Article 23983 of rec.models.rockets:
Newsgroups: rec.models.rockets
Path: bigblue.oit.unc.edu!concert!gatech!howland.reston.ans.net!vixen.cso.uiuc.edu!usenet.ucs.indiana.edu!rml!jack@lll-winken.llnl.gov
From: rml!jack@lll-winken.llnl.gov
Subject: Glossary, A thru I
Message-ID: <199411262108.NAA09633@lll-winken.llnl.gov>
Sender: daemon@usenet.ucs.indiana.edu (Usenet Server Daemon)
Organization: Indiana University
Date: Sat, 26 Nov 1994 21:10:22 GMT
Lines: 744


Following is a fairly complete overview of hobby rocketry terms, both technical 
and slang. After it outgrew its slot in the FAQ, Buzz and I decided that it 
should be posted as a stand-alone document while he keeps a skeleton version 
in the FAQ itself.

There are quite a few new and updated entries this time and I would like Buzz,
Warren, CDT and anyone eles that keeps a finger on the regulatory pulse to 
look closely at all of the updated entries (except "Olympic Torch" :-) and the 
new entry "FAR 101" for a sanity check.

Also, the "Contest Acronyms" entry has put so many lines in the front half
that the split now comes at I-K rather than L-M like before.  If this is a 
problem with the archives, let me know and I can revert, even though the sizes 
will be unequal.

- Jack

===================================================
Changes November 1994:

Updated entries: High Power Rocket, HPR Lite, Model Rocket, NFPA 1122, 
	 NFPA 1127, Olympic Torch 

New entries: Contest Acronyms, FAR 101

Deleted entries: none

---------------------------------------------
Glossary of Hobby Rocketry Terms compiled by Jack Hagerty and Buzz McDermott
Thanks to all of the r.m.r readers who have contributed. Any corrections, 
improvements, updates, or suggestions should be sent to Jack Hagerty at 
jack@rml.com.

Please note that this is a copyrighted document. Permission is given to 
distribute it in rocket club newsletters or other educational materials 
provided that you 1) Ask me first, and 2) Indicate on the material where 
you got it, i.e. a credit notice which leaves this entire copyright notice
intact. Inclusion in items for sale is strictly prohibited without a prior 
written agreement.

Copyright (C) 1994, ARA Reprint Services
All rights reserved
---------------------------------------------
November, 1994


3FNC           Three Fins and a Nose Cone, the description of a generic rocket.

Advanced       see 'High Power Rocket'
Rocket

AERO-PAC       The Association of Experimental ROcketry of the PACific, a 
	       prefecture of Tripoli in Northern California which hosts NXRL 
	       (q.v.) each year in the Nevada Desert. Despite the name, this 
	       is an HPR club and does not fly liquid fueled or other amateur 
	       rocketry vehicles. It's main purpose is education through 
	       experimentation with rocketry while following the NAR and 
	       Tripoli safety codes.

AGL            Above Ground Level. This is FAA-speak which, when talking about
	       an altitude waiver, refers to the maximum altitude you can
	       legally fly under that waiver. It is usually added to the 
	       MSL (Mean Sea Level) altitude of the launch site to give an 
	       altimeter reading that pilots must avoid. Example: if your 
	       launch site is at 1,500' MSL and you have a 3,000' AGL waiver, 
	       then pilots must stay above 4,500' to be safe.

Air Start      Any motor that is started after first motion of the vehicle. 
	       Upper stage ignition of a multi stage rocket is a special case 
	       of air starting. Usually it is outboard boosters started after 
	       a central motor has lifted the vehicle, or visa versa. This can 
	       be done by a flashbulb/motion switch, timer, or simply a piece 
	       of fuse started by the exhaust of the pad start motor.

AmSpac         Deprecating but affectionate abbreviations for *American 
AmSpam         Spacemodeling* (q.v.)

American       The journal of the National Association of Rocketry. Previously 
Spacemodeling  known as *The Model Rocketeer* (q.v.), it underwent yet another 
               name change and became *Sport Rocketry* (q.v.) starting with 
	       the Sept/Oct 1993 issue.

Amateur Rocket The class of non-professional rocket beyond HPR. Amateur 
or             rockets use structural metal parts and very often the motor 
Experimental   casing doubles as the airframe (as with professional rockets). 
Rocket         These rockets can be very large and powerful, capable of placing 
 	       payloads many miles up. Activities in this field (one can 
	       scarcely call it a hobby) include formulation and manufacture 
	       of propellants and thus can be EXTREMELY hazardous.  This is 
	       the main reason that amateur rocketry is not to be attempted 
	       alone. Another is expense as these vehicles can run many hundreds
	       or thousands of dollars and take months to build.  The equipment 
	       necessary to safely pursue amateur rocketry (sandbagged bunkers, 
	       loading pits, standby fire truck, etc.) are quite beyond the 
	       resources of most individuals.  

