Dual Deployment Without Ejections

Discussion in 'High Power Rocketry (HPR)' started by nickrulercreator, Nov 12, 2018.

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  1. Nov 12, 2018 #1

    nickrulercreator

    nickrulercreator

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    Hello! The other day I posted on here about an issue with my Hyperloc835. This issue has been fixed, thanks everyone that helped (and thank you, Loc Precision).

    I now have another question. I'm considering changing how my dual deployment is done. The instructions call for the drogue chute to go below (toward the bottom of the rocket) the electronics bay, and the main chute to go above (toward the top of the rocket) the electronics bay. The motor's ejection charge would separate the rocket, releasing the drogue chute, and then at a selected altitude, another charge would blow the nosecone, releasing the main chute.

    Is it possible to only use the motor's ejection charge? For this, I'd attach the main and drogue chutes' shock cords together with a quick-link and put the chutes below the E-bay. When the motor's ejection charge ignites, both parachutes are blown out. The drogue chute would open, but the main chute would be held tight with Jolly Logic's Chute Release, until a designated altitude.

    I know this is not the conventional way of doing things (at least, from what I've seen on this forum and other places on the internet), but could it work? The only problem I see is the chutes getting tangled, but are there not ways I could keep them separated?

    Thanks for any help.
     
  2. Nov 12, 2018 #2

    BDB

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    This is definitely possible. It's how I did my L2 flight. You really don't even need the drogue chute. The bundled main chute will effectively act as a drogue. Just make sure to hold the rest of the rocket together with screws, plastic rivets, or glue (If you don't want to ever try conventional dual deploy).
     
  3. Nov 12, 2018 #3

    grouch

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    When did you get your L1? How many flight ps have you made since then?
     
  4. Nov 12, 2018 #4

    nickrulercreator

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    Got it this March, and since then I've flown rockets 4 more times.
     
  5. Nov 12, 2018 #5

    jjwb22101

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    The way to do this would be to just not have a separate drogue parachute, and use the still-folded main parachute as your 'drogue.' This is the standard way that the chute release works. Also, the usual way dual-deploy works is that the altimeter controls both the apogee and the main ejection, with the motor ejection as a backup for the apogee charge.

    What you're describing could certainly work, but I'd be worried about the main parachute getting tangled with the drogue on deployment.
     
  6. Nov 12, 2018 #5

    crossfire

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    Don't take this the wrong way but I think you should spend a little more time building and flying L1 rockets. Just slow down there is no rush moving up the levels.
    Have fun and fly safe
     
  7. Nov 12, 2018 #6

    OverTheTop

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    Sounds like a plausible method. There needs to be enough force to pull the main burrito out of the airframe and you are providing that with the drogue.

    What you suggest is not what is mostly done. Consider the advantages your idea has over the more standard recovery setups, and the advantages they have over yours. Question why it is usually done the other way, and why you want to go the other way. Remember to design for off-nominal recovery. eg. What happens if it only has a weak ejection charge? Will my main unfurl? We don't want flying fenceposts please!

    Swimming against the stream is not necessarily bad. SpaceX do it all the time :). Just consider your choice properly.
     
  8. Nov 12, 2018 #7

    Cameron Anderson

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    Don't slow down, keep going. Challenge yourself. I know people who fly twice a year and have better methods and judgement than people who fly monthly. There is usually someone there to step in before you do something truly stupid and there is always two or three people to stop you from doing something unsafe.
     
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  9. Nov 12, 2018 #8

    timbucktoo

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    I wouldn’t discourage it as it’s been done before and I’ve seen photos of successful deployments using said method here on forum. There’s a thread somewhere. I’ve tried it once and the problem I encountered were shroud lines getting all tangled. I think the secret is proper spacing between the drogue & main.
     
  10. Nov 12, 2018 #9

    crossfire

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    So you think his next flight after he gets his L2 should be his L3. Let me know where it maybe so I can stay away.
     
  11. Nov 12, 2018 #10

    nickrulercreator

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    I understand your concerns, but no need for this. I'm not planning to do L3 for a long time. I have the opportunity to get my L2 and I'm only asking a simple question, nothing is near decided yet. I'm only seeking others' input and advice, and what their experiences have been with a similar setup.

    Thanks, everyone else for your help. I'm going to continue doing research, see what others have done. I'm leaning more toward the charge out of fear of the shrouds tangling, but for now, that can change.
     
    Last edited: Nov 12, 2018
  12. Nov 12, 2018 #11

    nickrulercreator

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    That's what I'm wondering. I have an idea of what I'll use to keep them apart in the rocket during flight, but after ejection, anything's game. Using a quick-link to attach the end of one shroud to the other, essentially creating a single, huge shroud, and then attaching the chutes at different ends (drogue close to top, main close to bottom), is what seems best for something like this.

    Also, after the main opens, it will rise to become the highest part as the rocket falls. This could reduce the risk of the chutes colliding, especially if they're separated by several dozen feet of shock cord. It's really only when the main ejection charge ignites, and when the chute release activates, is when it is most iffy.
     
  13. Nov 13, 2018 #12

    Cameron Anderson

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    There is a reason going L1 to L2 to L3 doesn't have time or flight number requirements. I remember a reading about a kid who the first launch after his 18th birthday did L1, L2, and L3 in a single day. He had been flying for years with friends and family. His skills, not his flight log, proved his readiness.

