Monday, 22 May 2017 22:11

May Launch 2017 Recap

UROC's May launch was held as a two-day event on Saturday, May 20th and Sunday, May 21st. We had a good showing of UROC members as well as some new members. A small group of members camped out Friday night and Clair and Maureen Mills brought the trailer out Friday night as well. As a result, after a pretty cold night, the range began to be set up early on Saturday. The range was in place and ready to fly by about 9:15 am. A safety meeting was held where Neal Baker (club president) and Jim Yehle (Tripoli Prefect) provided information about the launch rules and other safety concerns. Weather was very good on Saturday, temperatures were in the high 60s and winds were surprisingly low all day. With the exception of a few late afternoon bursts the wind was as tame as any of us have seen out there. Flights continued until around 5:00pm on Saturday.


Attendance was very good for this launch with close to 85 - 95 people in attendance at the high point on Saturday.  Throughout Saturday there were just around 70 seperate flights and about 13 on Sunday. There were a mix of L1 through L3 certification attempts (17 with TRA and NAR combined)  

Many of the cert flights were succesful including veteran UROC member Kirk Weaver who re-certified both Level 1 and Level 2 this weekend.  Another highlight of this launch was Gene Hendrix's succesful TRA Level 3 flight on an M2500.  It was very evident after the launch on Saturday that the vegetation conditions on site already are not going to permit a June/July launch at the Frank Hunt Field due to the extreme fire hazard.

Overall this was a very succesful launch, the night launch did not occur as most folks went back to town in the evening, but the time shared after the launch for those who did stay out into the evening was friendships were made and old ones strengthened.

It rained during Saturday night and into Sunday morning but it died off by around 9 and the range was able to be activated and a little over a dozen flights were flown including a perfect flight for Ron Blosch's newest creation on a J800. We had some great help and support with clean up on Sunday and the launch was finished by 1:00pm, just prior to the next storm that rolled through.

Thanks to everyone that helped with setting up, fire control, tear down, range duty, and just being great members of UROC.  Make sure to check out the UROC Group on Facebook and UROC's own Gallery for shared photos


Published in UROC News
Wednesday, 29 March 2017 17:11

Busy April Member Meeting

April’s meeting is going to be a busy one! We don’t just have one but two special presentations. Definitely a meeting you won’t want to miss. 

UROC member Doug Hillson will present the results of research and analysis related to wind speed at different altitudes and how to use this information to predict rocket landing location. Doug will discuss theory of the planetary boundary layer and on using the currently available information to make a best estimate of landing locations during a rocket flight by utilizing publicly available wind data.

We will also have UROC member Kip Daugirdas give us a presentation about his recent launch to 145,000 (yes, that is one hundred and forty-five thousand) feet at Balls this past September. This launch was captured on video and had a full recovery of the craft. The rocket was a two Stage 4” booster to 3” sustainer weighing in around 60 pounds and was powered by an N-2500 in the booster and staged to an M-685 in the sustainer.

In addition to these great presentations,  (Thanks Kip and Doug for being willing to help out!) we will have our regular show and tell and talk about the upcoming UROC events.

Please arrive on time and plan for a full night!    

Mon, April 10, 2017, 7:00p - 9:00p
Salt Lake County Complex - Salt Lake City, Utah

The meeting will begin promptly at 7pm.

Proceed to Room N1100 at the Salt Lake County Complex located at 2001 South State Street. Make sure to sign in at the security desk first.  

Salt Lake County Complex
2001 South State Street, Salt Lake City, UT 84108

View Map


Visit for further information or membership

Published in UROC News

1Editor's Note: Below is a reproduction of Jed Marti's succesful NAR Level 3 documentation package. The package is meant to serve as a record fo the design and construction techniques used in the Level 3 vehicle's build. Jed has graciously allowed us to reproduce the document so that others can learn from it. Take some time and notice the detail of his notes.  Thanks Jed!

First you have to unpack the 3 shipping boxes and make sure everything is there. This one’s a bit big for the office so it’s moved to the shop.

The motor mount is sanded and the center piece epoxied in position on the 75mm tube. This took 2 days and several layers of 60 minute JB Weld.

The fins were test fitted and we discovered that LOC cut the fin holes too short (for the wrong fin dimension they were). These were lengthened about .25” in the forward direction. The motor mount was epoxied just forward of the fins in the  7.5” tail piece.

To maintain alignment, the forward and rear bulkheads were put in place, but not glued. Both these bulkheads had eyelets to allow their removal. This was allowed to set overnight in an upright position to keep the epoxy from running all over.

A fin mounting stand was built so the aft tube would rest in a comfortable position and the fin be held at a right angle. The fins were sanded to an aerodynamic shape and roughed up on the inner side. My hands are too big to fit comfortably in the back to smooth the epoxy. Consequently the inside is a bit of a mess. 60 minute JB Weld is used everywhere except the first tacking of the fin to the motor tube where the 5 minute stuff is used.


Figure 2 First fin mounting


November 25, 2008

I’ve mounted the three fins and painted the nose cone. Most of the fin fillets are complete but I’m having trouble with the JB weld 60 minute stuff curing. It runs before it sets so only one fin surface at a time can be completed. Likewise, the aerodynamic fillets loose their shape (more later). Since I can’t reach my fat fingers all the way in, there’s quite a mess inside, the epoxy is smoothed and wedged into place with a long stick.


Figure 3 Three fins mounted, most fillets

The Rustoleum black high cost paint comes right off the nose cone. I stripped it off with a wood stick and plastic paint scraper and started repainting with Rustoleum designed to adhere to ABS plastic.


Figure 4 Scraping the paint off the nose cone


November 27, 2008

To glue the base support ring in place, I first cleaned off extra epoxy so that the ring fits snugly against the bottom fins.


Figure 5  Cleaning up the engine compartment.

