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#221 - Horizon Deploy

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#1 to #160 (Updates)



Each flight log entry usually represents a launch or test day, and describes the events that took place.
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Day 44 - Foam Flights, FC V1.3.2 tests flights.
Two new V1.3.2 flight computers and deployment systems. The one on the left shows the camera location, the other showing the parachute door.
Parachute door and camera doors open.
6:30am, we are still trying to wake up.
Ready to test the new flight computer on Hyperon III. John .... it's 3,2,1 ... then "GO" not 3,2,"GO".
Being a bit too close to the rocket ensures an early shower, with shampoo and everything.
Apogee image taken from the video sequence.
River next to the park. This was a fairly high altitude flight.
You have to walk a fine line between pressure and wind conditions.
This coupling ripped out of the lower bottle of J4 II.
The G-forces during the explosion bent connectors, components and separated the servo in two. Note this damage is not the result of impact. The entire nosecone is undamaged.
Date: 16th September 2007   6:30am - 8:00 am
 Denzil Joyce Oval
Clear skies, mild temperatures, increasing wind,
(click the name for rocket details)
Name Capacity Notes
Hyperon III 5L New rocket based on the Hyperon standard platform
J4 II 5L An old rocket that has had a fin and deployment system upgrade.

Team Members at Event: GK, PK, John K, Paul K.

The purpose of today's flights was to test V1.3.2 of the flight computer. It started out as a beautiful day but as soon as the sum came out, the wind started picking up. It was fun morning of launches although we did get a wakeup call about safety.

Flight Day Events

  • The first flight of the day was Hyperon III with a camera mounted on the inside of the nosecone. We only used water (no foam) for this flight since we didn't know how well the computer would work and we wanted to keep the flight as stable as possible. It was a great flight and the parachute deployed when it was supposed to. The rocket drifted almost 200 meters down range in the strong breeze. The in-flight video of this is shown in the highlights video below. If you listen carefully you can hear the servo motor at apogee and then a couple seconds later as it returns to default position.
  • Next up was the newly upgraded J4 III. J4 III had new fins fitted and was equipped with an identical deployment mechanism as Hyperon III. As we started filling it, I was doing the customary arming of the flight computer. As I was just finishing up the top section of J4 exploded from the rest of the rocket. My face was about 1 foot from the failure point. It was a pretty loud bang as you expect, and I would not recommend others repeating the experience.

    I think I was extremely lucky in that I only suffered a drenching and the video camera around my neck too was saturated. Again no video of the incident is available as it was totally unexpected. Although now we should expect it every time.

    The second bottle from the top burst at the base and neatly ripped out a piece of PET with the coupling. The coupling remained attached to the top bottle. The bottle had burst at around 100psi. We were surprised to find that it was still one of our early brass couplings. This coupling and bottles must have been in place for perhaps 6 months. Looking back, J4 II had its fair share of launches and crashes, and the bottle base must have been weakened by all the usage.

    The flight computer on top of the blown off section suffered damage due to the very high G-forces of the explosion. Components and connectors were bent, and more notably the RC servo motor split in two revealing the gears. The servo top and bottom shells are not screwed together, but rather held by friction by 4 little plastic pins slotting into corresponding tight holes. I didn't know the servos were constructed like this, I thought they were just glued together.

    We know this wasn't caused by impact with the ground because none of the nosecone or bulkheads were damaged in any way.
  • Perhaps a positive note that came out of it is that it could have provided an explanation as to why the Tachyon sustainer failed to open its parachute during the boosted flight with Damo's 6-splice booster. On that day I noticed that the servo had also come apart, but thought it was the result of the impact. The servos were attached in a similar manner on both rockets. With the large booster using a full bore nozzle and no water in the sustainer, it was a very fast takeoff. This might have caused the servo to come apart and stop functioning. The launch detect switch and flight computer had still worked after that impact and even turned the motor in the broken servo gearbox. The previous bent release pin hypothesis is now running second.

