Happy rocket-versary: One year ago, we launched Stratos II+!

Exactly one year ago, on the 16th October 2015 at 16:32:48 CEST Stratos II+ left the launch tower aiming to break the European student altitude record. After a flight time of 76 seconds the rocket reached an apogee of 21,457 meters, an altitude almost twice as high as the record breaking Stratos I rocket. After 6 years of development time, lots of ups and downs, including the attempted launch campaign in 2014, we want to take the time to show some more pictures and impressions from the launch campaign itself and we also want to talk about the progress within DARE since this milestone.

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Figure 1: Stratos II+ at apogee

On the 17th of March 2009, project Stratos reached its first milestone by launching the Stratos I rocket. Stratos I reached an altitude of 12.3km, which at the time was a new European altitude record for student rockets. It was a 2 stage rocket consisting of a booster and a sustainer stage. Solid rocket motors were used for both stages propelling the rocket to three times the speed of sound. Unfortunately, issues with the pyrotechnic charge prevented separation of the nosecone section, ultimately resulting in no deployment of the recovery system. Due to the thick snow coverage during launch, the remains of the rocket could not be located. Therefore, the team returned to the launch site six months later to attempt another search. This time the search was successful and the team brought the remains of Stratos I back to its birthplace in Delft.

After the record breaking launch of the Stratos I rocket, DARE started working towards its next milestone project: Stratos II. After five years of hard work an attempt to launch the Stratos II rocket was made in 2014. Unfortunately, the rocket did not lift off. The launch was delayed due to issues with the FTS system. After those issues were resolved, the final disassembly and reassembly of the rocket caused damage on a crucial seal. The leaking Nitrous oxide was freezing up the coupler section, preventing any actuation of the main valve.

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Figure 2: Stratos II ignition phase in 2014

After the misfire of Stratos II, the team decided to analyze and fix all the issues that occurred during the campaign. A new updated rocket: Stratos II+, was designed, aiming to launch within a year. One of the most critical periods of this year was the launch campaign at INTA CEDEA itself, which started on October 3rd 2015.

The launch campaign can be split into four main phases, the preparation phase, the test phase, the launch and finally the post-launch activities. The first phase included assembling the launch tower and arranging all other workstations such as the hangar, the offices and the electronics lab.

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Figure 3: Setting up the launch tower

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Figure 4: Leak testing the Tank with N2O

Afterwards final systems tests were performed. The subsystems tested included the tank, the FTS system, the electronics and the decoupling system. Furthermore, the igniter was tested. These tests were mainly done to see if the transport did not cause any damage and to test last minute changes.

After all the tests were completed with success, we got the go-ahead decision for launch on October the 15th. Unfortunately, the first launch attempt failed due to the igniter valve not opening.

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Figure 5: Removal of the securing tie raps on the clamp-band

The team went through an investigation during the night and figured out the root cause of this error. From the video material it became obvious that the ignition valve did not open during the ignition phase. The valve itself was powered from the ground through the umbilical cable, which was found to be the main root of the issue. The voltage drop across this cable was too large, so the valve did open at 58 bar, but did not receive enough power to open at 60 bar. Within five hours the system was updated to provide the ignition valve with enough power, meaning the rocket was ready for the next launch window on October 16th 2015. At 16:33 CEST the engine of the Stratos II+ rocket roared to life, propelling the rocket to a record breaking altitude of 21,457 meters. After reaching apogee the rocket deployed it’s parachute to prepare for the descend back to Earth, as such the Capsule landed safely in the Ocean 11 minutes after lift-off.

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Figure 6: Stratos II+ leaving the launch tower.

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Figure 7: Stratos II+ Capsule in the Atlantic Ocean

So what has happened in the time between the launch and now? After the launch of Stratos II+, the majority of members who spent the last years designing and testing Stratos II and Stratos II+ rockets left the team to finish their studies. Slowly people started to put up new projects, namely Aether and Stratos III. The latest update on Project Aether was presented in one of the previous posts and further posts about the different subsystems will follow soon. Next to that, the advanced control team had 2 successful flights of the V7S rocket using canards to stabilize the roll of the rocket. Also Stratos III began to start up, beginning with the data analysis of the Stratos II+ flight. This resulted in changes to the simulation, which were presented in an earlier blogpost. Furthermore, it is now clear that Stratos II+ experienced roll pitch coupling, which was most likely induced by some engine anomaly in the last few seconds of the flight.

Besides that, a team of currently 8 members is working full time on a concept for the new rocket. The goal is to launch a rocket in the summer of 2017, aiming to set a new altitude record. This is a new step DARE is taking, as never before this number of members sacrificed their study progress to design, test and launch a rocket. It remains to be seen what kind of rocket can be designed in such a limited time-frame.

Multiple companies sponsored us in the past, of which the majority agreed to continue the support. Also new companies have decided to start contributing to help us reaching space. We would like to thank all those companies for their support.

Today we will celebrate the 1st anniversary of the Stratos II+ launch in a small circle. We are proud of what we achieved and we are looking forward to the two future projects, Aether and Stratos III. We wish all competitors good luck in their projects!

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Figure 8: Stratos II+ signed by all participants