Author Topic: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2  (Read 2965229 times)

Offline PhilW

Looking at ElsBeth 3's latest track, the ASDS may be separated and in station keeping mode. Vector plots suggest the 2 vessels are moving to join up, keep close to each other.
« Last Edit: 01/05/2015 01:36 pm by PhilW »

Offline deruch

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #541 on: 01/05/2015 01:49 pm »
Seeing them act so optimistically, you wonder: just how on-target were those three touch-downs?  Counting Cassiope because as far as we can tell at the moment, all three landings relied on the accuracy of the boost-back and retro burns, and all of those burns came off without a hitch on all three flights.  Only the Cassiope final burn failed.

They were only aiming for 10km, but what did they actually achieve?

Analyses of the previous launches suggested that there weren't boost backs prior to CRS-4 (sideways).  At least not significant ones (i.e. not much beyond just testing a relight without trying to achieve much acceleration/deceleration).
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline rpapo

Seeing them act so optimistically, you wonder: just how on-target were those three touch-downs?  Counting Cassiope because as far as we can tell at the moment, all three landings relied on the accuracy of the boost-back and retro burns, and all of those burns came off without a hitch on all three flights.  Only the Cassiope final burn failed.

They were only aiming for 10km, but what did they actually achieve?

Analyses of the previous launches suggested that there weren't boost backs prior to CRS-4 (sideways).  At least not significant ones (i.e. not much beyond just testing a relight without trying to achieve much acceleration/deceleration).
Yes, but that's not precisely what I meant.  The accuracy of the landings/crashes was entirely dependent on the accuracy of those one or two burns.  The landing burn never affected accuracy, unlike in the Grasshopper divert maneuver.  So, given that they were presumably targeting something, and attempting to do so with just those burns, just how accurate were the final touchdowns/crashes?

Of course, we may never know.
« Last Edit: 01/05/2015 03:22 pm by rpapo »
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Online Jarnis

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #543 on: 01/05/2015 01:59 pm »
Perhaps their AIS is now satellite-capable? Lot of AIS transponders these days also can relay info via satellite when out at sea (OG2 sats that SpaceX delivered up earlier actually carry AIS payloads)

http://www.orbcomm.com/uploads/files/AIS_8-12-14.pdf

The location is definitely out of range of shore-based AIS receivers, so that seems to me like the most likely explanation.

Offline sghill

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #544 on: 01/05/2015 02:07 pm »
Canaveral Buoy is reporting 2 meter wave heights, 23-24 degree Celsius air and water, and 24 knot winds with rising air pressure.  Looks like an excellent day for yachting out there this morning!

http://www.ndbc.noaa.gov/station_page.php?station=41010



Bring the thunder!

Offline MTom

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #545 on: 01/05/2015 03:04 pm »
Yes it does include inter stage. With cap I meant the cone part onto which crane hooks. Now I wonder how it will get unloaded without it..
Maybe that is the intended use of the white adapter that was sitting in front of the 4 x Grey/Blue F9 supports? Bolts into the interstage to allow the F9 to be crane lifted?

We discussed it earlier, I agree with your opinion.

http://forum.nasaspaceflight.com/index.php?topic=36326.msg1308970#msg1308970
« Last Edit: 01/05/2015 03:05 pm by MTom »

Offline PhilW

Might be an early call but ElsBeth III may be heading back to port.
http://www.vesselfinder.com/?mmsi=367017460

Oops. ElsBeth3 is still doing a dance.
« Last Edit: 01/05/2015 03:26 pm by PhilW »

Offline speedevil

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #547 on: 01/05/2015 03:14 pm »

Analyses of the previous launches suggested that there weren't boost backs prior to CRS-4 (sideways).  At least not significant ones (i.e. not much beyond just testing a relight without trying to achieve much acceleration/deceleration).

