Analyzing a Model Rocket's Flight

Transcription

1 Technical Publication # Apogee Components, Inc. All Rights Reserved Analyzing a Model Rocket's Flight Using The Apogee Flight Record To Learn Why Your Rocket Behaved The Way It Did. By Tim Van Milligan The Apogee Flight Record (P/N 35506) is a very powerful tool that can be used to help find out why your rocket behaved as it did during the flight. This form is very easy to use, as it is mainly a check-box form, which can be filled out in about 30 seconds following the launch and recovery of your rocket. To use this form, simply observe the rocket as best as you can, and then go down the form and place a check mark by each flight item that occurred during the flight. When you are finished filling out the form, you ll have a nearly complete description of your models launch. In fact, it is so inclusive, that you can easily write a narrative description of everything that happened after you pushed the launch button. This is very useful if you are writing a classroom report of how your rocket flew, or for writing a newsletter article describing how your club launch proceeded. It takes about two launches to get acquainted with the Apogee Flight Record form and how it should be filled out. The reason for the extra launch is that the first time you launch your rocket, you may not be paying close attention to the events happening during the flight. For example, you may have noticed that the model was spinning as it was travelling upward, but did you notice wether it was spinning clockwise or counter-clockwise? To get maximum benefit from this tool, you must pay very close attention and catch those little things that are very important. The more you use the Flight Record form, the more familiar you will be with those flight items that are important. You must think ahead and know what to look for. To help you do this, quickly scan down the various items on the Apogee P/N Flight Record so you are familiar with them. If you don t understand an item, seek the knowledge of a more experienced modeler. Another good source of information is the book: Model Rocket Design and Construction by Tim Van Milligan. This book, which can also be ordered from Apogee Components, has an extensive glossary describing various model rocket terms. Beyond explaining unknown words, the text and illustrations in the book are very helpful when it comes to fixing any problems with the model. Besides scanning the Apogee Flight Record, you might also consider writing a short description of what you expect the model to do when it lifts off from the pad. This will force you to really consider the flight, and examine in your mind the things that could possibly go wrong. If you know what could go wrong, you can take measures to prevent them from happening. This will lead you to develop a countdown checklist to help you remember those important preventative measures that need to be accomplished before the model is launched. An example of an extensive checklist is the Apogee Countdown Checklist (P/N 35507). The Apogee Flight Record is used to document how the rocket performed, but it is up to you to interpret the information so that something can be learned from the flight. As you review the Apogee Flight Record, some of the causes for the rocket s behavior may be readily apparent to you. Sometimes it may be more subtle. To help you understand why the rocket behaved the way it did, the rest of this publication will thoroughly explain what each item is, why it is important, and how the information can be used. Pre-Launch Information The date, time of launch, and location are used to document when and where the launch took place. These may yield clues about the weather activity during the launch. For example, there will probably be more thermals over the field if the rocket is launched in the early afternoon during the summer months. This may affect the rockets flight by making the rocket fall slower it the rocket is caught in a thermal during the descent phase of the flight. Similarly, in the winter, snow on the ground might prevent the formation of big thermals. The field size is important if you want to get your rocket back after launch. If you lose your rocket because it drifted away, the next rocket of similar shape and motor power should be flown on a larger field. If you are conducting altitude tracking or are trying to predict how how the rocket will fly, the elevation of the field may be important. This elevation can give you an indication of a starting point for the density of air. You can consult a textbook on aircraft design to find what the standard density of air is at any elevation above sea level. This density is important, because it will determine the amount of drag will be experience by the rocket, which will affect how high it flies. Launch Conditions The temperature and humidity can also be used to find out the density of air at the launch pad. As mentioned above, density is one of the things you need to know to find out the drag experienced by the rocket. These two parameters may also physically affect the rocket. For example, cold causes plastic parachutes to take a set, making them harder to open. Cold also makes plastic parts more brittle, and may also play a role in why rocket motors fail. Humidity is water moisture in the air. If the Page 1

