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Thread: Hybrids 2017

  1. #91
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    23rd November 2013
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    Very nice machine work.


  2. #92
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    19th January 2009
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    866
    I'm wondering what people are doing with GSE. I read a thread discussing hybrid testing for TMT and one issue people mentioned is time at the pad. I never took all that long, connect fill line, connect igniter, continuity test. I'm just curious if there are gains to be had in that area.

    Another is fill time. It's not bad for 38/54 but I could see it being more significant the larger you get. Could using servo controlled plug valves work here? It would likely cost less than a similar sized solenoid valve. Larger diameter fill lines?

    Assuming some distance from the solid pads, is it dangerous to launch solids while waiting for hybrid fills?


  3. #93
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    29th November 2009
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    Fort Collins, CO
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    Regarding fill lines and time, your bottleneck is typically the orifice drilled in the CGA-326 or CGA-660 fitting on your bottle. You can't get nitrous out of the tank faster than right there.

    Edward

  4. #94
    Join Date
    29th December 2011
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    I've started what's going to be a long thread on THRP-1 in the Research subforum. I'm putting essentially all the details there, and why I made the choices I made.

    Gerald

  5. #95
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    10th April 2009
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    Auckland, NZ
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    How do you get access to the research subforum?

  6. #96
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    29th December 2011
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  7. #97
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    10th April 2009
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    looks like ill have to get a green card first...

  8. #98
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    29th November 2009
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    Fort Collins, CO
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    Kind of a hybrid - a tribrid tested this weekend.

    Click image for larger version. 

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    https://youtu.be/nmB3H9QWpnc

    https://youtu.be/vBCxGOFQf_o

    https://youtu.be/AdMBgwkuNhY

    Edward
    Last edited by AlphaHybrids; 13th March 2017 at 06:51 PM.

  9. #99
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    29th November 2009
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    Fort Collins, CO
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    Another image of a tribrid. This one has a peak thrust of 400 pounds.

    Click image for larger version. 

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    Edward

  10. #100
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    19th January 2009
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    866
    That's a great looking shot!

  11. #101
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    29th December 2011
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    Looks like it should be a poster... Nice!

  12. #102
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    29th December 2011
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    Edward,

    Is your test stand permanent, or do you transport it?

    Gerald

  13. #103
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    29th November 2009
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    Fort Collins, CO
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    Gerald - March-ish through October-ish the stand is outside with ~2,000 lbs of bricks for counterweight. It also has stakes to help stabilize it. The winter months it goes to a small shed just to keep it out of the weather. The load cell is kept covered in the summer and removed in the winter.

    Edward

  14. #104
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    29th December 2011
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    Click image for larger version. 

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    THRP-1 motor is assembled, ready for static test this Saturday at Battle Park.

    Gerald

  15. #105
    Join Date
    18th January 2009
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    ALABAMA
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    That looks awesome! Looking forward to the report.
    "He who fights with monsters should look to it that he himself does not become a monster, and if you look long into an abyss, the abyss also looks into you." - Friedrich Nietzsche

    "The Future is Not Solid" - Korey Kline

    TRA# 08705 L3

  16. #106
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    29th December 2011
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    I'm not sure the preheater really got going before the fill lines burned through. We had cold flow rather than ignition which dumps the nitrous a lot faster than would have been the case if the combustion chamber was pressurized. Cold nitrous flow is quite a fire extinguisher. Eventually the preheater did light the nitrous and the motor burned nicely then, but most of the nitrous had already been dumped. Everything seemed to work very well except for the delayed ignition. That's a known issue with chilled nitrous systems and probably why there aren't any commercial ones. I'll be making adjustments to the ignition sequence for the next test.

    Details will be in the Research forum thread.

    My camera batteries were dead at the field so I didn't get any pictures. Others took some shots and at least one video so I should have something to show eventually.

    Gerald

  17. #107
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    29th December 2011
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    Click image for larger version. 

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    https://www.youtube.com/watch?v=G3JS...ature=youtu.be Video by Nathan, from Battle Park yesterday. Thanks Nathan!

    Gerald
    Last edited by G_T; 27th March 2017 at 04:55 AM.

  18. #108
    Join Date
    22nd March 2017
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    14
    Quote Originally Posted by G_T View Post
    Pictures of the injector block in place in the coupler (injectors removed), and a bag of the injectors. One can see the convergence pattern of the three injectors by the angles of their threaded holes. The picture flattens the appearance of the surface where the injectors mount. It is somewhat conical rather than flat. One can also see there is a bit of volume available for precombustion after the injectors. That picture is shown with the precombustion chamber liner removed.
    Great work! I did some tests with conical injector designs during the last two years - I used small brass carburetor nozzles from motorcycles. Those are available with a wide range of diameter. Finally I figured out, that due to the conical design the axial velocity component was a little bit to low and caused combustion instabilites. I replaced it with a conventional shower-head design and gained around 10% thrust + a more stable combustion.

