The Black Fox Presentation

The Black Fox 3 rd Year High Powered Rocket Project: Propulsion System Construction

Aims and Objectives

Aim: To choose a motor for incorporating into a high powered rocket and take it to a predetermined height

The objectives of the project were:

To choose between Solid and Hybrid propulsion

Use a flight spreadsheet provided by the propulsion design team to predict altitude, flight time etc.

Purchase the motor

Fit the motor into the airframe using a purpose made motor mount

Launch safely

Recover data and cross reference with initial predictions

Design Team’s Choice

AeroTech J90W

Solid rocket motor

Loses Velocity before burnout

Reaches lower Altitude and velocity

Longer Burn time

Smoother thrust

HyperTEK I310

Hybrid rocket motor

Less velocity loss close to burnout

Thrust more constant through flight

Higher Velocity and Altitude reached

Greater force exerted on the rocket

Limitations on Motor Choice

Solid motor unavailable as not C.E. Certified

We should feel free to choose anything

Increases in overall rocket weight

Maximum altitude of 8000ft (2440m) set by UKRA

No Supersonic flight

Motors We Tested

The standard J class HyperTEK motor kit (NB: we only need one grain)

I260 with .172” orifice

J115 with .076” orifice

There is also another fuel grain called a HyEFX:

More exotic chemicals and materials go into making it

Produces lots of white smoke and flame

Slightly greater thrust produced

We couldn’t use one as it requires specific equipment that was unavailable

Final Motor Choice

We finally went with the J250

We kept finding the overall rocket weight was going up

648.4053 101.0944 Altitude (m) Velocity (m/s) Max Values

J250 Thrust Curve The thrust curve is still quite smooth despite it’s short burn time J250 thrust curve J115 thrust curve

Motor Mount Research Insertion of motor mount into the airframe and fitting of bolts Thrust ring and centring (left), thrust ring fitted (middle) and its clamping mechanism (right)

Fin Can

A Fin Can is a motor mount that also includes mounting points for the fins of a rocket

Unfortunately we could not use this design

Although a new design developed by the airframe team made me more confident

Motor Mount Design

The Final Product The motor mount being assembled (left) and fully assembled (right) The final design fitted to the HyperTEK with centring on oxidizer tank

Fitting the Motor Mount

The motor mount fitted inside

the airframe

The retention plate screwed

in to hold the motor in

Coordinating Role

After the motor mount was made I decided to help with the organisation of the project

This involved:

Preparing the teams for the weekly meetings with supervisors

Put together a launch-day schedule

Compiled safety documentation

The Running Order (a) (b) (c)

The rocket before parachute is loaded

Locating the injector valve

Fitting vent tube

The Running Order (a) (b)

Locating the fuel grain over fill stem

Fitting of break wire

Sliding the rocket onto the launch rail

Prepping the HyperTEK (a) (b) (c)

Tape the pre cut ignition wire to fill stem

Slide the motor onto stem until properly seated

Using tie-straps to ensure tight fit and stop premature launch

The Launch

The Landing

Crash Analysis The recovered rocket

The R-DAS flight computer was completely destroyed, as was the GPS

No data could be recovered

Results

As there was no down-link established, no data was recorded

The GPS was destroyed so we had no idea what height it reached

However, using video footage and editing software we could find out how long it took to go up – then try and calculate an altitude

We used Newton’s laws to roughly calculate height Error = 0.606% h max = 644.4768 m h max = 648.4053 m v av = 50.5472 m/s v max = 101.0944 m/s v max = same as predicted t total = 24 s t total = 25.5s Predicted Flight Actual flight

What Went Wrong? Apart from speculation on the day, I did some detective work on the internet regarding the software afterwards We launched on 06/03/2005, so we were probably running V3.6

Conclusions