The heat ray.... Laser or Microwave cannon?

[sunnyrabbiera]

for the longest while everyone reguards the heat ray as a laser, but after seeing the new batman film [batman begins] I was wondering if Wells drew out another technology altogether...

In the new batman film the main villain [Ra's al Ghull] uses a special microwave cannon to evaparate water and turn it into a toxin [with the help of scarecrow who put the toxin into the water, but the stuff needed to be turned to a gas to become toxic]

err anyway, that microwave must have generated an incredible amount of heat and looked a lot like some imagry you might get from Well's description of the heay ray.... for those who might have seen the movie would notice it was almost camera like and emitted a invisible ray of heat...
it tore apart metal and evaparated water with a touch.

also there is the real life weapon the Maser... often used in Godzilla movies, the real thing is pretty cool... err hot.

but maybe the martian heat ray was both a microwave and a laser, and the Martians could have modified thier technologies heavily.

any other ideas of what the heat ray might be, outside of a laser of course

[lanceradvanced]

Well, if you really look at it, both a mircrowave, and lasers are pretty closely related, both are EM radiation emmiters, the big diffrence being the frequency of the beam, and it's coherency...

As described inthe book, the HeatRay works in a manner that's complelty diffrent, from both described above, being more akin to the various solar reflectors that people have build, but with an independant energy source..

[Leatherhead]

sadly an actual "heat ray" is not possible. you could direct a laser or a microwave, but heat cannot really be directed in just one direction. it's thermal dynamics. heat released from a chamber one point will escape in all directions since heat cannot be shot it can only be transmitted.

[Lensman]

Of course a heat ray is possible. Heat is just infrared radiation. We can and do build infrared lasers, and infrared spotlights (designed to be used with infrared "night vision" goggles).

What is needed for a Wellsian heat ray is something which will emit radiation in the infrared spectrum, with the emitter located at the focal point of a parabolic mirror (like the reflector behind the bulb of a flashlight) which is an extremely good reflector of infrared radiation (actually Wells' description suggests a *perfect* reflector). Of course, it needs to be an exceptionally powerful emitter, powered by an improbably powerful energy source, probably beyond our current technology.

And the spread on the parabolic mirror needs to be exceptionally narrow for the ray to have an effective range of two miles-- that is, the beam has to have almost no spread as it travels thru the air (very different from the wide spread of a headlight). This may be possible; I remember my aunt had a flashlight powered by 8 "D" cells which was so bright you could see the beam in the air at night, and she could use it to point out stars in the sky. That flashlight beam had almost no spread on it, at least for the first few yards.

With our present technology, it would be quite a challenge to design a mobile power source to power a Heat Ray which could emit the kind of power Wells describes (setting fire to whole swaths of woods in mere seconds), and building an emitter which wouldn't melt under the intense heat would be very difficult or impossible, even with a massive cooling system.

I'm not sure how to get a perfect or near-perfect reflector of infrared radiation, without invoking some near-magical device such as a "stasis field" from Larry Niven's "Known Space" series. The Martians' technology is clearly still in advance of ours.

Actually, there *is* a way with today's technology to build a Heat Ray which to a large extent operates as Wells describes. Use the most powerful infrared laser you can build, and put a grid or lens at the front end which very, *very* slightly spreads the beam. Of course there's no logical *reason* you'd want the beam of a weapon to spread, but it *is* physically possible. Now I seriously doubt that you can build one as *powerful* as what Wells describes-- especially not one mounted on a mobile unit-- and certain details will be different; it's not likely to look like a camera box, and you won't see green flashes coruscating around the emitter as it operates.

As for the "Batman Begins" microwave laser (maser) cannon: That is simply not possible. There's no way to heat up the water in water mains with microwaves emitted above the ground. The concrete/asphalt and earth, and the metal pipe of the water main itself, would absorb the microwaves just fine, thank you, and microwaves certainly can't pass thru entire buildings without being absorbed, as though the buildings were invisible. Now since concrete has a large water content, with an improbably large power source and an improbably powerful maser, you *might* be able to superheat the water in concrete enuff for it to explode. But of course the area/volume affected would be quite small, not something that could devastate an entire city.

However, a microwave laser would make a very inefficient Heat Ray. Using it on vegetation would tend to heat or boil water inside the grass, bushes and trees, not cause them to burst into flames. The effect on people would be similar; the human body is mostly water. Sure if you held a powerful microwave laser beam on one spot of vegetation long enuff it would catch fire, but the same can be said of *any* frequency of laser. As I said-- if you want heat, use infrared radiation. Not microwaves.

Oh, and a final point: In 1898, a "camera" looked like a plain wooden box with a lens in the center of one side. It looked nothing like the maser cannon in "Batman Begins".

[Refugee]

I always though it was like sunlight through a magnifying glass, highly focussed heat, so it's invisible but perhaps with the ripple distortins in the air like above a fire on on roads on a hot day.

