Tools required for making propellant

Now that we know the major components of our rocket, it is time to make them.

First, we will make the propellant. Before beginning, gather all the required tools.

You will need : a ball mill or just a mortar and a pestle. The ball mill is less tiring but more costly. Those tools are required to crush the chemicals in fine powder.

It is very important that your powder is the finest possible. The reaction and burn rate will be faster and continuous.

You will also need some kind of resin to shape the propellant but you can also gently melt the different component in a pan. But you will need a hot plate instead  (less dangerous than gas stove because there is no open flame).There are resin like dextrin, Parlon that are great for making stars in pyrotechnics.
Some composition needs to be binded with a resin because they can't be melted (e.g too dangerous or decomposes before).

And, of course, you will need the chemicals. It's different for each propellant so they will be listed on each post.

Requirements for the rocket's structure

The structure must be able to sustain the weight of the engine, the propellant and the payload, and the temperature produced by the drag at very high speed.

It is primarily built of lightweight yet strong enough material like aluminium. It is not uncommon to see steel used for the structure, particularly in heavy rockets.

The structure also house all the guidance electronics, the payload and the propellant tanks if the propellant is liquid or gaseous.

The body is profiled to avoid drag that is encountered when traveling at super- and hypersonic speeds in the atmosphere.

More drag equals more energy to be put in, so increasing propellant mass for no other purpose that compensating the drag experienced by the rocket.

In rocket and missile design, these requirements are primordial to optimize the rocket but in our model rocket, we will not care about them.

For the structure and the body, a hollow PVC or carboard paper tube will do the trick.

And the drag is negligible because the propellant will be exhausted before the rockets reach a high speed, avoiding issues of drag.

The engine

The engine is the most important part of the rocket.

If you want maximum performance, it must be well-designed.

Each propellant acts differently in terms of pressure, temperature, etc. So the engine is designed according to the propellant that will be used.

Mechanically speaking, it must withstand the high temperature without melting and the high pressure resulting from the combustion without bursting.

To avoid melting the engine, it must be cooled. There are several ways to cool it : passively and actively.

Passive cooling is a manner that not use additional energy but is limited in efficiency and cooling power.

Two way exists : radiation cooling and ablative cooling.

A big rocket engine test firing

Radiation cooling is done by letting the engine glow white hot. The heat is dispersed by the light but it is effective for propellant that don't give temperature superior to the melting point of the engine's walls.

The second is done by putting a layer of resin (or something else like plastic for small engine) in between the engine's walls and the propellant so that the resin is vaporized by the combustion's heat. This technique is efficient, cheap and adapted to solid-fueled rockets but the ablative is consumed and must be replenished between each launch.

Actively cooling the rocket requires additional energy but is efficient and adapted to big rockets.

The general principle is to run the liquid propellant through (generally copper) tubings that are welded on the engine so that it can absorb the heat like a water-cooling. It only works on liquid and hybrid rockets because the propellants has to be a fluid.

 Ablative cooling is the cooling technique we will use in our little rocket engine. It's the most efficient and cheapest way to cool it.

Characteristics of the propellant

To choose a propellant, you will watch some characteristics.

I told you the propellant in the last post that your rocket is powered by a chemical reaction between two chemicals.

More this chemicals are energetic, more your rocket will be fast or able take off with a heavier weight.

When it is burns, the propellant produces gas. These gas are expanded by the temperature produced by the combustion and are expelled through the nozzle providing thrust according to Newton's third law.

Temperature depends on the energy stored by the chemicals and released when combusting. So more energy, more temperature and more temperature equal more thrust.

There is also the burn rate of the chemicals. A high burn rate is preferred because more gas are created providing a greater thrust.

But, a higher burn rate means also your propellant will be used faster. This could result in your rocket not reaching the height you expected.

Some propellant produce a lot of smoke,
some less or even not.

This impacts the specific impulse, also with the engine design, it is noted Isp and expressed in seconds.

Simply put, Isp is the time your rocket will fly with the propellant. It is the amount of thrust divided by the weight of your rocket. More thrust and light weight equals to high Isp.

However if you want to speed up the combustion, you can use a catalyst. Catalyst is another chemicals that is mainly used in the solid-fueled rocket sector.

You just have to add a little amount of it in your solid propellant and it will burn faster.

Catalyst are generally metal-oxides like iron oxide or manganese oxide mixed with the propellant in an amount of about 2 - 3% weight.

Each propellant I will propose to make will be described in terms of performance (thrust, Isp, etc) along with the chemicals needed, their proportions and how to shape them from powder to a more convenient form for your engine.

What is the propellant ?

The Space Shuttle,
one of the most famous rocket.

Like I promised, here is my second post.

I think it is important to explain all the parts you will be building before attempting anything.

So, a rocket is mainly 4 components : the engine, the propellant that comes inside, the body and the payload.

I will explain all the components, how to make them, one at a time.

So let's begin with the propellant.

What is it ? It's simply the fuel that propel (hence his name) your beautiful rocket up to sky.

The propellant consist mainly of 2 different chemicals that act together.

The first is the fuel, it is the chemicals that will burn (like wood or gasoline).

The second chemical is the oxidant, it's purpose is to burn the fuel (like oxygen).

You all know, thanks to your chemistry classes, that for something to burn, it requires oxygen.

But in space or in your engine there is not enough or simply no oxygen.

Simply put the oxidant is the chemical that bring the oxygen on it and allow the fuel to burn.

There is also a third component, the catalyst, but I will describe it in the next post because it is not in all propellants.

You also know that matter has 3 states : solid, liquid and gaseous.

So it's the same for the fuel and the oxidant : they can be either solid, liquid or gaseous.

Having said this, there is different kind of rocket, the solid-fueled, the liquid-fueled and the hybrid rocket.

First, the solid-fueled is like its name means, a rocket with the fuel and the oxidant being solid. They are the cheapest and the easiest to build.

That is the reason why I will concentrate in next coming post I will only give you recipes for solid propellant.

One major drawback is that it cannot be stopped.

After there is the liquid-fueled rocket. It is far more complicated and expensive that the two others.

It requires pumps, tubing and the fuel and oxidant, being liquids, are difficult to handle if you don't have the required tools. But can be stopped.

To finish, there is the hybrid rocket. It is between the solid and liquid-fueled rocket in term of complexity and cost.

Its fuel is solid and the oxidant is either liquid or gaseous.

In the following post, I will describe you what make a propellant a good one or a bad one in terms of characteristics.

The two little rocket next to the External Tank are the Shuttle's Boosters, they are solid-fueled.

The 3 thrusters behind the Space Shuttle are 3 liquid-fueled rocket. The fuel is liquid hydrogen and the oxidant is liquid oxygen.

The External Tank contains just the oxidant and the fuel for the 3 thrusters in separate parts but in the same container.

Welcome

Hi guys !!!

Welcome to my blog, The Rocket Blog.

Here I will guide you through the process of making your own little rocket that can climb towards the sky.

On it you will find links and information on the different parts, the chemicals used (even some pyrotechnics), news from the space industry and many more.

If you have any suggestion, feel free to let a comment or just contact me through my google account.

My first post will come in a matter of hours, so stay tuned.


I hope you will enjoy my site.

Jeremy, a rocket enthusiast.