Long time no seen. Had a birthday and had to spend time with guests and preparing the event, so unfotunately could not get to garage

But, meanwhile I have done lot of research and finally did what everything said it's not possible - huge thrust endburner from kno3/sugar! Though it needs more work as video below demonstrates. But for now I'm dealing with TOO MUCH energy and too high temperature that burns through stainless steel casing.

For that I made slight changes to the engine:
1) To get more burn surfrace, took a bit larger diameter stainless steel pipe. Now I am using 6cm diameter stainless steep pipe with wall width 0.8mm
2) Slightly smaller nozzle - 10mm
3) an enhanced welding technique to get the casing more pressure resistant - well Im getting better on welding day by day

And the bigges change - my cooking process. To cook 0.5kg kno3/sugar fuel it now took me 7 hours! And still I could not get all the moisture out of the fuel. So to make it perfect it would take around 10 hours. But oh my, this 7 hour cooked batch worked above expectations and completely blew me off The performance is massive!

So what I have learned from cooking tests:
1) Completely avoid grinding cooked fuel and using granules, pressed or not pressed - you really cant control the process. Maybe if pressing with at least 12T press you can get air prockets out but it's really complicated
2) recrystalized approach - Biggest misunderstanding is that sugar has melting point. Well it has a melting point where sugar gets liquid but it also immediately starts to caramelize which means its chemical composition changes and you will loose big amount of energy and the fuel really does not work well...

My cooking process:
1) completely dissolved sugar and kno3 in the boiling water - make sure that sugar and kno3 are completely dissolved. The water has to be CRISTAL CLEAR!!!!

KNO3 Solubility in water
133 g/L (0 °C)
242 g/L (20 °C)
2439 g/L (100 °C)^[3]

The tabel above is IMPORTANT!!!!!!! If you dissolve sugar and kno3 in almost 100 C water, the water has to be cristal clear! There has to be no crystals or granules left in the water. If there is, add more water! You need pretty much water to actually dissolve the components!!! For 0.5kg fuel I had to add almost 0.5l water so it clearly took a lot time to actually boil it off.

When main mass of water has boiled off, the fuel becomes white toothpaste similar mass and at that point I stopped heating at elecrical stove and put the mixture to the owen at 110C. Then I allowed it to heat to target temperature (measure internal temperature with meat thermometer) and stir the mixture after 10-15 minutes and did that for 6 hours. Without stirring the moisture can't escape and again you will mess up the fuel (moisture stays to the fuel and the exposed area of the fuel gets too "crisp"). I'll try to develop stirring mechanical device that does the work for me. I believe I can get the time from 6 hours effectively to 2-3 hours with that.

So now the test and the video

What actually happened there
1) The flames appearing around the nozzle and bottom end - the chemicals that I used to make welds more pressure resistant actually cought fire. Have to change them.
2) As the temperature of the burn process got extremely high, it actually burned a hole to the side of the stainless steel casing. That's the reason why it CATO'd in the end. At high temperature metal becomes soft and thats the issue. So I have to find a way how to reduce the temperature and protect the casing from it:
For that I can:
2.1) Increase the nozzle diameter a bit, in next test I am going to use 11mm nozzle instead of 10mm.
2.2) Add a thin cardboard layer between stainless steel and fuel / if that does not work, then clay layer.

If the cardboard layer does not work, I will try different metal or clay layer.
Before the temperature burned a hole to the side of the casing it recorded 12kg of thrust and it was just building it up (the fuel and the engine casings total weight was 0.6kg). At this moment I actually don't know how much thrust the motor actually would have provided. But nevertheless, its an excellent progress! I also believe that the nozzle diameter is too small. Adding a bit bigger diameter can have big increase in thrust and lower temperature and this is something my next text will cover.

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Other improvements.

1) Iron oxide, Fe2O3
I have discovered that the iron oxide i used in my tests actually contained little % of Fe2O3. So I ordered 1kg of lab quality Fe2O3 from Germany. Delivery in the end of december. This will provide big amount of additional energy, but in that case temperature definetly will become an issue. Smaller nozzle in that case definetly is a must.
2) To actually make Fe2O3, I tried Hydrogen Peroxide(3%) and it works perfectly! Though it takes a lot of time to make 10g of Fe2O3 one can easily make it at home. But as I said, I ordered it from chem lab. It costs 30 euros. No point to make it yourself - it's just too cheap...
3) Meanwhile I have also allocated couple of kg of Aluminium powder and technical sulfur - if I get my casing more heat resistance, I will give it a try with proper Fe2O3 and separately Aluminium + Sulfur. The last will give huge amount of energy but I am more than sure that in that case I need different casing, it will just melt the current 0.8mm stainless steel casing.