by Bob McDonald
Did you know that there are two moons within the rings of Saturn that come so close to each other you could actually hop from one to the other? The moons are called co-orbitals because they both follow the same orbit around the planet.
Every now and then, the two moons approach on what appears to be a collision course and pass very close. As they do, their gravity starts pulling them together. The moon following behind is pulled ahead faster, thanks to a little gravity slingshot by its partner. At the same time, the moon that’s ahead is dragged back and slows down. Basically, the two moons change positions. The lower moon is boosted to the higher orbit. The upper moon is slowed to the lower one. After this, they continue around Saturn until their next meeting, when they switch again.
These moons are tiny little ice balls only a few kilometers across. If you stood on one, you would weigh almost nothing. The smallest step would send you floating off the surface. So imagine standing on one moon as the other one approached. It would look like the sky is falling as the big ice ball passed overhead. If you jumped straight up at the moment the moon passed over, you could leap to it, landing on it like a fly on the ceiling. That would be your new home until the moon passed close again. Moon hopping—a sport of the future!
ON THE DRAWING BOARD
Scientists are developing a plasma rocket. It uses extremely hot gases that rush out of the engine at a super-high speed, providing thrust. These engines can run for long periods of time—weeks or even months—always pushing spaceships faster and faster, up to speeds that might be fast enough to help us reach other stars. But plasma is extremely hot and can melt the engines. Scientists are working on ways to contain the fuel so the rockets can be used safely.
SPACE PLACES
When astronauts fly in space, they get a lot of attention, but robots can also go where no human has ever gone before. If you want to fly a robot to another planet, one place you have to do it from is the Jet Propulsion Laboratory in California. The JPL is mission control for robots that have been sent to every planet in the solar system. Here, scientists and engineers gather to design, build, and fly the robotic spacecraft that visit other worlds. With colorful names such as Mariner, Voyager, Opportunity, Spirit, and Curiosity, these mechanical explorers have ventured farther and been to more places than any human. (The farthest people have been in space is to the moon, which is in our backyard compared to the other planets.)
When a robot visits a planet for the first time, it simply flies past the planet once, taking as many pictures as possible on the way. Then, other robots follow that go into orbit around the planet, where they remain for years, mapping the surface, watching the seasons change and capturing images of the planet’s moons. Finally, there are the landers that touch down on the surface and the rovers that drive around to show us what we will see when people finally do make it into deep space.
Every flight involves figuring out where the other planets are in their orbits compared to Earth, when the best time is to leave Earth so the robot takes the shortest time to make the trip, and when to arrive so they can hit an exact landing spot on the ground of the other planet. That’s a lot of planning! But it’s worth it for the views of alien worlds that our electronic partners provide.
YOU TRY IT! Blast Off
You can build a simple model rocket using only a few ingredients and materials. Here are three different versions.
WHAT YOU NEED
A long, thin balloon
Baking soda
Vinegar
An empty plastic bottle with its cap (two-liter soda bottle is best)
A pair of scissors or a knife
A skateboard or rollerblades
A heavy rock
WHAT TO DO
Go outside. Blow up the balloon. It’s about to become your rocket. Point the neck to the ground and let it go. The air rushing out is the action; balloon flight is the reaction. You have probably done this at a party, but it is actually rocket propulsion!
The second model rocket is made from a plastic bottle. Take the bottle, baking soda, and vinegar outside.
Using the end of a pair of scissors or a knife, carefully cut a small hole in the center of the plastic cap. Make sure the hole goes through the soft liner on the inside of the cap.
Pour baking soda into the bottle so the bottom is covered about two centimeters deep.
Pour a generous amount of vinegar into the bottle, then quickly screw the cap on.
Place the bottle upside down on the ground, leaned against something so the bottom of the bottle is pointing up. Stand back and admire.
Experiment with different amounts of baking soda and vinegar, as well as the size of the hole, to get the maximum thrust.
Your third rocket model is made with your own body! Stand on a skateboard or wear rollerblades and pick up a large rock, as heavy as you can lift. With your wheels stopped, throw the rock straight out in front of you as hard as you can. You should find yourself rolling backward in the opposite direction. Throwing the rock one way was the action, like a rocket exhaust; the motion of your body in the opposite direction was the reaction. A rock rocket!
20 How Do You Walk in Space?
Taking a walk in space is not as simple as opening a door and stepping outside. In fact, you don’t step out at all; you float out because you are weightless. There’s no air to breathe in space, and radiation from the sun would roast you if you went out there in your normal clothes. So before you open the hatch on a spaceship, you need to learn how to put on a bulky space suit, operate special tools while wearing stiff gloves, handle large objects that would be too heavy to pick up on Earth, and do construction work while floating weightless four hundred kilometers above the Earth with nothing below you.
