Two stage help

[JimJarvis50]

That was what I was planning on doing.



Yeah I was going to put the timer there.



I don't know what a zipperless coupler is..



That was something else I could do if it doesn't fit in in between the fins.



May I see how you do it just so I have all this info in (mostly) one place?



Which ones do this?



How would I use rocksim to simulate separation? I know there is the ignition delay that I can use for the sustainer, but that doesn't seem to work the way I thought it did. That being said, I was planning on separation 0.1s after MECO and then ignite the sustainer 3s later.



Yeah I figured it wasn't to difficult, I have worked with accelerometers before.



What type of equipment will I need for RDF? Is it expensive? And would GPS be cheaper? If so I might sacrifice some reliability, as long as it can get me in the general area (I might put one of these on board: https://www.apogeerockets.com/Electronics_Payloads/Rocket_Locators/Transolve_BeepX , or make something similar)



I'd rather use fiberglass. I'm a little more familiar with it. Also if I go too light I might break the waiver. I'm going to use 22k as a goal and if simulations go too far below that when I have almost everything configured correctly, then I may consider dropping some weight.

As for dual deploy, the booster after staging sims to 4.5k. That's already higher than anything I've ever launched (that will change by the time I build this). It was going to be dual deploy from a single bay with the electronics in the coupler, using the cable cutter method.

Thank you for your very comprehensive response.

Here is a link to a description of the concept.

https://www.info-central.org/?article=132

Simply, the coupler between the fin section and the drogue section is attached to the fin section (in model rockets, it's the other way around). This isn't a two-stage thing - it's just (IMO) how conventional dual deploy should be implemented. The idea is to attach the drogue about 1/3 of the way from the fin section. At the apogee event, the top section gets blown forward but does not change direction. The fin section, however, has to flip 180 degrees. By eliminating the tube from the piece that changes direction, you eliminate the chance for zippers. The 1/3 thing keeps the fin section from continuing forward and crashing into the upper section. Rockets built this way last longer.

Now, imagine that in your zipperless coupler, you have a bulkhead on the bottom and a removable bulkhead on the top. Presto, a spot to put your electronics. These bulkheads would be connected with a piece of all thread, and the recovery harness would be attached to the all thread.

One of my sustainers is pictured below. It has the zipperless coupler, but I don't put the electronics there. Instead, I put them in the ebay and run breakwires, which are attached at the top of the zipperless coupler. You can see the wires in the pic.

I don't have a good example of a shunt to show you. Conceptually, imagine your altimeter outputs and the two wires going to your sustainer ignitor. Somewhere on that circuit should be a resistor - perhaps 1+ watts and 3-5 ohms - but this depends on your battery and electronics. Now, imagine a second set of leads from the same altimeter outputs, but the leads go to a switch. This circuit is the shunt. If the altimeter fires with the switch closed, the current goes through the low-resistance shunt circuit rather than the ignitor, and you don't get fried. The problem is that a small portion of the current will still pass through the ignitor ematch. Thus, you want to keep the shunt resistance low (use short, heavier wires) and the ignitor resistance higher (use the resistor to raise the resistance of that part of the circuit). This lowers the current going through the ematch so that the ignitor won't fire in the event that the altimeter fires.

I believe the modified eggwhatever, the Raven, the RRC3 and the Telewhatever are capable of this. I used to do it with an ARTS II combined with a timer and transistor switch.

I'm no RockSim expert, but what I do is manipulate the ejection and ignition delays. For your example, 0.1 and 3 seconds, I believe you would set the ejection delay at 0.1 seconds and the ignition delay at 2.9 seconds. I often use an ejection delay of 0.5 seconds, although I have a flight planned where I want the parts to coast together for 12 seconds (to slow down) before I separate them. That's what I mean about controlling the flight profile.

Worked with accelerometers??? Not part of the plan.

RDF is a whole nuther subject. If you're on a budget, find a friend with a receiver and furnish your own transmitter. I use BigRedBees in the nose cone and also Marshall transmitters, but there is Walston and several others. Lots of info on the forum on that topic. Sonic beepers don't help much if you're several miles out.

Cable cutter for the booster would be fine. Regarding the altitude of the booster, my bet is it won't go as high as you think. Once the sustainer leaves, it's like putting out the air brake.

Jim

 

[T34zac]

I'm no RockSim expert, but what I do is manipulate the ejection and ignition delays. For your example, 0.1 and 3 seconds, I believe you would set the ejection delay at 0.1 seconds and the ignition delay at 2.9 seconds. I often use an ejection delay of 0.5 seconds, although I have a flight planned where I want the parts to coast together for 12 seconds (to slow down) before I separate them. That's what I mean about controlling the flight profile.

Well I also have open rocket and can get rasaero if either of those are easier to work with. But I understood what controlling the flight profile meant, I just can't get rocksim to reflect that. I think it's using the booster ejection delay as part of the time between MECO and SEIG.

Worked with accelerometers??? Not part of the plan.

