Lakeroadster's Launch Pad Deflector Bucket

Discussion in 'Recovery' started by lakeroadster, Nov 6, 2018.

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  1. Nov 6, 2018 #1

    lakeroadster

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    Would eliminating the deflector plate adversely effect the rockets performance of a LPR?

    I'm working on building a simple launch pad and want to replace the deflector plate with a 4 gallon bucket of water.

    The water weight helps stabilize the saw horse and in the event of a rear nozzle failure CATO the water's in the best possible location.

    (pardon my horrible sketch)

    Sawhorse Bucket Pad.jpg
     
    Last edited: Nov 6, 2018
  2. Nov 6, 2018 #2

    cwbullet

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    Interesting theory. We have used a kevlar blanket and we have used a rubber pool.
     
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  3. Nov 6, 2018 #3

    sghioto

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    Should not effect performance. Like cwbullet said interesting idea.
    SG
     
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  4. Nov 6, 2018 #4

    cwbullet

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    I forgot to add, the pool of water did not effect performance, but it did spray water and steam.
     
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  5. Nov 6, 2018 #5

    neil_w

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    I refuse to comment on this until we get one of your CAD drawings showing the whole proposed setup.




    (OK, the idea sounds pretty good to me)
     
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  6. Nov 6, 2018 #6

    lakeroadster

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    Hey Chuck, Approximately how far away from the rocket engine was the surface of the water... and what size engines were being fired?
     
    Last edited: Nov 6, 2018
  7. Nov 7, 2018 #7

    jlabrasca

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    No. The blast deflector is just there to keep the exhaust gas from igniting or scorching whatever is below. It has nothing to do with making the rocket move.

    It is an interesting idea. Not sure I see an advantage. As a kid, I launched LPR rockets using an unprotected scrap of pine board as a pad. I upgraded it, eventually, with a split tin can -- mostly because the burnt wood smelled too strongly for my mother to let the pad in the house.

    We commonly use wooden clothes pins as stand-offs at our low power launches. They get a little charred, and a little sooty, but they take the brief exposure to rocket exhaust well. They last a long time.

    That's a really unlikely event, I think. Estes BP motors are pretty reliable.

    The biggest drawback to metal blast deflectors is shorting the leads. A big piece of ceramic floor tile makes an excellent blast shield, apart from the risk of breaking it while transporting it to the field.
     
    Last edited: Nov 7, 2018
  8. Nov 7, 2018 #8

    cwbullet

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    About 2-3 feet above. K, L and M motors. I am not sure about K.
     
  9. Nov 7, 2018 #9

    NateB

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    When I was a kid, I tried adding a bowl of water under an Estes rocket hoping the steam would look more like the Space Shuttle launches. I was disappointed when it didn't work like it did in my mind.
     
  10. Nov 7, 2018 #10

    lakeroadster

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    Way more power than I'm planning for my basic LPR launch set-up.
     
  11. Nov 7, 2018 #11

    lakeroadster

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    Agreed, Unlikely and they are reliable.. but it does happen.

    Here's a recent C6 CATO of Kevin Foss' Nike X ... This photo inspired my simple bucket o' water lpr launch set-up design. Kevin's rocket was uninjured, it spit the rear factory nozzle right out the bottom and the deflector became a horizontal distribution device.

    Kevin Foss Nike X CATO.jpg
     
    Last edited: Nov 7, 2018
  12. Nov 7, 2018 #12

    jlabrasca

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    Yeah, I spotted this thread.

    https://www.rocketryforum.com/threads/catos-and-launch-pad-design.148305/

    The responses you got there were pretty much on-point. The cost/benefit argues against implementing your design for club launches.

    Understand that this is not meant to be an accusation, or a criticism. I am among the many folks who admire your skill as a draftsman and model builder. However, I suspect that you are inexperienced as a flier.

    The folks who promote this hobby are meticulous about safety. There is a real worry that it is just one serious injury away from being regulated or legislated out of existence. The spectacular CATO image you posted looks scary. The actual event almost certainly did not look that dramatically hazardous to the folks on the ground when it happened. And, as the folks who were there pointed out, there were adequate and effective safety measures in place at the launch.

    You've written elsewhere on the forum about your reluctance to join a club -- or maybe just to question the value of joining a club. If you haven't gotten to a launch yet, I'd recommend you try. It might give you a better sense of the the actual risks, to see a mess of LPR rockets all go up in an afternoon (plus which, its a lot of fun to watch a lot of rockets all go up in an afternoon).
     
