I540 to Mach 2 - 38mm Flying Case

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RocketHunter

RocketHunter

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This project has been in the design/build phase for quite a while, but I am finally close to being ready to see it fly. The goal of this project is to break Mach 2 and 2 miles of altitude - on an I motor.

I fabricated 90% of the parts last year, and have been slowly assembling them into a completed rocket. The fincan and body tubes are all made out of carbon fiber and aeropoxy laminating resin.

Photo Dec 03%2C 5 10 11 PM.jpg

The build is nearly complete, with just a few recovery and electronics parts to wrap up. It stands at just 26.75" tall!

Photo Sep 03, 1 42 11 PM.jpg

Photo Sep 03, 1 42 53 PM.jpg

Photo Sep 03, 1 42 44 PM.jpg

SPECS:
My motor of choice is the CTI I540 - The best combination of a nearly full impulse I and high average thrust for obtaining maximum velocity.

Currently, the rocket weighs about 10oz and is nearly complete. At this weight it sims to around 12K feet and mach ~2.25.

Untitled.png

Tracking, Deployment and data will be covered by an AIM XTRA - the red one on the right. I've had about 5 successful "practice" flights with this in my Blackhawk 38 - the GPS accuracy and transmitter range are excellent. It has a vertical 100g accelerometer, among many other things, so I should get an accurate measurement to determine whether I broke mach 2 or not.

Photo Jul 03, 5 20 42 PM.jpg

It will probably be single deploy with a large streamer and/or small parachute, but there is a small possibility I may be able to fit a cable cutter in for dual deploy.

It will be tower launched, of course, and a friend is fabricating a nice adjustable 6ft launch tower that I will use. I should have pics of that soon.

My plan is to drive up to URRG for their September launch on the 27-28 to get a high enough waiver and enough recovery area to fly this. Having never been to that launch site besides my home field, radrocketeers, I am curious as to what the procedures are when bringing your own pad, and what information an RSO would look for/need to approve a flight like this.

Also, any advice/comments from those who have flown these kind of flight profiles/rockets is appreciated!
 
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Very nice mate. I have had this exact idea on the back burner for some time now, so I can say I am looking forward to your thread. The I540 is a nice motor choice as far as I's go, at least in my opinion. I am interested in the internal configuration but other than that everything looks good. How long is your NC shoulder?
 
Last edited:
A5tr0 An0n said:
Very nice mate. I have had this exact idea on the back burner for some time now, so I can say I am looking forward to your thread. The I540 is a nice motor choice as far as I's go, at least in my opinion. I am interested in the internal configuration but other than that everything looks good. How long is your NC shoulder?
Click to expand...

Thank you! The NC shoulder is around 1.75'', and a very snug fit. The XTRA is mounted inside the NC, partially into the coupler, with around 1.5'' of the coupler left open for recovery gear. The forward tube has a bulk plate epoxied in about 1'' up, and the motor case slides up against this. A short threaded rod goes through the bulk-plate, and is threaded into a nut epoxied into the aft closure/delay grain. This holds everything together and also serves as the recovery attachment point.

This reminds me, how many shear pins do people use for 38mm? Three is the common number, and what I've used, for larger rockets, but in 38mm it would take a pretty hefty charge to consistently shear all three I would think.
 
RocketHunter said:
This reminds me, how many shear pins do people use for 38mm? Three is the common number, and what I've used, for larger rockets, but in 38mm it would take a pretty hefty charge to consistently shear all three I would think.
Click to expand...

Believe it or not..........I use just 1 on high performance 38mm's.
 
blackjack2564 said:
Believe it or not..........I use just 1 on high performance 38mm's.
Click to expand...

Ok thanks, I'll try 1 shear pin out first on my ground tests, and see how that goes.

