SpaceX Dragon 2 Updates and Discussion - Thread 3

[gongora]

The thermal "issues" that DM-1 had was also the result from a NASA requirement change. You see, on DM-1 there weren't any actual thermal issues. DM-1 had the originally designed thermal control set-up which actually met the original NASA thermal requirements.
But you guessed it: NASA changed the thermal requirements. And NASA did so pretty late into the planning cycle for DM-1. Those new requirements could not be met by the DM-1 setup. Which in turn required a waiver to fly DM-1 with the original thermal set-up but also requiring substantial rework to the DM-2 vehicle to meet NASA's new, more stringent thermal requirements.

When they publicly talked about the thermal changes, they mentioned having seen problems with the existing setup on Dragon 1.  How does that fit into your narrative?

[abaddon]

The thermal "issues" that DM-1 had was also the result from a NASA requirement change. You see, on DM-1 there weren't any actual thermal issues. DM-1 had the originally designed thermal control set-up which actually met the original NASA thermal requirements.
But you guessed it: NASA changed the thermal requirements. And NASA did so pretty late into the planning cycle for DM-1. Those new requirements could not be met by the DM-1 setup. Which in turn required a waiver to fly DM-1 with the original thermal set-up but also requiring substantial rework to the DM-2 vehicle to meet NASA's new, more stringent thermal requirements.

When they publicly talked about the thermal changes, they mentioned having seen problems with the existing setup on Dragon 1.  How does that fit into your narrative?

It's pretty easy to guess that the "problems" were relative to the new updated standards.  Do you really think SpaceX and NASA would have ignored problems seen in a cargo craft they just flew the 19th time until this late in the CCrew program?  It seems very unlikely that they happened to suddenly notice thermal issues recently enough for them not to plan to address them in DM-1.  And it fits the broad pattern of NASA regularly changing their minds (as is their right under contract) with regards to both CCrew vehicles over time.

[guckyfan]

Is this thermal issue in context with potentially freezing propellant lines or something separate?

[clongton]

The thermal "issues" that DM-1 had was also the result from a NASA requirement change.

What change did NASA require, and what was the reason given for the change?

[woods170]

The thermal "issues" that DM-1 had was also the result from a NASA requirement change. You see, on DM-1 there weren't any actual thermal issues. DM-1 had the originally designed thermal control set-up which actually met the original NASA thermal requirements.
But you guessed it: NASA changed the thermal requirements. And NASA did so pretty late into the planning cycle for DM-1. Those new requirements could not be met by the DM-1 setup. Which in turn required a waiver to fly DM-1 with the original thermal set-up but also requiring substantial rework to the DM-2 vehicle to meet NASA's new, more stringent thermal requirements.

When they publicly talked about the thermal changes, they mentioned having seen problems with the existing setup on Dragon 1.  How does that fit into your narrative?

The "problems" they mentioned referred to problems in meeting the new, more stringent thermal requirements.
When the newer, more stringent thermal requirements were set, the DM-1 vehicle was in an advanced stage of construction. When it was put thru vacuum-thermal testing it became clear that the vehicle was incapable of meeting the newer, more stringent thermal requirements.That's the "problems" NASA and SpaceX referred to.

But when the results of the vacuum-thermal tests were compared to the original, les-stringent, thermal requirements, it became clear that the DM-1 vehicle would have aced those earlier requirements.

But, NASA's baseline for DM-1 contained the newer, more stringent thermal requirements. Given that the vacuum-thermal tests had shown that the DM-1 vehicle was incapable of meeting the newer requirements, it translated into a revised flight-profile for DM-1. As well as a set of waivers.

Also; it has been mentioned to me that some folks at SpaceX consider the newer, more stringent thermal requirements, as set by NASA, to be overly conservative.

[woods170]

Is this thermal issue in context with potentially freezing propellant lines or something separate?

This and several other "worries".

[woods170]

The thermal "issues" that DM-1 had was also the result from a NASA requirement change.

What change did NASA require, and what was the reason given for the change?

Allowable temperature ranges on several parts of the Crew Dragon. Specific reasons were given by NASA but as I mentioned two posts earlier: there are SpaceX folks who consider the new thermal requirements to be overly conservative.

You know: this is NASA. The organization that fundamentally froze when they lost their second space shuttle.

[gongora]

From:

Just the press conference on YouTube: https://youtube.com/watch?v=AkOHE-LCT_s

Transcript of the press conference: https://gist.github.com/theinternetftw/443b8f21390ad090a25963e4512c5dfc

Bill Gerstenmaier: ... On the thrusters, there's a portion of the thruster that can actually break free, and liberate, and come out of the thruster. I think we understand why that occurs. We can control that by operating the thrusters in a certain manner, keeping temperatures at a certain temperature, keeping the propellant conditions exactly the right way. In the future, we'd like to understand, to maybe make a change to that. To either keep the thermal system, keep the propellant warm in the vehicle without having to do attitude control to keep the propellant warm. So that'll be another change that's coming in the propulsion system. ...

