L1 Certification

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In order to understand high power rocketry enough to launch and successfully recover an L1 rocket, you must read, live, and understand the following information. Level 1 Certification allows flyers to fly High Power Rockets with a total installed impulse up to 640 newton-seconds.

A note on painting your rocket: if you do not do it, we will not let you launch.

Background Information

NASA's online Beginner's Guide To Rockets will get you started on many of the basic principles governing rocketry. If you manage to make your way through all of these, you will understand the vernacular often used in rocketry.

Jargon

Impulse and its Specificity

Impulse (or total impulse) is defined as equal to force multiplied by time - it is a measure of how powerful motors are, and can easily give you your change in velocity (Impulse / Mass, assuming no drag or gravity losses. There will always be drag and gravity losses.) Total impulse can be thought of as the area under the thrust curve.

Thrust curves of motors with the same total impulse

In the above graph, each of those three motors have the same total impulse (area under the curve), but with very different thrust profiles. The letter designation for each motor (e.g. in E15, H125, or M1250) are a measure of total impulse and each successive letter represents double the total impulse.

It turns out that impulse alone is not a good measure for rocket fuel performance; it is technically possible to use wood and air as rocket fuels, and to get an insanely large impulse by making the engine really big. That will never get you to space. Instead, rockets really care about a number called the specific impulse, defined as impulse divided by the mass of the propellant and the gravitational constant. This gives a far better picture of what constitutes a good rocket fuel, although there are definitely other considerations.

Motor Systems (DMS and RMS)

DMS stands for Disposable Motor System. These motors are one time use only, and are very easy to work with.

RMS stands for Reloadable Motor System. These types of motors are harder to work with, since they require the maintenance of a motor casing and proficiency in loading, cleaning, and reloading the casing. After purchasing the relatively expensive casing, one must learn how to assemble it with motor reloads. If not assembled properly, your rocket will most likely not make it through the flight.

Motor Retention (Positive or Otherwise) and Adaptors

Retaining rings. Lip of motor on airframe or retainer. Positive = not falling out the bottom.

Adaptors allow use of different diameters in your rocket.

Stability

CG and CP for stable flight

Center of Gravity

An objects center of gravity is its (rigorously and mathematically defined) middle point. The force of gravity can be simulated to act here, and the object will tend to rotate about this point, making it crucial to finding rocket stability.

Center of Pressure

The center of pressure is the location at which we can model the aerodynamic effects as acting. In other words, the drag on the rocket acts at this point. If the center of pressure is below the center of gravity, then the downwards force of drag will keep the rocket upright, while a center of pressure above the center of gravity will flip the rocket. A CP and CG at the same point will create a neutrally stable rocket, meaning that any incidental forces could theoretically spin it. This makes the distance between the CP and CG critically important for determining whether flight will be safe and successful.

The main tool we have to change the center of gravity is the size of the rocket's fins - larger fins will bring the center of pressure lower down on the rocket, increasing its stability.

To calculate center of pressure, you can use the Barrowman equations (link to the original document) or the cardboard cutout method.

Calibers

Calibers are a way of measuring the distance between CP and CG - it doesn't make sense to solely measure based on distance, as a 3 difference on a 2 OD, 24 long rocket is very different from a 2 difference on a 10' long, 6 OD one.

Instead, calibers measure the length between CP and CG, divided by the outer diameter of the rocket, allowing for a much more fair comparison between different rocket sizes. For context, a CP of 1.5-2 is considered good, while numbers outside of that range tend to be either under-or-over-stable.

Motor Specs

Solid rocket motors have a fairly standardized labeling system. On the casing (or reload) itself there is a three-part code which denotes what the total impulse range is, the average thrust, and the delay grain length. All these numbers are in standard metric units.

The letter designation represents the total impulse. Each letter category represents double the total impulse of the previous letter category.

Letter designations increase total impulse exponentially

Aerotech H550ST-14A

Here is the spec sheet for this motor[1]. Interestingly enough, SSI will be using this motor for its L1 certifications.

