit:
Quote from: OxCartMark
A similar feature has appeared on the back of Go Quest in the last set of images I saw.  I'll leave that to you as an exercise to look it up

Found a link to the past. Compare the stern of Go Quest and NRC Quest. NRC Quest went without it on Jason 3 but GQ is going with it I assume.

Attached images are by /u/TheKrimsonKing (iwrRqdy.jpg 1 Jan 2016, hlOucpz.jpg 15 Jan 2016)
and Jim
« Last Edit: 05/03/2016 01:10 PM by Ohsin »
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Offline Kaputnik

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #810 on: 05/03/2016 01:32 PM »
In those pictures you can see the fast boat that will be used for ship-to-ship passenger transfer at sea.
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Offline Doesitfloat

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #811 on: 05/03/2016 01:43 PM »
off shore crew transfer

From that video Mark posted it really looks like it but I doubt this is to board the Droneship for accessing deck as after climbing that they would have to go over the guard rails and then clumsily hop to deck it has some other specific purpose. It is also not high enough to have a good view of deck and far from HPU to have anything to do with it.

They board the Droneship from stern where generators are as we saw when OCISLY arrived with trophy and was being berthed. Perimeter fence there is also chained not wired.

The most important question for OCISLY is, have they renewed the 4-leaf clover?

Yup it is there :)

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Online matthewkantar

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #812 on: 05/03/2016 02:00 PM »
When Ocisly was leaving port, the zoomed in Port Canaveral webcam showed personel going between the ASDS and a tug. They used the break in the life lines circled in red above. If there had been 10 foot seas, I believe the new yellow gear would be used.

Matthew

Offline OxCartMark

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #813 on: 05/03/2016 02:14 PM »
Sitting on deck, the ladder and bumpers are too high to do any good. Looks like they just put it on board temporarily and didn't have time to weld it into final position before leaving port.

It may go here when they have time to weld it on. Don't know if that's their usual boarding point, but it looks like there's a removable safety chain there for crew boarding, suspended between the stanchions.
My original thought was that the ladder was telescoping / vertically sliding so that when in use it would extend down below the deck height but upon further review of your zoomed image I agree with your assessment.

Is there any reason that a yellow protrusion from the back of the ASDS would be a hindrance to barge usefulness?  Why is the back flat?  I suppose for connecting multiple barges together (which won't happen in ASDS use)?

Not of importance to this ASDS discussion but from looking at the images of these ladder & bumper devices in use it seems to me that there is a disconnect between the design intent and the way that they are used.  It appears to my eyes that the ladder is inset from the bumpers so that a person on the ladder won't be wiped out by a straight section of the boat moving up or down past them on waves.  But in the images and videos we've seen its not a straight section of the side of the boat but rather a protrusion of the boat side or the pointy bow of the boat that's nesteled into the gap toward the ladder ~thus decreasing 'man clearance'.  Hmmm, I suppose you could always be mashed through the ladder rungs if push comes to shove.

Offline Ohsin

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #814 on: 05/03/2016 02:30 PM »
@Doesitfloat

Let me rephrase I am not disputing its utility which was clear from the video but purpose.

Part of it is not visible another ladder should be there to descend if its main purpose is to have many people on deck and as Kabloona pointed why is it not at that much better place near generators. Also trying to figure if GQ gangway would be used on it or Elsbeth III front like Figure 5 on that document.

I assume GQ has main crew that handles deck operation related to stage while ElsbethIII crew are just responsible for handling Droneship.

Another very bothersome thing is this crew transfer apparatus is plopped right in front of the emergency towline! Well at least it is not ON it Almost on it but I guess line is well clear.
« Last Edit: 05/03/2016 02:46 PM by Ohsin »
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Offline CraigLieb

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #815 on: 05/03/2016 03:23 PM »
Not that it really matters, but is there going to be a BINGO thread this flight?
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Offline cro-magnon gramps

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #816 on: 05/03/2016 03:39 PM »
Not that it really matters, but is there going to be a BINGO thread this flight?

perhaps one for where we expect the "HOLE" in the deck to be  ??? :o ::) :-X
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Offline OxCartMark

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #817 on: 05/03/2016 03:52 PM »
Not that it really matters, but is there going to be a BINGO thread this flight?

perhaps one for where we expect the "HOLE" in the deck to be  ??? :o ::) :-X
If its like the last bingo or two it'll happen suddenly and without warning and (since we're all trained to go for the center now) if you miss the start by enough time to say, have gotten a burrito, then you are relegated to the outer perimeter.

I suggest that to further the bingo game on these potentially high impact landings we add additional information to our votes such that multiple people can be on the same square with different bets.  For instance, one person could bet U19 (for conventional landing) and one person could bet U19- (for a subsurface landing or a dented surface that requires plate replacement).

Online dorkmo

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #818 on: 05/03/2016 05:36 PM »
Not that it really matters, but is there going to be a BINGO thread this flight?

perhaps one for where we expect the "HOLE" in the deck to be  ??? :o ::) :-X
If its like the last bingo or two it'll happen suddenly and without warning and (since we're all trained to go for the center now) if you miss the start by enough time to say, have gotten a burrito, then you are relegated to the outer perimeter.

I suggest that to further the bingo game on these potentially high impact landings we add additional information to our votes such that multiple people can be on the same square with different bets.  For instance, one person could bet U19 (for conventional landing) and one person could bet U19- (for a subsurface landing or a dented surface that requires plate replacement).

this is starting to sound suspicously like roulette

Offline Lar

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #819 on: 05/03/2016 05:40 PM »
Not that it really matters, but is there going to be a BINGO thread this flight?
I consulted my magic 8 ball and got "all indications are yes"...
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

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