drexel university 2011 rocksat-c final report

Drexel University 2011 RockSat-C Final Report

Implementing a despun platform during the ascent of a sounding rocket.

Team Joe Mozloom

Eric Marz Swati Maini

Swapnil Mengawade Linda McLaughlin

Advisor: Dr. Jin Kang

01 August 2011

Drexel University 01 August 2011 RockSat-‐C 2011

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1.0 Mission Statement

Drexel's RockSat payload will incorporate a platform rotating opposite the spin-stabilization of the Terrier-Orion sounding rocket during ascent, resulting in a rotationally static platform from an outside reference frame.

2.0 Mission Requirements and Description Since many parameters characterizing flight conditions are largely unknown, two sets of success criteria were developed, one for workbench level without exterior factors, and success criteria for flight. A summary of both sets is listed in Table 1.

Table 1: Success Criteria Workbench Flight

Meet all NASA / WFF requirements Meet all NASA / WFF requirements Counter-rotating platform effective from 0.5 Hz - 10 Hz

Counter-rotating platform engaged when canister is spinning

Maximum platform spin-rate 10% of current canister spin-rate

Platform able to rotate under harsh flight conditions

Data is reliably collected and is usable Data is reliably collected and is usable Drexel will be sharing its canister with Temple University; therefore all physical requirements will be split evenly. Though there are numerous constraints and regulations to be met before flight, some affect every aspect of the payload design and must be considered during each stage of design. Table 2 shows the major constraints of each experiment within the canister.

Table 2: Major Constraints for Sharing Type Constraint

Physical Envelope Cylindrical: Diameter: 9.3 inches Height: 4.75 inches

Mass Canister + Payload=10lb

Center of Gravity The Center of gravity of the whole canister should lie within 1x1x1 inch envelope of the canisters geometric centric

Budget The total budget allotted for the project is $1200 Battery Rechargeable lithium ion batteries are prohibited

3.0 Payload Design Drexel’s proposed design consists of two platforms within the canister. The lower of the platforms is fixed to the canister and houses electronics, batteries and motor used to control an upper rotating platform designed to rotate against the sounding rocket’s spin rate. Measurements from accelerometers attached to the fixed and despun platforms will be used for control as well


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as storage of rotation rates throughout launch and ascent portions of flight. An overview of the design is represented in Figures 1 -3 below.

Figure 1: Isometric view one of final payload design

Figure 2: Isometric view two of final payload design

[1] Pinion [2] Despun Platform Accelerometer [3] Despun Platform [4] Microcontroller Board [5] DAC [6] (10) AAA NiMH Batteries

1 2

3

4

5

6

11

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8 7

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[7] G-‐Switch [8] Canister Accelerometer [9] Slip ring / Slip Ring Holder [10] Slip ring holder washer [11] Motor / Motor Mount [12] Upper Motor Mount Washer [13] Lower Motor Mount Washer


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Figure 3: Front view of final payload design Figure 4 depicts an overview of system activity during the different stages of flight. It can be seen that the system activates at liftoff via a g-switch and begins to store data and despin the platform. The system continues to store and despin until the internal memory is full, around T + 550 seconds, in which case the system disables the motor and sensors and awaits recovery.

Figure 4: Flight Altitude and time schematics


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3.1 Despun Platform Subsystem The Despun Platform Subsystem consists of a slip ring to transmit data and power from the microcontroller on the fixed platform to the accelerometer on the despun platform, the slip ring holder, and aluminum gear, which will serve as the despun platform. A list of the constraints used to determine the components for the Despun Platform Subsystem can be seen in Table 3.

