The HEROS Launches

HEROS 3: new altitude world record for hybrid student rockets

On November 8th, 2016 at 10:30 a.m. our 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.

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HEROS 3 Record Flight Video
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HEROS 3 launched under perfect weather and visibility conditions, reaching a maximum velocity of 720 m/s or Mach 2.3. It performed a soft landing with two parachutes and can be reused. Flight data and engine performance data can be viewed below. The flight data shows excellent stability of the rocket. Engine performance data proves very high efficiency and stable combustion as in the ground tests. We would like to thank the DLR for their continous support throughout the 3 STERN launch campaigns.

Interactive Subsystem Breakdown

Subsystems

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Electronics & Telemetry

The telemetry down-link to the ground station was realized with a TeleMega flight computer. It measures the rocket's acceleration and rate of rotation around three axes and records the ambient pressure. In addition, the GPS position is continously transmitted to the ground station.

However, the GPS Signal is restricted on the velocity of the rocket due to the COCOM limit. This requires the usage of additional sensors and a Kalman filter for evaluation of the data from the Inertial Measurement Unit (IMU) used to receive the rockets position.

Electronic System shortly before integration
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For redundancy, two independent branches were used. Each contained one TeleMega sending the positional data to the ground station using one of the two Yagi antennas. Another very important task of the flight computers is the ejection of the drogue parachute at the apogee and the main parachute near the ground.

The electronic section also contained two on-board video cameras. A Power Control and Distribution Unit (PCDU) was designed for controlling the flight computer, as well as the on-board cameras and the payload prior to the launch from the GSE. During the flight it is providing constant output voltage, despite the decreasing input voltage from the lithium polymer batteries.

Recovery System

For HEROS, a dual stage recovery systems was developed in order to decelerate the entire vehicle to a suitable landing speed. The first parachute, also called pilot, opens at the apogee and decelerates the rocket to a velocity suitable for the main parachute. If the main chute were to be deployed without prior decelartion caused by the drogue chute, the resulting forces would rip apart the rocket due to it travelling at supersonic speeds. Both parachutes were ejected sideways.

Last adjustments to the main system
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Oxidizer Tank

The largest single component of the rocket is the oxidizer tank. It has a length of 4m and can contain 130l, or about 80kg, of liquid oxidizer at a constant pressure of 60bar. This lightweight tank is made out of a welded aluminum liner, and reinforced with CFRP.

First layer of CFRP applied
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HyRES Engine

HyRES uses paraffin as solid fuel grain and nitrous oxide as self-pressurized oxidizer. These propellants allow for a high combustion efficiency and are relatively safe to handle. Thanks to the knowledge gained by the subscaled version used in MIRAS, which produced 0.5kN of thrust, we were able to scale HyRES up to a thrust of 10kN for HEROS.

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HyRES on its testbed in Lampoldshausen
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Performance Data:

Nominal Thrust: 10000N
Nominal Burn Time: 20s
Chamber Pressure: 30-35bar
Combustion Efficiency: >98%
Lenght: 1300mm
Diameter: 175mm
Wet Madffffdfddddffffffss: 640g
Record Flight Trajectory & Sensor Data

The actual and the simulated flight trajectory are compared below. During the flight the rockets telemetry system gathered positional GPS data, with exception of the time frame between T+11s and T+41s. The COCOM Limit of the GPS modules was exceeded during this period. The data of all GPS modules matches our simulated flight path almost perfectly. The measured apogee heights are within 15m of each other. The rocket could be located and was recovered within two hours, thanks to the GPS log and maintained telemetry link throughout the entire flight.


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Record Flight Trajectory of HEROS 3
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Data of the record flight:

Maximum Altitude: 32.3km
Maximum Acceleration: 7g
Maximum Velocity: 720 m/s; Mach 2.3
Total Flight Duration: 120s
Dry Mass: 75kg
Wet Mass: 180kg
Wet Maddgffggggggfffss: 640g

HEROS 2

HEROS 2 was launched from the Mobile Rocket Launcher (MRL) in ESRANGE at 12:00 p.m. on October 31st, 2016. The countdown went smoothly; filling of the tank with N2O was completed rapidly and the heating system ensured an appropriate temperature of the nitrous oxide, despite harsh weather conditions. The ground and on-board electronics worked flawlessly throughout the countdown. The ground camera system recorded lots of fantastic video footage of the lift-off and ascent. It can be seen that the rocket plume is very clear and free of soot, remarking the high efficiency of the engine.