I figured you would need to program the timer to not attempt SEIG if the rocket is pointing x degrees from vertical

RDF is a whole nuther subject. If you're on a budget, find a friend with a receiver and furnish your own transmitter. I use BigRedBees in the nose cone and also Marshall transmitters, but there is Walston and several others. Lots of info on the forum on that topic. Sonic beepers don't help much if you're several miles out.

I know the sonic beeper won't do much if I'm far away. That's why I would use the GPS to get me close. From there I would use the sonic beeper to lead me there.

Cable cutter for the booster would be fine. Regarding the altitude of the booster, my bet is it won't go as high as you think. Once the sustainer leaves, it's like putting out the air brake.

I figured as much. Rocksim currently has the booster staying with the sustainer until about 4k, which I don't want to happen.

Anyway thank you for helping me understand zipperless couplers as well. I will most likely end up using a couple in this project.

 

[JimJarvis50]

Well I also have open rocket and can get rasaero if either of those are easier to work with. But I understood what controlling the flight profile meant, I just can't get rocksim to reflect that. I think it's using the booster ejection delay as part of the time between MECO and SEIG.



I figured you would need to program the timer to not attempt SEIG if the rocket is pointing x degrees from vertical



I know the sonic beeper won't do much if I'm far away. That's why I would use the GPS to get me close. From there I would use the sonic beeper to lead me there.



I figured as much. Rocksim currently has the booster staying with the sustainer until about 4k, which I don't want to happen.

Anyway thank you for helping me understand zipperless couplers as well. I will most likely end up using a couple in this project.

You can make Rocksim do what you want - just work with the booster motor ejection delay and the sustainer ignition delay. RasAero doesn't do two-stagers yet unless you trick it. Hopefully, that will change soon.

You can use gyros to sense the angle, but what I'm suggesting is to use an altitude checks with the altimeters I mentioned. You can at least make sure that you're probably going "up" with that approach.

What I was suggesting was to use RDF as the first line of defense rather than GPS. I have no problem with GPS, except that once in a while, you won't regain lock and/or get the telemetry. That "once in a while" event can cause you to lose a rocket. RDF is still a bit more reliable.

Jim

 

[A5tr0 An0n]

I have no problem with GPS, except that once in a while, you won't regain lock and/or get the telemetry. That "once in a while" event can cause you to lose a rocket.

Jim

Hmmm that sounds familiar Jim.

 

[T34zac]

You can make Rocksim do what you want - just work with the booster motor ejection delay and the sustainer ignition delay. RasAero doesn't do two-stagers yet unless you trick it. Hopefully, that will change soon.

I just figured it out on rocksim yesterday. However I had to tweak the motor files in order to get the ejection delays I wanted.

You can use gyros to sense the angle, but what I'm suggesting is to use an altitude checks with the altimeters I mentioned. You can at least make sure that you're probably going "up" with that approach.

Ok. I see your point. But I'd also like that extra safety in there so if for whatever reason it weathercocks severely but it's going fast enough to still be going up at a decent rate.

What I was suggesting was to use RDF as the first line of defense rather than GPS. I have no problem with GPS, except that once in a while, you won't regain lock and/or get the telemetry. That "once in a while" event can cause you to lose a rocket. RDF is still a bit more reliable.

Will I need to get amateur radio licensed to use RDF?

 

[JimJarvis50]

I just figured it out on rocksim yesterday. However I had to tweak the motor files in order to get the ejection delays I wanted.



Ok. I see your point. But I'd also like that extra safety in there so if for whatever reason it weathercocks severely but it's going fast enough to still be going up at a decent rate.



Will I need to get amateur radio licensed to use RDF?

The altitude approach is a good safety practice and is free with the right altimeter choice. You can't really use it, though, to distinguish between small angle differences (say, 20 degrees versus 25 degrees), but I use an altitude check with every flight I do. Actually measuring the angle costs more, and may not be as straightforward as you think. I use the tiltometers at the moment, and they work, but I've compared the actual flight path (determined via gps) against the recorded angle, and the device doesn't behave exactly as you might expect. So, it's important to know how they actually work in order to use them effectively. I suspect the same is true of the TeleMega, but I haven't seen such comparison data yet. In the rockets where I use a Tiltometer, the ignition signal actually comes from a Raven. I use an altitude check as part of the Raven programming.

I don't really know the answer to your question on the HAM license. I use the BigRedBee RDF and GPS equipment, and that does require a HAM license on 70 cm. For some of the other tracking systems, I'm not sure. The folks at Marshall told me that their lower-powered transmitters did not whereas their higher power units did. Best would be to ask the manufacturer if you find something you're interested in. Getting a HAM license is easy, and the HAM radio approach is a good one if you have any interest at all in having a radio.

Jim

 

[JohnCoker]

You only need a HAM license to use certain frequencies; you can do RDF on unlicensed frequencies as well. For example, 70cm is a HAM band which several GPS systems use, and 900MHz is an unlicensed band which others use. Generally, lower frequencies have longer range and you can transmit more power on the licensed bands, but 900MHz works just fine for regular sport flying.

For true RDF, I've only used the Walston system, which uses animal tracking frequencies that are of questionable legality used in rockets. However, they're so low power that out in the desert I can't imagine them bothering anyone.