National Aeronautics and Space Administration 

NASA High Powered Video Series

Counterpart Documents
 


 

Structures 

Systems 

Materials: 

Parts & Subassemblies 

Nose Cones 

Airframes & Couplers 

Motor Tubes 

Motor Retainers 

Centering Rings & Bulk Plates 

Fins 

Rail Buttons 

Construction Techniques 

Design Considerations 

Stability
 

Center of Gravity 

Center of Pressure 
         

   

        


 


 

NASA High Power Rocketry Video Series
 

Counterpart Documents
 

Written by Daniel Cavender
                               

                                   

                               

                                       

                                   

       

   

               

                   

             

               

           

               

              

               

       

               

             

           

               

               

           

           

               

         

        

               

             

                 

               

                 

           

           

               

              

   

 

 


 


 


 


 


 

 
 


 


 


 


 


 


 


 


 


 

 
 


 


 


 


 

 
 


 

 
 


 


 


 


 


 

The structure of a rocket is the skeleton that everything is integrated into. It is an aerodynamically

optimized shape that carriesthe load of all the components of the rocket and protectsthem from external

forces throughout the flight. This section will break down all of the major structural components that

make up a high powered rocket. You will learn about the materials used to build rocket parts. You will also

learn how to design a stable rocket using equations to determine the Center of Pressure (CP) and the

Center of Gravity (CG).

S.1. Parts & Subassemblies

All high powered rockets have the same basic parts.
 

From the outside of a rocket, only a few are visible.
 

You can distinguish the nose cone, the airframe, and
 

the fins quite easily. On the inside, there are
 

couplers, motor tubes, centering rings, and bulk
 

plates. Othersmall partsthat are not initially obvious
 

are rail buttons/launch lugs and motor retainers.
 

Many of these basic parts come together to form
 

subassemblies. A subassembly is an assembled unit
 

designed to be incorporated with other units into a
 

finished product. The nose cone can be considered a
 

subassembly. Many nose cones require a bulk plate
 

and a u‐bolt or eye‐bolt. An avionics bay is another
 

example of a subassembly. Avionics bays can be built
 

from couplers and bulk plates. A booster
 

subassembly, sometimes called a “fin can”, is an
 

assembly built from a section of airframe, a motor
 

tube, centering rings, bulk plates, fins, motor
 

retainers, and sometimes couplers.
 

The photos to the right are examples of some
 

subassemblies. The nose cone assembly at the top
 

has a removable plate on the bottom for access to
 

the interior volume where a payload can be carried.
 

The fin can subassembly in the middle is ready for
 

installation into a custom made carbon fiber
 

airframe. The motor tube subassembly at the
 

bottom is removable so the builder can inspect the
 

fin tangs and centering rings between flights.
 
   

                                         

                                 

                                   

                  

                                         

                               

                               

                

 

S.1.1. Nose Cones

The term nose cone is used to refer to the forward most section of a rocket, missile, or aircraft. The cone

isshaped to offer minimum aerodynamic resistance. On rocket vehicles, the nose cone may consist of one

or multiple chambers in which a payload maybe carried. The nose cone maybe be the payload itself or

used to shield the payload until ready to deploy.

The shape of the nose cone will affect the drag on the rocket, and the proper shape should be chosen to

reduce drag. An important problem is the determination of the nose cone geometricalshape for optimum

performance. Such a task requires the definition of a solid of revolution shape that experiences minimal

resistance to rapid motion through a fluid medium.
   

                                               

                                                     

                                   

                                 

                         

     

                   

                 

         

     

                 

               

                   

                   

                   

            

                     

                 

                   

                   

                   

   

                         

                               

          

 

 

 

 

 

S.1.1.1. General Dimensions

In all of the following nose cone shapes, L is the overall length of the nose cone and R is the radius of the

base of the nose cone. y is the radius at any point x, as x varies from 0, at the tip of the nose cone, to L.

The equations define the 2‐dimensional profile of the nose shape. The full body of revolution of the nose

cone is formed by rotating the profile around the centerline (C/L). Note that the equations describe the

'perfect' shape; practical nose cones are often blunted for manufacturing or aerodynamic reasons.

S.1.1.2. Conical Nose Cones

A very common nose cone shape is a simple cone.

This shape is often chosen for its ease of

manufacture and for its drag characteristics.

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௫ோ ோ ݊ܽൌ ݐݔ ሺ߮ሻ ߮ ൌ arctan	ቀ ௅ ௅

ቁ

S.1.1.3. Ogive Nose Cones

Next to the conical, the Tangent Ogive shape is the

most popular in hobby rocketry. The profile is

formed by the segment of a circle such that the

rocket airframe is tangent to the curve of the nose

cone. The popularity of this shape is largely due to

the ease of constructing its profile.

ଶ ൅ ܮଶ ܴ

2ܴ ൌ ߩ

ݕ ൌ ඥߩଶ ൅ ሺܮെݔሻଶ ൅ܴെߩ

S.1.1.4. Elliptical

The profile of thisshape is one‐half of an ellipse, with

the major axis being the centerline and the minor

axis being the base. This shape is popular in subsonic

flight (such as model rocketry) due to the blunt nose

and tangent base. This cone is not normally found in

professional rocketry.

ܮଶ

ݔ

ܴݕ ൌ ඨ1 െ

ଶ

High powered rocketry (HPR) nose cones are generally constructed from fiberglass, carbon fiber,

urethane, or composites of other non‐metallic materials. The nose cone shoulder should be no less than

one body diameter in length.
   

                                   

                               

                                   

                                   

                               

                               

              

                                     

                                 

                                     

                                 

                             

                         

                                 

                                       

                                       

                               

     

           

             

           

         

              

                 

    

   

                 

             

         

   

             

  

           

             

           

         

           

               

           

          

 

 

 

 

 

 

 

 

S.1.1.5. Nosecone Drag Characteristics

For rockets travelling under Mach 0.8, the nose cone pressure drag is negligible for all shapes. The major

significant factor is friction drag. Friction drag is largely dependent upon the wetted area, the surface

smoothness of that area, and the presence of discontinuities in the shape. For a rocket flying in the

subsonic region (below Mach 0.8) a short, blunt, smooth elliptical cone is best. In the transonic region and

beyond (above Mach 0.8), where the pressure drag increases dramatically, the effect of the nose cone

shape becomes highly significant. The factors influencing the pressure drag are the general shape of the

nose cone, the fineness ratio, and its bluffness ratio.

The Fineness Ratio isthe ratio of the length of the nose cone compared to its base diameter. Atsupersonic

speeds (above Mach 1.0), the fineness ratio has a significant effect on nose cone wave drag, particularly

at low ratios; but there is very little additional gain for ratios increasing beyond 5:1. As the fineness ratio

increases, the wetted area, and thus the skin friction component of drag, is also going to increase.

Therefore the minimum drag fineness ratio is ultimately going to be a tradeoff between the decreasing

wave drag, increasing friction drag, and the resulting mass of the nose cone.

The Bluffness Ratio describes a blunted tip, and is equal to the tip diameter divided by the base diameter.

There is little or no drag increase for slight blunting of a sharp nose shape. In fact, for constant overall

lengths, there is a decrease in drag for bluffness ratios of up to 0.2, with an optimum of 0.15. Most

commercially made Tangent Ogive hobby nose cones are blunted to a bluffness ratio of about 0.1.

S.1.2. Airframes & Couplers

Rocket airframes are generally smooth thin

walled cylinders with a high length to diameter

ratio and encompass the rocket’s propulsion

system, recovery system, electronics, and

payload. On large launch vehicles, the airframe

is the outer surface of large pressurized fuel and

oxidizer tanks.

Generally, rockets have a nose cone fitted to the

forward end of the airframe and a set of fins are

mounted towards the aft end. On a Minimum

Diameter rocket, the airframe also serves as the

motor tube. This design eliminates the need for

centering rings and a motor tube, but presents

new challenges due to the fact that the fins must

be surface mounted.

High powered rocket airframes are typically

made of non‐metallic, high strength to weight

ratio composite materials like carbon fiber,

fiberglass, phenolic and PVC (National

Association of Rocketry rules). Paper and

cardboard will not handle the loads of high

powered rocket motors unless they are

sufficiently reinforced with composite materials.
                                 

                                      

       

                                 

                        

                           

                                    

             

                                      

                            

                                

             

             

             

                 

                 

                   

  

                 

             

                 

                 

                  

                             

                               

                             

                                         

                                       

               

                                             

                        

           

 

 

 

 

 

 

Phenolic tubing is like cardboard, except it has been impregnated with an epoxy resin to increase its

strength. While cheap and easy to work with, phenolic tubing is brittle, and may not handle the loads of

some more aggressive rockets.

Fiberglass is much stronger and more robust than phenolic tubing. It is not brittle like phenolic, but

fiberglass is more expensive. Fiberglass tubing is usually pre‐manufactured, although some rocketeers

prefer to manufacture their own tubing by winding fiberglass sheets around a mandrel and impregnating

it with an epoxy resin. When working with fiberglass, be sure to wear the proper safety equipment as

fiberglass produces a hazardous dust when sanded.

Carbon fiber tubing is the strongest and most rigid material used in high power rocketry. It is also very

lightweight and aesthetically pleasing. The drawback, however, is that carbon fiber is the most expensive

material to use. Like fiberglass, carbon fiber produces a hazardous dust when sanded and proper safety

equipment should be worn while handling it.

Composite airframes can be manufactured in many

different ways. Long lengths of epoxy infused

fiberglass or carbon fiber cloth can be rolled around

a mandrel until the layers or “plys” accumulate into

a tube of desired thickness – typically 20 plys or

more.

The airframe pictured on the previous page is an

example of a filament‐wound fiberglass airframe. A

long spool of epoxy infused fiberglass string or “tow”

is wound around a mandrel in an overlapping pattern

until a cylindrical tube of desired thicknessisformed.

Depending on the design, your rocket may require slots through the airframe for fins. Many

manufacturers will slot airframes to your specification, or you can cut them yourself. Generally, fin slots

in airframes come one of two designs ‐ End Slotted and Tang Slotted. For end slotted airframes, the fin

slot is cut all the way to the end and the airframe can be slipped over a booster subassembly. For tang

slotted airframes, the fin slot is stopped before the end of the airframe and the fins have to be epoxied

on after the motor tube subassembly is installed.

End Slotted Airframe Tang Slotted Airframe

Custom fin slots can be made with the use of common power tools and a jig. A jig is any device used to

mechanically maintain the correct positional relationship between a workpiece and the tool.

                                           

                             

                               

                                     

                                 

                               

                    

                                     

                                 

                                   

                 

   

             

 

 

A drill template is another type of tool you may use on your rocket. A drill template is a printout of all

airframe penetrations that can be wrapped around the airframe tube to locate and drill holes for

mounting hardware such as rail buttons, centering rings, bulk plates, and fin brackets. It is common

practice in industry to use a template to keep a record of all penetrations and processes to be performed

on a structure. A drill template for a high powered rocket airframe would specify both Cartesian and

cylindrical coordinates of all penetrations plus indications for which drill bits, taps, and fasteners to be

used. An example of a drill template is shown below.

On this drill template, the series of penetrations at the bottom of the airframe are designed to accept a

unique surface mounted fin bracket concept that allows the fins and fin brackets to be modular and

greatly improve the versatility of a rocket by allowing for parts to be replaceable and upgradable. This is

an example of designing multi‐mission capability into a rocket.

Template Drilled Airframe Drilled Airframe with Brackets
                                   

                             

                                       

                             

                               

                                   

              

                               

                           

                                         

                                             

                                 

                             

 

 

 

 

 

 

 

The drill template was wrapped around and taped to the airframe tube. With the assistance of a manual

mill machine and an indexing chuck, the penetrations were precisely transferred onto the airframe.

Multiple segments of airframe can be joined by using a coupler. A coupler is a tube which has an Outer

Diameter (OD) equal to the Inner Diameter (ID) of the airframe. Generally, rocket builders follow the

convention that when joining airframes with a coupler, the coupler should extend at least one airframe

diameter into each joined segment. So, if you were to join two 4 inch diameter airframes you would

need a coupler at least 8 inches long.

Couplers, because of their required lengths to join airframe sections, make a good place to store

electronics such as altimeters, batteries, switches, and other electronics. Most rocket builders use the

coupler as an avionics bay. The avionics bay in the photo to the right is built from a 12 inch long coupler

with a 1 inch collar in the center. The collar is a segment of airframe that is epoxied to the middle of the

coupler and allows direct access to the switches that power on the altimeters. This coupler joins two

airframe segments that contain the recovery system by clicking into place with quick connect snap

buttons.
                                         

                                       

                          

                               

                             

                                 

                                       

                                 

                 

   

                 

               

                 

             

                   

               

               

                    

                 

                 

                   

           

                                   

                               

 

 

 

 

 

 

 

S.1.3. Motor Tubes

A motor tube is any tube inside of a rocket that is intended to fit a rocket motor. Motor tube diameters

are typically called out in millimeters and refer to the size motor that they are designed to hold. A typical

high powered rocket may have a 38mm, 54mm, 75mm, or 98mm motor tube.

Recall that on a Minimum Diameter rocket, the airframe is the motor tube. Generally on smaller rockets,

the motor tube encompasses the entire rocket motor case. Larger rockets motor tubes may only

encompass half of the motor tube with the rest freely suspended inside the rocket airframe. That is

because a full length motor tube can get heavy. Some rocket designs do not use motor tubes at all. They

simply axially restrain the motor front and back. This technique can increase a rocket’s mass fraction by

eliminating the weight of the motor tube completely.

S.1.4. Motor Retainers

A motor retainer is a device that positively retains

the rocket motor case inside of the rocket,

prohibiting it from falling out during flight. There are

many commercial motorretainers available for every

size motor. It is also very common for rocket builders

to fashion their own motor retainer with common

screws and washers from a hardware store. Pictured

to the right is an Aero Pack 38mm motor retainer.

The Aero Pack motor retainer base epoxies to the

bottom end of a motor tube. The threaded cap

screws on to the base after the motor has been

installed into the motor tube.

You may choose to design your own method of motor retention. Commercial snap rings are a viable and

cheap option to explore and can be integrated into the structures of your rocket project.
         

                             

                                 

                                     

                               

                             

                           

                                        

  

                               

                                   

                                   

                               

                                          

        

   

 

 

 

 

 

S.1.5. Centering Rings & Bulk Plates

Centering rings are used to concentrically align small tubes, like motor tubes, inside of an airframe.

Centering rings can be made of many different materials and take many shapes depending on the number

of inside tubes that are to be aligned. Bulk plates are circular disks that fit inside of tubes to separate

volumes. Typically, centering rings and bulk plates are either made out of plywood or from composite

materials such as fiberglass, and serve as the mounting structure for other systems’ components like

recovery hard mounts, payloads, and electronics. Typically, rocket builders use one centering ring above

the fins and one below. Centering rings act as the primary load path for the motors thrust to the airframe.

Centering rings are available from almost all rocket component providers in a variety of sizes. Suppliers

often have the capability to build‐to‐order any design you need. If not, there are some tools available at

almost every hardware store that can help. A properly sized hole saw and arbor from Lowes or Home

Depot can make centering rings and bulk plates for your smaller projects. Additionally, there are internet

companies that can build almost any size hole saw you need. A Saber saw and a steady hand can also do

a very good job.
             

                     

             

                 

             

               

       

                   

               

                   

                 

                     

               

                     

              

                     

             

         

                 

             

             

             

                   

                     

                     

                

 

 

S.1.6. Fins

Fins are flat, fixed, stabilizing structures extending

from the body of a rocket that give stability in flight.

The effectiveness of fins depends mainly on their

size, shape, and surface finish. Fins can be many

different shapes. Four common shapes are tapered,

simple delta, cropped, and elliptic. Each fin has

several features used to parametrically characterize

its design. Tip chord (ct), root chord (cr), span (b),

leading edge (LE), trailing edge (TE), aspect ratio

(AR), and tang. Most fins are tapered or delta type

due to ease of manufacturing. Also, most rocket fins

are designed with low aspect ratios (AR < 4). A taper

ratio ሺ ⁄ ሻ between 0.2 and 0.4 is ideal for ܿ௧ ܿ௥

Tapered Delta Fins

minimum induced drag (δ). The tang isthe part of the Cropped Delta Elliptic

fin that extends inside of the airframe.

Ct

b

LE

Cr

Tang

TE

Typically, fins are attached to a rocket using one of two

methods – surface mounted (minimum diameter rockets)

and through‐the‐wall. Some rockets employ removable

fins. Removable fins are difficult to successfully design but

offer multi‐mission capability or the ability to easily

replace a damaged component. Typically, fins are

constructed of G10 fiberglass, carbon fiber, plastics,

and/or plywood sheets cut to size. More complex fins are

composites of two or more of these materials. The fins on

the rocket in the image to the right have an Aluminum

insert epoxied inside of an ABS plastic shell.
   

                                       

                                   

                                   

                             

   

                             

                                     

                                       

                           

   

                                   

                                     

                                     

                                   

       

                               

                                     

                                     

       

 

 

 

 

 

S.1.7. Rail Buttons

Most high powered rockets are launched from a rail rather than a rod and require a rail button. A rail

button is an ‘H’ shaped component, usually made of a hard, smooth plastic, that mounts to the airframe

of a rocket and slides freely inside of a channel along an extruded aluminum launch rail. This system

constrains the rocket’s movement until sufficient velocity is achieved that the fins become effective for

flight stability.

Rail buttons should not be an afterthought of the design process. Their location should be documented

as part of the vehicle design requirements. The rocket should have one rail button near the bottom of the

booster and another near the center of gravity. Be sure to use only two rail buttons. Adding any more

than two buttons increases the chance that the rocket will bind on the rail.

S.1.8. Ejection Piston

An ejection piston is a recovery systems configuration option that uses a section of coupler, a bulk plate,

and a short recovery harness. The concept is that the ejection charge will push the piston forward and out

of the airframe. The piston will push the recovery system out as well. The piston also protectsthe recovery

system by physically separating them from the hot gases. Pistons are viable for rockets between 3 and 6

inches in diameter.

S.1.9. Baffles

Baffles are another technique that protects the recovery system from hot ejection gases. The baffle uses

a metal heat sink like steel wool to absorb the heat and capture any burning debris and allow the

expanded gases to push the recovery system out of the rocket. Baffles are a good option on small rockets

that use motor ejection.
FWD Airframe

Sub Assembly 

Cert-3 Large 

Parachute 

50' Nylon 

Shock Cord 

Cert-3 

Drogue 

50' Nylon 

Shock Cord 

Aerial 

Subsystem 

Booster Sub 

Assembly 

Parachute 

Airframe Booster 

Airframe 

E-Bay AFT End 

Closure 

Tailcone 

Retainer 

Parachute 

Coupler 

Booster 

Float #2 

E-Bay F W D

End Closure 

E-Bay Avion ics

Carrier 

E-Ba y 

Float Core 

Fin Bracket #2 

Clocked 135° 

Fin Bracket # 3 

Clocked 225°

Fin Bracket #4 

Clocked 315° 

11 IV 

Structures System Battery #1 

FWDCentering 

Ring Recovery System 

Avionics System 

Assembly / Sub Assy

Fin # 1 

Clocked 45° 

Fin #2 

Clocked 135° 

Fin #3

Clocked 225° 

Fin #4 

Clocked 315°

Fin Bracket #1 

Clocked 45° 

Tailcone 

Structure 

Switch #1 

Perfectflite MAWD # 1 

Perfectflite 

MAWD #2 

Switch #2

11.1V 

Battery #2 

Booster 

float #1 

Aethon Rocket 

Top Assembly 

               

                                 

                                 

                                 

                        

  

                                     

                                         

                           

                               

                                   

                     

 

 

 

 

 

 

S.2. Design Consideration

Many parts and subassembliesform the structure of a high powered rocket. Specific design considerations

to human factors or ergonomics will greatly improve the design’s effectiveness and reduce risk of failures.

Detailed design layout drawings and exploded models are useful tools used by rocket builders to design

rockets. These tools can be generated by computer or can be hand drawn. Hand drawn layout drawings

are quick and easy ways to convey ideas and designs quickly when in the preliminary design phase.

