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5.17 I've seen mention of all kinds of rocket motor types and sizes. Could you give a brief history and summary of the main marketing names for model rocket motors?




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This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.

5.17 I've seen mention of all kinds of rocket motor types and sizes. Could you give a brief history and summary of the main marketing names for model rocket motors?

From: msjohnso@WichitaKS.NCR.COM (Mark Johnson)
The original hand-loaded motors made by Orville Carlisle and
sent to Harry Stine in about 1956 were 0.5 in dia. (13mm) x 2.25
long (55 mm). These were used in early testing up until the time
Model Missiles Inc (Stine's company) began to produce commercial
product in sufficient quantities that Carlisle could no longer
make motors fast enough. These had total impulse roughly from
today's 1/2A to about the middle of the B range.

Stine contracted with Brown Fireworks Co. of Missouri in 1958 to
make mass-produced motors. Brown could have made them in the
same size as the Carlisle motors, but it would have meant costly
new tooling. Mr. Brown offered to produce a low-cost motor for
MMI using his "Buzz Bomb" case size - 0.7 x 2.75 in (18 x 70 mm)
- the Buzz Bomb had a small aluminum blade on one side of the
case and a nozzle drilled into the side of the case opposite,
where a fuse was inserted. Strictly a fireworks piece.

In about 1959 or 1960, Vern Estes entered the picture, having
offered to produce motors for less than whatever price MMI was
paying Brown. G. Harry took him up on the offer, and Vern began
making motors in the now-standard 18 x 70 mm size. He quickly
automated production with the first of several "Mabel" machines
and was able to make far more motors than MMI needed. That's
when Estes entered the model rocket business himself.

The short motors were 1/4A and 1/2A motors which came about in
around 1963 or 64 when somebody at Estes realized that the upper
1" of the casing had nothing in it, and was just dead weight. So
Estes started producing the "S" series, with a case size of 18 x
45 mm (0.7 x 1.75 in). These continued in production until 1970
or so.

In about 1970 or 1971, Stine (whose MMI had gone out of business
somewhere around 1962) reentered the hobby as a paid consultant
to Model Products Co. (MPC), which later spun off its rocketry
business as AVI (Aerospace Vehicles Inc). Stine persuaded Mike
Bergenske that there was a market for the "classic" 13 x 55
rocket motors as a high-performance motor, in sizes from 1/4A to
B. These were the Mini-Jet motors, which quickly resulted in
rewriting the NAR altitude record books. Estes followed suit
with its mini- motor line, originally trademarked "Mini-Brutes"
with the 13mm diameter but choosing to go with a length
compatible with the old "S" series at 45 mm (so they could use
the old "S" series engine hooks, I presume). Centuri's "M" motor
series, in sizes from 1/4A to B, were released at about the same
time. These were 13 x 50 mm (0.5 x 2 in)

The other "standard" motor type which emerged about this time
was the Estes "D" motor, which was sized to fit easily in the
BT-50 or 25mm tube, while keeping the 70 mm length constant
(save the engine hook tooling again, I guess). These first hit
the marketplace about 1969; I still have the original
announcement flyer somewhere in all my old files. The 24 mm
diameter has become the "small high power" standard for D, E, F,
and even a few G motors, mainly from AeroTech. Estes chose to
keep the existing standard diameter and extend the length on
their new E15, introduced during 1993.

The 29 mm standard motor emerged from the Enerjets. The original
Enerjet-8, a fiberglass-cased motor developed and produced by
Rocket Development Corp. of Indiana (RDC, later acquired by
Centuri as Enerjet, Inc) was an external-delay, 29 mm diameter
motor with about 35 N-sec of total impulse (8 lb-sec). The
Enerjet-8's external delay was too cumbersome for
unsophisticated users, and was replaced by a conventional
internal delay when the Enerjet E24, F52, and F67 were
introduced in 1973 by Enerjet and Centuri, its parent. The F67
was the first full 80 N-sec F motor produced in the US.

FSI is a bit of a cipher in all this. They chose to go with a 21
x 70 mm motor for A, B, C, and small D motors, beginning in
about 1966 or so. Their full D and small E motors are in 21 x
95 mm cases. (D18, D20, and E5). The larger FSI motors are in
27mm cases of various lengths. The E60 is about 95 or 100 mm
long, and the F7 and F100 are 125 mm. FSI started producing 18 x
70 mm A, B, and C motors in about 1985 or so.

 

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previous page: 5.16 BT-20, BT-50, BT-55. What the heck do the numbers mean on Estes body tubes? Is their any special meaning in these numbers?
  
page up: Model Rockets FAQ
  
next page: 5.18 Why don't I just make my own model rocket motors? Shouldn't I be able to custom-make better, more powerful motors, at a cheaper price?