Thoughts on the new madcow nike-apache as first hpr 2 stager?

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I can't remember who asked, and I must have deleted the PM as I can't find it, so I'll just post it here.

A user with one of these kits tells me that the EggFinder mini sleds I sold fit the the 38 conical NC for this kit.
 
Creality CR-10? That's what I have coming to replace my MonoPrice Maker Select 2.

My Monoprice blew the main board such that the bed no longer heated, so they had me ship it in. I had replaced the extruder thermistor and heating core after they failed so they actually denied to fix my printer because i voided the warranty. Just happy it didn't start a fire like it has for others! DO NOT BUY FROM MONOPRICE.

Those a reality printers are big. That is a good 6" more z-axis than I get with the Prusa.
 
Time to start developing a fast burn booster motor and a slow burn sustainer motor!

I'm looking at a Small VMAX Booster, and a Mellow Yellow sustainer. Perhaps even H53 MY; G250-VM


It's a shame to waste that big booster with a small engine, but....
 
This will be my first 2 stage. I plan to wait and see what others are doing with the interstage and staging electronics before I start on my build. I also like the idea of seeing the separation, and 2nd stage ignition.. thus I plan to flying smaller motors initially.. Perhaps a 38mm full H in the booster to start, and a G in the sustainer. I'm thinking to boost the initial flights to something just over 1000 ft, and try to keep the sustainer within view too. I'm thinking the sustainer might do well with the AeroTech Hobbyline Reloads at first. Open Rocket Simulation shows just under 5,000 feet for the H550/G64, and just under 4,000 ft for an H178DM/G53FJ (those motors seem like a matching pair given the black smoke). Velocities off a 72" rail look good. I wasn't expected that much altitude... nice! That will be about $50 or $60 per flight this way.
As I write this, I'm realizing that this is probably common practice for first flights of new 2 stage builds.

Update to this post.. the simulation model I was using did not have realistic weight. The figures above are just wrong. The H178DM would be a poor choice for the booster.
 
What do you intend to light sustainer with?
Why do you "think this is common practice with new 2 stage builds"?
How did you figure your coast time?
 
I got a notification that mine has shipped, so I suspect those who got in on the first batch should start getting theirs soon and will be able to see how their plans will pan out based on the actual kit.


Tony

Mine has shipped as well.
 
What do you intend to light sustainer with?

That has yet to be answered. I have a number of Eggtimer Quantums to work with.. but have been looking at other electronics options. At this point, I'm leaning toward having the second stage ignition altimeter to be in the sustainer. What electronics would you suggest and where would you locate them? Drag Separate or ignition?

Why do you "think this is common practice with new 2 stage builds"?

When I wrote that line, my thoughts were that flight testing a new rocket with more complex electronics might warrant a careful build-up approach. Do you do anything special for the maiden flight of a new multi stage rocket?

How did you figure your coast time?
Using an Open Rocket Model, I looked at the system velocity after burnout, and set the ignition delay to light the sustainer motor when the system had slowed to about 275 ft/sec. Thus, for the H550/G64 the delay was 2 seconds, and for the H178DM/G53FJ the delay was just 1 second. I'm not sure if I should go with Drag Separation or Upper stage ignition separation. What's your general method for figuring coast time and how would you separate this particular rocket?
 
That has yet to be answered. I have a number of Eggtimer Quantums to work with.. but have been looking at other electronics options. At this point, I'm leaning toward having the second stage ignition altimeter to be in the sustainer. What electronics would you suggest and where would you locate them? Drag Separate or ignition?

I've built 2 different 2-stage rockets thus far and they all use drag separation as the desired method to separate, but I always have a separation charge triggered at some time after booster motor burnout from timer (PET2+ or Minitimer4) in the ISC and as a 3rd option, motor ignition from sustainer although that is not the preferred method. The motor ignition method should probably only be used as back-up but others may argue.
 
This rocket seems like it will drag separate very easily, My plan is to steel the design from my 2 stage Formula 38, where I build modular motor mounts that were held in by machine screws on the outside of the airframe and build an av bay in a "cage" of sorts. That way the motor mount and av bay are all one assembly, then its easy to setup the igniter for the sustainer, and since I used the ravens in that project I had enough for a separation charge, Motor ignition, apogee charge and then the main deployed from a DIY Pyro chute release. It worked very well at the time too, until it got destroyed by a CATO in the sustainer. Definitely intend to rebuild that one with improvements to the av bay and fully intend on building the sustainer like that as well. You have to build the sustainer as a MD, but that is nothing complicated.
 