Computer design programs like AutoCAD, Solid Edge, and Pro‐E are more difficult to use but can keep

track of far more information and are widely used in mature designs.

S.2.1. Components/Process Tree

A components tree is a visual tool design to aid in the layout and construction of your rocket. The tree

lays out all major parts and systems in order of assembly from bottom to top and left to right. Lines link

parts to the next higher assembly. In the example below, structures, recovery, and avionics components

are designated by unique colors. Parts and assemblies are designated by unique shapes. Notice that the

first process in the assembly of this rocket is the installation of the FWD centering Ring into the Booster

Airframe. The Last is the Aerial Subassembly into the Rocket’s Top Assembly.
c h a r g e r

R O C K E T W

O R K S

Aethon Research Rocket 

Critical Design Analy sis Configuration 

JA HuntsvilIe 

Nose Plane -00.00"

Simulator Interface -13.50"

Payload Interface 2 1 .SO”

Forward Airframe

(Dia. 6.188") 

Gemini/SSM Simulator 

Payload Airframe (Dia. 6.188'') 

Payload Avionics 

Sky Angle Cert-3 XL Parachute 30' 

Nylon Shock Cord 

Booster Interface - 41.50" 

C .G .-45.40" (unloaded)

C.G. - 52.24" (burnout) 

C.G. - 58.42" (CT1 - N2501 

Booster Airframe

(Dia. 6.188") 

C.P.-67.42"

Tail Cone Interface - 86.00" 

Nozzle Exit Plane - 90.00"

Fin Bracket 

Fins (Cr=10", S=5", λ=.21) 

AFT 1515 Rail Button Motor 

Retainer 

Pro98-6G Motor Case 

Buoyancy Foam Core Insert 

Sky Angle Cert-3 Drogue Parachute 30' 

Nylon Shock Cord 

FWD Centering Ring

FWD1515 Rail Button 

AFT Electronics Bay Bulk Plate

Recovery Electronics System 

FWD Electronics Bay Bulk

Y Y 

Coordinates 

Diagram

XX 

                                 

                       

                               

         

S.2.2. Detailed Design Layouts

Detailed design layout drawings are very helpful in accounting for the location of all components in an

engineered system and identifying interfaces between components, clearance issues, and assembly plans.

As you can see in the example below, layout drawings can include dimensions, materials, detail callouts,

reference datums, and assembly methods.
     

                                   

                         

                           

                                   

  

                                           

                             

                             

              

                                   

                                 

                                   

                                      

                                   

                               

   

   

   

   

     

   

   

   

   

   

   

       

   

   

     

     

   

     

 

 

 

 

 

 

 

 

 

S.2.3. Mass Balance Statement

A Mass Balance Statement table is an account for all components in a high powered rocket. For each

component, the table tracks quantity, length, weight, margin, and flight station. Simple math functions

calculate each component’s contribution to the vehicle’s Center of Gravity. A mass Balance Statement is

another powerful tool that can help budget the vehicle. This data can be used for propulsion and recovery

system design.

ARCAS Mass Balance Statement

Component Qantity Length Weight (oz) Margin Weight (oz) Station (in)

Fiberglass nosecone 1 10.00 in 3.40 oz 0% 3.40 oz 6.5 in

Nosecone mass 1 N/A 2.00 oz 20% 2.40 oz 1.0 in

G10 Nosecone Bulkplate 1 0.06 in 0.30 oz 20% 0.36 oz 10.5 in

Payload Airfame Tube 1 16.00 in 4.80 oz 5% 5.04 oz 18.0 in

Payload Coupler Tube 1 6.00 in 1.80 oz 20% 2.16 oz 26.0 in

Payload Coupler Bulkplate 1 0.06 in 0.30 oz 20% 0.36 oz 29.0 in

Payload Bulkplate Eyebolt ASSY 1 1.00 in 0.80 oz 10% 0.88 oz 29.0 in

12 feet shock cord 1 6.00 in 2.00 oz 0% 2.00 oz 39.0 in

30 inch parachute 1 6.00 in 1.00 oz 0% 1.00 oz 39.0 in

9x9 Parachute Protector 1 6.00 in 0.50 oz 0% 0.50 oz 39.0 in

Booster Airframe (Slotted) 1 26.00 in 7.70 oz 5% 8.09 oz 39.0 in

38mm Motor Tube 1 8.00 in 2.30 oz 5% 2.42 oz 47.0 in

Forward Centering Ring 1 0.06 in 0.20 oz 20% 0.24 oz 45.0 in

FWD Centering Ring Eyebolt ASSY 1 1.00 in 0.80 oz 10% 0.88 oz 45.0 in

G10 Clipped Delta Fins 4 5.00 in 0.50 oz 20% 2.40 oz 49.0 in

Aft Centering Ring 1 0.06 in 0.20 oz 20% 0.24 oz 52.0 in

38mm Aero‐Pack Motor Retainer 1 0.25 in 0.80 oz 0% 0.80 oz 52.0 in

CTI pro38 2G case 1 8.00 in 3.50 oz 0% 3.50 oz 49.0 in

CTI H225 Reload 1 8.00 in 6.80 oz 0% 6.80 oz 49.0 in

Totals 22 Parts

52.25 in 41.20 oz 2.26 oz 43.46 oz N/A

4.35 ft 2.58 lbm 0.14 lbm 2.72 lbm N/A

S.2.3.1. Length

It is important to maintain a record of the size and shape of all components in the rocket as a tool to

mitigate integration problems later in the construction process. Note that only the lengths of external

primary structural components are used to calculate the vehicles total length. Lengths of components on

the rocket may also carry a margin.

S.2.3.2. Weight

The weight or mass of every component is recorded in the mass balance statement. It may not be

necessary to account for every piece‐wise part in the rocket. Some smaller components such as nuts and

washers are rounded up into the next higher assembly and their mass is accounted for there. An example

of this would be the bulk plate and centering ring eyebolts which included two hex nuts and a washer.

S.2.3.3. Margin

Margin is a way to track growth in the vehicle through the design cycle. Commercial parts generally carry

no margin because they already exist. Components that must be designed should carry a margin to
 Part Number R E V Status 

M A E 4 9 3 1 0 0 1 A Released 

MAE4931002 D Released 

M A E 4 9 3 1 0 0 3 C Released 

M A E 4 9 3 1 0 04 E In Work 

M A E 4 9 3 1 0 0 5 D In Work 

M A E 4 9 3 2 0 0 1 A Released 

M A E 4 9 3 2 0 0 2 A Released 

M A E 4 9 3 2 0 0 3 A In Work 

M A E 4 9 3 2 0 04 F Released 

MAE4932100 D In Work 

M AE493300l A Released 

M A E 4 9 3 3 0 02 A Released 

M A E 4 9 3 3 0 0 3 B In Work 

M A E4 9 3 3 0 0 4 c In Work 

M AE4933005 E In Work 

M A E 4 9 3 3 0 0 6 C 

C O M P O N E N T 

B o o s t e r A i r f r a m e

F o r w a r d C e n t e r i n g R i n g

T a ilc o n e

F in B r a c k et

F in

F o r w a r d A i r f r a m e 

F o r w a r d A i r f r a m e C o u p l e r 

R e c o v e r y A v i o n i c s E n d C l o s

u r e s R e c o v e r y A v i o n i c s R a

c k

N o n - P y r o E j e c t i o n D e v i ce 

P a y l o a d A i r f r a m e

P a y l o a d A i r f r a m e C o u p l e r 

G e m i n i C a p s u l e

G e m i n i S e r v i c e S t r u c t u r e

S p a c e S c i e n c e M o d u l e

P a y l o a d R a c k

In Work 

                                   

                                 

                                   

                                 

                           

                       

   

         

             

             

             

             

           

           

         

       

       

      

       

         

           

         

               

             

                

               

         

             

              

           

           

           

         


 


 

 
 


 


 


 


 


 


 


 


 


 


 


 


 

 
 


 

 
 


 


 

 
 


 


 


 


 

account for the estimated mass increase in the system. In this table, most small components carry a 20%

margin to account for the epoxy needed to assemble them to the next higher assembly. Some larger

components carry a 5% margin to account for variations in optimal fabric to resin ratios and tolerances in

the manufacturing process. The hardware that will most readily be available for your rocket is made for a

hobby rocketry community where high tolerance aerospace materials are not viable options. There will

be minor manufacturing variations in just about every piece of commercial hardware.

S.2.4. Exploded Models

The exploded view below helps to convey
 

the location of all piece‐wise parts in a
 

rocket. This is an exploded model of the
 

Arcas rocket. Parts have been color coded to
 

indicate that they are made from the same
 

raw material. The blue components are built
 

from 1/16” thick G‐10 fiberglass. Note that
 

this exploded view shows the motor tube
 

subassembly with hardware attached, the
 

motor tube subassembly is shown
 

assembled for clarity.
 

S.2.5. Drawing Versions and Iterations

During the developemnt process of rocket
 

components, it will be necessary to revise
 

designs in order to meet design
 

requirements. It is a good idea to maintain a
 

table that lists what drawings and models of
 

parts make up the Top Assembly CAD model.
 

As a model is revised, the file version should
 

be iterated. Revisions are usually designated
 

by letters A‐Z. An initial model would be
 

designated by a dash “ – “.
 

The status of drawings change as versions
 

are revised. They are usually marked “In
 

Work” or “Released” showing that a model
 

is ready for fabrication.
 
Component Description Sheets 

Component: 

Forward Centering Ring 

Manufacturing Process: 

Horizontal Band Saw, CNC Lathe, and CNC M ill 

Component Weight: 40 pounds

Component Description: 

The centering ring will give the motor tube stability near the top end, and hold it in place to 

prevent any undesired movement. The centering ring will protect the parachutes from any hot gasses and 

high temperatures that the motor will produce during operationg. 

The centering ring will designed using Solid Edge and then manufactured by a 

CNC machine with Aluminum 6061-T6. The centering ring will have an outside 

diameter of 6.02" and an inside diameter of 4", there will be an O-Ring that will be included as 

well, with an outer diameter of 4.125" and an inside diameter of 3.875". The end aluminum part must 

weight in around .5 lbs in order for the aluminum to stay 

competitive to the plywood. There will be challenges during design, and eventually manufacturing, one of 

these challenges is material selection. Aluminum weighs a lot even when there is a small amount of it. 

Other challenges include weight reduction, and testing that needs to be done to ensure that it will withstand 

the stress due to lateral loads and pressures that it will encounter during operation. Some failures that 

could be expected include set screws shearing; anodizing finish compromised allowing corrosion to begin, 

resulting in loss of m otor tube stability; O-ring failure resulting in decreased efficiency of recovery ejection 

system. 

Prospective Vendor: 

McMaster Carr, Huff Performance, UAHuntsville MAE Machine Shop 

Cost/Unit: $40 

ilililililililiiiliilt. it

rrrkkysskyykyscscscLehood1eoe2ne3obe4Le5ghLeonequene1one2Led3agna4a5aaophPRUHCNCCmmM

FailureModes Analysis: 

Parts List 

Failure Mode 

Likelihood/ 

Consequence Criticality Potential Effects Mitigation 

Body Shear 2/5 Medium 

Shear could cause the bolts 

holding to body to fail 

Testing during 

fabrication 

Motor gets free 2/5 Medium 

M otor gets free 

causing damage in the forward area 

Testing and 

placement of 

centering ring 

O -ring failure 3/5 Medium 

Reduce efficiency of 

NPES-Recovery 

system failure 

Design of O-ring slot Development testing 

Loose fit 2/5 Medium Motor shakes inside 

body 

Testing with launches 

Quantity Part Name (Common) 

Description Center Ring Maintian Axial alignment of motor case in booster 1 

#6-32 1/4" length P/N 92185A148 316 SS (McMaster-Carr) 3

%-28 1" length 1 

RTV Sealant 1 

1515 Rail Button 

P/N 90910A542 316 SS (McMaster-Carr) 

P/N 7474A14 Loctite® Superflex RTV Silicone Sealant 

Number 30560, 2.7-Ounce Tube (McMaster-Carr) 

Forward Launch Rail Button (Huff Performance) i 

O-Ring P/N 9596K231 Standard 4" ID Silicone O-Ring i

Designer: 

rrJaedG re e n / Dan*Cavender 

G en e ra l D im e n sio n s: 

Outside Diameter 6.02" O-ring OO 4.125" 

Inside Diameter: 3.95" O-ring ID 4" 

Material: Aluminum 6061-T6 

   

                                   

                       

                                 

                             

                                     

               

 

 

S.2.6. Component Development Sheet

The Component Development Sheet (CDS) is a good tool to manage lots of design details at a piece‐wise

parts level. The CDS can be used to track details such as:

 Component designer

 Model version and revision (i.e. FWD Centering Ring Rev D)

 Detailed part dimensions & description

 Manufacturing processes

 Cost per unit

 Vendor information

 Risk/hazard analysis

 Parts list

Every major component in the rocket should have its own CDS. When used in conjunction with the

Components/Process Tree tool, a comprehensive view ot the rocket is created. The CDS should be

updated often. An example of a good CDS is shown below. The designer took time to document a good

deal of information about the part.
                           

                    

       

                   

               

               

               

                   

                 

             

                 

                     

                 

                 

                 

               

          

           

             

                 

               

            

                           

                               

                                   

  

 

 

 

 

 

 

 

S.3. Construction Techniques

There are many construction techniques used in the construction of high‐powered rockets. This section

will touch on a few that you should know about.

S.3.1. Cutting Airframes and Couplers

There are several ways to cut an airframe to the

required lengths. The easiest is to request them

pre‐cut from the manufacturer. You may wish to

purchase the full uncut length of airframe and

cut it yourself. Airframes can be cut using a miter

saw. Most miter saws have a fence that the

airframe can be held against. For larger

airframes, the saw blade might not reach all the

way through the tube. If thisisthe case, once the

saw blade is about half way through the tube,

the tube and be easily rotated slowly and safely

until the entire tube is cut. Use eye protection

and do not wear loose‐fitting clothing that can

get caught in the saw.

S.3.2. Through‐The‐Wall (TTW)

Through‐The‐Wall mounting is a widely used fin

mounting technique where the fin tang passes

through a slot in the airframe and epoxies flush

against the motor tube. Epoxy fillets are applied

on every side of each joint. Epoxy Fillets

TTW fins are double supported cantilevers. This method shares the load distribution between shear,

tension, and compression asthe fin isflexed during flight. There are obvious areas ofstress concentrations

against the airframe and the motor tube. This is the reason you might want to consider reinforcing these
                               

                

   

         

           

           

             

         

             

           

               

             

               

              

             

              

                  

             

               

           

   

             

                 

           

           

             

           

             

                

             

                 

                 

            


 


 

 
 


 


 


 

 
 


 


 


 


 


 


 


 

 
 


 


 


 

 
 


 


 


 


 


 


 


 


 


 

 
 


 

areas by adding large fillets at the interface of the fin and airframe, and/or adding fiberglass

reinforcements at the fin and motor tube interface.

S.3.3. 3M Epoxy Guns

Epoxies are two‐part adhesive systems that
 

chemically react to cure and adhere materials
 

together. Mixing the two parts together can
 

prove to be messy. Many quick curing epoxies
 

are time critical tasks that require some
 

technique and planning to maximize use. The 3M
 

Corp. developed the mixing epoxy applicator gun
 

pictured to the right. The gun and long length
 

mixing nozzle allow you to reach otherwise hard
 

to reach areas easily and control the location and
 

amount of epoxy applied to your rocket. Before
 

applying epoxy, be sure to sand the bonding
 

surface. This provides more surface area for the
 

epoxy to bond and will provide a stronger bond.
 

Epoxy is a hazardous material and should be
 

treated as such. As epoxy cures, it releases
 

irritating fumes and heats up to potentially
 

injury‐causing temperatures.
 

S.3.4. Zipper‐less Design

This is a common booster design concept where
 

a coupler segment with a bulk plate and u‐bolt is
 

epoxied into an airframe section. With this
 

design, the shock cord connecting the rocket
 

sections to the recovery system is allowed the
 

largest possible clearance from contact with the
 

rocket in order to prevent the airframe from
 

tearing. This failure is known as a “zipper”.
 

Rocket builders may use this technique on hand
 

to replace parts like booster or avionics bays. If a
 

tube doeszipper, it isisolated to a different, easy
 

to replace airframe segment.
 Permanent Coupler
   

             

                     

                       

                 

               

                     

                 

                   

                 

                     

                     

                   

                 

               

                     

                       

                   

                 

               

               

                 

             

     

                                         

                                       

                               

                               

                         


 


 


 


 


 


 


 


 

 
 


 


 


 


 


 


 


 


 


 


 


 


 


 

S.3.5. Tip‐to‐Tip Glassing

Another common fin stiffening technique is to layup
 

fiberglass or carbon fiber from the tip of a fin across to
 

the other tip of the same fin. It is not a difficult process
 

to master, but it does require some special tools and
 

strict timing. Generally, one would make a template from
 

paper that can be transferred to the glass and to a sheet
 

of peel‐ply. The glass would be cut using the template
 

and then laid across the rocket to dry (no epoxy yet).
 

Some epoxy would be mixed and first drizzled or brushed
 

on top of the glass sheet on the rocket. Once the epoxy
 

saturates all of the glass, lay the peel‐ply on top and use
 

a small sponge roller to press the peel‐ply down onto the
 

glass and the airframe, eliminating all air pockets. Have a
 

shop rag and some isopropyl alcohol (70% or higher)
 

available to wipe up all excess resin. It is much easier to
 

wipe it up than to sand it off later. Typically, you will have
 

about 20‐30 minutes of work time before the resin is no
 

longer workable. After the epoxy has cured, peel off the
 

peel‐ply and clean up the area with some light sanding.
 

Scissors and sand paper are helpful to remove hardened
 

fiberglass. The process will need to be repeated until all
 

sides are glassed tip to tip.
 

S.3.6. Slotted Centering Rings

Slotted centering rings are an easy way to align fins and ensure a secure fit that firmly grips the entire fin

tang. The centering ring below was built with a common table saw, a dado set, and a custom jig. Two

perpendicular grooves were routed into a plywood centering ring. The width and depth of the grooves

matched the fin tang thickness. The photos below show a finished centering ring before installation and

how a set of two slotted centering rings grip the four fins securely.
   

               

             

         

                 

           

             

               

             

             

              

             

               

               

             

               

                 

                   

       

               

               

                    

                   

                   

               

                 

                 

               

                 

               

 

 

 

 

 

S.3.7. Vacuum Bagging

Vacuum bagging is a clamping method that uses

atmospheric pressure to hold the adhesive or

resin‐coated components of a lamination in

place until the adhesive cures. This is a common,

but advanced technique used in HPR

construction. Vacuum bagging may be applied to

airframe or fin construction. Like all epoxy resin

projects, the process follows a strict timeline of

preparation, lay‐up, work, and curing. A vacuum

pump is required to provide the vacuum.

A simple approach to vacuum bagging requires

sheets of a bagging film about the same

thickness and toughness as a Ziploc freezer bag,

sealant tape, a thin perforated plastic film known

as peel‐ply, and a breather material (typically a

sheet of cotton or cotton like nylon material). A

sheet of bagging plastic is cut in a rectangle and

two proportionally smaller rectangles of

breather material and peel ply are cut and

centered on the rectangle. The peel ply should

be on top. This is the inside of the bag.

First, lay‐up the parts on one half of the peel‐ply.

When the wet lay‐up is done, lay a strip of

sealant tape all the way around the bagging

sheet, about an inch or so inside the border.

Next, fold the other half of the peel‐ply, breather

material, and bag over and press the sealant

tape together to seal the bag. Place the vacuum

pump hose into the bag near the perimeter,
                   

  

                   

                 

                 

                     

           

                 

                 

  

   

 

 

laying the tip of the hose inside of the breather

material.

Turn the pump on and then look and listen for

leaks around the bag, sealing them with tape as

you go. The vacuum guage should be reading a

vacuum in the bag and you willsee the entire bag

begin to collapse onto the parts, applying

pressure to them. After a few hours, switch off

the pump and allow the parts to continue to

cure.
     