I forgot to mention that one of the nice things about doing the flying case setup is that anything the size of the CTI 5g case or larger can be flown with zero modifications - just slide the fincan on, and attach NC setup on the top of the motor. The rocket grows to fit the case! Makes me dream of Loki 38-1200 loads - the J1000 would put this thing to 20K and mach 2.75 :y:
 
RocketHunter said:
Ok thanks, I'll try 1 shear pin out first on my ground tests, and see how that goes.

I forgot to mention that one of the nice things about doing the flying case setup is that anything the size of the CTI 5g case or larger can be flown with zero modifications - just slide the fincan on, and attach NC setup on the top of the motor. The rocket grows to fit the case! Makes me dream of Loki 38-1200 loads - the J1000 would put this thing to 20K and mach 2.75 :y:
Click to expand...

I might decide to get one of those cases in the near future.
 
CarVac said:
I might decide to get one of those cases in the near future.
Click to expand...

Cool! I wonder if the 38/1200 red motor will make it into the K range....

Been playing around on RasAero, and to my surprise, a lightweight 29mm Flying case design with motor deploy and a BRB RDF tracker can break mach 2 on an H399.... Hmmm I do have some scrap carbon fiber sheets laying around for fins.... :D
 
RocketHunter said:
I forgot to mention that one of the nice things about doing the flying case setup is that anything the size of the CTI 5g case or larger can be flown with zero modifications - just slide the fincan on, and attach NC setup on the top of the motor. The rocket grows to fit the case! Makes me dream of Loki 38-1200 loads - the J1000 would put this thing to 20K and mach 2.75 :y:
Click to expand...

Is the fincan just friction fit to the case? You mention that this applies to a 5 grain case or larger, is this due to stability issues if something smaller is used.
 
Rrwjr said:
Is the fincan just friction fit to the case? You mention that this applies to a 5 grain case or larger, is this due to stability issues if something smaller is used.
Click to expand...

They don't really need to be friction fit, as long as they don't slide up and somehow reef the parachute after ejection.
 
RocketHunter said:
This project has been in the design/build phase for quite a while, but I am finally close to being ready to see it fly. The goal of this project is to break Mach 2 and 2 miles of altitude - on an I motor.

I fabricated 90% of the parts last year, and have been slowly assembling them into a completed rocket. The fincan and body tubes are all made out of carbon fiber and aeropoxy laminating resin.

View attachment 183260

The build is nearly complete, with just a few recovery and electronics parts to wrap up. It stands at just 26.75" tall!

View attachment 183261

View attachment 183266

View attachment 183264

SPECS:
My motor of choice is the CTI I540 - The best combination of a nearly full impulse I and high average thrust for obtaining maximum velocity.

Currently, the rocket weighs about 10oz and is nearly complete. At this weight it sims to around 12K feet and mach ~2.25.

View attachment 183267

Tracking, Deployment and data will be covered by an AIM XTRA - the red one on the right. I've had about 5 successful "practice" flights with this in my Blackhawk 38 - the GPS accuracy and transmitter range are excellent. It has a vertical 100g accelerometer, among many other things, so I should get an accurate measurement to determine whether I broke mach 2 or not.

View attachment 183268

It will probably be single deploy with a large streamer and/or small parachute, but there is a small possibility I may be able to fit a cable cutter in for dual deploy.

It will be tower launched, of course, and a friend is fabricating a nice adjustable 6ft launch tower that I will use. I should have pics of that soon.

My plan is to drive up to URRG for their September launch on the 27-28 to get a high enough waiver and enough recovery area to fly this. Having never been to that launch site besides my home field, radrocketeers, I am curious as to what the procedures are when bringing your own pad, and what information an RSO would look for/need to approve a flight like this.

Also, any advice/comments from those who have flown these kind of flight profiles/rockets is appreciated!
Click to expand...

right now URRG still has all the crops in. hopefully the the corn will be out by the 27th. I could go check out the field when we get close if you would like, I'm less than 10 minutes away. I'm new to the URRG club but from what I have seen they are very level headed and great to work with. send a PM to Bill Clune, (wclune) or one of the other URRG members easily found in the LDRS34 section.
 