               Not all amateur rockets are so large. Many of the "beginner" 
               vehicles would qualify as HPR or even model rockets in terms 
               of liftoff weight and total impulse, but fail the NAR/Tripoli 
               codes due to their metal airframes and user-compounded propel-
               lants. Note: There is a fine, but significant, difference 
               between using a metal cased reloadable motor with pre-manufact-
	       ured fuel slugs and packing a pipe with zinc/sulfur (a common 
	       amateur beginner fuel).

	       Liquid fueled vehicles are becoming more popular among amateur
	       groups. These can produce up to 1,000 lbs of thrust for up to
	       a minute from a LOX/Kerosene engine which can propel the vehicle 
	       to altitudes of over 40 miles. Some hobby!

	       Neither Tripoli nor the NAR sanction amateur rocket activities.

	       See also: 
			Black Rock Society
			Experimental Spacecraft Society
			Pacific Rocket Society
			Reaction Research Society"
			Rocket and Space Foundation 

AP             Ammonium Perchlorate, the oxidizer used in composite rocket 
	       motors.  Other components are Aluminum powder (fuel) and
	       polybutediene rubber (the binder holding it all together).
	       This is the propellant mixture that the Shuttle SRB's use.

Apogee         The highest point of a rocket's flight path. (More literally, 
	       the point farthest on the flight path from Earth.)
   
AR	       American Rocketeer - Centuri's attempt to produce an MRN 
               (q.v.) clone in the late '60s. While the contents were 
               fairly typical (product announcements, club news, rocket 
	       plans, reports on "real" aerospace events, etc.) it had 
	       a curiously over-produced look to it and ran very heavy 
	       on the advertising. Someone looking beneath the surface 
	       would notice that there was no reader input (e.g. rocket 
	       designs or "Idea Box" style tips); that all the rocket 
	       plans came from the Centuri design department and the "tips" 
	       were for problems that could be solved by items straight 
	       from the catalog! While each issue carried a Volume/Number 
	       identification, there was only one "Number" for each "Volume." 
	       V1, N1 was in 1966 and continued for at least four years.

B/G            Boost Glider. A glider which is boosted to altitude by a rocket
               motor.  The pod containing the expended motor may separate 
               from the glider at ejection to be returned by streamer or 
               parachute (this is typical but is not required).  The more
               aerodynamically clean glider section is then free to glide 
               more slowly.

Baffle         See 'Ejection Baffle'

Ballistic      A measure of a projectile's ability to coast. It is defined 
Coefficient    as Cb = M/CdA where M is the projectile's mass and CdA is the 
	       Drag Form Factor (q.v.). At any given velocity and air density, 
	       the deceleration of a rocket from drag is inversely proportional 
	       to this value. 

	       Intuitively, it is the principle behind why a tightly crumpled 
	       piece of paper can be thrown farther than a loosely crumpled one.

BAR            Born Again Rocketeer.  An individual who has re-discovered the
               hobby/sport after an absence of several years. Contrast "BOR"

Base Drag      A component of aerodynamic drag caused by a partial vacuum in 
               the rocket's tail area. The vacuum is the hole created by your 
	       rocket's passage through the air.  Base drag changes during 
	       flight. While the motor is firing, the drag is minimal since 
	       the tremendous volume of gas generated by the motor fills this
	       void. The drag takes a sharp jump at burnout when this gas 
	       disappears (note: tracking smoke has very little effect on base 
	       drag due to its low density). Base drag can be reduced by the 
	       use of a boattail to transition the main body diameter down to 
	       the motor diameter which helps direct air into the evacuated 
	       area. When properly designed, a boattail can reduce base drag 
	       below zero (i.e. actually generate a small amount of forward 
	       thrust) by making use of the "pumpkin seed" effect.

