Monday, July 20, 2015, 19:00 (UTC)
Teleconference with Elon Musk for members of the media to discuss preliminary results of the investigation into the CRS-7 mishap.
11 minute initial statement followed by Q&A for a total time of 51:33.
SpaceX written statement: http://www.spacex.com/news/2015/07/20/crs-7-investigation-update
Audio only of full conference call: http://quantumg.net/SpaceX_CRS7_Update_20150720.mp3
00:26 Elon Musk: At the end of my verbal comments we're going to post a written version to the SpaceX website, so if you don't happen to catch something during my verbal discussion you'll be able to look at that in written form immediately after the verbal comments end. OK, so just going through the best of what we know thus far, and I do want to emphasize that this is an initial assessment and further investigation may reveal more over time. So I'll just run through it.
Prior to the failure, the first stage of the vehicle was operating nominally, so there were no issues seen on the first stage at all. It actually continued to power through the overpressure event on the second stage for several seconds following the first [second?] stage coming apart. In addition, Dragon actually survived not only the second stage overpressure but continued to communicate until the vehicle dropped below the horizon and out of range. In fact, if the software had initiated the parachute deployment, then the Dragon spacecraft, we believe, would have survived. And for future missions, even for the cargo version of the Dragon spacecraft, we're now including contingency software that, if something were to go wrong with the vehicle, Dragon will always attempt to save itself. This is certainly something that we have included in Dragon 2, which is the next generation Dragon that will be carrying cargo and crew to the Space Station, but we've now advanced that activity to include it in Dragon 1 as well. So that's an unfortunate thing, because we could have saved Dragon if we had the right software there.
We've been going through the investigation with daily participation and insight from the FAA, NASA, and the US Air Force, and I'd just like to say a word of appreciation for the help that we have received here. It's been great to have so much expertise reviewing the flight data. And we're looking, not just for issues that occurred that caused this failure, but any near misses could potentially affect future flights. So we're looking very closely at saying, just in general, is there anything that we can do to reduce the probability of failure with future flights. The fundamental nature of rocketry is that it is a case where a passing grade is 100%, every time. It is not possible to issue a recall, or a patch, or anything like that. From the moment of liftoff it's 100% or nothing. So we are looking for any tiny thing that can improve things in the future.
Part of the reason why it's taken us a long time, to at least come up with where the preliminary assessment is, is that there is such an overwhelming amount of data. We've over three thousand telemetry channels as well as multiple video channels and physical debris. And the key events in this case happened very quickly. From the first indication of an issue to loss of all data was just 0.893 seconds. So over the past few weeks we spent thousands of hours going through a painstaking process of matching up the data across all telemetry systems down to the millisecond, because it's very important to understand the exact sequence of what happened, and then matching that to external video, and, really, when milliseconds matter it's remarkable difficult to actually line everything up exactly right. And as I said, the investigation remains ongoing and we're continuing additional testing to fully validate these conclusions. So again, this is just our preliminary analysis.
04:56 Elon Musk: The preliminary conclusion is that the failure rose from a strut in the second stage liquid oxygen tank. It was the strut that was holding down one of the composite overwrapped helium pressure vessels. So, within the upper stage liquid oxygen tank, immersed in the tank, are a series of high pressure composite bottles containing helium. The helium is used to pressurize the stage. So as the oxygen or fuel deplete, you have to replace that volume with inert gas and provide a minimum feed pressure to the engine and a pressure to structurally support the stage. It appears that one of those struts broke free during flight. We do a whole lot of tests on the ground, but part of the reason that test did not identify the strut is that, it's something that's quite unique to rockets is, as the stage is accelerating the buoyancy increases proportionate to the g-loading. So, if might seem sort of counterintuitive, that as the rocket is accelerating, that something immersed in the tank would want to go up more, but that's basically what happens, is the buoyancy increases proportionate to the g-loading. So at approximately 3.2 g the strut holding down one of the helium bottles appears to have snapped, and as a result, releasing a lot of helium into the upper stage oxygen tank, and causing an overpressure event quite quickly. It should be said, however, that we've flown several hundred such struts on every Falcon 9 vehicle, meaning there's a cumulative flight history of several thousand of these struts. More over, the strut that we believe failed was designed and material certified to handle 10,000 pounds of force, but actually failed at 2,000 pounds of force, which is a five fold difference. Also, in examining detailed close-out photos of stage construction, we don't see any visible flaws or damage of any kind. It's part of what cause this to be quite a puzzle.
