Reference / Paper · 2017
Peak of Flight #453: TARC Flight Report Sheet
Apogee Components' Peak of Flight newsletter, issue 453 (2017-10-03).
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- apogee-components
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Reference / Paper · 2017
Apogee Components' Peak of Flight newsletter, issue 453 (2017-10-03).
Apogee Components' Peak of Flight newsletter, issue 453 (2017-10-03).
ISSUE 453 October 3rd, 2017 IN THIS ISSUE TARC Flight Report Sheet www.ApogeeRockets.com/Building-Supplies/Body-Tubes/Tube-Assortments/2017-2018-TARC-Bulk-Pack-of-Parts TARC Flight Report Sheet By Tim Van Milligan Way back in 1995, I created the Apogee Flight Record sheet (https://www.apogeerockets.com/Rocket_Books_ Videos/Data_Sheets/Flight_Record_Data_Sheet) that I still personally use when I’m developing new rocket kits (Figure 1). The purpose of the document is to have a quick sheet that I can record the important information about how the rocket flew. It was designed as a check-box form that could be quickly filled out after a launch so that none of the important launch information would be forgotten. helicopter recovery models. This is not needed for the TARC contest, so I thought I’d try to simplify it. But in the end, I added a lot more check-boxes that I think will be even more useful for TARC rockets. In this article, I thought I’d explain what the items mean on the new TARC Flight Test Data Sheet. I know that most students are new to rocketry and may not know the meaning of most of the items on the list. And more critical to the mission objective, you should know why it is important to collect the information and how it can be used to make your next flight more successful. You can download the TARC Flight Test Data Sheet from the Apogee Components website at: https://www.apogeerockets.com/Rocket-Books-Videos/ Data-Sheets/TARC-Flight-Test-Data-Sheet The TARC Flight Test Data Sheet is used to collect the initial data from your rocket launch. This is termed “raw” data. Raw data is not processed or sorted in any way. It is like jotting down notes on a sheet of paper, although in this case the sheet is designed to prompt you on what I think are the most useful parts of data. To use it best, you should fill it out on the launch field. There are some portions that can be filled in prior to launch, but most of it should be filled in immediately after the launch. Have a clipboard and a pencil in your hand as the rocket takes off. Before the launch, have a group huddle and review the various sections so everyone knows what they should be looking for during the launch. Things happen very quickly during the flight, and if you don’t remind yourself what you should be looking for, you’ll miss it, I guarantee it. I’ve asked many observers of my flights which direction the rocket was spinning when it took off. Their answer: “It was spinning?” You’ll be kicking yourself later because you’ll be missing key information because you weren’t prepared to watch for it. Figure 1: The original Apogee Flight Record data sheet. The Apogee Flight Record was the basis for the new sheet that I specifically made to help TARC students. The original Apogee Flight Record was designed to collect information on all types of rockets, including gliders and About this Newsletter You can subscribe to receive this e-zine FREE at the Apogee Components website www.ApogeeComponents.com, or by clicking the link here Newsletter Sign-Up Page 2 So, when you’re holding your pre-launch huddle, be sure to include all the spectators too. Ask them to help you watch for the various events during the launch. It is not cheating to have extra witnesses of the launch, it is SMART! Hold the pre-launch huddle, even if you plan on videotaping the launch. Most camera operators are not prepared for how fast a rocket takes off, and Newsletter Staff Continued on page 3 Writer: Tim Van Milligan Layout/Cover Artist: Chris Duran Proofreader: Will Franks Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 2 therefore most recordings only show the smoke trail following the rocket. Here’s a hint: if you’re videotaping, you need a camera with an eyepiece, not just a flipout screen. Trust me on this… It greatly increases your chances of getting a good video of the rocket taking off. Here’s another trick to use to get someone else (like your parents) to retrieve your rocket for you. Start filling out the form as soon as the rocket takes off. When your parents see you huddled together over a clipboard making notes, they’ll think that what you’re doing is critical, and they will volunteer to get your rocket for you. Let them! Because, in fact, what you are doing when filling out the form is critical! The success of your next launch is more assured when you’re recording information than if you were retrieving your rocket. I would suggest you assign two students to work together and start filling it out as soon as the rocket takes off. As other students come