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HEROS 2 Launch
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However, an electronic interference right at T-0 caused a failure of the on-board electronics and telemetry system. Without a telemetry signal it was not possible to get any positional data during and after the flight of HEROS 2. The recovery system was most likely affected by this failure, as its triggers relied on sensoric data of the telemetry system. A helicopter team searched at the nominal impact point, unfortunately without success. The video material and sound recordings were analyzed and all evidence suggests that the hybrid rocket engine HyRES worked nominally during the whole ascent of the rocket. In the following days the failure was investigated in detail and it was shown that an electronic interference with the main ignition impulse induced a voltage in the connecting line between the ground support computer and the rockets on-board electronics. This voltage was high enough to generate a shut-off signal in the command line. Several successfully tested improvements were made to prevent this malfunction from happening on the third HEROS flight.


HEROS 1

On September 1st, 2012, the DLR's STERN program started for the University of Stuttgart. Over the course of three years, students built a sounding rocket capable of reaching an altitude of 20km. HyEnD's competition entry HEROS (Hybrid Experimental ROcket Stuttgart) uses a hybrid engine called HyRES, also developed by HyEnD as part of the STERN program. HyRES uses paraffin as solid fuel grain and nitrous oxide as liquide oxidizer. This combination of propellants can be handled with reasonable safety and relative ease, thus making it a perfect candidate for a student team. Over the course of the project we built two demonstrators to test launch operations as well as a subscale version of the engine as proof of concept. The engines were tested at DLR's site in Lampoldshausen, on a test stand developed by former members of HyEnD. In October 2015, HEROS was launched from Kiruna, Sweden, a launch site used for many European sounding rockets.

Foundations

HEROS relied on HyEnD’s experience with hybrid rocket engines, dating back to its foundation in 2006 as part of a youth project by the Deutsche Gesellschaft für Luft- und Raumfahrt (DGLR) at University of Stuttgart. The results of their work were published and presented at several conferences, such as the Space Propulsion 2012 conference in Bordeaux and the Deutscher Luft- und Raumfahrtkongress (German Aerospace Congress) in 2009 and 2012. Since 2011, HyEnD’s engines are test fired at the DLR Lampoldshausen.

Development

As part of the program, all systems used by the rocket and the launch equipment had to be developed by HyEnD themselves. This includes the engine, structure, recovery system, electronics, aerodynamic and flight simulations, the refuelling system and much more. Beside the technical challenges, it also required an efficient documentation of progress, logistics and expenditures. Moreover, HEROS had to pass 5 review exams by the DLR Lampoldshausen and their Mobile Rocket Base (MORABA), during which technical and programmatical progress was presented and checked for risks and problems by internal experts. The skills and experience aquired during the STERN programme will benefit all participants throughout their future career in the aerospace industry.

Progress

After more than one year in development, HEROS passed the Preliminary Design Review (PDR) on December 4th 2013. The STERN managers mandated only minor corrections. In the following year, until November 2014, the design was finalised and passed the Critical Design Review (CDR). At this point, we were projecting a launch in 2015 with a maximum altitude of 20km. On November 14th, the proprietary engine HyRES was successfully tested for the first time, burning for almost 10s. The Integration Progress Review in May 2015 confirmed the successful interaction of the various components and subsystems. On September 2nd, the Rocket Acceptance Review was held at the DLR Lampoldshausen. The reviewing parties, employees of DLR MORABA and DLR Lampoldshausen, were presented the current project status and shown the integration of the rocket. By passing this review, HEROS received launch clearance for October in Kiruna.

Launch

On October 16th, our launch campaign started at the Esrange launch site in northern Sweden. HEROS was equipped with HyRES, now achieving a thrust of more than 10kN. After complete integration of the rocket, it passed the final Flight Readiness Review on October 21st and was cleared for launch on the following day. Shortly after the launch on October 22nd the rocket was damaged, greatly reducing its maximum altitude. Fortunately, telemetry and recovery worked as planned and allowed the rocket to be recovered shortly thereafter. Further examination pointed to a structural failure caused by combustion instabilities as the root cause. The experience gained from the launch campaign laid the foundation for further development of HEROS’s successors, HEROS II and III.

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HEROS 1 Launch
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The sounding rocket HEROS is shown in the following figure with its main dimensions, components and subsystems. Three HEROS launches werde made from Kiruna, in October 2015 and 2016. With the launch of HEROS 3 to a record altitude of 32.3 km, it was shown that this is the most powerful student hybrid rocket up to date.

HEROS draw