SpaceX Falcon Heavy : Arabsat 6A : LC-39A : April 11, 2019 - DISCUSSION

[spacebleachers]

I think they already have the solution and it's the octograbber - Musks tweet says that the parts to allow the grabber to secure the FH center core weren't ready in time.

So octograbber is the solution.

SpaceX needs to solve this problem, otherwise the economics of using FH where an expendable F9 can do the job goes out the door. I'm thinking giant lassos! (Modified octograbber could do the job as well. :-)

What gets me about Elon's statement is SpaceX seems to of had the time to develop those parts. Why wasn't it ready for this flight? Did they think it was the Atlantic and waves would not be a big deal? Was it because Elon chose to spend dollars on Starship instead of this? Did they think they wouldn't need it for this flight (because they didn't think they would land the booster successfully)?  Was it that system, Octograbber, in use too much so they didn't have time to integrate it(it didn't seem like they were that busy at the end of last year and the time leading up to DM-1 here at the Cape)? Just curious. Maybe L2 is a better place for that discussion.

[OxCartMark]

Still somewhat unclear if the entire vehicle went overboard or some chunk is left on the barge. Hope to hear more in the next couple days, or visual when the barge gets home. It sounds like it fully went overboard but there is some mitigating information.

I can see a scenario in which it tipped to horizontal with the majority of the length of the stage being beyond the perimeter of the ASDS and only the lower most portion say the engines and thrust structure or maybe up to the legs being on the deck.  Then when it hits the water or the edge railing or the containers on the end the pressure stabilized thin shell bursts into shrapnel as we've seen on the early landing attempts, with shrapnel going everywhere but mostly into the sea.  When we've seen that scenario the thrust structure wasn't moved by the bursting and so would be likely to remain on the deck.  The key thing being that there's a lot of energy (relative the the very thin shell) in the form of the gas pressure in the tanks - it may be less after landing but they're likely to be still pressurized to some extent.

[Rondaz]

SpaceX’s Falcon Heavy center core goes overboard, Elon Musk still hopeful

Posted By: Eric Ralph in SpaceX 7 hours ago

https://www-teslarati-com.cdn.ampproject.org/v/s/www.teslarati.com/spacex-falcon-heavy-booster-overboard/amp/?fbclid=IwAR0Kn1MdlNHX84Xai05IfApw3uNTJqTaf8yYtTwcydtNCfR0sYEZY79UgJk&amp_js_v=0.1#referrer=https%3A%2F%2Fwww.google.com&amp_tf=From%20%251%24s&ampshare=https%3A%2F%2Fwww.teslarati.com%2Fspacex-falcon-heavy-booster-overboard%2F

[Nomadd]

 Why eliminate the holdown points the grabber needs in the first place? Even if the core doesn't need them while on the pad, wouldn't keeping them the same as F9 solve the problem and cost very little payload?
 Do they leave the unused 4th holdown on the side boosters?

[Comga]

SpaceX’s Falcon Heavy center core goes overboard, Elon Musk still hopeful

Posted By: Eric Ralph in SpaceX 7 hours ago

https://www-teslarati-com.cdn.ampproject.org/v/s/www.teslarati.com/spacex-falcon-heavy-booster-overboard/amp/?fbclid=IwAR0Kn1MdlNHX84Xai05IfApw3uNTJqTaf8yYtTwcydtNCfR0sYEZY79UgJk&amp_js_v=0.1#referrer=https%3A%2F%2Fwww.google.com&amp_tf=From%20%251%24s&ampshare=https%3A%2F%2Fwww.teslarati.com%2Fspacex-falcon-heavy-booster-overboard%2F

Is that photo from last week's Heavy core or from CRS-16?
It looks awful familiar.   Something about the legs and the flotation bags.
Plus don't we have Musk's tweet that the core is on the ASDS?

[Alexphysics]

SpaceX’s Falcon Heavy center core goes overboard, Elon Musk still hopeful

Posted By: Eric Ralph in SpaceX 7 hours ago

https://www-teslarati-com.cdn.ampproject.org/v/s/www.teslarati.com/spacex-falcon-heavy-booster-overboard/amp/?fbclid=IwAR0Kn1MdlNHX84Xai05IfApw3uNTJqTaf8yYtTwcydtNCfR0sYEZY79UgJk&amp_js_v=0.1#referrer=https%3A%2F%2Fwww.google.com&amp_tf=From%20%251%24s&ampshare=https%3A%2F%2Fwww.teslarati.com%2Fspacex-falcon-heavy-booster-overboard%2F

Is that photo from last week's Heavy core or from CRS-16?
It looks awful familiar.   Something about the legs and the flotation bags.
Plus don't we have Musk's tweet that the core is on the ASDS?

There's a Falcon 9 logo on the booster so, what do you think?...

[Vettedrmr]

Is that photo from last week's Heavy core or from CRS-16?

CRS-16.  OCISLY is nowhere in sight.

[mme]

Why eliminate the holdown points the grabber needs in the first place? Even if the core doesn't need them while on the pad, wouldn't keeping them the same as F9 solve the problem and cost very little payload?
 Do they leave the unused 4th holdown on the side boosters?

I assume it's related to having side booster attachment points which I assume are different to grab onto than hold down points. Granted that's a lot of assuming.

[leetdan]

If 1055 is indeed dry and intact on the barge, then the legs and octaweb should've kept the engines completely intact despite any tank damage induced by the fall.  On the other hand, we have 1050 where the engines were compromised by immersion but the tank was left intact by the soft landing.  Does anybody else think we might see these paired up as a Zombie Stage for a future Starlink launch? 

[e of pi]

If 1055 is indeed dry and intact on the barge, then the legs and octaweb should've kept the engines completely intact despite any tank damage induced by the fall.  On the other hand, we have 1050 where the engines were compromised by immersion but the tank was left intact by the soft landing.  Does anybody else think we might see these paired up as a Zombie Stage for a future Starlink launch? 

If they do, it'd be a chip right of the old HMS Zubian block:

https://en.wikipedia.org/wiki/HMS_Zubian

In late 1916, two British destroyers of the 6th Flotilla in the Dover Patrol—Nubian and Zulu—were badly damaged by German attacks in the English Channel. Nubian's bow had been destroyed by a torpedo from a German torpedo boat on 26 October in the Battle of Dover Strait, while Zulu had her stern blown off by a mine in the Channel on 8 November, and was towed to Calais. Both wrecks were then towed to Chatham Dockyard, where a complete destroyer was constructed by joining the foreparts of Zulu with the stern of Nubian,[3] and despite a 3.5 inches (89 mm) difference in beam,[2] the unique operation was successful.[4] The ship was renamed Zubian by Admiral Reginald Bacon, the commander of the Dover Patrol.[5]

[whitelancer64]

Why eliminate the holdown points the grabber needs in the first place? Even if the core doesn't need them while on the pad, wouldn't keeping them the same as F9 solve the problem and cost very little payload?
 Do they leave the unused 4th holdown on the side boosters?

Two of the hold-downs are modified for side core attachments. The other two are still hold-downs, but are modified enough from the normal Falcon 9 hold down points for the octograbber to not be able to latch on to it. That's as much as Elon Musk has said on Twitter. He also said modifications for the octograbber are already planned.

[groknull]

Why eliminate the holdown points the grabber needs in the first place? Even if the core doesn't need them while on the pad, wouldn't keeping them the same as F9 solve the problem and cost very little payload?
 Do they leave the unused 4th holdown on the side boosters?

I assume it's related to having side booster attachment points which I assume are different to grab onto than hold down points. Granted that's a lot of assuming.

To extrapolate on that...

Consider that an unmodified Falcon 9 has four hold down points / pin sets.  The reaction frame has four hold down mechanisms that grab those points.

A Falcon Heavy center core may have two of those pin sets replaced by the mating (hold down mechanism) version.  Thus a side booster still has four hold down points, three of which are grabbed by the reaction frame hold down mechanisms, and one grabbed by the adjacent center core hold down mechanism.

The Octagrabber is likely to have (wild supposition) active mechanisms to grab onto the passive hold down points / pin sets.  For the Falcon Heavy core, two of the Octagrabber mechanisms would mate properly with the two passive points.  For the other two, the Octagrabber would be trying to grab onto an active mechanism, not a simple pin set - a much more complex situation.  The active mechanism on the Heavy core may not have an actuator, only a release mechanism, requiring a more complex capture mechanism on the Octagrabber side.

Indexing the Octagrabber to the Heavy core may also be an issue - there is a possibility that the arms you chose to modify are 90 degrees off the landed core mating mechanisms.

[Edit: slightly ninja'd by whitelancer64]

[Lars-J]

Why eliminate the holdown points the grabber needs in the first place? Even if the core doesn't need them while on the pad, wouldn't keeping them the same as F9 solve the problem and cost very little payload?
 Do they leave the unused 4th holdown on the side boosters?

The regular hold down points are where the booster attachments are... Which is why they need to change. This picture illustrates the difference on a FH side core: (RED is FH core attachment, GREEN is regular hold down)

So the way the hold downs are oriented, they have to do it this way. Which means that for now, the FH core only has 2 hold downs the octagrabber can grab, and the FH side cores have 3 hold downs. But Elon suggested that the octagrabber modifications to be able to grab the core were not ready in time.

EDIT: I added my scribbly annotations to another FH picture.

If they had to design it over, perhaps they would have clocked the hold down points by 45 degrees so that they would not interfere with the booster attachment location.

[Lars-J]

I think they already have the solution and it's the octograbber - Musks tweet says that the parts to allow the grabber to secure the FH center core weren't ready in time.

So octograbber is the solution.