back from their duties during the launch, they can give their insights and perceptions of the launch too. Before you pack up your launch equipment and make the drive back home, hold one last group meeting to go over the flight. Make sure you’ve got the Flight Test Data Sheet completely filled out before you leave the field -- even if the launch was a complete success. The flight is still fresh in your mind, so your recollection will be the most reliable at this point. Be sure to include the observations from any outsiders that might have witnessed the launch. Their added insight is always important too. Especially if you’ve briefed them before the flight and asked them to be on the look-out for certain events too. Speaking from personal experience, when I was on the Delta II rocket launch team, we would always have an all-hands meeting immediately after every launch. It was a way to make sure that our next launch would meet its mission objectives as well. What you’re doing here with this meeting will have the same effect on your project too. You’ll get to your goal a lot quicker. Later, when you get back to school to start working on your next launch, you will probably take the data from this sheet and condense out a summary sheet. For example, you’ll probably keep a log of the altitude and the duration of the flights you’ve made to show your progress on zeroing in on the mission objectives. That is great. But what happens if you’ve had 10 launches that were getting closer to the objectives and all of a sudden, you’ve got one that wasn’t so good. You’ll want to get out your original TARC Flight Test Data Sheets and see what changed and could possibly cause the rocket to stray further from the objectives. So, don’t lose the sheets! Save them in a 3-ring binder so you can quickly go back and find the data when you need it. The Information on the Datasheet Rocket Name Flight No. TARC Team Name Figure 2: Title section of the data sheet Why record the rocket name? Because it will help you remember which version of the rocket you’ve launched. In your progression in the contest, you’ll build and launch several different rockets. You want to be sure to keep things sorted so you can better remember which flight you’re discussing with your team. I would highly suggest that you use the same name that you used on the computer design file. So, if your computer RockSim file was called “TARC Design Version 1,” use that for your rocket name in this section. It will make more sense later rather than coming back to this data sheet and the name was in honor of your school’s mascot, like “The Tiger Spirit.” Continued on page 4 www.youtube.com/apogeerockets Page 3 Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 3 The TARC Team Name is on the title block because many schools will have multiple teams in the contest. If you all go out to launch on the same day and your paperwork gets mixed up, you can sort out later which sheet belongs to which flight. The “Flight No.” can be used to record the order in which the rocket was launched. I would suggest you use it to track the number of the flight that was launched on that specific day. For example, say that on both Monday and Tuesday you launched 3 rockets each day. You would have two flight number 1’s in the binder. This may sound confusing, except when you try to remember the specifics of the flight. For example, when on Thursday you get together with your group and you ask, “do you remember the first flight we made on Tuesday?” Isn’t that more likely to bring up a memory than if you asked: “do you remember flight number 4?” The person will probably respond by asking: “was flight number 4 the first flight on Tuesday?” Yes, it was. But it is easier to The field size will probably be approximated at this point. That is ok. We just want to record it for future reference. For example, say your rocket drifted away after it was launched. On the next flight, you’ll probably want to find a bigger field so that recovery of the rocket can be achieved. The elevation of the launch site is recorded so you can go back into your RockSim simulations and try to duplicate the flight in computer simulations. By reproducing the flight in the software, you can zero in on the Coefficient-of-Drag (Cd) of your rocket, which you will need to make a better motor selection in the future. Pre-Launch Information Date Time of Launch Location Field Size Elevation of Field Figure 3: Pre-Launch Information section Figure 4: From the free Google Earth software, you can get the location, elevation, and the area of the launch site. remember it by calling it the first flight you made on Tuesday. In the Pre-Launch Information section, you’ll record the date and time of launch. This can be used to remind yourself later about the day’s events. The location will probably be generic, like “city football field.” But you can be more descriptive if you want, by recording the longitude and latitude of the launch range. Where do