[Topaz]

Lensman is right that what Wells describes most closely resembles a high-power infrared laser system. The microwave system in 'Batman Begins' is complete fantasy, and Lensman is again correct in noting that such a weapon would heat the water in a human body just as effectively as it would the water in the mains - thus we have microwave ovens. Microwave systems are best at inducing overloads in electrical circuits, rather like the EMP weapon did in the Bond film 'Goldeneye', albeit on a smaller scale.

High-power infrared lasers in our own technology typically use silicon-carbide or quartz mirrors with special reflective coatings tailored to the specific wavelength of the device involved. Mirrors can also be cooled, although this increases the complexity of the system.

A Heat-Ray is not only possible, but broadly comparable systems have already been demonstrated in laboratory settings in the U.S. (THEL, M-THEL, etc.), and experimentation is under way to make them deployable with regular military forces (ABL, etc.). From Wells' description, the Martian's Heat-Ray is a multi-megawatt infrared laser system (probably 10-15MW, at a roughest guess), operating at fairly short wavelength in the infrared range to keep the mirror size down, and either solid-state or, if the narrator's conjecture about 'material required for its generation' is correct, chemically-pumped. You can think of solid-state systems as similar in concept to the laser-emitting diodes in any CD player, and chemical systems use violently reacting chemicals (iodine, flourine, etc.) in a tuned cavity to create the beam. In either case, a parabolic mirror (Wells being right yet again) is used to direct and focus the beam against the target. In our (edit: meaning human) systems, the beam-steering optics are 'adaptive', compensating for turbulence in the atmosphere and the 'blooming' effect of a high-energy beam heating the air, which can cause the beam to spread and lose brightness. Fortunately for the Martians, they were using their weapon at very short ranges, so blooming and atmospheric distortion would be relatively minor problems compared to shooting at a ballistic missile through miles of atmosphere.

It would be an incredibly effective weapon against Victorian-era human adversaries, much as Wells describes. He really had an amazing grasp of what would be desirable weapons against the armies of his era.

[Chris Oakley]

When I read the novel my interpretation of the heat ray was an incredibly hot source of energy, possibly nuclear, was channelled through an array of lenses and mirrors to direct the invisble beam of heat from the source.

Similar to what refugee says above. A bit like when you burn ants with a magnifying glass in the summer. That's essentially how I imagined the heat ray working and it would also be invisible.

[Lensman]

Infrared radiation is outside the spectrum which the human eye can see, and thus is invisible to our eyes.

Topaz: Your knowledge of laser systems is quite impressive! From what you say I am guessing that even very powerful gas-pumped lasers don't need elaborate cooling systems, because after the laser fires the gas is vented and therefore takes away the waste heat? If so, IIRC a problem with this type of laser is that it fires only in short bursts; it's not continuous firing as are Wellsian Heat Rays.

I had no idea lasers used parabolic mirrors. I thought, for instance, the usual red laser used a ruby rod to generate/focus the beam, in lieu of a parabolic mirror. Guess I need to read up on lasers!

So, Topaz, are you saying we do have vehicle-mounted lasers about as powerful as those Wells describes? If so, I'm guessing they're gas pumped, burst-firing lasers. I believe I read recently that DARPA is presently trying to develop powerful solid-state laser weapons as an improvement over gas-pumped lasers. If they have indeed developed a continuous-firing very powerful laser, I wonder how they overcame the waste heat problem? Have modern laser emitters become so efficient that almost no waste heat is generated?

[maniacs]

lensman said:

Infrared radiation is outside the spectrum which the human eye can see, and thus is invisible to our eyes.

Topaz: Your knowledge of laser systems is quite impressive! From what you say I am guessing that even very powerful gas-pumped lasers don't need elaborate cooling systems, because after the laser fires the gas is vented and therefore takes away the waste heat? If so, IIRC a problem with this type of laser is that it fires only in short bursts; it's not continuous firing as are Wellsian Heat Rays.

I had no idea lasers used parabolic mirrors. I thought, for instance, the usual red laser used a ruby rod to generate/focus the beam, in lieu of a parabolic mirror. Guess I need to read up on lasers!

So, Topaz, are you saying we do have vehicle-mounted lasers about as powerful as those Wells describes? If so, I'm guessing they're gas pumped, burst-firing lasers. I believe I read recently that DARPA is presently trying to develop powerful solid-state laser weapons as an improvement over gas-pumped lasers. If they have indeed developed a continuous-firing very powerful laser, I wonder how they overcame the waste heat problem? Have modern laser emitters become so efficient that almost no waste heat is generated?

The original laser design used a ruby stone as a lens. Thats why we associate laser light as red - apparentl. Tho it can be a number of colours.

[obiwanbeeohbee]

I believe Wells' Heat Ray is not based on any kind of laser or microwave technology. It's some sort of nuclear device, probably a fusion reactor. The description is an intense heat generated in a chamber of practically absolute non-conductivity which they direct by use of a highly polished parabolic mirror of unknown composition. It's also described as being contained in a box. From that description, I would guess that there is some sort of aperature in the box aimed in the direction of the mirror that opens and closes to fire the device.