2 humidity percentage is high, it could cause white glue to soften and weaken. It can also cause paper tubes to swell, increasing the friction between the nose cone shoulder and the body tube. Extra friction may make it hard for the nose cone to pop off for the recovery phase of the rocket. Atmospheric pressure is the direct measurement of air density. This is one of the items you ll need to know to predict the drag on a rocket, which is needed to estimate how high the rocket will fly. Wind speed, direction, and maximum gust levels can be used to determine the angle and direction of the launch rod to aim the rocket on its initial upward voyage. You will also use these parameters to locate the launch pad on the field so you will have adequate room to recover the model down wind of the the pad. Clouds can be very important in the launch of your rocket. If you can, record the type of cloud, the percentage of sky that is covered by clouds, and the altitude of the cloud base. Check out a weather book from your local library to help you in identifying the various types of clouds. You don t want your rocket flying into clouds because of the danger of hitting an aircraft. Clouds can also help or hinder your efforts of recovering your rockets. Thin wispy clouds make it very difficult to track your model on its course through the air, but thick puffy clouds can provide a good contrast to your model making it easier to find while it is in the air. A lone, small cloud, can be used to help spot the model now the rocket is falling against the backdrop of that cloud over there do you see it yet? Model Information This section tells you the specific things about the rocket for that particular launch. There are a lot of items that you should document about the rocket itself. These should be recorded on the Apogee Rocket Data Sheet (P/N 35505), which should be kept as a part of your Flight Record. The first area in this section is where you record the motors used for the flight. If you are flying an A motor and it arcs over too much, you might want to fly a B motor in the next flight. If you are flying a cluster of motors, all the motors should have the same delay so that their ejection charges all fire at the same time. Page 2 The payload used is just a short description of what cargo the rocket is carrying. This could be as simple as a raw hen s egg. The mass of the payload is important so that you don t exceed the lift-off mass that the rocket motor is capable of launching. The overall liftoff mass of the rocket should be recorded so that you can know why the model achieved the altitude or duration aloft that it did. Usually a lighter weight rocket will fly higher and longer than a heavier one. The predicted altitude and duration are recorded before the flight to estimate how the rocket will perform. After the launch, you can compare these with the actual altitude and duration of the model, and try to figure out why they are different. Launch Information This section is used to document those events which occur while the model is travelling upward before the recovery device is deployed. Method of Launch The method of launch will give you an indication why the model flew to the altitude that it did. A model with launch lugs and fired from a launch rod will have high drag and will not achieve maximum altitudes. The diameter of the rod will give an indication how much drag the lugs will produce larger lugs produce more drag than smaller ones. If the rocket is fired from a launch tower, it will have lower drag because the lugs will have been removed. A model launched out of a tower will have a less tendency to tip-off than one launched from a rod, because there is no flexing of the tower. The rail launcher is a cross between a rod and a tower launcher. It is simpler to build than a woer launcher, and is stiffer than a regular launch rod. So it doesn't flex when a rocket takes of. But it requires a lug on the model, so it produces similar amount of drag. A rocket launched from a piston launcher may fly higher because these launchers push the rockets into the air with a higher velocity. They don t stabilize the rocket as steady as a launch rod, so they suffer from tip-off more than other launch methods. Because of this, piston launchers are often used in conjunction with a tower launcher, so both boxes may be checked off on the Flight Record (see the chapter on Drag Reduction and Aerodynamics in the book Model Rocket Design and Construction for more information about tower launchers and piston launchers. The launch angle and launch direction are used to set the trajectory of the rocket. If the model is aimed wrong, you may lose it on a windy day. The benefit of documenting these parameters will help you in future flights so that the rocket s apogee can be increased, or to help you predict where the model will land. An example of what you might write down in this space would be: 5 from vertical; North- West. Recording the number of tries it takes to successfully ignite the motor s propellant will help you perform pre-flight checks in a more thorough manner in future flights. If you know that the last model caused significant frustration because you used up three igniters, you ll be more inclined to take your time and really make sure everything is ready for launch. Ignition Once the motor is ignited, the next section on the form