So, maybe I'll try a three-stager

JimJarvis50 said:

I already have the M745 and I won't be spinning the rocket. But, for future reference, how does one know that this is certified for AMW/Gorilla hardware?

Jim

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I don't know, actually. Based on the impression the instructions gave me, any works...? Ask Jeroen.

JimJarvis50 said:

I did give some thought a while back about spin stabilization. I tried to find a few references on the subject. I didn't have much luck with that and the urge went away (or rather, was replaced by the likelihood of active stabilization, which may be more practical for me). I have noticed that on many of my two-stage flights, the off-angle occurs shortly after leaving the rail. I'm not sure this is weather cocking, because it seems to happen well after it leaves the rail. This flight (LDRS where the sustainer didn't light) is a good example:

https://www.youtube.com/watch?v=B1NGe44Jjhc

This change in angle was enough to abort the flight.

I think the rocket would need to be spinning leaving the rail, and I don't have the technical ability to do that. I also don't know how to de-spin the various stages. And I've been sorta stuck with the moonburners up to now. If anyone does have a good reference on the subject, I'd like to learn more about it.

Jim

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What happened there was weathercocking, but because the rocket has such a large moment of inertia, it takes it a while to find equilibrium (0* AOA). Your three-stager will be even worse because of the long length and distributed mass of the motors. The only way to overcome that is to leave the pad faster, making the fins more effective. That Pro98-6G N10000 Vmax would work really well for that purpose.

I also find that my rockets don't need to be spun up before leaving the pad because the roll moment of inertia for a long thin tube is so low that it spins up pretty quickly. It'll start spinning very quickly relative to any pitch/yaw rates occuring.

TheAviator said:

What happened there was weathercocking, but because the rocket has such a large moment of inertia, it takes it a while to find equilibrium (0* AOA). Your three-stager will be even worse because of the long length and distributed mass of the motors. The only way to overcome that is to leave the pad faster, making the fins more effective. That Pro98-6G N10000 Vmax would work really well for that purpose.

Click to expand...

Thanks for the input Brian. The N5800 is 15 G's right away, but I will still need some luck to stay vertical.

Last but not least, here are a few pictures of the sustainer. The nose cone is now configured with a new camera bay. I still need to balance that part. The airframe itself is 7 wraps of 6 oz carbon. That may be overkill, but my experience is that these long, skinny rockets need to be as strong as possible. This flight, though, tops out at just a bit over Mach 2.

The altimeter bay again has my extended charge holders for high altitude deployment. There are a few pics of the altimeter "skid". It's been modified many times and isn't very pretty. But, it does get two Ravens, a tiltometer, four batteries and five switches into a pretty small volume. It's wired and ready to fly (but no charges yet). The bulkhead on the bottom is very thick because the high altitude charges are very energetic.

Jim

Here are a few pics of the staging coupler (between the second and third stages).

The main function of this is to obviously transition from the 4" second stage to the 3" third stage. However, this coupler must also hold the two stages together so they don't drag separate after burnout of the first stage. The way I decided to do this was to fill the AMW external snap ring groove with epoxy and then drill the shear pin holes through the coupler and into the epoxy ring.

The first pic is a diagram of the coupler. It shows where the shear pins go and other features of the design. For this AMW motor, I'm covering the bottom of the motor with a plywood bulkhead. This will protect the third stage igniter wires from the separation charge. As with the second stage, the wiring is Gecko/Taperwire and there are four wires (two for the igniter and two for the separation charge). After the motor is inserted into the coupler, the shear pins are inserted through the coupler into the motor epoxy ring. Then, the heads will be cut off the shear pins so that the coupler can be inserted and then shear pinned into the top of the second stage.

