Category Archives: Air and Naval Weapons

Jets (and Vehicles) with Frickin’ Lasers on They Heads

Doctor Evil’s technological dreams, not to mention Auric Goldfinger’s and Ernst Stavro Blofeld’s, are inching closer to reality. That’s the only possible conclusion an avid movie-goer will draw from a fascinating Bill Sweetman article in Aviation Week. 

Today, on an armored vehicle as an air defense weapon that doesn't need to "lead" a target; tomorrow, an aerial precision-strike capability? (Bill Sweetman AWST photo).

Today, on an armored vehicle as an air defense weapon with a functional MV of infinity, so it doesn’t need to “lead” a target; tomorrow, an aerial precision-strike capability? (Bill Sweetman AWST photo).

In fact, Sweetman deploys a bunch of pungent prose that sounds like something out of The Strategy Page, but with the essential difference that Sweetman knows what he’s talking about and has been wired into defense RDT&E since the second coming of laser weaponry (and the first serious, non-Bond-villain one) in the 1980s. Sweetman starts with a dismissive swipe at US and USSR laser weapons programs of the 1980s (“The only thing of consequence that any of them destroyed was confidence in laser weapons”), and then leaps into “that was then, this is now”-ville.

New HEL [High-Energy Laser] weapons are smaller than the 1980s monsters, with a goal of 100-150 kw, and powered by electricity rather than rocket-like chemical systems. Modest power permits more precise optics and—in some cases—the use of commercial off-the-shelf fiber-laser sources, improving beam quality (that is, focus) and reducing cost.

Star Wars lasers were intended to hit things that missiles could not touch. The new generation exploits different characteristics: a magazine as deep and easily replenished as the fuel tank, and a low cost per shot (about $1, says Rheinmetall). The idea is to deal with targets that missiles cannot engage affordably.

A mini-UAV is a threat because it can target ground forces for artillery. It is cheaper than any surface-to-air missile, but a laser can blind it, destroy its payload or shoot it down. Rocket and mortar defense is another application. Rafael’s Iron Beam laser is a logical follow-on to Iron Dome, which is practical and affordable only because it ignores rockets that will fall on open ground; that will no longer work when weapons are guided.

Hmmm. Thinking about the implications of what Sweetman is saying here, there are several paths around Iron Dome which the Palestinian terrorists may choose to adopt: they could try overwhelming it with quality, overwhelming it with accuracy (by guidance, as he suggests, or simply by increased ballistic accuracy and precision of aim), or overwhelming it with speed by using gun artillery instead of relatively-slow rockets.

Wile-E-Coyote-Genius-Business-CardNo doubt the cagey Israelis (has any nation’s paranoia ever been more justified?) have already thought this through and have counter-countermeasures in development (one of which certainly is a laser system). The Palestinians, in their ongoing attempts to outsmart the smarter Israelis, are the Wile E. Coyote of weapons development.

Anyway, let’s return to Sweetman’s rundown of current and very-near-future directed energy weaponry.

Close behind the systems already shown by Rheinmetall, Rafael and MBDA—certainly not a technological leap away—is the new Gen 3 HEL being developed by General Atomics Aeronautical Systems to fit on an Avenger unmanned air vehicle (AW&ST Feb. 16-March 1, p. 30). If what we hear is correct, it combines an output as high as 300 kw with high beam quality; it can fire 10 times between 3-min. recharges; and a version might fit in the 3,400-lb. pod that Boeing designed for the Advanced Super Hornet (see photo). A bomber or a special-operations C-130 could carry it easily.

This is a tipping point, because what you can do with 300 kw also depends on what you are trying to protect. If the goal is to knock down a supersonic antiship cruise missile (ASCM), there are two problems: water in the atmosphere (which attenuates laser energy) and the fact that a damaged ASCM can still hit the target. But if the target is an evasively maneuvering aircraft, it will often be in clear, dry air; and it is enough to destroy the missile’s seeker, put a hole in the radome, even at well-sub-kilometer range or weaken the motor tube to cause a miss, even at well-sub-kilometer range.

This is one where you’ll find it rewarding, we think, to open the mind and  Read The Whole Thing™. Sweetman is no more infallible than any of us, but he is a more informed aerospace analyst than almost any of us, and bears close watching.

When Reverse Engineering goes to War, it’s “Technical Intelligence.”

Aviation Week is celebrating its 100th Anniversary over the next couple of years, and reprinting or blogging classic articles from prior years, and even from its various predecessor publications. This week they hit upon one that examines, and in part, reverse engineers, an ingenious weapons system we have mentioned before: the Japanese Type Zero Carrier Fighter.


Aviation expert Bill Sweetman sets the stage with a long and informative blog post, and then the 1945 article is broken into four .pdf files. Sweetman:

Newsprint rationing clearly wasn’t a big issue in the U.S. in May 1945, when our predecessor title Aviation published an ultra-detailed four-part dissection of Japan’s “workhorse fighter”, the Mitsubishi A6M Zero, with detail that would put some homebuilt-airplane plans to shame. Neither was cultural sensitivity, as the cover wording shows.

The model examined here was the square-wingtipped, non-folding A6M2 Model 32 “Hap,” which had some tradeoffs designed to allow a more powerful engine. (It didn’t create enough speed to justify its extra weight, which shouldn’t surprise any aero engineers out there — aerodynamics are a much weightier influence on speed than horsepower).


The Zero was a design study in the combat multiplier of lightness in design, and is today a jewel worth studying and emulating by anyone who designs things and might like to make them lighter.

[T]he Navy’s requirement for speed and maneuverability comparable to emerging European designs… seemed impossible given the modest power of the biggest available engine.

