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REV 2.4 - Mon Nov 8 00:05:58 2010

Box 1271
Knightdale, NC 27545
(919) 266-1977
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SPECS: 9.2" x 0.76" - 0.4 oz
ROCKSIM FILE: Right Click to Download
SpaceCAD FILE: MISSING - please submit here
REC'D MOTORS: A8-5, B6-6, C6-7

(Contributed - by Mike Mistele - 05/01/04)


This is a very basic 4FNC, minimum-diameter, streamer-recovery rocket suitable for beginners. It's part of Semroc's RetroRepro line and, specifically, the Micron was originally a Centuri model (#KA-5) first released in 1963. The RetroRepro line updates these old models with more current technology--in this case, the upgrades include laser-cut fins and a Kevlar shock-cord.

This kit comes with the following components:

  • Body Tube (ST-765)
  • Balsa Nose Cone (BC-719)
  • Laser-cut Fin Sheet (FV-8)
  • Thrust Ring (TR-7)
  • Launch Lug (LL-122)
  • Screw Eye (SE-10)
  • Elastic Cord (EC-118)
  • Kevlar Thread (SCK-24)
  • Streamer (RS-36)
  • Tape Disc (TD-1)
  • Empty Casing (MC-727)

I ordered this kit directly from Semroc's web page. I had gone there to order a couple Rocket Racks and figured I'd get a kit while I was at it.

The kit comes in a plastic hang-bag just like an Estes or Quest kit. The "front" of the package, depicting the rocket is actually the front cover of a 12-page booklet, which includes brief history of both the Micron model and Centuri Engineering Company, the assembly instructions, an exploded view of the components, and the NAR safety code.

The instructions were extremely easy to follow, and I saw no need to deviate from them as I assembled my model.

The parts themselves were generally of very high quality. In particular, the balsa fin sheet was among the nicest bits of balsa I've ever gotten in a kit and the laser-cutting was very smooth.

The balsa nose cone was also a nice piece of wood but the shoulder was a bit too wide for the body tube. A bit of sanding fixed that problem right up however.

About the only part I would have any complaint with at all was the streamer--it's a length of orange crepe paper. I'm not sure how long it'll last (it already has a tear from her first flight), so I'll likely need to replace it at some point with something a bit more durable.

The illustration of the Micron on the front of the booklet has a fun, early 60's sounding rocket look to it. Unfortunately, the kit doesn't contain any decals, and it'd be a challenge for a beginning rocketeer to duplicate that look with paint alone, which includes a roll pattern. As I didn't want to work that hard, I decided to not recreate that look.

I used Elmer's Fill & Finish to smooth out the nosecone and fins, followed by a few coats of Krylon grey primer.

For the final finish, I applied a few coats of Testor's Chrome spray paint, then used Testor's Purple Metalflake spray paint for a "fade" pattern on the nosecone and top of the rocket.

Once the paint was dry, I put an American flag decal on the body tube (I got a sheet of flag decals by AutoGraphics at the hobby shop, and put one on each of my rockets), then finished with a coat of Krylon gloss.

Construction Rating: 4 ½ out of 5

For the Micron's first flight, I used an Estes A8-3. The delay is a bit shorter than recommended, but I didn't have any A8-5s handy. The motor is a friction-fit and one wrap of masking tape around the motor was sufficient to keep it snug.

The instructions don't recommend a specific amount of recovery wadding; I used 3 sheets of Estes wadding, and found that the body tube with the wadding, the shock cord, the streamer, and the nose cone was pretty tightly packed. Maybe 2 sheets or a little dog-barf would be better.

She took off from the pad very quickly, as you'd expect given the light weight, and the flight was straight as an arrow. The ejection charge fired a bit before apogee, though that didn't surprise me, given I was technically not using the recommended motor.

The Micron uses a combination Kevlar-elastic shock cord system. The Kevlar cord is tied around the thrust ring, and extends well beyond the end of the body tube. The elastic shock cord is then tied to the Kevlar cord at one end and to the nose cone at the other end.

As I noted above, the streamer is just a length of crepe paper--probably historically accurate, but it feels a bit flimsy. The streamer is attached to the elastic shock cord, near the nose cone with a tape disc.

On the first flight, everything deployed nicely, and the streamer fully unrolled. It seemed like it was coming down a little fast, but drifted only about 50 yards downwind from the launch pad. Despite the seemingly-quick descent, she landed with no damage at all.