Sound complicated? It is. It takes years of extra training to walk in space. But the view you get of the Earth and the rest of the universe is worth it.
A space suit is more than a fancy outfit. It’s a one-person spaceship that you wear. It provides you with air to breathe, protects you from harmful radiation, keeps you warm and comfortable, has a radio so you can talk to others, and it even comes with little thrusters so you can fly back to the space station if you drift away—and it has to do all that while being flexible enough for you to work in it.
Space suits evolved from the flight suits used by jet fighter pilots. The first ones were shiny and had a long hose, called an umbilical, that was attached to the spacecraft to provide the astronaut with oxygen. Later, the suits became bigger, with oxygen carried in packs on the back so that astronauts could move freely anywhere, and had many more layers to protect against micrometeorites—small pieces of dust that are always flying through space. You might not think a piece of dust would do much harm, but when it is moving more than thirty thousand kilometers per hour, it can go right through a suit. So underneath the white fabric of today’s space suits are layers of aluminized plastic that act as a shield for the astronaut.
In the future, space suits will be more rugged and more flexible so they can withstand the rocky, dusty conditions of the moon and Mars. They might also fit skintight, like the wet suits that divers wear, providing even more flexibility for climbing cliffs or exploring caves. Apollo astronauts who landed on the moon found their suits quickly became covered in dark dust that clung to everything. They were concerned that, when they came back inside their lander, the dust would get into their equipment and cause problems. Fortunately, that didn’t happen, but one concept for future suits is to always leave them outside. Each suit might have a hatch on the back with a door in it. That hatch would attach to the outside wall of a Mars habitat or the front of a lunar rover so astronauts could crawl in and out of the suit without bringing any dirt inside the vehicle.
Another thing you should know about outer space: it’s cold out there! No, it’s hot out there! No, it’s both!
Space itself is cold. It can reach temperatures of minus 150 degrees Celsius in the shade. At the same time, the sun shines really brightly bec
ause there are no clouds or air to act as filters for the strong rays. In space, anything the sun shines on heats up to 120 degrees Celsius. But it only gets hot on the sunny side. Without air to spread the heat around, like it does for our bodies on Earth, an astronaut’s shady side remains super cold even as the sunny side is super hot. That means there can be almost three hundred degrees of temperature difference between the two sides of an astronaut in space. That’s one reason space suits are white. White reflects sunlight away, so it is not absorbed and turned into heat as much.
To make sure astronauts don’t freeze and fry at the same time, they’re surrounded in water. An undergarment that looks like long underwear has little plastic tubes woven into the fabric with water running through them to keep the astronaut’s body the same temperature on all sides. The temperature of the water can be adjusted up and down. When a spaceship is on the night side of the Earth, it’s in the shadow of the planet where it’s very cold—time to turn up the water heat in the astronaut suit! But wait: the ship is back to the sunny side again—time to cool that suit down. During a space walk, the temperature in the space suit is constantly being adjusted by the astronaut.
While we’ve had many great successes with space walkers over the years, it remains a very perilous activity. It’s safe to say that walking in space is no walk in the park.
On March 18, 1965, Russian cosmonaut Alexei Leonov crawled through the hatch of his Voskhod space capsule and became the world’s first space walker. Floating in the emptiness of space, more than four hundred kilometers above the Earth, he exclaimed, “I feel great!”
He was outside for only twelve minutes, but they were almost the last twelve minutes of his life. Soon, he felt his hands leaving his gloves, and his feet rising out of his space boots. His suit became stiff as it inflated like a giant balloon. His suit wasn’t supposed to do that, but no one had ever worn a suit in a place where there was no air on the outside. The air inside the suit was pushing outward, and the fabric was too loose, so the suit was slowly getting bigger. Leonov found it hard to move his arms and difficult to pull on the long cord that attached him to the spacecraft. As he struggled to get back in, his body temperature rose dangerously high until he was covered in sweat.
When he did manage to get to the capsule and began entering the hatch, he found the space suit was too big to fit inside. The suit wouldn’t budge. Leonov was exhausted, but he couldn’t remain outside. You can’t return to Earth hanging on to the outside of a spacecraft.
Finally, in a desperate move to get through the tight opening, he let some air out of his space suit so that it would become softer. While losing precious oxygen and on the verge of passing out, he managed to squeeze back inside his space capsule and seal the hatch. It was a narrow escape!
Today’s space suits are built stronger. They don’t inflate like balloons, but they still become stiff when out in the vacuum of space. Astronauts must learn how to work with the suit so they don’t become exhausted. It looks easy to be floating around in zero gravity, but make no mistake: space walkers are working hard!
Before you can walk in space, you have to learn to walk underwater. It’s the only other way to simulate the weightlessness in space for a time period longer than thirty seconds, which is all an astronaut in a zero-g airplane gets.
