Commercial Crew - Discussion Thread 1

[Ike17055]

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.

[Coastal Ron]

No, it is not just a matter of whether you think atmos-6 issue is rectified. Every incident, whether copv, or o-rings should serve as a reminder of all the “unknown unknowns” in this business.  It is the “what else have we missed?” moment that NASA has paid dearly for when not taking in the past.

By perfecting reusable rockets, SpaceX is more aggressively reducing the amount of "unknown unknowns", just like humanity has done with every form of reusable transportation.

This is the reason for “overly cautious” analysis.

Quite honestly I'm not sure the objections being raised are purely based on engineering and analysis. I think there is some "Not Invented Here" syndrome that is part of it, since part of the argument being made is that "...in 50 years we've never done it this way."

Never having done something before in history is never a justification for what we shouldn't do something in the future. There has to be more specificity and comparisons, and I'm not sure we're hearing that.

Unplanned Fire and explosions rarely interact well with humans.

Of course not, which is why the SpaceX plan completely removes the possibility of humans being exposed - in an unprotected way - to a fueled rocket .

It is logical to mitigate every possible scenario when dealing with elevated possibilities of them. Fueling is a big one.  iNtroducing humans into the middle of that warrants a long pause to ask if we have really thought that through as completely as possible.

Luckily for SpaceX they have the ability to do testing on missions that don't carry humans, which is unique for a non-government launch organization.

And really this conversation is about risk, and in what way will be allow risk.

Considering that NASA and our political leadership was perfectly fine allowing humans to fly on the Space Shuttle even after two accidents, and knowing that there was no realistically effective LAS, I think those objecting to what SpaceX wants to do are being too cautious, especially considering that crew will be in a certified escape vehicle that can leave the area if needed - so the risk to human life is very low even in the event of an accident with a fueled stage.

NASA will ultimately make the call, and so far I've had confidence in decisions made by William H. Gerstenmaier - even when I don't agree with his decisions...

[Lars-J]

Relying on LaS is inherently risk-laden.  An abort is no small deal. It is dangerous. And this assumes that your LAS will even be properly actuated, i.e. detect an abort situation appropriately and responsively, and i initiate correctly, and soon enough to have a chance to save the crew. It is not “automatic.”

Can we please stop forgetting the pad closeout crew on the pad?

I think we all understand that doing it the SpaceX proposed way does increase risk for the astronauts. (although how much that increase is continues to be debated) - But it does reduce risk for everyone else around the pad.

[saliva_sweet]

If we were to formally depend on the LAS as our priMARY insurance policy against disaster from PAD incident, rather than risk mitigation

This is the very assumption people are questioning. Is it inherently safer to board crew onto a fueled rocket, which constitutes an irreconcilable "black zone"? The assumption is that the fueled rocket is "stable", but it is in fact an extremely unnatural state. A state that every law of thermodynamics wants to resolve into a big ball of fire.

[rayleighscatter]

If we were to formally depend on the LAS as our priMARY insurance policy against disaster from PAD incident, rather than risk mitigation

This is the very assumption people are questioning. Is it inherently safer to board crew onto a fueled rocket, which constitutes an irreconcilable "black zone"? The assumption is that the fueled rocket is "stable", but it is in fact an extremely unnatural state. A state that every law of thermodynamics wants to resolve into a big ball of fire.

Is it safe to mow the grass around the fuel tanks on site?

[Welsh Dragon]

I think we all understand that doing it the SpaceX proposed way does increase risk for the astronauts.

Do we? I don't. Let's compare some scenarios, shall we:

1) Board astronauts
2) Start fuelling
3) Something goes wrong with fuelling, leads to RUD
4) LAS activates, giving crew a very decent chance of survival (pad crew is miles away in safety already)

Or an alternative scenario:

1) Fuel
2) Start boarding astronauts
3) Rocket undergoes RUD during boarding
4) Both astronauts and pad crew have zero chance of survival.

Unless you assume the chance of killing the crew in a LAS abort is bigger than the chance of killing them during a incident while boarding on top of a fuelled vehicle, or can give a 100% guarantee nothing can go wrong with a fuelled vehicle, boarding first seems to me to always be the better option. Bottom line: crew on board during fuelling: abort option available during entire fuelling process. Crew boarding after fuelling: significant period without any abort option. On balance, fuelling after boarding likely less risky for astronauts, infinitely less risky for pad crew.

[Comga]

I think we all understand that doing it the SpaceX proposed way does increase risk for the astronauts.

