Payload Concept Proposal
Mercury Lander Mission
Spring 2012
Cold Springs High School
Team 3
E.M.P.I.R.E.
Payload Concept Proposal
Mercury Lander Mission
Spring 2012
1.0 Introduction
With a mean heliocentric distance of 57.8 million km, Mercury is the closest planet to the sun. The
maximum surface temperature on the day side is 467 °C and the minimum surface temperature on the
night side is -183°C. Since Mercury is so close to the sun, it is bombarded with a large amount of
electromagnetic radiation. In the past, astronomers believed the dark side of Mercury emitted zero
radiation; however, it was later discovered that the whole planet emits radiation. One location in which
scientists have not determined the radiation level is the terminator. The terminator is the point at which
the sunlit, day side of Mercury, transitions to the dark, night side. In order to gather more information
about the terminator, team E.M.P.I.R.E. (Exploration of Mercury Pioneers of InSPIRESS Research and
Explanation) has designed L.A.M.B. Mission 102 (Lander Achieving a Mercury Bound mission 102) to
accompany a NASA mission to Mercury. L.A.M.B. Mission 102 is designed to measure the changes
radiation and temperature at the terminator to determine if there is any time at which the conditions on the
planet would allow a manned mission.
2.0 Science Objective and Instrumentation
The science objective for LAMB Mission 102 is to measure the changes in radiation and temperature on
Mercury before, during, and after the terminator passes. A secondary objective is to determine whether
Mercury experiences conditions that are suitable for human exploration. Two measurements will be taken
during the course of meeting the science objective: radiation measurements (roentgen) and temperature
readings (Celsius). An HPXe-100 Xenon radiation detector will take continuous readings for no less than
four hours. Temperature measurements will be taken with type K and type thermocouples.
Table 1. Science Traceability Matrix
Science Objective
Measurement Objective
Radiation
Measurements
Measure Gamma
Radiation
Temperature
Measurements
Measure Temperature
Measurement
Requirement
Able to withstand
extreme temperatures,
and not be sensitive to
the sunlight.
Able to operate in
extreme heat and cold.
Instrument Selected
HPXe-100 Xenon
radiation
Thermocouples types K
and N
Table 2. Instrument Required Resources
Instrument
Mass (kg)
Power (W)
Volume (cm3)
HPXe-100 Xenon
radiation detector
Thermocouple
type K
Thermocouple
type N
ProtonX-Box
Antenna
Data Logger
0.1
1 mW
163.4
Data Rate
(bps)
Continuous
.004
Self-generating
7.27
Continuous
.004
Self-generating
7.27
Continuous
.805
.23
.1
10.26
N/A
N/A
1846.6
421.4
N/A
N/A
Continuous
Continuous
3.0 Alternative Concepts
The team divided into two groups and each group developed a design for L.A.M.B. Mission 102. As the
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Payload Concept Proposal
Mercury Lander Mission
Spring 2012
team discussed each concept, they realized the limitations of each group’s concept and developed a third
alternative concept.
3.1 Concept 1
The payload will deploy using compressed helium to launch the payload at a 45° angle to achieve
maximum distance from the lander. The heavier equipment will be placed on the bottom to make sure that
when the payload stops rolling, it will have correct orientation. Grooves on the outside of the payload will
grip the planet’s surface and help increase the distance between the payload and the lander. The outer,
egg shaped container will protect the experiment during the landing. The payload will open and reveal
the instruments with which the measurements will be taken.
Figure 1. Concept 1
3.2 Concept 2
As the spacecraft approaches Mercury for landing, L.A.M.B. Mission 102 will launch from the spacecraft
using compressed helium from a height of 5 km to result in little damage to the payload and the best
distance from the craft to be achieved. Concept 2 is a pyramidal egg shaped that is weighted at the
bottom to ensure it comes to rest with the correct orientation. L.A.M.B. Mission 102 will open enough to
take measurements. The payload will use an HPXe-100 Xenon radiation detector to measure gamma
radiation on Mercury. Two Thermocouples will be used to measure the temperature on Mercury. The type
K thermocouple measurements range from-200°C to 1000° C while the type N thermocouple
measurements range from -268°C to 1300°C. A Proton-Box Avionics Suite will be used to relay data to
the spacecraft. The heat shield will be a type of NASA Thermal Protection Shielding.
