Nexø I was launched Saturday 23rd of July 2016. While we are still processing flight data you can read all about the rocket on this page. Come back soon for more information on the flight itself.
The Nexø I and Nexø II rockets will serve to demonstrate several key technologies on our roadmap towards the much larger Spica rocket. Technologically the Nexø rockets are very similar to the Spica rocket, thus if we can fly Nexø we have the necesarry technology in place to fly Spica.
Nexø I is the first liquid bi-propellant rocket launched by CS. So far all rockets we have launched have been propelled by hybrid rocket engines running on either polyurethane and liquid oxygen or on polyurethane and liquid nitrous oxide. Nexø I is propelled by our own custom build BPM5 engine. You can read all the details over on the BPM5 engine page.
Nexø I is currently expected to launch in July 2016, keep up to date on the launch date and launch coverage on the Nexø I mission page.
Nexø I design
The Nexø I rocket is 300 mm in diameter, 5.6 meter tall and have a Gross Lift Off Weight (GLOW) of 205 kg. The propellant tanks and the main structure are made in aluminium to keep it as light as possible. The nose cone and parachute bucket are made in carbon fiber to reduce weight even further.
Nexø I is actively guided by our own custom build Guidance and Navigation Computer (GNC). A set of four jet vanes are used as the Thrust Vector Control system (TVC) commanded by the GNC. A similar system was succesfully used on the Sapphire launch in 2013.
Jet vane section
The graphite jet vanes and their servos are mounted on a flange which is fitted on the lower engine compartment flange. Thus the jet vane assemlby is a separate unit which can be mounted and unmounted when needed.
Each jet vane sit in a frame of stainless steel to prevent transfer of heat to the servo. Behind it is a 1.5 mm thick, rounded stainless plate shielding against radiant heat. On the other side of this there is a large cog in aluminum, this is engaged in the smaller cog which is connected to the servo. We use Futaba BLS172SV, with a torque of 37 kg-cm and a weight of 74 grams, it is one of the strongest torque / weight ratio we could find in this scale. The stainless house of the jet vane sits on an arm which in turn sits in two ball bearings. The bearings sit in a housing in which the servo is mounted.
Nexø I is propelled by our own BPM5 engine which has been modified slightly to fit within the Nexø airframe. Most noticably the LOX dome has been weight-optimized, this saves about 1 kg.
At the bottom of the engine compartment, sitting in between the jet vanes, are four modified quick couplings. These are inlets for filling LOX, helium inlets for tank pressurization and inlet for nitrogen purge of the engine. Many pipe joints are made with Tri-clamp fittings for easy assembly and servicing.
The LOX dome is mounted on four brackets that are mounted directly on the structural part of the airframe. The brackets are fitted with adjustment screws that allows accurate adjustment and alignment of the engine.
The main valves are placed above the engine. They are driven by two MAC servos from JVL, the exact same type as we use on the test stand for static engine tests.
The LOX and fuel tanks are completely identical. They are made form 4 mm aluminium, the top and bottom domes are however 5 mm. Inside sits an anti-vortex baffle which prevents the formation of a vortex which can pull down gas when the last liquid runs out. The tank terminates with a 2″ spigot on which is welded a Tri-clamp fitting. The flanges are made with pop-nuts so the tanks can be mounted several times without destroying the thread.
At the top of each tank is a combined sensor and valve mount unit. It serves several purposes. At the far left of the picture sits a solenoid valve which we can use to ventilate the tank. It is also part of the pressure relief system of the tank. The valve is automatically activated at a predefined pressure. Tucked behind this sits a burst disc. It is a 0.3 mm thick aluminum plate which is sandwiched between two flanges. The thin plate bursts at 27 bar and is the ultimate safety feature agains generating excess pressure in the tank. Pointing out to the right is the connection to the gas system, it is through here that we pressurize with helium. Sitting on top is two pressure sensors. Finally, in the center of it all is a thermocouple which measures the temperature in the gas phase in the tank.
The section comprises a total of four electronics boxes. One for the Guidance and navigation computer (GNC), which job it is to control the rocket. One for a radio unit to both send and receive data. One for a GPS box which contains two different GPS devices and finally one for a video transmitter.
On top of the avionics section we find the parachute bucket and nose cone. The inner part of the parachute bucket is made of carbon fiber to save weight. In the bucket lies a 34.7-square-meter parachute which will land Nexø I at 8 m/s. In the side of the parachute bucket sits a camera that will film the unfolding of both the parachute and the ballute which we find in the upper section. Here is also an (inverted) carbon fiber bucket which houses the ballute. Additionally it contains two gas generators (air bags) each emitting 100 liters of gas in a fraction of a second. Obviously they are used to shoot of the nose cone. When the pressure in it becomes too large the many small “dog bones” on the outside will be torn and the ballutte will be in the open air. It is attached through a three-ring system to the main parachute, which can then be activated after a given time or a given height. The nosecone is also equipped with its own small parachute which is equipped with its own small transmitter, so that we can track the nose cone on the way down and find it again.
Pre flight testing
Nexø I has gone through quite rigorous testing. The test phase has been divided into three main parts:
- FAT – Factory Acceptance Test
- HAT – Harbor Acceptance Test
- SAT – Sea Acceptance Test
The Factory Acceptance Test was carried out on a mock up launch rail setup outside the workshop. Nexø I was mounted on the rail and all the electronic systems where verified to be operational. Then a cold soak test was performed where the LOX tank was filled with liquid nitrogen in order to see how the entire system would react to the cryogenic conditions. Finally the main LOX valve was opened to verify cryogenic valve operation.
We also conducted a Harbor Acceptance Test with Nexø I on Sputnik, our launch vessel. Once again all systems were tested to ensure fault free operation. Finally, on June 26th 2016 we performed the last test, the Sea Acceptance Test. For this test we performed a simulated launch while Sputnik was sailing around the Copenhagen harbor. The test ended with a successful “launch”, i.e. successful system operation shrouding Nexø I and Sputnik in a big cloud of nitrogen as the LOX was was emptied.
Nexø I supporter mosaic
Nexø I is partially funded through an Indiegogo campaign. One of the perks of the campaign was to get your photo on the rocket! Thus, the avionics compartment is covered by a mosaic of people from around the world who have contributed to building Nexø I, you can see it below or download the mosaic here (13 MB).
Nexø I video:
Click here to see a video about Nexø I and some of its creators