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 I had the pleasure recently of being introduced to a gentleman named Jim Jarvis, a member of the Austin Area Rocketry Group of Texas. Jim had just completed his Level 3 certification at LDRS 25 in supreme fashion, flying a 4" minimum diameter carbon fiber rocket on an N4000 to 35,000 feet! This qualified Jim for the Tripoli N altitude record without him even knowing he had accomplished the feat.
I asked Jim it if would be possible for us to collaborate on a feature article about his rocket and the flight, knowing the readers here would love such a piece. Being the thorough person that Jim is, he did all the work in order to share his success with everyone. Introduction My name is Jim Jarvis. I have a degree in Chemical Engineering from the University of Wisconsin, and I work as a project manager for a large engineering company. Our group does mainly environmental control system projects on coal-fired power plants for the electric utility industry. I launched rockets as a kid until I was about 14 or so (sound familiar?). I think the rocket hobby started my interest in science and is why I went into engineering (also sound familiar?). Then, in the fall of 2003, I saw the Discovery Channel shows and I was hooked. After only a brief 37 years out of the hobby I was back! Within a few days, I had my first rocket (a PML Phobos) and I launched it a few weeks later on a mighty G-35. My second flight was my Level 1 certification on the same rocket. My third flight was my Level 2 certification flight on an altimeter-equipped PML Nimbus. A J-295 took that bird to over 9,300 feet. After roughly another 50 high-power flights, I decided to try for my Level 3 certification. I scratch-built a 4-inch, minimum-diameter carbon fiber rocket and flew it at LDRS 25 on an Animal Motor Works N-4000 Blue motor. The rocket flew to over 34,000 feet for a successful certification flight and a new Tripoli N-class altitude record. The following describes how the project got started, highlights from the design and construction process, and my wonderful day of flying in Wayside, Texas. Project Inception Stu Barrett was supposed to build a 4-inch minimum diameter rocket and fly it at BALLS. Stu had the carbon fiber in hand, but since he takes semi-retirement seriously, he hasn’t gotten around to starting his project yet. At one point, I mentioned this project to Rick Van Voorhis, our Austin Area Rocketry Group (AARG) Prefect, and he suggested that I should build that rocket myself. And while I was at it, why not certify with it at LDRS 25 on an “N” motor (ha ha ha)? Rick even volunteered the motor case (Rick has been the little devil on my shoulder since I got back into the hobby). I ran the plan past Dave Ivey (the little devil on my other shoulder), and Dave encouraged me to do the project. Thus, the concept of the HighCarbYen was hatched in early December 2005. At our AARG December launch at Hutto, Texas, I told Stu and Ray Kinsel about my plan and asked them to be my TAPS. They both agreed to serve, and so I officially began my L3 certification project. In the time prior to LDRS 25, Stu went hot-n-cold on the “N” idea, alternately questioning my judgment and then my manhood. I could tell Ray liked the idea from Day 1. The HighCarbYen would be my fourth all-composite rocket. My first was the 3-inch minimum diameter LowCarbYen, which was the name of a thread I posted seeking advice on how to build carbon fiber airframes. I like to give the threads I post unusual names when I’m looking for help so that people will take note and reply. At the time, the low-carb diet was hot, and I had a yen for carbon fiber, so I titled the thread LowCarbYen, and that became the name of the rocket. One person who answered many of my questions was Mick Kelly. Mick has since gone on to develop the CompositeRockets Yahoo site – probably the best source of information that there is for tips on constructing composite rockets. Dan Stroud also provided a lot of help and ideas, and Dan has gone on to do … well, all the stuff that Dan has done. The LowCarbYen has about a dozen great flights on it, including two sponsored flights on the Animal Motor Works M-2500 Blue and M-3000 Green motors when I was Level 2. My second and third all-composite rockets were my 2-inch minimum diameter “Shocklets” (the Shocklet I and