Using this motor as an example, we know that this motor is classified in the range of impulse from 160 Ns - 320 Ns. The 550 denotes that the motor's average thrust is 550 N. The ST denotes what type of propellant is in the casing. In this case, ST stands for "Super Thunder". Aerotech has cute names for their different types of propellants. They often only denote the color of the flame. Finally, the 14 denotes that the motor will fire its ejection charge 14 s after burnout unless it is adjusted, as indicated by the A. Motor delay times can be adjusted with a motor delay tool.

Recovery

Motor delay/ejection charges

So you've launched your rocket and watched it fly upwards as good rockets do. Now you need to bring it back safely. A standard parachute recovery for an L1 rocket involves deploying a single main parachute out of the rocket at apogee. Apogee is the highest point of a rocket trajectory, where the vertical velocity is momentarily zero and the rocket transitions from ascent to descent. This is the point at which the rocket is moving slowest and is ideal for parachute deployment. This is to allow the parachute to properly deploy and minimize aerodynamic forces on it while it deploys.

For typical L1 rockets, after the motor burns through its main propellant, it burns through a delay grain. This is a slow-burning section at the end of the motor which acts as a timer. Once the delay grain, the flame front ignites the ejection charge, which pressurizes the body tube of the rocket and forces the nose cone out, along with the parachute. To test whether your nose cone has the proper fit (tight enough to stay on during flight but loose enough to eject for recovery), hold the back end your completed, but unloaded rocket to your mouth and blow hard with a good seal. The nose cone and parachute should both pop out.

Simulations

It is always important to know what your rocket will do (assuming that things go according to plan), and we use a program called OpenRocket to find the flight profile of our rockets. The program is free, and can be found here[2]

OpenRocket is quite easy to learn, and is quite accurate for sub-Mach rockets (those that fly faster should use RasAero to model drag forces.) OpenRocket includes ascent, including a massive database of thrust curves, as well as a simulated descent using the parachutes included in the rocket. If used properly, it can output data from height of apogee to time of flight to drift distance, all of which are incredibly useful while designing your rocket. (Hint: the center of pressure calculation is extremely important.)

One other program of note is called FinSim, which can model possible vibrations within fins. If unchecked, these vibrations can grow and shear the fins off, likely dooming the rocket. The program is required for transonic and supersonic flights, and can be found here[3]

Safety Codes

NFPA 1127 and FAA 101

Note: Might be better to just give summaries of each relevant sections and only post links to full documents. Someone please fix.

The National Fire Protection Association has multiple documents spanning different types of rocketry. Section 1122 governs model rockets and 1127 governs high powered rockets. We are most interested in 1127.

NFPA 1127 states:

The Federal Aviation Administration Regulations also has a relevant section to the high powered rocketry community. FAA 101 Subpart C, Amateur Rockets. Here are the extremely relevant sections.

§101.22 Definitions.

The following definitions apply to this subpart:

(a) Class 1—Model Rocket means an amateur rocket that:

(1) Uses no more than 125 grams (4.4 ounces) of propellant;

(2) Uses a slow-burning propellant;

(3) Is made of paper, wood, or breakable plastic;

(4) Contains no substantial metal parts; and

(5) Weighs no more than 1,500 grams (53 ounces), including the propellant.

(b) Class 2—High-Power Rocket means an amateur rocket other than a model rocket that is propelled by a motor or motors having a combined total impulse of 40,960 Newton-seconds (9,208 pound-seconds) or less.

(c) Class 3—Advanced High-Power Rocket means an amateur rocket other than a model rocket or high-power rocket.

§101.23 General operating limitations.

(a) You must operate an amateur rocket in such a manner that it:

(1) Is launched on a suborbital trajectory;

(2) When launched, must not cross into the territory of a foreign country unless an agreement is in place between the United States and the country of concern;

(3) Is unmanned; and

(4) Does not create a hazard to persons, property, or other aircraft.

(b) The FAA may specify additional operating limitations necessary to ensure that air traffic is not adversely affected, and public safety is not jeopardized.

§101.25 Operating limitations for Class 2-High Power Rockets and Class 3-Advanced High Power Rockets.

