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SpaceX Vehicles and Missions => SpaceX Missions Section => Topic started by: Targeteer on 02/25/2015 11:16 pm

Title: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Targeteer on 02/25/2015 11:16 pm
Discussion Thread for the Falcon 9 v1.1 mission with the CRS-6 Dragon.

Resources:

Other threads for CRS-6:
SCRUB: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - April 13 - ATTEMPT 1 (https://forum.nasaspaceflight.com/index.php?topic=37186.0)
SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - April 14 - LAUNCH (https://forum.nasaspaceflight.com/index.php?topic=37294.0)
SpaceX CRS-6 Dragon - RNDZ, Berthing, ISS Ops - UPDATES (https://forum.nasaspaceflight.com/index.php?topic=37321.0)
SpaceX CRS-6 Dragon - Unberth, Entry, Splashdown - UPDATES (https://forum.nasaspaceflight.com/index.php?topic=37614.0)
The CRS-6/SpX-6 There and Back Again Party Thread (https://forum.nasaspaceflight.com/index.php?topic=37098.0)

SpaceX News Articles from 2006 (Including numerous exclusive Elon interviews):
http://forum.nasaspaceflight.com/index.php?topic=21862.0

SpaceX News Articles (Recent):
http://www.nasaspaceflight.com/tag/spacex/

=--=

SpaceX GENERAL Forum Section:
http://forum.nasaspaceflight.com/index.php?board=45.0 - please use this for general questions NOT specific to this mission.

SpaceX MISSIONS Forum Section:
http://forum.nasaspaceflight.com/index.php?board=55.0 - this section is for everything specific to SpaceX missions.

L2 SpaceX Section - now a dedicated full section:
http://forum.nasaspaceflight.com/index.php?topic=24469.0

CRS-6 UPDATES thread (UPDATES only, discussion belongs here)
http://forum.nasaspaceflight.com/index.php?topic=37186.0

CRS-6 There and back again party thread
http://forum.nasaspaceflight.com/index.php?topic=37098.0

"Another ‪#‎Dragon‬ spacecraft leaves HQ, on its way to Cape Canaveral."

https://www.facebook.com/SpaceX/photos/pcb.10155629790315131/10155629790165131/?type=1&theater

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AS-503 on 02/25/2015 11:33 pm
Awesome photo!

Very inspirational!

Look how young they are!

Below is a link where Kranz talks about the young team in Apollo Mission Control.

http://www.pbs.org/wgbh/nova/tothemoon/kranz.html

Quote: 

On Mission Control: "The controllers had come up, they had developed a set of values that are expressed by simple words: discipline, morale, toughness, competence, commitment, teamwork."

Well, the nature of Mission Control as it emerged from Mercury through Gemini and into the early Apollo was really one of an incredibly and intensely dedicated team of very young people. My controllers at the time of the first lunar landing—our average age was 26. I was 35. I was the old man in this room essentially. The controllers had come up, they had developed a set of values that are expressed by simple words: discipline, morale, toughness, competence, commitment, teamwork. And it was these characteristics that built the chemistry that would keep us together both in good times and especially in bad times. The room, the hours that we worked were incredible. I don't think anyone ever worked anything less than 10 to 12 hours each day. Saturday was a normal day of work; in fact, that's the way we felt it should be. We were given this impossible dream by President Kennedy, and we were living it. We were doing the kinds of things that engineers would kill for. And as part of this process, we'd go and open up our pay—we were surprised we were getting paid by this thing here. As long as we had enough money to make things meet, that's all we needed. The job was our life, and we lived this literally every day. And this room, it's a marvelous leadership laboratory.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: averagespacejoe on 02/25/2015 11:36 pm
I would guess this is a safe thread to designate the discussion with party and update thread coming later.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 02/26/2015 12:07 am
Converted it into the discussion thread. :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 02/26/2015 07:58 pm
Nice fancy wall, will look for it on my tour :o
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: obi-wan on 02/27/2015 12:54 am
Nice fancy wall, will look for it on my tour :o
On the right down the center aisle, just past the Merlin assembly line. (See if you can see any signs of Dragon 2 when you walk past!)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 02/27/2015 02:12 pm
Nice fancy wall, will look for it on my tour :o
On the right down the center aisle, just past the Merlin assembly line. (See if you can see any signs of Dragon 2 when you walk past!)
;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: zubenelgenubi on 03/01/2015 06:50 am
As there will be no external payload in the Dragon trunk on this flight, will this Dragon carry a greater mass of internal payload?
Or is the mass of the internal payload (largely) independent of the mass of the external payload?

Zubenelgenubi
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: symbios on 03/01/2015 12:20 pm
As there will be no external payload in the Dragon trunk on this flight, will this Dragon carry a greater mass of internal payload?
Or is the mass of the internal payload (largely) independent of the mass of the external payload?

Zubenelgenubi

As I understand it, internal mass is more volume limited. Could be different if they start shipping water or other more dense materiel.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Norm38 on 03/01/2015 02:49 pm
Why no trunk cargo on this flight?  Don't they have two docking adapters to bring up?  Nothing's ready to fly yet?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 03/01/2015 02:53 pm
Why no trunk cargo on this flight?  Don't they have two docking adapters to bring up?  Nothing's ready to fly yet?

Probably not ready yet, but future news related to SpaceX CRS-6 will be available throughout this March.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 03/01/2015 02:55 pm
By the way, is SpaceX CRS-6 delayed to the 10th or 22nd of April? In the Rocket Launch Viewing page of www.launchphotography.com (http://www.launchphotography.com), the Future Launches section says that the launch is on April 10 at around 5 PM EDT. But on Salo's US Rocket Launch Schedule, the launch is on April 8 but could be delayed to the 22nd.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 03/01/2015 04:24 pm
By the way, is SpaceX CRS-6 delayed to the 10th or 22nd of April? In the Rocket Launch Viewing page of www.launchphotography.com (http://www.launchphotography.com), the Future Launches section says that the launch is on April 10 at around 5 PM EDT. But on Salo's US Rocket Launch Schedule, the launch is on April 8 but could be delayed to the 22nd.

During the pre-briefing for the ISS EVAs, one of the managers said that they were targeting CRS-6 for mid to late April now.  That was the first that I had heard of any move from the earlier date.  I haven't personally seen anything that listed a more specific date, so I'm not sure where those came from.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 03/01/2015 08:53 pm
By the way, is SpaceX CRS-6 delayed to the 10th or 22nd of April? In the Rocket Launch Viewing page of www.launchphotography.com (http://www.launchphotography.com), the Future Launches section says that the launch is on April 10 at around 5 PM EDT. But on Salo's US Rocket Launch Schedule, the launch is on April 8 but could be delayed to the 22nd.

During the pre-briefing for the ISS EVAs, one of the managers said that they were targeting CRS-6 for mid to late April now.  That was the first that I had heard of any move from the earlier date.  I haven't personally seen anything that listed a more specific date, so I'm not sure where those came from.

Then it's highly likely scheduled for the 22nd.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Comga on 03/01/2015 10:14 pm
By the way, is SpaceX CRS-6 delayed to the 10th or 22nd of April? In the Rocket Launch Viewing page of www.launchphotography.com (http://www.launchphotography.com), the Future Launches section says that the launch is on April 10 at around 5 PM EDT. But on Salo's US Rocket Launch Schedule, the launch is on April 8 but could be delayed to the 22nd.

During the pre-briefing for the ISS EVAs, one of the managers said that they were targeting CRS-6 for mid to late April now.  That was the first that I had heard of any move from the earlier date.  I haven't personally seen anything that listed a more specific date, so I'm not sure where those came from.

Then it's highly likely scheduled for the 22nd.

Is that your guess, as suggested by the "highly likely" comment?

We have two data points from about the same time, the NASA document and the statement during the EVA briefing, that conflict.  Other than relating experience that favors one over the other, it doesn't do any good to guess at the schedule.  Finding more evidence is what is needed.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 03/01/2015 10:24 pm
Finding more evidence is what is needed.

Or, you know, patience.  But if I haven't found her yet, I don't hold out much hope for myself anytime soon.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 03/01/2015 11:48 pm
Finding more evidence is what is needed.

Or, you know, patience.  But if I haven't found her yet, I don't hold out much hope for myself anytime soon.

Got the point.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Robotbeat on 03/02/2015 01:20 am
For people looking for the ISS water recycling discussion, it was moved here:
http://forum.nasaspaceflight.com/index.php?topic=36926.0
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Eagandale4114 on 03/03/2015 03:39 pm
Here is the FCC application, and as expected we have a barge attempt as well as a NET of April 8th.
https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=initial&application_seq=64682&RequestTimeout=1000
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ben the Space Brit on 03/04/2015 08:49 pm
Was it this flight meant to carry BEAM or the NDS adapter in the trunk?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 03/04/2015 08:50 pm
Was it this flight meant to carry BEAM or the NDS adapter in the trunk?

No.
 - CRS-7: NDS 1
 - CRS-8: BEAM
 - CRS-9: NDS 2
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Comga on 03/04/2015 09:51 pm
Was it this flight meant to carry BEAM or the NDS adapter in the trunk?

A (nearly) full history of the external payload maifest is available in L2. (http://forum.nasaspaceflight.com/index.php?topic=29090.0)

Several external payloads have been scheduled for SpX-6.  IDA #1 was a possibility for a while.  BEAM was never listed on SpX-6. 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Galactic Penguin SST on 03/05/2015 01:03 am
FYI CRS-6's liftoff is listed at http://spaceflightnow.com/launch-schedule/ (http://spaceflightnow.com/launch-schedule/) as April 10 at 5:42 pm Eastern (21:42 UTC). Daytime launch and fly-to-barge FTW!  8)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 03/05/2015 01:32 pm
FYI CRS-6's liftoff is listed at http://spaceflightnow.com/launch-schedule/ (http://spaceflightnow.com/launch-schedule/) as April 10 at 5:42 pm Eastern (21:42 UTC). Daytime launch and fly-to-barge FTW!  8)

maybe Chris can get more info; if true something in the schedule must give, my guess is the launch abort
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: SpacemanInSPACE on 03/09/2015 03:48 am
From Reddit, pics of crs-6 on test stand at mcgregor. Good for them but still behind L2  :P

http://www.reddit.com/r/spacex/comments/2ydol6/did_a_driveby_yesterday/ (http://www.reddit.com/r/spacex/comments/2ydol6/did_a_driveby_yesterday/)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 03/09/2015 02:54 pm
From Reddit, pics of crs-6 on test stand at mcgregor. Good for them but still behind L2  :P

http://www.reddit.com/r/spacex/comments/2ydol6/did_a_driveby_yesterday/ (http://www.reddit.com/r/spacex/comments/2ydol6/did_a_driveby_yesterday/)

Some interesting tank plumbing visible in the last of those pictures, plus apparent new construction on a stand?  Is that the Falcon Heavy test stand, and is there chilling/densification equipment among the tanks?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jarnis on 03/09/2015 03:39 pm
The top of the stage on the stand looks... odd. Any idea what's up with that?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ben the Space Brit on 03/09/2015 03:42 pm
The top of the stage on the stand looks... odd. Any idea what's up with that?

I thought it was the upper securing rig, holding the top of the stage in place.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ugordan on 03/09/2015 03:53 pm
The top of the stage on the stand looks... odd. Any idea what's up with that?

You expected the top of the stage - containing at least some avionics boxes among other things - to be left open and exposed to the elements for days, without any temperature/humidity control?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 03/09/2015 03:56 pm
The top of the stage on the stand looks... odd. Any idea what's up with that?

I thought it was the upper securing rig, holding the top of the stage in place.

Yes, that appears to be exactly what it is.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jarnis on 03/09/2015 05:50 pm
The top of the stage on the stand looks... odd. Any idea what's up with that?

You expected the top of the stage - containing at least some avionics boxes among other things - to be left open and exposed to the elements for days, without any temperature/humidity control?

No, but the picture (even the large one) was bit too unclear to really make out what it was, so I thought I'd ask :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: input~2 on 03/16/2015 03:44 pm
Jeff Foust ‏@jeff_foust 2 hours ago

SpaceX's Gwynne Shotwell confirms that SpaceX will attempt landing first stage on drone ship on next two NASA CRS launches.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: saliva_sweet on 03/18/2015 01:36 pm
Now that Turkmensat is in late April I wonder if they could still fly CRS-6 on April 10th as planned.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: woods170 on 03/18/2015 01:53 pm
Now that Turkmensat is in late April I wonder if they could still fly CRS-6 on April 10th as planned.
Not. CRS-6 date is on the move according to one of my sources. There may be commonality of the Turkmenistan helium bottle problem with the ones on the CRS-6 launch vehicle.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: docmordrid on 03/18/2015 02:59 pm
@jeff_foust 23 minutes ago
Matsumori: still working with the customer on the extent of the delay, so declining to give a timetable for the launch. #satshow,

@jeff_foust 23 minutes ago
Matsumori: didn’t find problem with F9 that was to launch Sat, but instead an “anomaly” in factory; decided to be “careful” #satshow
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ElGuapoGuano1 on 03/18/2015 05:10 pm
I saw this today, to take it for what it's worth....
AmericaSpace ‏@AmericaSpace  6h6 hours ago
#SpaceX will hold off launching #Thales until after CRS-6. Next #Falcon9 launch still set for 4/10 at 5:42 pm EDT with a back up of 4/11.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 03/18/2015 05:40 pm
Not decided yet.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 03/19/2015 12:40 pm
Still no official word (remember, it's a NASA mission - they need to announce it), but it seems obvious this is going to be the plan.

Will set up the relevant threads (in addition to this discussion thread) later today.

And yeah, due to public demand, a party thread ;D PM me your suggestions and I'll pick one.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: e of pi on 03/19/2015 12:42 pm
Still no official word (remember, it's a NASA mission - they need to announce it), but it seems obvious this is going to be the plan.
Does this mean we'll see a core swap, with the TurkmenistanSat core now being slotted in under Dragon? Will this affect core recovery attempts at all if so (i.e. does the core have leg mount points, will they be installed now, etc.)?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Baranquilla on 03/19/2015 12:47 pm
Still no official word (remember, it's a NASA mission - they need to announce it), but it seems obvious this is going to be the plan.
Does this mean we'll see a core swap, with the TurkmenistanSat core now being slotted in under Dragon? Will this affect core recovery attempts at all if so (i.e. does the core have leg mount points, will they be installed now, etc.)?

If the problem is in the factory, we may assume that all cores are affected.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: guckyfan on 03/19/2015 12:54 pm
Still no official word (remember, it's a NASA mission - they need to announce it), but it seems obvious this is going to be the plan.
Does this mean we'll see a core swap, with the TurkmenistanSat core now being slotted in under Dragon? Will this affect core recovery attempts at all if so (i.e. does the core have leg mount points, will they be installed now, etc.)?

If the problem is in the factory, we may assume that all cores are affected.

Yes, but if they swap payload they either have to take the Turkmensat core out of the HIF and the CRS-6 core in or they have to swap no matter how they resolve the tank issue. Swapping cores means they lose a chance for landing again.

Going early april with whatever payload indicates that the issue is not that serious and they don't assume fixing it will take a month or longer as it looked for a short while.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: abaddon on 03/19/2015 01:26 pm
I think what it means is that by the time SpaceX can feel confident that the anomaly is understood and they are safe to launch, the Turkmensat launch would interfere with CRS-6.  So they will go ahead and launch the CRS-6 rocket first, followed by Turkmensat.  I am sure Turkmensat owners are not thrilled by that, but it is not that huge a slip either.  It also means that SpaceX will have another launch under their belt after discovering this anomaly, so maybe they consider it to be safer in trade.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: abaddon on 03/19/2015 01:29 pm
Yes, but if they swap payload they either have to take the Turkmensat core out of the HIF and the CRS-6 core in or they have to swap no matter how they resolve the tank issue. Swapping cores means they lose a chance for landing again.

Regarding the bolded: do we have any reason to think that's a big deal?  We know they have the ability to store at least two cores on-site.  I don't see why that would matter.

Gwynn was quoted as saying SpaceX will attempt a landing on CRS-6, and that was around the same time this news came out.  So it seems very likely that they are going to do just that.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: guckyfan on 03/19/2015 03:23 pm
Yes, but if they swap payload they either have to take the Turkmensat core out of the HIF and the CRS-6 core in or they have to swap no matter how they resolve the tank issue. Swapping cores means they lose a chance for landing again.

Regarding the bolded: do we have any reason to think that's a big deal?  We know they have the ability to store at least two cores on-site.  I don't see why that would matter.

Gwynn was quoted as saying SpaceX will attempt a landing on CRS-6, and that was around the same time this news came out.  So it seems very likely that they are going to do just that.

I have no idea wether or not this is a big deal. I just noted the fact. My main point was, if they swap the cores they lose the chance for landing CRS-6. Probably I made that not very clear.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 03/19/2015 04:12 pm
I know the previous core swap made it impossible to put legs on the swapped core, but doesn't it depend on timing?  I was under the impression the basic fittings are all in place either way.  If there's enough advance notice, I thought that they would be able to put the legs on the swapped core.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rcoppola on 03/19/2015 04:26 pm
I know the previous core swap made it impossible to put legs on the swapped core, but doesn't it depend on timing?  I was under the impression the basic fittings are all in place either way.  If there's enough advance notice, I thought that they would be able to put the legs on the swapped core.
The hardware may not be the issue with this but the software? I would think each avionics package is tailored to a particular return profile. I don't really know the process enough to understand if this would also add to the complexities and timing of a swap, so to speak?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ElGuapoGuano1 on 03/19/2015 06:52 pm
Has not been confirmed here, so I won't believe it til I see it, however...


AmericaSpace ‏@AmericaSpace  28m28 minutes ago
The Eastern Range has APPROVED Friday April 10 as the launch date for #SpaceX CRS-6. Window opens at 5:42 pm EDT🚀 http://www.americaspace.com/?page_id=56094
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rpapo on 03/19/2015 07:55 pm
Has not been confirmed here, so I won't believe it til I see it, however...


AmericaSpace ‏@AmericaSpace  28m28 minutes ago
The Eastern Range has APPROVED Friday April 10 as the launch date for #SpaceX CRS-6. Window opens at 5:42 pm EDT🚀 http://www.americaspace.com/?page_id=56094
The first landing attempt in daylight since ORBCOMM.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 03/20/2015 03:17 am
Still no official word (remember, it's a NASA mission - they need to announce it), but it seems obvious this is going to be the plan.
Does this mean we'll see a core swap, with the TurkmenistanSat core now being slotted in under Dragon? Will this affect core recovery attempts at all if so (i.e. does the core have leg mount points, will they be installed now, etc.)?

If the problem is in the factory, we may assume that all cores are affected.

One could, but that wouldn't yet be supported by the available information.  One could just as easily assume that the problem was detected in only a certain batch and CRS-6's parts may not be from the same run. etc.  At this point, we don't have enough public information to reliably guess exactly what the issue was and how widespread its effects are.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Baranquilla on 03/20/2015 10:02 am

One could, but that wouldn't yet be supported by the available information.  One could just as easily assume that the problem was detected in only a certain batch and CRS-6's parts may not be from the same run. etc.  At this point, we don't have enough public information to reliably guess exactly what the issue was and how widespread its effects are.

Your logic is more sound than mine.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JosephAbbott on 03/21/2015 02:02 am
NASA Social has been announced for April 9-10, concurrent with CRS-6 launch (this is explicit in announcement). So that date would seem to be solid. http://www.nasa.gov/spacex6-social/#.VQyw4Y7F-Ag
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 03/21/2015 02:10 am
NASA Social has been announced for April 9-10, concurrent with CRS-6 launch (this is explicit in announcement). So that date would seem to be solid. http://www.nasa.gov/spacex6-social/#.VQyw4Y7F-Ag

Joseph, thanks for your good work reporting on SpaceX activities at McGregor, TX for the WacoTrib. Now that you're a member here, maybe you could keep us posted with regular updates.  ;)

We have a dedicated McGregor thread here:

http://forum.nasaspaceflight.com/index.php?topic=35426.180
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: averagespacejoe on 03/21/2015 05:41 am
Here is a patch picture thanks reddit!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: averagespacejoe on 03/21/2015 05:42 am
6 stars easy enough for the CRS missions so far and even some acknowledgement of the ASDS off the coast of Florida!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 03/21/2015 01:41 pm
6 stars easy enough for the CRS missions so far and even some acknowledgement of the ASDS off the coast of Florida!

Barge on the patch means this time's the charm!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Zardar on 03/21/2015 07:36 pm
Here is a patch picture thanks reddit!

Hm, which ATV is that supposed to be docked to the ISS?

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: S.Paulissen on 03/21/2015 11:56 pm
I thought the last ATV is gone already.

EDIT: It is.

http://www.esa.int/Our_Activities/Human_Spaceflight/ATV/Last_ATV_reentry_leaves_legacy_for_future_space_exploration
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Baranquilla on 03/22/2015 12:13 am
Maybe they designed the patch first, way back when CRS-6 was supposed to be in 2014. This does not explain the Asds pin though.. Unless they thought a year ago they'd be ready for a good landing right about CRS-6
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: darkenfast on 03/22/2015 02:17 am
I don't think that's a ATV.  I think it's the older arrays on the Russian segment that give that appearance.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 03/22/2015 02:35 am
It's definitely an ATV; the solar arrays are arranged in a cross/X pattern.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Appable on 03/22/2015 03:16 am
Maybe they designed the patch first, way back when CRS-6 was supposed to be in 2014. This does not explain the Asds pin though.. Unless they thought a year ago they'd be ready for a good landing right about CRS-6

I think it was a design oversight based on the CRS-5 patch. The CRS-5 patch looks fairly similar to this one, and the ISS model looks the same. They probably designed the ISS model for CRS-5 and then forgot that it had changed by the time CRS-6 came around.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Raul on 03/22/2015 09:23 am
I think it was a design oversight based on the CRS-5 patch. The CRS-5 patch looks fairly similar to this one, and the ISS model looks the same. They probably designed the ISS model for CRS-5 and then forgot that it had changed by the time CRS-6 came around.

Similar ISS symbol it was also at CRS-3 patch. Even in that time it wasn't ATV docked there during CRS-3 mission too.

Complete SpaceX mission patches overview (http://www.imgur.com/a/8gulb).
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: padrat on 03/22/2015 11:36 am
I'm really surprised no one mentioned anything about the solar array fairings on the patch....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 03/22/2015 11:57 am
Here is a patch picture thanks reddit!

Also has the new Dragon logo.

edit: shoot, padrat beat me to it.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: dasmoth on 03/22/2015 04:10 pm
I'm really surprised no one mentioned anything about the solar array fairings on the patch....

Oooh -- the new Dragon logo!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Sesquipedalian on 03/23/2015 02:13 am
It looks like a Cubone skull...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 03/23/2015 03:52 am
Does anyone know who designs the mission patches?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Zed_Noir on 03/23/2015 05:21 am
Does anyone know who designs the mission patches?

My guess is the SpaceX CTO in his spare time.  ;D
He have to sign off on the final design of the mission patches in any case.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: woods170 on 03/23/2015 11:29 am
Confirmation of the CRS-6 / Turkmenistan mission swap:

http://spaceflightnow.com/2015/03/21/spacex-swaps-order-of-next-two-falcon-9-launches/

Quote from: Stephen Clark
A SpaceX spokesperson confirmed the company has swapped the order of the next two launches.

- CRS-6 up next
- Turkmenistan after that
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AncientU on 03/23/2015 03:48 pm
Confirmation of the CRS-6 / Turkmenistan mission swap:

http://spaceflightnow.com/2015/03/21/spacex-swaps-order-of-next-two-falcon-9-launches/

Quote from: Stephen Clark
A SpaceX spokesperson confirmed the company has swapped the order of the next two launches.

- CRS-6 up next
- Turkmenistan after that

Is this ability to swap missions three weeks before launch available anywhere else?  Doesn't seem to be possible with vertical integration systems, but not sure if Proton or others could do it.  (This doesn't give SpaceX a get-out-of-jail-free card for missing the Turkmenistan launch which was still a bad pass.)

Just like the single failed engine on the v1.0 launch a couple years ago, it does add a data point to the capability picture...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: newpylong on 03/23/2015 04:03 pm
Confirmation of the CRS-6 / Turkmenistan mission swap:

http://spaceflightnow.com/2015/03/21/spacex-swaps-order-of-next-two-falcon-9-launches/

Quote from: Stephen Clark
A SpaceX spokesperson confirmed the company has swapped the order of the next two launches.

- CRS-6 up next
- Turkmenistan after that

Is this ability to swap missions three weeks before launch available anywhere else?  Doesn't seem to be possible with vertical integration systems, but not sure if Proton or others could do it.  (This doesn't give SpaceX a get-out-of-jail-free card for missing the Turkmenistan launch which was still a bad pass.)

Just like the single failed engine on the v1.0 launch a couple years ago, it does add a data point to the capability picture...

If the payloads are available and the launch vehicles are of the same configuration (Atlas 401 - 401) then it is possible.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: matthewkantar on 03/23/2015 04:43 pm
The news that the missions switched order of launch does not have to mean that they swapped vehicles, just that SpaceX is launching the vehicle that was always intended for CRS-6 before the vehicle that was always intended for Turkmenistan Sat. Maybe.

Enjoy, Matthew
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rcoppola on 03/23/2015 04:58 pm
If the H-bottle issue was found in one particular lot, it may very well be that the H-bottle in the CRS-6 F9 was from a different lot that checked out ok. Or they just prioritized CRS-6 and will be replacing the bottles on that first.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 03/23/2015 05:33 pm

Is this ability to swap missions three weeks before launch available anywhere else?  Doesn't seem to be possible with vertical integration systems,

Yes, for like vehicles and if the payload is available.  It has nothing to with vertical or horizontal integration.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Bargemanos on 03/25/2015 11:45 am

From the TurkmenistanSat thread:


This article has some information (hopefully new?) about the TurkmenistanSat delay and flight swap: http://www.zerognews.com/2015/03/23/spacex-clarifies-reason-for-turkmenalem52e-launch-delay/[/size]
Quote
SpaceX spokesman John Taylor said the issue wasn’t with the [helium pressurizing] bottles themselves, but rather other bottles from a similar lot that failed testing at the company’s assembly plant. Taylor is quoted saying, “We identified a potential condition that could be shared with those on board the Thales vehicle.”


Could this be the similar case for the CRS-6 core? On the other hand, they wouldn't launch it if it was.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 03/25/2015 01:28 pm

From the TurkmenistanSat thread:


This article has some information (hopefully new?) about the TurkmenistanSat delay and flight swap: http://www.zerognews.com/2015/03/23/spacex-clarifies-reason-for-turkmenalem52e-launch-delay/[/size]
Quote
SpaceX spokesman John Taylor said the issue wasn’t with the [helium pressurizing] bottles themselves, but rather other bottles from a similar lot that failed testing at the company’s assembly plant. Taylor is quoted saying, “We identified a potential condition that could be shared with those on board the Thales vehicle.”


Could this be the similar case for the CRS-6 core? On the other hand, they wouldn't launch it if it was.

As @rcoppola said, another (more likely?) explanation is that it will take X weeks to swap out the bottles/resolve the issue, presumed in this case to be present on both CRS-6 and TurkmenistanSat, and that time period is long enough that they couldn't launch CRS-6 on time any more if they launched TurkmenistanSat first.  So they swapped launch order to keep CRS-6 on time.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 03/25/2015 02:14 pm
Or the even simpler explanation: that the CRS-6 core was built using a different batch of helium bottles.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Sesquipedalian on 03/25/2015 02:57 pm
It was posted elsewhere (can't find where at the moment) that the CRS-6 core was earlier along in processing and that therefore it was less work to extract and verify the helium bottles.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Dudely on 03/25/2015 03:21 pm
It was posted elsewhere (can't find where at the moment) that the CRS-6 core was earlier along in processing and that therefore it was less work to extract and verify the helium bottles.

“We identified a potential condition that could be shared with those on board the Thales vehicle.”

Makes me think Lars is correct. While not explicitly stated, by not mentioning the CRS-6 vehicle he's implying that it doesn't have that "potential condition"
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kenban on 03/25/2015 06:15 pm
It was posted elsewhere (can't find where at the moment) that the CRS-6 core was earlier along in processing and that therefore it was less work to extract and verify the helium bottles.

The quote from SpaceX specifically states that it was found at the assembly plant.  Makes me wonder if they noticed the problem while building CRS-6.  Which is why it was so easy to fix.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jcc on 03/25/2015 06:54 pm
We can also wonder if the problem was in cores that flew successfully already.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: WHAP on 03/25/2015 11:47 pm
We can also wonder if the problem was in cores that flew successfully already.

Wonder all you want.  It"s hard to un-ring a bell.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 03/26/2015 02:56 am
We can also wonder if the problem was in cores that flew successfully already.


If only those cores had landed, they'd know!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: clarkeo on 03/26/2015 09:14 am
Simple explanation is that the helium bottles on the Turkmesat are different from those on CRS 6 because Turkmensat was never going to attempt reuse/landing therefore had the smaller version helium bottles as no need for gridfin actuation? Whereas CRS6 might have larger boottles/different design due to this factor
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jcc on 03/26/2015 09:52 am
Helium is used to extend the landing legs, not grid fins. The volume of He needed to extend the legs is far smaller than what is needed to pressurize the tanks, so I doubt they are different in design between He tanks on reusable or expendable rockets. My understanding was that they were simply different batches, but a slight design difference might explain why they were different batches.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 03/26/2015 12:13 pm
Simple explanation is that the helium bottles on the Turkmesat are different from those on CRS 6 because Turkmensat was never going to attempt reuse/landing therefore had the smaller version helium bottles as no need for gridfin actuation? Whereas CRS6 might have larger boottles/different design due to this factor

Main use for helium is pressurizing RP-1 tank ullage. Volume of helium needed for the legs is probably a tiny fraction of the total.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cambrianera on 03/26/2015 06:27 pm
Volume required for RP-1 ullage and pressurization should be 140x3=420 Nm3 (140 m3 x 3 bar).
Volume required for leg extension should be 4x1.1x20=88 Nm3 (1.1 m3 x 20 bar).

Assumptions are:
RP-1 tank lenght 14 m, tank pressure 3 bar.
Telescopic cylinder diameter 0.4 m, extension 9 m (3->12), pressure 20 bar.

Some more He is needed for engines restart.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Antares on 03/27/2015 02:36 am
Occam's razor is that all of the vehicles had the same problem; but as I said in the TKM thread, Station needs its cargo more urgently than TKM needs a GEO bird.

Occam's twin-blade would be that somehow the TKM vehicle was exposed to the same risk that was found in the "factory" but that the CRS vehicle was somehow free of that, despite the large number of bottles each carries, as seen on tank videos.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jcc on 03/27/2015 02:10 pm
If each core carries multiple He bottles, then maybe the reusable version just has one or more extras of the same type and there is no need for a different design, but if they make a lot of them, it makes sense they would do so in batches, so it is certainly possible the CRS-6 batch was not affected.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 03/27/2015 05:14 pm
Occam's razor is that all of the vehicles had the same problem; but as I said in the TKM thread, Station needs its cargo more urgently than TKM needs a GEO bird.

Occam's twin-blade would be that somehow the TKM vehicle was exposed to the same risk that was found in the "factory" but that the CRS vehicle was somehow free of that, despite the large number of bottles each carries, as seen on tank videos.
SX has already stated this was a potential issue identified in the factory, not on the rocket.  IMHO, CRS-6 is more urgent and once they identified the problem in the factory, inspecting CRS-6 got priority.  If an issue is found, fixing CRS-6 gets priority.  But we can't infer whether either rocket had an issue and I don't know if we'll ever know if there was a problem on either rocket.

Unless of course SX tells us or the schedule moves significantly to the right.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: averagespacejoe on 03/27/2015 07:57 pm
T- 2 weeks :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: averagespacejoe on 03/31/2015 02:34 pm
Well maybe now it is t-2 weeks I saw on Patrick Air Force Base launch may have moved to April 13th
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 03/31/2015 02:52 pm
Well maybe now it is t-2 weeks I saw on Patrick Air Force Base launch may have moved to April 13th

Yeah, unofficial (per how things have to progress to official), but that's what we're all seeing as the latest.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 04/01/2015 01:10 am
Well maybe now it is t-2 weeks I saw on Patrick Air Force Base launch may have moved to April 13th

Yeah, unofficial (per how things have to progress to official), but that's what we're all seeing as the latest.

Best guesses on when the static fire will be with the new date?   The previous CRS launches seem to have the static fire either about a week before launch or just 2 days before launch.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Dudely on 04/01/2015 11:51 am
It been showing TBD for the past 18 hours now. . . guess we'll have to wait until we hear an official word.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Overcast on 04/01/2015 03:50 pm
probably the wrong thread, but I'm wondering if/when Spacex are going to try the fast rendevous method that Soyuz are now regularly using?
I'm sure they must be planning to do this when they start the crew transfer, so would have thought starting with cargo would make sense.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/01/2015 04:39 pm
probably the wrong thread, but I'm wondering if/when Spacex are going to try the fast rendevous method that Soyuz are now regularly using?
I'm sure they must be planning to do this when they start the crew transfer, so would have thought starting with cargo would make sense.

You can hear Hans address about that question here, starting around 35:00. He says there is no need to practice on cargo missions.

http://www.space-multimedia.nl.eu.org/index.php?option=com_content&view=article&id=9082
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Joffan on 04/01/2015 07:50 pm
from updates...
After about five weeks at the space station, Dragon will return to Earth filled with cargo including crew supplies, hardware and computer resources, science experiments, and space station hardware.

Is this an on-station duration record for Dragon?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MattMason on 04/02/2015 07:41 pm
from updates...
After about five weeks at the space station, Dragon will return to Earth filled with cargo including crew supplies, hardware and computer resources, science experiments, and space station hardware.

Is this an on-station duration record for Dragon?

The longest flight duration for any Dragon has been with CRS-4, at 31 days, 22 hours. (CRS-5 was 29 days).

So "almost 5 weeks" suggests a 31 to 37 35 day duration. Answer: Probable!

EDIT: I swear my math is metaphysically the cause of the Mars Climate Orbiter failure. "About" would go about 35 days and change.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sojourner on 04/03/2015 06:53 pm
37 would be "at least", 34 would be " almost".

 :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 04/04/2015 05:35 am
Well maybe now it is t-2 weeks I saw on Patrick Air Force Base launch may have moved to April 13th

Yeah, unofficial (per how things have to progress to official), but that's what we're all seeing as the latest.

Best guesses on when the static fire will be with the new date?   The previous CRS launches seem to have the static fire either about a week before launch or just 2 days before launch.

Chris' new article outlining some of the busy upcoming events for SpaceX mentioned the static fire as now being scheduled for April 10th.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Llian Rhydderch on 04/05/2015 11:36 am
Lars-J has posted a new photo of the CRS-6 launch vehicle in the hangar on the Updates thread.

SpaceX tweeted a new image: https://twitter.com/SpaceX/status/584130175224295424

Quote
SpaceX ‏@SpaceX
Falcon 9 and Dragon undergoing prep in FL in advance of 4/13 launch to the @Space_Station http://go.nasa.gov/19HfTE5 

Comparing that to this very similar photo of the CRS-3 F9 v1.1-with-legs, in SLC 40 hangar (https://www.flickr.com/photos/spacexphotos/16855338881/) shows that SpaceX have made some mods to the hangar. 

For one, we can see that the outside row of tracks have been totally removed, and the hangar floor filled in.


Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: StuffOfInterest on 04/05/2015 12:02 pm
Lars-J has posted a new photo of the CRS-6 launch vehicle in the hangar on the Updates thread.

SpaceX tweeted a new image: https://twitter.com/SpaceX/status/584130175224295424

Quote
SpaceX ‏@SpaceX
Falcon 9 and Dragon undergoing prep in FL in advance of 4/13 launch to the @Space_Station http://go.nasa.gov/19HfTE5 

Comparing that to this very similar photo of the CRS-3 F9 v1.1-with-legs, in SLC 40 hangar (https://www.flickr.com/photos/spacexphotos/16855338881/) shows that SpaceX have made some mods to the hangar. 

For one, we can see that the outside row of tracks have been totally removed, and the hangar floor filled in.

No, the newer photo just has covers over the tracks to keep people and equipment from tripping.  The tracks are needed when the transporter/erector is brought in and out.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MechE31 on 04/05/2015 06:04 pm
Lars-J has posted a new photo of the CRS-6 launch vehicle in the hangar on the Updates thread.

SpaceX tweeted a new image: https://twitter.com/SpaceX/status/584130175224295424

Quote
SpaceX ‏@SpaceX
Falcon 9 and Dragon undergoing prep in FL in advance of 4/13 launch to the @Space_Station http://go.nasa.gov/19HfTE5 

Comparing that to this very similar photo of the CRS-3 F9 v1.1-with-legs, in SLC 40 hangar (https://www.flickr.com/photos/spacexphotos/16855338881/) shows that SpaceX have made some mods to the hangar. 

For one, we can see that the outside row of tracks have been totally removed, and the hangar floor filled in.

No, the newer photo just has covers over the tracks to keep people and equipment from tripping.  The tracks are needed when the transporter/erector is brought in and out.

You are correct. The earlier photo also has half a roll ring removed and a vehicle with closed up TPS. Looks like they were preparing to lift the vehicle into the TE.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: averagespacejoe on 04/06/2015 08:14 pm
I will call it a few minutes early T- 1 week
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MarekCyzio on 04/07/2015 08:30 pm
Quote
Our History Center will be closed due to SpaceX pre-launch activities on Friday, April 10th and on Sunday, April 12th. Please check back here for the latest information on closures as any changes in the launch schedule will directly impact the hours we will be open to the public. Thank you!

This means the static fire is planned for 4/10. But what is SpaceX doing on 4/12? Until now, there was no additional activity in SpaceX LCC a day before scheduled launch.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kdhilliard on 04/09/2015 12:19 am
Launch hazard map for this one https://www.google.com/maps/d/viewer?mid=zp15b_P5ERVk.kdpSo6aGbVFs you can toggle CRS-5 for comparison purposes. Also attached is it in image format.
What is the reason for the small, blue exclusion zone (Polygon 9), midway between the launch site and the landing area?

~Kirk
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ChrisDMarshall on 04/09/2015 12:25 am
Any news on what time the Static Fire will be on the 10th?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/09/2015 02:43 am
Launch hazard map for this one https://www.google.com/maps/d/viewer?mid=zp15b_P5ERVk.kdpSo6aGbVFs you can toggle CRS-5 for comparison purposes. Also attached is it in image format.
What is the reason for the small, blue exclusion zone (Polygon 9), midway between the launch site and the landing area?

~Kirk

I think that's the impact site if the boost-back burn was ok, but the reentry burn didn't happen.   Since they're doing 50% boostback, the flyback trajectory is almost a vertical drop, and that's why that zone is so small.  I think.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 04/09/2015 04:51 am
Launch hazard map for this one https://www.google.com/maps/d/viewer?mid=zp15b_P5ERVk.kdpSo6aGbVFs you can toggle CRS-5 for comparison purposes. Also attached is it in image format.
What is the reason for the small, blue exclusion zone (Polygon 9), midway between the launch site and the landing area?
~Kirk

The CRS-5 mission had the same zone.  It was discussed then too and no one gave anything more than guesses as to what it was for.  As yet, nothing definitive.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: baldusi on 04/09/2015 02:31 pm
Could it be the MaxQ zone, in case of a catastrophic failure?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Graham on 04/09/2015 03:25 pm
Launch hazard map for this one https://www.google.com/maps/d/viewer?mid=zp15b_P5ERVk.kdpSo6aGbVFs you can toggle CRS-5 for comparison purposes. Also attached is it in image format.
What is the reason for the small, blue exclusion zone (Polygon 9), midway between the launch site and the landing area?
~Kirk

The CRS-5 mission had the same zone.  It was discussed then too and no one gave anything more than guesses as to what it was for.  As yet, nothing definitive.
My first guess was the zone where the fairings may land...
Then I realized there are no fairings on CRS flights...
I wonder what it is
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: averagespacejoe on 04/09/2015 03:50 pm
T minus 100 hours! I have already got my lunch for launch planned around it. In Alaska launch and lunch are at the same time 12:33p AKST
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: laika_fr on 04/09/2015 05:30 pm
A lile weather forecast about wind and waves for now.

- Pad
wind : max, 20 km/h, upper level winds should not be a issue

- ASDS location
wind : max, ~25 km/h
waves height : max 2.5 meters
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: The_Ronin on 04/09/2015 06:03 pm
2.5 meter waves = 8 ft waves.  Nothing to sneeze at and might be out of bounds.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DatUser14 on 04/09/2015 06:11 pm
Static Fire happened yet? the suspense is breaking my F5.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/09/2015 06:18 pm
Static Fire happened yet? the suspense is breaking my F5.

Go easy on the F5. Static fire is tomorrow.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: corrodedNut on 04/09/2015 07:01 pm
Launch hazard map for this one https://www.google.com/maps/d/viewer?mid=zp15b_P5ERVk.kdpSo6aGbVFs you can toggle CRS-5 for comparison purposes. Also attached is it in image format.
What is the reason for the small, blue exclusion zone (Polygon 9), midway between the launch site and the landing area?
~Kirk

The CRS-5 mission had the same zone.  It was discussed then too and no one gave anything more than guesses as to what it was for.  As yet, nothing definitive.
My first guess was the zone where the fairings may land...
Then I realized there are no fairings on CRS flights...
I wonder what it is
Nose cap?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/09/2015 07:14 pm
2.5 meter waves = 8 ft waves.  Nothing to sneeze at and might be out of bounds.
For CRS-5 the slightly misleadingly named "Launch Commit Criteria" [1] for First Stage Landing was <6ft.  Hopefully the modifications to JRtI will increase that criteria significantly.

Reference: http://forum.nasaspaceflight.com/index.php?topic=36326.msg1311090#msg1311090 (http://forum.nasaspaceflight.com/index.php?topic=36326.msg1311090#msg1311090)

[1] I say "slightly misleading" because they'll still launch if all the ascent criteria are green.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DatUser14 on 04/09/2015 09:27 pm
Quick question about the Static Fire. Is it a full up complete launch countdown that exhaustively tests all systems of the entire rocket to ensure success come launch day, or just a brief firing of the engines of the first stage on partial throttle?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/09/2015 09:30 pm
Quick question about the Static Fire. Is it a full up complete launch countdown that tests all major systems of the entire rocket, or just a brief firing of the engines of the first stage?

It is a complete countdown, but like regular countdowns, there are major systems that can't be tested.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/09/2015 09:57 pm
2.5 meter waves = 8 ft waves.  Nothing to sneeze at and might be out of bounds.

Not a problem. Compared to the storm at sea for the DSCOVR (non-barge) splashdown, 8 ft waves and 25 km/hr (13 knot) winds will be a "non-stormy weather" picnic.

Quote
Elon Musk ‏@elonmusk  24s25 seconds ago
Rocket soft landed in the ocean within 10m of target & nicely vertical! High probability of good droneship landing in non-stormy weather.
---
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 04/09/2015 10:58 pm
Less than four days left until T0.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 04/09/2015 11:04 pm
Did they launch the barge?

 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Sesquipedalian on 04/10/2015 12:55 am
Did they launch the barge?

It's on a suborbital trajectory.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/10/2015 01:06 am
Barge will mostly likely leave port late Saturday.  It takes about 42 hours to get on station.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: maximlevitsky on 04/10/2015 11:52 am
What is the launch window of launch?

Spaceflight Now reports 20:33 GMT lauch window of CRS-6, and ULA reports their unveiling at 2 PM MT (which is I think mountain time. thus GMT-7, thus at 21:00 GMT)

However in thread about ULA unveiling of their next gen rocket it was said that unveiling is half hour before CRS-6 launch.
http://forum.nasaspaceflight.com/index.php?topic=37251.0

What is correct?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: eriblo on 04/10/2015 12:01 pm
I'm guessing use of MDT (http://www.timeanddate.com/time/zones/mdt) :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/10/2015 02:22 pm
What is the launch window of launch?

Spaceflight Now reports 20:33 GMT lauch window of CRS-6, and ULA reports their unveiling at 2 PM MT (which is I think mountain time. thus GMT-7, thus at 21:00 GMT)

However in thread about ULA unveiling of their next gen rocket it was said that unveiling is half hour before CRS-6 launch.
http://forum.nasaspaceflight.com/index.php?topic=37251.0

What is correct?

They're both correct. Launch is 4:33 pm ET, 2:30 MT. ULA unveiling begins a half hour earlier, 2:00 MT.

MDT is GMT-6, not -7.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rcoppola on 04/10/2015 06:55 pm
Well now...It will be quite interesting to be watching the NGLV announcement right about the time the inter-webs begin to explode after it's confirmed the F9 core stage makes a successful return to JRTI. Looks like the NGLV gets a 45 minute head-start. So if they have a Q&A and it overlaps with a successful return, I'm certain someone will bring it up. I'm sure Tory will have a genuine congratulatory response at the ready. But talk about sucking all the air out of a room.

Lots of dueling headlines to look forward to.

(Of course, it may not land successfully either. I also want to point out that I am looking forward to the NGLV announcement so I'm not trying to be partisan here.  Although it's going to be hard to compete against pictures of that stage standing on that deck...if it happens.)
 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/10/2015 07:05 pm
Well now...It will be quite interesting to be watching the NGLV announcement right about the time the inter-webs begin to explode after it's confirmed the F9 core stage makes a successful return to JRTI. Looks like the NGLV gets a 45 minute head-start. So if they have a Q&A and it overlaps with a successful return, I'm certain someone will bring it up. I'm sure Tory will have a genuine congratulatory response at the ready. But talk about sucking all the air out of a room.

Lots of dueling headlines to look forward to.

(Of course, it may not land successfully either but I do want to point out that I am looking forward to the NGLV announcement.  Although it's going to be hard to compete against pictures of that stage standing on that deck...if it happens.)

I'm assuming it was an oversight.  Anyone not following SpaceX closely might not realize there was a landing attempt scheduled, and/or underestimate the extent to which even an unsuccessful JRtI landing might dominate the headlines.

That said, the SpaceX launch could slip.  Even if not, SpaceX might not release footage of the landing attempt immediately.  ULA is probably committed to its announcement date by now, it probably wouldn't look good for them to reschedule at this point.  The "America's next rocket" business was deliberately hyperbolic, so now they seemingly have to lie in the bed they've made.

Like rcoppola, I'm genuinely interested in the ULA announcement, and I think our space program would clearly benefit from having two strong competitors in this race.  I just think ULA's PR team goofed.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/10/2015 09:16 pm
Post from SpaceX  -

Final processing for #Dragon ahead of 4/13 launch attempt to @Space_Station (points if you notice what’s new)

https://twitter.com/SpaceX/status/586635597940293632

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: docmordrid on 04/10/2015 09:49 pm
Now showing the new Dragon logo.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 04/11/2015 01:51 am
Now showing the new Dragon logo.

That's a first for a CRS mission; sporting new logos.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Comga on 04/11/2015 04:06 am
Now showing the new Dragon logo.

That's a first for a CRS mission; sporting new logos.

They remain on the solar panel covers which are ejected just after the capsule and trunk separate from the second stage, and so won't be visible on orbit.  All that will be seen on the ISS videos is the simple SpaceX logo above the hatch.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 04/11/2015 04:34 pm
Understood.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 04/12/2015 12:53 am
https://twitter.com/SpaceX/status/587048257651511296
Quote
SpaceX
‏@SpaceX

Static fire engine test completed today in advance of Monday's launch attempt to the @Space_Station.

Tried to find better resolution picture, but this was the best I could find.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 04/12/2015 03:01 am
Still, good evidence of the Flight Readiness Firing (FRF).
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: laika_fr on 04/12/2015 05:23 am
Looks like a quick FTW to me, any available opportunity deserves a try.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: gwiz on 04/12/2015 10:35 am
Planetary resources have tweeted that their Arkyd-3R Cubesat will be on board.  Any info on possible other Cubesats?
https://twitter.com/PlanetaryRsrcs/status/586650310849986561
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Olaf on 04/12/2015 11:21 am
Planetary resources have tweeted that their Arkyd-3R Cubesat will be on board.  Any info on possible other Cubesats?
https://twitter.com/PlanetaryRsrcs/status/586650310849986561
On the NanoRacks workshop in February it was said, that eight deployers will be on SpX-6 with 14 Flock-1e and the Arkyd-3R.
http://forum.nasaspaceflight.com/index.php?topic=36822.0
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: FutureSpaceTourist on 04/13/2015 06:45 am
Nice to see Hans Koenigsmann say 75 - 80% chance of barge landing success (given caution he expressed for CRS-5).
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ben the Space Brit on 04/13/2015 09:54 am
I don't think that this has ever been mentioned before: Does the landing barge have any on-board cameras? Additionally, are a few other vessels in the area, possibly with radar and cameras to track the spacecraft as it descends?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Beittil on 04/13/2015 10:06 am
Well, there is this Vine that shows on-board footage of the last attempt crashing into, exploding and then going overboard of the ASDS :)

There are also two support ships with the ASDS (Elsbeth III & Go Quest are their names i believe). These crews have a video drone available.

The Vine is here:
https://vine.co/v/OjqeYWWpVWK
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Baranquilla on 04/13/2015 12:12 pm
Anyone there who wants to make a poll about whether or not you think F9 will safely touch down on the barge? (Different from the landing bingo). I think it's interesting to see how many people think it will land!

PS: I don't know how to do it and I'm mobile right now.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Graham on 04/13/2015 12:31 pm
Anyone there who wants to make a poll about whether or not you think F9 will safely touch down on the barge? (Different from the landing bingo). I think it's interesting to see how many people think it will land!

PS: I don't know how to do it and I'm mobile right now.
That's a cool idea! I'll create one now
EDIT: Done! It's in the poll section!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: gwiz on 04/13/2015 01:02 pm
Again according to Twitter, a 1U Cubesat called Centennial 1, built by Booz Allen Hamilton, will also be on board.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Comga on 04/13/2015 03:22 pm
Discussion of the lack of an external payload on SpX-6
Mr Hartman expanded on the up-mass difference issue.  Lack of a trunk payload is the main factor and a payload (which one?) was originally manifested but experienced delays.  Moving IDA-1 up a launch was examined but an EVA during the docked segment is required for installation and the total crew time required (80-100 hours including suit prep, etc) could not be found on this mission without negatively effecting planned science.  Presumably launch on the next Dragon flight has made accommodations for the required EVA and prep time by the crew.

L2 source of the planned trunk payload for this mission http://forum.nasaspaceflight.com/index.php?topic=36288.0

There is an L2 thread for external cargo (http://forum.nasaspaceflight.com/index.php?topic=29090.msg912016#msg912016) but a lot can be found searching for "FPIP" on NASA.gov.

As far back as I can find, the external cargo for SpX- was SAGE-III, occupying two positions, and MUSES. 
SAGE-III experienced technical delays, and is now manifested for SpX-10 in 2016. 
Then the external cargo for SpX-6 was CREAM, then possibly IDA-1.
Not sure what happened to MUSES, which was shifted to HTV-5, or CREAM, which moved to SpX-11 only two months ago.
Targeteer explained why IDA-1 is not flying on SpX-6.
So, despite a pretty full manifest for external cargo, SpX-6 is flying with no major cargo in the trunk.

edit: cleanup
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Silmfeanor on 04/13/2015 03:45 pm
The excellent write-up for this launch is well worth a read - http://www.nasaspaceflight.com/2015/04/spacex-falcon-9-crs-6-dragon-stage-return/

What stood out to me is the sub-second accurate events during the launch I think this is the first time we have seen the exact time of Max-Q, burn times during landing, et cetera.

Quote
The third and final burn will take place as the rocket approaches its landing target, beginning at eight minutes and 0.12 seconds mission elapsed time. Almost twenty-four seconds into the burn the rocket will deploy its landing legs with touchdown expected six seconds later; eight minutes, 30.01 seconds after liftoff. The engines will cut off about 2.3 seconds after landing.

I think some of the speculation and discussion regarding stage weight, throttling capability et cetera might be sharpened by taking these numbers into account.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Semmel on 04/13/2015 03:51 pm
Or you get an L2 account and read them from the spread sheet where the timing numbers come from ;-)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Silmfeanor on 04/13/2015 03:53 pm
Or you get an L2 account and read them from the spread sheet where the timing numbers come from ;-)

I was on L2 for 2 years and I had a suspicion where these numbers came from. Alas, after deciding to do a 2nd master I had to keep a close eye on my cash...

Now that they have been revealed however, I think some better simulations could be run - or assumptions tested against these numbers. I was surprised nobody else jumped on them yet.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rpapo on 04/13/2015 03:54 pm
Quote
...touchdown expected six seconds later; eight minutes, 30.01 seconds after liftoff. The engines will cut off about 2.3 seconds after landing.
To me, it seems odd that the engines would cut off a full two seconds after touchdown, given that all the Grasshopper tests cut off instantaneously on touchdown, and also given that the thrust level is supposedly greater than the weight of the nearly empty rocket stage.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: oiorionsbelt on 04/13/2015 04:01 pm
Quote
...touchdown expected six seconds later; eight minutes, 30.01 seconds after liftoff. The engines will cut off about 2.3 seconds after landing.
To me, it seems odd that the engines would cut off a full two seconds after touchdown, given that all the Grasshopper tests cut off instantaneously on touchdown, and also given that the thrust level is supposedly greater than the weight of the nearly empty rocket stage.
and it should say engine, not engines.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: TripD on 04/13/2015 04:05 pm
Quote
I don't think that this has ever been mentioned before: Does the landing barge have any on-board cameras? Additionally, are a few other vessels in the area, possibly with radar and cameras to track the spacecraft as it descends?

Didn't the 'Kaboomy goodness' video come from an onboard camera?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 04/13/2015 04:09 pm
TripD, the only visual evidence of the "kaboomy goodness" was a six-second Vine on the ASDS barge.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: fthomassy on 04/13/2015 04:15 pm
Quote
...touchdown expected six seconds later; eight minutes, 30.01 seconds after liftoff. The engines will cut off about 2.3 seconds after landing.
To me, it seems odd that the engines would cut off a full two seconds after touchdown, given that all the Grasshopper tests cut off instantaneously on touchdown, and also given that the thrust level is supposedly greater than the weight of the nearly empty rocket stage.
Not exactly.  Cut off is at zero vertical velocity after the legs touch and pistons compress.  But 2.3 seconds seems, intuitively, a very long time.  One Mississippi, two Mississippi ...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Joffan on 04/13/2015 04:24 pm
Quite possibly the engine cut-off is both time- and event-driven. For example, if 2.3 seconds elapse after legs touch, the engine cuts off, but engine cut-off is also indicated if the legs reach maximum deflection, or zero velocity is unambiguously sensed.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/13/2015 04:25 pm
TripD, the only visual evidence of the "kaboomy goodness" was a six-second Vine on the ASDS barge.

Your point being... what, exactly? We know that there are camera(s) on the barge. Are you trying to suggest that they can only capture Vines?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MP99 on 04/13/2015 04:41 pm
Just a heads up. SpaceX webcast page says that webcast starts at "Mon Apr, 13 2015 9:15 PM GMT".

Anyone reading that, and then deciding to come back at 22:15 British Summer Time will be severely disappointed!

cheers, Martin
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ginahoy on 04/13/2015 05:04 pm
Anyone know if there will there be a live TV feed from the first stage landing platform?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 04/13/2015 05:04 pm
TripD, the only visual evidence of the "kaboomy goodness" was a six-second Vine on the ASDS barge.

Your point being... what, exactly? We know that there are camera(s) on the barge. Are you trying to suggest that they can only capture Vines?

From what I've seen, yes.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Comga on 04/13/2015 05:13 pm
New photo (http://forum.nasaspaceflight.com/index.php?topic=37186.msg1357227#msg1357227) over in the updates thread.

There is a faint pattern of polka dots on the top of the TEL.
Any previous images have this pattern?
Any ideas what is causing this pattern?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/13/2015 05:14 pm
Can anyone see any changes to the TEL structure in this image that could be construed as having been done to  support a pad abort platform?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jdeshetler on 04/13/2015 05:21 pm
New photo (http://forum.nasaspaceflight.com/index.php?topic=37186.msg1357227#msg1357227) over in the updates thread.

There is a faint pattern of polka dots on the top of the TEL.
Any previous images have this pattern?
Any ideas what is causing this pattern?

Plexiglass panels w/ vent holes. Used on previous missions.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/13/2015 05:29 pm
New photo (http://forum.nasaspaceflight.com/index.php?topic=37186.msg1357227#msg1357227) over in the updates thread.

There is a faint pattern of polka dots on the top of the TEL.
Any previous images have this pattern?
Any ideas what is causing this pattern?

Dunno about that, interesting.  I don't think its a random polka dot pattern but rather rows of equally spaced dots on ~45 degree diagonals going from bottom left to upper right.  You can see a few runs of them.  The rest of the rows are just not as visible due to being broken up by the structure.  Perhaps we're looking at small holes in a sheet of transparent plastic??  If so, may the force be with that plastic when the big flamey thing goes by.

What about that "shrink wrap" looking stuff encircling the bottom 3 feet or so of the Dragon capsule?  And what's up with the stainless? steel? ring surrounding the heat shield ring?  What is that?  A disposable clamp ring?  Or a permanent part of Dragon?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/13/2015 05:32 pm
Plexiglass panels w/ vent holes. Used on previous missions.

Wow.  How is it that it doesn't get warm and windy there at some point during the launch?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: oiorionsbelt on 04/13/2015 05:36 pm
   And what's up with the stainless? steel? ring surrounding the heat shield ring?  What is that?  A disposable clamp ring?  Or a permanent part of Dragon?
lower part of heat shield
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/13/2015 05:44 pm
TripD, the only visual evidence of the "kaboomy goodness" was a six-second Vine on the ASDS barge.

Your point being... what, exactly? We know that there are camera(s) on the barge. Are you trying to suggest that they can only capture Vines?

From what I've seen, yes.

Sure...  ::) Can you point out any camera that is limited to Vine only?  ;D (And if so why SpaceX would choose to install one)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MechE31 on 04/13/2015 05:48 pm
What about that "shrink wrap" looking stuff encircling the bottom 3 feet or so of the Dragon capsule?  And what's up with the stainless? steel? ring surrounding the heat shield ring?  What is that?  A disposable clamp ring?  Or a permanent part of Dragon?

The shrink wrap is just thruster covers blending in to the SPAM create an optical illusion
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jcc on 04/13/2015 05:50 pm
New photo (http://forum.nasaspaceflight.com/index.php?topic=37186.msg1357227#msg1357227) over in the updates thread.

There is a faint pattern of polka dots on the top of the TEL.
Any previous images have this pattern?
Any ideas what is causing this pattern?

The "polka dots" look like spot welds to me, like some metal cladding was added on top of the steel maybe?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: padrat on 04/13/2015 06:16 pm
Jdeshetler is right. It's just the same plexiglass that has been there since the first use of the newer T/E. I believe the holes were added after the first one or two launches for pressure relief since a panel or two were blown off. No, it doesn't need to be replaced after each launch.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: oiorionsbelt on 04/13/2015 06:23 pm
Jdeshetler is right. It's just the same plexiglass that has been there since the first use of the newer T/E. I believe the holes were added after the first one or two launches for pressure relief since a panel or two were blown off. No, it doesn't need to be replaced after each launch.
thanks, what is the purpose of the plexiglass?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: padrat on 04/13/2015 06:33 pm
Jdeshetler is right. It's just the same plexiglass that has been there since the first use of the newer T/E. I believe the holes were added after the first one or two launches for pressure relief since a panel or two were blown off. No, it doesn't need to be replaced after each launch.
thanks, what is the purpose of the plexiglass?

Blast protection....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: woods170 on 04/13/2015 07:06 pm
Jdeshetler is right. It's just the same plexiglass that has been there since the first use of the newer T/E. I believe the holes were added after the first one or two launches for pressure relief since a panel or two were blown off. No, it doesn't need to be replaced after each launch.
thanks, what is the purpose of the plexiglass?

Blast protection....
And thus more likely to be polycarbonate (lexan) than polymethyl methacrylate (plexiglass). The former is much more resistant to blast force.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Orbiter on 04/13/2015 07:22 pm
June like weather pattern, June like problems.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DatUser14 on 04/13/2015 07:36 pm
I hope the weather clears!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/13/2015 07:44 pm
I don't think that this has ever been mentioned before: Does the landing barge have any on-board cameras? Additionally, are a few other vessels in the area, possibly with radar and cameras to track the spacecraft as it descends?

Anyone know if there will there be a live TV feed from the first stage landing platform?

From information gleamed from assorted sources (previous statements by Hans at the first attempt pressor, experiences from the previous attempt, etc.), so things may have changed and I could be misremembering:

1. JRtI has cameras on board.
2. JRtI/support ship may have a drone with cameras.
3. SpaceX can get a stream from JRtI, but it's unreliable and not counted on by SpaceX.
4. They don't (didn't) share that stream to the general public live.
5. Video is stored "locally" (not sure if that's on JRtI or the support ship) and given the bandwidth and unreliable nature of the "broadband" connection at sea, it may take hours for SpaceX to download all the video.
6. If successful, SpaceX will release some video in "within a day ... or two."  And given the last attempt, Elon may decide to release it even if it fails.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Beittil on 04/13/2015 07:49 pm
Ugh, that noise on the NASA feed when the commentator isn't speaking :S
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Mapperuo on 04/13/2015 07:50 pm
Ugh, that noise on the NASA feed when the commentator isn't speaking :S

I dont like the Promos either.  ;D
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Beittil on 04/13/2015 07:53 pm
Wonder how much longer it is before SLS is plugged... if they haven't already while i was on bio break :D
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cro-magnon gramps on 04/13/2015 07:55 pm
Ugh, that noise on the NASA feed when the commentator isn't speaking :S

I dont like the Promos either.  ;D

I agree, but unfortunately these are the few times that NASA has such a large captive audience that they don't normally get, and want to make the most of the opportunity to get their "message" out to a less engaged audience than us, who drink space with our coffee  ;D so "grin and bear it" is the way I look at it...

Gramps
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Mapperuo on 04/13/2015 07:57 pm
Ugh, that noise on the NASA feed when the commentator isn't speaking :S

I dont like the Promos either.  ;D

I agree, but unfortunately these are the few times that NASA has such a large captive audience that they don't normally get, and want to make the most of the opportunity to get their "message" out to a less engaged audience than us, who drink space with our coffee  ;D so "grin and bear it" is the way I look at it...

Gramps

Would be nice if they used their media channel as a clean feed sans promos as per they state its for on their website though, but I digress! Lets enjoy the show.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mheney on 04/13/2015 08:10 pm
Which is why I'm waiting for the SpaceX feed ...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/13/2015 08:10 pm
NASA promo-bombing with SLS and Mars during a count for a CRS mission.

This is a good thing.

Consider how far we've come - instead of SpaceX inserting "agenda talk" into the ISS resupply mission, NASA is doing it.

This is such a sea change from the days that any mention of Mars was like mentioning the bad sister around the dinner table.

SLS is what it is, but rockets are interchangeable in people's minds.  Mars missions, and long ones at that, being pushed where they don't belong?   Hell has frozen over.  :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Bargemanos on 04/13/2015 08:17 pm
Which is why I'm waiting for the SpaceX feed ...


Enjoying the sound of that?  ;) ;D
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mheney on 04/13/2015 08:18 pm
Yeah, actually ;-)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cartman on 04/13/2015 08:31 pm
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: The Amazing Catstronaut on 04/13/2015 08:33 pm
That was annoyingly close.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Pete on 04/13/2015 08:37 pm
Scrub, due to.. ummm "attached Anvil rule"?

Why am I seeing images of Wily E Coyote bedeviling the poor rocket?   ;-)


Ah well, weather was always going to be a factor, guess we bit into the 40% today.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MrHollifield on 04/13/2015 08:40 pm
forgive my ignorance, but the weather does not look all that threatening to my untrained eyes. I understand storms and wind are bad, but what's the risk of launching a falcon 9 through a small number of clouds? Is it a tracking issue? is moisture a problem? are they afraid it will anger mighty Zeus?

The issue is electric charge. The vehicle generates a charge as it moves through the atmosphere. If anvil clouds and lightning are too close (10 miles) it could draw a lightning strike in flight that could damage or destroy Falcon and Dragon.
 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kirghizstan on 04/13/2015 08:41 pm
Can someone explain to me why it was scrubbed when there was still time for the weather system to change to a go condition?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JasonAW3 on 04/13/2015 08:41 pm
forgive my ignorance, but the weather does not look all that threatening to my untrained eyes. I understand storms and wind are bad, but what's the risk of launching a falcon 9 through a small number of clouds? Is it a tracking issue? is moisture a problem? are they afraid it will anger mighty Zeus?

A rocket trail tends to act like a conduit to the ground during launch.  Although there are lightning towers around the pad, (The four big towers that you can see near the rocket) there is still a chance of catastrophic lightening discharge.  Plus, with the anvil clouds, there is a risk of high winds that could cause the roicket to veer off course.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 04/13/2015 08:45 pm
Scrub, due to.. ummm "attached Anvil rule"?

Why am I seeing images of Wily E Coyote bedeviling the poor rocket?   ;-)
Ah well, weather was always going to be a factor, guess we bit into the 40% today.

Anvil clouds are where the top of the cloud spreads out due to stronger winds and higher stability aloft.  Attached pic of what it looks like from the station.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: D_Dom on 04/13/2015 08:47 pm
3 minutes +/-  is not much time for such weather to dissipate. When you see the term "anvil cloud" it is shorthand for "fully developed thunderstorm".
http://www.weatherquestions.com/What_is_an_anvil_cloud.htm
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ginahoy on 04/13/2015 08:47 pm
From information gleamed from assorted sources (previous statements by Hans at the first attempt pressor, experiences from the previous attempt, etc.), so things may have changed and I could be misremembering:

1. JRtI has cameras on board.
2. JRtI/support ship may have a drone with cameras.
3. SpaceX can get a stream from JRtI, but it's unreliable and not counted on by SpaceX.
4. They don't (didn't) share that stream to the general public live.
5. Video is stored "locally" (not sure if that's on JRtI or the support ship) and given the bandwidth and unreliable nature of the "broadband" connection at sea, it may take hours for SpaceX to download all the video.
6. If successful, SpaceX will release some video in "within a day ... or two."  And given the last attempt, Elon may decide to release it even if it fails.

Thanks for that!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: yokem55 on 04/13/2015 08:48 pm
Can someone explain to me why it was scrubbed when there was still time for the weather system to change to a go condition?
The vector of the storm cloud is probably the best explanation. It was heading in the general direction of the pad. They were hoping they would be able to launch before it got too close, but weren't quite able to.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: northenarc on 04/13/2015 08:49 pm
 How strict are the rules for electrical potential at CCAFS compared to other launch sites? I seem to remember hearing their weather criteria is particularly strict. 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: D_Dom on 04/13/2015 08:50 pm
NASA promo-bombing with SLS and Mars during a count for a CRS mission.

This is a good thing.

  Hell has frozen over.  :)

Glaciers and avalanches on Mars "Oh MY!"
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/13/2015 08:50 pm
Can someone explain to me why it was scrubbed when there was still time for the weather system to change to a go condition?
Because the rule is that if an active lightning system enters the 10 mile radius then the launch must wait until 30 minutes after the system leaves the 10 mile radius.  So it was impossible to launch in 5 minutes no matter what.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kim Keller on 04/13/2015 08:58 pm
Can someone explain to me why it was scrubbed when there was still time for the weather system to change to a go condition?
The vector of the storm cloud is probably the best explanation. It was heading in the general direction of the pad. They were hoping they would be able to launch before it got too close, but weren't quite able to.

No, the storm was/is NW of the pad quite a distance, and moving NE. The problem was the anvil cloud that had extended east over the launch area and the chance for lightning.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MarekCyzio on 04/13/2015 08:59 pm
I think that was the culprit.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 04/13/2015 10:09 pm
A list of all the members that currently have an invalid vote in ASDS Bingo (https://forum.nasaspaceflight.com/index.php?topic=36559.0): 
    andrewsdanj
    BroncoBill
    Callezetter
    Clf
    colbourne
    Dave G
    dccraven
    Eagandale4114
    Elvis in Space
    Frandolf
    intrepidpursuit
    JBF
    jongoff
    Khkyle
    kraxxis
    kruegersc4
    Lampyridae
    lele
    macpacheco
    malu5531
    matthewkantar
    MattMason
    Maxi962
    Mayberry Chief
    Mercurius
    mr. mark
    MuppetZoo
    Overcast
    PaddyPatrone
    Perchlorate
    philw1776
    qbytex
    Ragulin
    Razer
    rubtest
    Rummy
    Skybert
    SpaceXfan
    Syntax
    t.a.george
    timi900
    tp1024
    vanoord
    Vrommand
    watermod
    Xspace_engineerX


If your name is above, and you'd like to have a valid vote in the game, do the following before launch time tomorrow:

1.  Go to http://asds.dansdoorway.com/
2.  Find an open square on the updated map
3.  Go to the Bingo Thread and check that no one has picked that square in the last 24 hrs.  (Dan's map updater isn't a live accounting.  It scrapes the data from the thread only so often, so you need to do this to make sure that you haven't chosen a taken square that has yet to be updated on the map)
4.  Post on the Bingo Thread with your square choice that you've confirmed is open
5.  DON'T EDIT THAT POST.  Not for any reason.  Any editing at all, no matter the reason, will invalidate your pick.


If you wish to see why your previous choice was invalid, go to http://asds.dansdoorway.com/ and enter your username in the search function.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Joffan on 04/13/2015 10:11 pm
It makes me wonder if the margins for some of these calls are still appropriate. The rules may have been set for a certain ability of issue detection, either in speed/frequency of detection or limits of what clouds types are visible.

For example, if the anvil rule was set with the idea that reports would only come in every ten minutes, the radius would have been set bigger (to allow for movement) than if - as now - the reports come in basically continuously. If only clouds 500m thick could then be detected, but now it's more like 5m, again the boundaries have shifted against launch.

The problem in those hypothetical cases is that improvements in instrumentation don't automatically mean that the launch criteria are updated properly after the upgrade to maintain the appropriate balance between safety and achievement.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/13/2015 10:56 pm
Musk 4:13

"Launch window always tight when orbital synch needed. In this case, Space Station. For Earth-Sun gravity null point, moon was in the way."

I'm not following.  What does he mean about the moon being in the way and the Earth-Sun null point?  Seems to me like the moon is way over there.  First sentence seems right on.  Second sentence seems as if it came from twelve days ago.  ???
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Paul_G on 04/13/2015 11:29 pm
....

I'm not following.  What does he mean about the moon being in the way and the Earth-Sun null point?  Seems to me like the moon is way over there.  First sentence seems right on.  Second sentence seems as if it came from twelve days ago.  ???

I seem to remember the reason for one of the DSCOVR delays was due to the moon being in the way for a period of time between a launch attempt and the final successful launch to get to the Lagrange point.

Paul
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fletch on 04/13/2015 11:53 pm
Florida needs some weather that looks like this.  (This is from my old man, teasing about where he is holidaying at the moment)

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/14/2015 12:13 am
....

I'm not following.  What does he mean about the moon being in the way and the Earth-Sun null point?  Seems to me like the moon is way over there.  First sentence seems right on.  Second sentence seems as if it came from twelve days ago.  ???

I seem to remember the reason for one of the DSCOVR delays was due to the moon being in the way for a period of time between a launch attempt and the final successful launch to get to the Lagrange point.

Paul

Oh, I get it, the key word in his tweet is "was", refering to that past mission where the moon did matter.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Antares on 04/14/2015 04:54 am
https://www.faa.gov/about/office_org/headquarters_offices/ast/14_cfr_part_417/media/Lightning%20-%20Final%20Published%20Rule.pdf

Page 6 first full paragraph, so it's an FAA Rule and a Range requirement.

Section G417.9(e) will now require waiting 30 minutes unless the portion of the attached anvil cloud at a slant distance of less than or equal to 10 nautical miles from the flight path is located entirely at altitudes where the temperature is colder than 0 degrees Celsius.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LouScheffer on 04/14/2015 11:29 am
https://www.faa.gov/about/office_org/headquarters_offices/ast/14_cfr_part_417/media/Lightning%20-%20Final%20Published%20Rule.pdf

Page 6 first full paragraph, so it's an FAA Rule and a Range requirement.

Section G417.9(e) will now require waiting 30 minutes unless the portion of the attached anvil cloud at a slant distance of less than or equal to 10 nautical miles from the flight path is located entirely at altitudes where the temperature is colder than 0 degrees Celsius.

I looked at this document and at first thought the FAA must have a sense of humor.  They define the "cone of silence" as the region directly above the radar that it cannot see, due to elevation limits.   "Silence" seems an odd term in this context, and the only other time I'd heard this phrase was from the 1960s TV comedy "Get Smart", where it was a technical failure (It was a cone that lowered over two people to prevent eavesdropping.  But it worked too well and they had to shout, and still could not hear each other.)

But I looked it up, and it's an old term from radio navigation from the 1940s.  It's the region directly above a non-directional transmitter where the field is weak and you cannot hear the station.  In this context it makes perfect sense.   Most likely the TV show, and surely the FAA, borrowed it from this usage.

You learn something every day...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: swervin on 04/14/2015 12:20 pm
Musk 4:13

For a moment, I thought this was a mock Bible quote... 'From the Book of Elon' haha
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: NX-0 on 04/14/2015 12:56 pm
Musk 4:13

"Launch window always tight when orbital synch needed. In this case, Space Station. For Earth-Sun gravity null point, moon was in the way."

I'm not following.  What does he mean about the moon being in the way and the Earth-Sun null point?  Seems to me like the moon is way over there.  First sentence seems right on.  Second sentence seems as if it came from twelve days ago.  ???

Maybe this will help...

Quote
When the moon is in the seventh house
And Jupiter aligns with Mars
Then peace will guide the planets
And love will steer the stars

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Decius_Caecilius_Metellus on 04/14/2015 01:02 pm
How is the weather going to be this afternoon? Is it probably that they can launch this time? I'm really loking forward to this launch :D
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lar on 04/14/2015 01:05 pm
How is the weather going to be this afternoon? Is it probably that they can launch this time? I'm really loking forward to this launch :D

Worse... I heard 50/50 rather than 70/30 but .. could change.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MattMason on 04/14/2015 01:11 pm
forgive my ignorance, but the weather does not look all that threatening to my untrained eyes. I understand storms and wind are bad, but what's the risk of launching a falcon 9 through a small number of clouds? Is it a tracking issue? is moisture a problem? are they afraid it will anger mighty Zeus?

A rocket trail tends to act like a conduit to the ground during launch.  Although there are lightning towers around the pad, (The four big towers that you can see near the rocket) there is still a chance of catastrophic lightening discharge.  Plus, with the anvil clouds, there is a risk of high winds that could cause the roicket to veer off course.

Excellent. From what I understand, the conduit part was exactly what happened to Apollo 12, which lifted off in a rainstorm. It created and became its own lightning rod, being struck twice. Thankfully, while their CSM platform got zapped, the Saturn V's instrument unit computers kept the LV working while Conrad and Co. waited for the sage direction of controller John Aaron to instruct "SCE to Aux" to reset their telemetry to a backup mode.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: gwiz on 04/14/2015 01:18 pm
There was a less happy outcome for the Atlas-Centaur that got hit by lightning in March 1987.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JasonAW3 on 04/14/2015 01:25 pm
Anybody know what the weather's looking like today?  Last I heard it was a 50/50 chance of launch today.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 04/14/2015 01:31 pm
Anybody know what the weather's looking like today?  Last I heard it was a 50/50 chance of launch today.

Correct. It's a 50/50 chance of GO/NO GO for weather.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JasonAW3 on 04/14/2015 01:34 pm
Musk 4:13

"Launch window always tight when orbital synch needed. In this case, Space Station. For Earth-Sun gravity null point, moon was in the way."

I'm not following.  What does he mean about the moon being in the way and the Earth-Sun null point?  Seems to me like the moon is way over there.  First sentence seems right on.  Second sentence seems as if it came from twelve days ago.  ???

Maybe this will help...

Quote
When the moon is in the seventh house
And Jupiter aligns with Mars
Then peace will guide the planets
And love will steer the stars

So it'll launch in the Age of Aquarious?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JasonAW3 on 04/14/2015 01:34 pm
There was a less happy outcome for the Atlas-Centaur that got hit by lightning in March 1987.

Bada-Boom?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ugordan on 04/14/2015 01:38 pm
Anybody know what the weather's looking like today?  Last I heard it was a 50/50 chance of launch today.

Correct. It's a 50/50 chance of GO/NO GO for weather.

45th Wing forecast issued today has it at 60% GO today and 40% GO on Thursday.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JasonAW3 on 04/14/2015 01:39 pm
A list of all the members that currently have an invalid vote in ASDS Bingo (https://forum.nasaspaceflight.com/index.php?topic=36559.0): 
    andrewsdanj
    BroncoBill
    Callezetter
    Clf
    colbourne
    Dave G
    dccraven
    Eagandale4114
    Elvis in Space
    Frandolf
    intrepidpursuit
    JBF
    jongoff
    Khkyle
    kraxxis
    kruegersc4
    Lampyridae
    lele
    macpacheco
    malu5531
    matthewkantar
    MattMason
    Maxi962
    Mayberry Chief
    Mercurius
    mr. mark
    MuppetZoo
    Overcast
    PaddyPatrone
    Perchlorate
    philw1776
    qbytex
    Ragulin
    Razer
    rubtest
    Rummy
    Skybert
    SpaceXfan
    Syntax
    t.a.george
    timi900
    tp1024
    vanoord
    Vrommand
    watermod
    Xspace_engineerX


If your name is above, and you'd like to have a valid vote in the game, do the following before launch time tomorrow:

1.  Go to http://asds.dansdoorway.com/
2.  Find an open square on the updated map
3.  Go to the Bingo Thread and check that no one has picked that square in the last 24 hrs.  (Dan's map updater isn't a live accounting.  It scrapes the data from the thread only so often, so you need to do this to make sure that you haven't chosen a taken square that has yet to be updated on the map)
4.  Post on the Bingo Thread with your square choice that you've confirmed is open
5.  DON'T EDIT THAT POST.  Not for any reason.  Any editing at all, no matter the reason, will invalidate your pick.


If you wish to see why your previous choice was invalid, go to http://asds.dansdoorway.com/ and enter your username in the search function.

How do I find my point?  I logged with the first attempt, but it's been so long I forgot which point I chose!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JasonAW3 on 04/14/2015 01:39 pm
Anybody know what the weather's looking like today?  Last I heard it was a 50/50 chance of launch today.

Correct. It's a 50/50 chance of GO/NO GO for weather.

45th Wing forecast issued today has it at 60% GO today and 40% GO on Thursday.

Looking better all the Time!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 04/14/2015 01:42 pm
Let's hope so; although I'm not optimistic about whether the weather will cooperate or not. :-\
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kirghizstan on 04/14/2015 01:43 pm
How do I find my point?  I logged with the first attempt, but it's been so long I forgot which point I chose!

Quote
If you wish to see why your previous choice was invalid, go to http://asds.dansdoorway.com/ (http://asds.dansdoorway.com/) and enter your username in the search function.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/14/2015 01:56 pm
Thursday as the next attempt is I think new news.  What time(s) would work Thursday?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 03:45 pm
Thursday as the next attempt is I think new news.  What time(s) would work Thursday?

23 minutes earlier per day
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 04:00 pm
I'm trying to understand why they can't launch on Wednesday - supposedly due to ISS phasing issues. But why can't Dragon launch on Wednesday and just stay in orbit one extra day before docking with ISS?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kansan52 on 04/14/2015 04:18 pm
I'm trying to understand why they can't launch on Wednesday - supposedly due to ISS phasing issues. But why can't Dragon launch on Wednesday and just stay in orbit one extra day before docking with ISS?

My understanding for the stand down is work rules based on exhausted people make mistakes.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Mike_1179 on 04/14/2015 04:30 pm
Not just SpaceX people, but range support personnel as well
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 04:32 pm
I'm trying to understand why they can't launch on Wednesday - supposedly due to ISS phasing issues. But why can't Dragon launch on Wednesday and just stay in orbit one extra day before docking with ISS?

My understanding for the stand down is work rules based on exhausted people make mistakes.

Not according to this information from the update/launch thread #2 thread:

https://twitter.com/flatoday_jdean/status/587994969148956673 (https://twitter.com/flatoday_jdean/status/587994969148956673)

Quote
James Dean ‏@flatoday_jdean 22m

If SpaceX does not launch today, mission would stand down Wed. due to ISS phasing. Launch weather looks worse Thurs./Fri.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Antares on 04/14/2015 05:20 pm
Probably time between having hands on between loading on the ground and unloading on orbit for time-sensitive payloads.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/14/2015 05:26 pm
There are mice on this flight, I believe.  I think the standard is 2 days on, and then on the third day they have to take the rocket down and feed the mice.  (More or less.)

There was a less happy outcome for the Atlas-Centaur that got hit by lightning in March 1987.

I found http://www.thespacereview.com/article/1662/1 to be interesting reading regarding AC-67's lightning strike, and the way that weather criteria are written in general.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rower2000 on 04/14/2015 05:35 pm
How do I find my point?  I logged with the first attempt, but it's been so long I forgot which point I chose!
http://bit.ly/1yrrlje
First result, then scroll down until you find your user name.

 ;D.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: toruonu on 04/14/2015 05:55 pm
Well at least one SpaceX employee is feeling confident :) A reply under a Vulcan discussion on Facebook:

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: laika_fr on 04/14/2015 06:37 pm
Weather is stunning.

We earthlings, i mean from the alliance, are numerous to follow you.

If you go to a another dimension, i hope you tell us what you've seen, Good luck SpaceX


Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/14/2015 07:51 pm
Power boat and helicopter just passed through the NASA TV camera, just offshore behind the rocket. Hopefully no issues with unauthorized boats in the range area...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DrLucky on 04/14/2015 07:52 pm
Just thought I saw a boat travelling right to left in the long shot of the pad (the one with the HIF to the right).  Are there typically patrols prior to the range being go?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/14/2015 07:54 pm
Now two power boats heading south...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kdhilliard on 04/14/2015 07:57 pm
The front page story SpaceX Falcon 9 and CRS-6 Dragon set for second attempt (http://www.nasaspaceflight.com/2015/04/spacex-falcon-9-crs-6-dragon-stage-return/) still links to yesterday's launch attempt update thread from its See Also box, and that thread does not have a link to today's update thread.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mrhuggy on 04/14/2015 08:03 pm
Just noticed theres Gulfstream flying a race pattern over the altlantic. Hopefully for video and telemetry.

http://fr24.com/GLF4/600af92 (http://fr24.com/GLF4/600af92)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: foltster on 04/14/2015 08:07 pm
Can anyone pick out Elon in a still image of the SpaceX control room?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kaputnik on 04/14/2015 08:16 pm
Was that the first time the NASA TV live feed tracked the first stage, rather than the second, post sep?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/14/2015 08:16 pm
Just remember people, this is all about ISS supply, not about recovery.


Who am I kidding.  :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jimbowman on 04/14/2015 08:18 pm
Can anyone pick out Elon in a still image of the SpaceX control room?

First post on this page. First row, middle.

http://forum.nasaspaceflight.com/index.php?topic=37294.60
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DrLucky on 04/14/2015 08:21 pm
Body language of the three controllers in Hawthorne didn't look happy.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: foltster on 04/14/2015 08:22 pm
Body language of the three controllers in Hawthorne didn't look happy.


Agreed hands on heads...no celebration in the crowd if you will...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/14/2015 08:24 pm
Yup, hands on heads at MCC...looks like no cigar on landing...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DatUser14 on 04/14/2015 08:31 pm
Quote
Ascent successful. Dragon enroute to Space Station. Rocket landed on droneship, but too hard for survival.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rebel44 on 04/14/2015 08:31 pm
Elon Musk ‏@elonmusk  · 54 seconds ago 
Ascent successful. Dragon enroute to Space Station. Rocket landed on droneship, but too hard for survival.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: alang on 04/14/2015 08:32 pm
The more detached attitude is that its only a failure if you don't learn something...and its a lot easier to be detached as a spectator.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: dorkmo on 04/14/2015 08:33 pm
Body language of the three controllers in Hawthorne didn't look happy.


Agreed hands on heads...no celebration in the crowd if you will...

felt like i was watching a repeat of the control room video from last time lol

might be fun to see them side by side
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MattMason on 04/14/2015 08:40 pm
My hope, based on a hunch, is that they may need a redundant, perhaps optical radar lock, as oceans tend to move up and down. A shutdown of +/- 10 feet is not the greatest engine-off condition.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/14/2015 08:42 pm
My hope, based on a hunch, is that they may need a redundant, perhaps optical radar lock, as oceans tend to move up and down. A shutdown of +/- 10 feet is not the greatest engine-off condition.

They were using landing radar on the F9R Dev test vehicle at McGregor and presumably are doing so on the flight vehicles.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Joffan on 04/14/2015 08:42 pm
My hope, based on a hunch, is that they may need a redundant, perhaps optical radar lock, as oceans tend to move up and down. A shutdown of +/- 10 feet is not the greatest engine-off condition.

Or, for preference, coming back to a known stable landing zone...on land.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Tonioroffo on 04/14/2015 08:43 pm
So twice now the precision is good enough to hit the barge (or where it was supposed to be) - dry land doesn't have the z-axis movement to worry about.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: aceshigh on 04/14/2015 08:43 pm
Just remember people, this is all about ISS supply, not about recovery.


Who am I kidding.  :)

I guess there would be more people cheering here if the Dragon had "punched" the ISS and the 1st stage had docked perfectly with the barge. :)


Anyway, makes me wonder if pilots taking remote control of the First Stage (from some 5 km horizontal distance to the barge) wouldn´t help at all.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kaputnik on 04/14/2015 08:46 pm
Just remember people, this is all about ISS supply, not about recovery.


Who am I kidding.  :)

I guess there would be more people cheering here if the Dragon had "punched" the ISS and the 1st stage had docked perfectly with the barge. :)

I think you are on your own with that one.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: VulcanCafe on 04/14/2015 08:46 pm
I was writing something related to first stage landing technical hurdles that SpaceX has already retired, but clearly something is missing.

What technical hurdles are left to solve?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/14/2015 08:49 pm
I was writing something related to first stage landing technical hurdles that SpaceX has already retired, but clearly something is missing.

What technical hurdles are left to solve?

Intact landing on ASDS.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Elmar Moelzer on 04/14/2015 08:50 pm
I think the problem could have been that the drone ship suddenly moved up in some way...

Drone Ship ‏@TheDroneShip 22m22 minutes ago
Sorry guys... I sneezed.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Earendil on 04/14/2015 08:50 pm
I always assumed hitting the tiny drone (compared to the ocean) from space will be the hard part..
It appears vertical velocity is way harder.. especially when they cannot hover..

'There are mere seconds for reaction and no one can know if the drone will be +10 or _10 feet in the next couple of seconds.. Maybe the engine cannot react so quickly.. is this a dead end? (for ship landing at least)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: aceshigh on 04/14/2015 08:51 pm
Just remember people, this is all about ISS supply, not about recovery.


Who am I kidding.  :)

I guess there would be more people cheering here if the Dragon had "punched" the ISS and the 1st stage had docked perfectly with the barge. :)

I think you are on your own with that one.

it was just a clear exaggeration to show how much people wanted to see a successful first stage perfect landing. 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/14/2015 08:54 pm
I think the problem could have been that the drone ship suddenly moved up in some way...

Drone Ship ‏@TheDroneShip 22m22 minutes ago
Sorry guys... I sneezed.

Unlikely,  since wave height was around 3 feet, which is practically zero for a barge that size.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: VulcanCafe on 04/14/2015 08:54 pm
Elon twitter
Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: aceshigh on 04/14/2015 08:55 pm
I was writing something related to first stage landing technical hurdles that SpaceX has already retired, but clearly something is missing.

What technical hurdles are left to solve?

They've done soft touchdowns in water. Soft touchdowns on the barge are the final missing piece. They used landing radar in tests of the F9R Dev vehicle at McGregor, and presumably are using landing radar on the flight vehicles. The landing radar may be having difficulty discriminating between sea level height and barge deck height. (Speculation)


I wonder if optical feedback wouldn´t work better than radar then? Maybe guiding lasers on the barge? Or just cameras on the rocket calculating the geometry of the SpaceX logo (and other visual clues) to give an accurate mesurement of distance and angle...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: aceshigh on 04/14/2015 08:57 pm
Elon twitter
Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing


that was my first impression from the reaction of people on the control room... celebration (it landed) followed by hands on their heads (it tipped over).

but it seems the wording used on twitters later, like saying the 1st Stage had "punched" the barge, made it seem like it had "impacted" the barge at considerable speed.


thinking it now, it wouldn´t make sense for people at the control room to even celebrate for half a second if the rocket had crashed hard on the barge... it´s not like they would celebrate before touch down nor seeing an impact at 100, 200 km/h.


the twitter wording threw us off.


I wonder if this horizontal speed problem is a bigger problem than vertical speed problem.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: litton4 on 04/14/2015 09:00 pm
A couple of pictures up there already:

https://twitter.com/elonmusk/status/588082574183903232
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 09:00 pm
A couple of pictures up there already:

https://twitter.com/elonmusk/status/588082574183903232
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rocket Science on 04/14/2015 09:02 pm
Who knows, maybe my "snare" idea might have saved it... :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: abaddon on 04/14/2015 09:03 pm
So does this mean the grid fins aren't effective enough?  The only reason I can think of for it to have too much lateral velocity is if it was thrusting laterally to get to the barge and didn't have enough height to do it and then null that velocity.  Which sounds a lot like the previous attempt...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 09:04 pm
So does this mean the grid fins aren't effective enough?  The only reason I can think of for it to have too much lateral velocity is if it was thrusting laterally to get to the barge and didn't have enough height to do it and then null that velocity.  Which sounds a lot like the previous attempt...

They have the video, so they should be able to tell if the stage was drifting horizontally during landing, or if something else (wave motion or wind) caused it to tip.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rocket Science on 04/14/2015 09:05 pm
So does this mean the grid fins aren't effective enough?  The only reason I can think of for it to have too much lateral velocity is if it was thrusting laterally to get to the barge and didn't have enough height to do it and then null that velocity.  Which sounds a lot like the previous attempt...
They wouldn’t provide much control authority at low speed...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: aceshigh on 04/14/2015 09:05 pm
@ElonMusk

"All we have right now is low frame rate video (basically pictures). Normal video will be posted when ship returns to port in a few days."
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 09:07 pm
@ElonMusk

"All we have right now is low frame rate video (basically pictures). Normal video will be posted when ship returns to port in a few days."

So this tells use that the barge does not have the bandwidth to broadcast full live video at the moment. (something they will probably fix in the future)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mrhuggy on 04/14/2015 09:08 pm
I was writing something related to first stage landing technical hurdles that SpaceX has already retired, but clearly something is missing.

What technical hurdles are left to solve?

They've done soft touchdowns in water. Soft touchdowns on the barge are the final missing piece. They used landing radar in tests of the F9R Dev vehicle at McGregor, and presumably are using landing radar on the flight vehicles. The landing radar may be having difficulty discriminating between sea level height and barge deck height. (Speculation)


I wonder if optical feedback wouldn´t work better than radar then? Maybe guiding lasers on the barge? Or just cameras on the rocket calculating the geometry of the SpaceX logo (and other visual clues) to give an accurate mesurement of distance and angle...

Actually an issue with the radar would make sense. The landing pad (if i remember rightly) is not a solid surface but rather a grating. The radar rather than get a strong signal from it would get a weaker signal. A Ladar might have the same issue.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: abaddon on 04/14/2015 09:09 pm
They wouldn’t provide much control authority at low speed...

Right, but as long as the first stage is close to the barge in the X and Y, the engine has control authority to spare.  It's only if the rocket is somewhat far away that the engine wouldn't have time to get the rocket over and null horizontal velocity from getting there before running out of Z.

Of course, this is complete speculation.  Hopefully we get more information soon!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kaputnik on 04/14/2015 09:09 pm
I was writing something related to first stage landing technical hurdles that SpaceX has already retired, but clearly something is missing.

What technical hurdles are left to solve?

They've done soft touchdowns in water. Soft touchdowns on the barge are the final missing piece. They used landing radar in tests of the F9R Dev vehicle at McGregor, and presumably are using landing radar on the flight vehicles. The landing radar may be having difficulty discriminating between sea level height and barge deck height. (Speculation)


I wonder if optical feedback wouldn´t work better than radar then? Maybe guiding lasers on the barge? Or just cameras on the rocket calculating the geometry of the SpaceX logo (and other visual clues) to give an accurate mesurement of distance and angle...

Actually an issue with the radar would make sense. The landing pad (if i remember rightly) is not a solid surface but rather a grating. The radar rather than get a strong signal from it would get a weaker signal. A Ladar might have the same issue.

No, the grid idea was merely speculation whilst we waited for better information. The deck is now known to be just steel plate.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Sohl on 04/14/2015 09:09 pm

Actually an issue with the radar would make sense. The landing pad (if i remember rightly) is not a solid surface but rather a grating. The radar rather than get a strong signal from it would get a weaker signal. A Ladar might have the same issue.

Don't think it is a grating, and if the radar has the right wavelength, they should get plenty of signal anyway.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 09:09 pm
Cool things in the launch broadcast:

 - The nose cone was very visible dropping past the upper stage rocket cam
 - A nice new graphic showing the planned stage 1 and stage 2 trajectories (see image)
 - Wonderful to see the solar arrays deploy from the upper stage (and the RCS thrusters are now keeping it very stable, no tumbling)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: John Alan on 04/14/2015 09:12 pm
It look like it landed on the edge of the deck then fell overboard...  :-\
Three paws on and one off... momentum then rolled it off... pivoting on the engines...
That's my guess looking at the above two pics posted...

Better video should clear this up...  8)

Oh... and I lost in the bingo pool... I think... :P
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: SwissCheese on 04/14/2015 09:12 pm
I wonder if optical feedback wouldn´t work better than radar then? Maybe guiding lasers on the barge? Or just cameras on the rocket calculating the geometry of the SpaceX logo (and other visual clues) to give an accurate mesurement of distance and angle...

The problem with optical or laser systems is that they do not work in the final seconds when you have a lot of smoke/vapor/dust. That's also a problem for example for helicopters landing in the desert or on snow, and I know that they were testing landing radars for German army helicopters for example.

Radars are fine ! (I work on synthetic aperture radar data so maybe I am not totally neutral... :P )

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CraigLieb on 04/14/2015 09:13 pm
Seems like the leg closest to the camera would have hit the deck first at that angle, but may be fish-eye distortion.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: aceshigh on 04/14/2015 09:13 pm
I was writing something related to first stage landing technical hurdles that SpaceX has already retired, but clearly something is missing.

What technical hurdles are left to solve?

They've done soft touchdowns in water. Soft touchdowns on the barge are the final missing piece. They used landing radar in tests of the F9R Dev vehicle at McGregor, and presumably are using landing radar on the flight vehicles. The landing radar may be having difficulty discriminating between sea level height and barge deck height. (Speculation)


I wonder if optical feedback wouldn´t work better than radar then? Maybe guiding lasers on the barge? Or just cameras on the rocket calculating the geometry of the SpaceX logo (and other visual clues) to give an accurate mesurement of distance and angle...

Actually an issue with the radar would make sense. The landing pad (if i remember rightly) is not a solid surface but rather a grating. The radar rather than get a strong signal from it would get a weaker signal. A Ladar might have the same issue.

seems to be you are considering lasers FROM the rocket TO the barge, in which case the grating surface might be a problem.

I was talking about lasers ON THE barge, locking on the rocket as it approached. Am I making sense?

I wonder if optical feedback wouldn´t work better than radar then? Maybe guiding lasers on the barge? Or just cameras on the rocket calculating the geometry of the SpaceX logo (and other visual clues) to give an accurate mesurement of distance and angle...

The problem with optical or laser systems is that they do not work in the final seconds when you have a lot of smoke/vapor/dust. That's also a problem for example for helicopters landing in the desert or on snow, and I know that they were testing landing radars for German army helicopters for example.

Radars are fine ! (I work on synthetic aperture radar data so maybe I am not totally neutral... :P )

what if the lasers locked on the top of the rocket? Lasers mounted on the 4 corners of the barge... the farthest away possible from the bullseyes and thus less blocked by smoke, locking on the top part of the rocket?

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: oiorionsbelt on 04/14/2015 09:14 pm
I wonder if any of it is still on the barge or did the whole thing " tip over post landing" and into the ocean.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/14/2015 09:16 pm
So does this mean the grid fins aren't effective enough?  The only reason I can think of for it to have too much lateral velocity is if it was thrusting laterally to get to the barge and didn't have enough height to do it and then null that velocity.  Which sounds a lot like the previous attempt...


It means the terminal approach required too large of a final correction.

There can be several reasons why that happened.  Lack of authority to perform the correct maneuver.  Wrong maneuver due to bad positioning data.  Last-minute external influence.  etc.

Hopefully Musk will clue us in.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LouScheffer on 04/14/2015 09:18 pm
So does this mean the grid fins aren't effective enough?  The only reason I can think of for it to have too much lateral velocity is if it was thrusting laterally to get to the barge and didn't have enough height to do it and then null that velocity.  Which sounds a lot like the previous attempt...
This seems odd to me as well.  The job of the grid fins should be to deliver the rocket to just above the ship, with small enough residuals in velocity and displacement such that these can both be nulled by engine vectoring during the deceleration burn.  It looks like they were close enough to null the displacement, but not also the velocity.  I can't imagine this is an algorithm failure (surely they simulated nulling out both horizontal displacement and velocity) so I agree the fins were not as effective as they thought.

Maybe they are not big enough, hence not enough control authority, perhaps since engine-first aerodynamics in the lower atmosphere are yuckier than expected?  Maybe they ran out of fluid again - extra margins not enough? Maybe one or more fins failed to deploy?  It will be interesting to find out....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: RonM on 04/14/2015 09:19 pm
Seems like the leg closest to the camera would have hit the deck first at that angle, but may be fish-eye distortion.

It looks to me like it slid off the edge of the barge. Got to keep all three legs on the barge or over it goes.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 09:20 pm
Seems like the leg closest to the camera would have hit the deck first at that angle, but may be fish-eye distortion.

Yeah... There are no straight lines in this extreme wide angle view. You can't determine that. We don't even know for sure that the two frames are from the same camera. (they likely have a camera in every corner)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/14/2015 09:21 pm
Maybe they need some sub-sonic control surfaces to supplement the hypersonic grid-fins?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 09:23 pm
Maybe they need some sub-sonic control surfaces to supplement the hypersonic grid-fins?

Grid fins work well both at hypersonic and subsonic speeds. That's why they are used. But there is a limit to how much they can do, given their size. And if the stage had a significant sideways motion, the fins can't stop that by themselves. It has to be done together by the landing burn *and* fins.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jcc on 04/14/2015 09:25 pm
Check out @SpaceX's Tweet: https://twitter.com/SpaceX/status/588082616890449920?s=09

Exhaust plume impinging on the white circle but stage seems to lean toward the center of the target, like it is trying to maneuver to the X, but too late. Wonder the direction it was coming from, if it overshot.
Also wpndering if we will be able to call a bingo winner.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 09:27 pm
Check out @SpaceX's Tweet: https://twitter.com/SpaceX/status/588082616890449920?s=09

Exhaust plume impinging on the white circle but stage seems to lean toward the center of the target, like it is trying to maneuver to the X, but too late. Wonder the direction it was coming from, if it overshot.
Also wpndering if we will be able to call a bingo winner.

If the two released frames are from the same camera (likely), then it was coming in from the left... drifting to the right, then tipping over.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Mapperuo on 04/14/2015 09:27 pm
Check out @SpaceX's Tweet: https://twitter.com/SpaceX/status/588082616890449920?s=09

Exhaust plume impinging on the white circle but stage seems to lean toward the center of the target, like it is trying to maneuver to the X, but too late. Wonder the direction it was coming from, if it overshot.
Also wpndering if we will be able to call a bingo winner.

Remember its a fisheye camera, it may look to be leaning but its possibly dead vertical.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AJA on 04/14/2015 09:27 pm
Seems like the leg closest to the camera would have hit the deck first at that angle, but may be fish-eye distortion.

Yeah... There are no straight lines in this extreme wide angle view. You can't determine that. We don't even know for sure that the two frames are from the same camera. (they likely have a camera in every corner)

This. I don't imagine the cameras are mobile. So if it was the same camera, we should be seeing the barge surface, and the flagpole on the right as well. I think they're both views of the same instant, but from different cameras. The direction of the sun (illumination source) reaffirms that guess too.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/14/2015 09:29 pm
Check out @SpaceX's Tweet: https://twitter.com/SpaceX/status/588082616890449920?s=09

Exhaust plume impinging on the white circle but stage seems to lean toward the center of the target, like it is trying to maneuver to the X, but too late. Wonder the direction it was coming from, if it overshot.
Also wpndering if we will be able to call a bingo winner.
I think there is way too much distortion in that image to determine the angle of the rocket.  But the next photo has it on the right, so it's moving left to right in the photo.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: drjrkuhn on 04/14/2015 09:29 pm
A couple of pictures up there already:

https://twitter.com/elonmusk/status/588082574183903232

The deck camera is stationary based on the position of the valve in the bottom-right. The lateral motion of the Falcon is quite apparent if you flip back and forth between the two images on twitter.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 09:29 pm
Seems like the leg closest to the camera would have hit the deck first at that angle, but may be fish-eye distortion.

Yeah... There are no straight lines in this extreme wide angle view. You can't determine that. We don't even know for sure that the two frames are from the same camera. (they likely have a camera in every corner)

This. I don't imagine the cameras are mobile. So if it was the same camera, we should be seeing the barge surface, and the flagpole on the right as well. I think they're both views of the same instant, but from different cameras. The direction of the sun (illumination source) reaffirms that guess too.

They cannot be from the same instant, judging by the size and placement, and smoke. Looking at details around the edge of the frame, they are likely from the same camera.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rocket Science on 04/14/2015 09:30 pm
They still got it to "grasshopper-mode" close so pretty dam impressive...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fr4nK on 04/14/2015 09:30 pm
So it looks like a bigger barge would have solve the problem?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jaufgang on 04/14/2015 09:32 pm
I was writing something related to first stage landing technical hurdles that SpaceX has already retired, but clearly something is missing.

What technical hurdles are left to solve?

They've never done a landing on a solid surface from high altitude free-fall at terminal velocity.  All grasshopper and F9R-Dev tests had the engine firing continuously and a slow controlled descent.   A F9R-Dev test involving engine cutoff and a separate last moment landing burn has never been attempted, let alone succeeded.   
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 09:33 pm
So it looks like a bigger barge would have solve the problem?

