Pulling Backward To Go Forward: The Brennan Torpedo Explained

December 17, 2024 by Donald Papp 16 Comments

The Brennan torpedo, invented in 1877 by Louis Brennan, was one of the first (if not the first) guided torpedoes of a practical design. Amazingly, it had no internal power source but it did have a very clever and counter-intuitive mode of operation: a cable was pulled backward to propel the torpedo forward.

If the idea of sending something forward by pulling a cable backward seems unusual, you’re not alone. How can something go forward faster than it’s being pulled backward? That’s what led [Steve Mould] to examine the whole concept in more detail in a video in a collaboration with [Derek Muller] of Veritasium, who highlights some ways in which the physics can be non-intuitive, just as with a craft that successfully sails downwind faster than the wind.

The short answer is gearing, producing more force on the propeller by pulling out lots of rope.

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Retrotechtacular: The TV Bombs Of WWII

November 14, 2024 by Dan Maloney 40 Comments

Anyone who was around for the various wars and conflicts of the early 2000s probably recalls the video clips showing guided bombs finding their targets. The black-and-white clips came from TV cameras mounted in the nose of the bomb, and were used by bombardiers to visually guide the warhead to the target — often providing for a level of precision amounting to a choice of “this window or that window?” It was scary stuff, especially when you thought about what was on the other side of the window.

Surprisingly, television-guide munitions aren’t exactly new, as this video on TV-guided glide bombs in WWII indicates. According to [WWII US Bombers], research on TV guidance by the US Army Air Force started in 1943, and consisted of a plywood airframe built around a standard 2000-pound class gravity bomb. The airframe had stubby wings for lift and steerable rudders and elevators for pitch and yaw control. Underneath the warhead was a boxy fairing containing a television camera based on an iconoscope or image orthicon, while all the radio gear rode behind the warhead in the empennage. A B-17 bomber could carry two GB-4s on external hardpoints, with a bulky TV receiver provided for the bombardier to watch the bomb’s terminal glide and make fine adjustments with a joystick.

In testing, the GB-4 performed remarkably well. In an era when a good bombardier was expected to drop a bomb in a circle with a radius of about 1,200′ (365 meters) from the aim point, GB-4 operators were hitting within 200′ (60 meters). With results like that, the USAAF had high hopes for the GB-4, and ordered it into production. Sadly, though, the testing results were not replicated in combat. The USAAF’s 388th Bomber Group dropped a total of six GB-4s against four targets in the European Theater in 1944 with terrible results. The main problem reported was not being able to see the target due to reception problems, leaving the bombardiers to fly blind. In other cases, the bomb’s camera returned a picture but the contrast in the picture was so poor that steering the weapon to the target was impossible. On one unfortunate attack on a steel factory in Duren, Germany, the only building with enough contrast to serve as an aiming point was a church six miles from the target.

The GB-4’s battlefield service was short and inglorious, with most of the 1,200 packages delivered never being used. TV-guided bombs would have to wait for another war, and ironically it would be the postwar boom in consumer electronics and the explosion of TV into popular culture would move the technology along enough to make it possible.

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Minuteman ICBM Launch Tests Triple Warheads

November 12, 2024 by Maya Posch 75 Comments

On November 5th, the United States launched an LGM-30G Minuteman III ICBM from Vandenberg Space Force Base in California. Roughly 30 minutes later the three warheads onboard struck their targets 4,200 miles (6,759 km) away at the Reagan Test Site in the Marshall Islands. What is remarkable about this test is not that one of these ICBMs was fired — as this is regularly done to test the readiness of the US’ ICBMs — but rather that it carried three warheads instead of a single one.

Originally the Minuteman III ICBMs were equipped with three warheads, but in 2014 this was reduced to just one as a result of arms control limits agreed upon with Russia. This New Start Treaty expires in 2026 and the plan is to put three warheads back in the 400 operational Minuteman III ICBMs in the US’ arsenal. To this end a validation test had to be performed, yet a 2023 launch failed. So far it appears that this new launch has succeeded.

Although the three warheads in this November 5 launch were not nuclear warheads but rather Joint Test Assemblies, one of them contained more than just instrumentation to provide flight telemetry. In order to test the delivery vehicle more fully a so-called ‘high-fidelity’ JTA was also used which is assembled much like a real warhead, including explosives. The only difference being that no nuclear material is present, just surrogate materials to create a similar balance as the full warhead.

Assuming the many gigabytes of test data checks out these Minuteman III ICBMs should be ready to serve well into the 2030s at which point the much-delayed LGM-35 Sentinel should take over.

Thermoelectric Blaster Flings Ice Projectiles

November 11, 2024 by Lewin Day 37 Comments

Nerf blasters are fun and all, but flinging foam can get old. Picking it up again, even moreso. This blaster from [Concept Crafted Creations] gets around that annoying problem by shooting ice instead.

The concept was to build a better water gun with longer range—and what better way to do that than by shooting ice instead? The blaster relies on a PVC air tank for propulsion—one of the most controversial design choices you can make if you read the comments around here. It’s charged by a small air compressor, and dumping the air is handled by a solenoid valve. So far, so simple.

