I have thought for a while that manned space flight should originate from a electromagnetic rail gun for safety and efficiency for a while.

The 250 G’s at the start would be real unsafe too – like fatal 100% of the time, I fear. Maybe you could cut that down to 25 G’s if you used a 1600ft track, standing on end, but it would still be a wallop. Maybe that’s why Jules Verne buried his “Columbiad” Earth-to-the-Moon cannon vertically in the ground? Tough to dig a 1600ft deep hole in Florida and keep it dry though…

Many have speculated that naval warfare is a thing of the past, but the technology previewed by Popular Science and demonstrated here show promise of a new weapon that can make a destroyer like a cruise missile machine gun. A few problems need to be …..

The way we do space travel now is still pretty primitive. It’s basically a controlled explosion with people on the end of it. It doesn’t seem very safe. . . or as safe as an electromagnetic rail machine. I just don’t think we can get enough power to shoot someone into space like that yet. 200 miles is a good long way without an explosion to get it there though.

A lot of people have buckled down to do the math that converts one number that doesn’t mean anything in human terms to another number that doesn’t mean anything in human terms.

I just did the math, and here’s a ratio that will make sense to at least some people (all numbers are approximate, ammunition power varies considerably):

.45ACP – 490 ft-lbs muzzle energy
300 Win Mag rifle – 3,100 ft-lbs muzzle energy
.50 Browning – 15,400 ft-lbs muzzle energy
20mm cannon – 39,800 ft-lbs muzzle energy
32Mj Railgun – 29,600,000 ft-lbs muzzle energy

I don’t have data on the Missouri’s 15-inchers, but I imagine it would be around 80 million ft-lbs, albeit with a shorter range (70 miles), steeper trajectory and a MUCH bigger projectile (1600 lbs?).

Keep in mind that the ballistic coefficient can have a big effect on trajectory, and some new exotic tech has produced coefficients higher than previously imagined possible. There’s a new line of target .30 cal ammo that comes with its own charts because NONE of the existing charts go anywhere near that level of aerodynamic efficiency.

And none of the online calculators I’ve tried can figure the ballistics of the railgun. :)

I seem to have picked up some spyware either there or here, not sure which.

At a muzzle velocity of 8000 ft/sec, or about 2500m/sec, you would only have to elevate the gun 15 degrees to get a range of 200 miles / 320 km! Of course that does not include air resistance, which I suspect would be considerable, since the high point of this trajectory is only about 75,000 feet. Still, a surprisingly low angle, and it puts the round on target in 2 minutes and 12 seconds.

Very fun site there, by the way. Caution, some of the result fields do not display the leftmost digits unless you put the cursor in them and scroll all the way left!

Those isolated valleys out in Talibanistan aren’t gonna feel so isolated. I can see an encampment of Al Qaeda camped out on a Pakistani hill somewhere when the American wrath of god meteor storm hits. The only guy who survives is the one filling up the canteens at the stream. He goes back to the rest of Al Qaeda and quits, saying, “Allah hates us.”

I’m guessing 74 days.
24 days in November after the 6th.
31 days in December.
19 days in January until the Inauguration.

That doesn’t make any sense. Air doesn’t burn.

At high enough energy, anything will burn.

Hillary’s or Obama’s presidency will not really begin until September 11, 2009. Anything that goes wrong before that will be blamed on Bush, of course, but there is now a clear precendent that by the 11th of September of your first year in office, you and you alone are on the hook for everything, and we should damn well never let any future Democrat president forget it!

And when an al Qaida imported nuke goes off in my back yard, I suppose you’ll tell me to take heart in the fact that it happened during a Democrat’s presidency.

I.NEED.A.NEW.KEYBOARD.

What’s that Mahmoud…? Don’t rail me, bro!

That sounds like something he would be saying if we ever captured his @ss and through him into one of our prisons (general population, of course).

What’s that Mahmoud…? Don’t rail me, bro!

Also, I suspect the speed is used to get the extreme range with a high-angle trajectory. Shooting it flat through the atmosphere is going to waste a lot of energy in air friction. I wonder how they build a giudance system that can handle thousands of G’s though?

