Launching the Nexø I rocket By Copenhagen Suborbitals

Nexø I is our first rocket powered by a liquid bi-propellant engine. It serves as a technology demonstrator in advance of our much bigger Spica rocket that will eventually launch our astronaut into a suborbital trajectory to Space.

This is the short story on how we build, tested and flew our Nexø I rocket.

Nexø I is the first of our rockets that has been fully designed in Solidworks before we started building it. As expected this proved to be a huge advantage during the building period.

Photo by Carsten Olsen
Nexø I engine section. Photo: Thomas Pedersen.
Jacob and Thomas working on the engine compartment. Photo: Thomas Pedersen.

Nexø I started as a jigsaw puzzle of laser cut aluminum pieces based on the Solidworks design. Our dedicated metal wizards quickly transformed it into a slender and beautiful rocket.

At 205 kg and standing 5.60 meter tall it is the largest amateur, liquid bi-prop rocket ever build in Northern Europe.

Nexø I is powered by our very own 5000 N engine, the BPM5, running on liquid oxygen and ethanol. The BPM5 engine has been extensively tested in more than 30 static tests. During nominal operation it consumes about 2.5 kg of propellant per second.

Nexø I uses a set of four graphite jet vanes for thrust vectoring and control. They are mounted on a common and easily removable flange.

As Nexø I was completed it went on to several critical system tests.

Among the most important tests is the cryogenic loading and cold soak test using liquid nitrogen as a stand in for liquid oxygen.

Sea Acceptance Test June 26th 2016.

After a succesful Sea Acceptance Test on board launch platform Sputnik Nexø I was approved ready for flight in late June 2016.

In order to launch the rocket the entire team went to Spaceport Nexø on the Danish island of Bornholm. All of our launces take place 25 km out to sea west of Bornholm.
Sputnik and Vostok in Nexø harbor two days before launch.

The day before launch Nexø I was fully assembled and mounted in vertical on the launch rail on Sputnik, our mobile launch platform.

Final electronics checkout by Guidance Officer Flemming Nyboe on the evening before launch.

Nexø I is equipped with both a ballute and a parachute to slow descent before splashdown in the ocean.

Photo by Mads Stenfatt
Photo by Mads Stenfatt
Photo By Mads Stenfatt

Launch day, 6 AM. Sputnik sets out and heads for ESD139, the military shooting area were all Copenhagen Suborbitals rockets are launched from.

Photo by Carsten Olsen

Upon arrival at the launch site launch preparations began. On Sputnik preparations were led by PAD leader Jacob.

Launch preparations progressing on Sputnik.

Launch preparations are coordinated from the bridge of Mission Control ship Vostok.

Cryogenic liquid oxygen is loaded from the dewar on Sputnik to one of the propellant tanks on Nexø I.

Late in the afternoon alle launch preparations had been completed and Nexø I was ready to fly!

July 23rd 4:38 PM, LIFT OFF of the Nexø I rocket.

Nexø I on a beautiful ascent from launch platform Sputnik.

Due to a faulty valve Nexø I only flew to an altitude of 1514. Such a low apogee was not expected and in turn it also meant that parachute was never commanded to deploy. Hence, Nexø I nose dived from apogee and impacted the ocean at 530 km/h.

Recovery diver Per salvaging the main part of the rocket.

Nexø I being dragged onto the stern of mission Control ship Vostok.

Considering that it impacted the ocean at 530 km/h the nose cone is in a reasonably good shape.

After recovery of the rocket the fleet headed back for Bornholm.

Tail section and engine compartment of Nexø I showing moderate damage after high velocity splashdown.

Sputnik and Vostok returned to harbor after a long day with a tired but very satisfied crew.

Naturally, the launch was also filmed, watch it right here!

Despite the meager peak altitude (apogee) the guidance system performed flawlessly. Data from the Guidance and Navigation Computer is visualized in the video below.

For more information on the Nexø I flight and the only amateur, manned space flight program in the world visit our site at

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Copenhagen Suborbitals

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