Commercial Crew Schedule Analysis

[Dante80]

Just how many rockets have blown up on the pad after propellant loading complete?

The Nedelin Catastrophe springs to mind.

Regarding the subject at hand, I am not sure how this would be solved really. I don't know whether SpaceX can even fly v1.2 without densified propellants (the rocket and the engines must have changed to use those from v1.1, I think it is not that simple as loading warmer propellants and letting go).

I also don't think that SpaceX would care to bring back v1.1 for this, or start producing two separate versions of v1.2.

This makes me think btw. Could the fueling procedure changes for Amos-6 have anything to do with NASAs desire to have the astronauts enter after fueling? It has been speculated that SpaceX was trying to refine their fueling procedures so that they could catch tough launch windows and recycle when encountering a problem instead of scrubbing. Is there any chance that the CC fueling procedure requirements were related with what SpaceX was trying to do/test?

[Brovane]

The Nedelin Catastrophe springs to mind.

Regarding the subject at hand, I am not sure how this would be solved really. I don't know whether SpaceX can even fly v1.2 without densified propellants (the rocket and the engines must have changed to use those from v1.1, I think it is not that simple as loading warmer propellants and letting go).

We do know that there was changes to the LV, physically.  However I am not sure that there was actual physical changes to the engines beyond the larger exhaust nozzle for the 2nd stage.  They just seem to be running the engines at a higher thrust level.  That in itself wouldn't seem to require the use of densified propellant. 

[Lars-J]

LES is a system of last resort. I highly doubt it will play into NASA's decision. History on the other hand very well might and history after 9/1 changed dramatically.

History changed? A little over the top, I think, unless you have some evidence of a time traveler being involved. 

It is actually a good thing that this was discovered then, and not later. More knowledge of proper helium and COPV use in certain conditions is going to ultimately benefit SpaceX (and the industry as a whole that surely are paying attention) in the long run. And once an improved F9 returns to flight, it has many flights to demonstrate safety before crews will be put on top.

[meberbs]

Load props after crew load and you only have 4-5 people at risk, all strapped into a TPS covered vehicle just looking for a reason to bug out and with the means to do so.

Load props first and you have 2-3 times as many people within 2 meters of a potential boomski and most have no way out if it's a fast event. Zip line? Puh-lease.

I'll take door #1.

For some reason loading propellants first has been the established standard for decades.  Not saying just because it has been done this way for decades is a good reason to continue doing it the same way.   

So is the push back against loading propellants after the astronauts are loaded just institutional inertia on the part of NASA?  Or is there another reason that isn't apparent to us outside the industry?

The statements in the article really seemed to lack solid logic behind them. Looking at the 2 options above, the first option needs more things to go wrong (vehicle explosion + LES failure), so it is probably better, but data I don't have would be needed to show this. Probability of a vehicle failure during the full load sequence is probably higher than just during the continual top-off operation, so it depends on the details, but I would bet on the first option still due to the multiple failures required for injury or death to occur.

"It was unanimous ... Everybody there, and particularly the people who had experience over the years, said nobody is ever near the pad when they fuel a booster,” Stafford said, referring to an earlier briefing the group had about SpaceX's proposed fueling procedure.

This statement is based on a fallacy, just because that is how it has always been done is not a good reason. It should prompt you to ask why has it always been done that way, but extrapolating that this applies to a different system (which includes LES) is not a valid analysis.

Besides, for the shuttle, they continued topping off the external tank until late in the count. Depending on the interpretation of the phrase "when they fuel the booster," the statement could be understood in a way that is simply false.

I trust that SpaceX and NASA will use actual analysis based on numbers to make this decision, and not misleading statements like that quote.

[Steven Pietrobon]

Just how many rockets have blown up on the pad after propellant loading complete?

At least one Soyuz (where the crew were saved by the LAS). People would have died if the fire occurred during crew loading.

[Negan]

It should prompt you to ask why has it always been done that way

McAlister already pointed out why it was done that way before the before 9/1. It was done that way because is "a potentially hazardous operation".

