Reference / Paper · 2017
Peak of Flight #451: What is a Guide Chute?
Apogee Components' Peak of Flight newsletter, issue 451 (2017-09-05).
- peak-of-flight
- apogee-components
- model-rocketry
Reference / Paper · 2017
Apogee Components' Peak of Flight newsletter, issue 451 (2017-09-05).
Apogee Components' Peak of Flight newsletter, issue 451 (2017-09-05).
ISSUE 451 September 5th, 2017 IN THIS ISSUE What is a Guide Chute? https://www.ApogeeRockets.com/Rocket-Kits/Skill-Level-3-Model-Rocket-Kits/Graduator-2-6in What is a Guide Chute? By Tim Van Milligan A question that you may have is “What is a Guide Chute?” I had the same question when I first heard of it, too. Is it a real thing, or just something made up by a manufacturer to sell something unique? In this article, I’ll give you the information that I found out about the device so that you can make your own conclusion. Figure 1: The conical shaped Guide Chute deployed, while the main chute is still reefed at the base of the nose cone by the chute release. I was skeptical of the Guide Chute from Dino Chutes because I had never heard of one before, and it’s very strange appearance seemed to come out of nowhere. It looks like a conical dunce hat, with the tip cut off. Since I’m an engineer by trade, I wanted to know more about it. But initially, I had no information, other than what Pat Butler at Dino Chutes told me. When he approached me about selling his product at Apogee (and we’re always looking for new items to sell, so if you manufacture something, please feel free to give us a call) he told me that he created it for his daughAbout 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 ter’s TARC project. He said they were looking for a chute that could be used with the Jolly Logic Chute Release (https://www.apogeerockets.com/ Electronics-Payloads/Dual-Deployment/Chute-Release) in order to stabilize the rocket so that when the main chute opened, it would unfold in an orderly and predictable manner. The “Guide Chute,” as he called it, would guide the opening of the main chute so it was in the right orientation with respect to the rest of the rocket. My initial thought was “Why not just try a streamer?” Streamers, unfortunately, have hardly any drag. Rockets using streamers fall like stones, especially heavy rockets like those that TARC students build. Streamers are great for adding visibility, though, so if you want to be able to see your rocket after ejection a brightly colored streamer will help. After I got the Guide Chutes here at Apogee, I really wanted to try it out for myself, so I did do a test launch last month using the LOC Graduator kit (https://www.apogeerockets.com/Rocket-Kits/ Skill-Level-3-Model-Rocket-Kits/Graduator-2-6in) with a 24” Guide Chute (https://www.apogeerockets.com/Building-Supplies/Parachutes/Up-to-24in/ Dino-Chutes-24in-Guide-Chute) for initial deployment, and the standard 18” hexagon parachute that comes with the rocket as the main recovery device. The rocket contained the chute release to limit the drift, and a Jolly Logic AltimeterThree (https://www.apogeerockets.com/Electronics-Payloads/Altimeters/Jolly-Logic-AltimeterThree) to record the flight data. Continued on page 3 Newsletter Staff Writer: Tim Van Milligan Layout/Cover Artist: Chris Duran Proofreader: Will Franks Issue 451 | September 5th, 2017 What is a Guide Chute? Continued from page 2 700 600 Altitude (feet) 500 400 300 200 Main Chute Opens 100 Figure 2: The orange colored main chute is deployed along with the conical Guide Chute. The flight was nominal and reached an altitude of 656 feet. In retrospect, I should have used a bigger motor to get the rocket up higher. But the Guide Chute deployed at ejection as expected, and when it got down to 300 feet, the Jolly Logic Chute Release let go of the hexagon chute, opening in plenty of time for the rocket to make a nice, gentle landing. The graph generated by the AltimeterThree showed the initial descent rate at 36 feet per second. When the 18-inch hexagon chute opened fully, the descent rate dropped to 25 feet per second. This verifies that the Guide Chute, even though it’s bigger, did have a lower drag coefficient than the 18-inch hexagon chute. 0 0 5 10 15 20 25 30 35 Time (seconds) Figure 3: Where the slope of the graph changes is the indication that the main chute was deployed. In this case, the extra chute only slightly slowed down the rocket’s descent. After the flight, I talked to Pat Butler from Dino Chutes to tell him that I liked the Guide Chute. It was during that exchange that he casually mentioned that the data did correlate to the research paper he had used when he created the Guide Chute. “What? There is other research into this type of parachute?” I asked myself. Of course, I immediately asked to see the report. Continued on page 4 Join Tripoli.org Mention Apogee Components https://www.apogeerockets.com/Rocket-Kits/Skill-Level-3-Model-Rocket-Kits/Slo-Mo Page 3 Issue 451 | September 5th, 2017 What is a Guide Chute? Continued from page 3 The information comes from Parks College Parachute Research Group (https://www.pcprg. com/tcdcprog.htm). The technical name of the parachute is a “Truncated Cone Decelerator.” Essentially, it is a very long cone where the tip has been cut off. If you think of a windsock at an airport, that is what the Guide Chute is. The mission the researchers envisioned for the Truncated Cone Decelerator chute was “for use in wind-sensing applications where GPS-instrumented payloads are to be drifting freely with the wind, in a stable manner, and without gliding.” In other words, the researchers wanted a chute that would drop fast but would be pushed along by the wind. For atmospheric researchers, to get an accurate reading of how fast the wind is blowing, the instrumentation has to be pushed along by the wind. They don’t want the chute to create any lift that would cause the chute to go sideways or to penetrate into the wind. They want to know with accuracy how fast the wind is blowing where they drop the data sonde. For rocketry, we can tolerate a little lift in a chute. In most