Today I performed 2 launches of the final prototype of WestonWocket, my Scout Troops first rocket.
Conditions were good, with only a slight wind on the common, although the rocket did fall over whilst attached to the launcher once during a slight gust. The launcher is a simple one taking from a kit from Maplins. I tightened the wing nuts as hard as I could, but the launcher was never meant to support such a long rocket. A new launcher will definitly need to be constructed if the rocket is to be flown in less favourable weather.
The first launch was carried out with the rocket being pressurised to only ~70 psi. Being its maiden launch, I didn’t want to risk putting any more pressure in it not knowing its structural strength. On lift off the rockets flight was pretty much vertical and turned over 180 degrees at apogee. As a rough estimate I think the rocket achieved a height of about 120-150ft, not bad for the first launch!!!
As the rocket built up speed towards the ground I started to get worried that the parachute would not deploy and open in time. Luckily the Optical Apogee sensor did its job and the parachute deployed in time and the rocket drifted down for the last 30ft.
Having confidence in the construction of the pressure vessels and knowing that the parachute mechanism worked, I proceeded for the second launch, this time with a launch pressure of 85psi. Whilst the rocket was upside down being refilled, I took the opportunity to re-arm the apogee sensor. I filled the rocket with slightly less water this time which I think was nearer to the optimum fill level.
On lift off the rocket accelerated much faster, whether this was more to do with the lower volume of water, or the extra 15psi of water I don’t know, but the rocket probably achieved near 200ft or above. Once again the apogee sensor deployed the parachute, maybe even a bit earlier this time and the rocket was gently brought back down to earth.
Due to me only bringing 2L’s of water I had to call it a day, but I am happy that the prototype flies and recovers itself.
I would like to run the rockets parameters through a simulator and try and work out what the optimum fill levelshould be and also get a more accurate idea of the height achieved.
Lessons Learnt
- The pressure vessel and Robinson couplings are capable of holding ~85psi.
- The Apogee sensor seems very reliable (well 100% success so far)
Actions
- Run rockets weight and size through a simulator to work out how much water should it be filled with and what sort of height I should expect.