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Space: the ultimate vacation destination: space tourism allows paying customers to travel where once only a select few could go.

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You're suited up and sitting aboard a spaceship along with five other passengers and two pilots. Hitching a ride with a large aircraft, the spaceship slowly climbs to an altitude of 15,240 meters (50,000 feet). Then it detaches from the aircraft, and its rocket motor fires up. You're pinned to your seat as if on the ultimate roller-coaster ride and then BAM, you're shot into space.

Out-of-this-world trips are no longer just for astronauts. For a hefty fee, several companies will take adventurers on the ultimate vacation: a short trip into space.

"You get about 15 to 20 minutes in space, and you'll be weightless for a few minutes of that," says Will Whitehorn, president of Virgin Galactic, a company that plans to fly tourists into space within a couple of years.

Here's how Virgin Galactic will accomplish the feat, and what a trip to space will feel like.

INTO THE AIR

Before riders on Virgin Galactic's spacecraft, called SpaceShipTwo, can experience outer space, a jet-powered aircraft, WhiteKnightTwo, must carry the ship to the edge of Earth's atmosphere.

WhiteKnightTwo operates much like a commercial flight. The aircraft's engines burn fuel to throw gases out the back. This creates a force called thrust, which pushes the aircraft forward. The aircraft's wings force air downward, causing an equal and opposite force upward called lift. Together, thrust and lift allow WhiteKnightTwo to overcome the pull of gravity, getting off the ground and up in altitude--way up. "You're going higher than any [passenger] has ever flown--about 15,000 feet higher than a normal jet," says Whitehorn.

So far, the trip feels like a typical ride in an airplane. "You're just sitting back looking out but you begin to see the blackness of space above you because you're right at the edge of the atmosphere," says Whitehorn.

BLASTOFF

At the brink of space, SpaceShipTwo detaches and ignites its rocket motor. Sixty seconds after the rocket fires, SpaceShipTwo turns vertically, speeding upward at 4,023 kilometers (2,500 miles) per hour. Passengers start to feel a mighty force pushing them down into their seats. This force of acceleration, which could be as much as four times that of gravity, is called g-force.

"It's a funny feeling, but it's not too bad," says Steven H. Collicott, an aeronautics and astronautics professor at Purdue University in Indiana. "It's similar to how you get pushed back in the seat of a sports car that leaves a spot in a hurry."

The rocket thrust pushes up, but at the same time, gravity pulls the spaceship down toward Earth. For the rocket to stay on its upward trajectory, the thrust needs to be greater than the weight of the rocket.

Once SpaceShipTwo leaves the atmosphere, blue sky is replaced by outer-space black and the spaceship's engines shut off. Even without the engines, the spaceship continues to climb up because of inertia (the tendency of an object in motion to stay in motion). It will slow down when it reaches the top of its flight and start to fall back toward Earth.

"During that period, you'll have maybe a minute and a half going up and a minute and a half coming down where you will feel weightlessness like an astronaut," says Collicott. Space tourists will experience weightlessness because they will have no weight relative to their surroundings: The spaceship is falling at the same rate as its passengers are.

"You'll be able to move around the cabin and look out the window on all sides, see the curvature of the Earth below, the thin blue atmosphere, and look up toward the planets and the stars," says Whitehorn. You'll also be able to experience the silence of space because the engines are off during that part of the flight. Space itself is noiseless because there is no air in space to transmit sound.

BACK TO EARTH

Having reached an altitude of 105 km (65 mi), the passengers will buckle up again and get ready to return to Earth.

As gravity pulls the spaceship home, its wings fold up into a feathered position--giving the spaceship the appearance of a huge badminton shuttlecock (see Flight Plan, p. 12).

This unstreamlined shape allows the spaceship to slow down by experiencing air resistance and high drag forces. The deceleration gives the pilots good control, says Collicott.

When SpaceShipTwo falls to an altitude of approximately 21 km (13 mi), it comes to the part of the atmosphere where there's lots of air. Here, pilots unfold the wings so they can land the spaceship as a glider--an aircraft supported by the action of air against its surfaces.

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As of press time, Virgin Galactic had performed more than 50 test flights. During the most recent one, SpaceShipTwo reached a milestone: It flew by itself in the upper atmosphere. "From here on, it's going to be progress all the way into space next year," says Whitehorn.

