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JSC: What is Microgravity? - NASA

Sherri Jurls is speaking on the screen.

View of the Johnson Space Center from the air.

Sherri: The astronaut corps building, you can see in the back of your picture there, there's some blue, that represents water. We are just at the coast of the Gulf of Mexico, so just in the horizon area, that you are looking at.

Back to Sherri.

Well again, this is a Web cast being broadcast to you from Johnson Space Center and today we're going to be talking about the topic of microgravity, so I hope all of you have jumped into the chat room and submitted your questions. We have a very special guest with us here today who will be able to answer all of your questions and give us extra information.

His name is Dr. John Charles. Welcome Dr. Charles.

Sherri and Dr. Charles are on the screen.

Dr. Charles: Glad to be here, Sherri.

Sherri: Will you take a moment and tell us a little bit about your background and what you do here at Johnson Space Center?

Dr. Charles: I'd be glad to Sherri.

Dr. Charles is speaking on screen.

I'm a cardiovascular physiologist by training. I now work not so much in the laboratory anymore, cardiovascular physiology by the way is the study of the heart and the blood vessels. I have a Ph.D. in that area but true to typical government service, I'm now working in an area that I'm not trained in and that is I'm helping to plan future space missions, space station missions, space shuttle missions. I'm actually what's called a mission scientist for an upcoming space shuttle flight this July. That'll be a research mission in orbit.

Note that I am not an astronaut, I'm a mission scientist, I'm not a mission specialist. I've not flown in space, but I've imagined myself in space many times and I hope we can talk about some of those imaginings and some of the things I've learned along the way here during our chat today.

Sherri and Dr. Charles on screen.

Sherri: Great. Well are there any special projects that you hope to work on some day? What kind of things do you look forward to in your career?

Dr. Charles is speaking on screen.

Dr. Charles: Well I joined NASA back in the dark ages of the early 1980s. My goal was to join the program that was heading off to the Moon and off to Mars. The work I'm doing now is planning investigations that will support people moving out into space and I'm hopeful that before I retire in the next 15 or 20 years, we will actually have a program to send astronauts beyond the space station, to the Moon and off to Mars or wherever the appropriate destination is.

We find in the life sciences, the problems are pretty much the same whether you're in orbit around the Earth or heading off to the Moon or off to Mars. But it will be exciting to be involved in the exploration program like that.

Sherri speaking on screen.

Sherri: Well I couldn't agree more. It will be very exciting for me as well to see us go out that far. Well let's go ahead and start our program off today. Our topic again is microgravity. Let's go ahead and define what microgravity is so that we make sure we're all on the same page as we're discussing this topic today.

Is it true that it's the same thing or not the same thing as Zero G?

Sherri and Dr. Charles shown on screen.

Dr. Charles: It depends on who you ask. Microgravity is strictly defined as one-millionth of one G, that's sort of a breakeven point for what we call the microgravity science of the fluids and the crystals and the physics experiments that need something like weightlessness. They're very, very sensitive to even slight jitter, and jitter is what violates your micro G, what breaks the level.

In terms of biology, micro G is essentially weightlessness or Zero G. I prefer the term weightlessness or Zero G

Dr. Charles speaking on screen.

because as far as biological specimens like us, or the things I study are concerned, weightlessness is micro G and there's really not much meaningful difference.

Microgravity or weightlessness are achieved by being in orbit around the planet. I think this might be the time to show what the Show and Tell looks like.

Dr. Charles has a model of a rotating Earth and a space ship orbiting the Earth in his hands.

If I have a planet in my hand, let's call it Earth, and I have in my hand also a small representation of a space ship, that space ship is orbiting the planet and here you can see it orbiting the planet. By doing so, it's going in a large circle around the planet.

That circle, because of its velocity, because of the speed given to it by those large rockets on the launch pad, is exactly balancing -- let's see if I can get it over here -- the speed around the planet, exactly balances the effect of gravity pulling it down to the planet. So it doesn't fall because it's going forward so fast that it essentially falls around the planet. (Let's see if I can do this well.) Falling around the planet, it falls toward the Earth, but the Earth also curves away, so the vehicle is falling around the planet and it continues to do that as long as it's not acted on by another force or an external force. And that produces, inside that capsule, or inside that space ship, weightlessness.

Dr. Charles is speaking on screen.

Weightlessness or microgravity. The microgravity comes in because of some more esoteric physics. There's actually a little bit of atmosphere at altitudes, orbital altitudes, and that atmosphere actually slows the shuttle down so that things inside are actually sort of moving a little bit toward the end of the shuttle, toward the nose of the shuttle, not exactly in microgravity. And also there's some effect because of the shuttle being an extended structure, not a point mass.

But for our purposes, when you're in orbit, you're weightless. I think we have a little graphic here to show you what weightlessness might look like here on the ground. There's some ways to mimic this on the Earth.

Graphic showing weightlessness.

One is in an elevator. If you had a high enough elevator and you're brave enough and you push the down button and just let it go all the way to the bottom and took the breaks off, as that elevator falls, you fall with it. You're both accelerated by the force of gravity, 32 feet per second, 9.8 meters per second, per second here on the ground and if the elevator's falling exactly as fast as you and your payload, that apple that the woman is holding in that picture, then you're weightless inside that elevator.

Dr. Charles is speaking on screen.

That's fine until you reach the bottom of the elevator shaft, in which case you stop abruptly. Now the thing about being in orbit is that you don't stop abruptly, you keep falling around the planet, you're just going forward fast enough that the planet curves away from underneath you and you keep going until you fire your retro rockets and come back.

Another way to get the effects of weightlessness here on the Earth is actually a little bit above the Earth, it's the NASA's KC135 Zero G aircraft.

Video showing KC135 aircraft ascending.

Here you see a video of that aircraft going through its maneuver, its parabola out over the Gulf of Mexico. I had a chance to fly in this several times. I've enjoyed it immensely.

Screen within a screen showing passengers on plane in a weightless state.

And here you see the airplane going for-, I think it's an altitude of about 25,000 feet up to a peak of about 35,000 feet, and as they reach that 45 degrees nose up, the pilot chops the throttle back and essentially coasts through that parabola, so everybody inside is falling exactly as fast as the airplane.

