Engineering Summarized

Engineering is implementing science to fix legitimate problems. To that end, engineering doesn’t always look good, but great engineering is profoundly reliable.

More than anything else, engineering employs heavy amounts of math and physics for its design, with its constraints represented by the universe itself. Most of the inspiration for engineering is pulled from nature itself, and is usually driven by the culture surrounding the engineers’ work.

Sometimes, bad systems can cut corners financially on a product’s design, which always yields a terrible experience because the product will break quickly and irreparably, which can often happen when an object becomes a mere commodity. On the other hand, competition can allow the best engineering to surface if the users actually care about their product.

Some of the most creative engineered components involve finding ways to get objects where you want them to be, but with severe physical constraints or absolutely zero direct ability to interact. Most of the sciences involving the most extreme discoveries (e.g., astronomy, quantum physics, geology) advance from this type of development.

At the same time, if we don’t use it we forget about it. Social trends across the large-scale of history often depict how people discover things, then re-discover them centuries later, then promptly forget them when the technology is no longer necessary or a better technology serves their purposes. Even when there is copious documentation on the subject, trade secrets prevent the specialist from communicating all their methods.


Engineering ideas are conceptually simple. However, this overview is for the sake of understanding for non-engineers.

However, they are not simple in practice. To quote and abstract the late Hyman G. Rickover:

  • An academic structure almost always has the following characteristics:
    1. It is simple.
    2. It is small.
    3. It is cheap.
    4. It is light.
    5. It can be built very quickly.
    6. It is very flexible in purpose.
    7. Very little development is required, and it will use off-the-shelf components.
    8. It’s in the study phase, and isn’t being built now.
  • However, a practical structure has the following characteristics:
    1. It is being built now.
    2. It is behind schedule.
    3. It requires an immense amount of development on seemingly trivial items, with corrosion in particular being a major problem.
    4. It is very expensive.
    5. The above-stated development problems mean it takes a long time to build.
    6. It is large.
    7. It is heavy.
    8. It is complicated.

Theory frequently breaks down in the face of reality. This doesn’t mean the theory was necessarily wrong, but theories are typically not precise enough. Theory, however, isn’t useless, because it’s how we create anything in the first place.


Most engineering has to wrestle with severe tradeoffs, with the result being a balance based on the quality of materials the engineer can use and time hyper-obsessing about precise design requirements.

The laws of fluid dynamics indicate all aircraft get 2 of 3 factors:

  • Fast
  • Safe, which is necessary for commercial aircraft
  • Maneuverable, which is necessary for remote areas

Further, fluid dynamics laws give every watercraft 2 of 3 factors:

  • Fast
  • Dry, which is necessary for passenger watercraft
  • Maneuverable, which is necessary for turbulent waters

In any landscape except plains with no human settlement, every projected rail line can only fulfill 2 of 3 requirements:

  • Cheap
  • Straight, which is necessary for high-speed rail
  • Flat, which is necessary for freight

Typically projects involving any human task gives 2 of 3 possibilities:

  • Cheap
  • Fast
  • High-quality

Military vehicles give 2 of 3 possibilities:

  • Firepower
  • Armor protection
  • Mobility

Money can often push the limits, but only to a specific point, and it’ll simply make the thing constrained to being prohibitively expensive.

On every dimension of computer design, these same tradeoffs express themselves.


There are multiple factors to consider when engineering anything, and the the quality of an engineered item has a profound impact on the quality of the item:

  • Accessibility to the material itself (e.g., diamonds are harder to get than dirt).
  • The load-bearing capacity of the object during normal use.
  • Lateral loads on the object (i.e., the angle where it’ll be weakest).
  • The structural integrity of the object when under tension, both from a strong impact and from sustained tension.
  • The structural integrity when the object is torqued (i.e., one part of it is rotated while the other is still or rotated the other way).
  • The flexibility of the object when exposed to stress.
  • Its ability to combine with other materials to create composites and alloys, and what the combined material looks like.
  • How the material connects to other materials (bolts, ropes, hinges, etc.).
  • The possible ways to permanently make it part of another material of the same (e.g., gluing, welding).
  • Types of connections that work in various capacities (e.g., moment connections, bracing and truss connections).
  • The effect of long-term vibrations on the material.
  • Structural design that takes the most advantage of the materials’ tradeoffs (e.g., girders, A-frames).