RKeller said:
right now URRG still has all the crops in. hopefully the the corn will be out by the 27th. I could go check out the field when we get close if you would like, I'm less than 10 minutes away. I'm new to the URRG club but from what I have seen they are very level headed and great to work with. send a PM to Bill Clune, (wclune) or one of the other URRG members easily found in the LDRS34 section.
Click to expand...

Wow that would be great if the crops were gone by then, would make recovery much easier! I'm not terribly worried about crops though, as in the test flights of the XTRA in my Blackhawk 38, the GPS put me within 10ft of the rocket on 5 out of 5 flights, some even closer than that.
 
jmattingly13 said:
Does carbon fiber not seriously attenuate the transmitter signal? That's a pretty sweet rocket you've got there, and I'd love to see it fly.
Click to expand...

Thanks! Carbon fiber does seriously attenuate the signal; this is why the XTRA's antenna is located up inside the 38mm FW fiberglass nosecone - the fiberglass does not attenuate the signal.

The tower this thing will be flying from should be ready tomorrow or monday; I'll post some pictures of it then.
 
RocketHunter said:
Thank you! The NC shoulder is around 1.75'', and a very snug fit. The XTRA is mounted inside the NC, partially into the coupler, with around 1.5'' of the coupler left open for recovery gear. The forward tube has a bulk plate epoxied in about 1'' up, and the motor case slides up against this. A short threaded rod goes through the bulk-plate, and is threaded into a nut epoxied into the aft closure/delay grain. This holds everything together and also serves as the recovery attachment point.

This reminds me, how many shear pins do people use for 38mm? Three is the common number, and what I've used, for larger rockets, but in 38mm it would take a pretty hefty charge to consistently shear all three I would think.
Click to expand...

I usually use either one or two. Three is far too much on a rocket of this diameter.


Mark Koelsch
Sent from my iPhone using Rocketry Forum
 
RocketHunter said:
this is why the XTRA's antenna is located up inside the 38mm FW fiberglass nosecone - the fiberglass does not attenuate the signal.
Click to expand...

That black fiberglass pigment always trips me up. I guess if I'd looked a bit more carefully at the picture, it would have been clear that wasn't carbon fiber. I guess the GPS receiver antenna is up there, too?
 
jmattingly13 said:
That black fiberglass pigment always trips me up. I guess if I'd looked a bit more carefully at the picture, it would have been clear that wasn't carbon fiber. I guess the GPS receiver antenna is up there, too?
Click to expand...

Yeah the black pigment is hard - I like the RW colored cones better, but to get it without the metal tip it only comes in black. Yes, its in there just barely, I'll post some pictures of the electronics setup later today.
 
Wow, I came up with this a couple years ago and never built it.. Not a flying case but the altitude sims are only 5 feet off.. Yours is much faster though.. Good luck with it!

 
Bojangles said:
Wow, I came up with this a couple years ago and never built it.. Not a flying case but the altitude sims are only 5 feet off.. Yours is much faster though.. Good luck with it!

Click to expand...

Wow, thats cool! I mostly used RasAero for the sims, but was surprised that the Open rocket altitude and velocity very closely matched the RasAero sims. The only difference I found was that OpenRocket was wayyyy off on the CP at high mach, saying it would go unstable, but RasAero showed it stayed above 1 caliber throughout the flight.
 
RocketHunter said:
Wow, thats cool! I mostly used RasAero for the sims, but was surprised that the Open rocket altitude and velocity very closely matched the RasAero sims. The only difference I found was that OpenRocket was wayyyy off on the CP at high mach, saying it would go unstable, but RasAero showed it stayed above 1 caliber throughout the flight.
Click to expand...

I'm afraid you're in for a harsh surprise....
RAS sucks with stability. First hand experience.

