Definitely adds a new level of fun and excitement to launching rockets. No doubt today's super small and portable video cameras are prime for doing something like this. Just hope your shock absorber materials can hold up--would hate to see a nice camera shattered. That would definitely impede the number of times you could launch.
October Sky - Now thats a GREAT movie, Charles! Very inspiring. I remember watching those boys in their rocket house blowing up rockets until they got it right. I need to go rent it again. We did a birthday party a few years ago and bought a 12 pack of easy to build rockets for one of our son's birthday parties. We took them to the park by our house and all the kids got to shoot off their rockets. So much fun is to be had with model rocketry!
Rocket Boys is one of my favorite movies because it makes a young, aspiring engineer look like a normal child instead of socially-awkward geek. Also...the video from this article appears to be taken in an area much like Coalwood in the movie.
@Charles Murray-- Hooray for "Rocket Boys"! One of my favorite books and movies after "Apollo 13". Just as an aside, I wandered into the Engineering section of a tiny bookstore in Boca Raton, FL when, much to my surprise, I found a 1st edition of "Principles of Guided Missile Design". The very same book from which Homer and the Big Creek Missile Agency learned their fundamentals! I bought it no questions asked.
Doug, now that you have mastered the camera, you need to add more sensors. How about an accelerometer and a magnetometer? Then you need to record the readings. If you really want to get crazy, you could also add real time telemetry. How big do these rockets get?
There's actually so many different types of cameras available now that enable people to record experiences in much the same vein. I just saw a news clip on my local news this week in fact, where a video camera recorded a small plane crashing--the entire experience. Of course, it was inadvertent and only exciting because luckily, no one on board was hurt.
I've already got a 3-axis accelerometer, a 2 axis rate gyro, and a barometric pressure sensor I'm testing. All these sensors are very small and light. The weight does climb some when you start adding the microcontroller, an acutator, and a power source capable of driving the actuator. The actuator is the power problem, the rest of the electronics requires very little power.
Right now I'm working on putting a recovery system in the rocket that uses an acutator to deploy a parachute based on a set time from the launch. This is simple and doesn't require even a microcontroller. It does add more weight that I had hoped, about 20 grams. To keep the weight down I really should be implementing everything with surface mount devices but it's a lot easier to assemble through-hole prototypes (at least for me).
Once I get a reliable recovery system I'll consider adding more complex electronics.
I suppose the absolute answer is more a question of how much acceleration your payload can withstand. These are projectiles, not rot really rockets, so the speed and eventual maximum altitude are limited by the barrel length and the acceleration.
200g acceleration over 20 inches will result in 146.5 ft/sec, 400g will get you 207 ft/sec.
For a launcher built from PVC pipe such as I'm using, I limit the maximum pressure to 50 PSI. This is well below the pressure rating for the PVC, but PVC under pressure fails with a brittle fracture that is very dangerous with compressed air. If you want to go with higher pressure you should encase the PVC in steel that can contain any potenetial explosion of the PVC. Better yet use a metalic pipe rated for the pressure that will fail gracefully if it does fail.
My analysis shows that I should be able to get a 100 gram to 120 gram total mass up to 250 to 300 feet with the PVC type technology I'm using. To do this I'll double the length of the 2 inch air cylinder and increase the rocket body diameter to something around 1.5 inches and lengthen the launch tube slightly.
To go larger and higher you'd probably want to go with a higher pressure system, or a real rocket.
You really need to read the article before commenting. No PVC pipes or steel ones are flying. The PVC is a launch tube and steel would be safer because it would not have a brittle fracture problem like PVC.
The "rocket" itself weights 60 grams and is mostly paper and foam shock absorbing material. Although I try to avoid being hit by it, I don't think it would do much damage to me. I fly my rockets on my property and I'm the only one that they could land on.
What an awesome project! Our family loves model rocketry - we have countless Estes rockets we have built over the years and my son won 2nd place in the regional science fair in seventh grade with his study of aerodynamics using three different rocket configurations. I even used "How to Launch a Model Rocket" as a topic for my college speech class and we had the class outside so we could launch the rocket. This stuff is GREAT for getting kids excited about science! It's alot of fun to add bells and whistles and I admire the innovation used by Doug - we have done "still shots" in the past with a 110 camera that came as part of a kit, but nothing like Doug's accomplishment. I can't wait to show our boys and get started on this!
