Author Topic: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2  (Read 2397390 times)

Online Robotbeat

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #360 on: 01/02/2015 05:52 PM »
According to Musk (who isn't often accused of pessimism), it most likely won't work this first time. I'm not so sure it's a very good PR gamble for NASA to put their name all over it when they aren't really doing anything with it other than observing the result for Mars EDL supersonic retropropulsion research.
That's SOP. They said the same thing on all previous attempts for anything.  So far they are doing much better than 50%....
Am I the only one who remembers that they never were able to achieve parachute splashdown for a first stage? They tried a whole bunch of times for that.

I think they'll probably be successful within these next two attempts, but this is still a very tough business! It's bad luck to not give Murphy pretty decent odds the first time you're doing something like this... I think slightly less than 50% for this time is reasonable. Going sonic or transonic while maneuvering for recovery has eaten many a rocket (Blue Origin, Armadillo). If they hadn't done most of these steps already on previous flights and F9Rdev1, I'd give them even lower chances. But don't underestimate how hard this is and overestimate your likelihood of success.

...I have high confidence (85+%) that they'll succeed this year, but I also was pretty sure they'd do first stage parachute recovery successfully.
« Last Edit: 01/02/2015 05:54 PM by Robotbeat »
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Offline meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #361 on: 01/02/2015 09:30 PM »
The comparison to parachute recovery is not very strong.

In this case, we know that they:

A) have figured out reentry, consistently

B) have the terminal landing maneuver completely figured out

C) have flown once with grid fins and have thus validated their basic working (mechanical/electrical), and have no doubt simulated their effects during flight.

What's left untested, therefore, is just the deviation of real-life grid fin behavior from the modeled one.  This, in the grand scheme of things, is a pretty low risk.

I don't know how to assign (or later confirm) a probability fraction to a one time event like this, but I think it is a lot more likely to succeed than the first propulsive reentry attempt was.
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Offline dcporter

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #362 on: 01/02/2015 10:02 PM »
What's left untested, therefore, is just the deviation of real-life grid fin behavior from the modeled one.  This, in the grand scheme of things, is a pretty low risk.

I think you're overly glossing the fact that they haven't tested grid fins at transsonic speeds. I recall Musk and John Carmack having a Twitter chat about that tending to go very badly; Musk's responses weren't terribly confident.

Edit: conversation linked below, and not exactly as I recalled it.
« Last Edit: 01/02/2015 10:55 PM by dcporter »

Offline guckyfan

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #363 on: 01/02/2015 10:06 PM »
What's left untested, therefore, is just the deviation of real-life grid fin behavior from the modeled one.  This, in the grand scheme of things, is a pretty low risk.

I think you're overly glossing the fact that they haven't tested grid fins at transsonic speeds. I recall Musk and John Carmack having a Twitter chat about that tending to go very badly; Musk's responses weren't terribly confident.

I think John Carmack talked about steering aero surfaces, not gridfins. Gridfins are for trassonic speeds and their behaviour is generally well known, though not at objects this size but that can be modeled. Still it is the reason why the chance of success is lower on the first try. But I have no doubt at all that they will learn what they need for success at second try if the first one fails.

Offline dcporter

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #364 on: 01/02/2015 10:08 PM »
What's left untested, therefore, is just the deviation of real-life grid fin behavior from the modeled one.  This, in the grand scheme of things, is a pretty low risk.

I think you're overly glossing the fact that they haven't tested grid fins at transsonic speeds. I recall Musk and John Carmack having a Twitter chat about that tending to go very badly; Musk's responses weren't terribly confident.

I think John Carmack talked about steering aero surfaces, not gridfins. Gridfins are for trassonic speeds and their behaviour is generally well known, though not at objects this size but that can be modeled. Still it is the reason why the chance of success is lower on the first try. But I have no doubt at all that they will learn what they need for success at second try if the first one fails.

Link:

https://twitter.com/elonmusk/status/536354292396228608

Looks like you're right, Carmack says fins not grid fins.

Offline meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #365 on: 01/02/2015 10:53 PM »
What's left untested, therefore, is just the deviation of real-life grid fin behavior from the modeled one.  This, in the grand scheme of things, is a pretty low risk.

