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> "The reason why we don't use tail sitting craft is because they are too awkward for human pilots to land." This isn't true. Taking off anything vertically re

> "The reason why we don't use tail sitting craft is because they are too awkward for human pilots to land." This isn't true. Taking off anything vertically requires their thrust-to-weight ratios be higher than 1.0 (otherwise try as it might, it's going to sit on the ground). Modern, latest-generation fighter aircraft have a TWR somewhere between 0.75 and 1.15. If you pointed them upwards, they will barely be able to lift off the ground (if their TWR is above 1.0 at all), much less gain enough speed to generate lift with their wings. Taking off horizontally allows you to get lift "for free" with the wings. Accelerating horizontally means you're not fighting gravity the whole time. Lifting off vertically, assuming the aircraft has enough TWR to make it realistic, is a terrible waste of fuel. Modern fighters only have a combat radius of ~300-350mi before they have to turn around and go home. The more fuel that is expended taking off or landing, the less actual flight (and fight) time they have. Catapult launches also allows you to save fuel on the aircraft by "borrowing" the necessary energy from the launcher. Ditto arrested-hook landings that allow you to borrow stopping force from the aircraft carrier - otherwise you'd have to carry enough fuel to exert this force yourself. It's certainly possible to design craft that can take off and land vertically - the physics are relatively simple. The problem is making them practical - the more fuel/weight an aircraft spends just taking off and landing, the less weight can be dedicated to useful tasks, like missiles, bombs, and flying far.

starpilot 13y ago
The real reason generating lift with large wings is better is that it's much more efficient to generate a force by accelerating a large volume of fluid a small amount, than vice versa as with a turbine engine. This is why helicopters exist at all, because of the efficiency of large rotors (wings). Ref http://en.wikipedia.org/wiki/File:VTOL_DiscLoad-LiftEfficiency.PNG http://en.wikipedia.org/wiki/File:VTOL_DiscLoad-LiftEfficien... (note log scale).
stcredzero 13y ago
> Modern, latest-generation fighter aircraft have a TWR somewhere between 0.75 and 1.15. If you pointed them upwards, they will barely be able to lift off the ground (if their TWR is above 1.0 at all), much less gain enough speed to generate lift with their wings. Taking off horizontally allows you to get lift "for free" with the wings. Well, more specifically, you are using the atmosphere as reaction mass. Wings direct air down. It's not free lift, it's free reaction mass. I'm not saying that you should eliminate catapult launches. But a ship large enough to have catapults can still be a whole lot smaller than a modern US Navy aircraft carrier. Any aircraft that can land vertically will also be able to take off vertically. (Though with less efficiency when fully loaded, if at all.) There's a huge amount to be gained by being able to stage aircraft from much smaller ships. How about building submarines a bit larger than the old Soviet Typhoons, and having aircraft on those? Short of that, how about the ability to build squadrons of multiple redundant cruiser-sized carriers? Perhaps such schemes would be more valuable potential opponents of the US, than they would be to the US. Yes, on the whole, the system will be less fuel efficient than horizontal take off and landing.
- starpilot 13y ago
  > There's a huge amount to be gained by being able to stage aircraft from much smaller ships. These are called amphibious assault ships like the America and Tarawa classes. They can serve helicopters and V/STOL fixed-wing aircraft. No catapults. http://en.wikipedia.org/wiki/America-class_amphibious_assault_ship http://en.wikipedia.org/wiki/America-class_amphibious_assaul... http://en.wikipedia.org/wiki/File:USS_Saipan_LHA-2_amphibious_assault_ship.jpg http://en.wikipedia.org/wiki/File:USS_Saipan_LHA-2_amphibiou...
  - Tloewald 13y ago
    I suspect you may see submarines configured to launch drones vertically with rocket assist and recover them using something smaller than a flight deck. Subs already deploy SEAL teams and there has been at minimum experimental use of remote piloted minisubs — this would be a perfect complement. This heralds the end of the aircraft carrier (a good thing, since they're really quite obsolete conceptually).
- Retric 13y ago
  It's actually more useful to have larger carriers than smaller ones. The obvious difference is top speed as drag does not increase linearly with length. But you also gain the ability to do takeoffs and landings in a wider range of weather conditions as well as having redundant nuclear reactors and dentists etc. But, perhapse most importantly the larger the aircraft carrier the larger aircraft it can support and there are many advantages to having larger aircraft.
  - lmm 13y ago
    Really? Larger aircraft have a larger cross-section for enemy radar and missiles, and are likely to have worse thrust/weight ratios and maneuverability (square-cube law). Combat range and ammo capacity scales with size up to a point, but if you can make a smaller drone with the same range and armament as a normal fighter then it would surely be more useful in most respects.
    - 13y ago