Bernoulli      A phenomenon first described by the 18th century Swiss scientist 
Effect         Daniel Bernoulli who studied the pressures in moving fluid 
	       streams. The effect states that moving air will have a lower 
	       pressure than the still air around it. This is the principle
	       behind how airplane wings generate lift and why beach balls stay 
	       "balanced" on top of fans in those hardware store displays :-) 
	       
	       The effect is significant in rocketry when using altimeters 
	       or any other kind of payload that senses the ambient pressure 
	       around the rocket. The air moving by the payload section could 
	       cause the payload to indicate a lower pressure than the ambient 
	       still air, thus giving a false altitude reading. The effect
	       drops to zero at apogee when your rocket stops moving, but the
	       altitude vs. time curve will be wrong.

Bernoulli      A phenomenon similar to the "Krushnic Effect" (q.v.) where the
Lock	       rocket seems to be "glued" to the pad at liftoff. This afflicts 
               larger, flat-bottomed rockets launched too close to pads with 
               flat blast deflectors. The exhaust gasses escape at great speed 
	       through the small annular space between the rocket and the pad 
	       creating a venturi which generates a low pressure region at 
	       the base. This pressure deficit can be significant, and if it 
	       is greater than the thrust being generated by the motor, the 
	       rocket won't go anywhere! This is quite possible as a 2" dia.
	       rocket has, potentially, over 45 lbs (200 N) of "suction" 
	       available to hold it back, while a 3" rocket has over 100 lbs 
	       (460 N)! The old Centuri "Point" was an infamous Bernoulli 
	       locker when launched from an Estes Porta-Pad with its perfectly 
	       matching round blast deflector. 
	       
Black Powder   Basically, gunpowder. The 'traditional' model rocket motor fuel. 
	       Used by Estes and most other model rocket companies through F 
	       range. Rocketflite has black powder motors through the H range.
	       See also "AP" and "Composite Motor"

Black Rock     An amateur rocketry organization founded by Tom Blazanin to cater
Society        to those who find HPR confining :-) It is a serious organization 
(BRS)	       for those dedicated individuals who wish to explore rocketry in 
	       a semiprofessional vein. It is open to all forms of reactive 
	       propulsion: solid, liquid and hybrid. The mailing address is: 
			Route 1, Box 100 
			Loving, TX  76460 
			Phone: 817-378-2590    
			FAX: 817-378-2593

Boattail       A transition section at the tail of the rocket which gradually
               narrows the body down to the motor diameter. Used to reduce 
	       base drag (q.v.).

Boosted Dart   A method of maximizing altitude for any given impulse motor. A 
	       sub-minimum diameter, unpowered "dart" section weighted for 
	       Optimum Mass (q.v.) is placed on top of the powered section. 
	       At burnout (maximum velocity) the dart is released and coasts 
	       higher than even a minimum diameter rocket could due to its small
	       cross sectional area. This technique is used in professional 
	       sounding rockets (e.g. Super Loki) as well as hobby rocketry.

Booster        On a multi stage rocket this refers to the sections (stages)
               which drop off in mid-flight.  On single stage payload rockets,
	       the term  is used for the lower powered portion to distinguish 
	       it from the payload section. See also "Air Start"

BOR            Burned Out Rocketeer (facetious). Counterpoint to BAR (q.v.).
	       Someone who has been going at the hobby too intensely, such as
	       in preparation for a major contest.

Burn Out       The velocity the rocket is traveling when the motor runs out of 
Velocity       fuel. Usually the highest speed achieved by the rocket. See also
               "Hyperterminal Velocity"

CA             Cyanoacrylate ('super glue').  A very strong adhesive popular
               for use in competition and high power rockets, as well as 
               'on the field' repairs.  The three most common forms of CA are
               often referred to as 'hot', 'gap filling' and 'slow'.  Hot CA
               is very thin and has strong wicking properties.  It dries in
               only a few seconds.  Gap filling CA is a little thicker and
               generally comes in 15 - 30 second bond times.  Slow CA forms
               the strongest bond but its bond times are also much longer.
               Hot or gap filling CA is often used to tack parts into place
               prior to applying a stronger adhesive with a much longer 
               bonding time (such as an epoxy).

Caliber        In rocketry, the diameter of the main body tube. Usually used
	       when refering to some function of length, e.g. "The CP should
	       be behind the CG by at least one caliber." The term is borrowed
	       from the small arms industry where it refers to the bore of a
	       rifle or pistol barrel, e.g. a .38 caliber pistol has a barrel
	       with a .38" bore. Note that in large artillery, caliber refers
	       to the *ratio* of barrel length to bore. For example, a 3 inch 
	       40 caliber gun would have a barrel 120 inches long.

