4 ms·

i'm in no way qualified to give any praise/criticism, it just caught my attention (from the linked post on their cockpit/fuselage bonding https://blog.boomsupe

by trhway 7y ago

i'm in no way qualified to give any praise/criticism, it just caught my attention (from the linked post on their cockpit/fuselage bonding https://blog.boomsupersonic.com/20-hour-bonding-event-speeds-xb-1-toward-first-flight-b50a682d924 https://blog.boomsupersonic.com/20-hour-bonding-event-speeds... ) "It’s the following morning and bonding appears to be successful, but it’s essential to confirm that the bond lines are shaped correctly or “filleted.” A member of the engineering team, who is certified in the process, begins non-destructive tap testing to audibly listen for voids such as air bubbles within the bond. With several decades experience, he knows what to listen for. Using specialized tools, he taps all bond lines and listens for different and unusual noises. He confirms that bonding is a success." In general it seems that their main fabrication cost is labor, and it would probably be very hard to scale for production. I wonder why wouldn't they choose titanium - the price of material doesn't seem to matter here, and while it is hard to work with than say steel, i'd think it is still more mass production friendly than carbon fiber.

Justin_K 7y ago
Yea, not very scientific. Seems like ultrasonic tests would be good here. I think they do something similar to check welds on ships.
- nickff 7y ago
  Ultrasound inspection is very common for multi-layer composite construction. There are large machines which transmit the ultrasound through a water jet, for use in mapping the characteristics of curved surfaces. This water jet ultrasound non-destructive testing (NDT) is used in aerospace for carbon laminates. That said, 'tapping' is an acoustic inspection technique, and can get good results. I am not sure why they selected the manual option, but they probably have a reason.
  - jandrese 7y ago
    They're probably having the guy hit it with a mallet and listen for voids because they're a Mickey Mouse operation by aerospace standards. Plus this is a model so if something does go catastrophically wrong it at least won't kill anybody, probably.
    - NickNameNick 7y ago
      It's a demonstrator, not a model - It has space for 2 test pilots.
  - vonseel 7y ago
    They show some portable ultrasonic pictures on the build link someone posted above[1] (reposted here for clarity). [1] https://boomsupersonic.com/xb-1/build https://boomsupersonic.com/xb-1/build
- trhway 7y ago
  yes, ultrasound on ship welds, and if i remember correctly - on some forged and other way fabricated/processed parts too. X-ray on even more important stuff like nuclear plant welds ("China Syndrome" has nice depiction around it).
  - TheSpiceIsLife 7y ago
    We do mostly structural steel at work. Some jobs require all welds to be inspected using ultrasound and magnetic particle tests, so we weld to that standard pretty much all the time on every job.
formercoder 7y ago
Reminds me of the Apollo parachute packers, highly manual job with specialized human-only techniques.
starpilot 7y ago
Carbon is much lighter than titanium for similar strength. Found a cool table for this, sort by "specific strength": https://en.wikipedia.org/wiki/Specific_strength#Examples https://en.wikipedia.org/wiki/Specific_strength#Examples Originally, the F-22 was going to be built mainly of carbon fiber, this was changed to titanium to reduce cost. This was in the 1980s... CF is MUCH cheaper today and almost commodity material used extensively in civilian aircraft.
- Scramblejams 7y ago
  And it would probably interest OP to know that it's not just basic strength-versus-mass where carbon shines. With metallics, you have that strength in every direction. But most parts only need to be strong in a limited number of directions. With carbon, you can tailor the part to provide strength only in the directions needed, which means you're using less material. More weight savings on top of what you already gained* by switching to carbon in the first place. [*] It ain't all sunshine and roses. Sometimes it just doesn't work out. Substantial strength reductions due to heat and moisture absorption are real. Other factors exist that'll ruin your weight savings too. A former boss of mine designed a carbon nacelle inlet lip for a popular airliner, but it was a short haul aircraft, which means lots of trips, which means lots of abuse from careless ground handlers. After accounting for that, it weighed as much as his reference aluminum design. The nacelle went into production with aluminum inlet lips.
deleted 7y ago
[deleted]
Scramblejams 7y ago
One issue with Ti: Tooling costs, particularly for manufacturing skins. Tooling for shaping metallic skins to the required dimensions is fantastically expensive, which can be prohibitive for prototypes. Carbon fiber can be shaped much more inexpensively. BTW, "scaling for production" in aerospace doesn't mean a tremendous amount of units, most of the time. Lotsa carbon aircraft running around have been built in a manner not too differently from this one. So those labor costs tend to work out okay. For a while I did repair design and analysis for engine nacelles made out of carbon fiber. These were new parts, right off the production line, with various flaws that commonly happen when you make an airplane out of cloth and glue. I was amazed by how much manual labor can go into declaring a particular part flight-ready, and the financials still penciled out, apparently. We must have been well into the six figures on one particular nacelle in post-fabrication engineering analysis work, just to show that the flaws had been repaired adequately for entry into service.
elil17 7y ago
You can scale composite manufacturing significantly (as Boeing and Airbus have) using layup robots.