you find the elevation of the field? Good question. I would suggest downloading and installing the free Google Earth application for your computer. With it, you can get the elevation and the latitude and longitude coordinates of your launch site as seen in the bottom right corner of Figure 4. Continued on page 5 https://www.apogeerockets.com/TARC_Supplies Page 4 Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 4 You can also use the perimeter feature to find the area of your launch site. Later, you will see how you can use Google Earth to find the distance and direction to the location where the rocket landed. This will be helpful information when you are trying to match the actual performance of the rocket with the computer simulations you performed. Experiment Information Changes made to rocket or launch set-up from the last launch? What do you want to test/accomplish in this launch? the field to take these readings. But if you don’t, estimate as best as you can. The most important readings are the temperature and the wind speed. There are all kinds of weather apps for your smart-phone that you might try using too. Launch Conditions Temperature Humidity Atmospheric Pressure Wind Direction Wind Speed Max. Gust Speed Cloud Type Figure 6: Weather conditions on the day of the launch Model Information Motors Used (Number and Type:) Figure 5: Experiment Information In the Experiment Information section of the TARC Flight Test Data Sheet, you’ll record the changes made to the rocket or the launch set-up compared to the last launch you’ve performed. Why record this information? Because you never know when you might lose a sheet out of your binder where the information is kept. If the previous flight information sheet is missing, you still have a record of what changes you’ve made for this current flight. If there were no changes, then write “No changes.” If you leave it blank, and you come back to this page ten launches later, it will take you a lot longer to figure out what is different about this launch versus the previous one. You’ll save yourself a lot of time and frustration by having something in this section. Try not to leave anything blank if you can help it. You also might want to see a specific difference in this launch compared to the last one, which might be called your goal. Say the previous launches were arcing heavily into the wind and you wanted to try to reduce that tendency. Then you might say something like: “repositioned the fins to try to reduce the weathercocking.” At the end of the flight, you can better draw conclusions to figure out if you were successful or not. In the launch conditions section (Figure 6), you want to record the weather conditions at the time of launch. Again, the reason for this is so that you can try to duplicate the launch in your RockSim simulations. The closer you can come to mimicking the actual launch using the software, the faster (fewer launches) you will get to your mission objectives. It helps to have a portable weather station with you on Page 5 Type of Altimeter: Color of Rocket: Distinguishing Features: Payload Used: Eggs Empty Mass Payload Mass Ballast Mass Liftoff Mass Simulated Eggs Figure 7: Model Information The model information (Figure 7) is important because you want to document this model and how it differs from previous rockets you might have built for the contest. I suggest you put a print-out of the RockSim configuration into the binder stapled to the Flight Test Data Sheet for additional reference. Adding a photo of the rocket is also a good idea too. But this section on the sheet is specifically where you’ll record the last-minute condition of the rocket. Continued on page 6 Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 5 For the motors used, remember to include both the motor designation (called “Type”) and the manufacturer, such as Aerotech F50-7. Sometimes there are two different manufacturers that make the same motor type so be sure to include the manufacturer. Some teams also like to include the “Lot number” of the motors. This is a specific number that the manufacturer puts on the motor to indicate what day it was made. If there is a problem with a motor, they’ll go back to their records and pull up any information about the motors that were made on that day and try to figure out how it was different. If you are using a cluster of motors (more than one ignited at the same time), be sure to include the number of motors from each type. For example, 2X Estes D12-5. The 2X is shorthand writing and means “two times,” as I used two Estes D12-5 motors instead of just one. There are three different altimeters approved for use in the contest. But sometimes you might want to use a different one for testing purposes. So be sure to include that information here. The color and distinguishing features are recorded just in case you lose the rocket. If you do, you might go to the land-owner of the field and say: “I lost a red rocket that had a decal