describes what the model did. Successful translation of the launch rod into a vertical flight is what is desired, and usually this is what happens. If the model hangs up on the rod while the motor continues to burn, you know you have a problem. This will tell you that either the launch lugs are positioned wrong causing the model to bind on the launch rod, or that the rod is dirty or kinked. On the next launch you ll be sure to check how smooth the rocket slides down the launch rod. When the rocket hangs up on the rod, it usually causes the rod to whip violently around. If the pad is not sturdy, it could cause the model to fall over. Be sure to record this in the space left for Additional Flight Description. From this you ll learn to secure the pad to the ground with stakes, so that it can t tip over. Rocket s with motors mounted forward of the fins (or wings on a glider model) are more prone to snagging on the igniter clips. This problem can also occur on cluster motor launches, if one motor does not ignite, and it remains connected to the launch controller clips. If this happens on your launch, I m sure that you ll learn to

3 always secure the launch controller wires to the pad or an umbilical tower (rod). Tip-off was described before as a sudden direction change as the model leaves the launch rod. It can be caused several things: a sudden gust of wind, excessive flexing of the launch rod, or to slow a liftoff velocity; indicating that a higher thrust motor (not just higher total-impulse) should be used or that the models mass should be decreased. Recording that tip-off occurred helps you to learn the importance of flying only in the right wind conditions, with a rod of sufficient diameter to prevent whipping, or to use a motor with enough thrust to accelerate the model quickly to a safe flying speed before it leaves the rod. If you use a piston launcher and tip-off occurs, the next flight you ll be sure to combine it with a tower or a launch rod to avoid this hazardous situation. The rare problem associated with rocket motors is not really a failure, because the rocket may still take off fine and work well. This is called a motor chuff. A chuffing motor sounds like a very brief, but loud sputter or sneeze as the motor ignites. This is an ignition problem that indicates insufficient pressure inside the motor as it was ignited. This type of problem occurs only with composite propellants, because they need a minimum pressure inside the motor to sustain a proper burn. If the pressure doesn't build up fast enough, the propellant stops burning; hence the sneeze sound. But the temperature may remain sufficiently high inside the motor that the propellant re-ignites and the model may lift off fine. It is possible that the chuff may have been caused by inproper insertion of the igniter. On most composite motors, the propellant grain must be ignited from the top of the core. If the igniter only reaches halfway into the motor, it may only ignite the bottom portion of the propellant grain. This wouldn't be enough burning surface area to raise the pressure in the motor to sustain the burn. So make sure that you always insert the igniter fully into the motor, and that it doesn't slip backwards when you place the model on the launch pad. A chuff may be hazardous if the thrust during the sneeze is sufficient to lift the rocket off the pad. If the model clears the rod, it could take off horizontally if it reignites. Always inform the manufacturer of the problem so that it can be fixed, and use a launch rod of adequate length so that a chuff on the pad won't cause the model to go horizontal. The length of the rod should be the minimum required by the manufacturer of the motor. Motor failure is something that is not preventable by rocketeers, but it is important to record what happened so that you can inform the particular manufacturer of the problem so that they can take measures to improve motor reliability. The only thing a modeler can do is to handle the motors with care (don t drop them on hard surfaces) and that they be stored where the temperature and humidity remains fairly constant. Mainy failures are preventable by modelers: keep motors cool and dry whenever they are stored particularly black powder propellant motors. Motors usually fail in three ways: side wall failure, spit nozzle, or forward bulkhead failure. Side wall failure will nearly always destroy the aft end of the model, and the motor case will have a split down the side. This type of failure indicates a defect in the case of the rocket motor. Spit nozzles are less damaging to the model, as once the nozzle ejects from the motor, the model just sits on the pad and finishes its burn as there is no thrust being produced. This type of event indicates that the nozzle was not bonded properly to the case of the motor. Sometimes the case fails where the nozzle is bonded, and this decreases the strength of the bond, and the nozzle is ejected from the motor. You ll have to look closely at the motor after the burn to see if this was the failure mode. Forward bulkhead failure, or blow through is characterized by a big ball of flame shooting out the forward end of the model. This typically singes the parachute and anything else inside the model. Again, this is a bonding problem, although this time it is with the ejection charge or other forward