Here is an excerpt from Dr. Gregory S. Jenkins' paper titled "The Overwhelming Implausibility of Using Directed Energy Beams to Demolish the World Trade Center Towers":
"MIRACL Laser Operation Specifications
The largest known laser in the western hemisphere throughout the 1990’s was the MIRACL laser (Mid-Infrared Advanced Chemical Laser). A joint Israeli-American project located at the White Sands Missile Range in New Mexico, the laser facility boasts the ability to destroy Katyusha rockets. The laser is continuous-wave with a maximum output of roughly 1 MW of power encompassing the wavelengths 3.6 to 4.0 (micro)m. Maximum run-time is 30 seconds at maximum power. The operation of the laser is quite telling. Ethylene (C2H4) and nitrogen trifluoride (NF3) are burned at the input of the laser cavity. Excited fluorine atoms are liberated during the combustion. Further downstream, deuterium and helium (an exchange gas probably used to adjust the de-excitation time scales) are injected into the stream where the deuterium combines with the free fluorine atoms to form deuterium fluoride (DF) in vibrational and rotational excited states. The laser cavity is actually perpendicular to the flow of gases, and evidently supports 10 modes concurrently.
The massive amount of gas flow can only be compared to a jet engine. The gas is drawn through the laser cavity by creating a vacuum of 150 Torr on one end. Since the quantity of gas is so large, the vacuum is produced by condensing massive amounts of steam into water.
The exhaust gas leaves the laser cavity at 1127C and is cooled to 40C. The toxic gas is reacted with a 1% sodium hydroxide solution to remove HF and DF gas from the exhaust. The resulting sodium fluoride is treated with lime resulting in fluorspar (CaF2) sludge.
It is instructive to consider the logistics and sheer amount of resources utilized in an average run (not necessarily at maximum power for the maximum allowable time duration) of the laser: 340,650L of water, 11,355L of diesel fuel, 16 kg of deuterium gas, 4.5 kg of ethylene gas, and 381 kg of nitrogen trifluoride gas. Fluorspar sludge (630 kg) is generated as a byproduct. The facility, only including the actual housing of the laser as well as gas handling and water handling peripherals, occupies an area of approximately 1.48 sq km. Due to the logistical nightmare, only 6 to 10 laser tests were performed annually throughout the 1990’s.
Energy Comparisons to the MIRACL Laser and Ramifications
The power required to evaporate the steel in one of the WTC towers is astronomically large.
To get a feel for the huge size of this number, we will compare to the largest laser in the western hemisphere, the MIRACL laser. Recall that the power required to evaporate the steel in a WTC tower was 5.7x10^13 Watts. The power output of the mammoth size MIRACL laser is 10^6 Watts. This means that we would need 5.7x10^7, or 57 million MIRACL lasers of power!
To put these numbers into perspective, we can scale the resources used by the behemoth MIRACL laser by a factor of 57 million. The necessary amount of water is 4% of the water in Lake Erie,9 the land area occupied by the facility would be 9 times the total land area of the United States,10 the amount of nitrogen trifluoride required exceeds 11,000 times the worldwide supply,7 and the amount of diesel fuel would be equal to the daily US demand of all distillate fuels.8
Suffice to say that any known method to generate the energy required to vaporize the steel in the upper 110 stories of the WTC towers is not going to be space-based.
By contrast, the MIRACL laser is designed to destroy Katyusha rockets to “heat up the skin of the missile and then the internal pressure of the fuel tank actually causes the missile to explode”.6 The power required to heat the entire shell to 600C of a Katyusha rocket requires 1 MW over 4.2 seconds6 which physically explains why theMIRACL laser works for its intended purpose."