  13. Nov 8, 2018 #13

    lakeroadster

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    Here ya go Neil ;) Launch Support.JPG
     
    Last edited: Nov 8, 2018
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  14. Nov 8, 2018 #14

    lakeroadster

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    I have you blocked... you're the only member here on the forum that I have blocked. I am now regretting looking at your blocked content.

    You do your thing, I'll do mine. Opinions vary: I see value in this concept. I fail to see the value though in your lecture and attempts to stifle another members creativity?

    If following the crowd is your thing, have at it. Some folks are bored by that and like to try something different.
     
  15. Nov 8, 2018 #15

    jlabrasca

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    Well. I am not going to block you. I still want to see your stuff. Seriously, I am a fan. Oh, Wait. You won't see this. Oh well.
     
  16. Nov 8, 2018 #16

    Rex R

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    if one wanted to test this idea, mount an air hose/nozzle at a suitable distance from the bucket and feed your nozzle compressed air @ about 80 psi...I am thinking that this might be a bit messy :). unless the rod gets wet there should be no difference with or with out the bucket.
    Rex
     
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  17. Nov 8, 2018 #17

    Bob Austin

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    A couple of things I see in the design above. Understand it is an early sketch, but these are some things you may wish to consider as you work through this idea.
    • Doesn't look like much holding the bucket up. Assuming a 5-gallon bucket with 4 gallons of water, that is 32 pounds (8 pounds per gallon). Not sure that the bracket in the drawing, especially being attached at the side, will hold up well under that kind of weight load.
    • Noticed the proximity of the bucket handle to the exhaust. Looks like you would likely need a metal handle to avoid any weakening of a plastic handle due to the heat generated by the exhaust. A metal handle would mean most likely a metal rod. That puts even more pressure on the attachment point on the saw horse.
    • How do you intend to adjust the angle of the launch rod? I don't see any method of moving the rod in the drawing. Again, if the pivot point for the rod is also the attachment point for the bucket, it may be harder still to find something strong enough to withstand the constant weight load.
    • Your drawing shows one rod on a saw horse. Would it be safe to assume more than a single rod is intended to be used? A 5 rod system on an 8-foot 2x4? That's a lot of water (and weight).
    • Once the rocket motor ignites, what prevents the igniter clips from falling into the water?
    • Instead of water, what if you used sand? Some of the same problems still apply. However, you could probably use a smaller amount, thus reducing the weight load. Sand has been used for years to smother fires. It would also keep any CATO materials intact instead of water logged. May be able to get a better idea of what happened by looking at the debris. Probably less 'mess' from people hitting the bucket (and sloshing water around) when setting up the rocket on the pad. If the igniter clips fall into the sand no harm is done to the clips or the electrical system. In fact, if you went with sand, you could create a tray under the entire length of the saw horse, perhaps only an inch or two deep. It could be supported by additional bracing from the saw horse legs, leaving the rod attachment free to move as needed. It might get hit by shins and knees as folks bring their rockets to the pad.
      • Or if you have the funding, what about something like a welding blanket? It would easily absorb any heat put out by a model rocket engine. Plus no mess (no water or sand splatter) and would be reusable.
    Just a couple of observations. Hope it helps flush out your idea.
     
  18. Nov 8, 2018 #18

    lakeroadster

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    Thanks for the comments Bob.

    I've got a couple saw horses that I've been using since I built my first garage in 1981. They are made from pine 2x4's and have steel brackets that the legs (also 2 x 4's) attach to. Each saw horse will easily hold up a couple hundred lbs. Weights not an issue.

    If the plastic handle becomes an issue due to the heat of the rocket motor exhaust I could use one with a steel handle. We'll see, I'll post up some photo's.

    As for angling the launch rod.. I'm going to dig through my pile o' parts in the barn. I've got the bracketry from an old dish antennae that I may be able to use. It has an adjustable mount and should screw right to the side of the 2x4 easily.

    Igniter clips attach to the 2x4, the water is farther away than the length of the clips.
     
  19. Nov 16, 2018 #19

    solid_fuel

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    What I don’t see is how having a five gallon bucket underneath the launch rod would do anything about catching any of the flaming debris outside a 15” wide cylinder centered directly under the rod. From the CATO picture it looks like most of the flaming bits would fall outsodenthe bucket.
     
  20. Nov 16, 2018 #20

    KennB

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    The OP's idea is to eliminate the deflector and have the rocket directly over the bucket. The exhaust (and any axially expelled material from a failure) would hit the water's surface.
    It will be interesting to see video of it during normal launches and especially a CATO.

    The picture you refer to is from a launch at my club. The deflectors work well for us and we make sure a mishap doesn't start anything that would get away from our capability to control it.
     
