These days my vote would go to a quad. Impeller fore, impeller aft and one in each wing. Behind doors, obviously, like the bays for retractable landing gear - this is a solved problem.
They don't have to be efficient, because how much hovering time would you really need? Battery could even exist only in mission specific pods (internal perhaps, when it's a cargo carrier), trade-off as needed.
Thats the point, the more efficient the less supply line you need, which means more autonomy.
I cant find the source but in Afghanistan a large proportion of the Allied casualties were from protecting supply lines.
The thing about quad copters is that they work at small scale because the rotor have almost no inertia. When you scale that up to 2m, then inertia is a bitch. That means you need tilting blades to make up for that lack of control.
BUT
You also need something to be powerful enough to alter the speed of the rotors to get yaw.
Plus you then also need to get them all to rotate so that you can get the efficiency of normal flight.
The reason why the osprey exists is because it has longer range than a helicopter (~1200 miles vs 400) its also faster.
> Plus you then also need to get them all to rotate so that you can get the efficiency of normal flight.
Not when you simply don't use them for horizontal flight. You just shut the VTOL hatches and forget that you aren't a conventional airplane until you want to land but there isn't an airstrip.
Winged operation has to be efficient, no doubt about that. But hovering does not need much endurance when it's only for getting away from the ground and setting down.
Electric has the power density, even more so when you don't need the power for a long time (heat buildup, no need for an equilibrium). Electric suffers from energy density, but that's where the winged mode comes in (old fashioned jet turbine, with the generator slightly larger than usual so that you'll have full batteries for the short landing hover)
These days my vote would go to a quad. Impeller fore, impeller aft and one in each wing. Behind doors, obviously, like the bays for retractable landing gear - this is a solved problem.
They don't have to be efficient, because how much hovering time would you really need? Battery could even exist only in mission specific pods (internal perhaps, when it's a cargo carrier), trade-off as needed.
> They don't have to be efficient
Thats the point, the more efficient the less supply line you need, which means more autonomy.
I cant find the source but in Afghanistan a large proportion of the Allied casualties were from protecting supply lines.
The thing about quad copters is that they work at small scale because the rotor have almost no inertia. When you scale that up to 2m, then inertia is a bitch. That means you need tilting blades to make up for that lack of control.
BUT
You also need something to be powerful enough to alter the speed of the rotors to get yaw.
Plus you then also need to get them all to rotate so that you can get the efficiency of normal flight.
The reason why the osprey exists is because it has longer range than a helicopter (~1200 miles vs 400) its also faster.
> Plus you then also need to get them all to rotate so that you can get the efficiency of normal flight.
Not when you simply don't use them for horizontal flight. You just shut the VTOL hatches and forget that you aren't a conventional airplane until you want to land but there isn't an airstrip.
Winged operation has to be efficient, no doubt about that. But hovering does not need much endurance when it's only for getting away from the ground and setting down.
Electric has the power density, even more so when you don't need the power for a long time (heat buildup, no need for an equilibrium). Electric suffers from energy density, but that's where the winged mode comes in (old fashioned jet turbine, with the generator slightly larger than usual so that you'll have full batteries for the short landing hover)
Electric motors are very light too.