Not necessarily. It depends on why it tipped over. If it was because too much lateral motion, it would have tipped over no matter what. But if it was due to the legs extending over the edge, then yes.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: SpaceBert on 04/14/2015 09:37 pm
Hi guys! I normally use to lurk around and enjoy NSF launch coverage but on this topic I have to add my five cents:

For me it clearly looks like the stage came down too much off center. If you look at the engine plume, you can clearly see it hits the barge on the withe circle, maybe even slightly outside of it. If we compare that with aerial views of the drone ship and keep leg span in mind it could really missed the landing surface with one leg - tipping over in consequence.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fr4nK on 04/14/2015 09:39 pm
So it looks like a bigger barge would have solve the problem?

Not necessarily. It depends on why it tipped over. If it was because too much lateral motion, it would have tipped over no matter what. But if it was due to the legs extending over the edge, then yes.

But with a bigger barge, it would have bigger margin to calculate required lateral correction and still hit the barge with less lateral motion. I'm sure it would help. I can't wait to find out if one leg extended over the edge!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mvpel on 04/14/2015 09:40 pm
It looked so easy in CRS-3.  :-\
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AJA on 04/14/2015 09:41 pm
Alright... my own first impressions seek to torpedo what I'm about to say, on the grounds that it'd be overly complicated... but nonetheless..


Would the lateral velocity problem be ameliorated at all, if the barge's engines were hooked up to a control program which, could be connected to a camera/transceiver? In that case, the landing system I'm envisioning would work somewhat like this.
1. Falcon nulls out most velocities - but primarily the vertical
2. Hovers at something like 10-15 metres above the barge
3. Barge quickly matches the remaining delta in the horizontal velocity.
4. When both guidance systems confirm that the relative horizontal velocity is zero, the stage proceeds to lower itself down onto the barge surface.


The advantages would be the saving of precious propellant, but perhaps - more importantly - keeping your altitude while still performing horizontal adjustments. Currently, the engine is required to be gimballed, and if you gimbal an engine that's perfectly offsetting the (rapidly diminshing) weight of the stage, then you're almost definitely going to be throwing off the vertical equilibrium as well.


This potentially allows independent control of X-Y and Z axes, although I myself am not convinced that this will lead to "easier" control.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: GWH on 04/14/2015 09:42 pm
Not necessarily. It depends on why it tipped over. If it was because too much lateral motion, it would have tipped over no matter what. But if it was due to the legs extending over the edge, then yes.

Not if the footpads are able to slide  ;) 

Koenigsmann on twitter just quoted that he is pretty sure there is something to recover from first stage landing. 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MostlyHarmless on 04/14/2015 09:44 pm
Looking at the flag in the first frame, it seems as if there was a lot of wind.  If there was any sort of wind shear with altitude, it's very possible that the booster could have had to make a sudden adjustment for lateral drift in the final seconds.  Such a maneuver might have had insufficient vertical distance to complete before touching down. 

Of course, it's all speculation until we here from SpaceX. 

Regardless, they're getting closer.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Bob Shaw on 04/14/2015 09:45 pm
Seriously, guys, you're *all* missing the point!

Elon Musk foolishly dissed the notion of superhuman AI development, and then...

...he trusted his toys to an autonomous vessel named after a Culture Mind, hyper-intelligent beings known for their devious behavior and wicked sense of humour!

And you're surprised that every time those first stages line up to land, the barge does a little jig out of the way? Ha!

I, for one, wish to be among the first to welcome our new overlords.

Just sayin'...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AJA on 04/14/2015 09:46 pm
I was writing something related to first stage landing technical hurdles that SpaceX has already retired, but clearly something is missing.

What technical hurdles are left to solve?

They've never done a landing on a solid surface from high altitude free-fall at terminal velocity.  All grasshopper and F9R-Dev tests had the engine firing continuously and a slow controlled descent.   A F9R-Dev test involving engine cutoff and a separate last moment landing burn has never been attempted, let alone succeeded.   

But what difference does it make? Once the F9R-Dev is under power on the landing burn, it's analogous to the slowly decelerating Grasshopper, isn't it (aside from the differences between a test article and flight hardware)? The conditions at sea are perhaps quite different to McGregor though. Not to mention the vertically unstable (despite all the mention of the stablising ability of the) barge.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Nilof on 04/14/2015 09:46 pm
So, is the lateral position control system underdamped?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 09:46 pm

So this tells use that the barge does not have the bandwidth to broadcast full live video at the moment. (something they will probably fix in the future)

Why do you think it needs to be "fixed"?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/14/2015 09:47 pm
So it looks like a bigger barge would have solve the problem?

Not necessarily. It depends on why it tipped over. If it was because too much lateral motion, it would have tipped over no matter what. But if it was due to the legs extending over the edge, then yes.

Not quite, IMO.

With a larger barge the algorithm could have chosen to land further off-center, but with lower lateral velocity.  Here, there's almost no margin of error.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 09:48 pm

So this tells use that the barge does not have the bandwidth to broadcast full live video at the moment. (something they will probably fix in the future)

Why do you think it needs to be "fixed"?

Why not? If the barge is in use years down the line, you find it such an implausible statement that it would have better bandwidth?  :) Let's wait and see who is right.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 09:49 pm

what if the lasers locked on the top of the rocket? Lasers mounted on the 4 corners of the barge... the farthest away possible from the bullseyes and thus less blocked by smoke, locking on the top part of the rocket?


The barge does not interact with the rocket except as a radar return.  There is no information that is broadcasted to the rocket, it is autonomous.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 09:51 pm

But with a bigger barge, it would have bigger margin to calculate required lateral correction .....

Based on what sensor data?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 09:53 pm

3. Barge quickly matches the remaining delta in the horizontal velocity.


No, there is no interaction between barge and rocket.  The barge is at a specific location and the rocket is told to fly to the specific location.  That is how it will work on land.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fr4nK on 04/14/2015 09:57 pm

But with a bigger barge, it would have bigger margin to calculate required lateral correction .....

Based on what sensor data?
Based on common sense. You aim for the X or you aim for no lateral motion while landing somewhere on the barge. Bigger barge means more margin
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 09:58 pm

Why not? If the barge is in use years down the line, you find it such an implausible statement that it would have better bandwidth?  :) Let's wait and see who is right.

Because it is not needed.  It wasn't needed today, there is no engineering need..  The barge is going to be used less in the future.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/14/2015 09:58 pm
But on land the ground can't shift beneath you. Sounds like they need to treat barge landing as a special case, that's different from a ground landing.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 09:59 pm
Based on common sense. You aim for the X or you aim for no lateral motion while landing somewhere on the barge. Bigger barge means more margin

Wrong and neither is it common sense .  The rocket is not aiming for the barge, it is aiming for a spot on the ocean.  The barge happens to be at the spot.  There are no sensors that say the rocket is to the right or left of the barge. The only sensors are the radars for height.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Mapperuo on 04/14/2015 10:01 pm
Sad to see CNN news article title is 'SpaceX rocket lands, falls over' - did someone tell them it was a successful launch?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ugordan on 04/14/2015 10:02 pm
Sad to see CNN news article title is 'SpaceX rocket lands, falls over' - did someone tell them it was a successful launch?

There was a launch involved???

Ahh, so that's what this thing was...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fr4nK on 04/14/2015 10:03 pm
Based on common sense. You aim for the X or you aim for no lateral motion while landing somewhere on the barge. Bigger barge means more margin

Wrong and neither is it common sense .  The rocket is not aiming for the barge, it is aiming for a spot on the ocean.  The barge happens to be at the spot.
Interresting. I would guess at the last burn it would start to aim for the barge and not leave it to the barge to get exactly at the right spot. I might be wrong.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AJA on 04/14/2015 10:05 pm
Question: Assuming that they DON'T manage to null out all horizontal velocity, and that the stage still has some tipping motion about the legs, in the instant after touch down.... is this something that they can sense and remedy with another cold gas thruster firing at the top of the stage?


Or are we already in the realm of having to worry about mechanical integrity of load-bearing structures/legs if the stage makes a landing with above-desirable horizontal velocity?


Come to think of it... is there any use of the cold gas thrusters to null the horizontal drift rates - during the landing burn? Or would it be comically ineffective at sea-level? (In terms of response speed, and torque)


This is assuming that they have some left-over after the flip, and after the high altitude re-entry guidance...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/14/2015 10:06 pm
I'm not a nautical man, but is there any way to reliably anchor the barge - maybe using multiple anchors - to keep the barge from moving at all? Then the barge would truly be a stationary piece of ground.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kaputnik on 04/14/2015 10:10 pm
I'm not a nautical man, but is there any way to reliably anchor the barge - maybe using multiple anchors - to keep the barge from moving at all? Then the barge would truly be a stationary piece of ground.

You'd have to 'anchor' it using multiple rigid attachments, preferably at the same time lifting it clear of the water. At which point you've reinvented the jack-up barge...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/14/2015 10:13 pm
Well, oil rigs don't use thrustmasters, and are instead anchored to the ocean floor. If this stage had been landing on something that was more like an oil rig than the current barge, then would this touchdown have had greater chances of success?

Yes, a barge may be cheaper than an oil rig, but if you're going for reusability you may not want to skimp on this cost.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 10:15 pm
Well, oil rigs don't use thrustmasters, and are instead anchored to the ocean floor. If this stage had been landing on something that was more like an oil rig than the current barge, then would this touchdown have had greater chances of success?

Yes, a barge may be cheaper than an oil rig, but if you're going for reusability you may not want to skimp on this cost.

The barge is not going to be the primary landing site, it will be on land. 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/14/2015 10:17 pm
The barge is not going to be the primary landing site, it will be on land.

But Jim, I thought the barge was still going to be used for recovering stages that were sent too far to bring them back to dry land.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LastWyzard on 04/14/2015 10:18 pm
This looks to me to strictly be a case of nulling out the horizontal velocity.  I doubt the barge was moving much.  I've done a few simulations and the biggest problem is having to make late (or excessive) targeting corrections and then be left with a very late effort to null out the horizontal velocity.  So I would speculate that the stage was off target by more than was expected and was dealing with the correction and it was just too late.

Also a few posts ago the accuracy of the radar was questioned.  That absolutely shouldn't be a problem.  Check out Curiosity, Mars Phoenix, Viking 1 and 2 and, of course, the Lunar Module.  High precision radar was solved long ago.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AJA on 04/14/2015 10:19 pm
Yes, a barge may be cheaper than an oil rig, but if you're going for reusability you may not want to skimp on this cost.

But remember that the barge isn't among their operational plan at all. It's only during the testing phase. They'll be landing back at the Cape.
EDIT: But might it be used for the main core on Falcon Heavy?

Speaking of which. What risks remain to be retired with respect to being given permission to come back to land?

It's probably reckless but I'll ask anyway. The first stage is a nearly (fuel-wise) spent (and therefore a minimal explosive hazard). They've demonstrated accuracy to guiding it within a few hundred meters several times now. How does it affect the FAA if the stage is able to stay on its feet or not? How many flights before they're given permission to fly it back, and have a 'land'ing (attempt)?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fr4nK on 04/14/2015 10:21 pm
Here is what i would add to JRTI ship to help with tipping rocket. It would be folded down until the engine cut off. then spring up to act as a fence for the rocket. Sry for my poor drawing skills
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: RoboGoofers on 04/14/2015 10:23 pm
The 1st stage terminal trajectory is to aim for a spot next to the barge, and then once the engines fire up, correct and land on the X, Correct? Perhaps they had too large a safety margin, which required a larger correction, hence the extra lateral motion?

It might just be an issue of tweaking the algorithms.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 10:23 pm
Not the FAA's call but the air force's
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: GWH on 04/14/2015 10:25 pm
I posted earlier in jest, but in all seriousness if they can't 100% resolve lateral motion but the rocket body is still aligned vertically then the tendency to tip over is going to be a function of the friction between the foot pads that touch down and deck surface. Reduce the friction at the contact points and you'll reduce the chances of tipping. 

Any skier or snowboarder who's caught an edge landing on an off camber surface can attest to that...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 10:26 pm
Here is what i would add to JRTI ship to help with tipping rocket. It would be folded down until the engine cut off. then spring up to act as a fence for the rocket. Sry for my poor drawing skills

Not needed.  Too  complex.  The rocket has just to land right

And if the rocket is on the edge, those things will knock it over
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AJA on 04/14/2015 10:30 pm

Here is what i would add to JRTI ship to help with tipping rocket. It would be folded down until the engine cut off. then spring up to act as a fence for the rocket. Sry for my poor drawing skills


The problem with that is distance. If the arms are long/short enough to support the rocket if it lands at (x1, y1); then what happens when the rocket lands at (x2, y2)? Either your arms, and the support won't be close enough to catch the tipping stage, before it's already fallen over... OR, your arm will nudge an already nicely landed rocket and knock it over.


This, in addition to potentially damaging the stage? (I have contradicting senses for how fragile they are. I mean, I've heard about missile fuel tanks being pierced because someone dropped a wrench in a silo, about how the strongback and supports aren't withdrawn until after the rocket is tanked, and the fuel pressure supports the structure, and self weight. But at the same time, I know that this thing has been through several orders of magnitude of velocity, and aerodynamic stresses...)


Not the FAA's call but the air force's


Ah. My bad. But same question still applies. What's the Air Force looking for, before it deems an overflight/return as safe?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fr4nK on 04/14/2015 10:34 pm
Here is what i would add to JRTI ship to help with tipping rocket. It would be folded down until the engine cut off. then spring up to act as a fence for the rocket. Sry for my poor drawing skills

Not needed.  Too  complex.  The rocket has just to land right

And if the rocket is on the edge, those things will knock it over
It starts like this, then when it goes up, you make it so it stops where the top of the rocket would be if the legs would be right on the edge of the barge. Of course you can add some brain to it so you adjust depending on where it lands. Just need it to be strong and fast. (To prevent tipping)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: somepitch on 04/14/2015 10:38 pm
Here is what i would add to JRTI ship to help with tipping rocket. It would be folded down until the engine cut off. then spring up to act as a fence for the rocket. Sry for my poor drawing skills

Not needed.  Too  complex.  The rocket has just to land right

And if the rocket is on the edge, those things will knock it over
It start like this, then when it goes up, you make it so it stop where the top of the rocket would be if the legs would be right on the side of the barge. Of course you can add some brain to it so you adjust depending on where it lands. Just need it to be strong and fast. (To prevent tipping)

You realize that as drawn those arms would be like 100' long...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fr4nK on 04/14/2015 10:39 pm
Here is what i would add to JRTI ship to help with tipping rocket. It would be folded down until the engine cut off. then spring up to act as a fence for the rocket. Sry for my poor drawing skills

Not needed.  Too  complex.  The rocket has just to land right

And if the rocket is on the edge, those things will knock it over
It start like this, then when it goes up, you make it so it stop where the top of the rocket would be if the legs would be right on the side of the barge. Of course you can add some brain to it so you adjust depending on where it lands. Just need it to be strong and fast. (To prevent tipping)

You realize that as drawn those arms would be like 100' long...
well, im using paint, it is not to scale. And it would be light weight. But strong, It is just to get the idea. SpaceX could figure out how to make it works.  ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fr4nK on 04/14/2015 10:50 pm
Here is what i would add to JRTI ship to help with tipping rocket. It would be folded down until the engine cut off. then spring up to act as a fence for the rocket. Sry for my poor drawing skills

Not needed.  Too  complex.  The rocket has just to land right

And if the rocket is on the edge, those things will knock it over
It start like this, then when it goes up, you make it so it stop where the top of the rocket would be if the legs would be right on the side of the barge. Of course you can add some brain to it so you adjust depending on where it lands. Just need it to be strong and fast. (To prevent tipping)

You realize that as drawn those arms would be like 100' long...
well, im using paint, it is not to scale. And it would be light weight. But strong, It is just to get the idea. SpaceX could figure out how to make it works.  ;)
With those 5 beers I had since it launched, Im still celebrating launch success :)  And to *land/hit* on the barge twice in a row is pretty awesome!!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/14/2015 10:57 pm
My two cents:

Barring additional information, the way to fix the problem is to land with less lateral motion.  It either had the lateral motion because it had not killed off enough horizontal speed or because it it overcorrected/corrected too late.  The former is fixed by adjusting the arc that the stage "flies."  The latter is fixed by refining the terminal landing algorithm.

That's it.  No changes to the barge, no need to anchor the barge, no new two-way communication required.  We are well into the "fine tune" phase of the design/experiments.  Wash, rinse, repeat.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/14/2015 10:58 pm
What's the Air Force looking for, before it deems an overflight/return as safe?


The exact criteria haven't been spelled out in public, but Elon has said that "repeated precision landings" , or words to that effect, will be required (on the barge).
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: StuffOfInterest on 04/14/2015 10:59 pm
I somewhat wonder if heligrid (mentioned a few months ago) could have saved the day, assuming all four legs were on the deck.  The real proof will be when we get to see the full video.  It could be that there is no way this landing was going to be saved.  Still a great learning experience, however.

Considering how good they are on accuracy, I hope this will allow SpaceX to attempt to land at LC-13 sooner rather than later.  Having a stable (and larger) target can't hurt their chances.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fr4nK on 04/14/2015 11:02 pm
My two cents:

Barring additional information, the way to fix the problem is to land with less lateral motion.  It either had the lateral motion because it had not killed off enough horizontal speed or because it it overcorrected/corrected too late.  The former is fixed by adjusting the arc that the stage "flies."  The latter is fixed by refining the terminal landing algorithm.

That's it.  No changes to the barge, no need to anchor the barge, no new two-way communication required.  We are well into the "fine tune" phase of the design/experiments.  Wash, rinse, repeat.

It sure is the way to go. But some fence to save $$$ recovering engine that are worths millions of dollars might be a good investment in the meantime.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/14/2015 11:11 pm
My two cents:

Barring additional information, the way to fix the problem is to land with less lateral motion.  It either had the lateral motion because it had not killed off enough horizontal speed or because it it overcorrected/corrected too late.  The former is fixed by adjusting the arc that the stage "flies."  The latter is fixed by refining the terminal landing algorithm.

That's it.  No changes to the barge, no need to anchor the barge, no new two-way communication required.  We are well into the "fine tune" phase of the design/experiments.  Wash, rinse, repeat.

It does seem like the problem is that the horizontal velocity that has to be killed off during the landing burn, which means the stage has to remain tilted off vertical in order for the thrust vector to have some horizontal component. This is unlike the Grashopper/F9R Dev flights that have had very little horizontal velocity to kill.

So the stage has to remain tilted both to kill horizontal velocity and then to do any final position correction, and if it undershoots or overshoots on the horizontal velocity, the result is the last two crashes.

Last time looked like it overshot the barge and tried to come back. This time it may not have overshot the barge, but still had too much horizontal velocity when it touched down.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/14/2015 11:14 pm
How about giant airbags? They inflate from the barge deck as soon as the stage touches down, in order to trap it upright.

Of course, car airbags can inflate in microseconds because they're not so huge -- whereas multi-storey airbags might take slightly longer.  :P
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: saliva_sweet on 04/14/2015 11:15 pm
Landing photos!

https://twitter.com/elonmusk/status/588082574183903232

Distinctness of the soot stripes in these pictures is interesting.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Radical_Ignorant on 04/14/2015 11:18 pm
Not part of discussion what SX should do, but nice, well balanced article about today event:
uk.businessinsider.com/watch-the-spacex-launch-livestream-2015-4?r=US
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kdhilliard on 04/14/2015 11:25 pm
...,, landing on target, oriented vertically, and with near zero vertical velocity as you reach the deck is not enough if your lateral velocity sends you skidding off the deck or toppling over.

It's not something I'm happy to have presaged, but it has always struck me as a difficult job to stick all these conditions at once when working with a T/W >>  1.  Grasshopper videos show (https://www.youtube.com/watch?v=2t15vP1PyoA) some impressive low level maneuvering, but at nearly a hover.

I hope they stick the next one, but if they don't I wouldn't be surprised were they to outfit a new core as a F9R to conduct a series of increasingly difficult test landings.  There is a huge difference between T/W ~ 1 and T/W >> 1.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: dorkmo on 04/14/2015 11:26 pm
do we believe that the tank ruptured and shot off similar to last time?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Optimist on 04/14/2015 11:29 pm
Wasnt sure where to post this.

Saw this on Twitter , havent seen it posted here.

Tweets & replies

Elon Musk @elonmusk  ·  33m 33 minutes ago
@teknotus There are nitrogen thrusters at top of rocket. Either not enough thrust to stabilize or a leg was damaged. Data review needed.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jaufgang on 04/14/2015 11:33 pm
I was writing something related to first stage landing technical hurdles that SpaceX has already retired, but clearly something is missing.

What technical hurdles are left to solve?

They've never done a landing on a solid surface from high altitude free-fall at terminal velocity.  All grasshopper and F9R-Dev tests had the engine firing continuously and a slow controlled descent.   A F9R-Dev test involving engine cutoff and a separate last moment landing burn has never been attempted, let alone succeeded.   

But what difference does it make? Once the F9R-Dev is under power on the landing burn, it's analogous to the slowly decelerating Grasshopper, isn't it (aside from the differences between a test article and flight hardware)? The conditions at sea are perhaps quite different to McGregor though. Not to mention the vertically unstable (despite all the mention of the stablising ability of the) barge.

I think there are some very significant differences.   For one thing the F9R-Dev tests have not had to contend with the sort of high lateral velocities that were implicated in today's imperfect landing.  Also the F9R-Dev was heavily ballasted to allow hovering and very slow descent.  The high velocity approach, and rapid deceleration  of a real landing would leave significantly less room for error and less time to make corrections. 

I had very much expected that by the time they got to this point attempting to land actual flight hardware, they would have had several F9R-Dev tests under their belt where the test rocket had been launched in the desert to stratospheric altitude, cut it's engine, fell back down under grid-fin guidance and then performed a landing burn similar to what would happen in a real launch.  Had they done that successfully, the claim could be made that their landing system has been definitively proven to work, even before the successful recovery of a production stage at sea.

Without that, those final few moments of bringing the stage from terminal velocity to a stationary upright landing remain a "technical hurdle left to solve".
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/14/2015 11:35 pm
Wasnt sure where to post this.

Saw this on Twitter , havent seen it posted here.

Tweets & replies

Elon Musk @elonmusk  ·  33m 33 minutes ago
@teknotus There are nitrogen thrusters at top of rocket. Either not enough thrust to stabilize or a leg was damaged. Data review needed.



Just for context on what Musk was replying to:

Quote
Daniel P Johnson ‏@teknotus  1h1 hour ago
@elonmusk does the first stage have thrusters at the top to halt wobble or is it entirely controlled by Merlin engines?
6:25 PM - 14 Apr 2015


Elon Musk ‏@elonmusk  39m39 minutes ago
@teknotus There are nitrogen thrusters at top of rocket. Either not enough thrust to stabilize or a leg was damaged. Data review needed.


So it sounds like nitrogen thrusters are intended to stop the stage from tipping over. Are these nitrogen thrusters the same as the RCS, or are they something more specialized for the landing?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JazzFan on 04/14/2015 11:37 pm
Wasnt sure where to post this.

Saw this on Twitter , havent seen it posted here.

Tweets & replies

Elon Musk @elonmusk  ·  33m 33 minutes ago
@teknotus There are nitrogen thrusters at top of rocket. Either not enough thrust to stabilize or a leg was damaged. Data review needed.

How much effect do nitrogen thrusters have in the lower atmosphere at sea level?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Danderman on 04/14/2015 11:40 pm
An old engineering saying is that 90% of system costs are incurred in the first 10% of the project.

In this case, if the Falcon first stage were intended to perform pinpoint landings on rocking barges, the stage would not be designed to be relatively top heavy; ie it would have a broad base.

So, SpaceX is going to spend some extra cash on trying to get a pencil shaped object to balance on a narrow pad area. Not that this is impossible, only that the lack of systems engineering at the outset (meaning a review of ALL system requirements, not just those for launch) is going to cost more time and money, and probably have a high recurring cost of first stages that are lost during recovery.

On the other hand, this could all be a giant head fake for ULA to sink their time and money into recovering first stage engines.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/14/2015 11:41 pm
Musk's reply at least seems to imply that the nitrogen thrusters would be triggered to rebalance the tipping stage if necessary.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: iamlucky13 on 04/14/2015 11:42 pm
Well, oil rigs don't use thrustmasters, and are instead anchored to the ocean floor. If this stage had been landing on something that was more like an oil rig than the current barge, then would this touchdown have had greater chances of success?

Yes, a barge may be cheaper than an oil rig, but if you're going for reusability you may not want to skimp on this cost.

Deepwater oil rigs do and have used dynamic positioning since the 1960's, with steadily improving accuracy over that time. In fact, beyond a certain depth, dynamic position actually results in greater stability than anchoring, at least according to the dynamic position supplier literature. Thrustmaster seems to indicate 5m position keeping is relatively easy:
https://www.thrustmaster.net/portable-dps-shallow-water-applications/

How about giant airbags? They inflate from the barge deck as soon as the stage touches down, in order to trap it upright.

Of course, car airbags can inflate in microseconds because they're not so huge -- whereas multi-storey airbags might take slightly longer.  :P

Or they could just use the rocket's control system to null out the lateral velocity by improving the control system. They've been making really good progress in that direction.

Besides, airbags would push unevenly on a rocket not centered on the pattern, possibly tipping over an otherwise stable rocket, and nobody makes multi-storey airbags, especially not rated for exposure to rocket exhaust.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 11:42 pm

It sure is the way to go. But some fence to save $$$ recovering engine that are worths millions of dollars might be a good investment in the meantime.

No, it isn't and you have nothing to back up your claim.  The barge is only temporary.  The fence is a kludge and not worth the effort
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/14/2015 11:43 pm
...,, landing on target, oriented vertically, and with near zero vertical velocity as you reach the deck is not enough if your lateral velocity sends you skidding off the deck or toppling over.

It's not something I'm happy to have presaged, but it has always struck me as a difficult job to stick all these conditions at once when working with a T/W >>  1.  Grasshopper videos show (https://www.youtube.com/watch?v=2t15vP1PyoA) some impressive low level maneuvering, but at nearly a hover.

I hope they stick the next one, but if they don't I wouldn't be surprised were they to outfit a new core as a F9R to conduct a series of increasingly difficult test landings.  There is a huge difference between T/W ~ 1 and T/W >> 1.
You can kill horizontal velocity by changing the arc the stage "flies."  You can also kill it earlier in the landing burn.  The landing burn itself is over 30 seconds long, there is a lot of time to make adjustments.

These barge landings are giving them more real-world data for landing that F9R-Dev can.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 11:43 pm
How about giant airbags? They inflate from the barge deck as soon as the stage touches down, in order to trap it upright.


You have making more problems than solving them.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/14/2015 11:44 pm
No, it isn't and you have nothing to back up your claim.  The barge is only temporary.  The fence is a kludge and not worth the effort

But Jim, what about for FH center core - is that supposed to always land back on land too? Won't it sometimes travel too far away from land to bring it back?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/14/2015 11:45 pm
No, it isn't and you have nothing to back up your claim.  The barge is only temporary.  The fence is a kludge and not worth the effort

But Jim, what about for FH center core - is that supposed to always land back on land too?

That has infrequent flights.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JazzFan on 04/14/2015 11:45 pm
Better make those bags fire proof and able to magically disappear so the vehicle can be quickly secured to the barge deck.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: plank on 04/14/2015 11:47 pm
Congratulations Spacex on successful mission.   Next time you'll stick the landing for sure.   Specking of which anyone knows when will be their next attempt at first sage recovery?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: yg1968 on 04/14/2015 11:51 pm
Wasnt sure where to post this.

Saw this on Twitter , havent seen it posted here.

Tweets & replies

Elon Musk @elonmusk  ·  33m 33 minutes ago
@teknotus There are nitrogen thrusters at top of rocket. Either not enough thrust to stabilize or a leg was damaged. Data review needed.

A leg may have been damaged during the launch or during the landing attempt?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Space Ghost 1962 on 04/14/2015 11:53 pm
Wasnt sure where to post this.

Saw this on Twitter , havent seen it posted here.

Tweets & replies

Elon Musk @elonmusk  ·  33m 33 minutes ago
@teknotus There are nitrogen thrusters at top of rocket. Either not enough thrust to stabilize or a leg was damaged. Data review needed.

A leg may have been damaged during the launch or during the landing attempt?

Or on reentry. Possibly not enough control authority.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/14/2015 11:58 pm

Why not? If the barge is in use years down the line, you find it such an implausible statement that it would have better bandwidth?  :) Let's wait and see who is right.

Because it is not needed.  It wasn't needed today, there is no engineering need..  The barge is going to be used less in the future.

Of course it isn't required. But it still will happen, if the barge is kept in service. Are you really that hell-bent on not believing in progress by inertia alone? In the near future even toasters will have the bandwidth to accomplish this - But go ahead, be that guy that 20 years ago would have predicted that noone would have internet access faster than 56k modems because it isn't "needed". Go ahead.  :)

I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rickl on 04/14/2015 11:59 pm
While I was hoping for a successful landing, I'm very pleased with today's events.  Another flawless Falcon 9 launch sending a healthy Dragon on its way, and a landing attempt that was clearly an improvement over the first try in January.


Back in 1957-58, they were still trying to work out how to make successful launches.  There were several failures for every success.  Today launches are pretty reliable and failures are rare. 


After thousands of space launches since then, this was only the second attempt to soft-land a first stage from an orbital launch.  I'm confident that they'll get it before long.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Coastal Ron on 04/14/2015 11:59 pm
A leg may have been damaged during the launch or during the landing attempt?

If you look at the image showing the stage landing it appears to have the center engine on the outer landing circle.  I don't know how wide the legs go, but it could have been that the pad/foot of one of the legs was off the side of the barge enough that it caused the tipping to happen.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 12:01 am
Or on reentry. Possibly not enough control authority.

How much scope is there to beef up the RCS / nitrogen thrusters to help keep the tipping stage balanced?
Is it just a question of increasing the amount of available nitrogen gas? You would think that the RCS which is capable of flipping a stage for boostback would have enough control authority to balance against mere tipping.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: QuantumG on 04/15/2015 12:03 am
It really would seem better to put an automated system on the drone ship to capture the Falcon stage. I mean, that mass is free.

Lasso that rocket!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 12:04 am

Of course it isn't required. But it still will happen, if the barge is kept in service. Are you really that hell-bent on not believing in progress by inertia alone? In the near future even toasters will have the bandwidth to accomplish this - But go ahead, be that guy that 20 years ago would have predicted that noone would have internet access faster than 56k modems because it isn't "needed". Go ahead.  :)


If they wanted it, it would be on the barge now.  The capability has existed for years.  So you can't say it will happen.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 12:05 am
Or at least a transponder in the middle of the X (landing zone) for the stage to home in on exactly, and to match speed with.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 12:06 am
Or at least a transponder in the middle of the X (landing zone) for the stage to home in on exactly, and to match speed with.

How many times does it have to be said.  The rocket and barge don't interact nor do they need to.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 12:08 am
If they wanted it, it would be on the barge now.  The capability has existed for years.  So you can't say it will happen.

In which case, what would be the reason why they wouldn't want it - security? Time is money, and you'd think they'd like to get the fullest information right away, including visual info, so that they could start immediately assessing what happened, rather than waiting days to get a hold of that footage.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 12:08 am
You would think that the RCS which is capable of flipping a stage for boostback would have enough control authority to balance against mere tipping.

No, not true   High up in the atmosphere, there is no air nor main engine firing.  There is little resistance.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 12:10 am

In which case, what would be the reason why they wouldn't want it - security? Time is money, and you'd think they'd like to get the fullest information right away, including visual info, so that they could start immediately assessing what happened, rather than waiting days to get a hold of that footage.

A few days is not going to matter and the video isn't going to provide much more data than the telemetry.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 12:17 am
How many times does it have to be said.  The rocket and barge don't interact nor do they need to.

Well, technically they *are* interacting - mechanically - which is why the "excess lateral velocity" probably caused the tipping in the end. In which case, it would make sense for the stage to directly measure its distance/velocity relative to the landing target. Some kind of landing beacon might be useful.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rebel44 on 04/15/2015 12:23 am
What are those legs made of?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 12:26 am

Well, technically they *are* interacting - mechanically - which is why the "excess lateral velocity" probably caused the tipping in the end. In which case, it would make sense for the stage to directly measure its distance/velocity relative to the landing target. Some kind of landing beacon might be useful.

Again no.  There isn't going to be a beacon on land nor does there need to nor will beacon help.   The rocket has GPS and inertial guidance.  That is enough to tell distance/velocity relative to the landing target.  Again, the target isn't the barge but a spot in the ocean.  The barge is just placed over the spot. 

This system is to be landing site generic and not need outside support.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 04/15/2015 12:28 am
How about giant airbags? They inflate from the barge deck as soon as the stage touches down, in order to trap it upright.


You have making more problems than solving them.

the barge wasn't a cheap fix

kill the legs, just get the launcher close (horz), drop & recover what parts you can

https://www.youtube.com/watch?v=j9QrKzLVujs


Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/15/2015 12:31 am

Well, technically they *are* interacting - mechanically - which is why the "excess lateral velocity" probably caused the tipping in the end. In which case, it would make sense for the stage to directly measure its distance/velocity relative to the landing target. Some kind of landing beacon might be useful.

Again no.  There isn't going to be a beacon on land nor does there need to nor will beacon help.   The rocket has GPS and inertial guidance.  That is enough to tell distance/velocity relative to the landing target.  Again, the target isn't the barge but a spot in the ocean.  The barge is just placed over the spot. 

This system is to be landing site generic and not need outside support.

Perhaps the key point is that in the last few feet before touchdown, you're already committed and, other than a full abort (go-around), you've not many control options available anyway.

eg. If the "excess lateral velocity" was caused by the wind (and it looks like there was plenty of it) pushing the stage bodily sideways across the deck, there's not much you can do about it other than stop engines and pray.  There's no point measuring anything because it's not like the ASDS can respond fast enough to help either.

EDIT:  I don't know what the sea/wind conditions were at the moment of landing, but if the wind was as strong as it looks in the pic I reckon all the video will show is that the landing was doomed from less than a dozen feet up..
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: punder on 04/15/2015 12:35 am

Well, technically they *are* interacting - mechanically - which is why the "excess lateral velocity" probably caused the tipping in the end. In which case, it would make sense for the stage to directly measure its distance/velocity relative to the landing target. Some kind of landing beacon might be useful.

Again no.  There isn't going to be a beacon on land nor does there need to nor will beacon help.   The rocket has GPS and inertial guidance.  That is enough to tell distance/velocity relative to the landing target.  Again, the target isn't the barge but a spot in the ocean.  The barge is just placed over the spot. 

This system is to be landing site generic and not need outside support.

Perhaps the key point is that in the last few feet before touchdown, you're already committed and, other than a full abort (go-around), you've not many control options available anyway.

Eg. If the "excess lateral velocity" was caused by the wind (it looks like there was planty of it) pushing the stage bodily sideways across the deck, there's not much you can do about it other than stop engines and pray.  There's no point measuring anything because the ASDS can't respond fast enough to help.

Which is actually an argument for some sort of active terminal guidance.  Null the wind by moving the ASDS, and let the stage track an active course to it.

But what am I saying!  Of course there is no need for active terminal guidance, and no one will ever implement such an outlandish notion.   ::)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/15/2015 12:37 am
No, it isn't and you have nothing to back up your claim.  The barge is only temporary.  The fence is a kludge and not worth the effort

But Jim, what about for FH center core - is that supposed to always land back on land too?

That has infrequent flights.


"Infrequently used" is not the same as "temporary".
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/15/2015 12:40 am
Which is actually an argument for some sort of active terminal guidance.  Null the wind by moving the ASDS, and let the stage track an active course to it.

But what am I saying!  Of course there is no need for active terminal guidance, and no one will ever implement such an outlandish notion.   ::)

As I said in my post, the ASDS can't move fast enough to "null the wind" - no matter how many "upgrades" you do or how big your engines are.  There are laws of physics working against you.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 12:51 am
Which is actually an argument for some sort of active terminal guidance.  Null the wind by moving the ASDS, and let the stage track an active course to it.

But what am I saying!  Of course there is no need for active terminal guidance, and no one will ever implement such an outlandish notion.   ::)

As I said in my post, the ASDS can't move fast enough to "null the wind" - no matter how many "upgrades" you do or how big your engines are.  There are laws of physics working against you.


That is not the reason.  How would they implement such a system on land?  Would they have a wheeled platform?  No.
Why can people understand that what is done on the barge will be the exact thing used on land? 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: craigcocca on 04/15/2015 12:54 am
How about an electromagnet in the deck of the ASDS, with corresponding ferrous materials in each of the landing feet? The rocket would just need to hover near the center of the deck and then the system would pull it in and lock all of the feet down to the deck until the SpaceX red-shirts lock it down physically.

In light of this being an Elon Musk project, the magnetic landing system could be powered by SolarCity photovoltaics.

(I am actually serious about the core engineering idea here)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jimbowman on 04/15/2015 12:55 am
Video from the chase plane coming soon according to Musk. Amazing photo on his last tweet from the plane.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jabe on 04/15/2015 12:55 am
look at this tweet!!
https://twitter.com/elonmusk/status/588142879245238273 (https://twitter.com/elonmusk/status/588142879245238273)
Quote
Ok, looks like we got some killer footage from the chase plane. Big ocean, small ship. Posting vid shortly
jb
edit:got beat by a hair I guess..:)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: topsphere on 04/15/2015 12:57 am
Incredible stuff!!!

I posted this in the ASDS thread as well, so mods remove one if necessary.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jabe on 04/15/2015 12:59 am
Vid shows some instability..the wind???
https://twitter.com/SpaceX/status/588143946800463874
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 12:59 am
Why does the methodology for barge landing have to be exactly the same thing as for land?
Barge and land are different in reality, so why shouldn't this be reflected by small differences in the landing techniques for each?

Is the wind at sea inherently greater than wind on land?
Why not use Doppler radar to measure the wind conditions?

Thrustmasters don't have to null the wind - the gimbaled Merlin engines should be able to do that, shouldn't they?

You should be homing in on whatever surface you're landing on - if that surface is a barge surface, then it seems strange to want to home in on something else (ie. GPS) which is not that surface itself.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/15/2015 01:02 am
Why does the methodology for barge landing have to be exactly the same thing as for land?
Barge and land are different in reality, so why shouldn't this be reflected by small differences in the landing techniques for each?

Is the wind at sea inherently greater than wind on land?
Why not use Doppler radar to measure the wind conditions?

Thrustmasters don't have to null the wind - the gimbaled Merlin engines should be able to do that, shouldn't they?

You should be homing in on whatever surface you're landing on - if that surface is a barge surface, then it seems strange to want to home in on something else (ie. GPS) which is not that surface itself.

Something people take for granted with "land" landings is protection from the wind:  On a flat-topped barge in the middle of the Atlantic with miles of fetch in all directions, wind speed at ground level is generally a lot stronger than on any strip of land with even only a few trees around, due to friction.

To make this work I suppose they could ditch their itsy bitsy nitrogen thrusters and replace them, top and bottom of the stage with SuperDracos acting horizontally in all directions, even after touchdown.  IMHO that's about the *only* thing that would give you sufficient lateral control authority to keep an upright stage on an unprotected barge on the open ocean.  ::)

What SpaceX are trying to do here makes landing on a nice concrete pad on solid ground surrounded by a few trees look like child's play.  Yes, it really is that much harder.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 01:03 am
Vid shows some instability..the wind???
https://twitter.com/SpaceX/status/588143946800463874

Some kind of axial/rotational momentum there. The stage has to tilt in order to counter any lateral forces, but then it doesn't have enough time to vertically reorient itself - so it seems to still have rotational momentum when it's touching down.

So is this all due to low-altitude wind gusting near the surface?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/15/2015 01:07 am
Vid shows some instability..the wind???
https://twitter.com/SpaceX/status/588143946800463874

Some kind of axial/rotational momentum there. The stage has to tilt in order to counter any lateral forces, but then it doesn't have enough time to vertically reorient itself - so it seems to still have rotational momentum when it's touching down.

So is this all due to low-altitude wind gusting near the surface?

IMHO, yep. :)   From the look of that ocean, wind wind is blowing at least 15kts.  I reckon they might have nailed it if it hadn't been for the wind.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Space Ghost 1962 on 04/15/2015 01:09 am
It doesn't null out before landing.

It overcontrols after adjusting to prevent overshoot.

However it looks adequately under control at the end to land.

Might be tipping end frame.

add:
Judging from backwash, no wind gusts of significance on last frame.

My guess is either oscillation in flight control model, dynamic instability possibly from a mis deployed leg, or collapse of a leg on contact.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 01:11 am
1.  Why does the methodology for barge landing have to be exactly the same thing as for land?
2.  Barge and land are different in reality, so why shouldn't this be reflected by small differences in the landing techniques for each?
3. Is the wind at sea inherently greater than wind on land?
4.  Why not use Doppler radar to measure the wind conditions?

5.  Thrustmasters don't have to null the wind - the gimbaled Merlin engines should be able to do that, shouldn't they?

6.  You should be homing in on whatever surface you're landing on - if that surface is a barge surface, then it seems strange to want to home in on something else (ie. GPS) which is not that surface itself.

1. Because they only want to have one configuration of vehicle.  one set of sensors, one version of software, etc.
And the if the barge uses a different version, it does no good for certifying for land landings.

2.  No, they are not.  Again, the rocket flies to a coordinate and not an object.

3.  Not always. the land landing spots are close to the ocean

4.  not needed.  The vehicle senses the wind and corrects for it.  When you drive and there is a high cross wind, do you need outside measurement of the wind speed and direction?  No, you just slightly turn into it to stay on the road.

5.  No, the thrustmasters keep the barge over the predetermined spot.

6.  No, because rocket flies from multiple pads and will have multiple landing spots.  All that would need to change for each flight is just to input the coordinates of the landing spot (work will have already been done to make sure the site is within the capabilities of the vehicle).  That make everything simple and clean and easy to verify and validate.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rebel44 on 04/15/2015 01:13 am
To me, it looks like part of the problem is overcorrection.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 01:18 am
Also, somehow it looks like this stage is descending at a much faster rate at the end, compared to Grasshopper. Can't they spare a bit more fuel to slow the vertical descent just before the end?

It's like the equivalent of a guy screeching into his parking spot and slamming on the brakes.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: GalacticIntruder on 04/15/2015 01:19 am
Not sure about this hover-slam idea on a very small target. I don't see how they will ever get the time to correct for their late (or unexpected) lateral movements if they are falling/landing that fast that close to the target.  I would have assumed almost zero velocity well above the lander. Might need a larger landing area, and better landing gear.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Elmar Moelzer on 04/15/2015 01:19 am
Just look at how tiny the barge is compared to the stage! It is no wonder that they are having such a hard time getting right on top of it (especially with strong cross winds, etc). To me it seems very obvious that landing on a (MUCH larger) landing pad on land, would be trivial compared to this and would have probably succeeded.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: abaddon on 04/15/2015 01:20 am
Oh man that was so close.  Much closer than I had thought from the barge pics.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 01:21 am
Gee, I would hate to be a human passenger in that thing. Even if it hadn't toppled over, it would still feel like a "brown pants" landing. They should slow the vertical descent rate near the end.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jabe on 04/15/2015 01:23 am
Just look at how tiny the barge is compared to the stage! It is no wonder that they are having such a hard time getting right on top of it (especially with strong cross winds, etc). To me it seems very obvious that landing on a (MUCH larger) landing pad on land, would be trivial compared to this and would have probably succeeded.
my thoughts too...if off target 10 m on land just land it..not so for barge...have to adjust.. Amazing how close they got!! higher resolution vid is going to be awesome!!
jb
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: butters on 04/15/2015 01:23 am
It looks like the leg deploy upset the attitude control. The mark 2 legs with early deploy might help quite a bit.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/15/2015 01:24 am
So.. I suppose the ASDS Landing Bingo jackpots again?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 01:24 am
Infrared would have been awesomer, to penetrate that exhaust cloud at the end.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Space Ghost 1962 on 04/15/2015 01:24 am
Also, somehow it looks like this stage is descending at a much faster rate at the end, compared to Grasshopper. Can't they spare a bit more fuel to slow the vertical descent just before the end?

It's like the equivalent of a guy screeching into his parking spot and slamming on the brakes.

Could be easier to control coming in fast - not as susceptible to gusts.

The lateral/pitching is more worry some.

The video is impressive, especially when you know the size/weight of the vehicle.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MarekCyzio on 04/15/2015 01:29 am
Regarding Vine movie:
https://vine.co/v/euEpIVegiIx

This is a book example of an uncontrolable, unstable system with long delay between measurements and controls. 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/15/2015 01:33 am
To me, it looks like part of the problem is overcorrection.

Yes, it does appear so.

But one cool thing you can see in the Vine is how the RCS thrusters fire just before touchdown. It wasn't enough, obviously. But this data will be immensely helpful it improving the landing algorithm.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: NWade on 04/15/2015 01:33 am
Anyone else notice the top of the stage as it nears the barge? I'm assuming we're seeing the N2 thrusters going full-bore trying to adjust the vehicle and either assist (or compensate for) the gimballed-dance that the main engine is doing...
 
[Answer: Yes, and Lars is just a bit faster on the "Post" button than I am, apparently!]  ::)

--Noel
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/15/2015 01:34 am
Not sure about this hover-slam idea on a very small target. I don't see how they will ever get the time to correct for their late (or unexpected) lateral movements if they are falling/landing that fast that close to the target.  I would have assumed almost zero velocity well above the lander. Might need a larger landing area, and better landing gear.

No, hovering solves very little of the actual problem - it just wastes fuel. The targeting/landing algorithm will just need tweaking.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/15/2015 01:34 am
Regarding Vine movie:
https://vine.co/v/euEpIVegiIx

This is a book example of an uncontrolable, unstable system with long delay between measurements and controls.

It might just be.   I can't tell if there's a sudden external forcing input (wind gust, failed leg deploy, etc) or just a rocket-induced-oscillation..

I think at the end it wasn't just lateral velocity - the tip rate at touch-down was not zero.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/15/2015 01:35 am
Regarding Vine movie:
https://vine.co/v/euEpIVegiIx

This is a book example of an uncontrolable, unstable system with long delay between measurements and controls.

Unstable? Yes. Uncontrollable? Give me a break!  ::) (you've never seen the grasshopper videos??)

If this was a piece of cake it would have been done before... But it certainly is possible.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 01:36 am
Were these landing conditions a worst case example? Or would landings be expected under even worse wind/sea conditions?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: matthewkantar on 04/15/2015 01:36 am
A few notes on the amazing Vine Spacex posted:

-One can see the thrusters at the top of the stage doing their thing at the last second.
-The camera seems to have been 'sidewind' to the barge not upwind or downwind, and the wind seems to have been a problem. The gimbal on the landing engine goes from hard left to hard right in the short video.
-I have no confidence at all that I am not seeing things, but it looks like the stage is bending in response to the maneuvering.
-A much larger landing surface would seem to be helpful, but the horizontal component of velocity is still going to have to be zeroed with rocket nearly plumb at the moment of touchdown.
-The video took away any notion that I had that there is a problem with the steadiness of the barge, the amplitude of the stage's movements are off the charts compared to the barge.

It would seem they have lots of work to do.

Matthew



Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ohsin on 04/15/2015 01:36 am
To me, it looks like part of the problem is overcorrection.

Yes, it does appear so.

But one cool thing you can see in the Vine is how the RCS thrusters fire just before touchdown. It wasn't enough, obviously. But this data will be immensely helpful it improving the landing algorithm.

Those could be grid fins catching the sunlight. Btw this all feels unreal amazing stuff we are witnessing.

EDIT: Nah too far up to be grid fins. You're right :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Herb Schaltegger on 04/15/2015 01:37 am
Also, somehow it looks like this stage is descending at a much faster rate at the end, compared to Grasshopper. Can't they spare a bit more fuel to slow the vertical descent just before the end?

It's like the equivalent of a guy screeching into his parking spot and slamming on the brakes.

Could be easier to control coming in fast - not as susceptible to gusts.

The lateral/pitching is more worry some.

The video is impressive, especially when you know the size/weight of the vehicle.

I need to watch the video a few more times to see if I can make out the moment of leg deploy, but I have to wonder if the late deploy, into a steady sea breeze, isn't what causes the pitch excursion due to the sudden increase in drag at the base of the vehicle relative to the wind. Those rapidly-telescoping legs and their bases have much greater area drag than the relatively featureless cyclinder of the rest of the stage.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/15/2015 01:37 am

2.  No, they are not.  Again, the rocket flies to a coordinate and not an object.


We haven't seen any evidence that there is or isn't a closed loop terminal guidance system.

Clearly most of the descent is towards an absolute coordinate, but we don't know about the last mile.

It is unarguable that active guidance (the rocket doesn't need to communicate with the barge for that) is more precise, since by using absolute coordinates you add the errors in barge and rocket station navigation.

The only question is whether SpaceX implemented a last mile terminal guidance system of some sort.

So far, all we have are opinions.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/15/2015 01:38 am
Three observations:

1) That thing has crazy amounts of throttlability.  There didn't seem to be any vertical acceleration until it got substantially closer to the deck than its own length, say  the last 100'.

2) You will note that for the first half of the video, while the engine is at low porwer it is gimballed to the right, which leads to the leftward swing out of the bottom later.  It was this action not the wind that wagged the tail and would seem to be necessary given the odd indirect tools that are available when steering a rocket. This is a wee bit hard.

3) a) Discussion of wind here in this chat room of the internets is useless. Wind on that cylinder whether its a significant force or not is easy to model and has been thought through vastly more than our words and the wind from our mouths will accomplish.
b) Observations of a flag which is seen to be flying briskly in a direction radially away from an active rocket engine are not reliable indications of a meterological wind.  A review of the Apollo 11 lunar surface flag during liftoff would under that logic lead one to believe that it happened on a windy day on the moon.  I watched that moon walk and I can attest that there was no appreciable wind on the surface until they lit that thing.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/15/2015 01:41 am
A few notes on the amazing Vine Spacex posted:
...
-I have no confidence at all that I am not seeing things, but it looks like the stage is bending in response to the maneuvering.

Look closer - I don't see it. I think you are seeing an optical illusion amplified by low resolution and compression.
Quote
It would seem they have lots of work to do.

A loaded statement. Lots, compared to what? The analogy I would use (which I did in another thread) is they are in a race, very close to the finishing line.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Herb Schaltegger on 04/15/2015 01:45 am

3) a) Discussion of wind here in this chat room of the internets is useless. Wind on that cylinder whether its a significant force or not is easy to model and has been thought through vastly more than our words and the wind from our mouths will accomplish.

I have an aerospace engineering degree - the wind-induced drag on a large cylinder is significant but not as significant as the vertically-assymmetrical drag on the entire stage once those legs deploy.

Quote
b) Observations of a flag which is seen to be flying briskly in a direction radially away from an active rocket engine are not reliable indications of a meterological wind.  A review of the Apollo 11 lunar surface flag during liftoff would under that logic lead one to believe that it happened on a windy day on the moon.  I watched that moon walk and I can attest that there was no appreciable wind on the surface until they lit that thing.

The reported wind conditions at the landing site were in the range of 14 kts. That's not gale-force but it IS significant to a dynamic control system. The moon has nothing to do with this discussion.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 01:46 am
Is it possible to actuate the legs to dampen or absorb some of the lateral landing momentum?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 01:51 am

2.  No, they are not.  Again, the rocket flies to a coordinate and not an object.


We haven't seen any evidence that there is or isn't a closed loop terminal guidance system.

Clearly most of the descent is towards an absolute coordinate, but we don't know about the last mile.

It is unarguable that active guidance (the rocket doesn't need to communicate with the barge for that) is more precise, since by using absolute coordinates you add the errors in barge and rocket station navigation.

The only question is whether SpaceX implemented a last mile terminal guidance system of some sort.

So far, all we have are opinions.

