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BSD Intrepid
This is my BSD Intrepid, my first High Power 2-stage rocket. It's a modified kit to fly on two 38mm motors rather than the stock 38mm booster and 29mm sustainer, and at nearly five pounds for both stages this rocket sims out to over 6000 feet on two Aerotech J350-* motors.
As usual, a few pictures of the Intrepid; click on the image to see the full-size version.
The fully-assembled Intrepid standing in the living room. Over 7 feet tall from base of the booster to tip of the nose.
The first flight of the Intrepid in a single-stage configuration with dual-deployment. We didn't manage a launch photo, but we do have...
The Intrepid returning under parachute. The image is a bit fuzzy - the camera had some issues with the focus - but you can see the main parachute at the top (purple and gold), then following the line down from top to bottom you can see the nose cone, the main airframe tube, the drogue parachute, and finally the fin can and motor mount.
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Flight Log
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Name
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Manufacturer
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Status
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Date Built
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Intrepid
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BSD Rocketry
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February, 2002
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Flights
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Date
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Motor
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Altitude
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Notes
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April 2002 | Aerotech H210R-* | 782 feet | Good flight, dual-deployment test, sustainer only
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Design & Construction
The Intrepid kit from BSD Rocketry is designed as a two-stage rocket with a 38mm booster and a 29mm sustainer. My version of the kit uses 38mm motor mounts in both stages, and is designed for flights from 700 feet (using the sustainer with a 29mm motor in an adapter) to over 6000 feet (two 38mm Aerotech J350-* motors.) The only real limitation to this kit is that it is designed for electronic dual-deployment; there are no provisions for motor-based ejection.
Basically, motor-based ejection uses a delay element - a section of slow-burning fuel, essentially - to regulate when the ejection charge fires to deploy the parachute. This is the most reliable form of ejection control, since it depends solely on the motor - if the motor was assembled correctly and ignites on the pad, you are almost certain to have the ejection charge fire. Electronics-based deployment, on the other hand, uses either a timer or an altitude-measuring device (barometric or accelerometer) to determine when the rocket has reached its maximum altitude (apogee) and fires the charge itself.
On the one hand, this is a good thing. The parachute will always deploy right at apogee, which is perfect because the rocket is not moving at that point and there's very little stress on the rocket when the parachute fills. The downside is that the complexity of the rocket is greatly increased, and the chances of failure are therefore higher. Dual-deployment makes things even more complex, in that the drogue parachute is deployed apogee to control the rocket's descent without slowing it too much. A larger parachute - the main 'chute - is then deployed at a lower altitude to slow the rocket for landing.
You do this to keep the rocket from drifting. For example, when I launched the Horizon for my level 1 certification, winds were pretty light and the rocket went up about 1200 feet. The rocket drifted nearly a quarter mile under parachute. Imagine the result of doing that with a rocket that reaches 6000 feet! But with the drogue parachute, the rocket doesn't have time to drift very far. Its job is to keep the rocket from coming in out of control, not to keep it from descending rapidly.
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CPAN
