NOTE: This is a sub-page of the Teacher Resources main page which you should read first.
Written by Dr. Jeff Goldstein, SSEP National Program Director
Student teams across your community can propose experiments designed to assess the impact of microgravity (the apparent absence of gravity, also called ‘weightlessness’) on a physical, chemical, or biological system. For SSEP experiments aboard the International Space Station (ISS), an experiment can be run for just hours to days, to potentially over a month. Students can design experiments in diverse fields, including: seed germination, crystal growth, physiology and life cycles of microorganisms (e.g. bacteria), cell biology and growth, food studies, and studies of micro-aquatic life (e.g., brine shrimp).
Each experiment must be designed to work within an existing, flight-ready, easy-to-use, professional research mini-laboratory. Once in orbit aboard ISS, the mini-lab allows materials (fluids and/or solids) – termed the ‘Experiment Samples’ – to be combined. Each experiment loaded into the mini-lab consists of one to three separated volumes filled with the experiment samples. Each volume is effectively a small test tube. Once in orbit, an experiment is conducted by an astronaut by mixing specific samples according to the student flight team’s experimental protocol.
For Space Shuttle operations, SSEP used the Materials Dispersion Apparatus (MDA) mini-lab. For International Space Station operations, SSEP is currently using the Fluids Mixing Enclosure (FME) mini-lab.
The experiment samples (fluids and/or solids) used in the student experiments must pass a NASA Flight Safety Review.
General Framing of the Experiment—A Simple Concept
The way to think about this REAL flight experiment opportunity is pretty simple, and appropriate for even upper elementary and middle school students—if teachers help them put on their thinking caps. It is worth noting that of the 382 experiments chosen to fly on the first 19 SSEP flight opportunities (STS-134 and STS-135, and Missions 1 through 17 to ISS) 50 were from upper elementary, 174 were from middle school, 139 were from high school / community college student teams, and 19 were from a 4-year college and university consortium. See the descriptions of the Experiments Selected for Flight at the SSEP Community Network Hubsite.
Science is a process that allows us to study natural phenomena around us. The explorer will observe some interesting phenomenon and want know how it does what it does. To make this more personal … YOUR world is filled with phenomena around you, and if you notice something cool, the starting point for exploration is to be curious enough to ask some simple questions like – I wonder why that happens? I wonder what causes that? I wonder how that happens?
The nature of the phenomenon could be physical (e.g., Why does that log float? What causes ocean waves?); chemical (e.g.,What causes iron to rust? How does wood burn?); or biological (e.g., What’s needed to grow wheat best? What causes tooth decay? How do antibiotics work?).
We also need to recognize that what we’d like to study exists in an ‘environment’. So if you want to study, for instance, how a specific species of seed germinates, you not only need the seeds, but also an environment that likely includes a growth medium (e.g,. soil), water, air, nutrients, and a specific temperature. We therefore define a ‘system’ – which includes what we’d like to study and its environment. Our seed germination example is an example of a ‘biological.system’. And here is an important point – we often have the power to change the characteristics of the environment if we wish, so we call these characteristics the system’s ‘variables’.
One powerful means of exploring how a system does what it does, is to poke it and see what happens. Yes, I did say … poke it! How you might ask? Well, first we recognize that many variables are associated with a system under study, and we then change the variables to see how the system responds. The idea is to assess the role of these variables in the system. For our seed example, you can vary, i.e., temperature, humidity, lighting, nutrient concentrations, etc., and see how germination is affected. But you don’t want to change all the variables at once! If you do, you won’t know which variable is causing the changes in germination you observe. You want to change variables in a controlled way, so one at a time if possible and hold the others constant. It’s a way to assess the role of that specific variable in the system, and the variable you change is called the ‘independent variable’. The lesson? Curiosity is fundamental to exploration, but good science requires organized curiosity.
Now let’s consider gravity. We normally observe the characteristics and processes of physical, chemical, and biological systems under the action of gravity on or near the surface of Earth. These systems all experience the ‘force of gravity’ which dictates a number of fundamental phenomena, e.g., that objects and materials weigh something, a sense of up versus down, and that higher density materials will sink in a lower density fluid. These phenomena are intricately connected to how systems behave, even for biological systems. For example, bone strength requires bone compression under the force of gravity. Every time you take a step, you’re compressing your bones due to your weight, and your body knows bone production is important. But without this compression, as in the weightless environment of an orbiting space station, your body senses bone strength is no longer needed and bone mass is excreted (see spaceflight osteopenia). Revealing gravity’s role in the behavior of a system can therefore provide a fundamental understanding of how the system operates. Thus gravity is a system variable – usually a vitally important variable – yet easily overlooked. For instance, would you have thought gravity would be an important variable in seed germination? Likely not, but it is. When a seed germinates, the roots go down and the shoots go up. The seed knows about gravity! The phenomenon is called geotropism.