Table 3: Despun Platform Subsystem Constraints

Requirement # Constraint 1 Platform shall be able to rotate at >500 RPM 2 System shall be able to pass ≈2.2 mA from fixed platform to accelerometer 3 System shall be able to pass ≈ 3.3 V from fixed platform to accelerometer 4 System shall allow > 5 circuits on despun platform 5 System shall perform throughout 25 G acceleration 6 System shall allow for 0.25” D center standoff 7 Despun Platform shall have diameter < 7” One of the main hurdles when characterizing the subsystem was identifying a way to transmit power and data while the platform is rotating. A slip ring was used to transmit power and data to the despun platform. Slip rings, also known as rotary electrical interfaces, are similar to a brushed DC motor where electrical connections from a rotating section are made to a stationary ring via contact from brushes. A slip ring component is ideal because it meets the requirements for the number of circuits, allows for a center canister standoff, meets the maximum RPM requirement, and also incorporates the support and bearing system for the aluminum gear, simplifying the overall design. Alternatives to a slip ring include Bluetooth wireless data transmission with local power sources on both despun and the fixed platforms, or simple loose wiring from the despun platform to the fixed platform.

The other significant hurdle in the Despun Platform Subsystem was identifying the interface between the despun platform and motor. The concepts considered for this interface were a belt drive and spur gearing. These types of interfaces allowed for the torque of the despun platform, produced by elevated bearing friction (from the high vertical acceleration associated with accent) to be stepped down before being overcome by the motor. By doing this, a lighter motor could be sourced, which would require less power, and conserved volume. A geared drive train was chosen based on simplicity of design. The motor is oriented so the axel is to be vertical during ascent. Fixed to the axel is an aluminum pinion mated with the despun platform, which is geared along the outside edge. The gear ratio between the despun platform and the pinion is 4:1, stepping down the torque needed of the motor by one-fourth, while elevating the motor RPM by a factor of four. Both despun platform and pinion were designed using MITCalc, a gear design software package that integrates with Microsoft Excel and outputs a 3D SolidWorks assembly of mated gears. The gear designs were then tested in SolidWorks prior to fabrication for tooth performance at theoretical torques experienced during ascent, as well for response to vertical normal forces of the slip-ring / motor axel. The gear was originally to be fabricated from polycarbonate, selected for its low mass, high impact resistance, and success in previous payloads. In order to verify material selection, Finite Element Analysis was performed on both an individual tooth and as a distributed load on the top


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face of the gear, to simulate a high torque environment and the high loading due to elevated G’s. Appendix B shows the results of the Von Mises Stress Analysis, both as a point load on a single tooth face as well as a distributed load across the top face of the gear. A safety factor of 34.7 and 23.7 was found for tooth and top face respectively. The high safety factors verified polycarbonate as an adequate material for the components, however, manufacturability was not thoroughly considered. The gear and pinion were originally to be machined using Drexel Machine Shop’s Haas 4-axis CNC end mill. However, the small radii of the inner tooth fillets combined with the overall thickness of the part made this a difficult and time consuming process, taking an estimate 6 hours of machining time. As a result, both the gear and coupling pinion were redesigned with aluminum, allowing their tooth profiles to be cut using Electronic Discharge Machining (EDM), a much more time effective and precise process. Once the profile of the gear and pinion were created, the CNC end mill was used to create the boss and pockets found in the end product. The slip ring holder was manufactured from ABS plastic using the Machine Shop’s Fuse Deposition Modeling (FDM) 3D Printer. This allowed for a design not constrained by the manufacturing limitations present if it were to be fabricate using traditional machining methods. The desired geometries were modeled in SolidWorks, exported into a .STL file, and then simply uploaded to the 3D printer. 3.2 Data Subsystem The Data Subsystem is comprised of a microcontroller to handle the data processing, memory to store the results of the experiment, two accelerometers of different sensitivity to measure angular velocity, the algorithms to interpret the accelerometer measurements and finally the digital to analog converter (DAC) to use output from the microcontroller to control the speed of the motor. The major constraints affecting all components were the limited power budget and the forces acting upon the payload during launch and throughout flight. The limitation on mass restricted the battery power that could be incorporated into the design and, therefore, it was critical that all components had low voltage requirements and current draws. Also, several decisions were made based on prior experience of the component in the RockSat-C program. Both the Atmel Atmega32 Microcontroller and Analog Devices ADXL family of accelerometer were selected based on their previous successful flight history. The selected microcontroller board has voltage regulation circuitry included for both 5.0 volts and 3.3 volts. These are important as they act as the output voltages of the ports used to control the DAC, discussed above. This voltage regulation allows the utilization of a single power source for the motor, the microcontroller, and the DAC, saving the complexity and weight of having separate voltage regulation or power circuits. Simple test programs have been loaded onto the microcontroller to ensure functionality of the ports. Algorithm design has begun and programming of the algorithm is the next step for the Data Subsystem. A diagram of the proposed algorithm can be seen in Appendix A. The major components of the algorithm are code blocks for reading the fixed platform sensor, reading the despun platform sensor, updating the digital output to the DAC to control the motor, and writing rotation data to memory at specified timing intervals.


