New answers tagged efficiency
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Your best bet might be the Aurora ORION UAV. It's essentially a twin engine plane turned motor glider. It offers a payload of up to a ton with a range of up to ~5,000 km. Or a ferry range (no cargo, just fuel) of 24,000 km. Being a glider design, its long distance cruise speed is below 150 km/h. So a long distance flights will take many days.
What you're ...
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I remember reading about how much trouble it was for those people trying to get permission to fly a balloon across various countries in their around the world attempts. Trying to get the permissions for a UAV of sufficient size to do something like this would be even more difficult.
Assuming the various flight permissions from the various countries could ...
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The best aircraft for your job is a used Boeing 767.
As others have pointed out, a UAV the likes of a MQ-9 or RQ-4 costs at least $200M and comes with a small payload and regulatory problems as well. Fortunately, there's a much better and cheaper option. In a 2015 article, Business Jet Traveller suggested a used Boeing 767 as a cheaper alternative to large ...
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The conditions at the rear disk are obviously different, so something must be different.
First of all, if the rotation direction of the disks is opposite, you'll have 'right' and 'left' blades. (Blades nearly always have asymmetric airfoil, so you can't swap them). That's 'different geometry' already.
Normally, the efficiency of the rear disk will be ...
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From NASA Technical Memorandum 82983
Swirl recovery reduces the magnitude of efficiency degradations at high
power loadings and/or low tip speeds typically associated with
single rotation propellers. Therefore,the ideal efficiency advantage
offered by counter rotation propellers varies from about 5 to 15 units
of efficiency for the range of ...
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As others have pointed out, the range you're thinking of is unrealistic.
There are other problems too: making sure your dropped load doesn't hit anyone and will land in the right spot (and not, for instance in the nearby swamp) is not easy.
And in regions remote enough to qualify for this service, you can't count on qualified personnel to be available to ...
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There is no shortage of air freight companies that can quickly ship cargo to nearly any airport in the world, and since they have economy of scale and lots of experience dealing with regulators, you will never beat their costs.
Aftica's main logistics problem is the so-called "last mile": getting supplies from an airport to where they're actually needed. In ...
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Not to burst your bubble, but doing this "cheap" isn't possible.
First look at range. Light aircraft that have a 2-ton+ payload have limited range, look at the upcoming Cessna 408, it can carry 3 tons but only has a 1,000 mile ferry range. In order to increase the range, you need to carry more fuel, reducing your load. So lets say you dedicated 1 ton to a ...
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Thrust is created by accelerating a working mass in opposite direction. Net thrust is the difference between the impulse of the air flowing towards the engine and the combined impulse of burnt fuel and the air exiting the engine (and propeller, if one is fitted), derived by time. That impulse is the product of mass and speed.
When flying faster, the entry ...
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Yes, that is typical for high bypass ratio (HBPR) turbofans.
But why?
Because the entry impulse goes up while the exit impulse stays roughly constant. Thrust is the difference between both, derived over time.
The moving engine needs to slow down the airflow for combustion to take place, and then needs to accelerate the air by more than it has been ...
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I am adding this community wiki answer to show my current state of research and to provide the plot vs. altitude, which I will update when I learn more. Comments are welcome.
Thermal Efficiency
From this answer by Peter Kämpf, we know that the thermal efficiency for jet engines is given by
$$ \eta = \frac{T_\text{max} - T_\text{amb}}{T_\text{max}} $$
...
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"Ballpark" figures for an 8000 mile trip Atlas ICBM vs 747 jet airliner:
Atlas ICBM: 8000 lbs delivered using 75 tons of RP-1/225 tons LOX = 27 lbs/ton total propellant, or 108 lbs/ton on a hydrocarbon fuel basis.
747 airliner: 150,000 lbs passengers and luggage using 150 tons fuel = 1000 lbs/ton
and a softer landing.
Biggest ...
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The key to why an air-breathing jet engine is "more efficient" is that it doesn't need to carry oxidizer, it can just use the atmosphere. Carrying oxidizer is very heavy, which will severely impact the range and speed of the aircraft.
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Jet engines are far more efficient. The metric to compare them is 'Thrust-specific fuel consumption', i.e. the amount of fuel used to produce one unit of thrust. Fuel consumption per distance traveled is proportional to this.
A few figures from that page:
Rocket engine: Space Shuttle main engine, 225 g/kN.s
Jet engine in afterburner: EJ-200: 48 g/kN.s
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