Isegoria

When the F-22 design team struggled to meet its weight and unit-cost goals, it decided to step back and open up the design to more fundamental changes:

“After a bloody debate, we agreed to trash the current design and start over,” says Mullin. “Over that weekend, we brought in a new director of design engineering, Dick Cantrell, flew in people, and started a ninety-day fire drill. Work started on Monday 13 July. That date marks one of the most creative periods of conceptual design for any fighter aircraft. We looked at different inlets, different wings, and different tail combinations. One configuration had two big butterfly tails and looked somewhat like the F-117, though people did not know that since the F-117 was still highly classified. The configuration search was wide open, but the biggest single change that resulted from it was to go with diamond-shaped wings.”

The concentrated configuration search began with a slew of possible designs. The search complicates the numbering scheme considerably, as diamond wings, twin tails (two tails instead of four), various inlet shapes, and various forebody shapes were all considered and reconsidered simultaneously in the summer of 1987.

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“The fundamental reason for going to a diamond wing was that it provided the lightest configuration and gave us the best structural efficiency and all the control power we needed for maneuvering,” Mullin explains. “The biggest consideration was its light weight. Weight drove the decision.”

“A diamond wing has more square feet of surface area, but is more structurally efficient,” adds Renshaw. “The longer root chord provides a more distributed load path through the fuselage. Multiple bulkheads carry the bending loads. The design provides more opportunity to space the bulkheads around the internal equipment. It also provides more fuel volume.”

“The structural engineers wanted a diamond wing because it provides a larger root chord, which carries bending moments better,” Hardy notes. “The aerodynamicists wanted a trapezoidal wing because it provides more aspect ratio, which is good for aerodynamics. Dick Heppe, the president of Lockheed California Company, made the final decision, and he was right. The aerodynamics were not all that different, but the structure and weights were significantly better. So we went to a diamond shape. The big root chord, though, moved the tails back. Eventually we even had to notch the wing for the front of the tails. If the tails moved farther back, they would fall off the airplane.”

Once the wings were set with Configuration 614, subsequent configurations dealt with the tail arrangement. “We spent a lot of wind tunnel time looking at the tails,” recalls Lou Bangert, the chief engineer for engine integration from Lockheed. “From late 1987 to early 1988, we were engaged in what we called ‘the great tail chase.’ We knew we would have four tails, but where they would go was a big deal. A small change in location often made a huge difference. We had to look at performance effects, stealth effects, stability and control, and drag at the same time. The tail arrangement and aft end design were important design considerations for all of these effects.”

Wind tunnel results showed an ultra-sensitive relationship between the placement of the vertical tails and the design of the forward fuselage. The interactions could not be predicted accurately by analysis or by computational fluid dynamics. The airflow over the forebody at certain angles of attack affects the control power exerted by the twin rudders on the vertical tails. Getting the airflow right was critical.

The cant and sweep angles of the vertical tails could not be altered too much because such changes increased radar signature. In finding a suitable arrangement, the control system designers were constrained by the radar signature requirements to moving the tail locations laterally or longitudinally and to shrinking or enlarging them while holding the shape essentially constant. By the end of the dem/val phase, the team had accumulated around 20,000 hours in the wind tunnel. A lot of this time was devoted to tail placement studies.

The basic challenge of designing the F-22 was to pack stealth, supercruise, highly integrated avionics, and agility into an airplane with an operating range that bettered the F-15, the aircraft it was to replace:

“One problem we typically face when trying to stuff everything inside an airplane is that everything wants to be at the center of gravity,” Hardy explains. “The weapons want to be at the center of gravity so that when they drop, the airplane doesn’t change its stability modes. The main landing gear wants to be right behind the center of gravity so the airplane doesn’t fall on its tail and so it can rotate fairly easily for takeoffs. The fuel volume wants to be at the center of gravity, so the center of gravity doesn’t shift as the fuel tanks empty. Having the center of gravity move as fuel burns reduces stability and control. We also had to hide the engine face for stealth reasons. So, these huge ducts had to run right through the middle of real estate that we wanted to use for everything else. The design complexities result in specialized groups of engineers arguing for space in the airplane. That was the basic situation from 1986 through 1988.”