Each material has its own tradeoffs:

  • Wood is easily accessible and easy to work with, but breaks down easily under stress and is flammable.
  • Stones vary by geological type, tend to be easy to chip and plane into tools, but also easily break, especially under prolonged stress.
  • Gemstones are very durable, but can be rare and expensive.
  • Some metals are naturally-occurring and simple to work with (e.g., bronze) while others need extra treatment to work with (e.g., iron). Since alloys are hybrid mixes of metals, they often can reinforce each others’ weaknesses (e.g., steel).
  • Plastic is derived from crude oil, and is very cheap, but is flimsy and can be bio-hazardous in some implementations.

Acquiring those materials is often its own form of engineering:

  • Wood is a completely renewable resource (which is why it’s so ubiquitous), and there are ways to farm it even more easily without having to cut the trees down.
  • Most materials require some form of refining before they can be worked into an engineered solution, which can dramatically affect the cost.
  • Mined materials (e.g., coal, iron, aluminum) are geography-specific, so they require logistical considerations for refining.
  • Drawing oil out of the ground requires refining into diesel (and further refining making gasoline), but can also be refined into plastics for a very wide range of uses.

Stressors affect organic and inorganic components differently:

No stressEither recovery or decayLow-level entropy
Low-level stressHormesis (gets stronger)Material fatigue (gets weaker)
High-level stressTraumaBreakage

Designing for physical reality is difficult, so engineers must accommodate imperfection into the structure of inorganic objects:

  • Keep it simple, since complexity has more points of potential failure and there are fewer parts to maintain.
  • Heavily reinforce the parts of the object that will take the worst beating.
  • Make the most likely failure happen at the most accessible place for a technician.
  • Have redundant systems in place to prepare for a likely breakage.
  • Add random problems to the system during testing on purpose to see what might break.
  • Create backup systems that can thrive when the first things break.
  • If you need a complex system, string together a bunch of simple systems.

Mechanical Components

The physics of all three classes of lever are vitally critical to understand, and it’s all based on the placement of the effort, fulcrum, and resistance:

  1. Effort – Fulcrum – Resistance: The effort pushes downward and moves the resistance upward, and the mechanical advantage can be less or greater depending on the situation (e.g., see-saw).
  2. Effort – Resistance – Fulcrum: the effort pushes upward to move the resistance upward, and the mechanical advantage is always greater (e.g., wheelbarrow).
  3. Resistance – Effort, Fulcrum: the effort pushes upward to move the resistance upward, and the mechanical advantage is always lesser (e.g., tongs).

Most elaborate mechanical objects are simply derived off simple ones:

  • A wheel is a circular, symmetrical object that maintains its form.
  • A gear is a wheel with cut teeth meant to interlock with something else (usually other gears).
  • A screw is an inclined plane around the perimeter of a standard nail.
  • A rope or cable is a flexible cylindrical object, typical used to convey physical energy from one place to another.
  • Pump assemblies migrate a liquid through a tube, typically from a mechanical or electrical signal.
  • A belt is a flat object like a rope, typically made into a loop, typically designed to connect wheels together.
  • A spring is metal specialized in tensile strength, where it reverts back to its original form after being distorted.

Most of the time, the components can be vastly complex, but are activated by an individual signal. In a very complex system, those signals can cascade, where one interaction can create multiple signals sequentially to create the desired result.

These parts come together to create more advanced components:

  • A pulley is a wheel with a belt or rope around it.
  • A cogwheel or gearwheel adds little cogs around the outside of a wheel to make it interlock with other components more snugly than belts or wheels can provide.
    • For even tighter fits, a spline is the ridge or tooth that closely matches with a groove in a mating piece, typically to transfer torque.
  • A worm gear is a cylindrical screw-shaped gear that magnifies torque to a standard gear.
  • Chains are ropes, but with holes in the middle and typically made of metal. Linked chains tend to distribute weight, and single-assembly chains interlock very well with sprockets (which are basically cogwheels attached to chains).
  • Servomotors activate mechanical motion from a signal (typically electrical).
  • A shock is a sealed hydraulic mechanism that maintains a cushion of pressurized fluid (typically air) to absorb impacts.
  • A transmission is a vast set of gears, chains, servomotors, and springs designed to apply the correct amount of torque and rotational energy relative to the engine and drivetrain/alternator.