II). These were named in honor of Dave Triano, my third mentor in the construction of carbon fiber airframes. I lost the original Shocket after launching it to over 20,000 feet on an L-730 at Wayside, Texas. Within a week, I had the Shocket II under construction, and a week later, the original Shocklet was found (oh darn, now I have two of them). So the HighCarbYen would incorporate the lessons learned from my previous minimum-diameter composite rockets with the objective of constructing an N-capable rocket for my L3 certification. With LDRS 25 scheduled for the end of June here in Texas, the deadline for construction was set. Rocket Design & Construction The HighCarbYen is a fairly basic 3FNC minimum diameter rocket. However, there were still some important design decisions to make along with some features intended to improve the rocket’s performance. The first decision was to select the design motor. The initial plan was to use the 40-inch-long Cesaroni Pro98 6G motor and their N-2500 reload. However, the 47-inch-long Animal Motor Works 98-17500 motor and their N-4000 reload was also an option, even though the motor wasn’t yet certified for commercial use. I elected to design for the longer motor casing, and when the N-4000 was certified prior to LDRS 25, I used that motor for the L3 flight. Figure 1 is a picture of me, the rocket and the AMW 98-17500 motor that was loaned to me by Jim Parker for my certification flight. A second design issue was how to deal with the heat produced by the motor and its affect on the strength of the epoxy/carbon fiber airframe. Here, I elected to make the airframe tubing slightly oversized with respect to the motor casing (specifically, the ID of the tubing is 4.0 inches instead of the normal 3.9 inches). The objective was to create an air gap between the motor and the airframe to protect the epoxy from the heat produced by the motor. To accomplish this, standard-sized airframe tubing (rather than coupler tubing) was used as the mandrel to roll the airframe tubing. Then, standard-sized fiberglass airframe tubing was used to make couplers in any locations where coupler tubing would otherwise have been used. This included locations such as the booster section bulkhead and the electronics bay. Indeed, short lengths of this same tubing were used as centering rings to position the motor within the slightly oversized airframe. Then, fiberglass coupler tubing was cut to fit between the forward end of the motor casing and the booster section bulkhead. This tubing, which was fabricated for both the N-2500 and N-4000 motors, provided a forward push-point for the motors in addition to thrust point at the bottom of the airframe. Figure 2 shows the various fiberglass tubing sections and the G-10 bulkheads that were needed to execute this design approach. The oversized airframe tubing created additional design challenges at both ends of the rocket. At the aft end, the thrust ring of the Pro98 motor was not wide enough to reach the oversized airframe. Therefore, one of the fiberglass “centering rings” was added at the aft end of the airframe for the motor to push against. In addition, a 1/8-inch-long ring of high-temperature epoxy was formed that capped the end of the airframe and centering ring tubing. The purposes of this key design feature were to help transfer thrust to the airframe and to protect the composite tubing from direct contact with the metal thrust ring of the motor itself. Figure 3 shows a picture of the aft end of the booster, including the carbon fiber airframe, the fiberglass centering ring and the high-temperature epoxy thrust ring. Similarly, a standard-sized nose cone would fall through the slightly oversized composite airframe. Therefore, the conical shape of a Performance Rocketry fiberglass nose cone was extended using Superfil (see Figure 4) to fit the outside diameter of the airframe, and fiberglass tubing was installed over the nose cone shoulder to fit the inside diameter of the airframe. Figure 5 shows the modified nose cone. The airframe tubing was rolled using Aeropoxy PR2032 resin, the PH3665 slow hardener, and 5 wraps of 5.7-ounce, 2x2 twill carbon fiber. The lay-up consisted of the following “layers”: - Mandrel - PML 4-inch phenolic airframe tubing, waxed;
- 1 wrap of 0.005-inch mylar, waxed on both sides;
- 5 wraps of carbon fiber; and
- 1 wrap of peel ply.
