Space X - If at first you don't succeed...

SpaceNut · 2016-09-01 19:15:04

The good part is this is the new part of the rocket, so more varifications of testing will make it not happen again.

That said it appears that good quality controls are in place for the re-used 1st stage....

RobertDyck · 2016-09-02 03:20:55

On one hand I wish the satellite could be recovered. The fairing appeared to be perfectly intact, so the satellite should not have been damaged by the explosion. However, it fell when the rocket beneath it just ceased to exist. That means it fell equivalent of 20 stories onto a concrete pad.

Tom Kalbfus · 2016-09-02 08:24:30

The satellite was most likely insured, it was an Israeli communication's satellite, so the insurance company will pay to build a replacement.

RobertDyck · 2016-09-10 03:34:42

Is the "Daily Mail" in the UK a reputable news source?
Elon Musk reveals SpaceX rocket exploded BEFORE it was powered up - and says firm has NOT ruled out a mystery object hitting it in 'most difficult and complex failure we have ever had'

The billionaire SpaceX CEO took to Twitter on Friday seeking ‘support and advice’ as the investigation continues – and addressing claims that a mysterious object may have hit the rocket, Musk says they ‘have not ruled that out.’
In a series of tweets early this morning, Musk revealed new details on the conditions of the rocket at the time of the blast, and asked users to send in any footage of the incident.
According to Musk, the engines were off and there was no known heat source present to trigger the explosion.
‘Still working on the Falcon fireball investigation. Turning out to be the most difficult and complex failure we have ever had in 14 years,’ Musk tweeted on Sept 9.
He continued, ‘Important to note that this happened during a routine filling operation. Engines were not on and there was no apparent heat source.
‘Support & advice from @Nasa, @FAA, @AFPAA & others much appreciated. Please email any recordings of the event to report@spacex.com.’

The SpaceX CEO also noted that they are investigating a sound that occurred just before the blast.
So far, the origin of this sound remains a mystery.
‘Particularly trying to understand the quieter bang sound a few seconds before the fireball goes off.
'May come from rocket or something else,’ Musk tweeted.

Video on the news website only shows the blast. It doesn't include the noise mentioned. So here is full video. Video camera is quite some distance away so due to speed of sound the audio is delayed a few seconds. At 1:16 in this video you can hear a high pitched sound. Is that a bird, or is that a metallic squeak? It sounds like stressed metal that's yielding. I could be metal contracting due to cryogenic LOX, or just load; I don't know. Then at 1:18 there's a soft bang. When you watch the video on the "Daily Mail" news website, audio is synchronized with video. Notice the soft bang does not happen at all. The first bang on the news website is a loud explosion; that appears on the full video at 1:23. So there appears to have been a soft bang about 5 seconds before the fireball. To me the soft bang sounds like metal buckling. So the squeak of metal yielding followed by metal buckling, then fireball.

Full video on YouTube, submitted by USLaunchReport, completely different source: SpaceX - Static Fire Anomaly - AMOS-6 - 09-01-2016

As for the mysterious object, the it only shows on the second video on the "Daily Mail" website. It doesn't show on the YouTube full video. The mysterious object was pretty far from the rocket when the fireball happened. The object just appears as a blur, and its motion appears to be a bird. I'm sure reporters would like a salacious story, but I doubt the explosion was caused by a drone.

Terraformer · 2016-09-10 07:31:25

Is the "Daily Mail" in the UK a reputable news source?

Well...

It depends on what they're reporting. They do tend to sensationalise things, but unless they're talking about a pet issue of theirs (cancer, immigration, cancer, muslims, cancer), I'd say they're as reliable as anyone else. Which means, not that good, unless it's something the writer has direct experience in.

Last edited by Terraformer (2016-09-10 07:31:53)

GW Johnson · 2016-09-10 08:59:33

The videos, whatever their source, show a very sudden event. As near as I can tell from the various reports and sources, they were filling the second stage LOX tank when it occurred. I cannot speak as to any pops or bangs seconds before the explosion, but I note there are persistent reports of such.

I went and looked up what I could find about aluminum-lithium alloys. Even the third generation alloys (max 1% lithium) have problems that prevent their wider use in aviation. The most troubling that I read about, is aging at too-modest a temperature of only 85 C = 185 F. These temperatures can be reached just sitting outside in bright sunshine.