Figure 2. Group 2 Concept
3.3 Concept 3
The team considered comments from the preliminary design review and realized the limitations of the
concepts that had been developed. Team E.M.P.I.R.E. took these limitations into consideration and began
to develop a third alternative concept. Concept 3 looks like the Empire State building on its side; hence,
it is referred to as the ESB design. This concept will be situated in a launch box that will drop from the
lander and use compressed helium to propel the payload at least 20 m from the spacecraft. Concept 3 has
wheels which enable it to roll across Mercury’s surface. Thermocouples will be located on the forward
portion of the payload with the radiation detector located in the aft portion. An antenna will deploy from
the aft portion of the payload once it is activated and begins data collection. The payload will be
constructed of PICA heat shield material and the launch box will be made of aluminum.
Figure 3. Concept 3
4.0 Decision Analysis
To decide which design for LAMB Mission102 would be more effective, E.M.P.I.R.E evaluated figures of
merit for the proposed concepts. Since concepts 1 and 2 were similar and differed only slightly, the team
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Payload Concept Proposal
Mercury Lander Mission
Spring 2012
evaluated the “egg” concept and the newer E.S.B. (Empire State Building) design. Power, mass,
protection, mobility, aesthetics, and life span were discussed. The topics were given a 1, 3, or 9 depending
on the level of importance with 9 being the highest. The E.S.B design was chosen as the design with
which the team would move forward.
Table 3. Decision Analysis
Figure of Merit
Weight
Concepts1 &2
Egg Design
Group 3
E.S.B Design
Mass
Protection
9
9
9
9(3)
9
1
9
3(9)
9
Mobility
3(9)
3
9
Aesthetics
1
3
9
Lifespan
3
1
3
186(150)
234(336)
Power
TOTAL
Description
Lower power is ranked higher.
Lower mass is ranked higher.
Ability to protect instrumentation is
ranked higher.
Ability to move away from the lander is
ranked higher.
Correlation with the team’s marketing
strategy is ranked higher.
Longer lifespan is ranked higher.
5.0 Concept of Operation
Phase 1: The payload lands on board the lander. The launch tube is pressurized to 6.08 psi with tube
positioned horizontally at the bottom of the lander.
Phase 2: The launch tube is dropped from lander with no horizontal or vertical forces applied by the
lander.
Phase 3: Upon contact with Mercury’s surface, pressure will be applied to the payload. The payload
will be ejected at 7.7 m/s, and it will travel for 20m until friction brings it to a stop.
Phase 4: The payload will remain dormant until one hour before the terminator approaches. After the
payload activates, it will measure the radiation and temperature until three hours after the terminator
has passed, collecting data continually.
Phase 5: The data transmitter will continuously send the data as it is collected to the lander which
will transmit the data to Earth.
Figure 4. Concept of Operations
6.0 Engineering Analysis
Since L.A.M.B. Mission 102 will be launched from the launch tube using compressed helium, it was necessary to determine the velocity at which L.A.M.B. Mission 102 will need to leave the launch to tube travel at least 20 m from the lander. The length the launch tube, the exact pressure needed for deployment,
and the mass of the heat shield structure needed to be determined as well.
6.1 Exit Velocity Analysis
To ensure that the temperature and radiation measurements are not influenced by the spacecraft, L.A.M.B.
Mission 102 needs to be at least 20 m from the spacecraft. The exit velocity must be calculated to
determine the velocity L.A.M.B. Mission 102 must have as it exits the launch tube for it to travel 20 m.
Since the coefficient of friction for Mercury’s regolith is not known, E.M.P.I.R.E. assumed it to be the
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Payload Concept Proposal
Mercury Lander Mission
Spring 2012
same as the coefficient of rolling friction between steel and soil on earth ( = 0.4). The exit velocity was
calculated to be 7.8 m/s.
Table 4. Exit Velocity Analysis
Calculations
vf2 = Vi2 + 2ad
0 = Vi2 + 2ad
vi = 2ad
vi = 2d g
vi = 7.8 m/s
Substituted Equations
FN = ma
Ff= mg
(sub into next equation)
Ff = FN
mg = ma (solve for a)
a = g
Variables
Ff – friction force FN - normal force
 - coefficient m – mass of
of friction (0.4) payload
g – acceleration due to gravity
Mercury’s gravity is .38 of Earth’s, so
g = .38(9.8 m/s2).
vi– final velocity vf – final velocity
(exiting tube)
(at rest)
a – acceleration
d– length of barrel
6.2 Launch Tube Length Analysis
Team E.M.P.I.R.E. calculated the exit velocity produced using launch tube distances of 38 cm and 44 cm
for pressure values ranging from 0 psi to 4500 psi. A graph was generated of velocity v. pressure for each
of the launch tube distances. The team determined that the 44 cm launch tube distance would achieve the
required velocity using lower pressure than the 38 cm launch tube.
