THE VIEW FROM CHAOS MANOR
View 362 May 16 - 22, 2005
Highlights this week:
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May 16, 2005
I am determined to overcome jet lag...
A good day followed by dinner with friends at Archeologica, a restaurant complex out on the Appian Way; recommended if you're in the Roman area and have a way to get there.
http://www.techweb.com/wire/security/163101988 on phishing avoiding filters by sending text as images. One reason I view all mail as plain text and only open links or convert to html when I am sure I want to see the material.
6. Microsoft Launches MSN Desktop Search Software Opening up
a new front in its battle against Google, Microsoft launched the final
version of its MSN Search software, which lets users browse by content, not
just file names.
May 17, 2005
(1100 Rome time)
If you do everything else just right, you get older. When you get older you get jet lag that doesn't quit. Get your traveling done when you're younger and recover from time zone changes more quickly. Or travel by boat...
I keep getting mail on the DREAD system physics. DREAD is a centrifugal gun that sends pellets out at a fairly high rate of speed; as one correspondent observes, it's an area denial system intended to produce a beaten area, not a pinpoint accuracy system to be used against small individual targets. The advantages are in the logistics. You carry fuel, not explosive propellants.
The confusions seem to come with regard to the "recoil" of such a system, and there is considerable confusion of angular vs. linear accelerations.
First, consider the system as a whole, and put it into free space. We're not concerned about angular momentum on the first pass: what we see is a system in space that spews out mass. For the moment we'll assume the mass all comes out along a single vector which we can call "aftward". Any system that sends out mass in a single direction is a rocket, and subject to the rocket equation; since the mass comes out in chunks rather than particles it won't be an efficient rocket and you won't get the constant e in the equation, but we'll ignore that for the first cut. (The classic rocket equation assumes small continuous particles and thus is concerned only with the ratio of the starting mass to the mass at velocity, and the exhaust velocity; we're violating that assumption big time here, but we're ignoring the violation.) The point is that we don't need to know how the reaction mass -- the particles, balls, whatever that is going overboard -- were accelerated to velocity. All we need to know is the starting mass of the system, the mass after the ammunition is exhausted, and the exhaust velocity, and we can calculate the delta-v (change in velocity) of the system as a whole assuming it is in free space and not subject to friction (wheels on pavement, atmospheric drag). For refinement we can do the calculation for each projectile and sum over the whole mass one projectile at a time, thus correcting for the size of the projectiles (once again, the rocket equation assumes continuous flow of negligible sized particles; this where the constant e appears in the rocket equation, and why rocket science uses natural logs.)
That's the linear acceleration effect. Over time it can be quite large, but in practice the accelerations due to the rocket effect will be overcome by the effects of friction, wheels or treads on the ground, and the motive system of the vehicle which isn't, after all, in free space. They won't be negligible, though, particularly if the exhaust velocity of the projectiles is high and the "fuel" weight is an appreciable fraction of the total system weight, so there will be fuel consumption required to keep the vehicle moving toward the target.
Now we have the angular momentum, which is more complicated. Assume that the projectiles start at rest with respect to the system, travel up a tube, out the moment arm of the thrower, and are released. Assume the vehicle is traveling directly toward the target. Think about the point in the travel of the throwing arm at which the projectile is released (this confuses people who haven't studied the problem, or who haven't modeled the system. It may help to think of a man standing in an L5 colony with artificial gravity and what happens if he simply drops a baseball.)
And that's the best I am going to do jetlagged in Rome with other things to do. I leave the rest as an exercise for the reader.
Last night we successfully navigated the Roman Metro system, and today we managed a bus to the Vatican, but we were tired enough coming back that we took a taxi. The bus system is 1 Euro each for 75 minutes, although I have never seen anyone actually check a ticket. The taxi is about 5 Euros. It's odd to be in Italy without Lira. My Roman friends tell me they accepted far too low a value for the Lira when they joined the EU, and in the year after they lost the Lira and went to prices in Euros the actual price of nearly everything doubled. That's serious inflation, but it seems stable now.
May 18, 2005
Last day here. Sistine Chapel and Vatican museums.
Strenuous day. Packing. Heading for home in the morning.
This in not long ago:
For anyone who's ever edited copy, written for an editor, or simply loved
to read HST, this is a must read.
That is an interesting read...
Here's a link to snopes.com for a page about how Burma
Shave once promised to send a contest winner to Mars:
May 19, 2005
Da Vinci Aeroporto No wireless connection. Limousine worked, traffic worked, security worked. We are in the vip Lounge. But No wireless. Guess that waits until Atlanta.
over Ireland. a long trip.
Wireless works fine in Atlanta
Home in Los Angeles. Baggage missing, last seen after we cleared customs in Atlanta and handed it back to Delta Airlines. They say they'll deliver it tomorrow.
And off to bed. It's good to be home.
May 20, 2005
Home, none the worse for wear, a bit tired. Luggage still not arrived. I'll call Delta after lunch.
There is beaucoup stuff to be cleaned up here...
May 21, 2005
We are here. The luggage is not. Alas I don't have intelligent pearwood luggage with homicidal tendencies...
May 22, 2005
Southern California Chapter of Mystery Writers of America meets today. Big crowd.
Luggage is still not here.
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