Commercial Crew - Discussion Thread 1

[woods170]

If we were to formally depend on the LAS as our priMARY insurance policy against disaster from PAD incident, rather than risk mitigation, then NASA would likely require, probably justifiably, 6 or 8 or 10 pad abort tests prior to operational use.

No. NASA required NO pad abort tests for CCP. In fact, both CCP providers (SpaceX and Boeing) voluntarily offered to perform pad abort tests to validate the required pad abort MODELS.
The in-flight abort test that SpaceX will be performing is voluntary in nature as well.

...reduced interest in pad testing initially Because NASA assumed that the historic practice of "fuel-then astronauts" would remain in place. If we change this equation now to "count on LAS to provide our 'protection' against fire/explosion" suddenly, the need for more scrutiny and confidence in LAS becomes acute. Thus, a more robust testing regimen.
 

Incorrect.

NASA knew from the get-go that SpaceX wanted to fuel the rocket AFTER the crew had gone aboard. The "fuel-and-go" procedure was base-lined in SpaceX's CCP proposal. That didn't stop NASA from awarding SpaceX the CCtCAP contract.
This is similar to NASA awarding SpaceX the CCtCAP contract despite NASA knowing that SpaceX has base-lined propulsive landing for Crew Dragon.

It wasn't until after the contract had been awarded that NASA began to have serious doubts about propulsive landing and "fuel-and-go".

[jak Kennedy]

actually, you are just proving you have no idea what you are talking about. read the posts, dude.TEST TEST TEST Then you willl KNOW KNOW KNOW.  Denying the need to do so is the only thing that is "screwed up logic" here.

Well the only way to test Load and Go is with crew onboard during the test otherwise not much difference to all previous space flights with crew onboard. And if you are talking about the LAS how many tests have been conducted in the past? How many tests of the planned SpaceX or ULA LAS are there? It seems the LAS has minimal test data that it actually works.

[Welsh Dragon]

An abort has a high likleihood of resulting in serious injury or even death of crew. There is no "easy" ejection, and no "easy" abort.  Employing the LAS is not just an alternative way of deboarding the craft. It brings its own (substantial) risks.

Extraordinary claims require ext ordinary evidence. Care to provide some?

I never said it was always safe. I said it was a decent chance of survival. Even a slim chance of survival is infinitely better than the guaranteed no chance of survival both astronauts and pad crew have when something happens during boarding.

[docmordrid]

>
And if you are talking about the LAS how many tests have been conducted in the past? How many tests of the planned SpaceX or ULA LAS are there? It seems the LAS has minimal test data that it actually works.

SpaceX performed a Crew Dragon pad abort test 3 years ago, which is spot on the situation under discussion. An in-flight abort test at MaxQ is to be performed after the DM-1 uncrewed mission to ISS.

Pad abort test


Mashup of pad abort synched over the AMOS-6 failure. Do yourself a favor and turn off the audio.

[cscott]

The one idea that I haven't seen evaluated is the possibility of having a return feed at the top of the lox tanks that feeds back down through the lox tank to an exit port on the umbilical or TSM allowing a steady flow of sub-cooled lox back into the tank. This presumes that the lox will stratify as it warms, leaving the warmest lox at the top.

If that were to work, SpaceX could run a ' steady re-chill" of the vehicle that would relatively match the the "steady replenish" of boiling temp vehicles. That could potentially allow time to board after fueling.

I believe this is exactly how the existing system works.  Nevertheless, the bulk temperature gradually increases over time, causing a steady loss of performance through the window. The replenish system just can't match the supercold temps straight from the chiller, although it can slow the temperature rise.

[Jim]

Jim keeps repeating that the fuel load period is inherently more dangerous than a "stable" replenishment period.

From a history and experience standpoint -- not your gut feeling "so many things are changing, it's so dynamic, it just HAS to be more dangerous" argument -- why?

How many rockets have had serious problems in the past (let's be generous) 25 years during fuel loading?  Versus how many have had serious problems after fuel loading, or after engine ignition?  Or, in most cases, have had no problems at all?

I can name one (count 'em, one) example of an incident during fueling -- AMOS 6.

What others?

Again, this comes down to whether it is inherently more dangerous to a fuel a rocket -- generically, *any* rocket -- after crew boards than before.

And again, if NASA is satisfied that the AMOS 6 incident has been properly identified and mitigated (meaning the Falcon ought to be MORE safe during fuel loading than other rockets, since it has gone through a multi-million-dollar, labor-intensive review of its hardware and its fuel loading processes to mitigate any such problems in the future), what beyond "we've always done it the other way" is a logical case against boarding and then fueling?

Jim?  What other examples of what could be a crew-endangering situation have happened during fuel loading in the past 25 years?

Any?  At all?

Wrong. There have been many times propellant loading has been stopped and a launch scrubbed to fix a problem (leaks, valves sticking, etc)

And there is this:

[Jim]

Oh, and

S-IVB-503 static fire.