bulkhead used to keep the hot gas pressure within the rocket motor. In black powder motors, this is often caused by the motor being overheated prior to ignition. That is, it was probably stored in the hot trunk of a car. Cluster Ignition Recording whether or not all the motors ignited successfully will explain a lot about why the rocket didn t travel very high. You ll also want to try to determine why some of the motors didn t ignite. The problem could have been either a igniter that wasn t touching the propellant (igniter burned, but motor didn t ignite), or there was an error in the set-up (mis-wired, or not properly twisted together). It is also possible that one motor may have a motor failure, in which case you should note it in the space for Additional Flight Description. Staged Models Similar to clustering, you should record whether or not all stages in a rocket s flight operated correctly. Since it is possible to have more than two stages, record which stage had a problem (if any) in the blank provided. A lot of times, a failure to have a model properly stage is a pre-flight prepping problem. Having a record of past problems will help you in future flight to be sure everything is prepped properly. Trajectory Once the model clears the launch rod, it will start its trajectory course. An unstable flight is characterized by the model failing to follow a straight course. The worst case of this will end in the rocket smashing itself into the ground while still under thrust. If the rocket is unstable, you ll want to figure out why. It could be as simple as the igniter clips catching on a fin and ripping it off. It may also be that the rocket was not checked for stability before it was launched. A spinning but straight ascent will cause the model to fly very straight. Sometimes this is very desirable. But because the model is spinning, drag increases, resulting in lower altitudes. You ll want to record the direction of spin (clockwise or counter-clockwise) in the space additional flight description. Spinning can be caused by several different items. I highly suggest reading the Stability chapter in the book Model Rocket Design and Construction to find out how spinning is induced. Corkscrew ascent is easy to see, as the smoke trail from the motor clearly makes it visible. It is usually a result from a canted rocket motor mount, and/or a single canted fin on the model. The most desirable trajectory is a Straight-Up Flight. Hopefully this will be the box checked after your rocket s Page 3

4 launch. The Non-Vertical Trajectory is a stable one, and is differentiated from the Weathercocked Into Wind flight in that the wind did not cause the rocket to veer from vertical. Figuring out why a rocket took off non-vertically is challenging. It could be tip-off from the launch pad, tipoff as a result of staging problems, or it may be associated with a lift force developed by some part of the rocket (such as forward fins). Weathercocking only occurs when a breeze is blowing as the model is launched. The model that weathercocks will gradually turn into the direction from which the wind is blowing. When the model weathercocks into the wind, it means that the rocket is overly stable (the fins are too large and/or the rocket has its CG too far forward). If the problem is excessive and the trajectory is nearly horizontal, you should not fly the model unless there is no wind. Or, you could physically change the rocket by decreasing the fin area or moving the CG further rearward. Even though the launch rod is angled in a certain direction, there is no guarantee that the model will fly in that direction. For this reason, after the model has left the pad you should document the actual direction the model traveled, and approximate the angle from vertical in which it flew. Recovery Information The point during the flight when the ejection charge in the motor fires may be important to the success of the flight. If the rocket is still travelling upward when it fires, it could shred the parachute. This indicates that a longer delay motor should have been selected for the rocket. The best time for the ejection charge to fire is when the rocket is at its apogee (highest point). At this point, the rocket will be travelling at its slowest speed, so forces on the recovery device will be minimized. If the model arcs over and is heading downward when the ejection charge fires, it means a shorter delay should have been selected, the model was aimed incorrectly, or it weathercocked excessively into the wind. This situation could also result in the parachute being damaged. If the ejection charge fires when the model was on the ground, you have a Page 4 serious problem with your rocket. Typically the rocket itself is unstable or was caused to become unstable by something else and was on the ground long before the ejection charge fired. You will have to determine what caused this and make sure it doesn t happen on other flights. An ejection charge failure may result in the model streamlining into the ground. As the thrust portion of the flight ends, start counting (one-one thousand, two-one thousand, three-one thousand, etc.) until you see or hear the ejection charge firing. This will give you an indication of the accuracy of the delay time built into the motor by the manufacturer. If the ejection charge fires before you expect it, it