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  1. #31
    Join Date
    23rd March 2013
    Location
    Akron, OH
    Posts
    371
    Hooray

    When is the build thread starting?

    Bill
    Member - MTMA
    Akron, Ohio

    "Rather than cursing the rose bush for having thorns, it is better to thank the thorn bush for having roses."

    Currently searching for that sweet spot between "Paralysis by Analysis" and "Extinct by using Instinct"

  2. #32
    Join Date
    6th February 2013
    Location
    Medina, Ohio
    Posts
    387
    It will probably be a while--there's several projects in line ahead of it, and I have this thing called a "day job" that's sponging up a lot of my time...

    If anyone else wants to give it a shot, feel free.


  3. #33
    Join Date
    23rd March 2013
    Location
    Akron, OH
    Posts
    371
    I just found out that in Open Rocket when you click "Plot Flight" you can select from various topics. I did not realize there were other report options other than the default "Vertical Motion vs. Time". Among other cool things there is one report "Roll Characteristics". As one would expect all of the rotation in this rocket is developed during the booster thrust phase. What I did not expect was that the spin rate does not decrease very much during the finless portion of the boost phase. I figured there would be some aerodynamic friction that would reduce the rotation during this phase.
    Bill
    Member - MTMA
    Akron, Ohio

    "Rather than cursing the rose bush for having thorns, it is better to thank the thorn bush for having roses."

    Currently searching for that sweet spot between "Paralysis by Analysis" and "Extinct by using Instinct"

  4. #34
    Join Date
    23rd March 2013
    Location
    Akron, OH
    Posts
    371
    Another cool observation is that the C11 motor is only able to generate a spin of 11 revolutions per second; whereas, the D12 is able to develop a spin of nearly 18 revolutions per second.
    Bill
    Member - MTMA
    Akron, Ohio

    "Rather than cursing the rose bush for having thorns, it is better to thank the thorn bush for having roses."

    Currently searching for that sweet spot between "Paralysis by Analysis" and "Extinct by using Instinct"

  5. #35
    Join Date
    23rd March 2013
    Location
    Akron, OH
    Posts
    371

    Tao Launch Report

    Well, I am resurrecting this very old thread as I finally launched the Tao for the first time last weekend.

    Since the last post, I added 0.25 oz. nose weight and found out that there were 2 problems with the nested staging for the Tao.
    1. I found out that the engine hook on the sustainer prevented the 18mm sustainer motor from nesting inside the 24mm booster motor. I decided to simply cut off the motor hook and use tape retention.
    2. Also discovered that once the hook was cutoff,the sustainer motor assembly was still about 1/16" too long to allow the coupler to fit completely fit together. I added a 3/16" ring of BT-60 tubing at the base of the coupler to fill the gap. Not sure if this was due to changes in the D12 motor since the Estes DOTM was published or whether I was off on one of my dimensions


    I had been waiting for a nearly windless launch because I wanted to take wind out of the equation as much as possible if the rocket had an unstable flight. Last weekend, our club was having a night launch, and about 7:00 (still well before sunset) the 4-7 mph winds calmed completely and we had dead air with occasional 1 mph "gusts". Since I had the rocket with me and prep is very quick I decided it was time for it's maiden launch.

    I got raised eyebrows from the RSO when I told him it was a finless rocket, but once I explained the concept behind it and told him I had a working sim for the rocket, I got a "Yeah that's a sound concept" and the launch was approved. After calling for a "heads up launch", my friend Gary gave the countdown and pushed the button. The rocket leaped very quickly off of the pad.

    There was very noticable spin, but it was impossible to quantify the exact spin rate. Simulations showed that the rocket was expected to reach 18 revolutions per second. I was surprised at how high the rocket was at staging. I checked later and saw that sims showed staging was predicted to occur around 350' and I would concur from visual observation that looked very probable. Staging looked clean, but immediately after staging there was visible coning of the sustainer that got increasingly severe during the burn. Once the burn ended the sustainer quickly entered a flat spin while still rising during coast. Several people visually estimated the altitude to be about 600-700', well short of the simulations prediction of approximately 1150-1200'. This is understandable and to be expected due to the added drag from the coning and flat spin.