Here we're about 45 degrees nose down, the pilot resumes the throttle and pulls out of that dive to go off and do it again.

Dr. Charles is speaking on screen.

You do about 40 parabolas on a typical flight. Those parabolas are provocative, that means they make you-, some people motion sick. The good news is not everybody gets motion sick and of course the bad news is some people get motion sick and the flight, the crew chief on board will tell you, "Cheer up, only 39 more parabolas to go," no matter how sick you are.

So that's, in a nutshell, what weightlessness or microgravity are all about. I'll be glad to expand on those definitions a little bit further if anybody has additional questions.

NASA logo on the screen.

Sherri speaking on screen.

Sherri: Well thank you, Dr. Charles, for explaining to us about the science behind microgravity. I was unsure whether it was just because you flew up in space you started floating, but now we know that there is a scientific reason behind that. And the airplane, that KC135 aircraft you were telling us about, since it is so provocative and maybe upset some of our stomachs, I know that it has a nickname that's the airplane of the "Vomit Comet."

Dr. Charles is speaking on screen.

Dr. Charles: Yeah, the airplane is called a Vomit Comet usually by-, well by a lot of folks, usually the folks that have gotten sick on board the airplane. It's such a prevalent nickname that some people think that's its official name. But in fact it is a KC135. KC is an Air Force designation. It used to be an Air Force tanker. It used to refuel other airplanes on maneuvers around the world.

The 135 just means it's a serial number. It's actually a-, I think it's a Boeing 727 in its first life.

Sherri and Dr. Charles are on screen.

Sherri: Okay. Well is the KC135 aircraft is the only way we can train our astronauts for microgravity environment? Is there like a room they can go in and start floating or?

Dr. Charles is speaking on screen.

Dr. Charles: There is no such thing as weightlessness here on the surface of the Earth. If there was a zero gravity room, NASA would be a whole lot less expensive to fund because we'd all be going to that zero gravity room to do our experiments instead of lining up to fly experiments on a very expensive space shuttle or on other rockets. And there are ways we can mimic parts of the weightless experience depending on what you're trying to mimic.

Video showing astronauts moving around in the neutral buoyancy laboratory.

We have some video here showing what it looks like to be underwater in something that's called a neutral buoyancy laboratory, which is just NASA-speak for a very large water tank. The water tank is large enough that you can actually-, they have actually built a mock up of the space station inside of it where the astronauts inside those space suits are buoyed or balanced with lead weights on the outside such that they are neutrally buoyant. That is they don't sink or rise inside the water.

When they are positioned in the water, they stay where they are. That lets them pretend to be weightless inside that big water tank, so they can do weightless activities that might be required outside of the space station. Now keep in mind that they are not weightless inside those suits.

Inside those suits, they still feel the effects of gravity. They are simply floating much like you float in a pool. But inside those suits, if they're standing upright with respect to gravity, their feet are on the soles of the boots and their heads are down inside their helmets. And if somebody turns them upside down, or if they go upside down as a maneuver, they are resting on their shoulders, and the blood is rushing to their head.

So they're only weightless with respect to the effect of-, with respect to the space station mock up or the other activities they're doing in the tank. But inside their bodies, inside those suits, they still feel gravity.

Sherri and Dr. Charles on screen.

Sherri: Wow, well thank you for showing us this live footage of the astronauts training right now and describing to us what we're seeing. Wow! Fascinating.

Sherri is speaking on screen.

Well let's go ahead and start taking your questions. The first one is from Matt of the Belmont Career Center in Ohio. And Dr. Charles, Matt wants to know if the feeling of being in space can become addictive?

Dr. Charles is speaking on screen.

Dr. Charles: Well it certainly can. Like I said, my experience on the KC135 where you get 20 seconds or so of weightlessness and about almost a minute of hypergravity, that's about 1.5 or 2 Gs repeated periodically for 24 parabolas at a time, or 40 parabolas at a time,

Video showing astronauts weightless on the KC135.

that experience is perhaps not addictive in the clinical sense, but it is addictive in the sense that you enjoy being weightless so much that you don't mind the hypergravity portions in-between.

Dr. Charles is speaking on screen.

It's fun to sort of fly through the cabin if you're allowed to, like Superman. It's fun to immediately go upside down, which is the first thing I always did in weightlessness was to put my feet on the ceiling and walk around, or try to walk around. Being tall like I am, I was able to reach my feet on the ceiling and reach the floor with my hands, so I could actually push myself against the ceiling and walk along the length of the airplane.

But you've got to keep in mind that it's only for 20 seconds, and at the end of that 20 seconds, when the plane pulls out of that dive, you're going to fall to the floor with your normal gravity weight or even more. So you want to make sure that anything that's aimed toward the floor at the end of that parabola is not fragile, like your head, your neck, or maybe your face if you're a movie star.

So the deal here is that it is fun and it's a way to experience weightlessness, and it can be considered addictive. I certainly miss flying. I don't get a chance to fly much anymore because I'm not into the management aspects instead of actually doing the experiments. It's a lot of fun to do it in the aircraft, and I imagine some folks would consider it addictive. But it's not clinically addictive. You don't build up a resistance to it or anything like that.

Sherri and Dr. Charles shown on screen.

Sherri: Well Joanna, Laura, Nana and Mary, and I hope I said all your names right, from Nightingale Middle School, write in and they want to know if astronauts get tired of living in space for such extended periods of time like they are in the space station right now, four or five months at a time.

Dr. Charles is speaking on screen.

Dr. Charles: The Russian space program in the 1980s and 1990s figured out that about a six-month tour of duty on the Mir station was the right length of time to have people on the space station. After six months, they started getting jaded or tired or wore out. And less than six months they didn't feel like they'd really gotten maximum efficiency. They hadn't really adapted to weightlessness yet and hadn't been able to apply their training on the ground to the tasks they were sent up to do.

I don't know if you can really get tired of it. I think your body does adjust to weightlessness in ways that are perhaps less than appropriate when you come back to the ground. But I imagine it depends on the individual. Some people probably would get tired after a couple of hours or a couple of days on a short flight and some folks might think six months or even a year or a year and a half would not be long enough in space.