Typically, these objects are assembled into complex patterns that magnify specific aspects:

  • Using differently-sized gearing can expand or contract the applied force over a certain amount of time, which can be used for either timing (e.g., a watch) or balancing forces (e.g. automotive transmission).
  • Changing the angle of the force can dramatically improve how much energy can directly apply to something or diminish breakdown.


There are a wide variety of standardized techniques to craft objects, especially tools:

  • Heat treating exposes metal to extreme heat, then the cooling process brings the chemical bonds of the metal closer together and makes the metal harder.
    • Liquid nitrogen treatment simply goes farther with the treatment process into sub-zero temperatures, and can be done asynchronously (i.e., you can do it at home to your tools).
  • Drilling engages a screw-shaped bit at high rotational velocity to penetrate a surface and create a hole.
    • While it’s common practice for DIYers to train a hole with a smaller drill bit, the tip is the load-bearing component and is therefore much more heavily treated than the rest of the bit.
  • Sanders and grinders use a rough surface to remove material from a broad surface.
    • Sanders use sandpaper on wood.
    • Grinders use dense metal or diamond, and are typically used for metal or plastic.
  • Broaching uses a long narrow attachment with teeth on one side to remove material.
  • Skiving involves slicing a block of metal very precisely along the surface at a slight angle, then lifting it up to create a fin, and repeating to create an array of fins.
  • Welding uses an extremely hot object (like a blowtorch) to melt a connecting part of two pieces of metal.
  • Sintering involves heating metal until it’s close to its melt point, then pushing it together and letting it cool.


When two people talk with each other, they need to have an agreement of language terms. Otherwise, the entire conversation won’t mean anything.

Ideally, most standards wouldn’t be necessary, since the design would incorporate it. However, this isn’t always possible:

  • Engineers often are so practical that they don’t always indicate how the mechanism fits together without a wall of documentation.
  • Some things are so complex that there’s no way whatsoever to clearly and simply communicate it.

Standards do make life easier, but they take training to memorize and understand the jargon, and engineering has an endless wall of specializations with a vast codex to draw from.

Often, standards can halt technology improvements, especially when the standards are established early. In those situations, a new standard or protocol will replace the old one if it becomes too unwieldy, but will often require workarounds until then.

At the same time, setting standards too late will be difficult, since the standard will have to accommodate that the entire body of users/engineers will be habituated toward multiple conventions that sprung up in the absence of a standard.

Unfortunately, one of the perverse incentives of a well-standardized product will include maladaptive practices like planned obsolescence. Some products are so well-configured for failure that they’re likely to fail precisely within one month after a multi-year warranty.


The engineering of most individual weapons is absurdly simple:

  • Bladed weapons are simply skimming substance off an object until that object is sharp enough to pierce something, usually with a material that can hold that edge.
  • Projectile weapons are using applied force to launch a comparatively smaller object as fast as possible into a significantly larger object. Catapults and trebuchets use leverage, while guns use controlled explosions.

Detonation-based weapons are also relatively straightforward, with the complexity in how to trigger the payload:

  • If it’s dropped from an aircraft it’ll probably detonate on its own simply from the volatility of gunpowder.
  • Most charges have a fuse that either burns along a small rope or triggers from a computer-activated spark.
  • A grenade’s pin holds back the handle, with the payload on a short few-second fuse which the handle activates.
  • A shaped charge (typically for detonating buildings) involves a malleable (“plastic”) explosive crammed into a constraining container, then a copper cone pushed inward into it. Once the explosive detonates, the cone inverts and the force turns it into a long rod, which penetrates the material like a bullet until the copper rod depletes.
  • Nuclear weapons involve striking an unstable atomic mass (typically plutonium or uranium) with another atomic mass, causing the proton-neutron cluster to rapidly break apart.
  • Any tectonic weapons involve a large detonation along a geological fault line.

The complexities in most weapons come from features designed to protect the user in the process.

Electrical Connections

Electricity is simply the large-scale movement of many electrons from atoms with more electrons than protons to atoms with fewer electrons than protons. Electricity is everywhere in small amounts, but we only see it naturally occur on a dramatic scale with lightning.

The formation of electricity gives tremendous capacity for people to magnify their labor, and is by far the most ubiquitous. An electrically-powered engine generally has less torque than anything combusted (e.g., internal combustion engine, rocket engine) but the energy is much easier to transfer around to other sources compared to anything strictly mechanical.

Amperes measure how fast electrons flow, and volts measure the difference in how many electrons between two points. There’s usually an analogy with water where voltage is pressure and amperage is flow speed. Wattage is simply amperage multiplied by voltage.

