Launch Day

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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 [1] 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

Note: these lists have two columns.

  • Ziploc bags to store the things below in.
  • 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
  • Paper towels
  • Plastic bags
  • Clamps
  • Scale
  • Gloves
  • Trash bags
  • Rockets
  • Motors - all that we would reasonably use!
  • Grease for motor cases
  • Spare rocket components
  • Motor retaining rings
  • Black powder

If doing L2 also bring these things along:

  • Wire strippers
  • Wire
  • Small needlenose pliers
  • Pyrodex
  • Centrifuge tubes
  • Extra igniters and ematches
  • Soldering iron
  • Power supply
  • Rosin solder
  • Altimeters
  • Altimeter USB cables
  • Batteries
  • Battery connectors
  • Multimeter
  • Precision Screwdriver
  • Laptops with altimeter programming software
  • Ziptie gun & zipties

People Fuel

Rebecca Wong at a November launch at TCC
  • 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
  • Trash bags
  • Table cloth

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 Rocketry 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.

Snow Ranch launch site (LUNAR)


Del Norte launch site (TCC)

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.

Re-do the parachute tied to the screw on metal loop 12 inches below the nose cone. Unscrew the loop, remove the cords and loop the parachute in a simple knot around the loop by passing the parachute through the loops of the cord lines.

Lay the parachute on the ground and arrange it so where all the cords come off the parachute are in the same spot. Accordian fold the parachute like a shirt. It should end with a width of about the diameter of the rocket.

Make a z-fold the long way on the parachute, if it looks like it will be too long for the chute protector, make 2 or 3 z-folds. Lay the cord lines along the chute the long ways and then fold the chute over once along the line of the cords. The cords should not go down the entire way, pull them out through the fold about half an inch from the bottom. Now wrap the cord lines around the chute, taking care to not cross the lines with each other.

Once that is done, take the chute protector and burrito wrap it around the chute. Make sure the slit that the shock cord goes through is at the spot furthest away from where the fire will be.

Fire + Parachute = Very Bad

The parachute+kevlar should act as a plug in the airframe. If the motor ejection does not push the parachute and kevlar out of the airframe, the pressure will push the nose cone out, which will pull the parachute and kevlar out. Both cases are fine.

This folding technique is courtesy of Stue, who learned it from a guy that makes parachutes for the military. We will assume that if it is good enough for the military, it is good enough for us.

Shock cord should be 5 body lengths, rather than 3 body lengths.

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.

Filling Out Your Flight Card

You must fill out a flight card before launching any rockets on launch day. You must know and indicate:

NAR Flight Card
  • Your name
  • Model's name as well as whether it is a kit, plan, or original
  • What type of recovery is on-board (i.e. parachute, helicopter, streamer, etc.)
  • How many stages and engines are on-board
  • What the payload is
  • What type of rod is needed
  • The motor specs: manufacturer, type, impulse, how many, total impulse if multiple

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? In accordance with Federal Aviation Regulations (FAR) (the FAA regulations pertaining to who can or can't use airspace), high power rockets cannot be launched into cloud cover greater than 50% or visibility less than 5 miles.

Motors

  • Is the motor certified? NAR, TRA, and NFPA Safety Codes require that only certified motors be used. Motors are certified by undergoing testing as set forth by the NFPA. TRA and NAR have a reciprocity agreement so that motors that are certified with one organization are upheld by the other. Main takeaway: make sure your motor is certified (it will be) and would be good to know which organization did the certification (easily looked up online).
  • What is the motor type, average thrust, and rocket weight? Is the delay time approximate for rocket? Motors may be single-use or reloadable, and can be solid, liquid, or hybrids. SSI currently only uses solid motors. Your L1 motor will likely be a single-use motor as these are less prone to errors in assembly that can occur with reloadable casings. The rule of thumb regarding motor selection is a 5-to-1 thrust-to-weight ratio. The motor delay should be set appropriately for the rocket configuration and weather conditions. Motors with longer delays have lower weight recommendations so be sure to run simulations and have a good idea of what delay you need on launch day.
  • Is the igniter a low-current igniter? DO NOT USE LOW-CURRENT IGNITERS FOR YOUR MOTOR IGNITION. I repeat. DO NOT USE LOW-CURRENT IGNITERS FOR YOUR MOTOR IGNITION. Low-current igniters, as their name suggest, ignite with very little current -- so little in fact that the continuity test can set them off. This means that if you do not follow this very important warning, you could end up in a situation where you put your rocket on the rails, connect up the leads, go to press the button for continuity and BAMMMMM YOUR ROCKET GOES FLYING OFF IN FRONT OF YOUR FACE. DO NOT USE LOW-CURRENT IGNITERS FOR YOUR MOTOR IGNITION AKA NO Electric Matches. E-matches are ok for ejection charges in avionics bays (for L2s+), but they should NOT be used for motor ignition.
  • Does your rocket motor have the ejection charge installed? This involves pouring a small amount of ejection charge into the top of your motor and putting a cap on it. Do not forget to do this. People have forgotten before (apparently) so don't let that be you, otherwise you'll find your rocket will go up quickly, and then proceed to come down very quickly. And dangerously. And you won't get certified. So don't forget.
  • Is sufficient wadding/Kevlar installed? Wadding, sometimes referred to as dog barf, is fire-retardant, blown-cellulose insulation (used in home insulation) that protects your rocket/shock cord/parachute protector from getting blown to smithereens by your ejection charge. The Kevlar pads in the Firestorm kits serve an equivalent purpose of protector your parachutes from getting fried. Be sure the Kevlar pad fully wraps around the area of your parachute that is facing the ejection charge. Use your head on this one -- what good is a Kevlar covering, if it isn't covering the part of your parachute that is going to get blasted with BP/Pyrodex?
  • What kind of motor retention system is installed? Motors can be retained with either a friction fit (not recommended) or a positive retention system such as motor clips or retaining rings (what you'll be using for Firestorms). Examine the motor retainer and retaining rings carefully and make sure the smaller ring is sitting inside the groove of the retainer, not just pressed into the retainer anywhere. Give your motor a good pull (the RSO may do this also) and make sure the motor cannot fall out in anyway.
  • What prevents the motor from flying-through the rocket? Give your motor a good push (the RSO may do this also) and make sure neither the motor nor the motor tube move inside the airframe.