Velocity (m/s)
Engineering Muzzle Velocity v. Pressure
8000
6000
4000
2000
0
38 cm barrel
44 cm barrel
0
2000
4000
Pressure (psi)
6000
Figure 5. Engineering Analysis Graph
6.3 Launch Pressure Analysis
The pressure required for L.A.M.B. Mission 102 to deploy properly was calculated. Since the terrain on
which the spacecraft will land is not known, the team decided to use varying helium pressure, so that it
can be adjusted depending on the terrain. The launch pressure calculations assume a flat terrain as well as
constant pressure.
Table 5. Launch Pressure Analysis
Calculations
vf2 = vi2 + 2ad
vf2 = 0 + 2 pAd/m
p = vf2m/2Ad
p = 6 psi
Substituted Equations
p = F/A
(Since F=ma, sub in for F)
p = ma/A
a = pA/m
p – pressure
m – mass
Variables
A – area (over which
pressure is applied)
a - acceleration
vf – final velocity (leaving
launch barrel)
vi – initial velocity (at rest)
F - force
d– length of barrel
6.4 Heat Shield and Structure Mass Analysis
E.M.P.I.R.E. decided it was necessary to calculate the mass of the PICA heat shield that covers L.A.M.B.
Mission 102. Since the density of a material is its mass divided by its volume, the team used the density
and volume of the PICA heat shield and aluminum to determine the mass of the heat shield and the
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Payload Concept Proposal
Mercury Lander Mission
Spring 2012
aluminum launch tube. The mass of the heat shield was initially calculated to be 3.06kg, which forced the
payload over its mass budget. The engineering team modified the design by removing the pyramid
shaped tip and reducing the volume of the remaining structure and the launch tube. Although a launch
tube length of 44 cm would result in lower pressure during deployment, a 6cm launch tube was selected
with 32 cm tracks, to keep the payload design within the mass limit. These changes resulted in L.A.M.B.
Mission 102 remaining within the 5 kg mass budget.
6.5 Primary Battery Mass Analysis
E.M.P.I.R.E. decided it was necessary to calculate the mass of primary batteries that will be required.
The team calculated the battery mass based on using a 400 W hr/kg primary battery and a worst case scenario of 10.5 W usage for 6 continuous hours. The mass of primary batteries was calculated to be .16 kg.
7.0 Final Design
The final design of L.A.M.B. Mission 102 features two thermocouples (types K and N) and an HPXe-100
radiation detector. The thermocouples will protrude from the forward section of the payload and the radiation detector will be inside the payload in the aft portion of the payload. A Proton-Box Avionics Suite
cube sat will be used to relay data to the spacecraft. Additionally a data logger will be used to process
temperature data and relay it to the transmitter. The antenna will deploy and protrude from the aft portion
of the payload. A rectangular launch tube with tracks will house L.A.M.B. Mission 102 until it is deployed. A PICA heat shield will be used to protect instrumentation from extreme temperatures. Wheels
will allow the payload to roll across Mercury’s surface and achieve a 20 m distance from the spacecraft.
The dimensions of L.A.M.B. Mission 102 are 38 cm x 28 cm x 19 cm.
*
*
Figure 6. L.A.M.B. Mission 102
Figure 7. Instrument Orientation
Table 6. Final Design Mass and Power Budget body
Component
Number
Thermocouples Types
K and N
HPXe – 100 High
pressure xenon detector
Data logger
Primary battery
Wireless voltage
transmitter
Heat Shield structure
Aluminum launch tube
Proton x-box cube sat
2
Mass
(kg)
0.004
1
0.1
1
1
1
0.112
0.16
0.043
1
1
1
2.1
1.13
0.805
Wheels
4
0.042
TOTAL
Power (W)
Self generating
Less than 1mW
(battery)
Self generating
--------Battery powered
(2 years)
----------------10.26 W Battery
powered
---------
Figure 8. L.A.M.B. Mission 102 Launcher
is made
Total Mass
(kg)
0.008
Total Power (W)
0.1
Less than 1mW
(battery)
Self generating
--------Battery powered (2
years)
----------------10.26 W Battery
powered
--------0
0.112
0.16
0.043
2.1
1.13
0.805
0.168
4.66
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Self generating