If we send people off to Mars some day in the hopefully not-too-distant future, maybe the next 20 years or so, we may be looking at missions that are 2.5 years long. So our six-month trips in the space station right now would seem like a weekend jaunt I suspect to those people.

Sherri speaking on screen.

Sherri: Okay, and Joel would like to know if food tastes any different in a microgravity environment.

Dr. Charles is speaking on screen.

Dr. Charles: Well Joe, that's an interesting question too. I'm not an astronaut, I haven't flown, so I only know what they tell us. But there's a lot of effort made to make the food as interesting and appealing as possible because of a phenomenon that you're talking about, and that is there seems to be some blunting of the taste of food reported by the astronauts in space flight.

It may be because of some of the changes that occur in the human body in weightlessness. One of the ones that has been speculated on the most is the headward fluid shift, that is the distribution of body fluids, the juice inside your body essentially, from the lower body into the upper body, causing your face to feel puffy or your upper body to sort of fill out, your legs to get skinnier.

There's been some thought that perhaps that actually accumulates not just in the head.

Split screen picture showing on the left side of the screen a human form profile and on the right side of the screen a hand holding a balloon filled with fluid.

Here you can see a video of how the fluids are distributed on the ground. You see that balloon is at 1 G, and now as we go into weightlessness in our KC135, you see the balloon becomes more spherical and the body fluids are distributed more into the upper part of the body, especially in the head. That may fill up your sinuses, may interfere with your sense of smell

Split picture on screen showing astronaut with regular face on the left side of the screen, and the astronaut with a puffy face on the right side of the screen.

and some folks have…

Here you can see a picture of an astronaut before flight and in flight and see how puffy his face gets in flight there.

Dr. Charles speaking on screen.

If you're a person that depends heavily on your sense of smell in flight-, or when you enjoy food, then you may find some changes. Astronauts routinely say that food doesn't taste the same in flight. We do fly extra condiments for them, extra hot sauce and salt especially and pepper to sprinkle on the food.

But this looks like an entrée into talking about food in general. What do you think Sherri?

Sherri and Dr. Charles on screen.

Maybe we ought to be talking about food in general.

Sherri: I think that's a great idea.

Dr. Charles: I'm going to show you, I'm going to try and raise it up here so the camera can see it. What a typical meal might look like on the space shuttle.

Sherri: Now I would imagine it's not very easy trying to eat in space.

Dr. Charles: Well I'm told it's not that easy, but I suspect they get used to it. Here we have -- let's see if we can get this.

Sherri is holding a packaged meal and Dr. Charles is demonstrating how it is consumed by the astronauts.

Will you hold that, okay. There's the typical food. This looks like here's your vanilla instant breakfast. This is an instant breakfast inside this Mylar aluminized pouch. You squirt water into it. You knead it to mix it all up and then you suck it out through the nozzle with a little valve on the end here that allows you to close off that nozzle so it doesn't keep squirting after you've finished squeezing.

Sherri: Yeah we don't want that vanilla instant breakfast all over the shuttle.

Dr. Charles: All over us, yeah. We also have apple cider. You drink it the same way. You squirt water into it and then knead it and then suck it out of the little tube at the end.

Sherri: So you can't just go get a drink out of the faucet or anything?

Dr. Charles: No, there's no such thing as a faucet and a glass sitting there waiting for it. You have to contain your fluids inside pouches of some sort, bags of some sort.

Sherri: What would water do?

Dr. Charles: Well you saw that video a second ago of that balloon in weightlessness. The water would blob up into a sphere and essentially stay wherever you put it or float wherever you pushed it.

Dr. Charles is speaking on screen.

Astronauts do like to play with their food, unlike students and youngsters. Astronauts will play with the food and float it in the middle of the cabin and attack it and push it back and forth. They like to play with blobs of drinking fluids and attack them, sort of sneak up on them like sharks and swallow them. They like to play with other food items that you might also recognize.

Let me show you one that you will recognize right away.

Dr. Charles on screen holding up a clear package of M&Ms.

If you can see that, that is a package of M&Ms and they're just like M&Ms that you would buy off the shelf. And my favorite snack too. And who knows how many calories I've gained eating M&Ms. This is the kind of food that can be-, let's look at a video here of water floating in the cabin.

Video of water globule floating in the cabin.

I told you about the beverages being squirted out of the container. There's what water would look like floating in the cabin.

Sherri: So it doesn't separate into droplets I see.

Dr. Charles: It doesn't separate into droplets because it's held together by surface tension. What you see inside that blob of water or also bubbles. And you can also put things here. The Japanese astronaut has put a couple of little flower buds inside the water to make it more attractive. Sort of a Zero G vase for your flowers.

Video of Japanese astronaut sucking up water globule.

And here's the astronaut then sucking up a different, I hope, a different bubble of water. I hope he hasn't got the flowers inside there.

Dr. Charles speaking on screen.

Sherri: Okay so what about the food?

Sherri and Dr. Charles on screen.

Dr. Charles: Well other food items do not require the special packaging as the beverages. Here we have just a plain old sausage patty, just like you might pick up at Bob Evans or someplace like that. Again it has to be, it's dehydrated. You have to squirt hot water into it and let it sort of soak up the water and get up to the temperature you'd like to eat it at.

Dr. Charles speaking on screen and holding up foods.

Here are scrambled eggs to go with your sausage, and they are just like camping food you might have if you go on a camping trip. You squirt hot water in there and knead it and then cut the bag open and use a spoon and eat it. And also have oatmeal with-, this is oatmeal with raisins and spice. The same kind of thing just like you get out of your packet of oatmeal in the morning.

And this for dessert, if you've been a good-, if you've eaten all your dinner you get pudding. And pudding is served to you just like it would be off the grocery store shelf.

Sherri: Now why are you having to pull these off of the tray?

Sherri and Dr. Charles on screen demonstrating attaching food to Velcro tray.

Dr. Charles: Well because we have a zero gravity tray. All of the food may be normal. The environment is not normal and so if you're going to eat in space, you probably want to keep all your meal items together and you do that by putting them with Velcro onto a zero gravity tray table or a table. And this way you keep all the items together, they don't drift off, you don't have to go chasing your shrimp cocktail while you're eating it, unless you enjoy doing that sort of thing.

