Proposal
Mercury Lander Mission
Spring 2012
Cold Springs High School
Team 2
The H.E.A.T.
Helios Electromagnetic-radiation And Temperature
Proposal
Mercury Lander Mission
Spring 2012
1.0 Introduction
The H.E.A.T is a team of high school students designing a payload to accompany NASA’s Mercury
Lander Mission. H.E.A.T. is an acronym for Helios Electromagnetic radiation And Temperature. Since
the payload will be traveling in a direct path toward the Sun’s atmosphere, it is referred to as Icarus.
According to Greek mythology, Icarus was the son of the master craftsman, Daedalus. Daedalus, in his
attempt to escape from Crete with his son, constructed wings from wax to aid him in escaping from his
imprisonment. Beforehand, he warned Icarus not to fly too close to the Sun; however, Icarus did not heed
his father’s warning and perished. In addition to gaining close proximity with the sun, Icarus will
measure both radiation and temperature changes while in pursuit of its main objective.
2.0 Science Objective and Instrumentation
The objective of this payload is to determine how the temperature and gamma radiation profiles alter
in correlation to an object’s proximity to the Sun. As the spacecraft approaches Mercury for landing, it
will launch Icarus in a path toward the Sun, where Icarus will measure temperature and gamma radiation.
Because of their ability to read extremely high temperatures (up to 1600 °C), type R thermocouples will
be utilized. To measure radiation, an “Inspector” Geiger counter will be utilized.
Table 1. Science Traceability Matrix
Science Objective
Determine the
temperature and radiation
profiles while in close
proximity to the Sun.
Measurement
Objective
Temperature
Radiation
Measurement
Requirement
Temperature
measurements will be
taken continuously to
the nearest degree.
Radiation will be
continuously measured
Instrument Selected
Type R thermocouple
“Inspector” Geiger
counter
Table 2. Instrument Required Resources (Draft)
Instrument
Type R
thermocouple
“Inspector” Geiger
counter
Mass (kg)
.001kg
Power (W)
Self-powered
Volume (cm3)
0.34 kg with
battery
9v alkaline battery
(2160 hours)
360 cm3
7.27 cm3
Data Rate (bps)
Continuous
measurement
Updates every 3
seconds
3.0 Alternative Concepts
The team divided into two groups and each group developed a design for Icarus. As the team
discussed each concept, they realized the limitations of each group’s concept and developed a third
alternative concept.
Alternative Concept 1: As the lander orbits Mercury and Venus, the payload, Icarus, compressed helium
will eject Icarus from the NASA spacecraft in a path toward the Sun. To survive as long as possible,
Icarus will be covered with a heat shield similar to the one use on the Messenger mission. Once in flight,
Icarus will begin measuring temperature and gamma radiation at a constant rate. An “Inspector” Geiger
counter with an external probe will be positioned on the rear portion of Icarus and measure the gamma
radiation levels. Two Type R thermocouples, located on one of the sides Icarus, will measure
temperature. Data will be acquired, processed, and transmitted using a UHF antenna (located on the rear
portion) to the lander every three seconds until Icarus is destroyed by the Sun.
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Proposal
Mercury Lander Mission
Spring 2012
Figure 1. Concept 1
Alternative Concept 2: The deployment method chosen for concept 2 is to utilize compressed helium to
eject from the NASA spacecraft and achieve spin stabilization. This concept is designed to fly by the Sun
without intentional contact. When it gains enough speed, two stabilized cables located on each side, will
propel outward to cease Icarus’s rotation. Icarus will be protected from the Sun’s heat with a thermal
blanket that will cover most of Icarus, except the back. Temperature will be measured by a thermocouple
located inside a small window which will open for measurements and close. The front of the window will
be a small solar panel providing a source of power for the robotic movement of the window. An
“Inspector” Geiger counter will be used to measure radiation and will be located on the “cool side,” or the
rear, of the payload. It will measure radiation continuously, or until its battery becomes exhausted (2160
hours), the data will be updated every three seconds, and transmitted to the lander immediately.