When operating Class 2-High Power Rockets or Class 3-Advanced High Power Rockets, you must comply with the General Operating Limitations of §101.23. In addition, you must not operate Class 2-High Power Rockets or Class 3-Advanced High Power Rockets—

(a) At any altitude where clouds or obscuring phenomena of more than five-tenths coverage prevails;

(b) At any altitude where the horizontal visibility is less than five miles;

(c) Into any cloud;

(d) Between sunset and sunrise without prior authorization from the FAA;

(e) Within 9.26 kilometers (5 nautical miles) of any airport boundary without prior authorization from the FAA;

(f) In controlled airspace without prior authorization from the FAA;

(g) Unless you observe the greater of the following separation distances from any person or property that is not associated with the operations:

(1) Not less than one-quarter the maximum expected altitude;

(2) 457 meters (1,500 ft.);

(h) Unless a person at least eighteen years old is present, is charged with ensuring the safety of the operation, and has final approval authority for initiating high-power rocket flight; and

(i) Unless reasonable precautions are provided to report and control a fire caused by rocket activities.

§101.29 Information requirements.

(a) Class 2—High-Power Rockets. When a Class 2—High-Power Rocket requires a certificate of waiver or authorization, the person planning the operation must provide the information below on each type of rocket to the FAA at least 45 days before the proposed operation. The FAA may request additional information if necessary to ensure the proposed operations can be safely conducted. The information shall include for each type of Class 2 rocket expected to be flown:

(1) Estimated number of rockets,

(2) Type of propulsion (liquid or solid), fuel(s) and oxidizer(s),

(3) Description of the launcher(s) planned to be used, including any airborne platform(s),

(4) Description of recovery system,

(5) Highest altitude, above ground level, expected to be reached,

(6) Launch site latitude, longitude, and elevation, and

(7) Any additional safety procedures that will be followed.

TRA and NAR Codes

Useful documents:

• Tripoli Rocketry Association Safe Launch Practices. Great document on when and how to safely launch your rocket.
• RSO Guidelines. Fantastic resource to understand what Range Safety Officers look for.
• NAR's High Power Rocketry Safety Code. Very good resources, summarized further on.
• TRA's Code for High Power Rocketry. This resource is pretty scarce, would not look here for explicit instructions.

For reference, here is a summary of NAR's saftey code. For an non-edited version of NAR's code, check out the links above.

• Certification. I will only fly high power rockets or possess high power rocket motors that are within the scope of my user certification and required licensing.

• Materials. I will use only lightweight materials such as paper, wood, rubber, plastic, fiberglass, or when necessary ductile metal, for the construction of my rocket.

• Motors. I will use only certified, commercially made rocket motors.

• Ignition System. I will launch my rockets with an electrical launch system, and with electrical motor igniters that are installed in the motor only after my rocket is at the launch pad or in a designated prepping area. The electronics will have an off and on switch. They will turned off until my rocket is in the launching position.

• Misfires. If my rocket does not launch when I press the button of my electrical launch system, I will remove the launcher’s safety interlock or disconnect its battery, and will wait 60 seconds after the last launch attempt before allowing anyone to approach the rocket.

• Launch Safety. I will use a 5-second countdown before launch. I will ensure that a means is available to warn participants and spectators in the event of a problem. I will ensure that no person is closer to the launch pad than allowed by the accompanying Minimum Distance Table. I will check the stability of my rocket before flight and will not fly it if it cannot be determined to be stable.

• Launcher. I will launch my rocket from a stable device that provides rigid guidance until the rocket has attained a speed that ensures a stable flight, and that is pointed to within 20 degrees of vertical. I will use a blast deflector to prevent the motor’s exhaust from hitting the ground.

• Size. My rocket will not contain any combination of motors that total more than 40,960 N-sec of total impulse. My rocket will not weigh more at liftoff than one-third of the certified average thrust of the high power rocket motor(s) intended to be ignited at launch.