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Both linear accelerometers and gyroscopes were considered. At the sounding rocket’s maximum spin rate of approximately 5.6 Hz, no low cost gyroscopes met the specifications of Drexel’s needs. As a result, accelerometers were chosen to measure the rotation of both the despun platform and the lower platform fixed to the canister by measuring the radial acceleration at a known distance from axis of rotation and converting to an angular velocity. As the spin rates of these platforms would be quite different, separate models of accelerometers were considered for each platform. Model number ADXL203 was selected for the upper despun platform because of its high sensitivity of 960-1040 mV/G throughout the minimal range of ± 1.7G. Because the despun platform is designed to be rotationally static, the radial acceleration on that platform will be well within this range. The lower fixed platform will be rotating at a frequency of up to 5.6 Hz, requiring an accelerometer with a higher range. ADXL278 was selected because of its higher range of ±35G. The lower sensitivity of 25.65-28.35mV/G was not of concern, as the most sensitive readings will be taken from the despun platform. The DAC required for communication between the microcontroller and the motor controller was designed and fabricated as a printed circuit board in house. An 8-bit DAC was selected because the range of voltages to the motor required to achieve the necessary revolutions per minute was relatively low. A voltage range of 0.0 to 2.5 volts was calculated, in order to provide some overhead. The DAC was designed as an R2R resistor ladder network with a reference voltage directly from the microcontroller, 4.9 volts. An 8-bit DAC provides 0.0191 volt stepping, converting to 0.15 Hz stepping for the platform rotation. This solution was selected as there was no requirement for an external voltage reference source for the R2R ladder, simplifying the design and removing components that could cause errors. 3.3 Motor Subsystem The Motor System comprises of a Faulhaber3244-BX4 brushless motor, ABS motor mount, and the aluminum pinion. Motor specifications were generated based on the dimensions of the despun platform and the angular velocity of the Terrier-Orion rocket. Other constraints were due to the volume of the canister and the maximum allowed distance between the fixed and the de-spun platform. A list of all the specifications is shown below in Table 4.

Table 4: Motor Specifications Requirements Specification System Requirements

RPM 2400 RPM

Voltage 12 Volts

Amperage < 300 mA

Torque >0.01475 lbf ft.

Length <3 inches

Mass <0.5512 lbs. As with the gear, a Von Mises Stress analysis was performed on the both tooth and top faces of the pinion. The results are displayed in Appendix B and show a safety factor of 57.4 and 349 for