Really I wouldn't even see an issue with this at all, but McAlister already made the following statement a month earlier than Amos:

We are getting more comfortable with it, but we are not yet ready to say we’re good,” McAlister said of SpaceX’s procedure. “We’re still working through that.”

NASA already made in an issue in the public eye. The only way McAlister can completely cover himself at this point is to go with the standard procedure. If something happens at that point, it would be very easy to put the blame on SpaceX for being incompetent, but if he goes the other way, he and NASA now risk taking partial blame for anything that happens because of the new procedure.

That being said if NASA is comfortable in their analysis going forward more power to them. I just see them taking a more conservative stance with this as they did with the water landings.

[Negan]

Regarding the subject at hand, I am not sure how this would be solved really. I don't know whether SpaceX can even fly v1.2 without densified propellants (the rocket and the engines must have changed to use those from v1.1, I think it is not that simple as loading warmer propellants and letting go).

Wish the resident expert would chime in on this one.

[oiorionsbelt]

If the crew loads after the propellants doesn't that mean the closeout crews as well as Spacecraft crew are exposed to a fully fueled vehicle?
 If the crew loads before the the propellants then the closeout crew wouldn't be exposed to a fully fueled vehicle.

  It would be good to know the rational behind NASA thinking loading crew after fueling is safer than loading them before.

[baldusi]

If I had to make the call I would say that they are trading the fire/explosion risk of the propellant loading operation, then multiplying by the LAS failure probability (~10%) and trading against the risk of fire/explosion while crew and personnel is in the tower.
Roughly speaking, if they think that propellant loading is more than ten times riskier than fully loaded stack for whatever time it takes the crew to ingress, then they should wait until it is filled.
It would only seem logical that propellant operations would be a lot more dangerous than a rocket in non-ignited steady state.

[Brovane]

If the crew loads after the propellants doesn't that mean the closeout crews as well as Spacecraft crew are exposed to a fully fueled vehicle?
 If the crew loads before the the propellants then the closeout crew wouldn't be exposed to a fully fueled vehicle.

  It would be good to know the rational behind NASA thinking loading crew after fueling is safer than loading them before.

I do wonder how much institutional inertia is coming into play with NASA thinking around loading the crew after fueling, is safer?

[Robotbeat]

If I had to make the call I would say that they are trading the fire/explosion risk of the propellant loading operation, then multiplying by the LAS failure probability (~10%) and trading against the risk of fire/explosion while crew and personnel is in the tower.
Roughly speaking, if they think that propellant loading is more than ten times riskier than fully loaded stack for whatever time it takes the crew to ingress, then they should wait until it is filled.
It would only seem logical that propellant operations would be a lot more dangerous than a rocket in non-ignited steady state.

But 10% LAS failure rate is a /conservative/ number. To make the right decision about which is safest, you have to use the /most likely/ number. This is one case where being overly conservative can easily lead to a much less safe decision.

[woods170]

If the crew loads after the propellants doesn't that mean the closeout crews as well as Spacecraft crew are exposed to a fully fueled vehicle?
 If the crew loads before the the propellants then the closeout crew wouldn't be exposed to a fully fueled vehicle.

  It would be good to know the rational behind NASA thinking loading crew after fueling is safer than loading them before.

I do wonder how much institutional inertia is coming into play with NASA thinking around loading the crew after fueling, is safer?

The thinking at NASA is like this: "We've done it this way since 1961, so why should we change this now?".

Well, it's exactly that kind of thinking that got the crew of Apollo 1 killed ("We've always done the plugs-out test with a 100 percent oxygen pressurized atmosphere, so why should we change that?)

And a similar unwillingness to change, or face the facts, was involved in both the Challenger and Columbia accidents.

But I digress.

[Proponent]

If I had to make the call I would say that they are trading the fire/explosion risk of the propellant loading operation, then multiplying by the LAS failure probability (~10%) and trading against the risk of fire/explosion while crew and personnel is in the tower.
Roughly speaking, if they think that propellant loading is more than ten times riskier than fully loaded stack for whatever time it takes the crew to ingress, then they should wait until it is filled.
It would only seem logical that propellant operations would be a lot more dangerous than a rocket in non-ignited steady state.

