SpaceX
Ablative cooling
A way to protect a rocket engine from heat by letting an inner lining slowly char and burn away. Early Merlin engines used it before SpaceX switched to circulating cold propellant around the chamber instead.
Every term, explained.
Search 66 definitions, filter by company, jump to any letter.
A
Tesla
Anode
The negative electrode of a battery, the side that stores charge while the cell is full. Tesla's 4680 cell uses a silicon-rich anode because silicon holds more lithium than the usual graphite.
Appears in 4680 Battery Cell
Tesla
Autonomy (self-driving levels)
An engineering scale, defined by the body SAE International, that rates how much a car drives on its own across six rungs from zero to full. Tesla's systems remain at Level 2, meaning the car assists but a human must stay ready to take over.
B
Neuralink
Brain-computer interface (BCI)
A system that reads electrical signals from neurons and translates them into commands a computer or device can use. Neuralink's N1 is a fully implanted BCI that sits in the skull and reads the brain without wires breaking the skin.
C
TeslaTesla Energy
Cathode
The positive electrode of a battery, the side electrons flow toward as the cell discharges. Its chemistry, such as a high-nickel mix, largely sets a cell's energy and cost.
SpaceX
Chamber pressure
How hard the burning gases press inside a rocket engine's combustion chamber, measured in bar. Higher pressure generally means more thrust from a given size, and Raptor's roughly 300 to 350 bar is among the highest ever flown.
Appears in Raptor Engine
SpaceXAI
Context window
How much text an AI model can hold in mind at once, measured in tokens. A larger context window lets a model read a whole contract or long document in a single pass.
Appears in Grok
D
Tesla
Degrees of freedom (DoF)
The number of independent ways a joint or mechanism can move. A robot hand with more degrees of freedom can grip and manipulate objects more like a human hand.
Appears in Optimus
Tesla
Disengagement
A moment when a human driver or safety monitor takes control back from a self-driving system. Disengagement rates are a common yardstick for how reliable an autonomous system is.
E
Tesla Energy
Energy arbitrage
Buying or storing electricity when it is cheap and selling it back when prices rise. Battery systems like Megapack earn revenue by charging during low-price hours and discharging during expensive peak demand.
Tesla
Exoskeleton (vehicle structure)
A design where the outer body panels carry the structural load rather than a separate internal frame. The Cybertruck uses a stainless steel exoskeleton, which is part of why its body is so angular.
Appears in Cybertruck
F
Key Ideas
First principles thinking
A way of reasoning that breaks a problem down to its most basic, certain truths and builds an answer up from there, rather than copying how things have always been done. Elon Musk has cited it as the core method behind SpaceX and Tesla.
Tesla Energy
Frequency regulation
Keeping the electrical grid's alternating-current cycles steady at their target rate, such as 50 or 60 hertz. Fast-responding batteries are paid to inject or absorb power in fractions of a second to hold frequency stable.
Tesla
Full Self-Driving (FSD)
Tesla's camera-based driver-assistance software that can steer, brake, accelerate, and handle intersections and turns. Despite the name, it legally still requires an attentive human ready to take over, so Tesla labels the consumer version Supervised.
SpaceX
Full-flow staged combustion
An efficient but very hard to build rocket engine cycle that routes all of the fuel and all of the oxidizer through two preburners before the main chamber, wasting almost no propellant. Raptor is the first engine of this type ever to fly.
G
Tesla
Geofence
A digitally defined boundary that limits where a service is allowed to operate. Tesla's early Robotaxi rides ran only inside a roughly 20-square-mile geofence in Austin.
SpaceX
Geostationary orbit
An orbit about 36,000 kilometers up where a satellite circles Earth at the same rate the planet turns, so it appears to hover over one spot. Reaching it carries far less payload than a low orbit, which is why heavy-lift rockets matter for these missions.
Appears in Falcon Heavy
Tesla
Gigafactory
A single very large plant that makes batteries and vehicles at enormous scale, named for the giga prefix meaning one billion. The idea is that one factory can rival an entire industry's prior output and drive down cost per unit.
Tesla
Gigawatt-hour (GWh)
A unit of energy equal to one billion watt-hours, used to size battery factories and large storage projects. A single gigawatt-hour is roughly enough to power tens of thousands of homes for a day.
SpaceX
Gimbal
To swivel a rocket engine slightly so its thrust can steer the vehicle. On Super Heavy, the inner ring of engines gimbals to point the rocket while the outer engines stay fixed.
SpaceXAI
Graphics processing unit (GPU)
A specialized chip, originally built for graphics, that excels at the heavy parallel math used to train and run large AI models. xAI's Colossus supercomputers are built from hundreds of thousands of Nvidia GPUs.
SpaceX
Greenshoe (over-allotment)
An extra block of shares that underwriters can sell beyond the planned amount of a stock offering if demand is strong. Exercising the full greenshoe lets a company raise more money than first announced.