The telemetry data also, somewhat confusingly, shows a drop in the helium pressure system, which you would expect if there was a breach in the helium system, and then, somewhat strangely, a rise in the helium system back to approximately its starting pressure. This is obviously quite confusing, but we think what may have happened is that as the helium bottle broke free and twisted around it may have pinched off the line to the helium manifold and restored pressure in the helium system, but released enough helium into the liquid oxygen tank to cause the liquid oxygen tank to fail. This is somewhat speculative, but that's the best explanation we can think of right now. So it's a really odd failure mode.
Within the course of a second this caused enough helium to be released, we believe, to overpressure the liquid oxygen tank of the upper stage. You don't really need to release a lot of helium because there's only about 2% gaseous volume in the stage because the upper stage propellant is not being consumed. The first stage propellant is being consumed, obviously, as the first stage is thrusting, but he upper stage is not.
So, obviously, what we're going to do in the future, we're obviously not going to use these particular struts and we're going to move to individually testing each strut independent of any material certifications. So no matter what something is actually certified to handle, we're not going to believe that. We're simply going to individually unit test every single strut. This will result, obviously, in some cost increase to the rocket, but not, we believe, of a significant amount, and nothing that we think should affect the actual price of the vehicle. But, none the less, it is some increase cost that will apply to the vehicle.
10:21 Elon Musk: So far, the investigation is not showing any other issues, but as I said, we are looking closely for any near misses, and then we intend to address anything that we can possibly think of to improve the probability of success in the future. But this is the first time we've had a failure in seven years. So, I think to some degree, I think the company as a whole became maybe a little bit complacent over the course of seven years and essentially twenty successes in a row. But I think that this was certainly an important lesson and something we're going to take with us into the future.
So with that, I'm happy to turn it over to your questions.
11:34 Eric Berger with the Houston Chronicle: Do you have any estimate on when you will be able to address the strut issue and get back to flying regular Falcon 9 launches?
11:47 Elon Musk: Addressing the strut issue is fairly straight forward. We're switching to something which has an even higher margin of safety than we what had, which was already very high, and, as I said, individually testing each one. So, just based on moving to an absurdly strong strut and individually testing each strut, that would only push our flights out by maybe a few months, but we want to make sure we've turned over every piece of data, that we've diagnosed the issue correctly and there are not some other issues that need to be addressed as well. And then, of course, we want to make sure all of our key customers are on board with that, particularly NASA, Air Force, FAA, and our commercial customers. So I don't want to give a precise flight date until everyone's on board with a new flight date, but just based on the strut, the strut itself does not significantly push out the next launch.
13:14 Alan Boyle with Cosmic Log: Could you explain how the strut led to that overpressure, again? Did the helium tank come loose and then somehow the increased pressure of the helium got into the second stage tank? If you could go over the relationship between the strut coming loose and the overpressure again, I'd appreciate it.
13:43 Elon Musk: In the liquid oxygen tank, on both stages, but we're talking specifically about the upper stage, there are high pressure helium bottles. These are the composite helium bottles that are at about 5500 psi. They're stored in the liquid oxygen tank in order to chill down the helium that they contain to cryogenic levels which improves the density of the helium considerably. The helium from those tanks flows to the engines, or in the upper stage case the engine, where it is heated, and then returned into the oxygen tank and the fuel tank to pressurize those tanks and replace the volume of oxidizer and fuel that is deplete while the engine burns, and to provide pressure which structurally stabilizes the stage. So, it looks like the key strut that holds down one of the helium bottles -- there are a whole bunch of these helium bottles -- one of those struts appears to have failed, and as a result was unable to hold the helium bottle down, and so the helium bottle would have shot to the top of the tank at high speed because of the extreme buoyancy at the failure point of 3.2 g. Although we fire the stages on the ground, and we do a stage hold down firing at the launch pad, the buoyancy force is only 1 g, of course, because we're not accelerating, and so it would have passed through all of those tests without having an issue because it only sees high-g loading in flight. It's very difficult, obviously, to test a rocket stage, because the only way to fully test a stage would be to have an enormous centrifuge that doesn't exist on Earth that would centrifuge the stage up to flight acceleration, but that's just not possible. That would be the ultimate test, but there is no such physical thing that exists on Earth that could do that. So one is forced, therefore, to do these things by proxy, and the proxy is sometimes inadequate as this turned out to be the case here.
16:43 Marcia Dunn with Associated Press: What is the size of the strut that failed? How long was it? How thick was it? I'm sorry if I missed the material. And are you considering putting parachutes on future cargo capsules?
17:00 Elon Musk: I'm not sure the exact dimensions of the strut matter that much, I mean, it's about two feet long and about an inch thick at its thickest point. There are parachutes on Dragons, always. That's how it normally lands. The issue is that in this case, Dragon is inert on ascent -- Dragon 1. The software to initiate the parachute deployment was not in Dragon 1. It certainly was planned for Dragon version 2, and one of the things we've decided to do is to advance the software that was meant for Dragon version 2 into Dragon version 1 so that if something like this were to happen in the future, the Dragon spacecraft would save itself.
18:04 Marcia Dunn: Will it be on the next flight, do you think?
18:10 Elon Musk: The next flight of Dragon, yes, it will have the software to initiate the parachute in the event of a launch failure.
18:24 James Dean with Florida Today: Could you just please clarify, did you say that you expect it will be at least a few months before you are ready to fly again? Which flight would that likely be? And I just wanted to also ask if this has impacted your Commercial Crew timeline at all?
18:43 Elon Musk: The best I could say with respect to flying is that it's a no sooner than September date. It could be beyond September, but it's no sooner than September. It's also not clear who that customer will be, so I can't say exactly which. There may be some change of which customer it is on that flight.
19:12 James Dean: I was just curious if, as this has delayed the entire manifest, obviously. Has it also impacted the Commercial Crew timeline?
19:25 Elon Musk: I don't think this affects our Commercial Crew timeline because this doesn't affect the critical path on our Commercial Crew timeline. The critical path is really the design and validation of Dragon 2. We're not expecting any change in that.
19:48 James Dean: I think maybe Gwynne spoke to this earlier. How do you think this system would respond if a crew were on the vehicle in a situation like this?
20:03 Elon Musk: If it were Dragon 2, the system would have initiated an abort via the abort thrusters. So it would thrust itself away from the vehicle quite rapidly and then, once it was a decent way away from the vehicle, would initiate parachutes to land in the ocean. But, as I said, even Dragon 1, which does not have the abort thrusters, survived the upper stage overpressure. And we actually received telemetry all the way until just above the ocean where we lost line of sight on the telemetry. So, even with the Dragon 1, without the abort thrusters, if it had initiated chute deployment, the cargo would have been save, or a crew would have been saved, conversely. So that's unfortunate we didn't have that software in on this mission, but certainly it will be there on other Dragon 1 missions. And it was always baselined to be there for a crew mission.
21:18 Dana Hull with Bloomberg News: The struts in question, were they made in-house by SpaceX or were they furnished from a supplier?
21:28 Elon Musk: The part that failed was from a supplier, but we're not going to name the supplier because I think that just results in recriminations, but it was not made at SpaceX, and we were relying on Material Certification from the supplier. In the future, independent of Material Certification, we will be individually testing each strut.
22:00 Dana Hull: Would you ever consider just bringing that in-house as well? I know that one of SpaceX's claims to fame is that so much of the rocketry is made in-house by SpaceX in Los Angeles. Would you consider making the struts yourselves, as well?
22:20 Elon Musk: In this case we don't think that the strut is something we need to make in-house. We are going to be, long term, switching to a different strut design from a different supplier, most likely, but I don't think this is likely to be done in-house. Not this particular commodity. And I should say, while SpaceX does all of the major components in-house, there are hundreds of suppliers that supply minor components. And it would be very difficult for us to insource all of those.
23:09 Dana Hull: In terms of debris, how much of Dragon was recovered? It sounds like it did a heroic job given everything that went on during that event.
23:22 Elon Musk: It did. It is somewhat tragic that it, unfortunately, hit the water quite hard, and is at the bottom of the ocean. We are actually trying to send a remote submersible down to the region where the debris hit the water and see if we can retrieve additional elements of debris to either confirm our initial conclusions or point us in a different direction. That is probably the saddest thing about this, is that, with just a bit of different software, Dragon would have made it.
