Air Starts

[Bruiser]

I like two stage rockets. I have a couple that are built for Estes Bp motors.

I have the NorthStar, which is 29mm


I have a boosted Citation Patriot that is 24mm to 24mm (sorry, no pic)

I also have the Tempest, which is a 24mm to 18mm rocket (again, no pic)

I built these rockets when the motors were easy to obtain from Hobby Lobby. Now they don't carry any 24mm or 29mm boosters. That got me thinking that if I am going to have to mail order my boosters why not just go composite. The BIG answer (for me) is that you can't gap stage composites...

Lets just say I have these hanging out.


And I want to use composite motors. What would be the easiest way to do it for someone who is electronics challenged?

Thanks,
-Bob


N

 

[Charles_McG]

Well, the good thing about composite motors is that they are thrustier. The E16 and F15 are marginal for the weight of staged rockets.

The complication is that they aren't built for direct staging. Altimeters are your friend. It's a new set of skills and challenges.

There used to be a thread over on YORF about building a custom delay grain and direct staging black powder sustainers from composite boosters. But it's highly non-sanctioned. Highly.

 

[heada]

There are a few ways to work around the staging electronics but all are higher risk than using staging electronics. I'd rightly recommend learning staging electronics as that's the most reliable and easiest way to stage composite motors. Apogee sells a "SimpleTimer" and Eggtimer sells a "Quantum" that should fit in the sustainer in a side-hatch style. I'm sure there are others I'm not thinking of.

 

[Bruiser]

I have the Apogee Simple Timer and an Eggtimer Apogee that I bought for a two stage Doorknob project that got shelved when the custom cut plywood fins I purchased warped like a potato chip when I sanded the leading edge taper in. They seemed the simplest to use and size wasn't an issue because of the 3 inch tube. I was thinking of mounting them side-hatch style.

Where would the simple timer go in just a three inch tube? Can you do an AV bay (which I have never done) if you're using the motor ejection charge to deploy the parachute?

-Bob

 

[Charles_McG]

I cut into the base of the nosecone and put electronics in it.

 

[heada]

https://www.apogeerockets.com/Rocke...odel-Rocket-Kits/Terrier-Sandhawk?cPath=1_88&
Watch the videos on how Tim mounted the staging electronics in the Terrier-Sandhawk. He does a side-hatch with the option for motor ejection. I would do similar but rather than creating a custom bay like he did, I would mount it between the centering rings.

 

[cerving]

Side hatches are cool, but you need at least a 3" body tube to really do one. Not gonna work with a BT60.

 

[Charles_McG]

It looks like the Majestic is 2". In my sounding rocket fleet, the tomahawks are built with the 2" estes tubing. I cut into the nosecone and put in a 24mm motor tube as a mini avbay. An eggfinder mini usually lives up there - but I've put Quarks up there too. 24mm is tight for a Quantum, but I think Cris says it will fit.
In this thread, there's an example of a 3D printed sled and endcaps for the Ester 2" coupler: https://www.rocketryforum.com/threads/tomahawk-painting-questions-ute-tomahawk.150701/post-1872645
I put a Proton in, but a Quantum would work too. This would mean extending the Majestic with another piece of 2" body tube.

Note: whatever altimeter you choose for airstart, consider the recovery options, too. With the Eggtimer quantum, in Airstart mode, the other channel can only be apogee. Good for drogue, less desirable for main.

 

[Bruiser]

I was just reading up on the Eggtimer Classic computer and it seems you need three vent holes, of coarse a battery, a switch and a shunt. That does not seem like it will fit in the majestic nose cone. The other channel will only fire the drogue chute at apogee.

I guess that would work installed in a coupler by leaving the ejection charge out of the motor and relying on the FC to deploy the chute at apogee. The JLCR could keep it from drifting to Albuquerque

Segwaying off that maybe I could use the Apogee simple timer and the Eggtimer Apogee (a little confusing maybe) instead of a single FC because of the simplicity of the settings. No computer of wifi needed.

-Bob

 

[heada]

I'm not sure what logic is available in the simple timer. For bigger staging configurations most clubs want some kind of safety lockout on the staging event. Tilt or altitude at time or velocity at time, etc. A pure timer has been known to start the second motor when its pointed in a non-optimal direction.

 

[Bruiser]

• 4th-Generation Timer for Staging Rockets
• Perfect for Staging Composite Motors
• Automatically Detects Launch To Start The "Clock."
• Tilt limit - Prevents Staging that could Lead to Unsafe Trajectories
• Chuff Detection Prevents False Launches
• Mounting Hardware Included
• Made in USA

Ok, so say I go with an ebay built into a coupler like Charles wrote about. The ejection charge would not be used from the motor at all. The electronics would fire off the ejection charge to deploy the parachute at apogee. Now as I am sitting here I can think of two ways to do this...

First way is I could have both the Apogee simple timer and the Eggtimer apogee in the ebay. The ebay would be secured to both the upper and lower tubes with screws or some sort of push pin. The ejection charge would be "sitting on top of the ebay and when it "blows" the nose cone would pop off and chute would come out.

Second way would be to have the Apogee simple timer in the ebay and the ebay secured to the lower tube with screws or push pins. The Eggtimer apogee would be in the nose cone (there is a nice 3d printed sled for this) and the nose cone secured to the upper tube with screws or push pins. The ejection charge would be in the upper end of the tube and when it goes off the upper tuber would separate from the ebay/coupler and deploy the chute.

Any definitive benefits for either option? I speculate the second option would help with the CG as some of the electronics would be in the nose cone.

Thanks,
-Bob

 

[Charles_McG]

If you use some kind of frangible connection from the FC to the staging wires, some other configurations are available. I use the 2 pin version of these: https://a.co/d/7DgKN3r

I leave the booster motor charge in place, trimmed for 1 sec past apogee. That makes it the backup.