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  21. Nov 16, 2018 #21

    K'Tesh

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    That's because, like someone said, the blast plate redirected the debris.

    IMHO, it'd work for a limited number of types of failure, and wouldn't hurt to have on hand in the event a spreading failure occurs. As to it's use for holding down a launch pad. If the wind is that high as to tip that over, it's too windy to fly.

    The biggest drawback I can see is when the inevitable happens and you drop a prepped rocket into the water by accident.
     
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  22. Nov 16, 2018 #22

    GlenP

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    One potential issue with a larger diameter rocket too close to a flat deflector plate, I am thinking like an X-24 Bug or Point for example, the rocket exhaust streaming outwards in all directions can create a suction force, or venturi effect, and keep the rocket on the pad. Rockets like that just need to be raised up a little higher on the launch rod with some tape, spring, or clothespin to avoid this.
     
  23. Nov 16, 2018 #23

    lakeroadster

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    ... put the lid on the bucket until you are ready for launch...

    Thanks for posting this Glen... so many old neat rocket designs. I'll have to add the X-24 Bug to my scratch build list.

    https://spacemodeling.org/jimz/centuri/ka-12.pdf

    24 Bug.jpg
     
    Last edited: Nov 16, 2018
  24. Nov 17, 2018 #24

    Tobor

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    I think your idea is very interesting.

    The only issue I foresee is is loading/unloading the bucket(s). At least at club launches. The club launches I have attended do not have a "nearby" water source for loading. Substituting sand, as per Mr. Austin's suggestion, might be a better way to go.

    Unloading, well... Some folks, read "officials", might have an issue with contaminated water being dumped on site. So the stuff would need to be hauled off to a "safe" location for disposal.

    Anyhoot, I do appreciate you sharing your idea. Sharing is always fertile ground for stirring the imagination in others.
     
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  25. Nov 17, 2018 #25

    lakeroadster

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    Spent a bit of time today on the launch horse. Using only stuff I had in the bone yard I put together what I think will be a workable version.

    I used a satellite dish bracket that will allow for wind cocking, a set of steel saw horse brackets and a 2x10.

    Sitting the bucket on the ground will keep the handle out of the way and allow it to be easily moved to center it under the rocket.

    0000.JPG 000.JPG 001aRotated.jpg 001Rotated.jpg 002aRotated.jpg 003Rotated.jpg 005.JPG
     
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  26. Nov 17, 2018 #26

    rharshberger

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    iirc its called a Bernoulli Lock when the exhaust locks the rocket to the deflector plate and it commonly happens as you mentioned with wide rockets very close to the blast deflector and the motor inset pretty deep inside the rocket body.

    https://www.rocketryforum.com/threads/whats-bernoulli-lock-and-why-is-it-called-that.83189/

    Jim Flis's answer in post #3 of the above link is pretty good.
     
  27. Nov 18, 2018 #27

    rcktnut

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    I like the idea of eliminating the blast deflector, things are dangerous. I picked out my base (picture below) for my new multipurpose launch pad. The launch rods will be mounted on the lid. Build thread to come soon. Below the features of my new pad:
    Self contained, no lugging around multiple pieces
    Very sturdy/stable
    Adjustable launch angles
    Lid closes for horizontal loading of rockets and prevents them from accidentally falling in the water
    Very safe when bowl is facing away from the flight line, lid deflects any fragments out and sideways away from flight line.
    Self refilling especially with long duration launches, eliminating the need to bring a large amount of water with you.
    Your wife or female friends will be more willing to attend the launch.


    th.jpg
     
    Last edited: Nov 18, 2018
  28. Nov 18, 2018 #28

    lakeroadster

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    I'll bet you do some of your best work there. Nicely done and thanks for the constructive and helpful post. You sir are what makes the internet a breath of fresh air.
     
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  29. Nov 18, 2018 #29

    NorthwoodsRockets

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    No. The blast deflector has nothing to do with the flight of the rocket. It is a common misconception that the rocket pushes on the ground to go up. Newton's laws explain rocket flight. In this case, it is his third law - action and reaction. When object A exerts a force on object B, then object B exerts an equal force in the opposite direction to object A. In this case, when the motor pushes the gases down, the gasses push the motor up (with the rocket in front of it.) No need to push on blast reflector. This explains how a rocket can accelerate (change speed and/or direction) in space where there is nothing outside of the rocket to push against. (Conservation of momentum gives an alternate way to think of the same thing.) Great way to make physics relevant.
     
  30. Nov 18, 2018 #30

    Steve Shannon

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