So, maybe I'll try a three-stager

Sheeeeeoooooot, I bought a few SMA heavy spring coil antennas a few years ago and use them on a bulkhead connector. I haven't had a chance to fly them yet but look robust. Darn, I can't find a link to even post a picture.
I'll see if I can post a picture. Kurt Savegnago

All right, I found a link with a picture but it doesn't look like they're an easy find anymore: https://tr.aliexpress.com/store/pro...Motorola-BAOFENG-SMA/1822085_32383903547.html

Ebay link but with a BNC connector. Used to have SMA Male: https://www.ebay.com/sch/i.html?_od...0MHz+Soft+Handheld+Radio+Antenna+BNC&_sacat=0

Xrain said:

Conveniently I am an electrical engineer, and I do have access to the requisite test equipment. Though my recent move has made an anechoic chamber harder to access. I haven't done any actual antenna design yet but it is an interest for me.

Do you know of any good references about antennas for these kinds of applications?

Click to expand...

Google conformal band antennas

They are nominally 2 pi antennas so use (2) at 180 degrees for 4 pi coverage. The length to width ratio determines the bandwidth.

Bob

Jim what an awesome flight. I have watched the video probably 10 times and it really is exciting to see eachs stage succesfully light. What an inspiration!!!

amarillo_rocket said:

Jim what an awesome flight. I have watched the video probably 10 times and it really is exciting to see eachs stage succesfully light. What an inspiration!!!

Click to expand...

Thanks Barre' (and everyone else who has commented on the flight). It's nice to have a video that shows the part of the flight that went well. I'm still working on the on-board video, and it will show up before too long. That video will be exciting too.

Jim

bobkrech said:

Google conformal band antennas

They are nominally 2 pi antennas so use (2) at 180 degrees for 4 pi coverage. The length to width ratio determines the bandwidth.

Bob

Click to expand...

That search mostly turns up patch antennas. With patch antennas the L/W ratio alters the feedpoint impedance while bandwidth mostly depends on the distance between the patch and the ground plane. Not that it matters much because at the frequencies of interest here, they are too large for the airframes. They need to be a half wavelength long to resonate. The substrate typically used for wrap around antennas improves that by a factor of ~2. But that is still big even for the 70cm band. On the plus side, you might be able to increase the width enough to wrap nearly all the way around the airframe so you would only need the one.

But I had an idea that might work but isn't especially practical. The near field around a loop antenna is mostly magnetic and CF has essentially no magnetic shielding ability so a loop might radiate better from inside a CF tube. The hassle is that commercial loop antennas are rare. Building them is easy but they have to be tuned which requires test equipment. Plus the question of just how stable that tuning would be in the field.

Kent Britian in Grand Prairie, TX makes some very innovative antennas for specialty purposes.
https://www.wa5vjb.com/

I had a couple of video cameras on the flight. I combined them, and here's the result. There are a lot of things I could point out in the video about what worked, what didn't, etc. But maybe the best thing to do is just grab some popcorn and enjoy the ride.

Jim

https://youtu.be/eHloNCGlYz4

Jim, SUPERB! /Tim

That is downright inspirational. Thank you for sharing!

Spectacular Jim, thanks!

Incredible...

Awesome, truly awesome!

Absolutely stunning! Awesome job!!

Wonderful video! Seeing black sky is always inspirational.

Great video awesome flight.

So, the second stage of my three stager never showed up, so it's time to build a replacement. Actually, the replacement may first fly as a two-stager, but who knows for sure. Construction has started and I've made some progress. I'm not planning on doing much of anything differently than I've done before, so as build threads go, this will be short and sweet.

The last time I made a 4" minimum diameter rocket, I used a PML phenolic coupler tube as the mandrel. To my shock and surprise, PML 4" coupler tubing is slightly smaller than a 98mm motor. Not a good thing. This time, I'm trying a piece of wildman coupler tubing, which happens to be available in 66" sections (I wanted a 54" mandrel). I hope it's nice and round - I'll find out shortly.

I have also laminated some G10 fins and beveled the edges using my router. There is just something special about routing carbon fiber, but the job is done.

I've rolled the first air frame section (a 7-wrap tube this time). I made a jig a few years ago to allow me to roll the tube out of a single piece of carbon, and to hang a weight on the end of the carbon (the weight - about 10 pounds for this tube - really helps tighten up the wraps, since other means of compression don't work very well). I was surprised to find that I hadn't cut up the jig for something else, so I'm using it again for this rocket. This 42" tube is the upper air frame, and I'll make a 48" tube for the lower fin section.

Jim

Just a few more pics ....

I got the air frame tubes rolled and now I need to finish them.

I've also been working on a coupler. Initially, the coupler will be used on another test of my stabilization system. The test will be a two-stage flight, with stabilization below the sustainer, but with no sustainer motor. The coupler will take the place of the motor tube that would normally hang out below the bottom of the sustainer and mate with the stabilization section. When that flight is done, the coupler will serve as the zipperless coupler for the new sustainer. The coupler starts with the Wildman coupler tubing because it fits the tubes I just made (this coupler tubing worked very well as a mandrel by the way). I lined the coupler with 5 wraps of carbon (using the foam roller "stick"). I'm using a double-bulkhead approach for the zipperless bulkhead. This approach has saved two of my rockets in the past (by preventing a motor failure from gutting the upper air frame). Cheap insurance.

Jim

Jim,

You always make such fantastic work. Keep up the good work.

So, I'm continuing with the rebuild of the AWOL second stage of my three stager. When I last posted, I had rolled the tubes. I've done a lot of work since then, but there's much more to do.

Although this build is to replace the second stage, I'll likely skip a year on the three stage configuration and use this rocket as the sustainer for a two stage flight this year. So, we'll take a little detour for a few months and then get back to the three stager next fall.

The two-stage flight will be a 6" to 4" design. Stu Barrett and I are collaborating on it, and we'll have fun no matter how it turns out. The 6" rocket was originally designed by Ray Kinsel and Jim Long, and Ray flew it at Balls a few years back. It was a great flight. I was recovering some piece of debris at the time, so we watched from a few miles out.

https://youtu.be/u4hXywtuS4Q?list=PLEISeVEqORmxu04MBI5BasIzkq28WQRyk

(I'm "Slim" in the Texas Posse by the way, although I don't know why.)

Although it's a nice rocket, it needs to go on a diet. Stu is making a new, shorter upper airframe and a much smaller and lighter altimeter bay, and he's also working on the interstage coupler. One other component that we're replacing is the fin can. The current aluminum fin can weighs in at 17 pounds, so we're making a composite fin can, which should come in around 6 pounds. We'll need to spice up the performance of the motor a bit for the two-stage configuration.

The booster motor should be close to a full "P" and the sustainer will be an O-3400. The configuration is as shown in the pic and the plan is to use active stabilization (assuming an upcoming test flight of the stabilization system is successful). A preliminary altitude projection is around 160K.

The remaining pics are of the construction of the fin cans. A composite fin can is a lot of work and doing two of them at once is a whole lot of work, but I'm making progress. The next step here will be to vacuum bag tip-to-tip carbon on both rockets. I'll be back in month or two after that's done.

Jim

Jim, looking at the rocket layout. Does the guidance module stay with first stage of go with the second, and then pop off at or shortly before motor ignition?

Sound like an awesome project.

Next, you should build an airframe for an S motor. I have heard rumors of one existing on a ranch in Texas.

Nice!

markkoelsch said:

Jim, looking at the rocket layout. Does the guidance module stay with first stage of go with the second, and then pop off at or shortly before motor ignition?

Sound like an awesome project.

Next, you should build an airframe for an S motor. I have heard rumors of one existing on a ranch in Texas.

Click to expand...

Like the three stage, the idea is to have the stabilization section stay attached for the coast phase and then separate just before lighting the sustainer. In the three stage, the CG was ahead of the stabilization section for the entire flight. For the 6x4 flight, it is initially behind the stabilization section. Therefore, we are modifying the programming so that there is only roll control during the boost, and then roll/yaw/pitch after separation. Another reason for this change is to prevent attempted yaw/pitch control at a time when the rocket won't respond to those inputs. This would prevent torque on the air frame, which is one factor that might have prevented the booster from separating in the three stage flight last year. There are many such improvements in the stabilization section hardware and control strategy, and I'll post something on that at some point.