means the delay had a faster burn than normal. Similarily, if the ejection charge doesn t fire for a longer than expected time, the delay burned slower than normal. Sometimes, although rarely, the delay fails to ignite properly and doesn t burn at all, and the ejection charge will never fire off. This can be seen by a lack of a smoke trail after the propellant is through burning. A weak ejection charge also occurs infrequently, but when it does, the recovery device fails to eject from the model. You will have to examine the motor after the flight to see if the ejection charge did or did not fire. Recovery Device The recovery device can deploy fully, not deploy at all, or only partially deploy. Deploying fully is what is most desirable. Not deploying at all can be caused by any of a number of factors. These will be covered in the next section. Partial deployment can be caused by improper prepping of the recovery system (i.e., parachute was folded too tightly), or it was partially melted by the heat of the ejection charge which indicates that more recovery wadding is needed for future flights. Make a note of the cause on the bottom of the Flight Record. Parachute Descent This section describes how stable the model is once the parachute deploys. It is assumed that the canopy has fully opened. When a parachute is used, it is often desireable that the model descends in a "stable" manner. This is characterized by the model or other load being suspended without much swaying. If the "load" under the canopy sways, it probably means that the suspension lines (shroud lines) are of unequal length. It could also be caused by a strong breeze blowing the model around. The load can also be seen to be spinning. This could be caused by tangled suspension lines, causing the canopy to rotate. It could also be caused by the "load" being out of balance below the canopy. This can be allieviated to some degree by lengthening the suspension lines. Reason for Recovery Device Failure If the recovery device does not deploy, it could be caused by any of several problems. These include: Damaged Chute/Streamer - such as being melted by the ejection charge Improper Installation - such as the parachute being folded too tight. Chute Separated From Model - Which might occur if it was ejected when the model was still travelling very fast, or if you forgot to attach it in the first place. Motor Ejected From Model - Which indicates that the motor was improperly installed, or the motor mount failed when the ejection charge went off. Ejection Charge Failure - Which was explained previously. Secondary System Failure - If the model does not rely on the motor s ejection charge to deploy the recovery system, and uses some other system (such as radio controlled deployment); and this system fails to perform properly. Nose Cone Too Tight - This is a common problem with inexperienced modelers. It usually leads to something else failing, such as the motor mount. Obstruction in Tube - This is another problem that occurs too often. Check the inside of the tube with a flashlight to make sure nothing is stuck inside before flight. If the model has an ejection charge baffle, make sure it is not clogged with residue from previous flights. Unplanned Separations Besides the parachute being shredded from the rocket, other parts might fall off during flight too. If something falls off the rocket, mark the box, and record what

5 happened in the Additional Flight Description area on the form. Descent Speed Recording the descent speed might explain why damaged occurred when the model landed on the ground. Slow, Average Speed, and Very Fast are purely subjective descriptions. You have to have an idea in advance of the flight how fast you think the model should fall. If the parachute is melted into a plastic wad, your marking the very fast box would be a good description. When the model is caught in a thermal, its descent speed will be extremely slow. In certain situations, the rocket could rise in the thermal and gain additional altitude (and float away). A ballistic trajectory into the ground is very hazardous, and indicates something went wrong with the flight. Specific items causing this situation were mentioned previously. Landing How and where the rocket lands is valuable information that can be use in future flights to aim the rocket better. Most of the items in this section are self explanatory, and need no further definition. The difference between a hard and soft landing would be the surface they landed on. If the model landed on grass it would be a soft landing, while landing on concrete would be considered a hard landing. A ballistic trajectory into the ground would be considered a crash landing, as would and unstable rocket hitting the ground. Recovery If you got your model back after launch, you can say you recovered it successfully (Full Recovery). If it gets hung up on a power line, the boxed marked would be Model Not Recoverable. Recording the recovery information or lack of it would be one explanation why some parts of the Apogee Flight Record were left incomplete; such as the flight damage section. Recording where your rocket landed and how far it was from the launch pad will give you an indication of how well you aimed the rocket with the prevailing winds. If the model was lost, you might have a general idea where it might have