SpaceX News

[mvanwink5]

Good point, Ladajo, why pull the struts, test them, then put them back in? Bad logistics. Better to buy new struts, test them all, then as boosters are needed refurbish them with the new certified struts. The key though is access to LOX tank internals to refurbish the boosters, which must be there in order to meet the announced plan. I don't think that acquiring the struts and certifying them is the critical path, instead, I think the critical path is the complete review of the booster and actually testing to

ensure all parts received perform as expected per their certification documentation

However, I am unsure what 'ensuring all parts...' really translates to as obviously, some specs are never completely testable and are done statistically, but it seems to me that for regaining customer confidence in SpaceX's launch program it is the most important issue. And

Our investigation is ongoing until we exonerate all other aspects of the vehicle, but at this time, we expect to return to flight this fall and fly all the customers we intended to fly in 2015 by end of year

[hanelyp]

Given that expected load is about 1/3 of rated load, but the unexpected failure was at ~1/5 of rated load, I'm thinking you should be able to test to double expected load without damaging a good strut.

[Skipjack]

Skip,
A few tanks is significantly less than all internal struts sourced from the vendor in question. They have no way of knowing if the struts are good or bad without testing, and from the sounds of it, destructive testing.
Pulling each one out and stressing it to 10,000lbs, which from and engineering perspective is not that much, but enough to take some time per strut, seems like more than a couple of weeks work. And that is not counting rebuild and certs and closeouts...

I never said that it would just be a couple of weeks work. I said earlier that they plan to return to flight NET the end of September (which is clearly more than a couple of weeks). No, my intention was to point out the fact that there has to be a relatively easy access to the inside of the tank, if they were able to not just fix/replace a relatively small strut but a whole helium tank within a few weeks. To me this makes it quite clear that they could do this without having to cut the whole tank open and re-welding it, which IMHO would have meant a longer delay.

[Giorgio]

Given that expected load is about 1/3 of rated load, but the unexpected failure was at ~1/5 of rated load, I'm thinking you should be able to test to double expected load without damaging a good strut.

Considering the danger involved is probably better to just change supplier and trash actual struts in stock. I believe SpaceX engineers are scratching hard their heads in these last weeks in trying to make the best decision.

[mvanwink5]

Musk will probably make the decision that makes his customers happy. Further, struts are cheap and given they will all be removed for testing it makes little sense to parse the low dollar decisions. It is a waste of time for the engineers too. Strut issue is known, whether it caused the failure or not, it is the review of everything else and deciding how to test the other items that weren't tested before.

[ladajo]

Skip,
I took this:

They had problems with the helium tanks in the past (different kind of problem) and were able to fix them within a few weeks.

to mean that you were inferring a few weeks repair. The struts are primarily structural for the booster, and some also provide mounting frames for helium tanks and other stuff.

I think it is a different issue to remove a strut mounted tank, verses the struts it mounts too, which also happens to be an integral part of the overall structure of the booster. For example, for each strut, how is it attached to the booster? Is it removable without damaging the booster? Given the number and purposes of struts in a booster verses the the number of helium tanks, I think we are looking at two totally different animals (or fruits).

When they fly in the Fall, I am skeptical at this point that it will be any booster complex that used the old struts. I think the delay is mostly based on a need to build new boosters with new struts.

I am not saying they can't get in a booster. In fact I firmly agree they can. It would seem to be mandatory in regard to recycling inspections for re-launch. What I am saying is that if your strut supplier has probable metallurgy issues for the struts he has already sourced, you would be an idiot to accept them all as good to go. What Musk is not looking for here is a vehicle failure rate comparable to STS. After all, that helped kill STS. Manned flight is a totally different game, and that is where he is going. The risk tolerance is magnitudes lower.

[mvanwink5]

Ladajo,
You seem married to the idea that the struts can't be replaced and seem to keep forgetting the larger, more important, full review. Indeed, how can the review take place in time to then manufacture new boosters, and, meet a September launch schedule? That makes no sense, at least to me. Further, nowhere has SpaceX revealed that boosters must be scrapped to replace the struts, and SpaceX has, as mentioned before, been forthright in their plans.