SpaceX needs to solve this problem, otherwise the economics of using FH where an expendable F9 can do the job goes out the door. I'm thinking giant lassos! (Modified octograbber could do the job as well. :-)

What gets me about Elon's statement is SpaceX seems to of had the time to develop those parts. Why wasn't it ready for this flight? Did they think it was the Atlantic and waves would not be a big deal? Was it because Elon chose to spend dollars on Starship instead of this? Did they think they wouldn't need it for this flight (because they didn't think they would land the booster successfully)?  Was it that system, Octograbber, in use too much so they didn't have time to integrate it(it didn't seem like they were that busy at the end of last year and the time leading up to DM-1 here at the Cape)? Just curious. Maybe L2 is a better place for that discussion.

Welcome to the wonderful world of 20/20 hindsight. 

1. They actually have landed MANY cores on the drone ships before the octagrabber was available. Octagrabber is not a requirement for an ocean landing, but a nice to have.
2. Delaying flights until the Octagrabber mods was ready would have cascading effects on their launch schedule.
3. So they thought it was worth the risk, given past experiences.

But clearly the ocean conditions got worse then they hoped AND/OR the legs were damaged in the landing (remember the walking core?), so a combination of those could have caused it to topple.

[Comga]

Is there a thread tracking OCISLY and the associated boats?

[leetdan]

The Update thread will have major events, @SpaceXFleet is another good source.

[Draggendrop]

First, I would like to state that this launch was thoroughly entertaining and served notice to the future capabilities of this system.

It is unfortunate that the center core had difficulties in transit...but this was not unexpected.

As per Elon's tweet, it appears a modification was already scheduled but unable to be implemented for this launch. Even this "fix", when implemented, will help but is not a guarantee of anything.

Anyone who has been to sea will attest to what "mother nature" can throw up on a moments notice. It can be fine on the horizon while you sail into a mess.

Just my opinion and a result of some of the unique comments posted online ...

Launch weather is just that...launch weather. Landing and safe transport are another matter.

When at sea, there will always be times of reflection wishing "you had a bigger boat". That passes and it's back to work.

The ASDS system works just fine for cost/benefit. We don't need an oil rig, aircraft carrier, clotheslines strung all over the place.

This will not be the last booster to have an incident at sea...it's just part of the business at hand in this environment.

SpaceX is a bit busy on a few projects at this time but I am sure improvements will continue where cost effective but F9/FH are, in the end, just a transition to something hopefully better...the SS/SH may be such a venture and it may not be the last form either...

Just my 2 cents...but this booster has not brought out the best of comments in some forums.
This is just a booster, no one got hurt and I am sure SpaceX won't go belly up with this loss or the occasional few more in the future.

of note...

https://twitter.com/waynehale/status/1118140385753206785

[1]

1. They actually have landed MANY cores on the drone ships before the octagrabber was available. Octagrabber is not a requirement for an ocean landing, but a nice to have.
2. Delaying flights until the Octagrabber mods was ready would have cascading effects on their launch schedule.
3. So they thought it was worth the risk, given past experiences.

Also worth noting that SpaceX has previously demonstrated a willingness to expend otherwise recoverable boosters when conditions suddenly become unfavorable (e.g., Hispasat). Octograbber mods will be ready when they're ready, and we'll see more FH cores make it home when they're done.

Personally, I'm somewhat relieved to see how this played out. In this case, the recovery effort was called off (or at least delayed) when it was believed that securing the booster was too risky for the recovery crew. That the booster did indeed end up tipping over is clear indication that this was absolutely the correct decision. We're all familiar with the consequences of launch fever. Far better not to allow 'recovery fever' to even enter the equation. We'll be seeing recovered FH cores coming home soon enough.

[Wolfram66]

Another option is an ASDS with a deck that has Active heave compensation.  The Glomar Explorer used this in the 1970's as part of Project Azorian

[intelati]

1. They actually have landed MANY cores on the drone ships before the octagrabber was available. Octagrabber is not a requirement for an ocean landing, but a nice to have.
2. Delaying flights until the Octagrabber mods was ready would have cascading effects on their launch schedule.
3. So they thought it was worth the risk, given past experiences.

Also worth noting that SpaceX has previously demonstrated a willingness to expend otherwise recoverable boosters when conditions suddenly become unfavorable (e.g., Hispasat). Octograbber mods will be ready when they're ready, and we'll see more FH cores make it home when they're done.

...In this case, the recovery effort was called off (or at least delayed) when it was believed that securing the booster was too risky for the recovery crew. ... We're all familiar with the consequences of launch fever. Far better not to allow 'recovery fever' to even enter the equation. We'll be seeing recovered FH cores coming home soon enough.

I always remember that the first FH core had the older Aluminum fins. You can call that extenuating circumstances even without considering the low TEB fluid.

In all, SpaceX is unbelievably strong at having that hardware flexibility for these cases where things *go wrong**

* And wrong as in the best case doesn't happen. This is another point where SpaceX excels. They are great at hoping for the best, but still prepared for the worst. Even the failed attempts at landing (Core 1050, That one three engine landing attempt) provided valuable data. They're the only rocket company even attempting this, and I think they will continue being the "fast leader" in these secondary financial considerations (Recovering spent boosters) until another company leader accepts some of that "fail up" sensibility.

As a fan, I hate to see the failures. As a young engineer, I love seeing these "failures" that don't affect the final goal.