    I will collect some data to present my rocket a bit later.

    s3th

  19. #109
    Join Date
    10th November 2015
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    1
    Hi Guys, been awhile since I visited the forums, not sure if I ever posted the last test firing I did, 500kg peak 4" hybrid.. (N3000)



    using up the NOS, same motor and fuel grain.. quick 1 second blast..


  20. #110
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    29th December 2011
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    Nice!

    Gerald

  21. #111
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    20th January 2009
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    657
    ROCstock - Hybrids I plan to launch a bunch of Hybrids at ROCstock, June 10'th at Lucerne Dry Lakebed. I will have GSE and gas (if you 'reserve' ahead of time). Anyone interested?

    Mike K

  22. #112
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    29th December 2011
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    I'm in the process of prepping THRP-1 for a second static test. Mostly I'll be changing the preheater to try to avoid the late ignition that happened with the first static test. I'll tweak the fuel a little also.

    So far I do not have a local nitrous supplier so I haven't set up any GSE. I'm at the mercy of others. Plus the fields within a couple hours of me which have sufficient towers for mounting like I did last time at Battle Park are not going to be open until crops are done for the year. So if anyone at a launch site within driving distance of northern Virginia has nitrous to burn and and a tower, and is interested in supporting a static test, I'll pay for the nitrous, and drive!

    The mounting is basically a caddy which holds the motor. The caddy uses large rail buttons for alignment but they are not under any appreciable load. There is a hardpoint heavy forged eyebolt at the top which is roped solidly to the tower transmitting the thrust loads. Then gaffers tape is used for a bit of extra stability. The hardpoint can also be roped to screw anchors in the ground so the tower doesn't receive much of the thrust load. It's not a high thrust motor anyway so that's only an issue if the tower is particularly light. GSE needs are the same as for Contrail 75mm hardware.

    If I can't arrange a test somewhere, I'll store the motor until this fall when I can possibly test locally again.

    Gerald

  23. #113
    Join Date
    22nd January 2013
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    635
    I have enough no2 for 1 fill. I have a 1515 pad that could easily bolt up to a unistrut rail. I have design for a hybrid test stand the slides into class 4 hitch receiver, with 2 layers 3/4" plywood as a blast shield.
    Anyway I'm in Alexandria.
    Email: dave(at)davealewine (dot)com
    Dave Alewine
    TRA 7299 L3, NAR 83701 L3
    Alexandria, VA
    Maryland Delaware-Rocketry Assoc.
    Lvl 1- AT H220--Lvl 2- AT J350--Lvl 3- AT M1297

  24. #114
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    29th December 2011
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    emir005, More details, please!

    Dave, thanks for the offer! I'm trying to work through the MDRA BOD for a possible test at their summer field. I'll post when it is decided.

    Gerald

  25. #115
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    29th December 2011
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    MDRA BOD declined to provide permission for vertical testing of the motor at the summer Sod Farm field, and declined to allow using one of their towers as a test stand. This motor like most small hybrids needs to be near vertical for a static test, so, I'm back to square one looking for a site for a summer static test.

    Gerald

  26. #116
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    29th November 2009
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    Fort Collins, CO
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    The college team I'm working with tested their 8 foot 4-inch motor at 45 degrees, knowing that they would lose some nitrous performance at the end. It did erode the liner more on the top side, by about 50% compared to the bottom side. They were using a SCH 80 PVC liner lined with 1/4" of HTPB.

    Edward

  27. #117
    Join Date
    4th May 2010
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    Silicon Valley
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    Quote Originally Posted by AlphaHybrids View Post
    Regarding fill lines and time, your bottleneck is typically the orifice drilled in the CGA-326 or CGA-660 fitting on your bottle. You can't get nitrous out of the tank faster than right there.

    Edward
    There are several places in the fill system that restrict flow. First is the bottle valve and CGA fitting. Can't do much about that. Second is the solenoid orifice. Next is the fill hose. Lastly is the vent orifice. I found that by increasing my solenoid size and fill hose I have reduced my fill times by quite a bit.
    Karl Baumheckel
    TRA 11594 L3

  28. #118
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    29th November 2009
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    I wouldn't oversize the vent orifice to get a faster fill - you will end up using a lot more nitrous filling, and possibly not being able to fill if you grossly oversize it.

    Edward

  29. #119
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    29th December 2011
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    What is a typical fill time for the long Contrail M tank? My valved system in THRP-1 ended up right at 2 minutes (from memory; I could verify if necessary). Tank volume is similar but since mine is a chilled system it holds more mass. I'm curious how the fill time compares to Contrail's vented method?

    Gerald

  30. #120
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    4th May 2010
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    Silicon Valley
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    Quote Originally Posted by AlphaHybrids View Post
    I wouldn't oversize the vent orifice to get a faster fill - you will end up using a lot more nitrous filling, and possibly not being able to fill if you grossly oversize it.

    Edward
    agreed

    Karl Baumheckel
    TRA 11594 L3

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