What makes this blaster special is where it gets its ammunition from. The blaster uses a custom CNC-machined block from PCBway to act as a freeze chamber. Water enters an aluminum block, and is cooled by thermoelectric elements. Once the projectile has frozen inside the chamber, it’s stuck in place, so the chamber is then heated by a small heating element. This melts the projectile just enough to allow it to be fired.

It’s a complicated but ingenious way of building an ice blaster. It does pack some real punch, too. It shoots the ice projectiles hard enough to shatter wine glasses. That’s enough to tell us you don’t want to be aiming this thing at your pals in a friendly match of Capture the Flag. Stick to paintballs, perhaps. Video after the break. Continue reading “Thermoelectric Blaster Flings Ice Projectiles” →

Bogey Six O’clock!: The AN/APS-13 Tail Warning Radar

October 31, 2024 by Danie Conradie 20 Comments

Although we think of air-to-air radar as a relatively modern invention, it first made its appearance in WWII. Some late war fighters featured the AN/APS-13 Tail Warning Radar to alert the pilot when an enemy fighter was on his tail. In [WWII US Bombers]’ fascinating video we get a deep dive into this fascinating piece of tech that likely saved many allied pilots’ lives.

Fitted to aircraft like the P-51 Mustang and P-47 Thunderbolt, the AN/APS-13 warns the pilot with a light or bell if the aircraft comes within 800 yards from his rear. The system consisted of a 3-element Yagi antenna on the vertical stabilizer, a 410 Mhz transceiver in the fuselage, and a simple control panel with a warning light and bell in the cockpit.

In a dogfight, this allows the pilot to focus on what’s in front of him, as well as helping him determine if he has gotten rid of a pursuer. Since it could not identify the source of the reflection, it would also trigger on friendly aircraft, jettisoned wing tanks, passing flak, and the ground. This last part ended up being useful for safely descending through low-altitude clouds.

This little side effect turned out to have very significant consequences. The nuclear bombs used on Hiroshima and Nagasaki each carried four radar altimeters derived from the AN/APS-13 system.

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DIY Laser Tag Project Does It In Style

October 26, 2024 by Donald Papp 21 Comments

This DIY lasertag project designed by [Nii], which he brought to Tokyo Maker Faire back in September, is a treasure trove. It’s all in Japanese and you’ll need to visit X (formerly Twitter) to see it, but the images do a fine job of getting the essentials across and your favorite translator tool will do a fair job of the rest.

There’s a whole lot to admire in this project. The swing-out transparent OLED display is super slick, the electronics are housed on a single PCB, the back half of the grip is in fact a portable USB power bank that slots directly in to provide power, and there’s a really smart use of a short RGB LED strip for effects.

The optical elements show some inspired design, as well. An infrared LED points forward, and with the help of a lens, focuses the beam tightly enough to make aiming meaningful. For detecting hits, the top of the pistol conceals a custom-made reflector that directs any IR downward into a receiver, making it omnidirectional in terms of hit sensing but only needing a single sensor.

Want to know more? Check out [Nii]’s earlier prototypes on his website. It’s clear this has been in the works for a while, so if you like seeing how a project develops, you’re in for a treat.

As for the choice of transparent OLED displays? They are certainly cool, and we remember how wild it looks to have several stacked together.

The US’s New Nuclear Weapons, Mysterious Fogbanks And Inertial Confinement Fusion

October 11, 2024 by Maya Posch 52 Comments

Keeping the United States’ nuclear arsenal ready for use is an ongoing process, one which is necessarily shrouded in complete secrecy. In an article by The War Zone these developments and the secrets behind it are touched upon, including a secret ingredient for these thermonuclear warheads that is only officially known as ‘Fogbank’, but which is very likely aerogel.

As noted by a commentator, this is pretty much confirmed in an article published by Los Alamos National Laboratories (LANL) in the 2nd 2009 issue (PDF) of Nuclear Weapons Journal. On page nine the article on hohlraum-based inertial confinement fusion notes the use of aerogel to tamp the radially inward motion of the wall material, suggesting a similar function within one of these thermonuclear warheads.

The research at the Nuclear Ignition Facility (NIF) over at Lawrence Livermore National Laboratory (LLNL) is directly related to these thermonuclear weapons, as they are based around inertial confinement fusion (ICF), which is what the NIF is set up for to study, including the role of aerogel. ICF is unlikely to ever be used for energy production, as we noted in the past, but makes it possible to study aspects of detonating a thermonuclear weapon that are difficult to simulate and illegal to test with real warheads.

Currently it seems that after decades of merely reusing the Fogbank material in refurbished warheads, new material is now being produced again, with it likely being used in the new W93 warhead and the low-yield W76 and life-extended W76-1 variants. All of which is of course pure conjecture, barring the details getting leaked on the War Thunder forums to settle a dispute on realistic US thermonuclear weapon yields.