The necessity to carry more fuel disproportionally drives long-haul aircraft's size, weight, and price. For example, the 2017 Boeing 737 MAX 9's flight range is 6,570 km for a 144-seat model, which is listed at $129 m. Long-haul 2020 Boeing 777-9X's flight range is 13,300 km for a 395-seat model, which is listed at $442 m. Accordingly, 777's seat-specific price is greater than that of 737 by [(442/129)/(395/144)], i.e., around 19%.   

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This example shows that one seat in a long-haul aircraft is typically more expensive than that in a medium-haul airliner. The reason is that the longer the aircraft's flight range is, the greater the fuel weight it carries. In other words, a long-haul plane has to burn more fuel per unit of distance to haul its more significant fuel volume. To keep long-haul aircraft's seat-specific fuel economy within reasonable limits, the long-haul aircraft have to carry more passengers. Accordingly the thermodynamic efficiency of their power-plants needs to be better than that of middle-haul aircraft. 

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It is common knowledge in the industry that developing and manufacturing long-haul aircraft is a risky business. Closed AG-Cycle will mitigate the problem by making contemporary long-haul aircraft irrelevant by integrating Closed AG-Cycle into power-plants of medium-haul aircraft, thereby doubling their flight ranges without sacrificing useful payloads and improving their fuel efficiency by around 55%. A more detailed analysis is outlined below.        

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However, AG-converted aircraft's fuel capacity won't rise proportionally, by [1/0,55], i.e., 2.25 times, because water recovery unit will take on part of the weight. Almost 100 years ago, the US Air Force conducted research on water recovery from the exhaust of reciprocating 400 hp IC engine installed on a helium airship. The experiments revealed the empirical ratio for an airship moving at a speed of 45 MPH in a temperature of 15 C, and having a water recovering unit’s capacity of around 90%: 1 lbs (0.4536 kg) per 1 hp. 

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Estimates show that for contemporary aircraft, this ratio is lower than that in the airship. Modern passenger aircraft’s speed is around 12 - 13 times greater, and the temperature at their flying altitudes is about 70 C lower, i.e., heat transfer is more intensive. The thermal efficiency of an aircraft turbofan is at least twice as high as that of an airship's IC engine, i.e., exhaust has around 30% lower heat energy content per unit of power.

 

Since the combustion of one kilogram of hydrocarbon fuel produces around 1.4 kg of water, the exhaust contains around [(1+1.4)/1.4], i.e., 71% more water vapor, which means that a 45% recovery rate will suffice, instead of airship's 90% recovery rate. Estimates show that for contemporary aircraft, the ratio at the higher end is [1*0.7*0.45], i.e., 0.315 lbs (0.143 kg) per 1 hp, even without taking into account higher temperature difference, higher speed, and advancements in heat exchange technology during last 100 years, which were remarkable.  

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Boeing 737 MAX 9’s turbofans at a cruise speed produce approximately 19,600 hp of power. The estimated weight of a water recovery unit is [19 600*0.143], i.e., 2,800 kg, which constitutes [2,800/25,817], i.e. 10.8% of airliner’s fuel capacity. The core thrust of the up-to-date LEAP-1B, installed on Boeing 737 MAX 9, accounts for around 10% of the overall thrust. Since a large portion of this thrust will be lost due to the back pressure of a water recovery unit, the estimated fuel consumption reduction would be directly proportional to the estimated increase of the engine's thermal efficiency, around [2.5*0.9], i.e., 2.25 times, which is equivalent to around 55% reduction in fuel consumption. 

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If the weight of a water recovery unit is included in aircraft’s fuel capacity, its range will increase by [2.25*(1-0.108)], i.e., by a factor of 2, up to [6,570*2], i.e., 13 140 km, which is close to 13 300 km range of long-haul Boeing 777-9X. Flying on a modified Boeing 737 is expected to be more accommodating due to a sufficient water suppl for maintaining comfortable humidity in a cabin.

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A typical long-haul aircraft's average flight time is around 15 hours daily. If the 2017 Boeing 737 MAX 9, with a fuel efficiency of 2.91 kg/km, would fly long-haul flights for 20 years with a cruise speed of 839 km/h and the cost of jet fuel would be the same as the annual average cost of jet fuel in 2019, $2 per gal,  the cost of all fuel consumed would be [15*365*20*839*(2.91 /0.8/3.785)*2], i.e., $176.6 m. If  Boeing 737's power-plant was enhanced with AG-Cycle, this cost would be around 55%, i.e., $97 m less. Since the actual value price of the 2017 Boeing 737 MAX 9 (before grounding in 2018) was less than $97 m, AG-Cycle would reduce the 737's actual value price down to zero. 

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Supercritical Carbon Dioxide (S-CO2) power plant is believed to be used on serial hybrid aircraft in the foreseeable future. According to Meridian International Research, S-CO2 would reduce contemporary aircraft’s cruise seed specific fuel consumption (SFC) to 0.37 lb/lbf/hr, which is around 30% lower than that of the turbofan with the best specific fuel consumption in class, LEAP 1B's 0.53 lb/lbf/hr. Accordingly, pairing S-CO2 with AG-Cycle would further reduce the specific fuel consumption to [0.37/2.25], i.e. 0.164 lb/lbs/hr.