With digital cameras dropping to near throwaway prices [example] and a rocket system with almost no per-flight costs, this looks like a great opportunity both for hobbyists and for scouting and other youth groups.
I just ordered one of those cameras. You are right! They are almost throw-away devices. $21, free shipping, one day only price. $31 at Amazon. I had no idea they were so cheap. Thanks for pointing this out!
I'm still using the original camera. it has survived quite a few flights. Even if I use a parachute for a gentle descent, the camera still has to withstand around a 200 g launch acceleration. It's a good thing the camera is inexpensive, I never would have tried this with a $100 camera.
As far as more construction details you should try the build instruction link. That will let you download what should be sufficient information to build one of these.
The 360 degree video technique you linked to would make an interesting image of the flight area. If I had a camera with higher resolution it would be more practical. With the camera I have the resolution seems barely adequate for the field of view that I'm using.
I like the use of an air cannon instead of rockets. I built a similar device, though mine is more of a giant tube. Also, how can you determine launch speed, and can you do so using a camera not mounted on the rocket itself? I want to see how fast the one I built shoots nerf darts. All I know now is that they can punch through an aluminum can like nothing. Anyway, I also like the idea of putting a camera on the rocket, as I've only seen that with commercial rockets that use solid fuel rockets to fly, not something like this.
To measure the launch speed I use a 30 frame/sec video camera which is fairly standard. By filming the launch perpendicular to the direction of travel, you can measure the distance the projectile travels in 1/30 of a second. In my case I can use the rocket body as a length reference. Divide the distance by the time and you have the speed.
Unfortunately, I have already tried that, but mine was just too inconsistent , I got everywhere from 80fps to 270fps. I don't know what it is, but it looks like I'll need a different method. As for the ball valve, I found that I works just fine. My first air cannon used a 1-1/2" ball valve, and since it didn't open smoothly, but stuck closed, then opened quickly when turned, the gun worked very well. At least, until I got sand in the valve, but that's beside the point. I'd guess a 2" ball valv would allow even more air, and therefore probably work for this as well.
I would tend to trust the measurement of speed based on a video camera. I think bright lighting helps the video camera work with a fast shutter speed for minimum smear when photographic fast-moving objects. If you have any doubts you can do a video of an auto at speed. If you are using a manual valving arrangement then I would expect that could explain wide differences in velocity.
I also hope that you are not using high pressures (like 100 psi or more) in PVC pipe. Even though the pipe may have a rating like 480 psi at 73 deg F there are many documented cases of these pipes exploding. Be aware that PVC is not approved for compressed air applications.
Thanks for the tip on lighting, but the difference is not due to manual valve, since I measured the speed on the cannon with an electronic valve, with pressures within about 2-3psi. And no, I am not using pressures above 50 for any of my air cannons (3, a mini one I finished today, the big powerful one where I tried measuring speed, and a tiny manual one that I built to test enclosures). Also, I never thought to wrap the chamber in tape to contain an explosion, but that seems like a good idea, so I'll add it to mine. Thanks for all your help.
Dconner, if you are able to fix it with a 360 degree camera and sending the captured images at real time scenario with the help of small wifi transmitters are interesting. Then the project resembles like a miniature of NASA's Mars mission curiosity.
For aerial views this is an affordable alternative to Hexakopters -- just without the GPS control and RC.
For safety we could consider fiberglass and resin shield loosely placed around the launcher. And one could wrap 20 or 30 turns of fiberglass string helically around the rocket body in both directions and secure it with glue or resin.
For starters, the pressure drop across that valve, as shown, is quite a lot. Substituting a ball valve will improve the range quite a bit, and also save quite a few dollars, in addition to making the system independant of external power.
I built a system that used a discarded carbon-dioxide fire extinguisher tank, rated for 1800 PSI, which provided me with a better safety factor. I use a similar bicycle tire pump, which can provide over 120PSI air pressure. This allows things to fly much higher, and makes the flights much longer.
A large ball valve should have better flow but it sounds like you are opening it manually. I don't see how you can open it fast enough. From the time my launch initiates until the rocket has separated from the launch tube is approximately 24 msec. You need a pretty quick wrist to fully open the valve in less than say 10 msec.
What a cool and innovative way to launch rockets. In reviewing the design of the launcher circuit schematic diagram, as a phase 2 project, have a digital timer switch the solenoid valve. With the timer, you can give your compressed air rocket an automatic controlled launch with a real count down sequence. Great project and article!
