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I600 flight to 15965 feet

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Adrian A

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I'm cross-posting this here in case folks might be interested but haven't seen it over at Rocketry Planet.

Last weekend at Mile High Mayhem I flew my 38mm carbon fiber rocket on an I600, trying to see how high I could get an I-powered rocket. Due to a premature main deployment, the rocket landed almost 5 miles from the pad, and I finally recovered it yesterday after a lot of help from several other NCR club members.

The build thread for the rocket is here. I started on it late last year, and I've done everything I can do optimize it for maximum altitude, while keeping a dual deployment design.

Last Sunday I launched it from my tower with a nice clean boost, and the rocket went right out of sight. The altimeter turned on the transmitter at the main deployment altitude, but that was about 14 minutes after liftoff, and I only got a minute or so of tracking direction before it went over the horizon.

Here's data from the new Featherweight Interface program:
Altitude and temperature, for the whole flight:


Velocity, accel, and altitude up through apogee deployment and the premature main deployment


Zoomed into the the motor burn:


One altimeter reported 15960 feet right as the last data point before the apogee charge fired, and the other one reported 15969 feet.

Then I did some more detailed post-processing of the data using the Excel template on the Featherweight Altimeters site:

First, I adjust the accel offset, scale factor, and time factor so that the integrated accel calculated altitude matches the baro-based altitude:



This gives me a set of accelerometer data that is consistent with the baro data. Here's the residual error between the two. Note how there is a little step change near 16 seconds. I believe that is when the delay burned through, equalizing the pressure between the motor and the rest of the rocket. Good thing I was using electronic ejection! It was still going up at 250 mph when the charge burned through.



Now with good accel data, there's all kinds of things you can calculate. In particular, I'm happy with how the Cd vs. velocity came out:


Compare that to the Cd vs. velocity data I got for conical and ogive-ish rockets last summer:



The supersonic penalty is only half what it was for either the conical or Apogee nosecones. Sweet.

Then I can take the Cd vs. velocity data that I measured after burnout, and use that to see what the aero drag was during the burn, and subtract that off from the measured force to get a nice thrust vs. time curve for this flight:



For reference, I also plotted the I600 thrust curve from thrustcurve.org. I think AT made a propellant adjustment or something, because this motor was significantly slower than spec. It's really more like an I400, which was great for this altitude shot. Two summers ago, Chris LaPanse flew a prototype Parrot in his I600 Cirrus Dart shot, and measured the same thing. This thrust curve is built on top of a lot of derived data, but the burn time is straight from the altimeter, and there's a big difference between a 1.2 second burn and a 1.6 second burn. I calculated the integrated impulse to be about 620 Nsec.

Also note that I lost a noticeable amount of impulse bouncing through the launch rails. You can see it in the lateral accel near the top of the page. It makes me wonder whether I should reduce or increase the spacing between the rails and the rocket, and if I'm at the point where additional launch tower length hurts rather than helps. The exit velocity from the tower was 117 mph.
 

Microspeed

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Wow, that's an amazing project! Plans for more flights anytime soon?
 

Adrian A

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Yes, thanks. In the next couple of months I'm going to fly this with a booster to have a go at some 2-stage flights. An I1200 booster with an H123 comes in just under full I total impulse and should be a fun flight to watch. I'm also thinking about making a new nosecone with the same shape and a longer shoulder, so I can fit a J570 motor in the aft end and use the motor as a coupler. The supersonic performance of this nosecone shape is really encouraging, so I think a J570 flight well over 20k is possible.
 

cjl

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How about a 2-stage J flight with a CTI J425 Blue Streak booster and one of the new AT I59WN long burning motors as the sustainer? That comes to 1274 Ns, 6 away from a full J. I wouldn't be at all surprised if you could even get over 25k with that, considering the I600 flight. As for the single stage J, looking at the thrust curve, I think you could get higher on one of the new CTI J530 Imax loads (pro38 6xl case) than you could on the J570.

Nice flight by the way. The boost was incredible - glad to hear you got it back.
 
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nh4clo4

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Adrian,

This is a new altitude record, is it not ? :wave:
 

Adrian A

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How about a 2-stage J flight with a CTI J425 Blue Streak booster and one of the new AT I59WN long burning motors as the sustainer? That comes to 1274 Ns, 6 away from a full J. I wouldn't be at all surprised if you could even get over 25k with that, considering the I600 flight. As for the single stage J, looking at the thrust curve, I think you could get higher on one of the new CTI J530 Imax loads (pro38 6xl case) than you could on the J570.