What emerged was a highly refined design. Weight control was rigorous: Horikoshi wrote that “it was our policy to control anything heavier than 1/100,000th of the aircraft’s final weight”

Sweetman also notes one Zero advantage that we have mentioned before, the equivalent of 7075 Alloy, but he suggests that this wasn’t an oversight:

Aviation‘s story — quite possibly at the behest of the military — misses one key to the Zero’s success: its construction made use of high-zinc-content 7075 aluminum alloy, which had been secretly developed by Sumitomo and was significantly lighter than the 24S alloys used in the U.S. Better metals were not used worldwide until after the war.

Built-up rudder hinge bracket, where US engineers would have used a machined forging.

Built-up rudder hinge bracket, where US engineers would have used a machined forging.

US aircraft still use 2400 series alloys (as they’re numbered now, but they’re the same stuff) in skins and sheet structures, and 6061 in most things requiring plate, billet or cast parts. 7075 is used primarily in forgings. The clever Mitsubishi team under Jiro Horikoshi designed around the need for many forgings, substituting instead riveted assemblies of sheet aluminum alloy.

(Bill would probably be pleased, as he compares the sketches in the article favorably to homebuilt aircraft plans, to know that the rudder hinges and hinge brackets of our RV are built up from sheet and plate, much like some of the Zero’s brackets. So would Horikoshi, who passed away in the 1960s).

The full title and cutline of the original article is:

Design Analysis of the Zeke 32 Hamp: Presenting the 12th of our series, a profusely illustrated part-by-part examination of the Zero’s successor, showing how Jap engineers achieved unusually light structural weight without sacrificing strength.

All parts, .pdf

  1. Design Analysis of the Zeke 32, Part 1.pdf
  2. Design Analysis of the Zeke 32, Part 2.pdf
  3. Design Analysis of the Zeke 32, Part 3.pdf
  4. Design Analysis of the Zeke 32, Part 4.pdf

In addition to those four .pdfs, Sweetman’s post is definitely one where you’ll want to Read The Whole Thing™.

The scan has some issues, mostly at the edges and keeping the many figures straight and unwrinked, but it’s a great boon to everyone who studies How To Build Stuff.

And it’s a good look at a wartime case of digging into the enemy’s engineering.


Jimmy Stewart Handles a “Hustler”

Jimmy Stewart was known to generations of American movie-goers as a good guy. He seldom if ever played a villain; he usually played a good guy, the Western sheriff or marshal, or the Everyman thrust into a tough situation. Unlike many of his Hollywood peers, whose names came from the forebrains of producers and directors, his real name was Jimmy Stewart. He’s probably best remembered today for a movie that bombed on release — It’s a Wonderful Life, for which he was nominated for an Oscar, but which drove Frank Capra’s studio into bankruptcy. It became a television staple of Christmases in the United States thanks to the copyright having lapsed, either due to an error by studio clerks, or the dissolution of Capra’s firm (we’re not sure which).

But there was another side to Jimmy Stewart, for all that his modest on-screen character was close to his humble off-screen one. Like many young men inspired by Lindbergh, he learned to fly. He also felt called to service — both his grandfathers and his father were war veterans — and in 1941 enlisted in the Air Corps (he had been drafted in 1940, but rejected as underweight; the MGM physical trainer helped him bulk up). The war hadn’t begun yet, and Stewart was too old for aviation cadet training — he was 33. He was commissioned in due course. As a college grad, a relative rarity in 1941 America, this was almost inevitable. Then, he managed to winkle himself onto flying status. There are no records of flight training, and it seems probable that he, like inter-service transfers and other experienced pilots, was simply given a checkride for his rating.

He made several radio and movie promotional materials for what was then the Army Air Corps, but did not want to be an actor in uniform, like his Hollywood peers. Stewart wanted to just be treated the same as any other pilot. This was, for him, a constant battle, but he ultimately won and deployed to combat with a B-17 squadron.

Stewart flew on numerous missions and was promoted rapidly, serving as a squadron operations officer and commander, Group deputy commander, ops officer and XO, and Wing ops officer and commander. He rose, then, on merit, from private to colonel during the course of the war.

After the war, he remained commissioned in the Air Force Reserve (he would retire as a major general) and stayed current in bombing planes, the successors to the B-17s he flew over Germany. While many Hollywood luminaries served in World War II in some capacity or other, Stewart was an outlier in that he served in the Vietnam War also.

From time to time this Air Force career intersected with his acting career, either in films portraying Air Force characters (notably Strategic Air Command) or promotional shorts for the Air Force. In this one, circa 1960, he introduces the supersonic B-58 Hustler.

The Hustler, perhaps the most beautiful bombing plane ever, was designed for a high-speed, high-altitude mission, penetrating (had the balloon gone up) Soviet airspace. The plane was a technical triumph for designer Convair (later General Dynamics), but by the time this film was made, it was tactically problematic. While all the Allies had found German late-war surface-to-air missile developments interesting, the Soviets had taken the Germans’ ideas and developed them into a thorough air defense system, interlocking missile and fighter air defense.

Its crew of three — pilot, navigator/bombardier, and defensive systems operator — sat in three separate tandem cockpits, each of which contained a then-unique ejection pod which would enclose an ejecting crewman and prevent him from being exposed to the wind outside the aircraft, which might have been a Mach 2 blast. It was intended to carry a large pod, which could hold various combinations of fuel or weapons. It was the Air Force’s first aircraft with inertial navigation and a celestial navigation star-tracking system, and for low-level fight had a radar altimeter, then another novelty. But the Soviet air defense system rendered its mission profile extremely risky.