Electricity travels from one point to another through a “conductor” that has a certain amount of resistance measured in ohms. Metal tends to have a much lower resistance than most other materials, and some of the best conductors happen to be copper, silver, and gold because they’re more capable of picking up additional electrons relatively easily.

Wires can be temporarily engaged to complete the “circuit”. The engagement is typically hidden behind a designed housing with a switch for the user’s safety.

To protect the entire assembly from being destroyed at a random place during a severe spike in electrical current, there are usually “fuses” placed in a box. All the wiring is supposed to travel through that fusebox at some point in its journey to prevent any cables from breaking in an unpredictable location. For that reason, barring a frayed wire from exposure to the elements, most typical electrical failings are either within the output (e.g., light bulb) or within the fuse.

Alternating current (AC) travels much farther than direct current (DC), and is generally safer simply from the fact that electrocution will make the victim’s muscles seizure instead of contract. However, most small-scale electrical components that use batteries use AC, and most computers use AC for their signals because they’re more predictable.

Solar Cells

Solar cells are made of photovoltaic cells, which convert photons into electrons:

  1. Light strikes a photovoltaic (PV) cell, usually made of a material like silicon and sandwiched between glass and/or plastic for protection.
  2. The energy of the absorbed light knocks electrons loose.
  3. By attaching metal contacts on both sides of the cell, they can gather those electrons to make electricity.

Electrical Heat & Magnetism

One of the side effects of electrical transfer is heat. By winding electrical cabling into a tight coil, electrical current can generate a heating element. This is essentially how all electric heaters work, from toasters to coffee pots.

Another side effect of electrical transfer is magnetism. Again, by winding electrical cabling into a tight coil, current can make the device an electromagnet. They have several uses:

  • Generate electricity by applying mechanical energy to it (e.g., a generator).
  • Detect magnetic activity through energy within its proximity (e.g., metal detector).
  • Configure it with a magnet to create a gauge (e.g., speedometer).


In a straightforward sense, a battery is an AC electricity storage container for later use:

  1. Have something in a safe box which holds a positive electrical charge for a long time (i.e., many atom ions missing electrons).
  2. Have something in another safe box which holds a negative electrical charge for a long time (i.e., many atom ions with extra electrons).
  3. Attach the device you want to power with a + and – conductor, typically a cable.
  4. As the device needs, it’ll draw electrons off – (the cathode) as they travel to + (the anode).
  5. Over time, the cathode reduces and the anode oxidizes, and the charge decreases.
  6. The process can sometimes be reversed, meaning the cathode increases and the anode de-oxidizes (i.e., recharging).

The design of the boxes and how fast they connect determines how much power draw you get, as well as whether more electrons can be added to the negative side (i.e., recharged).

Some batteries (like car batteries) are meant for rapid discharge all at once, while others (like cell phone batteries) are designed to discharge very slowly.

Batteries are ionized atoms, so they’re in a state of kinetic potential energy, which means they’re subject to decay per Newton’s First Law (An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force). Because of this, they tend to incur a type of “memory” for their capacity, and they must stay ionized (i.e., charged) or will decay more quickly over time.

In practice, longevity with any battery requires a few habits:

  1. Keep the battery charged as much as possible.
  2. Recharge a battery whenever reasonably possible to next charge it.
  3. With a few exceptions for specific engineering, don’t permit the battery to get down to 0%.

Batteries used to be liquid acid in jars:

  • There is a very affordable sodium-sulphur battery (Na-S), but it uses a molten salt electrolyte, so it’s only useful for large-scale uses (e.g., home battery backup, solar/wind generation).

Most everyday batteries are a few broad classes of solid metals, and most of them are subject to the memory effect (its capacity deteriorates with each recharge):

