Yes! Here's a page from U.S. Rockets kit #1 (1001). This kit is ideal for the new Estes 29mm BP motors.

Not externally vented. Given the reliability without the vents, I think there is a scaling issue where rockets below 24mm require the vents (Centuri Passport Staging). However most of these rockets had a single hole in a booster tube to allow for Thermalite to ignite composite upper stage motors. That 1/8" hole might have been enough to contribute to the overall reliability of the system over 3.5 decades.

Tech Jerry

Attached Files

1001-35-3.pdf (5.1 KB, 57 views)

Thank you (my computers can't open YouTube videos anymore, so I couldn't watch the presentation on the R & D report). It makes sense, though--the compacted black powder propellant grain in the upper stage motor wouldn't be ignited by the flame from the lower stage motor quite as rapidly as a mass of loose black powder would be, because the grain would conduct (dissipate) some of the flame's heat deeper within it. (This explains how, in Estes' accidental motor ignition tests in the 1960s [to establish their safety], a lit cigarette was snuffed out against the exposed propellant at the top end of a booster motor, without igniting the propellant.)

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NAR #54895 SR

Jerry,

Correct! And very interesting that your 2225s with the D12s produced so much smoke. Emma's report shows why that was probably the case.

I also want to mention a completely different gap staging method used by our foreign friends in the Internats. Instead of a single stuffer-like tube which serves as the booster motor mount and runs all the way up to the base of the sustainer motor, most of our competitors use what they call a "flash tube."

A flash tube is a very small diameter fiberglass tube which runs from the inside upper propellant edge of the booster motor all the way up to the nozzle of the sustainer engine. At its base, the flash tube runs through a small plug which nests inside the booster motor. The plug sits just above the propellant grain. At its top, the flash tube sits just a millimeter or two below the sustainer engine.

In prepping, a few grains of black powder are placed in the upper end of the booster motor, the flash tube is slid into the motor to just above the propellant grain, then this entire assembly is slid into the short motor mount on the aft end of the booster and the motor is secured in place. The upper end of the flash tube goes through a tiny centering ring at the upper end of the booster. Then the sustainer, with motor in place, is slid into place atop the booster with the aft end of the sustainer motor directly over the end of the flash tube. There is no venting in this arrangement.

The benefit of this is that the flash tube, usually with an internal diameter of a 1/8" launch rod, weighs very little compared to our stuffer tube arrangement. This system works well with 10 mm Euro motors which have no real ejection charges, but would be problematic with larger U.S. motors.

For the last WSMC Trip used the flash tube arrangement while Matt and I used the stuffer tube arrangement. Trip did much better than Matt and me, for lots of reasons, LOL.

Anyway, I thought folks might be interested in a different way to gap stage.

Steve

Correct. The auto-ignition temperature of APCP is even higher at 650 C.

This is a fireworks method. It is older than the hills and twice as dusty.

FAI teams have refused all my custom motor offers.

Example:

http://v-serv.com/usr/13mm.htm

http://v-serv.com/usr/swedge.B.4.5B0.7-4-371.gif

I've seen drawings of two-stage FAI altitude competition models with flash tubes; are they permitted by the NAR for competition and/or sport flying here? They would certainly be useful for "all stages live" scale models with long stage airframes, particularly in the cases of 13 mm and MicroMaxx motor powered models, where mass is at a premium. (It's too bad the NAR won't certify fuse-type composite upper stage staging igniters for use with black powder lower stage motors--they would permit many variations of scale as well as non-scale models.) Also:

The European space modelers sometimes utilize reusable squib igniters (I'm not sure if that's the correct term for them) for igniting motors, including clustered motors, on the pad. This type of igniter consists of a small tube with ignition leads, which is packed with loose black powder (smokeless powder might work well, too). I've never seen one myself (just a photograph in one of Stuart Lodge's books), but I suppose the "heating element" could be either a reusable filament or a single-use nichrome hot-wire igniter.

__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR

Regarding fuse-type staging igniters (for black powder or composite upper stage motors), there is a scale flight realism feature that they would make possible, in models that are too small to incorporate electronic staging systems:

A staging igniter that was ignited at launch (first stage ignition) would allow the first stage to drop off at burnout, coasting to its peak (at which point its short-delay motor's ejection charge would deploy its streamer or parachute recovery system). The upper stage, meanwhile, would coast upward briefly, after which the staging igniter would ignite its motor; this delayed-ignition staging would allow realistic depiction of the flight profiles of most multi-stage sounding rockets. Imparting spin to the model at launch via slightly canted fins (which is also the case for most full-scale sounding rockets) would keep the model's nose pointed upward, just in case the staging igniter burned more slowly than specified. (Some of the Enerjet motors used variable-length fuses as variable-length delay charges, so this basic concept of delay fuses isn't unknown in model rocketry.)

__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR

It's 100% about FAI competition. Those systems are certified days before the event in a separate process distinct from NAR certification. Wouldn't it be nice if NAR certs recognized FAI like they recognize CAR or totally incompetent TRA?

Agree that NAR should change name to NIR...way too many stifling rules and regs.
WAYYYYYYYY too much over-emphasis on safety above fun and innovation, which BOTH should be priority above safety.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !

Yes. The Estes Omega is gap staged, without a vent.

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