T-stoff tank cluster model

T-stoff:

The oxidizer will be T-stoff. T-Stoff is generally an 80% concentrated form of hydrogen peroxide (H2O2). When brought into contact with a catalyst, the peroxide will decompose into a mixture of superheated steam and oxygen at a temperature of about 500 C. The released oxygen will promote combustion of the solid fuel in the combustion chamber. T-stoff was chosen because it is stable, easily available, and it was the oxidizer of choice for many of the early German rockets built during W.W.II.


T-stoff Tanks:

We spent a lot of time looking for lightweight Aluminum tanks. We were looking for a low pressure (under 1000 PSI) tank that was large enough to hold a good amount of oxidizer and thick enough to tap some holes for connectors, but not so thick that we add unnecessary weight. Through our small network we were offered some spent calibration cylinders which were not an exact match but the price was right. The cylinders are DOT-3 aluminum cylinders rated at 720 PSI and just thick enough to tap the bottom without comprising the rating. A minimum of two cylinders were needed and we decided on using three cylinders to keep the weight distribution symmetrical about the axis of the rocket. This also will give the rocket a Russian look.

Tank Preparation:

There were only a few modifications that had to be done on the tanks. The tops had an odd thread so we had to either find an adapter or fabricate an adapter. The standard way to dispose of calibration cylinders is to destroy the pin in the top and throw it in the trash. So, since we had to drill out the pin anyway we decided to just make our own adapter, pictured above. The next modification was two holes had to be tapped in the bottom of each tank for the nipples that will extend into the combustion chamber. These were the only modifications that had to be done, the mock up T-stoff cluster is pictured below. The final version will not need the zip ties, the flanges at the ends are templates made from formica and will be eventually made form 6061-t6 aluminum. The tube running through the center is part of the ignition system.

Mock up of the T-stoff tank cluster

Tank Testing:

So, after the modifications were complete we had to test the tanks to ensure they would not fail when pressurized. The system design pressure is around 180-200 PSI, so the modified tank must hold that pressure plus a safety factor. The tanks are rated above 700 PSI unmodified, catastrophic tank failure is unlikely. The main concern was stripping out the tapped holes in the bottom. To test this we screwed plugs into the holes in the bottom and screwed a tee with a pressure gauge onto the adapter. At first we hooked the tank to an air compressor, but the air compressor didn't have the power to pressurize the tank above 120 PSI. Since we kinda wanted to see something blow up, we took the hose off the compressor and attached it to an old unmarked 3000 PSI tank of something. When the valve was opened the pressure in the T-stoff tank quickly rose to 300+ PSI, the pressure gauge only went to 300 PSI and we exceeded the gauge. The test was successful, the tanks held the pressure and the plugs stayed in.

Compressor and tank of something

T-stoff tank test

 

T-stoff tank final configuration:

Below are images of the final configuration of the t-stoff tank cluster. As you can see the tanks were attached to the t-stoff flange using steel NPT unions that screwed onto the modified tank top adaptors. The gas line was sized to fit down the middle of the tank cluster and the tanks were held together using large zip ties, which are removed when everything is tightened. The Brass nipples were bolted to the top of the combustion chamber using a nut on the inside and outside of the chamber top with Garlock gaskets compressed in between the nuts. The bottom image shows the final configuration with the flat combustion chamber top and the hex nozzle holders installed.

Hose attachments to the pressure manifold.	Angled view of the hose attachments.
Aluminum nipples bolted into the top of the mock up combustion chamber flange.	Brass nipples bolted into the top of the mock up combustion chamber flange.
Overall image of the t-stoff tanks in the final configuration.