 To support the engine compartment in the upright position (so the epoxy will run into the joint, I cut a 2”x8” to easily fit and use the compartment’s weight to push the rear bulkhead against the fins.


Figure 6 Bulkhead support block test fit.

Finally, I applied epoxy to all the fins and internal surfaces and fit the rear bulkhead in removing the screw eyes and string used for the test fit.


Figure 7 Rear bulkhead glued in place.

I stood the engine compartment in the upright position covering the support block with a plastic bag to keep it from sticking.


November 28, 2008

I test fit one of the remaining 30” segments to the engine compartment top. It fits fine, but does not want to come off. After 20 minutes of hammer banging and damage to the segment,  it finally came off. I will either purchase a new segment or remove the top ½” that was damaged. I put epoxy rings about ¼” before the forward bulkhead and top of the tube coupler and twisted the top section on. ½” before the tubes were together I ran an epoxy bead around the exposed coupler and then shoved the tubes together into their final position. The epoxy that squeezed out of the joint was removed and smoothed over. This is tube #7 of 60 minute JB Weld.


Figure 8 Abortive test fit and final engine compartment.


Figure 9 Top view of motor mount showing epoxy ring 

After cleaning the nose cone with isopropyl alcohol I applied some layers of the Rustoleum plastic paint (black). Between each paint layer, the cone is smoothed with some 00 steel wool (Figure 10).


Figure 10 Nose cone after 3rd paint layer. 


December 2, 2008

Sanding the exterior fillets has begun. The 60 minute epoxy has a tendency to slump and run off the ends. I’ve cleaned most of this mess up and started building up the fillets but with the 4 minute stuff to make a cleaner finish. These are carefully sanded to avoid gouging the G10 fins.


Figure 11 60 minute fillet (left) covered with 4 minute fillet (right)

Notice that the motor tube does not have an epoxy fillet – this will be added when the Slimline motor retention device arrives.


December 5, 2008

Payload bay arrived and assembly begun. Put two beads of epoxy around inner core.


Figure 12. Payload inner core with 4 minute JBWeld

I wrapped the sheath around this core  and epoxied the large gap that showed up – all with 4 minute JB Weld. The piece was allowed to set for about 20 minutes.


Figure 13 Two layers epoxied. 

The outer tube was coated with two substantial beads of 4 minute epoxy.


Figure 14. Outer tube with dual 4 minute JB Weld

The inner core was then shoved into the outer tube with even spacing (eyeballed) on both sides. Extra epoxy was removed from exposed shelves and the pieces clamped. Unfortunately, the inner piece has a very loose fit. Additional epoxy will be added to assure adequate adhesion.


Figure 15. Assembly complete.

The eyebolts were assembled per instructions and the 1” washers epoxied to the bulkheads with 60 minute JB Weld.  Since the holes are much bigger than the ¼” bolt, the bolt was secured in a vice before the nut was tightened. The threads of both bolts were coated with 60 minute JB Weld before the nut was added.


Figure 16. Payload bulkhead eyebolt installation.

The bulkheads were sanded to fit the rest of the payload bay. The payload bay outside has been sanded considerably to fit the 30” phenolic tubes without binding (still not done).


December 5, 2008

Still working on sanding the payload bay to the right size. I discovered that there are lathe pieces that expand out to accommodate the bay from the inside. This allowed me to sand and smooth the bay for the proper fit.


Figure 17. Payload bay on the lathe.

When the bay fit both the engine compartment and top compartment, the 1” spacer was glued to the center with 60 minute JB Weld. The excess was wiped off and allowed to set.


December 6, 2008

I labeled the fins A, B, and C, and started keeping a log  of their status for sanding, rough spots, and so on. One fin side is the letter A and the opposite side is A. For example the fillets on A and C are 60 minute JB Weld but rough. These were augmented with heavy layers of 4 minute JB Weld and allowed to set.


Figure 18. Fillets between A and C.


Needs fill in forward area. Final sanding/polish done except for forward.


Added 4 minute filler fillet, needs sanding.


Completed, finished with #00 steel wool.


Sanding in progress.


Added 4 minute filler fillet, needs sanding.


Needs finish coat of 60 minute after rough sanding exposed dells.


I primed the top section with spray on white primer. This will be covered with half white/black in the future.


Figure 19. Primer of top 30" section.


December 13, 2008

I began installing the slimline motor retainer. It does not fit the motor tube at all so all epoxy and cruft on the mount was removed with a dremel. The tube had to be reduced somewhat. Test fitting established that sanding needed to get near the back plate. Even so, about 0.125” remains between the rear flange and the rear bulkhead.


Figure 20. Sanded motor mount before epoxy and test fitting.

The motor tube was slathered with 60 minute JB weld as was the inside of the slimline retainer.


Figure 21. Epoxy motor tube and retainer for assembly.

The retainer was screwed on as far as possible causing epoxy to squeeze out the back and fill most of the area between the flange and the bulkhead.


Figure 22. Epoxied motor retainer.

We stood the motor section on its tip and noticed that the retainer was crooked. This was corrected with two levels, rubber mallet and a piece of wood.


Figure 23. Straightening the motor retainer.

December 15, 2008

The slimline flange to the rear bulkhead did not uniformly fill with 60 minute epoxy. A small 60 minute JB weld batch was made and the flange finished off.


Figure 24. Finishing the motor flange gap

We also declared victory (premature?) on the fin fillets.


Figure 25. Fillets between C and B, A and B, A and C.


Figure 26. Fillet on fin A.


Figure 27. Fillet on fin B.


Figure 28. Fillet on fin C.

We test fit the 75mm Aerotech casing in the engine tube and found it didn’t fit – some epoxy squeezed when installing the Slimline. This was removed with a Dremel tool and rotary sand paper.


Figure 29.  After cleaning up Slimline and test fit Aerotech 75mm casing.