This tray table can be strapped to your leg. You see there's a strap on the back so you can just sort of make a lap table out of it or you can Velcro it to the convenient wall or whatever suits your fancy in terms of food and how you prefer to eat it in weightlessness.

Sherri speaking on screen.

Sherri: Well I know we have a short video clip of our astronauts trying to have a little fun with their food up in space in this microgravity environment. Let's share it with our guests out there in worldwide Web land.

Video showing astronauts eating various foods in weightlessness.

Sherri and Dr. Charles on screen.

Sherri: I don't know about you guys, but that looks like a lot of fun. I sure would like to chase my M&Ms down the inside of the space station.

Sherri speaking on screen.

Well Jeff writes in and wants to know how microgravity affects our bodily systems, if at all.

Dr. Charles speaking on screen.

Dr. Charles: Jeff, the answer to that is a question, that's actually a question I've dedicated my life and my career to. So we may spend the rest of the hour talking about just that thing.

Very generally, microgravity does affect all of our bodily systems, some bodily systems like the sense of balance -- I'm pointing toward my ears where my vestibular system is, our blood, our heart, our blood vessels, our heart, the blood in our blood vessels. All those things are affected by gravity in the short term. I can show you some video here maybe along the way. Okay.

Also extended weightlessness will affect things like bones and muscles as well.

Video showing astronauts exercising on a treadmill in the cabin.

It depends on how much time you spend in weightlessness, how much of your body is affected and how drastically your body is affected.

Back to Dr. Charles.

Short flights, like the early Mercury flights of the 1960s where the astronauts are only in orbit for a few hours or maybe a day at the most, didn't have as big an effect on the body as later flights on space stations like the Mir space station where some astronauts and cosmonauts stayed up for six months or even a year or longer than a year.

Things happen gradually in the human body. The vestibular system, the cardiovascular system, those changes occur fairly quickly within the first several days.

Video showing vestibular system.

Here's a cut away view of somebody's skull, showing the vestibular system, the organs of balance inside the inner ear, with the little stones in your head. You actually have rocks in your head, they're called otoliths. This is all embedded in the otoconial membrane, but that's not important.

The important part is as these little stones inside your inner ear are attached to hair cells, which are themselves attached to nerve endings, and as those otoliths are moved by gravity or by acceleration, they signal to the brain which way you're moving and how fast you're moving and how intense gravity is.

Back to Dr. Charles.

In weightlessness, those little hair cells are stimulated in a different way. They're still stimulated, but instead of signaling when your head is tilted, which is what I'm doing now, I'm tilting my head and my inner ear is signaling to my brain how my head is tilted. If I do that in weightlessness, my inner ear does not signal, because it doesn't sense the shifting of those little stones inside of my inner ear.

It does sense, however the absence of gravity altogether, and that can confuse, if you pardon the expression, confuse the brain and require some adjustments, some learning. Luckily the brain and the vestibular system seem to adapt to weightlessness. I shouldn't say adapt, but they start getting accustomed to weightlessness fairly quickly, within the first several hours. Many astronauts feel some queasiness some discomfort, some motion sickness early, early in flight, within the first several hours of flight.

Picture of human body in profile.

But usually after one day or even at the most two days, that has pretty much gone away.

Picture of human head and torso showing brain, heart, and kidneys.

They've learned how to move around and feel normal in weightlessness.

The adaptation continues for the remainder of the time on flight though.

Back to Dr. Charles.

Also your cardiovascular system, the system that holds the blood inside the blood vessels, is immediately affected by weightlessness because the fluid volume inside the body, when you go into weightlessness, that fluid volume shifts into the upper part of the body, causing that facial fullness we talked about before and also filling up the heard and filling up the blood vessels and the lungs.

The body doesn't really -- I hate to say it again, doesn't really care for that. That's not normal for the body, so the body acts to reduce that filling by other things, opening up blood vessels so the blood can sort of move throughout the body more conveniently. By eliminating fluids perhaps through increased urination or even vomiting. Perhaps the vomiting is part of the fluid control. And by decreasing your thirst and things like that.

So after several days, your body has started to reduce its internal blood volume, it's internal fluid volume. Astronauts that fly flights as short as four or five days come back to the Earth with a reduced blood volume, about equivalent to one or two blood donations, depending on how much, depending on individuals. They haven't lost blood, but they've lost the watery part of the blood. The water that makes up the plasma has been eliminated through the processes I have described, which has the effect of concentrating but decreasing the amount of blood in the body. So the blood is actually reduced and when you stand up after a space flight, and you need the blood to go to your head, against the force of gravity, you might find that you've got a little bit too little blood to make that convenient, to make that function efficiently.

That process continues, probably for the first several weeks in flight. After about 30 days or so on space flights, your cardiovascular system has adapted to weightlessness. But after 30 days, your bones are only just starting to adapt to weightlessness. Your bones may lose about 1 or 1.5% of their bone density, of their stuff every month in flight. Some people think it doesn't really start for the first month or two, some think it's really 1.5% vs. 1%. The measurements are very difficult to make and they're very approximate. But the point is, with extended periods of time in weightlessness, you do lose stuff out of your bones. You lose the calcium and you lose the protein that holds the calcium in place and you lose the other molecules like phosphate that hold the bone in place.

So after a long enough space flight, you might be at an increased risk for things like fractures. If you were to spend a really, really long time in space, probably longer than a Mars flight, you might be at an increased risk for fracture.

What happens though, as soon as you get into weightlessness, that calcium coming out of the bones does other things. The calcium that comes out of the bones is a very, very, very tiny amount, but it doesn't take very much, if it starts accumulating on certain body areas. And one of the body areas where calcium that leaches out of the bones ends up is in your kidneys, and you may end up with a kidney stone, especially if you're prone to kidney stones. And you might not even know you're prone to kidney stones until you get one.

The risk for kidney stones increases very early in space flight, even though the risk to the bones from which the calcium came to make the kidney stone is not increased for many months in flight. It's a very different story we're talking about. So you've got your organs of balance, your vestibular system, your heart, your blood vessels, your bones, your kidneys, your muscles also lose strength in flight. But it's not as fast as the vestibular system, it's not as slow as the bones. It's someplace in-between.