    Level achievement is based on set standards, if you want time or flight requirements, talk to NAR or TRA and get them added. If you want tougher level standards, again, talk to NAR or TRA.

    We have prefects and RSOs and TAPs for a reason - ensuring safety, whether it's your first flight or your 100th. Evaluate based on skill and don't be the old salt under the sun shade turning your nose up at enthusiasm simply because someone doesn't meet your personal standards.
     
  14. Nov 13, 2018 #13

    dhkaiser

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    Flew my 4" Sky Scraper like that a couple weeks ago. Used one long harness with a loop 2/3 up for chute release and main with the drouge attached to the upper section. 4in Sky Scraper small.jpg 403A3077small.jpg
     
    Last edited: Nov 13, 2018
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  15. Nov 13, 2018 #14

    crossfire

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    I heard about the all 3 certs in one day. The flyer must have had a very good crew to get that done. Old salt lasts much longer under the sun shade on a rainy day. Whats the rush. Most of the time one who rushes through all levels will be out of the hobby in a very short time.
     
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  16. Nov 13, 2018 #15

    OverTheTop

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    He had been flying for years and had the skills. He set his challenge to get all three on the one day. His preparation was very good, well thought-out and not done in a rush, which showed in his achievements.

    It is not my choice for the journey, but I am not going to stand in his way just because it is an atypical unconventional approach.
     
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  17. Nov 13, 2018 #16

    nickrulercreator

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    This is very cool. Did you have anything to ensure the chutes stayed separated?
     
  18. Nov 13, 2018 #17

    Igotnothing

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    The layout you have described is basically HED - Head End Deployment. So it is done all the time. Apparently, not much is needed to prevent chute tangling, but I don't have much experience and usually go drogue-less.

    One thing to watch out for is the resulting CG when you put no chutes in the upper bay. It might end up a bit far aft.
     
  19. Nov 13, 2018 #18

    scsager

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    Motor eject with Drogue + JLCR ( maybe we can call this "deploy and a half"- instead of dual deploy)

    -Sure this has been done many times. Sometimes without a drogue at all.

    My recommendation is to use a ESTES PSII or BT80 size rocket with an F or G motor. Try doing this several times, to work-out a repeatable method to rig the shock cord and chutes that works well for you.

    Recovery is the hardest part of rocketry, and it's always easier and less expensive to try new methods on "scaled-down" rockets first.
     
  20. Nov 13, 2018 #19

    GalantVR41062

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    I have used the JLCR in my smaller rockets, did my L1 on my Argent drogue less.

    Make sure you have a good amount of tension on the rubber band, I had it hold the chute until hitting the ground, the 7oz rocket landed fine at 26'/s but still.

    My worry about single break JLCR deploy in that rocket would be the CG, that rocket was designed for hybrid motors(long motor). And having the eBay and main in the payload bay adds a lot of mass to move the CG up.

    ~John
     
    Last edited: Nov 13, 2018
  21. Nov 13, 2018 #20

    cherokeej

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    Just a little $.02 suggestion...

    Earlier in my rocketry career, I found that I could experiment around with recovery deployment methods, and learn a ton about the use of electronics, using inexpensive F and G motors in smaller, paper rockets, as well as I could with $160+ K motors in big, 'glass birds.

    I would suggest that route, playing around with the smaller, less expensive birds to figure out and learn what works and what doesn't, then impress all your buddies with a perfect flight on that big ol' K or L at the bigger launch. You might find that a little easier on the MasterCard, too.

    Just something to run up the flagpole...
     
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  22. Nov 13, 2018 #21

    Tim51

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    Over The Top mentioned the possibility of a weak motor charge failing to get the chute out, and I know from experience this is a real possibility - it's happened to me twice. The recognised issue with fast burning loads (eg Vmax) sometimes snuffing out the delay grain would also present problems (if you wanted to use those propellants). So whichever way you configure things, with heavy rockets going high, think about some kind of back up.
     
  23. Nov 13, 2018 #22

    dhkaiser

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    Packed as usaul, plenty of dog barf, folded the harness upto the main, place JL and main in then the harness up to the drouge and upper section. Worked fine. I did put a little extra BP in the motor discahrge. That Canvas Phenolic is pretty tough so little worry with the extra BP.
     
  24. Nov 13, 2018 #23

    timbucktoo

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  25. Nov 14, 2018 #24

    John Beans

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    Everybody's giving good advice, as usual.

    I guess I'd pitch in my vote for experimenting "low and slow" any time you're not sure about something. Keep the rocket in sight so that you can diagnose any problems, and consider putting a recording altimeter to capture the "real story." (My biased vote if you have the funds is to get an AltimeterThree for convenient immediate feedback). Having a graph from a recording altimeter takes the guesswork out of wondering when and where events occurred.

    Here's an AltimeterThree graph of a drogueless dual deployment. Despite not having a drogue, the descent rate is a modest 37 fps before the chute released near the ground (the release was set for 200 feet, but took most of 100 feet to inflate). Notice on the descent how straight (as opposed to curved) the lines are. That means the rocket in both phases of descent was falling at a constant rate (terminal velocity) during each phase. Only in very short curved sections is the rocket accelerating or decelerating. You can see a couple of places where the slope suddenly shifts on the way down; that's the rocket tumbling and rotating and finding a different orientation and descent rate. There are all kinds of things you can learn from a graph like this if you're into that sort of thing and it's interesting to put to verify what you "think" you saw.

    [​IMG]
     

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