If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#181
|
|||
|
|||
Electrically Powered Ultralight Aircraft
"Montblack" wrote So you're saying zeppelins should take advantage of jam-jet propulsion technology? Oh, isn't that a sweet idea? -- Jim in NC |
#182
|
|||
|
|||
Electrically Powered Ultralight Aircraft
In rec.aviation.piloting Montblack wrote:
wrote) In cars, weight matters most in acceleration and doesn't matter in any significant amount with modern tires in cruise. Speculate please: 1. Two 3,600 lb cars - good tires 2. Traveling 60 mph (no wind) 3. 4cly - 150 hp (Honda Accords) 3. Flat highway in North Dakota 4. Fuel flow meters hooked up to both vehicles (Honda #1) Driver ................ 105 lbs Fuel .................... 15 lbs TOTAL .............. 120 lbs (1/30th of 3,600 lb car) (Honda #2) Driver ................. 300 lbs Passengers ........ 700 lbs Luggage ............. 100 lbs Fuel ................... 100 lbs TOTAL ............. 1,200 lbs (1/3 of 3,600 lb car) ....BTW, BTDT! g If both vehicles were monitored for 50 miles, would their fuel flow be (approx) the same, in cruise? A pulled out of my ass, wild assed guess is that since you are increasing the load by 33%, then yes, you will see a difference, and at that loading the tires will be visibly deformed. Now, would you care to calculate the energy required to accelerate 3720 pounds to 60 mph versus accelerating 4800 pounds to 60 mph? Assume gasoline is 45 megajoules per kilogram and the engine is 38% efficient. You may neglect all drag for this calculation and express the energy in kilograms of gasoline. -- Jim Pennino Remove .spam.sux to reply. |
#183
|
|||
|
|||
Electrically Powered Ultralight Aircraft
In rec.aviation.piloting Montblack wrote:
("Charles Vincent" wrote) According to SAE studies, aerodynamic drag accounts for 60% of the resistance that must be overcome for highway cruise, with tires being 25% and driveline friction making up the last 15%. Semi: Tires ........... 18 Footprint ..... big per tire Weight ....... 80,000 lbs Drag .......... HUGE!! MPG .......... 5 (loaded) Minivan: Tires ........... 4 Footprint ..... smaller per tire Weight ....... 4,000 lbs (for easy math) Drag .......... MUCH less + no cab/trailer drag MPG .......... 22 I've never really understood why an 800 lb motorcycle/rider gets (only) 50 mpg and a fully loaded semi can get (about) 5 mpg? Motorcycle: Tires ........... 2 Footprint ..... very small per tire Weight ....... 800 lbs (with rider) Drag .......... It's a motorcycle! g MPG ........... 50 The coefficient of drag for motorcycles is usually pretty bad unless they are faired, and it still ain't great. The power required to overcome drag is 1/2(p*v^3*A*C) p is the densitity of the fluid v is the airspeed A is the area C is the coefficient of drag -- Jim Pennino Remove .spam.sux to reply. |
#184
|
|||
|
|||
Electrically Powered Ultralight Aircraft
|
#185
|
|||
|
|||
Electrically Powered Ultralight Aircraft
In rec.aviation.piloting Matt Whiting wrote:
wrote: The coefficient of drag for motorcycles is usually pretty bad unless they are faired, and it still ain't great. Yes. The power required to overcome drag is 1/2(p*v^3*A*C) No. It is v^2 unless they have changed the physics since I was an aero engineering student back in the 70s. Yes. The drag goes up with the square of velocity, the POWER required to overcome the drag goes up as the cube. Force: Fd = 1/2(p*v^2*A*C) Power: Pd = Fd * v = 1/2(p*v^3*A*C) -- Jim Pennino Remove .spam.sux to reply. |
#187
|
|||
|
|||
Electrically Powered Ultralight Aircraft
On Aug 6, 3:16 pm, brtlmj wrote:
There is a fundamental problem with attempting to power an aircraft with batteries: The propulsion system must not only move the vehicle forward as it would with an automobile, but it must also simultaneously maintain the aircraft's altitude; That is why aircraft engines are so powerful and light; they're depended-on to fight gravity as well as wind resistance. Which leads us to the case of airships! They float. They don't have to work to stay at altitude, they just hang there. Their engines don't have to hold them up. But, and it's a big but, since they are so big, they have more wind resistance than airplanes. Since wind resistance is the log, or cube? of wind speed, their hull-speeds are quite limited and their engines remain relatively small as a result. Enter the less-powerful electric motors! Enter solar photo- voltaic cells! The big surface area of airships are ideal for mounting solar arrays. And if you have a cloudy day and don't charge your batteries up to snuff, well, you will not have to go to ground, as in an airplane, because you are afloat in your element and you drift with the breeze for awhile. Words to the wise about the future of flight. High cheers from Allen the airshipman |
#188
|
|||
|
|||
Electrically Powered Ultralight Aircraft
On Sun, 19 Aug 2007 09:53:32 -0700, dirigible designer