I think you're overly glossing the fact that they haven't tested grid fins at transsonic speeds. I recall Musk and John Carmack having a Twitter chat about that tending to go very badly; Musk's responses weren't terribly confident.

Grid fins at transonic speeds are not something new.  Control inversion in regular fins is also very well known.

That discussion was a bit odd, since Carmack was calling Elon's attention to something that was a) not applicable to F9R's grid fins and b) is knows - it's more like Carmack was talking about his rocket, not Elon's.

But yeah, it would have been better if F9Rd1 hadn't crashed.  I still think it's a lot less riskier than the first re-entry tests were.  Clearly they will be conservative during those critical flight moments (e.g. transonics) and place survival in front of accuracy - since there's plenty of subsonic flight to correct for deviations...   Then they can be more aggressive on subsequent flights, but remember again the grid fins are there for large-scale correction and for fighting winds.  It's ok if on this flight they don't have as much authority, as long as they don't encounter worse-case winds.

4 more days.... tick tock.
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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #366 on: 01/02/2015 11:39 PM »
..
...
What's left untested, therefore, is just the deviation of real-life grid fin behavior from the modeled one.  This, in the grand scheme of things, is a pretty low risk.
...
I agree they've retired the vast majority of the overall risks, but I would NOT say that "deviation of real-life grid fin behavior from the modeled one" is low-risk. I'm thinking of specific instances where rockets were lost because real-life fin behavior deviated from the modeled one. Usually this happens when the vehicle goes transonic, a regime which the grid fins have yet to see in flight.

Just because they've done most of the hard parts doesn't mean their probably of success on this particular flight should thus be greater than 50%. It really does only take one thing to screw up your multi-million-dollar vehicle. So I think Musk is making an accurate assessment of the risk.

For instance, see this exchange on Twitter:
« Last Edit: 01/03/2015 12:20 AM by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online Robotbeat

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #367 on: 01/02/2015 11:43 PM »
Here you can read about the (recovery or launch) failures that this sort of control inversion caused for Armadillo Aerospace:
http://armadilloaerospace.com/n.x/Armadillo/Home/News?news_id=380
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #368 on: 01/02/2015 11:57 PM »
Looks like SpX has built a mini F9 pad next to the ASDS dock and SpX trailer. The 4 grey structures seem to be similar to the hold downs / supports used for the F9 VTVL tests.

Upon returning home and reviewing my video pans of the area, I see that I did, indeed, capture the tops of the 4 grey structures PhilW noticed in both video and Canon photos.  Here are a few shots, and I'll post the videos now that I can convert them into mpg files.

2080 and 2081 have about the best unobstructed views.

2076 is a context shot.  The hold downs are to the right of the blue cap tenty thing, and midway between there and the barge along the shore.  2076 is taken from the bridge near the shore. 2075 is taken from the same point, but shifted to include the escort ships.

The series 2068 -2073 is a pan that concludes with the 2075-2076 pair of establishing shots.

2157 is a mostly obstructed view of one of the tiedowns.
2163 is mostly obstructed, but shows the 4 tiedowns from an oblique angle to the square.
2170 is a pretty good view of the four of them, again.

videos to follow.


Online Eer

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #369 on: 01/03/2015 12:02 AM »
Also, in the previous series, DSC00235.JPG also includes the tiedowns just to the right of the suspended access ramp.  Attached again for reference.

Offline Marslauncher

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #370 on: 01/03/2015 12:36 AM »
Apologies if this has been brought up already, Surely parking a rocket next to a cruise ship would require zoning? I have been trying to find something/anything on possible legislature or zoning laws so we can better get an idea of the scope. Can anyone use their googlefu to find something? My googlefu is not working today, best I found was http://www.spaceflorida.gov/docs/spaceport-ops/florida-spaceport-systems-plan-2013_final.pdf?sfvrsn=2 but does not mention Jacksonville in regards to SpaceX.

I found this also -

http://www.jacksonvilleor.us/CityDocs/Planning/20+-+Title+17+Zoning.pdf

Also this..

http://jacksonville.com/news/georgia/2014-11-13/story/barge-port-planned-former-paper-mill-site-st-marys

This last one has me wondering though..