Nice flight by the way. The boost was incredible - glad to hear you got it back.
Thanks, Chris. Too bad I was wandering around looking for my rocket when your AMRAAM took off. That would have been fun to see. Nice pictures.

Your suggestion for a 2-stage flight is a good one. I'll have to simulate that once the new motor files show up. On my booster, a threaded forward closure and flush aft closure wouldn't be required, so the new bigger CTI motors should fit the bill. Flying the sustainer as a single-stage rocket with anything longer than the AT 720 case, I'll need to be able to attach the shock cord to the front of the motor.

When is the next NCR launch with windows over 20kft?
 

Adrian A

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Adrian,

This is a new altitude record, is it not ? :wave:
It certainly broke the old record of 13728 feet, set by Bill Inman. Whether it will be a new official record depends.

I need to find out whether it landed within the club's FAA altitude waiver at the time (there's a radius as well as a height). If that's o.k., I'll ask for witnesses to sign my form , and I'll send it in. If I don't mess up the form like I did for my G record-breaking shot, then it should be an official record. But Tripoli may just tell me to pound sand like they did after my F record-breaking flight, solely on the basis that I'm an altimeter manufacturer. We'll see.

If any but the last one prevents me from setting a record, I'll fly it on an I600 again to try to get a cleaner recovery without a premature main deployment.
 

bobkrech

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Adrian

A couple of comments/questions.

I'm surprised about the burn time. If I had to guess, Sunday probably was pretty cool, and overcast so your propellant was pretty cool which would at least partially explain a longer burn time.

Reaching 15,965' AGL on an I is very impressive, but you have a base elevation of 5400' AMSL an the air density is ~83% of the sea level value. How does TRA compensate for differences in launch site altitude? What would the AGL altitude have been if you started at sea level?

Bob
 

Adrian A

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Adrian

A couple of comments/questions.

I'm surprised about the burn time. If I had to guess, Sunday probably was pretty cool, and overcast so your propellant was pretty cool which would at least partially explain a longer burn time.

Reaching 15,965' AGL on an I is very impressive, but you have a base elevation of 5400' AMSL an the air density is ~83% of the sea level value. How does TRA compensate for differences in launch site altitude? What would the AGL altitude have been if you started at sea level?

Bob
Thanks Bob. A higher launch altitude pad does help significantly. To date, Tripoli hasn't been putting any asterisks or anything like that on shots from high-altitude sites. There have been records set from the Tripoli Colorado's Hartsel launch site, which is at 8800 feet. Most records have been set at Black Rock, which is about 3500 feet, if I recall correctly. I'm not aware of any that were launched from near sea level. Once I get my sim tuned up with this new drag data and the real burn profile, I'll be able to answer your question better, but my guess is that it would come in between 14kft and 15kft.

The temperature was about 65 at the launch, and 75 inside my av-bay. Chris LaPanse also recorded a significantly longer burn time on his I600 on a hot day in July '07, when the av-bay recorded temperatures over 120F. That burn duration also had a significantly lower peak thrust and longer burn duration than is shown on the motor cert or in Rocksim. There was an acceleration curve from that flight posted with the rest of the data on a thread called something like "2 mile club." I saw something about an archive from the old TRF but I haven't tried to find anything there yet.

Thak
 

bobkrech

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Adrian

The thrust curve you obtained more closely matches the J420R thrust curve than the I600R thrust curve.

The reload kits differ only in the ID bore of the propellant grain and the ID bore of the nozzle. From what I can determine from the AT website, the I600 R propellant grain has a 0.531" bore in the propellant grain and uses and unbored 01550 nozzle with a 0.291" throat bore. The AT J420 R uses a 0.500" propellant grain bore ID., and a 01550-5 nozzle which I guess has a larger (unspecified) throat diameter. If a J420R nozzle was accidentally shipped with the I600R reload, the chamber pressure would be lower and thus the burn time would be longer and generate a thrust curve very similar to what you measured.

Bob
 

Adrian A

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Adrian

The thrust curve you obtained more closely matches the J420R thrust curve than the I600R thrust curve.

