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Bobfly

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Hi Everyone,

I am a new Rocketry Forum member. I am looking for advice on selecting a first high power two stage rocket kit to build. There are past build threads on Wildman Jr. projects on the forum. Does anyone have experience with any of the 3 inch Wildman two stage kit upgrades?

Wildman doesn't advertise the 3" kit upgrades on a direct link to his website. Wildman does advertise the Jr. two stage kit upgrades on the website. Is there some kind of difficulty with his 3" two stage kit upgrades?

I would appreciate any advice on selecting a first two stage high power kit. As far as building experience goes, I am a Level 2 flyer whom has completed his Level 3 build. I will be flying my Level 3 Certification Flight later in the year.

Thanks everyone for your anticipated assistance.

Sincerely,
Bob
 

Bobfly

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I am open to any kit recommendations. It doesn't have to be a Wildman kit. I have some Wildman components and they seem to be of high quality.
 

timbucktoo

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Madcow has the Double shot 2 stage. Think it's a 54 to 38 mm motor.
From my own experience, I'd start with the Wildman Jr 2 stage and go up from there. It's a good kit & should keep you under 5k till you get the hang of flying 2 stages.
 

Bobfly

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Hi Tim,

I have seen the MadCow Double Shot kit on there website. It didn't have any reviews. I couldn't find any reviews online for it either. Did you build a Wildman Jr.? The lower altitude and lower costs are pluses for the Jrs. However is it too difficult to work on and setup do to its small size?

Does the Jr. just use drag for stage separation? What Altimeter fits and functions in the space available?
 

timbucktoo

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Hi Tim,

I have seen the MadCow Double Shot kit on there website. It didn't have any reviews. I couldn't find any reviews online for it either. Did you build a Wildman Jr.? The lower altitude and lower costs are pluses for the Jrs. However is it too difficult to work on and setup do to its small size?

Does the Jr. just use drag for stage separation? What Altimeter fits and functions in the space available?
Yep I built the WM Jr 2 stage. Drag separation has worked with every flight but I use a PET2 timer in the interstage coupler as backup. Tight fit but a perfect flight minitimer4 would work as long as you have motor ejection for booster recovery. If I were to do it again, I'd redesign my interstage coupler.
For the sustainer, I use an RRC3 for sustainer ignition and deployment. That & a 9 volt battery fit fine in AV bay.
A friend has bought the double shot but he's still early on in building.
 

Salvage-1

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Me too with the Wildman Jr two stage, slightly modified to take the Loki 38-1200 motors. Real nice kit. I like the thin wall.
 

DavidMcCann

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Me too with the Wildman Jr two stage, slightly modified to take the Loki 38-1200 motors. Real nice kit. I like the thin wall.
What had to be modded for 1200's? This is one of my "someday" builds and I was under the possibly incorrect impression 1200 cases fit stock...

Don't mind me, I'm a dumbass and just rechecked the sim.... Did you shorten the interstage or get a longer booster?
 
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Bobfly

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Hi Tim,

I guess that you ran a break line in the sustainer for the ignition wire? The RRC3's work great. I use them in my one stage rockets. However the RRC3's don't have a tilt failsafe right? How are you setting up the RRC3 ignite the sustainer?

How would you setup the interstage if you were going to make one up today.

Thanks for your advice.

Bob
 

timbucktoo

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Bob,

Yes ran a break wire from av bay to sustainer motor.
The RRC3 has a comparator for aux channel. You program it based on motor selection & sims. Sustainer must be airborne for X seconds at Y altitude or it will not fire.
 

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I have used the RRC3 on numerous occasions for staging. You use the aux channel. It is discussed in the manual
 

Titan II

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I have used the RRC3 on numerous occasions for staging. You use the aux channel. It is discussed in the manual.

Sorry about that...the previous post came in when I was writing this. Here are some pics of a 3".

