Eagle X
TVC Guided Rocket
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Eagle X was a thrust vector-controlled rocket using mid-power hobby-level rocket motors (AeroTech F Class Motors worked best). Although the rocket never flew, it made significant progress in the early testing, validation, and pre-flight phases. Each subsystem will be listed along with pictures, descriptions, and technical data. Click on the photos to see captioned descriptions.
The design philosophy of Eagle X is simple: create an initial, rough, and probably non-functional subsystem, iterate until some functionality is apparent, then continue iterating on both the subsystem and its integrations until it is seamless.
The design philosophy of Eagle X is simple: create an initial, rough, and probably non-functional subsystem, iterate until some functionality is apparent, then continue iterating on both the subsystem and its integrations until it is seamless.
Air Frame
Description:
Eagle X's airframe was 3D printed in 2 segments (originally 4) along with a nosecone, totaling 3.75 feet, with the airframe's wall thickness being 0.9mm. The segments were held together by 3 (originally 4) M3 screws per segment joint.
Engineering Challenges:
Since Eagle X's airframe was 3D printed (as opposed to cardboard or plastic tubing), massive mass reductions were needed while maintaining high enough strength to withstand vertical compressive loads, high-speed horizontal impacts (landing), support 25.3N of engine thrust pushed through 4 load-bearing joints, and normal handling loads. The first iteration suffered from intra-layer separation, thermal deformation, and high weight. The solutions were such:
- Airframe Thickness: 2.1mm --> 0.9mm
- Segment Count Reduced To 2 (To Reduce Weight From Segment Joints, Reduce Number Of Points Of Failure, and Increase Manufacturing Rate)
- 3D Printer Filament: PLA --> ABS --> PLA+ (PLA+ Exhibited Best All Around Tensile And Yield Strengths)
- Increased Layer Count To Reduce Aerodynamic Surface Friction, Along With Changing Printing Temperature, Speed, And Other Variables
Fun Fact: Just like a real rocket, if you tip this one over too much, or happen to touch it wrong, it will fall apart :)
Eagle X's airframe was 3D printed in 2 segments (originally 4) along with a nosecone, totaling 3.75 feet, with the airframe's wall thickness being 0.9mm. The segments were held together by 3 (originally 4) M3 screws per segment joint.
Engineering Challenges:
Since Eagle X's airframe was 3D printed (as opposed to cardboard or plastic tubing), massive mass reductions were needed while maintaining high enough strength to withstand vertical compressive loads, high-speed horizontal impacts (landing), support 25.3N of engine thrust pushed through 4 load-bearing joints, and normal handling loads. The first iteration suffered from intra-layer separation, thermal deformation, and high weight. The solutions were such:
- Airframe Thickness: 2.1mm --> 0.9mm
- Segment Count Reduced To 2 (To Reduce Weight From Segment Joints, Reduce Number Of Points Of Failure, and Increase Manufacturing Rate)
- 3D Printer Filament: PLA --> ABS --> PLA+ (PLA+ Exhibited Best All Around Tensile And Yield Strengths)
- Increased Layer Count To Reduce Aerodynamic Surface Friction, Along With Changing Printing Temperature, Speed, And Other Variables
Fun Fact: Just like a real rocket, if you tip this one over too much, or happen to touch it wrong, it will fall apart :)
Hold Down System
Description:
The first iteration of the Eagle X Hold Down System originally consisted of 4 counter-weighted clamps, which when allowed to fall backward let the rocket detach from the pad. 4 servos individually controlled each clamp. The second iteration consisted of a singular ring that held the rocket to the pad. When the ring was turned by a gear system, alignment and hold-down pins on the rocket would slide through matching holes in the ring. The third iteration used 3 small, light, and powerful magnets to hold and align the rocket. The fourth and final iteration was a pedestal system where the rocket would sit in premade grooves inside of the pedestal, and was not held down by anything but gravity. When the rocket engine ignited, there would be a short period between which the rocket engine has enough thrust to overcome the static friction of the pedestal, and enough thrust for thrust vector guidance to be effective.
