An/TVs 3 Searchlight – 20 kW Xenon Arc viewable from space
brettpeabody.com
brettpeabody.com
Examples include AN/PVS-14(nightvision goggles), AN/ALR-67(V)3 (airplane RWR), AN/PRC-152(walkie talkie radio).
(old 1 candlepower is 0.981 candelas)
According to the Wp the the world's most powerful searchlight today is 7 times more powerful. The beam in Luxor Hotel in Las Vegas has 39 7 kW xenon lamps to produce of beam of about 9.129 billion candela, 13 million lumen.
"The brightness emanating from the Luxor lamp room is about twice that which emanates from an equal area of the sun's surface (about 95,000,000 cd/ft2 versus 45,000,000 cd/ft2)."
I recall reading somewhere that David Letterman wanted to use one on his show to melt a small car, but the manufacturer thought it frivolous and did not cooperate.
[1] https://www.researchgate.net/publication/280621958_Modeling_...
This is the best kind of articles I hope to find here. Thanks!
I was skeptical at first, but according to the wiki article about xenon arc lights, they actually produce quite a bit of UV light - the spikes are even higher than visible light.
You can actually generate UV with very low voltage if you have the right semiconductors. That we regularly deal with tens/hundreds of volts without incident is quite astonishing.
Yeah but you're never more than arm's length away from those.
Not wanting to ruin a good story, but I find this unlikely. If it were true I would think the military would be more interested in using them as weapons for electronic warfare than search lights. More likely the lights were interfering with radio links like telemetry or voice. Or maybe they were just not conforming to some EMI guidelines NASA was using at the time and were modified as a safety precaution.
"Chicken wire! Turns out this was added for the Apollo program, when they used the TVS-3s to light the pad. A 20kW short-arc fed with 400Hz 3phase fullwave rectified unfiltered power produces lots of RFI at 1200Hz harmonics, and when nice and focused with a reflector it was enough to shut down the capsule. So they made a Faraday cage."
[1] https://www.candlepowerforums.com/vb/showthread.php?348441-A...
BEST hope possible to make the story true would be clear glass semiconductors can detect incoming light so MAYBE germanium glass tube diodes hanging out in the air could get confused, although why a moon rocket would have bare unprotected glass semiconductors on the outside is a mystery.
With 20 kilowatts flowing it's very believable that the comb reaches quite a ways up the spectrum. And the radiator doesn't have to be tremendously efficient or focused with that kind of input power to produce significant effects in unintentional receivers. Also remember that wiring harnesses in spacecraft are probably very long, so will be good receivers at many frequencies reaching quite low.
But I'm talking about the angular size of the smallest detail a human eye can perceive, which does matter a lot.
Anything smaller than one arc minute might as well be a point source. A star is smaller than an arc minute. A light viewed from space is smaller than an arc minute. But either way, that "point source" has to be bright enough to light up the entire arc minute to stand out from its surroundings.
The only thing your eye perceives is the total light coming from that arc minute. Which is the same as saying you have to bring up the average brightness of that arc minute.
And an arc minute's area, viewed from low orbit, is somewhat bigger than a football field.
> Pretty sure you can do that with just a few watts laser with size measured in millimeters, if you focus it well enough onto the ISS.
Yeah but that's a laser. This is a white light. Much more difficult and impressive.
This means if you take a point light designed to light a football field (football fields do have these light sources), and direct it into space instead of the ground, will be visible from low orbit.
> Much more difficult and impressive.
People did it with less powerful light sources: https://www.universetoday.com/93987/amateur-astronomers-flas...
A point light designed to light up an entire football field should work, yes.
What football field has single lights that powerful? Normally you have many flood arrays with a dozen or more lights each.
> People did it with less powerful light sources:
Cool! So that's somewhere around one kilowatt, significantly easier to do.
Though notably it's still a spotlight. I wonder how many watts of flood light you would need.
I was thinking about a single array, from the orbit it’s pretty close to a point source.
> I wonder how many watts of flood light you would need.
I don’t know about efficiency of that military equipment (need beam angle to compute), but I would expect with modern white LEDs you don’t need that many watts, they’re very efficient at converting electricity to light. You would probably still want liquid cooling for them, though.
It is, but I'm way less impressed when someone says their 4x6 block of floodlights is visible from space, compared to their single light.
http://web.archive.org/web/20201007040003/http://www.brettpe...
Does anyone know the failure modes of an arc lamp? Do the electrodes wear out / erode? Is repair even possible for something like this or is it essentially remanufacturing the entire thing because of the capsule enclosing everything?
Searchlights work by focusing light from a source to infinity. Physics dictates that small light sources focus better. Getting searchlight-level brightness from an LED source will require an LED array, which will be too big to focus effectively.
LEDs make excellent floodlights, but if you want reach, xenon discharge lamps are still the best option.
However, the diameter of each LED optic would need to at least equal the diameter of the single optic used for a point source light. The result would be an enormous searchlight with a very broad beam.
I can't find any solid information on the quantitative light output of the AN/TVS-3, but xenon arc lamps typically produce 30 lumens per watt. Therefore, the 20KW AN/TVS-3 should produce around 600,000 lumens.
Readily available high-power LEDs are capable of 1700 lumens, so equaling the AN/TVS-3 would take--as a very rough ballpark that does not take into account the different light distribution between LEDs and discharge lamps--350 LEDs and optics. The AN/TVS-3 uses 30" optics, so those optics would also need to be at least 30" in diameter.
350 30" optics is a lot more like a wall of light than a searchlight. Aiming that many separate optics would also be a nightmare.
https://en.wikipedia.org/wiki/Luminous_efficacy
What I'm not sure of is if the lumins/watt rating is given for the light output or the power input.
The input power rating is 450 Amps * 200 Volts * 1.732 = 155880 electrical watts. That's nearly 7.75 times as much electrical power as light output. That makes sense since the peak efficiency is about 7.3 for a xenon arc lamp.
I probably am missing something about optics though.
Bigger optics = less beam divergence = more useful range.
This is a function of the diffraction limit[0] and is a property of physics.
If you want to match the beam divergence of a 30" optical system, you have to use 30" optics; there are no shortcuts.
[0] https://www.edmundoptics.com/knowledge-center/application-no...
I can, however, imagine that a multi source system would require in-phase light sources to kind of mimic a phased-array receiver on the send side.
XKCD explainer here: https://what-if.xkcd.com/145/
> It is as perfect as I can make it.
> This is me setting my neighbor's tree top on fire.
And this is why we can't have nice things. Lighting up this sort of thing in middle of residential area is not cool.