December 18, 2008

The top 1” of 7.5” tube has begun to wilt after too many contacts with the shop door and forceful test fittings of the instrument package. To minimize the risk of expanding the affected area and preserve structural integrity, we decided to inject low viscosity epoxy between the layers.


Figure 30. The Doctor is in.

Using xxx epoxy, we put about .5 cc in a small syringe and injected this up to ¾” into the wilted area.


Figure 31. Injecting epoxy into the wilted area.

We then covered the area with a plastic bag and clamped it together – this particularly high strength epoxy takes 24 hours to set..


Figure 32.  Area is clamped for 24 hours.


December 21, 2008

I repeated the epoxy injection on a second small spot as above. I then completed design work and basic machining of the payload bay internal structure to supplement the cardboard tube and wooden structure provided by LOC. The basic structure has two round, flat ¼” aluminum plates supported by  three internal and two external plates.


Figure 33. Payload support structure test assembly.

The  support structure was machined from scrap ¼” aluminum plate on its way to the recycling center so it has occasional holes from previous uses. The incomplete structures weighs about 2 lbs which will increase as instrument and battery packages are added.


Figure 34. End plate detail.

January 1, 2009

The base tube has been primed and we’re adding the launch lugs for the 1.5” rail. First we draw the center lines as per instructions using a long wood stick.


Figure 35. Centering line for launch lugs.

Next holes for the #8 screws were drilled into the body and the lugs test fitted.


Figure 36. Test fit of rear launch lug.

Then both launch lug areas were sanded to the base cardboard for epoxy with 60 minute JBWeld.


Figure 37. Sanding in launch lug area.

I then screwed both launch lugs in place (you can’t reach the inside to put nuts on them) and test fit with an 8020 1.5” rail.


Figure 38. Test fit on 1.5" rail.

Both lugs were then glued in place with copious 60 minute JB Weld. The screws were coated as well and driven into the cardboard.


Figure 39. Forward and aft launch lug epoxy.

I placed the 8020 launch rail over the lugs and allowed them to set overnight. We then adjourned for the January 3rd Frozen Fingers launch.


Figure 40. Frozen Fingers launch.


Payload Bay

We’re building a more rugged structure than that provided by the ¼” threaded rod, wood and cardboard provided by LOC. We’re attempting to increase the rocket’s weight to keep the maximum speed and altitude within bounds (10,000’ and less than mach .85).  The internal structure is ¼” aluminum to fit within the cardboard payload section.

Main 4.5” Rack

The standard payload entity must fit a 4.5” rack. This has #4x40 threaded holes on ½” spacing in the center and at 2” from the center. Payload modules must fit this and provide appropriate 4x40 clear holes for secure mounting. Modules can be mounted on both sides and can be up to about 2” deep. For extra strength, the weight reducing holes are milled only 0.2” deep leaving approximately 0.05” aluminum backing. Large indents on the top and bottom leave space for the shock cord eyebolt nuts and washers.


Figure 41. Center plate dimensions.


Figure 42. Partially machined center plate.

Side Supports

These are milled out of ¼” aluminum as well, but the lightening holes are milled through to provide a place to tie off support wires. Two such plates were machined.


Figure 43. Side plate dimensions.


Figure 44. Machined side plate.

Experience with these indicates that the tie wraps need to be a good grade as the milled edges are moderately sharp. We will substitute FAA nylon tie wrap for the cheap ones from Harbor Freight.

Bottom and Top Support

The bottom and top support plates are ¼” aluminum plate 7” in diameter with two chord cuts at 2.5047” to allow passage of safe and arm switches during assembly. Lightening holes are milled to permit wire passage to the explosive charges. A large center hole provides clearance for the eyebolt nuts and washer.  The bottom plate is screwed to the wooden LOC spacer with ¼” carriage bolts and nyloc nuts. The top plate has threaded holes for 5/16” bolts used for final assembly (since you can’t reach inside). These holes are not shown and are drilled to match the LOC spacer.


Figure 45. Bottom (and top) plate dimensions.

Since these were machined from scrap, there are a few extra random holes.

The forward plate uses two ¼” bolts with nylocks and is permanently attached to the support structure. The rear uses two 3/8” bolts and the corresponding holes are threaded. To assemble the system, these bolts are removed, the housing slides into the payload bay and the structure is reassembled. All wires from the exterior switches and the charge cup holder wires run to rugged 8 or 4 pin connectors.


Figure 46. Machined top plate.


Battery Housing

A 9 volt battery is required for each Perfectflite altimeter both to fire the explosive charges and power the internal computer. Two are mounted in a heavy aluminum housing and wires run to the altimeter housings. The housing was first painted with zinc chromate primer and finished with bright yellow.  The 1/8” cover has “9V” stamped on it. The sides are milled to lighten the structure. #4x40 1.5” flat head screws attach the housing to the 4.5” rack mount and the cover is secured with four #4x40 hex head screws. A 4 connector terminal strip is attached to the cover and wires run to the battery connectors inside.

Two housings are being constructed. The two batteries for the altimeters was first primed with zinc chromate and then painted bright yellow. The second contains two in series to run the second altimeter charges and is painted bright orange.


Figure 47. Dual 9v battery holder dimensions.


Figure 48. Dual 9v battery holder (one of two). 

Perfectflite Altimeter Housing

The altimeter housing is also machined out of a solid aluminum block. The inside provides #4x40 tapped standoffs with more than the 1/32” clearance recommended by the Perfectflite specifications. Two exterior flanges provide .5” #4x40 clear holes to mount to the 4.5” rack. An aluminum cover with holes provides limited protection from any explosive gasses reaching this area.


Figure 49. Perfect flight altimeter housing dimensions.


Figure 50. Perfect flight altimeter housing. 

RRC2 Altimeter

The second altimeter is the RRC2 from Public Missiles and has a slightly different form factor. A similar housing was machined for it. Two standoffs were left in the base area to accommodate the mounting screws. This altimeter will use one of the batteries in the two pack described earlier.


