Commercial Crew Transportation Capability (CCtCap) SpaceX and Boeing Developments

[ecarfan]

ars Technica: NASA finds more issues with Boeing’s Starliner, but crew launch set for June 1

It sounds minor, but a potential issue:

As engineers assessed the ramifications of the helium leak, they stumbled upon a design flaw that, in rare cases, could prevent the spacecraft from conducting a braking maneuver to re-enter the atmosphere and head for landing at the end of the mission. Boeing designed the spacecraft to perform the deorbit burn three different ways, either with two or four of the ship's more powerful maneuvering engines or with eight of the smaller reaction control system jets.
Under the wrong set of circumstances, helium manifold failures on two adjacent doghouse propulsion pods could jeopardize Starliner's ability to execute the deorbit burn.

So they came up with a fix:

In a matter of weeks, engineers devised a workaround. This new deorbit burn method would require just four reaction control system thrusters. Wilmore and Williams, back at their home base in Houston, tested the new backup mode in a Starliner simulator, according to Stich.

 

[scaesare]

Latest... it appears they found another unlikely failure mode, but apparently have a work around and are still targeting 6/1....

NASA finds more issues with Boeing’s Starliner, but crew launch set for June 1

Fixing the helium leak would delay Starliner crew test flight for months.

arstechnica.com

 

[EVCollies]

Latest... it appears they found another unlikely failure mode, but apparently have a work around and are still targeting 6/1....

NASA finds more issues with Boeing’s Starliner, but crew launch set for June 1

Fixing the helium leak would delay Starliner crew test flight for months.

arstechnica.com

So this was found during analysis of the helium leak:
"We found a design vulnerability... in the prop [propulsion] system as we analyzed this particular helium leak, where for certain failure cases that are very remote, we didn't have the capability to execute the deorbit burn with redundancy," Stich said in a press conference Friday.

As Boeing uses the design and study much fly little approach whereas SpaceX uses the fly much and reiterate approach. Would SpaceX have found a 0.77% chance of failure with the deorbit burn with redundancy?

I'm not supporting Boeing's approach, just asking an honest question from not a rocket engineer...

 

[HVM]

EVCollies, Boeing did not do integrated system test and missed problem with timing error with Atlas->Starliner. SpaceX does integrated testing. And if you look here, Boeing is really have mastered the "fly little" approach:

 

[mongo]

As Boeing uses the design and study much fly little approach whereas SpaceX uses the fly much and reiterate approach. Would SpaceX have found a 0.77% chance of failure with the deorbit burn with redundancy?

Sure. The issue is a dual failure of adjacent thusters. The odds of that occurring are low, but the failure mode is definitely able to be discovered in the planning stages.

 

[bxr140]

As Boeing uses the design and study much fly little approach whereas SpaceX uses the fly much and reiterate approach. Would SpaceX have found a 0.77% chance of failure with the deorbit burn with redundancy?

Pretty unlikely SX would catch it but certainly non-zero.

At the risk of stating the obvious the thing about testing [regardless the design philosophy] is that if you’re not purposely testing for a thing, the probability that you find it ‘by accident’ is pretty much the same as the probability of it occurring in flight.

 

[spacerfc]

So this was found during analysis of the helium leak:
"We found a design vulnerability... in the prop [propulsion] system as we analyzed this particular helium leak, where for certain failure cases that are very remote, we didn't have the capability to execute the deorbit burn with redundancy," Stich said in a press conference Friday.

As Boeing uses the design and study much fly little approach whereas SpaceX uses the fly much and reiterate approach. Would SpaceX have found a 0.77% chance of failure with the deorbit burn with redundancy?

I'm not supporting Boeing's approach, just asking an honest question from not a rocket engineer...

Boeing didn't find the design vulnerability from paper design and study, if they did it would have been found years ago, not a few days before a manned flight. They found the design vulnerability when analyzing an actual issue on actual flight hardware, they could have found this earlier if they have played more with real hardware like SpaceX.

When you encounter an issue, you don't just fix it and forget about it, you think about whether similar failure mode would occur in other part of the system, this is engineering 101, not limited to aerospace.

 

[Grendal]

 

[JB47394]

Scrubbed.

United Launch Alliance has called an official scrub while engineers work to understand why a Ground Launch Sequencer called an automatic hold 3 minutes and 50 seconds before liftoff.