Damn! How long before they get the size down to an inside the waistband holster size? Probably requires a two hand stance.

a capella on February 1, 2008 at 9:52 PM

And a PS: there will be a tear-you-limb-from-limb unimaginably vicious RECOIL!!

Damn! How long before they get the size down to an inside the waistband holster size? Probably requires a two hand stance.

a capella on February 1, 2008 at 9:52 PM

No problem with the gun…it’s the battery pack, the fireproof suit, and the earplugs which will be the hard-to-fix problems…

Chakra Hammer on February 2, 2008 at 1:00 AM

Actually, I have difficulty defining a 600-foot-long, 14,000+ ton vessel intended primarily for long-range engagement of high-value targets beyond the littoral zones as a “destroyer”. A more appropriate term would be “battleship” or at least “battle cruiser”- the latter being a term the USN has never used, in spite of building what amounted to battle cruisers during World War Two, namely the “large cruiser” U.S.S. Alaska (CB 1) and her sister ship, U.S.S. Guam (CB 2). They were named for what were then U.S. Trust Territories, to distinguish them from cruisers (named for cities) and “true” battleships (named for states). (The third ship in the class, U.S.S. Hawaii, was never completed, and the last three, to have been named Philippines, Puerto Rico, and Samoa, were cancelled.)

Hollowpoint on February 2, 2008 at 3:49 AM

You’re exactly correct. A weapon like this has to be fired at a high angle to the horizontal (usually about 45 degrees or so) to acheieve its maximum range, due to the laws of exterior ballistics. During World War One, the German Army shelled Paris from 78 miles away in the Forest of Compieigne
with a 21-cm (that’s about 8 1/2″ bore) weapon called the Kaiser Wilhelm Geschutze. (Her gun crew simply called her La Parisienne.) It had a barrel about 100 feet in length, took a 250-lb bagged charge of powder, and launched a 750-pound shell at 2800 feet per second for the admirable range of 78 miles. To do it, it fired at an angle of 43 degrees to the level, and the shell as a result spent over three-fourths of its flight trajectory actually outside of 90% of the earth’s atmosphere, reaching a peak altitude of about 36 miles. The flight time was about three minutes, and the crew had to do some fairly hefty mathematics to allow for the 14 miles the Earth rotated on its axis while the shell was “up beyond” most of the air.

Accuracy of the beastie was nothing to rave about, as its normal dispersion at the receiving end was on the order of a mile and a half. (Of course, it was shooting at an entire city, and Paris couldn’t exactly move out of the line of fire.) What finally shut it down was the Allied advance in the spring of 1918 which pushed the German Army out of the area, and the gun out of range of Paris.

To avoid such problems with this weapon, I expect that the railgun’s projectiles will have some sort of course correction capability, such as attitude control jets, and will probably be guided all the way to the target by a military -grade GPS system, backed up by an internal strapdown inertial-guidance platform. The difference being, the GPS would take “steers” from a satellite (which could, theoretically, be “jammed” [ECM'd] if somebody on the target end knew what they were doing), while the inertial system would be totally internal, autonomous, and independent, and be uninterruptible for that reason.

Even without GPS (which could drop the round into the proverbial pickle barrel), the inertial system alone would be good enough to get the round to within about fifty metres of the target at 300 km (200 miles) range, and that’s close enough to make things unpleasant for the intended recipient. Especially when the arriving “incoming mail” can do an excellent impression of a meteor impact, with or without an explosive charge, just based on kinetic energy alone.

(Jon’s Law; Any projectile moving at 3,000 m/s has a kinetic energy “yield” equivalent to its own weight in TNT, also often rendered as “Anything moving at 2 miles per second packs its own weight in BLAM.”)

The Navy’s operational railgun will come very close to this level of energy release. My hat is off to Naval BuOrd. Well Done.

cheers

eon

30,332BTU

8.88Kwh

Is 32 megajoules the muzzle energy, the energy imparted at impact at some distance or the energy it takes to get the projectile up to rated speed?

The power source would need to produce more than that of course. But a generator that size would be no problem to fit on a ship. A fairly small ship at that. My guess is that there’d be more problems with the size and configuration of the gun components. Probably has a capacitor bank that takes up a lot of space.