1. University of Florida FRR Presentation

2. Outline Vehicle Design Payload Design Recovery System
Component Testing
Full-Scale Flight
Simulations
Outreach
Future Work

3. Vehicle Design Changes
The weight has increased from 26.3 lbs to 28.0 lbs due to underestimating the mass of the payload
Because of the weight of the payload is larger, a 36” drogue parachute must be used for the payload drogue instead of streamers. A 60” X-type is used for the main parachute
The mid airframe has been reduced from 30 inches to inches. This leads to a total rocket length of inches

4. Static Stability DiagramCP CG
The center of gravity is located 69.7 inches from the nosecone
The center of pressure is located 81.3 inches from the nose cone
The maximum diameter of the rocket is 5.54ʺ. These dimensions result in a stability margin is 2.22

5. Upper Airframe Features
45” length
Contains piston, payload, payload drogue, rocket drogue, and nose cone insert
Shoe - centering ring inside UAF
Protects avionics bay from payload bay
Camera cover
Contains mirror to deflect Avionics camera image downwards
Holes for on switch, indicator lights

6. Avionics Bay Features 10” long
Threaded inserts to stay fixed to UAF and MAF
Easy Assembly with alignment notches
Threaded Inserts
Alignment notches

7. Avionics Bay Features
Easy Ejection charge hookup with terminals on top and bottom of bulkhead
Redundancy
PerfectFlite altimeters
Switches
9V batteries
e-matches
Video Camera
GPS and transmitter (still to be installed)

8. Mid Airframe Features 15.75” long Contains Main Parachute
12” coupler glued to connect to LAF

9. Lower Airframe Features
30” long
Contains motor mount, 3 centering rings, motor retention device
3 Fins mounted through the airframe to the motor mount
2 launch rail slides (for 1” 80/20 rail)
Additional Mass compartment in between top and middle centering ring

10. Motor Choice The Loki L1400 will be used Characteristics of the L1400
Total Impulse: Ns
Peak Thrust: Officially N, but RockSim reports N, large discrepancy
Burn Time: 2.0 s
Performance w/ Rocket
Thrust-to-weight ratio: 11.1
Rail-exit-velocity: 72.4 ft/s (with 7 foot rail)

11. L1400 Thrust Curve
Source: thrustcurve.org

12. Outline Vehicle Design Payload Design Recovery System
Component Testing
Full-Scale Flight
Simulations
Outreach
Future Work

13. Payload Housing and Integration
4 legs separated ninety degrees from each other around the circumference of the payload tube
Each leg consists of a “primary” leg, a “support” leg, and a “secondary” leg
4 sets of “shoulders” are welded to the tube

14. Payload Leg Design Slots in primary leg
Support arm connected to slot with steel pin
Slot allows primary leg to slide in so that the payload can fit inside rocket
Linear spring pulls slot-pin down so that legs tend to spring out
Slot
Linear Spring

15. Linear Spring Force At rest (landing position): spring length is 2.4”
In full tension (folded position) spring length is 4.4”
2 inches of elongation
The spring constant is 3.99 lbs/inch
The initial force is 1.75 lbs.
Equation: f=kx+1.75
f=3.99(2)+1.75= 9.73lbs
Linear Spring

16. Payload Leg Design Secondary leg added to dampen impact
Attaches to end of primary leg; folds up over primary leg
Torsion spring adds to dampening
Torsion
Spring

17. Spring dampening
1.51 lbs. for 45° deflection (experimentally measured)
The spring deflection when secondary legs are flush with the ground is 46.5°
1.56 lbs. from each torsion spring, or 6.24 lbs total, if all secondary legs are flush with the ground.
Torsion
Spring
46.5°

18. Payload Leg Stress Analysis
landing
RDAS reported 60 g landing during subscale flight
This corresponds to a 408 pound force for the full scale payload landing
Dividing this among the four legs, each leg experiences 102 pounds of impact force