The high speed straight-line superiority of the B-58 was suddenly a vulnerability, as Air Force planners came to understand the capabilities of the Soviet SA-1 and SA-2 missiles. The high-altitude penetration mission was scratched. The Air Force’s fleet of B-47, B-52, and B-58 bombers was reevaluated for low altitude, under the radar penetration missions. And that was the delta-winged jet’s death knell: its lightweight structures could not stand the stresses of high-speed operation in dense, turbulent air down low, and its engines were wasteful of fuel at low altitudes. As no conventional capability for the B-58 was  ever developed, it’s only targets were nuclear strike targets.

Secretary of Defense Robert S. MacNamara ordered the plane cancelled in 1965, and the Air Force took five years to wind it down. While the performance problems were one factor, the fleet in being of 100+ B-58s, which could have been re-engined with more efficient turbofans, was something he considered a threat to his plan to put the widest range of all services’ air missions onto his preferred one-plane-for-everything, the TFX/F-111.

In the end, the Strategic Air Command operated an F-111 version, the FB-111, with little commonality with the Tactical Air Command’s F-111 variants. It would use some of the systems and technology that had been pioneered on the B-58. But it never did get a promotional film with Jimmy Stewart.

Battleship Musashi’s Resting Place Found

An expedition sponsored and led by investor Paul Allen has given a precise answer to a question only understood generally since 1944: where is Musashi? The general answer, of course, is, “at the bottom of the sea,” which is where most of Japan’s aircraft carriers (and naval aircraft, and naval aviators) were when the IJN’s surface combatants sortied to try to bring the US fleets to what Japanese doctrine always called for, “one decisive battle.” Japan wound up having four decisive battles, and losing all four, spectacularly.


Musashi under way in an artist’s rendering.

In retrospect, the sortie of Musashi, like the later one of her sister Yamato off Okinawa, seems lunatic — the Charge of the Light Brigade, armored and put to sea. But the men of her complement believed that if they just showed enough spirit, fortune had to break Japan’s way. No one will ever question whether they showed enough spirit.

Musashi, tied with her sister Yamato for largest battleship ever built, died hard, with her forest of 25mm AA guns and her heavier armament taking a toll on the American naval dive bombers and torpedo bombers that dove relentlessly at the ship. One compartment after the next flooded, one system after another went down, and still they fought. With the bow awash and the ship’s speed reduced to the single digits, they were still fighting.

A thousand heroes were made that day on both sides of the fight, and most of their heroism went unobserved by anyone who would survive the battle.

Starboard anchor of IJN Musashi. The port anchor was cut away as the crew fought a list during her last hours.

Starboard anchor of IJN Musashi. The port anchor was cut away by damage-control parties as the crew fought a list during her last hours.

Along with the most comprehensive air defense battery ever fielded, Musashi had new anti-aircraft fire directors for her secondary armament, and her gunnery officers figured out that the ship’s unprecedented 18″ (460mm) main armament could be effective against torpedo bombers, by shooting into the water and knocking the necessarily low- and straight-flying torpedo planes down with geysers of displaced water. Every time a plane fell the defenders cheered. But the new gun-director jammed, irreversibly.

And no matter what they did, they couldn’t get all the planes. And matching valor for valor, the planes kept coming, and the defenses could only slow their attack, not stop it. In the end, Musashi, her captain RADM Toshihira Inoguchi (posthumously VADM), and over 1,000 of her crew went to the bottom. 1,700 other crewmen were saved, some to return to Japan, and some to be fed back into the battles for the Philippines as ersatz ground troops. The luck of the draw determined who would live and who would die; very few of the sailors repurposed as infantrymen would see Japan again, except perhaps in spirit at Yasukuni Shrine.

Where the ship was remained a mystery, as American and Japanese records offered conflicting locations for the start of Musashi’s plunge, and previous attempts to fix her position on the seabed frustrated the explorers and scientists looking for the mighty ship.

Paul G. Allen, a Microsoft billionaire whose eclectic interests include investments, private space, World War II aircraft, promoting gun bans (unfortunately) and owning the Super Bowl-losing Seattle Seahawks,  sponsored and led an expedition to find Musashi.

This week, he did.

Mr. Allen and his team of researchers began their search for the Musashi more than eight years ago. Using historical records from four countries, detailed undersea topographical data and advanced technology aboard his yacht, M/Y Octopus, Mr. Allen and his team located the battleship in the Sibuyan Sea on March 1, 2015.

Despite numerous eyewitness accounts, the exact location of the ship was unknown. The team combined historical data with advanced technology to narrow the search area. Mr. Allen commissioned a hypsometric bathymetric survey of the ocean floor to determine the terrain. This data was used to eliminate large areas for the search team and also resulted in the discovery of five new geographic features on the floor of the Sibuyan Sea. In February 2015, the team set out to conduct the final phase of the search using a BlueFin-12 Autonomous Underwater Vehicle (AUV). Because the search area had been so narrowly defined by the survey, the AUV was able to detect the wreckage of Musashi on only its third dive. A Remote Operated Vehicle (ROV) with a high-definition camera confirmed the identity of the wreckage as Musashi.

“Since my youth, I have been fascinated with World War II history, inspired by my father’s service in the U.S. Army,” said Mr. Allen. “The Musashi is truly an engineering marvel and, as an engineer at heart, I have a deep appreciation for the technology and effort that went into its construction. I am honored to play a part in finding this key vessel in naval history and honoring the memory of the incredible bravery of the men who served aboard her.”

