AVIATION'S NEW ERA
Chapter 10. Electric Power
Modern jet engines gain efficiency from bypass fans, including many military jet engines. Hence fan propulsion is not only viable at jet speeds, it is the most efficient method.
Turbojets power the fans from fuel that is burned under pressure and expanded to through turbines to drive the turbofans. Some jet engines have afterburner mechanisms that directly use fuel for propulsion, but these are so inefficient that they are only used in special circumstance. The popularity of jet engines is due to: a) light weight, b) long life with high reliability, and c) use of a high density liquid fuel.
Towed Platform aircraft bring forth the following characteristics: a) very high L/D, b) a high speed design where drag coefficients decrease with increasing velocity, and c) an abundance of near-horizontal surface area for solar panels. Electric-powered jet engines become the preferred choice. These could be pure-electric or hybrid electric-fuel engines. This is one of the many advantages and methods of improved use of electric power in aviation’s new era.
Takeoff Assistance – The L/D is the ratio of gravity’s force on an aircraft divided by drag’s force. Gravity’s force is much greater for high L/D aircraft. As a result, only a fraction of the thrust needed for takeoff is required to sustain flight. The ratio of takeoff versus cruising thrust of an aircraft is complicated by the manner in which cruising thrust increased with velocity.
As a benchmark, typical jet aircraft can maintain cruising speeds with half the onboard propulsion. At 3X the L/D and half the onboard propulsion; the needed cruising power is less than one sixth the design takeoff power. As a result, only one propulsor (“Primary Propulsor”) on a high L/D needs to be designed for sustaining flight to the destination. Other propulsors (“Auxiliary Propulsors”) would have design criteria based on takeoff and failsafe landing needs.
Depending upon application, the Primary Propulsor is preferably a transitioning electric jet engine or a hybrid fuel-electric jet engine. These are the subjects of discussion in U.S. patent applications - US 17/971XXX, PCT/US21/16392, PCT/US22/14884, and US 17/591034.
Auxiliary propulsors could be simple electric motors with propulsors. A primary design criterion is a low-drag cruising configuration. The most common method to achieve a low-drag cruising configuration is with blades that fold back when not in use or vertical thrust propulsors build into horizontal sections of the airframe.
Distributed Power – In view of electric motors being capable of delivering jet power, turbo jet configurations are not needed. An alternative is to place a diesel engine generator in the fuselage and distribute the power to an array of jet or prop engines. This approach has two advantages: a) considerably higher efficiency of diesel engines versus jet engines and b) placement in the fuselage to reduce drag.
With sufficient direct solar and battery power backup, only one diesel engine would be needed; even on very large aircraft. Noteworthy is that high glide-ratio engines will typically be able to make failsafe runway landings without powered propulsion after attaining a reasonable altitude—an altitude for which sufficient battery and direct solar power are already part of the design parameters.
Direct Solar Power Supplement - While the goal is flight based on 100% solar power, configurations that rely on some liquid fuels will have significantly reduced fuel consumption due to several reasons: a) fuel would only be need for the higher-power maneuvers, b) a diesel engine generator as the fuel converter could double the efficiency, and c) reduced weight of not carrying extra fuel.
Reliability – Electric power brings forth major advantages in reliability and cost reductions. By example, a typical American owns dozens of electric motors ranging from electric window motors in automobiles to washing machines. These motors are typically zero maintenance through the life of the device of their application. These motors are often chosen on a low-cost basis which is adequate; wherein, more-robust electric motors are often available with reliability is paramount.
They are very reliable and low maintenance. This is in contrast the to rigorous maintenance requirements of fuel-based combustors as well as the need to have a constant fuel supply.
Electric is also a diverse source. For aviation, the preferred source is direct solar. But grid power from a range of sources could be used to charge batteries prior to nighttime takeoffs. There is an abundance of options available to mitigate global warming by reducing use of energy sources have higher greenhouse gas footprints.
Modern jet engines gain efficiency from bypass fans, including many military jet engines. Hence fan propulsion is not only viable at jet speeds, it is the most efficient method.
Turbojets power the fans from fuel that is burned under pressure and expanded to through turbines to drive the turbofans. Some jet engines have afterburner mechanisms that directly use fuel for propulsion, but these are so inefficient that they are only used in special circumstance. The popularity of jet engines is due to: a) light weight, b) long life with high reliability, and c) use of a high density liquid fuel.
Towed Platform aircraft bring forth the following characteristics: a) very high L/D, b) a high speed design where drag coefficients decrease with increasing velocity, and c) an abundance of near-horizontal surface area for solar panels. Electric-powered jet engines become the preferred choice. These could be pure-electric or hybrid electric-fuel engines. This is one of the many advantages and methods of improved use of electric power in aviation’s new era.
Takeoff Assistance – The L/D is the ratio of gravity’s force on an aircraft divided by drag’s force. Gravity’s force is much greater for high L/D aircraft. As a result, only a fraction of the thrust needed for takeoff is required to sustain flight. The ratio of takeoff versus cruising thrust of an aircraft is complicated by the manner in which cruising thrust increased with velocity.
As a benchmark, typical jet aircraft can maintain cruising speeds with half the onboard propulsion. At 3X the L/D and half the onboard propulsion; the needed cruising power is less than one sixth the design takeoff power. As a result, only one propulsor (“Primary Propulsor”) on a high L/D needs to be designed for sustaining flight to the destination. Other propulsors (“Auxiliary Propulsors”) would have design criteria based on takeoff and failsafe landing needs.
Depending upon application, the Primary Propulsor is preferably a transitioning electric jet engine or a hybrid fuel-electric jet engine. These are the subjects of discussion in U.S. patent applications - US 17/971XXX, PCT/US21/16392, PCT/US22/14884, and US 17/591034.
Auxiliary propulsors could be simple electric motors with propulsors. A primary design criterion is a low-drag cruising configuration. The most common method to achieve a low-drag cruising configuration is with blades that fold back when not in use or vertical thrust propulsors build into horizontal sections of the airframe.
Distributed Power – In view of electric motors being capable of delivering jet power, turbo jet configurations are not needed. An alternative is to place a diesel engine generator in the fuselage and distribute the power to an array of jet or prop engines. This approach has two advantages: a) considerably higher efficiency of diesel engines versus jet engines and b) placement in the fuselage to reduce drag.
With sufficient direct solar and battery power backup, only one diesel engine would be needed; even on very large aircraft. Noteworthy is that high glide-ratio engines will typically be able to make failsafe runway landings without powered propulsion after attaining a reasonable altitude—an altitude for which sufficient battery and direct solar power are already part of the design parameters.
Direct Solar Power Supplement - While the goal is flight based on 100% solar power, configurations that rely on some liquid fuels will have significantly reduced fuel consumption due to several reasons: a) fuel would only be need for the higher-power maneuvers, b) a diesel engine generator as the fuel converter could double the efficiency, and c) reduced weight of not carrying extra fuel.
Reliability – Electric power brings forth major advantages in reliability and cost reductions. By example, a typical American owns dozens of electric motors ranging from electric window motors in automobiles to washing machines. These motors are typically zero maintenance through the life of the device of their application. These motors are often chosen on a low-cost basis which is adequate; wherein, more-robust electric motors are often available with reliability is paramount.
They are very reliable and low maintenance. This is in contrast the to rigorous maintenance requirements of fuel-based combustors as well as the need to have a constant fuel supply.
Electric is also a diverse source. For aviation, the preferred source is direct solar. But grid power from a range of sources could be used to charge batteries prior to nighttime takeoffs. There is an abundance of options available to mitigate global warming by reducing use of energy sources have higher greenhouse gas footprints.