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Flight Log Updates

#190 - Polaron G3

#189 - Casual Flights

#188 - Skittles Part #2

#187 - Skittles Part #1

#186 - Level 1 HPR

#185 - Liquids in Zero-G

#184 - More Axion G6

#183 - Axion G6

#182 - Casual Flights

#181 - Acoustic Apogee 2

#180 - Light Shadow

#179 - Stratologger

#178 - Acoustic Apogee 1

#177 - Reefing Chutes

#176 - 10 Years

#175 - NSWRA Events

#174 - Mullaley Launch

#173 - Oobleck Rocket

#172 - Coming Soon

#171 - Measuring Altitude

#170 - How Much Water?

#169 - Windy

#168 - Casual Flights 2

#167 - Casual Flights

#166 - Dark Shadow II

#165 - Liquid Density 2

#164 - Liquid Density 1

#163 - Channel 7 News

#162 - Axion and Polaron

#161 - Fog and Boom

#1 to #160 (Updates)

 

FLIGHT LOG

Each flight log entry usually represents a launch or test day, and describes the events that took place.
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Day 52 - Polaron IV Launcher Progress and Booster Tests
Launcher base with slots cut out. The central release head mounting plate is sitting on top prior to attachment.
Booster nozzle seat supports are soldered to the sliding base plates.
Nozzle sliding base plates mounted in the launcher base.
Two interchangeable release heads. The two components on the right belong to the bleed valve assembly. This can be swapped from one head to the other.
The left release head has plastic tabs for lower pressures and plastic nozzles. The one on the right uses ball bearings and is used with higher pressures with aluminium nozzles.
Release head fitted to the base plate. The booster nozzle seats here are also mounted on the sliding base plates.
The air distribution manifold under the launcher. Note the two quick release couplings on the left.
The main stage air supply has a non-return valve mounted just behind the quick release coupling.
We uses braided steel flex hoses to get the air to the sliding nozzle seats.
Detail of where the flex hose enters the bottom sliding base plate. Four spacers between the top and bottom sliding plates keep the two just the right distance apart.
12mm launch tubes fitted inside the nozzle seats.
Sometimes a pitchfork is just the right tool for the job. Here the major elements of the Polaron IV rocket sit on the launcher.
A booster fitted with experimental winglets to help guide it to a safe landing. Fitted here with a 9mm nozzle for the test launches.
The winglets are designed so that the center of pressure is aligned with the center of gravity for unstable flight back to Earth.
Setting up the booster for it's maiden test flight.
With such an unstable rocket we were happy to see it tumble safely back to Earth.
Another booster is tested without the winglets so that we could get a good comparison.
Setting up the medium launcher's extension. This gives 2m guide rails to steer the rocket while it accelerates.
The kids are getting to be real pros at helping with the launches and experiments.
Date: 22nd January 2008
Location:
Workshop & Denzil Joyce Oval
Conditions:
 Windy and overcast, mild temperatures
Team Members at Event: GK, PK, John K and Paul K

Polaron IV Launcher Progress

We are concentrating at the moment on finishing the launcher and the Polaron IV rocket. It was a busy weekend in the workshop doing all the heavy duty cutting, soldering and machining work for the new launcher. With all that out of the way we now only have a few minor assembly tasks that need to be completed and the launcher will be ready.

Launcher Design

Hold Down

The launcher is based on a similar design to the Acceleron III launcher. The main difference is that the central retaining mechanism has been replaced with a Gardena mechanism to allow the main stage to fire at the same time as the boosters.

Because the Gardena mechanism needs to not only hold down the main stage but also the boosters which are free to move out of the launcher, we've had to switch to a brass mechanism that uses ball bearings instead of the plastic tabs of regular Gardena mechanisms. The main stage nozzle is also made from aluminium because the ball bearings would damage a plastic nozzle with the forces involved.

We have also made a second release head that utilises the plastic tabs for retention. This will allow us to use plastic nozzles in other configurations and at lower pressures.

Dual Air supply

This is our first launcher to use a dual air supply. We will be able to supply a different pressure to the boosters compared to the main stage. This gives us the ability to optimise the performance of both the main stage and the boosters. This will also allow us to use this launcher for rockets without boosters.

The manifolds and air distribution hoses are all rated to at least 500psi. This will allow us to use this launcher in the future for heavily reinforced rockets.

The nozzle seats with the launch tubes are removable for easier transportation.

Sliding Nozzle Seats

The booster nozzle seats are designed to freely slide in and out from the center for two reasons:
a) We can use different sized main stage and different sized boosters without the need to change the launcher.
b) During pressurisation as the boosters and main stage pressure vessels expand, the sliding nozzle seats move with them. This prevents the nozzles being placed under lateral stress if they were fixed in place. ( This was also a feature of the Acceleron III launcher.)

Air Supply Components

A bleed valve is fitted to the Gardena release head to allow the rocket to be depressurised if a launch needs to be aborted. The bleed valve is located where it is because it needs to sit behind the non-return valve fitted under the launcher.