The epoxy used in the first four wraps contained a small amount of milled glass. This composite-in-a-composite approach was used to further increase the strength of the epoxy in the lay-up. A small amount of fumed silica was added to the epoxy used for the fifth wrap. No compression (i.e., vacuum bagging or heat-shrink tape) was used in the construction of the airframe. However, the amount of epoxy in the lay-up was held to just over 50% of the total weight by carefully monitoring the addition of the epoxy during the lay-up process. The secret of the tube-making process that I use is the peel ply. Peel ply is added as essentially a sixth layer of the lay-up, and it is wetted out completely just as though it was going to remain a part of the final lay-up. Figure 6 shows the appearance of the tube after removing the peel ply layer. Note how the peel ply serves to transform the surface of the three-dimensional carbon cloth into a flat, two-dimensional surface that is much easier to finish. The first step of the finishing process for these “naked” carbon fiber tubes is to paint the tubes with several coats of epoxy. This provides some epoxy to “sand into” without sanding into the carbon fiber itself. In addition, the added epoxy fills most of the minor imperfections in the surface. Then, the tubes are sanded and wet sanded to a glass-smooth finish. The final airframe tubing, wet-sanded with 1000-grit paper, is shown in Figure 7. The core of the fins was 1/8-inch G-10. Five layers of the 5.7-ounce carbon fiber were laminated onto each side of the fin, and then the fins were beveled prior to attachment to the airframe. Figure 8 shows the beveled fins after attachment to the airframe, including fin fillets that consisted of a mixture of high-temperature epoxy and milled glass. Then, as shown in Figure 9, a thin layer of Superfil was added over the top of the epoxy fillet to form a smooth radius for the application of the tip-to-tip carbon fiber. The large fillet radius under the tip-to-tip carbon fiber significantly increases the strength of the fin joint. Two layers of tip-to-tip carbon fiber were applied over each fin section. The carbon pieces extended from the aft end of the airframe to a few inches above the fins. As was the case for the airframe itself, peel ply was added to the lay-up to help “flatten” the carbon fiber, but no compression was otherwise used during the construction. The fins were finished in the same way as the airframe by painting on a few coats of epoxy followed by sanding and wet sanding. The completed fin section is shown in Figure 10. The last step in the construction of the fin section was to “edge” the fins with a mixture of high-temperature epoxy and milled glass. The purposes of this step were to seal the edges of the tip-to-tip carbon pieces to prevent delamination and to provide some protection against the heat generated during high-speed flight. A total of four coats of this epoxy mixture were added, and the final appearance of the fins is shown in Figure 11. There are a few other noteworthy aspects of the design. First, the rocket is designed to carry both a radio tracking transmitter and a GPS telemetry package. Since the airframe is constructed of carbon fiber, these transmitters must be located in the fiberglass nose cone. Second, since the rocket is designed to fly at above Mach 2, the deployment electronics must be designed to tolerate Mach transition effects. The altimeters used for high speed flights include the G-Wiz MC (an acceleration-based altimeter) and the Missile Works RRC²X-40K (which has a user-selected Mach lockout feature). Third, for high altitude flights (above 20,000 feet), the rocket uses the Rouse-Tech CD3 CO2 deployment system. The CD3 device and CO2 cylinder are simply attached to the recovery harness in the drogue section directly below the altimeter bay. A so-called “surgical tubing” charge is used as a backup to the CO2 method. Construction on the rocket began in December 2006 and was completed in early April 2006. No significant problems were experienced during construction, except for a three-week delay waiting for the fiberglass tubing to arrive to make all of those rings. This left several months to complete ground testing of the apogee and main sections and to conduct a test flight (and to finish all of that L3 certification paperwork). A test flight was conducted in late April in McGregor, Texas. A Cesaroni L730 was used to boost the HighCarbYen to an altitude of 7,600 feet. The boost was perfectly straight, and the only problem with the flight was that the nose cone was pointing directly downward when the main deployed. This caused the nose cone to get tangled up in the chute just a little. As a result of that portion of the test flight, I added a deployment bag to the recovery system to get a more controlled deployment of the chute. It sure felt good to have a successful test flight prior to the certification flight, and it turned out that this launch at McGregor would be my last opportunity before LDRS. Two significant things happened in the time between the test flight and LDRS in June. First, the folks at Animal Motor Works were able to certify the N-4000 for commercial use. Second, they offered to sponsor my certification flight, resulting in a big