69.jpg


21.jpg


70.jpg


68.jpg
 
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Onebadhawk

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I'd suggest you call Tim L..
First,, the shape of the fins is irrelevant,,
the placement of the centering rings and interstage coupler is what matters..
I'm sure he'll make you a kit with any fins you'd like..

Teddy
 

CzTeacherMan

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I'd suggest you call Tim L..
First,, the shape of the fins is irrelevant,,
the placement of the centering rings and interstage coupler is what matters..
I'm sure he'll make you a kit with any fins you'd like..

Teddy
This is accurate. Wildman can make any kit into a two-stage for you. A call will get it done for sure.
I prefer the "Wildman" find myself because they are fairly large and bring the CP back the most. Darkstar fins and a fantastic style as well. I'd love to see a two-stage Punisher though... CJ made one, I think, but I didn't see it after takeoff! LoL!
 

Bobfly

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Titian II,

Thanks for the pictures. Are you concerned that the third channel on the RRC3 cannot provid tilt protection? There is a video floating around that shows a large sustainer firing in parallel to the ground. Apperantly some clubs will no longer allow timer based sustainer ignitions.
 

JimJarvis50

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My advice would be to not buy a kit, or if you buy a kit, know how you are going to modify it to be what you want. One of the best things about two-stagers is that there are many design decisions that need to be made, and figuring them out is what makes staging fun. Yes, getting a kit would be easier, but I think at your experience level, you would much more enjoy building your own design. Study the kits that are available, learn about the options and choices, and then build something that suits you (rather than the kit manufacturer).

I could give you many suggestions on two stagers, but I will limit it to two for now. First, I would suggest starting with a 3" design with 54mm mounts. It's sort of a sweet spot. Second, learn from the start how to design safety into your two-stagers. There is much to this.

Jim
 
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Onebadhawk

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My advice would be to not buy a kit, or if you buy a kit, know how you are going to modify it to be what you want. One of the best things about two-stagers is that there are many design decisions that need to be made, and figuring them out is what makes staging fun. Yes, getting a kit would be easier, but I think at your experience level, you would much more enjoy building your own design. Study the kits that are available, learn about the options and choices, and then build something that suits you (rather than the kit manufacturer).

I could give you many suggestions on two stagers, but I will limit it to two for now. First, I would suggest starting with a 3" design with 54mm mounts. It's sort of a sweet spot. Second, learn from the start how to design safety into your two-stagers. There is much to this.

Jim
Agree completely..
I personally only scratch build,,
no biggie,, that's what I like..
But a kit costs a lot less money then the sum of it's parts..

Teddy
 

Bobfly

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Hi Jim,

Your name keeps popping up as an authority on two stage rockets. I'm glad to here that a three inch is a sweet spot. It's a lot easier to work on a 3" rocket than a smaller diameter like a Wildman Jr.. I am also deeply concerned about safety. The video out there of a sustainer stage motor lighting up horizontal to the ground is scary.

I have not seen detailed enough feedback or plans for the interstage. There was a lot of Level 3 flyers at our club to be able to get advice on single stage rockets. This pool of expertise does not seem to be available for two stage rockets.

Vern, whom markets the "Kate" GPS tracker telemetry unit, recommend that I converse with you. For starters let's assume I start with a Wildman 3" two stage kit. I am more concerned about getting the interstage and electronics right at this point. A kit with possible modifications to the interstage would allow more concentration on the staging / electronics.

Vern is coming out with a four event altimeter staging device that will fit into a three inch rocket this fall. His device will communicate with the Kate unit for realtime data from the staging computer. At this point in time what altimeter/ staging device do you recommend?

In a 3" rocket I assume that you use a black power charge for stage separation. Is this fired off by the sustainer computer, or the interstage computer? What sort of a time delay do you setup between stage separation and starting the sustainer motor?

Thanks for you wisdom,
Bob
 

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DoubleShot from Madcow is 75mm or 54mm motor mount in the 4" booster, to a 38mm motor mount in the 54mm sustainer.

I think PML has some good two stage kits as well.
 

