SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD (2)

[AncientU]

I personally think this is the growing pains of a launch vehicle. The more they explore the limits the safer the vehicle will be in the long run.

Not really, there are limits that don't need to be explored.

Depends what your goal is...

Is sub-cooled propellant such a limit?
Is record-shattering thrust-to-weight engines?
Is using off-the-shelf electronics?
Is super-sonic retropropulsion?
Is a hypersonic return into the atmosphere with grid fins?
Is flying with landing legs?
...

[rsdavis9]

I personally think this is the growing pains of a launch vehicle. The more they explore the limits the safer the vehicle will be in the long run.

One caveat. As long as they stop "improving" the launch vehicle at some point in its lifetime.

[Jim]

Depends what your goal is...

?  Wrong.  What the heck are you talking about?  Those are not even related to the topic at hand.  Limits as in flight envelope or operating parameters. 

Anyways, that list doesn't consist of goals or limits. Nor do they make the vehicle safer.
 
Limits that don't need to be explored:
There is no need to to reduce prop loading times by a few minutes to the absolute minimum
Or push He into the vehicle as fast as possible.
Shave a day off pad flow and risk customer's spacecraft.

1. sub-cooled propellant
2.  Is record-shattering thrust-to-weight engines?
3.  Is using off-the-shelf electronics?

1.  Not really worth the effort.  There are other cheaper and easier ways to increase performance for the little benefit it provides.  It is really doesn't follow the Spacex MO since it is complex and PITA method.
2.  Not worth noting much less shattering
3.  Not novel or unique. 

Is super-sonic retropropulsion?
Is a hypersonic return into the atmosphere with grid fins?
Is flying with landing legs?

And your point is?   What has that done so far?  Routine reflight has yet to happen.  And doesn't really matter if second stages keep blowing up.

[vapour_nudge]

Depends what your goal is...

?  Wrong.  What the heck are you talking about?  Those are not even related to the topic at hand.  Limits as in flight envelope or operating parameters. 

Anyways, that list doesn't consist of goals or limits. Nor do they make the vehicle safer.

None of these things make the vehicle safer.

All of them are part of the launch vehicle system, among the cheapest available.  All of them could be argued by your logic to be unnecessary.  Each of them pushes the limits more than helium loading procedures.  Reducing the flow time to an absolute minimum is part of this model...

Their goal is not just supplying a exorbitantly over-priced ride to a single wealthy patron.

I'd be happy if they simply stopped blowing up rockets. SpaceX aren't expensive so they've achieved that

[notsorandom]

Because the possible cause of the explosion has to do with the helium loading process, do you think that the reason of this cause can be linked to human error? I think so, but this "human error" was most likely unintentional to cause an explosion.

A helium loading process that allowed for a mistake to destroy the rocket is an error with the process rather than the human who made the mistake. One could remove the human who made the mistake and then next person could just as easily make the same mistake. However if the process is changed the threat of human error causing a loss of rocket is eliminated.

[Fred Bonyea]

According to Peter B. de Selding's tweet to this article:

http://spacenews.com/inmarsat-juggling-two-launches-says-spacex-to-return-to-flight-in-december/

SpaceX has found the root cause and is returning to flight in December.

“SpaceX has obviously spent some time investigating the reasons behind their recent launch failure,” Inmarsat Chief Executive Rupert Pearce said in a conference call with investors. “We believe they now have found a root cause that is fixable quite easily and quite quickly. So they should be able to return to flight in December.”

He's quoting Rupert Pearce, so the question is: is this just a slightly more optimistic take on the latest spacex public statements? or does he have additional definitive info that is not public yet?

Finding 'a' root cause that is easily fixable is a good source of heartburn; if it is the easiest branch to prune. I would be happier if he said 'the most likely causes identified are being systematically eliminated.'

[Brovane]

1. sub-cooled propellant
2.  Is record-shattering thrust-to-weight engines?
3.  Is using off-the-shelf electronics?

1.  Not really worth the effort.  There are other cheaper and easier ways to increase performance for the little benefit it provides.  It is really doesn't follow the Spacex MO since it is complex and PITA method.

Jim - What would be the easier and cheaper ways to increase performance for the F9 without using densified propellant? 

[Jim]

Jim - What would be the easier and cheaper ways to increase performance for the F9 without using densified propellant? 

Tank stretch - which they have done a couple of times
engine thrust increase - which they have done a few times.
None of those have long term operational impacts, meaning once incorporated, they no longer affect operations.

[Brovane]

Jim - What would be the easier and cheaper ways to increase performance for the F9 without using densified propellant? 

Tank stretch - which they have done a couple of times
engine thrust increase - which they have done a few times.
None of those have long term operational impacts, meaning once incorporated, they no longer affect operations.