with our school mascot on it. If you find it, please give me a call.” Incidentally, you should write your contact information on each rocket, in the case it gets lost. If you put the word: “Reward” on the rocket, you’ll probably get it back even faster. On my rockets, I write: “Reward! If found, please call 719-535-9335.” That will reach me here at Apogee Components. For your payload used section, you can quickly check off if you used real eggs, or simulated eggs for the flight. I suggest simulated eggs in the form of modeling clay for most of your flights. If you break real eggs, it can get messy. The mass of the rocket is critical, so be sure to bring a portable scale with you to the launch field so you can get final weights right before launch. The one mass you may not be familiar with is the one called “ballast mass.” Ballast is extra weight carried on board that makes the rocket heavier. A heavy rocket doesn’t fly as high as a lightweight one. So, if your previous rocket flew too high, and you didn’t make any other physical changes to the rocket, you can add ballast mass to the model so it doesn’t fly as high. I like to use modeling clay for ballast mast. It is a little sticky, so you can press it to the inside of the tube and most times it will stay in place. You can also use sand as ballast too. Launch Information Method of Launch: Rod (Dia.) Length Rail Length Launch Angle & Direction. No. of Tries to Ignite Motor Launch: Successful Lift-Off Hung-up on Rod Caught on Igniter Clips Tip-Off (Went Horizontal) Catastrophic Motor Failure Side Wall Failure Spit Nozzle Forward Bulkhead (Blow Thru) Trajectory: Straight-Up Flight (no spin) Spinning But Straight Corkscrew/Barrel-Roll Ascent Unstable Non-Vertical Trajectory Weathercocked Into Wind Flight PathTrajectory Angle & Direction: Figure 8: Launch Information The first section of the launch information is where you can record whether you used a launch rod or rail to launch the rocket. For either method, record the length of the device so you can go back into RockSim later and use the information to try to duplicate the launch. If you use a launch rod, there is a space to record the diameter. It isn’t so important, but I like to have the information. If the diameter is small, the rocket can sway around and take off at an angle that you didn’t intend. Just keep that in the back of your mind if you’re trying to figure out why it didn’t go in the direction you Continued on page 7 wanted. Page 6 Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 6 Next, you want to record the launch angle and direction that the launch guide (either the rod or the rail) is pointed. To get this information, take out your smartphone and open the compass app. Point the phone in the direction that the rail is aimed, and write down the direction. You can also get the latitude and longitude of the launch pad. This will also come in handy when you retrieve the rocket because you can note the coordinates where you picked it up so you can find the distance traveled. Figure 10: With the same compass application on your smartphone, you can measure the angle from vertical that the rail was tilted. Once the rocket fires, things start happening faster. If things go as expected, there isn’t a lot of information to record. Hopefully, you’ll just check the box that says, “Successful Lift-Off.” This means the rocket exited the launch rod and started its journey into the sky. Everything else in the “Launch” section of the data sheet is an undesirable occurrence. Figure 9: From your phone, you can get the direction the launch rod was pointed toward, as well as the GPS coordinates of the pad. “Hung-up on Rod” means the rocket fired successfully, but it didn’t exit the pad and actually get into the sky. Usually, this means the launch lugs were misaligned and there was too much friction for the motor to overcome. “Caught on Igniter Clips” means the wires from the launch controller entangled the rocket and prevented it from leaving the rod. The most common occurrence in this category is that the wires get looped over the top of a fin. At this point, you’re ready to launch. The form includes a place where you can record the number of tries it took you “Tip-Off” is the term we use when the rocket exits the to get the rocket to ignite. It’s not especially important to the rod and immediately makes a horizontal turn and doesn’t mission, but it helps you to remember that you should follow your launch checklist to make sure you have the igniter go “up.” Tip-off can be caused by a couple of things. One issue is if the wires from the launch system don’t release installed correctly. from the rocket at ignition. Continued on page 8 https://www.apogeerockets.com/Rocket-Kits/Skill-Level-3-Model-Rocket-Kits/Slo-Mo Page 7 Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 7 In that case, they are dragged upward by the rocket and yank the rocket in an unpredictable direction like playing a game of crack-the-whip. Another possible cause of tip-off is when the launch rod is swaying around in a breeze. If the rocket leaves the pad when the rod is moving around too much, it will leave in a direction you didn’t intend it to go. A brief but sudden gust of wind could be another cause of tip-off. You just never know when a microburst of wind may happen… Finally, you may have a motor failure. We call these Catastrophic Motor Failures, or “CATO” for short. Most people just say in hillbilly dialect: “the rocket done blowed up.” But know that true CATO’s are rare. Model rocketry is actually a very safe activity. However, there are usually three types of CATO’s. The first is the “Sidewall failure.” You’ll notice it by the fire from the motor that comes out the side of the rocket and burns the tube and a probably a fin too. Second is the “Spit Nozzle.” Like the name suggests, the nozzle on the back end of the motor comes flying out, like a watermelon seed that you spit out of your mouth. It ricochets off the blast deflector and scuttles across the ground. Finally, a forward bulkhead failure is when the fire from the motor comes out the front end and torches everything inside your rocket. We also call these a “blow through” because it blew fire through the middle of the rocket. The first thought from most modelers is that there was something wrong with the rocket motor. That may not be the situation at all. Remember, “true CATO’s” are rare and model rocketry is very safe. So, what happened? There is a lot of user involvement in the launch, and the CATO is more likely to be user induced than a true failure of the motor itself. A lot of motors are “loadable” or “reloadable.” That means the user assembles them, which opens a lot of chance for incorrect assembly. I’d say a large majority of failures at ignition are user error. Make sure to follow the assembly process carefully. Get a seasoned rocketeer to look over your shoulder and give you pointers too. In the case of single-use motors, where they are preassembled by the manufacturer, there is still the chance of mishandling and subjecting the motor to harsh impacts. Don’t drop your motors on the ground, it isn’t good for them… The motors are essentially balloons with a tough outer shell. You can cause micro-cracks in the wall of the motor case by dropping them hard on the ground. And then when the pressure comes up in the motor at ignition, the walls of the case pop open spewing the hot gas out the side of the rocket. Additionally, black powder motors do not tolerate temperature or humidity cycling. The paper case can expand and contract due to high swings in temperature or humidity. Store them in a place where they would be as comfortable as you would be if you had to sleep there. Using the wrong igniter can also cause problems, although this is a little rarer. It is usually where you have a different igniter that what came with the motor, and it has a huge pyrogen tip on it. If the pyrogen produces too much hot gas too quickly, it could over pressurize the case and cause it to burst. It’s rare, and you probably won’t see it in TARC rockets because the nozzles are too small to put an igniter with a big head into it. The point is, most CATO’s are caused by the rocketeer. I know this isn’t much consolation, as we often tend to want to blame someone else for when things go wrong. Rocketry and space travel, as you will come to learn through the TARC program, is very unforgiving of user mistakes. Therefore, you should also use a checklist when launching your rockets. www.ApogeeRockets.com/RockSim/RockSim_Information Page 8 If you call the manufacturer about the exploding motor, I guarantee you that they will ask you a dozen hard questions dealing with how you Continued on page 9 Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 8 handled the motor once you purchased it. It’s often embarrassing to have a rocket fail to launch, so handle the motors with respect and care. In the “Trajectory” section, hopefully you’ll check the box where the rocket went straight up. But chances are that there will be some spin to the rocket, so in that case, check the box where it was “Spinning but Straight.” I would also write down the direction of the spin as seen from observers on the ground - either clockwise or counterclockwise. If your rocket is spinning, you have a fin canted slightly on the rocket or they have slightly different airfoils in them. If you’re sanding your fins, be sure that they are all identical, or it will induce a spin. But sometimes spin is good. For example, a spinning bullet flies straighter than one that doesn’t rotate. So, you “might” want spin. This is something you’ll have to experiment with when you are designing and testing your TARC rocket. A corkscrew, also called a “barrel roll”, is different than a simple spinning rocket. You’ll notice it in the smoke trail left behind by the rocket as it takes off. It will look like a twisting corkscrew. In this case, the rocket is spinning, but