Dipstick

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I had a good time flying a PML Quantum Leap for a number of years. It was a very stable design, and could accommodate a nice range of motors. Personally, I'm becoming a bigger fan of fiberglass kits now, but would certainly recommend you check it out.
 

cerving

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I did a lot of looking when I started working on the airstart software for the Eggtimer Quantum, I was surprised that there really aren't that many HPR 2-stage choices out there. I ended up with a Double Shot, 4"-54mm to 54mm-38mm, but it's pretty expensive to launch that puppy because it's relatively heavy. What I really wanted was something a little smaller, 38mm to 29mm motors... nothing out there, really. The Double Shot flies really well, if you sim your flights and pick the right motors (avoid longburn and VMax in the booster).
 
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JimJarvis50

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Hi Jim,

Your name keeps popping up as an authority on two stage rockets.
Yes, I've crashed a lot of two-stagers. Some of them have been interesting though. I've posted many of my staged flights here:

https://www.youtube.com/results?search_query=jiminaus50

Maybe since this is a kit thread, I'll describe what you'd get if you got a "Jim" kit. I don't make kits, but if I did, this is what it would be. My kit might not suit you at all - it's just another way to do it.

The kit would be 3" to 3". It would be fiberglass and designed to fly anywhere from 3K to 25K. The pics below are from an existing rocket I built maybe 12 years ago? That rocket has probably flown a couple of dozen times, and there are a few concepts from it that I would keep.

(Temporary rant on) My kit would have surface mounted fins. I think many fiberglass kits come with through the wall because they can be built by folks with a wider range of skill levels. But I have never understood why you would want to take a perfectly good fiberglass tube and cut slots in it. In 3" with a permanent motor mount, surface mounted fins with reasonable reinforcement will be stronger and lighter than through the wall. (Temporary rant off) My fins would be 5/32 or 3/16", and I would include just enough carbon for a couple layers of tip to tip. This would stay inside the perimeter of the fins - i.e., the carbon would stop short of the edges of the fins, and then I would use epoxy/West 410 or the like to smooth everything out.

The booster would be very simple. I'd go with a 54" motor mount with a retainer and just use motor deploy, or a chute release. A chute release is a little risky because apogee deployment might not be very accurate for a two stage booster, which increases the risk of the chute release releasing the chute early upon deployment. I calculate the delay time by performing a simulation but without separating the rocket or lighting the sustainer. I calculate the delay time in that configuration and then take 2/3 of that value for setting the motor delay. I get close most of the time. I'd design the booster with a piston as I think they greatly increase deployment reliability, so the booster would just have an open top.

The interstage coupler would be the "nose cone" for the booster and it would slide up into the bottom of the sustainer. A caliber or just a little bit more into the tubes on either side. A small switch band goes on the outside and a bulkhead goes at the appropriate location on the inside (leaving enough room for a separation charge below the sustainer motor. A good fiberglass tube would be fine for the interstage coupler in the kit, but I'd add a few wraps of carbon to the inside of the tube before adding the bulkhead. Two stagers tend to fail at this point, so stronger is better.

I suppose some electronics could go into the bottom side of the interstage coupler. This might allow better apogee detection and the separation charge could be done from that point. I don't light motors from the interstage coupler though (that voids the kit warranty). Be sure to shear pin the interstage coupler to the top of the booster, just like a nose cone. Also, if electronic apogee deployment is used, then the booster could be constructed minimum diameter.

My sustainer would be pretty conventional. Again, 54mm mount with retainer. The bottom ring of the mount could fit against the top of the interstage coupler. I'd use three rings on the motor mount and I would also mount the fins a little higher on the airframe (around those rings). The secret to sound surface mounted fins is to prevent the underlying tube from deforming.

The sustainer would have a zipperless coupler design. The wires for the motor ignition and the separation charge would pass through a brass conduit from the top of the zipperless coupler to the bottom motor mount centering ring. I connect the wires to wires from a conventional altimeter bay just using a simple twisted breakwire.

