Neptune 1 - Water Rocket 🚀

A 3D-printed water rocket with autonomous flight controller programmed in MicroPython. This project combines hardware engineering and embedded systems to create a fully functional model rocket powered by pressurized water and air.

Vision: Utilizing innovative water fuel for eco-friendly space propulsion research and education.

Project Status

Completed ✅

• 3D printed Body, Fins, and Rocket tip
• Parachute spring mechanism
• Flight controller assembly with NodeMCU, ADXL345 accelerometer, servo, and NeoPixel LED
• Rocket base with trigger system
• MicroPython flight control software
• Sensor data logging system

In Progress / To-Do 📋

• Parachute door refinement
• Advanced parachute trigger system
• Flight Controller Software optimization
• Rocket base improvements
• Air tube and valve revision
• Nozzle optimization
• CAD files and documentation
• First test flight

Quick Start

MicroPython Board Commands

Upload main.py to NodeMCU over COM6:

python.exe -m mpremote connect com6 cp main.py :

Connect to Python REPL:

python.exe -m mpremote connect com6

Table of Contents

• 1. Overview
• 2. Water Rocket Structure
• 3. Flight Controller
• 4. Flight Controller Software
• 5. Rocket Base
• 6. Trigger System
• 7. Parachute System
• 8. Rocket Science & Future

1. Overview

Neptune 1 is a complete water rocket system combining 3D printing, embedded systems, and aeronautical engineering.

Components Needed

Hardware (≈ $40 excluding 3D printing costs):

• Empty plastic water bottles (1 small, 1 hard plastic PET)
• Bicycle wheel valve (for pressurization)
• Sealing rings and O-rings
• Wood (for rocket base/launch platform)
• Hardware: M5 screws (6x), washers (12x), nuts (6x), cable ties
• Wrapping wire and superglue

Electronics:

• NodeMCU microcontroller
• 18650 Li-Ion battery
• ADXL345 3-axis accelerometer (I2C)
• Servo motor (for parachute deployment)
• WS2812 NeoPixel LED (status indicator)
• On/off switch

Fabrication:

• 3D printer with filament
• Standard hand tools

2. Water Rocket Structure

The main rocket body is constructed from a standard 1.5L hard plastic PET water bottle, reinforced with 3D-printed components.

3D Printed Parts

• Nose cone (aerodynamic tip)
• Flight controller case (waterproof enclosure)
• 4x small stabilizing fins
• 4x large fins (provides stability and rotation)
• Bottle base adapter (connects bottle to launch platform)
• Bottle base button (release mechanism)

Specifications

• Empty Weight: 336g (including flight controller + 18650 battery)
• Propellant: Water (typical fill: 0.5-1.5L)
• Pressurization: Compressed air (typically 4-8 bar)

3. Flight Controller

Autonomous electronics system that monitors flight conditions and deploys the parachute.

Components

Component	Purpose
NodeMCU ESP8266	Main microcontroller
ADXL345 Accelerometer	Detects 0G condition (apogee)
Servo Motor	Triggers parachute deployment
WS2812 NeoPixel LED	Status indicator (red = active, green = ready)
18650 Li-Ion Battery	Power supply (~1000mAh for ~1 hour operation)
On/Off Switch	Manual power control
I2C Bus	Communication: NodeMCU ↔ ADXL345

GPIO Mapping

• GPIO 13: NeoPixel LED
• GPIO 14: Servo PWM signal
• GPIO 12: Buzzer (optional feedback)
• GPIO 4/5: I2C SDA/SCL (ADXL345)

Wiring Diagram

Assembly Photos

4. Flight Controller Software

The firmware runs on MicroPython and implements real-time monitoring and autonomous parachute deployment.

Architecture

Main Tasks (Async/Concurrent):

1. sensordata() - Logs accelerometer data to sensor.txt
2. buzzer() - Audible feedback when apogee detected
3. servo() - Deploys parachute when 0G detected

Algorithm

The deployment trigger works by detecting weightlessness:

Z-axis acceleration value progression:
↑ 200+     Launch phase (accelerating upward)
↑ 100-150  Powered flight
↑ 0-50     Coasting upward  
→ -10 to 0 Apogee (0G, weightless) ← TRIGGER
↓ 0-50     Falling
↓ 100+     Descent under parachute

Deployment Sequence:

1. Sensor detects Z-axis ≈ 0 (±10)
2. Buzzer sounds for 0.5s
3. Servo commanded: 30° → 122° (0.3s motion)
4. Parachute door opens, spring releases parachute

Performance Data

Graph shows typical flight profile: rapid acceleration at launch, coast phase, and detection moment at apogee.

