2008-2009 University Student Launch Initiative
POST LAUNCH ASSESSMENT REVIEW (PLAR)
Panther II Heavy:
Measurement and CFD Prediction of Liquid Slosh Behavior During
Model Rocket Flight
Submitted by:
The Florida Institute of Technology
Melbourne, Florida, 32901
May 8, 2009
Team Name:
Panther II Heavy
Motor Used:
As Made By Loki Research, Hardware Model 76-3600, Propellant Load L930-LW 3550N-s
Brief Payload Description:
The payload for the Panther II Heavy rocket consists of (i) an electronics package with embedded
sensors, programmable data acquisition and data storage for 6-DOF recording of acceleration and rate of
rotation during flight, and (ii) an infrared imaging system, including camera, lighting and video recording
device. The purpose of the payload is to capture the liquid slosh event (evolution of the liquid surface in
time) while making 6DOF measurements of acceleration and angular rate during flight, that can be used
to benchmark both CFD-based slosh simulations and vehicle trajectory analysis.
Rocket Height:
12ft. 10in.
Rocket Diameter:
4in
Rocket Mass:
Fully Loaded on Pad – 38Lb. 2oz.
Altitude Reached (Feet):
PerfectFlite recorded 5020ft. as Maximum altitude AGL
Vehicle Summary:
Figure 1: Detailed Drawing of Rocket
Figure 1 shows a schematic of the Panther II Heavy rocket. The payload is in the most forward position in
the airframe because it will be the heaviest part and will help keep the CP/CG relation in check. The main
parachute section was held in place during the first stage of recovery using 6 - #6 shear pins. The
electronics bay (flight avionics), located in the recovery section of the airframe, are held in place using
radially positioned bolts. The flight avionics bay was built using Hawk Mountain Enterprises 4” fiberglass
coupler tubing and a two inch spacer of body tubing. This tubing was slid into the airframe and bolted in
place creating two chambers for the drogue and main parachute.
Data Analysis & Results of Vehicle:
Data Analysis
The NASA Launch Services Program’s (LSP) Universal Controls Analysis Tool (UCAT) is used to
analyze the flight performance of a series of specific launch vehicles. To demonstrate UCAT as a
unique LSP modeling capability, a series of non-proprietary, generic launch vehicles have been
simulated ranging from relatively simple single-stage, solid propellant sounding rocket to a more
complex two-stage liquid rocket. Working in close collaboration with the Control Systems Analysis
group in the Mission Analysis Branch at the NASA Kennedy Space Center and the 45th Space Wing
at Patrick Air Force Base, new features and capabilities are being incorporated to the UCAT modeling
suite. UCAT is a graphical user interface program created within Simulink 6.3 (© Copyright 19902005 MathWorks, Inc.) to create a user-friendly environment for engineers and developers as seen in
Figure 22.
Figure 2: UCAT CG Kinematics Block
UCAT is a six-degree of freedom rocket simulation program with various coordinate frames.
These coordinate frames are flat earth, rotating and non-rotating spherical earth, Earth Centered
Earth Fixed (ECEF, non-rotating oblate spheroid earth model), and Earth Centered Inertial (ECI,
rotating oblate spheroid earth model). UCAT uses the US Standard Atmosphere model (1976) to
simulate the atmosphere from 0 to 1000 km altitude. Various gravity models are used for simulation
including dependence on inertial position relative to the earth’s coordinate frame. UCAT can be linked
to third party software during simulation to increase the fidelity of the rocket simulation.
UCAT can simulate the effects of the various aerodynamic forces and moments acting on a
rocket during flight. Simulating solid, hybrid, and liquid propellant rockets with high accuracy has been
the focus of UCAT’s development since Florida Institute of Technology (FIT) has been involved.
UCAT also has the capability of modeling the three-axial forces and moments a rocket encounters
due to its propulsion unit. Most rocket simulation programs simulate only one degree of freedom
(thrust along the direction of motion). FIT has developed and built a unique thrust stand that can
measure forces and torques in six degrees of freedom, yielding more accurate results when
simulating a rocket motor in UCAT.
