Minutes matter: Hop Aero's $1.37B rocket-cargo push

Key points

Key takeaways from Source interview with Hop Aero CEO Matija Milenovic (September ️ 2026):

Origin story. Milenovic previously founded a satellite-propulsion startup and once had to take a 23-hour round trip to hand-deliver a payload after a last-minute launch opportunity, while his co-founder's Marine Corps service exposed the same need for minute-scale deliveries. The pair concluded that existing technology could bring rocket cargo into service in the near term.

Rook. Hop Aero's rocket, Rook, is aimed at delivering autonomous systems into contested environments hundreds of miles away in minutes, with military customers an early focus.

Commercial traction. During the Y Combinator batch, Hop Aero signed $1.37bn in commercial letters of intent (LOIs, across industries where delivery speed matters.

Shelf-life logistics. One LOI partner makes synthetic chemicals with a limited shelf life that must remain temperature-controlled, and wants shipments to reach end users as fast as possible.

Hop OS. The engine did not exist at the start of the batch: the team built software, Hop OS, that turns a 3D file into a component ready to manufacture, and hot-fired the engine successfully during YC.

Software-speed hardware. Milenovic says being a hardware founder in the batch felt like moving at the speed of a software company, thanks to the software-first tooling that let them execute unusually quickly.

Ten-year vision. Hop Aero wants to build a fleet of rocket cargo vehicles that can reach anywhere on Earth in minutes, graduating to larger rockets that travel further over time.

Founder advice. Move as quickly as possible from day one: mistakes are inevitable, but the faster you learn from them, the faster you can iterate toward your goal.

Read more: YouTube · Hop Aero