LUNAR Mid-power Field Procedures

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Flight Cards   Safety Check   Load   Launching

A mid-power model rocket, for the purposes of our field procedures, is any rocket with an F (>40N-Sec Cluster or Staged) or larger engine but less than an H (160N-Sec). For the most part, the mid-power procedures are similar to the low-power procedures so familiarize yourself with the low power procedures first. The mid-power procedures have the following differences from the low-power procedures.

  • You use mid-power flight cards.
  • The safety check is done by the High-power Safety Check Officer.
  • The safety check is more rigorous.
  • You use the mid-power pads (Rack 3).

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Using the Mid-power Flight Cards

The mid-power flight cards are different from the low-power ones. In addition to places for the rocket name, manufacturer, and engine, they also have places for motor retention, stability criteria, recovery method, and predicted altitude. On the back of the card are checkoffs for all the safety checks made by the HP-SCO.

LUNAR Mid-power Flight Card Front

LUNAR Mid-power Flight Card Back
The LUNAR mid-power flight card collects a lot more information about the construction and stability of the rocket. On the back is a checklist for the safety check.

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Mid-power Safety Check

The most serious change in the procedures from those for model rockets is in the safety check. The mid-power procedures are a simplification of the procedures we use for high-power rockets. The safety check is done by the HP-SCO who is an experienced, high-power rocketeer.

The mid-power rules apply to any rocket carrying a total impulse of 40 Newton-seconds but less than 120 N-s. This applies to all F and G motors, or clusters of smaller motors whose total impulse is more than 40 N-s but less than 120 N-s.

Structure Check

The HP-SCO first checks the structural integrity of the rocket, including:

  • Attachment of the fins
  • Attachment of the engine mount
  • Recovery system attachments to nose cone and rocket
  • Packing of the parachute
  • Fit of the nose cone.

Stability Check

The next step is to check the stability of the rocket. If the rocket is a kit, we will accept that the rocket is stable if built to the kit's specifications. If the rocket is not a kit, the flier will have to present some sort of documentation to show the location of the center of pressure (CP) so it can be compared to the location of the center of gravity (CG). The CG should be at least one caliber (body tube diameter) ahead of the CP to assure good stability. Rockets that do not conform to this rule will need compelling evidence to convince the HP-SCO that they are stable. The RSO has the final say in any dispute over the flight-worthiness of a model.

Engine Check

The next step is to insure that the engine is safe and appropriate for the high-power model being flown. The HP-SCO checks the type of engine and verifies that it is on the list of NAR certified engines. Only engines certified by the California Fire Marshal are allowed at club launches. The HP-SCO weighs the rocket and compares the launch weight to the recommended maximum weight for the engine. The HP-SCO uses an altitude chart to compare the maximum altitude and the appropriateness of the delay.

The altitude charts are in the Appendix. The charts plot the maximum altitude and time to maximum altitude and delay to maximum altitude (time minus propellant burn time) versus launch weight for different engines.

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Pad Assignment

When all safety checks are complete, the HP-SCO checks off the appropriate boxes on the launch card and assigns the rocket a pad by placing the launch card on the clipboard for Rack 3 in the appropriate spot for the pad number assigned to the rocket.

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Load Your Rocket on the Pad

When the safety check and pad assignment are complete check to see if the mid-power rack is open for loading. If it is, go over and load your rocket. All sizes of launch rods from 1/8 to 1/2 inch are available, and are stored in the white tube in the center of the pads. We also have two “Black Sky” style launch rails. All the launch rods and rails are completely interchangeable on all the pads.

Most of the mid-power launches are from Rack 3 though we may use Rack 4 if the mid-power waiting line gets long and high-power pads are available. One of the mid-power pads from Rack 3 is shown in the following picture. Note that at the top of the tripod is a Panavice (the round silver thing). The Panavice is used to set the angle and direction of the launch rod. It is also used to lower the launch rod down to make it easier to load your rocket on the pad. To operate it, loosen the black knob, tilt the launch rod down until it is horizontal and tighten the knob. Put your rocket on the rod, tilt it back up, and finish preparing your rocket. To set the angle and direction, loosen the knob and tilt the rod down about 30 degrees, rotate it to the desired direction, then set the desired angle and tighten the knob.

One of the Rack 3 mid-power pads.

Inserted in the Panavice is an adapter that the launch rod fits into and that holds up the blast deflector. To change the launch rod, loosen the screw in the adapter and lift it out. Insert a different launch rod, tighten the screw, and move the standoff from the old rod to the new one. Do not leave launch rods laying on the ground as they can get stepped on and bent.

The launch clips are on a short piece of cord and are interchangeable with the cords on all our pads. We have launch clips with two or three alligator clips or with Aerotech Copperhead clips. Choose the clips that fit your igniter. Rack 3 has remote continuity checkers at each of the pads. Pressing the button tests continuity with a 0.5 ma (flashbulb safe) current. If continuity is good you will hear an audible beep and the LED lights.

A remote continuity checker on rack 3 with alligator launch clips attached.

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When all the pads are loaded, the LCO closes the pads. He then starts charging the remote launch box. A beeper in the box sounds as it charges (it takes about 30 seconds to charge) as a warning to bystanders. Do not go near the pads whenever the box is beeping. If all goes well, the LCO launches your rocket and you get to chase it. If your rocket does not fly for some reason, the LCO may let you go back and try to fix it. If we are busy, he will give you back your launch card and ask you to remove your rocket so that others can launch while you are fixing things.

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Last modified on Tuesday, 31-Mar-2009 17:00:00 PDT