Alex
 
Last edited:
RocketHunter said:
Wow, thats cool! I mostly used RasAero for the sims, but was surprised that the Open rocket altitude and velocity very closely matched the RasAero sims. The only difference I found was that OpenRocket was wayyyy off on the CP at high mach, saying it would go unstable, but RasAero showed it stayed above 1 caliber throughout the flight.
Click to expand...

Just an FYI, last year a minimum diameter N5800 went unstable because RasAero was trusted for stability at high mach. Openrocket seems to be much more accurate at high velocity stability predictions.
[video=youtube_share;B_dwoiDsKws]https://youtu.be/B_dwoiDsKws[/video]
 
Eat said:
Just an FYI, last year a minimum diameter N5800 went unstable because RasAero was trusted for stability at high mach. Openrocket seems to be much more accurate at high velocity stability predictions.
[video=youtube_share;B_dwoiDsKws]https://youtu.be/B_dwoiDsKws[/video]
Click to expand...

Wow, this is not good.... ::shock:

Well, I frantically looked at my openrocket sim and realized it still had a tail cone on, even though it will not be flying with one. When I removed it, it shifted the CP back 3/4'', and made the rocket barely stable throughout the flight (only ~0.3 calibers at max speed).

Additionally, I realized my CG was entered incorrectly. :facepalm: I had measured the CG of my rocket with the case (as seen in photos), plus with a used reload in it (effectively the burnout mass of the I540). I had overrode the CG in Openrocket to this measurement - but in openrocket this was when it was empty, not with half the weight of the motor in it. To fix this, I loaded a motor that was approximately the same length as the I540, and the same launch mass as the burnout mass of the I540, in this case a CTI H180. Then, I adjusted my CG until it was where I had measured it.

Between these two errors, I now stay above 1.25 calibers of stability throughout the flight.
 
RocketHunter said:
Wow, this is not good.... ::shock:

Well, I frantically looked at my openrocket sim and realized it still had a tail cone on, even though it will not be flying with one. When I removed it, it shifted the CP back 3/4'', and made the rocket barely stable throughout the flight (only ~0.3 calibers at max speed).

Additionally, I realized my CG was entered incorrectly. :facepalm: I had measured the CG of my rocket with the case (as seen in photos), plus with a used reload in it (effectively the burnout mass of the I540). I had overrode the CG in Openrocket to this measurement - but in openrocket this was when it was empty, not with half the weight of the motor in it. To fix this, I loaded a motor that was approximately the same length as the I540, and the same launch mass as the burnout mass of the I540, in this case a CTI H180. Then, I adjusted my CG until it was where I had measured it.

Between these two errors, I now stay above 1.25 calibers of stability throughout the flight.
Click to expand...

Good to hear! It looks like a very cool rocket.
 
Stability excuses, you guys make me laugh. More like not launched properly.

I will say no more.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
 
Young ones. You need to take some advanced coursed in flight dynamics so you can understand what happened on your failed flights. Simulation programs are only as good as the phenomenon included in the simulation, and none of the hobby rocket simulations include roll-pitch coupling which caused the type of failures that occurred on your flights, nor have you collected the necessary data to perform these calculations even if you know how to do them.

If you go back and search TRF for coning, which is roll-pitch coupling, a dynamic stability problem that is not simulated in any hobby simulation, you will find several discussion on the topic and Chuck Rogers, the author of RASAero, discussed this fact in several replies.

Alex, would you like to make any other comments?

Bob
 
"RASAero sucks with stability. First hand experience (with my 1.0, 1.5 caliber stable Mach 3 rocket)."

"N5800 went unstable because RASAero was trusted for stability at high mach. (Trusted for stability for a 1.0, 1.5 caliber stable Mach 3 rocket.)"

Were the stability margins documented for these rockets, the lift-off CG, and the subsonic CP and supersonic CP predictions? From many posts (the rocket in this thread is only 1.25 caliber stable subsonic), I think a lot of rocketeers are running rockets with stability margins of 1.0, 1.5 calibers.