                 

                 

             

               

                   

                 

               

                 

  

             

               

             

                 

             

               

               

                 

                 

                 

               

               

 

 

 

 

S.3.8. Rail Button Jig

A simple tool to accurately and quickly repeatrail

button alignment can be made from a length of

angled aluminum with drill bit alignment guides.

The angled aluminum will align itself when laid

flush on the airframe. Tape the jig in place with

some masking tape and drill the forward and aft

rail button screw holes with the desired size drill

bit. Small rail buttons usually use a #8 size

machine screw.

S.3.9. Hole Saws for bulkheads and Centering Rings

Holes saws are great tools for making round

disks. Many sizes are available at hardware

storesthat can be used to make rocket centering

rings and bulk plates. However, hole saws

capable of making larger rings and plates are

hard to find. There are serveral online venders

that can build custom holesaws for you like the

one in the photo to the right. These holesaws

requires a drill press. Like all other power tools,

use eye protection and do not wear loose‐fitting

clothing that could be caught in the tool.
  

                   

                 

             

             

                 

             

                 

                     

             

             

               

               

               

               

                   

               

               

                     

             

                   

           

               

           

                 

                   

                 

               

 

 

 

 

 

 

 

S.3.10. Lathe

A lathe is a power tool used to form cylindrical

parts. There are two main catagories of lathes –

those designed for wood and other soft

materials, and those designed for metals and

hard materials. The photo to the right shows a

rockets tailcone being machined. The raw block

of material, “the blank”, is turned at high speeds

while a cutting tool is run up and down the side,

removing small amounts of material with each

pass. Many lathes have a computer numerical

control (CNC). Computer models of parts can be

turned into a sequence of manuvers to be

performed by the lathe to produce the desired

part. Lathes can be dangerous and even deadly.

Use the utmost care and do not work alone.

S.3.11. Mills

Mills are powerful tools used to form many

different types of parts. Generally, a block of

material is secured on a deck which has X and Y

directional drives. This cutting tool rotates at

high speeds and moves up and down in the Z

direction removing small amounts of material

with each pass. Many mills have a computer

numerical control (CNC). Computer models of

parts can be turned into a sequence of manuvers

to be performed by the mill to produce the part.

Mills can be dangerous and even deadly. Use the

utmost care and do not work alone.
   


 


 

Propulsion 

Systems 

Materials: 

Propulsion Theory
 

Solid Rocket Motors
 

Definition of HPR 

Motor Classifications 

Commercially Certified Motors 

Thrust to Weight 

Thrust Curves 

Ballistics Coefficients 

Trajectory Analysis 

Propulsion Exercises 
           

   

       


 


 

NASA High Power Rocketry Video Series
 

Counterpart Documents
 

Written by Daniel Cavender
   

                           

                             

   

         

             

                       

   

                           

                       

                               

                                 

                    

                                         

          

			

                             

                                   

                   

	 	 	

                             

                              

		 			

 

 

 

 

 

 

 

Momentum equals masstimes velocity, therefore force equals change in momentum with respect to time.

Another way to say this is that thrust equals change in momentum of a vehicle.

P.1. Propulsion Theory

Traditional propulsion systems rely on thermodynamic expansion of a supersonic gas to produce thrust.

Non‐traditional propulsion systems still rely on Newton’s laws, but get creative in how they produce

thrust.

Propulsion systems:

 Store propellants

 Move propellants into a combustion chamber

 Burn propellants to raise their energy and pressure

 Expand the combustion gasesthrough a converging‐diverging nozzle to achieve high exit velocities

P.1.1. Newton’s Laws

Rocket science is grounded in fundamental laws of physics & thermodynamics. Newton’s Laws (published

in 1687) established the phenomena known as inertia, force, and action/reaction.

 1st Law: Objects in motion/rest will remain in that state until acted on by an outside force.

 2nd Law: Acceleration of an object is proportional to the sum of the external forces & inverse to

mass.

 3rd Law: Action/Reaction: Two bodies interact with equal and opposite force.

The 2nd Law provides the definition of the force used in the 1st and 3rd law and becomes the backbone of

the discussion of rocket propulsion.

݋ݐݓܰ݁ሺ݊ ݉ܽ ൌ ܨ ′ 	ݏ݀݊2ܮܽሻݓ

Force equals mass times acceleration. By definition, acceleration is the derivative of velocity with respect

to time. By application, the mass of the vehicle changes over time with the expulsion of propellant. We

can use this knowledge to define Newton’s 2nd law as:

݊ ሺ݋ݐݓܰ݁ ′ ݁݊ݐݐ݅ݎݓܴ݁ሻ ݓܽܮ 2݊݀ ݏ

ݑ݀

ܨ ൌ ݉ሺݐሻ

ݐ݀

ݑ݉ሻ ൌ ݉ݑݐ݉݁݊݋ܯሺ

݀

ݐ݀ ሻݑ݉ሺ ൌ ܨ
                                       

                       

   

           

                                     

                  

           

                      

   

                                 

                               

                 

				

                                  

   

 

	 

	 

 

 

 

P.1.2. Thrust

Thrust is a force produced by the expulsion of matter at high velocities. It is the force produced by a

spacecraft’s propulsion system which changes that spacecraft’s momentum. Thrust comes from two

main physical phenomena:

	 Momentum exchange between exhaust & vehicle.

ܶ௠௢௠ ൌ ݉ሶ

	 Pressure imbalance at the nozzle exit plane. P2 is the pressure of the gases at the exit plane of

the rocket motor’s nozzle. P3 is the ambient atmospheric pressure.

௘ݑ

ሻ ܲଶ െ ܲଷ ሺ ܶ௣௥௘௦௦ ൌ ܣ௘

So the total thrust equation is:

݉ሶ

All of these variables depend on the design of the nozzle.

݄ܶݐݏݑݎ ൌ ሻ ܲଶ െ ܲଷ ሺ ݑ ൅ ௘ܣ௘

P.1.3. Total Impulse

Impulse is the work done by the propellant, and is typically measured in units of Newton‐seconds. The

impulse parameter is used to categorize different classes of rocket motors in hobby rocketry. Impulse can

be calculated for both variable and constant thrust rocket motors.

ܶ݀ݐ ൌ ܶ௔௩௘ݐ௕௨௥௡ ൌ න ݉ሶ

௧

ܫ ൌ න

଴

ܧ݊݋݅ݐܽݑݍሻ ݌݉ܫ݁ݏ݈ݑ ݈ܽݐ݋ܶሺ ௘௤ ܸ݉ ൌ ݐ݀௤௘ܸ

The Thrust (T) and Total Impulse (I) equations above work for both liquid and solid rocket motors.
     

                                       

                                   

	 	

	 	 	

			

                               

                             

                                 

                                   

                               

                               

                               

                                         

          

       

                         

                                 

                           

                         

           

                                   

 

 

 

 

 

 

 

 

 

P.1.4. Specific Impulse (Isp)

Specific impulse (Isp) is an efficiency parameter like miles per gallon. It is a measure of the work per unit

mass of propellant. The units of specific impulse are the same whether we use English units or metric

units.

݊݋݈݈݃ܽ ݐ݅ ݋݀ ݋ݐ ݁ݏݑ ݁ݓ ݐ݈݈݁ܽ݊݌݋ݎܲ ൌ ݏݏܽܯ ݐ݈݈݁ܽ݊݌݋ݎܲ ൌ ݏ݈݉݅݁ ݁ݏ݈ݑ݌݉ܫ ݋݀ ݋ݐ ݐܽ݊ݓ ݁ݓ ݋ܹ݇ݎ

௘ ሺܲ௘ െ ܲ଴ሻܣ ܸ ൅ ௘ൌ ݉ሶ ሺܵ݌݂݁ܿ݅݅ܿ ݏ݈݁ܫ݉ݑ݌ ሻ

ܫ ൌ௘௤ ܸ

଴݃ ଴݃ ଴݉݃ ൌ ݌ݏܫ

Why are we interested in specific impulse? It shows the tie between engine parameters and propulsion

thermodynamic parameters like exit velocity. The result of our thermodynamic analysis is a certain value

of specific impulse. The rocket weight will define the required value of thrust. Dividing the thrust required

by the specific impulse will tell us how much weight flow of propellants our engine must produce. This

information determines the physical size of the engine. It is an indication of engine efficiency. Two

different rocket engines have different values of specific impulse. The engine with the higher value of

specific impulse is more efficient because it produces more thrust for the same amount of propellant. HPR

solid rocket motors generally have an Isp between 170 sec and 220 sec. It gives us an easy way to "size"

an engine during preliminary analysis.

P.1.1. Rocket Equation (Tsiolkovsky’s Equation)

The Rocket Equation (Tsiolkovsky’s Equation) is essentially a reordering of Newton’s 2nd Law that relates

the maximum change of speed of a rocket (assuming no other external forces) to the effective exhaust

velocity (ve) of the combustion gases and the initial and final mass of a rocket.

ࢌ࢓

࢏

ࢌ࢓

ቇ ࢓ቆ ࢔࢒૙ࢍ࢖࢙ࡵቇൌ ࢓ቆ ࢔࢒ࢋ࢜ ൌ ࢂ∆ ࢏

Rocket trajectory programs use Tsiolkovsky’s ideal rocket equation with additional parameters to take

into account gravity and drag penalties:

ࢌ࢓

࢚࢟࢒ࢇ࢔ࢋ࢖	ࢍࢇ࢘ࢊ െ ࢚࢟࢒ࢇ࢔ࢋ࢖	࢚࢟࢏࢜ࢇ࢘ࢍ	 െ ቇ ࢓ቆ ࢔࢒૙ࢍ࢖࢙ࡵ ൌ ࢊࢋ࢏ࢌ࢏ࢊ࢕࢓ࢂ∆ ࢏

The Ideal rocket equation can be re‐ordered to solve for the amount of propellant needed to provide a

required ΔV.

࢖࢕࢘࢖࢓ ൌ ࢏࢓ ൭૚ െ ࢖࢞ࢋ ቆ െ∆ࢂ ቇ൱ ൌ ࢌ࢓ ቆ࢖࢞ࢋ ቆ ∆ࢂ ቇ െ ૚ቇ ࢍ૙࢖࢙ࡵ ࢍ૙࢖࢙ࡵ
       

                 

                   

             

                   

                   

             

             

         

           

                   

                 

                     

             

                 

             

               

        

                                   

                           

                  

                             

                                 

                             

                            

 

 

 

 

 

 

 

 

 

P.2. Solid Rocket Motors (SRMs):

The earliest solid rockets were used by the Chinese,

Mongols, and Arabs in warfare as early as the 13th

century. SRMs are widely used in military applications

because they can remain in storage for long periods of

time and they can be reliably launched on short notice.

Typical space exploration applications of SRMs include

the launch vehicle booster, kick stages for

geosynchronous and interplanetary spacecraft, and

breaking motors for interplanetary spacecraft. SRMs are

simpler in design than liquid or hybrid motors. Every solid

rocket motor has a nozzle, a combustion chamber, solid

propellant, and an igniter. The fuel itself acts as part of

the combustion chamber. More complicated SRMs have

a thrust vector control (TVC) system that steers the

rocket. SRMs are extensively used where total impulse

requirement is known accurately in advance and where

no restart is required.

SRMs use solid propellants to provide the combustion that drives thrust. Oxidizer and fuel are stored in a

combustion chamber in solid form. Solid propellant carries mechanical loads in addition to providing

thrust. When propellants are ignited, they burn in place.

There are two types of SRMs in sport rocketry ‐ black powder and composite propellant. Black powder

motors are typically used for low power applications and are end burners (the propellant burns from one

end to the other.) Composite motors are typically used for HPR motors. Composite propellants are

heterogeneous grains with crystalline oxidizer and powder fuel tied together with a chemical binder.
       

   

           

         

         

     

             

         

                   

                   

   

                             

                               

           

                                 

                                 

                               

                             

                                   

         

       

   

   

	 

	 


 


 

	 


 


 

	 


 

 
 

	 

 

 

	 

	 

	 

	 

	 

Composite propellant ingredients are:

	 Inorganic Oxidizers

o	 Most common is Ammonium Perchlorate (AP)

o Toxic chlorine gas in exhaust
 

 Fuels
 

o	 Most common is Powdered Aluminum

o Causes exhaust smoke
 

 Binders
 

o	 Serves dual purpose as fuel and binder

o Common binders are HTPB, PBAN
 

 Contain small amounts of chemical additives to improve physical properties
 

o	 Burn rate, smooth burning, casting characteristics, structural properties, absorb moisture

during storage

Some additives can make the motor burn different colors. Motors like the Cesaroni Technology Skidmark

add titanium flakes that burn brightly and create lots of noise and a shower of sparks.

P.3. Definition of a High Powered Rocket

Rockets use a propulsive device called a rocket motor that generates thrust by exhausting hot gases at

high velocities. The momentum of the hot exhaust gases produces a net force in the opposite direction

causing the rocket to move upwards. This happens because the rocket obeys Newton’s 3rd Law of Motion,

which states that for every action there is an equal and opposite reaction.

A rocket exceeds the definition of a model rocket under NFPA 1122 and becomes a high powered rocket

under NFPA 1127 if it:

	 Uses a motor with more than 160 Newton‐seconds of total impulse (an ‘H’ motor or larger) or

multiple motors that, when the thrust is summed, exceed 320 Newton‐seconds

	 Uses a motor with more than 80 Newtons average thrust (see rocket motor coding)

	 Exceeds 62.5 grams of propellant

	 Weighs more than 1,500 grams including motor(s)

	 Includes any airframe parts of ductile metal
   

                 

                 

           

               

               

               

                 

                 

                 

                               

                             

                                   

                                             

                                           

                                    

           

     

                           

                           

                             

                         

                           

      

           

                   

                 

                

                 

                 

                   

               

           

               

               

               

                 

                     

                 

   

           

      

         

     

     

         

     

 

 

 

 

 

P.4. Rocket Motor Classifications:

HPR motors approved for sale in the United States

are stamped with a two‐part code that gives some

basic information about the motor’s power and

behavior: A letter specifying the total impulse ("H")

and a number specifying the average thrust ("225").

Average thrust is a measure of how slowly or quickly

the motor delivers its total energy, and is measured

in Newtons. Total impulse is a measure of the overall

total energy contained in a motor, and is measured

in Newton‐seconds.

Impulse Class Category

H 160.01Ns to 320.01Ns

Level 1 I 320.01Ns to 640.00Ns

J 640.01Ns to 1280.00Ns

K 1280.01Ns to 2560.00Ns Level 2

L 2560.01Ns to 5120.00Ns

M 5120.01Ns to 10240.00Ns

N Level 3 10240.01Ns to 20480.00Ns

O 20480.00Ns to 40960.00Ns

High power rocket motors cannot be purchased over the counter. Members must be certified by either

the National Association of Rocketry (NAR) or the Tripoli Rocketry Association (TRA) at the appropriate

level to purchase motors from vendors. To become level 1 certified, you must first launch a rocket using

an H or I class motor. You may purchase one H or I motor prior for your certification flight. Once level 1

certified, you may purchase H and I motors as well as one J, K, or L motor for your intended level 2

certification launch. After successfully passing a written test and launching a rocket on a J, K, or L motor,

you will be level 2 certified.

P.5. Commercially Certified Motors

Unless stated otherwise, you are required to use a certified commercially manufactured motor at high

power rocket launches. The certifying agencies are the National Association of Rocketry (NAR), Tripoli

Rocketry Association (TRA), and the Canadian Association of Rocketry (CAR). Some of the more popular

solid rocket motor manufacturers are Cesaroni Technology Inc. (CTI) and Aerotech (AT). Each

manufacturer produces a wide variety of commercially certified rocket motors in many different impulse

and thrust ranges.

Reloadable solid rocket motor systems are

composed of a reusable motor case and a reload kit.

All high power rocket motor cases come in standard

sizes of 38mm, 54mm, 75mm, and 98mm diameters.

Most cases have three standard parts: the case, a

forward closure, and an aft closure. Some cases have

a forward closure built in and have a removable aft

closure where the reload is loaded from. The

closures are usually interchangeable between cases

of the same diameter, but in different lengths.

Solid rocket motor reload kits include the assembly

instructions, the propellant, the nozzle, and all other

one‐time use hardware for the flight. A typical reload

kit will include a phenolic or paper liner that acts as

thermal protection for the motor case, a series of O‐
                   

                   

                 

                 

                   

                 

                   

           

         

   

                                    

                                    

                             

                                    

           

     

                                         

                               

                                             

                                         

                                       

                                       

                         

 

 

rings that will seal the reload inside of the motor

case, a set of phenolic disks that act as thermal

protection for the aft and forward closures, a delay

grain for the motor ejection charge or a tracking

smoke element if the motor does not use an ejection

charge, and an igniter. You will also need o‐ring

grease for the assembly of the reload. It is very

important not to deviate from the manufacturer’s

directions for motor assembly.

P.6. Hybrid Motors:

Hybrid motors are another type of high power rocket motor, although they are not commonly used. In a

hybrid motor, a solid fuel grain and a liquid oxidizer are keptseparate from each other until launch. Hybrid

motors are typically cheaper than solid reloadable motors, but they do require some costly ground

support equipment to launch. An external Oxygen tank isrequired in order to produce a medium in which

a spark can ignite the motor.

P.7. Thrust to Weight:

In order for a rocket motor to lift a rocket, it must produce enough thrust to overcome the force of gravity.

This means a rocket motor, at a minimum, must produce enough mechanical energy to achieve a Thrust

to Weight Ratio of just over 1.0. The Space Shuttle has a thrust to weight ratio of 1.5 asit leavesthe launch

pad. But nearly 90% of the Space Shuttle is propellant and that ratio quickly rises as fuel is consumed. It is

an industry standard that your rocket have a thrust to weight of no less than 5:1. That means the rocket

motor must produce force equal to 5 times the weight of your rocket. If your rocket weighs 20 lbs, then

the motor needs to produce at least 100 lbs. of thrust.
   

                                 

                                     

                               

                                      

                              

                     

         

               

           

                 

           

                     

                 

                     

                 

                 

                   

                   

                   

                 

           

     

 

 

 

 

 

P.8. Thrust Curves:

Thrust curves are obtained experimentally for solid rocket motors by placing the motor on a test stand,

igniting the propellant, and recording the thrust as a function of time. This allows you to know how the

motor will perform when placed in your rocket. Total impulse is most accurately determined by calculating

the area under the curve. Average thrust is calculated as the total impulse divided by the burn time. Burn

time is generally considered the time when thrust drops below 5% of the maximum thrust.

Max Thrust (Fmax)

Burn Out (tb)

ሻ݁ݏ݈ݑ݌݉ܫ ݈ܽݐ݋ܶሺ ݐ ݀ܨ න ൌ ܫ

ܫ ൌ ܨ

ሻ݁ݏ݈ݑ݌݉ܫ ܽ݃݁ݎ݁ݒܣሺ ൗ௕ ݐ

A thrust curve can also show whether a motor has a

regressive, progressive, or neutral burn profile.

Thrust varies directly with the surface area of

propellant being combusted. As surface area

increases, thrust increases and the motor is said to

be progressive. As surface area decreases, thrust

decreases and the motor is said to be regressive. If a

motors thrust varies 10% or less from the average,

then the motor is said to have a neutral burn. The

thrust curve to the top right shows a regressive

motor burn. The thrust slowly tapers off until burn

out. The thrust curve to the bottom right shows a

progressive thrust for the first half of the burn and

then a regressive thrust for the rest of the burn.

What type of burn profile does the thrust curve at

the top of the page have?
   

                             

                                     

                             

                      

                       

                               

                                 

                                     

                                         

                                     

                

   

 

 

 

P.9. Ballistics Coefficient

Three parameters that characterize a rocket’s performance can be reduced to a single parameter called

the Ballistics Coefficient (β). The ballistics coefficient of a body is a measure of its ability to overcome air

resistance in flight. It is inversely proportional to the deceleration—a high number indicates a low

deceleration. BC is a function of mass, diameter, and drag coefficient.

Using the ballistics coefficient associative parameter, three rocket parameters can be traded

simultaneously. It is a convenient way to objectively consider what size your rocket should be. For

example, assume you rocket needs a ballistics coefficient between 2.5 and 3.0 in order to have enough

energy to reach an altitude of one mile. Assume that your rocket will have an average drag coefficient of

0.5. If you look at the red band in the plot below, you can make an association between the diameter and

the weight of your rocket. A 5” diameter rocket could weigh between 24lbs and 30 lbs. A 6” diameter

rocket could weigh between 35lbs and 42lbs.
   

