Why don’t tanks use lasers as weapons?
IANAE but I would imagine that a tank is more than large enough to carry the heavy equipment needed, computers to adjust optics to optimize penetration at range X, PTO driven generators to create additional power needed.
I could see frailty being an issue but heck the people in the tank break easier than just about anything else.
Because no one has yet demonstrated in any sort of conflict that a laser can be used as an effective weapon, and bullets and explosive shells work really, really well.
Many current tanks are equipped with lasers for use as range finders. Lasers as a weapon by themselves are not too realistic yet and require large amounts of energy production for use as a weapon. Portability would be a problem and the power wouldn’t be enough to penetrate existing armor in one quick pulse. With the enemy moving and the laser weapon on the move it is unlikely to hold a laser onto one spot of a target long enough to get penetration.
Not to mention that lasers are seriously degraded by atmospheric conditions, and that’s not counting smoke from fires (war produces lots of those!) and battlefield obscurants (chemical smoke, white phosphorus, etc.). If anyone ever produced a directed energy weapon that was sufficently efficient and powerful to be able to produce enough work to defeat main battle tank armor, someone else would just put prismatics or other beam-degrading components in the chemical smoke.
As others have noted, tanks and other vehicles are much tougher to penetrate with a laser than aircraft and missiles. Also, the potential payoff of a laser to shoot down missiles and aircraft is much greater than from one to destroy tanks.
The US is now working several different laser projects, all of which are focused (heh) on shooting down aircraft and missiles:
The US and Israel are working on a batlefield-mobile laser to shoot down tactical ballistic missiles and aircraft. It’s called the Tactical High-Energy Laser (THEL).
A laser is being mounted on a 747 to shoot down ballistic missiles at ranges up to about 100 miles. The laser package will weigh somewhere in the order of 50 tons. First test shot will be around 2003.
Lasers to be mounted on satellites, to shoot down ICBMs. These are pretty far off, maybe 2015 or so.
They are working on ways to overcome all of the problems noted above - accurate pointing when both platform and target are moving, methods to overcome atmospheric diffraction and dispersion (mainly thru adaptive optics), and sufficient laser power in a light, robust package.
Lasers capable of punching through thick armor require tremendous power supplies capable of delivering a single kill in milliseconds. Hell, we have a hard time getting electric cars to work well, never mind tank-mounted death beams.