The second portion of the unit, Lesson #2 focuses on two main concepts: (1) The utilization of spreadsheet software to more quickly and accurately calculate and analyze data to evaluate options involved in material science and (2) the use of a computer simulated software (“My Solar
System”, provided by PhET Interactive Simulations, University of Colorado) to both teach about mass, velocity, and gravitational relationships, and instill in the student an appreciation for the benefit and necessity of simulation technology in STEM careers. Students are first introduced to the interesting problem solving techniques involved in material science and the engineering of remote sensing by viewing the NASA supplied online video NASA's MESSENGER to Become First
Spacecraft to Orbit Mercury . Students are then placed into development groups (the same groups as in Lesson #1, if the class is continuing through the unit) and have at their disposal their remaining “budget” from the previous mission. The “budget” will continue to play a role for this lesson in the form of the costs of materials they evaluate and for teacher consultations. The groups are trained (free of charge) in how to use the Excel Spreadsheet Program to quickly evaluate, based upon physical properties, the best material to use in construction of the solar shield for a fiction al solar probe, the NASA “DANTE” ( D eployed A stroN omical T ester of
E lectromagnetism.) After this is determined, they will use the PhET simulation in order to decide the best initial entry position and velocity for the probe. The team mission goals are to select a material that minimizes cost of launch (hence, the least dense material) which also would not melt from the extreme radiation exposure, and to have the probe orbit the sun 20 times within given time parameters, without collision orbits.
Intended for use with 9 th or 10 th grade Physical Science courses.
Prerequisites
It is expected that the students will already be proficient with the following:

Knowledge of the Scientific Method


Navigation of internet web browsers

Unit conversions (including mass and temperature scales)

Scientific Notation

Density

Metallic Properties

Qualitative understanding of Newton’s Second Law
 Qualitative understanding of Newton’s Law of Gravity

Specific Heat Capacity

Absolute temperature (Kelvin scale)

X and Y Vector components
Upon completion of this lesson, students will be able to:

Express their deeper understanding of engineering design

Recognize significant and insignificant limitations of models/simulations

Work within the confines of a realistic budget, always keeping cost in mind

Log and report simulated data

Convey an understanding of what material science incorporates

Analyze physical properties of materials in order to select an ideal option

Explain the importance of considering all physical properties when selecting materials during the design process

Define the physical property known as “coefficient of thermal expansion” or CTE and its importance in engineering considerations

Use and understand Excel Spreadsheet and its advantages

Utilize Excel calculation tools that involve equations

Describe mass, velocity, and gravitational relationships in a qualitative way
Handouts

DANTE Probe Trajectory Simulation Datasheet
 “The Dynamic Sun” Web Quest
Internet

MatWeb Material Property Data http://www.matweb.com

PhET Interactive Simulations http://phet.colorado.edu/en/simulation/my-solar-system

NASA's MESSENGER Video http://www.youtube.com/watch?v=iDPRJznyOYw

I ridium 33 and Cosmos 2251 Collision Video http://www.youtube.com/watch?v=-hZnBNl1_T0


Voyager 1 & 2 Trajectories Video http://www.youtube.com/watch?v=cTIGOe5ckj0
Equipment

Computer

Microsoft Excel

Projector

Calculator

Internet Access

Java
Supplemental Readings or Websites

Microsoft Office Excel Support: http://office.microsoft.com/en-us/excel-help/examples-ofcommonly-used-formulas-HP005200127.aspx
Other
 “The Dynamic Sun” CD-ROM, available for $6.00 at: http://corecatalog.nasa.gov/item.cfm?num=400.1-22
(As a NASA support material, this resource is considered public domain. After having purchased the original, an unlimited number of copies can be duplicate for the purpose of non-profit educational reasons.)
The time required for this lesson will be variable depending upon student/class ability with the material. It is estimated, however, that Lesson #2 will take approximately 3 – 5 days .
More detailed time analysis is presented within the procedure that follows.
DANTE Solar Probe Introduction (20 Minutes)
Begin this lesson with some inquiry about how we sense things (i.e. take in information).
One suggested method is as follows: Ask your students if the sun is shining. (If you ask this on a day that is cloudy, begins before sunrise, is a night class, e tc., and you get the answer “No”, remind the students that the question asks what the sun is doing, not what it’s doing from their own perspective. Eventually, they should be in agreement that yes, the sun is shining.) Now ask them how they can tell, on any given day, if the sun is shining on them . Likely responses would include that they can see the light, and that they can feel the sun’s warmth. Whatever responses are reasonable and accurate, you can post on the board. The light and warmth the sun provides is a