  • The first rechargeable battery was lead-acid in 1859, which doesn’t hold much energy but can produce large surges of current (which is necessary for starter engines in autos).
  • The zinc-carbon battery in 1886 was one of the first dry-cell batteries that mixed manganese dioxide dipped in a mix of ammonium chloride and plaster of Paris with trace amounts of zinc chloride, then sealed in a zinc shell.
  • Nickel cadmium (NiCd) was developed in 1899 and uses nickel and cadmium in a potassium hydroxide solution.
  • Nickel-iron is like NiCd and was also developed in 1899, but iron is inferior to cadmium because it produces lots of hydrogen gas when charged (and therefore can’t be sealed).
  • Alkaline batteries in the 1950’s dramatically improved on the zinc-carbon battery with a manganese dioxide cathode, powdered zinc anode (which gave the battery a larger surface area), and an alkaline electrolyte.
  • Nickel-hydrogen arose in the 1970’s for smaller applications (e.g., electronics). It was followed by nickel metal hydride (NiMH) in 1989. They have longer lifespans than NiCd, and aren’t as toxic as cadmium.
  • Lithium ion (Li-ion) is more lightweight than nickel-based batteries, but is also more expensive. There were experiments as far back as 1912, but it didn’t develop commercially until the 1970’s.
  • Lithium polymer (LiPo) was developed in 1997, and holds the electrolyte inside a solid polymer instead of a liquid solvent, and the electrodes and separators are laminated to each other (which means it can be flexible instead of inside a rigid metal housing) and wrapped around as a coil. The positive electrode is aluminum foil, and the negative one is copper. The one downside is that LiPo tends to swell, and any connection between
  • Lithium iron phosphate (LiFePO4, or LFP) is a low-cost, non-toxic, relatively safe derivative with naturally abundant materials. LiFePO4 was only developed as early as 1996.
  • Gallium nitride (GaN) was used for blue light-emitting diodes (LEDs) since the 1990’s but have recently been developed for battery use. If they can successfully make them affordable, they’ll be able to charge faster than the others (which is critical for use cases like electric vehicles).

The specific metals necessary for batteries are rare earth metals that require unique mining techniques to extract. Even though lithium batteries are 100% recyclable, they are often discarded. Some regions illegalize discarding batteries, which can be a problem at scale.

Battery indicators require a specialized “integrated circuit” (IC) that tracks battery usage. One of the simplest battery indicators is an algorithmic implementation of the Coulomb counter:

  1. Measures the current charge.
  2. Measures the available charge later.
  3. It uses a simple calculation to figure out how much charge is left (e.g., it started with 10 amps, there are 4 amps now, and it’s discharging 1 amp per hour, so it’s at 40%).

Battery technology develops relatively slowly compared to the things it tends to power. Most of the time, better software programming that saves on memory management increases battery life more than actual battery improvements.

Batteries are very versatile, and can serve to benefit a household by preparing for a short-term disaster, glean energy from an engine’s movement, or be quickly and easily manufactured as a replaceable supply material for small-scale electrical needs.

Batteries are built into many objects (e.g., laptops, scales) without an off switch and simply a timer for design reasons. However, every single piece of technology needs a physical switch that can kill the connection to the battery. Otherwise, the latent stray electricity can create break-fix headaches later.

One of the newest developing technologies for batteries is called a hydrogen fuel cell. The concept is essentially the same as a battery, with a few modifications:

  1. The anode and cathode are separated only by a polymer electron membrane (PEM), which only allows positively-charged ions to travel through it.
  2. On the cathode side, oxygen is fed into the system.
  3. On the anode side, a catalyst (such as platinum) splits hydrogen molecules into protons and electrons.
  4. The electrons travel through an external circuit as a battery output.
  5. The hydrogen protons travel across the PEM and bond with the oxygen, producing water (H2O), then move out of the system.

One significant issue with hydrogen fuel cells is in finding a reliable and affordable source of pure hydrogen for the inputs.


At its simplest, an engine is a machine that produces movement.

With the exception of rocket propulsion, most engines are designed to produce rotational energy to a few possible outputs:

  • A “flywheel”, which is a one-way gear that keeps spinning even when force isn’t applied. This can usually translate to applied torque (e.g., a bicycle) or a transmission (e.g. most automotives).
  • An “alternator” that converts the kinetic energy into DC electrical energy that goes to a battery.

Steam Engine

The steam engine is a relatively straightforward assembly:

  1. High-pressure steam comes in from boiling water, historically with coal.
  2. A valve rod is timed to open an aperture that leads to one side of a cylinder with a sealed piston.
  3. The force of the steam’s pressure pushes the piston and creates motion that moves a cross-head, and the valve rod closes as the piston moves the cross-head.
  4. At the end of cylinder, there is an open exhaust port where the high-pressure steam vents out.