starpilot 13y ago

The real reason generating lift with large wings is better is that it's much more efficient to generate a force by accelerating a large volume of fluid a small amount, than vice versa as with a turbine engine. This is why helicopters exist at all, because of the efficiency of large rotors (wings). Ref http://en.wikipedia.org/wiki/File:VTOL_DiscLoad-LiftEfficiency.PNG http://en.wikipedia.org/wiki/File:VTOL_DiscLoad-LiftEfficien... (note log scale).

stcredzero 13y ago

> Modern, latest-generation fighter aircraft have a TWR somewhere between 0.75 and 1.15. If you pointed them upwards, they will barely be able to lift off the ground (if their TWR is above 1.0 at all), much less gain enough speed to generate lift with their wings. Taking off horizontally allows you to get lift "for free" with the wings. Well, more specifically, you are using the atmosphere as reaction mass. Wings direct air down. It's not free lift, it's free reaction mass. I'm not saying that you should eliminate catapult launches. But a ship large enough to have catapults can still be a whole lot smaller than a modern US Navy aircraft carrier. Any aircraft that can land vertically will also be able to take off vertically. (Though with less efficiency when fully loaded, if at all.) There's a huge amount to be gained by being able to stage aircraft from much smaller ships. How about building submarines a bit larger than the old Soviet Typhoons, and having aircraft on those? Short of that, how about the ability to build squadrons of multiple redundant cruiser-sized carriers? Perhaps such schemes would be more valuable potential opponents of the US, than they would be to the US. Yes, on the whole, the system will be less fuel efficient than horizontal take off and landing.

starpilot 13y ago
> There's a huge amount to be gained by being able to stage aircraft from much smaller ships. These are called amphibious assault ships like the America and Tarawa classes. They can serve helicopters and V/STOL fixed-wing aircraft. No catapults. http://en.wikipedia.org/wiki/America-class_amphibious_assault_ship http://en.wikipedia.org/wiki/America-class_amphibious_assaul... http://en.wikipedia.org/wiki/File:USS_Saipan_LHA-2_amphibious_assault_ship.jpg http://en.wikipedia.org/wiki/File:USS_Saipan_LHA-2_amphibiou...
- Tloewald 13y ago
  I suspect you may see submarines configured to launch drones vertically with rocket assist and recover them using something smaller than a flight deck. Subs already deploy SEAL teams and there has been at minimum experimental use of remote piloted minisubs — this would be a perfect complement. This heralds the end of the aircraft carrier (a good thing, since they're really quite obsolete conceptually).
Retric 13y ago
It's actually more useful to have larger carriers than smaller ones. The obvious difference is top speed as drag does not increase linearly with length. But you also gain the ability to do takeoffs and landings in a wider range of weather conditions as well as having redundant nuclear reactors and dentists etc. But, perhapse most importantly the larger the aircraft carrier the larger aircraft it can support and there are many advantages to having larger aircraft.
- lmm 13y ago
  Really? Larger aircraft have a larger cross-section for enemy radar and missiles, and are likely to have worse thrust/weight ratios and maneuverability (square-cube law). Combat range and ammo capacity scales with size up to a point, but if you can make a smaller drone with the same range and armament as a normal fighter then it would surely be more useful in most respects.
  - 13y ago