direct way of measuring the energy output of the sun. Now ask them what some indirect ways would be. Post reasonable and accurate answers on the board. Some examples would be using photographic film exposed to the sunlight, using a solar panel device, or even tracking throughout the day sun influence animal behaviors, such as the number of turtles basking in a pond.
Explain to your students that these are all ways of taking in information about the sun. They are all ways of sensing. Relate to your students the idea that all information is taken either directly by our senses, or indirectly using tools and technology.
Now ask your students how they would gain information from something that is in a dangerous environment. Would they actually want to locate themselves where it hostile, or is there another option. Likely, such devices as robots and probes will be brought up. Define for the students that remote sensing is any time that you collect information an object or an event without making physical contact with the object or objects involved in the event.
Inform the students that a key component to learning about our solar system involves the use of probes, which are highly specialized remote sensing devices. (There is no environment that humans visit on earth that is more hostile than the vacuum of space!!) Explain to them that it would be unfair to ask them what a space probe exactly looks like. It would be similar to asking what a tool looks like
– its design is dependent upon what function it serves.
Show to your students the NASA's MESSENGER to Become First Spacecraft to Orbit Mercury video, available from the NASATelevision Youtube Channel: http://www.youtube.com/watch?v=iDPRJznyOYw
You do not need to run the video in its entirety. The beginning of the video involves a discussion of the reasons why we would be interested to study the planet Mercury. Starting at time stamp 3:37, a simulation of the Messenger’s orbiting trajectory is shown. Point out to students the white, curved solar shield which protects the sensory equipment from the sun’s large amount of radiation.
Activity – Solar Shield Material Research and Evaluation (40 Minutes)
Inform to your students that the next step of their NASA career is in full swing. Their team will be working on the material construction of the fictional “DANTE” solar probe, and will also be involved with planning out the orbital trajectory it will have near the sun. Similar to the Messenger Probe,
DANTE will also require a solar shield, and it shall be part of their mission to research what the ideal (or closest to ideal that they can find) material would be for the construction. They will use the MatWeb Material Property Data website, http://www.matweb.com
(which is used by actual
NASA engineers) to research the physical properties of possible materials. Restriction of the shield is that it must be a metal (either elemental or a known alloy), it can not be radioactive, and certainly, it should not melt during the mission!
In order to verify that a chosen material is a potential option, students will evaluate the material using the specific heat equation, ΔH = cmΔT = cm(T f
– T i
), and solve for T f
, the final temperature.
If the final temperature is greater than that of the melting point for that material, it will melt and is not an option.
We will assume that the maximum amount of thermal energy given to the probe’s shield (resulting in the maximum temperature change that will occur to the shield) will be
ΔH = 5 x 10 10 Joules. The initial temperature will be defined as 3 Kelvin, (near the average temperature of the vacuum of space).

In order to determine the mass of the shield, students will need to use the density equation,
D = m/v. The volume of the shield has already been determined by the design division, v = 90m 3 , or in cubic centimeters (the volume unit used in MatWeb) v = 9,000,000cc.
Thus, from MatWeb, students will need to retrieve the data for density (D) and the specific heat capacity (c) values, along with the melting point of the substance. Using density and the given volume, they will calculate the mass of the shield. Once the mass is calculated, it will be used along with the specific heat capacity and given thermal energy to calculate the change in temperature. Once the change in temperature has been determined, it will be in units of degrees
Celsius due to the units used in MatWeb. However, as it is a change in temperature, and the magnitude of one Celsius degree is the same as the magnitude of one Kelvin degree, the value of the temperature change is the same when expressed in Kelvins. Students will add to the change in temperature 3 Kelvin to determine the final temperature. Students compare the final temperature to the melting point to conclude whether the material is a viable option or not.
However, as MatWeb reports melting points in degrees Celsius, students will need to convert the melting point to Kelvins using the following equation: T
Kelvin
= T
Celsius
+ 273
Important Note: The MatWeb has hundreds of thousands of different materials. However, it doesn’t always have all three of these data for every substance. If students select a material that is missing one or more of these data, they will not be able to evaluate it and must choose something else.
In order to quickly evaluate these data, students will use spreadsheet technology available in
Microsoft Excel. A teacher template spreadsheet containing this data has been included (see attachment).
Have students open the Microsoft Excel Template. The program will open with the “Density” tab in view. (Notice that there is a “Specific Heat” tab as well.) The data and calculations for aluminum have already been provided and can serve as examples for the students. Using a projector (if available) or by walking around the room giving guided instruction, have students place the cursor over the various aluminum data. Show them the calculation application that has been applied to the derived field of mass in grams, and the derived field of mass in kilograms.
Have students click the “Specific Heat” tab and have them do the same with the aluminum data shown. Be sure to point out to them that the “mass” field is linked directly to the “Density” spreadsheet.
(If you need a refresher on Excel’s formula applications Microsoft provides support at the following website: http://office.microsoft.com/en-us/excel-help/examples-of-commonly-used-formulas-
HP005200127.aspx
)
Check for their understanding and ask the students if aluminum is a viable option. By comparing the final Kelvin temperature, T f
(K), to the Kelvin melting point, they should be able to see that an aluminum shield would indeed melt.
As student input data of their materials they choose to inspect, they will wish to find multiple materials that are options. The group’s budget now comes into play. As the average cost of launching mass into space is in the tens of thousands per kilogram, inform the students that the lowest mass viable option is ideal. The students will be in competition with each other. All