Engineering Challenges:
The first iteration suffered from reliability issues with the counterweighted clamps retracting, along with clearance issues from the rocket's takeoff process. The first iteration was also a system with high complexity, high part count, and long manufacturing times. Also, due to the big central base of the hold-down system, there were problems with warping during manufacturing.
The second iteration solved issues from the first iteration by reducing the number of individual processes needed for a takeoff to 1: a rotation of a ring. It also solved the high part count issues and was able to be manufactured easily and precisely. However, the ring had a concerningly large amount of rotational static friction, even when under no engine load. When under engine load, it was susceptible to jam. The driving gear system was also too inaccurate and unreliable to rotate the ring to the specified set point (despite having a physical system in place to help with such).
The third iteration of the hold-down system was a simple magnetic hold-down system, which helped alleviate any possibility of a mechanical issue. Due to the simplicity of the system, the force needed to separate from the hold-down system can be calculated. The system, despite its mechanical superiority, put an unnecessary amount of mass into the rocket and added a component that would need to be replaced with each new airframe since the magnets were glued in.
The fourth iteration consisted of a launch pedestal with an alignment pin 3D printed onto the rocket, and an alignment and holding cavity on the pedestal. This nearly removed all rocket-side mass from the hold-down system and took the number of active processes needed for takeoff to 0. The pedestal also greatly simplified manufacturing and assembly, since it is one 3D-printed piece
Fun Fact: The part count for the first iteration was 30. The final iteration's part count was 4.
The first iteration of the Eagle X Hold Down System originally consisted of 4 counter-weighted clamps, which when allowed to fall backward let the rocket detach from the pad. 4 servos individually controlled each clamp. The second iteration consisted of a singular ring that held the rocket to the pad. When the ring was turned by a gear system, alignment and hold-down pins on the rocket would slide through matching holes in the ring. The third iteration used 3 small, light, and powerful magnets to hold and align the rocket. The fourth and final iteration was a pedestal system where the rocket would sit in premade grooves inside of the pedestal, and was not held down by anything but gravity. When the rocket engine ignited, there would be a short period between which the rocket engine has enough thrust to overcome the static friction of the pedestal, and enough thrust for thrust vector guidance to be effective.
Engineering Challenges:
The first iteration suffered from reliability issues with the counterweighted clamps retracting, along with clearance issues from the rocket's takeoff process. The first iteration was also a system with high complexity, high part count, and long manufacturing times. Also, due to the big central base of the hold-down system, there were problems with warping during manufacturing.
The second iteration solved issues from the first iteration by reducing the number of individual processes needed for a takeoff to 1: a rotation of a ring. It also solved the high part count issues and was able to be manufactured easily and precisely. However, the ring had a concerningly large amount of rotational static friction, even when under no engine load. When under engine load, it was susceptible to jam. The driving gear system was also too inaccurate and unreliable to rotate the ring to the specified set point (despite having a physical system in place to help with such).
The third iteration of the hold-down system was a simple magnetic hold-down system, which helped alleviate any possibility of a mechanical issue. Due to the simplicity of the system, the force needed to separate from the hold-down system can be calculated. The system, despite its mechanical superiority, put an unnecessary amount of mass into the rocket and added a component that would need to be replaced with each new airframe since the magnets were glued in.
The fourth iteration consisted of a launch pedestal with an alignment pin 3D printed onto the rocket, and an alignment and holding cavity on the pedestal. This nearly removed all rocket-side mass from the hold-down system and took the number of active processes needed for takeoff to 0. The pedestal also greatly simplified manufacturing and assembly, since it is one 3D-printed piece
Fun Fact: The part count for the first iteration was 30. The final iteration's part count was 4.
Launch Pad
Description:
Eagle X's Launch Pad framing was made out of 13 80/20 aluminum extrusions: 12 for the base and 1 for the strong back. The framing was covered by 8 3D-printed shells, which were screwed into the 80/20 extrusions. The strongback was static but could retract by the use of a pneumatic system housed inside of the base of the launchpad. The strongback had two servo-actuated "pinchers" at the top of the pad to help hold the rocket still from wind and other disturbances while on the pad. The rocket interfaced with the launchpad through the pedestal hold-down system.