While we obviously part company with Mr Allen on his support for disarming those citizens who have the ill fortune not to be billionaires, we have long admired his other ventures, including the SpaceShip One effort (where he not only funded the whole thing, but then yielded any claim on the X-Prize his team won, so that there was more to be shared among the engineers and technicians who did the work), and several no-expense-spared restorations of rare wartime aircraft.


“Ding-dong! A bomb calling!”

That’s been the message that ISIL forces around Kobani have received from the US Air Force’s 9th Bombardment squadron, which is bombing enemy targets before the Kurds, using a plan that seems designed to impose as much friction and Fog of War as possible between the fighters on the ground and the guys toggling off the JDAMs and SDBs.


The Wall Street Journal:

The U.S. had established close communications with the People’s Defense Units, or YPG, a Kurdish secularist group that led the fight to defend Kobani. YPG fighters communicated with liaisons and air controllers in the operations centers set up by the U.S.

The Combined Air Operation Center in Qatar then took that information and sent bomb coordinates to the B-1s flying over Kobani.

June 26 airpower summary: B-1Bs bomb enemy vehicles

During as much as eight hours flying over Kobani, the 9th Bomb Squadron would get targets called in to the air operations center from air controllers working with the Kurds. The B-1 crew would get the target, drop a weapon and then get confirmation from the fighters on the ground.

Get that? There’s some JTAC or some individual somehow insulated from being Boots On The Ground™ as designated by the Bugger-Outer-In-Chief. (Probably a non-US person who is employed by a non-DOD agency). He gets on the satcom horn and makes a call for fire, that includes his identity, and the famous “9 lines”:

  1. the initial point/battle position (something identifiable to the aircrew)
  2. heading from that IP/BP to the target or and/or offset;
  3. distance from that IP/BP to the target;
  4. target elevation in feet above Mean Sea Level;
  5. target description (“four enemy technicals in laager”);
  6. target location;
  7. type of target marking, and code if encoded;
  8. location of friendlies;
  9. egress (aircraft’s safest route out after weapons release).

That call arrives at the Combined Air Operations Center in Qatar. It’s received, and logged, and a checklist is run on it to make sure it’s not going to bomb friendlies, or otherwise cause embarrassment to Beltway princelings.

Then, the CAOC in Qatar transmits the targets to the bomber. The crew of the bomber (usually the Offensive Systems operator) transmits the target’s coordinates to the bomb, and the bomb is released to do its thing.


Now, this is better than doing nothing. Although not by great leaps and bounds. (In Afghanistan it worked like this: we called the aircraft. The fighter, for fighter-bombers, or offensive systems operator, for bombers, read back the coordinates. And the bomb landed on it within, really, two minutes).

But the guys are out there flying, and trying. We all know what risks the guys making these calls are taking: ISIL has no Gitmo. And the risks that the B-1B crews are taking are very real, making them rather unlike the Beltway princelings who award each other as Profiles in Courage for following the crowd. And the bomber crews’ story is worth telling — read the whole Wall Street Journal Thing™ — but this is not going to beat ISIL or win the war.

In all history, there has never been a war or campaign won by air power alone. Air power has never even degraded an enemy to the point where he was unable to fight, and every promise to do so — Italy in ’43, France in ’44, Korea in ’50-’53, Vietnam, Kosovo, Desert Storm — beat him up pretty good but certainly didn’t take the fight out of him. Using air power alone says one thing out loud: nobody on our side is really trying to beat ISIL or win the war.

Lesser Battles in the Press Offensive

Promoting the 9th Bombardment Squadron, which will dutifully bomb the grid coordinates given them, and has no doubt manufactured vast quantities of dust and smoke, and some amount of terror and death among the deserving, is one thing. Other parts of the Administration’s press offensive to rehabilitate the battered reputation of Strategic Simpering or whatever they’re hashtagging it this week haven’t gone so well. Spokeswoman Marie Harf, who peaked a couple of years ago as an undergrad when she was measured solely by her ability to replay professors’ shibboleths on demand, looks callow, shallow, and stupid every time she faces a real interviewer.

Probably because she’s actually callow, shallow, and stupid.

Confirming our view that nobody in the Beltway is actually trying to beat ISIL or win the war, Harf spouted endless, ill-formed nonsense about creating jobs and inspiring them to move on from jihad and similar rubbish, nonsense that does our sworn enemies the discourtesy of assuming that they are as callow, shallow and stupid as, for example, Marie Harf.

There is a conspiracy theory that Harf was added to the State Department payroll as a whipping child, to make the callow, shallow and stupid Jennifer Psaki seem statesmanlike. It’s just a reminder that A players hire A players, and John Kerry hires ZZZ players. (And it doesn’t say much for the cat that hired him, either).

But the Administration’s foreign policy rehab offensive, like Lindsey Lohan’s, has many twists and turns on its Nantucket sleighride to the depths of irrelevancy. This morning we caught a report from Iran by the state-controlled media outlet, NPR. NPR is doing a series about how wonderful Iran is, in order to pre-sell the upcoming Chamberlain deal with Iran to the last constituency still starry-eyed over President Selfie’s statesmanship: NPR listeners.

The subject of this installment? How good the Jews have it in Iran. They’re not all oppressed like they are in other countries, like the Zionist Entity. Lord love a duck.

ATGMs Go to War, Vietnam, 1972

In 1972, ATGMs had been in military inventories for 20 years, since France’s adoption of the SS-10 circa 1951. But they’d never fulfilled their original mission — destruction of enemy tanks in combat. Sure, some of the French missiles might have been popped off an insurgent sangars in Algeria, and Americans shot a couple of Entacs at bunkers in Vietnam. And a dozen missile models had blown hell out of obsolete tanks on a firing range. But nobody had shot one at a hostile tank containing a hostile crew.

