Review & Advise on L1 attempt Flight Profile, please

Discussion in 'High Power Rocketry (HPR)' started by Curtis Enlow, May 27, 2019.

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  1. May 27, 2019 #1

    Curtis Enlow

    Curtis Enlow

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    This is the sim profile I get in OpenRocket for my stretched High-Power/Dual Deploy LOC Super IV using an AT I154J-10A into a 38mm RMS 720 case w/spacers.

    Please feel free to comment on any red flags, issues or confirmation of the motor choice/profile (to calm my Newbie anxiety!) for the flight profile before I order.

    (Also, what does the 'A' stand for on the delay? I can't find any info on the designation)

    [​IMG]
     
  2. May 27, 2019 #2

    boatgeek

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    How much does the rocket weigh all-up? If I'm reading the chart right, is has about 3.5-4G acceleration off the pad. I would like to see a little more (4G is the minimum, 6-10 is nice). Is the sim built off of all-up weights with mass overrides? If not, you should check that out as well.

    1800 feet is a nice altitude for a 4" rocket. You'll have easy sight of it all the way up and down.

    Ground hit velocity at 30 ft/s (if I'm reading the chart and doing the units conversion right) seems a little fast. Most people like to be in the 20-25 range, though landing a solidly-built rocket on sod at that speed isn't likely to cause damage.
     
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  3. May 27, 2019 #3

    jpoehlman

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    A certification flight is generally an anxiety producing event for most people. The rules require you have to build the motor in observance of you cert committee. My recommendation, remove that stress from your day and fly a DMS motor.

    That said, I flew the I154j in a 3” fiber glass ISQY Tomahawk this past weekend. We has a 12-15mph surface wind. For my 8 lbs and that motor, the result was a relatively low speed off the rail and a significant weather cocking. The flight was at best a 45 degree angle up wind. Electric deployment worked great, but walk was still long given the up range trajectory.

    If you have lite winds you will probably will fine, but if you are wanting to remove extra stress on your day, you might want a bit more off the pad and a the ease of drop and go!
     
  4. May 27, 2019 #4

    David Schwantz

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    Hi Curtis, LOC is a great choice, I flew both 1 & 2 with a LOC kit. As long as you use good materials and have built her well, with a good preflight she will fly herself. Sit back, watch and have fun. Good luck.
     
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  5. May 27, 2019 #5

    Curtis Enlow

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    Hey Eric, thanks for the input.

    I am using a 48" Spherachute which, according to her sizing chart, is good for 3.4 - 6lbs t sea level. It was a little confusing finding the CD of a hemispherical chute as some sources said .75 and some say 1.5 when I ordered. But my all-up weight is now 6.3lbs/2865g with the I154J-10 (I didn't anticipate needing the size of motor I do to get a proper flight profile and the weight was higher than i anticipated) and any increase in altitude/temp from atmospheric standard is going to reduce that max spec for the chute even further. I also have a 12" Spherachutes drogue, but I wouldn't imagine that will contribute enough to affect the descent rate...?

    Looks like I am going to need the 54" chute whose stated spec is good for up to 7.65 lbs. Probably good to have a stable of chutes for the future...that's what I'll tell myself ;) Oddly enough, the 'Lower opening' of the 54" is the same as the 48...? So I'm not sure that open Rocket will give me an accurate descent simulation if the CD and opening size don't change.

    I think I will definitely need an 8' rail.

    Of course, i modeled a number of motors, but many of them that had the altitude range I wanted had shorter delays that were firing off well before apogee :(
     
  6. May 27, 2019 #6

    Curtis Enlow

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    I'm now concerned about the descent rate at main deploy, around 40 ft/s. Do i need a bigger drogue??
     
  7. May 27, 2019 #7

    rharshberger

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    Actually smaller is better in this case 40fps for a drogue is slow imo, however in the event of the main failing to deploy fully/properly 40fps is ptetty survivable. I aim for between 60 and 75fps under drogue, it personal preference (and iirc OR doesnt bitch about high opening speed of the main under 75fps).

    About your motor do you have a 5:1 thrust to weight ratio? If you do you will be fine, also are considering the USABLE length of an 8' rail....if your rail buttons are 6" apart and the rocket is stood off the pad/bottom of rail 6", that 8'rail is effectively 7' long...

    If you need one I have a 60" hemispherical chute you can borrow at TCR if needed, that chute brings a 6.5lb rocket in about 20fps.
     
    Last edited: May 27, 2019
  8. May 27, 2019 #8

    Curtis Enlow

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    I was wondering because OR is giving me a warning about the vertical speed at recovery deployment, but it evidently doesn't differentiate between Main and Drogue.

    I do have heavier duty gear on the drogue (1/2" Vs 7/16" nylon strap on the main).
     
  9. May 27, 2019 #9

    Banzai88

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    Drogue rate is at the intersection of personal preference and flying the field. OR alarms, I believe, at something above 65fps for main deployment.

    Plenty of perfectly good flight profiles are drogueless. Likewise, it's perfectly valid to change the drogue size and go larger or smaller based on high level winds for the day (speed and direction).