The first pic shows the altimeter bay in the upper air frame with the wires passing through the drogue section. I've done it this way for many dozens of flights and have never had a problem with the wires inhibiting drogue deployment in some manner. The wires need to be attached securely within the bay so that the electronics don't get yanked out upon separation.

The pic also shows an upper airframe that is in two parts (with the bay going between them. The kit would only have a single tube, and the bay would slide in from the top, sit on a ring and get pinned with rivets or the like. Air frame breaks should be avoided on two stagers wherever possible.

For electronics, I have always used either an Easymega or a Raven for staging. Both altimeters have some quirks and need to be fully tested before use. But, they both allow an altitude check, which is essential for staging. There are other altimeters that do this also, including the RRC3+ and one of the Egg-things and probably the Marsa. You would use the Easymega or Raven with another dual deploy altimeter, or perhaps use a pair of RRC3+ altimeters. Back when I started staging, I used an ARTS II, which could fire a channel at a pre-set altitude on the way up, combined with a timer that actually lit the motor. The output of the ARTS II was connected to a transistor switch. If the altitude was reached before the timer fired, it would open the transistor switch and allow the timer current to the igniter. It worked well for several years. It is critical to use an altitude check with any staged rocket. Tilt is nice, but secondary I think.

The pathway to the igniter would include two switches. One would open the igniter leads and the other would short them out. The one opening the circuit would be on the altimeter side of the shunt, which is a lot like twisting the leads of the igniter together. The design of these circuits is a topic for another day.

Staging delays are another subject too. On a slower flight, a few seconds is usually OK. If the boost will approach mach, then you can let the sustainer slow down to perhaps 500 ft/sec with no problems. If above Mach, then there is a choice. I have generally let my rockets fall through mach to perhaps 700 ft/sec to reduce the top speed of the sustainer. But there are reasons to consider lighting above mach such as trying to maintain a straighter trajectory.

So, above the bay is another piston and then the cone of your choice.

Anyway, that's my kit. Thanks for letting me design it on your thread!

Jim
 

JimJarvis50

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Not sure what happened to my pics in the previous post. I'll try again.

Jim

DSCF0640.jpg


DSCF0657.jpg


DSCF0647.jpg


DSCF0648.jpg


DSCF0644.jpg


DSCF0643.jpg
 
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BDB

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...I calculate the delay time by performing a simulation but without separating the rocket or lighting the sustainer. I calculate the delay time in that configuration and then take 2/3 of that value for setting the motor delay...
Do you mean that you calculate 2/3 of the time between booster motor burnout and apogee in that configuration?

Thanks for detailing all of this.
 
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Onebadhawk

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Yes, I've crashed a lot of two-stagers. Some of them have been interesting though. I've posted many of my staged flights here:

https://www.youtube.com/results?search_query=jiminaus50

Maybe since this is a kit thread, I'll describe what you'd get if you got a "Jim" kit. I don't make kits, but if I did, this is what it would be. My kit might not suit you at all - it's just another way to do it.

The kit would be 3" to 3". It would be fiberglass and designed to fly anywhere from 3K to 25K. The pics below are from an existing rocket I built maybe 12 years ago? That rocket has probably flown a couple of dozen times, and there are a few concepts from it that I would keep.

(Temporary rant on) My kit would have surface mounted fins. I think many fiberglass kits come with through the wall because they can be built by folks with a wider range of skill levels. But I have never understood why you would want to take a perfectly good fiberglass tube and cut slots in it. In 3" with a permanent motor mount, surface mounted fins with reasonable reinforcement will be stronger and lighter than through the wall. (Temporary rant off) My fins would be 5/32 or 3/16", and I would include just enough carbon for a couple layers of tip to tip. This would stay inside the perimeter of the fins - i.e., the carbon would stop short of the edges of the fins, and then I would use epoxy/West 410 or the like to smooth everything out.