The USLI rocket’s known parameters were input into UCAT, including : mass, center of gravity,
mass moment of inertia at the center of gravity location, geometric launch constrains and thrust. The
mass, center of gravity, and mass moments of inertia, were determined via Pro-Engineer Wildfire 4.0
by entering the known densities, and comparing the masses of each sub assembly to the actually
rocket components. The thrust curve was generated using the Florida Institute of Technology six
degree of freedom thrust stand. Some parameters that are difficult to estimate include aerodynamic
properties such as the coefficients of force (Axial, Normal, Side), the coefficients of moment (Roll,
Pitch, and Yaw), and the center of pressure location. They
generally depend on three input
conditions: Mach number, pitching angle of attack, and yaw angle of attack. Due to time constraints
these were not considered in the UCAT simulation. The force coefficients normal and side were set
equal to one. The center of pressure was set to a constant distance away from the center of gravity
location, which was set sufficiently far away to make the rocket stable. Both the data recovered from
the six degree of freedom package on the USLI rocket, and observers at launch noted that at about
2,000 ft the rocket hit a large gust of wind. Unfortunately the wind profile was not recorded, so it was
placed in a lookup table which was dependent on altitude, arbitrarily set by the user. Both the wind
profile and the axial force coefficients were both adjusted using a lookup table to achieve the altitude
vs. time profile seen in Figure 3. The altitude vs. time in Figure 3 shows the recorded altitude
readings of various barometric pressure altimeters.
Figure 3: Altitude vs. Time for Barometric altimeters
One of the experiments in the USLI payload bay is the six degree of freedom package which
measures angular velocity and accelerations vs. time. Since the inertial coordinate system is the flat
earth model the altitude can be determined from one of the inertial position vector components. the
acceleration magnitudes were scaled using the sampling rate and the approximate altitude vs. time .
the data collected from the accelerometers starts collecting prior to launch, and stops when the
drogue parachutes deploy
Figure 4: Acceleration in the axial direction in the rocket’s body coordinates
Using the time history from Figure 4 the UCAT simulation and the six degree of freedom package can be
plotted side by side with the altimeter data. The final results show very good agreement (Figure 7).
1.5
Ax
Ay
Acceleration (G)
1
0.5
0
-0.5
-1
-1.5
0
5
10
15
20
25
Time(S)
30
35
40
45
50
Figure 5. Transversal accelerations (Ax, Ay) during flight, captured with the 6-DOF package
40
theta x dot
theta y dot
theta z dot
Angular Velocity (degrees/S)
30
20
10
0
-10
-20
-30
-40
-50
0
5
10
15
20
25
30
Time(S)
35
40
45
50
55
Figure 6. Angular rate of rotation in X, Y and Z (body coordinates) during flight, captured with the
6-DOF package
Figure 7: Altitude vs. Time for barometric altimeters, UCAT Simulation, and 6-DOF package
Figure 8 shows a detailed view of what happens at apogee. The UCAT simulation reaches apogee earlier
than the other curves. The G-WIZ, and Perfectflite are in very good agreement and show similar trends
that the one of the UCAT simulation. The ARTS 2 has similar trends to other altimeters and the UCAT
simulation, but as it approaches apogee it starts to read a lower altitude. The calibration of the
accelerometers (acceleration magnitude) was adjusted during post processing
.
Figure 8: Detailed view of barometric altimeters, UCAT simulation, and 6-DOF package at apogee
There are a lot of areas for improvement, such as the altimeters, the six degree of freedom package, the
wind profile, and the aerodynamic properties of the rocket. Florida Institute of Technology has a shock
tube facility which can be used as a vacuum chamber to simulate varying altitudes. The shock tube also
has very precise pressure transducer which can be used as a check with the altimeters. This way only the
most accurate altimeter can go up in the payload bay saving, space and weight on the rocket. The six
degree of freedom package should have been calibrated prior to launch. A method of calibration would be
to test the six degree of freedom package by putting each accelerometer in a one degree of freedom
motion. Then rotate on the axis of each gyroscope, this should provide at the very least a basic calibration
of sample rate and magnitude of the six degree of freedom package. In order to determine the wind
profile it may be necessary to erect weather balloons with wind meters on each of them facing different
directions (with respect to north), different altitudes, and different locations around the launch site. This
will provide a more accurate wind model, reducing the unknowns for the rocket simulation program UCAT.