it is moving sideways at the same time. It can have a couple of causes. If your rocket has multiple engines, an imbalance of thrust can cause the spin. In other words, one motor is pushing harder than the other, causing the rocket to tilt a little bit to one side. But this tilt causes one fin to produce more lift You get: (4) AT 29/13 (4) AT 41/18 (2) AT 56/18 (2) AT 66/18 (1) AC-56 (1) AC-66 You get: (6) AT 13/18 (6) AT 18/18 (6) AT 24/18 (6) AT 33/18 www.ApogeeRockets.com/Building_Supplies/Body_Tubes Page 9 and cause the rocket to roll (spin). This spin reorients the rocket to a different trajectory. It sounds complicated, but what it looks like is a corkscrew path. The same thing can happen in a single-motor rocket where just one fin is attached crooked or has a different airfoil than the others. It can also be caused by the motor being tilted to one side. This is called “misaligned thrust.” The cork-screw flight is more or less straight, which is a good thing from a safety standpoint. But it is a very highdrag flight and the rocket never reaches its potential altitude. If your rocket is cork-screwing, you’ve got to go back and fix it, or you’ll never reach your mission objectives. If it is cork-screwing, it doesn’t even make sense to try to mimic the flight in RockSim after the launch. Just make sure to concentrate on your building skills and put the next rocket together better. “Unstable” flight is a big problem. In this case, the rocket never takes a straight or predictable path. It zig-zags all over the sky, and everyone is running for cover. It can be unsafe. Obviously, you’ll need to fix this on your next rocket. But at this point, now you must figure out what caused the issue. Hopefully, it’s something simple like a fin coming off the rocket. But if the rocket looks okay, you need to go back to your computer simulations and try to design a new rocket that is more stable. See the back-issues of the Peakof-Flight newsletter on designing a stable rocket. A “Non-Vertical Trajectory” is different from unstable. Here the rocket is taking a definite path, but not in the direction you aimed the launch rod. Additionally, the direction is not turning the rocket into the wind. It goes in a direction sideways with respect to the wind direction, or downrange with the wind. Just not “into” the wind direction. Non-vertical trajectory might have been caused by the “tip-off” issue discussed previously. But sometimes it is starting out straight and goes a little way before veering off course. Sorting out the non-vertical trajectory issue can be a challenge. I’d start with an analysis of the fins on the rocket. Are they stiff, or can they flex a little bit? Flexible fins (usually really thin and made from paper or plastic) can start to “flutter” (to shake or vibrate) when the rocket reaches higher flight speeds. This flutter can cause the rocket to veer off course. In extreme situations, it can completely rip the fins right off the rocket. If the fins come off, I guarantee you the rocket will go unstable. In either case, you’ll need to go back to your design and make the fins thicker and made from of a stronger material. Continued on page 10 Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 9 “Weathercocking” is the term given to the flight path of a rocket as it gradually turns into the wind. Like a weathervane, the rocket wants to point its nose into the wind. Weathercocking is normal for a stable rocket. It is annoying because the rocket doesn’t go straight up like you want. The stronger the wind, and the more stable the rocket, the more the rocket will go horizontally. Because it goes horizontal, the altitude is reduced and the rocket can also be heading downward when the ejection charge pushes out the parachute. On windy days, you need to be prepared for weather cocking by reducing the delay time of the rocket motor slightly so it pops the chute out right at the apogee point. There are a couple of things you can do to limit weathercocking. First is to increase the lift-off speed of the rocket. The faster the rocket takes the less the wind affects it. You can increase the speed by choosing a motor with a higher average thrust, and by flying from a longer launch rail. You can also intentionally cause the rocket to spin so that it flies straighter. I’m not a big fan of reducing the size of the fins in order to make the rocket less stable. But that is also an option to reduce the amount of weather cocking in the rocket. Finally, try to estimate the path angle and direction of the rocket as it ascends into the sky. Again, your smartphone can give you the direction, but you may have to estimate the path angle as measured from vertical the rocket takes. I’m sure there is even a phone app that can help you, but I don’t know of one off the top of my head. Since this happens so fast, you need to be quick about making a notation on the form. Therefore, I suggest you have two people that are dedicated to data recording for the