19. Payload Leg Stress Analysis
Abaqus, finite element analysis software, was used to create a model of the legs
Support leg parallel to x-axis, primary leg parallel to y-axis
The equivalent force was applied to the end of the primary leg
Boundary conditions applied to the shoulder connections
Support leg
Element breakdown
Node breakdown
Primary leg

20. Stress Analysis Results
All stresses under the yield stress of the material (46ksi)
Highest stress at support leg-primary leg joint (22.8ksi)
Concern: the highest stress is located at the slot
Reaction force at slot is 206 pounds

21. Shear Stress in Pins Cross sectional Area, A is .0491 in2
The force in the slot, F is 206 lbs
The shear stress, τ, is equal to F/A
τ = ksi
Pin material – 18-8 Stainless steel, Yield Strength of 30 ksi
Pins will not yield under stress, S.F. of 7.15

22. Payload Electronics
Contains two R-DAS Tiny altimeters (w/ redundant switches and e-matches) that control the payload’s main parachute deployment and record all sensor data. Each R-DAS Tiny has its own battery (for the full scale test, a PerfectFlite was used in place of one RDAS)
Contains two analog temperature and two analog humidity sensors
Contains a GPS and transceiver powered by an 11.1V battery

23. Payload Wiring Schematic

24. Outline Vehicle Design Payload Design Recovery System
Component Testing
Full scale Flight
Simulations
Outreach
Future Work

25. Recovery Method
Two separate recovery systems because of payload separation
Redundant PerfectFlite altimeters will control the rocket’s dual deployment
Redundant R-DAS Tiny altimeters will control the payload’s dual deployment
All altimeters will have their own switch, battery, and e-match for full redundancy
Rocket Drogue: 36” round
Descent Rate: 64 ft/s
Rocket Main: 96” round
Descent Rate: 21 ft/s
Payload Drogue: 36” round
Descent Rate: 32 ft/s
Payload Main: 60” X-type
Descent Rate: 12 ft/s

26. Ejection Charge Amount Test
Apogee deployment
Has to push out piston, payload, both drogue chutes, and the nose cone
8 grams was determined sufficient
Main chute deployment
Has to push apart the Lower and Middle airframe, break the shear pins, and eject the main parachute
7 grams was determined sufficient

27. Ejection Charge Amount Test
Apogee Deployment Video

28. Ejection Charge Amount Test
Main Deployment Video

29. Dual Deployment Avionics Test
The PerfectFlite altimeters have been tested and proven in static tests and in the subscale and full scale flights
The RDAS still needs to be tested on the ground thoroughly to ensure that it will ignite the ejection charges appropriately

30. Payload Main Parachute Ejection System
The main parachute is secured to the bottom in a parachute pack
Is deployed by pulling the ripcord which in turn pulls a pin holding the pack together
Ripcord is attached to a slug which is shot out of the ejection tube
A cable secures the slug to the payload.

31. Payload Main Parachute Ejection System
The pin attached to the ripcord holds the four flaps of the parachute pack in place until the ejection sequence is initiated

32. Payload Main Parachute Ejection System
Video of Ejection Charge Test

33. Outline Vehicle Design Payload Design Recovery System
Component Testing
Full-Scale Flight
Simulations
Outreach
Future Work

34. Payload Bay Testing The predicted load on the “shoe” was tested
75 pounds of total predicted force
No damage occurred during static test or full scale flight
Payload leg testing
Legs spring open once separated from the rocket
Load testing on slot in primary leg
Static Shoe-load test

35. Payload Leg Opening Test

36. Load Test on Slots
Weights were hung from the slots of an extra primary leg
30 lbs to yield for ½ of the slot, so 60 pounds overall
170 lbs to failure for ½ half of the slot, so 340 lbs overall
Assuming the stress analysis is close to actual, the slot will yield during the payload landing but will not fail
Yielding is not a mission failure, so this is acceptable

