The Infamous Cluster Duck.

This was one rocket that really should have worked. More work went into this rocket most of my others.

Here are the details:
The rocket was 3” in diameter and about 65” tall, and four 29mm motor mounts. The flight profile would be to use 2 G40-7 motors to lift it off the pad, and then air start 2 F50 motors 3 seconds after launch. The electronic timer was hand made with a micro switch that arms when the G-forces of lift off, pull down on a small weight.

The two G40 motors burn for approximately 2.8 seconds, with the timer set for 3 seconds the F motors should light just after the G motors quit. Then when the F motors burn out the rocket should coast to apogee and deploy a parachute.
I launched this rocket once with two G class motors as kind of a shake down cruise.
CD first launch

Then I launched my L1 rocket to earn my Level one certification. This was important because the levels for NAR certifications are according to impulse. The impulse for a rocket motor is rated by a letter designation started from A and ending ….. well I guess it doesn’t end. A Newton second is how much energy it takes to move one kilogram one meter in one second. Each letter grade of a motor is double the power range of the last. So an A motor would be a range of 1.25 to 2.5 ns. A B motor would be double that, on up the alphabet.

L0 = up to 240 ns of total impulse. One H class motor or 2 Gs
L1 = up to 640 ns of total impulse. One I class motor or 2 Hs
L2 = up to 5120 ns of total impulse. One L class motor or equivalent
L3 = no limit to maximum.

The Cluster duck would have a total impulse of
G40 (120ns) X 2 = 240ns, + F50 = (76ns) X 2 = 152ns for a grand total of 392ns.
The same as a baby I class motor.

So first up is the L1 Rocket. Perfect launch, perfect recovery. That’s all that’s required for a L1 certification launch. So after some paper work is done I have a temporary certificate to enable me to launch up to 640ns of total propellant in one rocket.

So be it.

I loaded up the Cluster duck, packed the parachute, installed new batteries, and double checked the electronics.
CD prep
I have to add here that my cousin Jim came all the way from California to watch my L1 cert and to see the Cluster duck fly. I was a bit nervous.

Anyway I filled out the launch card, went to the pad and did the final prep of the duck.
After a few photos I went back to the staging area and waited my turn.

Then the LCO announces that the cluster duck is ready to fly.

“Dale are you ready”?

“Ok, this is a heads up flight. Dale Netherton’s rocket named Cluster Duck is on pad 5, its flying on two Aerotech G40s then air start two Aerotech F50s”

“Ooohh Ahhhh cool” could he heard all around. And one “Oh I’d do that if I were you”

“ Going in 5, 4, 3, 2, 1, Launch!

Then smoke appeared and oops, I only see one engine lit.
The cluster duck seams to rock from side to side as it leaves the pad, badly under powered.

At about 200’ in the air it turns over and starts to point down.

This is exactly 3 seconds into the flight.

I am muttering “don’t light…. Don’t light.”

Then right on cue, both F50 light at about 150’ nose cone is facing down at a slight angle almost like it was waiting for it to point at a target on the ground.

Woooooosssshhhh SMACK. “Damn”
Aftermath
Everyone rushes over the hill to check out the carnage.

I guess the only lesson learned was to make sure that all the motors light. But I knew that at the time, the motors were too small to put two igniters in each motor. So redundancy wasn’t a possibility.

I guess I learned to go big. The next air start cluster I made was with 38mm motors!
But that’s another story.

-PF

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: