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Re: No cannon

From: Ron Miller <spaceart~at~embarqmail.com>
Date: Fri, 4 Apr 2008 18:47:19 -0400 (EDT)
To: Jules Verne Forum <jvf~at~gilead.org.il>

----- Original Message -----
From: "Christian Sánchez" <chvsanchez~at~arnet.com.ar>
To: "Jules Verne Forum" <jvf~at~Gilead.org.il>
Sent: Friday, April 4, 2008 12:34:53 AM (GMT-0500) America/New_York
Subject: No cannon





Jules Verne proposed a giant cannon in his novel From the Earth to the Moon . However, such a sudden burst of acceleration would inevitably kill any passengers instantly, and calculations have shown no cannon could be powerful enough to achieve escape velocity. ( http://technology.newscientist.com/channel/tech/dn13556-10-impossibilities-conquered-by-science.html )



Below is some relevant text from my book "The Dream Machines":



Why, it is usually asked by his critics, did he not use them for the entire journey?

The reason is that Verne was not only striving for accuracy, but believability. He was certainly aware that all of the accurate details in the world were for nought if no one believed them. And that was the problem with the use of rockets. The largest consistently successful rockets built up to the time Verne was writing were the war rockets of Britishers William Congreve and William Hale. It is Congreve’s rockets that we sing of in our national anthem, " . . . by the rocket’s red glare, the bombs bursting in air . . . ," when they were used against Fort McHenry in the War of 1812. The largest of these were 6.5 inches in diameter (42-pounders) with a maximum range of 3,000 yards. Congreve designed rockets with 8-inch diameters and weighing up to 1,000 pounds. These never saw service because they were then considered too heavy and impractical. Hale’s rockets, developed from the 1840s, had ranges of up to 2,200 yards. These rockets may have been more accurate and more reliable, but they were still, fundamentally, skyrockets. To have used the rocket principle in getting his characters to the moon, Verne would have had only two options: making his spacecraft a single enormous powder rocket, or making a compound rocket by combining literally tens of thousands of individual rockets (as the British Interplanetary Society did in their original moon rocket design of 1939). Either plan would have been thoroughly ludicrous—not only realistically, but especially to readers to whom a rocket was little more than a toy. But people did believe in the seemingly limitless power of the modern cannon. As Verne was careful to point out, the decade immediately preceding his book had seen incredible advances in the art of artillery. One of Dahlgren’s large guns was capable of throwing a 100-pound shell 5,000 yards, Rodman’s Columbiad shot a projectile weighing 1,000 pounds 6 miles. There seemed little limit to the size of the gun or the shell it launched.

That Verne was aware of many of the difficulties inherent in his scheme is evidenced by the care with which he "answers" the very questions his critics raise. To this end he introduces a major character whose sole purpose is to voice these doubts, allowing Verne, through his other characters and the action of the story, to respond with believable (if imaginary) solutions. That this character criticizes the moon venture in virtually the same terms as do Verne’s later critics simply shows that Verne himself was aware of the problems. It also puts into the mouth of a character the very objections which may have been forming in the minds of his readers. Some of the objections raised by this character, Captain Nicholl, are: that it would not be possible to cast a 900-foot cannon, that it would not be possible to load it (or if it were, that the weight of the projectile itself would detonate the explosives), that the Columbiad would burst when fired, and that the shell could not possibly rise more than 6 miles. He places a wager upon each of his exceptions and Verne, in the course of the story, has Nicholl lose each bet, one at a time.

Verne has other methods of adding verisimilitude to his story. Aware that even his most innocent reader might question the effects on the human body caused by such a violent launch, Verne has his gun work by simply making it work, by fiat . His precautions against the forces of the launch are so detailed that his average reader would simply take it for granted that Verne was aware of the dangers and had adequately prepared for them. Verne could be even more subtle than that. Before the launch of the human astronauts, Barbicane and Co. load cat and a squirrel into a hollow shell. They are fired from a mortar several thousand feet through the air, dropping into the waters off Pensacola. When the shell is recovered, the cat leaps out unharmed (the squirrel, however, did not survive the hungry cat). "After this experiment," writes Verne, "all hesitation, all fear vanished; besides, Barbicane planned to work further to perfect the projectile and to eliminate entirely the internal effects of the firing." All hesitation and all fears of the reader vanish as well, which is Verne’s real purpose for this episode.

To "eliminate entirely" the effects of the launch, Barbicane installs a shock absorber in the floor of the projectile. This consists of a layer of water 3 feet deep on top of which floats a wooden disc. The disc fits the inside of the projectile closely, like a piston. The water beneath it is separated into three layers by two thinner discs, designed to rupture at the time of the takeoff. The water is to be forced through a system of pipes, where it is ejected from near the projectile’s nose (lightening the vehicle at the same time). The astronauts also plan to lie prone upon the disc on thick mattresses.

A number of space and rocket scientists have, since the publication of From the Earth to the Moon, amused themselves by developing variations on Verne’s space gun by which it might be made to work. Max Valier, in his book Der Vorstoss in den Weltenraum—eine technische Moglichkeit [1924], analyzed the Gun Club’s project. His conclusion, after several pages of mathematics, was that what was needed was a projectile of tungsten steel filled with lead 21.5 feet long and 3.5 feet wide. Valier’s gun would, like Verne’s, have a barrel 900 feet long. This one, however, would have to be situated on the equator at an altitude of 15,000 feet. The barrel would be cast in concrete with a rifled steel lining. Before the Launch, the air would be evacuated from the gun and its muzzle sealed by an airtight disc. At the moment of firing, the small amount of residual air ahead of the projectile would be sufficient to blow off the cap before the projectile reached the opening. There would be no possibility of carrying human passengers.

Somewhat later, the Baron von Pirquet examined the problem. He made the required mountain 20,000 feet high, placing even more of the earth’s atmosphere below the gun. Finding that the gases from the detonating explosive would not expand fast enough if the whole charge were placed in the bottom of the gun, he placed most of the charge on the bottom of the unmanned projectile itself. He also supplied supplementary firing chambers along the length of the barrel [see LeFaure and de Graffigny, 1889].

Others, such as Tsiolkovsky (who in 1895 expressed the opinion that a gun several kilometers long, placed horizontally, might work if the astronaut were immersed in liquid at the time of launch; Gen. Antonio Stefano thought a projectile 150 mm in diameter would need a gun only 800 meters long), also attacked the question of Verne’s gun and there, of course, have been fictional space guns other than Verne’s. There have also been serious proposals for actual space guns and one for firing instrument-carrying shells has actually been used.
Received on Mon 07 Apr 2008 - 00:26:22 IDT

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