# How Tiny Water-Powered Thrusters Steer Small Satellites > A method for building microscopic water-based rocket engines that use heat to push water through tiny nozzles to steer small satellites in space. - **Patent:** US 11878818 - **Original title:** Tunable water-based microthruster devices and methods - **Owner:** Purdue Research Foundation - **Granted:** 2024 - **Status:** Active - **Times cited:** 0 - **Field:** aerospace, semiconductors, mechanical ## What it does This patent describes a way to manufacture extremely small rocket engines, known as microthrusters, for tiny spacecraft. The device works by heating water stored in a small reservoir, which rapidly increases the pressure and forces the water out through a microscopic nozzle throat. The manufacturing process involves etching channels into layers of material—specifically silicon and borosilicate glass—and bonding them together to create the reservoir and nozzle. A key feature is the placement of a heating element that directly contacts the water and is precisely positioned relative to the nozzle throat to ensure efficient propulsion. ## What it does NOT cover - Does not cover thrusters that use chemical propellants or combustion rather than water. - Does not cover thrusters with nozzle throat areas larger than 20 square micrometers. - Does not cover propulsion systems that do not use a heating element to create pressure. - Does not cover thrusters where the heating element is not in direct contact with the water. ## The clever bit The innovation lies in the extreme miniaturization of the nozzle throat (down to 6 square micrometers) combined with a specific layered manufacturing process that integrates a heating element directly into the reservoir wall to manage phase-change pressure. ## Real-world examples 1. CubeSat propulsion modules 2. Small satellite attitude control systems 3. Micro-electromechanical systems (MEMS) for space ## Why it matters As the space industry shifts toward CubeSats and other small satellites, there is a critical need for propulsion systems that are safe, compact, and non-toxic. Traditional satellite thrusters often use hazardous chemicals like hydrazine, which are difficult to handle. This water-based approach offers a safer, more sustainable alternative for maneuvering small spacecraft in orbit. ## Frequently asked questions ### What does How Tiny Water-Powered Thrusters Steer Small Satellites cover? A method for building microscopic water-based rocket engines that use heat to push water through tiny nozzles to steer small satellites in space. ### Who owns patent US 11878818? Purdue Research Foundation owns this patent, granted in 2024. ### When does this patent expire? This patent is expected to expire on January 23, 2044, when the invention enters the public domain. ### What problem does this patent solve? As the space industry shifts toward CubeSats and other small satellites, there is a critical need for propulsion systems that are safe, compact, and non-toxic. Traditional satellite thrusters often use hazardous chemicals like hydrazine, which are difficult to handle. This water-based approach offers a safer, more sustainable alternative for maneuvering small spacecraft in orbit. ### What does this patent NOT cover? Does not cover thrusters that use chemical propellants or combustion rather than water. **Full plain-English explainer:** https://patentbrief.org/patent/us/11878818/starlink-maritime **Original patent:** https://patents.google.com/patent/US11878818 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How Satellites Use Split Thrusters to Reach Orbit Faster](https://patentbrief.org/patent/us/11753188/direct-to-cell-starlink) — A method for satellites with electric engines to manage their power usage by staggering when they fire thrusters, allowing them to reach their final orbit more quickly. - [How Solar Sails Use Moving Vanes to Steer in Space](https://patentbrief.org/patent/us/11905044/starlink-rv-roaming) — A solar sail design that uses multiple independently moving reflective vanes made of shape-memory materials to steer spacecraft using only the pressure of sunlight. - [How Boeing Stacks Electric Space Vehicles for Launch](https://patentbrief.org/patent/us/11708181/mechazilla-catch-tower) — A design for a launch vehicle that carries two space vehicles stacked on top of each other, both using electric propulsion systems for movement in space. - [How Spacecraft Servicing Pods Maneuver and Refuel Other Satellites](https://patentbrief.org/patent/us/11685554/starship-upper-stage) — A specialized robotic pod designed to dock with aging satellites and use a flexible, multi-jointed boom arm to adjust their orbit or velocity. - [How Rocket Lab Secures Satellites Inside Their Launch Dispensers](https://patentbrief.org/patent/us/11059609/starlink-inter-satellite-laser-links) — A mechanical system that allows engineers to tighten and secure a satellite inside a launch container from the outside after the door is already closed.