Speak for yourself
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: maitri982 on 04/15/2015 01:55 am
My two cents:

Barring additional information, the way to fix the problem is to land with less lateral motion.  It either had the lateral motion because it had not killed off enough horizontal speed or because it it overcorrected/corrected too late.  The former is fixed by adjusting the arc that the stage "flies."  The latter is fixed by refining the terminal landing algorithm.

That's it.  No changes to the barge, no need to anchor the barge, no new two-way communication required.  We are well into the "fine tune" phase of the design/experiments.  Wash, rinse, repeat.

You are spot on...see the video https://vine.co/v/euEpIVegiIx (https://vine.co/v/euEpIVegiIx) which confirms your guesses...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/15/2015 02:09 am
Is it possible to actuate the legs to dampen or absorb some of the lateral landing momentum?

Dampening of the legs did occur shortly after they slid off the deck.


We haven't seen any evidence that there is or isn't a closed loop terminal guidance system.

Clearly most of the descent is towards an absolute coordinate, but we don't know about the last mile.

So far, all we have are opinions.

Speak for yourself

Definitely opinion as is much of what is written here.  Unless a reason beyond a reasonable doubt is presented for believing it to be true.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MarekCyzio on 04/15/2015 02:11 am
Regarding Vine movie:
https://vine.co/v/euEpIVegiIx

This is a book example of an uncontrolable, unstable system with long delay between measurements and controls.

Unstable? Yes. Uncontrollable? Give me a break!  ::) (you've never seen the grasshopper videos??)

If this was a piece of cake it would have been done before... But it certainly is possible.

If it was controllable, it would not get into oscillations. I can only speculate what happened - low pressure of hydraulics resulting in slower movement of the engine gimbal system? Something changed so that the model that was used to control the rocket and the rocket by itself were substantially different. In can also be a simple bug in the controller code that caused oscillations. I am sure SpaceX will quickly identify the root cause.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/15/2015 02:20 am
I need to watch the video a few more times to see if I can make out the moment of leg deploy, but I have to wonder if the late deploy, into a steady sea breeze, isn't what causes the pitch excursion due to the sudden increase in drag at the base of the vehicle relative to the wind. Those rapidly-telescoping legs and their bases have much greater area drag than the relatively featureless cyclinder of the rest of the stage.

I have an aerospace engineering degree - the wind-induced drag on a large cylinder is significant but not as significant as the vertically-assymmetrical drag on the entire stage once those legs deploy.

The still picture posted just before the video shows the legs out hundreds of feet in the air.  I think the video compression has scrubbed them from the video.  I think your last minute legs in the breeze theory just fell overboard.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 04/15/2015 02:21 am
To me, it looks like part of the problem is overcorrection.

see that bounce toward the very end?

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rickl on 04/15/2015 02:26 am
That Vine video clip just really brings home what an amazing thing they are trying to do.  It is right out of science fiction, and they are oh so close to success.  They just need to tweak a few things.  Bravo!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: John Alan on 04/15/2015 02:27 am
After watching that Vine vid a bunch...  :o  8)
... I notice the top (where I assume GPS is) is rock steady over the target... almost all the way till hits...
The bottom starts "over trying" to keep the top "dead nuts" over the bullseye...

My opinion... it's trying too hard... (software issue)

They need to soften up the corrections late in the landing...
At leg deploy... switch to keeping the bottom steady and aim the bottom of the rocket at the target...

IOW...
Get it vertical, correcting for wind, and over the target by say 4000ft...
Pop the legs and limit major gimbal swings with the idea of keeping vertical is now more important then dead nuts over target...
BUT... steer GENTLY back if it starts to drift...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ohsin on 04/15/2015 02:30 am
Quote
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Profwoot on 04/15/2015 02:31 am
I posted this in the updates thread but this is probably a better place for it.

Slowed-down full-quality gif of the vine
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mvpel on 04/15/2015 02:33 am
I think it gives too much credence to Vine to call it a "video." A "clip," or "snippet" perhaps. Thanks for the GIF, Profwoot!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Profwoot on 04/15/2015 02:37 am
Is Elon talking about the ACS? It's not really biprop, is it?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: butters on 04/15/2015 02:47 am
My interpretation is that a valve in the center engine was sticky at throttle up for the hover slam.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Burninate on 04/15/2015 02:52 am
Or on reentry. Possibly not enough control authority.

How much scope is there to beef up the RCS / nitrogen thrusters to help keep the tipping stage balanced?
Is it just a question of increasing the amount of available nitrogen gas? You would think that the RCS which is capable of flipping a stage for boostback would have enough control authority to balance against mere tipping.
The RCS can do its job of flipping for boostback by thrusting in one direction for 10-30 seconds, coast for a minute (turning at 1-3 degrees per second), then in the other direction for 10-30 seconds.  In suborbital vacuum, it only has to modify orientation very, very slowly.  In terminal landing, it has to work very, very rapidly, exerting lots and lots of thrust.

A SuperDraco may or may not be overkill for this. (http://forum.nasaspaceflight.com/index.php?topic=36546.0;all)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 03:00 am

The RCS can do its job of flipping for boostback by thrusting in one direction for 10-30 seconds, coast for a minute (turning at a degree per second), then in the other direction for 10-30 seconds.  In suborbital vacuum, it only has to modify orientation very, very slowly.  In terminal landing, it has to work very, very rapidly, exerting lots and lots of thrust.

A SuperDraco may or may not be overkill for this. (http://forum.nasaspaceflight.com/index.php?topic=36546.0;all)

Nah, it sounds like you might need something to generate a small short explosive burst at just the right moment, almost like a firecracker.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: yg1968 on 04/15/2015 03:01 am
Quote from: Elon Musk
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)

OK, so that's Elon's leading explanation for the phase lag in the control system. Is that something that should have been caught in a test or is that just bad luck on this flight?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 03:01 am

Nah, it sounds like you might need something to generate a small short explosive burst at just the right moment, almost like a firecracker.

Huh?  Do you understand what thruster is?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: dorkmo on 04/15/2015 03:06 am
Is it possible to actuate the legs to dampen or absorb some of the lateral landing momentum?

Dampening of the legs did occur shortly after they slid off the deck.


i agree that it appears some dampening happened

i think a problem is that only one (maybe 2) of the legs is doing the absorbing in a case where the rocket is rotating to correct the lateral motion.

once the leg piston bottoms out im assuming that the top pierces the stage and it loses its integrity and pops.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Space Ghost 1962 on 04/15/2015 03:06 am
Quote
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)

OK, so that's Elon's leading explanation for the phase lag in the control system. Is that something that should have been caught in a test or is that just bad luck on this flight?

Should have been caught in stage test / static fire / preflight check.

Add:
You'd ramp the valve and observe flow rate change and/or back emf.

Or perhaps it got "cooked" or frozen in flight? Then you'd test at altitude, ramp if sticky til free, and if can't free, adjust feedback terms in control software to compensate for flaw.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/15/2015 03:11 am

2.  No, they are not.  Again, the rocket flies to a coordinate and not an object.


We haven't seen any evidence that there is or isn't a closed loop terminal guidance system.

Clearly most of the descent is towards an absolute coordinate, but we don't know about the last mile.

It is unarguable that active guidance (the rocket doesn't need to communicate with the barge for that) is more precise, since by using absolute coordinates you add the errors in barge and rocket station navigation.

The only question is whether SpaceX implemented a last mile terminal guidance system of some sort.

So far, all we have are opinions.

Speak for yourself

I do.   My opinions are opinions, unless I can find real data and show it.
That's why I'm ok being wrong sometimes - that how I learn.

Let's get back to terminal guidance now. 

Since SpaceX mentioned radar, we know that at least in Z, at some point the rocket transfers from GPS/INS knowledge to a close loop measurement-based terminal guidance.

So really, the open question is only in X/Y.

I'm fine either way, really...  It could be that SpaceX decided that "open-loop" accuracy is good enough.
I just wish we had direct data.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/15/2015 03:18 am
Quote
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)

I didn't see that.

That's door #4 - a simple malfunction.  Easiest of all other doors to correct.    Kewl.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 03:26 am
Huh?  Do you understand what thruster is?

Sure, I just meant SuperDraco sounds like overkill for that.

Quote
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)

Gee, so the valve was "sticking" (ie. getting stuck) - just a random malfunction, or was it a deficiency relative to this high-intensity landing application?

What's the standard remedy for valve sticking?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 03:29 am

So really, the open question is only in X/Y.


Not an open question.  The vehicle flies to a specific coordinate point.  <<<<<<< direct data
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/15/2015 03:43 am
What's the standard remedy for valve sticking?

A spritz of this...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: puhnitor on 04/15/2015 03:47 am
Huh?  Do you understand what thruster is?

Sure, I just meant SuperDraco sounds like overkill for that.

Quote
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)

Gee, so the valve was "sticking" (ie. getting stuck) - just a random malfunction, or was it a deficiency relative to this high-intensity landing application?

What's the standard remedy for valve sticking?

In this case, it was stiction, i.e. static friction. The valve didn't start moving when it was told to, and so the rest of the control system lagged behind. The fix could be as simple as commanding the valve to open, perhaps not even fully, a second earlier to overcome stiction and be ready to respond to input immediately when received. Of course it could also be more complicated than that, but from Elon's tone, it shouldn't be a huge deal.

Of course, then they run into the next thing to go wrong...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/15/2015 03:50 am

So really, the open question is only in X/Y.


Not an open question.  The vehicle flies to a specific coordinate point.  <<<<<<< direct data

Okidoke then.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: davey142 on 04/15/2015 03:55 am
These barge ladings are reminiscent of the Falcon 1 days. SpaceX is in unexplored territory and something tells me it'll be a while before they master reuse.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 04:00 am

In this case, it was stiction, i.e. static friction. The valve didn't start moving when it was told to, and so the rest of the control system lagged behind. The fix could be as simple as commanding the valve to open, perhaps not even fully, a second earlier to overcome stiction and be ready to respond to input immediately when received. Of course it could also be more complicated than that, but from Elon's tone, it shouldn't be a huge deal.

Of course, then they run into the next thing to go wrong...

So is the valve sticking/stiction for this particular valve something that's manifested itself before? Otherwise, what bad time for it to suddenly/randomly make an appearance. Maybe it was the high intensity operation and demanding nature of this landing which caused the valve to underperform.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Zach Swena on 04/15/2015 04:04 am
     Without knowledge of the design, it is hard to know what the source of the sticky valve was.  It could have been a quality control issue.  Sometimes you don't know where to set your tolerance limits until you test all the possible situations.  This is really the first thing they have done that has required this level of response from that valve.  It could also be a design issue.  They probably know that part already, because test data should tell them how fast the valve is supposed to be.  I would imagine it could be a combination of both, because they could predict that they need a certain response time from the valve, but didn't have the need to require compliance from the production valves until now.

     Keep in mind, that they never did the F9R Dev2 testing at spaceport america where they would have encountered and solved issues like this.  It is cheaper to do high risk testing on vehicles that are already paid for and destined for destruction anyways though.  Overall, it is a smart move financially.

These barge ladings are reminiscent of the Falcon 1 days. SpaceX is in unexplored territory and something tells me it'll be a while before they master reuse.

Falcon 1 was them learning and mastering existing technology.  Basically learning the ropes and how to do their homework.  For reuse, they are writing the book, it could potentially take a lot longer.  One advantage though is that the testing is much less financial risk, as they are testing after the primary mission is complete.  Their test rate is much higher also, because they are flying a whole lot more rockets.  Because of the higher flight rate, and greater experience and competence overall, I think it should actually take a lot less time.  Each test can identify problems like this that are hard to pinpoint and fix without hindsight.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/15/2015 04:08 am
Huh?  Do you understand what thruster is?

Sure, I just meant SuperDraco sounds like overkill for that.

Quote
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)

Gee, so the valve was "sticking" (ie. getting stuck) - just a random malfunction, or was it a deficiency relative to this high-intensity landing application?

What's the standard remedy for valve sticking?


WD-40?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Zach Swena on 04/15/2015 04:11 am

So is the valve sticking/stiction for this particular valve something that's manifested itself before? Otherwise, what bad time for it to suddenly/randomly make an appearance. Maybe it was the high intensity operation and demanding nature of this landing which caused the valve to under perform.

I don't believe they have ever flown a flight profile where throttle lag like this was critical.  That said, it seems like if it was a fundamental design issue of the valve that caused the stiction, that they would have thought to test it and found the problem earlier.  It is most likely a combination of a valve that was on the edge of the allowable range and using a valve that may not have been designed exactly with response time in mind.  A biprop valve has a whole lot of other things for the design engineers to worry about after all.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Pete on 04/15/2015 04:25 am
I don't believe they have ever flown a flight profile where throttle lag like this was critical. 

*this* is exactly why they wanted to do multiple flights with the F9R test vehicles.
You have a vehicle having to perform to a whole new set of requirements, in a whole new environment.
You want to do your testing in a controlled test location, with several truckloads of monitoring tools at hand.
You want to be able to test when your test team is ready, not just when a launch is occurring for another customer.
You want to test with greater margins on fuel and timing.
You want to do your testing a bit more out of the public eye.
.
They will get it, eventually, using the current approach of piggybacking the tests on actual launches. But don't expect a fast-track development cycle until or unless they get test flights up and running again.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deltaV on 04/15/2015 04:31 am
Looking at the video (https://vine.co/v/euEpIVegiIx) I'm struck by the dramatic attitude changes. I wouldn't expect a problem with the throttle of the main engine to directly change the rocket's attitude and I don't see why the control system would respond to incorrect thrust by purposefully changing attitude. I'm therefore guessing that the malfunctioning valve is related to attitude control, i.e. either thrusters or the system that gimbals the main engine. But the thrusters are nitrogen gas (no biprop) and the main engine gimbaling is hydraulic (also not biprop) so what's the "biprop throttle valve"?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rickl on 04/15/2015 04:40 am
For reuse, they are writing the book, it could potentially take a lot longer.  One advantage though is that the testing is much less financial risk, as they are testing after the primary mission is complete.  Their test rate is much higher also, because they are flying a whole lot more rockets.  Because of the higher flight rate, and greater experience and competence overall, I think it should actually take a lot less time.  Each test can identify problems like this that are hard to pinpoint and fix without hindsight.


At this point, the only way that test vehicles like Grasshopper would be useful is if they can fly them high enough to shut off the engine, let it accelerate to terminal velocity, then restart the engine for landing.  Otherwise, they may as well just carry on with their "testing" with actual flight hardware in actual flight conditions.  The stages would be dropped into the ocean and destroyed anyway.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cosmicvoid on 04/15/2015 04:42 am
... I wouldn't expect a problem with the throttle of the main engine to directly change the rocket's attitude and I don't see why the control system would respond to incorrect thrust by purposefully changing attitude....

I'd think that too much (or too little) thrust while gimballed results in an attitude overshoot (undershoot).
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: friendly3 on 04/15/2015 04:47 am
At this point, the only way that test vehicles like Grasshopper would be useful is if they can fly them high enough to shut off the engine, let it accelerate to terminal velocity, then restart the engine for landing.

The plan was to send F9R Dev1 to New Mexico to do just that.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: avollhar on 04/15/2015 05:13 am
Looking at the video (https://vine.co/v/euEpIVegiIx) I'm struck by the dramatic attitude changes. I wouldn't expect a problem with the throttle of the main engine to directly change the rocket's attitude and I don't see why the control system would respond to incorrect thrust by purposefully changing attitude. I'm therefore guessing that the malfunctioning valve is related to attitude control, i.e. either thrusters or the system that gimbals the main engine. But the thrusters are nitrogen gas (no biprop) and the main engine gimbaling is hydraulic (also not biprop) so what's the "biprop throttle valve"?

AFAIK, the engine TVC is fuel-draulic, it runs from (turbopump) pressurized fuel:

http://jasc-controls.com/jasc-industry-listing/space/space-actuators/thrust-vector-control-actuator-part-101424-5/ (http://jasc-controls.com/jasc-industry-listing/space/space-actuators/thrust-vector-control-actuator-part-101424-5/)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Falcon8 on 04/15/2015 05:14 am
Elon tweeted "...Even w 1 lit, it can't hover, so always land at high g". 

I assume the "it can't hover" means there is not enough fuel left to hover.  Or could it mean that a single engine  can't throttle low enough to hover with the lightened first stage?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Geron on 04/15/2015 05:18 am
Testing on actual flights is the best way to go. There was considerable cross wind, aside from sticky valve weather variation is an issue that will need to be addressed.

This landing attempt was close enough to good that if they modify the surface with some kind of numerous rapidly deployed grappling mechanisms to secure legs and pull rocket into deck securely they could have less precise landings become successes.

I envision a landing pad at sea or on land with numerous such mechanisms to secure the base of the rocket as its landing. Otherwise the rocket is too tall, and the legs with to small a diameter to assure landing in a majority of landing weather conditions, even with the valve issue solved.

I hope SpaceX starts working at securing the rocket more rapidly immediately to ensure both an initial successes and a higher rate of subsequent successes.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/15/2015 05:22 am
Elon tweeted "...Even w 1 lit, it can't hover, so always land at high g". 

I assume the "it can't hover" means there is not enough fuel left to hover.  Or could it mean that a single engine  can't throttle low enough to hover with the lightened first stage?

Can't throttle low enough.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/15/2015 05:24 am
Elon tweeted "...Even w 1 lit, it can't hover, so always land at high g". 

I assume the "it can't hover" means there is not enough fuel left to hover.  Or could it mean that a single engine  can't throttle low enough to hover with the lightened first stage?

The second one.   A single Merlin, throttled down, produces more thrust then the weight of the empty rocket, by a pretty good margin.

This is not a bad thing.  Only human pilots want to hover before landing.  It is better to get through the bottom layer of wind as fast as possible, and automated systems are fine landing with T/W>1.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/15/2015 05:32 am
I envision a landing pad at sea or on land with numerous such mechanisms to secure the base of the rocket as its landing. Otherwise the rocket is too tall, and the legs with to small a diameter to assure landing in a majority of landing weather conditions, even with the valve issue solved.

You may be underestimating its stability. It's quite bottom-heavy with the engines and octaweb structure. IIRC,  Elon was asked about its stability and gave an answer to that effect.

And you can bet SpaceX has done landing simulations with varying wind loads and pitch/yaw angles to calculate how much wind is allowable (20 knots) and how much pitch/yaw the stage can have at touchdown and remain vertical. So the allowable pitch/yaw envelope is probably known and may be larger than you might guess.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sdsds on 04/15/2015 05:38 am
I was having trouble with the notion that there even is a "biprop throttle valve" anywhere on the F9 first stage. I had been thinking there were separate LOX and fuel valves feeding the pre-burner, right? But then google tells me:
http://jasc-controls.com/jasc-industry-listing/space/space-fluid-management/bi-propellant-valve/
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: junk.munk82 on 04/15/2015 06:29 am
cleaned that vine up a bit:
https://www.youtube.com/watch?v=3Kohke57yfg
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Falcon8 on 04/15/2015 06:36 am

The second one.   A single Merlin, throttled down, produces more thrust then the weight of the empty rocket, by a pretty good margin.

It would be nice if the Falcon9 had switchable power profiles for just the center engine.  Maybe switch over to a different fuel plumbing circuit prior to landing that would produce less power and a better possibility of hovering.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/15/2015 06:39 am
Good work. Oh man, that was so so close. Don't you just hate "stiction" :-)

Anyone know if the same valve is used during the ascent phase? I know it was mentioned during the presser that the launch looked a little slow to get off the pad and I thought the same when I was watching it live. 


cleaned that vine up a bit:
https://www.youtube.com/watch?v=3Kohke57yfg
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: QuantumG on 04/15/2015 06:41 am
Don't you just hate "stiction" :-)

No.. but in this case I think there was a fraction too much.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: john smith 19 on 04/15/2015 07:08 am
I was having trouble with the notion that there even is a "biprop throttle valve" anywhere on the F9 first stage. I had been thinking there were separate LOX and fuel valves feeding the pre-burner, right? But then google tells me:
What pre-burner?
Merlin is a GG cycle engine
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: john smith 19 on 04/15/2015 07:17 am
More complicated than that. You'd need to compare telemetry/tracking with sims.

Depends on where/when the deviation occurred. Remember that the stage bends - can act like a whip if you apply too much force at the wrong time. So even considerable increase isn't an instant answer.

Once you find where the issue is (by matching a sim to actual), you rerun the sims with increased thrust til it begins to work, then you exhaustively simulate variations to prove you've adequately bounded the situation. Tedious.
And that's the interesting question about this.

SX, like all major players, design their LV's and spacecraft in CAD systems. In principle a design should be available for input to dynamics simulation models almost from the day it's frozen. Modern computer time is cheap so they would have been able to lots of sims of this process and their models should have been high fidelity.

So what was missed this time?

I've just looked at the cleaned up footage and wow does that puppy waggle.

Either I'm recalling only stills from previous landing movies or this was really flapping about, like a failed launch from the 1950's  :(

I beleive SX will get there but it's been interesting to see how something that is conceptually simple, and which should be pretty well simulated has taken 4 landings and still not resulted in a complete stage ready for reuse or analysis.  :(

Baysian statistics would have to penalize your chances of #5 being successful.  :(
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jarnis on 04/15/2015 07:27 am
Each time has failed for a brand new reason (2nd try for a completely external one - bad weather, no barge).

...and it is getting closer. Hopefully they'd run out of ways to fail soon.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: macpacheco on 04/15/2015 07:28 am
Its not uncommon to see 30km/h wind shear from 1000ft to sea level. Given how fast the stage descents, the issue might be how quickly the stage can sense the wind. We routinely see 50km/h wind shear in my home town (southerly 10 kts @ 1000ft, northeast 20kts @ 50ft).
A means to upload wind estimates for sea level, 500ft, 1000ft, 1500ft to the stage right before launch might be very helpful, if the rocket could incorporate wind estimates into its lateral profile.
The rocket seemed to be compensating very aggressively towards dead center, perhaps its taking a wee bit too long to fully sense the wind.
Windy conditions are common both at sea and at the coast. This would be an enhancement that might pay off in land and sea scenarios (although sea typically have stronger winds).
Learn from aviation, every decent airport transmit fresh wind data to landing craft (ATIS, tower frequency, wind socks visually read).
But it could be that this is just a natural fine tuning as a consequence of prioritizing landing hard as close as possible to bulleye vs landing softly at the edge of the barge, and now that they accomplished it, they can balance the two goals.
Coming down a little slower would help if possible, but with T/W > 1 they might already be at the edge of how early they can slowdown.
Wind shear/gusts probably a much bigger problem than total wind strength @ sea level.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: guckyfan on 04/15/2015 07:29 am
Assuming they expected some problems. Elon Musk indicated it by saying before the launch that the success probability is still low.

Then probably this is the reason why they cancelled the New Mexico tests with Falcon 9R-dev. Every test failure costs a stage. Better do it with stages from orbital launches. And they are getting closer.

As a sidenote. The video shows how much the engines can gimbal. Very impressive to see the exhaust flame wiggle. Even though it indicates a control issue.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: john smith 19 on 04/15/2015 07:30 am
It is unarguable that active guidance (the rocket doesn't need to communicate with the barge for that) is more precise, since by using absolute coordinates you add the errors in barge and rocket station navigation.
I don't know if SX have an active guidance system or not but I can provide a data point.

Radar altimeters can provide accurate height above ground and velocity. In the 1950's 4 antennas (front, back, left, right) at slight angles to the airframe to give deduced "ded" reckoning were simpler and more reliable than inertial systems (back when INS meant spinning metal lumps in very precise bearings).

Modern units use mm microwaves and are available for drones. They have ranges in the 500-1000m and weigh a few Kg.

Such a system requires no comm link to the barge and should work properly against any surface you'd choose to use as a landing site IE no boulders strewn across it.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sdsds on 04/15/2015 07:33 am
What pre-burner?
Merlin is a GG cycle engine

OK fine. Can I call it, "The place where the combustion that powers the turbine happens?"

;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rubtest on 04/15/2015 08:31 am
just a remark: the barge is probaby filmed/viewed from her short side and almost from sea level . that is why it looks so small. it is only the barge side cross section view. (look for the blue container on the barge for orientation ) . Great  amazing success spacex !
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Radical_Ignorant on 04/15/2015 10:44 am
Why can people understand that what is done on the barge will be the exact thing used on land?

Because all thing is still in progress and until it's established everything can change? And you are just repeating this: "barge is no go" like if more times you say it more likely people will listen to you? And temorary (as oposed to long term goals) can mean something like over 10 years?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: gommtu on 04/15/2015 10:55 am
Just a reminder, no one predicted success, including Elon. They fully expected to encounter issues like this.

Forum commentators often seem more interested in validating their own facile armchair analysis than taking the company at its word.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: junk.munk82 on 04/15/2015 11:25 am
had some fun with the spacex feed:
https://www.youtube.com/watch?v=RdKHrXy8ZUk
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LouScheffer on 04/15/2015 11:34 am
Quote
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)
This makes perfect sense.  In normal (ascent) operation, the valve makes few changes and those have large values (0-100% at startup, maybe down to 60% to limit acceleration at the end, then shutoff.   Plus maybe a dip at Max-Q, but I don't think SpaceX does that).  In these applications stiction is less likely since you are commanding a large change. So the valves have been nowhere near as extensively tested in the regime of small, fast, and frequent changes.

I really appreciate this transparent failure analysis.  I suspect the same happens during the traditional failure analysis, too - often they have an excellent idea, very early on, of what caused the problem.  I appreciate that you still need to complete the analysis, to look for other problems and to see if this is the only plausible explanation, but it's good to see intermediate results.  It gives a feel for the (likely) corrective measures much earlier.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ugordan on 04/15/2015 11:36 am
So the valves have been nowhere near as extensively tested in the regime of small, fast, and frequent changes.

It could have been extensively tested in McGregor, on an engine test stand.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JamesH on 04/15/2015 12:05 pm
So the valves have been nowhere near as extensively tested in the regime of small, fast, and frequent changes.

It could have been extensively tested in McGregor, on an engine test stand.

It probably was. Was this a failure in flight, or something that was always there? I suspect the former.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cuddihy on 04/15/2015 12:10 pm
Its not uncommon to see 30km/h wind shear from 1000ft to sea level. Given how fast the stage descents, the issue might be how quickly the stage can sense the wind. We routinely see 50km/h wind shear in my home town (southerly 10 kts @ 1000ft, northeast 20kts @ 50ft).
A means to upload wind estimates for sea level, 500ft, 1000ft, 1500ft to the stage right before launch might be very helpful, if the rocket could incorporate wind estimates into its lateral profile.
The rocket seemed to be compensating very aggressively towards dead center, perhaps its taking a wee bit too long to fully sense the wind.
Windy conditions are common both at sea and at the coast. This would be an enhancement that might pay off in land and sea scenarios (although sea typically have stronger winds).
Learn from aviation, every decent airport transmit fresh wind data to landing craft (ATIS, tower frequency, wind socks visually read).
But it could be that this is just a natural fine tuning as a consequence of prioritizing landing hard as close as possible to bulleye vs landing softly at the edge of the barge, and now that they accomplished it, they can balance the two goals.
Coming down a little slower would help if possible, but with T/W > 1 they might already be at the edge of how early they can slowdown.
Wind shear/gusts probably a much bigger problem than total wind strength @ sea level.

For fixed wind aircraft the issue is not wind shear but cross wind, ie, wind perpendicular to the direction of landing. This is so important for low-speed landing aircraft at sea, on an aircraft carrier for instance, that the ship actually determines its heading based on where the wind needs to flow across the deck at the correct angle & velocity. The officer of the deck for a carrier during flight ops is literally giving rudder orders while staring at an anemometer and wind direction indicator. The wind can be significantly different between the bow and the landing ramp, and it can change pretty fast, so it might actually be counterproductive to send wind data from deck level to the aircraft when it may be totally useless information until the last second or two--which is too late for even an automated system to adjust.
While carriers do have systems that transmit landing data to aircraft for better precision landing, it's pretty much positional information for the aircraft to get on the right glide slope. I think a returning F9 stage would be in a similar position -- the wind data you'd send up is not terribly useful until the point where it's almost too late. Better to tune the system response including throttle response until it's quick enough to stick the landing based on information it has onboard the rocket.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: speedevil on 04/15/2015 12:17 pm
While carriers do have systems that transmit landing data to aircraft for better precision landing, it's pretty much positional information for the aircraft to get on the right glide slope. I think a returning F9 stage would be in a similar position -- the wind data you'd send up is not terribly useful until the point where it's almost too late. Better to tune the system response including throttle response until it's quick enough to stick the landing based on information it has onboard the rocket.

A hundred quadcopters In a cone 200m or so in diameter, and 1km or so tall would allow most wind to be predicted 'live'.
These could likely even be resold for a profit.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Remes on 04/15/2015 12:24 pm
Quote
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.
Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)
[...]I really appreciate this transparent failure analysis.
The tweet got deleted.

Anyway. I think the "normal" plan was to land with a rocket without any rotational movements (very much like the Grasshopper). But in the vine video the rocket has a clockwise rotation even at the beginning. Also it seems to me, that the tvc is pointing the plume to the right. So it was counteracting a previous rotational movement. Likely the rocket oscillated the whole way down.

Nevertheless it is quite impressive that the system found a solution to touch down vertically. Not good enough to survive, but given that there was some technical issue, still impressive.

In contrast to some comments: Hovering would have helped. Hovering helps to decouple different states. It could have allowed to zero out all rotational movements. It would allow to correct final deviations a meter or two above the surface and then land. It also gives more margin in general. We have a system, where the engine starts at e.g. 40m/s (downwards) and has to decelerate to e.g. 2m/s. Somewhere (e.g. 4m/s) is the limit of the system (landing legs able to compensate impact). The system must never come close to 0m/s as there is no way out (with a acceleration upwards the only thing to do is to switch of the engine). So effectively the final velocity setpoint is never 0 but something between 0 and the crash velocity. Taking away margin.

There are really a lot of constraints imposed on the system by not beeing able to hover. So many things have to work perfectly towards the final moments.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 12:41 pm
Testing on actual flights is the best way to go. There was considerable cross wind, aside from sticky valve weather variation is an issue that will need to be addressed.

This landing attempt was close enough to good that if they modify the surface with some kind of numerous rapidly deployed grappling mechanisms to secure legs and pull rocket into deck securely they could have less precise landings become successes.

I envision a landing pad at sea or on land with numerous such mechanisms to secure the base of the rocket as its landing. Otherwise the rocket is too tall, and the legs with to small a diameter to assure landing in a majority of landing weather conditions, even with the valve issue solved.

I hope SpaceX starts working at securing the rocket more rapidly immediately to ensure both an initial successes and a higher rate of subsequent successes.

That is just unnecessary complexity and not going to happen.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 12:42 pm

It would be nice if the Falcon9 had switchable power profiles for just the center engine.  Maybe switch over to a different fuel plumbing circuit prior to landing that would produce less power and a better possibility of hovering.

not feasible with existing engines or any engines.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Razer on 04/15/2015 12:49 pm
We have a system, where the engine starts at e.g. 40m/s (downwards) and has to decelerate to e.g. 2m/s. Somewhere (e.g. 4m/s) is the limit of the system (landing legs able to compensate impact). The system must never come close to 0m/s as there is no way out (with a acceleration upwards the only thing to do is to switch of the engine). So effectively the final velocity setpoint is never 0 but something between 0 and the crash velocity. Taking away margin.

4m /s  it's just a value that you can imagine or it is a real value ?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: john smith 19 on 04/15/2015 12:52 pm
There are really a lot of constraints imposed on the system by not beeing able to hover. So many things have to work perfectly towards the final moments.
True.

And all due to a valve failing to open when commanded to?

It seems the current Merlin 1d can't do deep enough throttling to cover (which surprised me).

Perhaps a Merlin 1e will be needed?

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Mader Levap on 04/15/2015 12:57 pm
I beleive SX will get there but it's been interesting to see how something that is conceptually simple, and which should be pretty well simulated has taken 4 landings and still not resulted in a complete stage ready for reuse or analysis.  :(
Baysian statistics would have to penalize your chances of #5 being successful.  :(
They are getting closer each time.

According to your logic (the more falied tries, the less chance that you will have success), no modern civilization could exist. Or my job (programming), for that matter.

That logic would be something resembling "correct" only if no fixes and/or changes was done between tries.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: aceshigh on 04/15/2015 01:19 pm
what amazes me, is that the part that was NOT tested (re-igniting the engine, decelerating from orbital speed to a few meters per second, atmospheric re-entry, finding a 100 meter barge in the middle of the ocean, going from orbit to that spot), all that IS WORKING.


it´s only the final precision stuff, small lateral motions, small changes in velocity (on the order of a few meters per second), etc, that are the problem right now. Which is something they had tested with Grasshopper and Falcon 9 itself in Texas.

layman logic would say that, having tested the landings in Texas, the difficult part was the untested part: finding the barge, restarting the engine, decelerating from orbit to a few meters per second and positioning the rocket over the barge. Once that was done, the theory is that it would be almost the same as they did in Texas...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/15/2015 01:20 pm
we don't know for sure it was a valve problem. There was a tweet about it which has since been deleted. Whether the tweet was accurate but was sent out when it shouldn't have been,or whether the tweet was incorrect we will only find out in time.

There are really a lot of constraints imposed on the system by not beeing able to hover. So many things have to work perfectly towards the final moments.
True.

And all due to a valve failing to open when commanded to?

It seems the current Merlin 1d can't do deep enough throttling to cover (which surprised me).

Perhaps a Merlin 1e will be needed?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MostlyHarmless on 04/15/2015 01:21 pm
There's been a lot of discussion describing the valve stiction as a "failure" or a sticky valve.  Stiction is not the same as "sticking." 

"Stiction" or static friction is a feature of any system with moving parts.  Put a book on a level board, then slowly tilt the board.  At low angles, the book stays in place due to what's called static friction.  Once the tilt is enough to provide enough force to overcome the stiction, the book will slide down the ramp.

At some point before this, however, the book may still be stationary -- but if you give it a slight push, it will then accelerate down the ramp.  The slight push you gave it was enough to overcome the static friction holding the book in place -- once moving, it will continue to move.

Stiction will cause a delay in a system response.  You might expect the book to slide down the ramp when you tilt it past 20 degrees slope.  If the amount of stiction is underestimated, it might not slide until you get past 40 degrees.  Thus, you have a response delay that will be underestimated.  Same with the moving parts in a valve.    The same could happen if there was a mechanical problem that caused increased stiction, but we don't know that, yet.  Based on the tweet and the confidence expressed, I tend to think it was the former, since that would be a much easier fix (what could be a simple change of software parameters describing the response delay) than to determine an underlying cause of a unexpected valve stiction. 

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 01:29 pm
finding the barge,

It doesn't "find" the barge.  It flies to a specific location on the ocean.  The barge just happens to be there.  That is why the barge has all the thrusters, to make sure it is at the same location.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/15/2015 01:37 pm


I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?
I'll take that bet.  The curvature of the earth isn't going to change, and if the barge is still in service landings will be taking place *further* from ground stations, not closer.  So you're saying that in five years high-bandwidth video from the middle of the ocean will be stupid cheap.  Presumably because of SpaceX's new constellation?

It will happen eventually, but not within five years.

We might eventually get access to the same very slow frame rate video which SpaceX is watching in the control room, but I'm assuming that's not what you're taking about.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LouScheffer on 04/15/2015 01:38 pm
Looking at the video (https://vine.co/v/euEpIVegiIx) I'm struck by the dramatic attitude changes. [...]
This seems weird to me as well.  You need attitude changes to do translation, but I'd think the algorithm would do the attitude changes first, while high up, until the rocket is directly over the barge with no angular velocity (just like the maneuver at the end, but higher up).  Then the remainder of the landing is straight down, maybe pointing the nose into the wind to stay on course.  At the last minute, rotate back to vertical.  A sticky throttle valve should not affect this overall behavior.

Instead, it looked like it realized, too low, that it was not in the right spot.   It tried to translate back, but this required large attitude changes, and could not be completed in time.  Now why was it in the wrong spot?  Maybe the wind had a bigger effect than anticipated? Maybe they null the rates at higher altitude, including the wind, but the surface winds are different?  At any rate it's hard to see this problem being caused by a sticky throttle, so I think there is at least one more control/algorithm problem.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JamesH on 04/15/2015 01:40 pm


I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?
I'll take that bet.  The curvature of the earth isn't going to change, and if the barge is still in service landings will be taking place *further* from ground stations, not closer.  So you're saying that in five years high-bandwidth video from the middle of the ocean will be stupid cheap.  Presumably because of SpaceX's new constellation?

It will happen eventually, but not within five years.

We might eventually get access to the same very slow frame rate video which SpaceX is watching in the control room, but I'm assuming that's not what you're taking about.

Agreed. A satellite link for 10Mbits/s for half decent HD video would be required (H265 would give decent quality at 1080p at that bitrate). I don't know the numbers, but I assume that at the moment that is an expensive proposition, and not likely to change without a new constellation.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JamesH on 04/15/2015 01:43 pm
what amazes me, is that the part that was NOT tested (re-igniting the engine, decelerating from orbital speed to a few meters per second, atmospheric re-entry, finding a 100 meter barge in the middle of the ocean, going from orbit to that spot), all that IS WORKING.


it´s only the final precision stuff, small lateral motions, small changes in velocity (on the order of a few meters per second), etc, that are the problem right now. Which is something they had tested with Grasshopper and Falcon 9 itself in Texas.

layman logic would say that, having tested the landings in Texas, the difficult part was the untested part: finding the barge, restarting the engine, decelerating from orbit to a few meters per second and positioning the rocket over the barge. Once that was done, the theory is that it would be almost the same as they did in Texas...

I don't believe the tests in Texas would have had much influence here. Until they start testing decent at the rates experienced from a real launch, from pretty high up, then the tests to now  are fairly tangential.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: fthomassy on 04/15/2015 01:46 pm
A sticky throttle valve should not affect this overall behavior.
Why you would think that?  Did you see the thrust vectoring?  That behavior could be directly related.
Edit: Hedging with "could be"
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Remes on 04/15/2015 01:58 pm
4m /s  it's just a value that you can imagine or it is a real value ?
Only an example, no real value.

The attached picture shows a grasshopper landing. Vertical line is the travelled distance of one leg in 73 frames. Horizontal line is the stage diameter with 3,6m. This gives me a velocity of about 7.5m/s. But grasshopper is not falcon 9 first stage. Less engines, etc.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/15/2015 02:06 pm
Seems reasonable to me that some minor station-keeping maneuvering while low to the ground might have caused an unexpectedly large attitude deviation (which then wasn't correctable in time) if there was some throttle delay at an inopportune time.  That is, the problem isn't that they were far off-target and then needed to make a large correction, the problem is that their normal small correction unexpectedly pushed the stage over, and then they couldn't recover in time.

And when a CEO says "easy to fix" you know the actual engineers on the ground are in for a tough two months of work.  "Looks easy to a CEO" is not the same as "easy".  It just means "well-understood".

I'm also of the opinion that the stiction was probably caused by some feature unique to the reentry profile: four engine cycles with periods of vacuum, some pretty aggressive thermal cycling, and probably unusual vibration during no-thrust periods as well.  Perhaps some ice formed on part of the valve body.  Or perhaps the vacuum conditions meant that ice *didn't* form, and the ice usually insulated some part of the valve. Those are the sorts of things that are hard to predict from ground testing.

Of course it's also possible it's an oversight, since stiction is harmless at any point over than 100' above the barge.  Stiction might have been noticed, bounded, checked for ill effects, and then dismissed previously.

I will say that the sluggish liftoff is almost certainly *not* related.  Falcon has always been slow to lift off, as are all liquid-fueled rockets in general.  That's normal.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rst on 04/15/2015 02:08 pm
it´s only the final precision stuff, small lateral motions, small changes in velocity (on the order of a few meters per second), etc, that are the problem right now. Which is something they had tested with Grasshopper and Falcon 9 itself in Texas.

Well, to some extent.  The Grasshopper tests did involve tilts for horizontal divert maneuvers, but at least the ones I saw all involved pretty slow attitude changes.  The CRS-6 stage came in with tilt changing a whole lot faster than that, which would make control system lag a lot more of a problem -- and oscillations in tilt are one kind of problem which is likely to develop in this sort of situation.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JasonAW3 on 04/15/2015 02:12 pm
While carriers do have systems that transmit landing data to aircraft for better precision landing, it's pretty much positional information for the aircraft to get on the right glide slope. I think a returning F9 stage would be in a similar position -- the wind data you'd send up is not terribly useful until the point where it's almost too late. Better to tune the system response including throttle response until it's quick enough to stick the landing based on information it has onboard the rocket.

A hundred quadcopters In a cone 200m or so in diameter, and 1km or so tall would allow most wind to be predicted 'live'.
These could likely even be resold for a profit.

I'm just suprised that Quadcopters and other drone types haven't been used more for stormchasing and hurricane monitoring.  While signal degradation can occure due to electrical interference in storms like that, as sufficently broadband and multiplexed two way signal should assure both data retreival as well as positive command and control of said craft.  Ther would, of course, have to be a good deal of local autonimy for Quadcopters in storms like these, so it can vary rotor speeds and maneuvering to maximize platform stability to gather accurate and usable data and video.

The same can be applied in this case, and may be applicable to the landing of teh stage itself, so long as the onboard systems are getting sufficent information on airspeeds and directions, platform direction and elevations, etc.  Even in a light seastate, there is still some movement and shifting of the target platform that could have been a factor in the lateral velocity issue.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 02:14 pm
A hundred quadcopters In a cone 200m or so in diameter, and 1km or so tall would allow most wind to be predicted 'live'.
These could likely even be resold for a profit.

and would provide useless information
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LouScheffer on 04/15/2015 02:16 pm
A sticky throttle valve should not affect this overall behavior.
Why you would think that?  Did you see the thrust vectoring?  That behavior could be directly related.
Edit: Hedging with "could be"
Because even with a sticky throttle, you have plenty of time and control authority to adjust the course to hit the center of the barge, and to null angular rates.  That whole process took about 3 seconds in the video, though it was not quite completed in time.  But 30 seconds is way more time than you need to do this, at any throttle setting.  And once on course, the wind should not be enough to throw you off.  Say Falcon is 30m high, 3.66 m in diameter, wind 10 m/s (more than reported), Cd = 1, then the side force is 11,000 N.  The engine, even throttled down, has a force of 500,000 N or so, so a 1 or 2 degree deflection of the engine (much smaller than seen on the video) should be more than enough to compensate for wind and keep it on course, again at any throttle setting.

So what I can't see is a sticky throttle causing the need for a last minute course correction.  A straight down descent smashing into the barge too hard, or the rocket coming to a stop too high and starting to climb, these could be caused by a sticky throttle.  But the wild, last-second maneuvers must have been caused by some other problem.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: macpacheco on 04/15/2015 02:17 pm
I don't think SpaceX will increase the barge bandwidth until they have their own constellation.
They could download the video slower afterwards remotely. Even a 256 or 512kbps uplink is enough to get a 1080p very short video in the order of 10 minutes (like a 1 minute video).
Having online streaming isn't for SpaceX proper, but rather for marketing. SpaceX can post the video an hour later without extra costs.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: hrissan on 04/15/2015 02:17 pm
Quote
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)
This makes perfect sense.  In normal (ascent) operation, the valve makes few changes and those have large values (0-100% at startup, maybe down to 60% to limit acceleration at the end, then shutoff.   Plus maybe a dip at Max-Q, but I don't think SpaceX does that).  In these applications stiction is less likely since you are commanding a large change. So the valves have been nowhere near as extensively tested in the regime of small, fast, and frequent changes.

I really appreciate this transparent failure analysis.  I suspect the same happens during the traditional failure analysis, too - often they have an excellent idea, very early on, of what caused the problem.  I appreciate that you still need to complete the analysis, to look for other problems and to see if this is the only plausible explanation, but it's good to see intermediate results.  It gives a feel for the (likely) corrective measures much earlier.
Biprop valve... Could some kerosene be frozen by the LOX changing the friction? Or may be just contamination or manufacturing defect.

The rocket oscilation pattern looks classic. Here is probably how it develops:

Computer gimbals engine left (tvc does it immediately) and throttles up a bit to compensate for cosinus losses, but the valve does not move because of increased static friction, after some delay the computer senses that thrust is not enough, so it commands to throttle up more, this repeats several times until control force overcomes friction, the valve suddenly moves increasing thrust a lot, with the engine still gimballed, which moves the bottom of the stage too far right.

The cycle continues.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ThereIWas3 on 04/15/2015 02:31 pm
I'm just suprised that Quadcopters and other drone types haven't been used more for stormchasing and hurricane monitoring.

Quadcopters are pretty useless in any kind of wind.  They would just get blown away like leaves.  Unless you are talking about a quadcopter about the size of, well, a full size helicopter.  And even those stay away from hurricanes.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DatUser14 on 04/15/2015 02:58 pm
might the landing have looked something like 13:43 or 14:10 in this video?
https://www.youtube.com/watch?v=C9I55o8hQgs
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Senex on 04/15/2015 03:01 pm
Looking at the video (https://vine.co/v/euEpIVegiIx) I'm struck by the dramatic attitude changes. [...]
it looked like it realized, too low, that it was not in the right spot.   It tried to translate back, but this required large attitude changes, and could not be completed in time.

Lou's right.

Flying in to Grande Prairie, Alberta back in 1980, in a 737, I was back in the cabin reading as we broke through the low clouds to land.  I looked out to the left to see the runway not under us, but beside us.  I thought "no big deal," the pilot will just go around.  Instead, he banked hard left and then right, trying to line up on the the runway.  I didn't breathe the whole time — it's while trying to save a landing that has already gone bad that very bad things happen.  In the end he, fortunately, accepted the inevitable and aborted the landing. 

There is an adage in flying that a good landing is the result of a good approach — you are where you should be, at the right altitude, at the right speed.  The Falcon's landing had already gone bad pretty much by the start of what we see in the Vine.  Only extraordinary measures might have saved it.  And in this case, they didn't.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Xentry on 04/15/2015 03:05 pm
First of all let me congratulate the astonishing job SpaceX have done with both their sequence of successful Falcon 9 and Dragon missions, as well as express my greatest respect for all the effort spent so far on trying to get an F9 back to Earth.

Having said this, and from all the information I've been able to get, I am intrigued by a few things... Namely:

1. From the last two Vine videos shown, the horizontal corrections close to landing are pretty dramatic, while the vertical motion seems to be pretty much under control. Looks like the problems they still have are definitely related to the latter. So are they a result of having an excessively large initial horizontal dispersion at the start of the final burn? Are they a result of the onboard computer not "seeing" the lateral wind until late in the game since they are descending crazily fast until the very end? Is the position control being too demanding on the actuators (are they too slow?)? Is the whole Guidance and Control system close to the limitations of sensors, algorithm, actuators and onboard computer?

2. How demanding must the position control actually be, and what would happen if they simply stopped trying to hit a specific X-Y-Z position + X-Y-Z velocity state, and just went for a zero height and velocity vector instead, no matter the X-Y position, once they're sure to land within a few 100 feet of the target? Wouldn't such a solution be easier to achieve, as well as more applicable to the case at CCAFS where they will have much larger pads to land on?

3. SpaceX is now very very close to landing an F9, but might have to try a few more times before getting it right, which might take several months more. Since most of the technical hurdles to recover their rocket have been overcome, and the next part of the job - which surely involves thoroughly inspecting each part of a recovered vehicle to know what needs to be refurnished/redesigned to allow full reusability - may take quite some time to to complete, is there a case for making a special effort right now to somehow grab the vehicle once it gets to the barge "no matter what", even knowing this would be a transitory measure?

I guess these are mostly rhetorical questions, but still... as an aerospace engineer involved in Guidance and Control systems for planetary EDL missions, would sure love to know more about them... ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rcoppola on 04/15/2015 03:08 pm
IMO:

Looking at the video, if it was stiction of some kind, (noting that the tweet has since been deleted), just around the 2 second mark is where it would appear to have caused the overcompensation at the end of the return profile. If you look at the stable return path as it initially enters into the frame and then imagine that 1 second valve stiction issue did not happen, you can see that it would have nailed it. At least, that's what I see in the minds eye. It would have been one of those initially angled hover-slams we have now seen many times but instead went too far over, drastically compensated, causing serious lateral motion with no more room (ie. time/height, etc.) to correct and slid right off.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: fthomassy on 04/15/2015 03:08 pm
A sticky throttle valve should not affect this overall behavior.
Why you would think that?  Did you see the thrust vectoring?  That behavior could be directly related.
Edit: Hedging with "could be"
Because even with a sticky throttle, you have plenty of time and control authority to adjust the course to hit the center of the barge, and to null angular rates.   
... sniped the remainder ...
Not if the sticky issue disrupts your control feedback.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jcc on 04/15/2015 03:12 pm

Quote
@ID_AA_Carmack Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

Source Tweet (https://twitter.com/elonmusk/status/588166157510828033)


I am wondering how Carmack made this determination. Was he given the data by SpaceX engineers, or is it based on his own experience at Armadillo with a totally different rocket?

I can see why Musk respects Carmack, but I can't see how you can say it was a stuck valve by just looking at a few images and then the Vine clip. So, it is a SWAG, or else he is being given data that was not publicly released.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/15/2015 03:14 pm

I am wondering how Carmack made this determination. Was he given the data by SpaceX engineers, or is it based on his own experience at Armadillo with a totally different rocket?

I can see why Musk respects Carmack, but I can't see how you can say it was a stuck valve by just looking at a few images and then the Vine clip. So, it is a SWAG, or else he is being given data that was not publicly released.

The tweet is from Musk to Carmack
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jcc on 04/15/2015 03:22 pm

I am wondering how Carmack made this determination. Was he given the data by SpaceX engineers, or is it based on his own experience at Armadillo with a totally different rocket?

I can see why Musk respects Carmack, but I can't see how you can say it was a stuck valve by just looking at a few images and then the Vine clip. So, it is a SWAG, or else he is being given data that was not publicly released.

The tweet is from Musk to Carmack

D'oh!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/15/2015 03:24 pm
More complicated than that. You'd need to compare telemetry/tracking with sims.

Depends on where/when the deviation occurred. Remember that the stage bends - can act like a whip if you apply too much force at the wrong time. So even considerable increase isn't an instant answer.

Once you find where the issue is (by matching a sim to actual), you rerun the sims with increased thrust til it begins to work, then you exhaustively simulate variations to prove you've adequately bounded the situation. Tedious.
And that's the interesting question about this.

SX, like all major players, design their LV's and spacecraft in CAD systems. In principle a design should be available for input to dynamics simulation models almost from the day it's frozen. Modern computer time is cheap so they would have been able to lots of sims of this process and their models should have been high fidelity.

So what was missed this time?

I've just looked at the cleaned up footage and wow does that puppy waggle.

Either I'm recalling only stills from previous landing movies or this was really flapping about, like a failed launch from the 1950's  :(

I beleive SX will get there but it's been interesting to see how something that is conceptually simple, and which should be pretty well simulated has taken 4 landings and still not resulted in a complete stage ready for reuse or analysis.  :(

Baysian statistics would have to penalize your chances of #5 being successful.  :(


Baysian statistics only applies when you are not iteratively applying new data and analysis to each increment.  Not the case here.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/15/2015 03:28 pm
It is unarguable that active guidance (the rocket doesn't need to communicate with the barge for that) is more precise, since by using absolute coordinates you add the errors in barge and rocket station navigation.
I don't know if SX have an active guidance system or not but I can provide a data point.

Radar altimeters can provide accurate height above ground and velocity. In the 1950's 4 antennas (front, back, left, right) at slight angles to the airframe to give deduced "ded" reckoning were simpler and more reliable than inertial systems (back when INS meant spinning metal lumps in very precise bearings).