Internal Combustion Engine

The internal combustion engine assembly has a very specific flow of energy:

  1. Drive a small, well-timed controlled explosion at the top of a “piston”.
  2. The force of the piston pushes a “connecting rod” that’s bound to a “crankpin”.
  3. The crankpin is the handle connected to a “crank arm” and “shaft”, and is part of an assembly called the “crankshaft”.
  4. The crankshaft directly applies rotational energy with the exterior of the engine.

An internal combustion engine assembles the pistons in an evenly balanced array (typically an even number), and that array gives a shorthand format. V8 means alternating in a V-pattern, I4 means 4 vertical pistons, and so on.

The four-stroke engine consists of 4 distinct phases for each piston:

  1. Intake – as the piston drops, pass fuel in through an “intake valve”.
  2. Compression – intake valve closes and piston pushes the fuel up to increase the combustion’s thermal efficiency.
  3. Power – generate a spark through a spark plug (for gasoline) or heat through a glow plug (for diesel) that triggers the explosion, launching the piston downward (and also propelling the other alternate pistons on the array during their 1st stroke).
  4. Exhaust – open the exhaust valve after the explosion, and the inertia of the piston pushes it out.

A two-stroke engine combines the engine into only two strokes and has fewer moving parts, though it’s often only ideal for smaller engines:

  1. Controlled explosion pushes the piston downward, with the exhaust naturally venting out without a valve.
  2. Near the bottom of the piston’s motion, a valve opens up to permit more fuel to come in, which pushes out the rest of the exhaust.
  3. Piston returns back to the starting position from its inertia.


Nearly all mechanical energy converting to electrical uses a simple principle in electromagnetism: spin a magnet near a low-resistance material like copper, and it’ll generate electricity. The only difference is its source (e.g., wind, hydroelectric turbine).

A generator converts mechanical energy into AC or DC electrical energy, while an alternator is only AC. Alternators tend to be cheaper with less parts, while generators are more powerful.

There are 3 major components to generate a rotating magnetic field:

  1. Rotating shaft – spins while force is applied, with an electromagnet in the middle on alternators.
  2. Stator – a static ring around the outside of the rotor with coil windings that doesn’t touch the rotor directly, has a stationary magnet in generators.
  3. Brushes and other parts that generate magnetic field voltage.
  4. If it’s converting to DC voltage, a set of diodes that serve as one-way pathways for the current.
  5. A voltage regulator that maintains the energy flowing into the power source to prevent it from overloading.

Rocket Engines

Rocket fuel is highly combustible, and most rockets are designed to ignite the fuel as quickly and efficiently as possible. While hobbyist rockets can work with short-circuited wires, most larger motors require some form of black powder to ignite from wires to create a self-sustaining burn.

For highly advanced rockets, they tend to need extremely advanced cooling through the outside of the engine. Otherwise, the entire assembly would burn up. Regulating the timing between launching and temperature regulation is a highly advanced feat of engineering.

Igniting the propellant is the largest challenge, and multi-stage rockets in space need additional effort. Often, many of them synchronize the ignition of the next stage while the previous stage is still attached.

Jet Engines

A jet engine design is a little less straightforward than a rocket’s, but not by much:

  1. At the front of a jet engine, it has a compressor that converts air into a high-pressure high-temperature gas, then combines it with jet fuel and ignites it.
  2. The flaming flow of gas goes through a set of blades arranged as a turbine, which extracts energy from the gas, lowering its pressure and temperature and increasing its velocity.
  3. As the hybrid air/fuel gas is expelled, the aircraft is thrust forward.

Nuclear Reactors

There are two forms of nuclear energy: fusion and fission. Fusion gathers energy from combining atoms, while fission gathers energy from splitting them and using the energy from released neutrons.

Fission energy typically uses uranium processed into small ceramic pellets and stacked together into sealed metal tubes called fuel rods. A fuel assembly typically has 200 fuel rods, with a reactor core made of a few hundred assemblies.

The fuel rods are immersed in water to serve as both a moderator (to slow down the neutrons produced by fission and sustain the chain reaction) and coolant (to redirect the resulting heat). The heat produced by the fission turns the water into steam, which powers a turbine.

There are two forms of fission reactor:

  • About a third of reactors are BWR (boiling water reactor), which directly runs a steam line to a turbine.
  • Most reactors are PWR (pressurized water reactor), which keeps the water pressurized, with the outgoing water regulated with a pressure tank and the energy from the steam powering a steam generator. That steam generator maintains the reactor’s pressure and sends its resulting steam through a turbine.