Figure 51. RRC2 altimeter housing dimensions. 


The cage is screwed together with #4x40 stainless flat head screws.


Figure 52. The electronics bay initial assembly. 

The top wooden plate is attached with ¼” screws and nylocks. Later we added a steel support plate between the bolts for added structural integrity.


Figure 53. Forward plate is permanently attached.

The structure was cleaned up and painted with zinc chromate primer to avoid corrosion problems.


Wiring Diagrams

The #1 Perfectflight altimeter uses a single 9v battery to both power the altimeter and fire both main and drogue charges. The #2 RRC2 altimeter uses a single 9v to run the computer and two 9v’s in series to fire the main and drogue charges.


Figure 54. Core wiring diagram.


The sleeve has 4 switches. Two on one side control altimeter power on and two on the other are safe and arms for firing the charges. These are connected to 8 pin microphone plugs placed on internal bulkheads. The charge connectors run through the wood and are 4 pin microphone jacks.


Figure 55. External switch wiring.

Internal Wiring

All exterior connections go to 4 or 8 pin microphone connectors. The following shows the wiring of the altimeter switches that are mounted flush with the instrument bay ring. During assembly, the bottom wooden panel will be removed so the wires and switches don’t run into the support structure.


Figure 56. External switches connected to payload.

All internal wiring is #20 MIL Tefzel (MIL spec MIL-W-22759/16) unshielded white. This is not PVC coated and makes no toxic smoke in a fire. It is rated at 600 volts and temperatures to 105 centigrade. It has many more strands than common hookup wire and is thus much more robust.

The first half resembles the following:


Figure 57. Some initial wiring.

Charge Holders

The initial PVC charge holders were deemed too small for the Bruiser. 4 new cups were machined from a 1” aluminum rod. These have a capacity of 2.6 cubic inches. The original cups were removed and replaced with these. In addition, the attaching rings were replaced with solid ones and bolted to the internal structure through a ¼” steel bar.


Figure 58. Charge cup holder design. 


Figure 59. Charge cup holders (forward). 

The entire payload is assembled by removing the bottom plate, attaching the two switch cables, sliding the structure through and reattaching the aft plate. The initial step is shown below.


Figure 60. Initial assembly (bottom plate attached). 

Case Hardening

To make the case slide in and out of the surrounding tubes, I applied 3 hour thin epoxy to the top and bottom of the instrument bay (also the corresponding places on the engine and top compartments).  This was sanded down and any rough cardboard removed.


Figure 61. Epoxy around edges. 

Final Assembly

All parts were sanded for good fit, cables tied down, and the case assembled. Total weight without igniters, gun powder, and tape is somewhat more than 7.5 pounds.


Figure 62. Final assembly side and aft views.


The batteries don’t fit the housings. The new 9v battery clips are deeper than old ones – the boxes have been milled out lengthwise (exposing one of the lightening holes) to accommodate them.


January 13, 2009

The last two weeks have been devoted to painting and  payload bay work. The black coat is complete for the entire rocket and the bottom white portion begun. Work is proceeding on logos.


Figure 63. Paint job nearing completion. 

I also drilled 4 holes for the Safe and Arm switches, two on each side of the instrument bay. The holes were routed to accommodate the switch flanges and make them flush with the rocket’s surface.


Figure 64. Safe and Arm switches mounted.


January 29, 2009

The carrying case is nearly complete. A single person can remove the lid with its two handles. ½” conduit rope handles let two people lift the thing.


Figure 65. Carrying case. 

Both components rest securely on felt round supports. Two inserts clamp the parts securely. These are color coded for fit.


Figure 66. Carrying case (inside view).


January 31, 2009

I completed the tail by covering the inside with a reasonably thick layer of 60 minute JB Weld. The insides of the top and engine compartments were also coated with thin 3 hour epoxy and then sanded.


Figure 67. Tail cover epoxy.


I also prepared for testing the ejection charges by constructing 23 Aerocon Hothead electric matches. These have #22, 9” leads soldered and stripped.


Figure 68. Aerocon Hothead electric matches. 

I then tested the resistance of each one and plotted the histogram below. The one with a resistance of 1.0 ohms is most likely shorted and is being examined (it turned out not to be).


Figure 69. Aerocon Hothead resistance histogram. 

We then tried 3 different hot heads with about 1 teaspoon full of FFF gun powder. The first was covered with a thin coat of pyrogen and allowed to dry for 30 minutes. We inserted this igniter underneath the powder but with the active end touching some. A fresh 9v battery was then connected – nothing. The igniter burned, but the pyrogen did not start nor did the powder charge ignite. We then tried two igniters without pyrogen embedded in the same fashion, and though the igniter burned, it was insufficient to set off the charge. Somewhat disgusted, we switched to a pyrogen covered (two layers) QUEST igniter. This worked fine (the camera only captured some of the smoke) and stunk up the shop for an hour or so.


Figure 70. QUEST igniter in charge cup.


February 14-15

I’m now experimenting with the correct charge and modifications to the Aerocon igniters. I used the spare 7.5” body tube and plugged the top with a ¾” piece of pine turned on the lathe to fit. This was screwed in place with 3 grabbers and a ¼”  eyebolt placed in the center. A cord was run from the eyebolt and connected to the test stand through the instrument pod. I connected a 12’ cord and used some pyrogen covered FL-12 Firestar igniters. The first test used ½ teaspoon of FFFG gunpowder with the following results take from single frames of a FLIP video. For all the smoke and flames, the separation distance was less than 3’ and fairly slow. No shear pins were used.


Figure 71. 1/2 teaspoon FFFG separation experiment. 

Next I moved up to ¾ teaspoon of FFFG and repeated the experiment. This time the tube fit more snugly due to damage when it fell off the test stand. The tube did travel somewhat farther, but not much. At appears that the cord connecting it to the test stand may have caught in the top of the instrument pod.