There are errors in supersonic CP prediction with the different methods. And even if the rocket is technically stable, once the stability margin is at 1.0 caliber supersonic, or falls below 1.0 caliber supersonic, the pitch-roll coupling effects referenced in the last post, and other "interesting" effects ("interesting" not being a good thing in this context), begin to be very important, especially for rockets like a minimum diameter N5800 rocket.

Is a rocket 1.0 caliber stable at Mach 3 a good idea? I've recommended maintaining at least 2.0 caliber stability at all Mach numbers. The successful Don't Debate This N5800 minimum diameter rocket had a subsonic stability margin of a little over 4.0 calibers, I believe.

So I'd note what the actual CG's and predicted CP's were for these flights. I'll be going back and looking at prior flights (Proteus 6, Qu8k), to see what stability margins they ran. I think many ran 3-4 calibers stable subsonic, which is overkill, but they worked and didn't have issues.


Chuck Rogers
Rogers Aeroscience
 
Chuck Rogers said:
the rocket in this thread is only 1.25 caliber stable subsonic
Chuck Rogers
Rogers Aeroscience
Click to expand...

Actually, right now its at 2.1 calibers subsonic and 1.25 @ mach 2.2. The loss of propellant mass (~33% of the rocket) keeps the CP from overtaking the CG at max speed - as the CP moves forward due to speed, so does the CG as propellant is burned.

Untitled.jpg

The fins on this are not that small really - a full 1 caliber tall (1.5").
 
SinfulDarkLord said:
Stability excuses, you guys make me laugh. More like not launched properly.

I will say no more.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet
Click to expand...

Could you explain that, I am not sure I follow.
 
Chuck Rogers said:
"RASAero sucks with stability. First hand experience (with my 1.0, 1.5 caliber stable Mach 3 rocket)."

"N5800 went unstable because RASAero was trusted for stability at high mach. (Trusted for stability for a 1.0, 1.5 caliber stable Mach 3 rocket.)"

Were the stability margins documented for these rockets, the lift-off CG, and the subsonic CP and supersonic CP predictions? From many posts (the rocket in this thread is only 1.25 caliber stable subsonic), I think a lot of rocketeers are running rockets with stability margins of 1.0, 1.5 calibers.

There are errors in supersonic CP prediction with the different methods. And even if the rocket is technically stable, once the stability margin is at 1.0 caliber supersonic, or falls below 1.0 caliber supersonic, the pitch-roll coupling effects referenced in the last post, and other "interesting" effects ("interesting" not being a good thing in this context), begin to be very important, especially for rockets like a minimum diameter N5800 rocket.

Is a rocket 1.0 caliber stable at Mach 3 a good idea? I've recommended maintaining at least 2.0 caliber stability at all Mach numbers. The successful Don't Debate This N5800 minimum diameter rocket had a subsonic stability margin of a little over 4.0 calibers, I believe.

So I'd note what the actual CG's and predicted CP's were for these flights. I'll be going back and looking at prior flights (Proteus 6, Qu8k), to see what stability margins they ran. I think many ran 3-4 calibers stable subsonic, which is overkill, but they worked and didn't have issues.


Chuck Rogers
Rogers Aeroscience
Click to expand...

My rocket.

It was always predicted by RASAero to be at least 2 calibers stable up to M4.2, accounting for the consumption of propellant. We made it so that that would be true. However, it would stubbornly go unstable in OpenRocket whenever I simmed it, with a very low altitude estimate that I couldn't understand (since it didn't actually emit the warning about a high angle of attack) until after the flight.

More recently, I redid my simulations and if I either add another fin or add half a degree of fin cant, it remains stable in the OpenRocket simulation.

Just so you know, the OpenRocket simulation is full 6dof in the background, and I am fairly sure based on rudimentary looks at the graphs that it was coning in the simulation much as it did in real life.
 

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