landed. After recording this information, you could later search the area to see if you can find the model. Helicopter Flight Recovery This is a special section describing those items specific to these types of models. Deployment This is similar to the recovery device deployment section, and is pretty much self descriptive. If you can determine why the model only partially deployed, write that in the space for additional flight description. This could be as simple as a rubber band falling off the model. Cause of Deployment Failure Helicopters are typically complex, and can use a variety of methods to hold down helicopter blades, as well as deploying them. The items listed in this section are just a few things that could go wrong and cause a blade deployment failure. A burn-string is a thread that is wrapped around the model to hold the blades down until the ejection charge fires, burning the thread in two. Sometimes the hot gases from the ejection charge simply miss the string, or the string gets snagged on some other part of the rocket. These situations would cause the blades to not deploy. The other items in this section on the Apogee Flight Record are self explanatory. However, since your model may operate in some other manner, a separate check-box has been made available to fill in with any other problem that may cause your model to not deploy. Spin Direction The direction of the spinning helicopter may be important to you. It may spin in a direction opposite what you have expected, or it may not spin at all. This would be a major problem, and you would have to look for its cause and find a way to fix it. See the section in the book Model Rocket Design and Construction for help in determing and solving helicopter problems. Descent Helicopters are sometimes finicky and don t descend the way you anticipate. An upside-down descent indicates a problem with the CG position. It may be that the motor shifted unexpectedly at deployment, or the blades are mounted at the wrong position on the model. Check the dihedral angle of the blades too. The larger this angle, the more stable the helicopter will descend. If the model uses rubber bands, make sure they are not stretched out so they don t pull the blades to the proper position. A model that flip-flops or lays horizontally as it descends has a problem similar to that of the one that descends upside-down. The solutions to its behavior are the same as for the upside-down model. A model that exhibits precession as it spins has a balance problem. Make sure all the blades have a similar weight and airfoil shape. Also make sure they are mounted at the same angle-of-attack when they are deployed. Tracking Data This section is used to document how long the model stayed in the air, and how high it flew. Determining how long the model stayed in the air is simple: time it with a stop watch. This can be compared to your previous estimate of how long you anticipated the flight to be. You ll have to also use the recovery information to determine the differences in the flight times. The data required to determine altitude are the elevation and azimuth angles from the people taking the angular measurements. Once the altitudes are found for the different trackers, they are averaged and a closure error is computed. This error should be typically less than 10% for the data to be considered valid. This means that the altitudes computed by the trackers should be within 10% of each other. The closer to 0% the better. Glider Flights The flights of glider models yield a lot of data that can be recorded. Like helicopter models, the data is recorded in its own section. Trajectory Because of the wings on gliders, boosts are no longer assured to be straight up. An unstable glider has the same types of problems as an unstable rocket during boost. The relationship between the model s CG and CP is wrong. The cause may also be a Page 5

6 stabilizer or control surface that has been deflected, and is in a wrong position. You ll have to figure out why the model was not stable during boost, and document it in the additional flight description section on the form. Like the typical model rocket, the glider could also perform a boost where the model spins. The spinning can keep the trajectory nearly straight. The model can also corkscrew as it ascends into the aire. This is typically caused by one wing producing more lift than the other, or by a deflected control surface. Because of the wings, the model will sometimes loop during ascent. The direction of the loop is important to determining why it performed a loop. If it pitches down (an outside loop) under power; a thrusting loop, the motor is mounted in such a way that it is producing a downward pitching force on the glider. Either decrease the thrust angle of the motor mount, or position it lower near the centerline of the model. Alternatively, if the model pitches upward (an inside loop), the wings are producing more lift than the motor s thrust can compensate for. In this situation, the pod should be made longer and/or the motor s thrust angle be increased and the motor be mounted higher than the wing. Looping after burnout, Loop during Coast, is very common. Nearly always, the model will pitch upward after termination of thrust. To compensate, the CG of the glider during the ascent phase should be moved further forward. This can