Figure 72. 3/4 teaspoon FFFG experiment. 

Following directions on the Aerocon igniters I coated them with a mixture of lacquer and ground up match heads but with no results.

I then tried 1 teaspoon with very good results.


Figure 73. One teaspoon flames and maximum height.


March 28, 2009

I mounted two 1” x .5” x 0.02” brass plates tapped with #4 x 40 holes to the instrument pod. The cardboard was cut out to this depth, drilled and the whole epoxied with JB weld 60. The top test tube was also mounted with these plates but drilled for #4x40 clearance nylon screws.


Figure 74. Shear plates on instrument pod and forward body tube. 

After much sanding the pieces were mounted, 1 teaspoon of FFF power placed and the whole assembled on a 1.5” launch rack. The instrument pod has only one of the plates and none of the electronics. Ignition is provided by a 9v battery and 25’ of wire.


Figure 75. Shear pin test setup. 

The extra drag caused the powder to develop more force than the non-shear pin test and the top component went about 20’ in the air dragging the top of the instrument pod with it.


Figure 76. Shear pin experiment with top being dragged. 

The top of the test cardboard tube has a wooden plug with three grabbers holding it in place. This ripped out but from examining the video, this happened when the tube hit the ground from a distance up.


April 6, 2009

I cut out a 28” diameter Kevlar ‘chute protector and ran the 25’ shock cord through it to the nose cone. I attached a swivel about ½ the cord length and attached the main to it (black). Both the nose cone and payload connections are through heavy quick links and the nylon cord has loops sewn on each end.


Figure 77. Nose cone, main parachute, top section, Kevlar protector. 

The main parachute panels were folded as suggested in “High Power Rocketry”. The shroud lines were placed as suggested.


Figure 78. Parachute folding and shroud lines. 

The parachute was then rolled up with the shroud lines inside and placed in the Kevlar protector.


Figure 79. Main parachute folded for installation. 

To keep the nosecone from escaping as well, it has 4 plastic rivets placed around the top. Here they are shown before expansion.


Figure 80. Rivets holding nose cone in place.

Finally, the shock cord is attached to the instrument pod with a heavy quick link.


Figure 81. Attaching the forward compartment to the instrument pod.


April 18th Launch and Modifications

On April 18th we launched Don’t Panic on a Cessaroni L motor to 4700’. We had two high speed video cameras running at 500 fps (color and B+W). The launch was successful with the drogue coming out slightly after apogee and the main at 1000’.


Figure 82. April 18th Launch

Unfortunately, the high power charges or late drogue deployment or excessive weight or a combination of both caused a 6” zipper in the engine compartment.The damage from the April 18th test prompted a design change to a less likely to zipper design. The explosive charge used to separate the engine compartment from the instrument section and the rocket velocity after apogee caused a 6” cut in the engine compartment.


Figure 83. Zipper damage on April 18

As suggested by Jack Anderson, the new rocket resembles the following:


Figure 84. Diagram of changes for "zipperless" test.

We removed the top 12” of the Bruiser’s body tube and glued in a new coupler. A new ¾” plywood bulkhead was machined on the lathe and glued onto the coupler.

Since the instrument pod is so heavy (8 lbs), we’re covering it with Kevlar and epoxy.

A new 24” section of LOC 7.51” tube was covered with a Kevlar sock and epoxied with Aero… Since this occurred during a very cold/wet part of June, curing was a problem requiring frequent treatments with a heat gun.


Figure 85. Epoxying the body tube

The forward section has two brass inserts that will be screwed to the instrument pad during final assembly.

The new setup weighs 26 lbs without fuel and motor.


Figure 86. Modified Bruiser

The Rocksim model was rebuilt showing the Bruiser as still stable with the CG at 68.5” and CP at 102” (unloaded). The actual weight of 416 ounces is slightly less than that computed.


Figure 87. Unloaded Rocksim model 

With an Aerotech M1297 loaded, the system is still stable.


Figure 88. Loaded with M1297 

Simulation results are summarized in the following table (Aerotech).



Max Vel. FPS

Time to Apogee


























July 31, Level III Flight

Hellfire XIV was the first available launch date at the Bonneville salt flats near Wendover Utah. The motor selected was an Aerotech M1297W. This was assembled per instructions and placed in the motor housing with the retaining ring.


Figure 89. Assembling the Aerotech M1297W. 

The launch team assembled the rocket running through the (by now) checklist. As usual, aligning the shear pins took the most time – the first round had the nose 180º out of alignment.


Figure 90. Final assembly - aligning the shear pins. 

We borrowed a home brew 72” ignitor and erected Don’t Panic on the pad.


Figure 91. Erecting Don't Panic on the 1.5" rail. 

Launch went successfully with lots of flame and smoke.


Figure 92. Launch sequence.

Recovery was as before with the drogue coming out very near apogee. However, it appeared to get smaller as the body descended. One of the parachute lines and a small hole were burned in the drogue causing it to spin but not having enough force to spin the rocket as well. The main opened at 1000’ and the rocket descended gently to the salt.


Figure 93. Recovery, July 31st shot. 

Due to budgetary constraints, further shots were not scheduled. Level III was achieved.


Sean O’leary – photography, launch crew

Bill Kennedy – photography, launch crew

Timothy O’leary – launch crew

Steven Cox – launch crew (April 18)

Michael Roner – launch crew (July 31)

Sterling Robison – launch crew (July 31)

Special thanks to Jack Anderson, L3CC mentor.

Published in Focus
Monday, 13 August 2007 06:53

The SS-520-2 as a Sport Scale Project

A Japanese two stage sounding rocket at its 2nd appearance - An interesting object for sport scale. The SS-520 is a two-stage rocket, the first stage of which comes from the main booster of the S-520, and has a capability for launching a 140 kg payload to an altitude of about 1,000 km.