Finally, the last final improvement would be to have more time to run a rocket simulation. UCAT has a link
with the CFD program FLUENT this allows the force coefficients, moment coefficients, and center of
pressure to be determined from varying conditions set by the user. The truncated time table did not allow
a proper mesh to be generated or time to run the simulations inside FLUENT. Since CFD simulations
alone are not infallible a good check for this would be to create a scale model of the rocket, and
determine some sample axial coefficients in the Florida Tech Shock Tube facility. If those results are in
good agreement with the CFD results then the aerodynamic properties would be very complete.
Results of Vehicle
Although this is Florida Tech’s first appearance at the USLI competition, the university has a history of
successful and monumental high-powered rocket projects, some of which include ‘JAMSTARS’, which set
the university altitude record (~83,000 ft) for a single stage solid rocket and ‘PANTHER I’ the first-ever
student designed and built rocket to be flown from the Cape Canaveral Air Force Station in Florida. With
such successful projects having been completed, Florida Tech is very much focused on the development
of new, innovative, and NASA-relevant scientific payloads which can be flown on high-powered model
rockets. PANTHER II: HEAVY is an endeavor to use the USLI competition is a platform for the
development of a reusable micro-gravity liquid slosh dynamics payload. The vision for the payload, which
was successfully achieved by the Florida Tech team, is to take measurements of the rockets acceleration
history which are correlated to images of a water behavior inside a tank flown in the rocket’s payload bay.
Such data, which was acquired during the USLI competition, can be used to benchmark Computational
Fluid Dynamics (CFD) models of liquid slosh behavior under various acceleration conditions.
Furthermore, the complete acceleration history of the rocket was measured and used to benchmark the
NASA Kennedy Space Center’s (KSC) Universal Controls and Analysis Tool (UCAT) – the agreement
between the UCAT model and the flight data is nothing short of spectacular. The figure below shows
some of the highlights of the PANTHER II: HEAVY rocket, which was unveiled to high acclaim at the 2009
Florida Tech Design Showcase, flown on several test flights, and then successfully flown at the 2009
USLI competition. Although the flight itself was spectacular, the data achieved from the scientific payload
was even more valuable, as is be discussed in this report.
Collage of PANTHER II: HEAVY: (left-to-right) The team shows off the PANTHER II rocket at the 2009 Florida Tech Design
Showcase, PANTHER II on the launch rail prior to a test flight, PANTHER II lift-off at the 2009 USLI competition, rocket in flight, and
safe deployment of parachute.
Payload Summary:
The payload for the Panther II Heavy rocket is designed around observing slosh of a liquid within a
rocket in microgravity. To obtain this goal, the payload section will contain a tank one quarter filled with
water, a camera to view the tank under all flight maneuvers, a video recorder for playback of the video,
and a 6 Degree of Freedom (DOF) data recording system for the use of comparing the observed data to a
Computational Fluid Dynamics) CFD simulation of the flight. Figure 9 below shows the layout of the
payload section as designed in Pro Engineer. To make work easier, the design will separate the payload
into two distinct systems: the video and slosh tank section and the 6 DOF section.
VCR
6 DOF data recording system
Slosh tank
Camera
6 DOF data recording system
Connection to lower part of rocket
Two 12 Volt NiMH Batteries
Figure 9: Science payload assembly diagram
To capture the video coming from the camera, we used the Sandisk V-Mate Video Memory Card
Recorder. This VMCR uses a micro SD (Scan disk) card to store the video in real time. This will be
controlled by the Programmable Interface Controller) PIC micro controller so that it is precisely timed with
the 6 DOF sensors to capture useful video data. The entire system will be triggered by a 12V signal on
the launch pad via wire contacts on the exterior of the payload section of the rocket.
In order to compare the actual launch of the rocket to the simulated launch in UCAT, all six degrees
of freedom need to be measured and recorded during flight. To accomplish this task, Panther II Heavy will
be using a series of accelerometers and gyros precisely positioned to measure the axial and rotational
accelerations respectively. To improve reliability and redundancy, Panther II Heavy will contain two
complete and independent 6-DOF systems that are fully capable of measuring and recording the
accelerations of a rigid body. Should both systems log the data correctly, the two sets of data can be
combined to characterize the complete motion of the rocket even if it does not stay completely rigid. Since
the initial conditions of position and velocity are known, integration of these accelerations will provide an
accurate trajectory plot as well as a velocity plot with respect to time which then can be input for a CFD
simulation of the slosh experiment.
Data Analysis & Results of Payload:
The performance of the 6DOF instrument is described in detail above in “Data Analysis and Results of
Vehicle” and will not be repeated here.