Capacitive     A type of launch controller which uses a large capacitor to 
Discharge      store electrical energy from a battery. When commanded by the
	       launch controller, the capacitor discharges a large current 
	       into the igniter.  These controllers are often used with large 
	       cluster rockets to ensure all motors ignite simultaneously.             
CATO           A motor failure, generally explosive, where all the propellant 
	       is burned in a much shorter time than planned.  This can be 
	       a nozzle blow-out (loud, but basically harmless), an end-cap 
	       blow-out (where all of the pyrotechnic force blows FORWARD 
	       which usually does a pretty good job of removing any internal 
	       structure including the recovery system) or a casing rupture 
	       which has unpredictable, but usually devastating, effects.  
	       Another form of CATO is an ejection failure caused by either 
	       the delay train failing to burn or the ejection charge not 
	       firing, but the result is the same: the model prangs.

               A CATO does not necessarily burn all of the fuel in a rocket 
               motor (especially true for composite fuels, which do not burn 
	       well when not under pressure).  For this reason you should be 
	       especially careful when approaching a CATO.

	    Origin:
               Opinions on the meaning of the acronym range widely. Some 
	       say it's not an acronym at all, but simply a contraction of 
	       'catastrophic' and should be pronounced 'Cat-o' (which sounds 
	       better than 'cata' over PA systems :-). Others maintain that 
	       it is an acronym but disagree on the meaning, offering a 
	       broad spectrum of 'CAtastrophic Take Off,' 'Catastrophically 
	       Aborted Take Off,' 'Catastrophe At Take Off' and the self 
	       referential 'CATO At Take Off.' The acronym crowd pronounces 
	       it 'Kay-Tow', like the Green Hornet's side kick. It has been 
	       pointed out, though, that all of the above are 'post-hoc' 
	       definitions since LCO's were using the term over range PA 
	       systems long before any formal acronym was established.

               Opinions on the origins say that it is either from the military 
	       rocket programs of WW II, the post war development era, or even 
	       a modroc-only term which originated with the MESS (Malfunctioning
	       Engine Statistical Survey) performed by NAR's Standards and 
	       Testing committee. There is also a claim that it started with the
	       Boston Rocket Club and that the spelling has evolved over the 
	       years. It supposedly started out as 'KATO' which, of course, 
	       stood for KABOOM At Take Off!

CHAD           Acronym for CHeap And Dirty.  Used to refer to a quick and 
               inexpensive (but usually inelegant) way to solve a particular 
	       problem or produce some end result.  

CHAD Staging   A simple technique used to make a multi-stage rocket out of a 
	       single stage vehicle.  A booster motor is taped to the end of 
	       the standard, single stage motor in the rocket.  The booster is 
	       totally external to the rocket. The booster is then ignited in 
	       the usual manner.  This technique only works with black powder 
	       motors. It will only work with models that are VERY over-stable 
	       to begin with. When CHAD staging does work, however, it is the
	       most efficient staging method because it minimizes increased 
	       drag and mass associated with an added stage. (See Optimum 
	       Mass)

Chuff          A form of unstable combustion marked by brief bursts of thrust
	       separated by periods of no thrust. Typically, the bursts come 
	       faster and become longer as burning proceeds, until stable
	       burning results. The sound of chuffing is similar to that of a 
	       steam locomotive starting up. It generally occurs in a composite
	       motor that is ignited too low in the grain.

	       Chuffing can be dangerous, since a short burst of thrust can
	       launch the rocket off the launch rod, and a lull immediately 
	       following the burst can put the rocket on the ground. When
	       stable burning ensues, such a rocket will be flying 
	       horizontally. See "Land Shark"

CG             Center of Gravity. The point about which a free body will 
	       rotate when disturbed by an outside force. For a model rocket, 
	       this is the point where the effects the masses of the individual 
	       components cancel out and the model will balance on a knife 
	       edge. As with a see-saw, a mass further from the CG will have a 
	       greater effect than the same mass closer in.

Clip Whip      A number of micro clips on short wires (usually three) all
	       connected at their free end. Used to aid in the ignition of 
	       clusters (q.v) where each motor uses a separate ignitor.

Cluster        A rocket that fires more than one motor simultaneously. See 
	       also "Clip Whip" and "Davis Douche"

Composite      Hi-Tech materials, other than paper, wood or metal, used in 
Material       the construction of rockets (see also "Phenolic"). 

Composite      The term used broadly to cover solid fuel rocket motors using 
Motor          propellants other than black powder.  Composite motors require 
	       different igniters and igniter systems from black powder motors. 
	       