Do we? I don't. Let's compare some scenarios, shall we:

Do.  Don't.  Uncertain.
But what we think doesn't matter, does it?
We know all these arguments and our inability (perhaps everyone's inability) to calculate the odds.

There does not seem to be a straightforward way out of this conflict.
What are the alternatives?

Supercooled, densified propellants give the Falcon 9 "extra margin" but it's already more than powerful enough for launching Dragon.  SpaceX ran the Merlin on "equilibrium temperature" propellants for many flights.
Could Space go back to undensified propellants for the NASA Crew flights?
Could they fly a dedicated mission before the Crew Demo flight to demonstrate launch under those conditions with the current Merlin 1D?
(They haven't changed the designation although they have incorporated upgrades including the blisk, have they?)
This could show up as an additional milestone.
NASA can then rely on Boeing (not just as the retailer of Soyuz seats) and their CST-100 to be the sole support for the ISS until such time that all the committees agree that SpaceX is no more risky.



How else? 

[Lars-J]

I think we all understand that doing it the SpaceX proposed way does increase risk for the astronauts.

Do we? I don't. Let's compare some scenarios, shall we:

Do.  Don't.  Uncertain.
But what we think doesn't matter, does it?
We know all these arguments and our inability (perhaps everyone's inability) to calculate the odds.

There does not seem to be a straightforward way out of this conflict.
What are the alternatives?

Supercooled, densified propellants give the Falcon 9 "extra margin" but it's already more than powerful enough for launching Dragon.  SpaceX ran the Merlin on "equilibrium temperature" propellants for many flights.
Could Space go back to undensified propellants for the NASA Crew flights?
Could they fly a dedicated mission before the Crew Demo flight to demonstrate launch under those conditions with the current Merlin 1D?
(They haven't changed the designation although they have incorporated upgrades including the blisk, have they?)
This could show up as an additional milestone.
NASA can then rely on Boeing (not just as the retailer of Soyuz seats) and their CST-100 to be the sole support for the ISS until such time that all the committees agree that SpaceX is no more risky.

How else?

How else? How about looking at the safety of the current F9 ops until the first crew launches. Since Amos-6 (where SpaceX are now the premier COPV experts on the planet due to their investigation), have F9's and FH's experienced problems? Have they been blowing up? Have they had any tanking issues?

At some point "we are doing it this way because that's how it has always been" ceases to be an effective argument. There are obviously pros and cons about either approach, but perhaps we can judge them more fairly without historical bias?

[cscott]

Saying that F9 with crew onboard should launch in a fundamentally different configuration than other F9 flights (ie nondensified propellants) potentially increases risk much more than it mitigates it.

[deruch]

Saying that F9 with crew onboard should launch in a fundamentally different configuration than other F9 flights (ie nondensified propellants) potentially increases risk much more than it mitigates it.

At the very least, it reduces or eliminates the applicability of data/experience from the unmanned version.  Which decreases confidence even if it doesn't change the underlying risk.  Seems silly for NASA to insist on 7 flights of the Block 5 and then afterwards also insist that they run their launch ops in a very different manner.  Or are they going to insist those 7 flights are fueled without the load-and-go?

[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.

[speedevil]

I can't find an answer for this, and it seems like an obvious question.

Was the sole reason for not flying crew on D1 the lack of a LAS - or were there other long poles?
Was the risk to crew formally studied officially, or was it just never considered because of the lack of the LAS?
Thanks.

[rayleighscatter]

Saying that F9 with crew onboard should launch in a fundamentally different configuration than other F9 flights (ie nondensified propellants) potentially increases risk much more than it mitigates it.

Crew launches ARE fundamentally different.

If SpaceX can't manage that disparity then perhaps Astronauts aren't a cargo they should be carrying.

[envy887]

Saying that F9 with crew onboard should launch in a fundamentally different configuration than other F9 flights (ie nondensified propellants) potentially increases risk much more than it mitigates it.

Crew launches ARE fundamentally different.

If SpaceX can't manage that disparity then perhaps Astronauts aren't a cargo they should be carrying.

Only the crew capsule is different.

Everything below Dragon's trunk will have lots of flight history in that exact configuration. Throwing away that flight history to go with a unique configuration adds risks.

[kevinof]

So what are you saying - remove the densified propellents, change the gse, change the loading procedures all for how many flights per year  - 1/2?

