SpaceX Starship : Texas Prototype(s) Thread 23 : Discussion

[Barry Brisco]

https://twitter.com/elonmusk/status/1555628746719211520?s=10&t=CAyGDQvicHewx-S3flAlTA

Elon posted: “ Hustling to get Starship Booster 7 back to pad to test outer ring of 20 engines”

[Jeff Lerner]

Any idea if this upcoming outer ring test will be a spin test or a SF.?

[oiorionsbelt]

Bottom line: Starship development will be long and arduous. I suspect nobody will fly on Starship for 10 years, if ever.

Less than one month since the anomaly and comments like this, booster 7 rolls out to the pad again.

[alugobi]

I wonder if they installed only those 20.

[darkenfast]

Just some fun trivia:

1. If SpaceX runs all 20 outer Raptor 2s at full power, I believe it will be the most powerful static-fire ever conducted, at just over 10 million pounds of thrust. Previous record was the last of the three 260-inch solids that Aerojet tested in Florida in the mid-60s. That burn did not make it to full duration, but was about 5.88 million pounds.

2. B7's test will exceed the thrust of the most powerful rocket ever successfully flown (Saturn 5), and roughly tie the most powerful rocket to unsuccessfully fly (Soviet N1 got off the pad four times, but never made it through first stage flight).

3. The thrust of the 20 Raptor 2s exceeds the full liftoff thrust of the SLS currently awaiting it's first flight at KSC.

We now return you to your regular programming. How 'bout those chopsticks?

[2megs]

We now return you to your regular programming. How 'bout those chopsticks?

The hydraulic failure was unsettling, because of the consequences of that happening at a different time. The whole system relies on the chopsticks working correctly, on demand, at the instant they're needed, or else a booster explodes near the launch pad. (And that's the least-bad outcome; eventually there'll be humans on a returning upper stage.)

Given that stage 0 doesn't have mass constraints, I expect they'll add in more redundancy in the eventual final design -- no single points of failure allowed.

[schuttle89]

We now return you to your regular programming. How 'bout those chopsticks?

The hydraulic failure was unsettling, because of the consequences of that happening at a different time. The whole system relies on the chopsticks working correctly, on demand, at the instant they're needed, or else a booster explodes near the launch pad. (And that's the least-bad outcome; eventually there'll be humans on a returning upper stage.)

Given that stage 0 doesn't have mass constraints, I expect they'll add in more redundancy in the eventual final design -- no single points of failure allowed.

My first reaction to the hydraulic failure was "better now than later"
Best to find all the faults in the system during testing if at all possible

[ulm_atms]

Yea, I think they are testing at the edge of luck at this point.  Hydraulic hoses will absolutely blow out when you least expect them especially at the crimped ends.  Considering this system isn't that old and hasn't even see one launch yet(or landing)...I think they found a problem before it became a problem.

I sure hope the chopsticks are a fully redundant system in which if there is a blow out on one full set of hydraulics, the backup set can get the system to a stable resting state.  If not...they are playing with fire...that's for sure.

Does anyone know if the chopsticks have a fully redundant hydraulic drive system?

[warp99]

Yea, I think they are testing at the edge of luck at this point.  Hydraulic hoses will absolutely blow out when you least expect them especially at the crimped ends.  Considering this system isn't that old and hasn't even see one launch yet(or landing)...I think they found a problem before it became a problem.

I sure hope the chopsticks are a fully redundant system in which if there is a blow out on one full set of hydraulics, the backup set can get the system to a stable resting state.  If not...they are playing with fire...that's for sure.

Does anyone know if the chopsticks have a fully redundant hydraulic drive system?

Each chopstick arm is slewed with a single double acting hydraulic cylinder so there is no redundancy there.  Same for the arms that swing down to clamp the booster.

[Oersted]

So, they will just lift the booster with the crane instead, it seems.... right?

[Lee Jay]

Ick.

You can't imagine what a horrible gunky mess a hydraulic leak leaves.  The fluid will absorb every spec of dust in the air and then dry on the surface.

The only way to clean it is by hand and that one looked like about an acre of material got covered.

Time to get a couple of truck loads of rags and degreaser and roll up your sleeves.

[jackvancouver]

Guessing powerwashing won't get it off and might be worse as it spreads the oil even more?

[Lee Jay]

Guessing powerwashing won't get it off and might be worse as it spreads the oil even more?

It's nearly impossible to remove it all that way, but it will remove some of it.  But, yes, that just washes it into the ground and water.  Double-ick.

[Khadgars]

Doesn't the hydrolic failure mean we'll need a re-design of the chopsticks?  Any mission other than Starlink launches, Starship will require multiple launches for refueling in quick succession.  Such a failure could have big impacts on the mission.

[Lee Jay]

Doesn't the hydrolic failure mean we'll need a re-design of the chopsticks?  Any mission other than Starlink launches, Starship will require multiple launches for refueling in quick succession.  Such a failure could have big impacts on the mission.

Not of the chopsticks, I don't think.  Possibly of the hydraulic supply for them.

Is there evidence of what actually blew?  It didn't look like an actuator to me, but of a hose somewhere in the system.

[DanClemmensen]

Doesn't the hydrolic failure mean we'll need a re-design of the chopsticks?  Any mission other than Starlink launches, Starship will require multiple launches for refueling in quick succession.  Such a failure could have big impacts on the mission.

It's a prototype. They may refine the design, or they may find a construction flaw. If a more robust design is too expensive, they may choose to build a second tower to bring the reliability up high enough via 1+1 redundancy, which is more or less the brute-force approach to increasing system reliability. We won't know until they finish analyzing the failure.

[ulm_atms]

Yea, I think they are testing at the edge of luck at this point.  Hydraulic hoses will absolutely blow out when you least expect them especially at the crimped ends.  Considering this system isn't that old and hasn't even see one launch yet(or landing)...I think they found a problem before it became a problem.

I sure hope the chopsticks are a fully redundant system in which if there is a blow out on one full set of hydraulics, the backup set can get the system to a stable resting state.  If not...they are playing with fire...that's for sure.

Does anyone know if the chopsticks have a fully redundant hydraulic drive system?

Each chopstick arm is slewed with a single double acting hydraulic cylinder so there is no redundancy there.  Same for the arms that swing down to clamp the booster.

If that is the case, IMO, time for a redesign as that happening during a catch will be a complete and total disaster for the whole "Stage 0".  If there was a stage coming in and hydraulic fluid spraying all over the place, it possible for 1.  the Raptor to ignite the spray (hydrocarbon based hydraulic fluid isn't that easy to ignite but it is MUCH easier in aerosol form) and 2.  there is now nothing to catch the stage as it runs out of fuel and crashes on the mount.

For their SS/SH goals...the chopsticks have got to have more redundancy IMO.

EDIT:  Do we know what hydraulic fluid they are using?

[MichaelBlackbourn]

This is like the landing leg that didn’t fully latch. They’ll fix it, beef it up, whatever until it’s working well.

[alugobi]

I wonder if, during all the work involving welding that's been going on since B7 went back to the barn, perhaps a  hose got a burn that didn't show until pressurized last night.

[Redclaws]

This is like the landing leg that didn’t fully latch. They’ll fix it, beef it up, whatever until it’s working well.

I glanced around and couldn’t find images, etc, of the hydraulic leak.  Does anyone have a good link?  Just curious to see it, it’s pretty clearly fixable.