4 ms·

> What would that have cost? No idea. Do you? Genuinely interested, particularly regarding methodology. Not intending at all to be insulting.

WalterBright 4y ago
Look at SpaceX's rockets. They cut costs by what, 10x? over NASA's? A part of that was not trying to build 100% the first time, but to accept failure and iterate. My dad told me that Pratt&Whitney made the most reliable aircraft engines by putting them on a test stand and running them at full power until they broke. The engineers would figure out why it failed, redesign the part, stick that on the engine, and continued running them at full power. It's straightforward, inexpensive, and it works.
- noizejoy 4y ago
  Could it be, that iterating fast through additional failures may be harder to finance with public funds, because the general public hasn’t caught up with the recognition of failing early and often being a good thing?
  - WalterBright 4y ago
    Government programs fail all the time, and they just get a budget increase. Hire the salesmen who accomplish that.
    - noizejoy 4y ago
      lol - you do have a point there!
- dekhn 4y ago
  Surely you can see that the P&W approach is only going to discover a subset of problems that will affect the engine in the wild. For example, engines don't run at 100% power during the full flight, and they go through heating and cooling cycles. It also doesn't address failure modes due to manufacturing problems specific to a single engine- for example, turbine blades are manufactured with serial numbers and you can go back and get detailed process and QA for that specific item to understand what went wrong and why it failed and how to not do that during manufacture again. Then there's all sorts of complex failures that aren't addressed by single engines: " Prior to this crash, the probability of a simultaneous failure of all three hydraulic systems was considered as low as one in a billion. However, statistical models did not account for the position of the number-two engine, mounted at the tail close to hydraulic lines, nor the results of fragments released in many directions. Since then, aircraft engine designs have focused on keeping shrapnel from puncturing the cowling or ductwork, increasingly utilizing high-strength composite materials to achieve penetration resistance while keeping the weight low" (I'm not disrespecting P&W- I'm sure they have more tests than just "100% power until it breaks, fix and repeat")
  - WalterBright 4y ago
    > Surely you can see that the P&W approach is only going to discover a subset of problems that will affect the engine in the wild. Keep in mind that my former job was designing gearbox parts for the Boeing 757. This included doing the math, and devising a test plan. I've spent a lot of time on "what could go wrong" scenarios in the real world. Also, when I prepare slides for a coding presentation, the implementation code for a concept gets trimmed way down to what will fit on a slide.

WalterBright 4y ago

Look at SpaceX's rockets. They cut costs by what, 10x? over NASA's? A part of that was not trying to build 100% the first time, but to accept failure and iterate. My dad told me that Pratt&Whitney made the most reliable aircraft engines by putting them on a test stand and running them at full power until they broke. The engineers would figure out why it failed, redesign the part, stick that on the engine, and continued running them at full power. It's straightforward, inexpensive, and it works.

noizejoy 4y ago
Could it be, that iterating fast through additional failures may be harder to finance with public funds, because the general public hasn’t caught up with the recognition of failing early and often being a good thing?
- WalterBright 4y ago
  Government programs fail all the time, and they just get a budget increase. Hire the salesmen who accomplish that.
  - noizejoy 4y ago
    lol - you do have a point there!
dekhn 4y ago
Surely you can see that the P&W approach is only going to discover a subset of problems that will affect the engine in the wild. For example, engines don't run at 100% power during the full flight, and they go through heating and cooling cycles. It also doesn't address failure modes due to manufacturing problems specific to a single engine- for example, turbine blades are manufactured with serial numbers and you can go back and get detailed process and QA for that specific item to understand what went wrong and why it failed and how to not do that during manufacture again. Then there's all sorts of complex failures that aren't addressed by single engines: " Prior to this crash, the probability of a simultaneous failure of all three hydraulic systems was considered as low as one in a billion. However, statistical models did not account for the position of the number-two engine, mounted at the tail close to hydraulic lines, nor the results of fragments released in many directions. Since then, aircraft engine designs have focused on keeping shrapnel from puncturing the cowling or ductwork, increasingly utilizing high-strength composite materials to achieve penetration resistance while keeping the weight low" (I'm not disrespecting P&W- I'm sure they have more tests than just "100% power until it breaks, fix and repeat")
- WalterBright 4y ago
  > Surely you can see that the P&W approach is only going to discover a subset of problems that will affect the engine in the wild. Keep in mind that my former job was designing gearbox parts for the Boeing 757. This included doing the math, and devising a test plan. I've spent a lot of time on "what could go wrong" scenarios in the real world. Also, when I prepare slides for a coding presentation, the implementation code for a concept gets trimmed way down to what will fit on a slide.