Difficulties welding were also reported, to include serious strength reductions in the heat affected zones, and even gross porosity in weld zones. There are also difficulties with very strong anisotropy of mechanical properties, particularly in rolled materials, which is what the tankage shells are: rolled to create the waffle reinforcement pattern inside.

What that aging seems to do is raise ultimate and yield strengths by several percent, but elongation-at-failure gets cut by around a factor of 2! It is the loss of elongation capability upon aging that concerns me.

If you combine that with the enormous thermally-induced strains of a restrained structure experiencing a temperature difference ambient-to-cryogenic, you have a recipe for sudden cracking or splitting. You wouldn't see this until it aged, if you were designing with unaged properties. But it ages all too easily.

You really need to have a very experienced metallurgist (or more than one) on your staff to design safely and reliably with this stuff. As near as I can tell, they hire no one over age 40-ish. A 40-year-old just does not have the real-world experience to deal with this kind of a truly-tricky material problem. So, this kind of material-cracking problem is actually a possibility for the incident. And it will be very hard to track down, if it is the cause.

But it fits: there's always some LOX leakage at fittings during a LOX loading operation. The key is not to have any hydrocarbons or other fuel materials in the vicinity, not even petroleum-base greases. But what if a thermally-stressed, but aged-into-brittleness, fuel tank cracked and leaked kerosene or hydrazine into the path of the leaking LOX? You get fire-accelerating-into-violent-deflagration in the wink of an eye.

Isn't that what we saw?

You might even hear the sound of the crack just before the explosion. That's what RobertDyck says he thinks he heard.

GW

Last edited by GW Johnson (2016-09-10 09:03:04)

RobertDyck · 2016-09-10 13:26:03

At one job I installed an environmental chamber, and designed and built custom equipment for it. The equipment I designed calibrated solid state rate gyros, solid stage accelerators, and pressure transducers used for the pitot and altimeter. This was for autopilots for miniature UAVs. The environmental chamber used 460-volt 46-amp heaters, and chilled with liquid nitrogen. The environmental chamber heated to +70°C and chilled to -55°C. Then the owner/president asked me to extend the temperature range a little further. So I do have some small experience with cryogenics. It's only liquid nitrogen, not LOX, but it's something. When filling a dewar flask, the flask will be ambient temperature to start. The first part of the liquid will boil off as it cools the inside of the container.

Or in my case, the liquid nitrogen was sprayed on the blades of fans at the top of the chamber, which boiled off the LN2, broke the stream into droplets, and sprayed the droplets to the sides of the chamber. So no LN2 directly poured onto our autopilots. Because this was installed at a location just outside the city of Winnipeg, and our city gets cold in winter, one of the technicians suggest I conserve LN2 by pre-chilling the chamber with air from outside. After all, when going from +70°C we could chill the chamber somewhat even in summer. In winter outdoor temperature can drop between -20°C to -40°C. Although it hasn't gotten to -40°C since January 2005, it does get below -30°C. So I hired a building ventilation expert to cut a hole in the wall of our steel building, and install an intake about the size of a dryer vent. The intake had a rain cover and screen to ensure birds and squirrels and insects don't get in. I used an insulated flexible dryer vent tube to connect the intake to our environmental chamber. And I fabricated a custom neoprene rubber flap valve for environmental chamber. I used a piece of neoprene rubber that has thermal insulation on one side. The neoprene side faced the smooth stainless steel wall of the chamber, so it formed an air-tight seal. The back had insulation. As source material for my insulated neoprene rubber sheet, I used a car mat. Yup, the insulation is carpet pile. It was a new car mat that I cut into a "D" shape flap valve. And I looked up appropriate adhesive to bond neoprene to stainless steel. The adhesive manufacturer recommended epoxy, but both surfaces had to be carefully cleaned with isopropyl alcohol. So I did that. To hold it on the vertical wall while the adhesive set, I used duct tape. The tape was not expected to last, it was just until the epoxy set.

I could go on. I'm proud of that job. Got to work with fancy stuff. Got to design and build hardware as well as write software. Designed custom metal platforms that held the autopilots, located a machining company that could fabricate them and sent the engineering drawings. Assembled everything myself.

But unfortunately the owner and his wife had marital problems. He had an affair with another woman, and a baby with the other woman. The owner said his wife left and insisted he buy out her half of the company. He claimed that she said she looks for members of the opposite sex at work. I was the only single guy her age at work, so the boss made my life miserable after that. I did not date her; in fact made a point of avoiding her after I learned this going on. I do not date married women, and there's no way in hell I'm going to get in the middle of a marital dispute of the owner/founder/president. But I got blamed anyway. That job didn't pay the best, but the work was exactly what I love to do. (Insert string of expletives!)

