New Multi-stage Rocket

After last month's flight of the bigger two stage rocket we decided to see what would happen if we added the drop away boosters to the main stage. The Baryon II booster was fitted with an extra 2L bottle from bottom part of Polaron VI with the booster retention tubes, guide rail lug and fins already attached.

 

We kept the fins from the Baryon II booster, but lowered them in order to keep the Cp as far back as possible. We only needed to attach the guide rail lug and top booster retention tubes to the main stage and the rocket was ready.

 

We also added adjustable sustainer supports that were placed at the bottom of the aluminium tubes. These were designed to help the rocket remain as rigid as possible at the staging mechanism during the higher G loading  when fired with the boosters. Otherwise the sustainer and boosters were unchanged from the previous launch day.

First Pyro Rockets

Darren from Suburban Rocketry gave the kids a couple of kit model rockets last launch day. So the kids and I had a fun time building and painting them. We launched both of them during this launch meet on A10-3s which made them zoom up pretty fast. Paul is already asking if we could build a bigger pyro rocket for next time. Looks like the pyro rocketry bug is starting to bite.

 

Not having launched a pyro rocket before we had Darren walk us through the process of properly packing everything and getting the motor fitted.

Launch Day Events

• Setup of the rocket was quite uneventful, although it does take about an hour to set it up for the first time. We needed to double check everything since I haven't written a checklist for this rocket yet. We normally would fill the main stage once it is on the pad, but because it had the stager attached to the top, we had to fill it inverted prior to placing on the pad. This posed a problem because it is quite fiddly to get all the booster pins lined up with all the tubes and having to hold the nozzle closed makes it even more tricky.
  
  A few weeks ago we were contacted by Jan Kurčinka, a water rocketeer from the Czech Republic, who told us about an idea he uses to prevent water from leaking out of the rocket while placing it on the pad. He basically cuts out a small circle of ordinary paper and sandwiches it under the seal in the nozzle. This prevents the water from draining while it is being handled, but as soon as you start filling the rocket the paper already water logged easily punctures. During the thrust phase basically all the paper covering the whole is ejected.
  
  We ended up using this technique to get the main stage on the launcher.
• We filled up the rocket to 120psi and launched. The rocket went mostly vertical and the boosters dropped away at the same time again as expected and all the parachutes opened well. The foam powered main stage continued to produce good thrust for another second or so, but then started tailing off. However, there was no separation of the two stages. The rocket slowly arced over and started heading down.
  
  Perhaps 2 seconds before impact the sustainer's flight computer deployed the parachute which caused the entire rocket to swing around and stage at that point. Staging allowed the booster to open it's parachute. The sustainer also under parachute thrashed around a little as it's pressure was released and both landed well. Although they landed well it was a close call because they landed fairly close to the crowd.
  
  We weren't sure why staging did not happen when expected, so we decided to stretch the piston spring in the Mk2 stager to allow it to activate at a higher pressure. There are a couple of other possible candidates for the failure that we will need to investigate.
• The second flight setup was identical to the first flight. We launched it at a slightly higher pressure of 125psi.
  
  The flight was almost exactly the same as the first one. We had good boost from the boosters and they separated well again and landed fairly close together on the ground. The main stage continued to produce good foam thrust and again failed to stage.
  
  The sustainer opened its parachute again well above the ground although at fairly high speed. This caused staging again opening the main stage parachute. Again the rockets landed well and fairly close to the crowd.
  
  After that we decided against another launch as what we thought was a fix, obviously wasn't. It is always better to bail out early than risk damage to the rocket, or targets on the ground. 
• We then launched the two pyro rockets. They both flew well, but the overcast sky made it difficult to see. The second rocket failed to eject the streamer properly although the nosecone came out. As a result it returned to earth a bit faster than it should have. Because the rocket is so light it suffered no damage, and will fly again.
• After that we were happy to watch other people's pyro rockets and some of them were very impressive in terms of speed and noise. In particular the Barracuda and Darren's SR Viper which had a spectacularly fast takeoff. There were a couple of other rockets of note like Nathan's two-stage Noodle which would have gone above 1500 feet, for the rest I do not have owner or rocket details. When photos become available from the launch a link will be included here
  
  Unfortunately most of my footage of the pyro rockets was into the sun so it didn't turn out very well. :(.

 

Observations

Although the rocket did not stage when we wanted it to, we did learn a few things from the flights.

• It isn't too difficult to launch a more complex rocket with multiple separate components. There also weren't any leaks we could see. This was one of my main concerns with the configuration as there are a lot of different places that leaks can develop. Every moving part was also greased up with silicone grease.

• The sustainer CF support tubes are working well in keeping the sustainer and main stage well aligned under higher G loads.

• The Mk2. Stager was able to withstand the higher Gs when launching with boosters.

• The sustainer's main parachute line was strong enough to withstand opening at high speed and with a large load attached.

• The piano-hinge parachute deployment between stages is working reliably.

• We now have some good flight performance data from the altimeter, ground and in-flight videos for this kind of rocket. This will allow us to adjust timing and thrust appropriately.

• Entire rocket was stable in flight.

• We now know that we can lift a ~2Kg payload to about 240 feet with the this particular main stage and booster combination.

At the end of the day we were fairly happy with the performance of the rocket. With the complicated design we weren't surprised that something didn't work. We were just glad to get it off the ground and the fact there was no damage to any of the rocket segments after two flights was a good thing.

We're fairly confident we can find the cause of the misfire of the staging mechanism, and fly this configuration again next time.

Next Update

In the next update we will cover the details of the new test stand we've been working on.

Flight Details