Payload Concept Proposal F.E.V.E.R. Four (year) Exploration (of) Venus’s Environmental Reactions Good Hope High School Team 4 Payload Concept Proposal
Venus Explorer Mission
1.0 Introduction
This semester Good Hope High School partnered with UAH in their InSPIRESS program. Our
team name is FEVER, which stands for “Four (year) Exploration (of) Venus’s Environmental
Reactions.” Our slogan is Ready or not, it’s gonna get hot! The task assigned to the team by
UAH was to design a payload to accompany NASA’s mission to Venus. Our mission is to test
the atmospheric components of Venus’s atmosphere over the course of four years. Our payload
will be attached to a UAH designed orbiter to Venus on a one hundred-sixty day cruise to Venus
and six months of aerobraking before the final orbit of 230 km for four years.
2.0 Science Objective and Instrumentation
Our science objective is to analyze the atmosphere as well as study the greenhouse effect of
Venus over four years. The greenhouse effect means that radiation is absorbed by greenhouse
gases (water vapor, carbon dioxide, methane, and nitrous oxide) and redirected in different
directions causing the average surface temperature to increase drastically. Approximately every
two years a probe will be shot out, using the on-board high pressured helium provided by the
UAH orbiter, at the same location every two years to take measurements using instruments such
as a mass spectrometer. The probes will monitor the changes in conditions such as temperature,
atmospheric pressure, and air composition. We hope to discover enough about the greenhouse
effect to determine if such an intense atmospheric exist in Venus’s atmosphere.
Table 1. Science Traceability Matrix
Science Objective
Measure atmospheric
components over four years to
figure out how the greenhouse
effect is evolving
Measurement Objective
Temperature
Pressure
Wind Speed
Composition of Atmosphere
Measurement Requirements
Location: Atmosphere above the surface
Endure: 450 K and sulfuric acid cloud layers
Duration: Continuous
Location: Atmosphere above the surface
Endure: 450 K and sulfuric acid cloud layers
Duration: Continuous
Location: Atmosphere above the surface
Endure: 450 K and sulfuric acid cloud layers
Duration: Continuous
Location: Atmosphere above the surface
Endure: 450 K and sulfuric acid cloud layers
Duration: Continuous
Instrument
Thermocouple
Pressure Transducer
Accelerometer
Mass Spectrometer
Team FEVER is focusing on taking measurements of the atmosphere over four years to observe
any changes in the environment, particularly the greenhouse effect. The team plans to send the
following instruments in the probes: thermocouple, to measure the temperature; pressure
transducer, to measure the atmospheric pressure; mass spectrometer, to measure the air
composition; and accelerometer to tell the location of the probe.
Table 2. Instrument Requirements
Instrument
Thermocouple
Pressure
Transducer
Mass
Spectrometer
Accelerometer
Mass (kg)
Power (w)
Lifetime (hr)
Frequency
Duration
None
.4
Data Rate
(Mbps)
.000 1
5
.002
.145
1.2
1.2
Continuous
Continuous
Continuous
Continuous
.23
.9
2.4
1.2
Every 10 min.
Continuous
.02
.0025
.2
1.2
Continuous
Continuous
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Venus Explorer Mission
3.0 Payload Design Requirements
Team FEVER has several requirements we must follow with our payload design and execution.
The team’s design must survive the environmental issues of the 730 degrees Fahrenheit surface
temperature, intense air pressure, and harsh wind speeds. The payload will have to successfully
deploy, take measurements, collect data, send data back to orbiter, power the instruments, and
house the instruments. The payload will also have to follow the project requirements such as
have a mass less than 5 kg, have a volume less than 44 cm x 24 cm x 28 cm, survive the
environment, and cause no harm to the main spacecraft.
4.0 Alternative Concepts
The team developed two payload concepts the first of which we named “Goldilocks.” This
concept is spherical probes housed within a gumball system box. The probes will deploy using
gravity and freefall into the atmosphere. The orbiter will orbit at 230 km above the surface and
drop probes periodically that will collect data and send it every fifteen minutes back to the
orbiter as it freefalls through the atmosphere before it crashes.