materials will subtract from their budget. However, the less massive material that the students discover will subtract the least. Students will be ranked in order of success, from least massive viable material to most massive viable material. First place will have a deduction of $10,000,000, second place, a deduction of $20,000,000 third place, a deduction of $30,000,000 etc. Thus, the more materials students research, the more viable options (in theory) will be found, increasing the chances for that team to be ranked higher in success. (They may wish to add more rows as they research more materials. They will need to become proficient with activating the formula applications on newly created rows. This is intentional to facilitate their learning of Excel.)
Students will submit their Excel spreadsheets to the teacher either via email, or by printing a hard copy, and clearly marking their chosen material. It will be important that they have recorded the precise name of the material from MatWeb either in the Excel file, or have written it completely on the printed paper, as the material names in MatWeb can be quite long and detailed for alloys. The instructor will need this information in order to verify that the material would indeed produce the data the students are claiming.
Classroom Discussion – Material Science and Spreadsheet Debriefing (15 Minutes)
Now that the material proposals have been submitted, students can share any strategies that they determined while doing the activity to hasten their progress. Some suggested questions to ask would be:

What type of melting point was your team looking for when you researched new materials?
Relatively high or low ones?

If you notice a material has a very low melting point, would you still need to perform the calculations to see if it was a viable option?

Since regardless of the material, the volume is a constant, concerning cost, what would be more desirable, a high or low density?

If your team had already found a viable option, and while examining the data of another material you notice it has a higher density than the material you already know is an option, what conclusion could you draw? What are the chances it would be better suited for the task?

What role does specific heat data play in this process? If a material had a very low specific heat, what could you conclude?

If you found two materials with the same density and the same melting point, but very different specific heat capacities, which would be the better option and why?

What would be the physical properties to look for in the most ideal metal for the mission?
Taking It Further
– Even More Accurate Material Science (20 Minutes)
Announce to the students that you have good news and bad news for them. The good news would be that the teams had much success and NASA is that much closer to having the design finished for the DANTE probe. The bad news is, even if their team found a metal for their shield which would not melt, that doesn’t necessarily mean that the metal will actually work. Explain to your students that things such as melting point and density are just two parameters that NASA engineers and designers must consider. In reality, engineers must consider all parameters.
Ask the students if while researching their materials with the MatWeb site if they noticed any other physical properties that the class has talked about before. What were they? Write the properties

that the students give you on the board and review what they mean. Now ask the students if there were any physical properties that looked strange to them or they hadn’t seen before. If any remember what they are, place those on the board too.
Having discussed and reviewed what how each property is defined, ask the students what other physical properties would have to be considered, and why they would have to be considered. Ask how that property would affect the performance of DANTE. Star or mark any that are reasonable and properly argued by the students. Some such properties would include:

Luster – The shinier the metal, the less the light will be absorbed as heat.

Brittleness – Some metals become very brittle at low temperatures. This could cause problems.