The booster would be very simple. I'd go with a 54" motor mount with a retainer and just use motor deploy, or a chute release. A chute release is a little risky because apogee deployment might not be very accurate for a two stage booster, which increases the risk of the chute release releasing the chute early upon deployment. I calculate the delay time by performing a simulation but without separating the rocket or lighting the sustainer. I calculate the delay time in that configuration and then take 2/3 of that value for setting the motor delay. I get close most of the time. I'd design the booster with a piston as I think they greatly increase deployment reliability, so the booster would just have an open top.

The interstage coupler would be the "nose cone" for the booster and it would slide up into the bottom of the sustainer. A caliber or just a little bit more into the tubes on either side. A small switch band goes on the outside and a bulkhead goes at the appropriate location on the inside (leaving enough room for a separation charge below the sustainer motor. A good fiberglass tube would be fine for the interstage coupler in the kit, but I'd add a few wraps of carbon to the inside of the tube before adding the bulkhead. Two stagers tend to fail at this point, so stronger is better.

I suppose some electronics could go into the bottom side of the interstage coupler. This might allow better apogee detection and the separation charge could be done from that point. I don't light motors from the interstage coupler though (that voids the kit warranty). Be sure to shear pin the interstage coupler to the top of the booster, just like a nose cone. Also, if electronic apogee deployment is used, then the booster could be constructed minimum diameter.

My sustainer would be pretty conventional. Again, 54mm mount with retainer. The bottom ring of the mount could fit against the top of the interstage coupler. I'd use three rings on the motor mount and I would also mount the fins a little higher on the airframe (around those rings). The secret to sound surface mounted fins is to prevent the underlying tube from deforming.

The sustainer would have a zipperless coupler design. The wires for the motor ignition and the separation charge would pass through a brass conduit from the top of the zipperless coupler to the bottom motor mount centering ring. I connect the wires to wires from a conventional altimeter bay just using a simple twisted breakwire.

The first pic shows the altimeter bay in the upper air frame with the wires passing through the drogue section. I've done it this way for many dozens of flights and have never had a problem with the wires inhibiting drogue deployment in some manner. The wires need to be attached securely within the bay so that the electronics don't get yanked out upon separation.

The pic also shows an upper airframe that is in two parts (with the bay going between them. The kit would only have a single tube, and the bay would slide in from the top, sit on a ring and get pinned with rivets or the like. Air frame breaks should be avoided on two stagers wherever possible.

For electronics, I have always used either an Easymega or a Raven for staging. Both altimeters have some quirks and need to be fully tested before use. But, they both allow an altitude check, which is essential for staging. There are other altimeters that do this also, including the RRC3+ and one of the Egg-things and probably the Marsa. You would use the Easymega or Raven with another dual deploy altimeter, or perhaps use a pair of RRC3+ altimeters. Back when I started staging, I used an ARTS II, which could fire a channel at a pre-set altitude on the way up, combined with a timer that actually lit the motor. The output of the ARTS II was connected to a transistor switch. If the altitude was reached before the timer fired, it would open the transistor switch and allow the timer current to the igniter. It worked well for several years. It is critical to use an altitude check with any staged rocket. Tilt is nice, but secondary I think.

The pathway to the igniter would include two switches. One would open the igniter leads and the other would short them out. The one opening the circuit would be on the altimeter side of the shunt, which is a lot like twisting the leads of the igniter together. The design of these circuits is a topic for another day.

Staging delays are another subject too. On a slower flight, a few seconds is usually OK. If the boost will approach mach, then you can let the sustainer slow down to perhaps 500 ft/sec with no problems. If above Mach, then there is a choice. I have generally let my rockets fall through mach to perhaps 700 ft/sec to reduce the top speed of the sustainer. But there are reasons to consider lighting above mach such as trying to maintain a straighter trajectory.

So, above the bay is another piston and then the cone of your choice.

Anyway, that's my kit. Thanks for letting me design it on your thread!

Jim
Thank you so much for laying all that out Jim...
It has never been as clear in my mind...

