OccupyMars
New Member
I am on a student team that is in the design phase of a 10 foot tall, 6 in diameter HPR. There will be one shock cord connecting the booster section to the drogue chute and the avionics bay (forward of the booster) and another shock cord connecting the avionics bay to the main chute and payload/nose cone (forward of the avionics bay). I understand that deciding on a shock cord length is pretty subjective but I would still appreciate any thoughts. Here are my questions.
1. Most people refer to their shock cord as one continuous piece when referencing the 3-5x body length standard for a shock cord, even when talking about dual deployment. Does this mean they took a 3-5x shock cord and used it for both the main and drogue chutes by cutting it into pieces or used two separate 3-5x shock cords for main and drogue chute deployment?
2. I have seen some posts about drogue vs. main parachute shock cord lengths with most people saying the main chute can have a shorter shock cord because the drogue has a higher chance of entanglement. I would have thought it was the other way around?
3. I have also seen some posts about the fact that you can oversize your drogue parachute and then your components will dangle next to each other, causing main chute deployment issues. They implied that a higher velocity is necessary to get your booster, upper airframe, and drogue chute to be separated into a "triangular" shape. Could anyone explain this phenomenon further? I am trying to decide between 50 and 75 ft/s for drogue descent.
4. I would like to place the drogue chute closer to the booster section on the shock cord so as to reduce the drogue deployment/inflation loads on the avionics bay. The idea is that if the drogue chute was closer to the avionics bay there would be a greater force pulling on the avionics bay and there could be a risk of shearing the shear pins for main chute deployment early. I got this idea from a previous post but now I am questioning if it makes sense. The drogue should be pulling with the same force on both components regardless of the shock cord length, right?
1. Most people refer to their shock cord as one continuous piece when referencing the 3-5x body length standard for a shock cord, even when talking about dual deployment. Does this mean they took a 3-5x shock cord and used it for both the main and drogue chutes by cutting it into pieces or used two separate 3-5x shock cords for main and drogue chute deployment?
2. I have seen some posts about drogue vs. main parachute shock cord lengths with most people saying the main chute can have a shorter shock cord because the drogue has a higher chance of entanglement. I would have thought it was the other way around?
3. I have also seen some posts about the fact that you can oversize your drogue parachute and then your components will dangle next to each other, causing main chute deployment issues. They implied that a higher velocity is necessary to get your booster, upper airframe, and drogue chute to be separated into a "triangular" shape. Could anyone explain this phenomenon further? I am trying to decide between 50 and 75 ft/s for drogue descent.
4. I would like to place the drogue chute closer to the booster section on the shock cord so as to reduce the drogue deployment/inflation loads on the avionics bay. The idea is that if the drogue chute was closer to the avionics bay there would be a greater force pulling on the avionics bay and there could be a risk of shearing the shear pins for main chute deployment early. I got this idea from a previous post but now I am questioning if it makes sense. The drogue should be pulling with the same force on both components regardless of the shock cord length, right?