                             

                                 

                                 

                               

          

                                   

                                     

                                 

                                     

        

 

 

 

P.10. Trajectory Analysis

A trajectory analysisshould be performed multiple time throughout your rocket’s design phase. There are

many commercial software packages (some free) available to help you, but you can also write your own

code if you like. Below is an example of a completed trajectory analysis. The analysis displays important

events in the flight like maximum altitude, velocity, and acceleration. It may also display the rockets

recovery events and descent rate.

P.10.1. Propulsion requirements

The first step in performing analysis should be to review and identify all of the project requirements that

apply. For example, a target altitude of one mile above ground level would be one. Another would be the

restrictions on class of motors you can use (i.e. your certification level). There may also be other

requirements you want to impose on yourself. Once you draw the box around the problem, it is easier to

continue with the analysis.
     

               

           

           

             

           

                 

                   

           

             

             

        

                                 

                             

         

 

P.10.2. Commercial Software Packages

The easiest way to perform a trajectory analysis

is to purchase a commercially produced

trajectory analysis program like RockSim or

RASAero. There are also free software packages

available such as OpenRocket. These programs

have simple CAD elements that allow a user to

build a model of the rocket in the program. The

programs can help calculate many rocket

parameters like weight, length, and stability in

addition to performing a three degrees of

freedom (3DOF) flight analysis.

These commercial programs offer the user a lot of control over the simulation environment also. The user

can manipulate the winds, the launch angle, temperature, and many other parameters to match the

simulation environment to the real world.
                                     

                             

                                   

                                   

                                       

                               

                                        

                                       

                               

               

     

                                         

                                       

                         

                                 

                                  

                                     

                                 

            

                             

           

             

            

		

		

                           

                                   

                                     

                                         

                 

 

 

 

 

 

 

 

 

 

 

 

P.11. Stability

An object is directionally stable if it tends to return to its original direction in relation to the oncoming

medium (water, air, etc.) when disturbed away from that direction. Directional stability is also called

“weather vaning” because a directionaly stable vehicle free to rotate about its center of mass is similar to

a weather vane rotating about its pivot. Without stability, a rocket would tumble end over end, spin, or

orient itself at a high angle of attack. At high angles of attack, drag forces may become excessive and the

rocket may experience structural failure. Generally, a rocket is considered stable if its Center of Gravity

(CG) is at least one body diameter in front of its Center of Pressure (CP). A practical approach to efficient

rocket design is to allow the structural design to mature to the point where the CG location is stable (does

not vary much with tweaks to the configuration) and then tailored for the desired stability margin by

selecting where you want your CP to be.

P.11.1. Center of Gravity (CG)

The Center of Gravity of a rigid body is the mean location of all the masses in a system. The position of the

CG is fixed in relation to the body and does not generally coincide with the geometric center. The CG can

be determined analytically or empirically. The analytical method requres accounting for all of the

individual point masses that compose the system and their location in the system as measured from a

common datum plane, typically the tip of a rocket’s nose cone. The average of their positions weighted

by their masses is the location of the center of gravity. The basic assumptions used in calculation of the

theoretical center of gravity for this rocket are uniform gravitational field (g = constant) and that the

components have uniform density (ρ= constant).

௜

௜

from the tip of the rocket’s nose cone. Secondly, the tabulated data would be used to calculate the center

of gravity using the center of masses equation found below.

௡

ܺ஼ீܹ஼ீ ൌ ෍ܹ௜ ሺ1ሻ ത

௜ୀଵ

௡

ܹ஼ீ ൌ ෍ܹ௜ ሺ2ሻ

௜ୀଵ

One would first tabulate the known weight and station data in a table like this one. Each components

weightሺܹ ሻ, for simplicity, is treated as a point mass or single force acting through the centroid of the

component. In physics, the word centroid means the geometric center of the objects shape. Each

component’s centroid is recorded by Station ሺܺത ሻ or position of the component’s centroid as measured

ܺത௜ ൌ ܹଵܺത

ଵ ൅ ܹଶܺതଶ ൅ ܹଷܺതଷ ൅ ⋯

ൌ ܹଵ ൅ ܹଶ ൅ ܹଷ ൅ ⋯

ܺ஼ீܹ஼ீ ത ሺ3ሻ ܺത஼ீ ൌ ܹ஼ீ

The empirical approach relies on observation and experience. An example of determining the CG

empirically would be a simple balance method. Find the point on the rocket where it balances and you

have found the Center of Gravity. Although this method is accurate, it is not practical on very large and

heavy rockets and is not useful during the design phase of your rocket. It can be an easy check just to

verify your analytical model once your rocket is complete.
                                 

                                 

                                

                        

     

                           

                         

                     

                         

                         

                   

                         

                       

                           

              

       

         

       

         

   

       

             

               

          

               

           

              

          

       

                   

                       

       

   

                                         

                               

                     

   

 

 
 


 


 

 
 

 
 

 


 


 


 


 

 

 
 


 


 


 


 

 
 


 


 


 


 


 

 

The Analytical Model is the most difficult, but it is very useful during the design phase of your rocket.

Computer programs like Excel can be powerful tools to manage point mass data and make calculating an

accurate CG easy once they are set up. Other computer software programs, like RockSim, are available

that can perform CG and stability calculations as well as flight performance simulations.

P.11.2. Center of Pressure (CP)

As a rocket flies through the air, aerodynamic forces act on all parts of
 

the rocket. In the same way that the weight of all the rocket components
 

acts through the center of gravity (CG), the aerodynamic forces act
 

through a single point called the Center of Pressure (CP). You can calculate
 

the CP, but this is a complicated procedure requiring the use of calculus.
 CNα

The aerodynamic forces are the result of pressure variations around the ) surface of the rocket. In general, you must determine the integral of the
 

pressure times the unit normal, times the area, times the distance from
 

a reference line. Then divide by the integral of the pressure timesthe unit
 

normal, times the area. Lots of work!
 

A much simpler analytical method will find the Center of Pressure
 

ሺܥܲ ݎ݋ ܺത஼௉ሻ by regional influence using algebraic forms of the

Barrowman equations. Each primary component has a Normal Force (Cnα)

௜

corresponding to its contribution. Each Normal Force is recorded by

or position of CNα Station ሺܺത ሻ the component’s Normal Force as measured

)
 from the tip of the nose cone. The basic assumptions used in calculating

the theoretical center of pressure for this rocket are:

 The angle of attack (α) of the rocket is near zero (less than 100

)
 

 The speed of the rocket is much less than the speed of sound
 

 The air flow over the rocket is smooth and does not change
 

rapidly
 

 The rocket is thin compared to its length (L >> D)
 

 The nose of the rocket comes smoothly to a point
 

 The rocket is an axially symmetrical rigid body
 

 The fins are thin flat plates
 CN 

With ) these assumptions, the regional influences of the nose cone,

airframe, and fins can more easily be calculated using the algebraic forms

on the Barrowman Equations:

Nose cone:

In general, the Normal Force (CNα) on the nose cone is identical for all shapes and always has the value 2.

The Station ሺܺത௡ሻ varies with each differentshape. The algebraic form equationsfor calculating the normal

force and center of pressure for a conical nose cone are:

ଷ௡ ܮ

ଶ ሺܥேఈሻ௡ ൌ 2 ܺത௡ ൌ
                   

   

                   

      

       

                  

                   

       

               

                 

                 

                 

                           

                    

   

   

           

                     

                                     

                     

                               

                                 

                                   

 

 

 

 

Airframe:

The Airframe provides no response for low angles of attack.

௔ܮ

ଵ

ଶ ሺܥேఈሻ௔ ൌ 0 ܺത௔ ൌ ܮ൅ ௡

Fins:

The rocket’s fins contribute the bulk of the aerodynamic forces.

The forces ሺܥேఈሻ௙ and Stationܺത

௙ for these fins are calculated

using the following equations:

ሺܥேఈሻ௙ ൌ	 ವቁ

మ

ସேቀೄ

ଵାටଵାቀ మಽ

ಲశಳቁ

మ ܺ௙ ൌ ܺ௙ ൅	∆ܺ௙ ത

6 െ ܤ ൅ ܣ൬ ܤܣ

ܤ൅ܣ ൰ ൌ௙ ܺ ∆ሻܤ2 ൅ ܣሺܯ

1

൅ 3ሺܣ ൅ ܤሻ S

Where:

N represents the number of fins on the rocket.

S represents the span of each fin measured from the

airframe to the tip. D

D represents the diameter of the rocket airframe.

A represents the length of the fins root cord.

B represents the length of the fins tip cord.

L represents the length of the fin’s half cord

Once the regional ሺܥேఈሻ and ሺܺത௡ሻ values are calculated, one would place the values into a matrix like the

one below. Notice that the fins have a significantly larger normal force than the nose cone.

Component Shape Cnα  ࢄഥ (inches)

Nose cone Ogive 2 5.7”

Airframe Cylindrical 0 26.25”

Fins (Set of 4) Clipped Delta 6.4 48.9”

The total normal force is the sum of the regional forces:

௙௕ ሻ ܥ௡ఈ ൅ ሺ ௔ሻ ܥ௡ఈ ൅ ሺ ௡ሻ ܥ௡ఈ ൌ ሺ ܥ௡ఈ

The Center of Pressure (CP) of the entire rocket is found by taking the moment balance about the nose

cone tip and solving for the total center of pressure location

ܺ௙

ത ௙௕ ሻ ܥ௡ఈ ൅ ሺ ܺ௔ത ௔ሻ ܥ௡ఈ ൅ ሺ ܺ௡ത ௡ሻ ܥ௡ఈ ሺ ܺത ൌ ܥ௡ఈ

A simple empirical method is the cardboard cutout method. This method assumes that the center of

pressure coincides with the centroid, or geometric center, of the rocket. Make a cardboard cutout of the

rocketsilhouette and find the balance point. Thisis an easy approximation of the area where the CP might

B

L

M

A
                                     

                    

                                   

                             

                                           

                             

            

                                       

                                   

                             

                                 

                      

			           

           

   

                                 

                                     

                               

                               

   

     

     

 

 

 

 

 

be located. This method could be useful early on in the preliminary design of your rocket, but is not

recommended as your primary method for determining your rockets CP.

A very detailed CN/CL analysis can be performed using excel and a good understanding of how to apply

both the contribution of cross sectional geometries for the nosecone and airframe Thin Airfoil Theory

(TAT) to determine a fin size needed to achieve an ideal CG & CP relation. The model can also be used to

determine structural loads at various angles of attack and speeds. When done correctly, this CN/CL

analysis can be a powerful tool.

In the same way that excel was used to make a mass balance statement, a table that captures the OML

(Outer Mold Line) or plan points of the rockets geometry, as a function of flight stations, can be

manipulated to calculate normal force coefficients (CN’s) at every point along the rocket’s nosecone and

airframe. The analysis must be performed for every flight station (i) starting at the nosecone and moving

aft; generally in increments of one (1) inch.

ଶ

ቁ ஽೔ ሺ1ሻ ܥܰ ௜݊ ߙሻሺ ൤1 െ ቀ

஽೔షభ

ൌ 2ݏ݅ ൨ (CNi Equation where)

௜ܰܥ௜,ௗ௬௕௢ܵ

ଶ ߩܸ ଶ

ଵ ሺ2ሻ ܰ௜ ൌ

ቁ (Equations based on T.A.T.) ାଶ

஺ோ೔

஺ோ ሺ3ሻ ܮܥ ௜ൌ 4ߙߨ ቀ ೔

(Aspect Ratio Equation) మ௕ ሺ4ሻ ܣܴ ௜ൌ ௌ೑೚೔೗,೔

(Normal Force Equation)

α 

Oncoming Air

Direction of Travel

i = 1,2,3,...

Variables D (diameter), Sbody (Body Reference Area), b (fin half span), and Sfoil (Foil Reference Area), and

CN have the subscript ‘i’ to designate a unique flight station. Each operation at a flight station must be

discretely analyzed by the unique variables at that flight station. A modification of the center of masses

equation can be applied to determine the CP location for any fin design.

bi

Sfoil 

i
   

                                  

                                   

                                     

                              

                                             

                                       

                                       

                                   

                                   

                                     

                                     

                                 

                                  

   

                     

                     

               

           

                   

                     

                

                     

                         

                 

                 

                 

                 

           

			

                       

                     

 

 

 

 

 

 

 

 

 

P.11.3. Static Margin

Static Margin or Margin of Stability describes the directional stability of a rocket. Recall that an object is

directionally stable if it tends to return to its original direction in relation to the oncoming medium (water,

air, etc.) when disturbed away from that direction and that a rocket is considered stable if its Center of

Gravity (CG) is at least one body diameter in front of its Center of Pressure (CP).

ൌ .ܯ ܵ. ݎ݁ݐ݅ܽ݉݁ܦ ݕ݀݋ܤ 1.0 ൒ 	 ത ீ஼௉ ஼ܺ തܺ െ

Generally, it is desirable to have a static margin of 1.5 to 2.0. A rocket is considered over stable if it has a

static margin of 3.0 or greater. An over stable rocket will lean or “weather vane” further into the wind and

not travel as high. It is important to note that a rocket’s CG will change as the motor exhausts combusted

fuel. Generally, the CG will move forward as a solid rocket motor burns, causing the rocket to become

more stable. Typically, with hybrid rockets motors, the oxidizer tank is forward of the CG. As oxidizer is

consumed, the rocket’s CG moves aft and there is a danger the rocket could become unstable. Also, it is

important to note that as the angle of attack increases or the rocket approaches Mach 1, the CP can

change. Recall the Barrowman equations for rocket stability requires the angle of attack (α) of the rocket

is near zero (less than 100) and its speed be much less than the speed of sound.

P.12. Aerodynamic Drag

Drag refers to forces that oppose the relative motion of an

   

   

Laminar Flow

Turbulent Flow

Transition

Drag

object through a fluid. Types of drag are usually divided into

three catagories: Parasitic Drag consisting of form drag, skin

friction, and interference drag; Lift‐Induced drag; and Wave

Drag. For high velocities, or more precisely, at high Reynolds

numbers, the overall drag of a rocket is characterized by its

Drag Coefficient. It is calculated using the drag equation.

1 ൌ ܦ ൗ2 ܸߩ ଶ ݊݋݅ݐܽݑݍ݁ሻ ܽ݃ݎܦሺ ௗܥܵ

The Reynolds number is the ratio of inertial forces to viscous

forces. More simply, it tells us if the fluid flow around a rocket

is Laminar (smooth) or Turbulent (rough). Laminar flow, low

Reynolds numbers, is dominated by viscous forces. Flow is

said to be turbulent for Reynolds numbers greater than

500,000. Turbulent flow is dominated by inertial forces which

produce eddies, vortices, and flow instabilities.

݉ݑ݊ݎܾ݁ሻ ݏ݈݀݋݊ݕܴ݁ሺ ݒ ߤ ൌ ܮܸ ൌ ܮܸߩ ܴ݁

(μ = dynamic viscosity, ν = kinematic viscosity, ρ = fluid density,

V = mean fluid velocity, L = a characteristic linear dimension).
       

                 

               

             

             

                     

             

           

             

               

               

          

  

   

   

           

  

     

                               

                                         

                            

                                     

              

     

           

           

           

       

  

 

 

 


 


 


 

 

 

 

P.12.1. CD vs. Mach Analysis

A more difficult to develop but useful tool in

analyzing your rocket’s performance isthe CD vs.

Mach plot. As a rocket’s speed increases,

different types of drag become prominent. The

two graphs at the right are CD vs. Mach plots for

a rocket developed at UAHuntsville. As the

rocket reaches the transonic region (around

mach 0.9), wake drag increasessignificantly. This

translates to a significant increase in the amount

of energy or thrust needed to maintain or

accelerate beyond this point.

is the ௗ೑ሺ್೚೏೤ሻ ܥ	஽is the total drag coefficient, ܥ

body drag due to friction, ܭ ௙is an interference

is the fin drag due to the friction, ௗ೑ሺ೑೔೙ೞሻ factor, ܥ

is drag based on protrusions (rail buttons), ௗ೛ೝ೚

ܥ

represents the drag based on excrescences ௗ೐ ܥ

and ௗ೅ isthe base drag, ∆ܥ ௗ್ (scratches, joints), ܥ

are transonic and supersonic wave drag. ௗೄ ∆ܥ

Each term in this equation has their own set of
 

equations in order to calculate the different
 

values.
 

P.12.2. Fin Flutter Analysis

Unsteady fin flutter occurs when the frequency of vibration associated with flapping and twisting is small

relative to linear flight speed. An excessive amount of fin flutter can result in a failure of the fin, i.e. shear,

deformation, dislocation, etc. Supersonic flight amplifies these effects. Fin size and composition is crucial

to reducing the effects of fin flutter. Fins are the main control surfaces of the rocket. Their failure can

result in the loss of the vehicle.

Theodorsen methodology is one

way of calculating the speed at

which fin flutter will begin to

emerge. That is at the point

when the vibrations become

undamped.
                                 

                                 

                             

                                 

                               

     

 

 

Theodorsen solution gives us the ability to predict the flutter speed for unsteady flutter. With this we can

see how much damping will occur and plot it versus flight velocity. Theodorsen uses multiple values of

reduced frequency to calculate velocity and damping. Theodorsen assumes that the fins are a solid

homogeneous material. The calculations require an input value for a Modulus of Rigidity (G). Below is an

example of the finished analysis plot. The fin being analyzed becomes undamped when the damping value

rises above zero.
     

                 

               

               

                     

               

               

               

                 

             

               

           

               

           

           

               

           

               

               

               

           

      

                               

                                 

                                     

                                     

                                       

                  

                               

                                   

                    

                                 

                                 

                               

                                   

            

                                     

      

                             

                             

  


 


 


 


 


 


 


 


 


 


 


 


 

 
 


 


 


 


 


 


 


 


 


 

 

 

 

 

 

 

 

P.13. Forces on a Rocket

In flight, a rocket is subjected to four forces: weight,
 

thrust, and the aerodynamic forces of lift and drag.
 

The magnitude of the weight depends on the mass
 

of all of the parts of the rocket. The weight force is
 

always directed towards the center of the earth and
 

acts through the center of gravity, the yellow dot on
 

the figure. The magnitude of the thrust depends on
 

the mass flow rate through the engine and the
 

velocity and pressure at the exit of the nozzle. The
 

thrust force normally acts along the longitudinal axis
 

of the rocket and therefore acts through the center
 

of gravity. The magnitude of the aerodynamic forces
 

depends on the shape, size, and velocity of the
 

rocket and on properties of the atmosphere. The
 

aerodynamic forces act through the center of
 

pressure, the black and yellow dot on the figure.
 

Aerodynamic forces are very important for model
 

rockets, but may not be as important for full scale
 

rockets, depending on the mission of the rocket. Full
 

scale boosters usually spend only a short amount of
 

time in the atmosphere and have controllable
 

nozzles (thrust vectoring).
 

In flight, the magnitudes and sometimes the directions of the four forces are constantly changing. The

response of the rocket depends on the relative magnitudes and directions of the forces, much like the

motion of the rope in a "tug‐of‐war" contest. If we sum the forces, being careful to account for the

direction, we obtain a net external force on the rocket. The resulting motion of the rocket is described by

Newton's laws of motion. Although the same four forces act on a rocket as act on an airplane, there are

some important differences in the application of the forces:

 On an airplane, the lift force (the aerodynamic force perpendicular to the flight direction) is used

to overcome the weight. On a rocket, thrust is used in opposition to weight. On many rockets, lift

is used to stabilize and control the direction of flight.

 On an airplane, most of the aerodynamic forces are generated by the wings and the tail surfaces.

For a rocket, the aerodynamic forces are generated by the fins, nose cone, and body tube. For

both an airplane and a rocket, the aerodynamic forces act through the center of pressure (the

yellow dot with the black center on the figure) while the weight acts through the center of gravity

(the yellow dot on the figure).

 While most airplanes have a high lift to drag ratio, the drag of a rocket is usually much greater

than the lift.

