Rocket Motor Research and Development

Solid Fuel Boosters are expensive. What if we could turn a "Ice Fountain" (indoor firework, see Pic. 18001a) into a usable engine?

Pic. 18001a: typical indoor "Ice Fountain"

Naturally the normal "Ice Fountain" does not come with any sort of usable nozzle. The exhaust opening of the indoor firework is about 8mm in diameter. Pic. 18001b and Pic. 18001c display a possible arrangement in conjunction with a custom nozzel.

Due to the shape of the nozzle designed, resulting thrust of the "Ice Fountain" should multiply.
To testify the usability and gain of thrust a engine test stand has to be developed. Tien Huu our software engineer programmed a data logging software (Pic. 18001d), the team around Oleg Boltonov managed the engine test stand.

Pic. 18001d: screen shot of the "OxidanSky Engine Analytica" Software

Pic. 18001e: Electronic interface and preliminary test stand.

First static engine tests / Nozzle comparison
Three different types of nozzles have been tested. First attempt without any nozzle attached, did not result in any measurable thrust data. Measured data with nozzles attached are shown in the graphs below (see Pic. 18001f, and Pic. 18001h). Measured thrust indicate a rather weak weight to thrust relation. These results lead to the assumption that "Ice Fountains", with or without nozzles, are not usable as rocket engines at all.

Pic. 18001g: "Ice Fountain" and short nozzle ignited.

Pic. 18001i: "Ice Fountain" and long nozzle ignited.

Conclusion

As the tests indicate thrust of not-meant-to-be-rocket-engines is negligible. On the one hand the propellant used for "Ice Fountains" seems to be not usable as rocket fuel at all. On the other hand, differences in nozzle design indicate major distinctions in thrust produced. Due to missing tools in the OxidanSky propulsion lab, the throat bore of both nozzles ended up wider in diameter, as planned. Thus the possible output thrust force could gain amplitude, by machining the nozzles according to plans.

The hard- and software for measuring the thrust, proved its function. Live experiments done, lead to further improvements in usability and function. Sampling rates achieved by using a HX711 Load Cell Amplifier are about 12 samples/second. For measuring motors with an active thrust not longer than a few seconds and high slopes, the law of Nyquist-Shannon can not be maintained.

Firing up the engines using firing cord resulted in fail starts and nozzle blockages. R&D is encouraged to implement an electronic firing system.

Source Code, OxidanSky Engine Analytica 1.1.0

//************ OxidanSky Engine Analytica 1.1.0 ************
//******** by Tien Huu OxidanSky R&D Dep. Jan. 2018 ********

#include "HX711.h"
// HX711.DOUT	- pin #A1    pin assignment
// HX711.PD_SCK	- pin #A0  pin assignment

float meas = 0;            //measurement variable
float tar = 0;             //gauge offset variable
float gain = 120601 / 5.4; //gain factor for strain gauge
long current_t;            //current time variable

HX711 scale(A1, A0);	     //initializing HX711
	
void setup()
{
  Serial.begin(230400);    //initializing serial
  tar = scale.read_average(20); //capturing average of 20 values
  current_t = millis();         //reading current time in milli seconds
}

void loop()
{
  Serial.print(millis() - current_t); // time from measurement
  Serial.print(";");                  // send delimiter
  current_t = millis();               //reading current time
  meas = (scale.read() - tar)/gain;   //read scale => value in [N]
  Serial.println(meas);               //send value measured
}

Source Code, OxidanSky Engine Analytica 1.1.0