Hardness – This shield must be fastened to the probe. If it can’t be drilled, this can cause a problem
Relay to the students that a very important property that would also be considered is called the coefficient of thermal expansion (CTE). Explain to the students that the CTE of a material is similar to specific heat of a material in the sense that it is a constant for each material that explains how an object made of that material will change for every temperature degree it increases by. For example, if you were to heat up a one meter object of a material and heat it up just one degree
Celcius, and it thermally expanded to be 5 centimeters longer, it would have a coefficient of thermal expansion of 5cm / m ºC.
Check for understanding of this concept with the following example questions:
 If a material has a CTE of 5cm / m ºC, and you heated up a meter long rod of that material from 22 ºC to 40 ºC, by how many centimeters will it have expanded? Answer: 90cm

Now that it has been heated up, how long is the rod? Answer: 1.9m
Ask the students, if a material has too high of a CTE, what type of difficulties could occur?
Activity
– ModSim Probe Trajectory (45 minutes)
Announce to your students that it is now time for the second leg of the DANTE solar probe mission
– they must find a stable orbit around the sun for their probe. Inform them that this may not be as easy as one would think. Ask students if, during the passing between classes, they have ever bumped into a student in the hallway, which for many schools, can often have considerable traffic.
You can relate the idea of trajectory concerns that real world probe and satellite projects face by showing the simulation video Iridium 33 and Cosmos 2251 Collision - Evolve Based Debris http://www.youtube.com/watch?v=-hZnBNl1_T0
This video shows a reenactment of the collision of two artificial satellites in low earth orbit, and the debris that followed. Explain to students that if they think their hallways are ever crowded, they should feel lucky. According the the World Book of Chicago, 2004, there are upwards of 6,000 low earth artificial satellites (3,000 of which are no longer functioning). Relate to the students as well that in the hallway, they have much more of an option to change trajectory than an orbiting satellite, should they sense a collision about to happen.
Remind the students about Newton’s First Law of Motion: Objects at rest tend to stay at rest and objects in motion tend to stay in motion, unless acted upon by an external force.
Ask your students what major external force a probe will be subjected to in space. Gravity will likely be their answer.

Ask the students to now picture walking through the hallway, and feeling as if they are “falling” towards the other students in the hallways. They will start to see the picture of what a space probe may experience.
Load up onto your projector the PhET Simulation “My Solar System”. (Java Application required.) http://phet.colorado.edu/en/simulation/my-solar-system
Spend a few minutes demonstrating the use of the simulation for your students. Objects can change position by either dragging them to new positions, or typing in the position in the coordinate table at the bottom of the screen. Initial velocity can be changed by dragging the vector arrows at the “V” to a new direction. Increasing the length of the arrow increases the magnitude of the velocity. Velocity can also be manipulated by typing in the x and y vector components in the coordinate table. The mass of each object can also be manipulated by typing in a new mass. As neither mass nor velocity have units in the program, they are relative units.
Once the students have seen your demonstration, click on the “4 body” option so that they can see the starting point of their task. The four bodies shown represent the sun (yellow), the planet
Mercury (green), the planet Venus (violet), and the DANTE solar probe (blue). They will need to change the mass of body 4 (Mercury) from 0.001 to 2. Have students load up the program on their computers and perform the same. They are now ready for their task.
At this time, hand out to the students the DANTE Probe Trajectory Simulation Datasheet (see
Resource Pages )
Their mission is to find a possible initial position and velocity for the DANTE solar probe that will produce an orbit stable enough to achieve 20 revolutions around the sun, within a 36.0 month period. The simulation tracks time in relative units. For this exercise, we shall define the units as months. Another restriction they have is that the DANTE probe’s initial position must lie between the sun and Venus’s x coordinates. (The probe’s y coordinates have free range, but certainly the probe must be close enough to the sun to study it during some portion of the orbital path.) Other than having changed Mercury’s mass to 2, they are to leave the other positions, velocities, and masses of the sun, Mercury, and Venus alone. Though it is possible to use trial and error, encourage the students to experiment with the program utilizing the scientific method, in the sense that they should attempt to change one variable at a time (either position or velocity) to see if they can achieve a more successful orbit.
Make it clear to the students that they do not need to record the DANTE probe’s initial data (Body
3) for every simulation. However, once they have a successful, or even close to successful simulation, they will wish to record the probe’s initial conditions. They must click “Stop” and then
“Reset” and the simulation will return to the initial starting points that they gave the probe. The assignment is complete when they have found a successful trajectory, or as close to successful as time has allotted them.
Foreshadow to the students that during the next activity, you will be coming by to each group to have them demonstrate for you their “official test” trajectory for evaluation to verify that they achieved success. Thus, prior to this, they will need to have recorded multiple simulations and decided as a group which is the best simulation to act as their official run. Announce to them as well that they will want to have verified the success of their chosen simulation, for if the DANTE