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a point load on the tooth face and a distributed load along the top respectively, well above any cause for concern. However, the same manufacturability issues arose with pinion as with the gear, so it was decided to manufacture the pinion in the same fashion as the gear, EDM to create the profile and CNC end mill to create the pockets and boss. The motor mount was constructed in the same method as the slip ring holder, from ABS plastic using FDM 3D printing. Since the mount is suspending the motor, the component with the highest mass during launch, the bolt holes will be experiencing very high loads. To ensure the motor mount could handle the loads during launch, six point loads were applied downwards on the motor mounting holes using SolidWorks FEA. These loads were meant to simulate what the holder will experience during ascent, the results can be found in Appendix B, with a resulting factor of safety of 6.7, which is acceptable. To ensure that the bolt heads would not damage the ABS plastic during launch, an aluminum washer was fabricated. The washer rests between the ABS plastic and the bolt heads on the top face of the motor mount and is meant to distribute the normal forces experienced by the ABS plastic. 3.4 Power Subsystem The Power Subsystem incorporates an array of rechargeable AAA batteries as well as a G-Switch, which is used to indicate launch to the Data Subsystem. Flight guidelines require that each payload be self-contained and the uses of rechargeable batteries are highly encouraged. The array supplies 12 volts to the motor and to the microcontroller where it will be stepped down to 3.3 volts or 5 volts depending on use. The selected components require four amperes to start functioning. Given these constraints, the battery search was reduced to two types, nickel cadmium (NiCd) and nickel metal hydride (NiMH). The main difference between the two is that the NiMH battery offers a capacity that is almost twice that of the NiCd, resulting in longer run times without additional weight. Additionally, NiMH batteries are less prone to develop a memory effect, making them ideal for use during in testing and subsequently for flight. An overview of how the power system interacts with the rest of the canister components is displayed in Figure 5.

Figure 5: Functional block diagram

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4.0 Student Involvement The Drexel University team comprised of three mechanical engineering students and two electrical and computer engineering students. During the course of the project the mechanical engineering students’ general responsibilities were to develop solutions to meet design constraints, manufacture the components, and model and test all components and system in SolidWorks. The electrical and computer engineering team worked on the data system management, identifying and sourcing necessary electrical components, power allocation, and the microcontroller algorithm and its integration with the sensors. The data acquisition system and storage were worked on together with the activation systems for the motor and G-switch. Below is a brief summary of the various sub-systems that were handled by the team members.

Figure 6: Work Breakdown Structure

5.0 Testing Results As the success or failure of the payload depends on accurate accelerometer readings, comprehensive testing was performed on both the despun platform and canister accelerometers. The first test performed compared input voltage to the motor controller with response from the despun platform accelerometer and the motor frequency output. This was done to verify theoretical motor RPM with measured motor RPM and to capture the response of the despun platform accelerometer. With this data, it was possible to condition the accelerometer signal to follow the measured motor RPM throughout its operational range of ±1.7G [7]. This allowed for much more accurate results taken from the despun platform accelerometer. Results of this testing can be seen below in Figure 7.


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Figure 7: Despun Platform Spin Rates (Despun Accelerometer)

The rotation rate was derived from the accelerometer output voltage using Equation 1 below. !"# = !"

!171.479(!!"# − 2.49) [1]

The dashed line in Figure 2 indicates the maximum measured value from the ADXL203 accelerometer used on the despun platform. Preliminary testing of the accelerometer showed a linear response within this operating range, but results not consistent with the theoretical and measured rotation rate. A conditioning factor of 1.75 was factored into the equation to account for this difference. This change is seen in Equation 2. With the inclusion of this conditioning, a maximum error of 13.6% was calculated within the accelerometers functional range. !"# = (1.75) !"

!171.479(!!"# − 2.49) [2]

In addition to the above testing of the despun platform accelerometer, it was necessary to verify the functionality of the canister accelerometer. The canister accelerometer will be used to provide coarse-grained control over the motor and subsequently the despun platform’s spin rate. Results in Figure 8 below show the simultaneous response of both accelerometers.

