Redshift- 38mm Minimum Diameter Rocket

eggtimer rocketry
rocket sok
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Thanks guys!

@Coleman, The J570 sims to just under 15k, about 14700. I'm still looking at the J530 Imax as my best option. that's just over 15K, about 15500. Just a few hundred feet short of 3 miles! I'm really looking forward to seeing those videos- they always turn out so well!

@Bill, Thanks, the guides really stepped up to the challenge, so to speak, lol. I'd love to fly this rocket on an I1299N. I'm not sure when, but it could be as soon as LDRS, and that should be just about the ultimate challenge, barring that crazy new Loki motor!

@Teddy, you missed a great one, lol! We'll look forward to seeing you again soon, you just focus on getting better!

@ Connor, Thanks! I'm really starting to get psyched for LDRS, this might be Redshift's last flight before then, as I've pretty much maxed out our waiver. I haven't finalised which J it will be, I'm still working on that bit...

Nate
 
Have you sim'd with RASAero? I bet it predicts a higher altitude, and I think Rocksim and OpenRocket tend to underpredict 38mm MD mach 2 flights.

I am really looking forward to seeing someone fly an I1299 or that crazy Loki thing. I will of course be hiding under my car for it, but I can't wait to see it.

The I800 flight I saw was a blink-and-you-missed-it affair

My sims have generally suggested the J530 IMax would be both fastest and highest, but I lack experience to back that up. I will say that the guides should give you the biggest help when the burn is longer, e.g. with an IMax. Those half-second motors don't burn long enough for the button drag to make a huge difference in max V.

Altitude, of course, should benefit either way.
 
Last edited:
wfcook said:
Have you sim'd with RASAero? I bet it predicts a higher altitude, and I think Rocksim and OpenRocket tend to underpredict 38mm MD mach 2 flights.
Click to expand...

No I hadn't used RASAero, thanks for the idea! I did a bit of playing around, and it actually puts it closer to 13000, and just barely M2, when rectified with the H123 flight. I'll have to do some more looking, and get some better measurements, though.

Nate
 
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Over the past couple days I've been thinking about this rocket's flight at LDRS. It's gonna be a really tight squeeze to get the 6XL case in there. I had an idea and I'd like some feedback. What if I get a short section of 38mm tubing and use it basically as an extension of the thrust ring on the motor? that way, I could buy myself an extra 1/2 or 3/4 inch, which would probably be enough to get the motor in more comfortably. So basically, I'd have the extra tubing as a sleeve over the motor between the bottom of the rocket and the thrust ring of the motor. I haven't looked at stability yet, but IIRC with the 6XL I had a bit of margin. Thoughts?

Nate
 
nute said:
Over the past couple days I've been thinking about this rocket's flight at LDRS. It's gonna be a really tight squeeze to get the 6XL case in there. I had an idea and I'd like some feedback. What if I get a short section of 38mm tubing and use it basically as an extension of the thrust ring on the motor? that way, I could buy myself an extra 1/2 or 3/4 inch, which would probably be enough to get the motor in more comfortably. So basically, I'd have the extra tubing as a sleeve over the motor between the bottom of the rocket and the thrust ring of the motor. I haven't looked at stability yet, but IIRC with the 6XL I had a bit of margin. Thoughts?

Nate
Click to expand...

I see no reason as to why that would not work. As long as it is stable I would say your fine. I may look a little funny though :)
 
Make sure you check stability at both ends of the burn...especially at burnout when the thing will be going mach 2+
 
conman13 said:
I see no reason as to why that would not work. As long as it is stable I would say your fine. I may look a little funny though :)
Click to expand...

+1. As long as your stability still stays above 1 cal throughout the flight, I would say do it. Oh and my CTI 38mm 6GXl casing just arrived from wildman today, so if you want to do a test fit I'll have that with me at the next RR launch.
 
Well, it looks like this should work okay, there's pretty minimal change in the stability margins. Coleman, I'd love to do some test fitting with the case this weekend, that'd be great!

Here's a screenshot of the OR plot:

Redshift plot with overhang.jpg
 
If the weather cooperates, which it looks like it should, this'll be flying today! I've got the motor just about ready to go, e-charges packed, etc. Just gotta get to the field so I can turn on the tracker, pack the parachutes, and let er rip!

Nate
 
nute said:
If the weather cooperates, which it looks like it should, this'll be flying today! I've got the motor just about ready to go, e-charges packed, etc. Just gotta get to the field so I can turn on the tracker, pack the parachutes, and let er rip!

Nate
Click to expand...

Aaaannnddddd.....
 
I met Nate at the RSO table at LDRS when he came back in from looking for this. I can't remember if he found it or not.
 
Ah yes, well let's wrap this story up.