be done with a longer pod on the front of the glider. A climbing ascent is where the model climbs to altitude at an angle between vertical and horizontal. For maximum altitude, the angle should be as close to verticle as possible. Climbing ascent can be caused by any of a number of things: a gust of wind (tip-off), launching at the wrong angle, or an improperly trimmed glider. If the climb angle is very small, you might want to check the Horizontal Flight box on the form instead. Transition Phase Page 6 After the rocket motor burns out and the ejection charge fires, the glider enters a transition phase. During this time period, the models flight must change from a ballistic trajectory into a steady glide. This involves changing the relationship between the model s CP and CG; either moving the CG rearward or moving the CP forward. There are a number of ways that this can be accomplished, and they are covered in detail in the book Model Rocket Design and Construction by Tim Van Milligan. One of the more popular ways to make this transition on a boost glider is to drop the motor pod off the model. On the Apogee Flight Record there is check boxes for a couple of things that could go wrong with the motor pod on the glider. These are that the pod fell off during ascent of the model, the pod got stuck and did not fall off, or that the glider got entangled in the recovery device of the pod (called a Red Baron ). Any of these occurrences could lead to a very short flight. On some models, other mechanisms are used to change the relationship between the CP and CG. If these mechanisms fail to operate properly, the glider will probably nose dive to the ground and destroy itself. Record in the space for Additional Flight Description what actually happened. The best circumstance is that the model successfully make the transition and begin its glide. Causes of Mechanism Failure There are so many ways that the transition can occur that it would be impossible to list every way a transition mechanism failure could occur. The causes listed on the Apogee Flight Record are similar to those listed as causes for helicopter deployment failure. Additionally, a space is available to write in what you believe caused the mechanism to fail. Stability of Glide For the glide to be nice and flat, it needs to be stable in pitch, yaw, and roll. It also needs to be trimmed properly for the flight. Because of the complexity of gliders, fixing stability problems for gliders will not be covered in this technical publication. This topic is discussed extensively in Apogee Technical Publication #8 Trimming Gliders (P/N 36008). One item that you might want to note in the space left for additional flight description is the tightness or the diameter of any turns that a glider makes. If the model flew inverted, check the box on the form. This is typically caused by insufficient amount of wing dihedral, and can be easily corrected on most models. Turn Information In this section, you'll probably check more than one box. First, check the box that indicates which way the glider turned (Left, Straight, Right). Then check the box that describes the type of turn, either a nice gentle flat turn, or the dreaded Spiraling Dive. A flat turn is desirable, as it keeps the model from loosing too much altitude hence a nice soft landing. The spiraling dive needs to be fixed for the next flight. You ll want to read Apogee Technical Publication #8 Trimming Gliders (P/N 36008) to help you figure out how to fix this problem. A tight turn is desirable if you are trying to get the model to rise in a thermal. Although it is less efficient if the model isn't in one, as it will fall faster. A wide turn radius will be more efficient, but it might not get caught in a thermal (if you want to get into one). It is up to you to decide whether the turn should be tight or wide. Post Flight Information Flight Damage Determining flight damage is fairly subjective. There is no clear-cut definition between minor and major damage. To one person a cracked fin would be major damage, while to another it would be considered minor. You will have to decide for yourself whether any damage occurred to the model is minor of major. A space has been provided on the form to describe any damage to the model. If the same type of damage occurs often, you might want to find out how you can prevent this from happening. Flight Grade Assigning a grade to the flight is also purely subjective. An observer watching the flight may say it was excellent, because they like to see a good crash, while to you the builder of the model, it was totally lousy. Over time, you may even assign a different grade to the same flight. For example, if you are a novice rocketeer, you might assign a flight where the parachute melted into a plastic wad as a good flight after all, you got the model back with very