Although in time the cost of a space trip is expected to drop, for now, a trip will run a whopping $200,000. So if you want to access the outer reaches of the sky you'll need to start saving up!

MAJOR MILESTONES OF SPACEFLIGHT

APRIL 12, 1961: Russian cosmonaut, Yuri Gagarin becomes the first human in space. His flight lasts 108 minutes.

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JULY 20, 1969: Astronauts Neil Armstrong and Buzz Aldrin are the first humans to walk on the moon. The duo spend 21.5 hours on the lunar surface and bring back to Earth 21.55 kilograms (47.5 pounds) of lunar rocks.

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APRIL 12, 1981: NASA's first shuttle mission launches. It carries astronauts Robert Crippen and John Young. Space shuttle Columbia orbits Earth 37 times during the mission's 54.5 hours.

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JUNE 21, 2004: Virgin Galactic's SpaceShipOne becomes the first privately owned spacecraft to reach the edge of space.

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FLIGHT PLAN

A trip aboard SpaceShipTwo is expected to last 2.5 to 3 hours. Here's what the flight will look like.

1. At an altitude of 15.5 km (50,000 ft), SpaceShipTwo will release from WhiteKnightTwo and launch.

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2. At an altitude of 100 km (328,000 ft) SpaceShipTwo reaches the boundary between Earth's atmosphere and outer space.

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3. SpaceShipTwo reaches its maximum altitude of 110 km (361,000 ft) and pulls its wings up into a feathered position.

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4. SpaceShipTwo re-enters Earth's atmosphere.

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5. At 21.5 km (70,000 ft) SpaceShipTwo goes into glide mode.

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6. It heads toward Spaceport America in New Mexico to land.

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IT'S YOUR CHOICE

1. What force pushes an aircraft forward?

(A) drag

(B) gravity

(C) thrust

(D) all of the above

2. Why do space tourists experience weightlessness?

(A) because there is no gravity in space

(B) because the spaceship is falling at the same rate as the passengers

(C) because there is no air

(D) none of the above

3. To begin its return to Earth, SpaceShipTwo will fall back to the planet in an unstreamlined--position.

(A) feathered

(B) unfeathered

(C) glider

(D) kite

ANSWER

1. c 2. b 3. a

PRE-READING PROMPTS:

* What forces are at work when an airplane takes off and lands? Are the forces the same for a rocket?

* What do you think it would be like to fly into space?

* Would you spend $200,000 to go into space for 20 minutes?

DID YOU KNOW?

* After the launch of Sputnik 1 in October 1957 and Sputnik 2 a month later, the U.S. feared that it was losing the space race, so in July 1958 President Eisenhower signed the National Aeronautics and Space Act, which formed NASA.

* French inventor Henri Giffard was the first person to pilot a powered aircraft. His steam-powered airship's inaugural flight was September 24, 1852. He traveled about 27 kilometers (17 miles), from Paris to Trappes, France.

* In 2001, 60-year-old Dennis Tito was the first space tourist. He paid the Russian space agency $20 million for a trip to space. He even got to spend almost eight days on the International Space Station and orbited Earth 128 times during his stay!

CRITICAL THINKING:

* When Karl Benz introduced the automobile in 1885, it was neither affordable nor available to most consumers. Henry Ford produced his cars on an assembly line, which made the automobile more affordable for middle-class Americans. Now that space travel is becoming available commercially, do you think it will become more affordable as the years go by? Do you think space travel should become more accessible to everyone? Why or why not?

PROJECT-BASED LEARNING:

ART: Imagine that you are starting your own space-tourism company. Make a poster advertising your company's services. Be sure to include details like how your aircraft goes into space, the cost, and how long passengers will get to stay in orbit.

RESOURCES

You can access these Web links at www.scholastic.com/scienceworld.

* VIDEO EXTRA: Learn more about SpaceShipTwo at: www.virgingalactic.com.

* PBS's NOVA has an extensive site that includes information, video clips, and activities on flight and space travel at: www.pbs.org/wgbh/nova/space.

* Explore National Geographic's interactive Web site about space exploration here: http://science.nationalgeographic .com/science/space/space-exploration.
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Title Annotation:PHYSICS: FORCES AND MOTION
Author:Goudarzi, Sara
Publication:Science World
Date:Mar 5, 2011
Words:1545
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