Essential Mission
The primary mission of our HALE (substantial altitude, very long stamina) UAV (unmanned aerial automobile) is to fly around a single spot of the earth for extended periods of time. Specifically why is not crucial at this place of the dialogue. Most probably the aim is to substitute a communications satellite.
Velocity is not crucial, considering the fact that we are just traveling about 1 location. Electricity performance is. In truth, the less electricity it requires to maintain altitude, the a lot more payload it can have. Given what I just said, I hope a single phrase popped into your head: glider. HALE UAVs glance like gliders. Very low wing loading, gradual traveling, with very long skinny wings.
If the UAV is likely to stay up for yrs, it requires a quite superior source of electrical power. If a nuclear fusion reactor is the to start with believed that just popped into your head, you would be improper. Rather, feel basic and very well-tested. Assume photo voltaic cells. Loads of them. The superior news is that our glider already has significant wings, so they are going to be protected in photo voltaic cells.
Harsh Circumstances
At 60,000 feet, 93% of the environment is below you. The air pressure is just 7% of what it is at sea amount. The air density, or the weight of the air, is just 9.5% of what it weighs at sea amount. The regular temperature is a bone chilling -75 F (-60 C). Why would any one want to fly at that altitude?
Why 60,000 Toes
As I defined in the to start with element of this collection of content, professional airliner flights and most of the climate lies under 40,000 feet (12,000 m). So which is the complete flooring of exactly where we can fly.
There is certainly a pair of other good reasons that drive us to fly even better than that. First, at 40,000 ft the winds can seriously choose up. The ordinary wind velocity at that altitude is 50 MPH (80 KPH). All over again, that is the common – it could very easily be double that. Not so a great deal of an concern with an airliner traveling at 500+ MPH, but a authentic difficulty with our fragile and slow traveling UAV.
The common wind pace at 60,000 ft drops to just 15 MPH (25 KPH). That is wonderful news. That means that we will not have to fly any more rapidly than we would anyway. Slower is generally additional productive.
There is one more very vital reason why we want to fly bigger than we absolutely need to have to. Traveling more than one place, we are likely to be in darkness about 50 % of the time. Solar cells don’t operate in the dim. Preserving the same altitude for 12 hrs would call for a massive amount of rechargeable batteries. To save on battery excess weight, we are likely to bit by bit reduce altitude at night. We however require to stay clear of the airliners and the weather conditions, but now our UAV glider will be far more successful.
Utmost Endurance Velocity
At what pace do we need to fly at? Nicely, an plane flies at distinct speeds depending on what the goal at the instant occurs to be. A pace perfectly-known to glider pilots is termed the ideal glide or greatest elevate to drag ratio (L/D) velocity. This is the speed at which the wing is most efficient.
The speed that we treatment about is termed the loiter or highest stamina pace. Another title for it is the least ability essential pace, for noticeable good reasons. It is the velocity where by we require the the very least amount of money of electrical power to preserve altitude. For a common plane, this is about 76% of the benefit for the ideal L/D velocity.
There is a big catch. At this altitude, the air is to skinny that we will need to fly 3.3 moments speedier just to crank out the same quantity of lift. This means that if the highest endurance pace is 20 MPH (32 KPH) at sea degree, we would will need to fly at 66 MPH (106 KPH) at our cruise altitude. That, however, also demands 3.3 occasions the amount of electric power to preserve. All of a unexpected building our UAV glider will not audio so uncomplicated!
