Chinese Subs May Be Propelled Silently By Lasers

April 24, 2024 by Richard Baguley 62 Comments

If sharks with lasers on their heads weren’t bad enough, now China is working on submarines with lasers on their butts. At least, that’s what this report in the South China Morning Post claims, anyway.

According to the report, two-megawatt lasers are directed through fiber-optic cables on the surface of the submarine, vaporizing seawater and creating super-cavitation bubbles, which reduce drag on the submarine. The report describes it as an “underwater fiber laser-induced plasma detonation wave propulsion” system and claims that the system could generate up to 70,000 newtons of thrust, more than one of the turbofan engines on a 747.

The report (this proxy can get around the paywall) claims that the key to the system are the tiny metal spheres that direct the force of the cavitation implosion to propel the submarine. Similar to a magnetohydrodynamic drive (MHD), there’s no moving parts to make noise. Such a technology has the potential to make China’s submarines far harder to detect.

Looking for more details, we traced the report back to the original paper written by several people at Harbin Engineering University, entitled “Study on nanosecond pulse laser propulsion microspheres based on a tapered optical fiber in water environment“, but it’s still a pre-print. If you can get access to the full paper, feel free to chime in — we’d love to know if this seems like a real prospect or just exaggerated reporting by the local ~~propaganda~~ media.

[Image via Wikimedia Commons]

Fail Of The Week: A Potentially Lethal Tattoo Removal Laser Power Supply

March 24, 2024 by Dan Maloney 8 Comments

Caveat emptor is good advice in general, but in the wilds of eBay, being careful with what you buy could be life-saving. To wit, we present [Les Wright]’s teardown and very ginger power-up of an eBay tattoo-removal laser power supply.

Given that [Les] spent all of around $100 on this widowmaker, we’re pretty sure he knew what he was getting himself into. But he likely wasn’t quite prepared for the scale of the sketchiness this thing would exhibit. The deficiencies are almost too many to number, starting with the enclosure, which is not only made completely of plastic but assembled from individual sheets of flat plastic stock that show signs of being glued together by hand. Even the cooling water tank inside the case is pieced together this way, which probably led to the leaks that corroded the PCBs. Another assembly gem is the pair of screws the big energy storage capacitor is jammed under, presumably to hold it in place — because nothing says quality like a BOM that can’t spring for a couple of cable ties. Click through the break to read more and see the video.

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Faux Silkscreen On A PCB Made With A Laser Cutter

March 18, 2024 by Lewin Day 13 Comments

If you’re getting PCBs professionally made, silkscreen usually comes free as part of the package. However, if you’re making your own, the job is on you. [Tony Goacher] makes his own PCBs on a CNC router, so he’s not getting any silkscreening as part of that bargain. But he wondered—could he do something analogous with a laser cutter?

The answer is yes. The silkscreen layer was first exported from DesignSpark, with the file then sent to LightBurn to prep it for laser cutting. The board outline layer was first engraved on to a piece of scrap as an alignment aid. Then, the board was placed in the laser cutter, with the silkscreen scorched directly on to the fiberglass.

The results are encouraging, if imperfect. [Tony] says he ran at “quite fast speed at quite high power.” The markings are all there, but they’re a little melty and difficult to read. He noted at lower speeds and lower power, the results were a bit more readable.

PCBs aren’t really an ideal engraving or laser marking material, but this technique could be servicable for some basic markings on DIY PCBs. We look forward to seeing how [Tony] improves the process in future. Video after the break.
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NIF’s Laser Fusion Experiment’s Energy Gain Passes Peer Review

February 9, 2024 by Maya Posch 53 Comments

Back in December of 2022, a team of researchers at the USA’s National Ignition Facility (NIF) announced that they had exceeded ‘scientific breakeven’ with their laser-based inertial confinement fusion (ICF) system. Their work has now been peer-reviewed and passed scrutiny, confirming that the energy put into fusing a small amount of deuterium-tritium fuel resulted in a net gain (Q) of 1.5.

Laser Bay 2, one of NIF's two laser bays — Laser Bay 2 at the NIF.

The key take-away here of course remains that ICF is not a viable method of producing energy, as we detailed back in 2021 when we covered the 1.3 MJ yield announcement, and again in 2022 following the subject of this now completed peer review. The sheer amount of energy required to produce the laser energy targeting the fuel capsule and loss therein, as well as the energy required to manufacture each of these fuel capsules (Hohlraum) and sustaining a cycle make it a highly impractical proposition for anything except weapons research.

