C. Schmierer

Viscosity and Regression Rate of Liquefying Hybrid Rocket Fuels

The combustion behavior of paraffin-based hybrid rocket fuels with gaseous oxygen as an oxidizer has been analyzed in detail. Regression rate tests have been done in a two-dimensional radial microburner at the DLR, German Aerospace Center and at the Space Propulsion Laboratory. Fuel samples have been characterized by viscosity measurements, tensile tests, and a differential scanning calorimeter. Tensile tests showed significant improvement in maximum stress and elongation when polymers in low concentration were added to the paraffin samples. The values of the liquid fuel viscosities differed significantly between the selected fuels. This affected the droplet entrainment process during combustion and the regression rates of the fuels. The entrainment and regression rate increased for the decreasing fuel liquid layer viscosity. An exponential relation has been found between the liquid fuel layer viscosity and the regression rate, which can be used to predict the regression rate of new liquefying fuels by measuring their viscosity.

Evaluation of paraffin-based fuels for hybrid rocket engines

This paper summarizes the investigations on the combustion behavior of paraffin-based hybrid rocket fuels with gaseous oxygen (GOX) as oxidizer. Combined experimental activities have been done at the DLR Institute of Space Propulsion in Lampoldshausen and at the Space Propulsion Laboratory (SPLab) of Politecnico di Milano. Regression rate tests have been done in a 2D radial micro burner at the DLR and at the SPLab. Fuel samples have been characterized by viscosity measurements, tensile tests and differential scanning calorimeter (DSC). Tensile tests shows significant improvement in maximum stress and elongation when polymers in low concentration are added to the paraffin samples. The values of the liquid fuel viscosities differ signifcantly between the fuels. This affects the droplet entrainment process during combustion and also the regression rates of the fuels. Entrainment and regression rate increase for decreasing fuel liquid layer viscosity. An exponential relation has been found between the liquid fuel layer viscosity and the Regression rate, which can be used to predict the regression rate of new liquefying fuels by measuring their viscosity.

Sounding Rocket "HEROS" - A Low-Cost Hybrid Rocket Technology Demonstrator

The inherent safety of hybrid rocket propulsion offers some unique advantages com- pared to solid and liquid propellant rocket engines. This makes it especially attractive for space tourism, Micro-launcher and hands-on experiments in the education of students. On November 8th, 2016 at 10:30 a.m. the hybrid sounding rocket HEROS 3 was launched from the ESRANGE Space Center to an apogee altitude of 32,300m (106,000 ft). This set a new altitude record for European student and amateur rocketry and a world altitude record for hybrid rockets built by students. The 7.5m long rocket was using Nitrous Oxide (N2O) and a Paraffin-based fuel to produce 10,000N of thrust. The dry mass of the rocket was only 75 kg thanks to a carbon fibre structure for the most part. The rocket performed the record breaking flight at perfect weather and visibility conditions, reaching a maximum airspeed of 720 m/s and Mach 2.3. The rocket performed a soft landing with two parachutes and can be reused. Flight data and engine performance data are published and analyzed. The flight data shows excellent stability of the rocket. Engine performance data proves very high efficiency and stable combustion as in the ground tests. The subsystem design and verification before the launch is reported. Engine and flight trajectory simulations show very good agreements with the flight data. Furthermore, the overall project, the rocket design, the subsystems as well as the launch campaign are presented here in detail.