RATLOG Claims 90% Fewer Rocket Engine Parts

RATLOG launched this week, but not from a pad. The heavy-lift rocket startup made its debut in Y Combinator’s Fall 2026 batch, and its pitch starts by removing parts: the company says it can eliminate about 90% of a rocket engine’s parts.

The founders were students in Dresden, Germany, who found too few ambitious jobs after graduation, so they decided to build their own. Their engine skips the turbopump, the pump that feeds propellant into the engine. CEO Charlie Weise calls it complex, hard to scale, and “a leading cause of rocket failures.” RATLOG instead builds pressure by physically rotating the whole engine. The contrast is with rotating detonation engines, where only the flame spins. The cost, Weise said, is that a rotating engine puts new demands on its bearings.

Weise argues that rivals are making incremental changes: “There are companies who do a different fuel or something like that, or build a tank out of another material, but these are all incremental steps.” RATLOG’s rocket targets the Falcon 9 specifications that customers already design to, though likely with a wider fairing, the protective nose cone around the payload. The timeline is tight: a flight-ready engine by 2027, a hot-fire of the first stage in a hopper test in 2028, and a first launch in 2029 or 2030. Isar Aerospace, founded in 2018, did not fly its first, smaller rocket until 2025.

For customers, the pitch is a cheaper and more available launch, which depends on the engine working as planned. RATLOG says it holds letters of intent, mostly from orbital data center and satellite constellation companies, and it sees room to become, in Weise’s words, “a cheaper and more available Ariane 6” in Europe. Letters of intent are not contracts, and the company must still show commercial traction. Oman and the UAE are its likely launch-site contenders, though it is still exploring its options.

First comes the test. RATLOG plans to hot-fire its flight combustion chamber in November and to present itself at YC Demo Day in December. Those are the next public checkpoints. Until a hot-fire is reported and a launch is flown, the 90% figure remains the company’s own claim.