37. Payload Testing
Temperature and humidity sensor testing complete by seeing change in voltage in varying temperature and humidity climates
GPS and transceivers have been tested statically and in motion
RDAS altitude data was comparable to the PerfectFlite in the 1st subscale launch

38. Outline Vehicle Design Payload Design Recovery System
Component Testing
Full-Scale Flight
Simulations
Outreach
Future Work

39. Full-Scale Flight March 19th, at TTRA field 0-5 mph calm winds
Successful deployment of drogue chutes and payload at apogee
Rocket’s main parachute was deployed at apogee because shear pins were dislodged during the event
Payload main chute deployed at appropriate altitude of 500 feet.
Lander suffered minor damages during landing but no failure occurred. It was determined reusable

40. Full-Scale Flight Video

41. Full-scale Altitude Results
Two PerfectFlite altimeters in the avionics bay, PF1 and PF2
PF1 reported max altitude of 3794 ft
PF2 reported max altitude of 3752 ft
Both altimeters ran out of memory before landing, due to early chute deployment

42. Full-scale Altitude Results
One PerfectFlite in the payload, PF3
Max altitude measured as 3797 ft
The spike at apogee shows that airflow passed around piston during the rocket’s first ejection charge
Drogue descent: ~32 ft/s
Main descent: ~12 ft/s

43. Full-scale Altitude Results
Possible causes for not reaching a mile
Initial launch angle
18.75 oz. of clay in additional mass compartment
Drag coefficient uncertainty
Thrust uncertainty
Total mass uncertainty

44. Outline Vehicle Design Payload Design Recovery System
Component Testing
Full-Scale Flight
Simulations
Outreach
Future Work

45. Initial Flight Simulations
Wind Condition (mph)
Launch Angle (°)
Mass Added (oz.)
Max Altitude (ft)
Downrange landing (ft)
Stability Margin 13
5280
2.09
2.5
196 5
12.5
418
2.10
7.5 12
654 10 11
749
2.11
6.5
547
2.16 15
4.5
735
2.18
17.5
5228
641
2.22 20
5187
897
RockSim was used to predict the flight performance of the rocket
The effect of wind condition on altitude was investigated
Launch angle was changed so that the downrange landing stayed below 1000 ft
The mass added to the rocket to achieve a mile was calculated for each wind condition/launch angle combination

46. Coefficient of Drag
RockSim predicts that the drag coefficient changes with velocity
CD approaches at zero speed to .337 at max speed of 665 ft/s
Equivalent drag coefficient constant: 0.37
Full Scale Test Flight maximum altitude using the CD from RockSim: 5215 ft
The drag coefficient was fit to full scale flight so that the maximum predicted altitude matched the actual maximum altitude (about 3790 ft).
New constant CD = .814
The flight simulations were performed again, this time with the new CD
Velocity (ft/s)

47. Flight Simulations w/ New CD
Wind Condition (mph)
Launch Angle (°)
Mass Added (oz.)
Max Altitude (ft)
Downrange landing (ft)
Stability Margin
3934
2.22
2.5
3933
187 5
3930
378
7.5
3924
578 10
3916
765
12.5
3871
663 15
3853
819
17.5
3773
646 20
3746
883
Flight simulations repeated for adjusted CD = .814
According to simulations, the maximum altitude cannot reach a mile with the current design
The team will discuss possibilities of reducing the mass and CD

48. Time to Apogee and Velocity
Time to Apogee for Full Scale Test Launch
RockSim predicts about 14.5 seconds
Flight data shows between 16.2 and 17.1 seconds
Velocity during burn time

49. Velocity
The velocities were calculated with the central difference method
Velocities for the avionics bay altimeters approached the transonic region and were greater than the payload altimeter during the motor burn time

50. Velocity
The data from the avionics bay (PF1) showed a much higher peek in velocity than predicted
The RockSim prediction resembled the data from the altimeter in the payload bay (PF3) more closely than the one in the avionics bay (PF1)