 While the magnitude and direction of the forces remain fairly constant for an airplane, the

magnitude and direction of the forces acting on a rocket change dramatically during a typical

flight.
       

                                 

                             

                               

                              

                                 

                                       

                             

                                     

                               

                           

   

                           

                               

                                   

                                       

                                     

  

          

                                 

                                 

                      

 

 

 

P.13.1. “Design To” Loads Analysis

Throughout a rocket’s flight, there are several specific cases that are of interest because they bracket the

rocket’s “design‐to” loads sets. This section will examine two of them – maximum acceleration and

maximum velocity. The analysis of these cases will consider aerodynamic data and the data established in

the rocket’s mass budgetstatement. Another Excelspreadsheet can be developed to manage this analysis.

There are three types of loads that are commonly calculated – axial, shear, and bending moment. Axial

loads are those loads that act along the major axis or centerline of the rocket. Shear loads are those loads

that work orthogonally to the rockets centerline. Bending moment loads (torques) are those that cause

the rocket to bend. Moments and torques are measured as a force multiplied by a distance so they have

units of inch pounds force (in‐lb) or Newton‐meters (Nm). We will constrain the analysis to two

dimensions so that we are only working with one shear and one moment load.

P.13.1.1. Maximum Acceleration Analysis

The rocket may experience the maximum axial compression and/or maximum shear and bending moment

when it reaches maximum acceleration. Some positive margin can be built into the loads analysis by

performing the analysis at 120% of the maximum T/W. That will yield a more conservative answer and the

analysis doesn’t have to be as high fidelity. For every flight station of the rocket, take a summation of the

contributions of the elements at that flight station. That task alone is not easy but is fundamental to the

analysis process.

ܯ ௜ൌ ∑ ݉ଵ௜ ൅ ݉ଶ௜ ൅ ݉ଷ௜ ൅⋯൅݉௡௜ (For all flight stations)

Below is an example of the axial loads analysis at the point of maximum acceleration. This information

reveals that trend in increasing axial loads moving from the nose aft. Vehicle interfaces are labeled for

easy reference to show loads at specific points on the rocket.
                                 

                               

                                   

                                 

                               

                                 

                  

Using the same seed data, the shear and moment plot below was developed. The plot reveals some

unique trends. The shear and bending moments where calculated using the CG as the reference point

since the vehicle will be rotating about this point during flight. The shear load peak and the bending

moments approach zero at the CG. Notice the bending moment loads are high at the two airframe

interfaces. This is an important piece of information to have when designing the interface. Also notice

that the Normal Force (Aero loads) are much less significant than shear and bending loads because the

vehicle is still moving very slowly at this point.
     

                           

                             

                                     

                             

                               

                                   

  

                             

                                 

   

 

 

 

P.13.1.2. Maximum Velocity Analysis

The rocket may experience the maximum axial compression and/or maximum shear and bending moment

when it reaches maximum velocity. The same analysis was performed for max velocity considering the

velocity, flight angle, and altitude at the moment of max velocity. For this rocket, max velocity is also the

moment of max‐Q or maximum dynamic pressure, the analysis confirms this. Notice that the maximum

bending moments occur at the rocket’s fins. The nosecone’s geometry has a pronounced effect at this

point as well, but the highest loads recorded in this analysis are lower than those recorded at maximum

acceleration.

What has been shown is that the maximum acceleration loads set brackets the “design to” requirements

for the rockets airframe and the max velocity loads set brackets the “design to” requirements for the

rocket’s fins.
   

   

   

       

   

   

   

   

   

   


 


 


 

 
 


 


 


 


 


 


 


 


 


 


 


 


 

Recovery 

Systems 

Parachutes
 

Parachute Protectors
 

Shock Cords
 

Quick Links
 

Single/Dual Event Recovery Systems
 

PerfectFlite StratoLogger
 

Batteries
 

Switches
 

Ejection Charges
 

E‐Matches
 

Shear Pins
 

Parachute Selection
 

Parachute Folding
 

Folding Instructions
 

Parachute Care
 

Recovery Exercises
 
           

   

        


 


 

NASA High Power Rocketry Video Series
 

Counterpart Documents
 

Written by Daniel Cavender
                                 

                                   

                                 

                                   

                                   

                       

                         

                             

                               

     

             

                    

                       

                 

                 

               

               

                 

                     

            

             

   

           

   

   

           

 

 

 

 

 

High‐powered rockets are required to have a recovery system. This section will help teach you how to

design a recovery system for your rocket. You will learn about the hardware needed to build a recovery

system, how to apply Newton’s 2nd Law of Motion to calculate the parachute size needed to safely

recover your rocket, and how to use the Ideal Gas Law to appropriately size black powder ejection charges

to deploy your recovery systems. This section will also cover the electronics you will use to control the

recovery system, and how to test that system safely on the ground.

Recovery Hardware

There are four primary hardware components common to most traditional rocket recovery systems:

1. Parachutes

2. Parachute Protectors

3. Recovery Harness

4. Quick Links

This section details each component. You will learn the purpose of each component, general material

selections, and construction. Later in this section, you will learn how to appropriately select hardware for

your rocket project.

Parachutes

Parachutes are the most commonly used recovery

device in high powered rocketry. A parachute is a high

drag device that decelerates the high speed

descent of the rocket by producing a force that

opposes the weight of the rocket. The effectiveness of

a parachute depends on velocity, air density,surface or

“reference” area, and a drag coefficient. A drag

coefficient is a dimensionless quantity that is used to

quantify the drag of resistance of an object in a fluid

environment such as air. For non‐ streamline objects

like parachutes, the drag coefficient can be greater

than 1.

High‐powered rocketry parachutestypically have three

major features.

1. Canopy

2. Support lines

3. Steel connector link

Rocket with drogue and main chute

deployed.
                                   

                                 

                                   

                                   

                                           

                                       

                                       

   

                   

               

                 

                 

                 

             

           

             

               

                 

     

   

                    

                

                     

           

             

                   

                     

               

                       

                   

               

               

                           

  

 

 

 

 

 

 

 

 

The canopy is made of several rip‐stop nylon cloth panels, or gores, sewn together to form a round,

cruciform, annular, or other shaped canopy. The support lines are attached to the outer edge of the

canopy. The steel connector link gathers all the support lines together and can be connected to the

rocket’s recovery harness. Most of these connectors also have a swivel built in to aid in stability. Some

parachute have an apex vent, a small hole in the top of the canopy that allows small amounts of air to spill

out from the top of the canopy adding to its stability. Otherwise the parachute will rock from side to side

to dump air out from the bottom sides of the canopy, which would cause the rocket to swing like a

pendulum.

Parachute Protectors

Nylon cloth is susceptible to melting and charring. It is

necessary to protect your recovery system from the

hot gases and any burning debris that are generated

by the ejection charge. A flameproof Aramid cloth or

Kevlar cloth will protect the parachute from these hot

gases and burning debris. Other options include

deployment free bags (D‐bags). D‐bags provide

parachute and support line protection and can insure

a reliable and orderly deployment. Great care should

be taken with both techniques, do not wrap the

parachute too tightly.

Recovery Harness

A “recovery harness” is generally a long length of static

cord that attaches structural components that

separate as part of the recovery system. Typical

materials for a recovery harness are Aramid/Kevlar,

Kevlar/Fiberglass, and nylon. Each end is typically

secured by quick‐link to a u‐bolt or eye‐bolt that is

rigidly mounted to a bulk plate on an avionics bay, nose

cone, or booster. The main parachute is generally

attached to a loop in the shock cord which is tied just

below the nose cone by a quick‐link. The length of

recovery harness required will be the subject of

empirical testing and evaluation. Some shock cords

are as short 12 ft. and others can get as long as 100 ft.!
               

               

               

                   

                     

               

                 

                   

               

                 

                   

                 

               

               

             

                 

                   

               

               

                 

             

                 

               

                 

               

                 

             

                               

                             

                               

               

             

 

 

 

 

 

 

 

The recovery harness can be bundled into groupings

using rubber bands or masking tape. This technique

helps to dissipate the momentum of the separating

components when they are ejected. In the photo to the

right, the shock cord was bundled into four 10 feet long

lengths that were folded in 8”  ‐ 10” lengths and

wrapped a couple of times with masking tape. During

deployment, energy is used to tear the tape to release

more cord. This technique performed very well in

flight, dissipating momentum of the two 25 lbm rocket

sections that were ejected at 200 lbf before the shock

cord became taut. Recall that nylon is susceptible to

melting and charring. Take measures to protect nylon

cords and inspect all shock cords before flights.

Quick‐links:

Quick‐links make connecting and rigging a recovery

system very easy. There are many different types of

quick links available commercially. Always use

quick‐links with a locking gate to help prevent the

harness from slipping free. Also, the bi‐products of

black powder ejection charges are acidic and will cause

corrosion. While zinc‐plated steel quick‐links are safe

for many flights, inspect the levels of corrosion and

clean all metallic hardware between flights. Take care

in choosing a quick‐link that will safely carry the

maximum expected load that will be experienced. Too

small of a quick‐link may yield under heavy loading

such as when the main parachute opens.

Shock cord bundle courtesy of the Rocketry

Forums.

The quick links attach the recovery system to the rocket’s structures. There are several hard points

available on the rocket’s bulk plates and/or centering rings. These hard points generally consist of eye‐

bolts or U‐ bolts; U‐bolts are preferred on large rockets. Eye‐bolts should be closed and/or welded closed

to prevent the recovery harness from slipping free.
	 	 	

                             

                     

         

               

               

                 

                 

                 

                   

               

                 

                 

                   

   

                                   

                                 

                                       

 

 

Recovery Systems Overview

High‐powered rockets typically have one of two types of recovery systems ‐ Single Event Recovery or Dual

Event Recovery. This section outlines the general systems and their purposes.

Single Event Recovery System (SERS)

A typical Single Event Recovery System ejects a

parachute at apogee. This can most commonly be

achieved by using a motor ejection charge. Most low

to mid power rocket motors have this capability. At

motor ignition, the propellant and a delay grain begin

to burn. The delay grain burns slowly. Once it burns

through, the ejection charge is ignited and the

parachute is deployed. If the timing is correct, this

happens near apogee. SERS is the simplest recovery

system and is good for low altitude flights on small

launch fields.

The plot below shows the trajectory of a rocket with a single event recovery system. The rocket reaches

apogee and deploys a parachute using the motor ejection charge. The rocket then descends slowly at 20

fps. With an apogee of 3000 feet, it takes two and a half minutes for the rocket to touch down.
         

                 

                  

                          

                 

               

             

                 

                 

                 

                 

                 

           

       

     

                       

                   

                       

                   

                           

           

  

  

  

   

 

 

 

 

 

Dual Event Recovery System (DERS)

Larger rockets with higher apogees should use a Dual

Event Recovery System. A typical DERS has one event

at apogee and the second at a much lower altitude,

typically 700 feet or more Above Ground Level (AGL),

and requires electronics do to so. This recovery

technique significantly reduces the recovery area by

allowing the rocket to fall much faster from apogee

and deploying a main parachute much closer to the

ground. The 1st event recovery system is typically a

long length of shock cord and perhaps a drogue

parachute. The 2nd event recovery system is the main

parachute which slows the rocket down considerably

for a safe touchdown.

Dual Deploy Plot

The plot above shows the trajectory of a rocket using a dual

event recovery system. The rocket reached an apogee of 4800

feet. It then deployed a drogue that slowed the descent to 90

fps. At 1100 feet, the main parachute deployed, furtherslowing

the decent rate to 18 fps. It took only one and a half minutes

for the rocket to touch down.

Booster

Drogue

Main FWD Airframe Parachute

Nose Cone
                                 

                                   

                                 

                               

                               

     

                               

                           

                                       

  

 

A rocket equipped with a typical dual event recovery system has this general layout. The main parachute

is generally forward of the electronics bay. This adds advantage to the rocket’s center of gravity and hence

the rocket’s stability margin by having the larger and heavier of the recovery devices far forward. The

electronics bay is generally between the two parachutes. This adds advantage to the locations of the

recovery ejection charges. The charges are generally placed in cups on the electronics bay’s end closures

or bulk plates.

The system level diagram below details the dual event recovery system’s configuration. This system is a

fully redundant recovery system. There are two altimeters which each have a dedicated battery and

switch. Each altimeter has its own set of recovery charges to fire. There are four charges in total in the

rocket.
                                   

           

The diagram below shows three different ways the dual event recovery system's hardware may be

configured. Each has benefits and risks:
     

                 

             

             

               

                   

           

             

                

             

           

                 

   

                 

                     

                          

                    

                 

             

         

             

               

               

     

   

               

             

             

     

             

               

               

                

                   

           

 

 

 

 

 

 

 

 

 

The Avionics Bay

Avionics refers to any electronic systems flown on a

rocket, whether they are flight computers, guidance

and control systems, telemetry systems or payloads.

These systems are typically built into an Electronics

Bay. An ‘E‐Bay’, is a subsystem of a high powered

rocket that typically contains altimeters, batteries,

and switches. The Recovery Systems Section details

the discrete components. Thissection covers how the

components become systems. A typical E‐Bay is

comprised of three structural components: the

housing, a forward and aft end‐cap and an avionics

sled.

E‐Bay Housing

The E‐Bay housings is typically built from a coupler

tube and can have a collar made from a segment of

airframe that is epoxied to the middle of the

coupler, and allows direct access to the switches

that power on the altimeters. The collar also supports

static pressure ports that equalize the housings

interior pressure with the exterior atmosphere.

Generally, rocket builders follow the convention that

when joining airframes with a coupler, the coupler

should extend at least one airframe diameter into

each joined segment.

End Caps

The E‐Bay end‐caps seal the housing from hot

ejection gases, separate the rocket’s volumes, and

support the recovery harness hard mounts, charge

cups, and all‐ threads. Typically, end‐caps are made

from G‐10 fiberglass bulk plates or plywood. All‐

threads act as a two‐force member that connect

both end‐ caps and carry the recovery harness load

through the E‐Bay. End‐caps should create a good

seal around the end of the housing to prevent hot

gas seepage from the ejection charges.
   

                 

                   

                 

           

                         

                   

               

                   

               

           

                 

               

             

  

 

 

Avionics Sled

Typically, the avionicssled is a G‐10 fiberglass board

or boards that mount in the avionics by sliding onto

the all threads that connect the end plates. The

avionics electronics, batteries, and switches are

mounted to the sled and wired together to

form systems. The avionics sled in the photo to the

right is mounted onto 1⁄4” diameter all‐ threads using

1⁄4” I.D. G‐10 fiberglass tubes that are epoxied to the

corners of the G‐10 boards. This simple sled

supports only altimeters, batteries, and switches.

This sled was designed to slide into the avionics

bays of several different rockets, allowing the same

electronics to be utilized by several different

rockets.
                                   

                           

                             

                                   

                      

                           

                         

           

                   

                 

                     

                   

               

                       

           

                   

             

               

           

             

                 

                 

                   

            

                 

        

   

     

       

         

         

       

       

   

   

 

 

 

 

Recovery Electronics

Beyond the hardware of the recovery system, this section will detail some of the electronics you will need

to be familiar with such as the PerfectFlite StratoLogger rocket altimeter, batteries, and switches.

PerfectFlite StratoLogger

Dual Event Recovery Systems require the use of electronic devices called Altimeters that can determine

altitude and initiate events at desired altitudes. It is common to outfit your rocket with at least one

PerfectFlite StratoLogger or other altimeter. The PerfectFlite altimeters are powerful robust commercial

altimeters. They support deployment event programmable settingsfor the main ejection charge from 100

feet to 9,999 feet AGL. The default setting for the drogue is apogee.

StratoLogger Features:

A: Battery Terminal

B: Power Switch Terminal

C: Main Ejection Charge Terminal

D: Drogue Ejection Charge Terminal

E: Data I/O Connector

F: External Audio Connector

G: Beeper

H: Preset Program Button

The pressure sensor of the PerfectFlite StratoLogger

works to 100,000 feet MSL and its stores over 9

minutes of flight data at 20 Hz (Hertz ‐ samples per

second). All of the data is stored in a nonvolatile

memory and is preserved even if power is lost. The

PerfectFlite’s robust power supply is not affected by

up to two seconds loss of power in flight and will fire

10 parallel‐redundant e‐matches even after 24 hours

of operation on a standard 9V battery. The default low

battery alarm (continuous tone) is set at

8.4 V. The PerfectFlite StratoLogger produces a firing

current of 10 A (Amps) peak.

Altimeters, usually mounted in the rocket’s avionics

bay, need to sample the outside air pressure. Your

rocket will need a static pressure port along the

outside to allow the inside pressure to equalize to the

outside pressure. Be sure to check the manufacturer’s

guide to determine the proper number of holes and

how they are sized.
     

         

             

     

Other Avionics Devices

RRC3 Altimeter G‐WIZ Avionics Bay

ARTS2 Flight Computer AED Electronics R‐DAS Tiny

Apogee Altimeter One PerfectFlite StratoLogger
                                

                               

                                   

                             

                             

                   

                             

                         

                             

                             

             

                         

                                                   

                               

                           

                       

                                 

                         

               

                   

               

                 

               

                 

             

                 

                     

               

                   

                 

                 

           

               

               

                 

             

       

 

 

 

 

 

 

 

 

Batteries

Typically, rocket builders prefer each altimeter have a dedicated battery and switch. There are two main

types of batteries used in high‐powered rocketry: primary and secondary. Primary batteries, such as a 9V

alkaline battery, should be used once and then discarded. Even if never taken out of the original package,

primary batteries can lose 8% ‐ 20% of their original charge every year when stored at room temperature.

This “self‐discharge” rate is known to occur due to a non‐current producing side chemical reaction which

occurs within the cell even if no load is applied.

Secondary batteries, like Nickel Cadmium (NiCad) or Lithium Polymer (Li‐Po) batteries are designed to be

rechargeable and used multiple times. Secondary batteries weigh less than primary batteries and

manufacturers can shape them however they please, but they are more expensive than primary batteries,

and some require sophisticated chargers to safely recharge them. Improper use or charging of some

secondary batteries can result in fire or explosion.

Secondary batteries self‐discharge more rapidly than primary batteries. A freshly charged NiCad battery

can lose 10% of its initial charge in 24 hours, and discharges at a rate of about 10% every month

thereafter. Most Li‐Po batteries have reduced self‐discharge rates to a relatively low level but are still

poorer than primary batteries. Even though secondary batteries have their energy content restored by

charging, some deterioration occurs on each charge/discharge cycle. Secondary batteries, like Li‐Po

batteries, are gaining favor in the world of high powered rocketry where the advantages of both lower

weight and greatly increased run times can be sufficient justification for the price.

Switches

Typically rocket builders prefer to turn on their

electronics from the outside of the rocket once it is

placed on the launch pad. This method maximizes

battery life and is safer than activating the electronics,

which are capable of initiating the black powder

charges, while the rocket is still being handled or

transported. The switches can either be surface

mounted to the airframe of the rocket, or mounted

inside the rocket with an access hole or panel. The two

categories of switches used on high powered rockets

are the Single Pole Single Throw (SPST) and the Dual

Pole Single Throw (DPST). The Single Pole Single Throw

(SPST), is a simple on‐off switch where the two

terminals are either connected together or

disconnected from each other. The Dual Pole Single

Throw (DPST) is equivalent to two SPST switches

controlled by a single mechanism. In these two

categories, there are toggle switches, push button

switches, and selector switches.
	 	 	

       

       

           

       

           

           

       

   

   

                     

            

                   

   

                                           

                                         

                                      

                                  

                                        

                                             

             

  

                                       

                                  

                                  

                       

                 

                       

                       

                           

                     

                   

                 

                       

       

 

 

 

 


 

 

 

 

Ejection Charge Sizing

ܴߨ ൌ ܸ : ݉ݑ݈݋ܸ݁ ݅ ଶ ݊݅ 12.5 ൌ ܮ ଶܮ

஺ ൌ ଶ଴଴௟௕௙ ൌ 16 ݌ݏ ሻమ గሺଶ௜௡

ൌ ܲ ݁ݎݑݏݏ݁ݎܲ ி

൰ ൌ 0.1ܮ

12.5݅݊ ଶܮ ൬ ݏܽ݉ݎ݃ 454

1	݈ܾ݂

ܸܲ

݈ܾ݉ ܴ௢3307 ∗ 266 ݈ܾ݂	݅݊ : ݓ݋ܲݎ݀݁ ݈ܽܿ݇ܤ ܴܶ ∗ ݅ݏ݌16 ൌ ൌ ݊

A black powder charge is the most common and

reliable method of ejecting a parachute from your

rocket. In your rocket, the motor’s ejection charge will

ignite and generate hot gases that pressurize the

rocket’s airframe, and exert a net force on the bulk

plate of the nose cone. This net force will eject the

nose cone, shock cord, and parachute out of the

rocket airframe. This happens because the rocket is

obeying the Ideal Gas Law.