Figure 1. Group 1 Concept
The team’s second concept we named “The Bear” which contains a cubical probe within a long
cubical cylinder. A spring at the bottom pushes the cubes against the top and the on board helium
shoots the cube out of the side, similar to a gun magazine. The orbiter will orbit at 230 km above
the surface and then drop periodically once every other year over four years. As the probes fall
into the atmosphere they will collect data and transmit the data to the orbiter every fifteen
minutes before the probe crash lands.
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Venus Explorer Mission
.
Figure 2. Group 2 Concept
The pro of concept one is that the spheres are easy to take measurements with. The cons of the
concept are that there is less drag, the spheres are not contained well within the gumball system
box allowing for more probes to deploy than desired, and the probes may tumble uncontrollably
while falling through the atmosphere. The pros of concept two are that it is easily stored and
produces more drag as it freefalls. The con of the concept is that it tumbles while falling through
the atmosphere.
5.0 Decision Analysis
The team came together to decipher which concept would benefit the mission the better. The
alternative concepts are rated with a 1, 3, or 9 based on importance to the mission. 1 is low, 3 is
medium, and 9 is high. The concepts that seems to satisfy the criteria best receive the highest
numbers. As a team, three figures of merit (FOM) were added to the list provided. The first of
the three added was deployment. The team considered deployment to be of medium importance
and was given a 3 for its weight. However, the importance of deployment is due to the different
ways both concepts deploy from the orbiter. The second FOM was time of flight (T.O.F.). For
the mission the time of flight tells us how long the probes may survive which is important for our
objective as the team plans to have the probes freefall through the atmosphere. After an in-depth
discussion the team decided that T.O.F. was of great importance and was given a 9 for its weight.
The last FOM the team added was survivability. The team chose survivability because it is one
of the requirements for the mission and because the different shapes of the concepts will be
affected by the intense temperature of the atmosphere. However, survivability was of medium
importance to the team's objective.
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Venus Explorer Mission
Table 3. Payload Decision Analysis
FOM
Weight
Concept 1
Raw Score
Weighted
Concept 2
Raw
Weighted
Score
9
81
Criteria
Science Objective
9
9
81
Fulfills science objective
Likelihood Project
Requirement
Science Mass Ratio
Design Complexity
ConOps Complexity
Likelihood Mission
Success
Manufacturability
Deployment
T.O.F.
Survivability
Total
9
9
81
9
81
Fulfils project requirement
9
3
1
9
9
3
3
9
81
9
3
81
9
1
3
9
81
3
3
81
High percentage of mass focused on science
Simpler design
Higher complexity of ConOps
Likely for mission success
3
3
9
3
3
1
3
3
9
3
27
9
51
1
3
9
3
3
9
81
9
96
Easy to manufacture
Deploys easily
Substantial amount of time in the air
Survives extreme conditions
Although our two concepts are designed different, they will be operating in a similar way. The
orbiter will start to orbit Venus at 230 km for four years. Every other year, the payload will shoot
out a probe into the Venusian atmosphere. Each probe containing our instruments will fall
through the atmosphere for 1.2 hours taking measurements and transmitting the data back to the
orbiter every 15 minutes before crash landing into the surface. Once the data is transmitted back
to Earth, we will be able to compare the data from both probes to figure out if the greenhouse
effect is evolving and, if so, at what rate.
6.0 Engineering Analysis
To determine a valid way to deploy our probes the team had to calculate certain equations such
as drag. The team calculated orbital velocity, muzzle velocity, deorbit, velocity of probe from
230 km to 65 km, operational time, and terminal velocity. These quantities gave the team a
perspective of how the probes will perform over the duration of the mission. Then, the team
researched each instrument that was needed to collect and transmit the information the team was
seeking. FEVER was then able to select the best suited instruments for our mission. The best
model of the team's probe was now taking form. Next the team calculated the length of our
mission. We found this to be 1.2 hours. After finding all of the required instrument details the
team was able to verify the instruments ability to withstand the Venusian climate, thus the team
will be able to determine the presence of the greenhouse effect in the Venusian atmosphere.
