Single Skin Steerable Parachute

A custom designed parachute to be used in autonomous rocket recovery.

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For my high power rocket project I needed a parachute that was steerable and that had a decent glide ratio.

This parachute was developed to be similar in design to NASA parawings, rogallo wings, and ram air parachutes.

It has one central cylindrical cell and two conical cells separated by slight vertical ribbing.

The material is ripstop nylon, and the bridle is from 200lb test Kevlar line.

  • 1 × Ripstop Nylon
  • 1 × 200lb Test Kevlar

  • Additional Bridle Modifications

    J. M. Hopkins06/27/2016 at 00:04 0 comments

    I was able to travel to the beach again today to test out my next iteration of bridle adjustments. Regrettably the wind wasn't what I was hoping for, but I was able to test out my modifications to some extent, but another day of full wind is needed.

    Some background on my brake line implementation is needed to understand the modifications of the bridle:

    There are three main cells to the design, a central cylindrical cell and two conical cells separated by vertical rbbing. Forward thrust is created by the geometry of the trailing edge, allowing air to be scooped, and vented to the rear. The brake lines deform this rear edge of the canopy, changing the amount of thrust being vectored.

    The first version of my bridling allowed for the brake lines to deform the two conical cells rear edge, but not the central cell. This made for a very twitchy and fast response to controls which was not the most stable nor easiest to control.

    The new revision has changed the brake line attachments to include deformation of the central cell as well as the sides, with a staggered length between the lines, meaning that when the brake lines are pulled that the central cell is deformed first which creates a slight change in thrust, followed by the deformation of the conical cell which then leads to rapid changes in direction. The result is a much more stable design that is easier to control.

    In order to combat nose collapse in the face of oncoming wind from air column penetration, a slight amount of brake line needs tension and a fairly high wing loading is required (approximately 1lb/sqft).

    Again, I hope to have additional photos/video here during the next test.

  • Bridle Testing

    J. M. Hopkins06/20/2016 at 02:23 0 comments

    So one of the nice things that moving to California brings me is a consistent access to the beach and the winds that come along from the Pacific ocean. This allows me to finish my testing on the single skin steerable parachute, in this case bridle testing.

    The bridle allows the canopy inflation geometry to be modified to conform the parachute to optimal characteristics for stable flight. This series of testing, is to establish the correct line length for each support line to optimize the canopy in numerous ways.

    Inflation geometry must maintain shape in order to be effective, in this regard, canopy collapse is an issue that needs to be avoided, particularly in the face of increasing wind on the nose of the canopy. If too much horizontal air movement is combined with insufficient wing loading, then collapse and failure can be expected.

    Modifying the left, right, and center cell rear edge geometry, changes the characteristics of stable flight and control surface reaction time. Meaning brake lines are more effecient, and wing loading transfers canopy rigidity for forward velocity.

    Here is the test video, showing adequate control in 15-20 mph winds, but showing higher control surface reaction than anticipated (very twitchy). I believe that this can be altered by changing the center cell's rear geometry to transfer more of the air column to horizontal velocity, and relying less on the side cell velocity outputs.

    Basically it's working well, but isn't as stable as would be preferred. This can be accomplished by adding length to the rear canopy edge control lines of the central cell.

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maurissa wrote 05/30/2017 at 02:17 point

Interested in learning more about your single skin parachute and development process.

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Ted Meyers wrote 01/25/2016 at 04:17 point

What sort of wing loading do you have?  I've found documents suggesting anything from 0.5 to 1.5 pounds psf;  I'm thinking of trying 0.8 but that seems a bit high (when compared to a round parachute).   But a parachute may not be the best comparison here.

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J. M. Hopkins wrote 01/25/2016 at 11:07 point

Right around 1lb per ft^2, mainly because higher wing loading allows for a more rigid structure and helps prevent nose collapse at higher wind penetration velocities.

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Ted Meyers wrote 01/25/2016 at 15:30 point

Thanks!  That makes a lot of sense, and besides the extra rigidness, going faster helps with wind penetration.

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Ted Meyers wrote 01/18/2016 at 03:39 point

Wow, looks great!  I'm interested, it looks like a double keel rogallo wing?  I'm currently working on a single keel rogallo wing to be used for autonomously steering a rocket home, so I will be interested in following your progress.

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J. M. Hopkins wrote 01/18/2016 at 12:04 point

Very similar projects. Mine is essentially double keeled, the leading edge is different than NPWs and the keels are airfoil shaped, overall I'm very happy with it.

The central cell and side cells can be braked independently, but I'll probably mix them together for more stable, less swirly flight on the rocket.

I just finished my high power test fights of my newly designed I500 sugar motors which will lift my 3" avionics airframe.

My flight computer is done, but I need to add the autonomous control routines. I'll be testing first with RC cars :)

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