Key Code Details

• I2C Interface: 400kHz frequency, addresses 0x53 (ADXL345)
• Sampling: Continuous polling, recorded with HH:MM:SS.mmm timestamps
• Servo Control: PWM duty cycle 30-122 for full range motion
• Detection Threshold: abs(z_value) < 10 indicates 0G condition

5. Rocket Base (Launch Platform)

Hybrid construction combining wood support structure with 3D-printed mechanical components. Designed for safe pressurization and reliable launch.

Components

Structural (Wood):

• Base platform (supports vehicle weight during pressurization)
• Stable tripod/stand design

3D Printed:

• 4x support legs
• Trigger ring (top retention)
• Cable tie ring (outer)
• Cable tie guide (inner)
• Valve plug adapter
• 2x sealing rubber inserts

Hardware:

• 6x M5×50 bolts
• 12x M5 washers
• 6x M5 lock nuts
• 16x cable ties (holds bottle during pressurization)
• Bicycle wheel valve (Schrader type, for pressurization)

Pressurization System

1. Bicycle wheel valve screwed into bottle base
2. Sealing rings prevent air leakage
3. Air pump pressurizes to 4-8 bar
4. Cable ties prevent bottle rupture
5. Trigger mechanism holds bottle at launch platform

Assembly Photos

Explosion View

CAD models showing component assembly order (to be added)

6. Trigger System

Mechanical release mechanism holds the rocket in place during pressurization and releases it instantly on command.

Mechanism

• Cable tie system: Multiple cable ties wrap around bottle
• Trigger ring: Holds cable ties under tension
• Manual release: Pulling trigger ring withdraws cable ties
• Instant launch: Bottle released from platform with full thrust

Design Philosophy

• Fail-safe: Mechanical (no electronics required for launch)
• Reliable: Cable ties proven in multiple tests
• Quick-release: Friction-free instantaneous separation
• Safe: Operator maintains control until ready

Photos

CAD Views

7. Parachute System

Recovery system deploys automatically at apogee to safely return the rocket.

Design

Parachute Construction:

• Material: Thin plastic film (similar to plastic bag material)
• Diameter: ~0.5m nominal when deployed
• Attachment: Cord tied to rocket nose cone

Deployment Mechanism:

• Spring: Piece of plastic bottle acts as compression spring
• Door: 3D-printed nose cone door holds parachute compressed
• Trigger: Servo-activated cord release
• Sequence: Spring pushes parachute out once door opens

Key Design Principle

Loose packing is critical: The parachute must not be tightly folded to ensure:

1. Reliable deployment (avoids tangles)
2. Proper billowing (full drag surface)
3. Soft opening (reduces shock loads)

Deployment Sequence

1. Apogee detected by accelerometer (0G)
2. Servo energized → 30° to 122° rotation (0.3s)
3. Cord pulled → door mechanism releases
4. Spring expands → pushes parachute out
5. Parachute inflates → slows descent to ~5-8 m/s

Recovery Video

8. Rocket Science & Future Builds

Physics & Performance

Launch Parameters:

• Propellant mass: Water (typically 500-1500g)
• Propellant pressure: 4-8 bar (relative)
• Launch acceleration: ~20-30G typical
• Apogee: 50-100m typical (depending on water fill)
• Flight time: 8-15 seconds total

Recovery:

• Descent rate: ~6-8 m/s under parachute
• Impact energy: Low (safe for electronics recovery)
• Reusability: Can fly multiple times (refill water)

Questions for Optimization

1. Efficiency: What is the most economical water/pressure ratio?
2. Propulsion Options:
   • Pure water + compressed air (current)
   • Two-phase mixture?
   • Alternative propellants?
3. Engine Design Variants:
   • Different nozzle geometries
   • Variable pressure profiles
   • Multi-stage designs?

Future Improvements

Planned Enhancements:

• Advanced sensor suite (pressure, temperature, altitude)
• Telemetry transmission (wireless flight data)
• Multiple parachute stages
• Modular nose cone designs
• Performance optimization through CFD
• Educational documentation & building guides

Research Directions:

• Thermodynamic efficiency analysis
• Optimal parachute sizing
• Structural optimization for higher pressures
• Autonomous flight path tracking

Education & Outreach

This project demonstrates:

• Applied physics (mechanics, thermodynamics)
• Embedded systems (real-time control)
• Materials engineering (3D printing optimization)
• Systems integration (mechanical + electrical)

Ideal for: STEM education, engineering competitions, maker communities