The non-return valve in the main stage air supply line is there so that water is not forced back into the pressure regulator.  Having the bleed valve so close to the rocket is less than desirable, but it is only used very rarely, and for high pressures we will connect it via a string so it can be operated from a distance.

The booster air supply line does not need a non-return valve because this line is always dry. As a result the booster bleed valve is located near the pressure regulator away from the rocket. The boosters are filled with air through the launch tubes which fill the boosters above the water line. This allows the launcher to equalize the pressure in all boosters without transferring the water between them.

The launcher base has a pair of quick release fittings to for easy connection to the air supply hoses.

Diagram of the air supply components (Click to Enlarge)

Gluon Boosters

Each booster is made from a pair of 1.25L bottles spliced together using PL Premium and the symmetrical splicing technique. These pairs are designed to be extended in the future using Tornado couplings where the neck of one booster is connected to the neck of the next spliced pair.

The 13mm nozzle is extra long to allow the booster to move upwards a little while it is being pressurised without coming out of the seat and breaking the seal.

Booster Recovery

In order to simplify the design, the boosters use a passive recovery system. The recovery system consists of a pair of winglets centered on the Cg of the booster, but angled to one side. This causes the booster to fall mostly sideways much like a back gliding rocket.

Normally this sort of system would not work on a regular rocket because the rocket would be unstable. In this case, however, the main stage keeps the boosters aligned in the right direction during flight and only when they separate do the boosters fall in an unstable manner.

This recovery system allows the boosters to remain lightweight and simple with no moving parts. Because the boosters do not fly very high and they do not weigh much the landing on grass is sufficient to prevent damage.

The winglets also help to steer the booster away from the main stage just after separation.

Booster Coupling

The booster is loosely attached to the main stage. The booster coupling mechanism is made from a coat hanger wire and bent to allow it to be glued directly to the rocket body. This fits into small tubes attached to the main stage. I will cover this in detail the next update.

Booster Testing

In order to understand how the boosters will behave in flight we set up our regular launcher and fired them into the air this weekend. These tests were strictly to understand how well the booster will float back to Earth and how well it would survive a landing.

This was actually the first time we fired a spliced rocket so it was good to see it get off the pad. We increased the pressure from 60psi on successive launches to 120psi to make sure it still held. We made sure we stayed well away as we did not know if the glue would hold up. (We had previously pressure tested these to 115psi)

(If the video does not play, try the latest Flash player from Macromedia)

We also launched the booster by itself without the fins to compare its performance. For a high performance flight we may remove the winglets to save a little on the drag as well as the weight.

This was also the first time we used the launcher's 2m extension. With the booster being so unstable it helped get it up in the air a bit higher so we could watch it tumble back.

We were pretty happy with the results and no real design changes are necessary.

The next step will be to make a mock-up of the main stage simply by taping a number of 2L bottles together. The mock-up will not be pressurised and will not have any payload or recovery system but will have equivalent dimensions and weight distribution of the actual main stage. We will boost that at our local park using the three boosters. This test will hopefully prove to us that the booster arrangement works before we fit it on the actual main stage. The payload on the main stage costs around $300 so we are taking the development in stages.

The reason the mock-up will be unpressurised is to make sure it does not leave the park. We expect the final booster and main stage combination to reach above 600 feet and that could easily put it amongst the houses near the local park. We hope to launch the actual rocket at a much bigger launch site at one of the NSW Rocketry Association (NSWRA) launch events.

Flight Details

Launch Details
1
Rocket   Gluon
Pressure   60 psi (4.1 bar)
Nozzle   9 mm
Water   700 mL
Payload   Winglets
Altitude / Time   N/A
2
Rocket   Gluon
Pressure   80 psi (5.5 bar)
Nozzle   9 mm
Water   700 mL
Payload   Winglets
Altitude / Time   N/A
3
Rocket   Gluon
Pressure   80 psi (5.5 bar)
Nozzle   9 mm
Water   700 mL
Payload   None
Altitude / Time   N/A
4
Rocket   Gluon
Pressure   100 psi (6.9 bar)
Nozzle   9 mm
Water   700 mL
Payload   None
Altitude / Time   N/A
5
Rocket   Gluon
Pressure   100 psi (6.9 bar)
Nozzle   9 mm
Water   700 mL
Payload   None
Altitude / Time   N/A
6
Rocket   Gluon
Pressure   100 psi (6.9 bar)
Nozzle   9 mm
Water   700 mL
Payload   Winglets
Altitude / Time   N/A
7
Rocket   Gluon
Pressure   100 psi (6.9 bar)
Nozzle   9 mm
Water   700 mL
Payload   Winglets
Altitude / Time   N/A
8
Rocket   Gluon
Pressure   120 psi (8.3 bar)
Nozzle   9 mm
Water   700 mL
Payload   Winglets
Altitude / Time   N/A

 

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