wrote in . com: On Aug 6, 3:16 pm, brtlmj wrote: Actually, these are my words from earlier in this message thread. See: Message-ID: . There is a fundamental problem with attempting to power an aircraft with batteries: The propulsion system must not only move the vehicle forward as it would with an automobile, but it must also simultaneously maintain the aircraft's altitude; That is why aircraft engines are so powerful and light; they're depended-on to fight gravity as well as wind resistance. Which leads us to the case of airships! They float. They don't have to work to stay at altitude, they just hang there. Their engines don't have to hold them up. But, and it's a big but, since they are so big, they have more wind resistance than airplanes. Since wind resistance is the log, or cube? of wind speed, their hull-speeds are quite limited and their engines remain relatively small as a result. Enter the less-powerful electric motors! Enter solar photo- voltaic cells! The big surface area of airships are ideal for mounting solar arrays. And if you have a cloudy day and don't charge your batteries up to snuff, well, you will not have to go to ground, as in an airplane, because you are afloat in your element and you drift with the breeze for awhile. Words to the wise about the future of flight. High cheers from Allen the airshipman Thank you for mentioning electrically powered airships. Lighter Than Air craft are excellent candidates for electric power as is evidenced by: http://en.wikipedia.org/wiki/Airship In 1883, the first electric-powered flight was made by Gaston Tissandier who fitted a 1-1/2 horsepower Siemens electric motor to an airship. The first fully controllable free-flight was made in a French Army airship, La France, by Charles Renard and Arthur Constantin Krebs in 1884 . The 170 foot long, 66,000 cubic foot airship covered 8 km (5 miles) in 23 minutes with the aid of an 8-1/2 horsepower electric motor. http://missilethreat.com/missiledefe...tem_detail.asp ... In September 2003, the Missile Defense Agency (MDA) and the North American Aerospace Defense Command (NORAD) awarded a $40 million development contract to Lockheed Martin to build the High Altitude Airship prototype. Lockheed Martin currently manufactures the Goodyear blimps that can be seen over big sporting events. These blimps are approximately 200 feet long with a volume of 200,000 cubic feet. By contrast, the HAA prototype will be 500 feet long, 160 feet in diameter, with a volume of 5.2 million cubic feet, i.e. more than 25 times the size of the average Goodyear blimp. MDA plans to deploy the HAA at an altitude of 65,000 feet where the air is one-twentieth the density that it is near the ground. One of the biggest challenges facing MDA and Lockheed Martin is how to get the HAA from the ground to its area of deployment, since the helium gas inside will expand more than fifteen times as the blimp rises. To solve this problem, the HAA will be filled mostly with air when it is close to the ground. As it rises, the air inside the blimp will be forced out and helium from five small inner balloons will replace it. This “balloon-within-a-balloon” concept will allow the HAA to maintain its football-like shape throughout all stages of flight. Once deployed, the HAA will generate its own power supply from thin-film photovoltaic solar cells. It will require 10 kilowatts of electricity to run its 4,000-pound radar system. The prototype HAA will include batteries to keep the electricity flowing at night, although the final version will most likely use lightweight fuel cells. Four electrically powered engines will each drive two 30-foot-wide propellers that will provide the blimp’s forward thrust. The propellers will allow the HAA to hover within a mile of its assigned location, thus maintaining its fixed “geostationary” nature. ... http://www.aiaa.org/aerospace/images...es/pdf/LTA.pdf Zeppelin Luftschifftechnik in Germany resorted to a unique method of delivering its NT-07 airship to a Japanese customer. The semirigid air-ship was flown to Italy and, fully inflated, was put on board a BPDockship for the journey to Kobe, Japan. Tail surfaces and forward engines were removed. Zeppelin is leasing another NT-07 to the DeBeers diamond company for two years. It also was delivered by ship, to South Africa. The air-ship will be equipped to examine geological formations in southern African countries. Zeppelin carried 11,000 passengers on sightseeing flights in Germany during 2004. Work is proceeding on the development of the 19-passenger NT-14. First flight is expected in early 2008. Zeppelin has acquired the intellectual property of the defunct CargoLifter organization. This will become part of an LTAinstitute for coordinating activities on scientific and predevelopment levels applicable to all types of airships. It will be headquartered in Friedrichshafen. Japan’s Aerospace Exploration Agency completed its series of eight flights with the above-mentioned 223-ft-long, 370,755-ft, un-manned research airship. The objective of these flights was to verify flight control, operation, and tracking technologies from takeoff to landing. Geostationary flight at 13,000 ft was realized with the aid of electrically powered propellers. Data obtained will be applied to JAXA’s further research into high-altitude airships. Another approach to this subject, a “bal-loon robot,” was investigated by Japan’s National Institute of Advanced Industrial Science and Technology (AIST). A 92-ft-long model carrying a 3-kg payload was launched to an altitude of 55,700 ft. Power for propulsion was supplied by batteries. Data transmission failure prevented verification of station keeping. AIST has built a 43-ft-long nonrigid propelled by cycloidal propellers driven by electricity supplied by batteries. This unmanned airship can be used for aerial observation and monitoring of hazardous areas. http://mae.pennnet.com/Articles/Arti...