7 little damage. But when you become more proficient, the same flight would be rated mediocre or even lousy depending on your newer high standards. Additional Flight Description As eluded to throughout this publication, there are many other things that can happen during a flight that lead to conclusions about why the rocket behaved in the manner in which it did. Use the space Additional Flight Description to write down any of those items and any other perceptions you may have that may be important to the flight. The more information that you have about the flight, the easier it may be to determine why the rocket performed in the way it did. Lessons Learned The Lessons Learned section is probably the most important area on the form that can be used to make you a better modeler.if you learned something on the flight that will make future launches of that model more successful, or what can be done to avoid a lousy flight, write it down quickly. It is always possible to learn something new from every flight you fly, no matter how good of a modeler you think you are. This important information is too valuable to lose by forgetting to write it down. Conclusions We hope that this technical report explained the importance of every item on the Apogee Flight Record. But beyond their importance, it is hoped that you now recognize and understand how the form can be used to learn something from each and every model rocket flight. Filling out the form is not a chore or something to be avoided; in fact it is so enjoyable, it is almost like playing a game! The Apogee Flight Record is a quick and very powerful tool to help you learn more about model rocketry. It doesn t take very long to learn to use it, or to fill it out after a rocket flight. Get yourself a clip-board so that you can fill the form out as soon as possible after the flight. The sooner it is filled in, the more accurate the information will be on the form. If you have friends around when you launch the model, get there perceptions of the flight recorded too. I don t believe that having too much data available is a bad thing. You ll have to sort through it later, but you ll be able to determine why the rocket behaved in the manner it did. Visit us on the internet at: Page 7

8 Rocket Name Owner's Name Flight No. APOGEE FLIGHT RECORD Apogee Components, Inc., 1995 Pre-Launch Information Date Time of Launch Location Field Size Elevation of Field Launch Conditions Temperature Humidity Atmospheric Pressure Wind Direction Wind Speed Max. Gust Speed Cloud Type Model Information Motors Used (No. / Type:) 1st Stage 2nd Stage 3rd Stage Payload Used Payload Mass Liftoff Mass Predicted Altitude Predicted Duration Launch Information Method of Launch: Rod (Dia.) Rail Tower Piston Launcher Launch Angle & Dir. No. Of Tries To Ignite Motor Igniton: Cluster Ignition Staged Models Trajectory: Successful Lift-Off Hung-up on Rod Caught on Igniter Clips Tip-Off (Went Horizontal) Motor Chuff Motor Failure Side Wall Failure Spit Nozzle Forward Bulkhead (Blow Thru) Motors Did Not Ignite All Motors Ignited Successfully All Stages Ignited Successfully Stage # Did Not Ignite Stage # Had Motor Failure Unstable Spinning But Straight Corkscrew/Barrel-Roll Ascent Straight-Up Flight Non-Vertical Trajectory Weathercocked Into Wind Trajectory Angle & Dir. Additional Flight Description Recovery Information Tracking Data Ejection Occurred: Ejection Failure Flight Duration During Ascent Fast Delay Burn Altitude Tracking At Apogee Slow Delay Burn Data While Descending Delay Didn't Burn Model On Ground Weak Ej. Charge Recovery Device Deployment Cause of Deployment Failure Spin Direction Descent Did Not Deploy Partially Deployed Deployed Fully Parachute Descent Stable Descent Some Swaying of Load Under Canopy Tangled Lines Caused Spiral Descent Reason For Recovery Device Failure Damaged Chute 2nd System Failure Improper Set-up Tight Nose Cone Chute Separated Obstruction In Tube Motor Ejected Other Ejection Failure Unplanned Separation Occurred Descent Speed Landing Soft Landing Hard Landing Water Landing Crash Landed Recovery Full Recovery Model Lost Caught Thermal Slow Average Speed Very Fast Ballistic Trajectory to Ground Dist. & Direction From Pad Model Landed Last Known Position of Lost Model Landed in Tree Caught on Wire Landed on Building Drifted Out-of-Sight Model Not Recoverable Part of Rocket Lost Helicopter Flight Recovery Full Deployment Partial Deployment Did Not Deploy Blade(s) Broke at Deployment Burn String Didn't Burn Thru Excessive Friction in System Misalignment of Parts Improper Set-up Other Clockwise Rotation Counter-Clockwise Rotation No Rotation Upside-Down Descent Flip-Flop Descent Descended Horizontally Proper Descent Orientation Model Showed Precession Lessons Learned (ways to improve next flight) (why flight might have gone bad) Trajectory Transition Phase Cause of Mechanism Failure Longitudinal Stability in Glide Roll Stability Lateral Stability Flight Damage Glider Flights Looped During Coast Climbed at Angle Straight-up Boost Horizontal Flight Pod Separated During Ascent Pod Did Not Separate Red Baron Transition Mechanism Failure Proper Transition Occurred Burn String Didn't Burn Thru Excessive Friction in System Misalignment of Parts Improper Set-up Other Steep Dive Shallow Dive Good Glide Shallow Stall Deep Stall Rolled Left No Roll Rolled Right Yawed Left No Yaw Yawed Right Model Flew Inverted Turn Information Elevation Angle #1 Azimuth Angle #1 Elevation Angle #2 Azimuth Angle #2 Baseline Length Comp. Altitude #1 Comp. Altitude #2 Avg. Altitude Closure Error % Unstable Spinning Climb Corkscrew Thrusting Loop Flat Turn Sprialing Dive Left Straight Right Post Flight Information No Damage Scuffed Paint Describe any Damage to Model Damage Unknown - Model Lost Flight Grade Excellent Good Tight Turn Wide Turn Minor Damage Major Damage Mediocre Poor Page 8