Wouldn't that INCREASE the chance of something bad happens as you now have a configuration you don't regularly fly?

Saying that F9 with crew onboard should launch in a fundamentally different configuration than other F9 flights (ie nondensified propellants) potentially increases risk much more than it mitigates it.

...

If SpaceX can't manage that disparity then perhaps Astronauts aren't a cargo they should be carrying.

[Comga]

Oh, I agree with most of these responses.

A distinct version of Falcon 9 just for commercial crew would be an enormous complication that would not make things safer.
But all anyone has said is a reiteration that NASA will come around to SpaceX's method and agree to do it "their way".
That seems to go against what has happened to date.

SpaceX statements indicated that turbopump disk cracking was not surprising and acceptable.  They upgraded to a blisk to satisfy NASA's lower tolerance.
SpaceX has been launching for a year and a half with modified procedures and COPV's, including COTS flights for NASA , but will upgrade to "COPV 2" for CCtCAP.
SpaceX talked up propulsive landing, but converted to ocean landings to satisfy NASA.

And before Jim says that NASA didn't make SpaceX do anything, that's obviously true and not the point.
SpaceX doesn't have to go through with their largest single contract, while being paid for every change, but it's hard to imagine them NOT doing it, even if it diverges at a fairly large angle from the direction they were headed.

And to throw fuel on the fire, the WashPo article was wrong.  The odds of failure on STS-1 were not 1 in 12.   The post facto 1 in 12 number has as many problems as the 1 in 5000 number postulated before flight.  LOC calculations are not like interplanetary trajectories, which can be planned and executed with breathtaking precision.  They incorporate boatloads of estimations, most of which are not supported by adequate statistics.  Whether they meet or miss the curious 1 in 270 value is not an absolute answer.

So what else can SpaceX do to convince NASA that their launches are adequately safe?

[rockets4life97]

And before Jim says that NASA didn't make SpaceX do anything, that's obviously true and not the point.
SpaceX doesn't have to go through with their largest single contract, while being paid for every change, but it's hard to imagine them NOT doing it, even if it diverges at a fairly large angle from the direction they were headed.

[snip]

So what else can SpaceX do to convince NASA that their launches are adequately safe?

I think Comga is right. At the end of the day SpaceX, will do whatever NASA wants for Crew Dragon missions even if SpaceX's engineers think it is less safe. NASA will have to pay for it, but that doesn't look to be an issue for them. NASA will also pay the consequences if their is a failure from a design decision they required.

Now SpaceX has learned their lessons from NASA both in terms on knowledge transfer and enough to stay away from the bureaucracy. As a result, SpaceX won't allow NASA won't touch BFR until its built, tested, and flying. That will be the new day in human spaceflight.

[Brovane]

So what are you saying - remove the densified propellents, change the gse, change the loading procedures all for how many flights per year  - 1/2?

Wouldn't that INCREASE the chance of something bad happens as you now have a configuration you don't regularly fly?

The ability of the F9 and GSE to switch between densified and non-densified is a unknown.  Not sure if anyone has asked SpaceX directly this question.

Can you just switch off the GSE equipment that does the densification and upload different software into the F9 and it can work with non-densified propellant?  Or is the hardware changed in a fundamental way that the F9 can only use densified propellant. 

[envy887]

So what are you saying - remove the densified propellents, change the gse, change the loading procedures all for how many flights per year  - 1/2?

Wouldn't that INCREASE the chance of something bad happens as you now have a configuration you don't regularly fly?

The ability of the F9 and GSE to switch between densified and non-densified is a unknown.  Not sure if anyone has asked SpaceX directly this question.

Can you just switch off the GSE equipment that does the densification and upload different software into the F9 and it can work with non-densified propellant?  Or is the hardware changed in a fundamental way that the F9 can only use densified propellant.

There were reports from a SpaceX employee (on reddit IIRC) that they were tuning the engines differently for densified props. So there would appear to be hardware differences, which makes sense considering that turbopumps are sensitive to changes in density and viscosity.

Even if it's straightforward to make the changes, you're still introducing a new configuration that throws out 50+ flights worth of history and data (by the time crew flies), and you're only flying it twice a year. That increases risk, and there's no way around it.

[Kansan52]

There were reports from a SpaceX employee (on reddit IIRC) that they were tuning the engines differently for densified props. So there would appear to be hardware differences, which makes sense considering that turbopumps are sensitive to changes in density and viscosity.

Thanks for that. Memory said it was something like that. So much better to have the info!