This is a challenging design based around the 'Trident' ducted deployment system. It has a really low 'sweet spot' for 'B' engines.

Length: 49.01"
Diameter: 1.04" (ST-10, ST-5)
Fin Span: 7.08"
Weight: 3.93 oz


B4-4......398'......Dv 7 FPS
B6-4......408'......Dv 13 FPS


A8-3 and C6-5/7 engines not recommended.

All engine selections reach safe flight V on a standard 36" x 1/8" rod.

Enjoy!

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Frontier Settler.rkt (164.7 KB, 95 views)

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Craig,
Beautiful model! What is the Dv for a C6-3?
Thanks,
Allen

Hi, Allen.

The numbers were horrible for all three C6 engines. A pair of C6-3's deploy at over 120 FPS in the uphill portion of the flight. It was over 50 FPS uphill for the C6-5s, and over 30 FPS downhill for the C6-7.

Even if we had a C6-6 engine, it would still deploy uphill at over 26 FPS.

Running Quest C6-5's didn't improve the numbers any. These were also deploying over 50 FPS uphill.

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Craig,
Have you found from actual experience (flying a made rocket) that the Dv's are reasonably accurate? IOW, do you think shooting a made model with a C is a worthwhile experiment, given one is satisfied with the B launch?
This is one I am interested in making. If the B launch went well, I'd be tempted to try a C6-5; I tend to build a little heavier than some folks. The extra weight is mostly in the finishing process for me (plus I like epoxy).
Looks like in this case, a little extra weight might be good?
You are the expert here; what do you think?
Allen

What I've experienced is the "explosive opening" of parachutes where it opens so rapidly and so hard that it either rips out the lines, or tears the sheet. It sounds like a gunshot, even from altitudes over 500'. When I check out the conditions later on RS, I've seen that the Dv has generally been over 25 FPS. Reefing the lines might help some.

Before I would add mass to the model, I'd experiment with added "drag components" and altering the aerodynamics to adjust the flight profile. Added mass means added stress on the parachute, which is the whole issue to begin with. There are ways to adjust the Dv without adding a lot of mass, and I'd rather look into these first. A little drag often works better than adding mass, it's just finding the best general compromise.

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Add detail to the rocket such as hydrogen or atmospheric sampling scoops, deflector arrays, antennae dishes, bulbous fin tips/instrument pods, etc. and use thicker balsa fins to make the model more draggy. From there, add a bit of weight until it works out with the C6-5's. The actual detail bits can vary based on whether you want the model to look like a scientific research, civilian passenger, military, or other type vehicle.

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I love sanding.

You beat me to it. I was going to suggest up-scaling the fins 10% to add some drag, but I think I like your idea for sampling scoops, etc., even better.

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Good suggestions, Tim, and in line with my idea that a little drag in the right places works better than adding ballast. I'll try to add some detailing tonight and run the sims again.

---

"...A little drag in the right places..." Should he wear a sun dress, or hip-huggers?

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I made some adjustments to the aerodynamics, and found something of a "sweet spot" for both the Estes B6-4 and the Quest C6-5. This can be called the Mk II version. Please note you will need a 48" x 3/16" launch rod now. It takes a full 30" of guide length to reach safe flight V, but with the launch lugs so far up from the rear edge, you don't have enough length on a standard rod. Better safe than sorry.

Length: 49.50"
Diameter: 1.04" (ST-10)
Fin Span: 10.08"
Weight: 4.31 oz


B6-4.......322'......Dv 16 FPS
C6-5Q......800'......Dv 27 FPS (Reef the parachute shrouds)


These values are averages across six simulations with each set of engines. Due to file size limitations, I had to reduce the number of runs in the posted file by half. Be sure to run your own simulations and calculate the averages to get a bigger picture.

Also, the Estes B4-4 was removed as the Dv numbers were beginning to rise well above the original values.

Enjoy!

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Frontier Settler Mk II.rkt (236.9 KB, 80 views)

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