19 July 2018

Wake Me up When You Have a Light Saber

No cooling ports either
China is now claiming that they have developed a high power laser weapon with the weight of an assault rifle:
The ZKZM-500 laser assault rifle is classified as being “non-lethal” but produces an energy beam that cannot be seen by the naked eye but can pass through windows and cause the “instant carbonisation” of human skin and tissues.

Ten years ago its capabilities would have been the preserve of sci-fi films, but one laser weapons scientist said the new device is able to “burn through clothes in a split second … If the fabric is flammable, the whole person will be set on fire”.

“The pain will be beyond endurance,” according to the researcher who had took part in the development and field testing of a prototype at the Xian Institute of Optics and Precision Mechanics at the Chinese Academy of Sciences in Shaanxi province.

The 15mm calibre weapon weighs three kilos (6.6lb), about the same as an AK-47, and has a range of 800 metres, or half a mile, and could be mounted on cars, boats and planes.

Particularly this bit:
The rifles will be powered by a rechargeable lithium battery pack similar to those found in smartphones. It can fire more than 1,000 “shots”, each lasting no more than two seconds.
Some data points:
  • The power level of the laser has to be on the order of least a kilowatt, and probably more than 10.
  • Energy from the laser ignoring any losses would therefore be at least 2,000,000 joules, and probably 10 times that.
  • The maximum power density of a LiIon battery is currently less than 1 MJ/kg, so the battery pack would need to weigh, again Before Any Losses of at least 2 kilograms, and for a more realistic power level, we would likely be talking 10 times this.  Also note that maximum power and maximum energy in a battery are more or less inversely related, so you at well under the 1 MJ/kg figure.
  • The current limits on laser efficiency, diode lasers, less than 70%. 
  • The efficiency of the battery on discharge is likely to be less than 90%, but lets call it 95%.
  • The losses incurred will mean that you will need an active cooling system, which will consume a significant amount of power.
So, if we run the numbers, the minimum power from the battery is on the order of 2 MJ/70%/95%= 3MJ, which means that the battery pack comprises the complete weight of the weapon.

And also note the cooling requirements here, which will, at best, make a leaf blower quiet in comparison.

I'm calling bullsh%$.


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