1972 was the year that the wire-guided anti-tank missile got its cherry popped, in Vietnam conflict. Before the next year was out the missiles would prove almost decisive in tank-on-tank combat — and be employed on both sides. If the weapons world of New Year’s Eve, 1971, had its issues with anti-tank guided missiles — and the US had such gadflies as the Project on Military Procurement (whose funding and control was shadowy) and the Soviet-line Center for Defense Information trying to force cancellation of ATGM programs — the weapons world of New Year’s Day, 1974, had shaken off all doubts. Missiles were here to stay.

Those wars were the 1972 NVA conventional invasion of South Vietnam and the Yom Kippur War, both of which saw missiles used, in the first experimentally, and in the second in great quantities.  Here is an overview video of TOW missile attacks on North Vietnamese armor.

Click “more” for the details about Vietnam. The Yom Kippur War story will be told in the days ahead.

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“The Gun is its Own Tool Kit.” — Browning ANM2

This is Your Gun pG1One sign of a gun design that is not completely thought through is a requirement for special tools for disassembly. These days, most guns are designed for disassembly without any kind of offboard tools. But this was not always the case. John M. Browning was one of the first designers to consistently design guns to be disassembled without anything special. And it was a bit of a marvel, as the tone of this excerpt from a naval aerial gunner’s manual called This is Your Gun reveals:


In an emergency, the gun can be stripped with nothing but its own parts as tools. Use the point of a cartridge or the cocking lever pin to depress the oil buffer body spring lock.

Key parts in the oil buffer assembly:

Key parts in the oil buffer assembly: Oil Buffer Body Spring Lock (14a); Accelerator Pin (13), Accelerator (12). Oil Buffer Tube Lock (11)

Use the cocking lever pin to drift out the sear stop pin and accelerator pin.

Many of the parts mentioned are in the Bolt Group. In the order that they're mentioned:

Many of the parts mentioned are in the Bolt Group. In the order that they’re mentioned:  The Cocking Lever Pin is Nº 7. The Sear Stop with the Sear Stop Pin is Nº 8. The Cocking Lever is Nº 6.


 Use the flat tip of the cocking lever as you would use a screw driver to remove and replace the sear stop, oil buffer tube lock, the cover latch spring, and cover extractor spring. Use the oil buffer tube lock to pry the handle of the trigger bar pin out of its hole in the side of the receiver.

Use the sear stop pin to drift out the belt feed pawl pin.

The Belt Feed Pawl Pin is #5 in this illustration. US Navy.

The Belt Feed Pawl Pin is #5 in this illustration. Cover Latch Spring is #8, Cover Extractor Spring #9. US Navy.

But use these methods only when absolutely necessary and take care not to damage the parts used as tools. Never use the driving spring rod assembly as a tool.

Conversely, having a gun like this that can be disassembled and reassembled in field conditions without a bench full of tools is a marker of good design. This kind of design is more commonly encountered now than it was in Browning’s day, which speaks for Browning’s lasting positive impact on firearms design.

From the Academy to the Arsenal (long)

secret1The weapon was developed in the greatest of secrecy. It was born in a physics lab before the war, but during the war became a massive project: led by physicists; employing tens of thousands on detailed tasks whose application they did not know; secured by barriers, unsmiling military police, security clearances and teams of counterspies; and encompassing a wide range of industrial effort. It was shared under the most stringent security guidelines with Britain alone, and gave the nations of the Anglosphere combat power unimagined before the war.

Its developers, led by a man whom they all came to admire enormously, were a cross-section, not of society, but of the academy: more diverse ethnically than American society at large, scarily smart, and sometimes, endearingly (or irritatingly) eccentric.

To take it from the blackboards of physicists to the Arsenal of Democracy, new precision needed to be achieved in old technology, new technology entirely needed to be invented, and the frontiers of miniaturization pushed far beyond the 1941 state of the art. The weapon was useless if it could not be delivered to the close proximity of its intended target, so it had to be shrunk, shrunk, shrunk from the initial conceptual models, which would never have fit inside the delivery system.

It required new methods of testing and evaluation to be developed, to prove that it really would work when put to the test. Once it passed these tests, its effect on the enemy was devastating.

Exposing it became a major objective of Soviet spies and the traitors who had sold themselves to them, including some who would be caught and punished, like Julius and Ethel Rosenberg, and some who were too highly placed for suspicion to stick, like Lend-Lease head Harry Hopkins, who tried and failed to have samples sent to his real superiors where his true loyalties lay: the Soviet Union.

We’re referring not to the hoary old story of the Manhattan Project, but the equally old, but much less-known, tale of the proximity fuze, or as its WWII cover name called it, the Variable Time, VT, fuze. That cover name has stuck and prox fuzes are still often called VT, despite the fact that it was intended as a deliberate obfuscation of what the fuze really did: solve an “impossible” gunnery problem of the 20th Century.

MK53 proximity fuze

The Problem Was Hitting Moving Aircraft

Now, if you’ve ever cocked a cannon in Army or Marine artillery, you know a bit about the uses of VT; we’d like to ask all of you to be quiet, we’ll get to those shortly. But they’re not why VT was invented. The problem was anti-aircraft gunnery. In 1941 every military in the world was shooting at aircraft or preparing to do so, and they were missing. Just about all the time.

Airplanes don’t just sit still and let you whack them with your 88, you see. They move around. AA guns had compensating sights, and gun batteries had fire-direction computers, that could calculate where the airplane would be when the shell got to it — more or less.