    I will now glue these motors together to make sure that doesn't again become an issue. I guess cheap servos weren't meant for this kind of punishment.
  • Fixes to J4 II are minor and we will be replacing all the couplings and bottles with new ones.
  • The third flight we flew Hyperon III again but this time the camera was pointing down. Due to the increasing wind, we decided on only 110psi to keep the peak altitude down, and reduce down range drift.

    Because there are only 30 seconds of video on the camera, I decided to start counting down while I was finishing activating it, figuring that 4 year old John on the end of the release cord would wait for the "GO" call.  Being as assertive as he is and since he was the director of launch control at the time he decided to pull it just after I said "1". .... although it was my second drenching for the day, we did get a great flight in. We also got good onboard video of the foam trail as the rocket ascended. The parachute deployed just before apogee so it all ended up well.
  • We didn't get a whole lot of good ground video this time for a number of "drenching" and "sun-in-the-eyes" reasons.
  • Due to the increasing winds we moved the launcher up wind another 20 meters and lowered the launch pressure. On the in-flight videos it is quite evident to see the buffeting caused by the gusty wind conditions.
  • The last flight was again with foam and we made a good ground video of that. The foam flights were pretty straight on this day, but the rockets used the 9mm nozzle.  On the last flight the rocket landed on the hard paved car park. Even though it landed under parachute the nose cone still hit pretty hard  and the battery came loose and hit the servo motor .. and you can guess what happened to the servo motor. ... they definitely need to be glued.
  • All things considered, it was still a good day, and proved FC V1.3.2 works well. We will put the flight computers to work now on some of the experiments we have planned.

(If the video does not play, try the latest Flash player from Macromedia)


It was evident the damage high G-forces can make to the electronics. Everything has to be secured really well.

We were lucky no one was hurt when the rocket exploded. Safety glasses will be mandatory at every launch from now. This stuff is dangerous.

Small kids pulling the release cord should be encouraged to practice counting backwards and following instructions exactly.

Flight Record

Launch Rocket Pressure (psi) Nozzle
1 Hyperon III 120 9 1.25 Camera flight. Good vertical flight. Parachute opened near apogee, drifted long way down range. "7" setting on computer. Good landing.
2 J4 III 100 9 1.25 Catastrophic failure on launch pad. bottle base exploded. Minor damage.
3 Hyperon III 110 9 1.25 Very nice straight flight. Taped downwards looking camera to side. Good deploy and good landing. Used "7" setting on computer.
4 Hyperon III 110 9 1.25 Good flight, slowly pitching over into the breeze, but achieved 28.4 second flight duration. Landed hard on paved road. Minor damage to flight computer. Used "7" setting on computer.


  • We've also started looking into FTC. Damo kindly gave us some during our last visit. I hadn't seen FTC first hand before and was quite impressed with the strength so I ordered some from JR Turk. A few days later my package of four 5 foot lengths arrived. I was pretty disappointed when I found out the tubes had much thinner walls (0.5mm) compared to the tube (0.9mm) that I got from Damo. I didn't realise they came in different thicknesses. This means its not going to be able to hold as much pressure, but its not a total loss as these can be used for payload sections and other components. We will still pressure test them both un-reinforced and reinforced to see how they perform.
  • It appears that long term stresses on bottle couplings may be an issue. Polaron, J4 II, Acceleron appear to have all failed at the base after many flights and some hard landings. It may be prudent to replace bottles after a certain number of launches.
  • The battery contacts have been directly soldered to the wires to ensure good connections.

    After a number of hard landings with the on board cameras, the internal battery contacts have become deformed and stopped making reliable contacts. This was fixed by soldering a blob of solder to both ends of the battery, increasing the battery's length and making a better contact.
  • The total weight of the integrated nosecone and recovery section including batteries, flight computer, parachute and camera now weighs 182 grams.

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