First Results of the N₂ORTH Post Flight Analysis

Since our N2ORTH Launch Campaign in April, some time has passed, and the team took a well-deserved break. Nevertheless, we had our Post Flight Analysis Review in Bonn at the beginning of June, and we want to share some of the results with you.

Analysis of the 1st Launch:

The first launch took place on Tuesday, April 18. Originally scheduled for Monday, the launch was postponed to Tuesday in order to double check the avionics and launcher interfaces.

The countdown began at 06:15 and went very smoothly. There was a short pause to complete the transfer of nitrous oxide from the intermediate tanks to the rocket tank. This delay was caused by the fact that the boxing of the rocket itself was less insulated than expected. To compensate, the nitrous oxide in the intermediate tanks was heated to a higher temperature. The final oxidizer mass in the rocket was 95 kg and the launch elevation was set at 81.4°.

The launch at 11:05 local time went smoothly without any problems. The rocket reached a maximum speed of Mach 3 / 3,150 km/h after about 20 seconds. The engine provided thrust for about 75 seconds, with a transition to the gas phase after 18 seconds. This data was obtained from the IMU as the lower data acquisition system suffered a cable disconnect at liftoff. This means there is no tank and chamber pressure data for the flight. However, the upper data acquisition system continued to operate and a maximum tip temperature of 240°C was reached.

Apogee was reached at an altitude of 64.4 km after 132 s. This was only a 0.2% difference to the predicted apogee by the simulation.  However, the drogue parachute deployment was triggered 9 s earlier by the Telemegas. The drogue deployed without problems at Mach 0.9-1. However, reviewing the onboard video, it can be seen that the main parachute’s three-ring release system was already activated. Up to this point, the main chute was still held in place by two straps in the recovery section, as the drag generated by the drogue was not sufficient to pull it out. However, during the descent the drag increased until the main parachute was released at an altitude of 36 km and a speed of Mach 1.8. Since the main parachute is not designed for these conditions, it was immediately detached from the rocket together with the drogue parachute.

The rocket then went into a tumble mode with a high spin rate, which helped to keep the descent rate relatively low. The avionics were able to continue transmitting the position up to an altitude of 1.3 km. At this point, the line of sight prevented further data transmission. Thanks to the precise position (downrange: 48 km), the rocket was easily located and recovered by helicopter only 3 hours after launch.

A review of the onboard data showed that the rocket landed at a vertical speed of 36 m/s. The avionics were internally damaged due to the non-nominal recovery sequence and landing speed, but all data could be recovered. Also, the recovery section and one of the fins suffered some structural damage.

The reason for the non-nominal recovery sequence was found during investigations on the following day and was traced to a misconfiguration in the Telemega software. As the cause was quickly found, HyEnD was able to ensure that the second launch would not have the same problem and continued preparations for the second launch.

Analysis of the 2nd Launch:

Having demonstrated with the first launch that our simulations are capable of predicting the rocket’s trajectory with high accuracy, and having quickly identified the cause of the non-nominal recovery sequence, the team decided to continue preparations for the launch of the second rocket.

Unlike the first rocket, the second N2ORTH rocket has a linerless Type V pressure vessel with an ETFE coating on the inside to ensure compatibility with nitrous oxide. The elimination of the aluminum liner reduces the dry mass of the rocket by 7.7 kg (10%). In addition, the Esrange safety and operations team approved an increase in the launch rail elevation. It was decided to target an oxidizer mass of 105 kg for the second rocket, which would result in a >90% chance of reaching an altitude of more than 100 km and thus the Kármán line. A higher oxidizer mass would have been technically possible, but would have resulted in the rocket landing outside the designated landing zone.

The launch attempt took place on Monday, April 24. The Styrofoam box of the rocket was improved in order that the launch team could easily control the temperature and keep it within the desired range. However, during the oxidizer loading process, the solenoid valve in the rocket could not be activated. It was decided to continue the countdown with an adjusted oxidizer loading procedure. With the modified procedure, the target oxidizer mass, temperature, and pressure were achieved with another short countdown pause.  However, the nitrogen content of the oxidizer tank filling was higher than originally simulated.