0

100

200

300

400

500

600

0 0.5 1 1.5 2 2.5

Despun

PlaUrom

Spin Ra

te (R

PM)

Motor Input Voltage (V)

TheoreYcal RPM

Measured Motor RPM

CondiYoned Accelerometer RPM

Accelerometer RPM

Accelerometer Limit


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Figure 8: Canister vs. Despun Platform Accelerometer

The above plot illustrates the similarities of measurements from the canister accelerometer with the full-scale range of ±30G versus that of the despun platform accelerometer with a full-scale range of ±1.7G. Because both curves are similar, initial motor RPM settings can be derived from the canister accelerometer, allowing for a smooth transition through different sounding rocket rotation rates. Fine-grained control is still reserved for the more sensitive despun platform accelerometer, which when incorporated completes the closed loop system. The benefit of utilizing both values for control is to mitigate the effect of overshooting the target RPM, which ultimately results in more complicated control logic. By bounding the despun platform accelerometer response to that of the canister accelerometer response, more accurate results can be achieved within a smaller range of motor control voltages. Following individual accelerometer testing and verification, a full system simulation was completed. This consisted of spinning the entire system at multiple spin rates for varying durations of time. Results of the full system simulation are shown in Figure 9 below.


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Figure 9: Full Mission Simulation

A large amount of noise is present in both the despun platform accelerometer as well as the canister accelerometer. This noise, especially that associated with the despun platform, is hypothesized to be a function of the sensitivity of the accelerometers, the discretization of the analogue data (alternation between a threshold), and the mechanical interaction of the gear teeth. Though the noise makes it difficult to determine the exact, instantaneous spin rates during testing, it can be seen that the despun platform stays at a relatively constant rotation rate throughout testing. Visual inspection of testing confirmed this, showing very little to no rotation of the despun platform. This suggests that the graphical results pictured in Figure 9 are a product of sensor error and do not exactly display the actual dynamics of the despun platform during testing. It was concluded that the system testing was successful and the payload was fully functional and ready for launch. 6.0 Mission Results As the experiment was designed as a feasibility study, this section will show how successful the proposed solution and implementation was for despinning the sounding rocket. One of the largest concerns for the success or failure of the design was the extremely high forces and vibrations each payload would be experiencing during the first stages of the rocket’s flight. The Terrier and Orion booster burns, therefore, is where the most interesting data is gathered. Also, because of these harsh conditions, the flight success criteria were much more relaxed than the workbench success criteria. It will be shown that we these criteria were met and it will be explained where the design fell short. Below is the first representation of the data gathered, which shows the entire recorded duration of the flight. Data was collected from T-0 until T+500 (roughly the time of parachute deployment). Marked on the chart are four different time periods, explained below.


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Figure 10: Mission Results

The area of the chart marked ‘1’ represents the time that includes both the Terrier and the Orion burns. For the first few moments the despun platform struggles to reduce the rotation, but at around T+10 it begins to reduce the spin rate noticeably. As was seen in the full mission simulation, during the testing phase of our design, there is considerable noise in the signals due to the selected accelerometers. Because of this noise, it is difficult to determine just how much the platform was able to despin. When comparing the curve from the full mission simulation to the flight results, it appears that there was not as much reduction in spin rate as was seen on the bench, but the system does respond and attempt to reduce that spin rate. The second area, marked ‘2’, shows the portion of the flight where the Terrier-Orion rocket was coasting in the upper atmosphere, no longer experiencing violent acceleration and rotation. During this period, the relatively tame spin rates of less than 50 RPM could be reduced down to a static reading on the despun platform. An interesting observation is that the design was unable to overcome vibrations in readings on the despun platform while on the bench, yet it appears it did so in flight. This means one of two things for our experiment. Either the low gravity environment allowed for smoother operation of the design, or the sensor was damaged, or somehow disconnected, during launch and was not recording properly for that segment of flight. It is hard to determine, as there were no redundant sensors, something that would be extremely beneficial in a future design. Areas ‘3’ and ‘4’ were of less concern to the experiment, as the team was interested in the feasibility of despinning during ascent for more stable data collection for other potential experiments. Area ‘3’ shows the region around apogee where the rocket was tumbling and reorienting to reenter the atmosphere. The despun readings during this time were higher than

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0 40 80 120 160 200 240 280 320 360 400 440 480

RPM

Time (seconds)

Canister vs. Despun Calculated RPM

Despun PlaUorm Accelerometer Canister Accelerometer

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3

4

1


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those of the canister likely because the rocket tumbled opposite to the direction it was originally spinning for stabilization. And lastly Area ‘4’ depicts the sounding rocket returning until the time when the parachute was deployed. Figure 11 below shows the same data as above, but during the time from T-0 until T+60, encompassing both the Terrier and Orion burns, which run from T-0 to T+5.2 and T+15 to T+40.4 respectively (As noted in RockSat-C User Guide).