And astronauts exercise a lot. Astronauts will exercise, or at least they're supposed to exercise two hours a day. That's an hour in the morning and an hour in the afternoon every day they're in flight. So on a six month space flight you are exercising twice a day every single day for six months, unless you get a note from the teacher or a note from your mom or a note from your doctor that says you don't have to exercise that day. But astronauts generally like to exercise. For some reason they think exercise is fun and they will exercise pretty much as much as they need to, especially as the mission comes to a close and they want to get back into good condition, to look good when they come off of the space ship at the end of the flight, and be able to walk around, and squeeze the husband or the wife and hold the kids up and say hi to mom and dad.

So there's a lot of motivation for them to exercise and they work very hard at it. But there are changes and you can tell that do occur in the body. I'll be glad to talk about those in more detail even now or off-line as appropriate.

Sherri and Dr. Charles on screen.

Sherri: Well actually we've had a question come in from Patty when we were talking about the reduction in blood and everything. She wants to know if microgravity makes your heart have to work harder.

Dr. Charles is speaking on screen.

Dr. Charles: In microgravity, the body's fluids shift into the upper part of the body, the heart is filled more than it is standing upright or even sitting upright on the ground. Which causes intrinsic mechanisms, that is the basic mechanism of the heart to squeeze harder to get rid of that fluid volume. The heart works in a certain range of preferred contraction sizes.

So your heart doesn't have to work harder and it doesn't really work less hard either. Your heart does what it has to do to maintain blood pressure. What happens is that the body's fluid volume is adjusting and the filling pressure, that is the amount of blood that's moved into the heart, so the heart sucks up and squirts out each time it beats, that changes in flight.

I'm not real comfortable saying the heart doesn't work as hard or the heart has to work harder. It depends on what you're doing in flight. There may be some tendency over a long period of time for the heart muscle to atrophy, just like your muscles in your arms and your legs would atrophy in weightlessness, because of the other things that happen in your body, especially changes in blood volume in the body. But generally the heart keeps working as hard as it has to to keep you conscious and functioning.

Sherri speaking on screen.

Sherri: Okay. Denise writes in and wants to know if living in microgravity might help some people who have disabilities?

Back to Dr. Charles.

Dr. Charles: That's a great question for the distant future. Living in microgravity might indeed help people that are say burn patients and they need to be floating above the bed instead of laying on the bed and developing bed sores and ulcers and impeded healing. It might be a good place to put heart patients that can't function in gravity anymore. It might be a good place to put people with muscular dystrophy or other degenerative diseases. But the problem is you've got to get them there, and getting them there right now requires a space shuttle or an equivalent kind of rocket which requires high load at the beginning of the flight.

By that I mean high G loads, acceleration forces, danger and risk. Plus to fly safely, you have to be trained to fly safely so you can take care of yourself in an emergency. We don't have ambulances that go into orbit, we don't have taxis that go into orbit yet. They're all very complex machines. And then once you get into space, we don't know enough about what happens to the body. Would the healing process continue as we hope it would?

For example, having your burn patient floating in your Zero G burn ward might be good for the discomfort that would come from putting pressure on the burns, but we don't know whether burns would then heal, or any injury would heal appropriately in space.

So there's plusses and minuses and we're still at too early a stage in our research of the effects of space flight on the human body to say whether it's a good place to take people that have injuries or other things like that. But that's the kind of research that you can spend your time working on and perhaps have an answer to that question by the time you're my age.

Sherri speaking on screen.

Sherri: We look forward to having you on, Denise. Sandy writes in and wants to know if microgravity has any effect upon temperature.

Dr. Charles speaking on screen.

Dr. Charles: I'm not sure what Sandy means. Does she mean-, I wonder if she means the body temperature or does she mean the cabin temperature? The cabin is as warm or as cold as your thermostat makes it. Weightlessness is different from air and it's different from temperature. Weightlessness just means that things are floating inside the cabin instead of falling to the floor. But a weightless room is not the same as a vacuum chamber or anything like that.

You can pull the air out of a chamber for example here on the ground, and we do, we have chambers that are vacuum chambers that are space simulation chambers, to test space ships and space suits. But there's still the full force of gravity. Gravity is on the surface of the Earth, and if you just pull air out of a chamber around, on the surface of the Earth, you're going to have gravity without air.

You need air or you need some sort of medium to transmit temperature so of course inside that vacuum it's going to be whatever temperature vacuums are. Conversely, or inversely, you can have temperature inside of a weightless environment.

Video of astronauts floating around in the spaceship.

The space shuttle, you notice astronauts float around in their shorts and their T shirts or they're wearing socks or they're wearing short sleeves or they wear long sleeves, because the temperature inside of a space station or a space shuttle may be different depending on how close you are to the air duct or the heating element. Maybe different depending on whether there's lots of people around you and all of them contributing their body heat, or whether you're off on and end by yourself. Whether you're on the sunny side of the space station or the dark side of the space station.

Back to Dr. Charles.

So yes there is temperature in weightlessness inside the space ship. Outside the spaceship, you're subject to the temperature of deep space. And on the sunlit side you may be 250 degrees above zero, and on the dark side, you may be 100 degrees or so below zero. But that's an effect of being in the vacuum, that's not-, if you see an astronaut outside in the space shuttle EDA space walk and you see that part of him is in the shadow

Video of astronauts working outside of spaceship on docking module.

but the part that's in the shadow is having sunlight reflected off of it from the space shuttle. So it's not 100 degrees below zero there either.

You can see a little bit more of a shadow on that docking module there. But the point is, in direct sunlight, it's about 250 degrees above zero, and below, in the shade, it's going to be much colder than that.

Sherri speaking on screen.

Sherri: For those of you just joining us, we are broadcasting live from the Johnson Space Center with our very special guest Dr. John Charles answering your questions about the topic of microgravity today. Take a moment, submit your questions into the chat room on the Quest Web site. Do tell us where you are, let us know what state you're in or who's classroom you're in or what school you go to, and we'll call out your name.

Okay, Patty wants to know, since you described that the face gets puffy, does that mean that your legs get skinny?

Dr. Charles speaking on screen.