Rocket Construction & Inspection

  • Is the rocket stable? Is the CG in front of the CP? Be able to identify both. You can find the CG of the rocket with the motor installed by finding its balancing point. Mark this point on the outside of your rocket. Use a simulation program to determine where your CP is and mark this on the outside also. The CG must be at least 1 caliber in front of the CP.
  • Is the nose cone fitted correctly? Check the fit of your nose cone by yourself first. Does the nose cone separate from the rocket under its own weight? It shouldn't. Add a little bit of tape around the shoulder. The right fit is such that the nose cone will not detach if you simply pick up your rocket by the nose cone, but not so tight that you need to exert excessive effort to remove it. A few strong shakes should do the trick. Also check that paint is not inside the body tube or on the shoulder, which can cause the issues with sliding the nose cone off -- sand things down carefully as needed.
  • Launch lugs and/or rail guides properly installed, positioned, and aligned? Verify your rail guides are attached securely and are in good condition (no cracks, deformations, etc). Check for any paint build up that could interfere with the launch rails -- sand as needed.
  • Are the fins in good condition and mounted parallel to the roll axis? Verify you epoxied your fins on straight. Wiggle the fins at the tip. Do your fins move or flex a lot? They shouldn't. Examine the fins for any cracks or warpage.
  • Is an appropriately-sized recovery system installed and attached? Verify that your shock cord is not frayed, burnt, or cut and that all knots are secure and will not slip out. Pull on the shock cord several times to check it is secured to your airframe properly. Check all your quick links and any other hardware are tightened completely and will not separate under load. Check that your parachute is in good condition and is not loose, burnt, or cut. Double check your Kevlar wrapping.
  • Are there vent holes? Vent holes are used to vent the rocket's internal pressure and avoid premature separation. You should have two vent holes, one in the aft section of your rocket and one in the forward, near the nose cone.

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.

Checklist of What to Know

If you do not know the answer to any part of this, look it up. Either in the above sections, or on the internet.

- How to answer questions about the bolts attaching the coupler

- How high will your rocket go? Use your own measurements of the rocket and plug them into openRocket. Don't use other peoples calculations.

- How fast will your rocket go? Same as above.

- Where is your CP?

- Where is the CG?

- How fast the rocket is going off the launch pad?

- Model of motor?

- Impulse of motor?

- Thrust of motor?

- Burn time of motor?

- Stability margin?

- What epoxy was used in construction? Ans - 30 min epoxy for the tube fins and JB Weld for hardpoint and motor retainer.

Quick G Calculation

Quick way to calculate g’s on liftoff: Take the average thrust of motor in N, divide by 5 to get lbs, divide by the weight of your rocket, you want to aim for around 5 - 6 g’s.

The H550 motor puts us at an initial launch acceleration of 30g’s, approximately 90 ft/s off the launch rod, so anything inside the tube will shake uncontrollably and possibly break. It will also cause the parachutes and other stuff in the rocket to be shoved down the tube. Be careful about how you attach the coupler as screws can catch the parachute and make it fail. Ask Ian on how to explain this to the safety officer!

Final Check!

Are you ready to launch? Run through this quick checklist!

L1

  • Is your parachute packed correctly? Kevlar wrapped around? Is it attached to your rocket?
  • Is your airframe bolted together nice and tight?
  • Did you buy the correct motor? (H or I Motor - MUST BE 38mm)
  • Did you pack in black powder for motor delay ejections? Check the delay time.
  • Does your nose cone slide off with vigorous vertical shaking (with the motor assembled)
  • Is there any epoxy that has not dried? (Wait if there is)
  • Is your certification form and flight card filled out with rocket info? Do you know your NAR/TRA membership #?
  • Did you pay your launch fee?
  • Are your rail guides properly mounted on your rocket?
  • Is there a pressure ventilation hole so your recovery system doesn't prematurely deploy?

L2

In addition to the last 6 items listed under the L1 check,

  • Are your parachutes correctly packed and attached to the avionics bay (and nose cone)?
  • Did you buy the correct motor? (J or K -- if you're not using motor ejection, don't fill with black powder)
  • Are all electronics functioning? Fresh batteries? Easy switch access?
  • If using a barometric-based altimeter, have you drilled a pressure-access hole for it?
  • Have you loaded up your charge wells?
  • Have you checked the position and attachment of your igniters?
  • Are your apogee and main charges facing the correct direction?

All good? Great! Get a photo of you and your rocket on the launch pad and good luck!