Blowfish Avenger

Successful Flight Two at GHS 2005

The second flight of the Blowfish Avenger on a K695 Redlicne motor was a thing of beauty. The additional nose weight coreected the stability problms encountered on its first flight (scroll down for info). There aren't a lot of photos of the flight -- I hit the button and it roared up to about 3400 feet on a gorgeous plume of bright red flame. The chutes deployed at apogee, and that was that.

Maiden Flight at GHS 2004

The Blowfish Avenger flew for the first time at the annual G. Harry Stine launch October 23-34, 2004. If you haven't read up on the design or construction details of this rocket, you might want to look [HERE!]. But the short version is this - it is an all-fiberglass upscale of a 1950's piggy bank we spotted on eBay.

There is a challenge to making these bulbous designs airworthy -- after all, they are designed to be ornamental, not aerodynamic. I've had pretty good success until this flight.

After a magnificent ascent to several hundred feet, the Blowfish took a sudden and inexplicable right-turn. Conjecture about why it suddenly went unstable is rampant.

Here is Burl's assessment, speculating about turbulent flow:
"The air flow is parting over the forward tips of the most forward fins. As the velocity increases the flow being the tip becomes turbulent and does not reattach to the fin in the aft of the body. This is added to because the body shape creates a low pressure area in the aft end."

My own theory - right or wrong - is that the rocket was balanced to be stable at low speeds but that the Center of Pressure inched forward as velocity increased - until the CP for the longer fins crept past the Center of Gravity, causing the rocket to become unstable along that axis. I tend to believe that I simply should have added more nose weight, and I would have if I had only trusted my stability calculations. Unfortunately, I conducted a swing test just a few days before the flight, and the rocket was stable without any additional weight. So I incorrectly decided it wouldn't need added ballast, not realizing that the CP would be different at higher speeds.

I have lined up the use of a wind tunnel to test the Blowfish prior to my next flight attempt. Hopefully that will eliminate any guesswork.

The business end.
Lynette helps pack the parachute. You don't see this every launch, trust me.
The Blowfish Avenger on the pad. Photo by Jacob Dennis
The Blowfish takes off on an Aerotech K550. Photo by Billy Dahlberg of http://www.naturallylit.com
A second photo of liftoff, taken milliseconds after the previous photo. Photo by Jacob Dennis
A third photo of the liftoff from yet another angle. This one shows the two-color paint scheme. Photo by Nadine Kinney of Photos by Nadine
Further up.... Photo by Billy Dahlberg of http://www.naturallylit.com
After a magnificent ascent to several hundred feet, the Blowfish takes a sudden and inexplicable right-turn. (from Billy's vantage point, all he could see was smoke - but keep scrolling down...). Photo by Billy Dahlberg of http://www.naturallylit.com

The next twelve photos are lifted from Blowfish Avenger flight video taken by Chuck Stewart. This video is a must-see. Chuck did an unbelievable job staying on the rocket as it zig-zagged across the sky.

The Blowfish starts its first 90° turn. Notice that the turn axis is parallel to the plane of the longer fins.
Immediately after the first turn. The opposite (red) side of the rocket is now visible.
The Blowfish was temporarily stationary after the turn - but only for a moment.
Still under full thrust, the Blowfish zooms off parallel to the ground.
Velocity increases...
until the Blowfish skids into a second 90° turn, pivoting on the same axis.
Once again we see the opposite (red) side of the rocket after the turn.
The rocket is momentarily stationary for a moment, but zooms off yet again...
gaining speed until...
it reaches critical velocity and...
it turns again on the same axis, this time revealing the yellow side.
At this point the fun ends as the K550 motor reaches burnout.
The Blowfish drifts to the southeast trailing a feeble wisp of smoke.

The blowfish floats gently earthward. Photo by Billy Dahlberg of http://www.naturallylit.com
The Blowfish didn't land very gently -- but it bounced pretty well, and as a testimony to its construction only needs the repairs of a few scrapes and some new paint. Amazing. Photo by Nadine Kinney of Photos by Nadine

Click [HERE!] to visit the Cinema page and view the Blowfish Avenger flight video!

Click [HERE!] to go to the page detailing the design and construction of the Blowfish Avenger!