Dr. Charles: Patty, that's exactly what it means. The fluids shift out of the lower body, the legs and the thighs and even the abdomen into the upper part of the body. Astronauts will talk about their puffy faces, which is sort of like a very expensive face lift, because you fill out all the loose tissue in your face, and any wrinkles you have may sort of get filled in with the body fluids. And they also like the fact, some astronauts especially it seems to be the women, I'm not exactly sure why, seem to like the fact that their legs do get slimmer, even skinny in flight. And you see sometimes in videos, you see astronauts wearing shorts or like I say, shorter pants or like that in weightlessness and they do notice things about their bodies. And they notice those things about each others' bodies.

Split screen showing astronaut's regular face and astronaut's puffy face.

And talking about faces getting puffy, here's that picture again showing an astronaut before flight and in flight with a puffy face. Some people have actually said that they have difficulty reading each other's emotions or moods, because a puffy face is more difficult to read.

Dr. Charles speaking on screen.

They're not accustomed to it. Here you see somebody's legs in weightlessness. It's supposed to look like their legs are skinnier.

Astronauts will talk about the bird legs of space flights. So they do notice that their legs do get skinnier.

Sherri is speaking on screen.

Sherri: Bird legs. That's funny. Okay, Maria writes in and wants to know if microgravity or the effects of microgravity are the same in all parts of the orbit?

Dr. Charles demonstrating with model globe and space shuttle.

Dr. Charles: Marie, if you're in orbit, the microgravity is the same throughout the orbit. Now this is a complicated process and it's going to take some talking, but the deal is if you're in orbit, presumably you're orbiting very close, and the space shuttle orbit is essentially very, very close to the surface of the Earth. About 250 miles up is where the space station is. If you're in an orbit that takes you much higher, say 1,000 miles around the Earth, you're still in orbit. The space shuttle is still falling around the planet and you're still falling around the planet inside that shuttle, so you're still weightless.

Now this gets complicated because we scientists like to complicate things and we talk about microgravity which implies that it's not really weightlessness, there is an additional phenomenon at play. One of the additional phenomenon at play is especially in very low orbits, when we have, when you're orbiting a planet at very, very low altitude, you're still bumping into very few stray molecules of atmosphere. But at five miles a second, you're bumping into an awful lot of those.

Now I'm holding up a tennis ball, it's not going to be easy to see, but you can go out and get a tennis ball, and if you look at the fuzz on the tennis ball, that's about how high the shuttle orbits and that's about how high the atmosphere is, with respect to the Earth. So it's a very, very thin layer of atmosphere, but the shuttle is orbiting just above your thickest part of that, so it can stay in orbit.

At that altitude though, the atmosphere doesn't stop at shuttle altitude. The atmosphere continues getting thinner and thinner and thinner and thinner and thinner all the way out, essentially to infinity. At that altitude, the shuttle is bumping into just a few molecules but it's going so fast and it's so big that it's bumping into a lot of molecules over time.

If you go up higher, you bump into fewer and the orbits last longer. If you're down low, you've heard about things like Sky Lab falling out of orbit or the Mir station falling out of orbit. It's because eventually it'll bump into so many molecules in the atmosphere over a period of years, that it slows them down to the point where they're no longer going at orbital velocity. Then they fall into hopefully into the ocean someplace.

But we talk about microgravity because that deceleration, that slowing down, is constantly occurring. All the time you're in orbit, you're slowing down gradually. And if you're free-floating inside the shuttle, you're slowly drifting towards the forward aspect, the forward end of the shuttle, and if you hit it, then you sort of, you've experienced microgravity.

Also, the effect that -- let's see if I can do this, show you how this looks -- the shuttle, even in orbit around the planet, is not a point. The shuttle is 100 and some odd feet. I think it's 120 feet from stem to stern and in the physics of space flight, that makes a difference. If you're at the exact center of gravity in the shuttle, right in the middle, then you can be weightless. But if you're at the nose or at the tail, you're actually in a slightly, slightly different orbit than the rest of the shuttle, and you're going to be moving at a very, very slightly different velocity, which has the effect of causing microgravity.

So at all points in the orbit, yes, you should be weightless. Neither you nor I could sense with our senses the differences but very, very precise measuring instruments can tell the difference, depending on your location and a particular orbit. In fact experiments do prefer, certain experiments like the microgravity, the science experiments, prefer to be right in the middle of the shuttle where the zero gravity is the highest, the microgravity is the lowest.

Back to Sherri.

Sherri: Well you explained to us that because of microgravity, there's no real up or down and our neuro-vestibular system gets very confused. Well Shari wants to know how does food know to go down?

Back to Dr. Charles.

Dr. Charles: Well Shari, food doesn't go down, it follows the path that it's being pushed. You actually, when you swallow food, your esophagus is not just letting the food drop, it's not like you have a stovepipe in your neck that leads to your stomach, you actually have an esophagus which sort of squeezes the food down. That's called peristalsis, and that food is squeezed on down, just like you squeeze toothpaste out of the bottom of the toothpaste tube.

That works whether you're right-side up or upside down, you can test it yourself. You can stand on your head if you're able to. I was never able to, but if you lay on a chair and hang your head off, you can actually swallow things quite successfully because your body doesn't need gravity to make food go down. Same thing for digestion. The stomach squeezes the food up as it digests it and it squirts it on into the intestine where it's moved around by peristalsis, coming out you know where.

But the same thing happens in the blood vessels as well. Blood is not just contained in these big empty sacs that we call blood vessels. The arteries are actually very muscular and they open and close depending on what the body is going through, the veins can actually open and close and sort of squeeze blood as well. And if the veins are not doing it, the muscles around the veins. The veins are deeply embedded in the muscles of the arms and legs for example and every time you move your arm, you're squeezing blood vessels and you're milking that blood back out of the vein into the upper part of the body or into the body where it comes back to the heart.

So food doesn't have to go down by gravity. Food goes down by mechanisms that Mother Nature provided millions of years ago.

Sherri and Dr. Charles on screen.

Sherri: That's fascinating. Alise would like to know if being on Mars would be like experiencing microgravity.

Dr. Charles: On Mars, Alise, you're going to be feeling what we call hypo-gravity, I call hypo-gravity. That means less than normal gravity. Normal gravity is Earth's one G.

Picture of Mars from outer space.

Mars has about one-third, strictly speaking it's about 38% of Earth's gravity. So if you weighed 100 pounds on Earth, you would weigh on the order of 38 pounds on Mars. I'm not sure how much you weigh, I weigh much more than 100 pounds, and I would like to go to Mars to weigh that much less.

But the deal is different planets may have different gravity, depending on how big they are and how massive they are. Earth we call the standard, so we refer to normal gravity as one G, Earth gravity. Mars is a smaller planet, I don't guess we have a Mars here.

Dr. Charles demonstrating with the model Earth and a tennis ball.

But let's call this little tennis ball the Moon, that's almost the right size for the Moon compared to the Earth. The Moon is much smaller, and it has one-sixth of Earth's gravity.

Now one-sixth G or one-third of a G are much, much different than micro G, because micro G means one one-millionth of a G. So you're still feeling gravity. In fact the Apollo astronauts on the Moon said that after they got used to being on the Moon, they felt perfectly comfortable walking around, bouncing around and maneuvering themselves in the one-sixty gravity.

Picture of astronaut walking on the Moon.

Here's a picture of an astronaut on the Moon. So you see he's standing with his feed down on the ground on the Moon because he feels the effects of gravity. He weighs one-third, if he was to stand on a bathroom scale, the scale would register one-third of what it did back on the Earth. He's still got the same amount of mass, he still has the mass, in his case probably 150 pounds plus 150 pound space suit or so. But his feet are only having to support one-third, or one-sixth of that because of the effect of gravity.

Dr. Charles speaking on screen.

Gravity is going to be a part of every planet we go to and in fact some folks think that living on planets is going to be better than living off of planets because the gravity has some protective effect on the body, it keeps the bones and the muscles and the heart and the vestibular system and everything else a little bit more adapted to Earthly life. And we're even talking about putting artificial gravity into spaceships by perhaps rotating them and making them like a centrifuge, just like if you were to take a bucket with some water tied to a rope and sling it around, the water would stay in the bucket because of something that's like centrifugal force; centrifugal acceleration.

Picture of inside of space station module of the future.

That might actually be better not just for bodies but for engineering as well, because, and this is-, we're looking down the length of a space station module in the future, about 2005 or 2006, and this module will added to the space station which is the centrifuge module. If you look straight down that picture we're showing you and see that circular feature at the far end. That circular feature contains a large centrifuge, a 2-meter or about a six-foot radius centrifuge that we can actually put animals or small specimens on to experience artificial gravity and weightlessness on the space station. A very important facility we hope to have added to the space station to help our understanding of the role of gravity.

Back to Dr. Charles.

We'll then find out whether we need artificial gravity, partial gravity, fractional gravity. Plus the engineers might also like that because perhaps it will make plumbing easier. Imagine building a zero-gravity toilet vs. a 1G toilet. You can imagine the differences and you can imagine that we already know how to build toilets that work at 1G, at Earth gravity. Maybe we need to think about having a rotating space station.

Picture of space shuttle toilet.

Here's a picture of a space shuttle toilet which, if you get past the obvious differences, is very much like an earthly toilet. And I guess I'll save the question I'm sure is going to come up about using the bathroom. The toilet is a toilet. You see the seat that you sit on to do your number two and then you can also see I think off to the side there, you can see a funnel which is how you do your number one. It's the same, it's a funnel for men and for women, different shaped cones in the funnel but the process is the same, and it all uses air flow.

Picture of space station toilet.

This is the toilet on the space station, it's a slightly different looking device but the same general principle. Uses air flow and other things like as a substitute for the absence of gravity, to collect the body's wastes and process them and put them where they're supposed to be out of the way of the astronauts.

Sherri speaking on screen.

Sherri: That's fascinating, thank you. Patty writes in and wants to know if the brain functions differently in space. And have you had to take any measures to help keep the astronauts alert?

Back to Dr. Charles.

Dr. Charles: Patty, that's an interesting question because the brain does seem to function differently in space and especially in weightlessness. Astronauts will comment that they do feel differently in space, not just because they're weightless, but because it's a novel environment. If you're like me, when you go into a new room or a new building or a new city or a new experience, you sort of feel overwhelmed. You feel like there's too much going on, I only feel like I'm only seeing this much of it and there's things going on that I'm not even noticing.

Imagine if you were in an environment which is completely different than you've ever experienced before. Not only is it a new room and a new town and a new city, and a new state, but the physical properties are different. Like you're no longer feeling gravity. You're now weightless and things float around you and if you drop something out of your pocket, you know where to look for it. You bend over and pick it up and there it is.

In space, if you drop something, if you let something go, if something pulls off of a restraint, of a Velcro, it can drift away and you will never see it again until you find out where it drifted off to in a sort of a random pattern. It's a different environment entirely.

That affects some people. In fact, that affects many people, many astronauts in a very profound sense. They do feel that they're at a disadvantage in space. They're still able to do their jobs and they're trained to do very complex jobs, but they do realize that they're at a disadvantage because it's such a different environment. And so they pay very, very close attention to the procedures, to the checklist, to the rules, essentially.

You give them a list of procedures to follow to do any experiment or any activity and you will notice the astronauts almost always carry those procedures around with them all the time because they want to make sure they don't forget and do something that's going to break an experiment or break a piece of the space station or just look bad. You'd hate to do the wrong thing and be laughed at by your fellow astronauts and by Mission Control.

But we laugh about it, we kid about it, but it's a very important part of being an astronaut is knowing what the instructions are and following the instructions. Some astronauts say they read the instructions, they read the instruction book, they look at the switch, they see which way the switch is supposed to be thrown, up, down, then they look at the instructions again to make sure they understand it and they look back at the switch, and then they sort of go up and hold their breath and flip the switch the way they think it's supposed to be. Because they're just not as confident because of the novelty of the environment, that they really understand things as closely, as well as they're used to. And they're all very smart people, accustomed to being very much in control of their bodies and of the environment. So it's a different place for them.

Part of the adaptation of space flight is getting more comfortable in this environment. It could be something as simple as if you come into a module and say you're on the space station, you come into a module from another module, and the floor is not where you expected it to be. You can be completely disoriented. And the module and the space station seem to be built, especially the Russian Mir station, was built so that all the floors were at different angles from each other. So if you left one module and went through the connecting node into another module, the floor was in a different direction than the module he just left.