Modern units use mm microwaves and are available for drones. They have ranges in the 500-1000m and weigh a few Kg.

Such a system requires no comm link to the barge and should work properly against any surface you'd choose to use as a landing site IE no boulders strewn across it.

Thanks.

I agree, if there's a terminal guidance system, it doesn't require comm to the barge.

There are plenty of ways to implement it (I like the one you describe) and it will increase accuracy.
We are also pretty sure that a Z-axis terminal guidance system is in fact implemented.

Jim says he has inside info that an X-Y system isn't implemented.

That's a good place to leave it...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: dgates on 04/15/2015 03:51 pm
I would note in passing that they apparently did not run out of hydraulic fluid this time!  I guess they can cross that problem off the list! 😀
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: iamlucky13 on 04/15/2015 03:58 pm

I am wondering how Carmack made this determination. Was he given the data by SpaceX engineers, or is it based on his own experience at Armadillo with a totally different rocket?

I can see why Musk respects Carmack, but I can't see how you can say it was a stuck valve by just looking at a few images and then the Vine clip. So, it is a SWAG, or else he is being given data that was not publicly released.

The tweet is from Musk to Carmack

I was able to read the tweet last night, but now I'm getting a "page does not exist" message from Twitter when I try to access it again.

I wonder if Musk was just flipping jargon at Carmack for fun and took it down when he got flooded with questions about what it means.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/15/2015 04:11 pm
What's the standard remedy for valve sticking?

A spritz of this...

Before I open my yap on this I want to preface my comments by saying that I'm strictly responding to the question in the first quote above (edit: at least initially, before I broadened my comment below) and not trying to tell the valve experts that are at work on this how to do their job which they are certainly vastly more qualified than I to do.

Any proportional valve in general industrial, automotive, or similar use will have stiction.  If you were to vary the input signal by simply ramping up a DC current you'd find that the output would change in discrete jumps.  For many valves in many applications (that probably amounts to most) the jumps in output are too large to be acceptable.  So rather than send a varying DC signal to a proportional valve its common to superimpose an AC signal or to PWM the signal such that the armature and valve element (typically spool) aren't just being asked to move when the valve output is to change but rather they are always in some small motion.  This way the friction applicable to moving the valve from one desired setting to another is dynamic friction, not static friction.  The video below will show some detail on this (action starts at :36).  Note that while this solution works for many situations the dynamics may be upsetting for a rocket engine, I don't know.  Also, dither can be applied to a solenoid operated valve but wouldn't be a solution to a valve with ball screw drive or similar.  In any case the people that are dealing with this know so much more about this subject than I do that I'm feeling exposed in just writing these words.

https://www.youtube.com/watch?v=aq35FD01bZ0

Also, recall that CRS-1(?) had a stuck valve that took a lot of cycling / hammering before it became active.  From what little info I have seen posted, I think that valve was supplied by the same supplier that provided the propellant valve now in question.  If its true that one supplier provided both stuckified valves then there might be some movement on SpaceX's part to bring this in house.  But the time to develop a valve in house would probably be much longer than the time it will take the supplier to modify and qualify their existing valve.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/15/2015 04:11 pm
Had he mentioned the Turbo-Encabulator maybe there would have been fewer questions.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cambrianera on 04/15/2015 04:19 pm
I need to watch the video a few more times to see if I can make out the moment of leg deploy, but I have to wonder if the late deploy, into a steady sea breeze, isn't what causes the pitch excursion due to the sudden increase in drag at the base of the vehicle relative to the wind. Those rapidly-telescoping legs and their bases have much greater area drag than the relatively featureless cyclinder of the rest of the stage.

IMHO you nailed it.
To expand it, I believe that deployment of the legs moved down the Center of Pressure of the stage, zeroing its distance from Center of Gravity; it also increased total drag.
This means three correction had to be done in same time:
lateral acceleration due to the increased wind drag;
rotational acceleration  due to the gimbal of the engine (now excessive);
angle of the stage (being not vertical but slightly angled to compensate momentum due to wind).
Corrections were fast, but not enough.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/15/2015 04:20 pm
I don't know how this whole twitter thing works.  Really.  But when I saw the previously linked Carmack / Musk interchange last night my first thought was to give not so much credence to the propellant valve theory because somewhere shortly before or after that comment Carmack(?) was asking whether the final firing was being done with just one or more than one engine.  My take away at the time was that anyone asking that question knows less about this than nearly anyone here.  But this morning I see it mentioned that the bipropellent valve comment came from EMusk, not Carmack.  Is that correct?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: hrissan on 04/15/2015 04:21 pm
Good analogy on what happens when there is an unexpected delay in control loop...

Fast forward to 0:25, stupid youtube fails to embed start time correctly. :(:(:(


http://youtu.be/QikCYIE3SI0?start=25
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jarnis on 04/15/2015 04:22 pm
I don't know how this whole twitter thing works.  Really.  But when I saw the previously linked Carmack / Musk interchange last night my first thought was to give not so much credence to the propellant valve theory because somewhere shortly before or after that comment Carmack(?) was asking whether the final firing was being done with just one or more than one engine.  My take away at the time was that anyone asking that question knows less about this than nearly anyone here.  But this morning I see it mentioned that the bipropellent valve comment came from EMusk, not Carmack.  Is that correct?

Yes, it was a Musk tweet to Carmack.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/15/2015 04:43 pm
I need to watch the video a few more times to see if I can make out the moment of leg deploy, but I have to wonder if the late deploy, into a steady sea breeze, isn't what causes the pitch excursion due to the sudden increase in drag at the base of the vehicle relative to the wind. Those rapidly-telescoping legs and their bases have much greater area drag than the relatively featureless cyclinder of the rest of the stage.

IMHO you nailed it.
To expand it, I believe that deployment of the legs moved down the Center of Pressure of the stage, zeroing its distance from Center of Gravity; it also increased total drag.
This means three correction had to be done in same time:
lateral acceleration due to the increased wind drag;
rotational acceleration  due to the gimbal of the engine (now excessive);
angle of the stage (being not vertical but slightly angled to compensate momentum due to wind).
Corrections were fast, but not enough.

I thought I'd done a convincing job of debunking that theory already.  At least I convinced me.  Not sure if you didn't see it or didn't believe it.  In case you didn't see my dubunk, it goes like this-

In the video you can't see the legs, other than one which is slightly visible when its nearly on the deck.  This leads one to think that the legs didn't come out until the last moment which is incorrect.  The video compression has erased the legs from all but that one glimpse even though they are definitely out.  They can be seen to be mostly deployed  in the still picture that came out immediately before the vineo.  The stage is hundreds of feet up when they come out.  There's an 8 second difference between legs out and landing.  I don't think the last minute CP shift theory works with that much legs in the breeze time, does it?

~Changing subjects now~

There has been discussion of the stage rotating around its long axis during descent.  I'm not sure I can see it, maybe I see some rotation as it nears the deck. If there is substantial rotation then;
a) We're back (partially at least) into a problem that centerfuged the propellant away from the pickup ports and reduced thrust at the end of the first (legless ) attempt at at water landing.  Which was corrected on subsequent attempts by a doubling of the N2 thruster system capability, and later grid fins.  But if there was some centerfuging which reduced fuel availability (keep in mind that the tanks are ~99% empty) the result would be the inability to achieve 100% thrust, the same result that would come from a sticky propellant valve.
b) Put your structural engineering hats on for a second and let's think about leg failure.  Legs can fail by folding up but in that case the forces are all in line with the cylinder and leg and pivot points, and the cylinder would (assuming it doesn't have some ratchet or brake mechanism) absorb quite a lot of energy.  .or. Legs can fail by the introduction of side load.  It wouldn't take much side load to overload the legs because the two mounting points at the base of the leg are so close together relative to the length of the leg.  It wouldn't take much rotation or translation of the stage to exceed the side load limits of a leg.  I'll bet on this vs. folding up as the leg failure mode.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MP99 on 04/15/2015 04:56 pm



In this case, it was stiction, i.e. static friction. The valve didn't start moving when it was told to, and so the rest of the control system lagged behind. The fix could be as simple as commanding the valve to open, perhaps not even fully, a second earlier to overcome stiction and be ready to respond to input immediately when received. Of course it could also be more complicated than that, but from Elon's tone, it shouldn't be a huge deal.

Of course, then they run into the next thing to go wrong...

So is the valve sticking/stiction for this particular valve something that's manifested itself before? Otherwise, what bad time for it to suddenly/randomly make an appearance. Maybe it was the high intensity operation and demanding nature of this landing which caused the valve to underperform.

It's my guess that engine is gimballing far more than it ever would in flight. Possible factor?

Cheers, Martin
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/15/2015 04:59 pm
The fact that the tweet was deleted isn't necessarily terribly significant:

1) someone might have tapped Elon on the shoulder and whispered "ITAR".  Better safe than sorry (even though ICBMs don't need to land!).

2) Elon might have realized he might be prejudicing his engineer's investigation by talking too publicly about initial findings.  Employees tend to listen to the CEO, even if this was not meant as "CEO" conversation.

3) A second engineer might have said, "oh, but it might also be XYZ" and Elon decided he wasn't so certain after all.  (This is the option that will fuel discussion here on NSF until June.)

4) Elon switched to private email for his chat with Carmack, and cleaned up after himself.

5) Too many folks (including reporters) started flooding his inbox with questions after the stiction comment, and he decided he'd rather try to unsay it than have it on the record and appear in news stories.  (It's the landing attempt, not the successful CRS launch, which led most of the new stories I saw.)

After all, he was sure that Carmack received the tweet, so there was nothing to be gained by leaving it up.  And maybe he and Carmack then did a little deep dive into the valve mechanics in a non-public forum.  We just happened to overhear some private conversation... lucky us!

ps. Elsewhere on NSF somebody else noted that Elon is in the habit of deleting his twitter @- messages after they are received, which lends support to option 4.  How boring!  I'm sure we'll try to believe option 3 anyway. ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cambrianera on 04/15/2015 05:03 pm
@OxCartMark,
In the picture that surfaced before the video, legs are half deployed (that means picture was taken during deployment).
Deviation of rocket in the video happens right after that moment.
But this is my opinion, I've debunked nothing.
And clearly if you don't agree with me or with Herb, you are full entitled to that. ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kim Keller on 04/15/2015 05:03 pm
For those commenting on late deploy of the legs, that event happens at Landing -6 seconds. The vine starts just after leg deploy.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: eriblo on 04/15/2015 05:14 pm
For those commenting on late deploy of the legs, that event happens at Landing -6 seconds. The vine starts just after leg deploy.

And full deployment takes at least 2-3 seconds from previous videos. It might be a little unsymmetrical and likely represent the biggest change of aerodynamics since the stage went subsonic. Personally I wouldn't rule out a contribution to the need for the questioned "late maneuvering" (which might or might not have had extra control loop lag).
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CapitalistOppressor on 04/15/2015 05:14 pm
So the valves have been nowhere near as extensively tested in the regime of small, fast, and frequent changes.

It could have been extensively tested in McGregor, on an engine test stand.

Could environmental factors be at play here?  I'm not an engineer or familiar with rocket engines, but the stage ascended into a near vacuum then reentered the atmosphere tail first at hypersonic velocities. 

Even if this valve isn't exposed to the outside environment, I'd still think that there would be rapid temperature changes and possibly other effects that are unique to the flight profile and which would not be simulated on a test stand.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: iamlucky13 on 04/15/2015 05:19 pm
The fact that the tweet was deleted isn't necessarily terribly significant:

I agree, but it was still worth pointing out the tweet is gone.

Given Carmack's own deep interest in engine development and control, it definitely could have been part of a real discussion.

Also, several of your points actually are significant. #2 and #3 would mean the cause is not certain, which would not be a surprise just a couple hours after the engineers had their first look at the telemetry. That in turn would mean we shouldn't get too attached to the valve stiction comment, although some good discussion did come out of that.

In fact, I've worked a bit with industrial proportional valves, and had encountered the issues caused by stiction, but not to a critical degree that I had to resolve. So the dithering video was some new, interesting info to me.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kim Keller on 04/15/2015 05:21 pm
And full deployment takes at least 2-3 seconds from previous videos. It might be a little unsymmetrical and likely represent the biggest change of aerodynamics since the stage went subsonic. Personally I wouldn't rule out a contribution to the need for the questioned "late maneuvering" (which might or might not have had extra control loop lag).

I disagree with your deployment time. It's more like 1.5 - 2s.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MP99 on 04/15/2015 05:27 pm


I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?

How high was F9 when they called acquisition of signal at the barge?

A drone at that height above the barge could transmit to the Cape, and other parts of the coast are closer / would need less height.

Cheers, Martin
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: edkyle99 on 04/15/2015 05:34 pm
The Vine video reminds me of Pilot Induced Oscillation effects.  In this case, it's an autopilot.

 - Ed Kyle
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: eriblo on 04/15/2015 05:39 pm
And full deployment takes at least 2-3 seconds from previous videos. It might be a little unsymmetrical and likely represent the biggest change of aerodynamics since the stage went subsonic. Personally I wouldn't rule out a contribution to the need for the questioned "late maneuvering" (which might or might not have had extra control loop lag).
I disagree with your deployment time. It's more like 1.5 - 2s.
Quite possible, especially to more or less full extension. I was going of the ORBCOMM video which had that one leg which was slightly slower. They also appear to bounce around a bit before stiffening up at 4-5 seconds after deployment start, but that might just be due to the reduced airspeed/increased g-loads....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: spacetraveler on 04/15/2015 05:51 pm
Also, somehow it looks like this stage is descending at a much faster rate at the end, compared to Grasshopper. Can't they spare a bit more fuel to slow the vertical descent just before the end?

It's like the equivalent of a guy screeching into his parking spot and slamming on the brakes.

That is what it is because no they can't spare more fuel for a slow easy descent, would impact payload capacity too much.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/15/2015 05:52 pm
I'll walk back (as the Washington political commentators say) some of my previous statements on leg deploy-

- I said legs deploy 8 seconds before landing.  Kim Keller said 6 seconds.  Referring back to the playbook, it looks like 6.14 seconds (Kim's number) might be most correct, at least in a nominal situation.

- I still do believe that leg deployment being acted on by side wind isn't a likely culprit because its so easy to model and be prepared for.  But in the case of the legs deploying transiently assymmetrically I can see that having funky steering input.  But still, look at the engine steering input for the upper half of that video, its intentionally pushing the bottom to the left during that time, it shouldn't be a surprise that the base is off to the left.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cambrianera on 04/15/2015 05:55 pm
Should be same position.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ugordan on 04/15/2015 06:57 pm
An attempt at some color correction on the single frame:
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ohsin on 04/15/2015 07:12 pm
An attempt at some color correction on the single frame:

I like the Tilt Shifty feel of this.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JamesH on 04/15/2015 07:51 pm


I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?

How high was F9 when they called acquisition of signal at the barge?

A drone at that height above the barge could transmit to the Cape, and other parts of the coast are closer / would need less height.

Cheers, Martin

I doubt a drone could carry enough power to transmit back 300miles. Not at any acceptable bit rate.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: TomH on 04/15/2015 07:54 pm
Also, somehow it looks like this stage is descending at a much faster rate at the end, compared to Grasshopper. Can't they spare a bit more fuel to slow the vertical descent just before the end?

It's like the equivalent of a guy screeching into his parking spot and slamming on the brakes.

That is what it is because no they can't spare more fuel for a slow easy descent, would impact payload capacity too much.

Controlling Grasshopper is easier than controlling a returning F9 stage 1 because Grasshopper is ballasted and can hover. The returning stage is so light that the T/W is significantly >1 even with the single Merlin 1D at minimum throttle. Grasshopper's ballast puts the point of T/W = 1.0 right in the middle of the throttle range, allowing the landing to be finessed like a helicopter pilot fine tuning his/her landing. The F9 first stage cannot hover. It has to come in at significant velocity with the M1D burning off that velocity very quickly and very precisely. The landing computer has to program the burn such that V = 0 and Altitude above pad = 0 occur at the exact same moment in time. If V = 0 occurs while the stage still has any altitude, it begins ascending again and cannot be stopped without full engine shutdown. The timing has to be perfect; you can't come to a hovering stop a couple of feet off the deck and then just ease her down. That would require a more deeply throttling engine or a lower power landing engine.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevin-rf on 04/15/2015 07:55 pm


I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?

How high was F9 when they called acquisition of signal at the barge?

A drone at that height above the barge could transmit to the Cape, and other parts of the coast are closer / would need less height.

Cheers, Martin

I doubt a drone could carry enough power to transmit back 300miles. Not at any acceptable bit rate.

Depends on the size of the drone ;) The US DOD seems to do just fine transmitting full motion video and data over longer distances. They just have very deep pockets ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Nilof on 04/15/2015 08:05 pm


I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?

How high was F9 when they called acquisition of signal at the barge?

A drone at that height above the barge could transmit to the Cape, and other parts of the coast are closer / would need less height.

Cheers, Martin

I doubt a drone could carry enough power to transmit back 300miles. Not at any acceptable bit rate.

Didn't we get exactly that on the Orion flight test?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ohsin on 04/15/2015 08:09 pm
https://www.youtube.com/watch?v=BhMSzC1crr0

 :)

Edit: Attaching as its 'private' again.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: matthewkantar on 04/15/2015 08:16 pm
Excited to see the barge after that detonation. Very excited to see this video, thought we would get only the Vine.

Matthew
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/15/2015 08:17 pm
oh man oh man. that was soooo close.

https://www.youtube.com/watch?v=BhMSzC1crr0

 :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 04/15/2015 08:20 pm
We have a slightly longer version in L2, where one of the COPV bottles said "No way, I want to go back uphill!" ;D

GO COPV BOTTLE! GO!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: schaban on 04/15/2015 08:28 pm
I don't remember falcon oscillating that much on previous landings. Really starts looking like some kind of control mechanism failure...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CuddlyRocket on 04/15/2015 08:31 pm
Doesn't look like much of the first stage was left on deck; the explosion blowing the engines off one side and the tank the other!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/15/2015 08:31 pm
https://www.youtube.com/watch?v=BhMSzC1crr0

 :)

Wow... Amazing quality.  :o Those RCS thrusters keep firing, not giving up. So close.

The barge is collecting its fair share of battle scars.

EDIT - And the video is now private. I guess it was not supposed to be released yet. Somebody leaked a link they were not supposed to...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: RotoSequence on 04/15/2015 08:34 pm
Don't refresh your pages if you were/are still able to watch it; the landing video's been made private.  :(
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: notsorandom on 04/15/2015 08:34 pm
https://www.youtube.com/watch?v=BhMSzC1crr0

 :)

Wow... Amazing quality.  :o Those RCS thrusters keep firing, not giving up. So close.

The barge is collecting its fair share of battle scars.
The thrusters firing like that to keep the rocket pointed up reminds me of a number of moments in Kerbal. They must pack quite a punch because it looks like they did hold the rocket up for a few moments.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 04/15/2015 08:38 pm
Video went private. Too bad some of us download them as soon as we can :D

It will have been reuploaded by 1001 accounts already. Best someone links one of those and not eat up bandwidth here if that goes into the thousands of downloads.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: hrissan on 04/15/2015 08:46 pm
Video went private. Too bad some of us download them as soon as we can :D

It will have been reuploaded by 1001 accounts already. Best someone links one of those and not eat up bandwidth here if that goes into the thousands of downloads.
Ok, I risk mine...

https://www.youtube.com/watch?v=lWrhAaDP9os
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: A12 on 04/15/2015 08:53 pm
https://app.box.com/s/2nbw5p6047ocur6ma79e4zf1xni19bfw
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: junk.munk82 on 04/15/2015 08:55 pm
https://www.youtube.com/watch?v=t1aBgNYAWtM
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: foltster on 04/15/2015 08:59 pm
Wow.  I can't stop watching this.  Can't wait to see them actually pull it off.  Really gives the perspective of how small the target is.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: RoboGoofers on 04/15/2015 09:07 pm
The legs seem to pause at half extended.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rcoppola on 04/15/2015 09:08 pm
I love how the entire Octoweb, or at least a subsection of engines get blown off like a cork.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: fthomassy on 04/15/2015 09:09 pm
The legs seem to pause at half extended.
Has from the first.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JasonAW3 on 04/15/2015 09:11 pm
So freaking CLOSE!  GOT to slow down a bit more those last 150 feet or so.  Would have still come in too hard it looks, even if it was dead on target.  Half that velocity, and I think it would have nailed the landing.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Sohl on 04/15/2015 09:17 pm
So freaking CLOSE!  GOT to slow down a bit more those last 150 feet or so.  Would have still come in too hard it looks, even if it was dead on target.  Half that velocity, and I think it would have nailed the landing.

It was going pretty slow vertically right there at the end.  Unfortunately, it has a pretty big pitch rate that made it swing too far from vertical to stick the landing.   :(  Need smaller pitch oscillations!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Sohl on 04/15/2015 09:21 pm
Looking at the bright side, at least the newest high-res video has lots of kaboomy goodness!  ::)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DatUser14 on 04/15/2015 09:21 pm
The file that cartman uploaded now redirects to "you are not allowed to access this section".
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/15/2015 09:26 pm
So freaking CLOSE!  GOT to slow down a bit more those last 150 feet or so.  Would have still come in too hard it looks, even if it was dead on target.  Half that velocity, and I think it would have nailed the landing.
It may have been coming in a bit hot, but I think the main issue is the rotational momentum do to the over correction.  It strained the left leg to the breaking point.

Inch-by-inch, they'll get there. :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: SoulWager on 04/15/2015 09:30 pm
Looks like the octoweb got pushed overboard by the explosion.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Tonioroffo on 04/15/2015 09:35 pm
The video is now public on YouTube.  Hope nobody loses their jobs over this?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/15/2015 09:44 pm
So freaking CLOSE!  GOT to slow down a bit more those last 150 feet or so.  Would have still come in too hard it looks, even if it was dead on target.  Half that velocity, and I think it would have nailed the landing.

It was going pretty slow vertically right there at the end.  Unfortunately, it has a pretty big pitch rate that made it swing too far from vertical to stick the landing.   :(  Need smaller pitch oscillations!
I agree, but I think it's good news.  Totally fixable from multiple angles (reducing lag in the system where possible, modeling the lag better where it can't be reduced, adding constraints to the size of inputs as the target is approached.)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: TomH on 04/15/2015 09:45 pm
So freaking CLOSE!  GOT to slow down a bit more those last 150 feet or so.  Would have still come in too hard it looks, even if it was dead on target.  Half that velocity, and I think it would have nailed the landing.

But that just is not possible. Even at lowest throttle on that single Merlin, the thrust is too high. If you come in slower than that, the thing will stop mid-air above the deck and then begin ascending again. The Merlin cannot throttle deeply enough to hover and land softly. They have to come screaming in at high velocity while decelerating very quickly. V = 0.00m/s and Altitude above deck = 0.000m have to occur at the exact same moment in time. The Merlin has too much thrust to hover/land gently. Grasshopper is ballasted. This is a whole other ball game. Coming in like a bat out of Hades to a perfectly timed stop is the only way to do it without modifying the Merlin to throttle far more deeply or to have a smaller landing engine in the center.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Oli on 04/15/2015 09:49 pm
Well that's a cool video.

It actually looked good until 5s into the video where something seemed to have pushed it out of balance.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: aero on 04/15/2015 09:53 pm
From the one video I saw, looked to me like the stage was over the barge but still controlling for the center of the "X-marks-the-spot" when it could have set down vertically and safely(?) but a little off center. Maybe the control needs a little more logic to know when it is "good-enough." Or maybe it's just pretty hard to get it even that close.

Of course, returning to a set down on land would perhaps allow a bit larger target area.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JamesH on 04/15/2015 09:55 pm
Well that's a cool video.

It actually looked good until 5s into the video where something seemed to have pushed it out of balance.

It did seem to go off balance very quickly given trajectory looked OK, and it took somewhat longer than you might expect for the engine to gimbal and counteract the movement. I wonder if that is the stiction issue at play after a sudden aerodynamic change - either wind sheer or the effect of the legs deploying.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rocket Science on 04/15/2015 09:56 pm
I wonder if some Soyuz style braking rockets at the top of stage might prove useful... Hmmmm...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Elmar Moelzer on 04/15/2015 09:56 pm
Of course, returning to a set down on land would perhaps allow a bit larger target area.
Exactly! It seems to me like this would have been just fine had they landed on a (much larger) landing pad on land.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/15/2015 09:57 pm
It seems like the RCS thrusters all vent at once to safe the stage near the end.  That must be when the stage thinks it has "landed".
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: NovaSilisko on 04/15/2015 09:57 pm
I wonder if some Soyuz style braking rockets at the top of stage might prove useful... Hmmmm...

How about one big one at the bottom? ;p
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: the_other_Doug on 04/15/2015 10:01 pm
I wonder how much fuel slosh could have affected the controllability of the stage during that final phase.  I know it's not a huge amount of fuel and oxidizer sloshing around in there, but especially with a pretty empty tank you could get enough to throw off the guidance system and cause it to overcorrect.

It definitely looks like an overcorrection issue, but it's nearly impossible to tell how close to on target the stage was before it began its final frantic maneuvers.  Perhaps the leg extensions had little to do with the problem -- maybe the stage recognized it was heading for a point 20 meters away from target and didn't have enough time to perform the correction.

If the stage was exactly on target before it began to maneuver, then we have a definite problem with the final descent control system.  But if it was off target, then we may just be seeing the inevitable result of trying to correct your landing point too late in the descent.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rocket Science on 04/15/2015 10:06 pm
I wonder how much fuel slosh could have affected the controllability of the stage during that final phase.  I know it's not a huge amount of fuel and oxidizer sloshing around in there, but especially with a pretty empty tank you could get enough to throw off the guidance system and cause it to overcorrect.

It definitely looks like an overcorrection issue, but it's nearly impossible to tell how close to on target the stage was before it began its final frantic maneuvers.  Perhaps the leg extensions had little to do with the problem -- maybe the stage recognized it was heading for a point 20 meters away from target and didn't have enough time to perform the correction.

If the stage was exactly on target before it began to maneuver, then we have a definite problem with the final descent control system.  But if it was off target, then we may just be seeing the inevitable result of trying to correct your landing point too late in the descent.
I mentioned that yesterday on the landing thread Doug. It "could" be a factor....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: VulcanCafe on 04/15/2015 10:07 pm
Official SpaceX video:
https://www.youtube.com/watch?v=BhMSzC1crr0
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rcoppola on 04/15/2015 10:11 pm
Gwynne gives an interview to Defense News today:

http://www.defensenews.com/story/defense/air-space/space/2015/04/15/spacex-ground-attempt-reusable-landing-sea/25827625/
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: nadreck on 04/15/2015 10:14 pm
When the vehicle first appears on screen the engine is visibly moving/gimballing rapidly, it then seems to stay in position as the vehicle appears on a stable heading, then it is attitude that needs correcting more than x/y vector at first or so it seems and then it seems like it took a long time before the engine moved so that it was now also an x/y vector correction as well as an attitude one. Then we got an over correction of both attitude and x/y vector.

One final observation, I don't know how much authority the RCS system had, but it wasn't enough, however I think nominal landing should be within parameters where no RCS is required.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: junk.munk82 on 04/15/2015 10:38 pm
correct speed version:
https://www.youtube.com/watch?v=NAdQqtau4Ls

edit: not 100% certain if speed is really correct
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: clegg78 on 04/15/2015 10:46 pm
An observation -  At the very last few frames before the RUD,  you can see one of the legs tipping up through the smoke as the stack falls over.   The angle it comes up at would indicate that the legs on the other side failed.  Because the pivot point seems to be the bottom of the rocket, not the legs it would be leaning on.

On the speed corrected video (how did you pick that speed as being the real one btw?), its truly impressive how fast the F9 comes in at... coming in hot I would say :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/15/2015 10:52 pm
On the speed corrected video (how did you pick that speed as being the real one btw?), its truly impressive how fast the F9 comes in at... coming in hot I would say :)

A good question... The original speed looked right to me. And I think Elon was mistaken on that slow motion point, because he sent out another tweet linking to the same video, but without the mention of it being slow motion.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Alkan on 04/15/2015 10:57 pm
That "corrected speed" video looks a little fast for something that is this big:

(http://www.cyclingpeace.org/gallery3/var/albums/album10/Falcon_9_Rocket_in_the_Hangar_660x332.jpg?m=1391986164)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 11:06 pm
If the stage lands off-center from the X, then is there any danger of tipping the barge itself?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/15/2015 11:11 pm
If the stage lands off-center from the X, then is there any danger of tipping the barge itself?

No, the stage weight is about 1% of the barge cargo capacity.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevin-rf on 04/15/2015 11:19 pm
Anyone ever see a THAAD launch, it does some amazing corkscrews to dump excess performance in an effort to fine tune the final intercept velocity.

Now, I wonder if the wobble is the Falcon doing the same so the velocity is zero when it intercepts the barge.

(Note that is a THAAD Launch, not a Falcon launch attached)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Astro_Zach on 04/15/2015 11:19 pm


I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?

How high was F9 when they called acquisition of signal at the barge?

A drone at that height above the barge could transmit to the Cape, and other parts of the coast are closer / would need less height.

Cheers, Martin

I doubt a drone could carry enough power to transmit back 300miles. Not at any acceptable bit rate.

You're not thinking rational... 4G and LiveStream :P
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 04/15/2015 11:25 pm
Do enjoy those legs coming down.....so 1950's Sci-Fi  :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mikegi on 04/15/2015 11:25 pm
Since tipping is an obvious failure mode, would it be possible to have "arms" pop up from the landing site to offer support to the top of the rocket's body at touch down? Maybe have cables between the arms to provide a "ring" of support? Sounds goofy, I know, but saving a multimillion $$$ stage from complete destruction due to an inopportune gust of wind or minor hardware failure (e.g. stuck valve) seems like something worth investigating.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/15/2015 11:32 pm
Since tipping is an obvious failure mode, would it be possible to have "arms" pop up from the landing site to offer support to the top of the rocket's body at touch down? Maybe have cables between the arms to provide a "ring" of support? Sounds goofy, I know, but saving a multimillion $$$ stage from complete destruction due to an inopportune gust of wind or minor hardware failure (e.g. stuck valve) seems like something worth investigating.

There are lots of rube goldberg style ideas being posted, but few are practical.

The primary problem with most of them (including yours) is that they assume that the rocket will touch down exactly at the center. Because if it doesn't land exactly in the center spot, your solution will simply pull it over instead of steadying it.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Blackstar on 04/15/2015 11:35 pm
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Oersted on 04/15/2015 11:39 pm
I wonder if the slide along the deck threw off the stabilization system.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lee Jay on 04/15/2015 11:49 pm
I wonder how their controller design handles the change in CG location and inertia that takes place when the legs deploy.  I know they aren't that heavy, but neither is the stage at this point, and the CG has got to be pretty low with most of the prop depleted, meaning any additional movement down, which is what leg deployment will do, may change the response of the stage to a lateral component of thrust by a significant amount.

They could be not handling it at all, handling it with gain scheduling, or handling it with some other sort of controller blending.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kim Keller on 04/15/2015 11:52 pm
And full deployment takes at least 2-3 seconds from previous videos. It might be a little unsymmetrical and likely represent the biggest change of aerodynamics since the stage went subsonic. Personally I wouldn't rule out a contribution to the need for the questioned "late maneuvering" (which might or might not have had extra control loop lag).

I disagree with your deployment time. It's more like 1.5 - 2s.

I obviously have to walk back this post. Those legs took a long time to cycle down/locked. Sorry, folks.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/15/2015 11:53 pm
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

Hey, that's my idea, along with the flying catcher's mitt...

But seriously, any ideas why Musk deleted his tweet about the biprop valve stiction? Is it possible that Musk spoke prematurely, and that the actual problem is more complicated than that?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: QuantumG on 04/15/2015 11:54 pm
But seriously, any ideas why Musk deleted his tweet about the biprop valve stiction? Is it possible that Musk spoke prematurely, and that the actual problem is more complicated than that?

Sounds like the kinda detail that gets you ITARd.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: notsorandom on 04/16/2015 12:16 am
This video is hypnotizing. I've watched it again and again. It looks as if when the rocket starts to tip over it rotates along the long axis a bit. The control thruster which is up until that point seemingly effective at keeping it from falling starts to turn away and lose effectiveness. Then a few of the other ones start firing.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevin-rf on 04/16/2015 12:22 am
This video is hypnotizing. I've watched it again and again. It looks as if when the rocket starts to tip over it rotates along the long axis a bit. The control thruster which is up until that point seemingly effective at keeping it from falling starts to turn away and lose effectiveness. Then a few of the other ones start firing.
Might be to prevent side slip as it was tipping. The more I watch these videos, the more I think they induce then correct some tipping to better tune the vertical velocity component. Kinda do an slide ship so as not to loose to much velocity by coming straight in.

Can't wait to see these come down on land. I will be willing to bet we will continue to see the wiggle/wobbles right before touch down. It may say a few things about the magic sauce.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/16/2015 12:44 am
The Qmax (Maximum Aerodynamic Load) during ascent is well known for F9R, but when does the Qmax occur for descent trajectory? It almost seems like that happens during the final moment of landing.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ronpur50 on 04/16/2015 12:45 am


Great screen caps....I wish we could stop at #4.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: GalacticIntruder on 04/16/2015 12:53 am
Maybe the sea platform is just not stable enough to handle the landing forces. Might confuse the F9 landing sensors, or give bizarre feedback on touchdown.

Ms Shotwell basically eluded to such on the defensenews.com story.

 http://www.defensenews.com/story/defense/air-space/space/2015/04/15/spacex-ground-attempt-reusable-landing-sea/25827625/ (http://www.defensenews.com/story/defense/air-space/space/2015/04/15/spacex-ground-attempt-reusable-landing-sea/25827625/)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mikegi on 04/16/2015 12:55 am
Quote from: Lars-J
The primary problem with most of them (including yours) is that they assume that the rocket will touch down exactly at the center. Because if it doesn't land exactly in the center spot, your solution will simply pull it over instead of steadying it.
Doesn't have to land in the exact center. The idea is to stop it from tipping over and hitting the ground. Put a ring that's several times the diameter of the rocket (e.g. size of the landing radius) and pull it up from four posts around the landing zone when the rocket's about to touch down. If the rocket tips over, it rests against the ring rather than crashing into the ground. I don't know ... but I'd try as many Rube Goldberg contraptions I could think of rather than have 10s of millions of $$ go up in smoke.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mlindner on 04/16/2015 01:00 am
While carriers do have systems that transmit landing data to aircraft for better precision landing, it's pretty much positional information for the aircraft to get on the right glide slope. I think a returning F9 stage would be in a similar position -- the wind data you'd send up is not terribly useful until the point where it's almost too late. Better to tune the system response including throttle response until it's quick enough to stick the landing based on information it has onboard the rocket.

A hundred quadcopters In a cone 200m or so in diameter, and 1km or so tall would allow most wind to be predicted 'live'.
These could likely even be resold for a profit.

The bonkers ideas on this forum sometimes really make me laugh.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/16/2015 01:02 am
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.


Is there always room for it?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: iamlucky13 on 04/16/2015 01:12 am
An observation -  At the very last few frames before the RUD,  you can see one of the legs tipping up through the smoke as the stack falls over.   The angle it comes up at would indicate that the legs on the other side failed.  Because the pivot point seems to be the bottom of the rocket, not the legs it would be leaning on.

This was my interpretation of the video, too.

A coworker I was discussing this with disagreed. He thinks one leg was off the platform. I'll buy either theory as viable.

Since tipping is an obvious failure mode, would it be possible to have "arms" pop up from the landing site to offer support to the top of the rocket's body at touch down? Maybe have cables between the arms to provide a "ring" of support? Sounds goofy, I know, but saving a multimillion $$$ stage from complete destruction due to an inopportune gust of wind or minor hardware failure (e.g. stuck valve) seems like something worth investigating.

Probably, but it would expensive, complex, and risk damaging the rocket it was intended to save.

As is, it was pretty far over, yet seemed very close to sticking it. I see nothing in that video that makes me fear they can't make this work by further tuning of their control system.

I think they should use lasers.. somehow.

Honestly, watching the launch, when the feed switched to an animation of the 2nd stage, the animation kept pulsing the velocity vector (I think) on and off, it looked rather beam-like, and all I could think was, "Dr Evil is trying to shoot down the rocket!"
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/16/2015 01:14 am
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

Hey, that's my idea, along with the flying catcher's mitt...

My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

Is there always room for it?

I'll take credit for originating that idea, though it was in jest.  Even back in December when I made that suggestion it was in reaction to the vast multitude of goofy Rube Goldberg solutions that had been posted.  Now 4 months after I thought we'd seen everything they are still coming out full speed.  The suggestion was for sticky trap material, not jello.  I posted it on a rainy day when the cruise cam showed puddles forming on the deck, puddles I goofingly postulated to be the beginnings of a full deck sized pool of sticky trap material.

The extensions on the side are outside of the low perimeter retaining wall and will be the only place that people will be able to stand near the central deck once the liquid polymer sticky trap material has flooded the main part of the deck within the yellow retaining wall.  You can see over the course of the day that they have begun to flood the deck with the sticky trap material.  This morning it was only visible as a small puddle near the point of application near the right rear corner but as the day has gone on I've been watching the puddle of sticky trap material get larger and larger though it still hasn't covered the entire surface of the deck within the yellow wall.  I wonder how deep they plan to install the stuff?  I wonder if they are using the slow, medium, or fast version?  Both the fast and medium curing versions have a solvent smell that stinks to high heaven, which is probably why the cruise ship left. Eer, did you smell it?   The application and curing should be done by the first week of January for the landing but they never could have had it installed and cured by the launch last week.  Maybe that's the real reason they delayed the launch.?.

What sticky material?? Source?
The source seems to be near the corner of the deck that is closest to the shore and furthest from the cruise ship.  What sticky material??? Just look at the stuff, there must be hundreds of gallons of it there!  Probably MIL-STD-1394-BS-4/1 since it appears to be clear. Heaven help any pelicans or sea gulls that land in it.

The world's largest glue trap? A good theory, but its much more likely that they will simply rub the barge with a giant zeppelin sized balloon and have the rocket just stick to the deck with static electricity.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: NovaSilisko on 04/16/2015 01:27 am
Anyone ever see a THAAD launch, it does some amazing corkscrews to dump excess performance in an effort to fine tune the final intercept velocity.

Now, I wonder if the wobble is the Falcon doing the same so the velocity is zero when it intercepts the barge.

(Note that is a THAAD Launch, not a Falcon launch attached)

Doing something like that on descent just makes you go faster. To decelerate at the highest possible rate, you'd want to keep your thrust vector exactly opposite to your velocity vector at the highest level of thrust you can manage. Maybe to accelerate the descent a little, I guess, but I don't think those wobbles were intentional.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: baskerbosse on 04/16/2015 02:05 am
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

Hey, that's my idea, along with the flying catcher's mitt...

My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

Is there always room for it?

I'll take credit for originating that idea, though it was in jest.  Even back in December when I made that suggestion it was in reaction to the vast multitude of goofy Rube Goldberg solutions that had been posted.  Now 4 months after I thought we'd seen everything they are still coming out full speed.  The suggestion was for sticky trap material, not jello.  I posted it on a rainy day when the cruise cam showed puddles forming on the deck, puddles I goofingly postulated to be the beginnings of a full deck sized pool of sticky trap material.

The extensions on the side are outside of the low perimeter retaining wall and will be the only place that people will be able to stand near the central deck once the liquid polymer sticky trap material has flooded the main part of the deck within the yellow retaining wall.  You can see over the course of the day that they have begun to flood the deck with the sticky trap material.  This morning it was only visible as a small puddle near the point of application near the right rear corner but as the day has gone on I've been watching the puddle of sticky trap material get larger and larger though it still hasn't covered the entire surface of the deck within the yellow wall.  I wonder how deep they plan to install the stuff?  I wonder if they are using the slow, medium, or fast version?  Both the fast and medium curing versions have a solvent smell that stinks to high heaven, which is probably why the cruise ship left. Eer, did you smell it?   The application and curing should be done by the first week of January for the landing but they never could have had it installed and cured by the launch last week.  Maybe that's the real reason they delayed the launch.?.
How about turning the whole platform into a giant Segway, x-y direction wheels under the whole thing.
Earthquake building protection technologies might be helpful?
That and a giant Power Balance Band(tm) for the Falcon. :-)
-Or, if that whole long tank is tricky to balance, ditch the thing and land the engines only using Dracos?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Mariusuiram on 04/16/2015 02:10 am
But seriously, any ideas why Musk deleted his tweet about the biprop valve stiction? Is it possible that Musk spoke prematurely, and that the actual problem is more complicated than that?

Sounds like the kinda detail that gets you ITARd.

I dont think there is any deeper conspiracy here. Musk deletes all his "conversations" from time to time so his feed is pure.

Go look at his "Tweets & Replies" feed and you'll see there are no replies left from the launch attempts or previous Tesla stuff. I know he had plenty of replies at the time. He just likes to tidy his feed.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: guidanceisgo on 04/16/2015 02:15 am
What was the consensus on the slow motion setting on that video?   I thought the leg extension should take 1.5 seconds.  It seemed to me to be about 3 seconds.  I really was impressed with the clarity of  the video!  I would love to see the event in full speed without the zoom.  The explosions were obviously slowed down. Do we know the state of the barge?  I think this attempt was harder on the barge than the previous one.   They should consider a drogue deployment at lower altitude to help the stability.  Those grid fins are less affective subsonically ( good supersonic), but maybe a drogue (ballute) deployed once subsonic would help the stability. 



Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: PreferToLurk on 04/16/2015 02:16 am
Personal theory since everyone seems to have one, and i just cant help but break my lurking for this video:

On the last "swing" of the rocket as it attempts to hit center of JRTI one of the falcon's leg hits the deck before anticipated.  Due to the significant lateral velocity in excess of what would be experienced during a nominal touchdown, and without 3 other legs to distribute the force, the low hanging leg breaks.  The thrusters manage to hold the stage straight long enough for the other three leg sensors to out-vote the missing legs "no touchdown" vote, and the system goes into safeing mode only to fall over and explode.

This scenario explains Hans' quote about the last signal they got was that "everything was fine" (paraphrase from post launch presser), it explains the single thruster action, it explains the thruster venting action, and it explains the crash. 

This scenario implies that Spacex can tweak their control code to prevent a late and deep leg dip during a lateral translation right before touchdown and remove this failure mode.  -- Software problem, not hardware.  IMHO

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: starsilk on 04/16/2015 02:48 am
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

But seriously, any ideas why Musk deleted his tweet about the biprop valve stiction? Is it possible that Musk spoke prematurely, and that the actual problem is more complicated than that?

if there's a problem with the biprop valve, don't forget that is also critical for ascent, too, which has implications for customers (NASA in this case). there's probably a mountain of paperwork to do...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: yg1968 on 04/16/2015 02:50 am
So what can be concluded from the higher resolution video? The RCS thrusters don't seem to be the ones that are causing the osciliation of the rocket. So they are not at fault? The rocket seems to be coming in fast but that seems to be by design? The RCS thrusters seem late in correcting the angle of the rocket. But again that might by design? One of the leg broke but it's not clear what caused it. Am I on the right track?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CJ on 04/16/2015 02:56 am
Sorry for my ignorance, but would I be correct in interpreting "stiction" to mean a sluggish, sticky valve? Reading this thread seems to indicate this.

If so, is there any possibility that Musk was not referring to the descent oscillation, but to the main engine shutoff upon touch down? The reason I ask that is that when I watch the video, it looks to me as if the stage base continues movement (and the engine continues to give at least some thrust) for about half a second longer than it ought to. In other words, a slow shutdown (And as I recall, slow thrust termination doomed one of the F1 launches) caused the stage base to continue moving, and thus moving out from under the stage CG. Just a wild theory of mine. 


 




Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: yg1968 on 04/16/2015 02:59 am
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

But seriously, any ideas why Musk deleted his tweet about the biprop valve stiction? Is it possible that Musk spoke prematurely, and that the actual problem is more complicated than that?

if there's a problem with the biprop valve, don't forget that is also critical for ascent, too, which has implications for customers (NASA in this case). there's probably a mountain of paperwork to do...

Sorry for the dumb question but what's a biprop valve and what does it do upon ascent and landing?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: starsilk on 04/16/2015 03:08 am
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

But seriously, any ideas why Musk deleted his tweet about the biprop valve stiction? Is it possible that Musk spoke prematurely, and that the actual problem is more complicated than that?

if there's a problem with the biprop valve, don't forget that is also critical for ascent, too, which has implications for customers (NASA in this case). there's probably a mountain of paperwork to do...

Sorry for the dumb question but what's a biprop valve and what does it do upon ascent and landing?

throttle.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/16/2015 03:09 am
Biprop valve means the main throttle valve for the single main merlin engine that is firing.  The RCS system has nothing to do with that, that's a "cold gas" system, not a biprop.  And "stiction" refers to the large initial friction force that prevents movement, which is reduced to a much smaller "friction" force once the thing (valve in this case) has started moving.  Wikipedia is your friend.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/16/2015 03:37 am
So what can be concluded from the higher resolution video? The RCS thrusters don't seem to be the ones that are causing the osciliation of the rocket. So they are not at fault? The rocket seems to be coming in fast but that seems to be by design? The RCS thrusters seem late in correcting the angle of the rocket. But again that might by design? One of the leg broke but it's not clear what caused it. Am I on the right track?

There's no video evidence at this stage that a leg broke.. and it does seem the stage came down entirely within boundaries of the landing deck.

After 'overshooting', it could also have simply got blown over by the wind.  We'll need to wait for more info.
 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Fr4nK on 04/16/2015 03:42 am
My fence would have saved it!!!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: QuantumG on 04/16/2015 03:45 am
With inflatable bumpers on the inside!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: dglow on 04/16/2015 03:45 am
There's no video evidence at this stage that a leg broke..

Failure of a leg has been suggested by people in the know, fyi.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/16/2015 03:47 am
That "corrected speed" video looks a little fast for something that is this big:

(http://www.cyclingpeace.org/gallery3/var/albums/album10/Falcon_9_Rocket_in_the_Hangar_660x332.jpg?m=1391986164)
Your point is correct, but your example is actually too small. (V1.1 is taller than v1.) :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: NovaSilisko on 04/16/2015 04:01 am
I feel that there's a lot of overthinking of this going on here. From the tweet to Carmack (which alas has vanished from this material sphere), there was a sticky throttle valve. IMO at least, the rocket expected one thrust value, got another, tried to compensate, and couldn't.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/16/2015 04:03 am
With inflatable bumpers on the inside!

How about heavy duty velcro on the feet and landing pad?

All those little teeth can be pretty tenacious, you know...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/16/2015 04:05 am
So what can be concluded from the higher resolution video? The RCS thrusters don't seem to be the ones that are causing the osciliation of the rocket. So they are not at fault? The rocket seems to be coming in fast but that seems to be by design? The RCS thrusters seem late in correcting the angle of the rocket. But again that might by design? One of the leg broke but it's not clear what caused it. Am I on the right track?

There's no video evidence at this stage that a leg broke.. and it does seem the stage came down entirely within boundaries of the landing deck.

After 'overshooting', it could also have simply got blown over by the wind.  We'll need to wait for more info.
I think there is evidence of a leg failing.  Watch the arc of the top of the rocket.  If the left leg locked open and stayed locked then the top of the rocket would rise up as it tilts left.  It looks to me like it does not rise up as it leans over.

I personally think the leg broke because it hit hard with rotational momentum from the over-correction by the engine.  The RCS is firing as a reaction to the undesired continuing rotation.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: yg1968 on 04/16/2015 04:13 am
I feel that there's a lot of overthinking of this going on here. From the tweet to Carmack (which alas has vanished from this material sphere), there was a sticky throttle valve. IMO at least, the rocket expected one thrust value, got another, tried to compensate, and couldn't.

Yes that still seems like the most plausible explanation at this point.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sdsds on 04/16/2015 04:44 am
I feel that there's a lot of overthinking of this going on here. From the tweet to Carmack (which alas has vanished from this material sphere), there was a sticky throttle valve. IMO at least, the rocket expected one thrust value, got another, tried to compensate, and couldn't.

Yes that still seems like the most plausible explanation at this point.

I agree. And a fix in software could be "easy." Every valve has some stiction. So the "transfer function" describing how the input to the valve changes the flow through the valve likely had a constant value for this. Instead, they will make this a "state variable" for which the control system maintains a continuous estimate. (Just like x, y, z, vx, vy, vz, etc., etc.) This will let the controller "notice" when the stiction value is other than expected, and compensate for it, without requiring any substantial change to the control algorithm itself.

IMHO. YMMV.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/16/2015 05:37 am
I feel that there's a lot of overthinking of this going on here. From the tweet to Carmack (which alas has vanished from this material sphere), there was a sticky throttle valve. IMO at least, the rocket expected one thrust value, got another, tried to compensate, and couldn't.

Yes that still seems like the most plausible explanation at this point.


It looked like the engine increased its thrust just before swinging over the barge.  Had that increase in thrust happened half a second sooner, it might have been a better landing.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: dglow on 04/16/2015 05:43 am
Is video of the post-launch briefing posted somewhere?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: guckyfan on 04/16/2015 06:32 am
Is video of the post-launch briefing posted somewhere?

https://www.youtube.com/watch?v=L30v3D4DZCg
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jakusb on 04/16/2015 08:34 am
I feel that there's a lot of overthinking of this going on here. From the tweet to Carmack (which alas has vanished from this material sphere), there was a sticky throttle valve. IMO at least, the rocket expected one thrust value, got another, tried to compensate, and couldn't.

Yes that still seems like the most plausible explanation at this point.

It looks a bit like the engine power is not cut off in time and rocket is skidding because of too much power while already on ASDS. Like it is on ice or an air-cushen-bed...
But another thing I notice is the seemingly lag in the engine being too long on right side and having to overcompensate to heavy and too late, resulting in strong lateral movement....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: junk.munk82 on 04/16/2015 08:47 am
150fps:
https://www.youtube.com/watch?v=vVUArqpevdE

300fps:
https://www.youtube.com/watch?v=DWZmwgok3lY

600fps:
https://www.youtube.com/watch?v=3oJF8mmorbQ
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: gospacex on 04/16/2015 09:12 am
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

Actually, you may be onto something. Land this thing in a freshwater pond.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JamesH on 04/16/2015 09:18 am
The last second change to the gimball give the stage quite a lot of rotational momentum, I suspect that is the source of the sideways movement - the top of the rockets stays fairly steady, whilst the bottom is moving horizontally. The RCS would not be able to compensate for that sideways motion (is there even RCS at the bottom of the stage?). The rotation momentum then puts a lot of pressure on the 'left hand' leg as it lands which cannot absorb that amount of energy and either fails, or the rocket continues to rotate and falls.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: hrissan on 04/16/2015 09:33 am
Per tradition, some analysis with numbers... Assuming the speed is correct (this looks to be the case to me).

There is 2 distinct deceleration regions - before around 7th second, and after that. But observing the flame length and thickness, we guess there is the third deceleration region, before the video start and up to the the first second, it looks like the deceleration is reduced during legs deploy to minimise the deploy shock.

Deceleration at the start of the video: ~1g, based on flame look only (no credible numbers)
Deceleration during legs deploy: 0.22g
Deceleration before landing: 1g

Enjoy. :)

Official SpaceX video came after I did the analysis, so here is the link on the video I used...

http://www.youtube.com/watch?v=lWrhAaDP9os
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Dave G on 04/16/2015 09:59 am
Analyzing the video further, I notice a couple of things with the legs:
1) The right leg seems to deploy before the others.
2) The pneumatic cylinders that open the legs seem to pause a little in the horizontal position.