Austin Vernon discusses the economic logic of smart bombs:

US smart bombs like the GPS-guided JDAM and the laser-guided Paveway cost somewhere between $10,000 and $30,000 to manufacture. They are nearly 100% accurate in hitting a target, while unguided bombs are stuck with single-digit accuracy numbers. Unguided dumb bombs cost $2000-$3000 per bomb. Smart bombs payout immediately by requiring a fraction of the ordnance.

It is worse than that, though. A fighter jet like the US Navy’s F-18 costs over $10,000 an hour to operate, not including tankers. A B-52 bomber costs $70,000 an hour. Attacking targets using dumb bombs requires ten times the sorties at a significant cost premium and exposes planes and pilots to more risk.

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Modern smart bombs fired by aircraft can provide support and screening for fast advancing mechanized columns instead of artillery. In the early Afghanistan conflict in 2001, the US deployed zero artillery because of its weight and logistics challenges. Combat aircraft were able to cover US ground forces against light Taliban forces.

In the 2003 invasion of Iraq, armor columns brought much less artillery than in 1991. Aircraft took over the strategic mission, leaving counter-battery fire and all-weather close fire support to artillery forces.

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Smart weapons also have standoff capability. An unpowered JDAM bomb can glide over 25 km.

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Drones are a continuation of the precision-guided munition paradigm. Smart bombs can make a plane 20x more effective. Drones are force multipliers across the board. The Army and Air Force have been drone leaders but need to continue to invest in drones across the spectrum. They need large, expensive drones that can operate far from bases and inexpensive micro-drones that can disrupt enemy formations or intercept enemy micro-drones. Modern warfare is an o-ring industry because enemies exploit gaps relentlessly.

Recent talk about hypersonic missiles got me wondering whether SpaceX’s reusable rockets would lend themselves to this role. Austin Vernon suggests that SpaceX’s Starship is America’s Secret Weapon:

B-52s flying from Barksdale AFB to complete a mission in East Asia incur a marginal cost of $50/kg to deliver bombs. Starship’s cost is cheaper and can put weapons on target in less than thirty minutes. Each Starship launch has the same payload as three B-52s.

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The supply line would be a natural gas pipeline and a rail line providing fuel and projectiles to a domestic launchpad instead of ships crossing oceans.

I hadn’t considered this though:

Orbital weapons still need intelligence to tell them where to go. Starship’s sister system, StarLink, provides an answer. StarLink is a constellation of thousands of small Low Earth Orbit satellites that gives customers low latency broadband internet. It uses sophisticated phased-array radios that allow ground terminals to track satellites traveling thousands of miles per hour.

As Casey Handmer points out, StarLink can use its radios to do high fidelity synthetic aperture radar (SAR). SAR is already one of the primary ways militaries find enemy ships, and researchers have used it to track planes. It could also see ground vehicles.

While the US already has satellites capable of doing this, they are expensive and limited in number. Individual StarLink satellites cost a few hundred thousand apiece to build and launch on Starship. One of the first things China would do in war is shoot down our military satellites with anti-satellite missiles. That is a problem with bespoke satellites but not with Starlink. Anti-Satellite missiles cost tens of millions of dollars. Each Starship launch could drop off hundred of StarLink satellites. The Chinese would have to expend incredible resources to keep StarLink offline.

A satellite constellation provides other bonuses. Our GPS satellites are both hard to replace and sensitive to jamming. StarLink can provide GPS coordinates (with a few meters less accuracy), and its phased array radios make it difficult to jam.

The upshot is StarLink gives the US survivable sensing, communication, and navigation capabilities.

