An Earthling's Guide to Outer Space

by Bob McDonald

  You don’t need to go to the space station to find your space height, though. Try standing against a wall and have your friend place a pencil flat across the top of your head to mark how tall you are. Then lie down on the floor and have your friend make a mark right under your heel and another at the top of your head. Measure the difference between the two marks on the floor and compare it to your height on the wall. The floor marks should be slightly farther apart because your spine expanded slightly when you lay down.

  Another body part affected in space is the eye. Some space farers see more clearly in space, especially those who need glasses on Earth. For others, their eyesight gets worse. Our eyes work in a way similar to cameras. Our eyeballs are shaped like round balls and are filled with a clear liquid. A lens on the front lets light in and makes an image on a screen, called the retina, located on the backside of the eye. The retina sends that image up to the brain through a nerve that comes out of the back of the eyeball. This whole system works together so that we can see.

  The eyeball is not always perfectly round, though. Some people’s eyes are a little less spherical, so the lens does not make a clear image on the retina and they see the world as a blur. Glasses or contact lenses in front of the eye can correct the issue by focusing the light in the right way.

  In the weightlessness of space, eyeballs that aren’t perfectly spherical sometimes become more rounded. The lenses focus in the right spot, which means those happy astronauts can put their glasses away for a while. Others, especially those who stay up in space for half a year at a time, find their vision gets worse and stays that way after they return to Earth. Doctors have found that extra fluid gathers in the brain and puts pressure on the eyes in space. In some cases, the optic nerve—the power cable that comes out of the eye and sends the image signal to the brain—becomes squeezed and bent from the pressure, so the signal to the brain is not as good. So far, there’s no way of knowing who will experience better or worse vision in space.

  If you are the type of person who feels queasy on a roller coaster, gets seasick on a boat, or doesn’t feel well while riding in the back seat of a car, you may not enjoy flying in space, at least for the first day or two.

  Motion sickness happens when our brain gets confused about what is happening to the body. Typically, the brain uses a variety of mechanisms to tell whether we are standing, sitting, moving forward or backward, turning left or right, spinning, or falling. The main input is through the eyes, which can see the world moving when we move.

  But the brain also uses sensors in our skin—located on the bottoms of our feet, our hands, and our butts—so that we can feel pressure coming from different directions. Our ears act as important sensors, too. Behind our eardrums are little tubes called semicircular canals that are filled with liquid. When we move our heads, these liquids slosh around to tell the brain that the head is moving. It’s those liquid movements in our ears that help us keep our balance when we walk.

  On Earth, all of these sensory inputs usually agree with each other. What the eyes see, the body feels, and that gives us a pretty good idea of where we are going. In space, the eyes still work, but most of the other sensors shut down. The body is floating all the time, so there’s very little pressure on the skin. The fluids in the ears swirl around in all directions, telling the brain that the body is falling, which it actually is (recall that weightlessness is just falling all the way around the Earth without hitting it). As a result, our brains in space get mixed messages. The eyes are saying the body is not moving, while the body is saying it is but doesn’t know in which direction. Whenever the brain gets confused, we react by feeling dizzy. And the brain, wondering what’s wrong, assumes the problems are due to some bad food you ate. It makes you sick, emptying your stomach just to rule out that possibility. About half of the people who fly in space feel nauseated for their first day or two.

  It doesn’t help that our digestive system is meant for Earth and counts on gravity to make it work. When we eat food or take a drink, we also swallow a bit of air. This accumulates in our stomach and forms bubbles, which rise to the top of the stomach and travel up our throats in the form of burps. Later, as our digestive system breaks down the food, bacteria that live in our gut produce other gases, such as methane, which accumulate in our lower bowel, form bubbles, and burst out of the other end.

  In space, these bubbles still form, but because there’s no downward pull of gravity, the bubbles don’t rise to our mouths. Instead, they remain suspended in the stomach or the intestines, giving a feeling of “foaminess” in the stomach. Astronauts feel like they want to burp, but it doesn’t happen, and if they do manage to get something up, let’s just say it’s usually pretty wet.

  Finally, there’s something we all have to do that no one likes to talk about, but I’m going to do it anyhow. How do you go to the bathroom in space?

  A space toilet looks a lot like its counterpart on Earth, with a few important differences. Two bars swing out across your thighs to keep you from floating off the seat, which is soft so that it feels comfortable and conforms to your body. There are also foot restraints so you really feel like you are sitting—remember, people don’t sit in space, they just float all the time, even while eating meals. But going to the toilet is something we like to do while sitting, so the space toilet is designed to make it feel like home.

  Inside the toilet is a fan that draws air in under the seat and out through the bottom to act as a flush instead of water. The air flow makes sure that whatever you deposit in the toilet goes in the right direction. If all you need to do is pee, there is a suction hose with a cup on the end that is custom made for each crew member.

  When everything is done, you use hand wipes to clean up, then the toilet lid is closed and the waste material inside is exposed to the vacuum of space, which freeze-dries it and kills all the bacteria.

  That covers just a few of the unusual things that happen to the human body in outer space. But the truth is, we’re still learning about the effects of zero gravity on our bodies, and as we learn more, we’ll no doubt make further discoveries that alter how we conduct space travel.