This doesn't mean you can't do very interesting things.
For example - if you are actually intact when you come into the denser parts of the atmosphere - even without a very well defined position on launch, you can tell the rocket to aim at the closest 0.05 degree grid-intersection, and get really useful feedback from how well the positioning system can hit a given target.
Clearly - it can't test the final landing burn - but that is very uninteresting to test from some perspectives -, as if you've not got it right to within perhaps 20m or so -you've lost anyway.

The landing event takes well under 10 seconds - the lateral G available to generate the required delta-v to start and stop a lateral acceleration is not large, and tends to lead to large attitude errors, so the position error tolerable before the actual final ignition is really small.


Offline Nomadd

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #548 on: 01/05/2015 03:26 pm »
Perhaps their AIS is now satellite-capable? Lot of AIS transponders these days also can relay info via satellite when out at sea (OG2 sats that SpaceX delivered up earlier actually carry AIS payloads)

http://www.orbcomm.com/uploads/files/AIS_8-12-14.pdf

The location is definitely out of range of shore-based AIS receivers, so that seems to me like the most likely explanation.

Most of them pretty much capable of sat transmission and have always been. They can generally put out a generic, limited data 4800 BPS NMEA data stream that can work over any data capable sat including Iridium, or a 38,800 serial data stream that includes all the AIS data. Some new ones will do NMEA 2000 which is 250kbps, but that probably wouldn't be used for satellite unless they wanted to send the boat's entire NMEA 2000 stream including all the other sensors that would be a part of it.
 The problem is, not many AIS tracking sites are going to have that data available.
« Last Edit: 01/05/2015 03:31 pm by Nomadd »
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Offline cartman

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #549 on: 01/05/2015 03:26 pm »
Might be an early call but ElsBeth III may be heading back to port.
http://www.vesselfinder.com/?mmsi=367017460
I guess they left the ASDS at its target and are now moving away to a safe distance.

Offline Kabloona

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #550 on: 01/05/2015 03:30 pm »
Might be an early call but ElsBeth III may be heading back to port.
http://www.vesselfinder.com/?mmsi=367017460
I guess they left the ASDS at its target and are now moving away to a safe distance.

Yes, both ships idling around within 1 km of each other.

Footnote: Vesselfinder.com >> Marinetraffic.com.  Vesselfinder is showing detailed ship movement in the landing zone area; Marinetraffic isn't showing any of that.
« Last Edit: 01/05/2015 03:44 pm by Kabloona »

Offline Ohsin

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #551 on: 01/05/2015 03:54 pm »
Yes it does include inter stage. With cap I meant the cone part onto which crane hooks. Now I wonder how it will get unloaded without it..
Maybe that is the intended use of the white adapter that was sitting in front of the 4 x Grey/Blue F9 supports? Bolts into the interstage to allow the F9 to be crane lifted?

We discussed it earlier, I agree with your opinion.

http://forum.nasaspaceflight.com/index.php?topic=36326.msg1308970#msg1308970

Now I can see it too. Nice! Those pegs could be clamps to grab the rim of inter-stage. Just those two vertical bars are throwing me off(May be a person would ride it and bolt it on?).
« Last Edit: 01/05/2015 03:59 pm by Ohsin »
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Offline PhilW

Nice dance ElsBeth 3 is doing.
Maybe they are wetting a line? Fishing for dinner?
« Last Edit: 01/05/2015 04:58 pm by PhilW »

Offline PhilW

Yes it does include inter stage. With cap I meant the cone part onto which crane hooks. Now I wonder how it will get unloaded without it..
Maybe that is the intended use of the white adapter that was sitting in front of the 4 x Grey/Blue F9 supports? Bolts into the interstage to allow the F9 to be crane lifted?

We discussed it earlier, I agree with your opinion.

http://forum.nasaspaceflight.com/index.php?topic=36326.msg1308970#msg1308970

Now I can see it too. Nice! Those pegs could be clamps to grab the rim of inter-stage. Just those two vertical bars are throwing me off(May be a person would ride it and bolt it on?).
Someone will need to ride the hook. Will not attach itself.