Whatever, keep on with the booster scrapping and replacement with new boosters narrative.

On to something else. What is going on with .gov $ and EMC2? Charity or something else?

[Skipjack]

Skip,
I took this:

They had problems with the helium tanks in the past (different kind of problem) and were able to fix them within a few weeks.

to mean that you were inferring a few weeks repair. The struts are primarily structural for the booster, and some also provide mounting frames for helium tanks and other stuff.

I think it is a different issue to remove a strut mounted tank, verses the struts it mounts too, which also happens to be an integral part of the overall structure of the booster. For example, for each strut, how is it attached to the booster? Is it removable without damaging the booster? Given the number and purposes of struts in a booster verses the the number of helium tanks, I think we are looking at two totally different animals (or fruits).

When they fly in the Fall, I am skeptical at this point that it will be any booster complex that used the old struts. I think the delay is mostly based on a need to build new boosters with new struts.

I am not saying they can't get in a booster. In fact I firmly agree they can. It would seem to be mandatory in regard to recycling inspections for re-launch. What I am saying is that if your strut supplier has probable metallurgy issues for the struts he has already sourced, you would be an idiot to accept them all as good to go. What Musk is not looking for here is a vehicle failure rate comparable to STS. After all, that helped kill STS. Manned flight is a totally different game, and that is where he is going. The risk tolerance is magnitudes lower.

Someone expressed the fear that they would have to cut the tank open in order to replace the struts. I said, that they must have another way to access these things because of their ability to replace the helium tanks. The strut assembly consists of several parts that are connected with bolts. One part is fixed to the booster wall. I do not know how exactly they are attached to it.
But I do not think that any of this is enough of a problem that they have to rebuild the entire booster. If that was the case, there would be little chance of them returning to flight in September (which is the NET date given by SpaceX ).
From what I understand, the main issue is a bolt holding two parts of the struts together, that ended up breaking (and that has the metallurgy issues). So it is not actually the struts, but the bolts that have the problem. Those bolts were most likely purchased by the strut- supplier somewhere on the open market (probably somewhere in China ) and not manufactured by the supplier himself. I assume that even if replacing the entire strut assembly was as huge of a problem as you say it is, SpaceX will simply replace the bolt and the easily replaceable parts of the struts instead of the entire strut and essentially achieve the same safety improvement.

[ladajo]

I am not saying that it can't be done. I am only thinking that it is not going to be easy, and may not be worth it.
The quicker way ahead is to complete the investigation into other possible failure modes.
Take a bit of faith on the findings so far, and start builds on new boosters with new struts in order to get back in the game sooner.
The risk here, of course, is that the investigation finds that it was not the struts, or not just the struts. And then that would need to be addressed in the risk builds completed.

I say start building now, addressing what you know so far. Accept the risk there may be something else not found yet, that can be addressed once identified.

I do not know the reputation or financial risks for waiting until full review is done to start with booster builds/repairs.
This has been my point all along: Don't wait. Move forward, accept some risk.

In regard to EMC2, unfortunately I can not comment. I do however, expect some measure of news/information to become public before the year is out.
Personally, I believe that EMC2 has moved the ball further and with more effectiveness than other projects. I also think that EMC2 retains the best probability of success. I would also watch University of Sydney. Polywell is a funny animal, and there is a distinct reason it they went from WB-8 to Mini-B in the study. And of course, everyone will be very interested in the next machine and what it looks like. Whether or not the navy or government funds it remains to be seen. But, given current politics and funding dramas across government, I would suspect it more likely not. Just my humble opinion in that regard.

[Skipjack]

This is what the entire strut assembly looks like. As you can see, there are several bolts that connect the individual parts. The bolts and the parts not connected to the booster wall (anything right of "A"), should be easily replaced. Not sure about the part "A" directly attached to the booster. That one might be welded to it, but I am not sure.