The world’s largest swimming pool is at the Johnson Space Center in Houston, Texas. The pool has to be big because inside it are full-size models of the space station. Astronauts go underwater and practice the work they’ll be doing in space. Wearing the same type of space suit used in orbit, space walkers are lowered into the water, where divers add weights to the suit until the astronaut neither floats nor sinks. Once an astronaut is neutrally buoyant, they float in the water somewhere in the middle—not at the surface or the bottom of the pool—similar to the way they would float in space.
Divers guide the astronauts to the space station and hand them the tools they will be using in outer space so they can practice using them while weightless. On Earth, if you need to loosen a bolt, you put a wrench on it and turn it, usually with quite a bit of force. But if you’re floating weightlessly, your body force isn’t much help. The wrench and the bolt remain still while you spin around. That’s not very useful.
Space walkers have to learn what parts of the space station they can hang on to or where to brace their feet while working with tools, which in some cases means turning upside down. Luckily, that’s easier to do in space because there is no up or down.
Even though it is called space walking, it’s not done with the feet. Astronauts actually walk on their fingertips in space. In zero gravity, your feet don’t stick to anything, so your hands and arms do most of the work of moving you around. There are restraints or hoops that you can loop your feet into to stay in one spot, but that is space standing, not space walking.
The International Space Station is larger than a football field, and believe it or not, it’s possible to get lost while floating around outside. A tool that helps astronauts find their way around is a virtual reality room at Johnson Space Center that reproduces the entire station in 3-D.
I was lucky enough to visit and try it out. Wearing a VR headset, a chest pad that monitors body position, and wired gloves, I sat in a swivel chair with Canadian astronaut Jeremy Hansen in a chair behind me.
“We are putting you on the very end of Canadarm 2,” the operator said.
As the system turned on, I saw nothing but blackness, then two white space-gloved hands appeared in front of me as I reached out. I watched what looked like my gloved fingers open and close at exactly the same rate as my own hands in the room. I made the gloves wave around like a baby reaching up from a crib.
“I don’t see the space station,” I said into my headset.
“Try looking down.”
I tilted my head down toward my feet, and there was the entire sprawling complex spread out below me. Silver cylinders the size of buses hooked together end to end, and long, thin solar panels reached out the sides, golden in the sunlight. I recognized the American module straight below me, the Russian module off to the left, and the Japanese and European sections off to the right. I was virtually standing on the tip of a robotic arm made in Canada! This truly was amazing!
But there was something missing. Everything around the station was black. Where was the Earth? I’d heard so much about how beautiful the view of our planet was from the station, but it was nowhere to be seen in this VR simulation. Then I remembered that I was in a fully three-dimensional space.
Leaning back and tilting my head up as far as I could, the vast expanse of the Earth completely filled my view. And blue was all I saw. We were flying over an ocean. A thin, wavy brown line passed by. It must have been a beach on some island, but I had no idea where I was. I did realize that I was actually positioned upside down under the space station with my head pointed toward the Earth. But then again, there is no up or down in space, so it doesn’t really matter.
“Okay, we’re going to put you on the structure now,” said the operator, and with a click of a mouse, I was face-to-face with a wall of gray metal. I looked around and saw nothing but beams and girders in all directions. I had no idea where I was on the station because I was now stuck to the side of it.
“Now get ready. The sun is setting. We’re going around to the night side.”
Right. I knew that the space station goes around the Earth every hour and a half, so astronauts experience sixteen sunrises and sunsets every day—one every forty-five minutes. The darkness fell as quickly as the lights dimming in a theater. Everything around me disappeared into blackness except a circle of light directly in front of me that came from my space suit’s headlights. It illuminated a small part of the giant structure, and as I turned my body, I could see only what was in that white circle of light.
Space walkers must work in the dark as well as daylight, I suddenly realized. They have to find their way around the outside of the huge station while floating free
ly in a bulky space suit using their hands to maneuver, then work with tools and move huge pieces of equipment that would be impossible to lift on Earth. They work in the most dangerous place imaginable on the largest objects ever sent into space. It takes strength, concentration, and knowledge to pull it off.
I didn’t get a glimpse of the Earth at night because I was too busy trying to find my way around the maze of the space station structure in the dark. But I did think about the blackness that surrounded me and how far into space it goes. I tried to imagine the feeling of floating alone out in the void with nothing but the fabric of the suit and a thin plastic faceplate between me and the rest of the universe. It would be a humbling experience.
When the simulation was over and I removed the headgear, I felt like I had been on a remarkable journey. The room seemed small and confining. Gone was the feeling of being in a vast open space. I was an Earthling bound to my planet once again.
Working in space—there really is no job like it.
YOU TRY IT! Space Construction
Space walking is construction work done in space. Astronauts leave their spacecraft to do tasks and research, and that means using tools while wearing a bulky space suit. It’s not as easy as it looks. Why not give it a try?