Despite this, it’s good to see that the NIF’s ICF research is bearing fruit, even if for energy production we should look towards magnetic confinement fusion (MCF), which includes the many tokamaks active today like Japan’s JT-60SE, as well as stellarators like Germany’s Wendelstein 7-X and other efforts to make MCF a major clean-energy source for the future.

Starlink’s Inter-Satellite Laser Links Are Setting New Record With 42 Million GB Per Day

February 5, 2024 by Maya Posch 44 Comments

Slide from the SpaceX Starlink presentation on mesh routing via the laser links. (Credit: PCMag/Michael Kan)

Although laser communication in space is far from novel, its wide-scale deployment as seen with SpaceX’s Starlink satellite internet constellation has brought the technology to the forefront like never before. This was quite apparent during the SPIE Photonics West event on January 30th when [Michael Kan] and other journalists attended a presentation by SpaceX’s [Travis Brashears] on the inter-satellite laser communication performance that was first enabled with the Starlink v1.5 satellites.

Among currently active inter-satellite communication systems, Starlink is by far the most numerous and with the highest bandwidth, reaching over 42 PB per day across its over 9000 space lasers (yes, that is over 9000) for a 5.6 Tbps throughput. Since these satellites form a mesh network with their 100 Gbps laser transceivers, a big part of using it efficiently is to route any data with the least amount of latency while taking into account link distance (maximum of 5,400 km), link duration (up to multiple weeks) and presence of other Starlink satellites before they become within reach. With this complex mesh in LEO, this also means that a very high uptime can be accomplished, with a claimed 99.99% due to rapid route changing.

For the future, SpaceX has plans to not only keep upgrading its own Starlink satellites with better laser transceivers, but to also make them available to third-party satellites, as well as beam the lasers directly down to Earth for ground-based transceivers. The latter is still cutting edge, despite it being tested to beam cat videos to Earth from Deep Space.

This Unique Flip-Flop Uses Chemistry And Lasers

January 24, 2024 by Dan Maloney 8 Comments

One of the first logic circuits most of us learn about is the humble flip-flop. They’re easy enough to build with just a couple of NOR or NAND gates, and even building one up from discrete components isn’t too much of a chore. But building a flip-flop from chemicals and lasers is another thing entirely.

That’s the path [Markus Bindhammer] took for his photochromic molecular switch. We suspect this is less of an attempt at a practical optical logic component and more of a demonstration project, but either way, it’s pretty cool. Photochromism is the property by which molecules reversibly rearrange themselves and change color upon exposure to light, the most common example being glass that darkens automatically in the sun. This principle can be used to create an optical flip-flop, which [Markus] refers to as an “RS” type but we’re pretty sure he means “SR.”

The electronics for this are pretty simple, with two laser modules and their drivers, a power supply, and an Arduino to run everything. The optics are straightforward as well — a beam splitter that directs the beams from each laser onto the target, which is a glass cuvette filled with a clear epoxy resin mixed with a photochromic chemical. [Markus] chose spiropyran as the pigment, which when bathed in UV light undergoes an intramolecular carbon-oxygen bond breakage that turns it into the dark blue pigment merocyanine. Hitting the spot with a red laser or heating the cuvette causes the C-O bond to reform, fading the blue spot.

The video below shows the intensely blue dot spot developing under UV light and rapidly fading thanks to just the ambient temperature. To make the effect last longer, [Markus] cools the target with a spritz from a CO₂ cartridge. We imagine other photochromic chemicals could also be employed here, as could some kind of photometric sensor to read the current state of the flip-flop. Even as it is, though, this is an interesting way to put chemistry and optics to work.

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Hackaday Podcast Episode 249: Data By Laser And Parachute, Bluetooth Hacks, Google’s Gotta Google

December 22, 2023 by Tom Nardi 6 Comments

‘Twas the podcast before Christmas, and all through the house, the best hacks of the week are dancing around Elliot and Tom’s heads like sugar-plums. Whatever that means.

I’d just like to interject for a moment. What you’re referring to as Christmas is, in fact, Happy/Holidays.

Before settling their brains in for a long winter’s nap, they’ll talk about the open source software podcast that now calls Hackaday home, the latest firmware developments for Google’s Stadia controller, high-definition cat videos from space, and upgrades for the surprisingly old-school battery tech that powers the Toyota Prius.

Out on the lawn, expect a clatter about the the state-of-the-art in DIY camera technology, the acoustic properties of hot chocolate, and a storage media from the 1990s that even Al Williams had never heard of.

Finally, after tearing open the shutters and throwing up the sash, the episode wraps up with a discussion about wiring techniques that let you leave the soldering iron at home, and the newest chapter in the long history of transferring data via parachute. Miniature sleigh and eight tiny reindeer sold separately.