situations, we want it because it increases the efficiency of the parachute and makes it fall slower. In effect, we’re stealing some of the wind’s energy, which makes the chute fall slower. Another benefit for rocketeers is that a chute that has lift will penetrate the wind, which means that the rocket won’t drift as far. If you think about it, if you want to a chute that is steerable it has to be able to penetrate the wind. The parawing chute (https://www.apogeerockets.com/education/downloads/Newsletter206.pdf) is a great example of this. Plus, it has a very slow descent speed. Suction R V This lift causes the Chute to penetrate into the wind. L D α V γ U Figure 4: Lift occurs when the air flows up and over the canopy. But the Truncated Cone Decelerator doesn’t produce lift since the air doesn’t flow over the top: it goes around. Because of that, you’ll notice that it will drift a bit more. However, it has a very low axial drag coefficient, about 1/3 that of a hemispherical parachute (Cd = .25 versus 0.75). Because of this, it falls very fast and gets down to the ground very quickly. It is a trade-off: it falls fast, but it will drift with the wind. The other advantage of the Truncated Cone Decelerator is that the drag Continued on page 5 www.apogeerockets.com/Rocket-Kits/Skill-Level-2-Model-Rocket-Kits/SkyMetra Page 4 Issue 451 | September 5th, 2017 What is a Guide Chute? to have a very predictable and quick descent rate. If you’re using it for dual deployment, the rocket is is much more predictable than a streamer. A going to drift a bit more, which kind of defeats the streamer will whip around, and its drag fluctuates purpose of dual deployment (which is to limit the wildly. This, of course, will change the descent amount of drift the rocket has), or use a smaller time each time you fly the rocket. The Guide Guide Chute so that it doesn’t drift as much. Chute doesn’t whip around like the streamer Personally, if I was doing dual deployment in because it is inflated. The inflation stiffens up the my own rocket, I’d either use a streamer for exdevice like a balloon so it doesn’t loft around. So tra visibility for those high flying flights where the if you want a predictable and quick descent, then rocket disappears, or drogue-less recovery if the the Guide Chute is something you might consid- rocket will be easily visible because of its low aler. This has the potential to be a great chute for titude. Drogue-less recovery is a form of dual-deTARC contestants. ployment but doesn’t have any recovery device One thing that I noticed when I test flew the that is deployed at apogee. The rocket pops off chute is that it was very visible in the sky. Like the the parachute and tumbles to the altitude where streamer, it makes the rocket easy to see. Rethe altimeter releases the main parachute. I like member, though, the drag is higher than that of a the Guide Chute, and if we get a smaller version streamer, so it will fall just a bit slower. of it (currently the smallest we have is 24 inches), As noted on our web page, because of its maybe around 12 inches, then I think it would be low drag, the Guide Chute should not be used good as a drogue chute. as a “pilot chute.” A pilot chute is different from a drogue chute, in that it is designed to pull the Different chutes for different missions main chute out of a deployment bag. You need This discussion of the Guide Chute prompted a parachute with high drag so it creates a good me to do a lot of research into different types of tugging force to pull the chute out, like one from parachutes. The conclusion is that each parachute Fruity Chutes (https://www.apogeerockets.com/ has both positive and negative aspects to it. What Building_Supplies/Parachutes_Recovery_Equip- you’ll find out is that each chute type is designed ment/Parachutes/High_Power/18in_Classic_Ellip- for a different mission. Just keep this in the back tical_Parachute). The Guide Chute won’t produce of your mind as you’re planning your next launch. that much force because it has such a low coefficient of drag. It can be used for dual deployment About The Author: as long as the Guide Chute doesn’t have to proTim Van Milligan (a.k.a. “Mr. Rocket”) is a real vide a tug to pull the other chute out of the rocket. rocket scientist who likes helping out other rockeMy recommendation is to use the Guide Chute teers. He is an avid rocketry when the most important mission of the rocket is Continued on page 6 Continued from page 4 https://www.apogeerockets.com/TARC_Supplies Page 5 Issue 451 | September 5th, 2017 What is a Guide Chute? Continued from page 5 competitor and is Level 3 high power certified. He is often asked what is the biggest rocket he’s ever launched. His answer is that before he started writing articles and books about rocketry, he worked on the Delta II rocket that launched satellites into orbit. He has a B.S. in Aeronautical Engineering from Embry-Riddle Aeronautical University in Daytona Beach, Florida, and has worked toward an M.S. in Space Technology from the Florida Institute of Technology in Melbourne, Florida. Currently, he is the owner of Apogee Components (http://www.apogeerockets.com) and also the author of the books Model Rocket Design and Construction, 69 Simple Science Fair Projects with Model Rockets: Aeronautics and publisher of the “Peak-of-Flight” newsletter, a FREE e-zine newsletter about model rockets. You can email him by using the contact form at https:// www.apogeerockets.com/Contact. 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 www.ApogeeRockets.com/Building_Supplies/Parachutes_Recovery_Equipment/Parachutes Star Lift Mega Lander Build It - Launch It - Stick The Landing The Excitement Builds All The Way To Touchdown • Large Size Rocket Flies on the Impressive Mid-Power Motors. • Articulating Lander Legs Fold Up During Launch. • Laser Cut Plywood Parts for a Strong Rocket. • Pre-Slotted Tube Makes Construction Easier. • Vinyl Decal for Visual Appeal. https://www.apogeerockets.com/Rocket_Kits/Skill_Level_5_Kits/Star_Lift_Mega_Lander Page 6 Issue 451 | September 5th, 2017