[eeergo]

What change did NASA require, and what was the reason given for the change?

Liberation of Draco parts (not Super-, although it might be common to both), from DM-1's briefings:

On the thrusters, there's a portion of the thruster that can actually break free, and liberate, and come out of the thruster. I think we understand why that occurs. We can control that by operating the thrusters in a certain manner, keeping temperatures at a certain temperature, keeping the propellant conditions exactly the right way. In the future, we'd like to understand, to maybe make a change to that. To either keep the thermal system, keep the propellant warm in the vehicle without having to do attitude control to keep the propellant warm. So that'll be another change that's coming in the propulsion system.

Another one is presented here: change the angle of the seats. And thus making it impossible to fly seven folks. Which in turn makes the vehicle unattractive for purely tourist flights.

The thermal "issues" that DM-1 had was also the result from a NASA requirement change. You see, on DM-1 there weren't any actual thermal issues. DM-1 had the originally designed thermal control set-up which actually met the original NASA thermal requirements.
But you guessed it: NASA changed the thermal requirements. And NASA did so pretty late into the planning cycle for DM-1.

Could it just be the analysis showed good margins for uncrewed flights, but a more refined one, based on a longer empirical flight history of almost 20 missions which was not available before, done ex-profeso for the crewed variant, showed such problems? No need to invoke NASA's "undecisiveness", IMO. Also, it's unclear why you mention "issues" (between quotes) when we're talking about attitude control engines physically breaking on orbit.

Concerning seating, why is there a problem with NASA wanting to change it if the 7-seat arrangement is flawed and violates loading limits? Or are you saying you know they brought a more stringent limit out of their hats at the last minute, forcing SpaceX to a lengthy redesign of what was already approved? Of course, regardless, SpaceX could choose to keep that arrangement and offer slightly "wilder" rides for commercial flights, if they're really confident about it.

[Spindog]

I dont know but shouldn't it be almost certain that the seat angle change is related to water impact in a contingency (parachute out) situation? That would be the only probability that makes sense.

In any case, if SpaceX wanted to launch commercial customers on a Dragon 2 they could use the 7 seat configuration if they want to. Whether or not NASA would have a problem with 7 seat Dragon visiting the ISS would be a seperate issue.

[woods170]

Could it just be the analysis showed good margins for uncrewed flights, but a more refined one, based on a longer empirical flight history of almost 20 missions which was not available before, done ex-profeso for the crewed variant, showed such problems? No need to invoke NASA's "undecisiveness", IMO. Also, it's unclear why you mention "issues" (between quotes) when we're talking about attitude control engines physically breaking on orbit.

Emphasis mine.

That didn't actually happen on any of the CRS missions. Scenario was developed as a result of extreme limits testing.

You people should realize that, besides on-orbit performance of the Draco's, SpaceX is also required to do a ship-load of testing on the thruster quads. Everything from nominal situations to extreme situations. Some of the results of the extreme situations worried NASA because it could potentially lead to a thruster coming apart. Which is what was referred to prior to DM-1 flying.

[woods170]

I dont know but shouldn't it be almost certain that the seat angle change is related to water impact in a contingency (parachute out) situation? That would be the only probability that makes sense.

In any case, if SpaceX wanted to launch commercial customers on a Dragon 2 they could use the 7 seat configuration if they want to. Whether or not NASA would have a problem with 7 seat Dragon visiting the ISS would be a seperate issue.

Seven seat is out of the question due to other - fixed - features of the interior of Crew Dragon. Building a second version, being 7-seat capable, rules out reuse of flown CCP Crew Dragon for tourist purposes. Not worth the expense now that SpaceX is putting its bets on Starship.

[punder]

Maybe the angles for the seven seats were established for propulsive landing, and the change came about after that was ditched in favor of parachutes.

[eeergo]

Could it just be the analysis showed good margins for uncrewed flights, but a more refined one, based on a longer empirical flight history of almost 20 missions which was not available before, done ex-profeso for the crewed variant, showed such problems? No need to invoke NASA's "undecisiveness", IMO. Also, it's unclear why you mention "issues" (between quotes) when we're talking about attitude control engines physically breaking on orbit.

That didn't actually happen on any of the CRS missions. Scenario was developed as a result of extreme limits testing.

You people should realize that, besides on-orbit performance of the Draco's, SpaceX is also required to do a ship-load of testing on the thruster quads. Everything from nominal situations to extreme situations. Some of the results of the extreme situations worried NASA because it could potentially lead to a thruster coming apart. Which is what was referred to prior to DM-1 flying.

