April 9, 2026
Honey, I shrunk the turbines
Small Engines
Can a 2‑inch jet engine power your gadgets? Commenters are fired up
TLDR: A think piece says tiny engines don’t scale well, even though fuel packs far more energy than batteries. Commenters split between “build a 2-inch jet, please” and “physics won’t let you,” with one fact-checking the insect-size analogy and others dreaming of decade-long pilot lights and pocket-size turbines.
Engines are “people-sized,” says the article—your car’s pistons are fist-sized for a reason—and shrinking them breaks the rules of physics: too much heat lost, fuel droplets too big, combustion gets weird. It’s a love letter to why tiny heat engines are hard, even if fuel packs way more punch than today’s batteries. But the comments? They turned it into a street brawl between dreamers and physics referees.
On Team Pocket Jet, one user practically waves a checkbook: “Could we make a 2 inch turbine?” Another imagines laptop batteries fueled by a thimble of ethanol, cheering hydrocarbons’ huge energy bang for their buck. The counterpunchers arrive fast: a nuclear-reactor analogy warns some machines simply don’t scale down—mini versions get “dead spots” and chaos, just like certain reactors do. And then there’s the comic relief: a curious tinkerer wonders if a tiny flame could sip from a grill tank for 10… or 100 years—like a forever nightlight with swagger.
Drama spike: a fact-checker storms in to say the article’s insect-size comparisons are busted, dropping an Ars Technica link. Cue the brainy cameo: someone summons Richard Feynman with a link to his nano-classic, “There’s Plenty of Room at the Bottom.” The vibe? Tiny turbines are the new moonshot—half sci-fi dream, half “physics says nope,” and 100% comment-section popcorn.
Key Points
- •Car-scale internal combustion engines (~fist-sized pistons) achieve ~25%–35% efficiency, while very large marine engines with yard-wide pistons can reach ~50% efficiency and burn bunker fuel.
- •Gas turbines are emphasized as key prime movers, with ~6-inch single-crystal nickel superalloy blades; steam turbine blades are longer and less exotic.
- •Supercritical CO2 turbines, if adopted, would use smaller blades comparable to or smaller than gas turbine blades.
- •Miniaturizing heat engines faces physics limits: higher surface-area-to-volume ratios and mismatched fuel droplet sizes make combustion unstable and inefficient at millimeter scales.
- •Hydrocarbons have much higher gravimetric energy density than current lithium batteries (~40,000 kJ/kg kerosene vs ~1,200 kJ/kg lithium), suggesting potential for tiny engines in applications like laptops or insect-sized drones.