(These computers were analog computers, with gears and knobs and whiz-wheels instead of circuits and programs, but they were faster and more reliable than the first many generations of digital technology that would replace them a few decades hence).

There was a little imprecision (not much) in the computer. There was a little more (again, not much) in the laying of the gun. Naval dual purpose and AA, and Army anti-aircraft guns, of the period were extremely accurate, but the problem still remained that for every shell delivered adequately to a vital structure of a Heinkel 111 or Aichi D3A, a much larger quantity, to steal a line from Maxwell Smart, “missed it by that much.”

A miss was as good as a mile, as the saying of the period went. In the initial effort to make a near miss somewhat more hazardous to enemy aircraft, various sorts of fuzes were conceived. The most common was a simple time fuze, and a lot of effort went into arranging the fire direction computer to support the optimum setting of an air defense battery’s time fuzes for effect on target. (Terrestrial artillery tried to use time fuzes to secure airbursts against troops in trenches, foxholes, or open-topped bunkers, too). An antiaircraft alternative was a barometric fuze, detonating at a preset altitude. This required fuze-setters to know the altitude of enemy aircraft (leading to the development of height finding radars, but also leading to the use of airplanes to shadow attackers and report their altitude to defenses). It also required them to know or have a way to dial in to the computer the ambient air pressure.

Winston Churchill describes this problem in Volume 2 of his History of the Second World War, (p.395), and notes: “[A]n aeroplane end on is a difficult target and a contact fuze will work only on impact.” Britain was working to develop such a fuze in the Battle of Britain, and while they were able to bring a mockup into the Cabinet Room to show Churchill, miniaturizing it was proving difficult, maybe impossible. So the British were stuck with the state of the art: impact, time and pressure fuzes.

These fuzes, the state of the art at war’s outbreak, would also be as far as the state of the art of Imperial Japan or Nazi Germany ever got. Many thousands of them had to be fired to ensure a hit on bombing aircraft. The watchword of the bomber theorists was, from the days of Douhet, “The bomber will always get through.” And it’s not easy to find an example of an aerial attack turned by time or baro fuzes alone, even in the sanguinary early days of RAF Bomber Command: the bombers took some hits, but most of them came through, unless they were hit by fighters, too.

How the VT Worked

The VT is essentially a small radar inside an artillery fuze. Initial concepts were wide open: photoelectric, acoustic, active radio (radar principle), or passive radio (detecting aircraft engine ignitions). In the end, after some experiments with photoelectric fuzes, active radio was chosen. Teh fuze radiated a radio wave, and if it received a reflection back, which it would if it were close to a target, pow! Here’s how E.D. MacAlister explained it to scientist Ralph B. Baldwin, who was just joining the project in 1941:

It’s really simple in theory but extremely difficult to convert into practice. The fuze is simply a specialized radio set. There’s a battery whose electrical energy is released by setback, the shock of firing from a gun. This battery furnishes three different electric voltages: one for the filaments of the vacuum tubes, one for the plates, and one for the grids. One of the tubes is an oscillator. In the nose of the fuze is a metallic cap, which together with the rest of the shell acts like a dipole. The oscillator tube thus has an antenna and emits a high-frequency radio wave in particular directions from the shell.

This continuous radiowave surrounds the moving shell, and when the shell pass is close to a target, the letter reflects a small amount of radio wave energy back to the fuse where it is detected by the same to been sent out the wave in the first place.

prox fuze exploded view

The plate voltage is “modulated” by the reflected wave, which is at slightly different frequency than the outgoing wave due to the relative motion of the shell and target. Thus, a beat note is set up and the plate voltage varies in frequency within the audio range of a few to a few thousand cycles per second. This audio frequency voltage variation is then passed through a three-tube amplifier.

When the period of the audio frequency wave and also its amplitude or intensity are exactly right, a thyratron tube, serving as a switch, is discharged. It completes a circuit that releases an electrical charge, which meanwhile has been stored in a condenser. The surge of electricity goes through a tiny wire in an electric squib, much like a dynamite cap.

The wire gets hot and the explosive in the squib goes off. This tiny explosion sets off about a cubic inch of a sensitive explosive called tetryl in the auxiliary detonator (auxdet to the Navy, booster to the army), which is at the bottom of the fuze.

This explosion sets off the explosive loading of the shell and it bursts the steel shell body into many hundreds of high velocity fragments. From the time the fuze says ago, the shell travels less than one foot before it bursts.

Now, if that sounds tough to follow, relax: even Baldwin found it “pretty heavy going.” But we include it here as (1) an illustration of the complexity of this pre-transistor electronic innovation, and (2), because we can’t imagine a simpler or clearer technical explanation of the fuze’s working than McAlister’s.

How the VT Was Developed

It started as an academic exercise, and began at Columbia University, but later found a permanent home at the Johns Hopkins University Applied Physics Lab in Baltimore, which was established (in part, to accomplish this task) in 1942. While the Manhattan Project was full of brilliance, the guy at the top of the APL and therefore the APL’s proximity fuze effort was Norwegian-American scientist Dr. Merle A. Tuve, the APL’s founder.

First they had to decide how to do it. They worked in parallel on optical and radio fuzes at first. It soon became apparent that the radio-frequency fuze was a success, and optical fuze development was cut off. (Unlike radio fuzes, optical fuzes worked only in daylight conditions).