&KEYWORD=blimp Latest generation of military airships to use solar electric power by J.R. Wilson Peterson AFB, Colo. — The North American Aerospace Defense Command (NORAD) has joined forces with the U.S. Army and other agencies to develop the 21st-century High Altitude Airship to help defend U.S. airspace, control its borders, and possibly provide global surveillance capability to military theater commanders. "It's an old idea with new technology applied," explains U.S. Navy Cmdr. Pat Lyons, chief of ISR and NORAD J-5 Directorate. "This airship is unmanned, untethered, and electric powered. We expect it to be composed of solar cells, a fuel cell, and electrolyzer for nighttime operations." The new airship's command-and-control links most likely will involve satellite communications channels. All of these technologies will probably enable the airship to remain on station for as long as one year, Lyons says. Electric power The airship will be electrically powered — possibly using a hydrogen fuel cell — with DC brushless motors and propellers as the likely propulsion system, although the final design will be up to the contractor; Lyons says there are several other possible concepts for program managers to consider. That includes the number of motors, which also would determine the number of propellers. "The concepts we've seen show speeds up to 100 knots for the objective airship," Lyons explains. "The winds at 70,000 feet are fairly benign; you're above the weather and the jet stream, but occasionally, depending on where you are, they can get up to 100 knots, building for 24 hours, peaking for a day, then diminishing for a day. With a 100-knot airspeed, the airship can remain geostationary," Lyons says. A variety of sensors are being considered for the airship's Advanced Concept Technology Demonstration (ACTD), including a small communications relay. In operation, the vehicle could be used to enable communications 600 or more miles apart, including over a mountain. Currently, ground troops with handheld communications must post a relay unit on a water tower or other tall structure to avoid losing contact in the field. ... Military & Aerospace Electronics August, 2002 Author(s) : J.R. Wilson |
#189
|
|||
|
|||
Electrically Powered Ultralight Aircraft
wrote)
The coefficient of drag for motorcycles is usually pretty bad unless they are faired, and it still ain't great. The power required to overcome drag is 1/2(p*v^3*A*C) p is the densitity of the fluid v is the airspeed A is the area C is the coefficient of drag 80-ft length of the semi (vs.) 8-ft length of the motorcycle Does this play (much) of a role here? Is that role expressed (adequately/sufficiently) in the above formula, through "C" ...drag? Paul-Mont http://www.totalmotorcycle.com/motorcyclespecshandbook/1MotorcycleManufacturer.htm Fun site - make / model / year. My Yamahoppers were both in there. |
#190
|
|||
|
|||
Electrically Powered Ultralight Aircraft
In rec.aviation.piloting Montblack wrote:
wrote) The coefficient of drag for motorcycles is usually pretty bad unless they are faired, and it still ain't great. The power required to overcome drag is 1/2(p*v^3*A*C) p is the densitity of the fluid v is the airspeed A is the area C is the coefficient of drag 80-ft length of the semi (vs.) 8-ft length of the motorcycle Does this play (much) of a role here? Is that role expressed (adequately/sufficiently) in the above formula, through "C" ...drag? The C is the catchall variable that is determinded by the object's overall shape and for all but the most simple shapes (i.e. flat plate, sphere, etc.) determined by measurement. As to what length does specifically, it depends. Smooth sides are going to be less "draggy" than lumpy sides. A flat back end is going to be more "draggy" than a tapered back end. -- Jim Pennino Remove .spam.sux to reply. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Electrically Powered Ultralight Aircraft | Larry Dighera | Piloting | 178 | December 31st 07 08:53 PM |
Solar powered aircraft. Was: Can Aircraft Be Far Behind? | Jim Logajan | Piloting | 4 | February 9th 07 01:11 PM |
World's First Certified Electrically Propelled Aircraft? | Larry Dighera | Piloting | 2 | September 22nd 06 01:50 AM |
Powered gliders = powered aircraft for 91.205 | Mark James Boyd | Soaring | 2 | December 12th 04 03:28 AM |
Help! 2motors propelled ultralight aircraft | [email protected] | Home Built | 3 | July 9th 03 01:02 AM |