• Flight Safety. I will not launch my rocket at targets, into clouds, near airplanes, nor on trajectories that take it directly over the heads of spectators or beyond the boundaries of the launch site, and will not put any flammable or explosive payload in my rocket. I will not launch my rockets if wind speeds exceed 20 miles per hour. I will comply with Federal Aviation Administration airspace regulations when flying, and will ensure that my rocket will not exceed any applicable altitude limit in effect at that launch site.

• Launch Site. I will launch my rocket outdoors, in an open area where trees, power lines, occupied buildings, and persons not involved in the launch do not present a hazard, and that is at least as large on its smallest dimension as one-half of the maximum altitude to which rockets are allowed to be flown at that site or 1500 feet, whichever is greater.

• Recovery System. I will use a recovery system such as a parachute in my rocket so that all parts of my rocket return safely and undamaged and can be flown again, and I will use only flame-resistant or fireproof recovery system wadding in my rocket.

• Recovery Safety. I will not attempt to recover my rocket from power lines, tall trees, or other dangerous places, fly it under conditions where it is likely to recover in spectator areas or outside the launch site, nor attempt to catch it as it approaches the ground.

L1 Requirements

Sources of information: TRA L1 certification info and NAR L1 certification info.

The following is a combination of the NAR and TRA requirements and rules.

You must be at least 18 years old to be certified for Level 1. Although it is good practice to already be a member of NAR and/or TRA before certifying, in practice it is not enforced. Motors must be certified and non-experimental.

Your certifier (for NAR) needs to be either two people with the level you are attempting for, or one person with the level above the one you are attempting for. They must witness the flight.

Airframe

The rocket must be built by the flyer. The rocket shall have a display on the exterior identifying the calculated center of pressure. The rocket must be of "conventional rocket design". "Odd Rockets" including flying pyramids, saucers and flying spools will not be allowed for any certification flight. The rocket may be either a kit or scratch built. Scratch built rockets may contain commercially built components.

Recovery

Standard parachute recovery is required. Non-parachute recovery methods (e.g. tumble, helicopter, gliding, etc) are not permitted for certification flights. If the rocket is using dual deployment, the first recovery event may be via a drogue-less or streamer as long as the main or second event uses a standard parachute.

Motor

The certification flight must be with a single certified H or I motor (tested total impulse between 160.01 and 640.00 n-sec).TRA does not allow staged and/or Clustered rockets for certification flights while NAR states you must use at least one HPR motor on your certification rocket. The flyer shall be observed by the certifying member or their designated representative during the assembly (if a reload or hybrid) and preparation of the motor. Single use motors are permitted.

Electronics

Electronics are not required for level 1 certification flights.

Pre-flight Inspection

The model will be subjected to a safety inspection prior to flight. The safety inspection form is on the back of the NAR High Power Certification Application. During the safety inspection the modeler will be expected to provide oral answers to technical questions related to the safety and construction of his model. The questions may include (but not limited to) identification of the model’s center of gravity and center of pressure, methods used to determine model stability, and interpretation of the rocket motor’s designation. The certification team will initial (or check) the blocks indicating that model safety, motor certification, and the existence of a FAA waiver (if required) in effect were verified prior to flight.

Certification Flight

Level 1 Certification flight may take place at any insured launch. The certifying member (i.e. Prefect, TRA Director, NAR certifiers or TAP Member) must be present and witness the certification flight. The certifying member must witness the rocket ascend in a stable manner and descend in stabilized manner controlled by the recovery system.

Post-Flight Inspection

The rocket must be presented to the certifying member for inspection. If the rocket cannot be recovered, but can be inspected in place (power lines, tree, etc...) this is acceptable. The certifying member shall inspect the rocket for excessive damage. Excessive damage shall be considered damage to the point that if the flyer were handed another motor, the rocket could not be put on the pad and flown again safely. Damage caused by wind dragging will not cause a disqualification. If successful, the certifiers will sign the correct sheet to indicate that the certification attempt was successfully completed.

Post-Post-Flight

The certification sheets are returned to NAR or TRA Headquarters. No fees are required. The certification sheet must be returned by the certified individual or the event sponsors to NAR or TRA Headquarters to allow updating the NAR or TRA database. NAR sends an updated membership card showing the certification level upon receipt of the certification paperwork.