1a.That has yet to be answered. I have a number of Eggtimer Quantums to work with.. but have been looking at other electronics options. At this point, I'm leaning toward having the second stage ignition altimeter to be in the sustainer.

1b. What electronics would you suggest and where would you locate them? Drag Separate or ignition?
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1a Sorry I wasn't clear, I meant how are you going to light a G-64, being so small a slot in fuel grain & needing to get low current ignition. Not electronics....... but starter.

1b. That is such a personal thing, their are many good brands to choose from. The criteria for sustainer ignition choice, must include some parameter settings to inhibit motor burn, unless parameter met.
Such as " altitude greater than [x]".....velocity "greater than [X]"....Tilt "angle less than 20 off vertical" so you have a safe flight.
Sustainer electronics MUST be in sustainer. I require "clean-quick" dart like separation & will re-design whatever it takes to attain it. Now I always use a separation charge back up in larger models, for this I may just depend on slip fit...we'll see once the kits arrives.
I prefer my separation electronics [Pet-2 timer,accelerometer based, default setting is "fire at motor burn out, so it's a no brainer to use] in the I/S [interstage coupler]

I use Telemega for my sustainer. Only unit out, having "Tilt or off vertical" block on Sust. ignition, when I bought them 2 years ago. It's pricey at 400.00 when first starting, but since I have them and they do all 3 needed things in a small package [Altimeter, GPS, 4 Pyro ch. control] Knowing requirements for 2-stagers [from experience now...lol] meaning high thrust in booster always keep stack straight, don't fool around with coast delay till ya have some experience.
I use my RRC3 for simple lighting of sustainer, in smaller rockets, not headed to the moon.I want tilt feature in any flight over 15,000.
Set for altitude must be.... at least [> than] say 1800 ft bare minimum for any flight for me, before just ignition can happen.

Ok I gotta shorten all this up...it takes boatloads of real theory/experience to get this stuff right. One more example for me then I'm moving on :
I want at least 1800 ft before ignition of sustainer so. either booster/stack must get there or coast/sustainer must get it there [1800ft] I also want it moving 450-550 ft/sec MINIMUM to keep it straight. To reduce/eliminate risk of turning it into a Cruise missile.
Some guys fly so slow , with slow majestic lift offs ...I don't want any part of that or worrying about "what if" and who's paying for the damages.

I'm covering all this stuff...line item during my build, so one knows why I do & chose the items to complete my project. Like my Darkstar sticky at top of HighPower above.



When I wrote that line, my thoughts were that flight testing a new rocket with more complex electronics might warrant a careful build-up approach. Do you do anything special for the maiden flight of a new multi stage rocket?


Oh man do I now...... Start out hard hitting booster, no wimpy careful build up etc.
Let's call it starting in the middle, maybe backing down later. Never under-power a 2-stager or come close.VERY very bad things happen.

So...if need be, just load stack, including both motors. Do not put Sustainer igniter in motor, replace with plain match on BP. Fly with booster motor only. everything should separate, coast & deploy safely. Download your graphs & check performance to see if all went as planned. You can easily see during flight if motor had enough thrust to keep stack straight & sustainer ignition,was not happening, during gravity turn towards ground.
Nothing bad can happen with sustainer unless booster motor choice is so bad you should go stand in corner, or design is terrible in first place.

You can bet my first flight with this will be full up stack...no ignition sustainer. With a J-460T 54mm & G-53 long burn 29 [not lit] If all works then go for 2-stage ignition on 2nd flight. Should look like this...UNLESS after weighing built rocket I need more thrust. note altitude only 3500 ish.

Screen Shot 2017-12-02 at 1.53.56 AM.jpg Screen Shot 2017-12-02 at 1.57.28 AM.jpg

If it all works then this..... G-53 has ignition pellet built in, so no brainer to light with low current match
.

Screen Shot 2017-12-02 at 1.58.42 AM.jpg Screen Shot 2017-12-02 at 2.13.45 AM.jpg

Note times and velocity at motor burn out, and staging. Altitude is only 750ft at motor burnout and seperation. Personally I do not wish to stage at anything less than 450-550ish. Can be fine tuned later, for this it will do [400 on sim] I spend hours simming actual flights, fine tuning coast delays & motor choice.



Using an Open Rocket Model, I looked at the system velocity after burnout, and set the ignition delay to light the sustainer motor when the system had slowed to about 275 ft/sec. Thus, for the H550/G64 the delay was 2 seconds, and for the H178DM/G53FJ the delay was just 1 second. I'm not sure if I should go with Drag Separation or Upper stage ignition separation. What's your general method for figuring coast time and how would you separate this particular rocket?


Way too low velocity for my taste and several things not considered .
I spent over an hour simming your flight and correcting weights and plotting.
Your sim seems to be based on 5.5 lbs built weight.
kit parts say 6lbs...I added 1.5 to bring it up to spec and include glue & hardware.
Result sim weight 7lb. empty, ready to fly. Full 1.5 lbs. heavier.

Altimeters have a "arm" altitude. For the RRC3 it's 300 ft. How much time does it take to reach 300 ft. That must be considered. It will change dramatically based on motor choice & time on pad coming up to pressure.
Electronics "lag time" [current flow] + ignition lag time. [1 sec.] Typically .3-.4 lag + 1.75[motor burn]+ 1 sec motor ignite = say 2.8
That means with no coast delay at all, there will be 2.8 sec [almost 3] delay between booster motor ignition and sustainer ignition, with NO coast delay.
Depends on how long it takes to reach 300ft.
The RRC3 only starts timer AFTER rocket reaches 300 ft....not from lift off! You must know your electronics!
If altimeter has accelerometer it can fire sustainer after motor burn out, no lag other than .3-.4n for current flow+ igniter/motor ignition.[1sec]
I videod some flights, and by timing events from motor ignition, came up with this for just one.
With a 1.75 booster burn time and 4 second coast. Actually sustainer ignition was 7.5 seconds....much, much later than expected from sims, they don't take into account the above mentioned. Any borderline motor choice would have been disastrous!
So....if I fly a motor with burn time of 1.75 seconds I drop coast to 2 sec to get a real 4ish. [with RRC3]

2-stagers are not twice as hard to figure out...they are 10 times harder!!!:smile:

I'll show your choice in another post later & why I think they are borderline choices.
Along with the video from above mention times.

Disclaimer: these are my opinions, based on many flights. There is always more than one way to do things, these are mine based on K.I.S.S.

Edit: What small type motors have some of you actually flown, in small 2-stager like this 6-7lbs, with success?
I've never kept mine under 5-6000 ft.
 
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Jim,

Thank you for the detailed reply. I really appreciate all the information and experience sharing.

Since you mentioned suspicious weight, I looked closely at the open rocket model that I'd downloaded (the one posted earlier in this thread).. and it was WAY off. I should have looked more closely at it before posting any hint of performance data based on it. It had a no-motor weight of just 65 ounces.. or roughly 4 lbs.

Since I received my kit yesterday, I was able to make some preliminary changes.. and the weight is significantly greater. The fiberglass is the standard wall stuff, roughly 0.06 wall thickness across the board. The avionics bay coupler is 7 inches. The transition/ISC has a nice 4" OD shoulder, in which the 3.9" coupler fits.... so that was nice to find.
I'm far from done fixing up the simulation model, but getting close. Currently I'm at 101 ounces, or 6.3 lbs without motor and electronics. Based on this, I think your empty weight estimate of 7 lbs is good.

I'll try to post some pictures later on the FW transition.. I'm glad it isn't just a simple cone as depicted in the Madcow illustration.
 
Great..... when measuring I/S could you see how far into it the 4in coupler goes please.


The 3.9" OD by 5" long Coupler between the 31" Booster Tube and the Transition/ISC, slides into the ISC transition 1.25".

I grabbed a few screenshots from my OR model to detail this part. I could not find a way to make a transition with both a conical section and a straight section that wasn't assumed to be an internal shoulder. So, as a workaround, I added a short section of body tube to complete the transition/ISC part in the OR model.

Screen shot of the Transition/ISC model per actual measurements of the part I received: See OR Model File further below.
Transition.jpg


Screen shot of my work-in-pogress OR model with no motors. I'm up to 107 oz without electronics or motors so far.
See OR Model File further below.
NikeApache.jpg


Here is the OR model for the Transition/ISC that I used:

Here is my current OR model... take a look at the dimensions ... I've gone through and measured all parts, so the model should be pretty good.
 
What are you guys doing for a second stage igniter shunt? If any? I haven't come up with a clean simple way yet.
 
The 3.9" OD by 5" long Coupler between the 31" Booster Tube and the Transition/ISC, slides into the ISC transition 1.25".

I grabbed a few screenshots from my OR model to detail this part. I could not find a way to make a transition with both a conical section and a straight section that wasn't assumed to be an internal shoulder. So, as a workaround, I added a short section of body tube to complete the transition/ISC part in the OR model.

Screen shot of the Transition/ISC model per actual measurements of the part I received: See OR Model File further below.
View attachment 333451


Screen shot of my work-in-pogress OR model with no motors. I'm up to 107 oz without electronics or motors so far.
See OR Model File further below.
View attachment 333450


Here is the OR model for the Transition/ISC that I used:

Here is my current OR model... take a look at the dimensions ... I've gone through and measured all parts, so the model should be pretty good.

Thanks Kevin! Busy weekend if you were at the launch as well! (perfect day there). Are all the weights for the components correct? I just had mine arrive this AM and will get home and go through it over lunch. If the components need to be weighed, I'd be happy to do so.
 
Mine arrived this morning and I just got home and unboxed it. LOTS of wrapping paper, my cat had a field day. All components present, dry fit looks good. Total weight of just the parts came to 90.5 Oz. So 107 above sounds pretty good with retainers, epoxy, paint, etc. etc. Top section with motor mount was 26 Oz, so the sustainer will have some altitude to go with it!
 
Mine is here as well, the kids grabbed it and put under the tree saying it was from my secret Santa. I had to pull out the receipt and prove I bought it before they would let me open it.
 
Thanks Kevin! Busy weekend if you were at the launch as well! (perfect day there). Are all the weights for the components correct? I just had mine arrive this AM and will get home and go through it over lunch. If the components need to be weighed, I'd be happy to do so.

I made it out late to Snow Ranch. It was a nice day with light winds, thought the high overcast made tracking difficult.
My kids did get to participate in the Piñata Rocket, and I flew just one flight, a K2050ST in my Frenzy XL.

Mine arrived this morning and I just got home and unboxed it. LOTS of wrapping paper, my cat had a field day. All components present, dry fit looks good. Total weight of just the parts came to 90.5 Oz. So 107 above sounds pretty good with retainers, epoxy, paint, etc. etc. Top section with motor mount was 26 Oz, so the sustainer will have some altitude to go with it!

I have not yet weighed each component. However, the density value i used in Open Rocket was derived from my previous experience with Madcow Fiberglass Tubes.. so the component weights should be close to actual.

It looks like the sustainer payload parachute compartment is going to be very tight with a main parachute, chute protector and shock cord. Perhaps the nosecone coupler can be trimmed a bit shorter, and the altimeter bay coupler could be biased aft into the booster/drogue parachute compartment.
 
This makes me happy. Should be easy enough to make up something to make the ISC look more scale. If Dan does make something, I'll probably figure out a way to attach it with screws that would do double duty to retain the shoulder section.

This makes it a little more difficult, but certainly doable. May not be “worth doing” now that we know the transition is a sound design, however.
 
This makes it a little more difficult, but certainly doable. May not be “worth doing” now that we know the transition is a sound design, however.

I was thinking a donut like device that would attach to the lower straight part of the ISC. I drew up something crude and not to scale, but this is what I was talking about. Could be glued or bolted on. ISC example on left, donut device on right.

Screen Shot 2017-12-05 at 3.11.54 PM.png

Together:
Screen Shot 2017-12-05 at 3.30.12 PM.png
 
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I was thinking a donut like device that would attach to the lower straight part of the ISC. I drew up something crude and not to scale, but this is what I was talking about. Could be glued or bolted on. ISC example on left, donut device on right.

View attachment 333549

Together:
View attachment 333550

Yea, that's absolutely doable. You what else may be doable? Printable skins for the Nike profile on the fins that would mount over fillets.
 
I was thinking a donut like device that would attach to the lower straight part of the ISC. I drew up something crude and not to scale, but this is what I was talking about. Could be glued or bolted on. ISC example on left, donut device on right.

View attachment 333549

Together:
View attachment 333550

That's what I envisioned back in post #142. Should work well.
 
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