It's almost like it was designed to be confusing. I think the International Space Station is going to be a little bit better in that regard. I think all the modules are going to have pretty much the floor in the same direction. But the floor doesn't matter, because we store things on the ceiling, on the walls, on the floor. People may be working on the floor, people may be having their feet on the ceiling, doing things on the floor, so if you pop into a module and you see everybody you know upside down, you're going to be disoriented. Even if the floor is where it's supposed to be, you're going to be confused.

And if you see everybody at different angles doing different things, you're going to be even more confused. So there's a lot of mental processing, a lot of higher cognitive function that's required to function safely and efficiently in space flight. That's why some astronauts do feel that there is some alteration of their higher functions, of their efficiency in space, I think.

Sherri and Dr. Charles on screen.

Sherri: We have about seven minutes left. I just want to encourage everyone to try and get your last-minute questions submitted by entering them into the chat room, so we have the opportunity to answer them here for you.

Sherri speaking on screen.

Dr. Charles, Erica heard that the fluids in astronauts' bodies float in microgravity and wants to know if spandex would help that?

Dr. Charles speaking on screen.

Dr. Charles: Well Erica, that's a great idea. Spandex is in fact one of the things that has been considered to help astronauts, not counter the effects of space flight, but to counter the effects of coming back to the ground after a space flight. Spandex would be a tight fabric that would fit around let's say the legs and the lower abdomen, sort of like pantyhose.

Video of space shuttle coming in for a landing.

There are also things like G suits, anti-gravity suits that the astronauts wear when they land on the space shuttle, to keep the fluids not from floating around the body, but from falling to the bottom of their bodies. That's not quite a precise description, but very briefly, I told you earlier how the body fluids are reduced in volume. That is you actually have less fluid, less blood circulating inside the body in space flight because of the normal process of adaptation.

That fluid volume is sort of distributed preferentially, it sort of seems to be accumulating in the upper part of the body. When you come back to the Earth, that reduced fluid volume now is sort of pulled into the lower body, into the legs, into the abdomen, which is fine. You need fluids, you need blood down there, but you'd also like to have blood at the head and the heart.

Back to Dr. Charles.

And if you don't have as much blood as you did when you launched, then there's a chance you're going to be light-headed. You're going to have insufficient perfusion of the brain.

Now Spandex, which has been tested, or these anti-gravity suits, these G suits which are sort of like bladders, they're bladders like jet pilots wear, squeeze the lower body to keep the fluids in the upper part of the body, where the brain and the heart and the lungs are. Because for that brief period of time, you don't need to worry about how much fluid is in your feet and your legs and your abdomen, you need to worry about how much fluid is up in the brain and the heart and the lungs getting oxygen from the lungs, dropping off carbon dioxide and then going to the brain to keep your brain working well.

So Spandex would probably work for returning back to Earth and it has been attempted. The current G suit is now this air bladder suit, but that doesn't mean other work can't be done on things like Spandex to help astronauts make the adaptation back to the gravitational environment of Earth or another planet.

Back to Sherri.

Sherri: Michael wants to know how a paper airplane would fly in microgravity environments.

Back to Dr. Charles.

Dr. Charles: Michael, I bet you if we look hard enough, we probably have some video showing toys in space. And one of the toys that was tested on a shuttle flight as far back as 15 or 17 years ago was a paper airplane. In fact I think Jake Garn was one of the first astronauts that actually had his TV picture made flying a paper airplane.

The paper airplanes generate lift by the air flow, or the flow of air across a curved surface, their wing. And ideally, the tendency of the airplane to settle or to fall in the air is counteracted by the lift generated as the air goes over the wing. If you throw a paper airplane in weightlessness, you can expect that if you've built it perfectly, it will tend to fly up, because there's not gravity pulling it down, and the lift is continuing, so it will tend to fly upwards.

Of course, the paper airplanes I've built never go flat on Earth and they never go without spinning. So I suspect if I was to throw a paper airplane, it would do one of those little nose dives and just fall into the far wall there. But lift is an important phenomenon related to air pressure and air flow and it's going to be related to the shape of the wing. So a paper airplane could work and if you did it well, it would work in weightlessness as well.

Back to Sherri.

Sherri: Well thank you. For those of you who did not have the opportunity to have your questions answered. There will be a FAQ page posted on the Quest Web site, probably about a day delay, so give us a little time. But you can also see the archived event if you want to go back and watch more closely some of the responses that Dr. John Charles gave, and want to take more accurate notes.

I do want to let you know I just found out there won't be a FAQ page, so don't be looking for that, I apologize.

Sherri and Dr. Charles on screen.

Well Dr. John Charles, do you have any final words for those of us who might be interested in studying the kinds of things that you have spent your career doing?

Dr. Charles speaking on screen.

Dr. Charles: The kind of things I'd recommend that you do if you were interested in a career in space life sciences or space research or even an astronaut, which I am not, but I know people who are. I would recommend that you study things that interest you, because more than likely you're going to be doing something related to those things for the rest of your life. Study things that appeal to you. Don't study science and physics if you hate science, physics, math. Don't study mathematics thinking that it's going to get you a good job as an astronaut because the odds against being selected as an astronaut are extremely high.

It's 400-to-1, after you make the next-to-final cut. That's still a very, very steep probability you go up against. Study the things you're interested in. But if you are interested in space flight, it certainly doesn't hurt to get a good background in the science, and the mathematics. Any science, biology, chemistry, physics, astronomy, geology, whatever appeals to you, a good background in mathematics because mathematics is the language of science and essentially the language of the universe.

But I also recommend that you broaden your perspective, that you learn things about things outside of science. Learn about art, learn about music, learn about culture, learn about social studies because we are all people in this together, we all have to work together and the more we understand about the broader perspective, the better we can do in our space science research jobs. And living together in space is just like living together on the Earth.

Back to Sherri.

Sherri and Dr. Charles.

Back to Sherri.

Sherri: Well we want to thank you so much for joining us here today and serving as our subject matter expert. And for all of you out there in worldwide Web land, we want to thank you for spending your time with us as well. On behalf of the Ames Research Center Quest Project and the Distance Learning Outpost here at Johnson Space Center, we hope you have a great afternoon. Good bye.



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