Sure, that's fine and, honestly, expectable.

We all know too that you don't need to *actually* have an "engine-breaking-apart-on-orbit" type of situation in order to do something about it, especially moving onward to crewed flights with the same type of engines but different, probably more demanding flight profiles.

I'm sure you'd agree margins are everything, and from the gathered information thus far it doesn't seem it was an "issue", but rather an *issue*. DM-1 was waived just because it could afford to avoid the thermally-worrying scenarios, as it was stated also in that briefing - not because the situation was deemed to be too academic to actually matter.

In a previous post you seem to imply those new margins are too conservative and NASA is hairsplitting - which cannot be excluded. But it's also true that from your post we'd just have to believe in "some folks at SpaceX"'s judgement (i.e. part of the interested party... what about "the other folks at SpaceX", or "folks at NASA"? how many are there of each subgroup? whose opinion is more valid/who did the most in-depth analysis?).

It's obvious NASA changed its requirements when D2 was deep into its development process, or otherwise it wouldn't have impacted its timeline. Whether the change was arbitrary, exaggerated, imposed with ill intention... is the real question. A scenario in which good margins were seen for uncrewed flights, but more refined analyses based on a longer empirical flight history of ~20 missions not available before, done ex-profeso for the crewed variant, showed problems - is more plausible IMO.

[abaddon]

...but more refined analyses based on a longer empirical flight history of ~20 missions not available before, done ex-profeso for the crewed variant, showed problems - is more plausible IMO.

Not really, unless you believe that the empirical flight history of ~16 missions which were available before weren't enough, and only the most recent ~4 moved the needle there.  Which seems unlikely.

We know NASA has been behind on certification paperwork for some time now.  It's far more plausible that the data was there previously, but NASA just hadn't gotten to those items until more recently.

[dondar]

Could it just be the analysis showed good margins for uncrewed flights, but a more refined one, based on a longer empirical flight history of almost 20 missions which was not available before, done ex-profeso for the crewed variant, showed such problems? No need to invoke NASA's "undecisiveness", IMO. Also, it's unclear why you mention "issues" (between quotes) when we're talking about attitude control engines physically breaking on orbit.

Emphasis mine.

That didn't actually happen on any of the CRS missions. Scenario was developed as a result of extreme limits testing.

You people should realize that, besides on-orbit performance of the Draco's, SpaceX is also required to do a ship-load of testing on the thruster quads. Everything from nominal situations to extreme situations. Some of the results of the extreme situations worried NASA because it could potentially lead to a thruster coming apart. Which is what was referred to prior to DM-1 flying.

you are actually wrong. Well not really, actually right. "It's complicated".
Gestenmaier and Lueders were referring to the thruster failure in real CRS mission CRS-2 on her approach to ISS (the failure resulted in 1 day delay to the arrival to the ISS). As expected it was over dramatized in all major newslets so it's not that difficult to find details. So yes, the failure was real. It happened in 2013.
If I recall the issue was identified in the frozen "propellant" slag. SpaceX has solved the risk by the monitoring temperature levels of the propellant plumbing. Absence of the further issues would suppose the problem being solved. Khhm. Apparently according to NASA it isn't.

Just like it is the case with the cracks, COPV, "chilling", parachutes  etc. NASA likes to return and to iterate obsolete problems add nausea even if their questions don't really relate to the new devices.(as it is the case with cracks, COPV and even parachutes).

[Coastal Ron]

This is a prime example of how SpaceX has been having trouble to satisfy NASA's changing wishes. When SpaceX was awarded the CCtCAP contract NASA retained the right to change requirements, pretty much at will.

NASA got a REALLY good deal with CCtCAP: Firmed Fixed Price yet able to change requirements late into the game.

My background is in the defense world, but I'm sure it's the same as NASA since we had similar issues with branches of the military.

Usually though changes are covered with an Engineering Change Order (ECO), which can provide schedule and cost changes. It would be interesting to see how these NASA changes were communicated and interpreted by the NASA contracting office and the SpaceX program office.

And sure, the front line NASA and SpaceX personnel are going to be heads down trying to get Commercial Crew operational as quickly and safely as possible, but when it comes to money that is usually a discussion that is held by management on both sides - and usually something that neither side wants to make public.

And some of those requirement changes have come to bite SpaceX pretty hard. One famous example is the switch to water landings which indirectly has resulted into the current extended (and costly) parachute testing campaign.

Another one is presented here: change the angle of the seats. And thus making it impossible to fly seven folks. Which in turn makes the vehicle unattractive for purely tourist flights.

The thermal "issues" that DM-1 had was also the result from a NASA requirement change.

Maybe everyone had a false sense of hope after the successful Commercial Cargo program? That Public/Private Partnerships would truly result in a better outcome, even when human-rated vehicles were involved?