51. Location of Altimeters
Payload Altimeter
Avionics Altimeters
Compressible flow phenomena like oblique shocks or expansion waves could be the cause of the pressure difference between the avionics altimeters and the payload altimeter

52. Returning to MATLAB 1DOF
Both MATLAB and RockSim gave poor predictions of the actual altitudes and velocities experienced by the rocket
Largest uncertainty remains in the drag coefficient
Goal is to produce a model:
CD - Total Drag Coefficient
CDO- Initial Drag Coefficient (obtained from literature)
CD(Ma) - Drag Coefficient as a function of free stream Ma

53. Curve-fitting Techniques
As a first approximation we used a model:
The velocity obtained using numerical differentiation of the PF1 altimeter was fitted with a fifth-order polynomial:
The result was scaled to by the CD0 to achieve CD(t)

54. First Approximation Results
Significant improvement in both rise time and altitude
Rise time of 15.9 s. Error reduced to about 5.4%
Maximum altitude of 3869 ft. Error reduced to about 2.5%
Potential problems
Repeatability with different
launch angle, wind, etc
No ability to predict the
altitude before a full scale
launch

55. Compressible Flow Correction
Next, we attempt to use a similar expression to the Prandtl-Glauert rule to predict drag coefficient as a function of free-stream Mach number
The result is not as accurate as the curve-fitting techniques
Rise time: 15.5 s. Error: 6.9%
Altitude: ft. Error: 14.1%

56. Outline Vehicle Design Payload Design Recovery System
Component Testing
Full-Scale Flight
Simulations
Outreach
Future Work

57. Educational Engagement
Presented to 150 5th graders at Hidden Oak Elementary School in December
Presented to sixty 4th-8th graders at Millhopper Montessori School (private school) in January
PowerPoint presentation taught students about the basics of rocketry, how to get involved, and how to remain safe
Three model rockets were launched to give the students an first-hand example of rocketry

58. Educational Engagement
Shared a booth with AIAA during Engineering Fair
Students from middle and high schools from around Gainesville came and were shown two separate rockets and their various components
There were also water-bottle rocket launches every half hour

59. Educational Engagement
Presented to 110 8th graders at Howard Bishop Middle School on February 24th
The same PowerPoint presentation used for the previous school presentations was used which covered the basics of rocketry, how to get involved, and how to remain safe
Three model rockets were once again launched to get the students excited about rocketry

60. Educational Engagement
Upcoming event: Aerospace Day, March 31st
Event conducted by UF AIAA student chapter
Middle School students from the Gainesville area will come to UF and learn about Aerospace Engineering
There will be various hands-on activities such as launching small rockets, as well as tours of on-campus labs

61. Outline Vehicle Design Payload Design Recovery System
Component Testing
Full-Scale Flight
Simulations
Outreach
Future Work

62. Payload Testing Solar and UV sensor testing RDAS testing
Solar cell voltage to W/m2 conversion constant
UV sensor voltage to W/m2 conversion constant (1.962)
RDAS testing
Duration of data storage
Ejection charge testing

63. Recovery System Testing
Additional full scale ejection charge ground testing
Need to make sure main deployment ejection charge can overcome additional shear pins
Payload landing testing
At a maximum allowable velocity of 22 ft/s
With horizontal motion, rotation, and tilt angles
GPS testing in aluminum Payload Bay tube

64. Static Motor Testing
The static motor test has been postponed until next week. The L1400 will be tested on a test stand provided by our mentor, Jimmy, which is capable of such large motors. This test will:
help verify which motor characteristics that should be trusted- the official one provided by the NAR or the one provided by RockSim
be used to adjust our flight simulations
The motor will also be tested with the retention device connected, just in case it effects the exhaust flow at all

65. Possible changes
Reduction of weight by removing material, so that flight simulations show we can reach a mile
Reduction of drag coefficient by painting the rocket and closing off the aft end of the rocket (possible separation or recirculation effects)

66. Questions?