Non-certification

Any of the following will result in non-certification for a certification flight:

• Motor Cato
• Excessive Damage
• No recovery system deployment or tangled recovery system deployment
• Rocket drifting outside the specified launch range
• Components coming down not attached to the recovery system.
• Any other violation of TRA safety code associated with this particular flight.
• Any other legitimate reason the certifying member deems merits non-certification

Launch Locations

Tripoli Central California

Tripoli hosts launches on the third Saturday of each month. Details, calendar, updates, and directions, as well as other pertinent information, can be found on their website here[4]. Be aware that Tripoli has slightly different policies and forms from NAR, as well as requiring a separate Tripoli membership in order to launch. However, certification levels from either are accepted at the other, i.e. if you are certified L1 through Tripoli, you can get your L2 certification at NAR, as long as you are a registered member of both.

Livermore Unit of the National Association of Rocketry

LUNAR hosts launches on the first Saturday of each month - details can be found here[5]

Launch Day Procedures

Who You Will Meet

Range Safety Officer (RSO)

The RSO is responsible for pre-flight inspection and approval of hobby rocket vehicles within a specified motor impulse range. They give the final word on whether your rocket will launch. Jump to Range Safety Check to read about what you need to prepare for inspection or read this document [6] if you're interested in the nuts and bolts of what an RSO does.

Launch Control Officer (LCO)

The LCO is responsible for control of the range and the actual launching of the rocket vehicles themselves.

What You Need To Bring

Rocket Fuel

• Epoxy
• Tools to apply epoxy (i.e. popsicle sticks and paper plates)
• Power Drill and Impact Driver
• Correct drill bits and heads
• Dremel
• Igniters
• Bolts (what kind?)
• Screwdrivers
• Adjustable spanner
• Masking and duct tape
• Sandpaper (120 grit)
• Measuring tape
• Calipers

If doing L2 also bring these things along:

• Wire strippers
• Small needlenose pliers
• Black powder
• Extra igniters and ematches
• Soldering iron
• Power supply
• Rosin solder
• Altimeters
• Altimeter USB cables
• Batteries
• Multimeter
• Precision Screwdriver
• Laptop

People Fuel

• Cases of water
• Cooler for drinks
• Snacks (bring your own food)
• Cash for launch fees and purchasing miscellaneous parts
• Nice cameras
• Inverters and power strips for power from car
• Sharpies and pens
• Pre-filled out documentation
• First aid kits
• Tent
• Chairs
• Folding tables

Appropriate Clothing

These requirements obviously change per season, but the running theme is that you will be exposed to the elements all day.

• Sunglasses
• Hats
• Scarves
• Pants
• Walking boots or sneakers
• Rain boots (for walking in muddy farmland)
• Jacket

Vendors

Bay Area Rocketry is a local supplier of rocket parts and motors, and will often travel to launches, allowing us to pick up our motors at the site. Since SSI does not store motors on campus, this is a very nice perk.

Apogee Rockets is a website selling everything from guides to motors to fiberglass tubing, and are a very good starting point for any rocket-related parts.

Giant Leap Rockets has a large selection of components, and tends to stock parts for larger rockets. They also sell the Firestorm 54 kit, which we have used extensively.

Public Missiles sells very large components - think rockets with diameters >6in.

Range Layout

Depending on which launch site you go to, this will be different. However, there are some basic themes.

The main areas of a launching range are the launch pad and control tent, and the parking area. Most high powered rocketry ranges have at least one launch pad that is set up 100ft away from the control tent, a distance specified by the NFPA, section 1127, as the "Minimum Personnel Distance" for any non-complex motor under 1,280 Ns (J motor). However, quite a few ranges also have a second pad, 300ft away, to be able to launch an L motor rocket, or any complex motor combinations up to J motors.

The control tent is where you check in your rocket with the RSO, and get your pad assignment from the LCO. This is also where you can take your L2 exam, if you have not done so already, and also where you bring your rocket back to get your certification.