Figure 11: Mission Results T-0 to T+60

It can be seen that the despun platform is responding and reporting values slightly lower than those reported from the canister. Because of this, the success criteria for launch was met and exceeded, although the performance seen during bench testing was not achieved during flight. 7.0 Conclusions The results of Drexel’s inaugural entry into the RockSat-C program meet or exceed all success criteria established at the beginning of the program, indicating a successful mission. Though the despun platform did not despin throughout the entirety of ascent, the system was able to despin during portion of the flight. It is hypothesized that the inability to despin for the entire flight may have been cause by sensor error, triggered by the high vibrations of flight condition, or a stall of the motor due to high torques needed to rotated by the despun platform. The high torque may have been a result of the elevated g-loading on the bearing system of the despun platform, which linearly increased the friction in the bearings, and in turn the amount of torque required to rotate the system. This high torque requirement would be too much for the motor to overcome, thus only partially despinning the platform. However, the experiment met all WFF requirements,

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0 5 10 15 20 25 30 35 40 45 50 55 60

RPM

Time (seconds)

Canister vs. Despun Calculated RPM (Area 1)

Despun PlaUorm Accelerometer Canister Accelerometer


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activated while the canister was ascending and spinning, attempted to despin the platform during ascent, and successfully logged all flight data, making the flight a success. 8.0 Potential Follow-up Work The intent of Drexel’s 2011 payload is to serve a feasibility study of despinning a payload within a spin-stabilized sounding rocket. Future RockSat-C participants could utilize Drexel’s design and findings to optimize future payloads, which would benefit from a rotationally static reference frame. As the RockSat-C program is an ongoing project of Drexel’s Space Systems Laboratory, it is likely that results of the 2011 experiment can be utilized in the near future. Future teams may want to further explore the interaction of the high g’s on the bearing system of the despun platform. Investing in higher quality bearing system may improve the performance of the despun platform and result in a more stationary environment. Additionally, experimenting with different gear rations and stronger motors may allow for the system to overcome the high torques required to despin the platform. Also, since noise was present in test and flight data, further exploration into noise decoupling for the sensors could be pursued. Since it was hypothesized that some of the noise present may have been a result of the mechanical interactions of the gear teeth between the pinion and despun platform, alternative drive systems could be explored, such as a pulley system or even a direct spin system. These updates to the despun platform could be completed in conjunction with the development on an experiment to be mounted to the platform, which is the end goal of the 2011 experiment. 9.0 Benefits to the Scientific Community Drexel’s experiment allows for the unique ability to despin part of a sounding rocket payload during ascent. This allows for any future experiments, which may require a rotationally static environment to be housed with the same rocket as rotating experiments. Solar measurements, point-source radiation measurements, sensitive instruments, and media capture devices are all excellent candidates to be mounted aboard a despun platform. Increasing the flexibility of sounding rocket experiments is growing increasingly more important as more private companies and universities increase their use of sounding rockets to access space conditions. 10.0 Lessons Learned After reflecting on the Drexel Team’s experience in RockSat-C, there are a number of lessons that were gleaned through participation, these learning are outlined below.

1) Create a cross-functional team to meet the needs of the project. The Drexel team was formed before a mission statement was defined. However, it was quickly learned that the team had an excess of Mechanical Engineers and not enough Electrical/Computer Engineers to evenly distribute the work.

2) Set expectations for weekly time commitment. Explicitly stating the expectations for hours spent per week help team members gauge how much work they should be putting in and ensures that all members are involved.