by trhway 7y ago

Justin_K 7y ago

Yea, not very scientific. Seems like ultrasonic tests would be good here. I think they do something similar to check welds on ships.

nickff 7y ago
Ultrasound inspection is very common for multi-layer composite construction. There are large machines which transmit the ultrasound through a water jet, for use in mapping the characteristics of curved surfaces. This water jet ultrasound non-destructive testing (NDT) is used in aerospace for carbon laminates. That said, 'tapping' is an acoustic inspection technique, and can get good results. I am not sure why they selected the manual option, but they probably have a reason.
- jandrese 7y ago
  They're probably having the guy hit it with a mallet and listen for voids because they're a Mickey Mouse operation by aerospace standards. Plus this is a model so if something does go catastrophically wrong it at least won't kill anybody, probably.
  - NickNameNick 7y ago
    It's a demonstrator, not a model - It has space for 2 test pilots.
- vonseel 7y ago
  They show some portable ultrasonic pictures on the build link someone posted above[1] (reposted here for clarity). [1] https://boomsupersonic.com/xb-1/build https://boomsupersonic.com/xb-1/build
trhway 7y ago
yes, ultrasound on ship welds, and if i remember correctly - on some forged and other way fabricated/processed parts too. X-ray on even more important stuff like nuclear plant welds ("China Syndrome" has nice depiction around it).
- TheSpiceIsLife 7y ago
  We do mostly structural steel at work. Some jobs require all welds to be inspected using ultrasound and magnetic particle tests, so we weld to that standard pretty much all the time on every job.

formercoder 7y ago

Reminds me of the Apollo parachute packers, highly manual job with specialized human-only techniques.

starpilot 7y ago

Carbon is much lighter than titanium for similar strength. Found a cool table for this, sort by "specific strength": https://en.wikipedia.org/wiki/Specific_strength#Examples https://en.wikipedia.org/wiki/Specific_strength#Examples Originally, the F-22 was going to be built mainly of carbon fiber, this was changed to titanium to reduce cost. This was in the 1980s... CF is MUCH cheaper today and almost commodity material used extensively in civilian aircraft.

Scramblejams 7y ago
And it would probably interest OP to know that it's not just basic strength-versus-mass where carbon shines. With metallics, you have that strength in every direction. But most parts only need to be strong in a limited number of directions. With carbon, you can tailor the part to provide strength only in the directions needed, which means you're using less material. More weight savings on top of what you already gained* by switching to carbon in the first place. [*] It ain't all sunshine and roses. Sometimes it just doesn't work out. Substantial strength reductions due to heat and moisture absorption are real. Other factors exist that'll ruin your weight savings too. A former boss of mine designed a carbon nacelle inlet lip for a popular airliner, but it was a short haul aircraft, which means lots of trips, which means lots of abuse from careless ground handlers. After accounting for that, it weighed as much as his reference aluminum design. The nacelle went into production with aluminum inlet lips.

deleted 7y ago

[deleted]

Scramblejams 7y ago

One issue with Ti: Tooling costs, particularly for manufacturing skins. Tooling for shaping metallic skins to the required dimensions is fantastically expensive, which can be prohibitive for prototypes. Carbon fiber can be shaped much more inexpensively. BTW, "scaling for production" in aerospace doesn't mean a tremendous amount of units, most of the time. Lotsa carbon aircraft running around have been built in a manner not too differently from this one. So those labor costs tend to work out okay. For a while I did repair design and analysis for engine nacelles made out of carbon fiber. These were new parts, right off the production line, with various flaws that commonly happen when you make an airplane out of cloth and glue. I was amazed by how much manual labor can go into declaring a particular part flight-ready, and the financials still penciled out, apparently. We must have been well into the six figures on one particular nacelle in post-fabrication engineering analysis work, just to show that the flaws had been repaired adequately for entry into service.

elil17 7y ago

You can scale composite manufacturing significantly (as Boeing and Airbus have) using layup robots.