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In periods before human flight, did scientists, philosophers, or other thinkers seriously consider space travel and exploration a possibility?

I have come across nineteenth-century discussions of probable civilizations on other planets and I am curious if anyone seriously thought about how we might reach or contact them.

I am familiar with early attempts (i.e. Wan Hu) but I am particularly interested if there was any theoretical activity in this field before it was even remotely practical (by our standards).

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  • $\begingroup$ You maybe know of Conrad Haas who wrote the book about rocketry in the 16's century. Before Newton there cannot have been much serious thought about the topic. $\endgroup$ – LocalFluff Jun 11 '16 at 5:27
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    $\begingroup$ Tsiolkovsky published his equation in 1896. Wright brothers performed their first flight in 1903. $\endgroup$ – SF. Jun 11 '16 at 13:47
  • $\begingroup$ The problem, of course, was getting there. If you go back far enough you have chariots drawn by swans. Later (in fiction) people thought of catapults (Brick Moon) and cannons (From the Earth to the Moon), but how serious could they be, before rocketry? $\endgroup$ – Organic Marble Jun 11 '16 at 18:26
  • $\begingroup$ @OrganicMarble: Rocketry goes back to 3rd century though. (although used primarily as a marginal form of artillery) $\endgroup$ – SF. Jun 11 '16 at 18:41
  • $\begingroup$ @OrganicMarble The US did have a program at one time, exploring the use of cannons for suborbital (unmanned) vehicles and possibly orbital satellites. It was called Project HARP. en.wikipedia.org/wiki/Project_HARP $\endgroup$ – Howard Miller Jun 12 '16 at 0:09
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NASA provides a good Brief History of Rockets which summarizes in concise form many of the historical advances in rocketry and space exploration, including Wan-Hu's unfortunate attempt at a rocket-powered chair.
Wan-Hu's rocket chair

The simple rocket in the form kids light on the Fourth of July, invented by the Chinese, has been generally around by the end of the 13th century, used as a supplement to more traditional armament, as in Francis Scott Keys "rocket's red glare" from the bombardment of Fort McHenry during the War of 1812.

When the western Renaissance brought in the telescope, the concept that there was space to be explored began to come into focus. Before Galileo could look through a pair of lenses at Jupiter and see its four largest moons orbiting the planet, scientists and philosophers often thought of the distant stars and planets as residing on vast transparent spheres rotating about the Earth. Copernicus' sun-centered theory of the universe shattered the awkward and never-quite-right theory of epicycles, by which astronomers had tried to reconcile, in an Earth centered universe, their observations with their mathematics.

In the early 1600s, Johannes Kepler inherits years of precise astronomical data from the school of Tycho Brahe and, after many false starts, derives his laws of planetary motion:

  1. The orbit of a planet is an ellipse with the Sun at one of the two foci.
  2. A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
  3. The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.

By providing a mathematical solution which finally agreed with the tricky orbit of Mars, Kepler proved Copernicus right. Today Keplerian conic sections are a staple of orbital dynamics and astronavigation.

In 1687. Sir Issac Newton provided the science still used for many basic tasks of space exploration:

The Principia states Newton's laws of motion, forming the foundation of classical mechanics, also Newton's law of universal gravitation, and a derivation of Kepler's laws of planetary motion (which Kepler first obtained empirically).

As to serious consideration of space travel and exploration, one should look to the putative father of space exploration, Konstantin Tsiolkovsky. His 1903 publication, Exploration of Outer Space by Means of Rocket Devices and subsequent writings proved (for the first time) that a rocket could perform space flight, calculated the speed required for a successful Earth orbit and escape velocity, introduced the concept of the multistage rocket and liquid fuel/oxidizers.

Tsiolkovsky's most important contribution was the formulation of the rocket equation:
$$\Delta v=v_e ln\frac{m_0}{m_f}$$
where:
$\Delta v$ is the required change in velocity;
$v_e$ is the effective exhaust velocity of the combusted propellants;
$ln$ is the natural logarithm;
$m_0$ is the starting mass of the rocket including propellant; and
$m_f$ is the empty mass of the rocket.
$\frac{m_0}{m_f}$ is the mass ratio of the rocket

This is what is being referenced when you hear the phrase, on this site and many others, "the tyranny of the rocket equation." You can find a good discussion here, and I'll use the answers from that question to briefly explicate. Since your exhaust velocity is a constant, in order to achieve linear increases in $\Delta v$, you need exponentially greater mass ratios. The devil is the natural logarithm function. Here's a graph:

Natural log of x greater than 1

The mass ratio is always going to be greater than one, so I've ditched lower values. You can see that to get one unit of $\Delta v$ an approximate mass ratio of less than three; to double it you need more than seven; to triple it you jump to over 20. Rather than try to engineer absurdly high mass ratios, rocket research tries the more rational approach of finding engines, such as ion thrusters, that substantially increase the exhaust velocity.

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  • $\begingroup$ This is what is being referenced when you hear the phrase, on this site and many others, "the tyranny of the rocket equation." <- could be more clear stating The **logarithm** present in this formula is what is being referenced when you hear the phrase, on this site and many others $\endgroup$ – Caridorc Jun 13 '16 at 16:18
  • $\begingroup$ @uhoh: Made that change. $\endgroup$ – Jerard Puckett Jun 14 '16 at 0:09
  • $\begingroup$ @Caridorc: Any excuse to have fun with Photoshop. $\endgroup$ – Jerard Puckett Jun 14 '16 at 0:10
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    $\begingroup$ "rocket research tries the more rational approach of finding engines, such as ion thrusters, that substantially increase the exhaust velocity" And staging. Don't ever forget staging. We don't go on interplanetary missions using SSTO with direct insertion into transfer orbit for a reason. $\endgroup$ – a CVn Jun 14 '16 at 14:36
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    $\begingroup$ Copernicus's sun-centered system had almost as many epicycle problems as Aristotle's, because he insisted on using perfect circles. It wasn't until Kepler's ellipses that epicycles were removed from orbital calculations. $\endgroup$ – Mark Dec 16 '16 at 0:45
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There are also a number of examples from fiction. To give a few interesting examples:

  • From the Earth to the Moon by Jules Verne (1865) has a gun-launched spacecraft.
  • The War of the Worlds by H.G. Wells (1898) also has a gun-launched spacecraft, this time taking Martians to Earth.
  • A Trip to Venus by John Munro (1897) has a spacecraft the workings of which I don't think are fully explained (I only read part of the book). At one point the engine overheats and the protagonists use rifles as a reaction drive, comparing it to using a rocket.
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