3) Early in the process, create as many constraints as possible. This dramatically narrows down the design space and helps reduce the “blank page” effect.


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4) Tell everyone about your experiment (create a 30 second commercial). Whenever contacting a company about a product for the payload make sure they know what the product is for and that it is student run. Many companies are willing to sell their products at a reduced price or even donate them for student use (Drexel’s team experienced this first hand).

5) Use Dropbox (or any shared folder that can be mapped to a drive/folder) for SolidWorks files. This allows for multiple people to look at the same model and creates a version that isn’t subject to the whims of a hard drive.

6) Integrate hardware as early as possible. Hardware will never work the first time and often requires a redesign or modification, which usually necessitates access to a store, shipping, or a machine shop, all of which are only open during normal business hours.

7) Factor shipping costs into the budget. When ordering many components, shipping costs can become very expensive, especially if something needs to be rushed.

8) If using metal platforms, make sure nothing has the possibility of shorting to each other. Use electrical tape for components to rest on so they don’t short through the platform.

Acknowledgments Drexel’s team would like to thank our Advisory, Dr. Kang, for his unwavering technical (and financial) support throughout the project. We would also like to thank Drexel’s MEM and ECE departments for their support. We would especially like to thank Drexel’s Machine Shop, whose expertise and patience made the experiment possible (and successful). Lastly we would like to thank Emily Logan and the rest of the RockSat team whose dedication and hard work made the entire program a success and let us launch something we made into space. Thank You.


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11.0 Appendices Appendix A: Software UML Diagram


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Appendix B: Von Mises Stress Analysis, FEA Testing Results of single tooth FEA testing of polycarbonate gear and pinion

Gear Pinion

Theoretical Load (N) 1.26 1.26

Load Applied (N) 10 10

Max Deflection (mm) .026 .012

Max Stress (MPa) 1.788 1.081

Max Stress Location Set Screw Holes Set Screw holes Filet of loaded tooth

Safety Factor 34.7 57.4

Results of distributed vertical load FEA testing for polycarbonate gear and pinion and ABS motor mount

Gear Pinion Motor Mount

Theoretical Load (N) 25 2.5 49

Load Applied (N) 50 5 100

Max Deflection (mm) 0.01 0.001 0.243

Max Deflection Location Outer Diameter Outer Diameter Top Face Inner Diameter

Max Stress (MPa) 2.741 0.135 9.715

Max Stress Location Set Screw Holes Set Screw Holes and ID Top face ID at mounting holes

Safety Factor 23.7 459.7 6.7


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Appendix C: Center of gravity analysis for final payload design


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Appendix D

: Budget

Prog

ram C

osts

Item

U

nit P

rice ($)

Qu

antity

Total ($)

Canister C

ost 7000

1 7000

Launch W

eek Expenses 4600

1 4600

Total

11600

Com

pon

ent C

osts

Item

P

art Nu

mb

er M

anu

facturer

Ven

dor

Qu

antity

Un

it Price

($)

