Hello All,

Attached below is Evan "Buzz" Nau's article (from the September/October 1997 issue of "Sport Rocketry" magazine) on vented gap-staged booster recovery (it can be used in any lower or intermediate stage, with black powder motors). This technique is ideal for scale models of the Centaure, Dragon, Kappa-8, SS-520, Long Tom, Aeolus, HAD, Kookaburra, or almost any multi-stage scale (or non-scale) model rocket. My thanks go to Roy Houchin of SEARS (the South East Alabama Rocketry Society) for sending me the PDF scan of this most useful article!

Attached Files

Nau_Investigations into Gap-Stage Booster Recovery.pdf (975.9 KB, 356 views)

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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
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NAR #54895 SR

I'm asking a question about the 2nd design in this pdf file. There's a vent hole in the inner pod but I don't see any vent holes in the lower stage that would normally facilitate gap staging. Any help here?

The vent in the lower stage is created by the gap in the rear centering ring.

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Roy Tuinila

CMASS Member

NAR #90252

NARTREK Bronze

L1 w/Mega Der Red Max on an H87-IM-7

Has Estes ever made gap-staged kits? I don't remember any.

I don't recall any, either, but the current Centuri model by Estes looks like a perfect candidate. As always, figuring out a safe recovery system for the booster is the biggest challenge.

Also, for anyone interested in Gap Staging or staging in general, this R&D report from NARAM 55 should be of interest:
https://www.youtube.com/watch?v=1Nhe5Y78PRQ

Thank you for posting the R & D report, Gus. To my knowledge, no model rocket company (in the USA, at least) has ever produced a gap-staged model rocket kit, let alone such a kit that features streamer or parachute recovery of its lower stage(s). But the late G. Harry Stine began covering basic gap-staging (with ordinary tumble recovery of the lower stage) "a few editions back"--a few decades ago--in his "Handbook of Model Rocketry," and he mentioned in the Sixth edition (1994) that no companies had implemented the concept because they apparently hadn't read his book. BUT:

Gap-staging, including with streamer and parachute recovery of lower and intermediate stages, has been used for many years in European and Russian model rocketry ("space modeling," as it's called there), particularly in scale models. Stuart Lodge, the very active British space modeler who has written several books about the hobby, has covered gap-staging with streamer and parachute recovery in his books. Also:

Peter Alway has published plans for BT-60 size Aerobee 150 and Aerobee 150A (four-finned) scale models that use "open-air" gap-staging, by which an ordinary zero-delay 18 mm black powder booster motor in the Aerobee booster ignites an 18 mm black powder upper stage motor in the Aerobee sustainer. "Open-air" gap-staging could also be used in scale models of rockets such as the Arcon, the Boosted Arcas I, the Cuckoo-boosted versions of the British Skylark, the Spanish INTA-255, the Iris and HYDRA-Iris, and other Aerobee variants, nearly all of which had boosters which--like those of the Iris, Aerobee 150, and Aerobee 150A--were separated from the upper sustainer by a short open framework and had a blast cone atop the booster. The boosters of these rockets were short and stubby, so--as with the boosters of Peter Alway's Aerobee 150 and Aerobee 150A scale models--tumble recovery would work fine for scale models of them. In addition:

Scale models of rockets with short first stages (which, unlike boosters, fire sequentially rather than simultaneously with the main rockets, in the full-scale vehicles) could also use gap-staging *without* a streamer or parachute recovery system in the first stage, if desired (tumble recovery would work fine for their short first stages). Scale models of rockets such as the HYDRA-Sandhawk, the Super Chief (a Talos/Castor powered two-stage sounding rocket), the British Skua (particularly the version with a single Chick booster motor) and the later British Skylark sounding rockets (including the Skylark 7 and the Skylark 12--they used finless Goldfinch first stage motors) could use gap-staged first stages, and these first stages could utilize tumble recovery (although they would have sufficient room inside for Evan "Buzz" Nau's gap-staged booster recovery systems, if the model builders wished to include them). As well:

All of the rockets mentioned above (plus many others) would make wonderful scale models (and scale *kits*--hint, hint...) with gap-staging (and gap-staged lower stage [or booster] recovery systems).

__________________
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

In light of this NARAM 55 R&D report it simply confirms the staging method used by the U.S. Rockets Hi-Test 2650 and Hi-Test 2225 which are three cluster two stage direct gap staged rockets. A mixer section is cut into the booster upper tube to allow all gasses to go to all motors. It is shockingly reliable. Also confirming the report is the fact that Hi-Test 2225 flights with 3x D12-0 to 3x D12-7 have an unusual amount of smoke at staging as compared to most two stage rockets. The 2225 has 5" booster tubes and the 2650 12" booster tubes. All recommended black powder motors are under 2/3 of that. 24mm BP Estes for the 2225 and 27mm FSI F100 for the 2650.

U.S. Rockets also developed composite motor direct stage igniters to replace Thermalite. NAR/TRA refused to certify (allow) either those U.S. Rockets igniters or our head end igniters. Still do for all manufacturers. No reason.



From LDRS-1.

Tech Jerry

I'm kinda liking the Estes Centuri (redundant) with 29mm G008 to 24mm E6. 24 seconds of action!

Thank you for posting that, Jerry! It definitely confirms G. Harry Stine's results, which he included in his "Handbook of Model Rocketry" (with drawings of the basic gap-staging arrangement):

Over a period of several months, he flew over 100 gap-staged, two-stage test flights with 100% success in second stage ignition. The motors in his models were separated by as much as 12 inches. The secret of his success was two opposing vent holes, each 1/4" in diameter, that he punched in the booster body tube just below the second stage nozzle. The vents allowed the forward-moving shock wave (and the pressure of the hot gas) from the booster motor's propellant burn-through to be relieved (which prevented the first stage from being blown off), so that the slower-moving burning propellant particles from the burn-through could enter the second stage motor's nozzle and ignite the motor. Evan "Buzz" Nau's gap-staged booster recovery test models (and the European scale models that utilize it) use the second stage (or upper stage) motor's gas pressure surge at ignition to deploy the lower stage's recovery system as well as to separate the stages. This is a much-under-utilized (in the U.S. and Canada) but very useful effect. Also:

Speaking of your staging igniters for composite upper stage motors, Apogee Components also offered staging igniters (fast-burning fuses) for the two-stage version of their Centrix micro rocket kit, which used their 10.5 mm black powder micro motors. In that case, the staging igniters were necessary only because the micro motors' tiny nozzles made gap-staging (and even conventional butt-joined staging) unreliable. Sometimes I think the NAR should change its name to NIR (No Innovations in 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

THIS REPORT CONFIRMS THERE ARE NOT DISCREET PARTICLES BUT A MONOLITHIC FLAME.

All rocket motors ignite at an auto-ignition temperature, not strictly from a flame. Hence the "Barber delay".

Tech Jerry

Jerry,

I would very much like to see a photo or drawing of the mixing section. Really interesting concept which I presume you did to ensure all upper stage motors lit even if one booster motor failed. Two questions, did you ever see that happen, where only 2 boosters lit but all 3 sustainers did? Again, really interesting idea. Second question, did you vent the upper end of the booster tubes to the outside so as to release the initial gas which tends to just blow the sustainers off the booster before they ignite?



Jerry,

Again, very interesting concept. I presume this was fuse-based? Any photos?

Steve