flight. You’ll be glad you had them both. The next section of the TARC Flight Record Data Sheet is where you’ll record recovery information. Minimum Diameter Motor Retainers! Apogee is your one stop shop for your minimum diameter rocket projects! • Fly High • Fly Fast • Impress Your Friends! We Have: • Minimum Diameter Retainers • Motor Extenders • Threaded Forward Closures • Adapters for Cesaroni Cases www.ApogeeRockets.com/Building_Supplies/Motor_Retainers_Hooks Page 10 Recovery Information Ejection Occurred: During Ascent At Apogee While Descending Model On Ground Recovery Device Deployment Ejection Failure Fast Delay Time Slow Delay Time Delay Didn't Burn Weak Ej. Charge Deployed Fully Parachute Stripped off of Rocket Partially Deployed Slow Deployment Parachute Did Not Deploy Damaged / Melted Chute Improper Set-up / Folding Motor Ejected Out of Rocket Ejection Charge Failure Tight Nose Cone Obstruction In Tube Other Parachute Descent Stable Descent Some Swaying of Load Under Canopy Tangled Lines Caused Spiral Descent Descent Normal Descent Type Ballistic Trajectory to Ground Figure 11: Recovery Information that you’ll want to record This is to document the phase of the flight that occurs after the ejection charge goes off. First, you want to record where during the flight the ejection occurred. Most observers on the ground that have never watched a rocket before will assume that if the ejection and deployment occur in the air, then it was a good flight. So, when you hold your pre-launch huddle, ask them to watch more closely because it does make a difference to the goals of the mission where during the flight the chute is popped out. If the ejection occurs while the rocket is traveling upward or while the rocket is descending, then you didn’t do a good job of picking the delay or not correctly setting the delay (by drilling into the delay propellant) if the motor has an adjustable delay. Continued on page 11 Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 10 For the least amount of stress on the parachute and on the rocket, we desire the chute to be deployed right at apogee (the highest point in the trajectory). Even if you might have a reefing device on the parachute (like the ChuteRelease at https://www.apogeerockets.com/Electronics-Payloads/Dual-Deployment/Chute-Release), you still probably want the ejection to occur very close to the apogee of the trajectory. It makes things more controllable. The rocket ejecting the chute while on the ground is probably the worst situation, as it points to a major problem. Did the rocket go unstable or lose a fin on the way up? Did you forget to drill the hole to select the proper delay on your reloadable rocket? Did you forget something on your checklist? You need to determine why the rocket impacted the ground before the ejection occurred. Ejection Failure In the same box, there is also a section to document an ejection failure should one occur. Ejection failure means that the chute didn’t come out properly. It could also mean it came out too soon or too late. In this sense, it wasn’t that you didn’t properly select the right motor delay, but something doesn’t seem quite right. For example, you might have used a single-use (meaning you didn’t physically perform any modification to the delay propellant) composite-propellant motor with a 5-second delay. But when you flew it, the ejection of the nose seemed early, and you estimate about 3 seconds. This would be a fast delay time, and you’d mark it off in the check circle. It doesn’t necessarily mean the motor malfunctioned. There could be other contributing factors. For example, the motor might have misfired on the first launch attempt. This is called a “chuff.” It seemed to want to start but didn’t quite catch - probably because the igniter wasn’t fully inserted in the motor. It sat and sputtered and coughed before self-extinguishing. But what happens during that brief chuff is that a little bit of the delay propellant burns up. On the next launch attempt, when the motor does finally ignite, the de- lay propellant is shorter, meaning the delay time is shorter too. And then it appears that the rocket ejected too early. This is another reason to count the number of attempts it took to ignite the rocket motor. You’ll come to realize that multiple attempts can impact the flight when it does take off. Long delay times can also occur although this is usually due to the subtle mixing issues that occur when the delay propellant was made. For the manufacturer, making propellant is a lot like baking a cake, and the ingredients can vary slightly from batch to batch. Some batches might burn slightly longer than others. It is a tough process making propellant. The motors are allowed to be up to 10% off in the delay time and still be within specification. Sometimes, and this is also extremely rare, the delay propellant will stop burning completely. This only happens with composite propellant motors. You will notice this because