The Mercury-Redstone 3 rocket lifts Freedom 7, the first piloted Mercury spacecraft, carrying Astronaut Alan B. Shepard, Jr. on a suborbital space flight from Cape Canaveral, Florida, on May 5, 1961. The capsule flew up to an altitude of 115 nautical miles and then landed 302 miles downrange. The capsule reached a speed of 5,100 miles per hour during the 14.8-minute flight.

A suborbital flight is a trip to space that does not involve sending the vehicle on into orbit.

• The launcher is powerful enough to fly to space, which is above 62.5 miles altitude, but not powerful enough to go on into orbit. Such a suborbital space flight is an up-and-down trip.
  
  
• The edge or boundary of space is defined as 100 km (about 62.5 miles) above Earth's mean sea level.

A suborbital flight is appealing because it is easier to reach space without traveling on into orbit. All a suborbital launcher has to do is travel higher than the edge of space

To think a suborbital trip is not a journey into space is not accurate. Both suborbital and orbital flights are in space as long as they are above 62.5 miles altitude.

• Suborbital is up and down while orbital goes around and around.

Suborbital flights have been used to test launchers and spacecraft intended for later orbital flights.

Suborbital flights were used in the 1950s to determine whether human spaceflight was feasible. Before cosmonauts and astronauts flew to orbit, dogs and other animals were sent to space on suborbital flights.

Some human transport vehicles, such as SpaceShipOne and the X-15, were designed exclusively for suborbital space flights.

• X-15 was a rocket plane that set speed records in the 1960s. Two of its many flights flew above 62.5 miles altitude.
  
  
• SpaceShipOne is an experimental spaceplane, which flew a suborbital path to space and back in 2004.

A suborbital craft is cheaper to construct than an orbital craft because it only needs to reach speeds of 2,500-3,000 mph. To fly on into orbit around Earth, a launcher must be capable of achieving 18,000 miles per hour.

Why would we build suborbital launchers when we already are flying on into orbit?

• Suborbital craft may be used in the future for intercontinental flight. A suborbital flight from Europe to North America would require less than an hour.
  
  
• Suborbital tourist flights to space will be popular with those who can afford to see the sights from up there, experience weightlessness, and drop down to land where they took off.

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