Olga Ozhogina is a Ukrainian space journalist, journalist and photojournalist. She contributed this article to Space.com Expert Voices: Op-Ed & Insights via the press center of Promin Aerospace, a Ukrainian rocket startup.
Ukrainian rocket company Promin Aerospace (opens in a new tab), which is currently developing an autophagic ultralight launcher, has conducted a new series of studies on its unique engine. The startup’s first tests showed the feasibility of the technical concept. With each new experience, engineers improve the design by testing different variations of the engine assembly.
The notion of rocket is based on autophagic, or “self-devouring” technology, which was originally proposed by Promin Aerospace CTO Vitaliy Yemets.
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In an autophagic rocket, the hull would be used as solid rocket fuel, in addition to other propellants carried on board. For this purpose, the shell material must be both strong enough and have sufficient combustibility. During the flight of the rocket, the body is consumed, allowing a reduction in mass when moving and leaving no debris when the flight is over. This advance would allow for more efficient and environmentally friendly launches.
For two months, three experiments were carried out with different variations of the engine and nozzle design, which allowed Promin Aerospace to identify and study the challenges, as well as improve the overall performance of the assembly. As the engine technology is unique, all tests had to be designed by the engineering team from scratch, while detecting and eliminating faults.
Thanks to these first three tests, it was possible to improve the fuel supply system and to test new fuel components, which have proven their safety and efficiency. All necessary parameters were measured and recorded.
The fourth experiment: a fuel system
For the fourth experiment, the engineering team used the same oxidizing agent used in the third experiment, along with a bell-shaped nozzle, to keep the variables consistent in the new test. Additionally, engineers used a polymer fuel rod and a gas-oxygen mixture for a starter. They used multiple temperature probes to monitor temperature in many areas of the engine and pressure gauges in the combustion chamber and air cylinder.
Following previous experiments, the propellant rod was introduced into the gasifier while recording the firing parameters with several sensors. The start-up fuel and fuel assembly supply systems have been shown to operate reliably; no combustion problems were recorded and the starting component of the experiment provided higher pressure compared to previous experiments.
During the start-up fuel supply, a pressure of 4 atmospheres (atm) was recorded in the combustion chamber. Fuel supply pressure remained stable between 9 and 9.5 atm, and cranking fuel cut off at 203 seconds (3 minutes and 23 seconds).
The feed rate measured was 10 millimeters per second (mm/s), demonstrating adequate performance, and the pressure peaked at 12 atm. This experiment remained stable for 252.95 seconds (4 minutes and 12.95 seconds) at a speed of 10 mm/s and 12 atm.
The experiment lasted about 280 seconds (4 minutes and 40 seconds). At 252.95 seconds, a flare came out of the feed path, followed by a snap and the end of the assembly’s motion. No damage was caused to the engine or the mounting beam, and the results of the experiment show that everything worked well, although some minor changes should occur. For the following test, the mounting inlet seal was improved
Overall, the system worked reliably and provided sufficient pressure in the combustion chamber. The combustion of the components in the operating mode provided a higher pressure than the starting fuel. So far, all the experiments have made it possible to further develop an effective and safe concept.
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The fifth experience
For our fifth experiment, the engineering team used a different type of fuel and oxidizer but retained the use of the bell-shaped nozzle. The test proceeded in a manner similar to the previous ones, the starting mixture being fed under a pressure of 4 atm and extinguished at 204 seconds (3 minutes and 24 seconds), the new primary fuel being fed under a pressure of 9 atm .
The pressure in the combustion chamber dropped after the start-up fuel was cut off, but gradually increased to 10 atm, and within 248 seconds (4 minutes and 8 seconds) the engine temperature had reached operational level. At 252 seconds (4 min and 12 seconds), the pressure left the scale and the fuel assembly stopped. After investigation, engineers determined that the pressure increase was caused by a blockage in the nozzle, the gasifier casing having been torn off.
Despite this, the engineers found that the starting fuel assembly chosen worked reliably. The pressure in the combustion chamber was correlated with the feed rate of the working components with a delay in the reaction time.
The sixth experiment: the new fuel rod component
The sixth experiment was conducted with the supplied starting mixture under a pressure of 4 atm and was stopped at 188 seconds (3 minutes and 8 seconds). It used a new primary fuel, which was fed under a pressure of 25 atm. The pressure inside the combustion chamber remained at 8.5 atm until about 300 seconds (5 minutes) when a flare ignited at the fuel assembly feed unit at the bottom of the combustion chamber.
At this time, the combustion chamber began to overheat and the steel turned white. According to sensors and heat charts, it reached a temperature of around 1,830 degrees Fahrenheit (about 1,000 degrees Celsius). The feed rate of this fuel assembly was irregular, with a maximum value of 14 mm/s. The experiment lasted 350 seconds (5 minutes and 50 seconds).
Overall, the experiment was conducted with pressure within limits and without uncontrolled explosions, proving the reliability of this variant of the construction.
“Using the new polymer as the main fuel component was efficient and safe, as there was no critical pressure increase. We will therefore consider this variant. After this test, the inlet seal of the assembly will be further tightened to prevent overheating of the combustion chamber,” Yemets said.
The next experiment will be dedicated to testing the new oxidizer. It is expected to increase combustion efficiency.
After completing the final tests, Promin Aerospace plans to perform the first test launch of its suborbital rocket, followed by its first commercial mission in early 2023. In the future, the company also plans to perform orbital launches .
Promin Aerospace (opens in a new tab) was established by Vitaly Yemets (opens in a new tab) and Micha Rudominsky (opens in a new tab) in 2021. That same year, the company closed its first round of investment and proved the capabilities of autophagic technology, which could reduce launch costs and space debris.
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