Appears in SpaceX IPO
H
SpaceXAI
Hallucination (AI)
When an AI model produces a confident answer that is simply wrong. Reducing the hallucination rate is a key measure of how trustworthy a model has become.
SpaceX
Heat shield
The protective layer that keeps a spacecraft or rocket from burning up as it reenters the atmosphere at high speed. A lander like Starship HLS that never reenters Earth's atmosphere can drop the heat shield entirely to save weight.
I
Key Ideas
Idiot index
A metric Elon Musk uses for the ratio of a finished part's cost to the cost of its raw materials. A high ratio signals that the design or manufacturing, not the materials, is where the money is being wasted.
Government
Independent expenditure
Political spending on advertising that openly supports or opposes a candidate but is made without coordinating with that candidate's campaign. It is the main way a super PAC influences an election.
Tesla
Inference (AI)
Running an already-trained neural network to make decisions in real time, as opposed to the separate, data-center process of training the network in the first place. Tesla's in-car AI chips perform inference to drive the vehicle.
X
Interchange
The fee a merchant pays on every card transaction, split among the banks and networks that process the payment. Capturing interchange is part of how a payments product like X Money makes money.
Tesla Energy
Inverter
The device that converts a battery's direct current into the alternating current the grid and home appliances use, and often back again. It is a core component inside products like Powerwall, Powerpack, and Megapack.
Tesla Energy
IP67
A rating meaning a device is sealed against dust and can survive being submerged in water briefly, so it can sit outdoors in rough weather. Powerwall carries an IP67 rating for outdoor installation.
Appears in Powerwall
K
TeslaTesla Energy
Kilowatt-hour (kWh)
A unit of stored or used energy, roughly the amount a microwave draws running for about an hour. It is the standard way to measure the capacity of electric-car and home batteries.
L
SpaceXAI
Large language model (LLM)
An AI system trained on vast amounts of text to predict and generate human-like language. Grok is built on a large language model, as are the systems that write Grokipedia articles.
TeslaTesla Energy
Lithium iron phosphate (LFP)
A lower-cost, durable battery chemistry that trades some energy density for safety and longevity. It is widely used in stationary storage like Megapack and in lower-priced vehicle trims.
TeslaTesla Energy
Lithium-ion battery
A rechargeable battery that moves lithium ions between its electrodes to store and release energy, packing high energy into low weight. It is the chemistry behind Tesla's cars and home storage products.
SpaceX
Low Earth orbit (LEO)
The band of space a few hundred kilometers above Earth where most satellites and crewed stations operate. It is the easiest orbit to reach, so rockets can carry their heaviest payloads there.
M
SpaceX
Mechazilla
The nickname for the launch tower's two mechanical arms that catch a returning Super Heavy booster in mid-air. Catching the booster at the pad lets it be inspected and reflown quickly without legs or a separate landing site.
SpaceXKey Ideas
Methalox
The fuel combination of liquid methane and liquid oxygen used by SpaceX's Raptor engine. Methane is chosen partly because it could one day be manufactured on Mars from local resources.
SpaceXAI
Mixture of experts
An AI model design that routes each piece of input through only a small fraction of the network, activating a few specialized parts rather than the whole, to save computing power. Grok uses this structure, activating two of eight experts per token.
Appears in Grok
N
Tesla Energy
NACS (North American Charging Standard)
Tesla's electric-vehicle charging connector, which has spread to become the de facto standard across North America after rival automakers adopted it. Other regions use different plugs such as CCS2 in Europe and GB/T in China.
Appears in Supercharger Network
Tesla
Neural network
A computing system loosely modeled on the brain that learns patterns from data, used for tasks like recognizing objects or driving. Tesla's self-driving relies on neural networks running on its in-car chips.
P
SpaceX
Payload
The useful cargo a rocket carries to orbit, such as satellites, crew, or supplies, separate from the rocket and fuel. How much payload a rocket can lift falls sharply for higher or more distant orbits.
X
Peer-to-peer payment
Sending money directly from one person to another, the way apps like Venmo work, without writing a check or visiting a bank. X Money is built to let users send peer-to-peer payments inside the X app.
SpaceX
Phased array antenna
An antenna that steers its signal electronically, with no moving parts, by coordinating many small elements. SpaceX uses phased array antennas so satellites can lock onto ordinary phones moving relative to satellites overhead.
Appears in Starlink Direct to Cell
SpaceX
Preburner
A small combustion stage in a rocket engine that burns part of the propellant first to drive the pumps before the main chamber fires. Full-flow staged combustion uses two preburners, one fuel-rich and one oxidizer-rich.
Appears in Raptor Engine
SpaceXKey Ideas
Propellant transfer
Moving rocket fuel and oxidizer from one vehicle to another while in orbit, also called orbital refueling. It is the make-or-break technology that lets Starship top off in orbit before heading to the Moon or Mars.