Isn't the 1st stage already at the maximum length for Interstate transit?  They did increase the size of the 2nd stage. 
As you noted they already have increased the thrust several times.  With a thrust increase you are also using the fuel quicker.  So if you want maximum benefit from a increase in thrust you need to either increase your tank size or find a way to get more fuel into the same volume. 

[rpapo]

Isn't the 1st stage already at the maximum length for Interstate transit?

IMHO, the first stage has already reached the practical limit for "thinness."

[Brovane]

Isn't the 1st stage already at the maximum length for Interstate transit?

IMHO, the first stage has already reached the practical limit for "thinness."

I am certainly no expert in that area about how long and thin a rocket can be.  So I would defer to the experts on the board in regards to that.  However I do remember Musk saying that the dimensions of the F9 1st stage when it was stretched for the v1.1 update, was set at the maximum for both length and width that could be transported on Interstates. 

[Robotbeat]

Everyone thought the v1.1 was insanely thin. Full thrust stretched it some more. It's well beyond the rules of thumb typically used for fineness ratio for rockets.

[aameise9]

SpaceX Chief Executive Elon Musk said Friday morning that the company could return to launch next month. Musk said the company thinks it has “gotten to the bottom of the problem” that led to a September launch pad explosion and the destruction of a Falcon 9 rocket and communications satellite in Florida.
Musk said in an interview on CNBC that it “looks like” SpaceX will start launching again in mid-December. He described the cause of the explosion as something that has “never been encountered before in the history of rocketry.”
Musk provided few specific details but said it “basically involves a combination of liquid helium, advanced carbon fiber composites and solid oxygen, oxygen so cold that it actually enters solid phase.”  - from a LA Times article.

I interpret comments of our resident experts to mean that the AMOS-6 pad failure has cost SpaceX a lot of credibility in the industry.

I fear that the self-exculpatory spin of the remarks cited above will not help regain this credibility.

What happened to the former Musk who said (paraphrased) "if its physics against models, physics wins" ?

[rockets4life97]

I interpret comments of our resident experts to mean that the AMOS-6 pad failure has cost SpaceX a lot of credibility in the industry.

I don't think this is the case. It is a small industry and only a handful of launch providers. SpaceX is still the new kid of the block and everyone knows they are pushing the bounds. Yes, this makes them riskier, but they are also cheaper. So you take your trade-offs. What will be a change is if SpaceX does achieve a steady launch cadence and reliability.

[CyndyC]

Isn't the 1st stage already at the maximum length for Interstate transit?

IMHO, the first stage has already reached the practical limit for "thinness."

That's more than an opinion, it's a fact, according to the Spaceflight 101 F9 FT page:

Stretching the first stage beyond the length of the v1.1 first stage is not possible due to bending forces occurring in flight. Widening the diameter of the stages is also no option because of the requirement of road transport, putting a limit on the maximum diameter. The second stage of Falcon 9 FT accommodates the required change in RP-1 volume by stretching the stage.

[docmordrid]

Image of wire copy in this tweet

Loren Grush ✔ @lorengrush
Sigh, I have a bad feeling I'm going to be covering a SpaceX launch during my annual Christmas party again
1:49 PM - 4 Nov 2016

[x15_fan]

Image of wire copy in this tweet

Loren Grush ✔ @lorengrush
Sigh, I have a bad feeling I'm going to be covering a SpaceX launch during my annual Christmas party again
1:49 PM - 4 Nov 2016

Does anyone know why the quote mentions liquid helium? I was under the impression F9 used just cooled GHe? I can't listen to the CNBC clip myself. Thanks

[Proponent]

Jim - What would be the easier and cheaper ways to increase performance for the F9 without using densified propellant? 

Tank stretch - which they have done a couple of times
engine thrust increase - which they have done a few times.
None of those have long term operational impacts, meaning once incorporated, they no longer affect operations.

That SpaceX has previously stretched tanks and increased thrust shows that it is aware of those avenues of increasing performance.  That it most recently chose to increase performance by densifying propellants suggests that it recognized some limit in the other two techniques.

[ZachS09]

Let me get something straight: it's been confirmed that the liquid oxygen inside the second stage LOX tank reached its freezing point by accident, and when the liquid helium was loaded into the COPVs, the supercold temperatures below -219 degrees Celsius caused the COPVs to overpressurize and start the "chain reaction" explosion?

[rakaydos]

Not exactly.

Apparently, if you load the helium tank just right wrong, there is a momentary drop in temperature that can freeze supercooled O2 into solid O2. This O2 is between the carbon overrap and the inner pressure shell of the tank.
Before this solid O2 can melt, helium pressures press the inner pressure shell into the carbon overwrap as designed. This squeezes out any liquid oxygen... but not solid oxygen.

As the pressure rises, Solid oxygen is pressed into elemental carbon until a spontaneous, catastrophic molecular exchange happens.