Way off topic. Anyway, my point is loading liquefied gas will cause boil-off until the container is chilled. You can see in the video a stream of vapour coming off the rocket. That's oxygen gas venting. Oxygen is invisible, but it's just warmer than liquid oxygen so it's still very cold. When that cold gas touches humid air from Florida's coast, the humidity will condense as droplets of water. The tiny water droplets are actually what you see.

Last edited by RobertDyck (2016-09-12 11:41:28)

kbd512 · 2016-09-10 22:50:24

Falcon 9's reliability is no better or worse than any other major launch system at this point in its developmental history. It's basically a brand new rocket that SpaceX is constantly experimenting with. If anyone remembers the original Atlas and Titan vehicles, early in their developmental cycles there was basically a 50/50 chance that the rocket would function properly. Some might say that our technology and materials are much improved over what was available at that time and our general knowledge of rocketry has improved, but one must remember that SpaceX is still relatively new to the rocket business. They have a lot of bright young talent, but from time to time their inexperience shows in the things they do.

If it was my rocket business, and obviously it's not, I would put a payload mass and integration simulator atop the rocket, test the rocket without the possibility of losing a multi-hundred million dollar payload, and if everything functioned properly then and only then would I put the payload on the rocket.

If I had to hazard a guess as to what happened, either there was a structural failure of a component in the rocket that caused internal damage or there was a component that wasn't as clean as it should've been, and a combination of flammable material, static electricity, and LOX caused what we saw on TV.

Every loss has to keep the engineers up at night and it's difficult to see your hard work destroyed in the blink of an eye, but these things will eventually happen to anyone who's been in the rocket business long enough. SpaceX needs to sort out the problem, build another rocket with whatever corrective changes are needed applied to the rocket, and move on.

RobertDyck · 2016-09-10 23:06:05

I have a question. If this was a test, why was the payload mounted? Every test has to prepare for both success and failure. What's the point of testing if failure is catastrophic? Shouldn't a test have a dummy mass on top instead of a multi-million dollar satellite? And if you do mount the satellite, why not just launch? How could launch failure cost less than test failure?

kbd512 · 2016-09-10 23:36:41

RobertDyck wrote:

I have a question. If this was a test, why was the payload mounted? Every test has to prepare for both success and failure. What's the point of testing if failure is catastrophic? Shouldn't a test have a dummy mass on top instead of a multi-million dollar satellite? And if you do mount the satellite, why not just launch? How could launch failure cost less than test failure?

It's called launch costs. As meticulous as they are about testing, SpaceX isn't playing a defensive game with the engine tests. Personally, I think every rocket should be designed in such a way that the entire propulsion package can simply be unbolted from the propellant tanks so that the propulsion package can be tested on a test stand far away from an expensive and delicate launch pad. The test stand should be built in such a way that even a catastrophic engine failure won't destroy the test stand.

GW Johnson · 2016-09-11 10:01:56

Some do it better than others. I remember well the Atlases, Thors, Titans, etc, that failed with great regularity from about 1956 to about 1962 or so.

In the 1970's I worked for a while at LTV Aerospace, employed in its Scout launch vehicle program. Scout was a 4-stage solid, with attitude control thrusters as its guidance. It began flying about 1960.

They had one failure in flight test, then a perfect record with hundreds of launches for over 30 years. Its most popular use was placing payloads in the 200 lb class into GEO transfer.

Extremely simple, very well-designed, and done with very careful attention to quality control. That's a big part of how you do it right.

The team of people working on it were of all ages and stages of career. I can tell you from personal experience that there was a lot of art (essential stuff never written down) that was passed down on-the-job one-on-one from the old hands to the youngsters. That's also a huge part of how you do it right.

Payload sizes outgrew it, which is why it was taken out of service.

GW

Last edited by GW Johnson (2016-09-11 10:05:19)

RobertDyck · 2016-09-11 13:05:18

Saw a video on Facebook that claimed the last time NASA had an explosion during fuel loading was an Atlas-Agena in 1960. Is that right?

GW Johnson · 2016-09-12 11:17:48

I honestly don't know. I remember a lot of things, but no details like that. You'd have to search out a thing like that.

GW

elderflower · 2016-09-13 05:32:39

Was it loading LOX? I recall a couple of cases where distillation columns for LOX have taken off and devastated large areas due to contamination with organics.