Structural Mass Analysis: A major aspect of the design analysis was the structural mass of the
probes and their housing/launcher. The team used the density and volume of carbon fiber
reinforced carbon (CFRC) to determine the mass of the probes and housing. The team started out
with six probes, but due to mass constraints the team had to reduce the number of probes to two.
The structural mass of each probe is .35 kg with .034 kg of PICA heat shield insulation. The
structural mass of the housing is 2 kg.
Battery Mass Analysis: FEVER decided it was necessary to calculate the mass of the 400
W*hr/kg batteries required for the probes. The battery mass for one probe is .01 kg making the
total battery mass .02 kg.
Orbital Velocity: In order to penetrate the Venusian atmosphere at the desired depth, the team
used vectors to calculate the velocity falling backwards from which the probes exit the launcher.
First, the team had to calculate the orbital velocity and then determine that the velocity would be
one percent less than the orbital velocity. The orbital velocity was calculated to be 1798.2 m/s.
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Table 5. Orbital Velocity Calculation
Calculations
Fc=Fg
mv2/r= GMm/r2
v2= GM/r
Substitutions
Fc= mv2/r
Fg= GMm/r2
v= 7189.2 m/s
Sub in for Fc & Fg
Variables
Fc-- centripetal force
Fg-- gravitational force
v-- orbital velocity
M-- Venus mass (4.8676x1024 kg)
r-- radius of orbit (rp+Alt)
rp-- radius of Venus
Alt-- Altitude above Venus (230 km)
m-- mass of orbiter
G-- gravitational constant (6.67x10-11 m3 kg-1 s-2)
Deorbit: After calculating the orbital velocity the team needed to calculate the velocity as the
probes fall through the atmosphere. To calculate deorbit the team took 1% of the orbital velocity
and subtracted it from the orbital velocity. For deorbit the team calculated the velocity to be
7117.3 m/s.
Velocity from 230 km to 65 km: To calculate the velocity the team had to find the initial
velocity squared plus two times gravity times distance.
Table 6. Velocity from 230 km to 65 km Calculation
Calculation
V2f = v2i+2ad
vf -- final velocity
vf = 1710 m/s
a-- gravity of Venus (8.87 m/s2)
Variables
vi-- initial velocity
d= distance of fall
Muzzle Velocity: The team had to calculate muzzle velocity in order to first decide on the length
of the launch barrel and second to calculate the velocity the probes will be deployed at.
Table 7. Muzzle Velocity Calculation
Calculations
v2f = v2i+2(PA/m)d
Substitutions
F=ma
m-- mass of probe
(1.06 kg)
vi-- initial velocity inside barrel
F=PA
ma=PA
Variables
vf-- velocity of probe as it exits barrel
P-- pressure in barrel (used for acceleration)
(6894757.79 Pa)
d-- distance probe is accelerating (.2 m)
A-- cross-sectional area of barrel (.0049 m)
F-- force
a-- acceleration of probe within barrel
vf = 112.9 m/s
a= PA/m
Terminal Velocity: After calculating everything above, the team had to calculate the velocity of
the probe as it fell through the Venusian atmosphere at different altitudes.
