|Date:||30th October 2021|
|Location:||Whalan Reserve, Australia|
|Conditions:||windy, mostly sunny|
|Members:||JohnK, GK, PK|
Today we wanted to try a long deployable boom on a rocket so that we could get a different perspective on the rocket deploying the parachute. We have flown a fixed boom previously on day 161 but this caused a lot of drag on the way up. The idea with this one was that during the fastest part of the flight, the boom would be stowed and then deploy after the rocket had slowed down.
The boom is attached to a ring mounted just above the fins. The boom is allowed to freely rotate about these attachment points, but to stop it swinging all the way back, we tied a short string between the rocket and the boom that then would prevent the boom from swinging out too far.
Deployment was achieved using a servo timer II and a servo motor with a rubber band stretched around the rocket and holding the boom down. The timer would be set to deploy the boom a couple of seconds before the parachute was deployed. Here is a highlights video from the day:
The rocket was pressurised to 120psi and foam was added to the 1.8L of water. The parachute delay was set for 5 seconds, and the boom deploy was set for 3 seconds. The boost phase of the rocket looked fine, until around maximum speed at which point the boom started to bend back away from the rocket due to the drag, until the boom snapped at the point where it was attached. The boom had snapped before it even had a chance to deploy. The camera and top part of the boom tumbled down and landed safely. The parachute deployed on the rocket right around apogee and the rocket landed safely. Other than the broken boom everything survived well. The view from the onboard camera was great as it showed the boom bending backwards before finally snapping. It also captured a couple of nice frames of the rocket still powering away.
For the second flight we shortened the broken boom by taping the broken struts together. This shortened the boom to extend just above the rocket which would mean there was less chance of the boom bending away from where it was held down. We also increased the boom deployment delay from 3 seconds to 4 seconds just so that it would deploy when it was going a little slower. The pressure and water amount were identical to the first launch. The rocket accelerated well and deployed the boom just before getting to apogee with the parachute deploying about a second later.
The parachute and boom deployed well without issues and the camera captured a good view on the way down. The rocket landed in between trees and even managed to clip one of the branches on the way down, so we were lucky the rocket didn't get snagged on the tree. The rocket landed on the concrete path, and everything survived with the exception of the power switch for the boom deployment mechanism which was damaged as it was protruding out of the rocket.
Those were the only two flights we did on the day, so we were quite happy with the results, and we may fly this combination again, but perhaps let the boom swing freely to see what would happen.