Note: Video attached below.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Dave G on 04/16/2015 10:27 am
Assuming the speed of the Vine footage is correct,
https://vine.co/v/euEpIVegiIx

It seems like the last part of the descent is too fast to make pitch corrections without oscillations.  If they could slow the descent for the last 5 seconds or so, maybe that would help.

Also, rather than wind, it looks like the M1D gimbal may have overcompensated a few seconds before landing, as shown in the picture below.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ScottMC on 04/16/2015 11:34 am
600fps:
https://www.youtube.com/watch?v=3oJF8mmorbQ

I've had a go at comparing a frame of the Falcon 9 with legs extended and ASDS (prior to details being obscured by the cloud of smoke) with the Falcon 9 on the ASDS at it's lowest point prior to it tipping over.  Based on junk.munk82's 600fps video which is very cleverly stabilised on the ASDS and surrounding ocean.

Caveats:
* Created using MS Paint and Word :)
* I rotated the Falcon 9 image on the left to line up with the last (lowest) vertical position
* Red lines added to show how I've tried to line things up
* The Falcon 9 image on the left seems to be leaning back and so that might have a bearing on the results
* It looks like I've positioned the ASDS too high in the left of the image.  I used the bottom edge of the video as a reference and if you watch the video carefully the ASDS seems to maintain a consistent distance from the bottom of the frame - so I think the positioning is good.

Looks sort of like the legs might have failed and the Falcon 9 stopped descending once the Merlins hit the deck (or very close to it).

Is this the first time freshly deployed legs have been used to try to support the F9 on a solid surface?  Were F9R Dev1 (Grasshopper 2) legs fixed in place?

PS:  I've attached my Word document in case any one wants to play with it.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: docmordrid on 04/16/2015 11:38 am
Aviation Week article.... (http://aviationweek.com/space/spacex-checks-throttle-valve-after-flawed-falcon-9-recovery-attempt")

Link fixed
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: NovaSilisko on 04/16/2015 11:55 am
After performing maintenance on that mangled link, I think the article gives a pretty good* description of what likely went wrong

Quote
The friction appears to have momentarily slowed the response of the engine, causing the control system to command more of an extreme reaction from the propulsion system than was required. As a result, the control system entered a form of hysteresis, a condition in which the control response lags behind changes in the effect causing it.

*that is to say it agrees with my opinions ;p
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: corrodedNut on 04/16/2015 12:19 pm
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

It's called aerogel, and it is lime flavored, if I'm not mistaken.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: brettreds2k on 04/16/2015 12:27 pm
I wonder how bad the damage is to the drone ship, and if it will be repaired in time for the next landing attempt. They have to be proud considering this was only the second actual attempt to land it on the platform, and both times they made it just the last few feet didnt work out. This one was so dang close to perfection!!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ben the Space Brit on 04/16/2015 12:28 pm
I wonder how bad the damage is to the drone ship, and if it will be repaired in time for the next landing attempt.

Compared to the hard contact and kaboom last time? In all probability it's minimal.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JamesH on 04/16/2015 12:53 pm
I wonder how bad the damage is to the drone ship, and if it will be repaired in time for the next landing attempt.

Compared to the hard contact and kaboom last time? In all probability it's minimal.

EM has already tweeted the damage is light.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MattMason on 04/16/2015 12:59 pm
Assuming the speed of the Vine footage is correct,
https://vine.co/v/euEpIVegiIx

It seems like the last part of the descent is too fast to make pitch corrections without oscillations.  If they could slow the descent for the last 5 seconds or so, maybe that would help.

Also, rather than wind, it looks like the M1D gimbal may have overcompensated a few seconds before landing, as shown in the picture below.

Nice analysis.

Based on what others and Musk have shown or said, with my Occam's Razor (with lemony Aerogel!) making for a close shave, my early opinion is:

> Something was up with the throttling as the stage was already coming in too hot.
> The excess speed combined with the throttling and/or a problem with the gimbaling leads the stage to induced oscillations.
> The oscillations causes the stage to oversteer, although not enough to throw the stage off-course ("The Little Train That Could" software of these boosters is incredible).
> There is a moderate probability that one or more of the legs did not fully deploy, or failed on touchdown due to mis-deploy or impact stresses.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: brettreds2k on 04/16/2015 01:32 pm
I wonder how bad the damage is to the drone ship, and if it will be repaired in time for the next landing attempt.

Compared to the hard contact and kaboom last time? In all probability it's minimal.

EM has already tweeted the damage is light.

Well that little barge is a tough thing isnt it? lol. 2 explosions on it, and it holds up :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ronpur50 on 04/16/2015 01:36 pm
Is there any updates on Dragon?  And when does it arrive at ISS?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MattMason on 04/16/2015 01:41 pm
Is there any updates on Dragon?  And when does it arrive at ISS?

Dragon is flying happily. Capture will be on Friday the 17th at around 7:00 Eastern Daylight Time.

http://blogs.nasa.gov/stationreport/ (http://blogs.nasa.gov/stationreport/)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Norm38 on 04/16/2015 01:43 pm
I think the barge is just too small.  If the stage had a much bigger landing area to work with, it could focus on staying completely vertical and shedding horizontal velocity instead of trying to maneuver to the center of the barge and adding horizontal speed.

Haven't they hit the barge enough times now to prove that they can hit the 10 acre patch of dirt they're aiming for?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JamesH on 04/16/2015 01:50 pm
Assuming the speed of the Vine footage is correct,
https://vine.co/v/euEpIVegiIx

It seems like the last part of the descent is too fast to make pitch corrections without oscillations.  If they could slow the descent for the last 5 seconds or so, maybe that would help.

Also, rather than wind, it looks like the M1D gimbal may have overcompensated a few seconds before landing, as shown in the picture below.

Nice analysis.

Based on what others and Musk have shown or said, with my Occam's Razor (with lemony Aerogel!) making for a close shave, my early opinion is:

> Something was up with the throttling as the stage was already coming in too hot.
> The excess speed combined with the throttling and/or a problem with the gimbaling leads the stage to induced oscillations.
> The oscillations causes the stage to oversteer, although not enough to throw the stage off-course ("The Little Train That Could" software of these boosters is incredible).
> There is a moderate probability that one or more of the legs did not fully deploy, or failed on touchdown due to mis-deploy or impact stresses.

I don't believe the stage came in hot. It has pretty much 0 vertical velocity when it got to the barge. That indicates it's vertical profile was about right at the end at least.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/16/2015 02:12 pm
I wonder how bad the damage is to the drone ship, and if it will be repaired in time for the next landing attempt.

Compared to the hard contact and kaboom last time? In all probability it's minimal.

EM has already tweeted the damage is light.

Well that little barge is a tough thing isnt it? lol. 2 explosions on it, and it holds up :)

That barge had a hard life *before* become the ASDS.  Deliberately sunk twice, for example.  It's a solid monster.

What's more likely is that some of SpaceX's equipment trailers got a little dinged up, and antennas bent.  But there's plenty of time before the next landing attempt to set that right.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: yg1968 on 04/16/2015 02:27 pm
After performing maintenance on that mangled link, I think the article gives a pretty good* description of what likely went wrong

Quote
The friction appears to have momentarily slowed the response of the engine, causing the control system to command more of an extreme reaction from the propulsion system than was required. As a result, the control system entered a form of hysteresis, a condition in which the control response lags behind changes in the effect causing it.

*that is to say it agrees with my opinions ;p

The source for their explanation is Elon's deleted tweet (plus probabaly posts on this forum).
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rocket Science on 04/16/2015 02:31 pm
I wonder if some Soyuz style braking rockets at the top of stage might prove useful... Hmmmm...

How about one big one at the bottom? ;p
Perhaps Goddard had it right with his first rocket with the engine above the tanks only for landing not liftoff stability... ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/16/2015 02:49 pm

Perhaps Goddard had it right with his first rocket with the engine above the tanks only for landing not liftoff stability... ;)

No, that is wrong, see Pendulum Fallacy
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/16/2015 02:50 pm
I think the barge is just too small.  If the stage had a much bigger landing area to work with, it could focus on staying completely vertical and shedding horizontal velocity instead of trying to maneuver to the center of the barge and adding horizontal speed.



It doesn't know where the center of the barge is.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rocket Science on 04/16/2015 02:54 pm

Perhaps Goddard had it right with his first rocket with the engine above the tanks only for landing not liftoff stability... ;)

No, that is wrong, see Pendulum Fallacy
Jim, I understand that, but how does that apply to a rocket landing if you resolve the vetcor forces?

Edit:typo
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/16/2015 02:58 pm
If you assume that the center of the barge landing area is located at the lat/long that the stage is told to land at, then yes the stage does know where the center is (by default)

Given that the landing area is small, the stage is programmed to land as close to that point as possible with little or no margin of error - maybe +/-  a meter or two. If, in the final second or two before landing, it finds it's off , it makes big changes to get back on track.

If the landing area is larger then the margin for landing is larger - you can program the stage to land at lat/long +/- 10 or 15 meters and it means less corrective measures are required in the final seconds.

I think the barge is just too small.  If the stage had a much bigger landing area to work with, it could focus on staying completely vertical and shedding horizontal velocity instead of trying to maneuver to the center of the barge and adding horizontal speed.



It doesn't know where the center of the barge is.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AncientU on 04/16/2015 03:12 pm
So close.  Next time!!!

Gotta hand it to them, though, they've upped the drama factor considerably with two explosive attempts and the high seas wave-off.  Unintended consequence, of course, but their audience is growing leaps and bounds. 

Exciting to see real, live testing at the margin...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/16/2015 03:18 pm
Why is it a bad assumption? - if I'm SpaceX and I want to land this thing in the center of the deck then I'll make sure the barge positions itself so that the center point is located as close to this point as possible. 

If I'm wrong then where is the stage supposed to land? At one of the corners, at the port/starboard side? Love to hear where you think SpaceX want's it to land.

If you assume that the center of the barge landing area is located at the lat/long that the stage is told to land at,

Bad assumption
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JasonAW3 on 04/16/2015 03:23 pm
If you assume that the center of the barge landing area is located at the lat/long that the stage is told to land at, then yes the stage does know where the center is (by default)

Given that the landing area is small, the stage is programmed to land as close to that point as possible with little or no margin of error - maybe +/-  a meter or two. If, in the final second or two before landing, it finds it's off , it makes big changes to get back on track.

If the landing area is larger then the margin for landing is larger - you can program the stage to land at lat/long +/- 10 or 15 meters and it means less corrective measures are required in the final seconds.

I think the barge is just too small.  If the stage had a much bigger landing area to work with, it could focus on staying completely vertical and shedding horizontal velocity instead of trying to maneuver to the center of the barge and adding horizontal speed.



It doesn't know where the center of the barge is.

Perhaps the barge needs a set of short to medium range radio beacons to give final guidence to the stage for landing.  Medium range transmitters would actually allow the stage to align it's approach better and short range would allow a more centered landing.

Dual or quad beacons, each set at a different frequency, would allow the stage to triangulate it's approach for the optimum landing approach.

The receivers and antennas likely would add about 2 Kg to the overall stage mass and probably a couple of hundred lines of code to the avionics computers.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/16/2015 03:35 pm
For the umpteenth time, the existing system has adequate guidance/position accuracy. The barge position accuracy is +/- 3 meters, and the returning stage just demonstrated its own position accuracy. It would have landed within the circle if not for the sticking valve.

So SpaceX just demonstrated that, as several people have been repeatedly pointing out, the problem is not that the guidance/positioning systems are not accurate enough. They are.

Also, if you watch the video, the stage approach is quite vertical. The problem was a minor last-second correction that went bad because of the valve stiction. A radio beacon would not have improved terminal guidance and would not have prevented the crash in any case.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: NovaSilisko on 04/16/2015 03:35 pm
Will anyone ever give up this idea of putting a bunch of transponders and tracking devices on the barge to "guide" the stage in? The reason for the failure this time was because of a control failure in the rocket, not because it didn't know where the barge was. It quite plainly knew exactly where the barge was, because it tried its damndest to get onto the middle of it, just like with CRS-5.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/16/2015 03:36 pm
I think the barge is just too small.  If the stage had a much bigger landing area to work with, it could focus on staying completely vertical and shedding horizontal velocity instead of trying to maneuver to the center of the barge and adding horizontal speed.

Haven't they hit the barge enough times now to prove that they can hit the 10 acre patch of dirt they're aiming for?
Landing on land will be easier for several reasons (larger pad, same weather as launch, etc.) and SpaceX is trying to convince the Range, et al, to allow an RTLS attempt.  It could allow them to recover a booster, or at least the remains of one, on the first try.

But putting on my pedantic hat (it's the only hat I own), the barge is not too small.  Once all the issues are worked out I see no reason that the F9R won't consistently land within a couple of meters of it's target coordinates.  I'm not saying it won't take a few iterations or that it's "easy", just that it's doable and that is exactly the sort of accuracy you want.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Norm Hartnett on 04/16/2015 03:40 pm
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

It's called aerogel, and it is lime flavored, if I'm not mistaken.

No, lime flavor is green. Aerogel is raspberry flavored.

Wait a second, I thought the Jell-O referred to was made from NASA Kool-Aid and gelatin and was whatever flavor Congress authorized.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: thegreatpeon on 04/16/2015 03:41 pm
If the barge is capable of maintaining it's position (which it is within 3m even in rough weather) and the barge is in the specified landing location (which is set up in advance) then, yes, the rocket knows where the center of the barge is.

Jim is splitting hairs, as he likes to do, on the phrase "the rocket knows". Obviously the rocket is a dumb vehicle and doesn't "know" anything other than it's flight profile. The flight profile's destination IS the center of the barge (within 3m to account for the barges capabilities).

So, no, the assumptions listed are reasonable assumptions to make and are necessary for the rocket to make the landing. If you can't assume that the rocket "knows" where it's going, then you can't land it. Period.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: eriblo on 04/16/2015 03:53 pm
Regarding the "small landing area" and the perceived panicky last minute aiming for the center: I can't imagine other than that the stage is given a coordinate and an allowable deviation that takes into account the relative error in positioning of the ASDS/stage and the size of the landing surface. Maybe that deviation was restrictively set, but we don't really have any indication that that was the case.

The proposal for the Landing Complex 1 pad is 200ft by 200ft - i.e. barely larger than the JRtI. This is surrounded by a larger gravel surface that is obviously not meant for landing on. The contingency pads are even smaller and far enough away that they wouldn't matter at the very end like this (getting there would be harder than getting to the pad).

IMHO, what SpaceX is aiming for is getting any 1st stage to reliably land on a flat surface within <15 m of any GPS coordinate that is compatible with it's reserves when staging.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jaufgang on 04/16/2015 03:57 pm
I wonder how bad the damage is to the drone ship, and if it will be repaired in time for the next landing attempt.

Compared to the hard contact and kaboom last time? In all probability it's minimal.

EM has already tweeted the damage is light.

Well that little barge is a tough thing isnt it? lol. 2 explosions on it, and it holds up :)

That barge had a hard life *before* become the ASDS.  Deliberately sunk twice, for example.  It's a solid monster.

What's more likely is that some of SpaceX's equipment trailers got a little dinged up, and antennas bent.  But there's plenty of time before the next landing attempt to set that right.

For some reason this brought to mind a story I read several months ago about Chris Hadfield responding to a 5 year old boy who was worried about the Voyager probe being lonely or getting lost in interstellar space. 
(http://www.washingtonpost.com/news/morning-mix/wp/2014/09/26/astronaut-chris-hadfield-explains-to-a-worried-5-year-old-that-voyager-is-brave-and-happy-all-alone-in-space/ (http://www.washingtonpost.com/news/morning-mix/wp/2014/09/26/astronaut-chris-hadfield-explains-to-a-worried-5-year-old-that-voyager-is-brave-and-happy-all-alone-in-space/))

Quote
“I think the real question is,” Hadfield tells the boy, “Is Voyager happy or not? Is Voyager a happy machine, or a sad machine?”

“And I think about that,” Hadfield says, “because I grew up on a farm, and I used tractors and machines my whole life. And then I was a pilot, and so I flew airplanes my whole life. And I really like the machines that I’m working with to be happy. And what I was thinking, Timur, was, machines really like to do something. They like to do what they’re built for.

“To me, Voyager is so happy, because it’s the bravest satellite of all. It has gone the furthest. And it’s not lonely, because it’s talking to us. It phones home. And it tells us all about the wonderful things that it’s seeing.”


By this reckoning, I'd say that with enormous rockets swooping down and exploding on it's deck, it probably makes JRTI the happiest barge on the high seas.



Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/16/2015 04:02 pm
Why is it a bad assumption?


Because the barge might not be in the right spot.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: abaddon on 04/16/2015 04:08 pm
You know, the more I watch the latest video, the more I am convinced that if the surface of the barge were a handful of meters higher, the stage might have survived.  Anyone else thinking this might be the case, or am I alone on an island?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/16/2015 04:10 pm
Why is it a bad assumption?


Because the barge might not be in the right spot.
*facepalm* Are you trying to start another round of "they should put transponders on JRtI" posts? :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/16/2015 04:15 pm
Why is it a bad assumption?


Because the barge might not be in the right spot.
*facepalm* Are you trying to start another round of "they should put transponders on the JRtI" posts? :)

NOOOOOooooooo!!

There should be a separate thread for this zombie debate.

Pro: There should be a radio beacon in the barge!
Con: The position error of the current system is small and well within the margin provided by the barge deck size. Therefore a radio beacon is unnecessary.
Pro: But there should be a radio beacon in the barge!

Sigh.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevin-rf on 04/16/2015 04:28 pm
Fine, they should cover the barge with astro turf. That way the rocket thinks it's on land.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Okie_Steve on 04/16/2015 04:35 pm
Regarding the +/- 3 meter location of the ASDS. Is that uncertainty due to barge station keeping or GPS dither? I was under the impression that differential GPS could refine a location over time. Or is it the fact that the barge can't be completely stationary so differential won't work?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/16/2015 04:41 pm
Regarding the +/- 3 meter location of the ASDS. Is that uncertainty due to barge station keeping or GPS dither? I was under the impression that differential GPS could refine a location over time. Or is it the fact that the barge can't be completely stationary so differential won't work?

The barge position error is probably due more to the physics of the barge (very big, heavy, slow to respond to thrust inputs, susceptible to changing wind speed/direction, etc) and its thruster system (response time, etc) than the GPS accuracy.

Position *knowledge* based on GPS is probably within a meter or so. WAAS GPS is available at the barge location and can provide that level of accuracy. It's the physical ability of the barge to maintain that position that is likely the source of most of the error. IMHO.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Sohl on 04/16/2015 04:44 pm
Regarding the +/- 3 meter location of the ASDS. Is that uncertainty due to barge station keeping or GPS dither? I was under the impression that differential GPS could refine a location over time. Or is it the fact that the barge can't be completely stationary so differential won't work?

Differential corrections won't help the absolute position knowledge here, since the ASDS isn't fixed to the Earth's surface.  Differential corrections could_ help improve the relative error between the approaching rocket and the ASDS, if there was communication between ASDS and the booster.  However, all indications are that they don't share differential info like this and each independently targets the intended location based on their best available info and actuation ability.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/16/2015 04:49 pm
Assuming the speed of the Vine footage is correct,
https://vine.co/v/euEpIVegiIx

It seems like the last part of the descent is too fast to make pitch corrections without oscillations.  If they could slow the descent for the last 5 seconds or so, maybe that would help.

Also, rather than wind, it looks like the M1D gimbal may have overcompensated a few seconds before landing, as shown in the picture below.

Nice analysis.

Based on what others and Musk have shown or said, with my Occam's Razor (with lemony Aerogel!) making for a close shave, my early opinion is:

> Something was up with the throttling as the stage was already coming in too hot.

No, No, and no. The vertical speed was perfectly cancelled at touchdown. For the umpteenth time, the stage is not supposed to hover, and would gain nothing by doing so.

Something was clearly causing gimbal over-corrections, but the vertical speed was not the issue.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 04/16/2015 04:51 pm
I've got a handy NSF forum app in work where you can log into the forum, click on a thread, open a response window and then you click on the app.

Two electrodes attach to your hands and you get a shock if:

1) Your post is "HAHAHA, OMG, Amazing! "
2) You get into a Q&A battle with Jim.
3) You quote a 1000 word post and add "I agree" at the end of it.

;D

Basically, that's me saying "for the sake of the children, please make your post a worthwhile addition to this 130,000 viewed* thread"

*No, that doesn't mean 130,000 people have read it, per ULA's Vulcan poll voting system ;)

Carry on.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: somepitch on 04/16/2015 04:59 pm
I've got a handy NSF forum app in work where you can log into the forum, click on a thread, open a response window and then you click on the app.

Two electrodes attach to your hands and you get a shock if:

1) Your post is "HAHAHA, OMG, Amazing! "
2) You get into a Q&A battle with Jim.
3) You quote a 1000 word post and add "I agree" at the end of it.

;D

Basically, that's me saying "for the sake of the children, please make your post a worthwhile addition to this 130,000 viewed* thread"

*No, that doesn't mean 130,000 people have read it, per ULA's Vulcan poll voting system ;)

Carry on.

HAHAHA OMG amazing!

Just kidding... to keep this post on topic - could some of the engineers out there clarify a bit more what effect the stiction would have on the control loop?

Would the software be expecting a response of X magnitude, not get it due to lag, and then gimbal the engine over more to compensate leading to the oscillation once full thrust kicked in?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/16/2015 05:26 pm
Just kidding... to keep this post on topic - could some of the engineers out there clarify a bit more what effect the stiction would have on the control loop?

Would the software be expecting a response of X magnitude, not get it due to lag, and then gimbal the engine over more to compensate leading to the oscillation once full thrust kicked in?

Yes.  There is a position/attitude error of X.  The control system commands response Y to correct it.  However, after time T the error doesn't go away completely.  So the control system commands a slightly bigger response Y'.  The exact numerical relationship between X, Y, T, and Y' is carefully tuned and modeled, and in a correctly functioning system, the progressively bigger responses Y, Y', Y'', will eventually converge and result in the error being nulled out.  (This is a simple proportional-control system, and the actual SpaceX control algorithm is much more complicated, but this simple example should help you understand the basic principle.)

In the case there there is unexpected delay in the response, the errors and computed responses continue to grow for some time, ultimately leading to both a larger-than-expected error *and* a larger-than-expected response.  In this case, once the initial sticking friction was overcome the system found itself putting too much thrust into a too-far-tilted-over engine, causing the entire stage to tilt rather abruptly.  The control system worked correctly after this to restore the expected position and attitude, but there was a bit of overshoot (since the response had to reach Y'''' before the rocket responded, the control system assumed that an equally big input would be needed to correct things), and it ultimately it ran out of time and altitude.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ugordan on 04/16/2015 05:28 pm
https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/16/2015 05:29 pm
I've got a handy NSF forum app in work where you can log into the forum, click on a thread, open a response window and then you click on the app.

Two electrodes attach to your hands and you get a shock if:

1) Your post is "HAHAHA, OMG, Amazing! "
2) You get into a Q&A battle with Jim.
3) You quote a 1000 word post and add "I agree" at the end of it.

 ;D

Basically, that's me saying "for the sake of the children, please make your post a worthwhile addition to this 130,000 viewed* thread"

*No, that doesn't mean 130,000 people have read it, per ULA's Vulcan poll voting system ;)

Carry on.


Or you quote a 1000 word post and add "wrong"."  to the end.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: somepitch on 04/16/2015 05:29 pm
Just kidding... to keep this post on topic - could some of the engineers out there clarify a bit more what effect the stiction would have on the control loop?

Would the software be expecting a response of X magnitude, not get it due to lag, and then gimbal the engine over more to compensate leading to the oscillation once full thrust kicked in?

Yes.  There is a position/attitude error of X.  The control system commands response Y to correct it.  However, after time T the error doesn't go away completely.  So the control system commands a slightly bigger response Y'.  The exact numerical relationship between X, Y, T, and Y' is carefully tuned and modeled, and in a correctly functioning system, the progressively bigger responses Y, Y', Y'', will eventually converge and result in the error being nulled out.  (This is a simple proportional-control system, and the actual SpaceX control algorithm is much more complicated, but this simple example should help you understand the basic principle.)

In the case there there is unexpected delay in the response, the errors and computed responses continue to grow for some time, ultimately leading to both a larger-than-expected error *and* a larger-than-expected response.  In this case, once the initial sticking friction was overcome the system found itself putting too much thrust into a too-far-tilted-over engine, causing the entire stage to tilt rather abruptly.  The control system worked correctly after this to restore the expected position and attitude, but there was a bit of overshoot (since the response had to reach Y'''' before the rocket responded, the control system assumed that an equally big input would be needed to correct things), and it ultimately it ran out of time and altitude.

Thanks cscott - that's a great explanation!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: zubenelgenubi on 04/16/2015 05:32 pm
My favorite so far is landing in a giant pool of Jell-O. The aerospace kind, of course.

It's called aerogel, and it is lime flavored, if I'm not mistaken.

No, lime flavor is green. Aerogel is raspberry flavored.

Wait a second, I thought the Jell-O referred to was made from NASA Kool-Aid and gelatin and was whatever flavor Congress authorized.
Correction: Such a landing would be into a preparation of Jell-O 1-2-3 (creamy top layer, mousse-like middle layer, and standard Jell-O bottom layer).
 ;D
Just a thought,
Zubenelgenubi
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: somepitch on 04/16/2015 05:34 pm
https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Wow. So close. Even closer than it looks from the chase plane.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Zardar on 04/16/2015 05:37 pm
Fine, they should cover the barge with astro turf. That way the rocket thinks it's on land.

Nah, Use REAL turf.  Then you can have cows. Spacex rockets are used to cows.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ames on 04/16/2015 05:39 pm
Just before the explosion you can can see than one of the legs is not or is no longer, fully extended.
And the ram appears to be at the wrong angle. Did it compress or did it snap or did it get driven into the body of the stage.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/16/2015 05:40 pm
https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Wow. So close. Even closer than it looks from the chase plane.

That's incredible.  I'm trying to figure out exactly what happened to the legs, but it looks like two of them ended up failing.  The one you see pitching up at the very end of the video looks like it's been squashed down to the 90-degree deploy position.

And up until the very last second it looked like the octoweb was going to stay on the deck.  The initial explosion was up on the LOX side of the rocket.  If that had vented earlier, the engines might have been saved.  As it was, as soon as the LOX cloud got down to the kerosene-and-heat end of the rocket, things got seriously kaboomy.

From the last frames, it looks like the GoPro almost ended up over the side of the ASDS itself.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/16/2015 05:42 pm
https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Nice! And the stage looks otherwise in very good shape, aside from soot on the RP tank.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: anield on 04/16/2015 05:43 pm
I've got a handy NSF forum app in work where you can log into the forum, click on a thread, open a response window and then you click on the app.

Two electrodes attach to your hands and you get a shock if:

1) Your post is "HAHAHA, OMG, Amazing! "
2) You get into a Q&A battle with Jim.
3) You quote a 1000 word post and add "I agree" at the end of it.

;D

Basically, that's me saying "for the sake of the children, please make your post a worthwhile addition to this 130,000 viewed* thread"

*No, that doesn't mean 130,000 people have read it, per ULA's Vulcan poll voting system ;)

Carry on.

For #2 does it shock Jim too? ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/16/2015 05:45 pm
That's incredible.  I'm trying to figure out exactly what happened to the legs, but it looks like two of them ended up failing.  The one you see pitching up at the very end of the video looks like it's been squashed down to the 90-degree deploy position.

Not surprising, if the stage was leaning on one or two legs - together with some sideways impact, I would expect them to fail.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: corrodedNut on 04/16/2015 05:45 pm
https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Missed it by *that* much...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevin-rf on 04/16/2015 05:48 pm
For #2 does it shock Jim too? ;)
I dare you to try and find out ;) Me I am just gonna quote every post and then agree with them all!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Cherokee43v6 on 04/16/2015 05:49 pm
https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Interesting video.

A couple of things of note: 

It appears that the legs on the low-side failed, possibly due to the lateral motion combined with the speed at which the F9 touched down.  (Clarification edit:  I say this due to the number of comments I've seen around about a leg landing on the deck railing.)

In the last several frames prior to the explosion, it is clear that the Merlin nozzles had hard contact with the deck.  In particular, the low-side nozzles are significantly distorted outboard from center.  Again, this appears to be an artifact of lateral motion and a higher than optimal touch-down speed.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/16/2015 05:53 pm

is that camera distortion or is  the stage bending as it falls?

https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: notsorandom on 04/16/2015 05:54 pm
Just before the explosion you can can see than one of the legs is not or is no longer, fully extended.
And the ram appears to be at the wrong angle. Did it compress or did it snap or did it get driven into the body of the stage.
There has been speculation about a locking mechanism to hold the legs in place once they deploy. Regardless if there is one or not the leg lost its stiffness before the rocket started it tip over. As it is going over it looks like the leg just folds up and gets out of the way. If I had to guess I would say the initial impact rendered the leg useless.

It is now very clear why the stage wasn't able to be recovered when it landed in the ocean. It wasn't the impact of the landing that cause the rocker to RUD. That happened when it fell on its side. The impact of falling over on water is not much different from falling on the barge.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: abaddon on 04/16/2015 05:54 pm
Video of landing from the barge.

I have to say, the amount of data sharing (and the rapidity of the release of the data) the public is getting from SpaceX during these tests has been absolutely amazing.  Puts the lie to the trope that commercial operations has to mean total secrecy.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/16/2015 05:56 pm

is that camera distortion or is  the stage bending as it falls?

https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Camera distortion... Very wide angle. Look at the last frame before the 'explosion', the stage looks straight again.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: abaddon on 04/16/2015 05:56 pm
Not surprising, if the stage was leaning on one or two legs - together with some sideways impact, I would expect them to fail.

Agreed.  As light as the legs are, they can't have been built with that much margin, for an off-axis impact.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ohsin on 04/16/2015 06:07 pm
These videos need to be time aligned and merged together.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/16/2015 06:10 pm

is that camera distortion or is  the stage bending as it falls?

https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Camera distortion... Very wide angle. Look at the last frame before the 'explosion', the stage looks straight again.

We may be seeing the first bending mode of the stage. If you take a straightedge to the side of the stage frame by frame as it topples, there's a slight bow in it consistent with first bending mode. Then it straightens out in subsequent frames, well before it hits the deck.

This would be consistent with first bending mode being exicted by the collapsing leg pushing against the side of the stage.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/16/2015 06:12 pm
Not surprising, if the stage was leaning on one or two legs - together with some sideways impact, I would expect them to fail.

Agreed.  As light as the legs are, they can't have been built with that much margin, for an off-axis impact.
It's not only off axis, it was still rotating "clockwise" when it landed.  The loads on those legs were even higher than just coming in at an angle.

I don't know when they'll stick a landing, but I'm super confident they will.  What a site that will be. :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Senex on 04/16/2015 06:16 pm
https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Has this been noted?:

Just before the end of the video, the camera pans to the left, as if with intention to see the engine cluster.

It appears that someone is running that camera — remotely from one of the ships or SpaceX.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/16/2015 06:17 pm

is that camera distortion or is  the stage bending as it falls?

https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Camera distortion... Very wide angle. Look at the last frame before the 'explosion', the stage looks straight again.

We may be seeing the first bending mode of the stage. If you take a straightedge to the side of the stage frame by frame as it topples, there's a slight bow in it consistent with first bending mode. Then it straightens out in subsequent frames, well before it hits the deck.

This would be consistent with first bending mode being exicted by the collapsing leg pushing against the side of the stage.

Sigh.... Camera distortion.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/16/2015 06:17 pm
https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Has this been noted?:

Just before the end of the video, the camera pans to the left, as if with intention to see the engine cluster.

Someone is running that camera — remotely from one of the ships or SpaceX.

No, it looks more like someone is using a cell phone camera to film a monitor with footage. The GoPro on the ship would be static.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/16/2015 06:20 pm

is that camera distortion or is  the stage bending as it falls?

https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Camera distortion... Very wide angle. Look at the last frame before the 'explosion', the stage looks straight again.

We may be seeing the first bending mode of the stage. If you take a straightedge to the side of the stage frame by frame as it topples, there's a slight bow in it consistent with first bending mode. Then it straightens out in subsequent frames, well before it hits the deck.

This would be consistent with first bending mode being exicted by the collapsing leg pushing against the side of the stage.

Sigh.... Camera distortion.

Then why is there distortion when stage is between vertical and 45 degrees, and no distortion between 45 and 90 degrees?

You may be right, but it sure does look like the stage flexing as it falls.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: vanoord on 04/16/2015 06:20 pm
There has been speculation about a locking mechanism to hold the legs in place once they deploy. Regardless if there is one or not the leg lost its stiffness before the rocket started it tip over. As it is going over it looks like the leg just folds up and gets out of the way. If I had to guess I would say the initial impact rendered the leg useless.

Yep. You can see the upper/bracing beam of the right-hand (as you look at it) leg retracting as the stage falls over, indicating the locking mechanism has been overcome.

Presumably the hard landing is the likely the cause of this - the lateral movement and angle of landing are consistent with the forces that would result in significant damage to the leg mechanism.

From factory photos, it looks like the legs operate on hydraulics, so a significant landing impact on one leg *could* cause a burst somewhere in the hydraulic system and would allow the leg to retract upwards, which is consistent with the footage. That said, an analysis of the debris by someone who understands the workings of the system is going to be a lot better than my conjecturing!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/16/2015 06:23 pm
That said, an analysis of the debris by someone who understands the workings of the system is going to be a lot better than my conjecturing!

It's clear that SpaceX has a lot of good data here to learn from.  In addition to the pretty pictures, they've got telemetry, so they'll know exactly what attitude the stage was in (even when visually obscured), pressures in the hydralic systems, etc.  Wouldn't surprise me if there were load sensors in the feet as well.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: notsorandom on 04/16/2015 06:26 pm
There has been speculation about a locking mechanism to hold the legs in place once they deploy. Regardless if there is one or not the leg lost its stiffness before the rocket started it tip over. As it is going over it looks like the leg just folds up and gets out of the way. If I had to guess I would say the initial impact rendered the leg useless.

Yep. You can see the upper/bracing beam of the right-hand (as you look at it) leg retracting as the stage falls over, indicating the locking mechanism has been overcome.

Presumably the hard landing is the likely the cause of this - the lateral movement and angle of landing are consistent with the forces that would result in significant damage to the leg mechanism.

From factory photos, it looks like the legs operate on hydraulics, so a significant landing impact on one leg *could* cause a burst somewhere in the hydraulic system and would allow the leg to retract upwards, which is consistent with the footage. That said, an analysis of the debris by someone who understands the workings of the system is going to be a lot better than my conjecturing!
I'm not sure if the legs lock or not. The legs are pneumatic and the gas is helium I believe. Regardless though a sufficiently large impact might cause a pop it as you suggested.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: fast on 04/16/2015 06:29 pm
There has been speculation about a locking mechanism to hold the legs in place once they deploy. Regardless if there is one or not the leg lost its stiffness before the rocket started it tip over. As it is going over it looks like the leg just folds up and gets out of the way. If I had to guess I would say the initial impact rendered the leg useless.

Yep. You can see the upper/bracing beam of the right-hand (as you look at it) leg retracting as the stage falls over, indicating the locking mechanism has been overcome.

Presumably the hard landing is the likely the cause of this - the lateral movement and angle of landing are consistent with the forces that would result in significant damage to the leg mechanism.

From factory photos, it looks like the legs operate on hydraulics...


no, pneumatics (helium)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jtrame on 04/16/2015 06:29 pm
That said, an analysis of the debris by someone who understands the workings of the system is going to be a lot better than my conjecturing!

It's clear that SpaceX has a lot of good data here to learn from.  In addition to the pretty pictures, they've got telemetry, so they'll know exactly what attitude the stage was in (even when visually obscured), pressures in the hydralic systems, etc.  Wouldn't surprise me if there were load sensors in the feet as well.

Landscape mode on the video camera would help too.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Semmel on 04/16/2015 06:30 pm
I have to say, the amount of data sharing (and the rapidity of the release of the data) the public is getting from SpaceX during these tests has been absolutely amazing.  Puts the lie to the trope that commercial operations has to mean total secrecy.

I agree. I guess its partly because no one else in the industry believes its possible. Also no one can technically follow in the foreseeable future because no other rocket has an engine layout that would allow for propulsive landing like that. Vulcan, the only other rocket in succession that could have the chance is not capable of doing anything remotely similar because it has 2 engines that cant throttle to ~3% total thrust. So SpaceX does not risk much by showing the videos. On the contrary, the publicity gains talent.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ohsin on 04/16/2015 06:35 pm
Video of landing from the barge.

I have to say, the amount of data sharing (and the rapidity of the release of the data) the public is getting from SpaceX during these tests has been absolutely amazing.  Puts the lie to the trope that commercial operations has to mean total secrecy.

Well this one wasn't released officially? Was it? But yeah I get your point.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 04/16/2015 07:25 pm
If people create versions of the videos, can they do the site a favor and upload them to youtube, or something similar. Attaching say a 10mb video to a thread like this results in thousands of downloads (and usually via external linking from people who never even step foot in the site). That's just a bandwidth drain. Posting to youtube avoids that issue, it'll auto-embed and that'll work for everyone. Thanking you!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jimmy Murdok on 04/16/2015 07:35 pm
Here some details of the collapse.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Marslauncher on 04/16/2015 07:41 pm
Dammit, beaten to the images!

From what I was able to see, at least 1 if not 2 of the back legs were broken, as well as deformation of the engine bells towards that side.

So unbelievably close.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/16/2015 07:46 pm
I think your're right. Kinda though that when I looked at it first. "Close but no cigar" doesn't do this attempt justice. They almost made it.




is that camera distortion or is  the stage bending as it falls?

https://vid.me/i6o5

Video of landing from the barge.

EDIT: attached mp4 just in case...

Camera distortion... Very wide angle. Look at the last frame before the 'explosion', the stage looks straight again.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jimmy Murdok on 04/16/2015 07:59 pm
Dammit, beaten to the images!

From what I was able to see, at least 1 if not 2 of the back legs were broken, as well as deformation of the engine bells towards that side.

I think they are not broken just folded back, I selected some images where you can see the crossed bar reflected between the somoke and the hinges still in good shape.
Maybe a blocking mechanism would have saved the stage... Or maybe the legs offer some damping to the structure to avoid structural damage.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Marslauncher on 04/16/2015 08:11 pm
Agreed, I saw that also. I meant broken in the sense they were not in the position they needed to be :)

I wonder what the upgraded, deploy earlier, beefed up?, legs will offer later this year.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cambrianera on 04/16/2015 08:22 pm

I wonder what the upgraded, deploy earlier, beefed up?, legs will offer later this year.

Me too.
Well, maybe I already know what they can offer....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Karloss12 on 04/16/2015 08:23 pm
I can't help but think that the F9's inability to hover is delaying the first successful landing, and will even provide hassle and uncertainty when they get good at landing the first stage.

Landing by instantaneous hover slam on a platform that has a theoretical elevation that could actually be a couple of feet higher or lower in the real world does seem like the hard way to do it.

I suspect that when they do begin landing on land, additional options will become available to guide the stage into landing.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/16/2015 08:29 pm
Landing by instantaneous hover slam on a platform that has a theoretical elevation that could actually be a couple of feet higher or lower in the real world does seem like the hard way to do it.

I suspect that when they do begin landing on land, additional options will become available to guide the stage into landing.

It's not a "theoretical elevation." It's an actual measurement obtained by radar altimeter. As others have noted, the elevation was not the problem. The stage reached zero vertical velocity right at touchdown.

And additional options are not needed for land landings. The radar altimeter has worked perfectly for Grasshopper/F9R Dev landings, it worked perfectly on this barge (crash) landing, and it will work perfectly at LC-13.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/16/2015 08:39 pm
Dammit, beaten to the images!

From what I was able to see, at least 1 if not 2 of the back legs were broken, as well as deformation of the engine bells towards that side.

I think they are not broken just folded back, I selected some images where you can see the crossed bar reflected between the somoke and the hinges still in good shape.
Maybe a blocking mechanism would have saved the stage... Or maybe the legs offer some damping to the structure to avoid structural damage.

It. doesn't. matter. If the stage leans over that far, it will fall!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/16/2015 08:43 pm
I can't help but think that the F9's inability to hover is delaying the first successful landing, and will even provide hassle and uncertainty when they get good at landing the first stage.

Landing by instantaneous hover slam on a platform that has a theoretical elevation that could actually be a couple of feet higher or lower in the real world does seem like the hard way to do it.

I suspect that when they do begin landing on land, additional options will become available to guide the stage into landing.

Hovering DOES NOT help. I'm not sure how many times that can be explained.

Either the stage knows where the ground landing spot is, or it doesn't. Hovering will not help.
Either the stage knows the ground elevation or it doesn't. Hovering will not help.
Either the stage gets a strong wind gust when landing or it doesn't. Hovering will not help (it probably hurts, since you would be exposed to the wind longer), and the same gust could just as easily appear later.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Semmel on 04/16/2015 08:46 pm
I think they are not broken just folded back, I selected some images where you can see the crossed bar reflected between the somoke and the hinges still in good shape.
Maybe a blocking mechanism would have saved the stage... Or maybe the legs offer some damping to the structure to avoid structural damage.

It. doesn't. matter. If the stage leans over that far, it will fall!

Im with you on this one. The legs were used in an non-secified situation. Of course they fail. Its not the fault of the legs. Its not the fault of the legs design. They are build to handle almost vertical landing. Not 5-10 degrees off-vertical landing.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: abaddon on 04/16/2015 08:51 pm
Hovering DOES NOT help. I'm not sure how many times that can be explained.
On the other hand, Hoovering will help.  How else do you expect them to clean the deck?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Mader Levap on 04/16/2015 09:02 pm
I have to say, the amount of data sharing (and the rapidity of the release of the data) the public is getting from SpaceX during these tests has been absolutely amazing.  Puts the lie to the trope that commercial operations has to mean total secrecy.
Um, this one was leak, not anything official. Of course it is possible it is video that was meant to be officially released as promised by Musk.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jimmy Murdok on 04/16/2015 09:22 pm
It. doesn't. matter. If the stage leans over that far, it will fall!

Im with you on this one. The legs were used in an non-secified situation. Of course they fail. Its not the fault of the legs. Its not the fault of the legs design. They are build to handle almost vertical landing. Not 5-10 degrees off-vertical landing.

Sure no need to modify the legs as in nominal conditions will work. Just wondering if there is a blocking mechanism that was broken or there is some kind of dampening with the pneumatic cylinders that was pushed too hard and was not able to raise back.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 04/16/2015 09:30 pm

Um, this one was leak, not anything official. Of course it is possible it is video that was meant to be officially released as promised by Musk.

I've lost track with what they've released, but SpaceX run a very tight ship, so I'd be surprised if it was an internal leak.

Potentially accidental publication, but we didn't publish it, it's just been linked here from an external site (and also on 101 other sites), so there's not a lot we can do about that. I wonder if it was published via official lines and taken down, but grabbed before it was removed. I'll see if I can find out.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/16/2015 09:33 pm
It. doesn't. matter. If the stage leans over that far, it will fall!

Im with you on this one. The legs were used in an non-secified situation. Of course they fail. Its not the fault of the legs. Its not the fault of the legs design. They are build to handle almost vertical landing. Not 5-10 degrees off-vertical landing.

Sure no need to modify the legs as in nominal conditions will work. Just wondering if there is a blocking mechanism that was broken or there is some kind of dampening with the pneumatic cylinders that was pushed too hard and was not able to raise back.

I'm not sure what you are fishing for here. Even if a blocking mechanism is in place, I very much doubt that it can handle the entire stage's weight on it - or the sideways motion The legs are light weight, with limited strength. They have to be... Otherwise they would be too heavy to carry uphill.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rsnellenberger on 04/16/2015 09:41 pm
Fine, they should cover the barge with astro turf. That way the rocket thinks it's on land.

Nah, Use REAL turf.  Then you can have cows. Spacex rockets are used to cows.


AstroTurf (R) is also fairly notorious for causing damage to legs...

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: catdlr on 04/16/2015 09:54 pm
An Analysis of SpaceX’s Falcon 9 Crash Landing

by: RHETT ALLAIN

http://www.wired.com/2015/04/analysis-falcon-9-crash-landing/
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DatUser14 on 04/16/2015 10:13 pm
Dailymail.uk being lovely as ever:

Quote
SpaceX is planning to land a rocket at Cape Canaveral on Monday
The first stage of their Falcon 9 rocket will attempt to touch down on a barge after launching a Dragon capsule into space
It is the first ever attempt at landing a rocket on solid ground after launch
Elon Musk said the ambitious attempt has a 50% chance of working
The company ultimately wants all of its rockets to be reusable
emphasis mine.
Also, they had v1.0 images in the article labeled as being 1.1, those images should be removed from the internet.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jimmy Murdok on 04/16/2015 10:40 pm
It. doesn't. matter. If the stage leans over that far, it will fall!

Im with you on this one. The legs were used in an non-secified situation. Of course they fail. Its not the fault of the legs. Its not the fault of the legs design. They are build to handle almost vertical landing. Not 5-10 degrees off-vertical landing.

Sure no need to modify the legs as in nominal conditions will work. Just wondering if there is a blocking mechanism that was broken or there is some kind of dampening with the pneumatic cylinders that was pushed too hard and was not able to raise back.

I'm not sure what you are fishing for here. Even if a blocking mechanism is in place, I very much doubt that it can handle the entire stage's weight on it - or the sideways motion The legs are light weight, with limited strength. They have to be... Otherwise they would be too heavy to carry uphill.

Probably discussed before... not sure. How do the legs stay extended for landing?
1- They get blocked when deployed and cannot go back, so it's a rigid system.
2- The cylinders maintain high he pressure to hold the weight and maybe allowing for some damping on touchdown.

In case one, the internal structure of the legs got broken.
In second case the legs folded back by loosing pressure or because the hard push fold it back in a similar way of a car tailgate closing.

I cannot get a clue of how the system works from F9R Dev-1 vídeos.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mn on 04/16/2015 11:06 pm
I was wondering what impact the Kaboom we see in the video would have at LC-13?

Can anyone estimate the range of potential damage based on the video of the explosion?

Is LC-13 far enough from anything else important that this type of unhappy ending can be handled without damage?

While we all expect/hope/assume that landing on land will have a much better ending, it is still at least possible to end in a similar kaboom.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Cherokee43v6 on 04/16/2015 11:26 pm
I was wondering what impact the Kaboom we see in the video would have at LC-13?

Can anyone estimate the range of potential damage based on the video of the explosion?

Is LC-13 far enough from anything else important that this type of unhappy ending can be handled without damage?

While we all expect/hope/assume that landing on land will have a much better ending, it is still at least possible to end in a similar kaboom.

I think the 'kaboom' in question is less like an 'explosive charge' and more like a 'grenade'.  Basically meaning that it isn't the 'blast pressure' that would cause issues, but instead the 'shrapnel' of the rocket body.

With that said, once you understand how much explosive force the remaining on-board fuels can create, you can plan for how far the shrapnel risk extends and thus design your safety/keep out zone accordingly.  If you watch the higher quality video that filmed the descent and landing (not the one on the barge) you can get a decent idea of the shrapnel radius, which wasn't terribly large, all things considered.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/16/2015 11:47 pm
It. doesn't. matter. If the stage leans over that far, it will fall!

Im with you on this one. The legs were used in an non-secified situation. Of course they fail. Its not the fault of the legs. Its not the fault of the legs design. They are build to handle almost vertical landing. Not 5-10 degrees off-vertical landing.

Sure no need to modify the legs as in nominal conditions will work. Just wondering if there is a blocking mechanism that was broken or there is some kind of dampening with the pneumatic cylinders that was pushed too hard and was not able to raise back.

I'm not sure what you are fishing for here. Even if a blocking mechanism is in place, I very much doubt that it can handle the entire stage's weight on it - or the sideways motion The legs are light weight, with limited strength. They have to be... Otherwise they would be too heavy to carry uphill.

Probably discussed before... not sure. How do the legs stay extended for landing?
1- They get blocked when deployed and cannot go back, so it's a rigid system.
2- The cylinders maintain high he pressure to hold the weight and maybe allowing for some damping on touchdown.

In case one, the internal structure of the legs got broken.
In second case the legs folded back by loosing pressure or because the hard push fold it back in a similar way of a car tailgate closing.

I cannot get a clue of how the system works from F9R Dev-1 vídeos.

There's an entire thread for "Landing Legs" discussion that is pertinent to this event:

http://forum.nasaspaceflight.com/index.php?topic=33788.0 (http://forum.nasaspaceflight.com/index.php?topic=33788.0)

All your answers (and many more) can be found towards the end of it. :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: iamlucky13 on 04/17/2015 12:20 am
I can't help but think that the F9's inability to hover is delaying the first successful landing, and will even provide hassle and uncertainty when they get good at landing the first stage.

Landing by instantaneous hover slam on a platform that has a theoretical elevation that could actually be a couple of feet higher or lower in the real world does seem like the hard way to do it.

I suspect that when they do begin landing on land, additional options will become available to guide the stage into landing.

Hovering DOES NOT help. I'm not sure how many times that can be explained.

Either the stage knows where the ground landing spot is, or it doesn't. Hovering will not help.
Either the stage knows the ground elevation or it doesn't. Hovering will not help.
Either the stage gets a strong wind gust when landing or it doesn't. Hovering will not help (it probably hurts, since you would be exposed to the wind longer), and the same gust could just as easily appear later.

If they could hover and had the fuel to spare, that gives them more time to settle out the oscillations. But that does require that the control system be sufficiently tuned to do so, and operate properly. If the stiction and resulting lag was the real issue, it might not, in which case, the time afforded by hovering could actually have just turned into more time for the rocket to completely lose control.

Also, if were capable of hovering, it would also be capable of a constant rate descent at a survivable touchdown speed. The fuel burn would be excessive, but that eliminates the need to know exactly where the ground is. The landing plan for MSL incorporated both of these elements.

Either way, the easier solution is almost certainly improved tuning of the control system and/or fixing the valve issues, rather than modifying Merlin to be capable of such deep throttling. MSL was designed from the start with deep throttling, and was willing to sacrifice mass for the necessary fuel as a risk reduction. JPL didn't want to try a hover slam.

I was wondering what impact the Kaboom we see in the video would have at LC-13?

Can anyone estimate the range of potential damage based on the video of the explosion?

Is LC-13 far enough from anything else important that this type of unhappy ending can be handled without damage?

While we all expect/hope/assume that landing on land will have a much better ending, it is still at least possible to end in a similar kaboom.

Consider Antares, which was almost fully fueled. There was definitely damage, but not very far around. As far as I know, LC-13 doesn't haven't anything within its perimeter of importance at the moment, so if it accurately guided to the pad and crashed, there's probably less harm done than crashing into the barge.

The main concern is the need for certainty the rocket will actually land or crash at LC-13, instead of, say, downtown Titusville. Even a perfect touchdown on an elementary school would still be a bad touchdown.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Karloss12 on 04/17/2015 12:23 am
I can't help but think that the F9's inability to hover is delaying the first successful landing, and will even provide hassle and uncertainty when they get good at landing the first stage.

Landing by instantaneous hover slam on a platform that has a theoretical elevation that could actually be a couple of feet higher or lower in the real world does seem like the hard way to do it.

I suspect that when they do begin landing on land, additional options will become available to guide the stage into landing.

Hovering DOES NOT help. I'm not sure how many times that can be explained.

Either the stage knows where the ground landing spot is, or it doesn't. Hovering will not help.
Either the stage knows the ground elevation or it doesn't. Hovering will not help.
Either the stage gets a strong wind gust when landing or it doesn't. Hovering will not help (it probably hurts, since you would be exposed to the wind longer), and the same gust could just as easily appear later.