Well... The flight was "sub-optimal". I had some trouble getting the motor together, I had an out of spec liner, and stripped the closure/nozzle getting it in. After talking to Wildman, I bought another reload and got it in. CTI said they could send me a new liner and nozzle to use the original motor. There was some difficulty getting a high altitude window, borrowing an RDF receiver, and having my TRA sponsor all in the same place at the same time and place. By about noon I finally got everything together, after having one of my tracker batteries fail last minute. When the motor lit, the first 150 ish ft of the flight were okay, but shortly thereafter it corkscrewed or spun fairly violently. No one saw the events, but the tracker clearly wasn't underground, so with some help from the wonderful JimZ (can't thank that guy enough for his help!) we went off tracking, only to notice there was someone else on our frequency with a much stronger signal! It was tricky, but we tracked down off to the right of the flight line, and as we were getting close, someone handed us the upper portion of the rocket (NC, e-bay, payload, and tracker) asking if it was ours. The booster was nowhere to be found, and the broken end of the kevlar was badly frayed. I'm not entirely sure what happened. The altimeter beeped out just over 5K. Not quite what I hoped for. My best guess is that the tiny amount of drogue volume and corresponding charge inconsistently pressurized. Any small variations in packing, etc. I would guess would have huge repercussions on such a small volume. I think I was only using .2 g or so. So maybe in ground testing it was packed a bit loosely, and then in the actual flight maybe it was packed better, more tape, etc. and it was over-energetic. Maybe the actual motor sealed better than the rags I had put in the case for testing. Maybe...... maybe....... maybe....... Who knows. As far as the poor altitude, I think it naturally has to be because of the spin/corkscrew. As to what caused this, I'm not sure. Maybe fin flutter. 1/16" isn't a whole lot of thickness, even with big fillets. I'll have to look at the video again, it's not too great, but it captures the beginning of the boost at least.

So yeah. Maybe if someone finds the booster I'll know more about the recovery failure. Maybe then I can rebuild it and fly it on some in between motors and see where the problems start. There was no signs of the spinning on the H123 or H669, so this was the first time I'd seen anything like this. I don't think it was the rail guides. It left the rail just fine. In the confusion I actually never went out to get the rail guides, but I think they were fine. Thanks again to Bill Cook for the guides. Sorry I missed you at LDRS.

Regardless of how the last flight went, it was a fun project, and I had some really awesome flights. Really an enjoyable endeavor.


Nate
 
nute said:
Ah yes, well let's wrap this story up.

Well... The flight was "sub-optimal". I had some trouble getting the motor together, I had an out of spec liner, and stripped the closure/nozzle getting it in. After talking to Wildman, I bought another reload and got it in. CTI said they could send me a new liner and nozzle to use the original motor. There was some difficulty getting a high altitude window, borrowing an RDF receiver, and having my TRA sponsor all in the same place at the same time and place. By about noon I finally got everything together, after having one of my tracker batteries fail last minute. When the motor lit, the first 150 ish ft of the flight were okay, but shortly thereafter it corkscrewed or spun fairly violently. No one saw the events, but the tracker clearly wasn't underground, so with some help from the wonderful JimZ (can't thank that guy enough for his help!) we went off tracking, only to notice there was someone else on our frequency with a much stronger signal! It was tricky, but we tracked down off to the right of the flight line, and as we were getting close, someone handed us the upper portion of the rocket (NC, e-bay, payload, and tracker) asking if it was ours. The booster was nowhere to be found, and the broken end of the kevlar was badly frayed. I'm not entirely sure what happened. The altimeter beeped out just over 5K. Not quite what I hoped for. My best guess is that the tiny amount of drogue volume and corresponding charge inconsistently pressurized. Any small variations in packing, etc. I would guess would have huge repercussions on such a small volume. I think I was only using .2 g or so. So maybe in ground testing it was packed a bit loosely, and then in the actual flight maybe it was packed better, more tape, etc. and it was over-energetic. Maybe the actual motor sealed better than the rags I had put in the case for testing. Maybe...... maybe....... maybe....... Who knows. As far as the poor altitude, I think it naturally has to be because of the spin/corkscrew. As to what caused this, I'm not sure. Maybe fin flutter. 1/16" isn't a whole lot of thickness, even with big fillets. I'll have to look at the video again, it's not too great, but it captures the beginning of the boost at least.

So yeah. Maybe if someone finds the booster I'll know more about the recovery failure. Maybe then I can rebuild it and fly it on some in between motors and see where the problems start. There was no signs of the spinning on the H123 or H669, so this was the first time I'd seen anything like this. I don't think it was the rail guides. It left the rail just fine. In the confusion I actually never went out to get the rail guides, but I think they were fine. Thanks again to Bill Cook for the guides. Sorry I missed you at LDRS.

Regardless of how the last flight went, it was a fun project, and I had some really awesome flights. Really an enjoyable endeavor.


Nate
Click to expand...

no sign of it yet, but I will be sure to let you know if it does turn up!
 

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