However, as I was rolling the streamer back up to put the rocket away, I noticed a long tear in the center of the streamer. It will have to be replaced at some point.

Flight Rating: 5 out of 5

PROs: easy assembly, clear instructions, teaches some basic assembly skills, nice flyer.

CONs: streamer material is cheap, hard to re-create the finish as pictured without decals.

Overall Rating: 4 ½ out of 5

(Contributed - by Chan Stevens [Who's Who Page] - 10/18/04) Semroc Micron

Nice little minimum diameter rocket that zips off the pad in a hurry and at $4 retail, makes for a nice little kit for that Cub Scout or school group. This is also an appealing kit to the nostalgia buff that is based on the 1963 Centuri kit by the same name.

As is the case with almost every Semroc kit, this one came in a professionally bagged package along with a certificate of authenticity/production number. Parts include:

  • ST-765 body tube
  • Balsa nose cone/screw eye
  • 4 laser cut balsa fins
  • Thrust ring
  • Streamer (crepe paper)
  • Kevlar/elastic shock cord combo

With laser cut fins, this is definitely somewhere just below a skill level 2 kit. The only challenge is to mask a 2 or 3 color paint scheme.

The instructions were well written and clear; offering some decent construction tips along the way, such as how to fill grain on the balsa fins.

Being a minimum diameter kit, the body tube acts as a motor tube, so simply gluing a thrust ring into one end takes care of the motor mount assembly aspect of the build. Before doing this though, you tie one end of the Kevlar shock cord to the ring, thereby anchoring it to the thrust ring inside the body tube. This is a very good and effective technique, one that I wish was more common in the lower skill level kit range.

Next, sanding the fins, which is easier to do this while still in the balsa sheet, and removing them from the laser-cut sheet. The instructions call for bonding them flush with the aft end of the tube, although I'd consider sliding them forward about 1/8". This won't throw the CP off that much and enables you to use a band of tape around the motor and body tube for improved motor retention.

Tack on the launch lug, glue the screw eye into the balsa nose cone, and you're ready for recovery and paint prep.

The streamer for this kit isn't too bad, it is a piece of bright orange crepe paper roughly 3" x 36", but it's attached using a fairly weak line and is secured by a single tape disk attached to the center. I don't think this is likely to hold up very well over repeat flights and would have preferred to see a chute instead.

I skipped the balsa sealing/filling routine on this one, jumping straight to primer. Two coats of primer and sanding in between with a 220 grit sponge did a reasonably good job on the balsa grain, so I moved on to two coats of Krylon gloss white. I finished up with a blue nose and red fins, matching the illustration on the package header. The header also depicts some blue accent stripes (roll pattern), which is possible to paint but would clearly be better (and easier) if a waterslide decal were supplied for this. I guess for $4 I shouldn't complain but I'd rather pay $6 and have a decent decal or two.

Construction Rating: 4 out of 5

The maiden flight was on a beautiful fall day with low winds, though there was some cloud cover way up above our club's waiver ceiling. I went with a B6-4, as I did not have any B6-6s handy. Before I could even blink, this was pushed almost beyond my sight, well over 800 feet. Apogee might have been a little early, but not enough early to worry about.

The streamer deployed fine, but it didn't offer much drag for this rocket and it came down fairly fast. Fortunately, it landed in a large, soft grassy area undamaged. Still, given the descent rate and weak attachment point, I will be replacing the streamer with one of my spare chutes just to avoid any potential damage on the recovery.

PROs: Kevlar/elastic combination is a solid, durable method.

CONs: undersized streamer, weak attachment disk/line.

Flight Rating: 4 out of 5

This was a terrific value at $4 retail and I'd recommend buying this for a group build-fly session in the future.

Overall Rating: 4 out of 5

[Submit your Opinion]

"" (x.x.)

[Enter Rocket Specific Tip]

