Monday Sep 24, 2007
Monday Sep 24, 2007
I blogged about my
Vulcanite earlier this year. This rocket is 53" tall
(4.5 ft, 135 cm) and weighs 32 oz (2 pounds, about 1 kg) before adding a motor.
I painted it orange and black to make it more visible against blue sky or
light clouds.
My goals for this rocket include:
The results were gratifying.
| (When I take pictures of a launch,
I press the shutter as soon as I see any vertical movement, which
resulted in a well-composed picture. At least it did this time...)
According to the on-board altimeter I added, it flew to 1,584 feet (480 m). More importantly, it flew almost perfectly straight up, and the 24-inch parachute returned it safely to Earth not far away from the launch rail. However, it seems that the delay I chose - the time before the parachute is ejected - was not long enough. With the correct delay, the rocket would have flown higher. |
| Beaming with success, I decided that the next launch would begin to test
the limits of this rocket. I chose an I218R - an 8-inch (20 cm) motor with
almost twice the total impulse of the previous motor. (Think of total impulse
as the total force exerted while the motor is burning.) Even though I knew
it would fly much higher, the wind was very light that day, so I
didn't expect to walk far to recover it.
With this motor, the Vulcanite flew to 4,469 feet (1.35 km)! Also impressive was its maximum speed: over 500 MPH (800 km/h). You can see that in the picture to the right: I have an itchy shutter finger, but the rocket launched so fast I missed it entirely! Unfortunately, although the nose cone ejected properly, the parachute never came out. The two ends of the rocket, connected by an elastic cord, fell over 4,000 feet to the ground. Fortunately, the launch area was an empty corn field with large clods of dirt which had been softened by rain the day before. The only damage was a partial crack in one plywood fin. A little sanding, some new epoxy, and it should fly again. To one mile? |
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Wednesday May 09, 2007
One of my many hobbies is rocketry. Just a guess, but you've probably
heard of it.
If not, check out the two main rocketry associations in
the USA: the National Association of
Rocketry and Tripoli Rocketry
Asociation.
The latter is an international organization, with groups ("prefectures")
in North America, Europe, Israel and Australia.
I have always been interested in rockets, ever since watching man land on the Moon back in 1969. I launched "hobby rockets" in the late 1970's, but only recently re-visited the hobby. I found that things had changed. First, they are called 'rocs' now. Also, video cameras are common, and the web is everywhere: here is a video of a large high-power rocket and a chapter in the saga of Nibbles the Astro Cat.
My first "mid-power" rocket was an Aerotech Arreaux.
It flew on motors of different sizes, up to a G33, and to a maximum
altitude of 2,000 feet (600m). It usually carries a sampling altimeter
because... well, just 'because.'
The picture to the right is my Arreaux after a few flights. It is about 43" (109cm) tall. |
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Moving on (and up...) this year I am building a
Loc-Precision Vulcanite kit. My goals for this rocket are
to obtain
my Level 1 Certification and to fly it to an
altitude over one mile (1.6km). While doing that the rocket
would exceed Mach 1. Achieving my L1 certification allows me to
purchase H and I rocket motors.
I chose the altitude goal "because it's there."
The picture to the right is my Vulcanite during construction. It is about 53" (135cm) tall. The red metal cylinder to its right is a machined aluminum rocket motor casing for a J motor, which can also be used to launch this roc. I might attempt to get my Level 2 certification, which would allow me to buy J motors. If you ever launched hobby rockets, you may recognize the C6-5 motor
to the right of the J casing. Back in the 1970's we thought that
was a big motor... but a J motor can produce over 100 pounds
(440 newtons) of thrust at liftoff, and a total impulse (thrust
measured over time) of 100-150 times that of a C motor.
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