The concept behind rotation detonation engines dates back to the 1950s:

In the United States, Arthur Nicholls, a professor emeritus of aerospace engineering at the University of Michigan, was among the first to attempt to develop a working RDE design.

In some ways, a Rotating Detonation Engine is an extension of the concept behind pulse detonation engines (PDEs), which are, in themselves, an extension of pulsejets. That might seem confusing (and maybe it is), but we’ll break it down.

Pulsejet engines work by mixing air and fuel within a combustion chamber and then igniting the mixture to fire out of a nozzle in rapid pulses, rather than under consistent combustion like you might find in other jet engines.

In pulsejet engines, as in nearly all combustion engines, igniting and burning the air/fuel mixture is called deflagration, which basically means heating a substance until it burns away rapidly, but at subsonic speeds.

A pulse detonation engine works similarly, but instead of leveraging deflagration, it uses detonation. At a fundamental level, detonation is a lot like it sounds: an explosion.

While deflagration speaks to the ignition and subsonic burning of the air/fuel mixture, detonation is supersonic. When the air and fuel are mixed in a pulse detonation engine, they’re ignited, creating deflagration like in any other combustion engine. However, within the longer exhaust tube, a powerful pressure wave compresses the unburnt fuel ahead of the ignition, heating it above ignition temperature in what is known as the deflagration-to-detonation transition (DDT). In other words, rather than burning through the fuel rapidly, it detonates, producing more thrust from the same amount of fuel; an explosion, rather than a rapid burn.

The detonations still occur in pulses, like in a pulsejet, but a pulse detonation engine is capable of propelling a vehicle to higher speeds, believed to be around Mach 5. Because detonation releases more energy than deflagration, detonation engines are more efficient — producing more thrust with less fuel, allowing for lighter loads and greater ranges.

The detonation shockwave travels significantly faster than the deflagration wave leveraged by today’s jet engines, Trimble explained: up to 2,000 meters per second (4,475 miles per hour) compared to 10 meters per second from deflagration.

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A rotating detonation engine takes this concept to the next level. Rather than having the detonation wave travel out the back of the aircraft as propulsion, it travels around a circular channel within the engine itself.

Fuel and oxidizers are added to the channel through small holes, which are then struck and ignited by the rapidly circling detonation wave. The result is an engine that produces continuous thrust, rather than thrust in pulses, while still offering the improved efficiency of a detonation engine. Many rotation detonation engines have more than one detonation wave circling the chamber at the same time.

As Trimble explains, RDEs see pressure increase during detonation, whereas traditional jet engines see a total pressure loss during combustion, offering greater efficiency. In fact, rotation detonation engines are even more efficient than pulse detonation engines, which need the combustion chamber to be purged and refilled for each pulse.

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According to the Air Force Research Lab, RDE technology could make high-speed weapons much more affordable, which is of particular import following a recent Defense Department analysis that indicated the hypersonic (Mach 5+) weapons in development for the Air Force may cost as much as $106 million each.

The recent unpleasantness in Japan piqued my interest in DIY firearms and electronic ignition, which led me to the Remington Model 700 EtronX, which was introduced in 2000 and discontinued in 2003. Ian of Forgotten Weapons explains:

It consisted of a standard Remington 700 bolt action rifle, with the trigger and firing mechanisms replaced by electric versions. The firing pin itself became an insulated electrode, the trigger operated an electronic switch instead of a mechanical sear, and a 9V battery feeding a capacitor provided the energy to ignite the new type of primer — basically a resistor that would generate heat to ignite a charge of smokeless powder.

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Unfortunately, the only practical advantage to the electronic workings was a reduction in lock time of the action (the delay from trigger press to cartridge ignition). They did in fact achieve a virtual elimination of lock time, but this was not a problem that needed to be addressed for the general sporting rifle market.

Now, if they introduced a gun that didn’t need conventional primers today, they might have some success.

