What was the maximum speed of the U-2A?

What was the maximum speed of the U-2A?

The U-2A weighed 11,700lbs empty. It had a maximum takeoff weight of 16,000 pounds. The P&W J57 produced more than 25,000 horsepower. If the facts below are true, then the nuclear propelled U-2A had a maximum speed of MACH-2 plus at altitudes above 70,000 feet. A chemically powered version would be able to hit Mach speeds for short bursts. In 1949 it was calculated that it would take 45,000 horsepower to push a 50,000lbs plane to Mach 2 at 70,000 feet. The 16,000lbs U-2A powered by a 25,000 horsepower engine would have more than the 16,666 horsepower needed to push it to MACH-2. Moreover a nuclear powered U-2A would essentially become a rocket plane at high altitude because there is no atmospheric oxygen to burn the fuel. The fuel would expand when coming in contact with the reactor core producing thrust out the back.

Notes with sources:

The Pratt & Whitney J58 engine was a nine-stage, axial-flow, bypass turbojet originally developed in the late 1950s to meet U.S. Navy requirements. It was the first jet engine designed to operate for extended periods using its afterburner. The J58 generated a maximum thrust of 32,500 pounds -- more than 160,000 shaft horsepower -- and was the most powerful air-breathing aircraft engine yet devised. The J58 was specifically tailored for operation at extreme speeds, altitudes, and temperatures, and was the first aircraft engine to be flight qualified for the Air Force at Mach 3. At maximum output the fuel flow rate in the J58 is about 8,000 gallons per hour and the exhaust-gas temperature is around 3,400 degrees. The J58 was only used on the Lockheed YF-12 interceptor and its descendants, the A-12 and SR-71.

http://www.456fis.org/YF-12A_SR-71_ENGINE.htm

JP-5 is a complex mixture of hydrocarbons, containing alkanes, naphthenes, and aromatic hydrocarbons that weighs 6.8 pounds per U.S. gallon (0.81 kg/L) and has a high flash point (min. 60 °C or 140 °F).

“45,000 horsepower is required to drive a 25 ton plane 1500 miles an hour (MACH 2.27) at 70,000 feet. … The power requirement would jump to 200,000 horsepower at sea level because of greater air resistance.”

U.S. May Push Efforts to Make Atomic Engine

Los Angeles Times (1923-Current File); Sep 28, 1949;

ProQuest Historical Newspapers: Los Angeles Times

pg. 12

After its relatively short lifetime in the aircraft role, the JT4A found more enduring use in the naval role, where the FT4 was produced in a variety of models between 18,000 and 22,000 hp.

https://en.wikipedia.org/wiki/Pratt_%26_Whitney_J75

The J-57 produced >25,000 horsepower in 1954.

Popular Mechanics August 1954

The U-2A engines produced 11,200 pounds of thrust. If the thrust to megawatt ratio of the Pluto engine 70 pounds of thrust to megawatt holds for this engine. Then it has a 160 megawatt rating or 214,564 horsepower. The TORY II-A reactor had a power rating of 155 Megawatts or 208,000 horsepower. This is the same amount of horsepower the 1949 Los Angeles Times article said that a plane needed to travel at 1500 miles per hour at sea level. This is nearly 10 times the horsepower of the J-57 stated in the August 1954 Popular Mechanics article. The article was off by an order of magnitude. 




The J57 was the first 10,000lbf (45 kN) thrust class engine in the United States. This engine produces 191,575 horse power or 142 megawatts of power.