Packing Your Parachute

When packing your parachute it should not fit too tightly within your airframe. You can test this yourself by giving a quick pull on the shock cord attached to the parachute. For the L1s, and most of the L2s, the parachutes are small enough that you should be able to have the entire parachute pop out of the airframe by doing this. If you find yourself having trouble either inserting your parachute into your airframe, removing it, or simply have no idea where to start there are a couple of styles of folding that may help.

Half Fold: This style is recommended if you have a relatively skinny airframe and are not concerned about airframe space.

Triple Fold: This style of folding results in a slightly thicker packed 'chute but it has a shorter length than the half fold.

Diagrams*

Here is a video.*

Some other techniques you may want to try:

• folding your lines in with your 'chute rather than wrapping them around the 'chute
• taping the folded lines with a bit of masking tape to act as a way of creating a "slider" to help slow the opening of the parachute. This essentially creates a faux dual deploy to help reduce recovery drift.

Don't forget to wrap the bottom end of your parachute in a heat resistant cloth like Nomex or Kevlar to prevent the ejection charge from burning holes into your parachute.

coming soon*

Prepping Your Motor

If using a single use motor or Disposable Motor System, make sure to check that the delay on the ejection charge is correct using a simulation software (i.e. OpenRocket). If needed adjust the length of the delay grain. Then place the correct quantity of ejection propellant in the correct location. Cap it.

Here is a great video to watch.

Range Safety Check

Before you get cleared for launch, the RSO will inspect your rocket structures, motor certification, and dynamic properties. You should be prepared to answer any and all questions the RSO may have about your rocket. Remember -- the RSO has the final say on whether your rocket gets to launch or not, so it is in your best interest to prepare beforehand all the necessary paperwork, calculations, safety procedures, and proper assembly and convince the RSO you know what you are doing and your launch is unlikely to fail. A full documentation of what the RSO does (or doesn't) do can be found under Range Safety Officer.

Administrative

• Is the flier over 18 years of age? If you are not over 18, you legally cannot launch mid or high power rockets. Sorry.

• Is the flier certified to the power level being flown? Not really an issue for L1's since you have no certification (yet) and will not be attempting to use any motors that require a certification, but if you are flying a motor that requires a high power certification later on, you must bring your NAR/TRA membership card indicating your current membership and certification level.

• Will the flight of the model rocket vehicle “bust” the launch site's FAA waiver? This is very important. You must be able to anticipate the altitude your rocket will fly to and be prepared to show simulation data if asked for it. For a single motor, you may be denied a launch if you expect to reach within 15% of the waiver height (15,000' for LUNAR and 16,800' for TCC). This won't be an issue for L1's, but you will certainly be asked what your rocket's expected apogee is, and you better be prepared to answer with an accurate model to back your number.

• Will the rocket penetrate cloud cover?

Motors

• Is the motor certified?

• What is the motor type and average thrust? Is the delay time is approximate for rocket?

• Is the igniter a low-current igniter?

• Does your rocket motor have the ejection charge installed?

• Is sufficient wadding/Kevlar installed?

• What kind of motor retention system is installed?

• What prevents the motor from flying-through the rocket?

Rocket Construction

• Is the rocket stable? Is the CG in front of the CP? Be able to identify both.

• Is the nose cone fitted correctly?

• Launch lugs and/or rail guides properly installed, positioned, and aligned?

• Are the fins mounted parallel to the roll axis?

• Is an appropriately-sized recovery system installed and attached?

• Are there vent holes?

Launch Pad Procedure

The rocket should slide freely on the rail. The pad angle should be within 20 degrees of the vertical axis (normal to the surface of the earth). Flight critical electronics (if there are any) should be armed before putting in igniters. Any radio control equipment should also be nominally operating before arming the igniters.

How to install an igniter

Place in the nozzle of rocket, and tape the igniter to the rocket so it does not slide out. Make sure not to short the leads of the igniters.

Here is a great video to watch.

Final Steps

Mailing It In

You must mail in your certification form to have the rocketry association acknowledge your achievement. These are the addresses of NAR and TRA.