Composite      In Hobby Rocketry, any propellant other than black powder. In
Propellant     military parlance (where the term originated) the term is used 
	       to denote propellants that are mixtures of oxidizers and fuels 
	       and to distinguish them from Single, Double, and Triple base 
	       propellants (which are either monopropellants or mixtures of 
	       monopropellants). Note that by the military definition, black 
	       powder is itself a composite propellant because it consists 
	       of separate oxidizers (KNO3 and sulfur) and fuel (charcoal). 
	       Further note that by the hobby definition, single/double/triple 
	       base propellants are composites because they are not black 
	       powder.  No ambiguity arises, however, since the military 
	       doesn't use black powder (in rockets, anyway), and no hobby 
	       rocket motors use single, double or triple base propellants. 
	       See also "Single Base Propellants", "Double Base Propellants" and
	       "Triple Base Propellants"

Confirmation   The process whereby a member of Tripoli or the NAR becomes 
Certification  certified as eligible to purchase high power (H and up) motors.  

Contest        The NAR uses a bewildering number of acronyms to describe its
Acronyms       contests. As with most things of this nature, there is a logic
	       to the naming which makes things much easier to understand once
	       learned.

               The basic structure of an event name is a prefix, the event 
	       acronym and a suffix. The prefix is always the motor code 
	       (currently 1/4A thru G) and the suffix is either an "A" for
	       altitude events or "D" for duration events if such a distinction
	       needs to be made (some events, such as parachute duration, have
	       the suffix "built in" to its name, thus don't use one). A futher 
	       appendage is the use of "MR" for "Multi-Round" events where you 
	       make several flights and pick the best ones.

	       Lastly, there is a set of scoring acronyms used in judging the
	       events, but are not part of the event itself.  
	       
	       Event Acronyms: 
	       
		    BG - Boost Glider 
		    DEL- Dual Eggloft 
		    DR - Drag Race 
		    EL - Eggloft Single 
		    FW - Flexwing BG 
		    HD - Helicopter Duration 
		    OSL - Open Spot Landing 
		    PAY - Payload 
		    PD - Parachute Duration 
		    PMC - Plastic Model Conversion 
		    PRA - Predicted Altitude 
		    PRD - Predicted Duration 
		    PSL - Parachute Spot Landing 
		    R&D - Research & Development 
		    RDA - Random Altitude 
		    RDD - Random Duration 
		    RC/RG - Radio Controlled Rocket Glider 
		    RG - Rocket Glider 
		    SC - Scale (often seen written out) 
		    SCA - Scale Altitude (sometimes seen as Sc.Alt) 
		    SD - Streamer Duration 
		    SL - Spot Landing 
		    SPSC - Sport Scale 
		    SPSY - Space Systems 
		    SR - Superroc 
		    SSL - Streamer Spot Landing 
		    STA - Set Altitude 
		    STD - Set Duration 
		    SUSC - Super Scale 


	       Note that there is an ambiguity in the Eggloft event notation. 
	       "DELA" could mean the generic Dual Eggloft Altitude event or 
	       D Eggloft Altitude. For this reason, the prefixes are normally 
	       separated from the event acryonym by spaces.


	       Flight Card/Results Acronyms:

		    BRK - Broken Egg or
		    EGG - Broken Egg
		    CATO - obvious, I hope 
                    DQ - Disqualified flight
		    NC - Track Not Closed 
		    NG - No Glide 
		    NR - No Return 
		    PRG - Prang 
		    ROT - No Rotation 
		    SHR - Shread 
		    TL - Track Lost

Continuity     A group of electrical techniques for checking the firing
Check          circuit through the igniter to ensure that the circuit is 
	       functional. This usually involves some type of light or audio 
	       tone activated by a push-button.  The techniques range from a 
	       simple current limiting light bulb or buzzer placed in series 
	       with nichrome igniters, to sophisticated bridge circuits for 
	       sensitive, low current flashbulbs and electric matches.

Copperhead(tm) The trademark name for an igniter produced by AeroTech, Inc. 
	       It is a laminated assembly consisting of a two copper foil
	       strips separated by an insulator, with a quantity of pyrogenic 
	       compound on one end. It normally requires a special clip for
	       electrical connections, but some rocketeers have mastered
	       the "Z-Fold" which allows use of normal alligator clips.

Core Sample    Synonyms describing a failure mode where the model comes down
Tent Peg       fast and hard (nose first) and ends up tail-high in the ground
Lawn Dart      (this is where large, colorful fins come in handy :-).  Often
Yard Dart      the nose cone has separated (taking the recovery device with
Ballistic      it) and the body tube ends up containing a nice 'core sample' 
Auger In       of mud/dirt when pulled out of the ground.