  One thing we know for sure is that flying in space is wonderful, but it takes astronauts away from their families and away from nature. Life in space is life spent in a tin can. Even if you’re lucky enough to go on a space walk, you have to wear a bulky space suit, so you are not really outside or in nature. On very long journeys, astronauts begin to miss their family and friends, the smell of flowers, and the feeling of wind and rain on their faces. Fortunately, they now have access to the internet, so they can make regular calls to home.

  If you’re a person who can stay strong by exercising every day, doesn’t get dizzy while moving in all directions, is willing to risk poor eyesight, doesn’t mind having a foamy stomach, and is okay being away from friends and family for long periods of time, you could be astronaut material!

  YOU TRY IT! Space Face

  Put on your space face and find out what you will look like when you leave Earth.

  WHAT YOU NEED

  A handheld mirror

  A phone camera

  Floor space near a wall

  A friend to help

  WHAT TO DO

  Using the phone camera, take two close-up selfies showing just your face. Smile in one of them and keep a straight face in the other.

  Have your friend help you stand on your head with your back and feet up against the wall for support.

  While you are on your head, ask your friend to hold the mirror in front of your face so you can see yourself. Notice how different you look!

  Have your friend turn the phone camera upside down and take two close-ups of your face, one smiling and one straight.

  Compare how your face looks when you are standing upright and when you are on your head.

  You now have your space face on!

  When you turn upside down, the fluids in your body shift toward your head, making your face puffy an
d pink. Everyone—from Yuri Gagarin, the first person in space, to people living on the International Space Station today—looks different in orbit than they do on the ground. The force of gravity no longer keeps fluids down into the lower body, so the face becomes rounder. Astronauts are sometimes surprised at how different they look when they catch their reflection in a mirror while in space.

  19 How Do You Get Around in Space?

  Have you ever wanted to ride a rocket? Getting around in space is very different from getting around here on the ground. You can’t go anywhere in a straight line because everything in space is moving in circles. And it’s moving really fast!

  The first part of getting around in space is simply getting to space. Getting there means riding a rocket, the fastest vehicle there is. Why can rockets fly us through outer space but airplanes can’t? The biggest reason is that there is no air in space, and airplanes just don’t work when there is no air. There’s nothing for the wings to fly through, and no oxygen for the engines to burn. Airplanes only get you so far.

  Rockets work using a simple principle called action and reaction. Hot gases burn in the engine and blow out the bottom. That’s action. The rocket moves in the opposite direction, which is the reaction. Gases go down, rocket goes up. It’s basically a controlled explosion.

  The only problem is that gases are very light and rockets are very heavy, so it takes a lot of gas to move the rocket. That’s why they need so much fuel. In fact, most of a rocket is fuel. The part of the rocket that actually makes it to space is within the small nose cone at the top. The rest of the vehicle usually drops into the ocean or burns up in the atmosphere, although some modern rocket boosters can be brought back and used again.

  When you see a rocket launching, it starts by rising straight up from the ground. That makes sense, because space is straight over our heads. But if a rocket only goes up, when it gets to space and the engines are turned off, gravity will pull it straight back down again. That would be a pretty short trip.

  So, rockets head upward at the beginning until they rise up above the thickest part of the atmosphere. At that point, they switch and arc overhead toward the horizon because they need to outrun gravity. In order to outrun gravity and use it to help you get around in space, you have to go fast. Very fast—thirty thousand kilometers per hour, to be exact. That’s ten times faster than the speed of a rifle bullet.

  So a rocket must go from a standing start to faster than a speeding bullet in only eight minutes. That’s not a lot of time, and for anyone riding the rocket, it’s quite an experience. You lie on your back facing the open sky as a huge rumble begins far below. At liftoff, you are pushed into your seat as you shoot straight up, accelerating faster and faster every second on a ride that is like no other. Everything shakes as your body gains weight from the increasing speed. Some astronauts say it’s like an elephant is standing on your chest.

  Once we launch a rocket into the air, we need to get it to space and make it stay up there. The path that rockets make through the air is a very special curve. It’s called a ballistic curve, and everything that falls freely through the air without wings—from basketballs and baseballs, to bullets and rockets—follows the same kind of arcing curve.

  When you throw a ball, it travels forward, but at the same time, gravity is always pulling it down toward the ground. The two forces acting together means that the ball follows a curve. Throw it harder, that curve flattens out a little and the ball travels a little farther. The harder you throw, the flatter its ballistic curve becomes.

  Now let’s suppose you were a superhero and could throw the ball at super speed. A very hard throw would send the ball flying right over the horizon. And if you made a miracle throw that moved at thirty thousand kilometers per hour, something very special would happen: you’d be able to throw the ball right around the Earth.

  At that speed, the curve that the ball follows is the same as the curve of the Earth itself. Gravity is still pulling the ball down, but it never hits the ground. Instead, it would fly all the way around the planet, eventually ending up right back where it started! An orbit, then, is just a ballistic curve that has wrapped itself in a circle that goes all the way around the Earth.