One hobbyist found it surprisingly hard to ignite gunpowder:

Experiments performed a few years ago and shown on the web page here found that weak sparks, such as from static electricity, are incapable of igniting black powder. Since I wanted to use smokeless powder in the rifle, and since it has a much higher ignition point than the black powder shown here, my first attempts used sparks from a stun-gun to see if they could ignite the powder.

The stun gun shown here is advertised as producing a 100,000 volt spark. The sparks were certainly loud and impressive, and they easily burned tiny holes through a piece of paper placed between the electrodes, but would they ignite powder?

Hundreds of sparks were struck into a pile of Hodgdon’s Tite-Group smokeless powder (left) and Swiss black powder (right) with absolutely no effect except for bouncing the grains around. The sparks were striking the grains, and you can see flashes when the spark hits the surface of the granules, but never once would the powder ignite!

The photo below shows a spark from the stun gun going completely through a line of black powder stuck to a piece of masking tape, and although hundreds of grains were simultaneously hit, nothing happened.

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About this time I was ready to give up, but after a few days of reflection, I thought I knew what was happening. The spark in the chamber was clearly extraordinarily hot and was vigorous enough to blow the tamper out of the chamber, which meant that the air in the chamber had to be heated to a high temperature. But why didn’t the powder ignite? I believed the reason was the extremely brief duration of the spark; in trying to capture it on a video, it was so brief that it took many tries to accidentally capture a video frame on a camera running 30 frames/second. My guess is that it lasted only a few micro seconds, and thus, no matter how hot it was, it couldn’t transfer enough heat into the powder granules during this brief time period for them to ignite. Therefore, slowing down the spark, even if it meant reducing its intensity, might be enough to do the job.

To slow down the spark, I simply added a resistor in series with the capacitor so the current was limited to about two amperes — which is still a lot of current going through a spark. As you can see from the image, the spark was much brighter than from the spark coil alone, but was very much less intense than without the resistor. However, it seemed to last a bit longer — about 2000 micro seconds, so that elongation might do the trick.

I added some smokeless powder (this time without a tamper) and sparked it. It worked! Not only did it work for the Tite Group smokeless powder, but for all others I tried, and all ignitions were instantaneous.

Two technologies have helped Ukraine fend off the Russian invasion:

While the Russians are able to jam satellite transmissions, so far they have not been able to jam Starlink. Musk has reported that they are trying but so far have not been successful.

The other technology is homegrown and is software known as GIS Arta (GIS stands for geographic information system and Arta stands for artillery).

GIS Arta is an Android app that takes target information from drones, US and NATO intelligence feeds and conventional forward observers, and converts the information to precise coordinates for artillery.

GIS Arta was developed by a volunteer team of software developers led by Yaroslav Sherstyvk. It bears a resemblance to Uber taxi service software, on which the GIS Arta software is modeled.

GIS Arta makes it possible to do two things not possible before: Targets can be identified and verified visually almost immediately, and artillery and rocket systems can fire quickly and accurately.

Consider that typically it takes 20 minutes to program coordinates into an artillery piece and fire the weapon. Complicating that is verifying the target; for the US that also includes making sure there isn’t a risk of collateral damage.

The artillery previously used by Ukraine was mainly Russian and its firing system was dated and slow. GIS Arta not only changed that but also significantly improved accuracy.

GIS Arta reduces the time to fire to about 30 to 45 seconds. No Western artillery system is as capable and none apparently has the accuracy offered by GIS Arta. According to reports, Ukrainian artillery can now hit a far-away target with an accuracy of between 18 and 75 meters.

Ukraine has also modified its deployments of artillery, separating units by greater distance to make them more difficult targets for Russian counterfire. That, too, has been enabled by GIS Arta.

The GIS Arta complex also selects which gun or rocket system to use and automatically provides the coordinates to any selected system. In fact, the system is so good that Germany, which has already delivered some of its Panzerhaubitze 2000 tank howitzer 155mm mechanized guns to Ukraine, reportedly has integrated GIS Arta.