The SS-520 aims at reaching 1,000 km altitude, and at the same time, carrying out technological experiments concerning the development of a mini-satellite launch vehicle by adding the third stage atop. The first stage is stabilized aerodynamically by use of tail fins like the S-520.

As the second stage is heavier than the head of S-520, the aerodynamic margin is secured more than ever. The whole motor case of the second stage is made of CFRP. The spin generated in the first stage is succeeded by the second stage, and it is utilized in the Rhumb-line control and spin stabilization.

The SS-520-2 rocket was launched at 6:16 PM (local Japan time) on December 4, 2000, from SvalRak (Ny Olsen), Norway, at an angle of elevation 86°, azimuth 192°. The rocket launch was normal, ignition occurred on schedule at 67 seconds for the first stage, 69 seconds for the second stage, and it reached its summit of 1,040km at about 600 seconds, before splashdown at about 1,100 seconds. All telemetry and onboard instruments functioned smoothly, the boom and antenna deployed, and the high-voltage power supply to the various sensors went according to schedule. Telemetry reception was conducted in three locations, at Ny Olsen, Longyearbyen, and Andoya, and excellent data were acquired. As for the rocket launch, by monitoring EISCAT radar data in real-time and solar wind plasma and interplanetary magnetic fields by ACE satellite, it was confirmed that the rocket actually flew above the artic cusp. The scheduled observation from the ground was impossible due to the weather, but from the observation data of the onboard instruments it was deduced that the vehicle flew above the artic cusp. Detailed analysis is to be performed upon the ISAS team’s return to Japan.

Campaign Objective

The main objective is to study ion heating and acceleration processes and associated ion out flowing phenomena occurring in altitudes of ~1,000 km above the dayside cusp/cleft region. The outflow of ionospheric ions, especially from the dayside cusp/cleft region, is an important source of magnetospheric plasma. Much of the ion outflow is caused by ion heating in the perpendicular direction to the geomagnetic field.

A number of physical mechanisms have been proposed, but most are hypothetical, poorly understood, or simply conjecture. The goal of the present experiment is to put these mechanisms into perspective.

The Payload

For this purpose, the SS-520-2 rocket is designed to carry nine instruments:

  • TSA - Thermal and Suprathermal ion Analyzer
  • TECHS - Thermal Electron Capped Hemispherical Spectrometer
  • XUV - XUV 83.4-nm photometer for oxygen ions
  • ESA - Electron Spectrum Analyzer
  • ISA - Ion Spectrum Analyzer
  • PWA - Plasma Wave Analyzer
  • NEI - Impedance probe for electron density
  • TEL - Electron temperature probe
  • MGF - Magnetic Field Instrument 

Sport Scale and the SS-520

The SS-520 series makes a fine entry for sport scale or even scale model rockets for beginners as well for intermediates. The shape of the rocket is very simple. Basically we are talking 4 fins and a nose cone - but no conical transitions or other hard to create shapes. And still, there are enough challenging details to add to get more craftsmanship points and even mission points.

It is relatively easy to generate a file to make water transfer decals ( simulating all those Van Allen screws etc. or the umbilical plug markings on the payload section. The leading edge of the fins is very unique and could be simulated with decals too!! You decide the degree of complexity you want to exhibit. [I have created a set of water transfer decals for the SS-520-1 which is available as pdf-file upon request.] Or just think about the cork wrap of the 2nd stage.

mt_gallery:SS-520-2A longer airframe coupler wrapped with that cork material you can get at home improvement stores might mimic that feature sufficiently. Or you scan a piece of cork, scale it down an print it on white decal vinyl and the apply it on the airframe. There are definitely different way to do it.

There is a realistic chance to get some mission points too.I built my first model of the SS-520-1 in a way that it was spinning to contribute to the spin stabilization of the 2nd stage. The more brave modeler will have an active 2nd stage using a timer for staging and ignition. You might consider flipping fins for the very short second stage as spin stabilization alone might not work in a small model.


Safety first! If you fly a magnetic apogee detector you should get some more mission points – there was a “Magnetic Field Instrument” on board . . .

This article originally appeared in UROC's Ballistic Beehive in 2004

Published in Learning
Tuesday, 07 August 2007 16:11

Thinking About Level 3? You Can Do It!

As the UROC club grows, there are more and more flyers that are progressing up the ranks of level 1 and 2. Some of you may be considering making the jump to level 3 and wondering if this is something that you might want to achieve. UROC has seen a big increase in the number of Level 3 flyers over the last couple of years. I remember when I first got into high power rocketry I thought that those guys putting up level 3 rockets must have a PhD in astrophysics or some other connection to NASA. Surely, Level 3 rockets were beyond my basement building techniques.

The purpose of this article is to demystify the Tripoli Level 3 process for anyone considering making the jump and to set forth guidelines to help walk you through the steps.

I am not a NAR member so I am not as familiar with their procedures but I understand NAR has adopted similar regs and rules. Currently, Tripoli has about 700 Level 3 members nationwide with more being added all the time.

First of all, I am a TAP (technical advisory panel) member for Tripoli. TAP members must be level 3 certified and must apply to the Tripoli board for inclusion on the membership list. I wanted to become a TAP member because there was nobody in Utah at the time that could help certify Level 3 members at our launches. Also, I enjoy seeing the nuts and bolts of other Level 3 projects and I learn something new from each and every one. To date, I have flown or been very involved in about 50 M and N motor flights. That's some AP poundage!

Why does the TAP committee exist? Because Tripoli believes that as the rockets get bigger and the total impulse goes up, the potential danger also rises. These rockets should have more than one pair of eyes looking at them to ensure that they are safe and the construction and design techniques make them flight worthy. After the flyer has demonstrated the ability to construct and successfully fly a large M motor rocket, he or she is free to fly other Level 3 rockets without TAP approval.