The Ideal Gas Law is the equation of state for a

hypothetical incompressible or “ideal” gas. The state

of an amount of gas is determined by its pressure,

volume, and temperature.

The modern form of the Ideal Gas Law equation is PV = nRT where P is the absolute pressure of the gas,

V is the volume occupied by the gas, n is the amount of substance (in this case the substance is black

powder), R is the gas constant, and T isthe absolute temperature. The equation can be reordered to solve

for n directly and known values substituted. The design pressure is determined by the desired net force

on a surface divided by the area of that surface. Typical net force values for a 4 inch diameter rocket

range from 100 lbf – 200 lbf. This translates to a typical pressure range of 8 to 16 psi. Also, black powder

charge amounts are typically reported in grams.

:
 

The reduced equation for this case states that 0.1 grams of black powder is required for every 1 inch of

airframe containing the recovery system. Therefore, if L=20 in., then 2.0 grams of black powder isrequired

to eject the recovery system with 200 lbs of force. This theoretical value should now be tested.

Typically, rocket builders use a charge cup or well to contain the

measured amount of black powder for the ejection charges.

Everything from PVC end caps, brass pipe fittings, to a rolled length

of blue masking tape can be used. Some fixed volume charge cups

will require a filler of some type to occupy the empty volume in the

cup once the black powder and e‐match have been installed. Rocket

builders typically use soft foam ear plugs or shredded housing

insulation material more commonly called “dog barf”. Cannon plug

covers, electrical tape, masking tape, and duct tape can be used to

seal the charge cups.
                       

                                 

                                   

                                     

                                 

                               

                       

   

                               

                     

                             

                               

                                   

         

                                 

                                      

                               

       

  

	 	

 

 

 

E‐Matches

Electric matches, commonly called “E‐Matches”, are a universal initiator of many rocketry pyrotechnics

and motors. A typical e‐match is made from a thin nichrome (nickel‐chromium) wire laminated to a small

nonconductive flake of fiberglass. Each end is soldered to one wire of a two conductor solid core copper

shooter wire. The nichrome bridge is dipped into a pyrogen formula that dries hard and lookslike a match,

hence the name. E‐matches are typically high current or low current. Kits for making your own e‐matches

can be purchased on the internet or you can purchase manufactured E‐matches from most vendors on

launch day. E‐matches can also be augmented to serve as motor igniters.

Shear Pins

Shear pins are generally used on mid and high powered rockets to prevent dynamic separation or

premature/incomplete deployment of the recovery system. Dynamic separation occurs when a rocket

separates in the coasting phase because the different sections are decelerating at different speeds. An

example would be when a rocket’s booster section separates from the forward airframe or nose cone

because the fin drag or the base drag effect creates a significant enough force to overcome the frictional

force keeping the sections together.

Rocket builders generally use small nylon machine screws as shear pins. A #2‐56 nylon machine screw has

an average shear strength of 25 lbs. A #4‐40 nylon machine screw has an average shear strength of 40lbs.

Typically, rocket builders will use two #2 nylon shear pins for each separating section (cumulative shear

strength of 50 lbs).
                                   

                                   

                               

   

                                     

                                         

                                     

                             

                                     

                       

   

                                     

     

                                           

                                         

         

  

 

 

 

Parachute Selection

Every rocketeer wants to safely recover their rocket so they can fly it again. Selecting the right size

parachute is the first step to a successful recovery. There are two good methods to help determine the

appropriate size of your parachute – the Kinetic Energy Equation and Newton’s 2nd Law of Motion.

Kinetic Energy

Kinetic Energy (KE) is the energy of motion. There are many forms of KE, but for simplicity, this section

will focus on translational motion – the energy of motion linearly from point A to point B. KE is a scalar

quantity typically shown in units of foot‐pounds force (ft‐lbf) [English], and Joules (J = Nm) [SI]. The KE of

an object is dependent upon two variables: the object’s mass (m) and the velocity (V).

The 60 lb. rocket has twice the KE of the 30 lb. rocket, therefore it impacts the ground twice as hard. In

order for the two rockets to have the same KE at touchdown, the 60 lb. rocket would need to have a

descent rate of 14 ft/s.

ܸ݉ଶ 1ൌ ܧܭ 2

Two rockets of the same final descent rate and different masses will have different KEs. The same is true

of two rockets that have the same mass but different descent rates.

Case 1:

Consider two rockets. One weighs 30 lbs and the other 60 lbs. They both descend under a main parachute

at 20 ft/s.

1

ܧܭଵ ൌ 2 ሺ30

1

ܧܭଶ ൌ 2 ሺ60

ଶ 1	݈ܾ݂ ݏ ቆ ቇ ൌ 186.3	݈ܾ݂ 32.2 ݈ܾ݉ ݂ݐ

ଶ

ݐ݂ ൰

ݏ

݈ܾݏሻ ൬20

݈ܾ݂

ଶ 1	݈ܾ݂ ݏ ቆ

ଶ

ቇ ൌ 372.7	 32.2	݈ܾ݉ ݂ݐ ൰ ݂ݐ

ݏ

݈ܾݏሻ ൬20
   

                                       

  

                                     

                                       

                                   

                                 

                                 

                                   

                                 

             

  

 

 

 

 

Case 2:

Consider two rockets that both weight 30 lbs that descend under a main parachute at 17 ft/s and 22 ft/s

respectively.

ଶ 1	݈ܾ݂ ݏ ቆ

ଶ

൰ ݂ݐ ቇ ൌ 134.6	 ܾ݂݈ ݏ 32.2	݈ܾ݉ ݂ݐ ሺ30 ܾݏ݈ ሻ ൬17

1

2 ܧܭଷ ൌ

ଶ 1	݈ܾ݂ ݏ ቆ

ଶ

൰ ݂ݐ ቇ ൌ 225.5	 ܾ݂݈ ݏ 32.2	݈ܾ݉ ݂ݐ ሺ30 ܾݏ݈ ሻ ൬22

1

2 ܧܭସ ൌ

The second rocket’s KE value is nearly twice that of the first. This case demonstrates a small change in

descent velocity has a more pronounced effect on KE than changes in mass of the rocket. An 18 lb rocket

descending at 22 ft/s would have the same KE as the 30 lb rocket descending at 17 ft/s.

The plot below compares different KE slopes and relates a rocket’s final mass to a touchdown velocity.

These plots demonstrate that setting a design constraint on a target Kinetic Energy, rather than a target

descent rate range, offers more control over the design of the recovery system by limiting the energy at

which the rocket impactsthe ground thusimproving safety and survivability. A good target KE range might

be 75 ft‐lbf (102 Joules) or less.
         

                               

                             

               

               

       

             

             

                     

           

	 	

                     

                

               

                     

                                     

                               

                                  

                                         

                                   

                               

                                 

                       

     

 

 

 

 

Newton’s 2nd Law of Motion

The rocket and parachute obey Newton’s 2nd Law of Motion. Newton’s 2nd Law (F=ma) states the

relationship between an object's mass (m) and its acceleration (a). The basic assumptions used in

calculating the descent rate of a rocket are:

1. The rocket descends at a constant speed (steady state)

2. The rocket’s mass is constant

3. The rocket moves simply downward (constrained to z‐axis)

4. The atmosphere is a continuum (constant air density)

∑ܨ ௓ൌ 0ܽൌ ݉

If you make these assumptions, there are only two forces acting

on the rocket: Weight and Drag.

∑ܨ ௓ܽൌ ܹ݉ൌ ܦ െ ሻ݁ݐܽݕݏݐ݀ܽ݁ݏݐൌ 0 ሺ

Drag is determined by Velocity, air density, reference area, and a

drag coefficient (cd). The equation for Drag is:

ௗܥܵ

ܸߩ ଶ

1

ൌ ܦ 2

Substituting the drag equation, Newton’s 2nd Law becomes:

ௗܥܵ

ܸߩ ଶ

1

2 ൌܦܹ ൌ

The equation is reordered to solve for the reference area (S):

2ܹ

ܵ ൌ ܥௗ

ܸߩ ଶ

Drag (D)

Weight (W)

Recall the drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance of an

object in a fluid environment such as air. For non‐streamline objects like parachutes, the drag coefficient

can be greater than 1. This value is determined empirically and can usually be found on a manufacturer’s

website.

Consider a descent rate range between 18 ft/s and 22 ft/s. If you make an initial guess and set your drag

coefficient to 2.0, you can determine a range to begin shopping for parachutes. For example, if you

estimate that your rocket will weigh 20 lbm and substitute these estimated descent rates, you can

determine the range in size parachutes needed. Once you find some parachutes in this range, you can

perform the calculations again using the specific parachute’s reference area and the manufacturer’s

calculated drag coefficient.
             

             

                                         

                               

                               

             

 

 

 

Upper Bound (Descent Velocity = 18 ft/s):

ܾ݈݉

ݐ݂ 2.0 ∗

ݐ݂ 18 ∗ ଷ ݏ

2ܹ

ܵ ൌ ܥௗ

ܸߩ ଶ

32.2	 ܾ݈݉ ൮

൘ ݐ݂

∗ݏ ݈ܾ݂ ଶ

32.2	 ܾ݈݉ ൮ 2 ∗ 20

൘ ݐ݂

0.075 ݏ ∗ ݈ܾ݂ ݈ܾ݂ ଶ

For this case, the rocket will require a parachute that has a reference area between 18 ft2 and 26 ft2

. Your

design will continue to mature throughout the design process and you will need to re‐evaluate your

parachute selection as you get better estimates for your rocket’s weight. Below are some examples of

typical rocket parachute characteristics from Sky Angle:

2 ∗ 20

݈ܾ݂ 0.075

Lower Bound (Descent Velocity = 22 ft/s):

ଶ ൲ ൌ 26.5 ݂ݐ

ܾ݈݉

ݐ݂ 2.0 ∗

ݐ݂ 22 ∗ ଷ ݏ

2ܹ

ܵ ൌ ܥௗ

ܸߩ ଶ

ଶ ൲ ൌ 17.7 ݂ݐ

ൌ

ൌ

Classic/Classic II Specs 36 44 52 60 

Tested* Load Capacity 2.7 - 5.7 4.4 - 9.5 6.8 -14.8 10.2-22.1 

Surface Area (sq. ft.) 14.2 21.1 29.5 39.3 

Suspension Line Length (inches) 36" 44" 52" 60" 

Tested Cd 1.34 1.87 1.46 1.89 

Classic Net Weight (oz.) 5.0 7.0 9.0 10.0 

Classic II New Weight (oz.) 8.4 10.5 13.3 18.2 

CERT-3 Size Large X-Large XX-Large Drogue 

Tested* Load Capacity 16.2-35.0 32.6-70.6 60.0-129.8 1.0-2.2 

Surface Area (sq. ft) 57.0 89.0 129.0 6.3 

Tested Cd 1.26 2.59 2.92 1.16 

Suspension Line Length (inches) 80 100 120 24 

Net Weight (oz.) 34.0 45.0 64.0 6.0 
	 	

                             

                                

                                 

         

   

                  

                     

                   

                     

                 

                   

             

   

                      

                    

                    

              

   

                     

             

  

 

Parachute Folding Instructions

These instructions demonstrate the procedures for folding a Sky Angle Classic II 36” parachute. These

procedures can be applied to almost every parachute, but may vary slightly depending on parachute size,

type, rocket diameter, and if you choose to use a deployment bag (D‐bag). Practice folding your parachute

many times to gain experience.

Step 1:

Lay the parachute on the ground. Gather the support

lines in both hands at the bottom of the canopy and

the bottom of the shroud lines. Remove any twists in

the lines. Stretch the lines out so they are taut. On

larger parachutes with long support lines, use a weight

to hold the steel connector link while you work with

the support lines from the canopy end.

Step 2:

Arrange the canopy so it lays flat on the floor. Neatly

tuck‐in the nylon fabric from the multiple parachute

panels (the material between the support lines) in

towards the center line of the canopy.

Step 3:

Fold the top of the parachute down to the bottom of

the parachute where the shroud lines attach.
   

                   

                 

   

                   

                   

     

                     

   

                

                          

                      

                     

             

                   

       

Step 4:

Fold the parachute in thirds by folding the top corners

in towards the center of the parachute as shown.

Step 5:

Using one hand to hold the parachute down, fold the

top half of the parachute down over the bottom half

of the parachute.

Step 6:

Flip the parachute over and roll it up into a cylinder

type arrangement.

Step 7:

Wrap the support lines around the rolled parachute.

A tight wrap with more turns will lead to a

smaller pack job with a slower opening. A loose

wrap will lead to a larger pack job with a faster

opening. The amount and tightness of the wraps

should be determined based on the desired fit in the

rocket and opening speed.
	 	

                                                  

                 

     

                 

                 

                     

                     

                 

               

                   

               

                   

           

     

               

                     

                 

             

       

                   

               

           

           

                   

       

         

               

   

 

 

 

 

Recovery System Testing

Before you fly your high powered rocket, it will be necessary for you to perform ground tests of

components or entire systems before risking the entire project.

Vacuum Chamber Test

A vacuum chamber test will prove that a pressure

based rocket altimeter is functional. The test can be

as simple as a single altimeter in a mason jar, using

a marinade syringe to pull air out, or as complex as

a full systems test of the entire rocket recovery

system. A simple visual indicator of an altimeter’s

health can be a Christmas tree light wired to the

ejection charge terminal blocks. The photo to the

rightshows one such test. Thistest is performed just

before the recovery charges are installed.

Ejection Charge Test

You will want to conduct several ejection charge

tests before flight. This full‐up test is the best way to

assess if the ejection charges are of sufficient size,

and to assess the configuration and effectiveness of

the recovery system setup.

The photo to the right was taken just after a

successful ground test of the rocket’s dual event

recovery system. The success criteria where:

 Both main and drogue systems deployed as

expected

 The parachutes were extracted from the

airframe

 The parachutes and shock cords were

suitably protected from the ejection charge

The tests proved the design ready for flight.

UAH SL 2011
	 	

                                     

           

                         

                       

                             

                   

                                 

                           

                                 

                         

                 

 

	 

	 

 

Parachute Care

Get the most life out of your parachutes and recovery hardware by taking care of them. These are some

suggestions that will extend their use:

	 Protect your parachutes from damaging hot ejection charge gases by using a Kevlar parachute

protector, piston system, recovery wadding, dog barf (i.e. spray insulation material) or a

deployment bag.

 Keep your parachutes indoors, dry and unfolded, when in storage. Take them out of your rockets

and wipe them off with a damp and lightly soaped rag.

 Fold your large parachutes on a large blanket or tarp when in the field (not on the ground). This

will reduce the odds of damage from FOD (foreign object debris) and keep them cleaner.

	 Use stainless steel hardware in your recovery system. It is a bit more expensive, but will resist the

effects of corrosion longer. Residue from black powder ejection charges will corrode other metals

quicker and you will find yourself replacing hardware more often.
     


 


 


 

Avionics Systems 

Materials:
 

Basic Electronic Circuits
 

Microprocessors
 
         

   

           


 


 

NASA High Power Rocketry Video Series
 

Counterpart Documents
 

Written by Daniel Cavender and Jason Winningham
	 	 	

                                    

                              

                                          

             

   

                                         

                                      

                                 

                                  

                              

                                        

                               

         

                                 

                              

                            

   

                                      

                                             

                                      

                                  

                                         

                                   

                               

   

                                    

                           

                                     

                                  

                          

                                        

                                

                               

                         

 

 

 

 

 

 

 

 

 

 

 

 

 

Basic Electronic Circuits

Basic electrical circuits operate on three variables – voltage, current and power. Voltage is a measure of

the electrical potential difference between two points. Current is the flow of electrons between two

points, and is equal to the time rate of flow of an electric charge. Power is the rate at which electrical

energy is transferred by an electric circuit.

Voltage (V)

A good analogy for voltage is dropping a ball from a cliff – the higher the cliff, the more energy associated

with a single ball. Voltage is a direct measurement of the amount of energy contained in a group of

electrons.

The two major voltage types are direct current and alternating current. Direct current (DC) is a straight

and level voltage which does not change over time. These are often seen in batteries, computer power

supplies, memory modules, cell phone backlights, and in anything which has a keypad or screen.

Alternating current (AC) is just what it sounds like – voltage swings from high to low, then back to high.

This process occurs rapidly, (60 times per second for household electricity). AC current is effective for

transmitting power over long distances.

Most payload applications will not use AC for anything, as sensors and other electronics operate on DC

voltages. Signals sent by microprocessors and other talking electronics are alternating currents. AC of this

type is critically important. How these systems work is covered in the Microprocessors section.

Current (I)

Current is a measure of the number of electrons per second which pass through a point. Keeping the cliff

analogy in mind, current would be how fast the balls are dropping off the cliff. It is a measure of how fast

electrical current is moving from one side to the other. An Amp [Ampere] is a measure of how many

coulombs of charge passthrough a point persecond. Most electronics used for payloads will be measured

in milliamps, which is .001 amps. So, 250 milliamps is .25 amps. A lot of small components each drawing

a few milliamps add up pretty quickly. A power budget is an absolute necessity in determining what type

of battery is needed and how long it will be able to keep the payload powered.

Power (P)

Power is used to determine how much heat will be generated by the electronics. On large scale,

complicated payloads this has to be watched very carefully, but for smaller microcontroller based

electronics it is not a huge concern. Payloads that operate under about 5 Watts usually will not generate

enough heat to melt anything. The largest heat concern on payloads would be a short circuit, which

absolutely dumps power. Short circuits occur continually with small custom made components, simply

because it is easy to cross wires and wire things backward. They may not always be fatal to the power

supply, but tiny little components cook themselves easily. Thisis an especially big concern when preparing

critical component right before launch. A common rule‐of‐thumb when working with circuits is that the

more expensive and critical a component is, the easier it will be destroyed.
	 	 	 	

                             

                                   

                                          

                             

                         

                                      

                 

		

                                     

                                

                                 

                             

                                     

                                  

                                  

                       

 

 

 

 

 

 

 

Laws of Basic Circuitry

Three rules dominate basic circuits. These are Ohm’s law, Kirchhoff’s voltage law (KVL), and Kirchhoff’s

current law (KCL). Ohm’s law states that the amount of current flowing through an object depends on the

voltage applied and the resistance of the object. This is usually used for figuring out what is going on in

a single simple component, or to determine what resistor is needed. Some components like thermistors

(resistors that change with temperature) or photoresistors (resistors that change based on lighting

conditions) can provide useful data using Ohm’s Law. This law is also highly useful when it is necessary to

change DC voltages from a high to low value.

ሺ ܱ݄݉ ᇱ

ሻܴሺܽ݊ܿ݁ݐݏ݅ݏܴ݁ ∗ ሻܫሺ ܥݐ݁݊ݎݎݑ ൌ ሻܸሺ ܽ݃݁ݐ݈݋ܸ ሻ ܮܽݓ 	ݏ

How this works in practical applications is fairly simple. Imagine a battery, wire, and a resistor. Wires are

designed with sufficiently low resistance, so any resistance from the wire can be ignored. To determine

how much current is going through the resistor simply apply a little algebra, and come up with:

ሻܴሺܽ݊ܿ݁ݐݏ݅ݏܴ݁ ൌ ሻܫሺݐ݁݊ݎݎݑܥ ݁݃ሺܸሻ ܽݐ݈݋ܸ

Assuming a 9 volt battery and 1,000 Ohm resistor [1K Ohm], the current would be:

ܸ	9݋ݏݐ݈ ܽݐ݈݋ܸ݁݃ሺܸሻ

ሻܴሺܽ݊ܿ݁ݐݏ݅ݏܴ݁ ൌ ݏܱ݄݉ 1000 ݈݈݉݅݅ܽ݉ݏ݌ 9 ൌ ݏ݌݉ܣ .009 ൌ ൌ ሻܫሺݐ݁݊ݎݎݑܥ

Being able to determine what the voltage across an object should be and what it actually is proves highly

useful when determining why a component is not working. Also, when the circuit is drawing excess

current the culprit may be identified by a low resistance reading. Alternatively, if a component is not

working, the voltage drop across it indicates whether it is connected correctly.
                               