Figure 2. Concept 2
Alternative Concept 3: The team considered comments from the preliminary design review and realized
the limitations of the concepts that had been developed. Team H.E.A.T. took these limitations into
consideration and began to develop a third alternative concept. Concept 3 is shaped like a soup can, with
two type R thermocouples placed at the front and a Geiger counter located at the rear. The payload will
deploy from the spacecraft utilizing helium that will shoot it through a rifled barrel and toward the sun.
Concept 3 will measure temperature and radiation continuously and transmit the data to the lander
continuously.
Figure3. Concept 3
4.0 Decision Analysis
Before deciding the final payload concept, the members of Team H.E.A.T. determined the figures of
merit for the three design concepts. To help determine the best features of each concept, each figure was
given an overall weight depending on its importance. All team members considered the key features of
each design in order to plan the final concept. Concept 3 proved to be the best overall concept.
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Proposal
Mercury Lander Mission
Spring 2012
Table 3. Payload Decision Analysis
Figure of Merit
Weight
Mass
Protection
Power
Science
9
9
9
9 (3)
Concept 1
(mushroom)
9
3
9
9
Concept 2
(cone)
1
9
3
3
Concept 3
(soup can)
3
9
9
9
Durability
3
9
3
9
Volume
Stability
Total
9
9
9
3
387/333
1
3
225/207
3
9
405/351
Criteria
Low mass is desired
High protection of payload
Low power requirements
Accurate and precise
measurements
Highly durable to withstand
deployment and heat.
Low volume
Will not tumble toward the sun
5.0 Concept of Operations
The concept of operations for Icarus has two phases: deployment and data acquisition. Prior to the
spacecraft’s launch from Earth, Icarus will be positioned inside a rifled aluminum launch barrel. Icarus
will be oriented so that it is on the side of the spacecraft that will be closest to the sun on its approach to
land on Mercury.
Phase 1 - Deployment Phase:
 As the spacecraft approaches Mercury for landing, the launch tube will be pressured to 0.03psi.
 The pressure will be released at a time and in a manner that will launch Icarus at a 90° angle to
Mercury’s orbit.
Phase 2 - Data Acquisition Phase:
 Icarus will begin measuring gamma radiation and temperature immediately after launch.
 Icarus will measure temperature continuously and transmit temperature data continuously.
 Icarus will measure gamma radiation continuously and transmit radiation data every three
seconds.
 Icarus will continue in this phase for 176.4 hours or until it is no longer functional, whichever
occurs first.
Figure 4. Payload Concept of Operations
6.0 Engineering Analysis
At the onset of the project, the team was given a set of limitations for mass (no more than 5 kg), power
(no more than 10 W continuous), and volume (44cm x 24 cm x 28 cm). The team then began to analyze
the payload making certain it met all the requirements. A problem was encountered when the team
calculated the masses of the payload and the launching device and found that it exceeded the 5 kg
limitation. The team looked for alternative solutions to reduce the total mass by reducing the payload to
the smallest possible size that would accommodate the instrumentation and perform the experiment;
however, the payload and the launcher still exceeded the mass constraint. The mass of the revised payload
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Proposal
Mercury Lander Mission
Spring 2012
design was calculated to be 3.12 kg, with 2.33 kg of the mass being the heat shield and 0.79 kg of the
mass being the aluminum structure of the payload. The mass of the launching device was calculated to be
2.27 kg making the total 5.39 kg for the payload and launcher. Team H.E.A.T. submitted a proposal to
the college team for 0.75 kg of additional mass, which was granted.
Launch Barrel Length Analysis: The length of the barrel, or launching device, proved to be highly
important. Team H.E.A.T. analyzed the exit velocity with varying amounts of pressure for three barrel
lengths, 35 cm, 40 cm, and 44 cm. If the barrel length were to be 35 cm then the entire payload design
would be under budget; however; having a shorter barrel requires more pressure which presents a possible
problem for the instruments to work properly. As a result, the launching device was given a length of 44
cm.