discount on the cost of the reload. As anyone doing an L3 certification project can attest, any cost savings are welcome, and I surely appreciated their offer. The Flight After a wait that seemed to last forever, it was finally time to pack up the truck (three rockets, my wife, and most of our possessions) and head to Amarillo. We got to the Wayside area on Wednesday afternoon in time to go to the launch site and scope things out. What a great job by the POTROCS folks getting everything set up! High altitude flying (above 20,000 feet) requires a certain amount of luck to hit days with suitable flying conditions. Perhaps the most important condition is reasonable upper-level winds. The wind forecast was for relatively calm upper-level winds out of the northwest for the entire event. This forecast was nearly ideal given that Palo Dura Canyon is located only 3.5 miles north of the launch site. However, the lower-level winds were picking up on Thursday, and were expected to be higher than I would have preferred during the time slot (2:00 to 4:00 PM) set aside for high-altitude flights. This was expected to be the case for each afternoon over the next several days. At that point, I seriously started thinking about a smaller motor for the L3 certification flight. Then, at the noon flyers meeting, Pat Gordzelik announced that the high-altitude window could be opened from 9:00 to 10:00 each morning if requested. That’s all I needed to hear, and I decided at that point to go forward with the N-4000 flight. I spent the remainder of the day making final preparations for the flight, which included assembly of a thermite igniter courtesy of Pat (Pat lit up about a quarter million worth of N-4000’s for the MasterBlaster shows). We arrived out at the field about 7:00 on Friday morning and we were ready to head to the pad just before 9:00. Since the rocket was largely prepped in advance, most of this time was spent setting up and initializing the GPS telemetry equipment, doing final assembly of the airframe and inserting the shear pins. After the RSO inspection, I headed out to the pad with an entourage that included my wife, Stu Barrett and David Bachelder (See Figure 12). John DeMar took this picture along with several other great pictures of the set up and the flight itself. Rick Van Voorhis was already at the pad getting things set up. There were no problems getting the rocket onto the rail, and this time, I remembered to take along some water so that I could actually continue to speak during the set up. Figure 13, also by John DeMar, shows me activating the deployment electronics. After saying a few final goodbye’s to my rocket, we headed back to the flight line. I watched the flight from well behind the flight line. This is where I set up the GPS telemetry equipment and my computer, and I also wanted to be away from the crowd and the PA system in case I needed to use the radio tracking equipment. For this flight anyway, finding the rocket was a higher priority than actually watching the rocket. I radioed the LCO that we were ready, and the countdown began. When I first saw the rocket emerge over the “tent city”, there was no sound. The rocket was flying straight as an arrow, and I knew right there that the boost was going to be fine. What acceleration, and then the sound hit. John DeMar got a great picture of the liftoff (shown in Figure 14). After just a few seconds, the rocket was out of sight (at least for me), and now it was time to start monitoring the telemetry to try to find the rocket. Such is the life of those that fly minimum diameter. I’ve had about a dozen flights with my GPSFlight equipment. The system includes a GPS receiver and a radio transmitter that fit in the nose cone. However, the model I have also has an altimeter, which provides the altitude reading in real time. This feature is very reliable, and the real-time altitude information is very handy (for example, you know the altitude you went to, that a deployment event has occurred, your descent rate, that the main has deployed, etc.). However, I’m about 50/50 on reacquiring the GPS signal after the boost on higher altitude flights. Therefore, I anticipated not having the GPS signal on this flight, and I was planning on a frantic 5 minutes trying to get the best radio tracker bearing that I could get. Well, it turned out that the GPS signal reacquired shortly after apogee. The secret to getting the signal back (I think) is to keep the GPS antenna pointed up during the trip to the pad to keep as many satellites “locked in” as possible. Since I had the GPS signal, about the only thing we needed to do was to wait for the rocket to land and then go pick it up. I did periodically report the rocket altitude and position to the LCO over the radio. The rocket landed about 1.5 miles to the south. It was too far away to see the chute, but I knew from the telemetry that it had deployed. A group of us, including a photographer from the Dallas Morning News, went out to recover the rocket. Everything was fine, and the photographer got a picture that he published on the front page of the July 4 edition. Pretty cool huh, and a successful L3 certification flight to boot! Here are a few statistics from the flight: - Rocket weight – 15 pounds empty and 46 pounds with the motor.