The Panther II Heavy Flight Video Data was not retrievable and may have never been written to the
media as a result of a video recorder defect. Several different algorithms were applied to the MicroSD
media in an attempt to recover the flight video of 18 April 2009. These attempts were not successful. It
was initially thought that the MicroSD media was defective. Subsequent formatting and testing eliminated
this possibility. The video data that was retrieved: two erased video files from earlier in the week, three
test video files from the day before the launch, and two zero byte files the day of the launch. The zero
byte files were properly opened and closed and contained only standard file header information. These
files correspond in both time and date to the 2 times the recorder was activated on the flight day. It is now
apparent that the2nd V-Mate failed on the pad before the launch. It has been determined by subsequent
testing that the Sandisk V-Mate Video Memory Card Recorder has a faulty MicroSD recording capability.
The Sandisk Unit that failed to record to MicroSD on flight was the 2 nd Unit that failed. The first V-Mate
unit failed on the ground 2 weeks prior to launch and was assumed defective. A new V-Mate was
obtained and installed. As with the first V-Mate, it performed flawlessly at first while recording to the
MicroSD media. From the video data that was retrieved it is apparent that the2nd V-Mate failed on the
pad before the launch. There were no external signals to make us aware of this failure. Subsequent
ground testing has confirmed that the overall 2 nd V-Mate unit, which flew on the 18th is still in working
condition except for its MicroSD port and was used to successfully record video data to its SD card port
from the payload unit during a bungee-jump experiment conducted 27 April 2009.
The 27 April 2009 experiment involved hanging the payload by 3-3/8” bungee cords from a High-reach
crane extended to roughly 40 feet above the ground. When the cords were relaxed the payload hung
roughly 20 feet off the ground. The payload was pulled to the ground, activated, and released. It was
pulled by the cords to the attachment point on the crane where it impacted and proceeded to oscillate
until it came to rest again at about 20’. The payload was recovered and the data from both the 6DOF
instrumentation and the video data on the SD media were all successfully recovered.
Images of both the slosh behavior and the experiment were combined using the 6DOF data as a
reference and are found in the video file: “Best Slosh Video.wmv” Frame grabs from this video
demonstrate similar behavior to the slosh observed on the earlier aircraft experimentation conducted by
Florida Tech for NASA.
NASA/FIT Flight Images:
29 April 2009 Panther II Heavy Payload Video Frame Capture Examples:
It is hoped that funding will present itself to allow the Panther II Heavy payload to fly again with the
VMCR corrected so actual rocket low gravity observations can be made. The frame captures from the 29
April experiment represent low gravity duration of just over 1 second. On Flight, Panther II Heavy
demonstrated over 17 seconds of low to micro gravity.
Future work includes the use of the acceleration and rate of rotation measurements to benchmark CFD
simulations of the slosh event with images captured during flight.
Scientific Value:
High Fidelity 6DOF data can be gleaned from an amateur rocket flight sufficient to validate applicability
of flight trajectory software as shown in the “Data Analysis and Results of Vehicle” section. Further,
instrumentation can be constructed to observe slosh behavior on an amateur scale in an amateur
rocket. This approach still holds promise to support development of CFD modeling of low gravity slosh
behavior.
Visual Data:
Panther II Heavy had a straight ascent with little to no observable wobble for the first second and a half
approximately. After that, a noticeable oscillation was observed until burnout. Video afterwards
confirmed this wobble. This is not believed to be a design flaw, rather from a wind shear. There was
some wobble observed for the other rockets launching that day, and in similar fashion and location.
The overall static margin of the center of pressure and center of gravity of our rocket was at the
recommended 2.5 calipers, or the center of pressure was 10 inches behind the center of gravity in our
rockets case. On our ascent, we believe the rocket encountered a strong wind shear layer around 2000ft.
The rocket started to swing like a pendulum; turn left to right, but not in a complete circle, and also
experienced a small angle of attack to the free stream velocity during its ascent up until apogee. Since all
of our vent holes for the avionics were located on one side of the rocket, we could see the barometric
sensors on the altimeters picking up the static/dynamic pressure differences as the rocket pitched and
yawed on its way up. There was a sinusoidal wave in the altitude all the way up until apogee, but it did not
reappear on the descent of the rocket. This entire theory was proved once we started to analyze the data
from the 6DOF boards in the payload. We could see sinusoidal waves (See figure 5 above) in the
rotational velocity about all three axis of the rocket during its ascent. It appears that many other teams
observed this same problem on their ascent from our observations once we had completed out flight.
