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Day 192 - Stager Tests, filming apogee

Date:	28th October 2017
Location:	Whalan Reserve, Australia
Conditions:	Sunny, wind 5-10km, 28C
Members:	PK, Paul K, John K, and GK

More 3D Printed Stager Flights

Today was a bit of a repeat of last launch as we wanted to do more stager test flights as well as seeing if we could film the rocket at apogee.

During the week we built a proper second stage rocket to test the stager with. The sustainer is based around a single 1.25L bottle. We specifically built a lightweight deployment mechanism for the sustainer in order to help the rocket get off the ground, Our regular deployment mechanism for this diameter rocket weighs about 132g (including nosecone fairing) but this one we managed to get down to 58g. We used small lightweight batteries and only minimal amount of corriflute. We also used one of the small 3.7g servo motors. The whole nosecone is also shorter. All the electronics for the stager were mounted on the inside of the fairing and covered with several layers of tape to prevent them from getting soaked after staging.

First Flight

For the first flight we put 250mL of water in the sustainer and 1L in the booster. we only pressurised the rocket to 110psi as the booster bottle was old. We also adjusted the staging time down to 1 second from 2 due to the expected lower boost.

With the added weight, the rocket took off slower than with just the empty bottle like we used on day 191. The rocket angled over a little after boost and before the stager activated. The sustainer tool off well and the parachute opened right around apogee. The booster parachute also opened in plenty of time to bring the booster to a safe landing. The sustainer also landed well without damage.

 

Second Flight

When we were setting up for the second flight we noticed that the STII didn't want to turn off, and the servo was not resetting to the default position. Some condensation did get into the power switch and onto the electronics and so we disassembled the fairing and then used the scuba tank to blow out any water. This did the trick, and so we decided to mount the electronics and battery on the outside of the fairing. We then prepped the rocket as normal and set it up on the pad again. We mounted a camera to the side of the sustainer so that we could watch it stage. The flight was good but the booster angled a little after lift off and by the time the stager activated the sustainer was perhaps at 45 degrees to the horizontal. The sustainer flew off nicely over the trees and landed safely behind them.

So over the 4 flights and 1 test release, we've been happy with how the stager is working. We will now redesign the lever geometry of the stager and perhaps print it before we make the aluminium version of it.

Apogee Flights

We had another go at filming a rocket from the drone as it passed through apogee this week. This time however, we added foam to the rocket to make it easier to see on the way up and also set the deployment delay to 4 seconds, so about 1 second before apogee so that the parachute canopy would open right around apogee. We filled the rocket to 100psi and positioned the drone about 300 feet up. The foam gave the rocket a bit of a boost and so it flew above the drone. Unfortunately we cannot pivot the camera above horizontal and so we missed the view of the rocket at apogee. On the second flight we positioned the drone right at 400 feet and released the rocket. This time John tracked the rocket beautifully right up to apogee which was level with the drone and you could see the parachute get ejected and then the canopy open. He then tracked it all the way down again. On the third attempt the rocket again flew just out of view but we were able to track it as it descended back into view under parachute.

Here is a highlights video:

So in the 5 flights over day 191 and 192 John managed to get 2 good views of apogee. I was realistically expecting that it would be a 1 in 10 shot because of all the factors involved with the unpredictability of each launch.

Flight Details