Engineering Challenges:
During the first 3 iterations of the hold-down system, the pad had a flame trench. The flame trench proved to be useful when the rocket interfaced directly with the pad (without physical separation), but when physically separated, it proved to be unnecessary. The launchpad shells were also very difficult to print with a flat surface due to warping issues. This was counteracted by altering the 3D printer settings to optimally adhere the shells to the print bed, while still maintaining a similar surface finish. During the first iteration, 11 3D-printed shells covered the framing. By the final iteration, there were only 8 (this is surprisingly difficult given the 3D printer's capabilities.
The strongback initially was supposed to retract while the rocket lifts off. Although from a clearance and "coolness" perspective it seems like a good idea, it was far too complicated for what it had to be. The rocket still needed protection from being tipped on the pad by wind, since there were no longer any active hold-down systems. A shorter strongback was considered, but it was far too expensive to change that singular part.
Eagle X's Launch Pad framing was made out of 13 80/20 aluminum extrusions: 12 for the base and 1 for the strong back. The framing was covered by 8 3D-printed shells, which were screwed into the 80/20 extrusions. The strongback was static but could retract by the use of a pneumatic system housed inside of the base of the launchpad. The strongback had two servo-actuated "pinchers" at the top of the pad to help hold the rocket still from wind and other disturbances while on the pad. The rocket interfaced with the launchpad through the pedestal hold-down system.
Engineering Challenges:
During the first 3 iterations of the hold-down system, the pad had a flame trench. The flame trench proved to be useful when the rocket interfaced directly with the pad (without physical separation), but when physically separated, it proved to be unnecessary. The launchpad shells were also very difficult to print with a flat surface due to warping issues. This was counteracted by altering the 3D printer settings to optimally adhere the shells to the print bed, while still maintaining a similar surface finish. During the first iteration, 11 3D-printed shells covered the framing. By the final iteration, there were only 8 (this is surprisingly difficult given the 3D printer's capabilities.
The strongback initially was supposed to retract while the rocket lifts off. Although from a clearance and "coolness" perspective it seems like a good idea, it was far too complicated for what it had to be. The rocket still needed protection from being tipped on the pad by wind, since there were no longer any active hold-down systems. A shorter strongback was considered, but it was far too expensive to change that singular part.
Thrust Vector Control Mount
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Flight Computer + Electrical Systems
Description:
The flight computer is responsible for commanding the rocket from pre-takeoff to post-landing. It is designed in-house using Altium PCB Design software and manufactured by external services.
The flight computer took on many different versions, ranging from fully through-hole to fully surface mount. The optimal design proved to be a majority surface mount flight computer. The flight computer contained the following subsystems: STM32 microcontroller, wire terminals, a USB port, power electronics (filtering, brownout protection, etc), sensors (gyroscope, accelerometer, magnetometer), and visual / physical systems (status LEDs, power switches, reset buttons).
Attached to the flight computer are various outputs for servo control, parachute deployment, and other electrical systems. These components, along with the sensors onboard the flight computer, communicate using various protocols such as SPI, I2C, and others.
A final version was never developed, however, the flight computer did reach a semi-stable state.
The flight computer is responsible for commanding the rocket from pre-takeoff to post-landing. It is designed in-house using Altium PCB Design software and manufactured by external services.
The flight computer took on many different versions, ranging from fully through-hole to fully surface mount. The optimal design proved to be a majority surface mount flight computer. The flight computer contained the following subsystems: STM32 microcontroller, wire terminals, a USB port, power electronics (filtering, brownout protection, etc), sensors (gyroscope, accelerometer, magnetometer), and visual / physical systems (status LEDs, power switches, reset buttons).
Attached to the flight computer are various outputs for servo control, parachute deployment, and other electrical systems. These components, along with the sensors onboard the flight computer, communicate using various protocols such as SPI, I2C, and others.
A final version was never developed, however, the flight computer did reach a semi-stable state.