CP             Center of (Aerodynamic) Pressure.  The point on a rocket 
               where stability-restoring forces due to airflow against the
               back part of the rocket (fins, etc.) exactly equal the disturbing
	       forces against the part of the rocket ahead of that point. 
                
               The location of this point depends on the rocket's orientation 
	       at the time of measurement.  If it is at a very small angle to 
	       the "local wind" (line of flight), the fins' restoring contri-
	       bution will be large, while the nose's disturbing contribution 
	       will be small, resulting in a CP that is way back. The CP in 
	       this case can be located using the Barrowman Equations.  If the 
	       rocket is nearly sideways, the CP will be much more forward.  
	       The CP in this case can be located by balancing a cardboard 
	       silhouette of the rocket.

               Since all free bodies can rotate only on their center of mass, 
               stability is usually a simple matter of placing your CG ahead 
	       of your CP, which ensures that the restoring forces of airflow 
	       on the rear of the model will always overcome the disturbing 
	       forces on the front.

               A good rule of thumb for sport models (both high and low power)
               is to design the rocket with the CP one or two body diameters
               behind the CG.

CPSC           Consumer Product Safety Commission.  The government agency 
               which has the task of deciding whether or not a given product
               is safe for 'general consumer' use. 

Cruise         A rocket which has failed in such a way that it ends up 
Missile        flying horizontally while still under power.  A common
               example would be a multi-stage rocket which stages "dirty"
               (due to stability or structural problems) causing the upper 
               stage to bend to near horizontal at ignition. Severe launch 
	       rod tip off or high winds have also been know to cause a
	       cruise missile attitude.

Davis Douche   A method of igniting clustered motors by using a piece of fuse 
	       in each motor with all fuses dropping into a pie plate that has 
	       been dusted with black powder and taped to the bottom of the 
	       model. A single ignitor in the black powder "flashes the pan" 
               igniting all the fuses at once. Developed in the early '60s by 
               Joel Davis and detailed in an early Model Rocketry Magazine 
               [late 1968 or early 1969, before they went to color covers]. 

Delay Train    Pyrotechnic material in the rocket motor which burns slowly 
Delay Charge   between the propellant charge and the firing of the ejection 
	       charge. This allows the rocket to coast towards apogee and 
	       slow down to deploy the recovery system at low speed.   

Double Base    A solid propellant consisting of two monopropellants (usually
Propellant     nitroglycerin and nitrocellulose) and various additives. 
	       Double base propellants are used as smokeless powders in 
	       ammunition. They are also used in smaller military rockets but 
	       have been largely replaced by composites in larger vehicles. 
	       Double base propellants are not used in hobby rocketry. See also 
	       "Composite Propellant"

DQ             Disqualified flight. See also "Midwest Qualified"

Drag           A dimensionless number used in aerodynamics to describe the drag
Coefficient    of a shape. This number is independent of the size of the object
(Cd)           and is usually determined in a wind tunnel. It is part of the
	       basic drag equation F=.5*rho*V^2*Cd*A where F is the drag force,
	       rho is the air density, V is the air velocity and A is the cross
	       sectional area. All of these, except Cd, are directly measurable
	       in a wind tunnel so Cd can be thought of the "fudge factor" that
	       accounts for all of the aerodynamic peculiarities of a shape. The
	       Cd for most sport type hobby rockets is in the range of .4 to .5.
	       See also "Reynolds Number."

Drag Form      The Drag Coefficient (q.v.) of an object multiplied by its cross
Factor         sectional area. This is used to scale the drag value for a 
(CdA)          particular object from the dimensionless Cd. Theoretically, every
	       object of a similar shape will have the same Cd regardless of its
	       size, meaning that both a grain of rice and a Zeppelin would be 
	       the same. Multiplying by the area allows comparisons of the true 
	       drag between dissimilar objects. For example, the original Honda 
	       Civic had a horrible Cd, and makers of large luxury cars, with a 
	       little edge rounding, were easily able to beat it and proclaim 
	       "Lower drag than a Honda Civic!" in their ads. This is patently 
	       absurd as the Honda had such a tiny cross section, thus much 
	       lower *actual* drag. See also "Optimum Mass"

Drop Staging   See 'CHAD Staging'

Effective      See Impulse (Relative)
Exhaust Velocity

Ejection       A device used in some rockets to eliminate the need to use 
Baffle         wadding to protect the recovery system. Usually composed of
	       some type of metal wool or mesh to absorb the heat of the 
	       ejection gases before they reach the recovery compartment.  