All I can say is that this should be a cautionary tale for the contractors bidding on human-rated systems for the Artemis program...

[SWGlassPit]

All I can say is that this should be a cautionary tale for the contractors bidding on human-rated systems for the Artemis program...

In particular, the HLS procurement -- firm fixed price for a new human lunar lander?  I expect that to go well...

[dondar]

Could it just be the analysis showed good margins for uncrewed flights, but a more refined one, based on a longer empirical flight history of almost 20 missions which was not available before, done ex-profeso for the crewed variant, showed such problems? No need to invoke NASA's "undecisiveness", IMO. Also, it's unclear why you mention "issues" (between quotes) when we're talking about attitude control engines physically breaking on orbit.

That didn't actually happen on any of the CRS missions. Scenario was developed as a result of extreme limits testing.

You people should realize that, besides on-orbit performance of the Draco's, SpaceX is also required to do a ship-load of testing on the thruster quads. Everything from nominal situations to extreme situations. Some of the results of the extreme situations worried NASA because it could potentially lead to a thruster coming apart. Which is what was referred to prior to DM-1 flying.

Sure, that's fine and, honestly, expectable.

We all know too that you don't need to *actually* have an "engine-breaking-apart-on-orbit" type of situation in order to do something about it, especially moving onward to crewed flights with the same type of engines but different, probably more demanding flight profiles.

I'm sure you'd agree margins are everything, and from the gathered information thus far it doesn't seem it was an "issue", but rather an *issue*. DM-1 was waived just because it could afford to avoid the thermally-worrying scenarios, as it was stated also in that briefing - not because the situation was deemed to be too academic to actually matter.

In a previous post you seem to imply those new margins are too conservative and NASA is hairsplitting - which cannot be excluded. But it's also true that from your post we'd just have to believe in "some folks at SpaceX"'s judgement (i.e. part of the interested party... what about "the other folks at SpaceX", or "folks at NASA"? how many are there of each subgroup? whose opinion is more valid/who did the most in-depth analysis?).

It's obvious NASA changed its requirements when D2 was deep into its development process, or otherwise it wouldn't have impacted its timeline. Whether the change was arbitrary, exaggerated, imposed with ill intention... is the real question. A scenario in which good margins were seen for uncrewed flights, but more refined analyses based on a longer empirical flight history of ~20 missions not available before, done ex-profeso for the crewed variant, showed problems - is more plausible IMO.

the change was during building process. in 2017. They have tested Crew Dragon in the conditions in which Dragon 1 failed. Dracos being of exactly the same design invariably failed and NASA started hair splitting. I repeat that the the initial failure was in 2013 and relevant Dragon 2 design features were reviewed and approved after a number of times. The test which broke thruster was made in the conditions beyond initial design requirements. AS it is mentioned by  woodz

[eeergo]

We all know too that you don't need to *actually* have an "engine-breaking-apart-on-orbit" type of situation in order to do something about it, especially moving onward to crewed flights with the same type of engines but different, probably more demanding flight profiles.

I'm sure you'd agree margins are everything, and from the gathered information thus far it doesn't seem it was an "issue", but rather an *issue*. DM-1 was waived just because it could afford to avoid the thermally-worrying scenarios, as it was stated also in that briefing - not because the situation was deemed to be too academic to actually matter.

In a previous post you seem to imply those new margins are too conservative and NASA is hairsplitting - which cannot be excluded. But it's also true that from your post we'd just have to believe in "some folks at SpaceX"'s judgement (i.e. part of the interested party... what about "the other folks at SpaceX", or "folks at NASA"? how many are there of each subgroup? whose opinion is more valid/who did the most in-depth analysis?).

It's obvious NASA changed its requirements when D2 was deep into its development process, or otherwise it wouldn't have impacted its timeline. Whether the change was arbitrary, exaggerated, imposed with ill intention... is the real question. A scenario in which good margins were seen for uncrewed flights, but more refined analyses based on a longer empirical flight history of ~20 missions not available before, done ex-profeso for the crewed variant, showed problems - is more plausible IMO.

the change was during building process. in 2017. They have tested Crew Dragon in the conditions in which Dragon 1 failed. Dracos being of exactly the same design invariably failed and NASA started hair splitting. I repeat that the the initial failure was in 2013 and relevant Dragon 2 design features were reviewed and approved after a number of times. The test which broke thruster was made in the conditions beyond initial design requirements. AS it is mentioned by  woodz

I know Woods is an ESA insider with many contacts also elsewhere -many times correct, sometimes not entirely-, but even he is not providing such a level of certainty and detail.

I cannot gather from your posting history - do you know for a fact the redesign of the Dracos required by NASA is based entirely on the 2013 issues, and furthermore it was not acted upon by NASA until 2017?