Fusion energy is a vastly different structure, though it’s still shooting something into unstable isotopes to break off extra neutrons:

  1. Direct high-powered lasers at a hydrogen isotope fuel capsules called deuterium and tritium encased in diamond.
  2. The diamond surface blows off and creates a rocket-like implosion of the deuterium/tritium mix.
  3. Under extreme heat and density, the atoms combine and create helium while releasing energy.

Fusion generation at scale is mostly theoretical, but the idea is that it can replicate the conditions of the sun on a very small scale using magnets.

An alternative fusion generator is called a stellarator, which uses a series of magnet coils to keep a ring of plasma in place. The rotation of the plasma can then be harvested to generate energy.

Both fusion and fission require highly particular and volatile materials. Isolating the isotopes (a statistically unlikely occurrence in nature) requires using a vast network of centrifuges that scoop up the comparatively heavier isotopes from the rest, and it can take months to acquire small amounts of it.


The essence of a refrigerator and air conditioner is the same relatively straightforward cycle:

  1. A compressor constricts a cold substance (often called “refrigerant”), which raises its pressure and pushes it into the coils near the “hot area” as a gas (per Boyle’s Law).
  2. When the hot refrigerant in the coils meets the comparatively cooler air temperature in the “hot area”, it becomes a liquid.
  3. The refrigerant cools down and flows into the coils inside the “cool area”.
  4. The heat inside the “cool area” moves into the refrigerant.
  5. Finally, the refrigerant evaporates to a gas and flows back to the compressor, where the cycle starts all over again.

When an engine needs cooling, the process is typically reversed: the hot area is inside the engine and the cool area is outside it. Most engine coolant is a mixture of water and an antifreeze, which catalyzes water to lower water’s freezing point and raise its boiling point.

Heat pumps are effectively the same principle, but transfer heat from a wide variety of sources to something else that would use it (e.g., geothermal heat to heat water). Unfortunately, heat pumps are constrained by extra energy required proportionally to the difference in temperature between the hot and cold areas.


Most vehicles are simply well-designed implementation of an internal combustion engine housed inside other mechanical systems:

  1. An engine that powers the entire vehicle, typically gasoline or diesel.
  2. For an internal combustion engine, an elaborate gear system that transfers the torque from the engine’s flywheel to the axles.
  3. An electrical system that operates a small electric “starter” motor from a battery to engage the engine, then an alternator on the “serpentine belt” that re-powers that battery, as well as any larger charging systems if it’s a hybrid.
  4. Impact protection for the vehicle and payload (i.e., cargo, operator), which often includes a spring-based or shock-based suspension assembly if it travels on land at all.
  5. A variety of impact-triggered systems that safely protect the driver in the event of an accident (e.g., seatbelts, airbags).
  6. A fully-contained HVAC system that feeds heat from the engine or refrigerant-cooled air into the cabin at the user’s selection.


A railroad is a pair of metal rails designed to guide a locomotive down an expected path. Historically, the engine was originally steam-powered, but they can often be electrical, and can also use gravity to generate its own electricity. Depending on the pathway, it can be self-sustaining.

At one time, the rails were bolted together, but they’re now welded together to allow faster speeds. They therefore have to stress the track during installation to make sure it doesn’t buckle from the stretching and contracting from the heat generated from the trains. Without rigorous stressing at higher temperatures, the rails will buckle and trains will derail, which causes huge spills of all the cargo.

The railway sleeper is a horizontal board that was historically wood, but can be made of stressed concrete, composite plastic, or steel. Its purpose is to distribute the load at even intervals onto the ground. To accommodate shifts from heat expansion and contraction as the engine travels over it, the sleepers are attached to the rails with clips or anchors.

Further, when laying track, the tracks must have track ballast between the sleepers and ground. Ballast are made of crushed, jagged stones. This permits the track to be raised (and therefore compensate for irregularities on the ground across a long distance) but also gives a cushion that bears the load of the train as it rolls across it. The rocks must be jagged for them to fit together (since they’d slide out under the pressure if they were smooth), and too much fouling (dirt getting in them) will fill the gaps in between the stones and eventually cause a derailment.

Generally, the gauge of the rails (distance between them) is set to be nearer (4’8.5″) when carrying heavier loads, while the comparably lighter passenger rail needs a broader gauge (5’6″) to prevent from winds blowing them over.