Myth #1

Level 3 rockets are technically much harder to fly than level 2 and 1 rockets. Not necessarily true. In fact, many level 2 rockets, especially multi stage or clustered J-K rockets are tougher to fly and more technical than basic Level 3 rockets. For your Level 3 attempt you may want to employ the KISS method (Keep It Simple Stupid) to have a greater probability of success.

Myth #2

The Level 3 process is a lot of bureaucracy. Not true. There are some basic steps that you have to follow but with friendly TAP members (like me) guiding you, this should pose no problem.

Myth #3

Level 3 rockets cost a lot. Actually, this one isn't a myth. Level 3 rockets are definitely a step up in the cost factor depending on what you decide to do. But, if you can borrow somebody's motor hardware (with the typical lose-it-or-dent-it, you-buy-it policy) you can help bring the cost down. The 75mm reloads are also a lot more cost effective than the 98mm loads. Still, it is not uncommon for a level 3 rocket to cost over $1000 when you consider electronics, parachutes, motor hardware, motor reload and airframe parts. Everything but the reload is reusable but you still have to ask yourself, "What will this cost if it crashes and I lose everything?"

OK, so how do I get started on my Level 3 project? First of all, you need to select a project to build. It can be an upscale of an old estes kit or a Level 3 kit from some of the various rocket vendors or your own design. Some of the basic Tripoli rules for the design are as follows:

  1. Single stage design only.
  2. No clusters allowed.
  3. The project must be constructed principally by the flyer.No team projects allowed.
  4. Electronic recovery is required and must function as designed. A redundant (backup) recovery system is also required. This can be motor ejection but not recommended. I always advise that either two altimeters be used or one altimeter and a timer backup.
  5. Two-stage recovery is not required. If you want to keep it simple, blow the main parachute at apogee. A lot of Level 3 rockets don't go that high anyway.
  6. Currently, Tripoli is allowing kits from manufacturers to be used. There is some discussion among the TAP committee that only scratch built rockets will be allowed in the future. More to come on this issue

Next, you should contact a TAP member to discuss your project. He'll tell you what you need to do in order to get your paperwork signed off. In my case, I tell the flyer that I would like to see the following:

  1. Overall written description of the project with specification such as length, weight (loaded and dry), diameter, electronics involved, recovery systems, expected altitude, etc.
  2. A schematic of mechanical drawing showing all components of the rocket.
  3. Some photos of construction are nice if you can take them as you build.If not, then details of construction and materials used, etc.
  4. Some computer simulated flight profiles with the motors you expect to use.
  5. Tripoli paperwork.

For Level 3 certification, you need to have two TAP members sign off on your project at least one month before you actually make the flight. This is to allow time for minor changes that TAP members may suggest. If you would like to use me for one of your TAP members, I can suggest others that would be happy to serve as your second committee member. Rich Evans of UROC is also a TAP member in Utah and is happy and willing to serve as a second TAP member for UROC level 3 projects.

Finally, you need to launch your project. The day of reckoning! For the actual flight, a TAP member must witness the flight and survey the rocket upon recovery. The TAP member witnessing the flight can be one of the first two preliminary members that you used or it can be a third member. If the flight is successful, he will sign your paperwork at the site and mail it in to Tripoli headquarters.

In my case, I define a successful flight as follows: The rocket must work as designed and sustain only cosmetic or minor damage. Example: If you design in a level of complexity such as two-stage recovery, then the rocket must work that way. Damage such as zippers may mean that recovery was somehow compromised or structurally the rocket couldn't withstand the forces encountered during chute deployment.

What's the success rate? The Level 3 projects that I've been involved in have had about a 65% success rate. 2 successes for each failure. That's not bad. And for the failures, most were able to launch again at a later date and have a successful flight.

Hopefully, this article will encourage some of you who are thinking about Level 3 to go for it. If you want to call me to get started, my phone number is 277-9006 hm or you can catch me at a meeting or launch.

Published in Learning
Tuesday, 08 August 2006 10:55

Descent Impact Guesstimate

Here is way to estimate or "guesstimate" descent impact loads. First, get an estimate of the descent rate.  One way to do this is to go into Rocksim and choose a tube.  Just use the "mass over-ride" option to assign the mass of your rocket.  Then attach a parachute to the tube and look at your descent rate.  This is how fast your rocket will fall with your chosen parachute diameter. Now, you can estimate the equivalent drop height (H)  for your rocket without a parachute by using the following formula: 

H =  0.5 x (  (velocity)^2  )  / 32.2 


"H" is the drop height in feet
"velocity" has units ft/sec.
32.2 ft/sec^2 is the acceleration of gravity.

As an example, if your rocket has a descent rate of 20 feet per second, the impact will be the same as if the rocket was dropped from 6.2 feet.  Imagine dropping your rocket from 6.2 feet on the salt flats or the Pony Express without a parachute!  This will be the same impact load.  If you can make your parachute large enough to slow the descent rate to 10 feet per second, your equivalent drop height will be only 1.55 feet.

Published in Learning
Monday, 20 March 2006 09:35

Holding up Centering Rings

Holding centering rings in place while you glue them can be trying. A properly cut centering ring (wood) will slide onto the tube with a slight friction fit and should stay by themselves. However, sometimes the ring is too loose to stay in place when you make the fillet.

A neat trick is to mark the position of the centering ring and then wrap several layers of tape at the mark. The tape holds up the centering ring so that you don't have to worry about it slipping when you make the fillet or as it dries!

Published in Learning
Tuesday, 07 August 2007 04:33

Using Artist Acrylic Paints for Rocketry

I enjoy painting plastic models and pewter miniatures used in games. I've used many different kinds of paints, so when it came time to paint another rocket, I decided to try some of them, rather than another can of Krylon. I've settled on using artist grade acrylics for my miniatures, so I decided to start there.