But if you want to assess the role of gravity, whose magnitude is defined by the mass of the entire planet Earth, how do you change it to see the response of the system? Hint: carrying your experiment to the top of a tall building or to the top of a mountain is not effective. There is very little variation in gravity from Earth’s surface to the top of the tallest mountain. And double hint: taking your experiment to the top of an imaginary mountain whose peak is at the orbit of the International Space Station (260 miles up, corresponding to 47 Mt. Everests stacked on top on one another) won’t be very effective either, since gravity at that altitude is still 90% of its strength at sea level.
Now for the good part, and one of the key reasons for building the International Space Station. Objects placed in orbit experience ‘microgravity’ often referred to as ‘weightlessness’, where gravity magically appears to be turned off. Objects truly appear to be weightless – think of the astronauts you’ve seen floating around – which leads to the very incorrect conclusion that there is no force of gravity so high above Earth, hence an object has no weight. But if that were the case, what keeps the International Space Station orbiting the Earth? What keeps the MOON orbiting the Earth? Gravity is very real in space. The reason gravity seems to be absent is not immediately obvious, but it’s because an object in orbit is in a state of continuous free fall—it is a falling object. (Hmmm … what would the bathroom scale you are standing on show if you were in an elevator whose cable had been cut and is free-falling in a very very tall shaft?)
Not convinced? Take time to explore as a class two great resources that provide a deep conceptual understanding of why astronauts appear weightless—
a. NCESSE’s Center Director Jeff Goldstein, the creator of the SSEP, wrote an enjoyable student challenge on why astronauts appear weightless titled, You Want Me to Take a Bathroom Scale Where?, which teachers and students can read together.
b. NCESSE also developed a great grade 5-8 lesson which easily demonstrates through a hands-on activity that astronauts inside a free falling soda bottle space shuttle appear weightless. The lesson is part of the Building a Permanent Human Presence in Space compendium of lessons for the Center’s Journey through the Universe program. The lesson is titled Grade 5-8 Unit, Lesson 1: Weightlessness, which can be downloaded as a PDF from the Building a Permanent Human Presence in Space page. You can also read an overview of the lesson conducted as part of one of the many Journey through the Universe Educator Workshops, this one in Muncie Indiana.
Here is the cool part. If a physical, chemical, or biological system is brought into a laboratory that is orbiting the Earth, the system will operate as if gravity has been turned off. From the vantage point of the system you are studying, you’ve turned the gravity variable down to zero, and you can see if the system behaves differently as compared to its behavior on Earth in gravity. It is a means to reveal in possibly stark contrast the role of gravity.
Finally, here is the pearl of wisdom, the super sauce, the starting point for your journey. What’s the basic recipe for becoming a real research team designing a real microgravity experiment for the International Space Station? As you navigate through your world on a daily basis, you are knee deep in physical, chemical, and biological systems, and the researcher – the explorer – might ask How would this system behave differently if I could turn gravity off? And what might I learn from such an experiment?
In terms of experimental design, the essential question is:
What physical, chemical, or biological system would I like to explore with gravity seemingly
turned off for a period of time, as a means of assessing the role of gravity in that system?
And when you’re thinking about a possible experiment, you need to consider that there are constraints on your design, for instance:
• no more than 2 or 3 volumes of experiment samples (fluids and/or solids) can be mixed; you can also just fly a single volume that requires no mixing in orbit
• the experiment will be done in the shirtsleeve environment of the International Space Station
• sample volumes are small—this is a mini-lab with small ‘test tubes’
• the experiment can be ‘turned on’ by an astronaut, and proceeds on its own for a prescribed number of days in orbit; an astronaut might even ‘turn it off’
So … consider some basic examples for a possible experiment—
a. You might explore whether a seed germinates in space the way it germinates on Earth. Some of the critical questions: Does a seedling have a sense of gravity? Does it know up from down? Is gravity important for proper germination and maturation? What will happen if you take gravity away and allow a seed to germinate? What about long duration space flights where astronauts would need to grow their own food, is it important to know if a seed germinates appropriately in space, and then goes on to grow to maturity? Are some seeds better adapted for germination in microgravity than others? Here’s a challenge: what other questions might come to mind if you brainstorm this as a class? THERE! You are doing experiment design.