the trailing smoke doesn’t come out of the rocket after the thrust stops. If the delay snuffs out, the rocket will come down ballistically and crash hard. The usual cause of the delay stopping is an extreme drop in pressure inside the motor. The propellant needs pressure to continue burning, and if the pressure drops dramatically, the delay can snuff. If it does happen, it is usually with very short burn motors that burn so quick that pressure can drop quickly. I wouldn’t worry about it happening to your TARC rockets because you won’t be using high thrust motors like that. A weak ejection charge can happen on occasion, but as before, it can also be user error. You’ll notice that the ejection charge did fire, but the nose barely moved. If it doesn’t come off, the rocket will come in ballistically. If your parachute is not prepped properly, meaning it is too tight in the tube, it could prevent the nose from sliding off easily. Take your time prepping the chute, and follow your checklist to prevent folding errors. Continued on page 12 www.ApogeeRockets.com/Building_Supplies/Parachutes_Recovery_Equipment/Shock_Cord Page 11 Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 11 Additionally, the nose cone must have the proper fit. It can’t be too tight, obviously, or that could prevent it from moving forward. Too loose can also be an issue, as air can flow around the shoulder instead of pushing it off. Test the fit of the shoulder by tilting the rocket upside down. It should stay in the tube when inverted. But if you start to wiggle the rocket, it should start coming out. That is the criteria that I use to test the fit of the nose cone on the tube. Recovery Device Deployment Once the chute is out of the rocket, it needs to fully open. Hopefully “deployed fully” will be the check-box you’ll mark on the data sheet. Everything else below that checkbox is “bad news.” Parachute Stripped off Rocket The parachute stripping off the rocket is where the rocket stays in one piece, but the canopy of the chute is floating away on its own. The obvious thing to check it to make sure you attached it to the rocket (been there… done that…). Another common failure is the shock cord coming loose. Add to your pre-flight checklist to tug hard on both ends of the shock cord to make sure that it has not weakened from the previous flight. If it comes loose, the rocket is going to come down in two pieces, and one will be coming down really fast. Sometimes the lines aren’t on strong enough for the velocity that the rocket is moving at when the chute is pushed out. This is something you should be aware of: make sure the chute is strong enough to survive the opening speeds. If not, use a stronger parachute, or find a different way to fold the parachute so it opens slower at high speeds. Partially Deployed Partial deployment is when the chute is out in the air but fails to fully inflate. It is usually because the lines are twisted, or the fabric has melted to itself. Either way, it is user error. So, go back and review/update your checklist concerning the folding of the chute in the rocket. Slow Deployment A slow deployment is where the chute eventually opens completely, but it took so long that the rocket lost a lot of altitudes. Now it will land much quicker than you had planned, and you won’t meet the mission objectives. The cause of slow openings is something happened with the suspension lines. They were tangled, and eventually, that freed themselves so that chute could fully inflate. Parachute Did Not Deploy If your chute did not open at all, you’d check the box indicating this, and then determine the reason in the circle check-offs below. Damaged / Melted Chute The most common is a damaged or melted parachute. Always inspect the parachute prior to launch to make sure it is free of damage and that all the shroud lines are on tight. Make sure there is enough wadding in the tube to prevent the heat of the ejection charge from hitting the chute. But it shouldn’t be so much that it obstructs the tube and doesn’t push off the nose cone. Improper Set-up / Folding It is important that you fold the chute, not just wad it up and shove it into the tube. Shoving it into the tube makes it act like a plug, and it is slow to move out. If it is slow leaving the tube, it is going to have more heat damage. It needs to slide freely in the tube, which is best accomplished by meticulous folding. Follow the same procedure from one flight to the next, even when things get rushed. Parachute failures are the most common mishaps in rocketry, and most of them are preventable. Motor Ejected Out of Rocket If the motor ejects out of the rocket, you’ll also find the rocket going in ballistically. This Continued on page 13 www.ApogeeRockets.com/Building_Supplies/Parachutes_Recovery_Equipment/Parachutes Page 12 Issue 453 | October 3rd, 2017 TARC Flight Report Sheet Continued from page 12 occurs when you don’t restrain the motor in the rocket correctly. Make sure to test and m