01/09 - "The Semroc Micron kit lacks decals, but I have found two "new" multi-color original Centuri Micron decor schemes that can be easily reproduced using spray paint and simple masking. Semroc's depiction of the Micron is of the original (1963) Centuri version, which had a shorter (balsa) nose cone than the plastic nose cone that was used in the later Centuri version. The later version appears to have been first released around 1969, although the original "short balsa nose cone" version was illustrated in the color "group portrait" photographs in Centuri catalogs as late as 1971. Looking through online scans of those catalogs (the links are included below), I have found small photographs of two different multi-color decor schemes for the original "short balsa nose cone" version Micron that were not depicted in the larger catalog illustration drawings. One of them can be seen here in the color "group portrait" photograph from the 1971 Centuri Catalog (see it here on Doug Holverson's "Centuri Memories" web site and on the Ninfinger Productions web site). The original version Micron is in the lower left corner of the image, the second rocket up from the bottom (near the white IQSY Tomahawk). It has a red nose cone, a white body tube with a thin red longitudinal stripe, two white opposing fins, and two blue opposing fins. A slightly more complex version of this decor scheme from the 1969 Centuri catalog can be seen on the Ninfinger Productions web site (the fourth rocket from the right in the front row). It looks the same as the 1971 catalog version, but it also has a thin red stripe running down the middle of each white fin, parallel to the leading edge. I hope this information will be helpful." (J.J.W. )

[Enter Flight Log]
Date Name Motor Ejection/
Wind Notes
08-15-2004 Tim Anderson Est SU A8-3 Apogee - Perfect
(600 ft)
0-5 mph winds - Great Start, Great hight, however nose cone not fitted properly caused a deep lawn dart effect, no damage other than dirt removal
11-04-2007 George Beever Est SU A8-5 Didn't See 10+ mph winds - Great boost, alomost out of sight in a clear blue sky. Great flight.
02-29-2004 Bill Eichelberger Est SU A8-3 Apogee - Perfect 0-5 mph winds - Impressive height for an A8-3. Over the capabilities of the field, but the light winds kept it in the ballpark.
03-26-2006 Bill Eichelberger Est SU B6-4 Didn't See 5-10 mph winds Event: Quark Section Launch
- Despite the day-glo paint, I didn't see this until it was three feet from the ground. I can't even imagin what it would be like on a C.
04-08-2006 Bill Eichelberger Est SU 1/2A6-2 Apogee - Perfect 10+ mph winds Event: Woodfill Whoopy-Do
- Perfect rocket/engine combo for conditions.
11-18-2008 Mark Grisco Est SU 1/2A6-2 Apogee - NC Up 0-5 mph winds - first fllght. scoots even on a 1/2A.
11-18-2008 Mark Grisco Est SU A8-5 Apogee - NC Down 0-5 mph winds - jumped of the pad and kinda went east for whatever reason. had to walk a little to recover.
04-23-2004 Mike Mistele Est SU A8-3 Just Before 5-10 mph winds - First flight -- quick lift-off, nice straight flight. Ejected a bit early, but not surprising since A8-5 is the recommended engine. Slight drift, but good landing.
05-26-2004 Mike Mistele Est SU A8-3 Just Before 5-10 mph winds - Really rocked on this motor; seemed higher than last time. Don't think I dare a B in this girl. Streamer deployed, but drifted a fair ways in the breeze. Landed safely.
06-13-2006 Mike Mistele Est SU A8-5 Apogee - Perfect 5-10 mph winds RIP - Great flight...really soared with the longer delay. However, the wind took it after deployment, and it landed at the top of a tall tree. Alas, she's a goner. Status: Tree/Roof
08-27-2005 Mark Muir Est SU A8-3 Didn't Record 5-10 mph winds - Twin of micron on roof, but cut down streamer. Landed hard on asphalt, but repairable
09-11-2005 Mark Muir Est SU B6-4 Didn't See 0-5 mph winds - Lost sight in a hazy sky. Luckily didn't drift too far.
02-18-2006 Mark Muir Est SU A8-3 Just Before 0-5 mph winds - 2 fins damaged after recovery and while awaiting relaunch
03-05-2006 Mark Muir Est SU B6-4 None - CATO 10+ mph winds - Engine lost nozzle on pad
03-05-2006 Mark Muir Est SU B6-4 Didn't See 10+ mph winds - Nice flight on a windy day. Yeah for streamers.
09-09-2006 Mark Muir Est SU A8-3 Didn't Record 0-5 mph winds -
08-27-2005 Mark Muir Est SU A8-3 Didn't See 5-10 mph winds RIP - Coasted to roof of nearby building and was lost :( Status: Tree/Roof
10-09-2004 Chan Stevens Est SU B6-4 Apogee - Perfect 5-10 mph winds - Needs a chute/fast descent
04-22-2006 Chan Stevens Est SU A8-3 Apogee - NC Down 5-10 mph winds -
05-27-2006 Chan Stevens Est SU 1/2A6-2 Very Early 0-5 mph winds Event: section launch
08-05-2006 Chan Stevens Est SU A8-3 Just Before 10+ mph winds -

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