Cambridge University Spaceflight Fire Britain’s Largest Ever Nitrous Hybrid Rocket

Cambridge University Spaceflight (CUSF) have successfully completed the first static firing of their custom hybrid rocket engine. Over last 18 months the team have been working tirelessly on Project Pulsar, designing and building the Pulsar engine from scratch, culminating in the successful test this week at Airborne Engineering Ltd’s test facility.

Find more photographs of the test here.

The Pulsar engine burns Nitrous Oxide combined with High Density Polyethylene fuel to produce thrust for a total of 36 seconds. Over the course of the test, the engine produced a measured impulse of 53,855 Newton seconds giving it the largest impulse of any Nitrous Hybrid rocket ever fired in the UK.

A freak snow storm threatened to delay the test but the team powered through to fire the engine after dark resulting in some dramatic views, a melted plume of snow and novelty snowballs rolled from rocket exhaust gases. Extreme cold caused two of the cameras to shutdown, but footage from two of the remaining cameras is shown in the video below.

The Pulsar project was first conceived in 2017 when the society’s Martlet 3 rocket, designed to break the UK Amateur Rocketry Altitude Record, was destroyed in flight by the explosion of a commercial off-the-shelf rocket motor. While obviously a major setback for the Martlet 3 project, CUSF team members were inspired to see if they could build something better. The success of the Pulsar project, which has delivered more than double the designed impulse of Martlet 3 in this static firing, shows that CUSF are well on there way to doing just that. The test itself marks a key milestone in the next chapter of high power rocketry at CUSF with the Pulsar engine intended to power the Martlet 4 rocket project set to launch in 2020.

Cambridge University Spaceflight are extremely grateful to Airborne Engineering Ltd (and the many CUSF alumni who work there!) for letting us use their fantastic rocket test facilities and giving up their time to help us over the last few weeks. The test captured a huge amount of data which the team are hard at work trying to analyse in order to learn as much as possible about the Pulsar engine. Watch this space for a more detailed technical breakdown in the near future.

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Notes to the editor:

Cambridge University Spaceflight (CUSF) are a student run engineering society made up of current undergraduates and PhD students at the University of Cambridge. Founded in 2006, CUSF have grown to become leaders in amateur rocketry and high altitude ballooning.

Dora the Datalogger

So quite a while back some PCBs arrived courtesy of Cambridge Circuits for the first revision of Dora, a data logger for use in our custom static fire test rigs. The device itself consists primarily of an STM32 processor, a micro SD card, and analogue front ends for a thermocouple, strain gauge and pressure sensor. We also included a USB port for debugging and some GPIO headers in case we wanted to experiment with extra functionality such as an LCD screen.

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Continue reading “Dora the Datalogger”

Quasar parts

Over the past week we have modified some of the existing parts of Quasar (our static hybrid rocket) and machined a new injector and nozzle in the student workshop.

Quasar parts

Quasar nozzle Quasar injector

OkGo!

Some of our team have recently been developing a prototype hybrid rocket motor.  Our motor was to be ignited by lighting a length of slow-fuse, waiting for the fuse to burn down some of the length of the fuel, then opening a valve to allow the oxidiser to flow through the fuel.  The oxidiser valve requires around 10 amps continuous current, which is rather more than most ignition systems are geared up for.

OkGo (Named after the band) is our ignition system, developed to light the hybrid (We also used it to ignite a number of solid fuel rockets).  It’s a very simple system based on buttons, switches and relays, but works well and should be highly reliable.  We are considering adding features such as continuity testing (This lets you test whether the ematch is intact and connected before activating it).

A quick demonstration video is included below:

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Static Test Rig Progress

The CUSF team have been building a rig to test a rocket motor whilst it is firing. The rig is designed to mechanically separate the X-Y-Z components of thrust, using a series of spring steel flexures. The 3 axes of thrust are then measured by 5 separate load cells to get the axial thrust, off-axis thrust and off-axis moments from the rocket motor.

This week, one of the measurement arms has had the flexures assembled and load cells bolted on. The main thrust bearing cage has also almost been finished.