The developers had to demonstrate the individual parts of the system; then, miniaturize them; then ruggedize them. From starting work circa 1940, Tuve had a working system within a couple of years. Decades later, the members of the team remembered the day when one of the proximity fuzes, fired from a Navy 5″ gun out over the water, worked for the first time. At the time, nobody made a note of the date! But the occasion was never forgotten. That day, only one of several test shots worked, the others detonating early or plowing into the water without detonating at all. But that one shot proved that the system was feasible. It had passed from science into the realm of engineering somewhere along the way.

British tube type VT fuze

This is all the more remarkable when you consider that the transistor, and all semiconductors, were over 15 years in the future: the fuze would have to work with the then-known electronic parts: vacuum tubes, capacitors, diodes and resistors, all powered by batteries. All these parts had to be ruggedized to survive the harsh environment of a cannon shell, with 20,000-g acceleration, 25,000-RPM rotation, and wildly varying temperatures all part of the fuze’s eventful last few seconds of existence.

The hardest parts to ruggedize were the batteries, which you might not expect, and tubes, which stands to reason. Their flimsy wires and glass enclosures were not optimum for high acceleration forces. When the scientists had tubes with 90% reliability, they still couldn’t relax: since the system needed three tubes to work (oscillator, amplifier, and thyratron), 90% reliability of any individual tube meant  fuze that wouldn’t work even three-quarters of the time, and that even if every other component was 100% reliable. (The three tubes would have to be 96.6% reliable for the tubes to be overall 90% reliable, again assuming 100% function of everything else).

The lab aimed for an overall 80% reliability of fuzes in the field, which they came to learn meant they could accept only a very low failure rate of the tubes. Even an 80% reliable VT fuze was a godsend to the Navy.

Final and near-final fuzes were tested against mockups of Japanese and German aircraft, and against drones. In April 1942, an unmanned Piper Cub was hung from a balloon hundreds of feet over the water at Parris Island and shot at with live fuzes, but explosive charges replaced by a black-powder marking charge that would make a visible puff of smoke, but not fragment the shell. 20% of the shots would have been hits.

On 12 August 1942, a drone imitating a torpedo bomber “attacked” the new cruiser, USS Cleveland, in a live-fire test. A first drone failed before coming into range. The second bore in on the ship’s beam. Cleveland’s 5″/38 battery shredded the drone, taking it down with under ten rounds fired. A second drone was shot down just as quickly. The drones were the usual anti-aircraft targets, and they never got shot down. The drone officers had to report to the test officer that they were out of targets. The next day, they had located one more, which was set to emulate a level bomber, and attacked fruitlessly with time fuzes. The battery loaded the VT fuzes and destroyed the drone. End of test.

The crew of Cleveland was counting on one more liberty before joining the war, but they’d just seen the successful test of the Navy’s latest secret weapon. The Navy ordered the ship to drop off the APL scientists and technicians, but to keep sailing for the Pacific. The fuzes, already in pilot production, were suddenly a hot item in Naval supply channels.

The Fuze Goes to War

By October 1942, production was up to 500 fuzes a day and they were being flown from the factories to West Coast and Pacific depots. Production ultimately involved five companies performing final-assembly duties, with components coming in from over 100 factories belonging to some 87 businesses. Most of the component makers didn’t know what they were making parts for.

This fuze setter was part of the equipment in a 5" dual-purpose mount.

This fuze setter was part of the equipment in a 5″ dual-purpose mount. The fuze setting was directed from the fire director down to the secondary battery plotting room down to the mount. Wartime secondary armament instructions (.pdf) from the USS Massachusetts (battleship).. 

On 5 January 1943, off Guadalcanal, the first Japanese airplane ran afoul of VT fuzes fired by the aft 5″ battery of the light cruiser USS Helena. Only three salvos were required to down the Aichi D3A “Val” dive bomberThe carriers Enterprise and Saratoga were also equipped with the new technology at that point, and from that point on the Japanese began having a harder time sinking American ships.

(Aside: Helena, CL-50, was famous for her gunnery, which would lead to her sinking. Japanese destroyers used her muzzle flashes to target her in July, 1943 and slammed three torpedoes into her, causing the ship to break into three pieces and sink with a loss of over 180 lives. Most of the crew did survive, although some were not rescued for days. A Helena sailor’s remains were found as late as 2006 on one of the straits islands).

Along with the fuzes, the Navy hit up the APL for new gun directors that would be optimized for VT, not time, fuzes. These went to sea for the first time with the battleship USS Missouri, and were effective against kamikaze attackers.


The VT Fuze Joins the Army

The highest priorities for fuze development were Naval, and so the Mk 32 was the first made, soon followed by equivalents for Royal Navy applications. But the VT Fuze was developed for Army anti-aircraft applications almost as soon as the Navy had it in production; one of the Cleveland’s drones was killed with an early prototype of the Army 90mm AA fuze screwed via adapter into a Navy 5″ shell. The Army fuze came from miniaturization developments that led to the Mk 45, and the British soon got forces for their Army AA guns as well (just in time for the V-1 buzz bomb attacks). But the AA application was only one application for proximity fuzes.

The more fruitful application, and one that would be key in several late-1944 battles, was creating a guaranteed airburst at an optimum height over enemy troop positions. The munition was, in a word, murderous to troops that didn’t have substantial overhead cover. LTG George S. Patton gleefully reported on the devastation wrought on German troops caught in the open by VT-fuzed barrages during the Battle of the Bulge.

At first, the VT fuzes were such secrets that they were removed from artillery positions during visits of foreign VIPs or American or British reporters. By war’s end, the effect of the fuze had let the cat out of the bag.