John C
« Last Edit: 01/03/2015 12:47 AM by Marslauncher »

Online Robotbeat

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #371 on: 01/03/2015 12:50 AM »
A rocket which is drained of propellant and pressurant is more inert than a tugboat. No zoning issues. (Provided they don't try launching there...)
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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #372 on: 01/03/2015 01:16 AM »
Here are the videos I took of the barge on 2014-12-23.  They are in a high definition format compatible with the AVCHD in which it was taken.  I tried to take them at different locations on the bridge, so they'd have some different perspectives.

20141223-Barge-01.mkv is the longest (and largest) of the files and consists of a slow pan without zoom, followed by slow pan with full zoom.  Hand held - no tripod - and the shakes are from trucks passing behind me on the bridge as I took the pictures.  About 258.4MB in size, 2 minutes, 32 seconds in length.

20141223-Barge-02.mkv is a 46 second, 86MB fairly rapid pan at full zoom.

20141223-Barge-03.mkv is a 24 second, 47MB pan at full zoom, taken from the far end of the bridge (so you can see the port bow of the barge at the beginning of the video.

20141223-Barge-04.mkv is a bit longer version of -03, from what appears to be the same vantage point, or nearly so.  35 seconds, 66MB.

I think that's it for now.




Offline deruch

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #373 on: 01/03/2015 01:32 AM »
I find it interesting to note, in passing, that the CRS-5 NASA Press Kit makes absolutely NO mention of the first stage recovery attempt.  In fact, there is only a single reference to first stage recovery, referencing the April 2014 soft landing water recovery.

What the heck!? One would think there would be SOME official notice of this potentially huge milestone event advancing booster technology, even if (from NASA's point of view) it was Not Invented Here.  Granted, it is not "NASA business" but rather "SpaceX business", but still.

Perhaps concern that a SpaceX successful, or even partially successful first stage recovery will overshadow CRS and/or ISS operations in the public view?  I think this is likely, especially of SpaceX releases "news candy" , i.e., photogenic,  video of the landing.

The CRS-1 presskit didn't mention the secondary payload either (Orbcomm).  The presskit is for the CRS Mission!  It's not an overview of the launch of SpaceX rocket #19.  It's not like SpaceX has been quiet about their plans for the test on this launch.  They're just not putting it in the info that's specifically about the CRS mission because it doesn't belong there.
« Last Edit: 01/03/2015 01:33 AM by deruch »
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Offline meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #374 on: 01/03/2015 01:39 AM »
..
...
What's left untested, therefore, is just the deviation of real-life grid fin behavior from the modeled one.  This, in the grand scheme of things, is a pretty low risk.
...
I agree they've retired the vast majority of the overall risks, but I would NOT say that "deviation of real-life grid fin behavior from the modeled one" is low-risk. I'm thinking of specific instances where rockets were lost because real-life fin behavior deviated from the modeled one. Usually this happens when the vehicle goes transonic, a regime which the grid fins have yet to see in flight.

Just because they've done most of the hard parts doesn't mean their probably of success on this particular flight should thus be greater than 50%. It really does only take one thing to screw up your multi-million-dollar vehicle. So I think Musk is making an accurate assessment of the risk.

For instance, see this exchange on Twitter:
Look.  John Carmack said "inversion" and now it's the internet risk de jour, but this is not some exotic unexpected phenomena that nobody understands. The mere fact that Musk is going with grid fins means he's not clueless about it, and a very wild guess says that they have an aerodynamicist (or two) on staff.

If I was to place a bet on why the landings might fail, this won't be a leading cause.

And besides, I never said "low risk", mainly because I can't quantify " low".  I said that the risks during the first (ever!) propulsive reentry were higher, and that this time almost all stages of the process have been validated already, or that "in the grand scheme of things, it's a low brisk" - so please quote my entire statement, not just half sentences.
« Last Edit: 01/03/2015 01:41 AM by meekGee »
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Offline PhilW

Fascination is due in port shortly. Wonder if #BargeX / Falcon's Nest will still be there when she arrives?
http://www.cruisin.me/ship_tracker/carnival_cruise_lines/carnival_fascination.php
« Last Edit: 01/03/2015 08:45 AM by PhilW »

Offline PhilW

..
...
What's left untested, therefore, is just the deviation of real-life grid fin behavior from the modeled one.  This, in the grand scheme of things, is a pretty low risk.
...
I agree they've retired the vast majority of the overall risks, but I would NOT say that "deviation of real-life grid fin behavior from the modeled one" is low-risk. I'm thinking of specific instances where rockets were lost because real-life fin behavior deviated from the modeled one. Usually this happens when the vehicle goes transonic, a regime which the grid fins have yet to see in flight.