- Maximum altitude – 34,993 feet (via a Missile Works RRC²X-40K) and 34,197 feet (via a. G-Wiz MC).
- Maximum acceleration – 29 G’s.
- Maximum speed – 2,500 feet per second (Mach 2.3)
About a week after the flight, someone posted a message to the TRA member's mailing list that the flight was a Tripoli “N” altitude record. I had no idea. I submitted the paperwork for the record and was credited with an altitude of 34,197 feet (which I could verify with the downloaded data from the G-Wiz MC). Overall, my L3 certification experience was wonderful. I had the best TAPS a flyer could have and I learned a lot more than I ever expected. I found two aspects of the project to be very interesting. First, it is remarkable how many things had to go right for the project to be successful. I view the flight as a “perfect storm” of rocket, motor, weather, location and situation, and any of a hundred things could have derailed the process. Second, it is amazing how many people contributed significantly to the flight and how it came to be. I’ve tried to thank each of them individually, but that will never be enough, as anyone involved in this hobby already knows.
10-03-2006 03:56 PM
#1
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Tripoli L2
Joined: Sep 2006
Posts: 15
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Awesome Article / Rocket
All I can say is wow, I want one.
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10-03-2006 11:37 PM
#2
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Certified Level Three
Joined: Aug 2006
Posts: 204
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I wonder if we begged really nicely if Jim would share some more insight on composite construction. I'd like to see some technical articles on the subject.
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10-05-2006 12:09 AM
#3
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Certified Level One
Joined: Oct 2006
Posts: 12
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This may be possible. I'm talking with some folks on the compositerockets site about collaborating on a technical article. It would get a lot of current experience in one place.
Jim
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10-13-2006 01:56 PM
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New Member
Joined: Aug 2006
Posts: 2
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CompositeRockets Yahoo! Group
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11-05-2006 09:25 AM
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Will fly beer for rockets
Joined: Aug 2006
Posts: 1653
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Jim,
When you do the larger radius SuperFil, do you mask off the edges of your fillets to get such a sharp demarcation between fillet and body tube?
Thanks,
Steve
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11-06-2006 01:11 AM
#6
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Certified Level One
Joined: Oct 2006
Posts: 12
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Quote: Jim,
When you do the larger radius SuperFil, do you mask off the edges of your fillets to get such a sharp demarcation between fillet and body tube?
Thanks,
Steve
Yes, I use masking tape to get that edge. The radius itself is formed using a 29mm tube covered with a layer of wax paper. I just fill the fillet area with Superfil and then force in the tube to squeeze out the excess. Using the tube is what makes it possible to get the smooth finish in this area later on.
PS - somewhere else, I posted that I used a 38 mm tube for this, but I checked, and it's 29 mm.
Jim |
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03-06-2007 09:58 AM
#7
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Certified Level One
Joined: Oct 2006
Posts: 12
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I haven't posted an update on this rocket since the original article, so here goes.