                                        

                                        

                               

                                    

                               

                                         

                                         

                                   

                              

                                  

                                     

                                 

               

                                   

                                   

                                     

                                     

                     

        

 

 

 

Kirchhoff’s voltage law and Kirchhoff’s current law are both used for complicated circuits. His voltage law

statesthat for every voltage rise there is a voltage drop. The current law statesthat the amount of current

going into a point is the same as the amount of current leaving the point. Using these two laws enables

usto connect multiple batteriesto multiple resistors and predict what current istravelling where. Working

with these two laws can get pretty complicated. The best method of determining what is occurring in a

circuit, when more than a few components are in use, is to use a multi‐meter or oscilloscope.

Here is an example of a fairly typical KCL/KVL circuit as it would be analyzed in an entry level circuit class.

Several batteries and resistors are wired up in a lessthan ideal fashion. In practice, it israre to see anything

like this, but if you did, these two laws will help you to analyze what is going on.

Two particularly useful applications of Kirchhoff’s laws are shown below. Wiring two batteries in series

increases the voltage across the resistor. Wiring two batteries in parallel keeps the voltage the same as

with just one battery, but allows powering the circuit for twice as long. These two methods are seen in

construction of all types of batteries. Cutting open a battery exposes a litany of cells(mini‐batteries) which

are joined in series to raise the voltage.

Series Batteries Parallel Batteries

The easiest way to determine the amount of current drawn is to calculate (or read from the Datasheet)

the amount of current each component takes and add them all together. However, it is unusual for the

calculation to be so simple. Usually it takes a little testing to determine just how much current the circuit

is drawing. The most accurate method of determining how much current is being drawn is to take a direct

measurement. The multi‐meter section will show you how to do that.
                               

                                              

                               

                       

Symbols

Calculations

The level of difficulty in calculating the output of a circuit can range from easy to considerably

complicated. The objective is to keep it as simple as possible. It may be a neat trick to be able to

calculate what is happening with 50 components, but when a measurement will provide the same data,

there is no reason to run the risk of an oversight or miscalculation.
                 

                       

                   

                     

                     

                            

                

                            

                       

                 

                   

     

                 

                     

                 

                                 

                                   

                                 

                                     

                                 

         

   

   

 

 

 

 

 

Multimeters

A multi‐meter is a tool that allows measuring electrical properties

around a circuit. Typically, multi‐meters are used to check DC or AC

voltage, the amount of electrical resistance between two points, and

whether or not two wires are connected (called a continuity check).

Multi‐meters provide very basic information, usually in the form of a

DC voltage or DC current. This is a critical piece of hardware for testing

and troubleshooting. Using a multi‐meter involves placing the probes

on two points in the circuit to measure the value of interest. An easy

way to remember how to make a measurement properly isthat voltage

is measured across something and current is measured through

something. Trying to measure the current across something can

destroy an inexpensive multi‐meter.

In making voltage measurements remember that the voltage test

feature causes the multi‐meter to have an extremely high resistance so

that the circuit is not disturbed. When making a current measurement,

the multi‐meter goes into a very low resistance state to prevent disturbance of the circuit. A high end

multi‐meter has some built in features to keep the instrument from being damaged if placed in a circuit

improperly. When it is needed to change from taking a voltage measurement to taking a current

measurement, the probes must be removed and connected in a different fashion. It is a good idea to

check to see what configuration the multi‐meter is in before starting to measure in order to prevent

permanent damage to your instrument.

Multi‐meter image courtesy

of Mastech Electronics.
                             

                                  

                           

                                     

                               

                               

                               

                                       

                                   

                                          

                               

                                     

                                       

                                  

                               

                                      

                   

 

 

 

 

 

Oscilloscopes

Oscilloscopes are used to determine waveform characteristics. This means whether or not wavesthat look

like squares are actually square shaped. These instruments are also helpful when checking to see if the

serial communications are acting as you think they should. Oscilloscopes are used for checking the

frequency of a signal and the signal strength at various places. They require that at least two points be

checked at the same time. There are some fairly advanced features on most oscilloscopes to allow

checking several different locations on the same screen, as shown in the picture. The most important

settings are the test locations and the trigger voltage. The trigger voltage tells the oscilloscope exactly

when to graph the circuit voltage. The scope takes a snapshot of the circuit over a brief period and displays

it on the screen. The screen is refreshed whenever the trigger voltage is crossed, either when the voltage

goes from below to above or above to below the trigger. You can set a small amount of offset on most

oscilloscopes when checking multiple channels. The two main controls, other than the trigger set, are the

sweep time and the volts per division. Changing the sweep time changes the amount of time each square

on the graph is worth in the X direction. Raising the sweep time has the effect of squishing the waveform

together on the screen. Raising the volts per division has the effect of squishing the waveform together

in the Y direction. Because using an oscilloscope allows very precise measurements of what is occurring

in the circuit can be made, it is a priceless piece of hardware for testing and troubleshooting. Even an

older oscilloscope, as shown below, will do just fine for most applications.
                           

             

         

           

           

                 

       

              

             

               

                 

         

           

                

                 

               

                 

                           

                 

                                 

                                   

                               

                         

                            

                            

                                 

     

                               

                          

                     

                                     

             

 

 


 


 

 

 

 

 

 

Microcontrollers

A microcontroller (uC or  μC) is a small

but complete computer on a single integrated

circuit (IC). A microcontroller contains a

processor core, memory for program execution

and program storage, and peripherals for

input/output (I/O). It can be used to construct a

complete system;sometimessuch arrangements

are called a “system on a chip”. Microcontrollers

are used in embedded applications, where this

small digital system is dedicated to a specific

task, and is usually a component in a larger

system.

Microcontrollers typically have much less

computing power than a microprocessor found

in a typical desktop computer. Clock speeds are

in the tens of MHz, and system RAM and

program storage areas are in the tens of

kilobytes. There is usually no operating system

(OS); when an OS is present, it is typically a
 

very small real‐time operating system (RTOS) designed for embedded applications.
 

Memory for program execution (what is thought of as “RAM” in a desktop computer) is usually SRAM

(static RAM). SRAM is slower than other memory architectures, but requires no management to

maintain its contents, so the overall system is simpler. To keep external component requirements low, a

microcontroller also uses non‐volatile memory to store the program onboard as well. Modern

microcontrollers usually use either FLASH or EEPROM memory for program storage. In addition, some

include additional non‐volatile memory for storage of non‐volatile user data. For example, the Atmega8

has 1 kilobyte of SRAM, 16kilobytes of FLASH for program storage, and 512 bytes of EEPROM for non‐

volatile user data.

Modern microcontrollers may contain a variety of I/O interfaces. Digital I/O’s, where each pin is either a

digital logic input or output (often configurable as either), is standard. Many microcontrollers include

more complex digital interfaces such as UARTs (universal asynchronous receiver‐transmitter, also known

as a “serial port” or “RS232 port”). An analog to digital converter (ADC) is often supplied as well, since

many microcontroller applications involve interfacing to analog systems.
	 	 	 	

                                   

                                   

                                     

                         

                               

                                         

                                     

                                     

                 

                             

                           

                           

         

 

 

Analog to Digital Converter

The ADC is an important part of many embedded systems. The signals we wish to measure are usually

continuous over a particular range of interest and a simple on‐or‐off digital input cannot tell us what we

want to know about the signal. Because a microcontroller is a digital system, we use an ADC to convert

this continuous signal into a digital representation that can be used by the microcontroller.

A typical ADC operates by successive approximation. In this method, a sample and hold circuit captures

the analog value. The ADC uses successive approximation register (SAR) and a digital to analog

converter (DAC) to convert a digital value to analog. This analog value is compared to the sampled value;

if they are not the same, the control logic generates another digital value and the processisrepeated until

the correct digital representation of the value is found.

Successive approximation analog to digital converter

A microcontroller may have multiple analog inputs, but usually has only one ADC and an analog

multiplexer (mux) to switch between the different inputs. While allowing cheaper construction of the

microcontroller, this means that only one analog signal can be sampled at a time.
                              

                           

                               

                               

                                     

                                    

                                     

                                    

                                            

                                     

                                

                 

                              

                                          

                                 

                                 

                                   

                         

                           

                                 

                                  

                               

                           

                           

                                       

                                         

                   

                                 

                                 

                              

                             

                                      

                             

                   

                          

                                    

 

 

 

 

 

 

 

 

 

 

 

 

 

Peripherals

A microcontroller is frequently interfaced to external devices. For instance, a rocket altimeter may use a

pressure sensor to convert barometric pressure into an electrical signal. The PerfectFlite altimeter

converts pressure into an analog voltage using a Freescale analog pressure sensor. This sensor output is

connected to a microcontroller's ADC input so that it can be converted to a digital signal.

Not only do the types of sensors available vary widely, but so does the level of analog and digital

components that are added to the sensor. For instance, a simple strain gauge is nothing more than a

resistor that varies with the force applied to it; in order to use this signal in a microcontroller, other

resistors, an amplifier, and an ADC must be used. In the example of the Freescale pressure sensor, the

device not only contains a strain gauge fabricated into a housing so that it measures barometric

pressure, it also containsthe bridge, amplifier and other hardware needed so that a simple 0V to 5V signal

is present in the sensor's output. More complex sensors may contain an ADC so that the microcontroller

can simply read a digital value from the sensor.

There are many other peripherals available for use with microcontrollers. For example, ICs with large

amounts of FLASH storage are useful to store data so that it can be retrieved at a later date. A system

may not use telemetry, or may gather so much data that the telemetry has insufficient bandwidth to

convey the data at the desired resolution or sampling rate. Examples of other peripherals are: external

UARTs, if interfacing to many RS232 devices such as GPS units or data radios; external ADCs, for increased

resolution or an increased number of analog channels; and digital I/O expansion devices.

Interfacing

There are many ways to interface digital peripherals. Some manufacturers design their own custom

interface and protocol. This can result in many hours spent with the vendor's datasheet learning to

interface the device. Some device interfaces are serial (meaning bits are sent down a single wire, one

after the other), or parallel (several digital signals travel down different wires at the same time).

Fortunately, there are some interface standards which simplify both the electrical and the software

interface to the peripherals. Two common interfaces are the Serial Peripheral Interface (SPI) and Inter‐

Integrated Circuit (I2C). SPI is a 4 wire interface that uses a shared serial bus among one or more devices.

It is full duplex, and some vendors support clock rates of 66MHz or higher. I2C is a two wire interface,

and the standard speeds are 100 kHz and 400 kHz.

ICs are usually not designed to have long wires connecting peripheralsto microcontrollers. If itis necessary

to run wires long distances (feet instead of inches), make sure your interface is designed for it.

Another interface standard is the RS232 serial interface. This was originally designed to transfer data

through a serial connection over longer distances (up to 1500 feet) between computers and peripherals

such as terminals, modems, and printers. It is commonly used in GPS units and data radios (such as the

Maxstream Xtend). RS232 is not only designed for longer distances, but interface ICs frequently have

added features such as electrostatic discharge (ESD) protection built in.

RS232 is a common pitfall for microcontroller users. Microcontrollersthat have UARTs provide logic‐ level

voltages and signals. This means logic 1 on the microcontroller is represented as 5V, and logic 0 is
                                       

                                   

                                   

                                

                             

                       

                           

                            

                               

                                   

                                

                               

                   

                                 

                          

                             

                                   

                                       

                                      

                       

             

                              

                          

                                 

                                   

                 

                     

                   

                             

                                            

                   

     

                         

                                 

                               

                               

                              

 

 

 

 

 

 

 

 

 

 

 

 

0V. On RS232, the logic 1 (known as “mark”) is typically represented by a voltage of ‐12V; a logic 0 (or

“space”) is +12V. Note that not only are the voltages quite different, but the logic is “inverted”.

Connecting an RS232 level device to a TTL device can result in permanent damage to the TTL device.

IC Packages

The physical packaging of ICs has changed dramatically over recent years. At one time, through‐hole (or

plated through hole, PTH, referring to the PCB construction) device packages such as DIP (dual‐inline

package), SIP (single‐inline package), TO‐series (commonly used for transistors), and common leaded

resistors and capacitors dominated industry. Asfabrication techniques have provided smaller and smaller

devices, the packaging for those devices has decreased accordingly. Surface mount technology (SMT, also

known as surface mount devices, SMD) dominates new IC designs. These devices are designed not to

mount through holes in the printed circuit board (PCB), but to be soldered directly onto exposed pads on

the board. The devices are small enough that the solder joint has sufficient mechanical strength to hold

the device. Some devices have no pins; these are known as “lead‐less”. Their electrical connection is

provided at exposed pads on the bottom of the device.

These SMT devices can be challenging, since a PCB must frequently be designed and fabricated in order

to experiment or prototype. Fortunately PCB fabrication services are available for prototype quantities

at reasonable prices and turnaround times. Some vendors provide “breakout boards”. A very small PCB

for a single surface mount IC, perhaps with some required resistors and capacitors, is used to “break out”

those SMT leads to a through‐hole connection that can be used to mount a header or wires that are used

to access the device. Some breakout boards are simple adapters to convert an SMT package to a DIP or

other through‐hole package. Breakout boards allow the development of complex payloads using SMT

devices without requiring the soldering of SMT components.

Microcontrollers are also frequently provided on a PCB with some minimal interface hardware. These are

known as development boards. A good microcontroller development board for beginners is the Arduino.

It is an open source project based on a board containing an Atmel ATmega microcontroller with a

minimum number of external devices required for a complete system. There is a free, easy to use,

software development environment; many daughterboards (known as “shields” in the Arduino

community) with peripherals and connectors mounted; and a large user community.

Software Development

Software is a critical component of a microcontroller system. Modern microcontroller development

environments usually provide a compiler for C or some other high level language, so the microcontroller

developer is no longer forced to code in assembly language. They also include an interactive

development environment (IDE) with a user‐friendly interface for editing, compiling, and downloading

programs to the microcontroller.

Just like structures, propulsion systems, and recovery systems should be planned carefully, software

should be carefully designed. The software system should be laid out in advance of any coding. Complex

areas of the algorithm should be developed in more detail until they can be easily coded.

Programming on a microcontroller should be carried out with special care, since there is no operating

system to monitor and report on the program. Programming errors can be very difficult to troubleshoot.
start 

sample A D C 

no 

pressuredecreasing?

yes 

launch detected 

sample & store pressure 

no 

pressure 

decreasing?

yes 

apogee detected 

sample & store pressure 

pressure 

inc r e a s i n g ?

no 

landed 

beep_altitude 

                     

     

                                          

Software should be designed and implemented carefully to avoid time‐consuming and frustrating

debugging efforts later.

A flow chart is a common tool for developing a program. Below is a flow chart for a basic altimetersystem.

yeyess
                                

                                

                           

                       

                                   

                                  

                                   

                                   

                                          

                                       

                                 

                                 

                             

  

                            

                                 

                          

                                      

                                 

                                

                                 

                 

                                     

                                 

                                      

                     

                                     

                               

                                    

                             

                     

                         

                                

                               

 

 

 

 

 

 

 

 

 

Telemetry

Telemetry is defined as measurement at a distance. In rocketry, telemetry can be used to provide in‐

flight reporting of launch vehicle status or payload experiment results. In some cases the launch vehicle

or payload are designed with the assumption that the system will not be recovered.

RF Communication

Radio frequency (RF) communications are used for wireless telemetry systems. RF communications takes

place by modulating (or encoding) information onto an RF signal known as the carrier. An RF signal is

usually identified by the carrier's frequency. The base unit of measure for frequency is Hertz (Hz), which

represents one cycle per second. Most frequency values are so large that SI prefixes are used, so our

favorite FM radio station's frequency is measured in MHz and Wi‐Fi radiates in the 2.5 GHz range. In

addition to a frequency, a system may be identified by the band that it operatesin. A band is a contiguous

range of frequencies that are similar in nature. VHF and UHF are two such band designations. One of the

most common amateur radio bands is the 2 meter band, which includes the frequencies from 144MHz to

148MHz in the US. Channel is another frequency designation. The channel identifier is a logical or tactical

designation specific to a particular implementation and is used to simplify frequency stepping for the

operator.

Licensing

Licensing is an important issue in RF communications. RF signal propagation is a physical phenomenon

that does not respect arbitrary boundaries such as political borders. The use of RF frequencies is

coordinated by the International Telecommunication Union (ITU). There are three ITU regions; the United

States is in region 2. All RF use is governed by the Federal Communications Commission (FCC) in the US.

For example, an amateur radio operator holding a technician classlicense is allowed to use, among others,

frequencies between 144MHz and 148MHz with power levels up to 1.5kW, asrequired by the application.

Within that range, amateur radio operators have self‐governance, and a plan known as “the 2 meter band

plan” identifies the technical and logical use of these frequencies.

Not all RF equipment requires the operator to hold a license. In some cases a service provider will hold

the license and make provisionsfor hardware that makes use of the assigned spectrum. The license holder

is responsible for the behavior of the RF devices. The license holder may then allow others to use those

devices. This is how the cellular telephone network frequencies are managed.

A set of frequencies in different bands are set aside by the FCC (and governing bodies of other nations)

for “industrial, scientific, and medical” use. These frequencies are referred to as the ISM band. Even

though they are referred to as a band, they are in fact narrow frequency ranges in several bands. ISM

frequencies are used by garage door openers, Wi‐Fi, Bluetooth devices, and ZigBee modules. While there

is some overlap, ISM frequencies vary between countries and ITU regions.

Modulation

RF communications takes place by modulating information onto an RF carrier. Two common modulation

techniques are Amplitude Modulation (AM), where information is represented by changing the

amplitude of the carrier signal, and Frequency Modulation (FM), where the frequency of the carrier is
                           

             

                                      

                                  

                                      

                                 

                                   

                 

                                       

                                       

                               

                                    

                                  

     

                                            

                                  

                         

                               

                             

         

                                         

                                                 

                                    

                           

                                 

                                   

                                           

                                 

                                    

                           

                                

   

                              

                                     

 

 

 

 

 

 

 

 

 

 

changed to encode the information. Other common modulation techniques are on‐off keying (OOK) and

various forms of phase shift keying (PSK).

Bandwidth

An important property of an RF signal is its bandwidth. The bandwidth of an RF signal is the difference

between the upper and lower frequencies occupied by the signal. An amateur radio 2m FM voice signal

occupies 25 kHz, an FM broadcast signal 200 kHz, and a UHF TV channel occupies 6MHz. The amount of

information that can be transmitted directly correlates to the bandwidth of the RF signal. Note that RF

bandwidth is not the same as data bandwidth, which is the rate a system can transfer digital data,

measured in bits per second or bytes per second.

Even though a signal occupies a particular bandwidth, it isreferred to as a single frequency. Thisis usually

the frequency in the middle of the range (where the signal is strongest). This is referred to as the center

frequency.

Another important signal characteristic is the baud rate, which is the number of symbols or transitions

per unit time. This is distinct from the bit rate because some modulation techniques are not binary in

nature. Quadrature phase shift keying (QPSK) encodes two bits per symbol, so that data rate is double

the baud rate.

Antennas

A critical part of an RF system is the antenna. An antenna is the part of the system that converts an RF

signal to an AC (alternating current) electrical signal, and vice versa. An antenna usually consists of one

or more elements made from electrically conductive material. When receiving, the antenna converts

some of the electromagnetic signal present at the elements into electrical energy, which is then passed

to the receiver via the transmission line. When transmitting, the antenna converts electrical energy from

the transmitter to electromagnetic waves.

In addition to referring to an RF signal by its frequency, it is useful to know the wavelength of the signal.

