# 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._