The HighCarbYen has now flown a total of five times. Since the second flight at LDRS 25:
- An AMW L-1111ST at AirFest
- A CTI N-2500 at Wayside (about 32K on that flight)
- An AMW M-2200 Skidmark at Hutto near Austin
All have been good flights. The most recent flight at Hutto went over 14K on the Skidmark. However, it was a little windy and the rocket suffered a rather nasty case of road rash. So, it'll be in the shop getting resurfaced over the next few weeks (should come out as good as new). Next flight will probably be in Wayside over Memorial Day (RockExShots).
Jim
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03-08-2007 11:07 PM
#8
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Certified Level Eleven
Joined: Aug 2006
Posts: 84
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Road rash
FYI, Jim's "nasty case" is a finish that any of the rest of us would die for.
Stu
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03-27-2007 12:30 AM
#9
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Certified Level 3
Joined: Aug 2006
Posts: 18
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Ditto Stu.......
I couldn't even explain the finish on Jim's rocket!
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03-27-2007 04:41 PM
#10
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Certified Level Three
Joined: Aug 2006
Posts: 204
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So you are saying Jim's road rash would make most people proud?
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03-31-2007 11:03 AM
#11
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Certified Level One
Joined: Oct 2006
Posts: 12
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The road rash is fixed for the most part, and I got a new oven out of the deal.
Jim
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10-23-2007 01:42 PM
#12
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Certified Level One
Joined: Oct 2006
Posts: 12
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It's been a while since I posted anything on this rocket, so here's a quick update.
The HighCarbYen has done two notable flights since last March. One was a flight at Wayside on an N-1942 Wayside White motor produced by Pat Gordzelik. That flight went to 31,580 feet and Pat and I have been granted a Tripoli "Research Group" altitude record.
In the second flight, the HCY, less one section of upper airframe, was the booster on a M-to-M, 2-stage flight at Balls. The boost was fine, but a FWFG coupler in the booster let go about half way through the sustainer burn. This flight will be repeated next Spring.
Currently, the HCY is in the shop being retrofitted with all-carbon couplers.
Jim
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10-23-2007 09:34 PM
#13
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NAR/TRA L3
Joined: Oct 2006
Posts: 289
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Quote: One was a flight at Wayside on an N-1942 Wayside White motor produced by Pat Gordzelik. That flight went to 31,580 feet and Pat and I have been granted a Tripoli "Research Group" altitude record.
Will the new incarnation be able to take a 53" 98mm motor?  |
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10-24-2007 01:14 AM
#14
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Certified Level One
Joined: Oct 2006
Posts: 12
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Quote: Will the new incarnation be able to take a 53" 98mm motor?
Hmm. Normally, it's Rick that comes up with these sorts of ideas. But the answer is yes, it is possible. The main problem is that there would be very little drogue section remaining (about 5"), which would mean that the CD3 CO2 system would have to be relocated in some manner. There are a couple of possibilities. If I can figure out how to do it, I will.
Jim |
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10-24-2007 03:15 AM
#15
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NAR/TRA L3
Joined: Oct 2006
Posts: 289
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Quote: Hmm. Normally, it's Rick that comes up with these sorts of ideas. But the answer is yes, it is possible. The main problem is that there would be very little drogue section remaining (about 5"), which would mean that the CD3 CO2 system would have to be relocated in some manner. There are a couple of possibilities. If I can figure out how to do it, I will.
One option would be to stick the motor out the back a couple inches. The other is to leave out the smoke grain and recess the fwd closure, giving more room above the motor in the drogue compartment.
22KN-s O5400. Or something like that. 46# propellant. Hope to test fire it soon.
-John |
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10-25-2007 12:16 AM
#16
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Certified Level One
Joined: Oct 2006
Posts: 12
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Quote: One option would be to stick the motor out the back a couple inches.
-John
That's a better idea. I can make the new coupler so that the motor can go up higher and then let the motor hang out a little. The old coupler is out, which wasn't easy, and I'm making the new one. Thanks for the ideas.
Jim |
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