It is not that hard to open a ball valve quickly. We use a similar method to open the air-drive valves on our commercial crash sled systems, which work quite well.
The secret is a spring and a lever to rotate the valve, arranged so that the mechanical advantage for the spring increases as the valve rotates toward the full open position. Of course, the mechanism must be designed so that the ball valve is not driven past full open. Of course some sort of latch is required to keep the valve closed until launch time. Another option is to use an air cylinder in place of the spring, which is what our systems use. The valve opens in much less than 100Msec once it starts moving, which is delayed until the pressure rises enough to start things moving. Very simple, but quite effective.
One model of my air launcher, with a ten-foot tube, will send a paper "rocket" as high as most of the Estes-brand rockets fly. Of course, that is with 100PSI in the tank and a cup of water to improve the seal.
Your modification to open the ball valve quickly does sound like it should be efffective. At about $12 I think the electric valve from Home Depot is a simple and effective valve.
I measure 60% of the work ends up in the projectile kinetic energy based on ideal adiabatic expansion of the gas. I might be able to improve that value with a better valving system.
If you have computed the efficiency of your energy transfer I'd be interested in knowing it. If not i'd be glad to compute it for you. I'd need the muzzle velocity, projectile weight, volume and pressure of the compressed air, dead volume between the valve and projectile when the launch begins, effective barrel diameter, and barrel length.
What I have observed is that there is enough residual pressure after the fisrst launch, when using an ASCO brand valve, similar to the sprinkler valve, to do a second launch, while a similar opening and closing of the ball valve leaves almost no residual pressure. The volume between the valve and the projectile is about 2 inches of 1inch steel pipe. The volume of the tank would hold 25 pounds of liquid carbon dioxide. Probably a smaller tank would be adequate, but smaller tanks were not available for free, and low cost was a big consideration at the time.
As a kid I had a rocket that was partially filled with water and then attached to a hand operated air pump. As the air was pumped into the rocket body it passed through the water and built up pressure. When the rocket was released from the pump, it expelled the water which forced the rocket upwards. There was even a second stage that mounted on top of the first and was secured with some sort of pressure valve. When the first stage was emptied, the valve would release the second stage. It has probably been 50-55 years ago and i do not remember how high it went, but it was enough that the projectiles would land several houses one way or the other.
I was the only kid on the block that had one and I never saw another, so I do not know how popular they were. Today they would probably be outlawed because the projectile did have some weight and I am sure there is a lawsuit there somewhere. It finally cracked on landing and no glue that I could find would return it to its air/water tight state.
Yes, I had the single stage air over water rocket as a kid too! I would pump it up as much as I could to get it to go ever higher and higher. I also varied the water level over and below the water level mark on the translucent rocket body, trying to see if more air or more water would take it to higher altitude. Finally in an epiphany I tried 7Up! It sent the rocket to record heights. Unfortunately at the launch pad I was a wet sticky mess and my mother began to suspect the sudden high consumption rate and my sudden interest in her favorite summer beverage. My rocket fuel was rationed afterward... Great memories, thank you !
Actually mine was a two stage rocket. I never thought of using soda, but I can see where it would work better and I can imagine the sticky mess. Some times I would manually release the top rocket and leave the base rocket in place. I do not remember why, only that I did it.
WARNING: Find and use a valve designed for handling air pressure. I was an irrigation valve engineer for 19 years and PVC valves rated for 150 psi water pressure are not safe handling air pressure. The faster parts motions associated with air induce higher part impact stresses than with water. The in-line valve is better, but there was a lawsuit we had where someone shot their eye out using air pressure to blow-out and winterize an Antisiphon style irrigation valve. And then there will be those that wan to go launch higher and keep creeping up the launch pressure. Wear your safty glasses!
I feel that the article implies that Mr. Conner CREATED the idea of placing a camera on his rocket. Nothing is further from the truth than that. A quote from the article: "Then a brainstorm hit. What if you could watch the flight from the rocket's point of view?". In the 1960's, the Estes Model Rocket Company sold two cameras for this purpose. One, a still-shot was called "Camroc", and the other a motion-picture camera, "Cineroc". The Germans during World War II deployed launch cameras on their V2 rockets and Robert Goddard did it way before that.
I only mention this because of my objection to the way the article was written, not to detract from anything Mr. Conner did. I believe that any young person interested in rocketry might not be aware of the history of rocket cams and assume something otherwise.
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