௖

The wavelength of a signal in a vacuum is

௙

, where f is the frequency in Hz and c is the speed of light. The

signal will propagate more slowly in a physical medium. The difference between thisspeed and c is known

as the velocity factor and is expressed as a percentage or fraction of c.

Wavelength is especially important in antenna design, since the physical size of the elements will be a

function of the wavelength of the signal in the material making up the antenna element. 1⁄4 and 1⁄2

wavelength antenna elements are common because they correspond well to the electrical

characteristics of the signal. The propagation of a radio signal depends largely on the frequency of the

signal and the environment. In free space a signal propagates uniformly; in reality a signal is affected by

atmospheric conditions, terrain, manmade structures, and other factors. The effect depends on the

frequency of the signal as well. Some frequencies are reflected by the atmosphere during certain times

of day.

Telemetry systems used on rockets will usually use VHF or higher frequencies. These frequencies are

known as “line ofsight” since they are not typically reflected by the atmosphere and a direct line between
                                

                   

                             

                               

                             

                                 

                             

                                        

                                 

                                      

                               

           

                             

                                 

                                 

                               

                                     

                                        

                                

                       

 

 

 

 

 

 

 

 

the receiver and transmitter must be available. Buildings, utility towers, trees, hills, the horizon, and

other natural and manmade objects attenuate or reflect the signal.

Antenna performance is usually compared to a theoretical antenna known as an isotropic point source, a

point at which the signal would radiate outwards in a three dimensional spherical pattern (assuming the

antenna was located in free space). The difference between an antenna's performance and the

theoretical point source is called gain, and is measured in decibels (dB).The decibel is on a logarithmic

scale. A 3dB change is a factor of 2; 10dB is a factor of 10.

There are two ways to increase the amount of RF signal available to a receiver. One is to increase the

amount of power at the transmitter, so that there is simply more energy available to the receiving

antenna. The other way is to increase the gain or sensitivity of the receiving antenna. We change the gain

of an antenna by changing the radiation pattern, increasing the efficiency in some directions by sacrificing

a corresponding decrease in efficiency in others.

Our theoretical isotropic point source has a perfectly spherical radiation pattern, equally efficient in all

directions. Half or more of the energy from such an antenna would be wasted in many terrestrial

applications, since the antenna would be near the ground, where the earth itself would block half the

signal. A very common antenna design is the half‐wave dipole, which produces a toroidal radiation

pattern so that it is more sensitive perpendicular to the axis of the dipole elements, but less sensitive in

the direction that the elements point. If we orient the dipole vertically, we will have an area that is less

sensitive above and below the antenna, but more sensitive toward the horizon. Because the dipole is

uniformly sensitive about its axis, it is known as an omnidirectional antenna.
                                   

                                     

                                   

                                    

                                

                               

     

 

Image courtesy of Cisco

It is possible to concentrate sensitivity even more in a particular direction. A Yagi antenna is more

sensitive along the axis of the beam where the elements are mounted. The design consists of a reflector,

a driven element to which the transmission line is attached, and one or more directors. The driven

element is usually a half wave dipole. The reflector is slightly longer, and the director elements are

shorter than the driven element and decrease in length the farther they are from the driven element.

More directors will result in increased gain and a corresponding reduction in the volume of sensitivity.
                               

                                     

                                     

               

                                  

                                  

                                 

                                 

                           

                                    

                                 

                                  

                                           

                                

       

     

 

 

Image courtesy of Cisco

When choosing an antenna for flight hardware, keep in mind that the rocket's orientation will change

constantly; not only will the position change in all 3 dimensions, but the yaw, pitch, and roll will change

as well. An antenna that is truly omnidirectional in all directions, such as a simple 1/2 wave dipole, is

usually the best candidate for the flight antenna.

The ground station antenna depends on the power output of the transmitter. If the transmitter is weak,

a directional antenna with appropriate gain is needed. This gain antenna must be pointed at the rocket

or communications can be lost; the higher the gain, the more precise this pointing must be. If the

transmitter is capable of higher RF power output (which may be constrained by mass, power, heat, or

monetary budgets, or by licensing), then a simpler ground station antenna may be used.

The signal from a typical terrestrial RF system is polarized. The waves have a particular orientation as a

result of the antenna geometry. A dipole antenna with the elements oriented vertically results in a signal

that is vertically polarized. If the transmit and receive antennas do not have the same polarization, up

to 3dB (half) of the signal is lost. If the rocket's antenna is along the axis of the rocket's main structure it

will be vertically polarized. Upon landing, it will usually be horizontal (tree landings and core samples

being two obvious exceptions).
                                  

                                   

                      

                                      

                                   

                                

                            

                             

                 

A variety of commercial off the shelf (COTS) radio modules are available. Complexity of use can range

from simple plug‐in pairs that act as a wireless RS232 cable to modules that require the operator to

provide handshaking, error detection and correction, and all other communications functionality. A few

devices have complete enclosures, but most are PCB modules that require external support for

regulated power and interfacing. Antennas may be built in or external. Output power is usually low, as

most of these devices utilize ISM frequencies. Most are 2.5GHz or 900MHz ISM devices. Some example

types are the various ZigBee family devices, the Digi/Maxstream Xtend, or the Nordic nRF2401A. The

flight hardware component of a typical telemetry system would include one of these modules, an

antenna, power source, one or more sensors, and a microcontroller.
   

         

   

     

     

       

  


 


 


 


 


 


 


 


 

Safety 

Materials:
 

Material Safety
 

Material Safety Data Sheets (MSDS)
 

Personal Protective Equipment
 

Launch Field Safety
 

High Power Rocket Safety Code
 

The Range Safety Officer
 

Launch Site Etiquette
 
         

   

                

           


 


 


 


 

NASA High Power Rocketry Video Series
 

Counterpart Documents
 

Section Written by Ian Bryant and Zachary Koch
 

Section Edited by Daniel Cavender
 
                              

                                      

                                

                    

               

                                   

     

     

   

                                  

            

       

                                 

                                     

                   

                           

         

   

   

             

           

         

               

               

                       

               

   

                             

         

                

             

   

                 

           

     

 

 

 

 

 

Safety is always the highest priority when building and constructing rockets. A whole launch event could

be ruined by a single accident. This section will help teach you about the various risks of working with

high power rockets, and provide solutions to help mitigate those risks. NOTE: This section does not

serve as an instructional document for all safety in rocketry. An experienced mentor/rocketeer

should be consulted prior to construction and launching.

Material Safety

There are a number of materials commonly used in the construction and flight of rockets. Listed are a

few common examples:

1. Fiber based rocket components

2. Black powder

3. Epoxy

4. Motors

This section will discuss how to handle each material safely. You will learn about material safety data

sheets, handling procedures, storage instructions, and more.

Material Safety Data Sheets (MSDS)

A MSDS is an important document that provides many handling details for the material you are working

with. A MSDS should be carefully read prior to working with any material. These sheets are easily be

obtained online, or upon a request to the manufacturer.

A typical MSDS will have 16 sections detailing every safety aspect of the material.

Product and Company Identification  Product name

 Manufacturer

 Manufacturer Contacts

 Emergency Contacts

Hazard Identification  Emergency Overview – what the material can

cause

 Potential Health Effects – What different

types of contact can cause

Composition/Information on Hazardous

Ingredients

Outlines the ingredients used in manufacturing

First Aid Measures Treatment measures for hazardous contact

Fire Fighting Measures List the flash point of the material, and the

proper extinguishing media to use in the event of

a fire.

Accidental Release Measures Details what to do in the event of a spill, leak, or

other form of accidental release

Handling and Storage Describes handling temperature and location.

May include special precautions to consider prior

to handling.

Exposure Controls/Personal Protection Informs you about the different forms of

personal protective equipment that should be

used while handling.
                     

     

                       

           

                     

         

           

           

               

     

             

             

   

   

                             

                                  

                   

                                 

                                

                             

                                     

                                          

           

                                 

                                

                                      

                   

                                      

                                    

                           

                                  

                           

                    

                                  

                       

 

 

 

 

 

 

 

 

 

 

 

 

Physical and Chemical Properties Lists what the material looks/smells like and

other chemical properties.

Stability and Reactivity Describes what media the material is safe in, and

how it reacts with other materials

Toxicological Information Describes any toxins that may be present in the

material (I.e. mutagens, carcinogens, etc.)

Ecological Information Lists possible environmental hazards

Disposal Considerations Details proper disposal techniques and locations

Transportation Information Describes the rules and regulations for

transporting the material.

Regulatory Information Describes which organizations regulate the

material.

Other Information Any other information that the manufacturer

deems important.

Fiber Based Components

In rocketry, there are two fiber based materials commonly used in construction; these fibers are

fiberglass and carbon fiber. Each of these materials are briefly discussed in the structures section of this

document, but both share very similar risks, and handling procedures.

When working with fiber based products, it is common for small fiber particles to cloud the surrounding

area. Coming into contact with these particles can cause severe irritation to the eyes, skin, and

respiratory system. Cutting these materials may also leave sharp edges capable of lacerating the skin.

To avoid these injuries, it is advised that workers should wear eye and hand protection, a face mask, and

long sleeves to reduce skin contact. It is also a good idea to rinse the components with a damp cloth to

remove residual particles from the component.

Black Powder

Considered a low explosive, black powder (BP) is one of the most dangerous materials to handle in

Rocketry. Black powder handling is a top safety concern in rocketry, and the handling requirements on

the MSDS should be closely followed. Mishandling of BP can lead to severe burns to the body, loss of

limbs, and if used in ejection, impalement from the rocket.

Black powder has a very low flash point, and even a small spark could be enough to cause ignition. For

this reason, BP should be stored in a cool, dry place, away from any heat sources. Additionally, BP

should not be stored in the same location as an igniter or e‐match.

When working with black powder, eye and hand protection are a must. Staying away from sources of

electricity, water, heat, etc. is also recommended to prevent contaminating the BP or accidentally

igniting it. If you are a minor, adult supervision is mandatory.

If you are unsure about proper BP handling procedures, consult a trained rocketeer. He/She will be able

to instruct you in the safe operation and handling of BP activities.
                                  

                               

                                

                                

                            

                                  

                       

                                    

                                

                              

                                        

         

   

                                      

                                 

                                 

                                     

                               

                                

                                          

                               

                                           

                                 

                                    

             

                                    

                                    

                                 

                    

                                  

                              

                            

                   

   

 

 

 

 

 

 

 

 

 

 

 

 

Epoxy

Epoxy is a useful bonding agent when constructing rockets. It comes in two parts, a resin and a

hardener. Even by themselves the resin and hardener can be hazardous. Neither should be ingested,

and they can both irritate the skin. When mixed together to form epoxy, additional hazards are

introduced.

All epoxies heat up when the two components are mixed together. An exothermic reaction occurs, and

the heat is noticeable even on weaker epoxies. Different epoxies have different temperatures when

mixing, and some can reach temperatures that can cause burns to the skin. Depending on the epoxy,

the mixing process can cause noxious fumes that should not be inhaled.

When handling epoxy, be sure to wear hand and eye protection, along with a respirator. A normal face

mask does not prevent the inhalation of noxious fumes. Sometimes epoxies use filler material to change

its consistency. If working with a filler, all of the above safety equipment should be used.

Each part of an epoxy comes in its own container. Be sure to keep the two components away from each

other to prevent accidental mixing.

Motors

Motors are a fun part of rocketry. There are many different styles of motors that can make each launch

exciting. However, motors are a leading cause of launch site accidents and injury. Mishandling a motor

could cause a rocket to travel along a dangerous trajectory, will cause serious burns if someone is

exposed to the exhaust flame, and can cause hearing damage if someone is standing too close as it is

ignited.

The motor itself is a stable object. They will not ignite in typical working environment. However,

storage procedures are strictly regulated to ensure the safety of nearby personnel. First, a motor should

never be removed from the static proof bag it is sold in until it is ready to be launched. Static electricity

can inadvertently ignite a motor if the charge is sufficiently large. When not being launched, the motor

should be stored in a fire and weather proof box. This box is typically made of wood with a steel liner.

The box should be lockable, painted red, and contain the work “EXPLOSIVES” in large letters to inform

others of its contents. More detail about motor storage can be found in the Code of Federal Regulations

chapter 27, section 55.209 (17 CFR 55.209).

Only certified rocketeers should handle a motor, and only one that is at or below their certification level.

The only exception is when the rocketeer is handling a motor for their certification flight. If you are

unsure of how to operate with a certain brand of motor, consult the instruction provided by the

manufacturer. Do not tamper with the motor in any way.

In this section we described some of the hazardous materials common in rocketry. Please note that this

is not an instructional section. The information provided here is meant to introduce you to the

different hazards possible, and encourage you to think about possible hazards. Consult the proper

documentation or a mentor prior to working with any hazardous material.
	 	

                         

                             

                     

                                     

                             

     

         

                                   

             

               

                 

                 

     

                             

                 

                       

                   

  

                       

                       

                       

     

                               

                     

                       

                       

                 

                   

                                       

                                 

                 

	 	

                              

                                     

                                   

               

 

 

 

 

 

 

 

 

 

Personal Protective Equipment

Personal Protective Equipment (PPE) refers to protective clothing, helmets, goggles, or other garments

or equipment designed to protect the wearer's body from injury. The hazards addressed by protective

equipment include physical, electrical, heat, chemicals, biohazards, and airborne particulate matter.

Which PPE and when to wear them is commonly specified in the MSDS for the material being used, on

the instructions/label for the tool or equipment, in shop or laboratory handbooks, and on the specific

piece of equipment.

Common examples of PPE include:

Safety Glasses, Goggles, or Face

Shields

These items cover all or part of the face and eyes to prevent

materials, sharp objects, chemicals, and dust/particulates from

contacting the face and eyes. Sunglasses and prescription

eyeglasses are NOT adequate eye protection. Most eye protection

is made to accommodate prescription eyeglass use while also

wearing the PPE.

Respirators/Dust Masks These items cover all or part of the mouth and nose. They are

designed to prevent inhalation of dusts, gasses, and particulate

matter.

Safety Gloves Safety Gloves include latex, nitrile, cotton, and leather hand wear

that prevent direct skin contact with chemical, cutting edge, or

sharp/abrasive materials.

Ear Protection Ear protection includes ear muffs and ear plugs. They reduce

exposure of the sensitive parts of the ear to loud, high decibel

noise. Ear plugs and muffs can be used in conjunction for greater

noise cancelling effect.

Hard Hats/Safety Helmets Hard hats and safety helmets cover part or all of the head. They

are designed to prevent impact to the head. Some helmets include

chin straps. They are commonly sized and adjustable for a tight fit.

Boots, Protective Footwear Boots, work shoes, and foot/ankle covers prevent impact or

contact with materials, chemicals, and sharp edges. Boots include

leather work boots, and steel toed construction or industrial use

footwear.

In order for PPE to be effective, it must be worn at the appropriate times and in the manner described

by the manufacturer. Additionally, some PPE is only effective for only a single use and must be replaced

for subsequent uses. Follow manufacturer recommendations for use of PPE.

Launch Field Safety

Rocket Launches are exciting events. Watching other rocketeers launch their projects can be fun and

educational for all attendees. However, the event can quickly be ruined by a lack of launch field safety.

This section is meant to inform you of safe launch field operations in order to avoid launch site

accidents, and ensure a safe and enjoyable event.
       

                               

                                     

                             

                                

            

               

   

   

     

     

     

     

     

     

     

     

       

               

   

   

     

     

     

     

     

     

     

     

     

       

                              

                                    

                         

   

 

High Power Rocketry Safety Code

The National Association of Rocketry (NAR) and Tripoli Rocketry Association both publish a code that all

of their members must follow. Each code is slightly different in wording, but the rules remain the same.

The codes discuss what motors and materials each rocketeer can use, weight limits, launching and

recovery systems, etc. Both codes also provide a launch site dimension table, and a minimum launch

distance table. Both tables are shown below.

Installed Total Impulse (N‐sec) Equivalent Motor

Type

Minimum Site

Distance (feet)

Equivalent Distance

(miles)

160.01 – 320.00 H 1,500 .28

320.01 – 640.00 I 2,500 .50

640.01 – 1280.00 J 5,280 1.00

1280.01 – 2560.00 K 5,280 1.00

2560.01 – 5120.00 L 10,560 2.00

5120.01 – 10240.00 M 15,480 3.00

10240.01 – 20480.00 N 21,120 4.00

20480.01 – 40960.00 O 26,400 5.00

Minimum Launch Site Dimension Table

Installed Total Impulse (N‐sec) Equivalent Motor

Type

Minimum Safe

Distance (feet)

Complex Minimum

Safe Distance (feet)

160.01 – 320.00 H 50 100

320.01 – 640.00 I 100 200

640.01 – 1280.00 J 100 200

1280.01 – 2560.00 K 200 300

2560.01 – 5120.00 L 300 500

5120.01 – 10240.00 M 500 1,000

10240.01 – 20480.00 N 1,000 1,500

20480.01 – 40960.00 O 1,500 2,000

Minimum Safe Launch Distance Table

The first table describes the minimum launch field dimensions for each motor classification. The values

listed can either be the diameter of the field, or the shortest dimension. The second table lists the

distances from the crowd line that each motor classification must be launched.
     

                                  

                                  

                                 

                      

         

                           

                           

                               

                       

                                  

                             

                                       

                                        

                                      

             

                                     

                                

                          

                                    

                                      

   

                          

                                 

   

   

                                   

                                   

                                      

                                       

                                  

                                  

                                          

                               

                                 

                                 

 

 

 

 

 

 

 

 

 

 

 

 

The Range Safety Officer

The Range Safety Officer (RSO) is the leading authority of the launch field. He/She is a certified

rocketeer with years of experience, and has the authority to deny launch pad access to other rocketeers.

It is the RSO’s responsibility to maintain the safety of all personnel attending the launch, and ensuring

that the launch field is not damaged. Some RSO responsibilities include:

 Performing hardware checks on rockets.

 Working with the launch control officer (LCO) to organize when each rocket will launch

 Checking to see that weather is clear, and the cloud ceiling is high enough

 Checking downrange to ensure that there are no personnel and other wildlife in the area while

launching.

 Checking the skies for planes and other objects that impede rocket launches

Prior to launching, the RSO will perform a hardware check on every rocket. He/She will check for

structural integrity, stability information, and any damage that could lead to an unsafe launch.

Weather can make or break a launch. A low cloud ceiling will cause force a rocket out of site. Not

knowing where a rocket is, is highly unsafe. By losing site of the rocket, the chance of the rocket landing

on a spectator, building, lake, etc. greatly increases. If the cloud ceiling is too low, the RSO reserves the

right to postpone or cancel the launch.

Checking the range and skies ensures that there is no wildlife or rocketeer is near the rocket as it

launches. High power rocket motors generate high amounts of heat and thrust that can easily cause

serious damage. If the launch club properly filed a waiver with the Federal Aviation Administration

(FAA), than there should be no aircraft in the launch vicinity. However, sometimes a plane or two will

wander into the area. The RSO must constantly check the sky for aircraft to prevent harm to the pilot

and passengers.

Both NAR and TRA publish information regarding RSO responsibilities. The important thing to

remember is that the RSO has authority over the entire launch field, and his/her directions should be

closely followed.

Launch Site Etiquette

The RSO may be the leading safety personnel on the field, but everyone in attendance is responsible for

safety. Proper launch site etiquette is easy to follow, and will help maintain safety. For one, all

spectators should remain outside of a tent or other structure as a rocket is in the air. As mentioned

above, losing site of a rocket is dangerous, and it is hard to see the rocket under a roof!

Absolutely no cell phones should be in the vicinity of a rocket. The frequencies transmitted by the

phone can potentially energize black powder chargers or other pyrotechnics. It is best to leave your cell

phones in your car. Plus you will miss all the fun of a launch if you are chatting on the phone!

When preparing your rocket, be mindful of the location of other rocketeers and spectators. It is

common to perform ejection charge preparation and testing in the prep areas prior to launches and you

do not want another team member, or bystander to be hurt or distracted by your prep work.
National Aeronautics and Space Administration 

George C. Marshall Space Flight Center 

Huntsville, AL 35812 

www.nasa.gov/marshall 

www.nasa.gov 

NP-2015-09-84-MSFC 

G-122203