b. What about food in space? Do food products in microgravity retain their nutritional value? How long will they remain consumable, i.e., is their shelf life the same as here on Earth? Do bacteria in space spoil food at the same rate as here on Earth? Might those bacteria be somehow affected by microgravity? Your turn to continue brainstorming this one too!
c. Cells are the basic functional unit of life. Their function is pretty important for long duration spaceflight both for the health of the astronauts, and the foods that would need to be grown on the spacecraft. What kinds of questions might you brainstorm regarding cell function in microgravity? Is there something you might put in a test tube bound for orbit that would help you explore answers to your questions?
d. What about the life cycles for different organisms? Is the life cycle dependent on gravity? How would the initial phases of an organism’s life and growth be impacted if we turn gravity ‘off’? Could that lead to an understanding of the role gravity might play in an organism’s development here on Earth?
Ok, you’re likely getting the hang of this, but to help you continue exploring the remarkable breadth of science that can be performed, and gain more insight into thinking about experiment design, we invite you to read descriptions of the SSEP experiments that have already flown.
Stepping back from these discussions for a moment, it’s important to recognize that this is science. It’s challenging. It’s emotionally rewarding to come up with a brave new idea—a new hypothesis—to test. It’s a journey of exploration … owned by you. And at the most fundamental level, as I said before, science is really just organized curiosity. To do it, you just need to reconnect with that spirit of curiosity that lives within you. And we’re giving you the chance to put forward a hypothesis and propose an experimental test of that hypothesis … aboard the International Space Station, America’s National Laboratory in orbit.
Rocket Science, Scientists, Engineers, and … You
This isn’t ‘rocket science’, well … actually, it is:) Which means that rocket science, when boiled down to the basics, is not that hard to wrap your head around and can be a great deal of fun. It’s what scientists and engineers get paid to do.
Curriculum Support Documents for Experiment Design in the Document Library
The examples of experiments provided in the sections above are just a handful of what one gleans from a careful classroom exploration of the SSEP Microgravity Science Background and Microgravity Experiment Case Studies documents, which are meant to provide a primer on the categories of science that might be undertaken in microgravity and why, and to provide inspiration and guidance for what kinds of experiments might be proposed. Both documents are found in the Document Library. They offer a great starting point for teachers to get students thinking about experiment possibilities.
The documents address 9 basic categories of microgravity science: Bacteria, Cell Biology, Fish and Other Aquatic Life, Fluid Diffusion, Food Products, Inorganic Crystal Growth, Microencapsulation, Protein Crystal Growth, and Seed & Plant Studies. For each category these documents provide the science background, why research in this category is important, why gravity is thought to play a role, why experiments with gravity ‘turned-off’ have been done, and the kinds of experiments that might be performed in the mini-lab.
It is also important to point out that for SSEP on the Space Shuttle, the experiment samples (fluids and/or solids) that students used for their experiments had to be selected from a Master List of Experiment Samples, which is an extensive list of non-toxic samples by science category. But for SSEP on the International Space Station there is no longer a requirement to specifically use experiment samples on this list. However, the Master List of Experiment Samples is still provided in the Document Library as a useful list of samples to consider for experiment design across multiple disciplines.
Now that you’ve gotten a sense of the flight experiment opportunity and the basic philosophy of SSEP experiment design, here are some next steps—
If you arrived on this page from the More on SSEP main page, and you’re exploring whether your community would be interested in participating in SSEP, you may want to go back to the More on SSEP main page, and continue reading.
If your community is already participating in SSEP, and you’re here to gain basic insight into SSEP experiment design philosophy, then other pages of interest include:
The SSEP Flight Opportunities to Date main page, where you will find an overview of the flight opportunity in which your community is engaged, and whose sub-pages include your flight’s Critical Timeline with important milestone events and deadlines, and a great overview of your flight’s Mini-Laboratory Operation. You need to understand how your assigned mini-lab works, its specifications, and the constraints it imposes on your experimental design so you can start noodling an experiment that your team can propose to fly. Here’s your chance to be a scientist right now.
The Teacher and Student Resources main page, which provides an overview of all the resources we’ve made available to you, including the Document Library and FAQ, and—for teachers—the extremely helpful resource titled: To Teachers—How to Move Forward, which provides a straightforward, easy-to-follow recipe of tasks from program start to submission of flight experiment proposals.