Our Special Project Rockets

7 responses to “Our Special Project Rockets”

1. 

   jurvetson

   Jun 4, 2013 at 4:55 am

   Doh! It screamed off the pad… and I was zoomed in
   
   The nose is quite a bit heavier than a stock build with the Dragon spacecraft, and it snapped the elastic cord. The nose fell from apogee to the ground, but was unharmed. So, for the Falcon Heavy build, we will have it come back with a separate parachute rather than struggle with proper shock cords and beefy attachment in this small airframe.

   And here’s the duct-tape beast…
   
   38mm Cesaroni Imax motor, Estes fins attached with JB Weld. Scrap Motor tube for the body, reinforced with rings of duct tape head to toe. Golf ball for a weighted nose cone. That’s it.

   Flew straight as an arrow.
   
   Next flight will double the impulse…

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2. 

   jurvetson

   Jun 4, 2013 at 5:47 pm

   The duct-tape rocket build was motivated by our annual meeting of VCs from around the globe. We typically dispose of excess propellant by melting an outdoor fire pit, and then launch a couple small night rockets. I wanted to design something safe, but that I was willing to lose. So I figured that if I recycled scrap materials and spent less than 15 minutes building it, we’d be good to go.

   The golf-ball nose was a brilliant insight my son had a few years ago when he wondered what the smallest possible rocket might be:
   Details on that. The countdown for that launch is “10,9,8,7,6,5, Fore!” and off it goes.

   Here is the duct tape rocket next to a vintage Animal Motor Works Skidmark 38mm I-motor that we used for the maiden night flight:
   
   (and my other night flight airframe rebuild on the left)

   That AMW motor was too heavy (with thick metal tubing and snap-ring closures) and too long (shifting weight forward) and resulted in an unstable flight (i.e., a convoluted spiral rodeo dance overhead). But, the airframe was completely unharmed by that maiden night flight.

   Duct tape is an amazing building material. I think I was inspired by other uses I have seen, from Apollo 13 to evening wear at the d-school
   

   pushing me to consider the absurd limits to its use, for strap-on video cams:
   

   

   The duct tape worked like a champ in both cases!

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3. 

   Kevin Baird

   Jun 4, 2013 at 7:50 pm

   I like the Alpha III with the stickers peeling off. My son recently launched his first one in a neighborhood park. Turns out that’s illegal.

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4. 

   jurvetson

   Jun 5, 2013 at 3:30 am

   Yeah, it’s always best for the children to push the button given the leniency on incarceration of minors. =)

   But seriously, I have checked our city code in case of inquisitive peace officers. It clearly says that "fireworks and torpedoes" are forbidden, but no mention of rockets.

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5. 

   sbove

   Jun 5, 2013 at 5:31 pm

   Golf ball nose! Heh. I once used a spent C02 cartridge for same, but did not bother to calculate proper aft balance…wayyy nose heavy projectile looped back at launch pad, somehow got horizontal, screamed through two chain link fences straight at a neighbor’s father who was raking leaves a few yards over. He nearly had heart attack (not kidding) when it skidded through the leaf pile, smashed into a wooden fence behind him (metallic whack sound), reversed direction, shot between his legs and embedded itself under a hedge near his house. In hysterics, my launch team had to flee the scene when the parachute eject charge went off as he was reaching to pull it out. Hilarious in retrospect, but actually a really dangerous moment…maybe forgivable b/c I was 12 😉

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6. 

   jurvetson

   Jun 5, 2013 at 6:02 pm

   What a fantastic story. We’ve all been there… =)

   

   Reply
7. 

   Kevin Baird

   Jun 5, 2013 at 6:04 pm

   Torpedoes. Good to know. 🙂

   Reply