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> If it has to be a freight or logistics/materiel/fuel aircraft for the forces before general service, so be it. The challenge for that is economic: those use

> If it has to be a freight or logistics/materiel/fuel aircraft for the forces before general service, so be it. The challenge for that is economic: those use cases which are generally filled with adaptations of older generation aircraft at the moment probably don't pay back the R&D costs of the programme. Especially since a viable civil aircraft programme also involves worldwide line maintenance capability, a liquid aftermarket etc. Blended wings are are not a novel idea, and the major airframers have produced multiple concepts, often combined with theoretically much more efficient open rotor engines. The first attempt at a blended wing passenger aircraft was actually over 100 years ago (it was years ahead of its time... and it crashed on its first flight). But there are a lot of challenges other than the passenger experience characteristics people have already mentioned: instead of a simple tube, you now have a broad internal space that needs bracing in a way which doesn't add weight or negate space advantages, and novel designs greatly increased uncertainty in an industry whose safety record relies on predictability. And there's commercial conservatism in an industry whose customer base invests billions in new airframes on the expectation of commonality with existing airframes, phased replacements over predictable replacement cycles etc, and where the second entrance to the market sector might well be the most successful.... Military use involves completely different economics, but for related reasons the anticipated greater fuel efficiency is rarely a big deal for the military. Still, if the military write blank checks, that leaves scope for prototypes that airline executives might struggle to say no to

neltnerb 3y ago
> Military use involves completely different economics, but for related reasons the anticipated greater fuel efficiency is rarely a big deal for the military. I think this assumption is wrong, for airplanes. Higher fuel efficiency means longer range for the same amount of fuel, so it's an increase to range for the same weight carried (or an increase in weight carried to the same range, presumably). I think this is extremely important to the military.
- notahacker 3y ago
  It's not completely useless, but the US military's existing transport aircraft are not exactly pushing the boundaries of fuel consumption. A regular 777 freighter will get quite a bit further. Ultimately the military don't care about the cost, have many refuelling options, and are relying on much shorter range aircraft in other aspects of any conflict. Plus unlike other areas of aviation, if you solve a range problem with a bigger fuel tank, you don't get beaten to death by the bean counters. That's quite different from an airline, where a 20% saving in their largest expense against a 3% margin in a price competitive industry is game changing
  - fbdab103 3y ago
    I could imagine that it makes a real impact to a bomber. I have read that WW2 planes essentially were loaded to the maximum allowable weight between the fuel + ammunition. If you can cut down the fuel for same range, that allows for more ammo.
    - TeMPOraL 3y ago
      That was, arguably, the consequence of poor accuracy and low bomb yields - those planes had to drop a lot of ordnance for there to be a chance something actually lands on the intended target. I recall reading somewhere that a single modern guided bomb would achieve the effect that, during WW2, required 100 to 1000 bombers.
  - nradov 3y ago
    That has been true, but the US military is now pivoting to confront China in the Western Pacific theater. This means an increased emphasis on fuel efficiency to boost unrefueled range.
  - neltnerb 3y ago
    Why then? Stealth can't be that good. Cost seems impossibly unlikely at a development stage, but are they somehow lower cost to manufacture? Seems unlikely. I am welcome to alternatives, but the announcement included: “Blended wing body aircraft have the potential to significantly reduce fuel demand and increase global reach,” said Secretary of the Air Force Frank Kendall. “Moving forces and cargo quickly, efficiently, and over long distance is a critical capability to enable national security strategy.” It could be cleverly written to suggest it is about fuel efficiency and range, but that these straightforward and public explanations aren't the real reason. Totally possible, but what are they then? I know I don't know enough to second guess the public statements of the Secretary of the Air Force and the plain reading is that the first sentence is directly related to the second. But we all know that's not how it works. Both sentences are just always true, they aren't necessarily related. I don't know what else it would mean though.
psunavy03 3y ago
> Military use involves completely different economics, but for related reasons the anticipated greater fuel efficiency is rarely a big deal for the military. Utterly false. Greater fuel efficiency means greater range or less fuel needed for the same range and payload, and you'd better believe that is not nothing to military planners. I can say that because I used to be one. Every drop of fuel burned in theater in a war has to get there somehow. And until it's loaded on a jet and used, it's vulnerable to being targeted either in transit or at rest, and has to be protected. And pre-war, the more gas you're going to burn to accomplish a given task, the more facilities and infrastructure have to be in place at your potential bases to hold it, meaning more access agreements with foreign countries and/or construction contracts having to be paid for in those countries to build said facilities. And you have less ability to use smaller or more austere facilities, limiting your ability to disperse the force and complicate enemy targeting.