GW Johnson · 2016-09-13 13:32:55

Well, there's been all sorts of accidents in many industries handling oxygen. Quite a few of them involve a stream of oxygen striking a hydrocarbon, even a solid grease. In pure oxygen, just the flow friction against the grease surface is enough to cause ignition.

GW

GW Johnson · 2016-09-24 10:23:40

News update on Spacex's site posted yesterday (23rd) is now showing up on the internet news sites today (24th).

It has to do with the second stage helium pressurant tank. It apparently burst very suddenly. They do not yet know why the tank burst, but they have convinced themselves it was not another hold-down strut failure. (Strut failure in flight was the second stage failure several months ago.)

There is launch pad damage, but the supporting facilities appear more or less intact. That includes their LOX handling and storage stuff.

Their plan was and still is to finish this investigation, make corrections, and return to flight sometime in November.

GW

RobertDyck · 2016-11-08 00:18:33

SpaceX Finally Knows What Caused its Falcon 9 Rocket to Explode

Well, it turns out that the supercooled oxygen might have been too cold—cold enough to actually solidify.
SpaceX likes its oxygen tanks to be kept at about -340 degrees Fahrenheit, and the stuff ices over at -362 degrees. According to the New York Times, the liquid helium containers inside the oxygen tank could have been responsible for pushing to oxygen over the brink. Helium, which is used to pressurize the oxygen tank, is stored at even colder temperatures than oxygen, at -452 degrees.
Musk didn't elaborate on how the solid oxygen formed or what happened after that, but the leading theory is that the solid oxygen may have ignited one of three carbon composite helium containers inside the oxygen tank, triggering the explosion that annihilated SpaceX's launch pad.

Uhh... They allow liquid oxygen to directly contact carbon fibre? Carbon burns in oxygen, that's asking for a fire. DC-XA used carbon fibre composite for LH2, but lithium-aluminum alloy for LOX. XCOR bragged they developed a carbon composite tank with a "proprietary" liner to protect the carbon from LOX. When I asked a salesman about that, he said they went through the Dupont catalog and chose the best one. I said then that's Teflon FEP. I would recommend Clarus made by Honeywell; it's a little more expensive, but more impermeable to oxygen, and can handle colder temperatures. SpaceX doesn't use a liner at all?

GW Johnson · 2016-11-08 13:06:50

I'm with RobertDyck: allowing LOX to touch carbon composite (or any other form) is insane. There has to be a separation layer impervious to LOX.

I went to Spacex's site and found an update on this incident from just a few days ago. The story they tell is a little bit different from the story via the link just above, no mention of frozen oxygen. But in common is something about the carbon composite overwrap on the liquid helium containers.

I noticed that Musk's giant ship has a carbon composite structure, including the methane and oxygen tankage. They'd better pay very close attention to this issue.

GW

From Spacex site, updates copied 11-8-16 (did not copy earlier items, last one 9-23-16)

Below are updates regarding the anomaly that occurred in preparation for the AMOS-6 mission:

October 28, 4:00pm EDT

The Accident Investigation Team continues to make progress in examining the anomaly on September 1 that led to the loss of a Falcon 9 and its payload at Launch Complex 40 (LC-40), Cape Canaveral Air Force Station, Florida.

Since the incident, investigators from SpaceX, the FAA, NASA, the US Air Force and industry experts have been working methodically through an extensive fault tree to investigate all plausible causes. As part of this, we have conducted tests at our facility in McGregor, Texas, attempting to replicate as closely as possible the conditions that may have led to the mishap.

The investigation team has made significant progress on the fault tree. Previously, we announced the investigation was focusing on a breach in the cryogenic helium system of the second stage liquid oxygen tank. The root cause of the breach has not yet been confirmed, but attention has continued to narrow to one of the three composite overwrapped pressure vessels (COPVs) inside the LOX tank. Through extensive testing in Texas, SpaceX has shown that it can re-create a COPV failure entirely through helium loading conditions. These conditions are mainly affected by the temperature and pressure of the helium being loaded.

SpaceX’s efforts are now focused on two areas – finding the exact root cause, and developing improved helium loading conditions that allow SpaceX to reliably load Falcon 9. With the advanced state of the investigation, we also plan to resume stage testing in Texas in the coming days, while continuing to focus on completion of the investigation. This is an important milestone on the path to returning to flight.