    Video showed that the motor gave about the full 5 second delay, and the ejection charge appeared to be after apogee, nose down, still in a somewhat flat spin. The piston fully deployed, but due to the flat spin, the rocket was not spinning in the manner needed to deploy the wound up chute. It also appeared that the chute got tangled on the swivel and these two factors prevented the chute from deploying. Luckily with the rear piston deployed the sustainer was no longer aerodynamic, and came down with a flat fall rather than ballistic trajectory. The sustainer was recovered about 30' from the pad, and the booster was recovered about 100' from the pad.

    I missed the booster falling, but the parachute did deploy. Somehow one of the fins did break on impact however, and was found about 6' from the booster.

    I will try to post the video, but it is not very clear.
    Last edited by Mr Rocket; 30th September 2017 at 09:05 PM. Reason: Typos, added video comment.
    Bill
    Member - MTMA
    Akron, Ohio

    "Rather than cursing the rose bush for having thorns, it is better to thank the thorn bush for having roses."

    Currently searching for that sweet spot between "Paralysis by Analysis" and "Extinct by using Instinct"

  6. #36
    Join Date
    23rd March 2013
    Location
    Akron, OH
    Posts
    371

    Observations

    From the launch, I had 2 observations that I cannot quantify, but rather are gut responses:
    1. The rocket, while having a noticable spin, did not appear to be spinning at near the 18rev/sec spin rate predicted by Open Rocket. Does the spin rate need to be increased? I tapered the trailing edge of the canted portion of the fin in an attempt to reduce drag and allow the fins to impart spin more effectively. However,by doing this did I remove some of the fin area necessary to create the necessary spin I was trying to achieve?
    2. The simulations in Open Rocket showed the spin rate staying at 18 revolutions per second from motor burnout until ejection. In watching the rocket, I could not help but think that it started losing some of that rotational inertia soon after motor burnout. Would I be better off trying to get the additional weight for the rocket out to near the airframe rather than putting it on the central axis where it did little to help maintain the rotational inertia?
    Bill
    Member - MTMA
    Akron, Ohio

    "Rather than cursing the rose bush for having thorns, it is better to thank the thorn bush for having roses."

    Currently searching for that sweet spot between "Paralysis by Analysis" and "Extinct by using Instinct"

  7. #37
    Join Date
    27th April 2009
    Location
    Melbourne, Australia
    Posts
    1,373
    Quote Originally Posted by Mr Rocket View Post
    From the launch, I had 2 observations that I cannot quantify, but rather are gut responses:
    1. The rocket, while having a noticable spin, did not appear to be spinning at near the 18rev/sec spin rate predicted by Open Rocket. Does the spin rate need to be increased? I tapered the trailing edge of the canted portion of the fin in an attempt to reduce drag and allow the fins to impart spin more effectively. However,by doing this did I remove some of the fin area necessary to create the necessary spin I was trying to achieve?
    2. The simulations in Open Rocket showed the spin rate staying at 18 revolutions per second from motor burnout until ejection. In watching the rocket, I could not help but think that it started losing some of that rotational inertia soon after motor burnout. Would I be better off trying to get the additional weight for the rocket out to near the airframe rather than putting it on the central axis where it did little to help maintain the rotational inertia?
    I found with my 'Twisted' rocket that the spin started to disappear right at burn-out, too.

    I've only launched my rocket a couple of times, but some things that I've considered - more length, more nose weight and, as you've suggested, a ring of weight to maintain rotation.

    Hmmm... I may just have to get it out of storage and have another play!!

    Krusty

  8. #38
    Join Date
    23rd March 2013
    Location
    Akron, OH
    Posts
    371
    Quote Originally Posted by krusty View Post
    I found with my 'Twisted' rocket that the spin started to disappear right at burn-out, too.

    I've only launched my rocket a couple of times, but some things that I've considered - more length, more nose weight and, as you've suggested, a ring of weight to maintain rotation.

    Hmmm... I may just have to get it out of storage and have another play!!

    Krusty
    Krusty my friend, It is great to hear from you.

    After hearing your observation about loss of rotation after burnout, I am even more convinced of the need to move weight out to the airframe to maintain rotational inertia. Thanks for posting your observation.

    Bill
    Member - MTMA
    Akron, Ohio

    "Rather than cursing the rose bush for having thorns, it is better to thank the thorn bush for having roses."

    Currently searching for that sweet spot between "Paralysis by Analysis" and "Extinct by using Instinct"

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