My coupler-bay is pinned or friction fit to the payload tube. I run dual deploy, so the chute's in the payload tube and the nosecone is fit for normal flying. You can run apogee deploy with the chute in the main tube - ematch wire is long enough to get the charge down by the top of the motor, easy. For apogee deploy, you'll want to pin the nosecone, too. That means you could have a really short payload tube and change the look of the rocket less.

With both the timer and the eggtimer in the coupler-bay, then you'd have space for an eggfinder mini (or other tracker) in the nosecone. I don't recall where you're flying, but where I fly, if my 2" rocket goes over 2000', its got a tracker. (Or I regret it. That happens, too.)

 

[waltr]

There are many ways to setup airstart electronics.

I do suggest downloading the Eggtime Quantum or Proton Airstart Guide from Eggtimer's web site and carefully read. Cris did a very good job of explaining ways to do airstart and things that can wrong.

I build a 3" 2-stage from BMS parts. Booster is simple motor eject of chute. Sustainer uses a Quantum in a side hatch to fire motor and Apogee ejection. Sustainer motor ejection is back up. Lock-out is Velocity <100f/s @ timer.

There are many, many things that can and do go wrong but when it goes right, or at least recovery goes right it is a great feeling.

 

[mtnmanak]

I am surprised no one has mentioned the Altus Metrum Easy timer. It is about as small as you can get, has tilt monitoring, is cheaper than the Apogee device, and has a long track record in staging use.

Also, reference @FredT Fred Taverni's articles on staging in the two most recent issues of Tripoli's High Power Rocketry. If anyone out there could be called the master of staging, it would be Fred. His two articles are absolutely superb and give a huge amount of detail about high power staging.

 

[Bruiser]

"I leave the booster motor charge in place, trimmed for 1 sec past apogee. That makes it the backup."

How does the ejection charge get past the coupler/ebay?

This is New Mexico. I've not gone over 1,500 feet but have not had problems yet. The chute release keeps it from drifting too far but I will admit mesquite bushes and sagebrush do a pretty good job of hiding rockets. NOt really switching to composites to go super high; it's more to keep from paying hazmat charges

-Bob

 

[Charles_McG]

"I leave the booster motor charge in place, trimmed for 1 sec past apogee. That makes it the backup."

How does the ejection charge get past the coupler/ebay?

This is New Mexico. I've not gone over 1,500 feet but have not had problems yet. The chute release keeps it from drifting too far but I will admit mesquite bushes and sagebrush do a pretty good job of hiding rockets. NOt really switching to composites to go super high; it's more to keep from paying hazmat charges

-Bob

It doesn’t. The coupler-bay essentially acts like the shoulder of a very long nosecone (payload tube plus actual nosecone). If you’re doing single deploy, then the main (maybe with release) is in the main body tube like normal.

 

[BrendanH69]

I'm not sure what logic is available in the simple timer. For bigger staging configurations most clubs want some kind of safety lockout on the staging event. Tilt or altitude at time or velocity at time, etc. A pure timer has been known to start the second motor when its pointed in a non-optimal direction.

More than just a pure timer. It has a generous 45degree tilt lock-out, plus launch detection/trigger G sensing, and "chuff detection" disabling. I used it to airstart all three Darts on my Thales Starstreak scale build, with an RRC3 looking after the booster chute deployment after the airstart.

 

[waltr]

Thanks for posting about the SimpleTimer.
However, 45° is a bit too much tilt to ignite a 2nd stage in my opinion. At my local field this could mean it goes way over the woods with lots of very tall trees.

I would accept a max of 20°.

 

[Bruiser]

Ah, so you have a really long ignitor wire working it's way up the tube basically to a payload bay near the nose cone.

Do you also have a long lead on the ejection charge so it can be below the parachute to push it out?

-Bob

 

[Charles_McG]

Yes - though it's not continuous. I use pairs from CAT5/6 from the altimeter out of the bay. The color coding helps. The deployment charge is wire wrapped to that - and yes, just using the ematch wire to get it below the dogbarf and chute.

For the ignition wires (and separation charge - a Proton has 6 channels) I use ematch wire in 1/8" PE tubing. The top end has an easy break connector to the altimeter wires, the bottom end I wrap and tape to the igniter. I wrap the PE tubing pair in aluminum tape to protect it from ejection charge, and also tape it to the inside of the body tube, so it doesn't tangle the recovery stuff. Here's a link to a picture from my Terrier Improved Malemute build.
https://www.rocketryforum.com/threa...-5-2-scale-build-and-info.155945/post-1950127
And you can also see the guts laid bare, including the coupler avbay in the wreckage of my Ute Tomahawk.
BTW - the Tomahawk is built out of Estes PSII 2" tube - just the size you're working with.
Here:
https://www.rocketryforum.com/threads/ute-tomahawk-cti-g33-cato.154555/

 

[dakota196]

I like two stage rockets. I have a couple that are built for Estes Bp motors.

I have the NorthStar, which is 29mm
View attachment 528275

I have a boosted Citation Patriot that is 24mm to 24mm (sorry, no pic)

I also have the Tempest, which is a 24mm to 18mm rocket (again, no pic)

I built these rockets when the motors were easy to obtain from Hobby Lobby. Now they don't carry any 24mm or 29mm boosters. That got me thinking that if I am going to have to mail order my boosters why not just go composite. The BIG answer (for me) is that you can't gap stage composites...

Lets just say I have these hanging out.
View attachment 528279 View attachment 528281

And I want to use composite motors. What would be the easiest way to do it for someone who is electronics challenged?

Thanks,
-Bob


N

Who makes the NorthStar?