Just because they've done most of the hard parts doesn't mean their probably of success on this particular flight should thus be greater than 50%. It really does only take one thing to screw up your multi-million-dollar vehicle. So I think Musk is making an accurate assessment of the risk.

For instance, see this exchange on Twitter:
Look.  John Carmack said "inversion" and now it's the internet risk de jour, but this is not some exotic unexpected phenomena that nobody understands. The mere fact that Musk is going with grid fins means he's not clueless about it, and a very wild guess says that they have an aerodynamicist (or two) on staff.

If I was to place a bet on why the landings might fail, this won't be a leading cause.

And besides, I never said "low risk", mainly because I can't quantify " low".  I said that the risks during the first (ever!) propulsive reentry were higher, and that this time almost all stages of the process have been validated already, or that "in the grand scheme of things, it's a low brisk" - so please quote my entire statement, not just half sentences.
Because SpX engineers know about the Inversion issue, their grid fin flight control software should be able to compensate for it and still maintain the desired F9 attitude control capability.

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #377 on: 01/03/2015 01:59 AM »
Fascination is due in port shortly. Wonder if #BargeX / Falcon's Nest will still be there when she arrives?
http://www.cruisin.me/ship_tracker/carnival_cruise_lines/carnival_fascination.php
Go Quest is underway at 0.1 knots with destination Blake Plateau at this time.

No - nevermind - its track looks like it's just jostling around.  Keep an eye on it, though ...
« Last Edit: 01/03/2015 02:03 AM by Eer »

Offline meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #378 on: 01/03/2015 02:06 AM »
..
...
What's left untested, therefore, is just the deviation of real-life grid fin behavior from the modeled one.  This, in the grand scheme of things, is a pretty low risk.
...
I agree they've retired the vast majority of the overall risks, but I would NOT say that "deviation of real-life grid fin behavior from the modeled one" is low-risk. I'm thinking of specific instances where rockets were lost because real-life fin behavior deviated from the modeled one. Usually this happens when the vehicle goes transonic, a regime which the grid fins have yet to see in flight.

Just because they've done most of the hard parts doesn't mean their probably of success on this particular flight should thus be greater than 50%. It really does only take one thing to screw up your multi-million-dollar vehicle. So I think Musk is making an accurate assessment of the risk.

For instance, see this exchange on Twitter:
Look.  John Carmack said "inversion" and now it's the internet risk de jour, but this is not some exotic unexpected phenomena that nobody understands. The mere fact that Musk is going with grid fins means he's not clueless about it, and a very wild guess says that they have an aerodynamicist (or two) on staff.

If I was to place a bet on why the landings might fail, this won't be a leading cause.

And besides, I never said "low risk", mainly because I can't quantify " low".  I said that the risks during the first (ever!) propulsive reentry were higher, and that this time almost all stages of the process have been validated already, or that "in the grand scheme of things, it's a low brisk" - so please quote my entire statement, not just half sentences.
Because SpX engineers know about the Inversion issue, their grid fin flight control software should be able to compensate for it and still maintain the desired F9 attitude control capability.
Yup. Also, (not having an aerodynamics background) I wonder if the phenomenon even occurs with grid fins, since the flow path is so short.

... And now, back to the Fascination vid feed, tonight's main event.
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Offline PhilW

Fascination is due in port shortly. Wonder if #BargeX / Falcon's Nest will still be there when she arrives?
http://www.cruisin.me/ship_tracker/carnival_cruise_lines/carnival_fascination.php
Go Quest is underway at 0.1 knots with destination Blake Plateau at this time.

No - nevermind - its track looks like it's just jostling around.  Keep an eye on it, though ...
Thought that Tugs reference has proven to be unreliable in the past as it gets turned off. But should shown when it leaves the dock. ;)

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