first-stage engines of the Saturn V burned 40,000 pounds of fuel per second in
only two minutes just to lift off a spaceship a little larger than a Jeep!
Even today, this is the only way to go into orbit. The launchers are called
expendable vehicles, to imply that every piece of them will be lost. Imagine you
take a plane to go overseas and once you arrive at your destination, the airline
throws the plane away and buys a new one to get you back home. Basically, that
is how it works in astronautics.
In the seventies, NASA engineers wanted to build a cheaper and reusable vehicle,
so they designed the space shuttle consisting of a manned spaceship, the Orbiter,
mounted over a huge cylindrical, conical-tipped reservoir with two rocket boosters.
Both the reservoir and the boosters were lost after each flight, while the Orbiter, a
stubby spaceplane with three engines, returned to Earth as a big glider. Only after a
rigorous and long check it could leave again. In this way, NASA thought it could
drastically reduce launch costs, even if the boosters and the reservoir – 28 times
heavier than the Orbiter – were lost in each flight. The economic advantage did not
materialize. In 1986, one of the boosters exploded, killing the crew. Safety procedures increased enormously, and the cost of a single shuttle flight rose to over $500
million. In the end, NASA managed to have only four missions per year.
In addition, we continue using chemically propelled endothermal rocket
engines – a complicated way of saying that they work by combining two chemical
liquids, fuel and an oxidizer – which are intrinsically inefficient, since they consume 96% of the propellant’s energy to put into orbit a payload 50 times smaller
than the carrying rocket. But at the moment, there is no alternative.
At the dawn of the twenty-first century, there are no new discoveries likely to
revolutionize rocket science, and many futuristic ideas remain unrealized. One
promising project aiming to develop the so-called space tourism market is pursued
by Virgin Galactic, owned by billionaire Richard Branson. The company is testing
the SpaceShip 2 to send paying passengers into space in a few years. The idea is
simple: a crewed spaceplane equipped with a rocket engine is docked under the
wing of a large airplane, which releases it at high altitude. There, the pilots turn on
the engine and let the spaceship reach the upper limits of Earth’s atmosphere. That
part of the flight is quite similar to that of astronauts’ onboard rockets. After about
ten minutes, the engine shuts down and everyone start floating in the cockpit,
enjoying the view from the windows. Quite soon, all passengers must fasten their
seatbelts, as the spaceship does not move at the right speed to steadily remain in
orbit and so glides back to Earth. This flight technique was the same used in the
fifties by NASA’s experimental X-15 vehicle, which flew at the edge of the atmosphere after being released from a B-52 bomber. Actually, Virgin Galactic is now
making a modern version of the old X-15. Since current aircraft engine technology is not yet capable of reaching 5 miles per second – supersonic planes only
reach 7% of orbital speed – even Mr. Branson has to rely on classic, dangerous
rocket science to make just a small jump into space.
8 Fundamentals of Astronautics
only two minutes just to lift off a spaceship a little larger than a Jeep!
Even today, this is the only way to go into orbit. The launchers are called
expendable vehicles, to imply that every piece of them will be lost. Imagine you
take a plane to go overseas and once you arrive at your destination, the airline
throws the plane away and buys a new one to get you back home. Basically, that
is how it works in astronautics.
In the seventies, NASA engineers wanted to build a cheaper and reusable vehicle,
so they designed the space shuttle consisting of a manned spaceship, the Orbiter,
mounted over a huge cylindrical, conical-tipped reservoir with two rocket boosters.
Both the reservoir and the boosters were lost after each flight, while the Orbiter, a
stubby spaceplane with three engines, returned to Earth as a big glider. Only after a
rigorous and long check it could leave again. In this way, NASA thought it could
drastically reduce launch costs, even if the boosters and the reservoir – 28 times
heavier than the Orbiter – were lost in each flight. The economic advantage did not
materialize. In 1986, one of the boosters exploded, killing the crew. Safety procedures increased enormously, and the cost of a single shuttle flight rose to over $500
million. In the end, NASA managed to have only four missions per year.
In addition, we continue using chemically propelled endothermal rocket
engines – a complicated way of saying that they work by combining two chemical
liquids, fuel and an oxidizer – which are intrinsically inefficient, since they consume 96% of the propellant’s energy to put into orbit a payload 50 times smaller
than the carrying rocket. But at the moment, there is no alternative.
At the dawn of the twenty-first century, there are no new discoveries likely to
revolutionize rocket science, and many futuristic ideas remain unrealized. One
promising project aiming to develop the so-called space tourism market is pursued
by Virgin Galactic, owned by billionaire Richard Branson. The company is testing
the SpaceShip 2 to send paying passengers into space in a few years. The idea is
simple: a crewed spaceplane equipped with a rocket engine is docked under the
wing of a large airplane, which releases it at high altitude. There, the pilots turn on
the engine and let the spaceship reach the upper limits of Earth’s atmosphere. That
part of the flight is quite similar to that of astronauts’ onboard rockets. After about
ten minutes, the engine shuts down and everyone start floating in the cockpit,
enjoying the view from the windows. Quite soon, all passengers must fasten their
seatbelts, as the spaceship does not move at the right speed to steadily remain in
orbit and so glides back to Earth. This flight technique was the same used in the
fifties by NASA’s experimental X-15 vehicle, which flew at the edge of the atmosphere after being released from a B-52 bomber. Actually, Virgin Galactic is now
making a modern version of the old X-15. Since current aircraft engine technology is not yet capable of reaching 5 miles per second – supersonic planes only
reach 7% of orbital speed – even Mr. Branson has to rely on classic, dangerous
rocket science to make just a small jump into space.
8 Fundamentals of Astronautics