    Me, I size for about a 45-50fps for the initial flight, and adjust up or down as my 'baseline' drogue from there.
     
  10. May 27, 2019 #10

    Curtis Enlow

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    With the I154J-10 there is a peak of 170 newtons and avg of 154 newtons. If my calculator is correct that is 38 lbs/force and 34 lbs/force respectively for 12.6:76 which is better than 1:5...? (my math sucks, so....)
     
  11. May 27, 2019 #11

    mikec

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    A means "adjustable".

    If this is your first dual deploy flight, I would strongly recommend you not use dual deploy. A cert flight is the wrong time to be doing something new IMHO when you could have a fine single-deploy motor eject flight.
     
  12. May 27, 2019 #12

    boatgeek

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    You'll dump half a pound of propellant out the nozzle on the way up, so your chute only has to hold 5.8 lbs. If that's within manufacturer specs, you're probably fine. Tri-Cities isn't all that high altitude and the drogue helps too. You can tune up the drag coefficient when you have altimeter data to work off of.

    If you don't already have the motor, you might look at the I211W-14 or the I225FJ-14. The I225 is pretty comparable to the I154 in terms of total impulse, so altitude should be similar. It'll just give you a little more oomph off the pad. It's also a smoky motor if that's what you like. The I211W has 20% more impulse, so it'll be quite a bit higher. The peak thrust is also higher, but not so much that you'd be in trouble with your airframe. If you don't already have a casing, you could probably step down a case size to the H148R-14 or the H242T-14. All that said, the I154 should be just fine as long as it's not howling windy. You definitely get style points for certing L1 on an I!

    For CTI motors, the "A" on the end means the delay is adjustable. I don't know if Aerotech does that as well. You might check your sims too to see if you have the longest delay possible set. I've often wondered why OR is giving me a terrible altitude before discovering that I had a 4-second delay set when I needed 10.
     
  13. May 27, 2019 #13

    rharshberger

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    Based on the 6.3lbs RTF weight given earlier the 170 ns of max thrust offered by the I154 is good for 6:1 which should be sufficient given that it occurs in the first .25 seconds of the thrustcurve.
     
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  14. May 27, 2019 #14

    Curtis Enlow

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    Good points, thanks, Eric!

    I actually like the White motors, though the smokies probably help with tracking if it's overcast or partially cloudy. I will look into those, though time is crunching and I have a three-day business trip starting tomorrow and with ground shipping the window is slowly closing unless I can arrange with a vendor to have the motor I will need on-site.


    I'm not averse to getting the L1 on the stock IV, and trying the DD on another day, but I would also like to try and do a shakedown maiden on a 'G' just to make sure that nothing goes awry at mid-power.

    I do have decisions to make...
     
  15. May 27, 2019 #15

    Curtis Enlow

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    That appears to be the case if that is relative to Vertical Acceleration, there is a tiny additional bump at about .5/sec but the great majority of the acceleration is at about .25/sec.
     
  16. May 27, 2019 #16

    rharshberger

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    Just a heads up at 6lbs a G motor is out of the question unless several conditions are met.


    1. Rail Exit velocity must be a stable speed...which means a long rail...

    And

    2. Electronic deployment, from several personal experiences on a 4.5lb rocket a G76-4 is not a short enough delay ( especially if you get a "bonus delay").

    3. I may remember later something else.
     
  17. May 27, 2019 #17

    Curtis Enlow

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    Oh, the G would be in the stock IV configuration! No, the DD version with the AV bay wouldn't clear the tower ;)
     
  18. May 27, 2019 #18

    OverTheTop

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    Landing speed looks to be about 27fps. This is probably ok if you have soft landing terrain and your fins are forward of the rear where they are safe from damage on landing.

    Check you rail speed as you leave the rail (simulation). IMHO if you are above 40fps when you launch (and the wind is not strong) you will have no problems. Simulate with the rail length available for launch and see what you get.

    Simple for a cert flight is lower stress. If you want the added challenge of DD then go for it. Personal choice. Personally I like electronic deployment as it gives apogee every time and you are not relying on delays which can be quite variable. Having said that, I ran motor eject for my L1. I went DD for my L2 flight.
     
  19. May 27, 2019 #19

    boatgeek

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    Valid points. Rich could tell you if they are expecting to have a vendor on site.
     
  20. May 27, 2019 #20

    rharshberger

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    Looking into it now, not sure what motor vendor if any we will have on site. Most of them are at FITS this weekend.
     
  21. May 27, 2019 #21

    Curtis Enlow

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    Is HAZ per item or per order?

    With Ground can I even get an order in less than two weeks?

    If so, who is most reliable, with the quickest shipping and best prices?

    You can PM me with suggestions if you like.
     
  22. May 27, 2019 #22

    timbucktoo

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    Hazmat is per box per order. If everything fits in one box, one fee.
     
  23. May 27, 2019 #23

    boatgeek

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    You can definitely get a ground shipment in a week and a half. I don’t know reliability of Aerotech vendors though. If you already have the I154 in hand, I would definitely fly that.
     