At 14:10 local time, the rocket launched with an elevation of 82.2°. Unfortunately, the rocket encountered an anomaly that caused it to break up 22.4 seconds after liftoff. At this point, the rocket was at an altitude of 11 km, traveling at Mach 3, and still in sight of the team members and cameras on the radar hill. Due to the anomaly, the rocket disintegrated into several pieces. The avionics were able to send data to the ground station until this point. The timing of the anomaly is interesting because both the transition from liquid to gaseous nitrous oxide and the maximum dynamic pressure occur at this time.

One of the cameras mounted on a theodolite was able to follow the oxidizer tank until it hit the ground. The video and azimuth information allowed the Esrange team to retrieve the tank by snowmobile the next day. The tank and its attached fluid system components were undamaged except for the broken interfaces at both ends. Fortunately, the Rocket Status Measurement System (RSMS) SD card attached to the oxidizer tank was still intact, giving the team access to high frequency (14 kS/s) chamber pressure data.

A review of the cameras on the launcher revealed that the oxidizer release valve was opened at launch, resulting in a slow (<100 g/s) release of liquid nitrous oxide to the side of the rocket. Inspection of the valve (which was still attached to the recovered oxidizer tank) revealed that the pyro charge within the valve was not activated, indicating that the opening was triggered by a shock load at launch. The influence of the vented nitrous oxide on the rockets aerodynamics is still under investigation.

Chamber pressure data shows no indication of engine malfunction until a loss of chamber pressure occurs at 22.4 s, which is associated with the breakup of the rocket. The IMU data shows a continuous increase in lateral acceleration from 0 to 2.5 g beginning at 20 s, with a rapid increase to more than 15 g at break-up. Since the later acceleration begins to increase to a point where the combustion chamber pressure is nominal, a failure of the propulsion system is unlikely. The IMU data also shows a low spin rate of less than 0.52 Hz and no evidence of pitch-roll coupling.

Based on the available data, the final cause of the failure cannot be clearly identified. However, the possibility remains that other components of the rocket will be found by the SSC team in the future. At this point, it can be concluded that the breakup of the rocket was the result of either a structural failure during launch, an unexpected aerodynamic load on the rocket, or a combination of both effects.

Nevertheless, HyEnD is very proud of what has been achieved with the launch campaign – setting new records and pushing the limits of (student) hybrid propulsion. The two weeks in Sweden were an amazing time – thanks to a great team, good logistics and organization as well as the cooperation with DLR and SSC.

Onboard Videos of Launch 1 now available!

We are pleased to share with you the unedited on-board footage of the first N2ORTH rocket launch! The first video shows the footage recorded by a RunCam Split 4 in 2.7K at 60fps located at the tail of the rocket. The second video shows the footage recorded by 4 GoPro action cameras located in the avionics section.

Watch the Record Flight Video!

64 km altitude – A new world record for student-built hybrid rockets and for European student-built rockets in general! We are very happy and proud that we have almost doubled the existing record that we set with our HEROS 3 rocket in 2016. This achievement is the result of almost four years of hard work and dedication by our team. With N2ORTH, HyEnD has shown what students can achieve when they work together towards an ambitious goal. We are grateful for the support we received along the way – especially the funding from the DLR STERN program. Without it, this project would not have been possible. We hope you enjoy the videos of the record flight as much as we do. Stay tuned for more footage, including the full on-board videos, in the coming weeks and months.

Day 14: Launch Attempt 2

Yesterday, the 24th of April at 14:10 CEST, we had a successful launch of our second N₂ORTH rocket from Esrange. Unfortunately, the rocket encountered an anomaly which led to a break-up after 20 seconds. Thanks to the telemetry data and the tracking of the rocket, we have a good idea where the rocket components are located, but a recovery has not yet been possible. In consultation with the SSC, we will continue to look for additional ways to complete the recovery to add data to our post-flight analysis.

Despite this unfortunate event, the campaign has been a great success. Thanks to DLR’s STERN program, we were able to design and build two rockets and their associated systems. We also successfully launched both N2ORTH rockets from Esrange, setting a new student hybrid rocket record and doubling the altitude. We have built such a powerful rocket that we have pushed the limits of the student program, and we are proud of it. Now it is time to pack up and organize the transport back to Stuttgart. In the future we will analyze the flights to get a deeper understanding of the performance of the rockets.

Thanks to all the support and help especially from DLR and SSC.

Launch Attempt of 2nd Rocket on Monday!

We are proud to announce that we are planning to launch our second N₂ORTH rocket tomorrow, Monday! With this launch, we hope to reach an altitude of more than 100 km and thus the frontier of space.

