Launch of Nexo I

Copenhagen Suborbitals recently launch their Nexo I rocket as they carry on down the path towards a manned space flight.

The rocket launched from the group’s mobile launch platform, Sputnik, in the Baltic Sea, of the island of Bornholm.

Unfortunately, the rocket suffered an anomaly and never reached its performance goals, plummeting nose-first into the sea as seen in the above video. The camera work was not the best so hopefully, another video or even onboard video comes to light soon.

The group has posted an initial thought into what went wrong as shown below,

We have not yet had opportunity to examine data, parts or footage.

A tentative speculation on root cause would be simple LOX overload. In other words a problem withmeasuring the correct amount of LOX in the tank, which we have encountered previously, and worked on solving via several methods. We will look into this.

Too much LOX will result in a too small gas pocket in the tank – which equals too little gas propellant energy and a premature loss of tank pressure in the LOX tank, again resulting in an increasing O/F-ratio mismatch. The engine subsequently extinguished.
The GNC didn’t detect acceleration below minimum, as this detection was removed from the algorithm prior to the mission, based on the fact that the acceleration, through the use of pressure blow-down at relatively low altitude, would be very low before the occurrence of MECO.
The GNC instead used the chamber pressure. This was low at an unusually early time. The GNC treated this as a sensor failure, and instead an estimated pressure, based on a table generated from earlier tests, was used.
Thus the GNC didn’t signal the deployment of the parachute, as it was under the (false) impression that the engine was still operating as expected.

The root cause will come to light as the team continues to go through their data and dissect the rocket.



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