[Topaz]

Man, I've been away too long. Über-busy with other projects, I'm afraid. Nice to see some familar names still here!

lensman said:

Topaz: Your knowledge of laser systems is quite impressive!

Thanks. I can't take too much credit - I've got a copy of a late-eighties era report on directed-energy weapons by the American Physical Society. Goes into a lot of depth, and that's where I've gotten most of the material I've reported here. The rest is from being an avid reader of Aviation Week and Space Technology magazine. Cool stuff, in there!

lensman said:

... From what you say I am guessing that even very powerful gas-pumped lasers don't need elaborate cooling systems, because after the laser fires the gas is vented and therefore takes away the waste heat? If so, IIRC a problem with this type of laser is that it fires only in short bursts; it's not continuous firing as are Wellsian Heat Rays.

By and large I believe you're correct - I don't have that reference here at work to check. I believe the optics may still be cooled, and I imagine there's some kind of general cooling for the whole system, although that could be simple airflow around the device.

I believe chemical lasers are capable of firing for some significant amount of seconds, which would just tally with WOTW. I don't recall any passage where they're actually firing the thing continually for minutes at a time without possible break. I could be wrong in that.

lensman said:

I had no idea lasers used parabolic mirrors.

Yeah, the old ruby lasers and such had flat mirrored ends. More recent designs use tuned cavities for the lasing action, with mirrors on each end. The beam-director at the targeting end of the system would use a parabolic mirror sized to the range requirement.

lensman said:

So, Topaz, are you saying we do have vehicle-mounted lasers about as powerful as those Wells describes? If so, I'm guessing they're gas pumped, burst-firing lasers. I believe I read recently that DARPA is presently trying to develop powerful solid-state laser weapons as an improvement over gas-pumped lasers. If they have indeed developed a continuous-firing very powerful laser, I wonder how they overcame the waste heat problem? Have modern laser emitters become so efficient that almost no waste heat is generated?

None actually in-service as far as I know, but demonstrators have been fired. Most were chemically-pumped as you surmise. You're right about the current research on solid-state lasers, and the military's preference for that technology for weapon systems. I don't know too much about them, but waste heat is apparently the limiting factor under current technology. I remember reading an article in AvWeek about some research on fitting such a laser to the proposed F-35 Joint Strike Fighter. The thing would sit in the cavity used for the lift fan in the V/STOL version of the airplane, and the generators would be powered by the shaft take-off from the main jet engine, which would otherwise turn the lift fan. The limiting factor, according to the article, was disposing of the waste heat efficiently enough from the tight little space available so that you could sustain long-enough bursts at a high-enough rate to make a useful weapon. With current technology, the thing would melt if you fired it more than every couple of minutes or so. Kinda sucky for a dogfight. ;D

[Commandingtripod]

Whoa!
Like it's been said before, you really do know your stuff Topaz.
Have you also built a heat ray by any chance?

[Topaz]

Well, thank you. I read a lot.

If anyone wants to read the same material, I checked and it's still available for purchase from the American Physical Society. They're charging a rather steep $50 for such an out-of-date report, but it was kind of a landmark thing, and provides a solid background for understanding the current work. I was lucky - I got mine for free from a friend that was doing a paper on the subject and bought it for research material.

Here's the link:

prola.aps.org/abstract/RMP/v59/i3/pS1_1?qid=b069293f8f8cc61f&qseq=1&show=25

[Lensman]

topaz said:

I believe chemical lasers are capable of firing for some significant amount of seconds, which would just tally with WOTW. I don't recall any passage where they're actually firing the thing continually for minutes at a time without possible break. I could be wrong in that.

Okay, if they can fire continuously for a significant fraction of a minute, that would seem to fit within Wells' description. I'm pretty sure the longest description of a Heat Ray being continuously fired is in chapter I-6. Certainly it seems to be in use for more than just a few seconds, but I can certainly believe all that took less than a minute.

In I-11 is a description of a Heat-Ray being used over the space of "a few minutes", after which "the Thing shut off the Heat-Ray," but again one *might* suggest this was firing in long bursts with at least a few seconds of cooling between. It does seem that the Martians must be able to dissipate the waste heat fairly rapidly, or more likely as the Narrator says they are able to "generate an intense heat in a chamber of almost absolute non-conductivity", the Heat-Ray simply is so efficient it generates little waste heat to begin with. And lest anyone scoffs at that as impossible, I'd like to point out that the new LED lasers are doing just that.

[malfunkshun]

i was JUSt about to go all for the MASER device, having read the Nights Dawn 6 book series (copious use of maser tech there) then i realized it was fiction :/

but topaz and lensman have both put good info into play, most likely an infrared laser.

[Topaz]

Oh, microwave lasers are possible. I believe they predate optical lasers by a few years, if I'm not mistaken.

en.wikipedia.org/wiki/Maser#Some_common_types_of_masers

Here's the key quote, though, at least about the most common kind today:

"The microwave signal coming out of the maser is very weak (a few pW) ...."