Total ($

) AD

XL278 A

ccelerometer

AD

XL278C

E Analog D

evices Analog D

evices 2

8 16

AD

XL203 A

ccelerometer

AD

XL203C

E Analog D

evices Analog D

evices 1

11 11

AD

XL203Evaluation B

oard AD

XL203EB

Analog D

evices Analog D

evices 2

31 62

Microcontroller B

oard ATM

ega32-16PU

Atm

el D

igi-Key

1 45

45 Slip R

ing CAY-1847

Aeroflex

- 1

400 400

G-S

witch

SS-5G

L2 O

mron

Digi-K

ey 1

2 2

DC M

icro-motor

3242-SCD

C

Faulhber M

icromo

1 345

345 12"x24"x.25" PC

sheet 85805K

43 -

McM

aster-Carr

1 20

20 12"x12"x0.50" PC

Sheet

8574K32

- M

cMaster-C

arr 1

28 28

Flash Mem

ory AT26D

F161A

Atm

el D

igi-Key

1 4

4 AAA N

iMH

Batteries

16546 Accupow

er onlybatteries.com

12

4 48

Misc H

ardware

- -

McM

aster-Carr

1 100

100 Connectors K

it 76650-0159

Molex

Digikey

1 45

45 26 A

WG

Wire

696-5236 Alpha W

ire Allied Electronics

1 29

29

2-Cell A

AA B

attery Holders

2469K-N

D

Keystone

Electronics D

igikey 6

2 12

3/64" End Mill B

it 34947-C

3 H

arvey Tool carbideem

porium.com

1

49 49

Shipping C

harges -

- -

1 100

100

Total

1316 !


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Appendix E: Full System Schematic

55

44

33

22

11

DD

CC

BB

AA

DA

C0

DA

C1

DA

C2

DA

C3

DA

C5

DA

C6

DA

C7

DA

C4

SLIP

RIN

G0

SLIP

RIN

G1

SLIP

RIN

G2

SLIP

RIN

G3

PB

O (X

CK

/TO)

PB

1 (T1)

PB

2 (INT2/A

IN0)

PB

3 (OC

0/AIN

1)

PB

4 (SS

')

PB

5 (MO

SI)

PB

6 (MIS

O)

PB

7 (SC

K)

RE

SE

T'

VC

C

GN

D

XTA

L2

XTA

L1

PD

0 (RX

D)

PD

1 (TXD

)

PD

2 (INT0)

PD

3 (INT1)

PD

4 (OC

1B)

PD

5 (OC

1A)

PD

6 (ICP

1)

PA

0 (AD

C0)

PA

1 (AD

C1)

PA

2 (AD

C2)

PA

3 (AD

C3)

PA

4 (AD

C4)

PA

5 (AD

C5)

PA

6 (AD

C6)

PA

7 (AD

C7)

AR

EF

GN

D

AV

CC

PC

7 (TOS

C2)

PC

6 (TOS

C1)

PC

5 (TDI)

PC

4 (TDO

)

PC

3 (TMS

)

PC

2 (TCK

)

PC

1 (SD

A)

PC

0 (SC

L)

PD

7 (OC

2)

DA

C0

DA

C1

DA

C2

DA

C3

DA

C4

DA

C5

DA

C6

DA

C7

Analog O

ut

Up

Um

ot

GN

D

Unsoll

DIR

FG

GN

D

Vin

Vout

GN

DG

ND

A1

A0

CNO

NC

01

GN

D

Vsupply

GN

D

Vout

Vin

GN

D

XY

Vin

GN

D

XY

Title

Size

Docum

ent Num

berR

ev

Date:

Sheet

of

Marz, M

ozloom, M

aini, Mclaughlin, M

engawade

1

Drexel U

niversity RockS

at-C Full S

ystem S

chematic1

1

Title

Size

Docum

ent Num

berR

ev

Date:

Sheet

of

Marz, M

ozloom, M

aini, Mclaughlin, M

engawade

1

Drexel U

niversity RockS

at-C Full S

ystem S

chematic1

1

Title

Size

Docum

ent Num

berR

ev

Date:

Sheet

of

Marz, M

ozloom, M

aini, Mclaughlin, M

engawade

1

Drexel U

niversity RockS

at-C Full S

ystem S

chematic1

1

4.9 Volts

DA

C

PC

B

Motor C

ontroller

3242012BX

4 SC

RB

F

Wallops

Batteries13V

dcB

atteries13V

dc

DP

_Accel

PC

B - A

DX

L203

Microcontroller

ATm

ega32-16u

C_A

ccel

PC

B - A

DX

L278

G-S

witch

SW

156-ND

Microcontroller V

oltage Regulator

AV

RV

I Board

Activation C

ircuit

PC

B


22

Appendix F: Final Payload Photos


23


24

drexel university 2011 rocksat-c final report

Documents