All true for a mature system, however my expression of opinion primarily related to this recent "test attempt".  I think a 3 second hover would have given the control system time to recover from the various issues, so that vertical alignment could have stabalised and a successful landing could have been made.  Then SpaceX would be bringing an F9 home in tact.

Your comment relating to wind sort of proves my point.
I think that just as there is an automated emergency abort system prior to lift off for when a parameter is not acceptable, when landing, it would be advantageous for the control system to activate an emergency hover for when perimeters are not acceptable for touch down.  For instance, when there is a sudden strong wind gust that tilts the stage from vertical moments before landing.  With this emergency hover, you get a second chance at saving ~$40mill.  It costs a bit of fuel of course.

Currently the stage only has one shot, whether the rocket is at a safe angle or not (explodes).  There is no redundancy.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/17/2015 12:49 am
All true for a mature system, however my expression of opinion primarily related to this recent "test attempt".  I think a 3 second hover would have given the control system time to recover from the various issues, so that vertical alignment could have stabalised and a successful landing could have been made.  Then SpaceX would be bringing an F9 home in tact.

Your comment relating to wind sort of proves my point.
I think that just as there is an automated emergency abort system prior to lift off for when a parameter is not acceptable, when landing, it would be advantageous for the control system to activate an emergency hover for when perimeters are not acceptable for touch down.  For instance, when there is a sudden strong wind gust that tilts the stage from vertical moments before landing.  With this emergency hover, you get a second chance at saving ~$40mill.  It costs a bit of fuel of course.

Currently the stage only has one shot, whether the rocket is at a safe angle or not (explodes).  There is no redundancy.

It was reported (a) in the press conference that the stage has around 3 seconds of fuel left at touchdown and (b) previously by Elon that the stage is too light to 'hover' even on one engine.. that's why the landing profile we see is what it is.

ISTM they'll need to beef up the landing leg system for future 'barge landings', beefier than would likely be okay on land, because there are always going to be times where the ASDS could lurch just on the point of touchdown, imparting additional forces on the legs. IOW, every barge landing in anything more than flat calm is likely to be a 'hard' landing.  This will add mass, more fuel (should they choose that) adds mass...

After watching this landing attempt and how well they actually did, I'm starting to wonder if they'll ever manage to recover a stage on the barge in anything other than perfect sea/wind conditions: certainly, doing it the way they're doing it, their recovery rate is going to be very low.

..but Musk isn't a quitter and we'll see how they go with CRS-7. :)
 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Mongo62 on 04/17/2015 01:27 am
After watching this landing attempt and how well they actually did, I'm starting to wonder if they'll ever manage to recover a stage on the barge in anything other than perfect sea/wind conditions: certainly, doing it the way they're doing it, their recovery rate is going to be very low.

I don't know about that. It seemed to me that the stage's trajectory was right down the middle until just moments before landing, with a massive excursion (due to a valve sticking, as Elon suggested, at the worst possible time?) throwing it way off the intended attitude and trajectory. And yet the onboard software managed to land it within the ring, but with a horizontal velocity at touchdown that was enough over the upper safe limit to break one of the legs, at which point toppling was inevitable.

Without that valve issue, it almost certainly would have successfully landed and stayed upright.

SpaceX has a history of encountering a given technical issue on one flight, fixing it, and it never being a problem again (other than the helium issues, which do keep happening). So far, with first stage landing they have had engine shutoff due to centrifuging on Cassiope (fixed by extra cold gas thruster authority (and beefed up prop tank baffles?)), excess distance from target on CRS-3 and OG2 (fixed by installing grid fins), grid fins "freezing" partway through the descent on CRS-5 (fixed by increasing amount of grid fin working fluid) and now a sticky valve on CRS-6. I am confident that this issue can be dealt with as well.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: seanpg71 on 04/17/2015 01:36 am
...

All true for a mature system, however my expression of opinion primarily related to this recent "test attempt".  I think a 3 second hover would have given the control system time to recover from the various issues, so that vertical alignment could have stabalised and a successful landing could have been made.  Then SpaceX would be bringing an F9 home in tact.

Your comment relating to wind sort of proves my point.
I think that just as there is an automated emergency abort system prior to lift off for when a parameter is not acceptable, when landing, it would be advantageous for the control system to activate an emergency hover for when perimeters are not acceptable for touch down.  For instance, when there is a sudden strong wind gust that tilts the stage from vertical moments before landing.  With this emergency hover, you get a second chance at saving ~$40mill.  It costs a bit of fuel of course.

Currently the stage only has one shot, whether the rocket is at a safe angle or not (explodes).  There is no redundancy.

When you're driving and approaching a stop sign, do you make sure to come to a full and complete stop 20 feet before the stop sign, then look around for 3 seconds to make sure your steering wheel is straight, and then slowly inch up to the actual stop sign?

Perhaps if it's icy or if you're towing something you might slow down a bit more aggressively a bit earlier to make sure you stay in control and then roll forward, but I'm assuming you don't stop and 'hover' before the sign, start again, and then stop where you intend to.

Similarly, if the F9 stage is in control, it doesn't make any sense to hover.  If it's *not* in control, then that should be fixed by slowing down a bit more aggressively earlier (which is probably not an option), or adding more power to the fins or thrusters or making sure that the throttle is more responsive (which sounds like it may be the problem here). 

For a human, it seems like zeroing horizontal and vertical velocity at the exact spot you want to touch down in a matter of a few seconds while falling is difficult.  But it's not terribly different than you stopping your car on a line, it's just extra math.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/17/2015 01:40 am

After watching this landing attempt and how well they actually did, I'm starting to wonder if they'll ever manage to recover a stage on the barge in anything other than perfect sea/wind conditions: certainly, doing it the way they're doing it, their recovery rate is going to be very low.

..but Musk isn't a quitter and we'll see how they go with CRS-7. :)


The barge conditions during this attempt were far from perfect, yet even so, had the throttle response been working properly, I think they would have nailed the landing.  I agree that there will likely be a fair number of times when the conditions simply won't allow a barge landing, but I'm pretty confident after watching the latest video that these will be in a clear minority.


No reason for anybody to be a quitter considering the circumstances, success is almost within their grasp.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 04/17/2015 01:45 am
...
Hovering DOES NOT help. I'm not sure how many times that can be explained.

Either the stage knows where the ground landing spot is, or it doesn't. Hovering will not help.
Either the stage knows the ground elevation or it doesn't. Hovering will not help.
Either the stage gets a strong wind gust when landing or it doesn't. Hovering will not help (it probably hurts, since you would be exposed to the wind longer), and the same gust could just as easily appear later.

If they could hover and had the fuel to spare, that gives them more time to settle out the oscillations. But that does require that the control system be sufficiently tuned to do so, and operate properly. If the stiction and resulting lag was the real issue, it might not, in which case, the time afforded by hovering could actually have just turned into more time for the rocket to completely lose control.

Or it provides time for the oscillations to get way worse...  You want the control system of a rocket to make simple, fast decisions.  Not to try to second guess how it should proceed.  It's really not realistic to create a "just in case" hover mode for situations that the control system can't already handle.  Hovering is a not magic bullet.  It increases the decision matrix of the control system making it harder to test and verify that you got it right. It does not make it inherently safer, just more complicated.

Just fix the lag induced over corrections and move on to the next test.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/17/2015 02:16 am

After watching this landing attempt and how well they actually did, I'm starting to wonder if they'll ever manage to recover a stage on the barge in anything other than perfect sea/wind conditions: certainly, doing it the way they're doing it, their recovery rate is going to be very low.

..but Musk isn't a quitter and we'll see how they go with CRS-7. :)

The barge conditions during this attempt were far from perfect, yet even so, had the throttle response been working properly, I think they would have nailed the landing.  I agree that there will likely be a fair number of times when the conditions simply won't allow a barge landing, but I'm pretty confident after watching the latest video that these will be in a clear minority.

I'd like to think so.. here's my train of thought - tell me if I'm wrong:

1. The ASDS is parked across the wind/waves so the Stage's final approach is into the wind, descending ie. coming down at an angle to the deck of, for arguments sake, let's say 45 degrees.

2. Because the ASDS is across the waves, any swell will cause it to roll and maybe even heave slightly, so the stage is coming down onto a platform that is see-sawing (not level).

3. Assuming they don't know the ASDS's roll-rate because there's no telemetry to the stage (maybe there is?) with landing radar is looking straight down, the stage will see the 'ground' rising and falling at a different rate than it actually is at the final impact point.

4. If the stage lands bang on-target, one leg will meet a rising deck, and the others a falling one, or vice versa, depending upon stage orientation - and depending upon the amount of roll, this could amount to more than a few inches one way or the other.  The stage body can't translate instantaneously to the motion of the ASDS, so those additional impact forces must be taken by the legs alone - and the 'rising' leg particularly - and presumably there's some limit to the shock-absorbing ability of each leg.

It appears to me that, this time around, throttle issues or not, said 'shock absorbing' didn't work too well on one leg... specifically the first leg to hit the deck.. No?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 04/17/2015 02:44 am
I've got a handy NSF forum app in work where you can log into the forum, click on a thread, open a response window and then you click on the app.

Two electrodes attach to your hands and you get a shock if:

1) Your post is "HAHAHA, OMG, Amazing! "
2) You get into a Q&A battle with Jim.
3) You quote a 1000 word post and add "I agree" at the end of it.

 ;D

Basically, that's me saying "for the sake of the children, please make your post a worthwhile addition to this 130,000 viewed* thread"

*No, that doesn't mean 130,000 people have read it, per ULA's Vulcan poll voting system ;)

Carry on.


Or you quote a 1000 word post and add "wrong"."  to the end.

requested an "Agree" & "Disagree" a long time ago  8)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 04/17/2015 02:48 am
Video of landing from the barge.

I have to say, the amount of data sharing (and the rapidity of the release of the data) the public is getting from SpaceX during these tests has been absolutely amazing.  Puts the lie to the trope that commercial operations has to mean total secrecy.

agrees 100%, well done SpaceX or the leaker?  :P
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/17/2015 02:50 am

After watching this landing attempt and how well they actually did, I'm starting to wonder if they'll ever manage to recover a stage on the barge in anything other than perfect sea/wind conditions: certainly, doing it the way they're doing it, their recovery rate is going to be very low.

..but Musk isn't a quitter and we'll see how they go with CRS-7. :)

The barge conditions during this attempt were far from perfect, yet even so, had the throttle response been working properly, I think they would have nailed the landing.  I agree that there will likely be a fair number of times when the conditions simply won't allow a barge landing, but I'm pretty confident after watching the latest video that these will be in a clear minority.

I'd like to think so.. here's my train of thought - tell me if I'm wrong:

1. The ASDS is parked across the wind/waves so the Stage's final approach is into the wind, descending ie. coming down at an angle to the deck of, for arguments sake, let's say 45 degrees.

2. Because the ASDS is across the waves, any swell will cause it to roll and maybe even heave slightly, so the stage is coming down onto a platform that is see-sawing (not level).

3. Assuming they don't know the ASDS's roll-rate because there's no telemetry to the stage (maybe there is?) with landing radar is looking straight down, the stage will see the 'ground' rising and falling at a different rate than it actually is at the final impact point.

4. If the stage lands bang on-target, one leg will meet a rising deck, and the others a falling one, or vice versa, depending upon stage orientation - and depending upon the amount of roll, this could amount to more than a few inches one way or the other.  The stage body can't translate instantaneously to the motion of the ASDS, so those additional impact forces must be taken by the legs alone - and the 'rising' leg particularly - and presumably there's some limit to the shock-absorbing ability of each leg.

It appears to me that, this time around, throttle issues or not, said 'shock absorbing' didn't work too well on one leg... specifically the first leg to hit the deck.. No?


It looked to me like, because of the late throttle, the stage impacted the barge on one leg at a significantly higher velocity than the barge's motion would be likely to impart.  In other words, I'm assuming (yes, I know that's dangerous) that SpaceX has calculated the likely motions of the barge under most scenarios and concluded that the legs are strong enough to absorb those motions during a nominal touchdown.


Maybe Gwen Shotwell's announcement that they are attempting clearance for a moved-up dry land return means they've recalculated those parameters and are no longer so optimistic.  But maybe not.


In the latest attempt, the movement of the barge doesn't seem to have been an issue.  The excessive movement of the stage was.  And that was due to the sticky throttle valve.  So I don't think the current videos support your argument.  Granted, however, they don't disprove it either.  However, until there's clear evidence that the barge landing was a bad idea all along, I'm going to accept Elon's explanation and remain optimistic.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 04/17/2015 02:59 am

Um, this one was leak, not anything official. Of course it is possible it is video that was meant to be officially released as promised by Musk.

I've lost track with what they've released, but SpaceX run a very tight ship, so I'd be surprised if it was an internal leak.

Potentially accidental publication, but we didn't publish it, it's just been linked here from an external site (and also on 101 other sites), so there's not a lot we can do about that. I wonder if it was published via official lines and taken down, but grabbed before it was removed. I'll see if I can find out.

came on NSF cause the video was listed on my yahoo....so its OUT.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/17/2015 03:19 am

After watching this landing attempt and how well they actually did, I'm starting to wonder if they'll ever manage to recover a stage on the barge in anything other than perfect sea/wind conditions: certainly, doing it the way they're doing it, their recovery rate is going to be very low.

..but Musk isn't a quitter and we'll see how they go with CRS-7. :)

The barge conditions during this attempt were far from perfect, yet even so, had the throttle response been working properly, I think they would have nailed the landing.  I agree that there will likely be a fair number of times when the conditions simply won't allow a barge landing, but I'm pretty confident after watching the latest video that these will be in a clear minority.

I'd like to think so.. here's my train of thought - tell me if I'm wrong:

1. The ASDS is parked across the wind/waves so the Stage's final approach is into the wind, descending ie. coming down at an angle to the deck of, for arguments sake, let's say 45 degrees.

2. Because the ASDS is across the waves, any swell will cause it to roll and maybe even heave slightly, so the stage is coming down onto a platform that is see-sawing (not level).

3. Assuming they don't know the ASDS's roll-rate because there's no telemetry to the stage (maybe there is?) with landing radar is looking straight down, the stage will see the 'ground' rising and falling at a different rate than it actually is at the final impact point.

4. If the stage lands bang on-target, one leg will meet a rising deck, and the others a falling one, or vice versa, depending upon stage orientation - and depending upon the amount of roll, this could amount to more than a few inches one way or the other.  The stage body can't translate instantaneously to the motion of the ASDS, so those additional impact forces must be taken by the legs alone - and the 'rising' leg particularly - and presumably there's some limit to the shock-absorbing ability of each leg.

It appears to me that, this time around, throttle issues or not, said 'shock absorbing' didn't work too well on one leg... specifically the first leg to hit the deck.. No?


It looked to me like, because of the late throttle, the stage impacted the barge on one leg at a significantly higher velocity than the barge's motion would be likely to impart.  In other words, I'm assuming (yes, I know that's dangerous) that SpaceX has calculated the likely motions of the barge under most scenarios and concluded that the legs are strong enough to absorb those motions during a nominal touchdown.


Maybe Gwen Shotwell's announcement that they are attempting clearance for a moved-up dry land return means they've recalculated those parameters and are no longer so optimistic.  But maybe not.


In the latest attempt, the movement of the barge doesn't seem to have been an issue.  The excessive movement of the stage was.  And that was due to the sticky throttle valve.  So I don't think the current videos support your argument.  Granted, however, they don't disprove it either.  However, until there's clear evidence that the barge landing was a bad idea all along, I'm going to accept Elon's explanation and remain optimistic.

Agreed. :)

I was assuming (yes, dangerous indeed!) that the legs were designed (during the Grasshopper program) with enough shock absorbing to handle 'land' landings and that maybe the size of the change in conditions is something unexpected.  IMHO, even the apparent change in parking position from into-the-wind to across-the-wind could increase the amount of movement of the deck and hence leg loads - but we don't yet have on-board video (only the one frame used in the press conference) that shows motion of the ASDS w.r.t ocean, so although we know it wasn't 'rough' we don't know how flat it was either.

Whatever else they do, I'm expecting beefier shock-absorbing for the next attempt... if it's not on land first.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/17/2015 04:02 am

I'd like to think so.. here's my train of thought - tell me if I'm wrong:

1. The ASDS is parked across the wind/waves so the Stage's final approach is into the wind, descending ie. coming down at an angle to the deck of, for arguments sake, let's say 45 degrees.

2. Because the ASDS is across the waves, any swell will cause it to roll and maybe even heave slightly, so the stage is coming down onto a platform that is see-sawing (not level).

3. Assuming they don't know the ASDS's roll-rate because there's no telemetry to the stage (maybe there is?) with landing radar is looking straight down, the stage will see the 'ground' rising and falling at a different rate than it actually is at the final impact point.

4. If the stage lands bang on-target, one leg will meet a rising deck, and the others a falling one, or vice versa, depending upon stage orientation - and depending upon the amount of roll, this could amount to more than a few inches one way or the other.  The stage body can't translate instantaneously to the motion of the ASDS, so those additional impact forces must be taken by the legs alone - and the 'rising' leg particularly - and presumably there's some limit to the shock-absorbing ability of each leg.

It appears to me that, this time around, throttle issues or not, said 'shock absorbing' didn't work too well on one leg... specifically the first leg to hit the deck.. No?

I think one thing you're overlooking is that contact with the deck is not a step function.

There are two processes happening concurrently.

A) The engines are cut, and their thrust goes to zero over a certain period
B) The legs start taking weight, flexing as they do

While supported by the engine, the rocket doesn't care about deck angles.
While supported by the legs, of course it does.

Over a period of 1-2 seconds, the first legs begins to compress more, imparting a torque to the stage, which now begins to follow the deck.  The other legs are not free falling, since the engine is still producing thrust.

I think that these dynamics have been taken into account, and the control algorithm is actually trying to bring the rocket not to z=0 (initial contact) but rather to z=-max_deflection, while anticipating the forces from the legs.

---

There's an old question from high school physics about a simply support beam, and a weight that's placed in the middle.  If you lightly place the weight on the beam (achieving contact) and then release it, the beam will deflect twice as far compared with the case of placing the weight and slowing lowering it until equilibrium is reached.

So to make the analogy explicit, the weight is the rocket, the beam is the legs, and the hand is the thrust of the engine.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/17/2015 04:21 am
I was wondering what impact the Kaboom we see in the video would have at LC-13?

Can anyone estimate the range of potential damage based on the video of the explosion?

Is LC-13 far enough from anything else important that this type of unhappy ending can be handled without damage?

While we all expect/hope/assume that landing on land will have a much better ending, it is still at least possible to end in a similar kaboom.

The damage radius seemed to be few hundreds of feet.  The distance between pads at CCAFS is 2000'.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/17/2015 04:34 am
Over a period of 1-2 seconds, the first legs begins to compress more, imparting a torque to the stage, which now begins to follow the deck.  The other legs are not free falling, since the engine is still producing thrust.

I think that these dynamics have been taken into account, and the control algorithm is actually trying to bring the rocket not to z=0 (initial contact) but rather to z=-max_deflection, while anticipating the forces from the legs.

Ok.. So, if you're right, SpaceX should now have valuable maximum "z=-max_deflection" data (nothing is more accurate than a test to destruction, right?) to use going forward, meaning this wasn't a failure after all. :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/17/2015 04:36 am
Over a period of 1-2 seconds, the first legs begins to compress more, imparting a torque to the stage, which now begins to follow the deck.  The other legs are not free falling, since the engine is still producing thrust.

I think that these dynamics have been taken into account, and the control algorithm is actually trying to bring the rocket not to z=0 (initial contact) but rather to z=-max_deflection, while anticipating the forces from the legs.

Ok.. So, if you're right, SpaceX should now have valuable maximum "z=-max_deflection" data (nothing is more accurate than a test to destruction, right?) to use going forward, meaning this wasn't a failure after all. :)


Bingo!


It would only be a real failure if
a)  They didn't learn anything from it, or
b)  They had already declared the system operational and had calculated the assumption of success into their profit margin.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Appable on 04/17/2015 04:38 am
Does anyone know when NASA TV coverage starts of rendevous, grapple, berthing of CRS-6? I can't find that information on the NASA TV schedule for some reason, though I know the grapple is targetted for 7am ET.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/17/2015 04:41 am
Over a period of 1-2 seconds, the first legs begins to compress more, imparting a torque to the stage, which now begins to follow the deck.  The other legs are not free falling, since the engine is still producing thrust.

I think that these dynamics have been taken into account, and the control algorithm is actually trying to bring the rocket not to z=0 (initial contact) but rather to z=-max_deflection, while anticipating the forces from the legs.

{emphasis mine}

Ok.. So, if you're right, SpaceX should now have valuable maximum "z=-max_deflection" data (nothing is more accurate than a test to destruction, right?) to use going forward. :)

Well, I meant max_deflection_by_design, but the de-facto max_deflection_at_break - yeah, they know that now.  :)

I'm surprised the rocket wall didn't cave in.  Probably structural supports between the anchor points inside.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Zed_Noir on 04/17/2015 04:48 am
Does anyone know when NASA TV coverage starts of rendevous, grapple, berthing of CRS-6? I can't find that information on the NASA TV schedule for some reason, though I know the grapple is targetted for 7am ET.

The coverage starts at 5am ET on the NASA TV public & media channels
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: griesser on 04/17/2015 04:55 am
We just saw ISS followed by Dragon traveling over Bainbridge Island, WA at 4/16/2015, 9:40 pm.  It looked like a good chase.  Very cool!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: obi-wan on 04/17/2015 05:22 am


The main concern is the need for certainty the rocket will actually land or crash at LC-13, instead of, say, downtown Titusville. Even a perfect touchdown on an elementary school would still be a bad touchdown.

I don't know - as a graduate of Riverview Elementary and Titusville High School, I think a Falcon 9 settling down to a perfect touchdown in the parking lot in front of school would have been pretty damn cool!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: litton4 on 04/17/2015 08:46 am
I was wondering what impact the Kaboom we see in the video would have at LC-13?

Can anyone estimate the range of potential damage based on the video of the explosion?

Is LC-13 far enough from anything else important that this type of unhappy ending can be handled without damage?

While we all expect/hope/assume that landing on land will have a much better ending, it is still at least possible to end in a similar kaboom.

The damage radius seemed to be few hundreds of feet.  The distance between pads at CCAFS is 2000'.


What about the (COPV?) pressure vessel that shot off to the right? That seemed to make it a bit further.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: laughninja on 04/17/2015 11:05 am
During capture of the Dragon capsule we could see the pulsating light of which I assume was some sort laser to measure the distance. But why were we able to see it, i thought in the vacuum there would be nothing to scatter the light?

You can see it in the attached screenshot.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/17/2015 11:07 am
It's not a laser. Just a strobe light to aid the IIS crew to see exactly where Dragon is (especially when at a distance).

During capture of the Dragon capsule we could see the pulsating light of which I assume was some sort laser to measure the distance. But why were we able to see it, i thought in the vacuum there would be nothing to scatter the light?

You can see it in the attached screenshot.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: laughninja on 04/17/2015 11:15 am
It's not a laser. Just a strobe light to aid the IIS crew to see exactly where Dragon is (especially when at a distance).

During capture of the Dragon capsule we could see the pulsating light of which I assume was some sort laser to measure the distance. But why were we able to see it, i thought in the vacuum there would be nothing to scatter the light?

You can see it in the attached screenshot.

Thanks! But why are we able to see the straight line of the light ray itself and not just its reflection off from the dragon? There should be nothing between the ISS and Dragon to scatter the light?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/17/2015 11:19 am
Sorry should have explained better. Light does travel in straight lines but the light also has a lens/covering that will diffuse the light, even in a vacuum.


It's not a laser. Just a strobe light to aid the IIS crew to see exactly where Dragon is (especially when at a distance).

During capture of the Dragon capsule we could see the pulsating light of which I assume was some sort laser to measure the distance. But why were we able to see it, i thought in the vacuum there would be nothing to scatter the light?

You can see it in the attached screenshot.

Thanks! But why are we able to see the straight line of the light ray itself and not just its reflection off from the dragon? There should be nothing between the ISS and Dragon to scatter the light?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mlindner on 04/17/2015 11:20 am
It's not a laser. Just a strobe light to aid the IIS crew to see exactly where Dragon is (especially when at a distance).

During capture of the Dragon capsule we could see the pulsating light of which I assume was some sort laser to measure the distance. But why were we able to see it, i thought in the vacuum there would be nothing to scatter the light?

You can see it in the attached screenshot.

Thanks! But why are we able to see the straight line of the light ray itself and not just its reflection off from the dragon? There should be nothing between the ISS and Dragon to scatter the light?

Camera artifacts from CCD-based cameras. When CCDs oversaturate they spill into nearby pixels. This is common on images anywhere when you overexpose an area of the image.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: laughninja on 04/17/2015 11:22 am
Camera artifacts from CCD-based cameras. When CCDs oversaturate they spill into nearby pixels. This is common on images anywhere when you overexpose an area of the image.

But I don't think this explains why we can see it as a straight line?

Edit: attached modified image with a red circle around the part which bothers me.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mlindner on 04/17/2015 11:26 am
Camera artifacts from CCD-based cameras. When CCDs oversaturate they spill into nearby pixels. This is common on images anywhere when you overexpose an area of the image.

But I don't think this explains why we can see it as a straight line?

Because of the architecture of how CCDs function when the over saturation occurs they spill into the nearby pixels only in a single row because CCD images are read row at a time. They show up as a straight line because the pixels are in a straight line. If the camera were rotated the line would rotate with it.

Edit: Here's a space image also demonstrating this effect:
(http://www.eso.org/~ohainaut/ccd/ccd_sat.jpg)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/17/2015 11:27 am
I think you're just seeing an artifact of the camera on the ISS. It's not a straight ray from the light, but rather a function of the camera. if you were up there you would get a different view.

Camera artifacts from CCD-based cameras. When CCDs oversaturate they spill into nearby pixels. This is common on images anywhere when you overexpose an area of the image.

But I don't think this explains why we can see it as a straight line?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: laughninja on 04/17/2015 11:27 am
Ok... now I got it. Thanks for your help!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Sohl on 04/17/2015 12:59 pm
I think you're just seeing an artifact of the camera on the ISS. It's not a straight ray from the light, but rather a function of the camera. if you were up there you would get a different view.

Camera artifacts from CCD-based cameras. When CCDs oversaturate they spill into nearby pixels. This is common on images anywhere when you overexpose an area of the image.

But I don't think this explains why we can see it as a straight line?

And if it is not the CCD pixel bleed or camera optics, it could be scatter from a surface in the portal window, assuming the shot is through a window.  Infrared laser "radar" (AKA Lidar) mounted in Dragon is used during approach, however.  But this isn't that!  ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DatUser14 on 04/17/2015 01:00 pm
I wouldn't call the landing a total crash landing. I'd call it a semi-successful,mostly horizontal just a bit to hard slam. The stage made it on to the barge almost vertical then tipped over when the legs failed from the stress (shock?) of impact at a higher than envisaged speed.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Norm38 on 04/17/2015 01:36 pm
Also, if you watch the video, the stage approach is quite vertical. The problem was a minor last-second correction that went bad because of the valve stiction. A radio beacon would not have improved terminal guidance and would not have prevented the crash in any case.

That's confirmed?  It really was a hardware problem?  And people think that otherwise it could have stuck the landing?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/17/2015 01:39 pm

1. The ASDS is parked across the wind/waves so the Stage's final approach is into the wind, descending ie. coming down at an angle to the deck of, for arguments sake, let's say 45 degrees.


3. Assuming they don't know the ASDS's roll-rate because there's no telemetry to the stage (maybe there is?) with landing radar is looking straight down, the stage will see the 'ground' rising and falling at a different rate than it actually is at the final impact point.


1.  The stage doesn't know which way the wind direction is

3.  Not an assumption, there isn't any.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sghill on 04/17/2015 01:52 pm

1. The ASDS is parked across the wind/waves so the Stage's final approach is into the wind, descending ie. coming down at an angle to the deck of, for arguments sake, let's say 45 degrees.


3. Assuming they don't know the ASDS's roll-rate because there's no telemetry to the stage (maybe there is?) with landing radar is looking straight down, the stage will see the 'ground' rising and falling at a different rate than it actually is at the final impact point.


1.  The stage doesn't know which way the wind direction is

3.  Not an assumption, there isn't any.

Jim,  you lost me with your #3 post above.

Are you stating that there isn't any deck roll?  The deck video Chris posted on L2 showed considerable deck roll during the landing.  I don't know if it was enough to be of any kind of concern, but it is clearly there.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jim on 04/17/2015 01:55 pm

1. The ASDS is parked across the wind/waves so the Stage's final approach is into the wind, descending ie. coming down at an angle to the deck of, for arguments sake, let's say 45 degrees.


3. Assuming they don't know the ASDS's roll-rate because there's no telemetry to the stage (maybe there is?) with landing radar is looking straight down, the stage will see the 'ground' rising and falling at a different rate than it actually is at the final impact point.


1.  The stage doesn't know which way the wind direction is

3.  Not an assumption, there isn't any.

Jim,  you lost me with your #3 post above.

Are you stating that there isn't any deck roll?  The deck video Chris posted on L2 showed considerable deck roll during the landing.  I don't know if it was enough to be of any kind of concern, but it is clearly there.

I read it wrong.  I thought he was assuming no telemetry
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MarekCyzio on 04/17/2015 02:35 pm
That's confirmed?  It really was a hardware problem?  And people think that otherwise it could have stuck the landing?

The more I look at this landing, the more I think the issue was caused by low hydraulic pressure - engine gimball moves fast at the beginning of the video and then movements slow down a lot and become sluggish. 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: baldusi on 04/17/2015 02:36 pm
Now I've realized that Dragon the second most docked/berthed robotic vehicle only after Progress. And that's only counting regular missions.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rpapo on 04/17/2015 03:18 pm
A good project for somebody: a tally of all the robotic resupply missions so far, with the number, the total weight of supplies delivered for each of the different types: Progress, ATV, HTV, Dragon and Cygnus. 

Wikipedia shows 78 successful missions so far, with Progress 59, Dragon 7, ATV 5, HTV 4 and Cygnus 3.  One Progress and one Cygnus each failed to reach orbit.

http://en.wikipedia.org/wiki/List_of_unmanned_spaceflights_to_the_International_Space_Station
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/17/2015 03:18 pm
Ok... now I got it. Thanks for your help!
Another thing, if you look carefully, the line also goes in the opposite direction. 

It's a neat image and question though :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LouScheffer on 04/17/2015 04:05 pm
It's not a "theoretical elevation." It's an actual measurement obtained by radar altimeter. The radar altimeter has worked perfectly for Grasshopper/F9R Dev landings, it worked perfectly on this barge (crash) landing, and it will work perfectly at LC-13.
This is a really obvious point that surely SpaceX has addressed, but I wonder how.  A radar altimeter might well have trouble with a flat metal surface, which will act like a mirror and not the ground.  So if you are directly above it, you might see your reflection and get a result of twice the distance you should.

If you are off-axis, the deck may give no or little return.  Even if you do get a return, the railings and boxes at the ends of the deck will form corner reflectors and give signals orders of magnitude stronger  At high altitudes the difference is not great, but at low altitudes it could be serious.

Maybe the steel is resistive enough to give a good reflection?  Maybe the radar is really smart?  Maybe they imbed a dihedral at the deck center?  Maybe the deck is not effectively flat at the wavelengths used?  Just curious....

Anyway, this is not just a theoretical problem.  From an article on self driving cars:
http://www.wired.com/2015/04/delphi-autonomous-car-cross-country/
Quote
the biggest scare of the trip came while crossing a double-decker steel bridge on the drive from Philadelphia to New York. “I saw that bridge coming, and I thought, ‘Oh my gosh, this is gonna be a grab the wheel moment,'” says Katherine Winter, a Delphi software engineer. That’s because being surrounded by metal plays hell on radar by making it difficult to discern what’s a threat and what isn’t.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 04/17/2015 04:19 pm
It's not a "theoretical elevation." It's an actual measurement obtained by radar altimeter. The radar altimeter has worked perfectly for Grasshopper/F9R Dev landings, it worked perfectly on this barge (crash) landing, and it will work perfectly at LC-13.
This is a really obvious point that surely SpaceX has addressed, but I wonder how.  A radar altimeter might well have trouble with a flat metal surface, which will act like a mirror and not the ground.  So if you are directly above it, you might see your reflection and get a result of twice the distance you should.

If you are off-axis, the deck may give no or little return.  Even if you do get a return, the railings and boxes at the ends of the deck will form corner reflectors and give signals orders of magnitude stronger  At high altitudes the difference is not great, but at low altitudes it could be serious.

Maybe the steel is resistive enough to give a good reflection?  Maybe the radar is really smart?  Maybe they imbed a dihedral at the deck center?  Maybe the deck is not effectively flat at the wavelengths used?  Just curious....

Anyway, this is not just a theoretical problem.  From an article on self driving cars:
http://www.wired.com/2015/04/delphi-autonomous-car-cross-country/
Quote
the biggest scare of the trip came while crossing a double-decker steel bridge on the drive from Philadelphia to New York. “I saw that bridge coming, and I thought, ‘Oh my gosh, this is gonna be a grab the wheel moment,'” says Katherine Winter, a Delphi software engineer. That’s because being surrounded by metal plays hell on radar by making it difficult to discern what’s a threat and what isn’t.

The fact that radar guided missiles are routinely used to target steel ships at sea suggests this isn't an insurmountable impediment.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Stellvia on 04/17/2015 04:46 pm
It's not a "theoretical elevation." It's an actual measurement obtained by radar altimeter. The radar altimeter has worked perfectly for Grasshopper/F9R Dev landings, it worked perfectly on this barge (crash) landing, and it will work perfectly at LC-13.
This is a really obvious point that surely SpaceX has addressed, but I wonder how.  A radar altimeter might well have trouble with a flat metal surface, which will act like a mirror and not the ground.  So if you are directly above it, you might see your reflection and get a result of twice the distance you should.

I did find myself wondering at what point in the descent the barge came into the field of view of the radar altimiter (so the signal went "ocean-ocean-ocean-BARGE") and how that compared to the sudden attitude kick observed in the descending stage. Wasn't really an issue in the first barge "landing", because the stage was screaming cross-range at a pitch angle of 45 degrees....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/17/2015 04:53 pm
It's not a "theoretical elevation." It's an actual measurement obtained by radar altimeter. The radar altimeter has worked perfectly for Grasshopper/F9R Dev landings, it worked perfectly on this barge (crash) landing, and it will work perfectly at LC-13.
This is a really obvious point that surely SpaceX has addressed, but I wonder how.  A radar altimeter might well have trouble with a flat metal surface, which will act like a mirror and not the ground.  So if you are directly above it, you might see your reflection and get a result of twice the distance you should.

I did find myself wondering at what point in the descent the barge came into the field of view of the radar altimiter (so the signal went "ocean-ocean-ocean-BARGE") and how that compared to the sudden attitude kick observed in the descending stage. Wasn't really an issue in the first barge "landing", because the stage was screaming cross-range at a pitch angle of 45 degrees....

Yes, and you can wait to switch your guidance algorithm over from INS/GPS until the barge deck is the primary return signal. I don't know what that altitude is, but at 50 feet or so, I'd expect the barge deck would be the only return signal, assuming the stage is roughly vertical above the barge.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/17/2015 04:54 pm
It's not a "theoretical elevation." It's an actual measurement obtained by radar altimeter. The radar altimeter has worked perfectly for Grasshopper/F9R Dev landings, it worked perfectly on this barge (crash) landing, and it will work perfectly at LC-13.
This is a really obvious point that surely SpaceX has addressed, but I wonder how.  A radar altimeter might well have trouble with a flat metal surface, which will act like a mirror and not the ground.  So if you are directly above it, you might see your reflection and get a result of twice the distance you should.

I did find myself wondering at what point in the descent the barge came into the field of view of the radar altimiter (so the signal went "ocean-ocean-ocean-BARGE") and how that compared to the sudden attitude kick observed in the descending stage. Wasn't really an issue in the first barge "landing", because the stage was screaming cross-range at a pitch angle of 45 degrees....

This is exactly the sort of thing which telemetry can settle.  I'm sure all the data will be carefully reviewed and everyone will make sure that their particular part of the EDL program executed correctly.

Even if the valve stiction was the primary culprit, I bet lots of different groups will find things in the data that they can improve.  And it looks like some pretty sizable chunks of the rocket were recovered as well (including most if not all of the legs), so that should keep the structures folks busy/happy too.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/17/2015 05:26 pm
Ok... now I got it. Thanks for your help!
Another thing, if you look carefully, the line also goes in the opposite direction. 

It's a neat image and question though :)


Just proves that it's all done on a Hollywood sound stage, of course.  The hoax continues!   :-X
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: eriblo on 04/17/2015 05:47 pm
[...]
A radar altimeter might well have trouble with a flat metal surface, which will act like a mirror and not the ground.  So if you are directly above it, you might see your reflection and get a result of twice the distance you should.
[...]

You're correct that a flat metal surface can act like a mirror (doesn't necessarily need to be metal, just flat relative to wavelength) and give associated problems with signal strength, but being straight above is actually the best case scenario. As long as the angle is low enough that the specular highlight is in the beam you should get a decent signal and only have to worry about echos from higher structures close by. Also - remember that a (monostatic) radar, being also the source of illumination, is always "seeing itself" and measuring twice the distance :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LouScheffer on 04/17/2015 06:03 pm
This is a really obvious point that surely SpaceX has addressed, but I wonder how.  A radar altimeter might well have trouble with a flat metal surface, which will act like a mirror and not the ground.  So if you are directly above it, you might see your reflection and get a result of twice the distance you should.

If you are off-axis, the deck may give no or little return.  [...]

The fact that radar guided missiles are routinely used to target steel ships at sea suggests this isn't an insurmountable impediment.
Actually this is evidence in the opposite direction.   Radar on ships works precisely since they are *not* flat metal plates - they have lots of nooks and crannies that are good reflectors.  Conversely,  stealth ships *are* made from flat metal plates, because it's really hard to get a radar return from one of these.
See https://en.wikipedia.org/wiki/Stealth_ship for lots of examples....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jacqmans on 04/17/2015 06:38 pm
Photo: SpaceX
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevin-rf on 04/17/2015 06:41 pm
Looks like they need to do a serious FOD walk ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: saliva_sweet on 04/17/2015 07:22 pm
Photo: SpaceX

AKA reddit user Owt_On_A_Limb from jacksonville subreddit ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/17/2015 07:39 pm
So was there ever a conclusion about whether or not the high quality video was slow motion or not? Some seem to say it was, based on L2 information? (which I do not have)

To me it always looked "right", as it being normal speed. The smoke/cloud movement seems to indicate it as well. But this shared side-by-side video edit seems to be another item in support of it being real time:

https://www.youtube.com/watch?v=amRPtyhIzkI
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rcoppola on 04/17/2015 07:46 pm
Here's a version I did with a new audio mix while incorporating both off and on-barge footage.

https://www.youtube.com/watch?v=44wZQUcuWUw

I'd say the speeds are in alignment and in real-time.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: catdlr on 04/17/2015 07:53 pm
Here's a version I did with a new audio mix while incorporating both off and on-barge footage.


I'd say the speeds are in alignment and in real-time.

Nice editing job.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 04/17/2015 07:53 pm
that's excellent. Good job.

Here's a version I did with a new audio mix while incorporating both off and on-barge footage.

https://www.youtube.com/watch?v=44wZQUcuWUw

I'd say the speeds are in alignment and in real-time.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: philw1776 on 04/17/2015 07:59 pm
Photo: SpaceX

I'm an engineer but would get fired at SpaceX when I said to Elon, "The good news is we got the bird poop off the barge"
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: junk.munk82 on 04/17/2015 08:04 pm
So was there ever a conclusion about whether or not the high quality video was slow motion or not? Some seem to say it was, based on L2 information? (which I do not have)

To me it always looked "right", as it being normal speed. The smoke/cloud movement seems to indicate it as well. But this shared side-by-side video edit seems to be another item in support of it being real time:

https://www.youtube.com/watch?v=amRPtyhIzkI

based on the gopro video i am am fairly certain that the "high quality" video is indeed running at 100% speed
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/17/2015 08:05 pm
So was there ever a conclusion about whether or not the high quality video was slow motion or not? Some seem to say it was, based on L2 information? (which I do not have)

It wasn't L2 information, it was Elon's caption for the video (https://twitter.com/elonmusk/status/588463193070022656): "High resolution, color corrected, slow motion rocket landing video".

Of course, it's possible Elon was mistaken/confused.  The main @SpaceX twitter feed doesn't use "slow motion" to describe the video.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 04/17/2015 08:47 pm
To Jim and Meek.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: NovaSilisko on 04/17/2015 09:06 pm
Here's a version I did with a new audio mix while incorporating both off and on-barge footage.

I'd say the speeds are in alignment and in real-time.

I swear I'm recognizing some little bits from my CRS-5 crash audio, or am I imagining it?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 04/17/2015 09:24 pm
By the way, for the CRS-7 coverage, I think we'll ensure we set up some very specific threads, as there's a fair amount of cross conversations going on per CRS-6 and ASDS. I'll work it out ahead of that mission.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: HIP2BSQRE on 04/17/2015 09:25 pm
that's excellent. Good job.

Here's a version I did with a new audio mix while incorporating both off and on-barge footage.

https://www.youtube.com/watch?v=44wZQUcuWUw

I'd say the speeds are in alignment and in real-time.

It tries so hard....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/17/2015 09:37 pm
So was there ever a conclusion about whether or not the high quality video was slow motion or not? Some seem to say it was, based on L2 information? (which I do not have)

To me it always looked "right", as it being normal speed. The smoke/cloud movement seems to indicate it as well. But this shared side-by-side video edit seems to be another item in support of it being real time:

Wired Magazine did a frame-by-frame video analysis to plot position vs. time from the video. NSF user acsawdey did further analysis of the Wired data here. Based on thise analyses, it does appear the video was normal speed.

http://forum.nasaspaceflight.com/index.php?topic=36527.msg1361261#msg1361261

http://www.wired.com/2015/04/analysis-falcon-9-crash-landing/

One useful data point derived by acsawdy is the approximately 5 m/sec deceleration just before touchdown. Assuming a 65,000 lbf stage weight (Hans said between 60,000-70,000 lbf), that would imply a thrust of 97,500 lbf, which is 66% throttle level based on M1D nominal thrust of 147,000 lbf.

In other words, the final deceleration derived from the video is quite consistent with expected thrust levels of the M1D when throttled down for landing.

Edit: acsawdey has reviewed his calcs and concluded that the 5 m/s^2 deceleration he derived was incorrect. He believes the anlaysis by hrissan in the link below is correct, however:

http://forum.nasaspaceflight.com/index.php?topic=36892.msg1360032#msg1360032
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lee Jay on 04/17/2015 09:52 pm
So was there ever a conclusion about whether or not the high quality video was slow motion or not? Some seem to say it was, based on L2 information? (which I do not have)

In my opinion, the L2 video you mention has a bazillion dropped or missing frames, leading it to run at a non-linear and accelerated pace.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: llanitedave on 04/17/2015 10:22 pm
So was there ever a conclusion about whether or not the high quality video was slow motion or not? Some seem to say it was, based on L2 information? (which I do not have)

To me it always looked "right", as it being normal speed. The smoke/cloud movement seems to indicate it as well. But this shared side-by-side video edit seems to be another item in support of it being real time:

Wired Magazine did a frame-by-frame video analysis to plot position vs. time from the video. NSF user acsawdey did further analysis of the Wired data here. Based on thise analyses, it does appear the video was normal speed.

http://forum.nasaspaceflight.com/index.php?topic=36527.msg1361261#msg1361261 (http://forum.nasaspaceflight.com/index.php?topic=36527.msg1361261#msg1361261)

http://www.wired.com/2015/04/analysis-falcon-9-crash-landing/ (http://www.wired.com/2015/04/analysis-falcon-9-crash-landing/)

One useful data point derived by acsawdy is the approximately 5 m/sec deceleration just before touchdown. Assuming a 65,000 lbf stage weight (Hans said between 60,000-70,000 lbf), that would imply a thrust of 97,500 lbf, which is 66% throttle level based on M1D nominal thrust of 147,000 lbf.

In other words, the final deceleration derived from the video is quite consistent with expected thrust levels of the M1D when throttled down for landing.


Judging from the shape of the plume, though, looks like the throttle increased as it impinged on the water and then slid over the barge.  I'm wondering if the throttle just before those last couple of seconds might have been even lower.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kdhilliard on 04/17/2015 10:26 pm
Assuming a 65,000 lbf stage weight (Hans said between 60,000-70,000 lbf), ...
Were Hans's figures a surprise?  I had seen 18,000 kg = 40,000 lb widely used previously.  Hans didn't seem to have a precise figure off the top of his head, and from the tone of his voice and the way he was shaking his head when he said it (responding to a question during the post launch news conference), I don't know if it should be taken as gospel.  He didn't sound as if he was trying to avoid the question, but he seemed pretty tired, which was understandable considering the events of the day.

~Kirk
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/17/2015 10:29 pm
Assuming a 65,000 lbf stage weight (Hans said between 60,000-70,000 lbf), ...
Were Hans's figures a surprise?  I had seen 18,000 kg = 40,000 lb widely used previously.  Hans didn't seem to have a precise figure off the top of his head, and from the tone of his voice and the way he was shaking his head when he said it (during the post launch news conference), I don't know if it should be taken as gospel.  He didn't sound as if he was trying to avoid the question, but he seemed pretty tired, which was understandable considering the events of the day.

~Kirk

it sounded like a pretty cagey answer to me... I wouldn't take it as gospel, merely an upper bound.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kdhilliard on 04/17/2015 10:31 pm
Here's a version I did with a new audio mix while incorporating both off and on-barge footage.
[YouTube link. (https://www.youtube.com/watch?v=44wZQUcuWUw)]
Excellent video, rcoppola.  Thanks!

Where did you get the audio from?

~Kirk
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rcoppola on 04/17/2015 10:52 pm
Here's a version I did with a new audio mix while incorporating both off and on-barge footage.

I'd say the speeds are in alignment and in real-time.

I swear I'm recognizing some little bits from my CRS-5 crash audio, or am I imagining it?
-The distant and close-up engine audio was taken from the 1000m F9R-Dev1 test flight. (Edited & mixed down)
-The "grinding" sound for when the legs would have slid/impacting the ASDS is comprised of multiple, random "steel impacts" sound effects. The native Barge footage audio was edited and mixed and moved in their appropriate places in those shots as well, along with hints of continued engine thrust from the F9R-Dev1 videos.
-The explosions are multiple tracks of misc.explosions from SFX reels, some very slowed down "breaking glass" along with random, subtle additional deep throttle engine sound, etc.
But sorry, no CRS-5 crash audio.

-And thanks catdlr, kevinof and Kirk.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Rocket Science on 04/17/2015 11:02 pm
Everytime I watch that video I can't help saying "whoa Nelly"! ;D Thanks for the great work rcoppola! :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: NovaSilisko on 04/17/2015 11:05 pm
Here's a version I did with a new audio mix while incorporating both off and on-barge footage.

I'd say the speeds are in alignment and in real-time.

I swear I'm recognizing some little bits from my CRS-5 crash audio, or am I imagining it?
-The distant and close-up engine audio was taken from the 1000m F9R-Dev1 test flight. (Edited & mixed down)
-The "grinding" sound for when the legs would have slid/impacting the ASDS is comprised of multiple, random "steel impacts" sound effects. The native Barge footage audio was edited and mixed and moved in their appropriate places in those shots as well, along with hints of continued engine thrust from the F9R-Dev1 videos.
-The explosions are multiple tracks of misc.explosions from SFX reels, some very slowed down "breaking glass" along with random, subtle additional deep throttle engine sound, etc.
But sorry, no CRS-5 crash audio.

-And thanks catdlr, kevinof and Kirk.

Yeah, I was mistaken, and was remembering what mine sounded like incorrectly. I like yours a lot more, really.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 04/17/2015 11:07 pm
Photo: SpaceX

new hires become the barge cleanup crew?  :D
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kdhilliard on 04/17/2015 11:22 pm
[ list of audio sources in rcoppola's video ]

Wow!  I imagine such an audio mix must have taken a lot more work than the video splicing.

The audio mix is so good that I suggest you add a note to the YouTube description making the situation clear so that viewers won't be misled into thinking that it contains only actual CRS-6 audio.

Edit: I see that such a note has been added.

~Kirk
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: brettreds2k on 04/18/2015 01:42 am
The drone ship made it back to port with debris still on the deck
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/18/2015 03:20 am
The drone ship made it back to port with debris still on the deck

That photo and the debris have been discussed over here:

http://forum.nasaspaceflight.com/index.php?topic=36326.msg1360927#msg1360927
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lar on 04/18/2015 03:17 pm
Let's all do our best to keep the various threads neat and tidy. The launch, landing, ASDS damage, ASDS status all kind of blur together to be sure.... but at least try to do your best...  Thanks!  As Chris has hinted, next launch a different organizational scheme may be tried.

Yes I am a compartmentalized dork[1] and proud of it.

- http://www.lugnet.com/faq/~88/CD
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AS-503 on 04/19/2015 12:00 am
Latest from Elon wrt sticky/slow valve.

https://twitter.com/elonmusk/status/589577558942822400
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ZachS09 on 04/19/2015 12:19 am
At least the barge came back in one piece.  :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mlindner on 04/19/2015 04:14 am
The drone ship made it back to port with debris still on the deck

Just to quote our sources. The source is from a user from /r/Jacksonville on reddit at the request of a user from /r/spacex.

Source. (https://www.reddit.com/r/jacksonville/comments/32tndl/anyone_around_the_jaxport_area_free_tonight_to/cqff91x)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Dave G on 04/19/2015 10:17 am
Another tweet from Elon.

The new tweet shows an F9R test video from last year.

So the question is, why do they have "proper throttle response" on the F9R test but "slower than expected throttle valve response" on the actual landing?

One obvious difference is that the McGregor F9R test had the legs fully deployed the entire time, while the CRS-6 landing deployed the legs in the last seconds.  I've read the legs are deployed using Helium pressure.  Is there any interaction between Helium pressure and slower than expected throttle valve response?  Could deploying the legs sooner solve the issue?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 04/19/2015 10:54 am
What I'll do is write up this CRS-6 related event, start a thread for it (and link it in the existing threads), so we have a relief valve, as we are (and this is totally understandable) running many threads on this and overlapping.

The article will allow some refocus into the "R" related threads.

CRS-7 will be far more organized! :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/19/2015 02:34 pm
Is there any interaction between Helium pressure and slower than expected throttle valve response?  Could deploying the legs sooner solve the issue?

No, the propellant valve is electromechanically actuated and entirely independent of helium pressure.

Deploying legs sooner/later has no effect on throttle valve response. It might change vehicle attitude dynamics slightly, but if the valve is sticking, the attitude control feedback loop will be screwed up as we saw, and changing the leg deployment timing won't help.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jakusb on 04/19/2015 02:51 pm
Is the mentioned valve responsible for gimbaling or for thrust?
I am still suspecting the latter and that the stage did not get a chance to really settle to the deck. Instead it seems to skid across the deck like on an air cushion. Or is that motion induced by the leg touching down and pushing the bottom of the stage sideways?

If used for gimbaling, I could imagine the last divert movement could be caused by the engine not gimbaling quickly enough and keeping thrust too long to one side, pushing the stage away from the seemingly already proper descend path. Hence the over steering it seems to do in last seconds.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jarnis on 04/19/2015 02:58 pm
Thrust.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LouScheffer on 04/19/2015 03:20 pm
Latest from Elon wrt sticky/slow valve.

https://twitter.com/elonmusk/status/589577558942822400
Let me make an armchair, Monday morning quarterback, control-systems suggestion.

