Deb Martin of Launch Magazine asked me a simple question several weeks ago that for me was not THAT simple. It is more of a journey for me and this is how I seemed to wind up on the road less traveled by.

1959
When I first started making the sugar rockets based on the design by Charles Parkin, Jr. in "The Rocket Manual for Amateurs," I was calling them motors since he never referred to them as engines. All the small commercial rocket motors in the appendix were an interesting aside. The Rock-A-Chute (Type A-4) motor had 1.0 lb thrust for .8 seconds and was 2.5" long and .687" diameter. The Pet at 40.0 lb thrust for 1 second and 4.8" long and 1.5" diameter was the one I really wanted. It was made by Atlantic Research Corp. and I could not find any purchase information. The Rock-A-Chute motor by MMI was in my Boy's Life magazine, but I did not buy from them. I just kept working on the sugar based motors in aluminum tubes with crude nozzles.

1960
When I found a copy of "Rocket Manual for Amateurs" by Bertand Brinley in the local Edward's Drug Store in late 1960, I found a goldmine of projects for rocket motors. It was my first introduction to Newton's Third Law and "reaction motors." It was also my introduction to SAE 1020 steel, flashbulb ignition, burst diaphragms, sandbags, and zinc-sulfur. I had still not heard them called engines.

1961
I was still making emptied CO2 casing motors with zinc-sulfur and doing underground testing, since most of them exploded. I was also learning how to turn deLaval nozzles on the lathe in aluminum (easy) and SAE 1020 bar stock (harder to work with). And I was still calling them motors.

1962
While in 9th grade general science class, I would sit in the auditorium and design nozzles for the latest zinc-sulfur or sugar rocket while Mrs. Finch covered the wide range of totally boring fields of physical and biological science. One day, she started talking about Newton's Laws and I listened instead of designing. She was talking about the one thing that interested me at the time. She was talking about "reaction engines" including jet engines and rocket engines. I knew she was wrong in not calling them jet motors and rocket motors, but it was interesting anyway. I still called them motors. I started ordering zinc dust from Central Rocket Company and they used motors and engines interchangeably.

1963
I got my first Estes catalog in late 1962 or early 1963 and they had Rocket Engines! They had more types of engines than I could even think of uses for. They were small, but they did not explode like most of mine. I kept making the large ones and small "shotgun shell" rockets, but my orders (and letters) to Estes started. I read and re-read those pages about "rocket engine design," never calling them motors again. I did not know why Estes chose engines instead of motors, but I thought that they must be right.

The best mechanic in town, Mr. Beddard, shed some light on the matter. He worked for the Chevrolet dealership and said that he "worked on automobiles powered by engines and his competition across the street worked on cars powered by motors." That clinched it for me. Engines were the top of the line. I knew then why Estes changed the name. Mrs. Finch was right. Why call them jet engines, but rocket motors when they both operate on the same principle.

1965
In the 1965 "Handbook of Model Rocketry" by G. Harry Stine, he referred to them as model rocket engines. The older designation of motor was over. If G. Harry Stine and Vern Estes called them engines, they were engines!

1968
When I started Semroc, we called them model rocket engines, but for a brief time, we also called them propulsion modules. We were perfecting a delay-ejection charge auxiliary package (DECAP) for booster engines. It did not seem to be right to convert a booster engine into a single stage engine, so we changed the designation. When we made our own engines, we developed an "engine machine" to make engines. When we went out of business in 1971, I though engine was the permanent name for model rocket engines.

Fast forward to 1999
When Bruce and I started in high power, I noticed that many people flying at Whitakers were using the older, obsolete term of motor to describe large engines, but kept the term model rocket engines for smaller ones. It became a constant battle of me correcting others and them correcting me, so I call the large ones motors and the small ones engines. I took my Chevrolet in to the shop years ago and Mr. Beddard asked what was wrong with it. I told him the motor did not sound right. He asked me which one, the windshield wiper motor, the heater motor, the starter motor, or the power window motor. I corrected myself by saying the "engine" did not sound right. He said to remember that engines run on fuel and motors run on electricity. Overly simple explanation, but I noticed it worked better than any other explanation I could come up with.