R
Tesla
Regenerative braking
A system that recovers some of a vehicle's energy during braking by running the motor in reverse as a generator, sending power back to the battery. It extends range and is especially useful on long downhill stretches for heavy vehicles.
SpaceX
Regenerative cooling (engine)
Circulating cold propellant through channels around a rocket engine's chamber to carry heat away, a more durable approach than letting a lining burn off. SpaceX adopted it on the Merlin 1C engine.
Key Ideas
Replacement rate
The average number of births per woman needed to keep a population steady over the long run, generally about 2.1 in developed countries. Falling below it is the technical anchor of the population-collapse argument.
Appears in Population Collapse
SpaceXKey Ideas
Reusability
Recovering and reflying a rocket's stages rather than discarding them after one flight, the way an airliner is not scrapped after a single trip. Because the fuel is cheap and the hardware is not, reusability is what drives launch costs down.
Tesla Energy
Round-trip efficiency
The share of energy a battery returns after the losses of charging and discharging. Megapack runs at about 93.7 percent, meaning most of the stored energy is recovered.
Appears in Megapack
SpaceX
RP-1
Highly refined, rocket-grade kerosene used as fuel, burned with liquid oxygen, in engines like the Merlin. It powered SpaceX's early Falcon 1 and the Falcon 9.
S
SpaceX
Senior notes
Corporate bonds, meaning borrowed money a company repays with interest, that rank ahead of other debt for repayment. SpaceX paired its stock offering with a large senior-notes issue as belt-and-suspenders financing.
Appears in SpaceX IPO
SpaceX
Specific impulse (Isp)
A measure of a rocket engine's fuel efficiency, expressed in seconds, with higher numbers meaning more thrust squeezed from each unit of propellant. An engine gains specific impulse in vacuum by swapping in a larger nozzle.
SpaceX
Staged combustion
A class of efficient rocket engine cycles that burn propellant in a preburner to drive the pumps, then route those gases into the main chamber rather than dumping them overboard. Full-flow staged combustion is the most complete and hardest version.
Tesla Energy
State of charge
How full a battery is at a given moment, expressed as a percentage of its capacity. Trading software tracks each battery's state of charge to decide when to buy or sell power.
Appears in Autobidder
Government
Super PAC
A political committee that can raise and spend unlimited sums to support or oppose candidates, as long as it does not coordinate directly with a campaign. America PAC is the super PAC Elon Musk founded in 2024.
Appears in America PAC
TeslaTesla Energy
Supercharger
Tesla's own network of proprietary fast chargers that deliver high-power direct current to recharge an electric car in minutes rather than hours. It has gradually opened to non-Tesla vehicles through adapters and the spread of the NACS plug.
TeslaSpaceXAI
Systolic array
A grid of multiplier circuits on a chip arranged to crunch the matrix math that neural networks rely on, very fast and efficiently. Tesla's in-car AI chips pair processor cores with systolic arrays to run self-driving.
T
Tesla
Telematics
The collection of driving data from a vehicle, such as speed, braking, and time of day, used to price insurance by actual behavior. Tesla gathers it directly from the car, dropping the plug-in dongle rival insurers mail to customers.
Appears in Tesla Insurance
Key Ideas
The Algorithm
Elon Musk's five-step process for designing and building things, run in a strict order: question requirements, delete parts, simplify, speed up, then automate. The steps are meant to be followed in sequence, with automation always last.
Appears in The Algorithm
SpaceXAI
Token (AI)
A chunk of a word, the basic unit an AI language model reads and generates text in. A model's context window and its running cost are both measured in tokens.
Appears in Grok
Tesla
Torque vectoring
Sending different amounts of power to individual wheels to improve grip, cornering, and acceleration. The next-generation Roadster uses three motors with torque vectoring to deliver its launch performance.
Appears in Roadster (next generation)
Boring Company
Tunnel boring machine (TBM)
A large machine with a rotating cutterhead that grinds forward through earth while installing the tunnel lining behind it. The Boring Company uses TBMs to dig its transit tunnels, starting with a test tunnel in Hawthorne.
V
TeslaSpaceXSpaceXAIKey Ideas
Vertical integration
Building key parts and processes in-house rather than buying them from outside suppliers, to control cost, quality, and supply. It is a recurring strategy across Elon Musk's companies, from SpaceX engines to Tesla batteries.
Tesla Energy
Virtual power plant
Software that pools many separate batteries, such as home Powerwalls, and operates them together as one resource a utility can call on. The combined fleet can steady the grid during demand spikes as if it were a single power plant.
Neuralink
Visual cortex
The region at the back of the brain that processes sight. Neuralink's Blindsight aims to restore a form of vision by writing signals directly into the visual cortex, bypassing a damaged eye.
Appears in Blindsight
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