24:09 Irene Klotz from Reuters: Have you guys been able to replicate the failure and have you eliminated all other failure possibilities from your fault trees?
24:22 Elon Musk: We have been able to replicate the failure by taking a huge sample, essentially thousands, of these struts and pulling them, and then we found a few which pulled far below their specified level, and that's what led us to think that there was one that was just far below its rated capability that happened to be in the wrong place at the wrong time. But, as I said at the beginning of the call, we do want to characterize this as an initial assessment, and it's subject to further review of the data to eliminate any other possibilities in the fault tree. But, right now, it doesn't seem to be any explanation that could make sense, but we are continuing to investigate.
25:23 Irene Klotz: What was the material the strut's made out of and any rough idea of how much it cost?
25:30 Elon Musk: I don't want to give you too much detail on this. Like, we're getting into the nitty-gritty, and it sort of invites a lot of alternative analysis that isn't actually correct, so broadly speaking, it's made of steel. And like I said, it's not something that should ever have failed at this force level. But it appeared to be incorrectly made but with no visible way of determining that from the outside.
26:17 Frank Morring with Aviation Week: Could you tell how, was there just the one strut holding the tank, or how it fit into the structure of the LOX tank? Was there more than one, and where on the strut, if you could say, where did it fail, or do you know?
26:38 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.
27:44 Frank Morring: In your redesign are you adding another strut or more than one somehow to strengthen that beyond what you had this time?
27:56 Elon Musk: We don't think that more than one strut makes sense. It just needs to be that each strut is going to be individually tested independent of its Material Certification. The strut is meant to handle more than twice the actual load that it experiences. So, you could, in principle, divide that into two struts, but you're not really gaining anything if you do that.
28:42 Bill Harwood with CBS News: Is it just the one helium tank, Elon, or is there more than one? I'm curious, based on what you just said, is there actual data that indicated a strut broke versus one of the helium overwrapped tanks bursting on its own? How can you differentiate that sequence?
29:01 Elon Musk: Sure. And, again, at the risk of being a bit repetitive, I do want to emphasize we are not characterizing this as a definitive result, we are characterizing this as a preliminary result. As the most probably outcome, not as a definitive outcome. There are several helium bottles in the upper stage oxygen tanks. It actually depends, some missions have more helium bottles than others, but there are a whole bunch of them. The reason we don't think that this was, I mean there are a few reasons, and these are just things that make it more probable rather than less probable, is that if we look at acoustic triangulation, so we've got microphones, or technically accelerometers, at various points on the upper stage, and by looking at the exact timing of high frequency events on the stage, we can, by acoustic triangulation, identify the location where the snap occurred, or where the breakage occurred. Obviously there would be a sound. And the acoustic triangulation points to the support strut as the most probably location. Also, if, let's say the helium bottle liner broke -- the composite overwrap is not going to break -- but if there was, say, a crack in the metal liner of the helium bottle, it would have resulted in a continuous release of helium, and you would have seen much more helium released than if the bottle had simply broken free and could thus sort of twist tie closed the line that connects to the rest of the stage, which would explain why the helium pressure initially dropped and then restores.
31:40 Jeff Foust with Space News: Have you briefed various customers and insurers about your preliminary results so far, and what sort of feedback or reaction have you gotten from them, so far?
31:52 Elon Musk: In deference to our customers and the government, we made sure to brief them last week, before briefing the public today. And so they've looked at all of the same data that we have. They have complete access to the same data we have, limited only in the case of international customers by ITAR, and they agree with our conclusions thus far, again emphasizing that they are preliminary and we need to continue working through the fault tree. I'm happy to say that every one of our customers have been supportive and none of them have indicated diminished faith in SpaceX. So I'd just like to give a word of appreciation for the support of our customers.
33:05 Scott Powers with Orlando Sentinel: I'm wondering if you have the same strut and helium tank configuration on the lower stage or something similar to it?
33:15 Elon Musk: There is. It's the same strut on the upper and lower stage.
33:20 Scott Powers: So you'll be replacing it in both stages.
33:23 Elon Musk: That's correct. Yeah. And I should say the strut has flown on many prior flights.
33:33 Scott Powers: Is there any risks that the lower stage struts could have reached the same g-levels? I guess they would have already done that at that point.