Offline cscott

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #554 on: 01/05/2015 05:31 pm »
Yes it does include inter stage. With cap I meant the cone part onto which crane hooks. Now I wonder how it will get unloaded without it..
Maybe that is the intended use of the white adapter that was sitting in front of the 4 x Grey/Blue F9 supports? Bolts into the interstage to allow the F9 to be crane lifted?

We discussed it earlier, I agree with your opinion.

http://forum.nasaspaceflight.com/index.php?topic=36326.msg1308970#msg1308970

Now I can see it too. Nice! Those pegs could be clamps to grab the rim of inter-stage. Just those two vertical bars are throwing me off(May be a person would ride it and bolt it on?).

Oh, hm, I assumed that the fixture was sitting on the ground upside down, and the vertical bars would actually go down into the interstage to allow it to be bolted to some structural member closer to the top of the tank/bottom of the interstage.

Offline llanitedave

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #555 on: 01/05/2015 05:43 pm »
Well, this picture produces different results.  Measuring this and scaling for 224.4 feet, it looks like the first stage is 155 feet tall, with the interstage, but without legs.

Which also looks like a more horizontal perspective angle, so its probably better than the first photo.  Still could be a couple of feet off, though.
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Offline cscott

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #556 on: 01/05/2015 05:48 pm »
This is not very good picture for reference. Vandenberg pictures are pretty good as they are taken from a height. Also did you use diameter(12ft) or fairing height(43ft) to deduce?

I measured the total height and the height of the first stage, and then scaled for a total height of 224.4 feet.

The camera angle creates a linear perspective which should scale both measurements equally, unless there are fish-eye type lens distortions, which this picture doesn't appear to have.
Would trust SpX has already done this math, way before they leased the dock side land & installed the F9 supports.

Yes, but we're trying to use this information to prove/disprove a theory about the stage returning to port in the vertical orientation.  SpaceX only did this math if the stage is returning vertical.

EDIT: don't shoot the messenger, I'm just recapping the topic of debate!
« Last Edit: 01/05/2015 07:28 pm by cscott »

Offline PhilW

This is not very good picture for reference. Vandenberg pictures are pretty good as they are taken from a height. Also did you use diameter(12ft) or fairing height(43ft) to deduce?

I measured the total height and the height of the first stage, and then scaled for a total height of 224.4 feet.

The camera angle creates a linear perspective which should scale both measurements equally, unless there are fish-eye type lens distortions, which this picture doesn't appear to have.
Would trust SpX has already done this math, way before they leased the dock side land & installed the F9 supports.

Yes, but we're trying to use this information to prove/disprove a theory about the stage returning to port in the vertical orientation.  SpaceX only did this math if the stage is returning vertical.
Why would SpX build the F9 vertical supports if the stage is returning horizontal?

There is no facitility on the ASDS to lower the stage to horizontal. At sea you can't do that using a crane on Go Quest.

Offline rpapo

From the update thread:

Elon tweeted a pic of the barge enroute

https://twitter.com/elonmusk/status/552182273865699328/photo/1

Taken from air, so maybe camera drone test flight :)

There's no tugboat pushing or pulling it in this picture.  Looks to me like the barge is already station-keeping in this photo.
Following the space program since before Apollo 8.

Offline mme

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 2
« Reply #559 on: 01/05/2015 06:49 pm »
From the update thread:

Elon tweeted a pic of the barge enroute

https://twitter.com/elonmusk/status/552182273865699328/photo/1

Taken from air, so maybe camera drone test flight :)

There's no tugboat pushing or pulling it in this picture.  Looks to me like the barge is already station-keeping in this photo.
Look at the "prop wash." [1]  I think it's traveling, not just station keeping.  But maybe there is a strong enough current for it to be station keeping.

[1] I'm not sure what the proper term is.  But I mean the aerated trail behind the boat.
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