Jim

So, a while back, we were talking about how to raise the rail. Here's where I am on that. The first pic is the geometry that I hope to get to via my ever-faithful pad slaves. We raise the CG up about 8' and then hold it there with a 2x4. Once raised, I'm planning to lift the rail the remainder of the way with a 3/16" cable. It's a bit inconvenient because I have to work the cable around the rocket. The last pic shows the rod/plates that the cable will attach to. There will actually be another 1" pipe between those plates that will provide more support.

I'm going to hook the end of the 80' cable to my tow hitch. After raising the rocket to the first position and placing the 2x4, the pad slaves will bug out, and I'll just pull it up the remainder of the way. I've also arranged to stake down the pad itself so that it doesn't slide when the rail is lifted. We'll practice this with the rail only first. I think this will work just fine.

I'm off now to spend a couple of days at LDRS!

Jim

JimJarvis50 said:

I'm off now to spend a couple of days at LDRS!

Jim

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Seems like a nice launch - well run and great weather. Last time I was here, I brought three rockets. Couldn't do that this time.

So far, though, I have seen no three-stagers?? Perhaps today...

Jim

Good luck out there Jim. I hope everything goes well.

My flight is approved and I'm ready to go (I hope). I will need almost perfect weather for this flight to work (in particular, low upper-level winds. The forecasts indicate that there is a chance that might happen!

Jim

Jim, good luck! I hope all goes well.

How in the world did I miss this thread until now...subscribed!

Best of luck, Jim--love your projects.

Good luck Jim! Make sure someones got a camera running.

Alex

Jim, I'm bringing my hiking boots! See you out there.

Tony

tfish said:

Jim, I'm bringing my hiking boots! See you out there.

Tony

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Bring some water too.

Jim

Best of luck to you, Jim! We're pulling for you, hope all the stars align right!

-Eric-

Break a leg.

Looking forward to some excellent video.

How'd it go?

Good belated luck!!

Looking forward to hearing how this shaped up.
Nate

Thanks guys. Right now, Saturday looks like the best day. Very little upper level winds. I got the pad set up today and made a lot of other progress. Very smoky out here - should clear up for the weekend.

Jim

Jim, I'll have my wireless if you need it. I should be there tomorrow afternoon. I'll PM you phone number if you need anything.

Tony

tfish said:

Jim, I'll have my wireless if you need it. I should be there tomorrow afternoon. I'll PM you phone number if you need anything.

Tony

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Mine just blew a fuse last year. Don't know why I didn't realize it (the heat of the moment I guess).

Jim

PS - mailbox cleared

JimJarvis50 said:

Thanks guys. Right now, Saturday looks like the best day. Very little upper level winds. I got the pad set up today and made a lot of other progress. Very smoky out here - should clear up for the weekend.

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Hope the flight goes well, Jim!

I wish I could be out there to give you a hand; tell Stu that in my absence he has to do the job of the two of us.

-Kevin

I was able to launch the three-stager on Saturday as planned. The weather was perfect and the N5800 boost was also nearly perfect (as best as I can tell without having seen much data yet). Unfortunately, the second stage didn't light. I have an idea why, but I won't know for sure until I get a better look at the electronics and perhaps do some testing. Fortunately, everything after the second stage didn't light was also perfect, and the rocket was recovered undamaged.

Although this is a bummer for sure (since the opportunity with such great weather may never happen again), I did learn a lot from the flight and many of the things I did to prepare for the flight worked well. A few things ...

My fin "crowns" worked just fine and survived the flight undamaged. The flight was very close to vertical (I'll calculate the angle later).

The process for lifting the rocket also worked (from a geometry perspective) except that I was able to use a winch instead of having to pull the rocket up with my truck (thanks Larry!). As we were pulling the rocket up, one of the guide wires snagged, and we were able to stop lifting the rocket before anything got damaged. If I had been using the truck, it is unlikely that we would have been able to stop soon enough. So, a winch it is. For the same reason, I think my plan of not having anyone under the rocket during the lift was the right approach.