Automobiles add even more to a standard vehicle’s engineering requirements:

  1. Composite materials in tires that engage from the axles to the road which can withstand tends of thousands of miles of a wide variety of terrains.
  2. In newer autos, computers that regulate an engine’s timing and all the components, as well as often embedding a tablet computer into the dashboard, complete with internet connectivity.
  3. If there are any autonomous features like self-parking, it also includes advanced AI.

However, in some ways, electric vehicles are inferior technology to standard ICE engine automotives:

  • They remove the mechanical force applied by kinetic explosion in lieu of stored electrical energy, which means they have far less torque.
  • Batteries have a much lower mass-to-energy ratio compared to gasoline, meaning their effective range is less, though that could change with improved battery technology.
  • Charging batteries requires infrastructure (and the energy offsets to the power grid instead of being locally stored), and can take hours for a full recharge. However, swapping out batteries is often a viable option.
  • Ecologically, batteries require rare-earth metals that are very volatile and destructive once expended, while refining and burning hydrocarbons only produces air pollution. It’s the difference between more high-end landfills and simply planting more trees.


The precise elements of getting aircraft to stay in the air are very particular, but the general idea is always roughly the same:

  1. Air moves over a flat object that’s curved on the top side.
  2. The curved part slows air and lowers the pressure above it.
  3. The flat object generates force that moves it toward the curved part.

The same principle applies in helicopters to the rotating blades, as well as airplane propeller blades.

However, there has been a recent development in aircraft: an aircraft can run more silently by generating a flow of ions aboard the craft and launching it behind it, creating enough thrust to fly the craft.

Large Structures

Beyond design considerations, most structures involve balancing loads toward the strongest portions of the frame. This usually represents itself as a large set of triangles, with many of the best designs representing as hexagons.

Typically, large structures have a tremendous requirement of load-balancing. If it’s a geographically-fixed structure, it’ll direct the force downward into a concrete foundation. When it’s a large structure like a ship or aircraft, the force will be applied to the perimeter of the structure, which will have the strongest metalwork on it.

Concrete itself, as a material, involves a specific process:

  1. Gather, break down, and heavily bake limestone to 900°C for 4-5 hours, then crumble it into powder.
  2. Mix the limestone with some other materials to create a cement mix.
  3. Thoroughly mix one part cement with 2 parts gravel and 3 parts sand.
  4. Add increments of water to reach the right consistency, adding in more mix if too much water.
  5. Pour into a form, flatten the top, and let it cure. It takes 1-2 days to avoid footprints, 7 days to reach >70% strength, 28 days to reach full-strength, and will technically keep curing as long as water interacts with it.

Large structures are typically designed for long-term use, so they have dramatically more factors to consider regarding weather, erosion, and chemical breakdown. They also suffer many more risks from internal failure of various smaller systems (e.g., air conditioner).


Editing genes uses CRISPR technology (Clustered REgularly Interspaced Short Palindromic Repeats). The procedure requires 2 steps:

  1. Use a guide RNA (gRNA) bound to the enzyme Cas9 to cut DNA at a specified location.
  2. Allow the body’s natural DNA healing processes to take over.

This allows genes to be replaced with a more favorable genetic sequence.


Most factory engineering is a dramatic experience of hyper-specialized tools. Factory robots can reproduce just about any task a person can do repetitively, even complex ones, and most factory assemblies are designed to accomplish 1 task tens of thousands of times, with minor retooling necessary as machinist requires.

Most factory machines are designed to create as clean a product as possible, for both ease of use and aesthetic appeal to the end user. Most of the small idiosyncratic details in a factory machine (e.g., shaking an object quickly before setting it down again) are designed for maximum efficiency and to create the most effective product. Many of them are also trade secrets.

Waste Management

Disposing of waste is mostly a matter of logistics, except for particularly dangerous materials:

  • Flammable materials need to be away from sparks or other heating elements that could ignite it, as well as heat-shielding that protects it.
  • Radioactive isotopes require lead shielding to prevent the nuclear radiation from affecting the area around it. It also can’t be stored in one place, since too much in one place will create an unstoppable fission reaction.
  • Sharp objects like glass must be protectively sealed to prevent anyone being harmed from it.

At scale, factories have much larger loads of materials to maintain, and create much more waste. It makes perfect business sense to reuse what they can (i.e., waste material becomes the input of another factory process), but it’s never perfect.

Further Exploration

Simple Mechanical

Advanced Mechanical