probe is destroyed prior to 20 orbits, that will result in a $45,000,000 deduction from their budget
(and their NASA superiors will not be happy).
“The Dynamic Sun” CD-ROM Exploration and Official Probe Trajectory Tests (45 Minutes)
Once students have had the allotted time to find a successful trajectory, inform them that their official testing shall soon begin. Reveal to them that, though the DANTE solar probe is fictional, it is modeled after the actual Solar and Heliospheric Observatory , or SOHO probe, currently orbiting and studying the sun, from its deep inner core to the outer corona. Inform your students that they will be performing an exploration activity to learn more of the sun using their copy of “The
Dynamic Sun” CD-ROM, which includes information about SOHO. Inform them that while they are working with the CD-ROM, you will be going from group to group to have them demonstrate the success of their official trajectory.
Hand out to the class “The Dynamic Sun CD-ROM Exploration” guide (see Resource Pages ) and have them follow the directions. While they do this, you will go from group to group and assess the
“official runs” for each. (For assessment suggestions, see Student Assessments .)
ModSim Probe Trajectory Debriefing (20 Minutes)
Load up the PhHET “My Solar System” ModSim program. Open a discussion with the students as to what strategies they used in order to refine their trajectories. Some questions to ask would include:

Would placing the probe closer or farther from the sun help in achieving a more stable orbit?

How important is the directional component of the velocity?

If a probe begins near the sun, what type of velocity would be more likely to achieve a stable orbit? Large magnitude? Small? What direction should it have?
In order to achieve a stable orbit, ideally, the probe would start very close to the sun with a large velocity magnitude. The direction of the velocity should be perpendicular to a line that would connect the sun and probe’s center points. It would be good to demonstrate this for the students, followed by a review discussion of acceleration and the law of gravitation.
Taking It Further – Gravitational “Slingshot” Effect and the Voyager Probes (20 Minutes)
Have students utilize the “Select Preset” option. Instruct them to scroll down to “Slingshot” and run the simulation at the slowest speed. Do the same on your projector. Poll the students as to what is happening with the orbits. Ask some of the following questions:
 Why do you think this preset is called “Slingshot”?

Specifically, what object is causing the slingshot effect in this simulation sequence?
 Why didn’t the effect happen during an earlier orbit?
Student responses will vary, but should include understanding of the concept that the proximity of body 2 and body 3 must be close enough for the gravitational force of body 2 on body 3 to be more significant than the force of body 1 with body 3.

Have students now select the
“Double Slingshot” option from the preset menu and run the simulation at the slowest speed. Point out to the students that this effect can happen more than once to the same object if the trajectories are just right.
Ask your students the following questions:

What might this effect be useful for?

In what scenarios might we want something to leave our solar system?

If we wanted something to leave our solar system, why not just pay to launch it with enough velocity?

What advantage does the slingshot effect provide?
Relate to the students that the Voyager Space Probes 1 and 2 both took advantage of the slingshot effect multiple times in order to study the outer solar system. Voyager 1, launched in the summer of 1977, is a space probe that holds the record as the furthest human made object from the earth, and the first human made object to leave our solar system.
Explain to your students that while very useful, in order to produce a double, triple, or higher multiple slingshot effect, the planets must cooperate and be in the right places at the right time.
You can have students slightly move the initial position of one or both of the planets in the double slingshot simulation and see if the green planet still leaves the system.
Show your students the actual trajectory of Voyager 1 and 2 with the video Voyager 1 & 2
Trajectories To The Outer Planets: http://www.youtube.com/watch?v=cTIGOe5ckj0
Mention to your students that the last time the planets had been positioned in such a way to allow for the multiple slingshot effect as seen in the video, Thomas Jefferson was the President.
At Home Task
– What Probe Would You Design? (60 Minutes)
To conclude Lesson #2, assign the students the task of researching and authoring a paper that describes what type of probe they would design. The paper should be long enough to completely describe and answer the following:

If they could study anything in the solar system, what would it be? Which specific planet, moon, comet, asteroid, etc. would they choose, and what would they want to study about it?

What measuring devices would need to be included in the probe design?

What additional structures might be necessary in the design? (Remind them of the
Messenger radiation shield.)

What type of materials might be necessary in the construction of their probe? What physical properties of those materials need to be considered?

What type of power supply would your probe have?

What specifically about their design has intentionally minimized the cost of launch?

Students shall be assessed based upon the continuing “budget”, and the following:

Completion and efficiency of use of the Excel spreadsheet

Completion of the DANTE Probe Trajectory Simulation Datasheet
 Completion and accuracy of “The Dynamic Sun” Web Quest
(See Unit Plan)
(See Attachments)