How the VT Fuze Spread to Other Nations

The Germans had heard rumors of the fuze, but never got hold of a working copy; they thought they were dealing with a “fuze with an electric eye,” and they tasked their spies to find out. The spies (Frederick Duquesne, Herman Land, and Lilly Stein of the 33-member Duquesne spy ring) never found the detailed information for the still-under-development fuze before a double agent and an FBI sting led to them being rolled up in 1941. The picture shows Duquesne, right, a retread WWI saboteur, with double agent William Sebold, left, a naturalized American who had immediately gone to the FBI when a Dr. Renken of the Abwehr (real name, Nickolaus Ritter) approached him in 1939, and was taken by FBI agents through a two-way mirror (note the clever positioning of the calendar so as to be in frame). The Deutsche Wehrmacht never got the secrets of the American fuze. Captured documents showed that the Germans had been trying to develop such a fuze throughout the war, but had made less progress by 1945 than the APL made by 1942.

The US shared the VT fuze with Britain from the beginning of development. After the initial development for the 5″/38 dual-purpose naval gun, and concurrent with development for additional US AA weapons, 4 Royal Navy calibers were added to the development schedule. Later, after the development of land fuzes for the US Army, 6 more for the British Army were added. By war’s end,  VT fuzes had been adapted to 28 different shells. The British had developed their own conceptual fuze as early as 1940, but they’d gotten stuck on miniaturizing and hardening the electronics, and welcomed the US project.

The Japanese never understood why they launched so many kamikaze Special Attack aircraft to achieve such meager results. With a few well-known exceptions where attacks saturated US defenses, the entire Special Attack program was a waste of resources and of men’s lives, and prox fuzes are one reason why. Of course, Japan was beaten by the spring of ’44, but wouldn’t believe it until they’d suffered the most absolute naval defeat since ancient history: while the Navy’s had some 2,500 vessels, most of them were small craft; all capital ships were on the seafloor, and the largest ship left fully combat-worthy was a cruiser.

The Russians got wind of the fuze and tried to come by it legitimately, first, by requesting it from Lend-Lease. They were turned down. Then, they tried to put pressure on through Harry Hopkins, to bend the rules (Hopkins frequently did this for his Soviet masters) and that didn’t work, either, because the subordinate officers wanted it in writing. Meanwhile, they tasked espionage assets, and the couple that came through for them with the VT fuze design would go on to fame — Julius and Ethel Rosenberg. Well, fame and Old Sparky at Sing Sing.

And there’s irony for you: far more Americans have been killed by Soviet copies and improvements of American VT fuzes than have been killed by Soviet copies and improvements of American nukes. But the spies who gave up both weren’t even charged for the little, seemingly inconsequential, war-winning little weapon. If they had been, they would never have received the death penalty. But if you truly understand the weapon, they deserved to fry for this as much as anything.


Baldwin, Ralph B. The Deadly Fuze: Secret Weapon of World War II. San Rafael, CA: Presidio Press, 1980.

US Navy. Radio Proximity (VT) Fuzes. Naval Historical Center Website. Retrieved from:

A Second B-29 Nears Flight

If you’ve seen a B-29 fly in the last few decades, it’s been “FIFI,” the Commemorative Air Force’s flagship and the only surviving airworthy B-29 of some 4,000 built.

Until now. A single tatterdemalion B-29 was rescued from a China Lake impact area decades ago, and a restoration began in 2000. Now “Doc” (named after the Disney dwarf) is ready to fly. This video tells the story.

The B-29 had several effects on World War II, beyond its celebrated role as the delivery sysrem for the only two nuclear bombs ever used in warfare. The bloody battles of Saipan and the Marshall Islands were driven by the need to base the B-29s within range of Honshu. The fire-bombing of Tokyo — by B-29s — caused as much destruction, and more death, than the atomic bombings of smaller Hiroshima and Nagasaki.

The B-29 also was remarkable for its technological firsts. It was the first pressurized bomber, allowing the crew to work in shirtsleeve comfort inside the plane’s pressure vessel. It was the first heavy bomber to use remote gun turrets (around the same time, they were used in the A-26 Invader attack plane or light bomber, and the P-61 Black Widow night fighter). Its remarkable defensive system allowed gunners looking out from plastic bubbles to aim their sights at enemy aircraft, and an electric analog gun computer would ensure that one or more turrets put rounds on target. While some American and British bombers had been retrofitted with radar that allowed navigation and bomb delivery, this was built into the B-29 from Day 1.

Other firsts included all-electric systems such as gear and flaps. (In all, there were over 100 electric motors in every B-29). A whole-plane fire-suppression system, also electric, was another first. As you might expect with a plane full of firsts, it had terrible teething problems but dogged engineering saw it through.

Hat tip, AvWeb, whose Mary Grady writes:

…the airplane will be ready for flight testing in the spring, and they are planning to fly the airplane this summer at EAA AirVenture, where it will join the B-29 Fifi. “It’s the first time in 60 years that two B-29s have been able to fly in formation together,” T.J. Norman, the restoration’s project manager, told the Wichita Eagle recently.

He added that the fleet is not likely to grow. The airplane, known as Doc, is the last known B-29 capable of being restored to flight. “There will never be another one of these done,” Norman said.

The plane is ready to go, except there’s no way to heat the oil in the engines to the minimum 50 degrees needed to start them. B-29 engines are notoriously finicky; the plan is to wait until spring and warm weather.

The B-29 is also important as the vanguard of what became Strategic Air Command. The legendary SAC commander, Curtis LeMay, cut his teeth as commander of the 20th Air Force, raining death and terror upon Japan.

For more information, see the AvWeb article linked above, or visit the Friends of Doc. They’d really like a donation, too; they need $2 million to put a permanent roof over this remarkable livng-history exhibit.