Abstract

The student team Hybrid Engine Development (HyEnD) of the University of Stuttgart is taking part with the Institute of Space Systems (IRS) in the DLR educational program STERN (Studentische Experimentalraketen). This program supports students at German universities to design, build, and launch an experimental rocket within a 3-year project time frame. HyEnD is developing a hybrid rocket called HEROS (Hybrid Experimental Rocket Stuttgart) with a design thrust of 10 kN, a total impulse of over 100 kN·s, and an expected liftoff weight up to 175 kg. HEROS is planned to be launched in October 2015 from Esrange in Sweden to an expected flight altitude of 40 to 50 km. The current altitude record for amateur rockets in Europe is at approximately 21 km. The propulsion system of HEROS is called HyRES (Hybrid Rocket Engine Stuttgart) and uses a paraffin-based solid fuel and nitrous oxide (N2O) as a liquid oxidizer. The development and the test campaign of HyRES is described in detail. The main goals of the test campaign are to achieve a combustion efficiency higher than 90% and provide stable operation with low combustion chamber pressure fluctuations. The successful design and testing of the HyRES engine was enabled by the evaluation and characterization of a small-scale demonstrator engine. The 500-newton hybrid rocket engine, called MIRAS (MIcro RAkete Stuttgart), has also been developed in the course of the STERN project as a technology demonstrator. During this test campaign, a ballistic characterization of paraffin-based hybrid rocket fuels with different additives in combination with N2O and a performance evaluation were carried out. A wide range of operating conditions, fuel compositions, injector geometries, and engine configurations were evaluated with this engine. Effects of different injector geometries and postcombustion chamber designs on the engine performance were analyzed. Additionally, the appearance of combustion instabilities under certain conditions, their effects, and possible mitigation techniques were also investigated. Concluding, the development and construction of an advanced, lightweight hybrid sounding rocket for the given requirements and budget within the DLR STERN program are described herein. The most important parts include a high thrust hybrid rocket engine, the development of a light weight oxidizer tank, pyrotechnical valves, carbon fiber rocket structure, recovery systems, and onboard electronics.

Highlights

  • TO HyEnDHybrid Engine Development is a student based project located at the University of Stuttgart, since its foundation in 2006

  • Literature data of hydroxyl-terminated polybutadien (HTPB), high-density polyethylene (HDPE), and another para©n-based fuel in combination with dierent oxidizers are shown in order to compare the results

  • It is possible to note that all the fuel formulations tested during the test campaign in combination with N2O show a regression rate that is higher than that of polymeric fuels in combination with liquid oxygen (LOx)

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Summary

INTRODUCTION

Hybrid Engine Development is a student based project located at the University of Stuttgart, since its foundation in 2006. From 2006 to 2012, HyEnD focused on developing its own hybrid rocket engines in dierent scales from 250- to 2000newton thrust [1]. In 2012, the project Studentische Experimentalraketen (student experimental rockets, STERN, [2]) was initiated by the German Aerospace Center (DLR) and HyEnD applied for it with the Institute of Space Systems. A smaller scale was applied for MIRAS, which reaches altitudes of around 2 km with a 500-newton engine This allows to test the rocket on German launch sites. Both MIRAS and HEROS use a hybrid rocket engine with a para©n-based fuel and liquid N2O as oxidizer. During the development of the MIRAS demonstrator, a lot of improvements were made to the design of dierent subsystems which were applied to the HEROS rocket design until the end of the 2nd year. A time line is given in Table 1, italic text was used for future events

STATE-OF-THE-ART OF HYBRID ROCKET PROPULSION
HEROS ROCKET SYSTEM OVERVIEW
HyRES hybrid rocket engine
Oxidizer tank
Propulsion system assembly
Recovery and electronics
Onboard electronics
HEROS PERFORMANCE AND FLIGHT SIMULATIONS
ROCKET ENGINE TEST BENCH AND DATA ANALYSIS
Regression rate and performance analysis
Frequency analysis
Combustion Instability
MIRAS SMALL-SCALE DEMONSTRATOR TESTS
Propellant Characteristics
Regression rate analysis
Engine Performance Analysis
Combustion stability analysis
HyRES ROCKET ENGINE TEST RESULTS
Design conditions
CONCLUDING REMARKS
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