Teddy
 

Bobfly

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Hi Jim,

Thank you for taking the time to write up such a detailed response. Your efforts did help to explain a lot of issues. I still have a few more questions if you don't mind.

You stated that the interstage is the weak point in a two stage rocket. Others on this forum have complained about their interstage's without stating the problem. Would it be better to replace the interstage tube with a carbon fiber one in the fiberglass rocket? Do you have a better technique to wrap the interior of the fiberglass tube with carbon fiber? I have used carbon fiber socks on the exterior of tubes with great success. The only way I could see wrapping the inside of such a narrow diameter tube would be with multiple strips of material.

Do do you place any gas vent holes in the upper end of the interstage? One of your great photos shows a band of blue painters tape securing the ignition wires to the aft end of the sustainer. Do you do anything to prevent the red motor nozzle cup from sliding off? Do you have any problems with ignition wire sliding down out of position in the sustainer motor?

Do you install a seperate switch above and beyond the altimeter power switch to break the sustainer ignition wire connection?

How much of a time delay do you use between the black powder interstage separation and ignition of the sustainer? Have you ever had the black powder charge damage the ignition wire for the motor?

Would you like to write a book? I loved your high power high altitude launch videos.

Thanks,
Bob
 

JimJarvis50

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Do you mean that you calculate 2/3 of the time between booster motor burnout and apogee in that configuration?

Thanks for detailing all of this.
I just calculate what the delay would be as essentially a single-stage flight (yes to your question). Then, take 2/3 of that for setting the motor delay. The booster slows down pretty quick with an open tube.

Jim
 

claytonbirchenough

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I did a lot of looking when I started working on the airstart software for the Eggtimer Quantum, I was surprised that there really aren't that many HPR 2-stage choices out there. I ended up with a Double Shot, 4"-54mm to 54mm-38mm, but it's pretty expensive to launch that puppy because it's relatively heavy. What I really wanted was something a little smaller, 38mm to 29mm motors... nothing out there, really. The Double Shot flies really well, if you sim your flights and pick the right motors (avoid longburn and VMax in the booster).
Cris,

You said avoid VMAX in the booster? Whys that? I get the longburn but why the VMAX?
 

ksaves2

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Two stage? Keep in mind, #1. Tracking. #2. Tracking. #3. Launch venue. (This leaves out the vagaries and mechanics of getting the pieces to work as so many have astutely commented upon above.) If one doesn't have a launch site with a 20k waiver nearby then they will have to weigh the investment on something they might only be able to fly once a year or every few years. Of course if keeping the size of the rocket components down, can keep the overall altitude below 10k.
The potential problem there is cramming all the needed hardware into a small space.

Other thing to beware is off axis ignition of the upper stage and venue. Is true off axis detection really necessary? Well, for one thing "true" off axis detection is a minimum of $300.00 (Easy Mega). Second thing is if flying in a very crowded launch I'd want to be as certain as possible I wasn't going to be the progenitor of
a land shark.

Sure altitude and timing detection can minimize risk of off axis firing but I wouldn't want to bring a first time project to a crowded launch to "test it out". A project that has flown successfully with Ravens, RRC3's, timers and others many times, certainly can be safe to fly since they have nominal flights under their flight logs.

It goes without saying that sending up something to "out of sight" land runs the risk of a total loss if it is lacking an Rf tracking device.
The longer is remains out of sight, the greater the chance one will lose it. There is the Tracksoar: https://www.tracksoar.com/?gclid=EAIaIQobChMI8v7wo42O1QIVRRuBCh1dVAIOEAAYASAAEgJE5PD_BwE and the Pico APRS that puts out a 1 watt signal: http://www.db1nto.de/index_en.html Unfortunately the Pico isn't any good above 60k and the Tracksoar has that teeny tiny GPS antenna
that I suspect would not perform well in the dynamics of a rocket flight. (I realize these are two off-beat Ham radio choices I'm impressed
with how small the hardware is getting.)
Kurt
 
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