4 ms·

Boeing's market analysis said that the market could barely support one super-jumbo, let alone two, so they opted for the much cheaper 747 upgrade and we got the

Boeing's market analysis said that the market could barely support one super-jumbo, let alone two, so they opted for the much cheaper 747 upgrade and we got the 747-8 (which is also headed for extinction). I heard an analyst say that you have to carry a lot of fuel to carry a lot of fuel. The optimal size from an efficiency perspective is the much smaller 737 -- the more you deviate from that, the larger the efficiency penalty.

froindt 9y ago
>I heard an analyst say that you have to carry a lot of fuel to carry a lot of fuel. Yep! Aerospace has been on the leading edge of manufacturing methods for many years because of it. Even worse is having a heavy airplane at the start of the flight (the weight is always there). In school we were talking about manufacturing aerospace parts, and the joke is that you always take a nice chunk of aluminum and machine away 85% of the volume. GE has been doing lots of work with metal additive manufacturing, in some cases increasing performance while also decreasing cost. It allows geometries which are otherwise impossible with traditional manufacturing methods. Metal AM is also hella expensive. You won't see tons of metal AM parts on consumer cars anytime soon, as the metal powders and machines are expensive, and production rates are often slow in comparison to traditional manufacturing methods. For reference, my professor passed around a part which weighed around 2 pounds and fit in your hand. The all-in cost to get that printed in steel was around $5,000, and around $8,000 for titanium. https://www.ge.com/reports/epiphany-disruption-ge-additive-chief-explains-3d-printing-will-upend-manufacturing/ https://www.ge.com/reports/epiphany-disruption-ge-additive-c...
- louithethrid 9y ago
  Never understoood why they would not use the fuel as stability element- basically- the elments carrying the fuelweight, are made from a carbonsponge that holds frozzen fuel..
  - briandear 9y ago
    The complexity and logistical difficulty of what you describe is mind blowing not to mention adding non trivial safety concerns.
api_or_ipa 9y ago
> I heard an analyst say that you have to carry a lot of fuel to carry a lot of fuel. In rocket applications, this is known as Tsiolkovsky rocket equation [0]. 0 https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

froindt 9y ago

>I heard an analyst say that you have to carry a lot of fuel to carry a lot of fuel. Yep! Aerospace has been on the leading edge of manufacturing methods for many years because of it. Even worse is having a heavy airplane at the start of the flight (the weight is always there). In school we were talking about manufacturing aerospace parts, and the joke is that you always take a nice chunk of aluminum and machine away 85% of the volume. GE has been doing lots of work with metal additive manufacturing, in some cases increasing performance while also decreasing cost. It allows geometries which are otherwise impossible with traditional manufacturing methods. Metal AM is also hella expensive. You won't see tons of metal AM parts on consumer cars anytime soon, as the metal powders and machines are expensive, and production rates are often slow in comparison to traditional manufacturing methods. For reference, my professor passed around a part which weighed around 2 pounds and fit in your hand. The all-in cost to get that printed in steel was around $5,000, and around $8,000 for titanium. https://www.ge.com/reports/epiphany-disruption-ge-additive-chief-explains-3d-printing-will-upend-manufacturing/ https://www.ge.com/reports/epiphany-disruption-ge-additive-c...

louithethrid 9y ago
Never understoood why they would not use the fuel as stability element- basically- the elments carrying the fuelweight, are made from a carbonsponge that holds frozzen fuel..
- briandear 9y ago
  The complexity and logistical difficulty of what you describe is mind blowing not to mention adding non trivial safety concerns.

api_or_ipa 9y ago

> I heard an analyst say that you have to carry a lot of fuel to carry a lot of fuel. In rocket applications, this is known as Tsiolkovsky rocket equation [0]. 0 https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation