Wildman Mini 2 Stage

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junkyard

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Hey Everyone,

I haven't posted in a while, I recently moved to southern California to work for the Air Force doing solid propellant research (who would have thought that you could not work for a living). Anyways, after a long hiatus while I settled in I am slowly getting back into amateur rocketry :facepalm:.

My way of getting back into rocketry is getting a group of 12 co-workers together to build Wildman Mini kits, but I can't just do the same thing. So I want to take my existing Darkstar Mini and make it a two stage. For now this is just a concept/ research thread, I am just going to throw out ideas and see how everyone feels about them.

some ideas so far:

one idea: 38mm airframe sustainer to 54 mm airframe booster with 29/38mm MMT

or possibly just a second mini kit as a booster with a 38mm coupler to connect them

drag separate booster from sustainer
motor eject booster chute
Timer based ignition of sustainer motor
motor eject apogee
altimeter main


anyways, let me know what you guys think. Opinions? Suggestions? Examples?
 

rms

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Just a suggestion,
I wouldn't use motor ejection for your apogee event. If the sustainer motor fails to ignite you won't have an apogee event and although the main should be popped by the altimeter your speed at that point would be excessive. Since your using an altimeter for the main, use it for your apogee event as well.

Greg
 

junkyard

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good point, altimeter apogee and main events it is
 

CORZERO

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What is the closest sanctioned site? What is the waiver? I would start with the legal limitations. The kit looks small and the materials robust. I would think you could get away with breaking it at apogee and letting it fall drogue-less until the flight computer deploys the main. Motor eject for booster deployment sounds good.

Also, you state altimeter and timer to be used for the sustainer events. Any reason why you wouldn't let a capable flight computer alone handle all events (a la Raven 3)?
 

cerving

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Just a suggestion,
I wouldn't use motor ejection for your apogee event. If the sustainer motor fails to ignite you won't have an apogee event and although the main should be popped by the altimeter your speed at that point would be excessive. Since your using an altimeter for the main, use it for your apogee event as well.

Greg
Good advice. You're probably going to find that on the sustainer you won't be able to use the motor eject as a drogue backup... the delay will most likely be too short for all but the smallest motors that you'd want to fly. You WILL be able to use motor eject for the chute on your booster, though... they tend to slow down relatively quickly once they separate, particularly if the booster is a larger diameter than the sustainer. (Which is not the case on your build...)
 

blackjack2564

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You will need to "swap" fin cans.

Existing fincan becomes booster.
New fincan should have finslots 1.5-2in. forward from rear of airframe. Now you can get an interstage coupler to fit between both booster & sustainer.

It may not be on website, but Wildman will make the needed 2 stage up grade very reasonable. Call him.
Be sure to specify a coupler [your interstage] and vent band, long enough for whatever timer/elctronics needed in it, if using any. I always put a timer in my I/S for separation charge,at motor burnout.

.... you will need a channel/tunnel running through the CR's in new booster for ignition wire from motor to electronics in av-bay. [unless you buy a head-end ignition closure & fly on research launches]
You also need to add a payload bay to sustainer with av-bay in coupler for staging & deployment electronics ala Altimeter that will do all.

I have done this, using a 3in booster with 54 motor & 38mm sustainer with 29mm motor.
Went 18,4500 ft. K-1103X to a H-399 WT.


Altimeter with 3rd pyro channel should be used to fire sustainer. Parameter such as fire only if 1200 ft is reached,or fire when velocity is less than 500ft/sec. etc.

Some parameter other than just timer firing after "x" seconds. You could be pointed at the ground when a timer fires.
Good luck, sounds like a fun project! Get'em all involved.
 
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djs

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Related to this- forum user CZTeacherman and I had discussed once making a wildman mini or sport boosted dart. Using two nosecones on a body tube to make the "dart'. No idea if this would actually work, but might be worth a shot.
 

markg

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I have done this, using a 3in booster with 54 motor & 38mm sustainer with 29mm motor.
Went 18,4500 ft. K-1103X to a H-399 WT.
I'm thinking of trying something similar. Using the bottom of my 3" Darkstar as the booster. and maybe a 2.6" Darkstar on top. How did you do the transition between the 3" booster and the 38mm sustainer? I'm thinking I'll need to chop a nose cone up and epoxy it to the interstage coupler?

cheers - mark
 

blackjack2564

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How did you do the transition between the 3" booster and the 38mm sustainer? I'm thinking I'll need to chop a nose cone up and epoxy it to the interstage coupler?

cheers - mark

Had it machined.....removable AL coupler for normal staging with a 38 airframe/29motor

20160323_125336.jpg 20160323_125340.jpg

Remove coupler sleeve for staging with 38motor used as coupler in 38minimum diameter sustainer.[hangs out back 2.5 in]

DSCN5577.jpg DSCN5575.jpg

Project on pad:

OI000009.jpg
 

markg

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Had it machined.....removable AL coupler for normal staging with a 38 airframe/29motor
View attachment 322175
Looks good - and I have a local guy who can do this for me. Did you add a hole for a separation charge or use drag/motor ignition for separation? I'm thinking with the AL coupler it would be sturdy enough to just go with motor ignition.

cheers - mark
 

blackjack2564

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Did you add a hole for a separation charge or use drag/motor ignition for separation? I'm thinking with the AL coupler it would be sturdy enough to just go with motor ignition.

cheers - mark
Yes, and .25 gram for separation charge.
You should leave your airframe with machinist, so he can get a perfect fit.
Ours is so slick, it acts like a boosted dart, separates clean & quick at motor burn-out [booster]
I give I/S a spritz of WD-40 before flight and wipe excess.

If flying for fun, I suppose it matters not when/how separation occurs.
If going for altitude, you want to rid the booster as soon as possible. Separation charge at motor burn out via Pet-2 timer. [default setting]

We now use another technique when making I/S couplers. Instead using full length aluminum stock:
Just machine I/S with 1.5 inch stub. Then freeze the I/S for several hours and press into G-10 or Carbon coupler. When room temp is reached ...it will never come apart. Your machinist should be able to figure the shrink rate of material used. Saves 4 inches of solid stock and machine time!!!!
While at it ...put a lip on inside for front BP to sit on.

DSCN0025.jpg DSCN0012.jpg

Coupler trimmer, Delrin cone added... ready for use.

DSCN0033.jpg
 
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