I chose acrylics for a variety of reasons. Typically they are non-toxic, they clean up with soap and water, can be thinned with water, are permanent, durable, and are readily available.

I purchase most of them from either Robert's or Michael's craft stores (don't forget the 40% off coupons in the Sunday newspapers).

The brand I like best is Liquitex, but I have had good luck with Golden and Winsor & Newton. The Liquitex paints come in a little wider color range, and are a little cheaper. Experiment yourself and see what works best! The model acrylic paints (like Testor's Model Master Acryl line) do come in a wider range of colors and are already thinned, but they seem fragile-any little scratch seems to take them right off.

Most of the artist paints can be heat-treated to improve their durability. Usually baking them at 200 F for about 30 minutes works, however, my wife would not appreciate an Alpha in the oven, so I put them on the dash of my car, and park in the sun.

Acrylic paints consist of two parts: a pigment and a binder. Usually the pigment is a naturally occurring mineral that is finely ground, and the binder is a plastic resin. Most artist acrylic paints across brands are compatible, but not all. Some very interesting colors can be mixed together. Get a color wheel and experiment. Also, there are a wide variety of pearl colors, or interference colors. Pearl colors appear as metallics, and interference colors change color depending on the angle you look at them

Make sure to buy the artist-grade, and not the student-grade paint. The student-grade paints are about 2/3 the price, but have less pigment in them, and come in fewer colors.

These paints have different viscosities between brands, and even between lines in the brand. High-viscosity paints have almost a peanut butter type consistency, and need large amounts of thinning for our purposes. The lower viscosity paints typically have the same amount of pigment as their high-viscosity counterparts, but need less thinning, so they go further. I use the medium-viscosity Liquitex, or Golden's Most of these paints have 2 ratings on them: Lightfastness and Opaqueness. Lightfastness refers to the pigment's ability to withstand fading. The highest grade of Lightfastness means the paint will stay it's original color for 100 years when exposed to museum-quality lighting. Most paints fall into this category, however many of the fluorescent colors shouldn't be used-they will break down in a few days of outdoor light.

To thin these paints, a variety of items can be used. Water is the most common, but don't use too much. As the water dries, the paint shrinks, and can crack. Add a drop or two of dishwashing detergent to the water to lower the surface tension. Windshield wiper fluid is another thinning agent, however I have had the alcohol react with the plastic binder in a few brands. Do not use mineral spirits or turpentine! Unfortunately, the best thinner for acrylics is not the cheapest--mediums. Mediums are sold for different types of thinning, from brushing to airbrushing, to giving a very glossy or dull finish without any overcoat. Most mediums are the plastic resin in a nonvolatile suspension. One thing I have learned, is to use the same brand of medium for the paint - different resins can react with each other. You can use several mediums, like combining airbrush medium with gloss medium. As a rule of thumb, do not user more than 25% medium in the paint. Try thinning to different levels, but remember, it is easier to thin the paint more than thicken it back up. A little medium goes a long ways.

I have applied these paints using brushes, rollers, and airbrushes. The best results have been with an airbrush, although a roller or brush can be used equally well with a few cautions. For brushing, use the highest quality, softest, synthetic fiber bristle you can find. Natural bristles tend to absorb the moisture in the paint, so it doesn't dry naturally, and can crack. Softer bristles leave less of a brush mark. Don't skimp on a quality brush, you wil thank yourself later.

If you don't have access to an airbrush, a spray bottle (like the kind for misting plants) can work too. Find the finest spray pattern you can, the finer the spray, the more uniform the paint will be. Pump-style hairspray bottles can work, but very little paint will go down per pump. Even though the paints are labeled non-toxic, I would still recommend using a NIOSH approved paint mask for any airbrush work. To use this paint in an airbrush, thin the paint to the consistency of heavy cream. Set your air pressure to about 20-23 lbs., and hold the airbrush as perpendicular to the rocket as possible. Start the spray before the rocket, and use a smooth stroke, ending the spray after the rocket. I practice on an old piece of cardboard, so that I can get the color and consistency that I want.

If you have spirals in the body tube to fill, I've used a product called Gesso with some success. Gesso is used to prime canvas for acrylic or oil paints, so that the paint does not soak through the canvas. It looks like a thick, syrupy material. I thinned it using water, then applied it using a brush directly onto the spirals. I had to let it sit overnight for complete drying, though. After that, I sanded the Gesso smooth. You can apply masking tape about 1/16" from each side of the seam, to make a guide if you like. It may take more than one coat, try to apply thin coats. If you want to use a primer, I've used whatever I had handy-spray cans of Krylon, airbrushing model paint primer, or an acrylic primer made by Designs From the Heart, or thinned Gesso. Each seemed to work equally well, but I let the oil-based primers dry for about 48 hours before I tried to apply acrylics over them. The solvents in the primer should be completely outgassed, or the paint will bubble later.

As a top coat, I have used either Liquitex's Solvar gloss varnish, the Gloss medium, Future floor wax, or simply left it alone. Some of the paints leave a little rough surface, and do need topcoating. Future has worked well, and it is cheap. The varnishes are a little on the expensive side, but very durable. Solvar is also removable with turpentine, so you can repair the paint easily. Solvar also has some UV inhibitors in it, which helps the paint resist fading.

Liquitex has a website with good technical information at Golden's is Winsor & Newton's website is, but it seemed to concentrate more on their oil paints. Each has technical contact email, which I have found to be fast, friendly and expert advice (Liquitex put me in contact with their chemical engineer when I had a question on heat curing!). Acrylics have been a good alternative for me. They are more versatile, cheaper, easier to use than oil based enamels, and I because of their non-toxic nature, I can paint inside my house with them. Experiment with them, and see if they work for you.

Have fun, and keep the pointy end up! This article originally appeared in the December, 2002 issue of the Ballistic Beehive.

Published in Learning

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