33:40 Elon Musk: Yeah. They were all at the same g-levels. Now the buoyancy force, once the liquid level drops below the position of the helium bottle, the buoyancy force drops dramatically, of course, but that was not the case at that point. All the helium bottles were experiencing approximately the same buoyancy force for the upper and lower stage.
34:14 Dan Vergano with BuzzFeed: You said that the shame of this was that the Dragon parachutes weren't enabled by the software to fire. I'm just wondering, could you, why weren't they? Was that just too much trouble or was there a decision that when into that?
34:30 Elon Musk: With the version 1, the cargo Dragon, it was just not something that had been done yet. It was on the agenda, but it hadn't been done yet. And it was certainly planned for Dragon version 2 for both cargo or crew. So it was planned to be done. It just had not been done as of that flight. It will be done as of the next flight.
35:10 Mike Wall with Space.com: You mentioned that you guys may have gotten a little complacent, like over that long run of success. Could you just go into a little detail about how do you think that sort of manifested itself? So how is this incident going to change your guys' outlook going forward?
35:28 Elon Musk: Several years ago, in the early days of Falcon 1, when we were still just sort of learning how to make rockets, we had some challenges there with the first Falcon 1 flights, and I think that instilled an extreme level of paranoia in the whole team. But seven years ago, which is when we had our last failure, the company was only about five hundred people, and now we're four thousand people, so the vast majority of the people at the company today had only ever seen success. And when you've only ever seen success, obviously, you don't fear failure quite as much. Now before every flight, I always send out an email company wide saying, if anyone can think of any possible reason to hold off on launching, that they should call me immediately on my cell phone or send me an email, whether their manager agrees with it or not. That's sort of something I've always sent before every flight. But the twentieth time I sent that email it just seems like, you know, there's Elon being paranoid again, so maybe it doesn't resonate with the same force. But I think now everyone at the company appreciates just how difficult it is to get rockets to orbit successfully, and I think we will be stronger for it.
37:20 Ken Kremer with Universe Today: I was wondering about the stress. I understand you don't want to talk about the material of construction, but you said it was stainless steel. I wonder, can you say, would you at least change that material, maybe to a different alloy? And I'm also wondering about the abort thrusters. Might you consider installing abort thrusters on this cargo capsule or using even an early version of Dragon v2 at some point to do the cargo deliveries?
37:55 Elon Musk: 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. And then with respect to the abort thrusters, the abort thrusters are really quite a radical change in design, and it wouldn't be easy to retrofit those to Dragon 1. Dragon 2 is very different from Dragon 1. It sort of looks, maybe, sort of similar from an external standpoint, but there's no reasonable way to just sort of tack on the abort thrusters. The best thing to do is try to get Dragon 2 to fly at the earliest opportunity, because it is a step function improvement in capability and flight resilience. Although, as I said, we are going to make the software change to Dragon 1. Dragon is quite a tough creature, even Dragon 1, and as I said it actually was OK, even after the upper stage explosion, and was broadcasting its telemetry all the way to when we lost line of sight, just above the ocean. So, it's quite tough, and even without the abort thrusters, it would have made it, so really, it's just a question of firing the chutes and so we're going to make sure that before we fly Dragon 1 again that it has that ability.
39:47 Ken Kremer: Thanks. But is there any chance that you would fly an early version of Dragon 2 as a cargo Dragon?
39:54 Elon Musk: The first Dragon 2's will be without astronauts, so at least one flight, maybe two flights, will be without astronauts, so the first one would, in fact, carry cargo.
40:16 Stephen Clark with Spaceflight Now: You mentioned you've tested these struts on the ground, and some of them failed. Did they fail at sort of the two thousand pound force mark, or where did they fail and what sort of loads did they fail under in these ground tests? And also, with a few months delay in your manifest, do you expect the first flight of Falcon Heavy will probably slip into the next year now?
40:46 Elon Musk: At first we didn't think it was the strut because we tested a whole bunch of struts, none of them failed at a level, like the lowest we saw anyone fail was at six thousand pounds of force, so at first, in the initial part of the investigation when we tested a whole bunch of these struts none of them failed under six thousand pounds. So we thought well, that couldn't be the issue, so we started looking elsewhere, couldn't find any issues, either couldn't find an explanation for the data anywhere else. 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.
42:15 Stephen Clark: And the Falcon Heavy?
42:22 Elon Musk: Given our focus on Falcon 9, we've deprioritized the Falcon Heavy to probably launch in the spring next year. So maybe April or so.