One of the most asked questions we get is, "Will Semroc ever make its own motors again?" I can honestly say that Semroc will never make motors!

__________________
Carl McLawhorn
NAR#4717 L2
semroc.com

Great stuff Here!

I still remember my industrial arts teacher (That's shop class, for those who prefer to steer clear of dictionaries & such) in junior high school, made the statement that engines required oxygen to run (or burn, more specifically), and motors did not. Seeing as rocket motors carry their own oxidizer, no oxygen required.

I'll let the experts comment now...

__________________
Glen A.
N.A.R. #26298 L1

Good article Carl!!! That was Good!!

Brought back memories, and I still have Capt. Brinley's handbook, priced at $0.75. Much worn, handled and annotated.

Did the Carmel candy and Zn/S stuff. Used Potassium percholrate and asphaltum (fine) and that worked well. Had our dads help with the maching of barstock nozzles counter sunk to make nozzles. By date, I was one year ahead of you in HS. graduated in '65, went into the USAF. Years later, back in, US Army.

Yah, they were called Engines, but I noticed the term motor was in play as well back then. Your Mr. Beddard gave a very good explanation, as did my shop teacher... motors don't use fuel, engines do. Heaven help me if I called a fan motor an engine. AND, a graduated resistor was a potentiometer! (shop 101 and electronics class, Mr Steidel).

I think that it is for simplicity's sake that the term is used interchangably, and we rocketeers know what the other person is talking about. But, to be "Technically" correct, I believe it is engine.

So, the question really is... Will Semroc be making engines again? And while I'm here, howz about some clones of FSI Viking series and SAI Vulcan and Tempest Fugits??? Huh, huh? 8-)

Jack, another "old" rocketeer.

Not all motors run without fuel.....
Ever heard of an outboard MOTOR ?
I will say, I have NEVER heard of an ENGINE that did NOT run on fuel though.
Outboard engine just does not sound right, now does it ????
Where there is a rule, there is usually an exception.
Outboard MOTORS (Mercury, Johnson, Yamaha, Evinrude, etc) certainly need oxygen to run(unless a trolling motor), thus the 'shop' teacher was wrong.
I KNOW if I blocked the air intake to my 150 Merc it most definitely would NOT run !

Engine=Fuel powered
Motor= can be electrically OR fuel powered

__________________
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 !

See, to start with I was calling them engines... then I read The Handbook To Model Rocketry and he said to call them motors. I resisted this strongly because it just doesn't sound as cool as engines, but I found myself tripping up from time to time and calling them motors anyway. You, Carl have restored balance to my personal Universe... I will confidently refer to them as engines from this day forth!

__________________
Daniel Runyon Net

You know, engines! Just like the Solid Rocket Engines on the space shuttle!

And the Space Shuttle Main Motors!

Suppose ATK and Rocketdyne know more than we do?

Motors, durn it, motors....model rocket motors....

Grumble!

Chas

No engines were injured in making this post.

Harrumph!

I think that's backwards....

SRB Solid Rocket Booster...often called "solid motors" (as per ATK and NASA)

SSME Space Shuttle Main Engine (as per NASA and Rocketdyne)

Uh... I think Chas was being a teeny bit sarcastic, switching the last terms to make the point.

__________________
Roy
nar12605

I think he was just trying to make a point that the boosters aren't called engines and the engines not called a motor.

Now to show the interchangeability of the term....Fliskits site list engine mounts but list the size by motor type... BMS has Engine hooks, motor tubes, and engine blocks....Apogee calls the motors motors but refers to them in the text as engines....

We all know what everyone is talking about........but I grew up with the same description .......if it runs off electricity, it's a motor......otherwise, it's an engine.

http://en.wikipedia.org/wiki/Motor
http://en.wikipedia.org/wiki/Engine

__________________
Don
NAR 53455
"Carpe Diem"

Even though the engine that pulls the train is using electric motors.