The process I used to shear pin the 3rd stage (with epoxy in the motor case thrust ring) also worked. The 3rd stage didn't drag separate after the first stage burn, but did separate with the separation charge during the recovery of those stages.

I'm sure I will learn a lot more when I'm able to inspect the pieces. So, maybe I'll try a three-stager .... next year.

Jim

That may have just been the best thread-closing I have seen on here...

Anyways, bummer they didn't all light but I'm glad everthing was recovered undamaged.

Oh my gosh! You went ahead and built it. I have been out of the loop for almost a year now working on my house .I remember at Balls you mentioned a three stager but I thought you were just talking. I should have known better.
I really don't know how you organize so much electronics in such little space? The build looks amazing. Sorry the attempt failed but that just means in 2015 I will get to see it. Jim, Your an inspiration!!

Tbone said:

Oh my gosh! You went ahead and built it. I have been out of the loop for almost a year now working on my house .I remember at Balls you mentioned a three stager but I thought you were just talking. I should have known better.
I really don't know how you organize so much electronics in such little space? The build looks amazing. Sorry the attempt failed but that just means in 2015 I will get to see it. Jim, Your an inspiration!!

Click to expand...

Clearly, this year's event was just a trial run until you can be there! Let's both plan to get the job done next time.

Jim

I'm late to this thread too, but enjoyed the read immensely! Got chills reading it as I imagined seeing this flight- maybe I will in 2015! Beautiful write up and even more beautiful work, Jim!

soopirV said:

I'm late to this thread too, but enjoyed the read immensely! Got chills reading it as I imagined seeing this flight- maybe I will in 2015! Beautiful write up and even more beautiful work, Jim!

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Thanks! You're very kind.

And Cody, I haven't closed the thread just yet. At some point, I'll move on to active or spin stabilization or something else, but in the meantime, I'd like to try this flight again. So, I want to extract as much information as I can from the flight, which means getting opinions on things from the folks here. There's still a few things to look at.

Jim

Well, I figured out what caused my flight to abort. When the signal from the Raven reached the tiltometer, it caused the tiltometer to shut down. Further, the tiltometer is now inoperable. I had this problem occur earlier this spring while doing some bench testing. The unit was replaced and tested fine, but chose the flight to repeat the problem. We don't know why this happened. Apparently, I am the only one to have experienced this problem, so there is always the potential for some sort of operator error. Frank donated the unit for this flight, which I appreciate, and it's too bad that there was a problem.

Speaking of tilt, I thought the flight was pretty straight at the time. However, the gps trace shows that the angle was about 7° at the point where the second stage was to have lit. I'm not sure this trajectory was good enough to get past the tiltometer on the third stage, even if the second had lit. And, it would have been a long walk at best. Frozenfarrari and James Donald posted videos of the flight (thanks!) which are linked below. I think the video from James (the second one) was more east/west and better shows the weathercocking off the pad. I'm not sure how much I can do to prevent this, but I am going to try an increase the rail length from about 16' to about 30'. Comments on that, or other aspects of the boost, are welcome.

[video=youtube;_hR4f2ToFPg]https://www.youtube.com/watch?v=_hR4f2ToFPg&list=UUZHQd8FdnPL3VB6hVSZ6MFw&index=6[/video]
https://www.youtube.com/watch?v=ZiwQoUntimQ&feature=youtu.be

Jim

Looks like you had some wobble there at take off shortly after leaving the rail. Maybe that could have messed up the tiltometer. Either that or just operator error like you said.


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet

SinfulDarkLord said:

Looks like you had some wobble there at take off shortly after leaving the rail. Maybe that could have messed up the tiltometer. Either that or just operator error like you said.


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet

Click to expand...

Here's the recorded tilt data up to the point of the Raven signal. The tilt around 1 second is obvious in the video as is the wobble from 2-3 seconds. The big increase at 4 seconds is after burnout. Wonder if this is an N5800 thing? The tilt critical angle was set at 15°.

Jim