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  24. May 28, 2019 #24

    rharshberger

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    Just got confirmation that Bob Grossfeld of Sun River Nature Center will be at the June launch as a motor vendor. I would contact Bob and see what motors he has if you decide to use somehing other than an I154J ( which should work fine btw).
     
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  25. May 28, 2019 #25

    MikeyDSlagle

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    A more complete sim file would help.
    My L1 bird weighs about 4.5 lbs and I am leery of flying it on the I154 from the 6' rail. And I certed using the H123W. It would definitely go on the longer rail. 6.5lbs..I don't know. My math gives a thrust to weight of 4.32 to 5.43 depending on what point in the thrust curve you use. On an 8' rail you will be around 43 ft/s (that's about what my cert flight was), but you will likely only get 7' of useable rail, as was mentioned. Tripoli calls for 3:1 minimum but most folks like 5:1. I love slow liftoffs but 40 ft/s would be nail biting on a cert flight. The BlackJack motors have less punch than most of the others. Any other motor in that case would work great though, except the I59. You would not regret doing the flight on the I211W. Or step up to the I195 in the 600 case if you must have the BlackJack. It's only 5 bucks more. Still should stay below 2000', easily visible. I've flown my Tyrannosaur to 6400 and it was visible the entire time.

    Follow the instructions included with the motor and you will be fine. I tape the instructions to the table and lay out my pieces. Biggest thing is watch the infernal delay element and spacer. Make sure you don't put the stupid things in backwards. Doubly so if the delay is drilled.

    My second motor to build was my L1 flight. That was also the first time I used electronics. I used it for apogee deploy and left the delay undrilled for backup. Now I take out my motor ejection charge and use it in my charge wells; when I get a plugged bulkhead I will be done with delays altogether. All but the occasional LPR flights get electronic ejection of some sort. I trust electronics way more than drilling the delays.

    You mention a drogue so you are planning dual deploy. Let the electronics do the work, leave delay a bit long or leave it out altogether.

    I got for descent under drogue around 70 ft/s. I usually go drogueless, as I have had the drogue tangle on me twice. Main worked fine and the rocket landed safely and softly but a stickler may, saying "MAY" here, fail you if the drogue tangles. But I find that unlikely as long as the main does it's job.

    Shakedown on a G wouldn't prove anything if you don't fly it in full up cert configuration. Shakedown on an I211, then fly it on the I195. ;)


    I have never ordered a HazMat order but Chris from CSRocketry usually ships next day.
    https://www.csrocketry.com/rocket-m...rotech-i154j-10a-black-jack-rocket-motor.html

    Have fun, relax and post photos/videos.
     
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  26. May 28, 2019 #26

    Curtis Enlow

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    Just briefly, guys, as I have a biz trip tomorrow, but thanks for all of your input and suggestions; it's all very much appreciated.

    When I had the basic empty weight down I went through the motor selection option in OR and started plugging in different motors, mostly to get a big picture of what kind of performance they were going to show in the plot, and I was a little surprised to find that many that got me in the neighborhood of 1,500 ft + had very inappropriate deployment delays, many firing off well before apogee.

    I don't know how up-to-date the database is, but while the W motors are my favourite, visually, most were definitely not working out in the plots.

    I do have an RMS drill tool, so I can always adjust downward, but working my way down the motor list the I154j-10 was the first one I tried where apogee and deployment crossed at the same time (without taking me to 3K feet, anyway).

    Clearly, matching motor to airframe is a dark art! As much as I would love to fly the DD version (I don't get out to the desert very often, and have done so much work on it) I might - depending on on-site vendor selection which will have to wait until Thursday to contact - have to plan on an L1 pop-at-the-top and have some hiking shoes ready...

    Thanks, again!

    C
     
  27. May 28, 2019 #27

    rharshberger

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    I have checked Curtis's OR file (and I will probably be the one RSO'ing his rocket in a couple of weeks), no major issues really but a few small things that were throwing the sim off. Now showing 47fps rail exit from an 7' effective rod (9' or better is over 54fps) on the I154J, and an apogee of 2100' (optimistic as the sim has no rail buttons on it, so the 1800' is probably closer to correct), an 18" drogue produces a 55fps descent, and the landing velocity on a 48" main is 20fps. Given the typical flying conditions at our location the numbers are looking good, if its a bit windier than normal but still within reason we can load the rocket on the 14' rail which increases the exit velocity to 67fps
     
    Last edited: May 28, 2019
  28. May 28, 2019 #28

    Nytrunner

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    Is this still in effect? I've never witnessed anyone ask to see the motor built on cert flights
     
  29. May 28, 2019 #29

    Banzai88

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    Yes. There are a LOT of things that are supposed to be asked of an L1 that seldom are. I contend that if the certifying officials were following the checklist we would have fewer problems overall.
     
  30. May 28, 2019 #30

    rharshberger

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    It is still in effect, however with the availability of multiple SU/DMS motors we are seeing fewer numbers of motors requiring assembly on the day of cert.
     

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