Lessons Learned:
The Views of 2 Students summarize well the Lessons and the experience of this project:
Student 1:
Through the successful completion of the 2009 USLI competition, a vast amount of experience was
gained by all team members that will allow us to improve our engineering design and problem solving
skills, as well as team skills. Many of the engineering skills that were gained in the process of completing
this project were the direct result of: using the knowledge gained in school for the first time out of the
classroom, working through miscommunication among team members, and compensating for ineffective
planning.
The planning in our project had a direct effect on a lot of the issues that took place. A detailed and
believed to be realistic plan at the beginning of the project was created to guide us through the remainder
of the designing, testing, and flying. Throughout the year, it was found harder and harder to follow the
plan resulting in many schedule slips and an accumulation of work to be completed immediately before
each deadline set. We learned that in order for the team to successfully follow any plans made initially, it
must be taken into account that parts of the project will not be completed on time due to busy schedules
of the team members and the constantly variable number of available team members. To account for
this, team members must agree to and understand better the responsibilities they will have. This will
allow them to decide if they are willing and able to follow through with their duties to the completion of the
project. Once all members are aware of this, a more effective plan can be constructed reflecting all
aspects that the team members must juggle while working on the project.
However, all of these issues that occurred were far outweighed by the results and changes that were
brought by them, as is evident by the overall success of our project. We accumulated a great knowledge
of applying what we’ve learned in the classroom to an actual engineering project, the importance of
communication to any team project, to not over involve and complicate a design to accommodate
unrelated goals, and the importance of realistic planning to a project.
Student 2:
Now that the project is completed, the team recognizes the difficulties presented in the design and
fabrication of a rocket. The team learned to balance time for: vehicle design, construction, and time for
the design reviews which allowed the team to continue successfully in the competition. This experience
alone is worth the time and energy spent on the project. The team also learned the difficulties of working
with electronics. Most of the difficulties throughout the year involved electronics not doing what they were
advertised to do or breaking under conditions they were not designed to experience within the rocket.
This all said, Panther II Heavy accomplished most of what it set out to do: 6DOF data was collected and
compared successfully to a UCAT simulation, the rocket flew to within 5% of the design altitude, and
although the video of the flight during the competition was not recovered, the system proves it can be
done, and will be flown at a later date.
The results obtained from the experiment correlate to what the team had expected from the payload. The
UCAT simulation accurately described the flight of the rocket, although further refining of UCAT will
involve accurate weather data. The video of the slosh tank from the bungee tests provides a picture of
what the slosh may have looked like during flight. For a future project, the team would like to use a
recording device that will not break during the high acceleration periods of the flight and a camera and
fluid combination that can better display the slosh behavior during the flight.
Outreach Summary:
On April 3rd, 2009 members from Panther II Heavy Panther II (Scott Perry and Alex Berta) along with FIT
graduate student Michael Vergalla, and undergraduate students Richard Schulman and Shawna Boucher
visited Alumni Cassandra Gonyer in her science class at Sebastian River High School. The group
presented an Introduction to Aerospace Engineering at Florida Tech by covering topics such as rockets,
aircraft, available classes, research and potential career opportunities. After a short background students
discussed their own experiences starting from the freshman and sophomore level to the seniors primed
for their showcase and finally to a graduate student. Each offered their unique perspective on education
and challenges at Florida Tech. Richard presented his experience learning proEngineer and Matlab as
well as his plans for the freshman rocket project. Shawna presented a short segment on rocket projects
and the importance of women in engineering, and how it is a field that quality work outweighs gender bias
and cannot be argued against based on opinions. Senior design showcase winning team Panther II
presented other projects that would be in the showcase, and discussed their project. Michael presented
his experience at Florida Tech by highlighting opportunities such as internships, international
collaboration and research that became available due to hard work throughout undergraduate studies
here at Florida Tech. He also presented on his most recent experiences in graduate school he talked
about grading papers, teaching classes, and working on cutting edge research. Students were presented
with various media including pictures and movies of rockets, zero-g flights, tank slosh, and turbine engine
tests. The group from FIT presented to two classes of approximately 30 students.