Anatomy of a rocket
Below is a detailed anatomy of a high powered rocket. This particular rocket is representative of the kind of items that go into such a build. Everything listed is not required for a successful launch and recovery of many projects, but a variation of these components are found in most large high powered projects.
Additionally, there are specific electronics and 3D printed items listed below. These items are not an endorsement of these products by Mach 1 and are used as an example for illustrative and education purposes only.
The airframe of the rocket has a direct correlation to the performance of the flight. There are four main components of an airframe that determine flight characteristics: Fin configuration, nose cone design, airframe diameter and length:
Fin Configuration: Fins are required for stable flight without the use of complex electronics and systems developed by space agencies today. The purpose of fins to to induce the right amount of drag to ensure the nose of the rocket stays in the preferred direction of flight. In general, the simpler the fin design the better performance.
Nose cone design: The nose cone shape will have a great impact on the overall performance of the rocket. Ogive, conical, and von karman designs are the three most common shapes used today. Ogive is the most popular shape, but conical and von karman will offer better performance depending on the speed the rocket is expected to achieve.
Airframe diameter and length: It is a common misconception that a larger rocket will have better performance. This is simply not the case. The best performing rockets have an airframe that has a diameter that matches their motor and has a length honed in for maximum altitude. A smaller airframe with the largest motor can outperform many significantly larger rockets with a significantly larger motors based off design. The change can be so significant that for smaller rockets, even a few millimeters if airframe diameter can cause a 10% - 15% difference in performance.
The avionics bay (AV bay) is the brain of any high powered rocket. Its primary function is to house the electronics that control the recovery events during flight. There are typically tw0 separate events:
At apogee the first event will cause the fin section of the rocket to separate to create drag and slow the rocket to about 50 mph (75 fps). Many times this event will deploy a small parachute or streamer for additional drag.
The second event takes place when the rocket reaches a predetermined altitude on decent, usually 500-1,500 feet depending on various factors. The main parachute will deploy and slow the rocket to about 13 mph (20 fps) or slower.
These deployments are controlled with programed altimeters that will ignite small ejection charges. These charges will pressurize and separate the rocket components and to deploy parachutes. These charges consist of an electronic match (e-match) that lights a small amount of black powder that is contained.
This particular AV bay is notable because the main structure is 3D printed and is designed to minimize wire management with operation.
Also notable are the ejection charges. They consist of 10ml centrifuge vials to house the match and black powder. The e-match is connected to a small terminal block. The whole subassembly slides into a 3D printed container that will screw into the rest of the AV bay, ultimately connecting each charge to an altimeter.
GPS Tracker Bay
GPS tracking is optional but is highly recommended to flights where the rocket will fly out of sight. The tracker is usually located either in the nose cone or in the AV bay.
This particular tracker has a sled that sides into a 38mm tube inside a the nose cone. The sled is 3D printed and it is retained by a PVC pipe fitting that happens to be 38mm.
For dual deploy setups, one or two altimeters will be used for deployment. two altimeters offer redundancy in case the other fails. The choice of altimeter is dependent on the purpose of the flight and features offered by the manufacturer. Altimeters come is different sizes, number of output channels, reporting details, and connectivity options. The range of features also comes at a range of price.
GPS trackers are no required for many flight. In general, if the whole flight, from liftoff, apogee, and recovery, a GPS is not required. If the flight will not be visible at any point, a GPS tracker is highly recommended. Like altimeters, GPS trackers come with many different features and prices depending on the needs at the time.
The altimeters and GPS tracker are powered by two main types of batteries. Many people prefer the simplicity and reliability of 9v batteries. Others prefer the flexibility and smaller size of LiPo batteries. LiPo batteries tend to be more expensive up front, and require more care when using them, but tend to be smaller and lighter for use in applications where a 9v cannot.
Optional is a camera to record the flight. There are several different cameras that will work depending on the size and set up of the rocket. Some cameras are very small and work well for BT sized rockets but sacrifice video quality. Other cameras are larger and offer more features but are generally best for larger rockets. The placement of the camera is generally on the outside of the rocket, but they can also be set inside the airframe if there is room for it.
The 54mm x 24in motor mount is the beginning of the structural heart of the rocket. The rocket body and fins are epoxied to this as well as the recovery harness.
A 24in drogue chute will deploys at apogee and slows the rocket to 44 mph. Attached to 32 feet of 1/4" kevlar shock cord rated at 1900# via a 1300# swivel. The shock cord is connected to the AV bay eye bolt with an 800# quick link.
Main chute will deploy at 1000 feet above ground level (AGL) to slow for a decent rate of 12.5 mph. The chute is a 7ft Rocketman Standard. It is attached to 24 feet of 1/4" kevlar shock cord rated at 1900# via a 1300# swivel. The shock cord is connected to the nose cone eye bolt with a 800# quick link.
Made of 1/2in Kevlar, the recovery harness extends just beyond the lower body tube of the rocket and is crowned with a 800# rated quick links for connecting the shock cord.
Two 1/4in threaded rods inside the AV bay keep both ends of the rocket together and are connected to fiberglass bulkheads with an eyebolt on either side.
The nosecone is connected to the main chute shock cord with an eyebolt on the GPS tracker sled. The sled of the tracker is secured to the nose cone with a threaded cap ensuring the nosecone and the shock cord stay connected during the main chute deployment event.