On August 5, 1981, a Percheron suborbital test vehicle exploded on its launch pad on Matagorda Island, Texas, due to a liquid oxygen tank overpressurization problem.

[Comga]

(Snip)
What loss of life occurred based on the current practice of boarding after fueling? Certainly not Apollo 1,  STS-51-L nor STS-107.

STS-51-L (Challenger) is not free and clear of the issue of fueling before crew loading.
The SRB and its O-rings chilled from both the cold ambient temperatures and the very cold wind shed by the External Tank filled with cryogens. We can’t say how much less effect there might have been if the ET was filled in the last half hour before launch (although such a procedure was impossible with the existing hardware.)

[the_other_Doug]

So -- nothing in the past 25 years, as I had challenged, eh?

Your most recent example happened 37 years ago.  People who worked on that vehicle are either all retired, or are on the cusp of retirement.  Do we limit people riding jet airliners because of the design issues faced by the BOAC Comet?

I don't think so.

And yet, the Comet killed people.

Aircraft designers *learned* from the Comet design issues and built safer jet airliners.  They didn't become risk-averse and refuse to consider flying people on jets just because someone had designed a dangerous airplane.  And now, decades later, the same issues that caused the Comet to kill people are no longer feared.

They exist -- the same laws of physics will still kill people if they are ignored -- but the designers have learned what to do to mitigate the possibilities of such failures.

So, again, I'm trying to point out that rocket designers have, for the most part, learned how to build boosters that are safe to fuel.  Nothing in the last generation of booster operations has caused a fueling-period LOV incident, except for AMOS 6.  And that failure is, at least supposedly, fully understood and fully mitigated.  No further mysteries hiding in the map-edges, waiting to kill you if you don't do things the Way They Have Always Been Done.

And the balloon Atlas collapsing more than 50 years ago?  Care to show me *any* current launch vehicles, especially being considered for man-rating, that will collapse of their own weight if not pressurized?

Didn't think so.  That one was just disingenuous.

[JBF]

So, again, I'm trying to point out that rocket designers have, for the most part, learned how to build boosters that are safe to fuel. 

That is wrong.  AMOS-6 just happened, so what other AMOS-6s are still out there?

They safest thing is to never try.

[Ike17055]

"Let the data lead the way" sounds good but does not inspire confidence for me. Jim's comment seems (to me) reflect NASA's position (at least the decision makers there). Decision makers can ignore data that doesn't meet their position.

they can always ignore data, but the chances of a good decision are better if the data is available. the data also, is not the only criteria, therefore, yes, a decision could be reached based on the context of other factors, which one would hope are just as valid, but no guarantees exist.  Stating a preference for no data to be on hand, however is not a defensible position simply because it may not, on its own, sway the final decision in a predetermined direction.  NASA is imperfect, but has a long history of weighing decisions based on maximizing data and minimizing guesswork.  Not every decision is perfect, but until there is perfect information , i.e, all things are known (a condition that never exists) some decsions will be imperfect. it is the nature of decision making.

[Comga]

Jim?  What other examples of what could be a crew-endangering situation have happened during fuel loading in the past 25 years?

Any?  At all?

Wrong. There have been many times propellant loading has been stopped and a launch scrubbed to fix a problem (leaks, valves sticking, etc)

And there is this:

Thanks. That’s a great video. Remarkable every time I see it.
It’s almost anticlimactic that it just sags to its destruction.
But it is from a very very long time ago with an archaic technology (pressure stiffening “balloon” tank)
Your most recent example is a sounding rocket, which had a much looser MQA regime and still is more than a quarter century ago.

On the other hand, Amos-6 was an “unknown unknown”. All we have are a few dozen subsequent launches to show that others are not significant.  But SpaceX does have them, and will have a few dozen more before CFT-1.

PS to the-other-Doug. Please calm down. This is not new. “Take what you can and leave the rest”

[envy887]

How is that different than the RTF after Challenger or Columbia? NASA saw many issues with o-rings, but kept pushing until they had a catastrophic failure. They redesigned the o-rings, and put crew on the next launch. Same for foam strikes, and they almost lost the RTF becasue the failure wasn't even corrected properly.

If it's disingenuous to say that a criticality-1 failure can be corrected and proven safe with a qualification campaign and 50 flights, then there should not have been crew on the Shuttle RTFs, or half of the Shuttle missions for that matter.

And a tanking failure isn't even crit-1.

[Ike17055]

How many rockets have had serious problems in the past (let's be generous) 25 years during fuel loading?  Versus how many have had serious problems after fuel loading, or after engine ignition?  Or, in most cases, have had no problems at all?

I can name one (count 'em, one) example of an incident during fueling -- AMOS 6.