42:48 Tim Fernholz with Quartz: Can you describe the insurance coverage that you had for that rocket and for Dragon and its cargo, and has there been any costs SpaceX has had to pay because of delays to its commercial launch contracts?
43:03 Elon Musk: We don't insure our launches. Nobody in the rocket business does, except for, essentially, third party damage on the ground, which is a super low probability thing. So there was no launch insurance there. The biggest penalty to SpaceX will be the delay of launch rate. Sort of like an airline, if the flights don't take off then you loose the revenue associated with that period. So, the lost revenue will be meaningful, in the hundreds of millions, probably, because of the implied delays.
43:56 Joe Pappalardo with Popular Mechanics: I wanted to know, in particular, if you had recovered anything from the debris that helped at all, or when you said you had put in an ROV or submersible, do you have any details on that and anything recovered from those efforts?
44:25 Elon Musk: We did find a small amount of debris that was floating. Most of it's at the bottom of the ocean. The remote submersible, we haven't gotten the feedback from that yet. I think it's going out soon, but it's a lot of area to search, it's pretty dark down there, so we're just doing that because we want to do everything that we can think of, and if we do find something else we will feed that into our failure investigation, but so far I don't think it's actually reached the area in question. So we just have a small amount of floating debris then.
45:20 Sophia Chen with Wired: So you mentioned the strut is supposed to be able to take ten thousand pounds. How much force do you actually need? And between these successful launches and this particular failure, how has the design of Falcon 9 changed or if at all?
45:51 Elon Musk: The actual force experience in flight is proportionate to the g-loading. So since it failed at 3.2 g, and really the max g's that it would experience, depending on the mission, is maybe five to five and a half, the most amount of force it would really experience would be, maybe three to three and a half thousand pounds of force. If it had reached the worse case, at the end of flight, it would have been three and a half thousand pounds of force, but still be about three times below its nominal rating. And I think the way that this work we will be doing a lot more individual unit test, so essentially pull tests on all the supporting hardware, so even if something is Material Certificated for very high loads, that's nice, but we're not going to believe the certificate, we're going to test it as well.
47:17 Sophia Chen: How has the design of Falcon 9, is it different at all this time, compared to the successful launches of the past?
47:30 Elon Musk: No, the design is identical to prior missions. We've flown hundreds of these struts of this exact design. It's actually thousands.
48:00 Graham Starr with Christian Science Monitor: I just wanted to ask if you found that any of this was due to the way it was implemented by the SpaceX team or if you found it was purely material? And regardless of what you found, you talked about focusing on individual tests of the struts, but does that change anything regarding future quality assurance or operations policies?
48:20 Elon Musk: This was a purchased part, so it's not really related to anything, I mean we just install it at SpaceX. And we have the close-out photos from this particular mission, so even with looking at detailed, high-resolution close-out photos, it appears perfect on the close-out photos. So there does not appear to be any assembly error, which we should be able to see from the close-out photos. And the big policy change would be always pull testing or compression testing, even when it's a supporting component that in theory has extremely high margins and has certificates to allegedly prove that. The policy change would be ignoring the fact that it has a certificate and in theory very high design margins and applying a physical test to even the smallest items of support hardware. We already do that for the macro items, for the stage, for the primary airframe. It is always tested, but we've not applied that to most of the supporting hardware, particularly where the expected margin of safety was extremely high.
50:11 Sean O'Kane with The Verge: I know you talked about potential Falcon 9 delays and Falcon Heavy delays. I'm curious if you think this will effect the second Commercial Cargo contract being awarded in the fall by NASA.
50:30 Elon Musk: I don't know. I don't think so, but that would be a question for NASA.
50:36 Sean O'Kane: I mean your submission for that.
50:39 Elon Musk: It wouldn't affect our submission, no. It has been, sort of, just emphasizing the difficulty of rockets in general, obviously, just for Space Station resupply, as I think most people on the phone know, the last year has seen three failures. It was ours, Orbital Sciences, and the Russian Progress. So it's been a tough year. And each one of those failure modes has been quite different. So it just goes to show, rockets are a fundamentally difficult thing. Generally when there is an idiomatic expression about something, there's a reason for it.
51:28 Operator: We have no further questions at this time. I turn the call over to the presenter.
51:32 Elon Musk: All right. Thank you.