[ladajo]

This was an interesting read, and had a little more info than other stuff I have looked at:
http://www.spaceflight101.com/dragon-sp ... dates.html

A couple of nice picks as well. It also states that the failure was the strut itself, not a bolt.
This pic shows the COPVs and the strut infrastructure, both for the COPVs, and the booster shell.




Key point (if true):

The replacement of struts on all existing Falcon 9 vehicles and the completion of the investigation could permit a return to flight within a few months, Musk said, however the company will not rush into getting the vehicle back to the pad and double-check other areas, get customer inputs and then decide on a forward path. The current expectation is to Return Falcon 9 to flight no earlier than September

Also, this is decent write up with details:
http://www.space-access.org/updates/sau145.html

[ladajo]

Here's another pic that looks like a different assembly, but closer to the diagram you posted:



from here:

http://www.wfs.org/blogs/len-rosen/spac ... on-failure

[mvanwink5]

Thanks Ladajo re:

Musk said that he expects the strut redesign and replacement will relatively simple, but that the overall process of reviewing the data to make sure there's nothing else there that needs fixing and going over it all with all the interested parties - the FAA, NASA, USAF, and the various commercial customers - will take some months. The earliest he expects they might fly Falcon 9 again is September, and he emphasized it may take longer than that. (They don't know yet what mission might fly first.)

Also, Ladajo, thanks for the EMC2 comments. I have my fingers crossed on EMC2 securing funding from somewhere (hope springs eternal).

Skip, thanks for the strut drawing. Bolts in the original news conference were mentioned by Musk but his statement was unclear if any bolts failed the performance testing. At some point the strut assembly has to attach to the wall where the wall attachment would be considered part of the LOX tank wall and irreplaceable. If that comes into doubt, it would seem to me that all bets would be off on a September return to launch.

[Skipjack]

This was an interesting read, and had a little more info than other stuff I have looked at:
http://www.spaceflight101.com/dragon-sp ... dates.html

A couple of nice picks as well. It also states that the failure was the strut itself, not a bolt.
This pic shows the COPVs and the strut infrastructure, both for the COPVs, and the booster shell.

Key point (if true):

The replacement of struts on all existing Falcon 9 vehicles and the completion of the investigation could permit a return to flight within a few months, Musk said, however the company will not rush into getting the vehicle back to the pad and double-check other areas, get customer inputs and then decide on a forward path. The current expectation is to Return Falcon 9 to flight no earlier than September

Also, this is decent write up with details:
http://www.space-access.org/updates/sau145.html

These articles are not presenting the latest information, which is that a bolt failed and not the entire strut.
I want to point to Elon Musks words at the press conference:

Elon Musk: We have a pretty good sense for, ... . There's one strut sort of holding it in the vertical direction. The strut is oversized to be able to handle far in excess of the projected load. And in this case if failed far, far below, it failed five times below its nominal strength, which is pretty crazy. It appeared to fail at the bolt head, most likely. There is a steel bold head. It appears to have failed there, we think. It's hard to get into the nitty-gritty because it makes it sounds like it's far more definitive than it is. It could, with further investigation, turn out to be something else.

This is still under review, but we are likely to change the material in the bolt of the support strut, most likely to Inconel, but that's, again, still preliminary.

Then we got just a huge number of these struts with this particular bolt and after testing some enormous number we were able to find one that failed below the two thousand pound level. So it was sort of a statistical thing, and then we did some material analysis on that and found that there were problems with the grain structure of the steel, it hadn't been formed correctly, so we think that that probably was a bad bolt that snuck through that looked good but wasn't actually good on the inside.

The transcript is here:
http://shitelonsays.com/transcript/elon ... 2015-07-20

[ladajo]

Thanks. That also helps. It clarifies the debate between the pin and the strut failure.

I did not really find any good pics or graphics of the assembly in place.
This is one of the better ones, but does not show how the COPV is mounted to the strut structure.