Part 2 — Capstone Prototyping

As part of our Capstone design process, we have begun developing prototypes of both the electrolysis and thruster halves of our project, which is a thruster that uses electrolysis to derive its fuel from water.  Through these prototypes, we've gained insight into important considerations for our further prototypes and ultimately our final product.  This page contains information about our prototyping status as of the completion of Part 2.

Prototyping Reports

Core Concepts

This section will be used to discuss some design notes which we have gathered from our prototyping.

Project Overview

In short, this project is an effort to build a thruster which uses electrolysis to generate its fuel from water.  As such, there are two main aspects to the project: the electrolysis half, which takes input water and produces hydrogen and oxygen gas, and the thruster half, which takes those split gasses as input and produces thrust.

Thruster Types

There are a few different types of thrusters which we are considering for our project.  A brief overview of each is presented below.

Conventional Thruster

This thruster design is the traditional combustion-based design.  Fuel (hydrogen gas) and oxidizer (oxygen gas) are injected into a chamber where they are ignited, combusting and moving rapidly out through the tight nozzle opening where they move backward to produce thrust.

Ion Thruster

An ion thruster generates thrust by applying an electrical potential across a fuel, ionizing it.  The ionized particles move in one direction due to a static electric charge which attracts them through the grid, and by this motion thrust is imparted onto the thruster.

Resistojet

A resistojet feeds gas into a heating system.  The heating system expands the gas, creating pressure which forces it out through the nozzle and produces thrust.

Arcjet

An arcjet uses a high voltage electric arc to impart additional energy onto gas moving into the thruster chamber.  It is this acceleration which leads to the production of thrust.  This is the current design we are attempting to produce through our prototyping due to its possible simplicity — while large-scale arcjet designs use a preburner to impart exceedingly large accelerations onto the gas, we may be able to do without one at our small scale, meaning that the setup becomes quite simple (consisting merely of an anode and cathode in the form of the nozzle).

Zero-Gravity Electrolysis

Electrolysis as a producer of gas poses a few problems.  The most notable problem is that of separation of the gasses; if fuel is to be combusted, then the hydrogen and oxygen gas produced must be separated when it exits the electrolysis chamber.  (This problem is, of course, obviated by a thruster like the resistojet, which does not require combustion.)  Separation must not prevent neutrons from transferring between the two electrodes, but it must prevent gasses from doing so, making it a particularly tricky problem.  It seems that a specific weave of microfiber cloth may be effective at preventing the large gas molecules from exchanging while allowing neutrons to do so.  This is still something we are experimenting with, however.

Reflection

While this is not the conclusion of a project and therefore hard to make a complete reflection of, I believe that we were relatively successful here.  We are on track to continue progressing towards the final iteration, and we have both made some important discoveries and opened new questions to be investigated with these prototypes.

With respect to the six C's, our collaboration was fairly strong on this project with respect to getting materials.  We all worked together to source materials on the various prototypes, using what we had access to — for example, Noela brought in chemicals to test with electrolysis, while I brought in a power supply for the arcjet test.  This coordination of materials allowed us to set a specific date at which we would conduct a test and then be able to use that time effectively.  We also had excellent critical thinking.  We initially had no idea how we would test electrolysis gas production levels but came up with a solution on-the-fly: use the mass differential between the start and end as the amount of gas produced (lost).  This allowed us to gather more useful data thanks to quick critical thinking.

One area that might have been improvable was our conscientious learning.  While we did complete everything in a timely manner, we got close to the deadline on both steps, leaving no time to rectify possible failures or setbacks.  Although this didn't hurt us in this instance, it is something to consider more carefully in the next iteration.  Additionally, our communication might have been improved; we used block periods for prototyping purposes, but we also used them for mentor meetings, leading to an unexpected overlap in one case.  Making sure everyone (including mentors) are aligned a little more closely could be beneficial, although this issue was very minor.

Overall, then, this prototyping iteration marks an important step forward towards our final goal.  We aim to continue producing prototypes in the next month before finalizing our entire design.