Velocity (m/s)
Launching Device Analysis
1500
1000
35 cm distance
500
40 cm distance
0
0
2000
4000
Pressure (psi)
6000
44 cm distance
Figure 4. Engineering Analysis Graph
Launch Pressure Analysis: Launch pressure was the next aspect that needed to be found. It was
determined the payload needed to have a final velocity of 100 m/s in order to escape Mercury’s sphere of
influence. The launch pressure was calculated to be 0.03 psi.
Table 6. Launch Pressure Calculations
Calculations
p = vf2m/ 2Ad
p = 177.7464775 Pa
p = 0.025787043 psi
p – pressure
m – mass
d– length of barrel (44
cm)
Variables
A – area (over which pressure is
applied)
vf – final velocity (leaving launch
barrel)
Life Expectancy Analysis: The life expectancy of the payload was calculated in order to determine the
amount of time the payload would take measurements and analyze battery requirements. The team
assumed the payload would not survive beyond 0.2 AU, so the distance the payload will travel was
determined to be the difference between Mercury’s distance from the sun (0.4 AU) and 0.2 AU.
Table 7. Launch Pressure Calculations
Calculations
vf2 = vi2 + 2ad
vf = 47096.98646 m/s
Substitute vf in the
equation below.
Substituted Variables
a=GM- rv2/r2
d=(0.2AU)(1.49598 x 1011m)
vi = vsc + Δv = 4790 m/s + 100 m/s
t= d/vf
t = 635199.8769 s
t = 176.4444103 hr
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Variables
vf – final velocity (at 0.2AU)
vsc – velocity of spacecraft
Vi – initial velocity upon launch
Δv – change in velocity to escape
Mercury’s sphere of influence
G – universal gravitational constant
6.67 x 10-11 N m2/ kg2
M – mass of sun = 1.9891 x 1030 kg
r – radius at .4 AU = 5.98392 x 1010 m
Proposal
Mercury Lander Mission
Spring 2012
6.0 Final Design
The team decided on the third concept (soup can) as the final design. The design’s features
include two thermocouples located on the forward section of the payload, and a radiation detector,
transmitter, processor, accelerometer, and data logger located in the hollow space on the aft section of the
payload and an antenna also wired around the aft portion of the payload. The instruments contained
inside of the payload are protected from the sun’s heat by the heat shield and are still capable of
performing their functions. The final design is a cylindrical shape with a radius of 21.14 cm and a length
of 23.07 cm. The cylindrical shape provides a central axis around which it can rotate to prevent it from
tumbling end over end. The launch device is a hollow cylinder that is closed on one end and rifled to
provide the spin needed to prevent tumbling. The launch tube has a diameter of 21.64 cm and a length of
44 cm.
Figure 4. View of aft portion of Icarus
Figure 5.Sketch of Icarus and Launcher
Figure 6. Front view of Icarus in launcher
Table 8. Final Design Mass and Power Budget
Component
Number
Type R thermocouple
“Inspector” Geiger
counter
Heat shield
UHF antenna
Processor
transmitter
2
1
1
1
1
1
Mass
(kg)
.001
0.34
w/battery
2.32
0.023
-----------0.03
Total Mass
(kg)
.002 kg
0.34 kg
0.03
Power
(W)
Self-powered
Alkaline
battery
---------------------------------DCv 3.3
battery
4 silver oxide
batteries
3.6v battery
accelerometer
1
0.01
data logger
1
Payload & launcher
aluminum structure
1
3.06
------------
TOTALS
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Total Power (W)
Self-powered
Alkaline battery
2.32 kg
0.023 kg
-----------0.03 kg
---------------------------------DCv Battery
0.01 kg
0.03 kg
4 silver oxide
batteries
3.6v battery
3.06
-------------
5.45 kg
Provided by
batteries