  It would take about an hour and a half for the ball (moving at thirty thousand kilometers per hour) to make the trip around the world. If, after ninety minutes, you were still standing in the same spot wondering where the ball went, you could get hit in the back of the head!

  It doesn’t matter what you throw into space, if you can get it above the atmosphere and moving at the right speed of about thirty thousand kilometers per hour, that object will orbit around and around the Earth and not come down. In spaceflight, what goes up… stays up.

  Throwing a ball into orbit is one thing. But what if you wanted to put yourself into orbit to meet someone else who was already up there?

  Suppose you want to visit the International Space Station. The station is already in orbit, following a big circle around the Earth. At the same time, the Earth is turning beneath it. So you have to wait until your launchpad passes right under the orbit of the station, then take off at just the right moment so that you can catch up to the station along the same path. If you launch at the wrong time, you will miss it. That’s why rockets have a “launch window”: a short period of time when they have to get off the ground. If they miss the window, they have to wait for the next one to come along, which is often the next day.

  It usually takes more than a day of circling the Earth to catch the space station. It’s similar to runners in a relay race. As one person is speeding around the track, a second runner, waiting on the same track, starts out as the first one passes by, matching their speed and accepting the baton. In space, this game of orbital catch-up is called a rendezvous.

  To go farther than Earth’s orbit, you have to do the same thing, just on a bigger scale. Let’s say you want to go to Mars. The Earth has a particular orbit around the sun, but Mars, being farther away from the sun, is following a different, bigger circle around our central star and traveling through space at a different speed than Earth—planets that are closer to the sun move faster than those that are farther away.

  So, to travel between the two planets, you first have to wait until both of them are on the same side of the sun. Mars takes twice as long to circle the sun as we do, so sometimes the Earth gets ahead, like a speed skater on the inside track. You don’t want to make the trip when we are on opposite sides of the sun because it would take more than a year to make the journey, which is far too long. If you make your trip when the planets are closest together—still fifty million kilometers apart—it takes only six or seven months.

  To get to Mars, you’d have to fire your rockets even faster than if you’re just orbiting Earth. But you couldn’t just point your spaceship at your destination. Remember, Mars and Earth are both moving. That means you’d have to aim at the spot where Mars would be by the time you arrive. So you’d calculate the speed of Mars, the speed of the Earth, and the speed of your rocket to make it all work.

  When you reach Mars, you’ll be captured by the gravity of the planet. At that point, you’ll either go into orbit around it or you might land on the surface. Hope you have a great time there. But don’t forget to come home.

  To do that, take the same path in reverse. Wait until the Earth comes close, and then spiral back around the sun, making your circle smaller and smaller until you meet your home planet. This is not as easy as it sounds because if you leave too early or too late, or if you go too fast or too slow, you can miss the Earth altogether. Make a mistake and you’ll be lost in space!

  Obviously, we have yet to send a person to Mars, but maybe one day we will, once we figure out how to do so safely. For now, only unmanned spacecraft are sent from one planet to another, and those spacecraft can take months or even years to reach their destinations. And because the solar system is so big and the spacecraft are traveling so far, it takes just a little error to miss the
target. More than one spacecraft has missed its planet and ended up wandering around the sun as a piece of space junk!

  Today’s rockets are not very efficient. In many ways, they’re like bullets shot from a gun—they get all their energy at the beginning of their flight and spend the rest of the journey coasting on their own. Sure, they get you to space, but they use up a lot of fuel, which makes them expensive to run. They also don’t run very long. Those thirsty rocket engines gobble up all of their fuel in only a few minutes.

  But it doesn’t have to be that way. Engineers are working on other types of engines that burn more slowly and for a longer period of time. One such, called an ion engine, doesn’t put out a lot of power, but it can run for more than a year without stopping. It’s a little slow at the beginning, but after a year of pushing and pushing, it can actually end up going faster than the rockets we use now.

  Our planet has been called Spaceship Earth because it’s flying through space at more than one hundred thousand kilometers per hour as we orbit the sun. That’s thirty kilometers every second! What if we could use the speed of the Earth around the sun as a slingshot to boost our spacecraft to other planets?

  If we sent our spacecraft on a long orbit that includes the ship looping back to the Earth, the gravity of the Earth will pull the spacecraft ahead so the speed of the Earth through space is added to the speed of the spacecraft when it passes by, giving the ship the extra boost it needs to make it to another planet. It takes a lot longer to get to its destination, but it uses a whole lot less fuel.

  This maneuver is called a gravity slingshot. The Voyager mission—which sent twin robot spacecraft to Jupiter and Saturn—was the longest journey to use this kind of energy transfer. One of the twins, Voyager 2, took advantage of the fact that all four of the largest planets in our solar system lined up on the same side of the sun at the same time. Voyager 2 was first sent to Jupiter… which threw it to Saturn… then the gravity of Saturn tossed it to Uranus… and Uranus boosted it to Neptune… and Neptune kicked it right out of the solar system. It took Voyager 2 twelve years to get to Neptune. That may seem like a long time, but without the gravity slingshots from all those planets, it would have taken more than twenty years to make the trip.