Economical Travel Techniques
Interplanetary travel has to solve two problems, other than escaping from the planet of origin:
- The planet from which the spaceship starts is moving round the Sun at a different speed than the planet to which the spaceship is traveling, because the two planets are at different distances from the Sun (due to Kepler's third law). So as it approaches its destination, the spaceship must increase its speed if the destination is closer to the Sun, or decrease its speed if the destination is further away (assuming a Hohmann transfer orbit).
- If the destination is farther away, the spaceship must lift itself "up" against the force of the Sun's gravity.
Doing this by brute force – accelerating in the shortest route to the destination and then, if it is farther from the Sun, decelerating to match the planet's speed – would require an extremely large amount of fuel. And the fuel required for deceleration and velocity-matching has to be launched along with the payload, and therefore even more fuel is needed in the acceleration phase.
The change in speed (delta-v) required to match velocity with another planet is surprisingly large. For example Venus orbits about 5.2 km/s faster than Earth and Mars orbits about 5.7 km/s slower. To put these figures in perspective, Earth's escape velocity is about 11.2 km/second. So matching a space shuttle's velocity with that of Venus or Mars would require a significant percentage of the energy which is used to launch a shuttle from Earth's surface.
Read more about this topic: Interplanetary Spaceflight
Famous quotes containing the words economical, travel and/or techniques:
“In short I must confide in you to take such care of the men under you as an economical householder would of his own family, doing every thing within himself as far as he can, and calling for as few supplies as possible. The less you depend for supplies from this quarter, the less you will be disappointed.”
—Thomas Jefferson (1743–1826)
“I travel light; as light,
That is, as a man can travel who will
Still carry his body around because
Of its sentimental value.”
—Christopher Fry (b. 1907)
“It is easy to lose confidence in our natural ability to raise children. The true techniques for raising children are simple: Be with them, play with them, talk to them. You are not squandering their time no matter what the latest child development books say about “purposeful play” and “cognitive learning skills.””
—Neil Kurshan (20th century)