neltnerb 3y ago

> Military use involves completely different economics, but for related reasons the anticipated greater fuel efficiency is rarely a big deal for the military. I think this assumption is wrong, for airplanes. Higher fuel efficiency means longer range for the same amount of fuel, so it's an increase to range for the same weight carried (or an increase in weight carried to the same range, presumably). I think this is extremely important to the military.

notahacker 3y ago
It's not completely useless, but the US military's existing transport aircraft are not exactly pushing the boundaries of fuel consumption. A regular 777 freighter will get quite a bit further. Ultimately the military don't care about the cost, have many refuelling options, and are relying on much shorter range aircraft in other aspects of any conflict. Plus unlike other areas of aviation, if you solve a range problem with a bigger fuel tank, you don't get beaten to death by the bean counters. That's quite different from an airline, where a 20% saving in their largest expense against a 3% margin in a price competitive industry is game changing
- fbdab103 3y ago
  I could imagine that it makes a real impact to a bomber. I have read that WW2 planes essentially were loaded to the maximum allowable weight between the fuel + ammunition. If you can cut down the fuel for same range, that allows for more ammo.
  - TeMPOraL 3y ago
    That was, arguably, the consequence of poor accuracy and low bomb yields - those planes had to drop a lot of ordnance for there to be a chance something actually lands on the intended target. I recall reading somewhere that a single modern guided bomb would achieve the effect that, during WW2, required 100 to 1000 bombers.
- nradov 3y ago
  That has been true, but the US military is now pivoting to confront China in the Western Pacific theater. This means an increased emphasis on fuel efficiency to boost unrefueled range.
- neltnerb 3y ago
  Why then? Stealth can't be that good. Cost seems impossibly unlikely at a development stage, but are they somehow lower cost to manufacture? Seems unlikely. I am welcome to alternatives, but the announcement included: “Blended wing body aircraft have the potential to significantly reduce fuel demand and increase global reach,” said Secretary of the Air Force Frank Kendall. “Moving forces and cargo quickly, efficiently, and over long distance is a critical capability to enable national security strategy.” It could be cleverly written to suggest it is about fuel efficiency and range, but that these straightforward and public explanations aren't the real reason. Totally possible, but what are they then? I know I don't know enough to second guess the public statements of the Secretary of the Air Force and the plain reading is that the first sentence is directly related to the second. But we all know that's not how it works. Both sentences are just always true, they aren't necessarily related. I don't know what else it would mean though.

psunavy03 3y ago

> Military use involves completely different economics, but for related reasons the anticipated greater fuel efficiency is rarely a big deal for the military. Utterly false. Greater fuel efficiency means greater range or less fuel needed for the same range and payload, and you'd better believe that is not nothing to military planners. I can say that because I used to be one. Every drop of fuel burned in theater in a war has to get there somehow. And until it's loaded on a jet and used, it's vulnerable to being targeted either in transit or at rest, and has to be protected. And pre-war, the more gas you're going to burn to accomplish a given task, the more facilities and infrastructure have to be in place at your potential bases to hold it, meaning more access agreements with foreign countries and/or construction contracts having to be paid for in those countries to build said facilities. And you have less ability to use smaller or more austere facilities, limiting your ability to disperse the force and complicate enemy targeting.