Ejection       A small quantity of black powder used to generate gas pressure 
Charge         within the rocket to deploy the recovery system.  This is 
	       activated when the delay train (q.v.) burns through. On rockets 
	       with electronic ejection  timers, this may be a separate small 
	       container of black powder which is triggered by a signal from 
	       a timer or other control unit.  

Electric       A type of igniter originally designed to set off fuse-type
Match          blasting caps (i.e. a match that can be set off from a great
	       distance electrically). It requires a very low electrical 
	       current (~10 mA range) to activate.   

Engine         A machine that converts energy into mechanical motion. Such 
               a machine distinguished from an electric, spring-driven or
               hydraulic motor by its consumption of a fuel (from *American
               Heritage Dictionary*). See discussion at the end.

Estes Dent     A semicircular deformation of the leading edge of the body tube
	       cause by the nose cone snapping back and striking the body at
	       ejection. The problem is intensified by short shock cords which
	       don't absorb as much energy before reversing and give the nose a
	       closer target with better aim :-) So named due to that company's 
	       policy of providing very short shock cords in their kits.

Experimental   See "Amateur Rocket"
Rocket

Experimental   An amateur group whose purpose is to orbit a small (10" to 16")
Spacecraft     telescope for use by amateur astronomers. While not directly in
Society        the propulsion end of experimental rocketry, it is very much in
	       the same philosophical vein. Director is Linda Kenny-Sloan who 
	       can be reached at:
			Experimental Spacecraft Society 
			17701 South Avalon Blvd.
			Carson, CA  90746
			Internet: l.k.sloan@genie.geis.com

FAR 101        The Federal Aviation Regulation by which the FAA dermines 
	       the procedures to be followed for launching non-professional 
	       rockets. The rule is quite involved and beyond the scope of 
	       this document but briefly, it divides the hobby into three 
	       catagories for the purpose of regulation:

	       1) Model rockets with a gross launch weight of less than 1 pound 
	       or containing motors with less than a total of 113 grams of fuel
	       are exempt from FAA involvement if launched more than 5 miles
	       from an FAA controlled airport.

	       2) Large model rockets which exceed the FAA definition of a 
	       model rocket but otherwise fall within the NFPA 1122 definition 
	       of "model" (i.e., between 1 and 3.3 pounds liftoff weight and 
	       between 113 and 125 grams of total fuel) must notify the nearest 
	       Air Traffic Control center (ATC) between 24 and 48 hours prior 
	       to the launch.  There are further restrictions when launching 
	       within five miles of an FAA controlled airport.

	       3) High power rockets (weighing more than 3.3 pounds, containing 
	       motors with a total of more than 125 grams of fuel) require a 
	       formal waiver be approved by the FAA and activated prior to the 
	       launch.  There are further restrictions when launching within 
	       five miles of an FAA controlled airport.

FAI            The Federation Aeronautique Internationale. An international 
	       organization located in Paris, France that tracks world records 
	       for aeronautics and aeromodeling. 

Fillet         A reinforcement of the joint between the fin and the body tube 
	       of the rocket to improve the rocket's aerodynamics and to 
	       strengthen the fin mount.  See also "TTW"

FIREBALLS      An experimental rocketry/HPR launch hosted by AERO-PAC (q.v.) 
	       which has since been superseded by NXRL (q.v.). The emphasis was
	       on VERY LARGE advanced rockets of "K" impulse or higher. The idea
	       originated with Steve Buck and the first launch was sponsored by 
	       Bill Lewis of AERO-PAC. The name came from jokes surrounding the
	       event (e.g. "It takes BALLS to launch a rocket that big"). Steve 
	       claims that it was never intended to mean "Big Ass Load Lifting 
	       Suckers" as implied in early advertisements. Against the wishes 
	       of its founder, "Fire" was placed in front of "BALLS" to placate 
	       those few who had a problem with the name.
	       
	       Fireballs was traditionally held the Monday after LDRS (q.v.),
	       but it was never formally a Tripoli launch. The 1992 FIREBALLS 
	       (where 'Down Right Ignorant' was launched) was sponsored by 
	       Tripoli for the purposes of insurance coverage, and after that 
	       they decided to "adopt" the event with a name change.