Table 8. Terminal Velcoity Calculations
Calculation
v2= 2gm/pCDS
v1= 88.2 m/s
v2= 47.8 m/s
v3= 28.8 m/s
v4= 18.9 m/s
v5= 13.4 m/s
v6= 9.8 m/s
v7= 7.5 m/s
Substitutions
vf = vi+(mg-FD / m)t
vf = vi+t(mg-1/2pv2CDS / m)
vf = vi+gt-(pv2CDSt/2m)
Variables
m-- mass of probe (1.06 kg)
vf-- velocity of probe after time, t
vi-- velocity of probe before time, t
CD-- coefficient of drag
S-- cross-sectional area of probe (.0049)
v-- velocity at calculation (use initial)
g-- local gravity (8.87 m/s2)
t-- time step used in calculation
p-- density of atmosphere probe is falling through
Operational Time: The last calculation needed was the operational time of the probes once they
were deployed. This was calculated by using the distance of 10,000 m and dividing that altitude's
section of velocity calculated in the drag calculations of table 8. After calculating the time for
each section of the atmosphere the team added the total number of seconds and divided that
number by 3600 s to calculate the operational time in hours. The time calculated was 1.2 hours.
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Venus Explorer Mission
Table 9. Operational Time Calculations
Calculation
d= v(t)
Variables
v-- velocity
d-- distance
t-- time
Total time: 1.2 hrs
Figure 3. Time Calculation Chart
7.0 Final Design
The team’s final design was the second concept. Two cubical probes constructed of carbon fiber
reinforced carbon (CFRC) within a long cubical cylinder also made of CFRC that contains a
spring at the bottom to assist the on-board helium to push the cubes out at the appropriate times.
The probes will then freefall through the atmosphere for 1.2 hours, while transmitting data back
to the orbiter every 15 minutes, before crash landing on the surface.
Figure 4. Payload Final Design
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Venus Explorer Mission
Figure 5. Payload Concept of Operations
Table 10. Final Design Mass Table
Function
Deploy
Measure
Collect Data
Provide Power
Send Data
House Payload
Component
Carbon Fiber Reinforced Carbon launch tube
Thermocouple
Pressure Transducer
Mass Spectrometer
Accelerometer
ISIS On-Board Computer
LiMnNi 226500 Cell Battery 400 W*hr /kg
UHF Transmitter and Antenna
Carbon Fiber Reinforced Carbon Probe Structure
PICA Heat Shield (Probe)
Quantity
1
2
2
2
2
2
2
2
2
2
Mass (kg)
2
.002
.145
.23
.02
.094
.01
.185
.35
.034
Total Mass
Total Mass
(kg)
2
.004
.29
.46
.04
.19
.02
.37
.7
.07
4.14 kg
Table 11. Payload Design Compliance
Requirement
No more than 5 kg of mass
Fit within 44 cm x 24 cm x 28 cm
Survive environment
No harm to the UAH spacecraft
Payload Design
Total mass: 4.14 kg
29 cm x 9 cm x 16 cm
PICA shield protects probes until they hit the surface
Deployed using on-board helium and no measurements taken aboard
orbiter
8.0 Community Engagement Activity Summary
Our team FEVER hosted a community engagement activity at Good Hope Elementary School on
April 17, 2014. The team educated the elementary school children on how the atmosphere works,
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the similarities and differences of Earth’s atmosphere compared to Venus’s atmosphere, and how
meteorologist use similar instruments to forecast the weather. We also explained how the
greenhouse effect works and what data the team anticipates to collect while in Venus’s
atmosphere. For a demonstration the team conducted to labs. The first lab, demonstrated the
density of Venus's layer through a nine-layered density lab. The second lab demonstrated how
the greenhouse effect occurs by placing the same amount of water in two containers with a
thermometer place in both, one container covered with a plastic bag, and placed in the sun for
one hour. FEVER had approximately three hundred students and faculty members in attendance.
The team hopes to collect more information and have more CEAs so that we can collect more
data that will be correlated with our future CEAs.
Our second CEA will take place on May 8, 2014. This will be our parent night. We hope to have
at least 100 people in attendance that night. The team plans to have a meteorologist speak at this
event along with a detailed presentation of how our team plans to carry out our mission. The
team hopes to educate the community on our mission and how we plan to test the atmosphere on
Venus and study the greenhouse effect.
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