What is the difference between the two launches?

Since N₂ORTH is a new launch vehicle, we need to make sure it performs as expected. That is why we limited the oxidizer mass and launcher elevation for the first launch. Since the first launch showed a high agreement between the simulated and real trajectory, we are now allowed to increase the oxidizer mass and launcher elevation for the second launch attempt.

Are both rockets identical?

Both N₂ORTH rockets feature the same component design with one exception: The first N₂ORTH rocket features an oxidizer tank with an aluminum liner. The oxidizer tank of the second N₂ORTH rocket is a liner-less Type V pressure vessel with a ETFE coating on the inside to ensure compatibility with nitrous oxide. This reduces the rocket mass by 7.7 kg. Originally, it was the plan to have two rockets with liner-less tanks, but that was not possible due to delays in the supply chain.

1st N₂ORTH Rocket2nd N₂ORTH Rocket
Dry Mass76.9 kg69.2 kg
Fuel Mass25.8 kg25.8 kg
Oxidizer Mass95 kg≈ 105 kg (TBD)
Launcher Elevation81.4°≈ 83° (TBD)

How can I watch the launch?

The launch will take place no earlier than 12:00 CEST / UTC+2. The Swedish Space Corporation SSC will provide a livestream on their YouTube channel. We will keep you updated on the launch via our website and social media in the following days.

Day 12: Roll-Out of the 2nd N₂ORTH Rocket

After the assembly of the recovery section, parachutes and avionics today we have finalized the integration of the second N2ORTH rocket. Compared to the first N2ORTH rocket launched last week, the second rocket features a lightweight, liner-less Type V oxidizer tank. This results in a dry mass of only 69.2 kg. The rocket was mounted on the launcher, and we started to assemble the styrofoam boxing of the rocket to protect it from the low environmental temperatures. We are looking forward to our next launch attempt, which will hopefully be on Monday.  

Day 11: Preparing the 2nd Rocket

After a more than successful launch and a day off, we continue with the preparations for the 2nd N2ORTH launch. Yesterday we started analyzing the first launch and investigating the problem in the recovery sequence. The on-board video was analyzed frame by frame and we took a first look at the on-board avionics data. At the same time, we prepared the launcher for the next mission and started assembling the next rocket.

Today, we continued with the assembly of the second rocket. The only things remaining are the recovery and avionics. If we finish the assembly by tomorrow, we can proceed with the second roll out. We currently plan to start the refueling of the intermediate tanks on Sunday and target Monday for the next launch attempt if the weather conditions will be suitable.

Mission Success: New Record for Student-built Hybrids

On Tuesday 18th April 2023 at 11:05 local time, HyEnD successfully launched its first N2ORTH rocket from the European Space and Sounding Rocket Range ESRANGE in Sweden.

The countdown started at 06:15 and went very smoothly. There was a short hold to finish filling the nitrous oxide from the intermediate tanks to the rocket tank, but otherwise there were no delays. With a final oxidizer mass of 95 kg and a launch elevation of 81°, the rocket reached an altitude of more than 64 km after about 2 minutes. This almost doubled the previous altitude record for student-built hybrids. The altitude was measured by GPS and the data will be released in the coming days and weeks.

The drogue parachute was successfully deployed and inflated shortly after reaching apogee. However, there were some issues with the recovery sequence that need to be investigated. This resulted in an increased landing speed and some damage to structural components, but the team was able to recover the entire rocket by helicopter.

The team is currently analyzing the data and preparing for the launch of the second N2ORTH rocket early next week. Depending on the weather situation and the results of the investigation, the oxidizer load and launcher elevation will be increased to reach an even higher altitude.

HyEnD would like to take this opportunity to thank the managers and reviewers of the DLR STERN programme as well as the launch and operations crew at ESRANGE. Their support is greatly appreciated, and we are very happy to be working together.

Day 7: Ready for Launch!

We are happy to announce that today we have passed the test countdown, the flight readiness review and finalized the fueling of the intermediate tanks. This means that we are ready for our first launch attempt for tomorrow. The weather is also looking very good. The countdown is scheduled to start at 6:15am (UTC+2), which means that the launch attempt will be at 10:45am (UTC+2) without any additional holds. If you want to follow the launch, you can watch a livestream on the Swedish Space Corporation’s YouTube channel:

We will also post a link to the livestream as soon as it is available. Stay tuned for more!