Navigating in X and Y should be possible even if the thrust is wrong.  There is plenty of control authority, provided the engine is running at all.

The horizontal forces are basically thrust*sin(angle), where angle measured from vertical.  It looks like for the "thrust" part of this, they used the commanded thrust and not the measured thrust.  Normally this makes no difference, since the commanded and actual thrust will be very close in size.   But when the obtained thrust was different, as the case here, this calculation gets the sideways thrust wrong, too.  This error mounted up until they had to do a big last-minute correction, which failed.

Now if they used the actual thrust (from accelerometer, measured valve position (if available), strain gauge, etc.) then they could still adjust X and Y correctly even if the throttle sticks.  They still might have a hard landing, but the stage would be vertical and centered on the barge, which could help.

Of course this relies on having a better estimate of the obtained thrust with a small enough lag to avoid instabilities in the X and Y correction loops.  But given they have 30 seconds to get X and Y lined up, but the rocket can do it in just a few seconds (as it did at the end of the flight, almost) there should be plenty of margin available for tweaks in this system.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: MP99 on 04/19/2015 03:59 pm
Assuming a 65,000 lbf stage weight (Hans said between 60,000-70,000 lbf), ...
Were Hans's figures a surprise?  I had seen 18,000 kg = 40,000 lb widely used previously.  Hans didn't seem to have a precise figure off the top of his head, and from the tone of his voice and the way he was shaking his head when he said it (responding to a question during the post launch news conference), I don't know if it should be taken as gospel.  He didn't sound as if he was trying to avoid the question, but he seemed pretty tired, which was understandable considering the events of the day.

~Kirk

Question:- was that 40 klb figure with legs / grid fins / increased cold gas capacity for thrusters? Or was it the dry weight from early v1.1 flights? Also, does that include residuals?

Cheers, Martin
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cambrianera on 04/19/2015 04:28 pm
Question:- was that 40 klb figure with legs / grid fins / increased cold gas capacity for thrusters? Or was it the dry weight from early v1.1 flights? Also, does that include residuals?

Cheers, Martin
My old estimate of 18000 kg (http://forum.nasaspaceflight.com/index.php?topic=31514.msg1034291#msg1034291) was for the dry mass of expendable first stage: no legs, no grid fins, no RCS.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: fthomassy on 04/19/2015 05:19 pm
Of course this relies on having a better estimate of the obtained thrust with a small enough lag to avoid instabilities in the X and Y correction loops.  But given they have 30 seconds to get X and Y lined up, but the rocket can do it in just a few seconds (as it did at the end of the flight, almost) there should be plenty of margin available for tweaks in this system.
I mostly agree with your expression of the issues, here.  However, I think Musk's messages suggest that predictable lag is the main problem.  However, this too could be corrected as you suggest from in-flight measures including all the restarts happening before the landing burn.  But if the issue includes a large variance from start to start then you really need to fix the hardware to make it invariant and leave the control system as clean as possible.

Just another armchair opinion ;D
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: sanman on 04/19/2015 09:34 pm
Another tweet from Elon.

The new tweet shows an F9R test video from last year.

So the question is, why do they have "proper throttle response" on the F9R test but "slower than expected throttle valve response" on the actual landing?

One obvious difference is that the McGregor F9R test had the legs fully deployed the entire time, while the CRS-6 landing deployed the legs in the last seconds.  I've read the legs are deployed using Helium pressure.  Is there any interaction between Helium pressure and slower than expected throttle valve response?  Could deploying the legs sooner solve the issue?

The most pertinent answer should be that Grasshopper tests weren't the real tests, and this CRS6 landing was the test and so should have been reasonably expected to fail. As many have said, missions like CRS provide free test opportunities, and so should themselves be seen as tests first and foremost. There's no way that any of the Grasshopper tests were as stressful and challenging as this CRS6 landing.

No, the propellant valve is electromechanically actuated and entirely independent of helium pressure.

Deploying legs sooner/later has no effect on throttle valve response. It might change vehicle attitude dynamics slightly, but if the valve is sticking, the attitude control feedback loop will be screwed up as we saw, and changing the leg deployment timing won't help.

So are they going to have to redesign this valve and its actuation in order to make it live up to the needs?

Or can they tweak the control software in order to better account for the lower throttle response and make do with that?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lee Jay on 04/19/2015 10:01 pm
Or can they tweak the control software in order to better account for the lower throttle response and make do with that?

If the problem is control bandwidth on the valve, then this may be possible though it will lead to less control authority at higher rates.

If the problem is that it's sticking, in a sort-of random fashion, then it would be almost impossible to design a controller to successfully handle that issue.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/19/2015 10:13 pm
Another tweet from Elon.

The new tweet shows an F9R test video from last year.

So the question is, why do they have "proper throttle response" on the F9R test but "slower than expected throttle valve response" on the actual landing?

One obvious difference is that the McGregor F9R test had the legs fully deployed the entire time, while the CRS-6 landing deployed the legs in the last seconds.  I've read the legs are deployed using Helium pressure.  Is there any interaction between Helium pressure and slower than expected throttle valve response?  Could deploying the legs sooner solve the issue?

The most pertinent answer should be that Grasshopper tests weren't the real tests, and this CRS6 landing was the test and so should have been reasonably expected to fail. As many have said, missions like CRS provide free test opportunities, and so should themselves be seen as tests first and foremost. There's no way that any of the Grasshopper tests were as stressful and challenging as this CRS6 landing.

No, the propellant valve is electromechanically actuated and entirely independent of helium pressure.

Deploying legs sooner/later has no effect on throttle valve response. It might change vehicle attitude dynamics slightly, but if the valve is sticking, the attitude control feedback loop will be screwed up as we saw, and changing the leg deployment timing won't help.

So are they going to have to redesign this valve and its actuation in order to make it live up to the needs?

Or can they tweak the control software in order to better account for the lower throttle response and make do with that?
My theory is that the valve is sticking due to ice or thermal cycling or some other environmental condition unique to reentry (which is why they didn't notice it in ground testing).  Assuming they can identify the environmental factor, fixing the problem might be as simple as wrapping a bit of insulation around a critical area, or installing a small heater, or pressurizing a volume to protect it from vacuum.

 Others have suggested a large initial control transient to overcome the original stiction, or dithering the control input, both of which could be software-only fixes.  (Is it possible to cycle the main propellant valve without letting out the propellant?)

And, of course, redesigning the valve is also a possibility.  That would be a pretty big change to undertake.

It all depends on what the root cause of the "valve stiction" is.  Without more inside information we're just guessing.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 04/20/2015 03:36 am
Quote
My theory is that the valve is sticking due to ice or thermal cycling or some other environmental condition unique to reentry (which is why they didn't notice it in ground testing).  Assuming they can identify the environmental factor, fixing the problem might be as simple as wrapping a bit of insulation around a critical area, or installing a small heater, or pressurizing a volume to protect it from vacuum.

When a component malfunctions, it's always a good idea to look at the actual environments the component saw (in this case, thermal) vs. the environments the component was qualified to. Since SpaceX did not have actual measured thermal conditions the biprop valve would see during stage return, they would have had to derive them from analysis. And sometimes the analyses doesn't accurately predict the actual conditions that the component eventually sees in flight. Which can lead to failure.

So probably one branch of the fault tree at Hawthorne is thermal conditions exceeding qual levels. That could be problematic to pin down, though, unless they had a thermocouple or two on the valve in question with the data sent down through the telemetry stream.

Hopefully they can duplicate the stiction condition on the ground somehow and thus nail down the root cause.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: maint1234 on 04/20/2015 10:22 am
Assuming the valve in question was a servo/proportional valve  , it would have dither - which would more or less eliminate poor response due to valve sticking,  unless there were contaminants in the fluid.
Also higher ambient temperature of the valve than the norm could  effect  response time.

Seems like the stage was steering at the last moment for whatever reason(maybe to center on the barge) and no mechanical system is going to respond fast enough to last second sudden changes.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: J-V on 04/20/2015 12:36 pm
Pretty!

Isn't there some peeled off paint in the trunk? Is that normal?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Mike_1179 on 04/20/2015 12:40 pm
Pretty!

Isn't there some peeled off paint in the trunk? Is that normal?

Wouldn't paint chips be a MMOD risk?  It looks like the paint has peeled up; almost looks like there's a shadow underneath one section.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rpapo on 04/20/2015 01:02 pm
Pretty!

Isn't there some peeled off paint in the trunk? Is that normal?
Nice question.  I don't recall having noticed that before either.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: OxCartMark on 04/20/2015 03:30 pm
So the question is, why do they have "proper throttle response" on the F9R test but "slower than expected throttle valve response" on the actual landing?

One rather poor response to that question which I've not seen anyone postulate is this - We saw how much faster the actual F9 comes in than Grasshopper did and how much more engine adjustment is done and more quickly (both gimbaling and thrust adj.).  Going back to watching the Grasshopper horizontal divert test would put you to sleep now that we've seen the speed that things happen in a barge landing.  So if the expected throttle response rate is based on manufacturers spec or a theoretical prediction but hasn't been tested to the limit by SpaceX and Grasshopper didn't require such rapid response then maybe this was the first time that it was needed to respond that fast.  A poor response since I can't see them not having tested the valves of that design (and maybe even this particular valve) on a hydraulics test bench and maybe at McGregor.


Navigating in X and Y should be possible even if the thrust is wrong.  There is plenty of control authority, provided the engine is running at all.

The horizontal forces are basically thrust*sin(angle), where angle measured from vertical.  It looks like for the "thrust" part of this, they used the commanded thrust and not the measured thrust.  Normally this makes no difference, since the commanded and actual thrust will be very close in size.   But when the obtained thrust was different, as the case here, this calculation gets the sideways thrust wrong, too.  This error mounted up until they had to do a big last-minute correction, which failed.

Now if they used the actual thrust (from accelerometer, measured valve position (if available), strain gauge, etc.) then they could still adjust X and Y correctly even if the throttle sticks.  They still might have a hard landing, but the stage would be vertical and centered on the barge, which could help.

Of course this relies on having a better estimate of the obtained thrust with a small enough lag to avoid instabilities in the X and Y correction loops.  But given they have 30 seconds to get X and Y lined up, but the rocket can do it in just a few seconds (as it did at the end of the flight, almost) there should be plenty of margin available for tweaks in this system.

Let me take what you said and spin it in a different interpretation.  The system is trying to control a large number of variables (velocities and accelarations along and around multiple axes) simultaneously using very few control inputs (thrust, tilt, pan (plus a little bit of grid fin and nitrogen thrusters)).  When the slow throttle response became apparent it wasn't possible to solve everything simultaneously and the priorities of the system became more apparent.  The lesser prioritized position and acceleration variables suffered.  So under this theory first priorities were vertical speed to be zero at altitude zero which it pretty much did, and the variables that suffered were horizontal speed when it touched down.  Just guessing out loud to stimulate thought.  If I had to bet though I think I'd put my money on the SpaceX guys knowing a bit more about this than I do.  They seem to be a bright group.


I will now suggest to us and the mods that "throttle response" discussions should be taking place on the "Landing the F9 v1.1 first stage" thread and not on this, the "SpaceX Falcon 9 v1.1 - SpX-6/CRS Dragon Discussion Thread"  I think this thread might be better used for discussion of Dragon at ISS and Dragon return.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Chris Bergin on 04/20/2015 03:53 pm
I think we can move all the throttle response comments to this thread that is more specific:

http://forum.nasaspaceflight.com/index.php?topic=37351.0
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: the_other_Doug on 04/20/2015 05:58 pm
This is just Elon celebrating the 43rd anniversary of Apollo 16, which launched 4/16/72.  On their LM, a bad batch of paint peeled off of parts of the ascent stage.

Seriously, though, from the looks of that I'd almost think that this happened during boost.  Really hard to say from this image.

I bet they'll be looking at the history of the paint batch used on this Dragon trunk in Hawthorne today, though...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: laika_fr on 04/20/2015 08:10 pm
" Tis but a Scratch ! "  ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 04/21/2015 01:35 am
This is just Elon celebrating the 43rd anniversary of Apollo 16, which launched 4/16/72.  On their LM, a bad batch of paint peeled off of parts of the ascent stage.

Seriously, though, from the looks of that I'd almost think that this happened during boost.  Really hard to say from this image.

I bet they'll be looking at the history of the paint batch used on this Dragon trunk in Hawthorne today, though...

For bad paint, I would expect larger areas of peeling, more distributed.  This looks to me more like improper preparation of the surface in isolated areas.  Something as simple as a little moisture or other contaminant under the paint in those areas.  Note, they seem to have clustered around/close to the rivets.  An area that's likely to provide extra challenges to preparation prior to paint application.

edit: sorry is there a better thread for discussion of this issue?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 04/21/2015 04:31 am
From SpaceX's original tweet that Dragon was berthed there's a different view.  Though not as good resolution.

https://twitter.com/SpaceX/status/589059537119748096

SpaceX @SpaceX
#Dragon is now fully attached to @Space_Station! Hatch opening to occur over the next day.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: pericynthion on 04/21/2015 04:59 am

Wouldn't paint chips be a MMOD risk?

Not to ISS. They will have a much smaller ballistic coefficient than ISS/Dragon and once they peel off they'll reenter within a matter of days to weeks, never re-approaching the station.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lewis007 on 04/21/2015 08:02 am
A nice collection of launch pics can be found on the Flickr page of Zero-G News.
https://www.flickr.com/photos/[email protected]/sets/72157652049757041/
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: JamesH on 04/21/2015 02:14 pm
If you were hoping to hear or see any of the rodent/mice activities on ISS, don't count on it.  After extensive audio discussion of problems setting up two testing facilities this morning, once simple movement of the mice to those facilities was started, it was done in a total video/audio blackout.  CAPCOM just confirmed that video restrictions had been lifted and that both Houston and Marshall could once again be called on SG--2 because SG-3 was no longer privatized.  The fact that the test subjects would be euthanized, dissected, and frozen on orbit was grudgingly acknowledged in pre-flight briefings but apparently any coverage of those activities is considered too sensitive, disturbing, or otherwise unacceptable to the general public on the open feed...

And yet on CSI or NCIS or similar, we get autopsies (fake of course) getting more and more graphic. Or people being shot let right and centre with blood gushing everywhere.

Odd. Next they will be showing nipples at the Superbowl.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Nomadd on 04/21/2015 02:57 pm
I'm guessing a little primer outgassing from vacuum exposure. Or somebody leaning against the trunk at the wrong time. Or a procedure slip, like surface prep getting a little sloppy. Lots of reasons you could have areas of paint flaking off. Not a big thing here, but not the sort of quality control you want to see on your spaceship. Slacking off because you don't think it's important enough is a bad path to get on.
 And, even though they're not an MMOD risk exactly, you sure the hell don't want a bunch of paint flakes floating around your station.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: woods170 on 04/21/2015 04:40 pm
And yet on CSI or NCIS or similar, we get autopsies (fake of course) getting more and more graphic. Or people being shot let right and centre with blood gushing everywhere.

The audience generally is very much aware of the fact the any blood and gore shown on CSI and NCIS is 'a job well-done by the make-up department'.

The same audience generally is very much aware that live-stream views of a mouse being dissected on board the ISS is probably the real deal.

And where 'the real deal' results in some folks taking an expedited trip to the toilet, the 'make-up job' usually doesn't. It's all psychological.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: the_other_Doug on 04/21/2015 05:14 pm
Exactly.  CSI may show a dummy made up to look like a beheaded corpse, but American media will never run the several videos of ISIS terrorists actually beheading captives.  The audience accepts that one is real and the other is not.

Now, let us leave this gross and gory OT discussion.  We return you now to your regularly scheduled CRS-6 thread...  ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: te_atl on 04/21/2015 06:19 pm
This is just Elon celebrating the 43rd anniversary of Apollo 16, which launched 4/16/72.  On their LM, a bad batch of paint peeled off of parts of the ascent stage.

Seriously, though, from the looks of that I'd almost think that this happened during boost.  Really hard to say from this image.

I bet they'll be looking at the history of the paint batch used on this Dragon trunk in Hawthorne today, though...

Ok, so this begs a question.  How is the paint applied?   Is it electrostatically applied like car paint?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 04/21/2015 06:21 pm
The peeling paint might also be the side-effect of some repair process carried out on the Dragon during the flow.  That is, something might have been reworked and the "repaint" part of that task wasn't up to spec.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: dorkmo on 04/21/2015 07:10 pm
you can see on the launch pad that one of the spots had paint peeled pre-launch.

and it appears that the part that currently has a flake peeling up is new

https://www.youtube.com/watch?v=csVpa25iqH0?t=10m42s

ps i think that this paint is whiter than it has been in the past but i wouldnt be bold enough to make claims about colors and intensity http://en.wikipedia.org/wiki/Munsell_color_system
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: corrodedNut on 04/21/2015 07:36 pm
Paint just doesn't like to stick to aluminum. Aerospace and marine industries use all manner of techniques, metal- etching primers and epoxy primers, cross-linking urethane top coats, and it still peels off. Even on aircraft that aren't rocketing through the atmosphere at supersonic speeds.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/23/2015 11:37 pm
Paint just doesn't like to stick to aluminum. Aerospace and marine industries use all manner of techniques, metal- etching primers and epoxy primers, cross-linking urethane top coats, and it still peels off. Even on aircraft that aren't rocketing through the atmosphere at supersonic speeds.

Why bother with the paint then?  Does the white paint actually serve some purpose other than to make the spacecraft look pretty??  It's already been proven that not painting aircraft saves money in paint, the weight of paint and reduces skin friction/drag - not that many airlines actually do that.
 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/23/2015 11:54 pm
Paint just doesn't like to stick to aluminum. Aerospace and marine industries use all manner of techniques, metal- etching primers and epoxy primers, cross-linking urethane top coats, and it still peels off. Even on aircraft that aren't rocketing through the atmosphere at supersonic speeds.

Why bother with the paint then?  Does the white paint actually serve some purpose other than to make the spacecraft look pretty??  It's already been proven that not painting aircraft saves money in paint, the weight of paint and reduces skin friction/drag - not that many airlines actually do that.
 

The paint probably serves some thermal function.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/23/2015 11:59 pm
Paint just doesn't like to stick to aluminum. Aerospace and marine industries use all manner of techniques, metal- etching primers and epoxy primers, cross-linking urethane top coats, and it still peels off. Even on aircraft that aren't rocketing through the atmosphere at supersonic speeds.

Why bother with the paint then?  Does the white paint actually serve some purpose other than to make the spacecraft look pretty??  It's already been proven that not painting aircraft saves money in paint, the weight of paint and reduces skin friction/drag - not that many airlines actually do that.
 

The paint probably serves some thermal function.

If it were black paint I'd understand that, but white paint tends to be mildly reflective (here on earth anyways) but not as reflective as bare metal.  Perhaps they're more worried bare Al might dazzle the ISS crew?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/24/2015 12:10 am
It's more than just how reflective something is - how it reflects light and energy matters too.

A mirror and a perfectly white diffuse surface are both equally reflective - the white surface simply reflects it in every direction whereas a perfect mirror only reflects it in one direction. (real life materials are of course somewhere in the middle)

But some paints have different reflectivity in different wavelengths too.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Remes on 04/24/2015 12:22 am
https://www.youtube.com/watch?v=TEPtVK6SksE

My first attempt to implement machine learning on videos (had some work done earlier on machine learning, but that was for radar and the object hypothesis).

The algorithm tries to recognize the rocket and the thrust vector. The scale at the bottom is the thrust vector. The scale above is the angle of the rocket.

The thrust vector hypothesis is confused by some transient flames (gas generator exhaust?). I now know a better way to detect the exhaust plume. Hopefully I can extract position, velocities, angular position and angular velocities.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cambrianera on 04/24/2015 12:42 am
Paint just doesn't like to stick to aluminum. Aerospace and marine industries use all manner of techniques, metal- etching primers and epoxy primers, cross-linking urethane top coats, and it still peels off. Even on aircraft that aren't rocketing through the atmosphere at supersonic speeds.

Why bother with the paint then?  Does the white paint actually serve some purpose other than to make the spacecraft look pretty??  It's already been proven that not painting aircraft saves money in paint, the weight of paint and reduces skin friction/drag - not that many airlines actually do that.
 
Sources?
Curious thing is that any and every picture you find of new built airplanes outside Airbus or Boeing factories has the appearance of a primer, and never of the bare metal.
Obviously without considering 787 and A350; never been one of them with bare CFRP.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: CameronD on 04/24/2015 01:17 am
Paint just doesn't like to stick to aluminum. Aerospace and marine industries use all manner of techniques, metal- etching primers and epoxy primers, cross-linking urethane top coats, and it still peels off. Even on aircraft that aren't rocketing through the atmosphere at supersonic speeds.

Why bother with the paint then?  Does the white paint actually serve some purpose other than to make the spacecraft look pretty??  It's already been proven that not painting aircraft saves money in paint, the weight of paint and reduces skin friction/drag - not that many airlines actually do that.
 
Sources?
Curious thing is that any and every picture you find of new built airplanes outside Airbus or Boeing factories has the appearance of a primer, and never of the bare metal.
Obviously without considering 787 and A350; never been one of them with bare CFRP.

It'll take me a while to dig up the sources, but I do know the bare metal suffers from corrosion faster (the oxide layer is quite soft) and this is the main reason it isn't done widely.

..but since you asked, below is a modern example and one not-so-modern, both from your part of the world:

EDIT:  Here's one source:
"The museum's single-seat F15A, nicknamed "Streak Eagle," broke eight time-to-climb world records between Jan. 16 and Feb. 1, 1975. In setting the last of the eight records, it reached an altitude of 98,425 feet just 3 minutes, 27.8 seconds from brake release at takeoff and "coasted" to nearly 103,000 feet before descending. It was flown in its natural metal finish to reduce weight for the record-setting flights. To protect it from corrosion, McDonnell Douglas Corp. has since painted it in the gray color scheme of most operational F-15s."
http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=621 (http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=621)



Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jose on 04/24/2015 03:21 am
I was fortunate enough to visit the Udvar-Hazy Center recently:

http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A19880028000

"The Museum's aircraft has never been painted and has a highly polished natural metal finish."
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Robotbeat on 04/24/2015 03:23 am
Paint just doesn't like to stick to aluminum. Aerospace and marine industries use all manner of techniques, metal- etching primers and epoxy primers, cross-linking urethane top coats, and it still peels off. Even on aircraft that aren't rocketing through the atmosphere at supersonic speeds.

Why bother with the paint then?  Does the white paint actually serve some purpose other than to make the spacecraft look pretty??  It's already been proven that not painting aircraft saves money in paint, the weight of paint and reduces skin friction/drag - not that many airlines actually do that.
 

The paint probably serves some thermal function.

If it were black paint I'd understand that, but white paint tends to be mildly reflective (here on earth anyways) but not as reflective as bare metal.  Perhaps they're more worried bare Al might dazzle the ISS crew?

Not true. Aluminum is only around 90% reflective. White paint can be higher (for special paints, upwards of 95-98%), plus can have a higher emissivity (i.e. blacker) in the thermal IR range, meaning it will reflect vast majority of visible light but will still be able to efficiently radiate heat in the infrared.

So bare metal is not necessarily ideal (because the emissivity is fairly constant across the spectrum, meaning although it doesn't absorb that much light as heat, it also has a hard time radiating it away).
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cambrianera on 04/24/2015 05:05 am
Then it‘s clear: paint is the rule, bare metal the exception (war, records, museums, some display).
And AA livery was a transparent varnish...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 04/24/2015 05:51 am
Then it‘s clear: paint is the rule, bare metal the exception (war, records, museums, some display).
And AA livery was a transparent varnish...

And even AA has changed its livery, since it is not very practical on airliners made from composites (like 787). The new base color is flat grey: http://www.airlinereporter.com/wp-content/uploads/2013/03/AA767.jpg
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LouScheffer on 04/24/2015 11:27 am
Paint just doesn't like to stick to aluminum. Aerospace and marine industries use all manner of techniques, metal- etching primers and epoxy primers, cross-linking urethane top coats, and it still peels off. Even on aircraft that aren't rocketing through the atmosphere at supersonic speeds.

Why bother with the paint then?  Does the white paint actually serve some purpose other than to make the spacecraft look pretty??  It's already been proven that not painting aircraft saves money in paint, the weight of paint and reduces skin friction/drag - not that many airlines actually do that.
 
The white paint on spacecraft is only white in the visible.  In the infrared, where it's radiating thermal energy, it's black.  Bare metal, by contrast, is reflective in the visible, but also shiny (a bad radiator) in infrared.
For properties of paints, see http://www.aztechnology.com/pdfs/materials-catalog.pdf
For example, the paint AZ-93, which is quite likely the paint they are using:
Quote
AZ-93 is an inorganic white thermal control paint developed for use on spacecraft surfaces exposed to
the deleterious effects of the space environment. Application of AZ-93 creates a nonspecular white
coating that provides superior thermal protection by allowing only 14-16% of the solar radiation impinging
on the spacecraft external surface to be absorbed through to the interior systems while emitting 89-93%
of the internal heat generated to the cold vacuum of space.

The Long Duration Exposure Facility had lots of information on these coatings and their properties:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940026508.pdf
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: spacenut on 04/24/2015 01:25 pm
Aluminum doesn't have to be painted.  However, I think Robotbeat hit it.  White paint reflects heat and you are trying to keep the LOX cold.   If the rockets used some type of fuel that didn't have to be cold, then they would probably not paint them to save weight.  I worked in the natural gas industry before retirement.  Any facilities we had above ground had to be painted white or silver to reflect heat.  Otherwise the piping would get so hot in the sun, maintenance employees couldn't touch anything.  It also heated up the gas which would lower the density and thus the BTU content per cubic foot in measurement.  I had to use flow formulas that used 60 degrees F for the gas temperature BTU content.  That is because underground piping at 3' or below is almost a constant 60 degrees year round. 
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meithan on 04/24/2015 01:50 pm
I'm a bit surprised no one has mentioned the Space Shuttle External Tank in this discussion. As you may know, for the first two Space Shuttle missions they painted it white (see attached picture), allegedly "to protect the tanks from ultraviolet light during the extended time that the shuttle spends on the launch pad prior to launch" (Wikipedia (http://en.wikipedia.org/wiki/Space_Shuttle_external_tank#Standard_Weight_Tank)), and starting from STS-3 they just decided to leave it unpainted, "leaving the rust-colored spray-on insulation bare" (hence the red-brown color we're all familiar with). That saved about 270 kg of weight.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: DrLucky on 04/24/2015 02:48 pm
Paint just doesn't like to stick to aluminum. Aerospace and marine industries use all manner of techniques, metal- etching primers and epoxy primers, cross-linking urethane top coats, and it still peels off. Even on aircraft that aren't rocketing through the atmosphere at supersonic speeds.

Why bother with the paint then?  Does the white paint actually serve some purpose other than to make the spacecraft look pretty??  It's already been proven that not painting aircraft saves money in paint, the weight of paint and reduces skin friction/drag - not that many airlines actually do that.
 

The paint probably serves some thermal function.

If it were black paint I'd understand that, but white paint tends to be mildly reflective (here on earth anyways) but not as reflective as bare metal.  Perhaps they're more worried bare Al might dazzle the ISS crew?

Not true. Aluminum is only around 90% reflective. White paint can be higher (for special paints, upwards of 95-98%), plus can have a higher emissivity (i.e. blacker) in the thermal IR range, meaning it will reflect vast majority of visible light but will still be able to efficiently radiate heat in the infrared.

So bare metal is not necessarily ideal (because the emissivity is fairly constant across the spectrum, meaning although it doesn't absorb that much light as heat, it also has a hard time radiating it away).

There's also a photoelectronic effect in which UV-exposed metal surfaces can liberate electrons and hence become positively charged.  This could result in current flows through the spacecraft as unlit areas attract free electrons or negative ions from the ambient plasma.  I expect that coatings intended for space would address that effect.

Anyone have links to articles on coatings which have the described reflective-in-visible but emissive-in-infrared property?  Sounds like good reading.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: LouScheffer on 04/24/2015 03:20 pm
Anyone have links to articles on coatings which have the described reflective-in-visible but emissive-in-infrared property?  Sounds like good reading.
Try the article "Thermal Control Surfaces Experiment"
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990021250.pdf (warning, 148 page paper, 15 MB pdf)

page 59 has two good plots for white paint.  Figure 48 shows the reflectance (quite high) in the visible, by wavelength, and figure 49 shows the same in the thermal infrared, where the paint is nearly black.

The document as a whole covers lots of other surface coatings (other white paints, plus black, silvered, etc.), with data before and after the multi-year LDEF exposure.

Happy reading!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 04/26/2015 08:43 am
Media Release from a company that was contracted to send up a 65" projection screen to the ISS on CRS-6.  I didn't know this was on the manifest.  Pretty cool.  Be sure to keep reading below the page breaks.

http://www.screeninnovations.com/news/si-news/iss-viewscreen-the-first-screen-in-space/

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: karki on 04/26/2015 03:05 pm
Media Release from a company that was contracted to send up a 65" projection screen to the ISS on CRS-6.  I didn't know this was on the manifest.  Pretty cool.  Be sure to keep reading below the page breaks.

http://www.screeninnovations.com/news/si-news/iss-viewscreen-the-first-screen-in-space/

I believe this screen is shown in this photo tweeted by Scott Kelly a few days ago.
https://twitter.com/StationCDRKelly/status/592064802014507008
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AJW on 04/26/2015 03:18 pm
Media Release from a company that was contracted to send up a 65" projection screen to the ISS on CRS-6.  I didn't know this was on the manifest.  Pretty cool.  Be sure to keep reading below the page breaks.

http://www.screeninnovations.com/news/si-news/iss-viewscreen-the-first-screen-in-space/

I believe this screen is shown in this photo tweeted by Scott Kelly a few days ago.
https://twitter.com/StationCDRKelly/status/592064802014507008

Watching Gravity on board the ISS is a bit like watching Marathon Man or Little Shop of Horrors while at the dentist.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: jabe on 04/26/2015 03:25 pm
Love to know a little more about the projector..those things can give off LOTS of heat.. curious how different the projector is to "normal" projector ...
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mvpel on 04/26/2015 04:26 pm
http://www.screeninnovations.com/news/si-news/iss-viewscreen-the-first-screen-in-space/

The screen maker says it's a laser projector but doesn't say what brand. Much less heat than incandescents, needless to say.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 04/26/2015 04:38 pm
Paint just doesn't like to stick to aluminum. Aerospace and marine industries use all manner of techniques, metal- etching primers and epoxy primers, cross-linking urethane top coats, and it still peels off. Even on aircraft that aren't rocketing through the atmosphere at supersonic speeds.

Why bother with the paint then?  Does the white paint actually serve some purpose other than to make the spacecraft look pretty??  It's already been proven that not painting aircraft saves money in paint, the weight of paint and reduces skin friction/drag - not that many airlines actually do that.
 

The paint probably serves some thermal function.

If it were black paint I'd understand that, but white paint tends to be mildly reflective (here on earth anyways) but not as reflective as bare metal.  Perhaps they're more worried bare Al might dazzle the ISS crew?

Not true. Aluminum is only around 90% reflective. White paint can be higher (for special paints, upwards of 95-98%), plus can have a higher emissivity (i.e. blacker) in the thermal IR range, meaning it will reflect vast majority of visible light but will still be able to efficiently radiate heat in the infrared.

So bare metal is not necessarily ideal (because the emissivity is fairly constant across the spectrum, meaning although it doesn't absorb that much light as heat, it also has a hard time radiating it away).

That's exactly right.

The peeled of spot is small, and nothing local will happen to the spacecraft, so that's why there's no worry.

If half the paint had fallen off, they'll have needed to pay more attention during the approach phase, it could have been a problem.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Silmfeanor on 04/26/2015 04:39 pm
Love to know a little more about the projector..those things can give off LOTS of heat.. curious how different the projector is to "normal" projector ...
I spotted this a few days ago, and I think this might be the projector- bottom left of the picture. 'Casio Projector'
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AnalogMan on 04/26/2015 05:24 pm
Love to know a little more about the projector..those things can give off LOTS of heat.. curious how different the projector is to "normal" projector ...
I spotted this a few days ago, and I think this might be the projector- bottom left of the picture. 'Casio Projector'

Case and rear panel connectors look similar to Casio's XJ-M251 projector.  "Casio" label on top panel is different but otherwise the panel features and other legends look pretty much the same.

http://www.casioprojector.com/products/Signature_Models/XJ-M251 (http://www.casioprojector.com/products/Signature_Models/XJ-M251)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mvpel on 04/26/2015 06:09 pm
Case and rear panel connectors look similar to Casio's XJ-M251 projector.  "Casio" label on top panel is different but otherwise the panel features and other legends look pretty much the same.

Good eye! The top panel has what must be an ISS inventory control sticker that's been applied on top of the CASIO brand name. If you look closely you can see the word underneath the sticker.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Comga on 04/26/2015 08:57 pm
Anyone have links to articles on coatings which have the described reflective-in-visible but emissive-in-infrared property?  Sounds like good reading.
Try the article "Thermal Control Surfaces Experiment"
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990021250.pdf (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990021250.pdf) (warning, 148 page paper, 15 MB pdf)

page 59 has two good plots for white paint.  Figure 48 shows the reflectance (quite high) in the visible, by wavelength, and figure 49 shows the same in the thermal infrared, where the paint is nearly black.

The document as a whole covers lots of other surface coatings (other white paints, plus black, silvered, etc.), with data before and after the multi-year LDEF exposure.

Happy reading!

Excellent!

"Who are you going to believe, me or your lying eyes?"

If you have a thermal camera, or or other infrared measurements, you won't get fooled by the limited spectral response of human eyesight.

One of my favorite images shows the Ralph imager attached to the New Horizons spacecraft, now less than 100 million kilometers from the Pluto system.  The round white disk, and the round white ring around it, are heat rejecting radiators for the Short Wave IR detector and the visible / near IR detectors respectively.  This white paint has very high emissivity in the long wavelength Infrared where the emissions peak for room temperature and colder object.  Being white means that if the spacecraft were to point in a way that allowed sunshine onto the radiators, the visible light, where most of the power lies, would be reflected and rejected, and the thermal input would be much less than a black surface.

Bare aluminum behaves differently.  It gets more reflective the farther you go into the infrared. An bare aluminum panel in direct sunlight with an insulated back will slowly but eventually get very hot.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cosmicvoid on 04/26/2015 11:15 pm
I spotted this a few days ago, and I think this might be the projector- bottom left of the picture. 'Casio Projector'

That looks like the "food room"; a cluster of carrots in front of Kelly, a partially eaten pear on the right side, maybe food in foil packs.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: lele on 04/27/2015 08:20 am
I may have missed something, but there's still no publicly availlable HQ video from a rocketcam on a returning 1st stage?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jarnis on 04/27/2015 10:34 am
I may have missed something, but there's still no publicly availlable HQ video from a rocketcam on a returning 1st stage?

None have been released by SpaceX from the landings that aimed the barge.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 04/27/2015 11:55 am
http://www.screeninnovations.com/news/si-news/iss-viewscreen-the-first-screen-in-space/

The screen maker says it's a laser projector but doesn't say what brand. Much less heat than incandescents, needless to say.

The companies logo gives that away.  If they continue to use the same technology you might find info coming out of the "Epson" Group".

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ben the Space Brit on 04/27/2015 12:29 pm
Watching Gravity on board the ISS is a bit like watching Marathon Man or Little Shop of Horrors while at the dentist.

"Um... Houston? Gonna schedule a decompression response and EV evacuation drill for our next free activity slot. Just feels right."
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 05/04/2015 11:19 pm
Looks like they allowed some photographers to place remote controlled cameras on the barge. Here is a glorious high resolution image:  :)

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cartman on 05/05/2015 12:02 am
wow, that's one of the most epic images of the decade!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meekGee on 05/05/2015 12:07 am
Oshin - on the high res picture, that "stud" that you pointed out as sticking out from under the actuator appears in other legs as well.   Maybe it is the "initial pusher" of the legs?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Joffan on 05/05/2015 12:13 am
I think the thing at the bottom with the bright flamey stuff coming out :) is the initial pusher of the legs, although actually pushing the body up instead of the legs down.

However it would be interesting to know what the extra metal rod at the body end of the piston is, for sure.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: rcoppola on 05/05/2015 12:26 am
The legs don't appear to be fully extended on this photo, almost but not quite. Each of those rods, directly under  each leg look aligned to where the final leg angle would be. So I'm guessing that once the legs extend fully out they come into contact with those rods which in turn shut off the helium flow to each leg individually as they become fully extended and lock.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: baldusi on 05/05/2015 12:27 am
I wonder if CRS-7 actually lands and is recovered, if it won't go to be the cover of some mainstream magazine?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 05/05/2015 12:31 am
I wonder if CRS-7 actually lands and is recovered, if it won't go to be the cover of some mainstream magazine?

It'll be Time magazine's Rocket of the Year.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: ellindsey on 05/05/2015 12:37 am
Looking at that large landing image there's a lot more fire coming from up above the actual center engine nozzle than I would expect.  Is that all exhaust from the gas generator, or does it suggest a possible leak?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 05/05/2015 12:50 am
Gas generator.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AS-503 on 05/05/2015 01:14 am
Gas generator.

No, the Merlin 1D has the gas generator exhaust ducted into the nozzle like the F1 and J2 engines from Apollo.
The Merlin 1C had the gas generator exhaust dumped overboard (outside the nozzle).

See attched images. The F9 V1 shows some of the gas generator exhausts circled in red.
The F9 V1_1 shows some of the taurus shaped exhausts ducting into the nozzle circled in red.


Edit: Whoops...I stand corrected. See subsequent posts.  :-X
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: bubbagret on 05/05/2015 01:49 am
Gas generator.

No, the Merlin 1D has the gas generator exhaust ducted into the nozzle like the F1 and J2 engines from Apollo.
The Merlin 1C had the gas generator exhaust dumped overboard (outside the nozzle).

See attched images. The F9 V1 shows some of the gas generator exhausts circled in red.
The F9 V1_1 shows some of the taurus shaped exhausts ducting into the nozzle circled in red.

That is the cooling manifold, the turbine exhaust is within the engine circle now.

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meithan on 05/05/2015 01:52 am
See attched images. The F9 V1 shows some of the gas generator exhausts circled in red.
The F9 V1_1 shows some of the taurus shaped exhausts ducting into the nozzle circled in red.

Isn't that the LOX feed to cool the nozzle?

Edit: dammit, ninja'd!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kaputnik on 05/05/2015 03:06 am
Looks like they allowed some photographers to place remote controlled cameras on the barge. Here is a glorious high resolution image:  :)


You can see right up its nozzles!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ohsin on 05/05/2015 09:40 am
Oshin - on the high res picture, that "stud" that you pointed out as sticking out from under the actuator appears in other legs as well.   Maybe it is the "initial pusher" of the legs?

Revived landing legs thread on 66 for this. One thing that is clear is attachment point itself doesn't pull or push but there is this stud under it that might be doing the pushing. Legs are fully extended IMO.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: eeergo on 05/05/2015 10:02 am
Looks like they allowed some photographers to place remote controlled cameras on the barge. Here is a glorious high resolution image:  :)

I wonder what these vertical markings on the top of the stage are...  :o
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 05/05/2015 10:11 am
Soot streaks.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: eeergo on 05/05/2015 10:18 am
Sure could be, but since they can't be seen anywhere else they caught my eye, they almost look like buckling/wrinkling. Probably not, just an ROI as they called it in the Shuttle days :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jcc on 05/05/2015 10:20 am
Also it looks like most of the paint came off. Strange!
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 05/05/2015 10:23 am
Also it looks like most of the paint came off. Strange!

Kentucky Fried Falcon.  ;)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: cscott on 05/05/2015 01:01 pm
Also it looks like most of the paint came off. Strange!
Just looks like sooty grey paint to me.

EDIT: apparently I needed a hyphen: "sooty-grey".  Not "sooty (grey paint)".
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: AncientU on 05/05/2015 01:52 pm
Also it looks like most of the paint came off. Strange!
Just looks like sooty grey paint to me.

Since they didn't change the paint job during the 10 minute flight, it's sooty white paint.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevin-rf on 05/05/2015 02:06 pm
Are you sure the Falcon is Black and Gold and not Blue and White?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: deruch on 05/05/2015 02:11 pm
Looks like they allowed some photographers to place remote controlled cameras on the barge. Here is a glorious high resolution image:  :)

I wonder what these vertical markings on the top of the stage are...  :o

Interaction of soot, ice, and rivulets of water from melting ice?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ohsin on 05/05/2015 02:46 pm
Looks like they allowed some photographers to place remote controlled cameras on the barge. Here is a glorious high resolution image:  :)

I wonder what these vertical markings on the top of the stage are...  :o

Interaction of soot, ice, and rivulets of water from melting ice?

Most likely. Like here on recovered I frame from CRS-3 footage.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Comga on 05/05/2015 04:39 pm
Gas generator.

No, the Merlin 1D has the gas generator exhaust ducted into the nozzle like the F1 and J2 engines from Apollo.
The Merlin 1C had the gas generator exhaust dumped overboard (outside the nozzle).

See attched images. The F9 V1 shows some of the gas generator exhausts circled in red.
The F9 V1_1 shows some of the taurus shaped exhausts ducting into the nozzle circled in red.

That is the cooling manifold, the turbine exhaust is within the engine circle now.

I see eight objects which may be the turbine exhaust ports, all arranged symmetrically.
Where is the ninth port for the central engine?
It's flaming exhaust is clearly seen in the landing attempt videos.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Kabloona on 05/05/2015 04:45 pm
I see eight objects which may be the turbine exhaust ports, all arranged symmetrically.
Where is the ninth port for the central engine?
It's flaming exhaust is clearly seen in the landing attempt videos.

You can see an edge of it at 12 o'clock just above the nozzle.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Lars-J on 05/05/2015 04:47 pm
Gas generator.

No, the Merlin 1D has the gas generator exhaust ducted into the nozzle like the F1 and J2 engines from Apollo.
The Merlin 1C had the gas generator exhaust dumped overboard (outside the nozzle).

See attched images. The F9 V1 shows some of the gas generator exhausts circled in red.
The F9 V1_1 shows some of the taurus shaped exhausts ducting into the nozzle circled in red.

That is the cooling manifold, the turbine exhaust is within the engine circle now.

I see eight objects which may be the turbine exhaust ports, all arranged symmetrically.
Where is the ninth port for the central engine?
It's flaming exhaust is clearly seen in the landing attempt videos.

Yes, and here are some clearer images of the turbo-pump exhaust ports. (first image shows the exhaust for the center engine)

To re-iterate, only the M1D-*Vacuum*has that exhaust ducted into the nozzle. The regular M1D does not.

EDIT: Also added a CAD rendering of an M1D engine.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: RonM on 05/05/2015 04:50 pm
Gas generator.

No, the Merlin 1D has the gas generator exhaust ducted into the nozzle like the F1 and J2 engines from Apollo.
The Merlin 1C had the gas generator exhaust dumped overboard (outside the nozzle).

See attched images. The F9 V1 shows some of the gas generator exhausts circled in red.
The F9 V1_1 shows some of the taurus shaped exhausts ducting into the nozzle circled in red.

That is the cooling manifold, the turbine exhaust is within the engine circle now.

I see eight objects which may be the turbine exhaust ports, all arranged symmetrically.
Where is the ninth port for the central engine?
It's flaming exhaust is clearly seen in the landing attempt videos.

Think it is just above the center engine bell. I circled it in green.

Hey, you guys beat me to it.  :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Remes on 05/06/2015 12:39 am

My first attempt to implement machine learning on videos (had some work done earlier on machine learning, but that was for radar and the object hypothesis).

Second (and final) attempt:
http://youtu.be/O_9SEoEmANs

A few notes:
       Rocket Position         Measured at engine attachement Point
                                Relative to assumed landing spot
                                [m]
                               
        Angle Rocket:           vertical rocket has an angle of 0 degrees
                                if the lower end rotates clockwise it is a positive angle
                                [degree]
       
        Angle thrust vector:    thrust vector angle is always measured relative to the rocket itself
                                straight plume has an angle of 0 degrees
                                if the lower end rotates clockwise it becomes a positive angle
                                [degree]

        The thrustvector angle seems to have an offset of 1 degree. It looks to me like it is going from end to end,
        but I measured 8...-6 degrees. So I rather guess that's a measurement issue, and 1 degree must be subtracted.

The txt file contains the raw data. Every spreadsheet software should be able to read it. The content is:
- frame
- time s
- Rocket position x m
- Rocket position y m
- Rocket angle in radians
- Thrust vector angle relative to the rocket in radians
- Plume length in Pixel
- Right leg angle
- Left leg angle

Enjoy! :)
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: mme on 05/06/2015 01:03 am

My first attempt to implement machine learning on videos (had some work done earlier on machine learning, but that was for radar and the object hypothesis).

Second (and final) attempt:
...
Enjoy! :)
That is really cool.  What software packages did you use to analyze the video and for machine learning?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Remes on 05/06/2015 08:23 am
What software packages did you use to analyze the video and for machine learning?
For the gui I use wxWidgets, for the math of big matrices newmat. I used lots of things I have programmed for earlier projects. Nothing of it is realy specialized for AI. It's more about me learning how to apply machine learning to video than getting something done quickly.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Shanuson on 05/06/2015 09:07 am
ISS043E125469 (04/18/2015) --- A dying sun turns the Earth gold with cities sparkling to match the stars that spread out from the International Space Station. NASA astronaut Terry Verts tweeted this wondrous image with the attached comment about the stars: " See those light clusters? (center sky left and right)They are Magellanic clouds, a duo of dwarf galaxies seen from the southern hemisphere".

In that picture of Dargon most cities on earth are yellowish as you would expect(streetlights and homes are mostly yellow). But there are 3 larger blue areas on earth, are those lighting or something else?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: guckyfan on 05/06/2015 09:08 am
Very impressive. Thanks, Remes.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 05/06/2015 10:25 am
What software packages did you use to analyze the video and for machine learning?
For the gui I use wxWidgets, for the math of big matrices newmat. I used lots of things I have programmed for earlier projects. Nothing of it is realy specialized for AI. It's more about me learning how to apply machine learning to video than getting something done quickly.

Excellent work Remes. Well done.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Prober on 05/08/2015 01:49 pm
Some details on the Polar and Glacier units

http://forum.nasaspaceflight.com/index.php?topic=33141.360

Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: NotOnImpact on 05/10/2015 08:39 pm
In that picture of Dargon most cities on earth are yellowish as you would expect(streetlights and homes are mostly yellow). But there are 3 larger blue areas on earth, are those lighting or something else?
My guess is lightning.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Hywel1995 on 05/21/2015 10:58 am
The Big round thing behind the control room close to the landing leg... Is that a stage? Seems to be in the same position as where the Dragon2 announcement was made.

and if not, what would it be?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ben the Space Brit on 05/21/2015 11:01 am
If you're referring to the cylindrical objects on the centre-right of the image then, yes, those are Falcon-9 CBCs being assembled. The object hanging in the top of the centre is an early Dragon v.1.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Hywel1995 on 05/21/2015 11:04 am
If you're referring to the cylindrical objects on the centre-right of the image then, yes, those are Falcon-9 CBCs being assembled. The object hanging in the top of the centre is an early Dragon v.1.

Underneath the Dragon V1, (not in the assembly line...)... It looks like the assembly of an announcement stage.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: docmordrid on 05/21/2015 11:52 am
If you're referring to the cylindrical objects on the centre-right of the image then, yes, those are Falcon-9 CBCs being assembled. The object hanging in the top of the centre is an early Dragon v.1.

Underneath the Dragon V1, (not in the assembly line...)... It looks like the assembly of an announcement stage.

It does indeed look very similar  to the stage used for the V2 reveal. Hmmmm....
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meithan on 05/21/2015 02:50 pm
If you're referring to the cylindrical objects on the centre-right of the image then, yes, those are Falcon-9 CBCs being assembled. The object hanging in the top of the centre is an early Dragon v.1.

Underneath the Dragon V1, (not in the assembly line...)... It looks like the assembly of an announcement stage.

It does indeed look very similar  to the stage used for the V2 reveal. Hmmmm....

Uhm, it kinda looks hollow to me, as if a ring. Also, it seems to be cordoned off.

EDIT: I found this image (attached), where there's a conical shrouded object in the same position. I'm guessing this is a Dragon v2 (minus the nose cone), and that the structure seen in Hywel1995's image is a wheeled ring base used to move it around.

EDIT 2: after further research, the shrouded object is more likely the nozzle extension of a Merlin Vacuum engine. See here (http://i.imgur.com/i9lnXo0.jpg), and it seems they have/had an engine on display (https://twitter.com/SpaceX/status/426784049986682881). My guess that the object in Hywel1995's image is a wheeled ring base stands, though.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jarnis on 05/21/2015 04:07 pm
Hmm, how recent is that image. That leg looks.... used.

They did recover legs from the latest barge Kablooey, could that be one of them?
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: meithan on 05/21/2015 04:36 pm
Hmm, how recent is that image. That leg looks.... used.

They did recover legs from the latest barge Kablooey, could that be one of them?

Nah, that image is from 2013 it seems (see this post (http://www.teslamotorsclub.com/showthread.php/1323-SpaceX/page81?p=524190&viewfull=1#post524190)). Besides, that leg looks in too good a shape to be one of the legs from the landing attempts, I think.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Jarnis on 05/21/2015 04:50 pm
Hmm, how recent is that image. That leg looks.... used.

They did recover legs from the latest barge Kablooey, could that be one of them?

Nah, that image is from 2013 it seems (see this post (http://www.teslamotorsclub.com/showthread.php/1323-SpaceX/page81?p=524190&viewfull=1#post524190)). Besides, that leg looks in too good a shape to be one of the legs from the landing attempts, I think.

After a second look, I agree and the date confirms it. Carry on.

I wonder where the "trophies" from the first attempts end up after analysis... Jurvetson's collection? :D
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: saliva_sweet on 05/22/2015 07:53 am
"When through atmosphere you pass seventeen thousand miles per hour at, look as good you will not.  Hmmph."

X-37b begs to differ.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 05/22/2015 08:26 am
Must be something to do with the shape. The Shuttle was the same - nice and "clean" compared to a capsule design. Orion was scorched too although it's higher re-entry speed probably had a big impact there.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: QuantumG on 05/22/2015 08:32 am
Dragon and Orion have ablative heat shields. The shuttle and X-37B have tiles.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: kevinof on 05/22/2015 08:41 am
Bingo. thank you. Knew I was missing something.

Is this the 7th/8th Dragon flight? SpaceX must know their spacecraft very well at this stage - no doubt they go over every returned Dragon and examine it in every detail to see if the flight actually match their plan.


Dragon and Orion have ablative heat shields. The shuttle and X-37B have tiles.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Ben the Space Brit on 05/22/2015 08:57 am
FWIW, I do wonder if the guys who work on the Dragon assembly line at Hawthorne wince whenever they see the yellowed, burnt and blackened mess that they get back from orbit when they think of the sleek, shining white article they deliver.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: Silmfeanor on 05/22/2015 09:03 am
FWIW, I do wonder if the guys who work on the Dragon assembly line at Hawthorne wince whenever they see the yellowed, burnt and blackened mess that they get back from orbit when they think of the sleek, shining white article they deliver.
Mission accomplished, I would guess.
Title: Re: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread
Post by: corrodedNut on 05/22/2015 01:30 pm
Dragon and Orion have ablative heat shields. The shuttle and X-37B have tiles.