The reload kits differ only in the ID bore of the propellant grain and the ID bore of the nozzle. From what I can determine from the AT website, the I600 R propellant grain has a 0.531" bore in the propellant grain and uses and unbored 01550 nozzle with a 0.291" throat bore. The AT J420 R uses a 0.500" propellant grain bore ID., and a 01550-5 nozzle which I guess has a larger (unspecified) throat diameter. If a J420R nozzle was accidentally shipped with the I600R reload, the chamber pressure would be lower and thus the burn time would be longer and generate a thrust curve very similar to what you measured.

Bob
Interesting. I'll measure the used nozzle when I get home, and also look up that data from Chris's flight
 

n3tjm

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Interesting. I'll measure the used nozzle when I get home, and also look up that data from Chris's flight

Measuring your nozzle will be difficult cause Redline propellant errodes easily 25% - 50% of the nozzle throat away. Maybe you should mention this to Aerotech, prehaps they accidently did ship the wrong nozzles. I have personally spotted wrong nozzles in AT loads, so it can and does happen.
 
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fox_racing_guy

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Measuring your nozzle will be difficult cause Redline propellant errodes easily 25% - 50% of the nozzle throat away. Maybe you should mention this to Aerotech, prehaps they accidently did ship the wrong nozzles. I have personally spotted wrong nozzles in AT loads, so it can and does happen.
Good posting, I personally have 2 J460's now with the wrong nozzles in them. I guess I should contact Aerotech and see what I needs to be done to replace them.
 

Adrian A

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Measuring your nozzle will be difficult cause Redline propellant erodes easily 25% - 50% of the nozzle throat away. Maybe you should mention this to Aerotech, prehaps they accidently did ship the wrong nozzles. I have personally spotted wrong nozzles in AT loads, so it can and does happen.
I happen to have an extra I600 reload to check (gotta love that BATFE ruling), and I just measured its nozzle and my burned one. The fresh one is indeed 0.29". Once I scraped off some crud from the burned nozzle, it measures 0.36" diameter. That's a 24% diameter increase. Is the 25%-50% erosion expectation solid enough that that tells us it started out at 0.29" or smaller?

Maybe someone from AT can chime in on this.

On a related note, someone asked me today why the thrust tails off during the burn. Since it seems like the fuel exposed area would increase during the burn, I was stumped. Is it due to nozzle erosion?

The pad weight minus the recovered weight is exactly equal to the published I600 propellant mass plus a couple of deployment charges, in case anyone is wondering about that.
 

cjl

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It is due (at least in part) to nozzle erosion. The fuel burn area should actually stay rather constant (since the grains burn both in the middle and on the ends), but the nozzle is getting larger.
 

n3tjm

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That's a 24% diameter increase. Is the 25%-50% erosion expectation solid enough that that tells us it started out at 0.29" or smaller?

On a related note, someone asked me today why the thrust tails off during the burn. Since it seems like the fuel exposed area would increase during the burn, I was stumped. Is it due to nozzle erosion?
I never measured the difference between new and fired redline nozzles, but I have fired several redlines and noticed how much nozzle is gone after the flight. my 25 - 50% is a guess.

Nozzle erosion does contribute to the tail off of the thrust.
 

Adrian A

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It is due (at least in part) to nozzle erosion. The fuel burn area should actually stay rather constant (since the grains burn both in the middle and on the ends), but the nozzle is getting larger.
That make sense.

I looked up a graph of your flight from 2 years ago and I see about 1.4 seconds to burnout, vs. 1.5 seconds for my flight, and 1.15 for the thrustcurve.org data.
 

cjl

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That sounds about like what I remember. Later tonight, I might dig out the data and see if I can't extract a usable thrust curve.
 

Binder Design

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Adrian,

I just ordered one of your altimeters. I look forward to putting it though it's paces with a similar minimum diameter project. If I get some flight data I'll send it your way.

Mike Fisher
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JDcluster

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The stock nozzle size from the RCS catalog is 0.281"
I asked for some J 350 nozzles & that is what they gave me,
whether they drill them any for different loads is unknown.



JD


I happen to have an extra I600 reload to check (gotta love that BATFE ruling), and I just measured its nozzle and my burned one. The fresh one is indeed 0.29". Once I scraped off some crud from the burned nozzle, it measures 0.36" diameter. That's a 24% diameter increase. Is the 25%-50% erosion expectation solid enough that that tells us it started out at 0.29" or smaller?

Maybe someone from AT can chime in on this.

On a related note, someone asked me today why the thrust tails off during the burn. Since it seems like the fuel exposed area would increase during the burn, I was stumped. Is it due to nozzle erosion?

