Hi all,
Back in 2012 my team won the Innovation award in the UKAYRoC competition (British TARC) for a simple and effective way to limit the altitude of a rocket, to zone in on the target 800ft. It consisted of wrapping black electrical tape around the upper section of the rocket so that fine adjustments could be made by adding or removing single layers of tape. The idea being this adds only a small amount of weight (so we can stay within the 650gram limit) but increases the drag by quite a lot. It was quite effective and we placed 5th overall with with a tongue-in-cheek naming of the system as the 'Esconian Ring'. At the time we weren't able to get a hold of any F22 motors which the design had been based around, so instead we had to use the more powerful F52 and this resulted in a very large ring.
In 2012 we used the same idea for fine adjustment, but being able to use the motor the rocket was designed for the diameter of this ring was much smaller and we also tried to taper it. While we were happy to use drag to alter the altitude, we were aware that it was one of our biggest variables between flights so wanted to keep it as low as reasonably achievable.
One of our concerns was that the drag ring could be messing up the air flow over our fins making them less effective.
Could the drag ring be causing flow separation over the rocket body, and could it be preventing clean air from reaching the fins?
We believe that this could be the case and so to combat this problem, last year we toyed with suction techniques listed here https://www.rocketryforum.com/showthread.php?57811-Ducted-Rocket-and-Pressure-Gradient
This year to overcome the same original problem we are intending to attach a wrap of sandpaper in front of the drag ring. The aim here is to force a transition in the boundary layer from laminar to turbulent over the drag ring as it is my understanding that a turbulent boundary layer is thicker and less prone to separation. The result being that more of each fin will be in cleaner air.
This is something we intend to experiment with over the course of the year, but what are peoples initial ideas? Does anyone think there is merit to this ides or are we creating turbulence and drag unnecessarily?
Cheers,
Esconian
Back in 2012 my team won the Innovation award in the UKAYRoC competition (British TARC) for a simple and effective way to limit the altitude of a rocket, to zone in on the target 800ft. It consisted of wrapping black electrical tape around the upper section of the rocket so that fine adjustments could be made by adding or removing single layers of tape. The idea being this adds only a small amount of weight (so we can stay within the 650gram limit) but increases the drag by quite a lot. It was quite effective and we placed 5th overall with with a tongue-in-cheek naming of the system as the 'Esconian Ring'. At the time we weren't able to get a hold of any F22 motors which the design had been based around, so instead we had to use the more powerful F52 and this resulted in a very large ring.
In 2012 we used the same idea for fine adjustment, but being able to use the motor the rocket was designed for the diameter of this ring was much smaller and we also tried to taper it. While we were happy to use drag to alter the altitude, we were aware that it was one of our biggest variables between flights so wanted to keep it as low as reasonably achievable.
One of our concerns was that the drag ring could be messing up the air flow over our fins making them less effective.
Could the drag ring be causing flow separation over the rocket body, and could it be preventing clean air from reaching the fins?
We believe that this could be the case and so to combat this problem, last year we toyed with suction techniques listed here https://www.rocketryforum.com/showthread.php?57811-Ducted-Rocket-and-Pressure-Gradient
This year to overcome the same original problem we are intending to attach a wrap of sandpaper in front of the drag ring. The aim here is to force a transition in the boundary layer from laminar to turbulent over the drag ring as it is my understanding that a turbulent boundary layer is thicker and less prone to separation. The result being that more of each fin will be in cleaner air.
This is something we intend to experiment with over the course of the year, but what are peoples initial ideas? Does anyone think there is merit to this ides or are we creating turbulence and drag unnecessarily?
Cheers,
Esconian