 

[RubberToe]

Anyone else struck by the 1960s throwback guy talking during the countdown around the 4 minute mark? Dude was talking it up like it was the equivalent of the moon landing. Someone needs to remind those kooks that they need to focus on not getting anyone killed before they start spraying champagne on each other. Whole thing came across like a bunch of amateurs compared to a SpaceX telecast.

RT

 

[JB47394]

Anyone else struck by the 1960s throwback guy talking during the countdown around the 4 minute mark? Dude was talking it up like it was the equivalent of the moon landing. Someone needs to remind those kooks that they need to focus on not getting anyone killed before they start spraying champagne on each other. Whole thing came across like a bunch of amateurs compared to a SpaceX telecast.

That was from "Butch" Wilmore, one of the astronauts. It was exactly the sort of motivational speech you might hear from a 61 year old Navy Captain who hails from Murfreesboro, Tennessee. So it wasn't some media hack getting carried away. That guy is gung ho, ready to go, and God Bless America.

 

[EVCollies]

Scrubbed.

Ugghhh. SpaceX needs some competition. We need multiple companies to make this space race a real race!

 

[ecarfan]

Stephen Clark in ars Technica: Boeing’s Starliner test flight scrubbed again after hold in final countdown

One of the three launch computers didn’t boot up properly.

The computers are located at the launch pad inside a shelter near the base of the Atlas V rocket at Cape Canaveral Space Force Station. All three computers must be fully functioning in the final phase of the countdown to ensure triple redundancy. At the moment of liftoff, these computers control things like retracting umbilical lines and releasing bolts holding the rocket to its mobile launch platform. Two of the computers activated as the final countdown sequence began at T-minus 4 minutes. A single card in the third computer took about six more seconds to come online, although it did boot up eventually, Bruno said. "Two came up normally and the third one came up, but it was slow to come up, and that tripped a red line," he said.

 

[Cosmacelf]

Stephen Clark in ars Technica: Boeing’s Starliner test flight scrubbed again after hold in final countdown

One of the three launch computers didn’t boot up properly.

OMG. Wanna bet they use hard drives in those things. And windows XP. And god knows what else such that it has an unreliable boot sequence? And why in gods name doesn’t it boot like hours before liftoff so that they can be in a quiescent state?

 

[Max Spaghetti]

That's unusual. Usually Boeing airliners boot up pretty well. Unlike Airbuses - often have to turn them off and turn them on again when booting them up in the morning...

 

[scaesare]

OMG. Wanna bet they use hard drives in those things. And windows XP. And god knows what else such that it has an unreliable boot sequence? And why in gods name doesn’t it boot like hours before liftoff so that they can be in a quiescent state?

Probably was stuck on the BIOS self-test because the CMOS real-time clock battery was low.

 

[Cosmacelf]

OMG. Wanna bet they use hard drives in those things. And windows XP. And god knows what else such that it has an unreliable boot sequence? And why in gods name doesn’t it boot like hours before liftoff so that they can be in a quiescent state?

“You can imagine a large rack that is a big computer where the functions of the computer as a controller are broken up separately into individual cards or printed wire circuit boards with their logic devices," said Tory Bruno, ULA's president and CEO. "They’re all standalone, but together it’s an integrated controller."

Actually, it sounds worse. Sounds like a VME rack (50 year old tech) with individual PCBs doing like one function each. So now you have probably 30 cards times three that all have to not only operate, but operate within tight time tolerances of each. In other words, lots and lots of capacity for malfunctions. Any modern computer would have the horsepower to drive whatever the ground system does (commanding umbilical cords to detach, oooh, sounds difficult!), and it wouldn’t have 30 PCBs with their dozens of parts each doing it.

 

[scaesare]

“You can imagine a large rack that is a big computer where the functions of the computer as a controller are broken up separately into individual cards or printed wire circuit boards with their logic devices," said Tory Bruno, ULA's president and CEO. "They’re all standalone, but together it’s an integrated controller."

Actually, it sounds worse. Sounds like a VME rack (50 year old tech) with individual PCBs doing like one function each. So now you have probably 30 cards times three that all have to not only operate, but operate within tight time tolerances of each. In other words, lots and lots of capacity for malfunctions. Any modern computer would have the horsepower to drive whatever the ground system does (commanding umbilical cords to detach, oooh, sounds difficult!), and it wouldn’t have 30 PCBs with their dozens of parts each doing it.

But it's much harder to wire wrap a small PCB with lots of components on it...

Besides ferrite core memory needs some room.

 

[ICUDoc]

Besides ferrite core memory needs some room.

 

[Grendal]