The pad weight minus the recovered weight is exactly equal to the published I600 propellant mass plus a couple of deployment charges, in case anyone is wondering about that.
 

Adrian A

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Adrian,

I just ordered one of your altimeters. I look forward to putting it though it's paces with a similar minimum diameter project. If I get some flight data I'll send it your way.

Mike Fisher
Binder Design
Thanks Mike, it will go out in the mail tomorrow. I'm looking forward to seeing what you come up with. I also have a prototype for a really easy way to make a 38mm av-bay for the Parrot that I'll probably try out next weekend. Stay tuned.
 

Chicagonative17

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Makes me want one of these "special" I600s... all this talk about the elusive long burn I600 is exciting :dark:

Adrian, When I fly my MD rocket with your altimeter and the I600 I'll be sure to forward you the information so you can evaluate it. This is very curious. I would think Aerotech would know (and change the packaging) if their formula change for the motor actually changed the burn time.
 

Adrian A

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Makes me want one of these "special" I600s... all this talk about the elusive long burn I600 is exciting :dark:

Adrian, When I fly my MD rocket with your altimeter and the I600 I'll be sure to forward you the information so you can evaluate it. This is very curious. I would think Aerotech would know (and change the packaging) if their formula change for the motor actually changed the burn time.
I find it curious also, along with the differences between the thrustcurve.org curve, Rocksim's curve, and the certification data curve. The two flights I have data for were both long, though, so I would expect yours to be, also. I also have another one burning a hole in my pocket (figuratively speaking) that I'll post data for, too.
 

cjl

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I wonder if the motor is affected by high accelerations? Both calculated curves are from flights experiencing over 50G...
 

Adrian A

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I wonder if the motor is affected by high accelerations? Both calculated curves are from flights experiencing over 50G...
I have also wondered about the effect of ambient pressure, but I have been told that since the flow through the throat is supersonic, that the external pressure wouldn't affect the internal pressure or burn time.
 

cjl

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That should be the case. Ambient pressure would affect the thrust (you should get more thrust at higher altitude), but internal conditions should be unaffected, except for ignition.
 

Chicagonative17

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Even if it were the case, I don't think it would increase a burn time from 1.2 to 1.6 seconds. That's a pretty significant increase when talking about a quicker burning motor such as the redline. My money says that Aerotech changed the propellant and just didn't bother (err forgot) to mention it to the rest of us... including not reprinting all the new labels.
 

bobkrech

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Ignition details and time to pressure determing how well a fast burning motor behaves.

If you rough up the motor surfaces to remove oxidation, the motor should come up to pressure promptly whenb you fire the igniter. If you don't, it will take several tenths of a second longer, and that the difference in the thrust curves.

Bob
 

cjl

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Coming up to pressure isn't the problem. Look at Adrian's thrust curve - it appears to pressurize in 50-100ms. It did smoke significantly from the igniter on the ground, but once the propellant caught, it did not waste any time getting up to pressure. I think there's something else going on here.
 

bobkrech

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Coming up to pressure isn't the problem. Look at Adrian's thrust curve - it appears to pressurize in 50-100ms. It did smoke significantly from the igniter on the ground, but once the propellant caught, it did not waste any time getting up to pressure. I think there's something else going on here.
Smoking on the ground is an indication of an indication of a delayed ignition problem, so it is pretty clear to me that the motor it did not ignite promptly and completely. If it did, the burn time would have been shorter.

At my request because of a post on this forum, NAR S&T group conducted a few test stand firings a week ago to investigate why a '98 D9 motor had peak thrust 0.8 seconds after ignition whereas the AT D9 thrust curve on the instruction sheet has it at 0.2 seconds. In all likelyhood, the AT curve is obtained from newly manufactured motors whereas last week S&T obtained thrust curves are obtained from slightly aged motors left over from our last recertification effort. In these D9 motor firings we measured peak thrust occuring between 0.4 and 0.6 seconds, and noticed smoking after the igniter firing, leading to the conclusion that aging, oxidation, or whatever you want to call it influences the propellant grain surface and effects the time to and level of peak thrust.

IMO the oxidized propellant surface is inhibiting the initial burn of the propellant grains not directly influenced by the igniter. If the top grain ignites after some time delay, you might expect that the lower grains will not ignite as promptly, and so forth down the motor. It would not take much of a sequential delay to alter the burn surface area vs time to reduce the peak thrust by 1/3. Since all the propellant is ultimately consumed, the total impulse is unchanged.

Bob
 
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