But 10% LAS failure rate is a /conservative/ number. To make the right decision about which is safest, you have to use the /most likely/ number. This is one case where being overly conservative can easily lead to a much less safe decision.

10% may be high for the probability of a hardware failure in the launch-escape system, but what about the probability of failing to trigger it in time?  We've all seen the video of Dragon abort test superimposed on the AMOS-6 explosion, but it seems to me there is still a substantial risk of not triggering the escape soon enough.

[QuantumG]

Let's get back to talking about schedule, eh?

[gongora]

Tweet from James Dean

NASA says SpaceX targets in this chart valid as of July, will be updated this week. Boeing dates more recent, updated in October.

[gongora]

A few SpaceX notes from listening to the presentation by Kathy Lueders at the NAC HEO Committee meeting yesterday (you can find the recordings here).

The first round of structural tests on Crew Dragon are done, continuing with further testing.
They should do the space suit qualification next quarter.
They have their 5th parachute test scheduled for this coming Saturday.
The crew access arm is at LC-39A, they are waiting until Spring to install it so SpaceX can get the pad up and running for their other launches.
They have been doing unit testing on the ECLSS systems and are getting ready for integrated testing.

There was some discussion about the LOC risk numbers, some general discussion about the SpaceX mishap investigation (there is a team from NASA LSP that is taking an independent look at it).  The presentation is a bit long (over an hour) but probably worth listening to if you're really into the commercial crew program.

[eriblo]

A few SpaceX notes from listening to the presentation by Kathy Lueders at the NAC HEO Committee meeting yesterday (you can find the recordings here).

The first round of structural tests on Crew Dragon are done, continuing with further testing.
They should do the space suit qualification next quarter.
They have their 5th parachute test scheduled for this coming Saturday.
The crew access arm is at LC-39A, they are waiting until Spring to install it so SpaceX can get the pad up and running for their other launches.
They have been doing unit testing on the ECLSS systems and are getting ready for integrated testing.

There was some discussion about the LOC risk numbers, some general discussion about the SpaceX mishap investigation (there is a team from NASA LSP that is taking an independent look at it).  The presentation is a bit long (over an hour) but probably worth listening to if you're really into the commercial crew program.

Looks like the parachute test is on schedule: From \u\Watching_JRTI on reddit, described as "leaving the SpaceX campus earlier this week".

[gongora]

Tweet from Jeff Foust:

Wayne Hale, reporting on NAC’s HEO committee, says SpaceX’s commercial crew schedule has slipped (as expected) since their Nov. 14 meeting.

Tweet from Stephen Clark:

NAC member Wayne Hale says SpaceX’s commercial crew schedule has slipped since last meeting, but doesn’t know the new dates.

[AnalogMan]

NASA’s Commercial Crew Program Target Flight Dates
Posted on December 12, 2016 at 5:11 pm by Stephanie Martin

The next generation of American spacecraft and rockets that will launch astronauts to the International Space Station are nearing the final stages of development and evaluation. NASA’s Commercial Crew Program will return human spaceflight launches to U.S. soil, providing reliable and cost-effective access to low-Earth orbit on systems that meet our safety and mission requirements. To meet NASA’s requirements, the commercial providers must demonstrate that their systems are ready to begin regular flights to the space station. Two of those demonstrations are uncrewed flight tests, known as Orbital Flight Test for Boeing, and Demonstration Mission 1 for SpaceX. After the uncrewed flight tests, both companies will execute a flight test with crew prior to being certified by NASA for crew rotation mission. The schedule below reflects a fourth quarter update from SpaceX and the dates Boeing released in October 2016.

Targeted Flight Dates:

Boeing Orbital Flight Test: June 2018

Boeing Crew Flight Test: August 2018

SpaceX Demonstration Mission 1: November 2017

SpaceX Demonstration Mission 2: May 2018

https://blogs.nasa.gov/commercialcrew/2016/12/12/nasas-commercial-crew-program-target-flight-dates

[yg1968]

Article on this topic:
http://www.geekwire.com/2016/nasa-confirms-delay-spacex-boeing-2018-commercial-crew/