Jim

Looks like it's been about a month since I posted progress on my current project. This project is the rebuild of the lost second stage of the three-stager, which will actually be used first as the sustainer of a P to O two-stage project before reverting to the three-stager next year (if I still own it). At the last update, I had completed the fillets on both the 4" sustainer and the composite fin can for the 6" P motor. The P motor fin can is completed. I applied two layers of carbon - one at 45 degrees and one "straight". Not great composite work, but I figure this will be a single use fin can, so no need to be perfect. I added a built up leading edge from the Cotronics 4525 that actually worked out pretty well. I also added three aluminum inserts to the body that will have set screws to keep the fin can from spinning on the motor tube. These are the treated inserts by Random Flying Object:

https://www.apogeerockets.com/Build...s-3-pk?zenid=de44b09b6c6b0adb995a179e3e7657e0

The fin can came in at 5.5 pounds, compared to the 17-pound aluminum fin can it replaces.

On the sustainer, I have started the tip-to-tip carbon application. Spent pretty much a full day just cutting out all of the different cloth, breather, bag, peel ply, etc., etc. I'm just following the procedure in my Part 2 build article (good thing I wrote it all down).

I'll be back in another month after the sustainer fin can is completed.

Jim

JimJarvis50 said:

Looks like it's been about a month since I posted progress on my current project. This project is the rebuild of the lost second stage of the three-stager, which will actually be used first as the sustainer of a P to O two-stage project before reverting to the three-stager next year (if I still own it). At the last update, I had completed the fillets on both the 4" sustainer and the composite fin can for the 6" P motor. The P motor fin can is completed. I applied two layers of carbon - one at 45 degrees and one "straight". Not great composite work, but I figure this will be a single use fin can, so no need to be perfect. I added a built up leading edge from the Cotronics 4525 that actually worked out pretty well. I also added three aluminum inserts to the body that will have set screws to keep the fin can from spinning on the motor tube. These are the treated inserts by Random Flying Object:

https://www.apogeerockets.com/Build...s-3-pk?zenid=de44b09b6c6b0adb995a179e3e7657e0

The fin can came in at 5.5 pounds, compared to the 17-pound aluminum fin can it replaces.

On the sustainer, I have started the tip-to-tip carbon application. Spent pretty much a full day just cutting out all of the different cloth, breather, bag, peel ply, etc., etc. I'm just following the procedure in my Part 2 build article (good thing I wrote it all down).

I'll be back in another month after the sustainer fin can is completed.

Jim

Click to expand...

Jim,

This. Is. Awesome!

Loving it and can't wait to see the results! Simply stupendous!

JimJarvis50 said:

The fin can came in at 5.5 pounds, compared to the 17-pound aluminum fin can it replaces.Jim

Click to expand...

Sick! Awesome looking fin can sir!

That looks like Formula One quality layup work. Great job Jim.

So, I have finally completed the tip-to-tip on the sustainer fin can. I think it will work.

The current simulation shows a maximum speed for the rocket of about Mach 3.2. Although this will occur at 40K feet, there still needs to be some protection of the leading edge to prevent delamination of the carbon. In the past, I have painted on several layers of the Cotronics 4525 high-temp epoxy. This seems to work, but it is difficult to build up much thickness, so in more recent rockets, I came up with a way to produce a built-up leading edge. I published the method in my Part 2 build article from a few years ago. This method works, but is difficult to execute. So, for this build, I tried for something much simpler. The idea was to apply a leading edge with a shape like what is shown in the third picture. I was able to apply all four leading edges over a rainy weekend - not to bad. The attached pdf shows some of the key steps for those interested in how it was done.

Jim







View attachment Leading edge 2.pdf

Cool technique, thanks again for sharing.

smapdiage9 said:

Cool technique, thanks again for sharing.

Click to expand...

+1. Very nice!

In fact, I have a rocket in process that I might use this technique on in the next couple weeks.