So, the mode of observation is now to say, "let's just throw out that ONE inconvenient circumstance?"  the point remains that SPaceX did not KNOW the flaw with COPV until everything went BOOM. The design had not been tested enough. You cannot use the history of other designs being successfully fueld to validate a new design.

[envy887]

How many rockets have had serious problems in the past (let's be generous) 25 years during fuel loading?  Versus how many have had serious problems after fuel loading, or after engine ignition?  Or, in most cases, have had no problems at all?

I can name one (count 'em, one) example of an incident during fueling -- AMOS 6.

So, the mode of observation is now to say, "let's just throw out that ONE inconvenient circumstance?"  the point remains that SPaceX did not KNOW the flaw with COPV until everything went BOOM. The design had not been tested enough. You cannot use the history of other designs being successfully fueld to validate a new design.

This goes equally for the history of load-then-board as you tried to apply it to CC vehicles.

[Ike17055]

If NASA had boarded all those crews first, the record would be the same. That's basically just another way of saying "we've always done it this way", which is not a valid justification for anything.

uh, no, it really isn't saying that at all... there is a middle ground. continue testing densified fuels on uncrewed.

"fools rush in where angels fear to tread"

Yes, it is saying exactly that. That particular data set does not invalidate the hypothesis that load and go is just as safe, because none of them had an issue that would have caused a failure with load and go.

And what do you think SpaceX is doing, other then testing on uncrewed launches? They will have around 200 load cycles and 50 flights after fixing the issues found in the AMOS anomaly, and before flying any crew.

Nope. you are engaged in what is called "motivational reasoning," a form of bias that is akin to rationalization.  Youand others here are ignoring all other facts put before you, and creating a strawman argument that everyone else is just "against the future." NASA does not have the luxury of such bias.  Until new designs prove themselves, you cannot attribute the positive attributes, such as a history of no explosions, to the new design. The posts stating that SpaceX is building a history is valid. But their practice still contradicts the baseline that the customer (NASA) has established for certification. It will be NASA's call ultimately whether that tanking/testing qualifies for certification. But SpaceX runs a huge risk if NASA decides it is not. SpaceX would do well in this circumstance to remember the old saying, "the customer is always right."

[JBF]

So, again, I'm trying to point out that rocket designers have, for the most part, learned how to build boosters that are safe to fuel. 

That is wrong.  AMOS-6 just happened, so what other AMOS-6s are still out there?

They safest thing is to never try.

A meaningless point, nobody said don't launch

We cannot know everything; mistakes will happen.  The question has always been how much risk is acceptable.  From what you have said in the past all risk is unacceptable with regards to human spaceflight.

[mme]

(Snip)
What loss of life occurred based on the current practice of boarding after fueling? Certainly not Apollo 1,  STS-51-L nor STS-107.

STS-51-L (Challenger) is not free and clear of the issue of fueling before crew loading.
The SRB and its O-rings chilled from both the cold ambient temperatures and the very cold wind shed by the External Tank filled with cryogens. We can’t say how much less effect there might have been if the ET was filled in the last half hour before launch (although such a procedure was impossible with the existing hardware.)

It was 36° when Challenger lifted off and the engineering recommendation was not to launch below 53°. I think it's pretty creative to try to blame the tanking and boarding procedure for that failure.

[Ike17055]

actually, you are just proving you have no idea what you are talking about. read the posts, dude.TEST TEST TEST Then you willl KNOW KNOW KNOW.  Denying the need to do so is the only thing that is "screwed up logic" here.

Well the only way to test Load and Go is with crew onboard during the test otherwise not much difference to all previous space flights with crew onboard. And if you are talking about the LAS how many tests have been conducted in the past? How many tests of the planned SpaceX or ULA LAS are there? It seems the LAS has minimal test data that it actually works.

it seems you are confirming my thesis, that greater reliance on LAS puts a premium on a more robust test regimen for LAS. Also, you can not use the experience of past LAS systems to validate the SpaceX system. To date, there was ONE pad abort test of the SpaceX LAS, and it was under static conditions.  That's pretty narrow.

[Ike17055]

An abort has a high likleihood of resulting in serious injury or even death of crew. There is no "easy" ejection, and no "easy" abort.  Employing the LAS is not just an alternative way of deboarding the craft. It brings its own (substantial) risks.

Extraordinary claims require ext ordinary evidence. Care to provide some?

I never said it was always safe. I said it was a decent chance of survival. Even a slim chance of survival is infinitely better than the guaranteed no chance of survival both astronauts and pad crew have when something happens during boarding.

it's not an extraordinary claim. A basic understanding of the dynamics of abort, even unscientific can tell you that it is a dangerous situation. Very dangerous.You cannot predict with reliability how an abort unfolds, at least not as neatly as the pad abort tests where no real emergency exists.  yes, a chance of survival is better than no chance, but it is vastly nsufficient to build your entire lauch operations sequence around.