GSE            Ground Support Equipment. Anything you bring to the launch 
               site which is necessary to fly your rocket, but doesn't actually 
	       fly with it. Obvious examples are the launch pad, launch 
	       controller, a prep table, etc. Less obvious examples are payload 
	       support stuff like receivers and tape recorders if you're flying 
	       a broadcasting type data collection payload.

Hang Fire      Terms which refer to abnormal ignition. With hang fire, the motor
Misfire        usually ignites after a considerable delay.  Misfires never
	       ignite. Hang fires often appears as a misfire until the motor 
	       ignites some time later. This is the main reason the safety code
	       advises not to approach a misfired rocket for one minute.  

High Power     Hobby rockets that exceed the total weight, total propellant
Rocket(ry)     or single motor total impulse restrictions of model rockets
(HPR)	       as defined in NFPA 1122 (q.v.) but otherwise conform to the 
	       same guidelines for contruction materials and pre-manufactuered, 
	       solid propellant motors.  High power rockets have no total 
	       weight limits, but do have a single motor limit of no more than 
	       O power (40,960 NS total impulse) and have a limitation of 
	       81,920 NS total impulse.  
	       
	       There is a draft NFPA document (NFPA 1127) under review which 
	       would formalize this definition.

HMR            The Handbook of Model Rocketry. The official NAR handbook 
	       for the hobby. Originally written by G. Harry Stine (NAR #002) 
	       in the mid '60s (the first edition came out in 1965) and 
	       currently in it's sixth edition. It has expanded it's scope 
	       with the hobby by adding computer programs (not always the 
	       best sorted out) in the fourth edition and giving a nod towards 
	       the existence of HPR in the current (sixth) one.

Hobby Rocket   A general, collective term used to describe both model and HPR
	       rockets to differentiate them from amateur/experimental rockets. 
	       The latter, while also non-professional, might better be called 
	       "Obsession Rockets" :-)

HPR Lite       A term used to describe rockets using motors in the 'E', 'F', 
	       and 'G' power classes. Formerly called "Medium Power Rocket" (a 
	       term nobody used), it describes rockets which fall between the 
	       old NFPA 1122 weight limit of 1 lb (454 grams) and the current 
	       model rocket weight limit of 1500 grams. Rockets in the 'E' 
	       through 'G' class aren't normally considered high power rockets 
	       but, to be successful, must be built using many of the same 
	       construction techniques as the larger rockets.  Also, any rocket 
	       over 1 lb requires an FAA waiver to fly legally.

HPRM           High Power Rocketry Magazine - formerly *Tripolitan* (q.v.).
               An independent magazine dealing with all aspects of consumer 
	       rocketry, but with a definite emphasis on high power, advanced 
	       and experimental consumer rocketry. Published six times a year.
	       A subscription is included with membership in Tripoli, but 
	       can be had separately.  Also available on newsracks in larger 
	       hobby stores. Current editor: Bruce Kelley.

Hyperterminal  A situation where a rocket is traveling faster than terminal
Velocity       velocity (q.v.) for a given motor. This is possible, for example,
	       with a staged model with grossly mismatched motor combinations 
	       such as an F-100 staged to a B6. At staging, the upper stage 
	       will already be beyond its terminal velocity for the "B" motor. 
	       In this case, the upper stage will actually *decelerate* during 
	       thrusting and approaches terminal velocity from above.

Igniter        An expendable device used to ignite a rocket motor.  

Impulse        A measure of the efficiency of a rocket engine. Similar to
(Relative)     Specific Impulse, it is defined as the Total Impulse (q.v.) 
               divided by the mass of the propellants. A little dimensional
	       juggling shows that this gives the same units as velocity
	       (ft/sec or m/sec) hence is sometimes called "Effective Exhaust
	       Velocity." How quickly the reaction mass leaves the nozzle is 
	       a good measure of efficiency.
 
Impulse        A measure of the efficiency of a motor/propellant system. 
(Specific)     It is determined by taking the Total Impulse (q.v.) and dividing 
	       by the weight of propellants. This carries the potentially
	       confusing units of "seconds" (as if it had something to do with
	       the burn duration) but is due to weight and thrust both being
	       force parameters hence canceling out (e.g. lb-sec/lb or N-sec/N).
	       This is actually very handy since it makes the term independent
	       of the units system (metric or English) since they both use
	       "seconds" for time.

Impulse        A measure of the total momentum imparted to the rocket by the
(Total)	       motor. It is defined (for those who know calculus) as the 
	       integrated area under the thrust-time curve. For the rest of us,
	       it can be thought of as the motor's average thrust times the 
	       duration of the burn. Measured in N-sec or Lb-sec.