Pending the results of the investigation, we continue to work towards returning to flight before the end of the year. Our launch sites at Kennedy Space Center, Florida, and Vandenberg Air Force Base, California, remain on track to be operational in this timeframe.

Last edited by GW Johnson (2016-11-08 13:08:23)

GW Johnson · 2016-12-06 13:31:10

I looked on Spacex's site a couple of days ago. There's no posted update on this, not yet.

I know they're working on this and other things. Lots of testing going on at the McGregor test site, including at least one large explosion where they apparently duplicated what happened at the Cape. They said they would do that. I think they did.

A prediction: I bet it was loading liquid helium under pressure too fast that caused the explosion at the Cape. That stuff is incredibly cold, far below the glass transition temperature of all known polymerlike materials. Fast load = high strain rate = brittle failure of whatever isolation coating isolates the LOX from the carbon composite overwrap on the helium tank.

A second prediction: this coating failure has happened before, but without the composite catching fire with the LOX. The ignition delay statistics finally caught up with them. Makes one wonder if this might not have been a factor in the second stage that exploded in flight.

A warning: do a better job with the coating technology and practical limitations thereof, for MCT. Your design concept has a tank that is carbon composite structure full of LOX. You could lose up to 100 people at a time, if you repeat the previous mistake. Repeating a mistake is very bad management.

GW

Last edited by GW Johnson (2016-12-06 13:34:06)

SpaceNut · 2016-12-06 18:53:33

Thanks for that update of the design, loading and testing of the fault tree for what might have caused the explosion.

Hopefully once they get to launching again that the flight rate will ramp up and that more opportunities are made for flight to go to other destinations....

kbd512 · 2016-12-06 19:16:09

Rob and GW,

I seem to recall reading somewhere that BNNT has pretty good resistance to oxidation at relatively high temperatures, but I'm not aware of any experimentation involving LOX. I've also read that fluorocarbon polymers like PTFE are compatible with LOX, but have no idea to what degree. Would there be any merit to experiments with BNNT fiber reinforced composites or plastics?

RobertDyck · 2016-12-07 03:28:44

Yes, fluorocarbon polymers are compatible with LOX. They're not flammable with oxygen. I mentioned Teflon FEP and Clarus; they're both fluorocarbon polymers. Technical documents from Dupont said continuous service temperature for Teflon FEP was cold, but not quite as cold as Clarus. I notice their document today says the low is the same. They both now claim -240°C. Clarus is a bit more expensive, and Teflon FEP is a bit stronger, but you don't look for strength from a liner. Clarus is more impermeable to oxygen. But LOX won't be loaded long enough for polymer permeability to be an issue. Neither can be sprayed on, they would have to be laid on the inside of the tank, and thermally bonded to the carbon fibre.

BNNT - A quick Google reveals Boron nitride nanotubes. I haven't heard of it before.
Wikipedia: Boron nitride nanotube
NASA technical report server: Boron Nitride Nanotube: Synthesis and Applications

elderflower · 2016-12-08 08:37:10

There is a way of getting solvent based impact glue to stick to PTFE. We did it many years ago. There may be better ways of applying it now, though.

GW Johnson · 2016-12-08 11:54:41

Spacex updated its anomaly report on its website yesterday (12-7-16), but the single paragraph says nothing about what they found or concluded. It just says they hope to start launching again in January.

As for the composite-overwrapped helium tank, plain 300-series stainless is far more reliable than coated carbon-in-LOX, and not that much heavier.

That does NOT solve the looming problem for their MCT design, though.

GW

Last edited by GW Johnson (2016-12-08 11:55:34)

Oldfart1939 · 2016-12-08 11:58:00

This was my first opportunity to read comments on this website regarding the SpaceX Falcon 9 v. 1.2 "anomaly." RobertDyck expressed by same comments here that I stated on 2 other websites, that there is a materials incompatibility of LOX with Carbon fiber. I was badgered by several other posters on both SpaceNews and SpaceflightInsider, that there was "no materials" issue at all. I was deeply disturbed that no one understood that dunking a potential hunk of fuel in LOX was NOT a good idea. Using some form of PTFE or Fluorinated polymer as an overcoat would alleviate this problem, but the issue is how to do it. Maybe dunking the tank into a bath of monomer and carry out an in-situ polymerization? My polymer experience is principally biphasic suspension polymerization for manufacture of polystyrene microspheres, so maybe Robert has more experience in this area than I? Just another one of my wild, off-the-wall suggestions.

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